text large_stringlengths 148 17k | id large_stringlengths 47 47 | score float64 2.69 5.31 | tokens int64 36 7.79k | format large_stringclasses 13 values | topic large_stringclasses 2 values | fr_ease float64 20 157 |
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The input tag is used to collect data in web forms and send that data to the web server. The input tag helps the server define the type of data that is being collected and may act in different ways depending upon the type of data it collects.
There are several different types of input tag:
- color (HTML 5)
- date (HTML 5)
- datetime (HTML 5)
- datetime-local (HTML 5)
- email (HTML 5)
- month (HTML 5)
- number (HTML 5)
- range (HTML 5)
- search (HTML 5)
- tel (HTML 5)
- time (HTML 5)
- url (HTML 5)
- week (HTML 5)
DTD: HTML5: <!doctype html>
HTML4 Strict: <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN" "http://www.w3.org/TR/html4/strict.dtd">
HTML4 Transitional or Loose: <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
INPUT Web Browser Support:
Browser support of the input tag depends mostly on what type of input tag you are using. However, modern browsers (Chrome, Firefox, Internet Explorer 6+, Opera, and Safari) all support the majority of input types.
HTML 5 Concerns: The default type for the input tag is text and if the browser does not recognize the type (because it is HTML 5 or some other type), it will send it as it does a text field. Therefore, if you decide to use the additional HTML 5 input types, browsers will still support them and submit them correctly to the server.
INPUT End Tag:
The input tag is a singleton tag. It has no end or closing tag.
In XHTML, this tag must have a closing slash:
The input tag is a singleton tag and has no contents
INPUT Valid Context:
The input tag is valid within the following tags:
a, abbr, address, article, aside, b, blockquote, body, caption, cite, code, datagrid, dd, del, details, dfn, dialog, div, dt, em, fieldset, footer, form, h1, h2, h3, h4, h5, h6, header, i, iframe, ins, kbd, label, legend, li, mark, menu, noscript, object, output, p, pre, progress, q, s, samp, section, small, span, strike, strong, sub, sup, td, th, tt, u, var
The input tag is used to create form input fields. The most commonly used input tag is the text input field. It is written like this:
<input type="text" name="text box">
If you write a text box, the type attribute is not required:
<input name="text box">
View live examples of input tags.
INPUT Special Notes:
The input tag is the primary method of soliciting form data from customers. By learning how to use it effectively, you will know a lot about how to build web forms. | <urn:uuid:53baebfc-a411-4f3c-8593-031384a23c4a> | 3.5625 | 721 | Documentation | Software Dev. | 77.110906 |
Hello Everyone. thanks for all the help. I am close to getting it...
A simplified formula for the hyperfocal length is:
usually d/D is very small so
d= diameter of accepted, maximum circle of confusion (set a priori)
F= focal length of positive lens
D= lens diameter
So, the hyperfocal length is farther out if the focal length increase and if the circle of (maximum) confusion is set to be small.
Let's do a numerical example:
d= 1 mm=0.1 cm
f#= 3 (focal length is 3 times the lens diameter).
H= 4/ (.3)= 13.3 cm
So the DOF goes from 6.65cm to "infinity". Infinity will include all those object distances where the objects are still imaged (not too small to be imaged as points). The circle of confusion at distance 6.65 cm is 1 mm. The circle of confusion at "infinity" is also 1 mm.
The circle of confusion at H=13.3 is 0mm (ignoring diffraction).
Now, focusing at infinity instead of focusing at H: the circle of at infinity is 0 mm. What distance can we call infinity in our example? Let's call that distance INF.
As we move away from INF (back or forward) the circle of confusion grows, eventually reaching size 1 mm. | <urn:uuid:4657693f-63f9-490e-a486-4b17e6ac1154> | 2.8125 | 295 | Comment Section | Science & Tech. | 79.656147 |
l = length
w = width
h = height
d = diagonal
S = surface area
V = volume
Enter any 3 variables for a rectangular prism into this online calculator to calculate the other 3 unknown variables. A cube is a special case where l = w = h for a rectangular prism.
* Units: Note that units are shown for convenience but do not affect the calculations. The units are in place to give an indication of the order of the results such as ft, ft2 or ft3. For example, if you are starting with mm and you know r and h in mm, your calculations will result with s in mm, V in mm3, L in mm2, T in mm2, B in mm2 and A in mm2.
A cube is a special case where l = w = h. So you can find the volume of a cube or surface area of a cube by setting these values equal to each other.
1. Given the length, width and height find the volume, surface area and diagonal of a rectangular prism
2. Given the surface area, length and width find the height, volume and diagonal of a rectangular prism
3. Given the volume, length and width find the height, surface area, and diagonal of a rectangular prism
4. Given the diagonal, length and width find the height, volume and surface area of a rectangular prism
For more information on cuboids see: Weisstein, Eric W. "Cuboid." From MathWorld--A Wolfram Web Resource. http://mathworld.wolfram.com/Cuboid.html | <urn:uuid:a7445c3e-6f80-4837-8d11-7850de234d16> | 3.6875 | 328 | Tutorial | Science & Tech. | 73.997296 |
C Programming and C++ Programming
Welcome! Cprogramming.com is your source for everything C and C++!
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C is a powerful system programming language, and C++ is an excellent general purpose programming language with modern bells and whistles.
Popular articles and tutorials for beginners and experts
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Once you know the basics, you can do all sorts of things with C and C++ - games, graphics and more
What's new in at Cprogramming.com?
- Developing for Android - An Introduction February 15, 2013
- Windows 8 Sensors development guide October 16, 2012
- Learn about working with Sensors on Windows 8 UltraBooks September 18, 2012
- Learn about how some companies are making cross-platform mobile games July 9, 2012
- Learn to make your applications more power efficient May 4, 2012
- Develop for UltraBooks and Join the Rebirth of personal computing April 17, 2012
- How to create a shared library on Linux with GCC December 30, 2011
Enum classes and nullptr in C++11 November 27, 2011
Integer to English Conversion Practice Problem November 21, 2011
Learn about The Hash Table November 20, 2011
C and C++ Source code
Learn from sample code written by fellow programmers
C and C++ References
C++ is a huge language, find what you're looking for here!
If you're stuck, ask for help on the message board, or look at our tips | <urn:uuid:5b3d0e2b-ce10-49d2-b054-6a6b202f9460> | 3.09375 | 308 | Content Listing | Software Dev. | 50.651688 |
What is a Concatenative Language
Recently there has been some discussion on the concatenative discussion group about the term "concatenative language" and what it actually means. In this post I provide my definition and attempt to deconstruct it.
The canonical example of a concatenative language is the Joy programming language by Manfred von Thun. I consider my language Cat to be concatenative as well. Factor by Slava Pestov is another language that describes itself as concatenative. For more examples of concatenative languages see the concatenative wiki and Wikipedia.
One problem that we have in the concatenative community currently has is lack of a rigorous definition. This makes it hard to determine whether a given language is concatenative or not, and makes any formal study difficult. The following is my attempt to provide a rigorous definition for a concatenative programming language:
"A concatenative programming language is language in which terms correspond to functions and in which the juxtaposition of terms denotes the composition of functions.".
For those readers not scared away yet, allow me to elaborate. A term is a valid and complete syntactic phrase that can be generated from the concrete (syntactic) grammar of a language. For example in Scheme "(f a 5)" is a term, as is "a" or "5" or "f". However, "(f" is not a term. Juxtaposition is just a fancy way of saying "two terms side by side". A concatenative language differs from the functional programming language paradigm where terms correspond to values (including functions) and the fundamental operation is function application. In the Lambda calculus for example -- which is the basis for functional programming -- all terms correspond to values, function application, or function abstraction (i.e. lambda expressions). However, in a concatenative language all terms correspond to functions on a tuple (e.g. a single stack, a pair of stacks, a pair of stacks plus a dictionary, or even a deque if you are really masochistic), or the composition of functions (which yields a new function, so is really a function).
So for example a literal term such as "42" in Joy or Cat is in fact a function that maps a stack to a new stack that is a copy of the original with the value 42 added to the top. For most practical purposes a programmer may think of the term "42" as being equivalent to the value "42". This in fact aids computations, but it can confuse the theory a bit. To have a correct and formal understanding of programming languages we have to understand the term/value distinction. IN very down-to-earth terms: the operation that pushes a value on the stack is different from the value that is on the stack.
At this point, some people may say, hey what about quotations? In Joy and Cat a quotation is a function that yields a new stack with a function on the top. This is consistent with what I have been saying.
While in theory a concatenative language does not require a stack, in practice most concatenative languages are stack-based, and at the same time most stack-based languages can be modeled formally as a concatenative language.
An interesting side note: it is not strictly neccessary to evaluate a concatenative language like Joy or Cat using a stack, it is simply convenient. One could for example devise an evaluator (e.g. an interpreter) that used term rewriting.
In practical terms a concatenative language is not really different from a functional language, except that there is less nesting of functions. Rather than writing
(f0 (f1 (f2 ... (fn x) ...))
We could write:
x fn ... f2 f1 f0
One of the interests of concatenative languages is that it is a formal computation model that closely models the actual processor of a lot of computers. It also corresponds nicely to both imperative and functional reasoning about code.
One interesting property of some concatenative languages that has me particularly interested is that we can replace any referentially transparent sub-sequence of terms with a new function that is defined as that sub-sequence. For example "a b c d a b c" can be replaced with "f d f" where "f" is defined as "a b c". This make automated code refactoring and analysis much easier. Hence the moniker chosen by Slava for his language Factor. This is also why I am actively studying the usage of concatenative languages for code size optimization (let me know if this interests you, and I'll tell you more).
I think that it may benefit the community to distinguish between pure point-free concatenative languages (e.g. those with no environment and control structures such as Joy and Cat) and those with an explicit environment (e.g. Postscript and Forth), as is done in the functional community.
Hopefully this blog entry didn't get too esoteric for my readers. Maybe I'll write about some neat C++ hacks next time. :-) | <urn:uuid:52c951b3-c5bf-4be5-b429-a06fb76785c5> | 3.140625 | 1,055 | Personal Blog | Software Dev. | 46.297023 |
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Information on the high energy radiation which strikes the Earth from space.
Comment by Professor Jim Al-Khalili on why he doesn't believe neutrinos really do travel faster than light.
The W and Z particles are the massive exchange particles which are involved in the nuclear weak interaction, the weak force between electrons and neutrinos.
What does it imply if the recent reports of neutrinos travelling faster than light are correct?
A great description of the Planck mission to study the first seconds of the universe which we can now see as the cosmic microwave background.
This is a fantastic site that covers more than just physics and tracks the history of our universe right from its beginnings. It has lots of information but also movies to watch and teacher resources.
NASA page detailing the evidence for the big bang obtained from the study of cosmic background radiation (the CMB).
A blog written by a group of physicists and astrophysicists on the stuff that interests them: science but also arts, politics, culture, technology, academia, and miscellaneous trivia
A wealth of info about the sun, the earth's magnetosphere, space weather, cosmic rays, solar wind etc
Catch up with the latest news, videos and info on the Planck mission, which is studying the Cosmic Microwave Background – the relic radiation from the Big Bang.
Showing 21 - 30 of 42 | <urn:uuid:839d2918-ef55-4378-b089-b14f319414ea> | 2.765625 | 379 | Content Listing | Science & Tech. | 51.406114 |
Welcome to PhysLink.com - Your physics and astronomy online portal. Stay a while! Check out our extensive library of educational and reference materials. Also, check out our fun section!
Is it true that a duck's quack doesn't echo? If so, why?
Asked by: Matt Schonert
I'm sorry to say that it's not true about the quack of a duck. Quacks echo as much as any other sound in nature. However, there is a way to avoid an echo, the problem is that it depends on your distance from the object reflecting the sound, and not the type of sound itself.
Sound travels in waves, and all of these waves have a specific wavelength (the distance from point on a wave to the exact point on the next). If by chance, the distance between the emitter of the wave and the reflector is exactly on one of the nodes of the wave... the sound will not reflect back at all. There will just be a standing wave created between one place and another, as all points on the wave would have zero net displacement. You can try this in the lab with a strobe light and a string oscillator. Also, if you have done the experiment with the column of water and the tuning fork, you will notice dead spots. These are distances where no matter what you do with the tuning fork, you won't hear anything coming from the tube.
The second way to avoid an echo, is to use a partially reflective material. This method is one of many that helps to hide aircraft from radar. If you position a half-reflective layer exactly one-quarter wavelength in front of a fully reflective layer, the wave will cancel itself out. By separating the layers by 1/4 wavelength, half the wave bounces off the first, and the other half of the wave bounces of the second. The travel time from the first layer to the second and back again, is exactly 1/2 wavelength, which means that the positive peak displacement is balanced exactly by the negative peak displacement. Again, no net displacement = no discernable wave return.
Answered by: Frank DiBonaventuro, B.S., Air Force officer, Tinker AFB, OK.
It isn't true.
I guess this guy actually tried it with a real duck and heard the echo himself.
It makes sense that even the duck's quack echoes since even with the superposition of waves, the duck shouldn't be able to cancel out only the echo under totally random conditions.
Answered by: Jonathan Osgood, Physics Undergrad, Wheaton College, Chicago, IL
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Blue Fiber Optic Light | <urn:uuid:007c39fa-d710-4dd0-a8d7-1b9907f03c47> | 3.296875 | 662 | Q&A Forum | Science & Tech. | 61.32827 |
"All locusts are grasshoppers, but not all grasshoppers are locusts," Greg Sword, an entomologist at Texas A&M University, says. The behavior that separates locusts from their grasshopper brethren is swarming. A single locust isn't worrisome, and locusts like to live alone for most of their lives. But when a group of locusts swarm, they can devastate the vegetation of an entire region, devouring everything in sight. They only start to swarm when the locust population increases to the point that individual locusts are crowded together, triggering a dramatic change in behavior and coloring. Mature locusts begin flying along with the wind, eating as much as their weight (2 grams) in vegetation every day. In areas of Africa where subsistence farming is practiced, large plagues of locusts can devastate the food supply of a region. "They can potentially affect the livelihoods of one out of 10 people on the planet," Sword says.
Australia suffered a massive swarm of Australian plague locusts last year. This year, locusts are making an appearance in China and Central Asia. Here in North America, however, much of the locust threat subsided when the Rocky Mountain locusts went extinct in the early 1900s. "There used to be epic, sky-darkening outbreaks," Sword says. But the huge populations of locusts were probably destroyed by pioneers building towns along the riverbanks where locusts laid their eggs. | <urn:uuid:8f172fea-f395-4473-a1af-cf944211cb49> | 3.484375 | 314 | Listicle | Science & Tech. | 43.02962 |
Scientists at DTU Space are engaged in measuring, modelling and scientifically analysing the Earth’s magnetic field.
Scientists are studying the magnetic field to learn more about the Earth’s core, where the field is generated, and to determine how constant variations in the magnetic field affect life on Earth. At the moment, the Earth’s magnetic field is decreasing by approximately 5 % per century, and scientists are unable to explain the reason for this or describe the consequences this will have.
DTU Space is heavily involved in the joint project regarding the Danish Ørsted satellite. The satellite sends measurements of the Earth’s magnetic field to scientists, who use these data to devise advanced models of the Earth’s magnetic field. Developed by scientists at DTU Space in close cooperation with NASA, the models are used all over the world to search for oil and minerals.
Moreover, the Institute is leading the joint European Swarm mission, whose objective is to measure the Earth’s magnetic field with greater accuracy than ever before. Swarm consists of three satellites that work in unison to measure the magnetic field. The constellation of three satellites provides measurements of the magnetic field that are almost ten times as accurate as previous measurements taken by lone satellites.
DTU Space has developed the magnetometers aboard the Swarm mission which will record the measurements of the magnetic field. The magnetometers are further refinements of those used aboard the Ørsted, SAC-C and CHAMP satellites, and the positive experience from previous missions has played an important role in developing the magnetometers destined for Swarm.
Facts on Earth's magnetic field
The Earth's magnetic field is created from electric currents in the fluid part of the Earth's core.
Researchers still do not know much about the core of the Earth, and studies of the magnetic field may contribute to changing this fact.
The Earth's magnetic field changes on a continuous basis, and this is of practical significance for both air travelers and satellites. This is because the magnetic field protects the Earth from charged particles from space.
When the magnetic field in an area suddenly becomes weak, charged particles may penetrate the field and harm both satellites and passengers in high-flying aeroplanes. | <urn:uuid:de9bb6b0-30bb-401c-aebf-8dc297a79507> | 3.625 | 452 | Knowledge Article | Science & Tech. | 35.710574 |
Powerful, stable, portable and mature, Perl is one of the most feature-rich programming languages with over two decades of development. Perl is portable and cross-platform. At the time of this writing, Perl can runs on over 100 platforms. Perl is good for mission critical large scale projects as well as rapid prototyping.
Perl is used for mission critical projects because its code is high quality. According to the Coverity analysis, Perl’s core code has been certified to be free of security flaws and has low defect density.
Perl is extendable. Perl has more than hundreds of thousands open sources modules on Comprehensive Perl Archive Network (CPAN). Those modules provide many powerful extensions to the standard library e.g., XML processing, graphical user interfaces and database integration that supports major database management systems including Oracle, Sybase, PostgresSQL, MySQL and many more.
Perl is an easy to use language. It is intended to be efficient and complete rather than elegant and minimal. Perl supports some major programming paradigms including object-oriented, procedural and functional.
One of the most remarkable features of Perl is text manipulation. Perl comes with a set powerful APIs for processing text that makes it perfect for working with XML, HTML and other mark-up languages. A key feature of text manipulation in Perl is regular expression engine. This is the reason why Perl is popular for both command line tools and web applications.
Perl is an open source project developing and evolving by an active community of programmers and professionals who really use it. You can use or distribute Perl freely under the term of Artistic License or GNU, GPL Licenses. Perl’s commercial support services are also available.
The latest stable version of Perl is 5.16. We are going to use Perl 5.16 for our tutorials.
Perl 6 is a totally different language that is fully object-oriented re-implementation of Perl 5. Perl 6 is still under development at the time of writing.
Larry Wall invented Perl in 1987 when he was a linguist, working as a system administrator at NASA. The beginning intention of Perl was a general purpose scripting language in UNIX to process reports easier and faster. Since then, Perl has been kept evolving with a lot of improvements and innovations to make it become popular among developers and professionals. | <urn:uuid:93b40ced-d5b1-4853-87a5-05aedc80ff5c> | 3 | 475 | Knowledge Article | Software Dev. | 43.795803 |
Global Warming! Global Warming!
You can tell who the real scientists are by whether they approach a problem as doomsayers, or whether they try to devise solutions to a problem.
Global warming just may have met its match. In research recently completed at Emory University School of Medicine, scientists have discovered a mutant enzyme that could enable plants to use and convert carbon dioxide more quickly, effectively taking more of that gas out of the atmosphere.
The findings were published online on January 19 and will appear in the February issue of the journal Protein Engineering Design and Selection. Ichiro Matsumura, PhD, assistant professor of biochemistry at Emory University School of Medicine, is the senior author and principal investigator. The lead author is research specialist Monal R. Parikh.
During photosynthesis, plants and some bacteria convert sunlight and carbon dioxide into usable chemical energy. Scientists have long known that this process relies on the enzyme rubulose 1,5-bisphosphate carboxylase/oxygenase, also called RuBisCO. While RuBisCO is the most abundant enzyme in the world, it is also one of the least efficient. As Dr. Matsu-mura says, �All life pretty much depends on the function on this enzyme. It actually has had billions of years to improve, but remains about a thousand times slower than most other enzymes. Plants have to make tons of it just to stay alive.�
Of course, plants could be designed to make diamonds out of the CO2 in the air just as well as be designed to grow faster. One approach creates a crystalline mineral, the other makes more cellulose. It really is a matter of choice.
The Kyoto Protocol has been shown to be ineffective, and unenforceable. It is an excuse for corrupt governments to feel they are actually doing something about a problem, when they are not. Fair enough. No one expects more of them at any rate. But please, you whankers, do not get in the way of people actually trying to achieve solutions. | <urn:uuid:5cd2eb9f-ce28-48b2-9ab8-c94f37f8e598> | 3.46875 | 422 | Personal Blog | Science & Tech. | 43.827999 |
Water, while one of the most abundant compounds on the planet and one of the most crucial compounds to life on earth, is one of the oddest. It exhibits physical characteristics that are completely anomalous from other molecules with similar size and structure. This page lists 63 anomalies that water exhibits, ranging from the well-known fact that at one atmosphere it expands upon freezing to the relatively unknown fact that water's viscosity decreases with pressure below 33°C. What many may not know is that water has more than the three phases that are typically associated with it—ice at low temperature, liquid water at moderate temperatures, and steam at high temperatures. In reality water (H2O) has 14 different phases, solid water (ice) contributing 12 different phases alone.
Since water behaves so strangely and is of such critical importance to life on Earth,scientists have long sought to fully understand all of its properties. One area of research is looking into understanding what happens to water at extreme conditions. It is believed that the accepted phase diagram of water at extreme temperatures and pressures may not be correct. For everyday life this doesn't matter. However, when you want to initiate a nuclear fusion reaction or understand the phase of ice that may be found on a celestial body, one needs a very accurate description of the water or ice at those conditions.
There are few places on earth capable of reproducing conditions as extreme as those described above. One place that can is the Sandia National Nuclear Laboratory, home of the Z machine. The Z machine is the largest X-ray generator in the world and can be used to create extreme temperatures and pressures with the goal (among others) of gathering data for the simulation of nuclear weapons. Understanding how water exists at the conditions generated in the Z machine is important; during its current operation the Z machine sends a 20-million ampere pulse of electricity through water which gets compressed to incredibly high pressures. Normally this water acts as an insulator and switch, but a series of planned upgrades to further strengthen the Z machine could mean different behavior from the water at such extreme conditions.
By passing the 20 million amperes of current through a small aluminum chamber, a magnetic field is created that isentropically compresses aluminum plates that sandwich a thin (25 micron) layer of water to pressures ranging from 50,000 to 120,000 atmospheres. For reference, what you experience at sea level is one atmosphere of pressure. What the researchers found was at these incredibly high pressures, water was squeezed into ice—ice VII to be exact, which was subsequently hotter than the boiling point of water at atmospheric pressure. As described by Sandia researcher Daniel Dolan, "Apparently it's virtually impossible to keep water from freezing at pressures beyond 70,000 atmospheres." Maybe that's a bit of an understatement, but it is very important to know for future operation of the Z machine and similar devices. The physical properties of ice—any ice phase—are vastly different from their liquid counter part.
As an aside, I have always enjoyed reading about and seeing videos of people who attempt to see who can light their grill the fastest, and have always loved the video of the guy who dumped a dewar of LOX on his grill bringing it to temperature in less than a second, vaporizing most of his grill in the process. What does this have to do with hot ice and the Z machine, you ask? Well, it turns out that at these pressures and temperatures the water underwent a phase transition from liquid to solid in less than 100 nanoseconds. Sadly since the ice here is so hot, it won't let you cool your beer any faster. | <urn:uuid:ba0a578b-26e9-4d53-9a29-556c82c14c12> | 3.734375 | 744 | Nonfiction Writing | Science & Tech. | 35.421202 |
One of the methods of learning PHP that I described in a previous post was to learn by searching for things when you need them. Here’s a guide to using that method.
Using Google as part of the learning process
There are many ways that you can utilize Google, or any other search engine, into your learning process. No matter what you’re learning, there will be things that you don’t know how to do. A search engine can help you achieve all of these tasks very easily.
Think of Google as your gateway to all of the resources available on the web relating to PHP. Using these resources, you can piece together your knowledge of the language until you are fluent enough to start to ween yourself off of them and write code independently.
There are basically two types of resources that you can find using a search engine: specific tutorials, such as this tutorial of how to make a login script, or reference pages, such as this reference page for print_r(). These are the only two types of resources that you need. The latter is much more important than the former.
Using just these reference pages, you should be able to piece together scripts that do what you need. After using this method for a long enough time (it really depends on your ability), you should be able to start to code on your own.
Try this method to learn PHP. It will require some prior knowledge of the language, but nothing more than a simple tutorial on the basics.
- Decide on a task that you want to complete. This can be anything. Here’s a few examples: a login script, a simple blog, etc.
- Map out everything that the script will need to do. Break things down one action at a time. For example, if you are working on a login script, focus on registering before you even think about logging in. Here’s more information about code planning and pseudocode.
- Start to code the script using only resources that you find using Google. This may be difficult at first, but you will eventually get the hang of it. There’s enough resources out there that any reasonable search query will get you where you need to go. For example, if I was looking for the function print_r(), I could search for ‘php output array’, ‘php print array’, ‘php echo array’, ‘php view array’, and all of these queries would lead me in the right direction.
- If you have a problem, try things until it works. Don’t ask for help unless it is seriously needed. If you do ask for help, do your best to get only what you need. Trying to speed up this process isn’t going to help you since it will just make it longer.
Reasons to try this method
I feel that this method helps to speed up your learning of the language. Instead of relying on specific tutorials for every (although you can still use them) or the instruction of others, you are completely independent as a coder. I also feel that you know something better if you taught it to yourself instead of having it spoon fed from someone else.
The use of this method doesn’t have to stop when you have mastered the language. You will always find problems that you may not know how to solve and you can always apply this method of independently searching for an answer. That’s a great skill to have, especially if you start freelancing or working on scripts that are not your own. | <urn:uuid:55682fb3-9c15-4296-bd14-2352a93f881c> | 2.78125 | 735 | Tutorial | Software Dev. | 64.873871 |
Euclid of Alexandria revolutionized the way that mathematics is written, presented or thought about, and introduced the concept of mathematical proofs. Discover what it takes to move from a loose theory or idea to a universally convincing proof.
Another popular type of proof is a proof by contradiction. This is also known as an indirect proof. Search the internet for explanations and examples of this type of proof. How might this approach be valuable in proving someone is innocent of a crime?
Search the internet for Euclid’s Elements and read about the parallel postulate and the controversy surrounding it’s improveability.
Read about the millennium problems, and the mathematicians who have won a million dollars. Andrew Wiles proved Fermat’s last theorem several years ago. Read about his struggle with this difficult problem. Could you have gone through that?
Research Godel’s incompleteness theorem. It basically states that we can NEVER prove EVERYTHING… He proved it!
Scott Kennedy’s Classroom http://www.mrkennedymath.doodlekit.com
Scott Kennedy’s Youtube channel http://www.youtube.com/user/scottjkennedy28
Introduction to geometric proofs http://www.sophia.org/introduction-to-geometric-proof-tutorial
The Millennium Problems http://www.claymath.org/millennium/
Euclid’s Elements http://www.claymath.org/library/historical/euclid/ | <urn:uuid:1b3aec25-a69e-4c31-8724-8bda9c9582f2> | 4.125 | 319 | Tutorial | Science & Tech. | 48.36141 |
Algorithm::Diff is a Perl module for computing the difference between two files, two strings, or any other two lists of things. It uses an intelligent algorithm similar to (or identical to) the one used by the Unix `diff' program. It is guaranteed to find the smallest possible set of differences.
Apache::Session is a persistence framework whose purpose is to provide session management to Web developers. It is designed to work with Apache and mod_perl, but it does not depend on them and will work with any Web server. This module provides a set of classes that give the developer maximum functionality. Session data can be stored in a database, flat files, or shared memory.
The Archive::Zip module allows a Perl program to create, manipulate, read, and write Zip archive files without calling an external program. Members can be added, removed, extracted, replaced, rearranged, and enumerated. They can also be renamed or have their dates, comments, or other attributes queried or modified. Their data can be compressed or uncompressed as needed, and members can be created from members in existing Zip files, or from existing directories, files, or strings.
The CDDB/CDDB_get Perl module gets the CDDB info for an audio CD. The included script was intended as a demo for CDDB_get, but over time it has gained powerful features like the ability to write to a database, offline mode, HTTP mode (including proxy), saving in standard XMCD format, and writing 'lame' commands.
CfgTie is a package of Perl modules and tools. These make it easier to configure and maintain Unix computers. The idea is that just about everything in your machines environment can be operable through a single consistent interface. This is a set of tools that make many of the various configuration subsystem in your machine appear to be Perl variables of some sort.
cgi_buffer is a group of libraries that may be used to improve performance of CGI scripts (and other content generation engines) in some circumstances by applying performance-enhancing HTTP mechanisms that are typically not supported by them. Currently, Perl, Python, and PHP4 are supported. The Python library may also be used as a wrapper around another CGI script. | <urn:uuid:3f377fdc-cd3f-4bab-bf96-98fba5e342d2> | 2.71875 | 460 | Content Listing | Software Dev. | 38.245746 |
If the obscuring torus has the same gas-to-dust ratio as in the Galactic ISM, and the dust is characterized a Galactic extinction curve, then the nuclear region of Sy2s should suffer a visual extinction that is related to the gaseous column density by the formula AV = 5 x 10-22 NH (cm-2). In general this is not the case: AV is lower than expected from the NH measured in the X-rays. This was first pointed out by Maccacaro et al. (1982). A visual extinction lower than that expected from the NH measured in the X-rays is also required to fit the IR spectrum of AGNs (Granato et al. 1997). We have collected a sample of Seyferts which both show X-ray (cold) absorption and whose optical or IR broad lines are not completely suppressed. The ratios between the broad lines provide information on the dust reddening towards the nucleus; however, the broad emission lines must be used with much care, since the extreme conditions of the broad line clouds can affect the intrinsic line ratios through radiative transport effects. By assuming the standard extinction curve we can estimate the visual extinction. The resulting distribution for the AV / NH ratio, relative to the Galactic standard value, is shown in Fig. 3. Most of the AGNs in our sample are characterized by a deficit of dust absorption with respect to what expected from the NH measured in the X-rays, in agreement with early claims. At higher, quasar-like luminosities there are even more extreme examples of this effect: objects that, although absorbed in the X-rays, do not show significant dust absorption in the optical and appear as type 1, broad line AGNs have been recently discovered in hard X-ray and radio surveys (Sambruna et al. 1999, Akiyama et al. 2000, Reeves et al. 1997). Puzzling enough, the early Chandra surveys presented to date have found only a few type 1 QSOs absorbed in the hard X-rays; this issue will be shortly discussed in Sect. 7.
Figure 3. Distribution of the AV / NH ratio, relative to the Galactic standard value, for a sample of absorbed AGNs.
The origin of the reduced AV / NH ratio is not clear. An obvious explanation is that the dust-to-gas ratio is much lower than Galactic or that in the inner part of the obscuring torus the dust is sublimated by the strong UV radiation field. However, if the dust content in the absorbing medium is significantly reduced, especially at the inner face, then most of the UV ionizing photons are absorbed by the atomic gas. This should create a huge HII region, which would emit strong (~ narrow) hydrogen lines corresponding to a large covering factor, i.e. much brighter than the emission lines from the NLR (see also Netzer & Laor, 1993). Also, a simple shortage of dust grains with respect to the gas mass would not explain other peculiar properties of the dust in AGNs, such as the absence of the silicate absorption feature in the mid-IR spectra of most Sy2s (Clavel et al. 2000) and the absence of the carbon dip in the UV spectra of some reddened Sy1s.
Another interesting possibility is that the dust extinction curve is much flatter than the standard Galactic. The high density of the gas in the circumnuclear region of AGNs is likely to favor the growth of large grains (probably through coagulation) which, in turn, should flatten the extinction curve and make it featureless. This effect is directly observed in the dense clouds of our Galaxy (Draine 1995). Within the context of the optical versus X-ray absorption, the effect of a flat extinction curve (due to grain coagulation) is twofold: 1) given the same dust mass, the effective visual extinction is lower, and 2) the broad lines ratio gives a deceiving (low) measure of the extinction. A more thorough discussion of the whole issue is given in Maiolino et al. (2000b). | <urn:uuid:90d6b2cf-b4de-4c24-977b-86130b8f2410> | 3.015625 | 844 | Academic Writing | Science & Tech. | 54.506623 |
Mono Lake - For Educators
These Nitzschia cells were found living within detrital material of Mono Lake. Image taken by David Patterson and provided courtesy of the microscope web site.
- Bringing Water To Los Angeles. This case study addresses the issue of freshwater resources in regions around Mono Lake and Owens Valley being diverted from natural communities and human... ( This site is likely no longer available. )
- Chain Reaction: Solar System. "Solar System" is a thematic exploration into extremophiles and space travel hosted by Chain Reaction, a site in which Arizona students and teachers join Arizona... (more info)
- The Goldilocks Zone. This is an article from "Teachable Moments in the News," a newsletter that takes recent Earth and space science related news stories and places them in a context relevant... ( This site may be offline. )
Microbial Life Activities
Living in an Alkaline Environment is a three-part activity that explores the ecology and diversity of life in alkaline environments.
Los Angeles and the Future of Mono Lake is a WebQuest exploring the biodiversity, natural history, and preservation of Mono Lake. This activity calls upon the resources housed in MLER and asks students, grades 9-12, to consider the preservation of the Mono Lake environment in relation to the needs of humans.
Other Mono Lake Collections
General Collection: Resources such as news articles, web sites, and reference pages provide a comprehensive array of information about Mono Lake.
Advanced Collection: Compiled for professionals and advanced learners, this collection includes resources such as journal articles, academic reviews, and surveys.
For additional resources about Mono Lake, search the Microbial Life collection. | <urn:uuid:3d5f0477-3c6b-4513-938c-36a9af1cd263> | 3.234375 | 343 | Content Listing | Science & Tech. | 26.685845 |
Science Fair Project Encyclopedia
- This article is about ether as a general class of chemical compounds. For other meanings, see Ether (disambiguation)
Ether is the general name for a class of chemical compounds which contain an ether group — an oxygen atom connected to two (substituted) alkyl groups. A typical example is the solvent diethyl ether (ethoxyethane, CH3-CH2-O-CH2-CH3).
Ethers are not to be confused with the following classes of compounds with the same general structure R-O-R.
- Aromatic compounds like furan where the oxygen is part of the aromatic system.
- Compounds where the carbon atom next to the ether oxygen is connected to oxygen, nitrogen, or sulfur.
Primary, secondary, and tertiary ethers
The terms "primary ether", "secondary ether", and "tertiary ether" are occasionally used and refer to the carbon atom next to the ether oxygen. In a primary ether this carbon is connected to only one other carbon as in diethyl ether CH3-CH2-O-CH2-CH3. An example of a secondary ether is diisopropyl ether (CH3)2CH-O-CH(CH3)2 and that of a tertiary ether is di-tert-butyl ether (CH3)3C-O-C(CH3)3.
Dimethyl ether, a primary, a secondary, and a tertiary ether.
- R-OH + R-OH → R-O-R + H2O
- This direct reaction requires drastic conditions and is usually not applicable. There exist several milder methods to produce ethers.
- R-O- + R-X → R-O-R + X-
- This is called Williamson ether synthesis. It involves treatment of a parent alcohol with a strong base to form the alkoxide anion followed by addition of an appropriate aliphatic compound bearing a suitable leaving group (R-L). Suitable leaving groups (L) include iodide, bromide, or sulfonates. This method does not work if R is aromatic like in bromobenzene.
- R2C=CR2 + R-OH → R2CH-C(-O-R)-R2 (under acid catalysis)
Ethers are of very low chemical reactivity. They are hydrolyzed only under drastic conditions like heating with boron tribromide or boiling in hydrobromic acid. Lower mineral acids containing a halogen, such as hydrochloric acid will cleave ethers, but very slowly. Hydrobromic acid and hydroiodic acid are the only two that do so at an appreciable rate.
Primary and secondary ethers with a CH group next to the ether oxygen easily form highly explosive peroxides (e.g. diethyl ether peroxide) in the presence of oxygen, light, and metal and aldehyde impurities. For this reason ethers like diethyl ether and THF are usually avoided as solvents in industrial processes.
Ether molecules cannot form hydrogen bonds among each other, resulting in a relatively low boiling point comparable to that of the analogous alkanes. Ethers are more hydrophobic than esters or amides of comparable structure.
In the IUPAC nomenclature system, ethers are named using the general formula "alkoxyalkane", for example CH3-CH2-O-CH3 is methoxyethane. If the ether is part of a more complex molecule, it is described as an alkoxy substituent, so -OCH3 would be considered a "methoxy-" group. The nomenclature of describing the two alkyl groups and appending "ether", e.g. "ethyl methyl ether" in the example above, is a trivial usage.
- Ethylene oxide, the smallest cyclic ether:
- Dimethyl ether, a propellant in aerosol cans:
- Diethyl ether, a common low boiling solvent:
- Dimethoxyethane, a high boiling solvent:
- Dioxane, a cyclic ether and high boiling solvent:
- THF, a cyclic ether, one of the most polar simple ethers that is used as a solvent:
- Anisole (methoxybenzene), a major constituent of the essential oil of anise seed:
- Crown ethers, cyclic polyethers that are used as phase transfer catalysts :
- Polyethylene glycol, a linear polyether, e.g. used in cosmetics:
- Functional group
- Petroleum ether , not an ether but a low boiling alkane mixture.
- Thioether, analogs of ethers with the oxygen replaced by sulfur.
- ILPI page about ethers.
The contents of this article is licensed from www.wikipedia.org under the GNU Free Documentation License. Click here to see the transparent copy and copyright details | <urn:uuid:eb8f4b39-a8bf-41c5-8e93-420c72d8488c> | 3.90625 | 1,058 | Knowledge Article | Science & Tech. | 38.746021 |
Science Fair Project Encyclopedia
For other meanings of diver, also see diving.
In the Authorized Version of the Bible, "divers" often means "diverse, various".
For a place in the Nord département, see Loon-Plage
Loon is also a US singer/rapper.
The loon (N.Am.) or diver (UK) is a type of aquatic bird found in many parts of North America and northern Europe. A loon is the size of a large duck, to which it is unrelated; its plumage is largely grey or black, and it has a spear-shaped bill. The loons compose a genus (Gavia), family (Gaviidae), and order (Gaviiformes) all their own.
These were previously considered the most ancient of the northern hemisphere bird families, but it has recently become clear that the Anseriformes (ducks, geese and swans) and the Galliformes (the pheasants and their allies) are older groups.
The European name diver comes from the bird's habit of catching fish by swimming calmly along the surface and then abruptly plunging into the water; the North American name loon comes from the bird's haunting, yodeling cry, a symbol of the Canadian wilds.
Loons swim well, and fly adequately (their bones are much denser than those of most birds), but are almost hopeless on land, and the larger loons have difficulty taking off, becoming airborne only after skimming the surface of the water for a couple of hundred meters. Because these birds locate their prey underwater mainly by sight, they prefer lakes with clear water.
Loons breed on inland freshwater lakes and ponds, but move to the coasts in winter, and often move much further south. The nest is usually a mound of plant material close to water. A pair may mate for life. Loons can live as long as 30 years.
There are five species of loon:
- Order Gaviiformes
- Family Gaviidae
- Red-throated Diver or Red-throated Loon, Gavia stellata.
- Black-throated Diver or Arctic Loon, Gavia arctica.
- Pacific Diver or Pacific Loon, Gavia pacifica (treated by some authorities as a subspecies of G. arctica).
- Great Northern Diver or Common Loon, Gavia immer.
- White-billed Diver or Yellow-billed Loon, Gavia adamsii.
- Family Gaviidae
The Common Loon is the national bird of Canada and is depicted on the Canadian one-dollar coin, which has come to be known affectionately as the loonie. It is also the official provincial bird of Ontario and the official state bird of Minnesota.
The contents of this article is licensed from www.wikipedia.org under the GNU Free Documentation License. Click here to see the transparent copy and copyright details | <urn:uuid:0b9a71d5-f2a6-4ffc-822e-1db74e0ff905> | 3.34375 | 617 | Knowledge Article | Science & Tech. | 49.89431 |
The May 3, 2012 issue of the journal Brain, Behavior, and Evolution tackled an issue which has millions of us humans wondering:
How does the cerebellum of the platypus develop???
Scientists (and I use that term loosely) working (and I use that term loosely too) at the Department of Anatomy, School of Medical Sciences, The University of New South Wales, Sydney, Australia examined a group of mammals, monotremes, whose young are incubated in a "leathery-shelled egg and fed with milk from teatless areolae after hatching."
Their research goal?
"To determine whether cerebellar circuitry is able to contribute to the coordination of locomotion in the monotreme hatchling, and to correlate cerebellar development with behavioral maturation."
When President Richard Nixon declared way on cancer during the 1970s, NIH had dedicated just $40 million dollars per year on research. Those were the days when 1 out of 23 women were expected to die from breast cancer.
Today, it's one out of 3. Clearly, something's not working.
So what do scientists do next? They research on platypus brains with the stated goal of finding something which can be applied to a bizarre species of biped known as homo sapiens.
Down-under researchers did find something astonishing. They found that the hatchling's attempt to locate a teat from which it can nurture itself results from:
"The findings indicate that cerebellar circuitry is unlikely to contribute to the coordination of movements in the monotreme peri-hatching period. Those activities are most likely controlled by the spinal cord and medullary reticular formation circuitry."
Gee, what a surprise!!! The platypus brain actually regulates infant platypus behavior.
Quick, call the Nobel Prize committee.
What's next? These brilliant scientists might soon combine RNA from felines and platypusses (is that a word?) and genetically engineer a new species of creature to be named platypussies. This is another example of why mankind so badly needs animal research. | <urn:uuid:e011b8eb-da2b-46c5-a4c3-89f412294aab> | 3.578125 | 436 | Personal Blog | Science & Tech. | 43.665417 |
exhibit models radioactive decay of nuclei and fundamental particles
with wooden cubes. There are 100+ hardwood cubes each with one
side painted red. These cubes are placed into a wicker bowl and
tossed onto a table. The cubes that land red side up are removed
and placed into one column at the bottom left edge of the table.
The smaller number of remaining cubes are then placed into the
basket and tossed again. The cubes that land with their red side
up are removed again. The process continues until there are no
The exhibit teaches about half-life; half of all the remaining
cubes "decay" after every 3 tosses. The decreasing columns
of cubes show an exponential decay in height. This exponential
decay results from the constant 1 in 6 probability that each cube
will decay on each throw.
The random fluctuations in the height of each pile are also visible
in the non-smooth profile of a curve connecting the heights of
the columns of cubes.
The crash of the cubes from the basket is such an interesting
sound that young children spend time throwing the cubes from the
basket and arranging them in piles.
The "decayed" blocks form an exponential pattern of | <urn:uuid:fe7f7598-f94d-426a-8a6f-7420993d4480> | 3.703125 | 256 | Knowledge Article | Science & Tech. | 50.329011 |
Plant and Animal Cells
An Internet Hotlist on Cells
created by R. Stewart
| Parts of a cell
| Cell Diagrams
| Cell Division
| Tutorials and Activities
You COULD look for books or magazines to find out about Cells, but why not use the power of the Internet instead? The links below will get you started.
The Internet Resources
Parts of a cell
- Animal and Plant Cells
- Bacteria are single celled organisms. Their cells do NOT have proper nucleii. They have a circular molecule of DNA which contains all their genetic information.
- The Cell--Diagram
- Dig into a fundamental unit of life for plants and animals, the cell. Includes images and a diagram
- Animal Cells
- This schematic represents an idealized animal cell, e.g., a liver cell. The columns to the left and right of the labels contain links to discussions of the particular structures.
- THE CELL PAGE!!
- CLICK ON THE LABEL FOR ANY ORGANELLE TO FIND OUT MORE ABOUT IT
- Mitosis Definitions
- Sites of Interest: Pictures and outline of the phases
- Mitosis Stages Real Cells!
- Stages of Mitosis Stage Animal Mitosis Plant Mitosis
- Mitosis World
- Cell division
- Mitosis is the process by which cells divide. The parent cell has already duplicated its chromosomes , providing both daughter cells with a complete copy of genetic information.
- An Introduction to Mitosis
- Mitosis is the process that facilitates the equal partitioning of replicated chromosomes into two identical groups. Before partitioning can occur, the chromosomes must become aligned so that the separation process can occur in an orderly fashion. The alignment of replicated chromosomes and their separation into two groups is a process that can be observed in virtually all eukaryotic cells.
- Cellular Biology
- Mitosis Animations
- animations of mitosis
Tutorials and Activities
- Cell Division Tutorial
- Learn the cell biology, the life cycles, and mitosis that govern the life and death of cells. Includes test questions.
- Online Onion Root Tips
- Determine for yourself the stages of mitosis by looking at actual slides of onion root tip cells
- Mitosis Wordsearch
- Unscramble the following words and find them in the wordsearch. Use the unscrambled words to fill in the blanks
- Cells Alive
- Animal cell models
Content by R. Stewart , firstname.lastname@example.org
Last revised Mon Dec 15 7:26:47 US/Pacific 2003 | <urn:uuid:e8c3182d-e84a-40dd-8f63-89fe15e7e767> | 3.828125 | 540 | Content Listing | Science & Tech. | 41.904076 |
On the same wavelength-- literally
The human brain is bombarded with all kinds of information, from the memory of last night’s delicious dinner to the instructions from your boss at your morning meeting. But how do you “tune in” to just one thought or idea and ignore all the rest of what is going on around you, until it comes time to think of something else? In "Frequency of gamma oscillations routes flow of information in the hippocampus", published in the 19 November issue of Nature, researchers at the Kavli Institute for Systems Neuroscience and Centre for the Biology of Memory describe a mechanism that the brain uses to filter out distracting thoughts.
Think of your brain like a radio: You’re turning the knob to find your favourite station, but the knob jams, and you’re stuck listening to something that’s in between stations. It’s a frustrating combination that makes it quite hard to get an update on swine flu while a Michael Jackson song wavers in and out. Staying on the right frequency is the only way to really hear what you’re after. In much the same way, the brain’s nerve cells are able to “tune in” to the right station to get exactly the information they need, says researcher Laura Colgin, who was the paper’s first author. “Just like radio stations play songs and news on different frequencies, the brain uses different frequencies of waves to send different kinds of information,” she says.
Gamma waves as information carriers
Colgin and her colleagues measured brain waves in rats, in three different parts of the hippocampus, which is a key memory center in the brain. While listening in on the rat brain wave transmissions, the researchers started to realize that there might be something more to a specific sub-set of brain waves, called gamma waves. Researchers have thought these waves are linked to the formation of consciousness, but no one really knew why their frequency differed so much from one region to another and from one moment to the next.
Information is carried on top of gamma waves, just like songs are carried by radio waves. These “carrier waves” transmit information from one brain region to another. “We found that there are slow gamma waves and fast gamma waves coming from different brain areas, just like radio stations transmit on different frequencies,” she says.
You really can “be on the same wavelength”
“You know how when you feel like you really connect with someone, you say you are on the same wavelength? When brain cells want to connect with each other, they synchronize their activity,” Colgin explains. “The cells literally tune into each other’s wavelength. We investigated how gamma waves in particular were involved in communication across cell groups in the hippocampus. What we found could be described as a radio-like system inside the brain. The lower frequencies are used to transmit memories of past experiences, and the higher frequencies are used to convey what is happening where you are right now.”
If you think of the example of the jammed radio, the way to hear what you want out of the messy signals would be to listen really hard for the latest news while trying to filter out the unwanted music. The hippocampus does this more efficiently. It simply tunes in to the right frequency to get the station it wants. As the cells tune into the station they’re after, they are actually able to filter out the other station at the same time, because its signal is being transmitted on a different frequency.
“The cells can rapidly switch their activity to tune in to the slow waves or the fast waves”, Colgin says, “but it seems as though they cannot listen to both at the exact same time. This is like when you are listening to your radio and you tune in to a frequency that is midway between two stations- you can't understand anything- it's just noise.” In this way, the brain cells can distinguish between an internal world of memories and a person’s current experiences. If the messages were carried on the same frequency, our perceptions of the world might be completely confused. “Your current perceptions of a place would get mixed up with your memories of how the place used to be,” Colgin says.
The cells that tune into different wavelengths work like a switch, or rather, like zapping between radio stations that are already programmed into your radio. The cells can switch back and forth between different channels several times per second. The switch allows the cells to attend to one piece at a time, sorting out what’s on your mind from what’s happening and where you are at any point in time. The researchers believe this is an underlying principle for how information is handled throughout the brain.
“This switch mechanism points to superfast routing as a general mode of information handling in the brain,” says Edvard Moser, Kavli Institute for Systems Neuroscience director. “The classical view has been that signaling inside the brain is hardwired, subject to changes caused by modification of connections between neurons. Our results suggest that the brain is a lot more flexible. Among the thousands of inputs to a given brain cell, the cell can choose to listen to some and ignore the rest and the selection of inputs is changing all the time. We believe that the gamma switch is a general principle of the brain, employed throughout the brain to enhance interregional communication.”
Can a switch malfunction explain schizophrenia?
People who are schizophrenic have problems keeping these brain signals straight. They cannot tell, for example, if they are listening to voices from people who are present or if the voices are from the memory of a movie they have seen. “We cannot tell for sure if it is this switch that is malfunctioning, but we do know that gamma waves are abnormal in schizophrenic patients,” Colgin says. “Schizophrenics' perceptions of the world around them are mixed up, like a radio stuck between stations.”
For further information, contact:Laura Colgin at +47 73550341/+47 986 92 523 or at
Kavli Institute for Systems Neuroscience and the Centre for the Biology of Memory
The scientific goal of the Kavli Institute for Systems Neuroscience is to advance our understanding of neural circuits and systems. By focusing on spatial representation and memory, the investigators hope to uncover general principles of neural network computation in the mammalian cortex. The institute is one of just 4 neuroscience institutes funded by the Kavli Foundation. The other three are at Yale University, Columbia University, and the University of California -- San Diego.
NTNU's Kavli Institute coexists with the university's Centre for the Biology of Memory (CBM) but the scope of the Institute is broader and more long-term. CBM is part of the Centre of Excellence scheme of the Norwegian Research Council. | <urn:uuid:bdb1f821-ec69-49ce-8919-f916b219bfed> | 3.265625 | 1,434 | Knowledge Article | Science & Tech. | 44.365518 |
The particles command performs some particules analysis on a matrix.
particles performs a thresholding on the matrix and returns the list of the particles found with the following information for each one: its center's coordinates, its area, the dimensions of its minor and major axes, the angle of its major axe, its perimeter, and a flag to say whether the matrix' values in the particle are above or below the threshold (a hill or a hole).
You can specify a range of values for the area: the particles out of the range will be filtered out.
Optionally you can ask that the result returned include each particle's shape as a list of points.
The section about Extensions for SmileLab presents ParticlesLib, a library of routines to apply pre-filters before particles and to post-process the results. | <urn:uuid:38d2678b-5ffe-46be-a64c-282451ce5d4c> | 2.71875 | 168 | Documentation | Software Dev. | 36.197856 |
SCapture Class. Last updated: 08/05/2008
Class shared methods:
I created the SCapture class to allow us capture still images from the screen. The SCapture class uses some Api methods to implement the capture. The main reason I used the Api functions such as BitBlt to build the bitmap image because the .Net way of capturing an image does not capture transparent image as transparent; check it here.
- FullScreen - Captures the full screen (all monitors in a single image).
- DisplayMonitor- Captures a display monitor.
- ActiveWindow – Captures the active window.
- Window– Captures a window specified by the handle or a point (overloaded).
- Control– Captures a control of a window specified by a handle or a point (overloaded).
- ScreenRectangle– Captures a rectangle image from the screen.
- All methods can capture images that include the cursor. New
Using the code:
Author name:vb Code:
- Private Sub ControlButton_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles ControlButton.Click
- 'Capture the image of this button including the cursor.
- Dim img As Image = SCapture.Control(Control.MousePosition, True)
- 'Save the captured image.
- img.Save(filePath, Drawing.Imaging.ImageFormat.Png)
- 'Also display the captured image in a PictureBox.
- Me.DisplayPictureBox.BackgroundImage = img
- Catch ex As Exception
- 'Show a MessageBox if the capture of image failed.
- MessageBox.Show("Failed to capture the control!" _
- & Environment.NewLine & ex.Message, "Capture Error!", _
- MessageBoxButtons.OK, MessageBoxIcon.Error)
- End Try
- End Sub
- I added a method DisplayMonitor that implements a monitor image capture.
- Also the FullScreen method is improved to capture a single image of all monitors that are installed on the system.
- I added an ability to all methods to capture images that include the cursor.
- I just changed the class name from ICapture to SCapture.
- I added an overloadable Window method that takes a point as one of its arguments and returns the bitmap of a window at the point.
- Changed all capture methods return types from Image to Bitmap.
You can check the demo project for the examples of how to capture images with various methods.
Please feel free to rate this post , comment and notify me about any problem associated with it. | <urn:uuid:61c27b19-4bdb-4208-bd60-9952a8af3f6b> | 2.6875 | 563 | Comment Section | Software Dev. | 40.977551 |
Q&A: General Astronomy and Space Science
Every picture of a spiral galaxy including our own, depicts a
very bright, spherical center ... I assume a dense cluster of
stars. We can see this bright center in distant galaxies, and
I've always wondered, why we don't see the bright center of our
own. Or, do we, and I don't know what I'm looking at? It seems
it would be far brighter than our Sun, even though we are at the
far edge of the galaxy. Thanks for helping me find it!!
There is a spherical region surrounding the central region of
our galaxy known as the "bulge" which is indeed dense with
stars. It is actually more luminious than it appears because its
light is diminished by absorption from dust as well as distance
by the time it reaches us. The Earth is situated in the middle
of the plane of our galaxy where the absorption towards the
center is maximum. The surface brightness, or brightness per
angular area, of the bulge is much less than the Sun's because
of this absorption and the fact that the stars, though dense,
still fill only a small fraction of the volume.
The galaxies that appear in the astronomy books are selected
because they are the most photogenic and are generally not
typical. We look at them face on which is a viewing direction
where there is little absorption. | <urn:uuid:c1711bfd-57a4-4c3c-9f5b-b24657848c6c> | 3.828125 | 294 | Q&A Forum | Science & Tech. | 61.58 |
Atmospheric Pressure I --The Paint Thinner Can
Chemical Concept Demonstrated
After the can is stoppered, it collapses.
The water inside the can is boiled. The water takes up more space as a gas than as a liquid, and this forces much of the air out of the can. When the heat is removed, the water returns to its liquid state and air, under normal circumstances, would be able to fill the space in the can again.
However, a stopper was added, preventing this from happening. Instead, the water returns to its liquid state, but the stopper prevents air from filling up the leftover space. This leaves whatever little air happened to be in the can after stoppering the task of filling the entire leftover space above the water. Because there is less gas per unit area inside the can than outside the can, the pressure inside the can is less than the pressure outside the can.
The greater pressure outside of the can pushes in on the can, and the lesser pressure inside of the can is unable to push back with equal force. The can, as a result, collapses.
This page viewed 971 times | <urn:uuid:67d37034-d587-4f2e-9316-7f58a698b156> | 3.8125 | 236 | Tutorial | Science & Tech. | 52.550192 |
Climate Change and Debris-Flow Events in Southern Norway
Matthews, J.A., Dahl, S.O., Dresser, P.Q., Berrisford, M.S., Lie, O., Nesje, A. and Owen, G. 2009. Radiocarbon chronology of Holocene colluvial (debris-flow) events at Sletthamn, Jotunheimen, southern Norway: a window on the changing frequency of extreme climatic events and their landscape impact. The Holocene 19: 1107-1129.
In an effort to explore this question using real-world data, the seven scientists conducted detailed investigations at three alpine slope-foot mires located in the valley of Leirdalen in an area known as Sletthamn, above the treeline among some of the highest mountains in southern Norway, where they say that "exceptionally detailed radiocarbon-dating controlled chronologies of Holocene debris-flow events have been reconstructed," which allowed them to analyze "the frequency and timing of debris flows since c. 8500 cal. BP which, in turn, are related to climatic variability, extreme climatic events and site conditions."
Results indicated "no obvious correlation between debris-flow frequency and a relative warm climate." In fact, they say that "debris-flow frequency was lowest post-8000 cal. BP during the Holocene Thermal Maximum," and that most of the "century- to millennial-scale phases of enhanced debris-flow activity appear to correlate with Neoglacial events," one of which was the "Little Ice Age." In addition, they write that "the Sletthamn record agrees quite closely with a compilation of other debris-flow records from widely distributed sites in east and west Norway." What is more -- citing the work of Berrisford and Matthews (1997), Stoffel and Beniston (2006), Pelfini and Santilli (2008) and Stoffel et al. (2008) -- they report that "there appears to be no consistent upward trend in debris-flow frequencies over recent decades," when one might have expected them to be growing in both number and magnitude if climate-alarmist claims were correct. Given these findings, the Norwegian and UK researchers conclude that there is little real-world evidence "for the association of higher debris-flow frequencies with an increasingly warm climate." In fact, they say that "the evidence suggests the opposite."
Berrisford, M.S. and Matthews, J.A. 1997. Phases of enhanced rapid mass movement and climate variation during the Holocene: a synthesis. In: Matthews, J.A., Brunsden, D., Frenzel, B., Glaser, B. and Weiss, M.M. (Eds.) Rapid mass movement as a source of climatic evidence for the Holocene. Palaoklimaforschung 19: 409-440.
Pelfini, M. and Santilli, M. 2008. Frequency of debris flows and their relation with precipitation: a case study in the Central Alps, Italy. Geomorphology 101: 721-730.
Stoffel, M. and Beniston, M. 2006. On the incidence of debris flows from the early Little Ice Age to a future greenhouse climate: a case study from the Swiss Alps. Geophysical Research Letters 33: 10.1029/2006GL026805.
Stoffel, M., Conus, D., Grichting, M.A., Lievre, I. and Maitre, G. 20098. Unraveling the patterns of late Holocene debris-flow activity on a cone in the Swiss Alps: chronology, environment and implications for the future. Global and Planetary Change 60: 222-234. | <urn:uuid:ada6d405-ae2d-4770-8868-b4dd01d8d033> | 3.15625 | 783 | Academic Writing | Science & Tech. | 55.661347 |
Geysers are impressive geothermal events where hot water from deep within the earth is periodically pushed through a small vent to the surface, creating a natural fountain. The water is sprayed from the opening up to several hundred feet in the air along with steam and various gases, including carbon dioxide, oxygen, and hydrogen sulfide. Geysers can erupt as frequently as every few minutes to as rarely as once every several years, and the eruptions can last from minutes to hours. Some geysers are so well studied that their eruption times can be reliably predicted down to the minute. Geysers are not permanent features because the heat source beneath the earth that they rely on is constantly shifting. New geysers can spring up from nowhere while active ones may suddenly stop erupting and even go dry. The term “geyser” comes from “Geysir,” the name of one of the geysers in Iceland. “Geysir” in turn came from the Icelandic word “giosa,” meaning “to gush.”
Roughly one thousand geysers are documented around the world and most are located within about fifty “geyser fields,” geothermally active areas that contain numerous geysers. Geysers are located in Mexico, South America, Japan, and Africa, and the largest geyser fields are located in Russia, Iceland, and New Zealand. However, the area with the most geysers is Yellowstone National Park in Wyoming, which is home to about five hundred geysers. Yellowstone Park is also the location of the most famous and reliable geyser, Old Faithful, as well as the tallest geyser, Steamboat, which erupts once every several years to heights of 300 to 400 feet.
Conditions Needed to Form a Geyser
It's obvious that geysers need a certain combination of conditions in order to form since they only occur in a few areas of the world. Geysers need three things, a source of water, a source of heat, and a reservoir system under the ground. The first two are relatively simple to obtain. The water comes from groundwater boosted by rainfall or snowfall. Additionally, some geysers obtain water from nearby rivers. All documented geysers are located over a shallow, volcanic heat source to obtain heat. This heat is needed to boil water and cause eruptions. However, the most important condition needed to form a geyser is the underground reservoir system. This system typically consists of a thin pipe leading from the surface opening to a chamber that holds most of the water. Most geysers have a system built into a special type of volcanic rock called rhyolite. This rock contains a high concentration of silica, which helps to create a water- and pressure-tight seal around the reservoir. Additionally, there must be several areas of constriction within the chamber and pipe. These constrictions help build up pressure in the reservoir that forces the water and steam to the surface.
If the conditions are not properly met, different geothermal features will form instead of geysers. For example, if the reservoir system is not constricted or the pipes are too large, if the temperature is too low, or if there is too much water then the geyser cannot erupt and a hot spring forms. If the water is too acidic or if the rock is too permeable then a mud pot forms. If there is enough heat but not enough water then a fumarole, or steam vent, forms.
Geysers can be generally classified as either fountain or cone geysers, depending on the structure of their reservoir system and opening:
- Cone geysers have a single, straight pipe underground that is connected to a chamber that holds water. The opening at the surface of these geysers has a cone around it that was created from minerals in the water. Cone geysers typically have long, high, and predictable eruptions with a continuous spray of water and steam. Old Faithful in Yellowstone is an example of a cone geyser.
- Fountain geysers have a reservoir system very similar to cone geysers, except the opening is within a filled pool like a hot spring instead of inside a cone. Eruptions from these geysers tend to be shorter in time and height than cone geysers. The eruptions also tend to not be a continuous spray, but instead are broken up by periods of inactivity. Great Fountain Geyser in Yellowstone is an example of a fountain geyser.
Additionally, there are some geysers that don’t fit in either category. For example, some geysers have an eruption similar to cone geysers but their opening is flat instead of cone shaped. Other geysers may have multiple chambers in their reservoir system instead of one, causing a series of eruptions.
How a Geyser Erupts
The eruption of a geyser is a complex, stepwise process involving heat and pressure. In the first step, cool ground water in the reservoir chamber mixes with boiling water brought up from deep within the earth. The chamber slowly fills with hot water and both the temperature and pressure in the chamber gradually increase. The high pressure in the chamber prevents the water from boiling at its normal boiling temperature and the water gets superheated. At a certain temperature above the boiling point some of the water starts to turn to steam and tries to escape through the pipe to the surface. However, the steam cannot readily escape because of various constrictions in the system. The steam builds up as bubbles that eventually make it to the surface along with a small amount of water. This loss of water causes the boiling point of the remaining water in the chamber to lower, which immediately converts much of the water to steam. This drastic increase in volume forces the steam and water out to the surface, causing an eruption. As the geyser erupts there is a steady decrease in temperature and pressure in the chamber. Once both fall below a certain level the eruption stops, the pool slowly refills itself, and the entire process starts over again.
The magnitude and frequency of geyser eruptions are affected by various conditions. For example, increases in rainfall seem to shorten eruption times while decreases in barometric pressure causes more eruptions. Additionally, tides also seem to affect geysers. It’s thought that low tides squeeze the reservoir system, restrict water flow, and inhibit eruptions while high tides open the system, allowing water in and causing more eruptions. The most impressive event that affects geysers is earthquakes. A 1959 earthquake in Yellowstone caused all the geysers in the park to erupt simultaneously and raised the temperature of the water in geysers and hot springs several degrees. Dormant geysers suddenly became active while active geysers permanently changed their eruption patterns. Earthquakes do not need to be directly near the geyser to have an effect either. An 8.5 magnitude earthquake in Alaska was found to have an effect on the eruption pattern of Old Faithful in Yellowstone.
A special class of geysers can erupt even when the water is below the boiling temperature. This is because the geysers contain a higher level of gases such as carbon dioxide or hydrocarbons. The gas lowers the hydrostatic pressure of the geyser so the water can boil at temperatures lower than the boiling point. Such geysers that are driven by gas instead of temperature are called “gassy geysers.” These geysers can be found in oil- and gas-producing regions around the world. Their eruptions tend to be much less predictable than those from typical water geysers. | <urn:uuid:6f18d784-5d1a-4ab1-ac87-8a3beff5f9ba> | 3.875 | 1,597 | Knowledge Article | Science & Tech. | 43.547667 |
Cuckoos don't bother building their own nests - they just lay eggs that perfectly mimic those of other birds and take over their nests. But other birds are wising up, evolving some seriously impressive tricks to spot the cuckoo eggs.
Cuckoos are what's known as brood parasites, meaning they hide their eggs in the nests of other species. To avoid detection, the cuckoos have evolved so that their eggs replicate those of their preferred targets. If the host bird doesn't notice the strange egg in its nest, the newly hatched cuckoo will actually take all the nest for itself, taking the other eggs on its back and dropping them out of the nest.
To avoid this nasty fate for their offspring, the other birds have evolved a few nifty ways to spot the fakes, which we're only now beginning to fully understand. One of the most intriguing finds is that birds have an extra color-sensitive cell in their retinas, which makes them far more sensitive to ultraviolet wavelengths and allows them to see a far greater range of colors than we humans can. This allows wary birds to detect a counterfeit egg where to our eyes they're all identical.
Fascinatingly, we're actually able to observe different bird species at very different points in their evolutionary war with the cuckoos. For instance, some cuckoos lay their eggs in the nests of the redstart. The blue eggs these cuckoos lay are practically identical to those of the redstarts, and yet they still sometimes get rejected. Compare that with cuckoos who target dunnocks. While those birds lay perfectly blue eggs, their cuckoo invaders just lay white eggs with brown splotches. And yet dunnocks barely ever seem to notice the obvious forgery.
Biologists suspect these more gullible species like the dunnocks are on the same evolutionary path as the redstarts, but they have a long way to go until they evolve the same levels of suspicion. What's remarkable is that the dunnock fakes are so bad and the redstart forgeries so good, and yet cuckoos are still more successful with the former than the latter.
It speaks to just how radically a species's behavior can be altered by the pressures of natural selection, or it might just be a bit of strategic cooperation on the part of the dunnocks. Biologists have suggested that these birds are willing to tolerate a parasite every so often because they don't want to risk accidentally getting rid of one of their own eggs.
Via BBC News. | <urn:uuid:561756ef-f2a6-4dad-b1e3-26d77ab0a41c> | 3.46875 | 521 | Truncated | Science & Tech. | 49.100089 |
As far as labels matter.
The NOAA report abstract is below. The report is here.
Sandy was a classic late-season hurricane in the southwestern Caribbean Sea. The cyclone made landfall as a category 1 hurricane (on the Saffir-Simpson Hurricane Wind Scale) in Jamaica, and as a 100-kt category 3 hurricane in eastern Cuba before quickly weakening to a category 1 hurricane while moving through the central and northwestern Bahamas. Sandy underwent a complex evolution and grew considerably in size while over the Bahamas, and continued to grow despite weakening into a tropical storm north of those islands. The system re- strengthened into a hurricane while it moved northeastward, parallel to the coast of the southeastern United States, and reached a secondary peak intensity of 85 kt while it turned northwestward toward the mid-Atlantic states. Sandy weakened somewhat and then made landfall as a post-tropical cyclone near Brigantine, New Jersey with 70-kt maximum sustained winds. Because of its tremendous size, however, Sandy drove a catastrophic storm surge into the New Jersey and New York coastlines. Preliminary U.S. damage estimates are near $50 billion, making Sandy the second-costliest cyclone to hit the United States since 19001. There were at least 147 direct deaths2 recorded across the Atlantic basin due to Sandy, with 72 of these fatalities occurring in the mid-Atlantic and northeastern United States. This is the greatest number of U.S. direct fatalities related to a tropical cyclone outside of the southern states since Hurricane Agnes in 1972. | <urn:uuid:010b8873-57ff-43ad-88e9-824d81cc2b33> | 2.75 | 314 | Knowledge Article | Science & Tech. | 37.587969 |
|Next stop: Mars.
This past weekend the
Mars Science Laboratory carrying the Curiosity Rover
for the red planet atop an
Atlas V rocket from
At five times the size of the Opportunity rover
currently operating on Mars,
Curiosity is like a
strange little car with six small wheels, a head-like camera mast, a rock crusher, a long robotic arm, and a plutonium power source.
Curiosity is scheduled to land on Mars next August and start a two year mission to explore
Gale crater, to help determine whether Mars could ever have
supported life, and to help determine how
humans might one day visit
Earth's planetary neighbor. | <urn:uuid:c4e1efce-04bd-4018-b26f-841a80568fc1> | 2.921875 | 140 | Content Listing | Science & Tech. | 29.295 |
Dr. Mary Schweitzer, assistant professor of paleontology with a joint appointment at the N.C. Museum of Natural Sciences, has succeeded in isolating soft tissue from the femur of a 68-million-year-old dinosaur. Not only is the tissue largely intact, it's still transparent and pliable, and microscopic interior structures resembling blood vessels and even cells are still present.
In a paper published in the March 25 edition of the journal Science, Schweitzer describes the process by which she and her technician, Jennifer Wittmeyer, isolated soft organic tissue from the leg bone of a 68-million-year-old Tyrannosaurus rex.
Schweitzer was interested in studying the microstructure and organic components of a dinosaur's bone. All bone is made up of a combination of protein (and other organic molecules) and minerals. In modern bone, removing the minerals leaves supple, soft organic materials that are much easier to work with in a lab. In contrast, fossilized bone is believed to be completely mineralized, meaning no organics are present. Attempting to dissolve the minerals from a piece of fossilized bone, so the theory goes, would merely dissolve the entire fossil.
But the team was surprised by what actually happened when they removed the minerals from the T. rex femur fragment. The removal process left behind stretchy bone matrix material that, when examined microscopically, seemed to show blood vessels, osteocytes, or bone building cells, and other recognizable organic features.
Since current data indicates that living birds are more closely related to dinosaurs than any othe
Source:North Carolina State University | <urn:uuid:f7dd7cfc-13cf-4119-97bd-f135372d4eb4> | 3.5625 | 332 | Truncated | Science & Tech. | 31.923137 |
Multiple inheritance means that a class
can have multiple superclasses and inherit from them.
Multiple inheritance can cause several problems:
- Name conflicts of instance variables.
- Methods with the same name from multiple parents.
- Instance variables no longer have simple constant offsets.
Variations of inheritance include:
- Using types of all arguments (not just the first) to determine the
- Method Combination (Flavors): the methods of multiple parents can
be combined, e.g. a window with border and title.
- SendSuper (Loops): a more specialized subclass method can call the
parent method. Useful e.g. to assign serial numbers to manufactured objects. | <urn:uuid:28eb9019-768b-4cd3-99f1-7dbc5d9d2da4> | 3.6875 | 143 | Knowledge Article | Software Dev. | 33.771865 |
String Theory: Two Types of Branes Are One
At energy levels where predictions from string theory and general relativity match up, D-branes and p-branes are equivalent. Though Polchinski was aware of Strominger’s work on p-branes — they discussed their projects over lunch regularly — both scientists thought that the two types of branes were distinct. Part of Polchinski’s 1995 work on branes included the realization that they were actually one and the same object.
It might seem odd that this hadn’t occurred to either of the men before 1995, but there was no reason to expect that the two types of branes would be related to each other. To a layman, they sound basically the same — multidimensional surfaces existing in a 10-dimensional space-time. Why wouldn’t you at least consider that they’re the same things?
Well, part of the reason may be based on the specific nature of scientific research. When you’re working in a scientific field, you are quite specific about the questions you’re asking and the ways in which you’re asking them.
Polchinski and Strominger were asking different questions in different ways, so it never occurred to either of them that the answers to their questions might be the same. Their knowledge blinded them from seeing the commonalities. This sort of tunnel vision is fairly common and part of the reason why sharing research is so encouraged within the scientific community.
Similarly, for a laymen, the dramatic differences between these two types of branes are less clear. Just as someone who doesn’t study much religion may be confused by the difference between Episcopalian and Catholic theological doctrines, to a priest of either religion the differences are well-known, and the two are seen as extremely distinct.
In the case of branes, though, the laymen would have had clearer insight on the issue than either of the experts. The very details that made D-branes and p-branes so intriguing to Polchinski and Strominger hindered their ability to see past the details to the commonalities — at least until 1995, when Polchinski finally saw the connection.
Because of equivalence, both D-branes and p-branes are typically just referred to as branes. When referencing their dimensionality, the p-brane notation is usually the one used. Some physicists still use the D-brane notation because there are other types of branes that physicists talk about. | <urn:uuid:2f9a1808-328b-46df-bfbf-f3ef9d0fe759> | 2.953125 | 525 | Truncated | Science & Tech. | 43.624167 |
Engaging, exciting, awe-inspiring. Words don’t do justice to this video from TED-Ed. If anyone can generate enthusiasm about ocean exploration, Robert Ballard can. His enthusiasm is palpable and his presentation filled with excitement and humor.
Ocean Explorer Ballard brings questions to light, asking why NASA’s (National Aeronautics and Space Administration) one-year budget to explore space is enormous enough to fund NOAA (National Oceanic and Atmospheric Administration) for about 1,600 years. He asks why are we ignoring 72 percent of the earth’s surface when there is amazing life below the oceans’ surface. Not just life, but ancient shipwrecks and large amounts of precious metals and minerals.
He and his colleagues have made amazing discoveries over the years below the surface of our unexplored oceans. The Jason Project, a program designed to bring students of all ages into the Science, Technology, Engineering and Math (STEM) fields is dear to him.
Read his National Geographic Explorer biography to find out more. | <urn:uuid:40158820-bfc2-47e0-a152-b51bab6f701c> | 3.171875 | 214 | Truncated | Science & Tech. | 38.320227 |
A copper wire with a bifilar winding that has the opposing magnetic fields cancel each other.
Take a enamel copper wire and nick the middle then twist the wire into a double helix.
Now curl the wire into a spiral. This will generate scalar waves when there is a current.
It is believed that scalar waves have strange effects including the distortion of the temporal field. In his time travel reports, Steven Gibbs says that the caduceus wound coil can create tachyons and alter temporal phenomena. He talks about how to make a caduceus coil for time travel.
The HDR caduceus coil built by Steven Gibbs should have the ability to generate an electromagnetic field that disrupts time waves and alters the flow of chronoton particles. My experiment with a watch subjected to the "gibbs effect" establishes that something is causing a disruption in the normal flow of time.
I believe this is caused by scalar waves emanating from the Hyper Dimensional Resonator or HDR created by inventor Steven Gibbs. These waves interact with those of the electromagnet to create a temporal disruption that can affect clocks. See videos of HDR at HDRusers.com
Steven Gibbs told me that in his caduceus coil he uses 21 gauge pure copper wire. Tin alloy will mess it up. Also, aluminum wire is a poison. It generates harmonics that are wrong.
The HDR caduceus coil is that round doughnut shaped object at the bottom of the left hand corner in the picture below. This is I believe what makes the HDR work and provides the missing factor for Steven Gibbs HDR.
Insides of a Hyper Dimensional Resonator (HDR) from Steven Gibbs
Return to Flux Cap Main Menu | <urn:uuid:f6a1fa6e-e35f-414f-9710-57aa106b506e> | 3.015625 | 352 | Knowledge Article | Science & Tech. | 52.005063 |
Hydrogen and Fluorine
Early in 1949 William L. Doyle, a chemist engaged in rocket propellant research at North American Aviation, made a deal with Herrick Johnston. Doyle would come to work at the Ohio State University Rocket Laboratory if given a free hand to investigate the performance of liquid hydrogen with his favorite oxidizer, liquid fluorine.*
In February 1949, Doyle reported for duty at the Ohio State laboratory. He did not like the experimental equipment, the operations, or the procedures, so he began to make changes.
William Doyle was a dynamic young man who knew what he wanted and just how to do it. The antithesis of the desk-bound supervisor and paper shuffler, he liked to be part of the action. He found his right environment at Ohio State where a senior engineer was responsible for his entire project-from inception, through design, fabrication, installation, operation, data analysis, and writing up the results. Doyle found this situation ideal and he made the most of it.
Doyle's interest in the hydrogen-fluorine combination was natural. It represented the combination of the ultimate fuel and the ultimate oxidizer, with a higher theoretical performance than hydrogen and oxygen. In addition, the mixture of 6 percent hydrogen and 94 percent fluorine by weight not only resulted in near-maximum performance, but also meant higher average propellant density for the combination. Doyle visited the men in the fuels and oil branch at Wright Field and convinced them to modify the Ohio State contract to include the work he wanted to do.
One of Ohio State's rocket test facilities was rebuilt to handle liquid hydrogen and liquid fluorine. The hydrogen flow system was encased in a vacuum jacket for insulation. A series of problems with maintaining the vacuum were solved. The flow of liquid hydrogen was measured by a dual system: the conventional way of measuring the pressure differential across a sharp-edged orifice as well as continuous measurement of the hydrogen tank mass. Once the hydrogen system was functioning, it gave little more trouble, but many problems were encountered in the fluorine system. The fluorine gas, procured commercially as a compressed gas, was condensed in the propellant tank by immersing it in a liquid air bath. Liquid fluorine flow was measured by the same methods used for hydrogen.
Doyle made his first liquid hydrogen-liquid fluorine run on 15 June 1950. He first operated the injector alone to see if the hydrogen and fluorine would ignite readily and spontaneously, which they did. He followed this experiment with rocket engine tests. By the first part of August, nine runs had been made and Doyle felt confident enough to invite his sponsors from Wright Field to witness a test. Judging from the mishaps reported for the first eight runs, Doyle was displaying a considerable amount of confidence. Don Kennedy arrived in response to the invitation and witnessed the tenth test on 11 August 1950. The run was perfect in Doyle's view, with a measured exhaust velocity of about 3600 meters per second at 20 atmospheres. Kennedy was greatly impressed and reported the results to his boss, Weldon Worth. Doyle continued the experiments and in mid-January 1951, Kennedy informed him that a group of high officials at Wright Field would visit Ohio State to witness a run with hydrogen-fluorine. Soon after the call, Doyle made a run at a high pressure (38 atmospheres) and measured an exhaust velocity of over 4300 meters per second. On 29 January, 14 people from Wright Field's Power Plant Laboratory arrived in terrible weather-a sheet of ice compounded by mist and drizzle. Icing difficulties delayed the run for an hour, but it was a success, lasting over a minute. Performance, however, was lower than obtained in earlier runs.14
One measurement necessary to determine performance-fluorine flow-had bothered Doyle from the start. Whereas the two flow measurements for liquid hydrogen checked with each other, the fluorine flow as measured by the orifice was lower than that measured by weighing the propellant tank. The difference was consistent-about 18 percent lower for the orifice. Five design changes were made to improve the orifice measurement, but the discrepancy remained.
Doyle was not the only experimenter having difficulty measuring the flow rate of liquid fluorine. Aerojet was having the same difficulty and investigators there began to suspect that the density of fluorine might somehow be wrong. This was heresy, for a number of eminent scientists had measured the density of fluorine and they all agreed. James Dewar and Henri Moissan had first measured it in 1897 and found it to be close to 1.14 grams per cubic centimeter at 83 K. The value In use in the 1950s was 1.13 grams per cubic centimeter at 77 K, determined by E. Kanda in 1937.
Near the end of April 1951, Kennedy telephoned Doyle that Aerojet, using a hydrometer, found that the density of liquid fluorine was 1.55 grams per cubic centimeter, considerably higher than the published value. Doyle used the Aerojet value with his orifice measurements and found that the 18 percent discrepancy with the weighing measurement disappeared! The greater density of liquid fluorine was an exciting discovery to rocket engineers, for it meant the oxidizer was even more attractive than first realized.**
Doyle made his 48th and last hydrogen-fluorine run in mid-April 1951 and turned his attention to the ammonia-fluorine combination. This ended the Ohio State rocket experiments with liquid hydrogen, although the properties work continued, as well as some small-scale combustion research of a fundamental nature. | <urn:uuid:f6b893b0-2e58-4246-a799-77aeaeae7977> | 3.515625 | 1,137 | Knowledge Article | Science & Tech. | 39.482274 |
DRIVING in the dark is about to get safer. Intelligent versions of the familiar reflecting Catseye could soon be embedded in the highway, marking out the road more than 10 times farther ahead and warning drivers of dangerous conditions.
The Intelligent Road Studs, developed by Astucia, a company in Retford, Nottinghamshire, contain sensors that allow them to detect icy, wet or foggy conditions. The brains behind the studs lies in their ability to communicate with each other using infrared beams. They can be set to change colour to warn drivers of hazards detected by studs farther down the road.
Instead of using reflectors, the studs are fitted with solar-powered light emitting diodes (LEDs). Even in poor weather, just one hour of daylight provides enough power to keep them going through the night. They can be seen from as far as 900 metres away, and can be programmed so that more ...
To continue reading this article, subscribe to receive access to all of newscientist.com, including 20 years of archive content. | <urn:uuid:af2cfc27-5e75-4cbc-9884-2e76fdb85682> | 3.328125 | 216 | Truncated | Science & Tech. | 54.834408 |
Lars Jensen photo
Lake Superior greatly ameliorates temperature extremes, slowing spring warming and the onset of winter. The average date of the last freezing temperature in spring is June 8, and the average first fall freeze is September 23; however, freezing can occur during any month. The freeze-free period, or growing season, averages 107 days annually.
The big lake's presence also increases precipitation in the lakeshore. Annual precipitation averages 79 cm (31 inches); annual snowfall is 320 cm (126 inches). Snow generally covers the ground from late November through late April.
The area is within the second-most cloudy region of the United States, characterized by an annual mean cloud cover of 70 percent. Much of the cloudiness occurs in autumn and winter and can be attributed to cool air flowing over Lake Superior being warmed along the shore and forming clouds. This condition also often results in rain, fog, and snow. Spring is relatively clear due to the cold water surface of the lake.
The prevailing wind is from the west, with average velocities ranging from 12 to 15 kilometers per hour (7 to 9 mph). High winds and storm conditions on Lake Superior are not uncommon. The highest recorded one-minute wind speed is 98 kilometers per hour (59 mph).
For more information
Climate Change (website)
Climate Change in National Parks (pdf)
Climate Change and the Great Lakes (pdf)
National Park Service Climate Friendly Parks (website)
National Park Service Great Lakes Inventory and Monitoring Network (website)
National Weather Service Forecast Office, Marquette, Michigan (website)
Did You Know?
Several species of plants in the Buttercup Family are aquatic, growing underwater in lakes and ponds. A few are even amphibious, meaning that a single plant lives partly on sand along a shoreline and partly submerged. Such plants have runners, like a strawberry plant, and grow roots along the runners. The submerged leaves appear quite different from the ones growing in air. | <urn:uuid:46b703d8-6da1-4971-9523-302ce7d497c7> | 3.578125 | 409 | Knowledge Article | Science & Tech. | 41.160708 |
|Dec22-12, 07:33 AM||#1|
Do all substances boil?
If no, which ones do not? If yes, is there a theoretical proof that a counterexample is impossible?
Most substances have a fluid phase which is a single phase at pressures above critical point pressure - but two separate phases at lower pressures. The solid sublimates into a gas at lower pressure, and at higher pressures it melts into a liquid.
Some substances have wide pressure range of boiling. For example quicksilver has a triple point pressure of just 0,165 mPa, at about -39 degrees, yet its critical point pressure is reputed 172 MPa, at +1477 degrees.
Yet other substances have relatively narrow boiling pressure range. Carbon dioxide has triple point pressure of 0,52 MPa, at -57 degrees, but its critical point pressure is 7,3 MPa, at +31 degrees.
Is it fundamentally possible for a substance to not boil at all, under any pressure or temperature, because the solid crystallizes from a single fluid phase under any pressures, such that triple and critical point are nonexistent because "degenerate"?
If yes, what substances are such? If no, what is the theoretical proof if the impossibility of such a substance?
|Dec22-12, 07:45 AM||#2|
Some solid substances will break apart, sublimate at every pressure or transform into other substances if you heat them - and without a liquid phase, they cannot boil.
A triple point at the critical point... I don't know.
Comparing this list with that one, all listed substances seem to have a triple point below their critical point.
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|Boil Boil Boiler||Materials & Chemical Engineering||0| | <urn:uuid:675cf148-073b-42ee-82a8-cfeca96e771c> | 2.71875 | 439 | Comment Section | Science & Tech. | 56.473729 |
C++ Program to Read a Set of Lines
This is a program to read a set of lines and find out the number of characters, word and lines in a given text and display each word of the text in different lines.
Void main ()
Int i=0, linecount=1, wordcount=1;
Char str ;
Cout<<”\n Enter the lines”;
Cin.get (str, 100, ‘#’);
If (str[i] ==’’ ?? str [i] ==’\n’)
If (str[i] ==’\n’)
While (str[i]! = ‘\o’);
Cout<<”\n the number of characters are”<<I;
Cout<<”\n word count=”<<wordcount;
Cout<<”\n line count=”<<linecount;
Cout<<”\n the entered word are”;
For (int j=o; j<I; j++)
If (str [j] ==’’)
- C++ Program to Input and Output String This is a simple program which is designed to take...
- C++ Program To Display Result Stored In An Array This program takes ‘n’ number as input , stores it...
- C++ Program to Sort Elements This program reads a set of numbers from the standard...
- C++ Program using If-else Statement This program shows the simple use of if-else statement. In...
- C++ Program showing constructor overloading Constructor is a member function with the same name as... | <urn:uuid:4c4e2c6d-6576-4637-be10-3fac869bc1d1> | 3.9375 | 364 | Content Listing | Software Dev. | 91.364375 |
Taking a Clue from Nature
Though weinberg and his colleagues at Symyx are the first to try to commercially apply combinatorial techniques to materials research, they didn’t invent the process. In fact, they were beaten out by a few billion years by a very creative innovator: Evolution. Cells have the ability to create a wide variety of molecules based on a limited number of building blocks and then select the ones that function best. In this familiar evolutionary process, cells create an enormous variety of DNA and protein molecules by arranging common building blocks in a different order. Natural selection does the rest.
Beginning in the early 1980s, researchers began imitating nature’s example. They started creating collections of peptides-short proteins that can bind to cell receptors and thereby regulate cell function. Just how well this regulation takes place depends on how tightly a peptide binds to a receptor, which itself depends on getting just the right sequence of peptide building blocks, amino acids. Researchers invented several methods that made it possible to arrange amino acids in different combinations and track the products they made. They found that they could easily create thousands of peptides in nothing flat. By testing these compounds for activity in cells, researchers could quickly home in on the most chemically active peptide and work out its structure.
These early successes didn’t win many converts among those who design new therapeutic drugs for a living. “There was enormous resistance from medicinal chemists in the beginning,” says Joseph Hogan, founder and chief scientific officer of ArQule-a Medford, Mass.-based combinatorial startup. “They felt it was completely inelegant and ugly” compared with the traditional approach of rationally designing and then painstakingly synthesizing compounds.
The approach also faced practical limitations. Because enzymes in the stomach break down peptides, most researchers considered them poor drugs. But the idea was in the air, and before long, new research teams showed that the basic strategy could go beyond peptides and turn out small organic compounds similar to those that make up most drugs.
By the beginning of the 1990s the craze for high-speed chemistry was sweeping through the pharmaceutical industry. Startups sprang to life to commercialize combinatorial know-how. Flush with hundreds of millions of dollars from investors, these companies set about creating libraries of potential drugs with as many compounds as big pharmaceutical companies had hoarded on their stockroom shelves during the past 100 years. Not to be left out, Big Pharma companies, such as Glaxo Wellcome and Merck, leaped into the fray starting their own combinatorial research efforts and striking deals with combinatorial chemistry startups. “In the mid-1980s, traditionalists were laughing at the idea of the combinatorial synthesis of drugs,” says Weinberg. “But they’re not laughing now.” | <urn:uuid:f59cbec8-7e84-4ea6-98b9-4a8a514876a2> | 3.40625 | 594 | Nonfiction Writing | Science & Tech. | 36.60908 |
Next: 6.3.2 Creating a FIFO
Up: 6.3 Named Pipes (FIFOs
Previous: 6.3 Named Pipes (FIFOs
A named pipe works much like a regular pipe, but does have some noticeable
- Named pipes exist as a device special file in the file system.
- Processes of different ancestry can share data through a named pipe.
- When all I/O is done by sharing processes, the named pipe remains in
the file system for later use.
Fri Mar 29 14:43:04 EST 1996 | <urn:uuid:bbfd5e35-1bea-4e29-a87f-eb3e56e54ac2> | 3.171875 | 121 | Documentation | Software Dev. | 71.783571 |
Want to stay on top of all the space news? Follow @universetoday on Twitter
One of the mysteries of Earth science is hotspots. While most volcanoes are found at plate boundaries, where two tectonic plates are rubbing against each other, volcanic hotspots can be anywhere, even in the middle of continents. What causes volcanic hotspots? One theory is the idea of a mantle plume.
A mantle plume is kind of like what’s going on inside a lava lamp. As the light heats up the wax in a lava lamp, it rises up through the oil in large blobs. These blobs reach the top of the lamp, cool and then sink back down to be heated up again.
Inside the Earth, the core of the Earth is very hot, and heats up the surrounding mantle. Heat convection in the mantle slowly transports heat from the core up to the Earth’s surface. These rising columns of heat can come up anywhere, and not just at the plate boundaries. Geologists did fluid dynamic experiments to try and simulate mantle plumes, and they found they formed long thin conduits topped by a bulbous head.
When the top of a mantle plume reaches the base of the Earth’s lithosphere, it flattens out and melts a large area of basalt magma. This whole region can form a continental flood basalt, which only lasts for a few million years. Or it can maintain a continuous stream of magma to a fixed location; this is a hotspot.
As the lithosphere continues to move through plate tectonics, the hotspot appears to be shifting its position over millions of years. But really the hotspot is remaining in a fixed location, and the Earth’s plates are shifting above it.
Two of the most famous places that might have mantle plumes underneath them are the Hawaiian Islands and Iceland.
We have written many articles about volcanoes and the interior of the Earth for Universe Today. Here’s an article about the difference between magma and lava, and here’s an article about magma chambers.
We have recorded an entire episode of Astronomy Cast about volcanoes around the Solar System. Listen to it here: Episode 141: Volcanoes, Hot and Cold. | <urn:uuid:91b603ce-acdc-4342-bb6a-a1bc1a846bd7> | 4.34375 | 471 | Truncated | Science & Tech. | 56.091455 |
Create a drop-down list with four options:
The <select> tag is supported in all major browsers.
The <select> element is used to create a drop-down list.
The <option> tags inside the <select> element define the available options in the list.
Tip: The <select> element is a form control and can be used in a form to collect user input.
HTML5 has added some new attributes.
New : New in HTML5.
|autofocusNew||autofocus||Specifies that the drop-down list should automatically get focus when the page loads|
|disabled||disabled||Specifies that a drop-down list should be disabled|
|formNew||form_id||Defines one or more forms the select field belongs to|
|multiple||multiple||Specifies that multiple options can be selected at once|
|name||name||Defines a name for the drop-down list|
|requiredNew||required||Specifies that the user is required to select a value before submitting the form|
|size||number||Defines the number of visible options in a drop-down list|
The <select> tag also supports the Global Attributes in HTML.
The <select> tag also supports the Event Attributes in HTML.
HTML DOM reference: Select object
Your message has been sent to W3Schools. | <urn:uuid:3a65d451-3494-448e-90f5-45a3eedf579a> | 3.125 | 291 | Documentation | Software Dev. | 45.062917 |
The role of crustal quartz in continental tectonism...
Gravity, surface heat flow and EarthScope seismic data are combined in a new tool for measuring the averaged abundance of quartz in the Earth's crust... And the results are surprising.
Slow fault slip after the 2004 M9.3 Sumatra- Andaman earthquake
The 2004 earthquake is the largest to occur since the dawn of GPS positioning. In the first two years post-event, GPS sites on the Andaman Islands continued to move upward and southwestward by up to half a meter. These motions serve to relax stress changes during the earthquake, but the mechanism is unclear: Poroelastic fluid movements, flow of hot rock deep in the Earth and continued fault slip at depth are all candidate processes. Large differences in motion at closely-spaced (10-30 km) sites however suggest that fault slip played a dominant role in the first two years. (Coming soon: Fault slip and viscoelastic flow also play about equal roles in transient deformation from the most recent two years of data, with fault slip slightly dominant!)
Slow opening of the Rio Grande Rift
The Rio Grande Rift in Colorado and New Mexico is often cited as the type-example of a "narrow" continental rift. Four years of continuous measurement at 26 GPS sites suggests that opening of the rift is occurring at rates of 1.5 to 2.5 millimeters per year, but comparison to regional GPS sites indicates that the strain is surprisingly broadly distributed (over more than 300 km width at 95% confidence). The eastern limit of rifting is unbounded by existing measurements, but total width may be 500 km or more. By comparison, the width of rifting across the eastern Basin-Range (a type example for a "wide" continental rift province) is only 120 km.
A thought: |
"Our future is being decided now in a struggle that pits two divergent rivers of intellect:
one that views truth as an objective reality, to be pursued through honest and open inquiry,
a second that views reality as a fluid, and truth as a football match in which the ball advances via advocacy.
But an ideology that neglects reality,
or relies on the manufacture of false doubt and obfuscation of the truth,
will collapse of its own corruption.
To which future do you belong?"
Afterthought: It is maddening that, in the 21st century, we are still arguing over whether markets should be entirely free or rationally regulated. Adam Smith, the so-called "father of free-market capitalism", knew the ovious answer to this question in the 1700s... as did any 19th century reader of Dickens.
Updated 10/Jun/2013 Tony Lowry | <urn:uuid:33ae84ee-1771-4886-a647-28f15f28b89d> | 2.96875 | 560 | Content Listing | Science & Tech. | 56.120082 |
Question: What are the main risks posed by the genomics revolution?
Juan Enriquez: So, anytime you bring a really powerful new technology to market there are multiple implications. You start changing the relative position of countries. When you brought the Industrial Revolution in, all of a sudden India and China went from being the dominant global powers to being powers dominated by those who understood how to apply this new technology.
When you brought the digital revolution in, all of a sudden, you could build a country like Singapore and take that country, which had the income per capita of Ghana in 1965, and make it something similar to the United States in one generation. As these things roll through the economy, who’s rich and who’s poor can shift very quickly depending on who is literate in this stuff. So, one of the risks is, our educational system doesn’t adapt, our society doesn’t adapt and we become illiterate in the world’s dominant language.
The second risk that you’ve got to think about is, these technologies are so powerful that, like the Industrial Revolution, they can have unintended consequences. Like the agricultural revolution, it can have unintended consequences. And we really have to think about how we apply them and one of the first things we should be doing is pushing a non-proliferation treaty that has real teeth to the application of life code for offensive purposes. That’s something that we have to get much more serious about.
The last thing that I think, and there’s a long list of these, but the three main things; the last thing I think we’ve got to think about is unintended consequences and I think there it is particularly important to have genes that are self-regulating that cutoff, that don’t reproduce outside of very specific environments and that allows us to understand what these things are doing and where they’re growing and to have control conditions on where they’re growing.
Having said all that, unless this is the first technology that humans have every invented that doesn’t harm a human being, we are going to have accidents. And we’ve had those with staircases, we’ve had those with airplanes, we’ve had those with automobiles, we’ve had it with electricity, and steel. I think the benefits are of such an order of magnitude that it is well worth pursuing this life science revolution and those countries that do it will be the dominant countries.
Question: How can this technology be kept out of the wrong hands?
Juan Enriquez: You know, there’s a whole series of debates as to how open you should be with this technology. So, the question then becomes do you create a super class of people who understand how life works, and how to apply it and how to read it and how to write it and how to keep everybody else in the dark, or do you broadly let this technology out there. This came to a head when scientists sequenced the 1918 flu, which killed so many people. Like, 1918 or 1914.
And in the measure that you begin to understand how that flu is constructed, what makes that flu, then you also begin to understand how other diseases are made. And then there was a second debate when people sequenced smallpox. Should you allow people to understand how smallpox is made? After a lot of debate and a lot of work, what people decided is, it makes a great deal of sense to be open in the system and allow people to begin to build the vaccines against this, to build better flu vaccines. I mean, we’re still making them in eggs that come out of chickens. And we can see the consequences of that with the current H1N1 lack of vaccines.
Whereas, if we allow this code to go out and we let it be open source, then we’re going to put together something where a lot people can be working on solving these problems.
Now, will there be some bad eggs out there? Yeah, there are. And there are bad eggs in a series of places. I think we need some control of the assembly mechanisms and the specific gene sequences ordered to assemble some of these things in such a way that if somebody starts making something particularly nasty, we (a) find out about it and we (b) ask, “What are you doing,” and, “Why are you doing this?”
Recorded on November 9, 2009
Interviewed by Austin Allen | <urn:uuid:480dc9c3-b38b-4b50-8ef7-f90ca11c55e3> | 2.796875 | 941 | Audio Transcript | Science & Tech. | 50.193013 |
Detritivores, also known as detritophages or detritus feeders or detritus eaters or saprophages, are heterotrophs that obtain nutrients by consuming detritus (decomposing plant and animal parts as well as organic fecal matter). By doing so, they contribute to decomposition and the nutrient cycles. They should be distinguished from other decomposers, such as many species of bacteria, fungi and protists, which are unable to ingest discrete lumps of matter, but instead live by absorbing and metabolizing on a molecular scale. However, the terms detritivore and decomposer are often used interchangeably.
Typical detritivorous animals include millipedes, woodlice, dung flies, slugs, many terrestrial worms, sea stars, sea cucumbers, fiddler crabs, and some sedentary polychaetes such as amphitrites (Amphitritinae, worms of the family Terebellidae) and other terebellids.
Scavengers are typically not thought to be detritivores, as they generally eat large quantities of organic matter, but both detritivores and scavengers are specific cases of consumer-resource systems. The eating of wood, whether live or dead, is known as xylophagy. Τhe activity of animals feeding only on dead wood is called sapro-xylophagy and those animals, sapro-xylophagous.
In food webs, detritivores generally play the role of decomposers. Detritivores are often eaten by consumers and therefore commonly play important roles as recyclers in ecosystem energy flow and biogeochemical cycles.
Many detritivores live in mature woodland, though the term can be applied to certain bottom-feeders in wet environments. These organisms play a crucial role in benthic ecosystems, forming essential food chains and participating in the nitrogen cycle.
Fungi, acting as decomposers, are important in today's terrestrial environment. During the Carboniferous period, fungi and bacteria had yet to evolve the capacity to digest lignin, and so large deposits of dead plant tissue accumulated during this period, later becoming the fossil fuels.
Saprophyte (-phyte meaning "plant") is a botanical term that is no longer in popular use. There are no real saprotrophic organisms that are embryophytes, and fungi and bacteria are no longer placed in the plant kingdom. Plants that were once considered saprophytes, such as non-photosynthetic orchids and monotropes, are now known to be parasites on fungi. These species are now termed myco-heterotrophs.
'Saprophages' are organisms that feed on decaying organic matter.
- Wetzel, R. G. 2001. Limnology: Lake and River Ecosystems. Academic Press. 3rd. p.700.
- Getz, W. (2011). Biomass transformation webs provide a unified approach to consumer–resource modelling. Ecology Letters, doi:10.1111/j.1461-0248.2010.01566.x.
- PDF, Tenore, K.R., SCOPE publication.
- biology online
- Hershey DR. 1999. Myco-heterophytes and parasitic plants in food chains an webs. American Biology Teacher 61:575-578.
- Leake JR. 2005. Plants parasitic on fungi: unearthing the fungi in myco-heterotrophs and debunking the ‘saprophytic’ plant myth. The Mycologist 19:113-122.
- Werner PG. 2006. Myco-heterotrophs: Hacking the mycorrhizal network. Mycena News 57:1,8. | <urn:uuid:f591aa14-41d0-4dbf-86d4-c0977c39e017> | 4.09375 | 799 | Knowledge Article | Science & Tech. | 34.156105 |
common name: an antlion
scientific name: Glenurus gratus (Say) (Insecta: Neuroptera: Myrmeleontidae)
Introduction - Distribution - Identification - Biology - Detection and Survey - Economic Importance - Selected References
Antlions are common, conspicuous insects in Florida. Florida has the richest antlion fauna in the eastern United States with 22 species in nine genera. Four species are found only in the Keys (Stange 1980a).
Wheeler (1930) called them "demons of the dust", whereas children in the southern United States coined the term "doodlebugs" to describe their antics. Although most people associate them with the funnel-shaped pitfall traps, most of the genera have other habits often reflected by their movements which can be very fast across the surface of the sand (Brachynemurus); slow, creeping movements (Dendroleon); or fast backward movements under the sand (Vella) (Stange 1980b).
One of the most striking antlions in Florida is Glenurus gratus (Say). The richly dark-marked wings are distinctive in Florida according to Stange (1980a). While most antlion larvae are found in the soil, the unusual, two-toothed mandibled larva of G. gratus lives in tree holes. Adults can be seen flying in forested areas during the summer months and sometimes are attracted to lights. This species is found throughout peninsular Florida.
Figure 1. Adult Glenurus gratus (Say), an antlion. Photograph by Lyle J. Buss, University of Florida.
In the United States, this species is known in Florida, Indiana, Kentucky, Mississippi, Missouri, New Jersey, Ohio and Tennessee (Stange 2000).
Antlion larvae share with other Planipennean Neuroptera the singular modification of the mandibles and maxillae to form a pair of sucking tubes. The curved, toothed mandibles and fusion of the hind tibia and tarsus are diagnostic in Florida except for the related Ascalaphidae. Ascalaphid larvae are easily distinguished by the cordate posterior margin of the head. Many of the genera can be distinguished by the mandible which can have one (Paranthaclisis), two (Glenurus), or three (rest of the genera) teeth.
Figure 2. Larva of Glenurus sp., an antlion. Photograph by James Castner, University of Florida.
Figure 3. Ventral view of larvae of Glenurus gratus (Say), an antlion. Photograph by Division of Plant Industry.
Figure 4. Dorsal view of the larval head of Glenurus gratus (Say), an antlion. Notice the two-toothed mandible, an identifying characteristic of this genus. Photograph by Division of Plant Industry.
Figure 5. Ventral view of the larval head of Glenurus gratus (Say), an antlion. Photograph by Division of Plant Industry.
Oviposition and eggs are not known, but all three larval instars live in dry hollows of trees among fine wood particles, squirrel frass and other fecal matter, and other assorted debris. These hollows are large enough to allow for free movement of the larvae under the surface of the debris and are structured so that rainfall does not fully soak the contents of the hollow. The larvae may dig or run after prey, but not rapidly. At times, larvae may simply lie in wait. They feed on assorted insects found in their microhabitat such as termites, beetle larvae, and ants.
Figure 6. Typical habitat of the larvae of Glenurus gratus (Say), an antlion. Photograph by Division of Plant Industry.
The authors found as many as three Glenurus larvae in one hollow, and in one instance, a larva of Dendroleon obsoletus (Say) was coinhabiting. Natural enemies and parasites are unknown. Larvae complete their life cycles in one or two years, depending upon the abundance of food and the duration of warm nights in their habitat during the year. Of two larvae reared by the authors, both constructed cocoons measuring 13 mm in diameter which were completely but shallowly buried beneath the debris. Cocoon construction to emergence of the adult required 28 days in both instances.
Larvae can be found by sifting dry organic material in tree holes, especially on Quercus virginiana Mill. Adults can be collected at night at lights and found in forests by beating plants.
Adult antlions are distinguished from all other insects by the four membraneous, similarly-shaped wings with a long hypostigmatic cell. Males of most species have a peculiar and unique organ at the base of the hindwing (pilula axillaris). The tube-like abdomen is similar in both sexes, although normally longer in the male, with the 1st sternite reduced. Male terminalia often have a postventral lobe, whereas the female terminalia are of more variable structure probably related to oviposition sites but usually with digging setae and a finger-like process (posterior gonapophysis). Adults are commonly confused with damselflies (Odonata), but the clavate antennae of antlions easily distinguishes them (Stange 1980a).
Both adults and larvae are predators and are economically beneficial. Adults commonly feed on caterpillars and aphids, whereas the larvae feed on surface dwellers such as ants and other insect larvae.
- Banks N. 1922. South American Glenurus and some other Myrmeleonidae. Canadian Entomologist 54: 58-60.
- Banks N. 1928. Revision of the Nearctic Myrmeleonidae. Museum of Comparative Zoology Bulletin Harvard 68: 1-84.
- Stange L. 1970. A generic revision and catalog of the Western Hemisphere Glenurini with the description of a new genus and species from Brazil. Contributions to Science, Los Angeles County Museum Natural History 186: 1-28.
- Stange L. 1980a. The ant-lions of Florida. I. Genera. Florida Department of Agriculture and Consumer Services, Division of Plant Industry, Entomology Circular 215: 1-4.
- Stange L. 1980b. The ant-lions of Florida. II. Genera based on larvae. Florida Department of Agriculture and Consumer Services, Division of Plant Industry, Entomology Circular 221: 1-4.
- Stange L. (2000). A Checklist and Bibliography of the Megaloptera and Neuroptera of Florida. Florida State Collection of Arthropods. http://www.fsca-dpi.org/Neuroptera/Neuroptera_of_Florida.htm (29 November 2012).
- Swanson M. (2006). Antlion Pit: A Doodlebug Anthology. http://www.antlionpit.com/ (29 November 2012).
- Wheeler WM. 1930. Demons of the Dust. W.W. Horton & Co., New York, 378 pp. | <urn:uuid:42fba03e-5e93-4346-b6aa-0dfe54d8eed2> | 3.265625 | 1,487 | Knowledge Article | Science & Tech. | 44.953759 |
Brief SummaryRead full entry
BiologyA gregarious bird, but less so than some other penguin species (2), the gentoo can form breeding colonies ranging from thirty to thousands of pairs (5). Arriving at suitable nesting ground between June and November (the exact date depending on the location) (2), each pair of penguins will set about the task of constructing a nest from stones, tussock grass and moss (2). The penguins tear up plants to use as nest material and fertilise the ground with their droppings, resulting in grass growing well the subsequent year, hence their favourable reputation with sheep farmers (5). Into these nests two white, spherical eggs are laid, which are incubated by both the male and female for 31 to 39 days (2). The penguin chicks fledge after 85 to 117 days, but continue to be fed by their parents for a further 5 to 50 days. Gentoo penguins, which reach sexual maturity at the age of two years (2), are not only faithful to certain nest sites, with most returning to the previous year's nest, but they are also loyal to breeding partners, with many forming long-lasting pair bonds (3). Walking with a rather comedic, waddling gait on land, the gentoo penguin shows its true talents when in the water. With its stream-lined body and 'flippers' that provide effective propulsion through the water (6), the gentoo penguin dives deep into the ocean in pursuit of its prey, and is capable of reaching impressive depths of up to 170 metres (3). The exact diet of the gentoo penguin varies depending on location, but can include Atlantic krill, other crustaceans, fish, cephalopods and polychaetes (2). | <urn:uuid:b4e35715-d3a2-44c8-bdf2-7dc5f24c0e0b> | 3.484375 | 367 | Knowledge Article | Science & Tech. | 48.887094 |
Jan 9, 2000, 10:11 PM
Post #2 of 3
Actually, you can also use the first example you wrote on Win32:
$path = "/home/www/blah";
From "Learning Perl on Win32 Systems" Chapter 10.3 - Using Pathnames and Filenames:
"The only portable delimiter is the slash. Of course, if you're using drive letters, your script isn't really portable anyway.
<BLOCKQUOTE><font size="1" face="Arial,Helvetica,sans serif">code:</font><HR>
"c:\\temp" # backslash (escaped for double quoted string)
'c:\temp' # backslash (single quoted string)
"c:/temp" # slash - no escape needed </pre><HR></BLOCKQUOTE>
There are a couple of tradeoffs associated with either approach. First we look at the backslash: if you use the backslash to delimit paths, you have compatibilty problems with scripts that need to run on UNIX systems. You also need to remember to escape the backslash inside of double-quoted strings (or use single-quoted strings, because they are not interpolated). Finally, you need to remember to use a slash if you're outputting URL paths."
If you're going to be working on Win32, you may wish to pick up this book:
Learning Perl on Win32 Systems
By Randal L. Schwartz, Erik Olson & Tom Christiansen
1-56592-324-3, 306 pages
First Edition, August 1997 | <urn:uuid:6953955b-b4e6-473e-939d-b3c5dbf2bf25> | 2.875 | 347 | Comment Section | Software Dev. | 58.624292 |
The Bad Astronomer writes "Using real data from Hubble Space Telescope of a planet orbiting another star, exoplanetary scientist Frédéric Pont created a lovely image of what sunset would look like from HD209458b, nicknamed Osiris, a planet 150 light years away. The Hubble data gave information on the atmospheric absorption of this hot Jupiter planet, and, coupled with models of how the atmosphere was layered, Pont was able to create a realistic looking sunset on the planet. The big surprise: the star looks green as it sets! Sodium absorption sucks out the red colors and blue is scattered away, leaving just the green hues to get through. It's a lovely application of hard scientific knowledge." | <urn:uuid:ccd394ec-3dbb-49aa-bffb-3b219bbbb6fd> | 3 | 141 | Comment Section | Science & Tech. | 41.800793 |
This is a collection of websites and internet resources that are hand-picked for teaching hydrogeology at the undergraduate level. If you have an internet resource or website you would like to share, please let us know.
Subject: Ground Water
- 4 matches General/Other
- Geology of groundwater occurrence
- Water cycle/groundwater-surface water interface
- Unsaturated zone/recharge
- Aquifer properties
- Groundwater flow
- Water supply/water resource evaluation
- Well hydraulics
- Water quality/chemistry
- Contaminant hydrology
- Groundwater modeling
- Field methods in hydrogeology
- Water and society, policy, and management
Results 1 - 10 of 20 matches
Virtual Field Trips part of SERC Web Resource Collection
GEO-SCI 587: Introduction to Hydrogeology part of SERC Web Resource Collection
An Educator's Guide to South Dakota's Natural Resources part of SERC Web Resource Collection
Water Quality Acquisition part of SERC Web Resource Collection
Winter Field Lab: Pond Hydrology part of SERC Web Resource Collection
Water-Borne Illnesses part of SERC Web Resource Collection
The Microcosmos Curriculum Guide to Exploring Microbial Space part of SERC Print Resource Collection
This book, a product of a science education program supported by the National Science Foundation, integrates biology and life sciences through hands-on activities. These activities present microbes ...
Guidelines for evaluating ground-water flow models part of SERC Print Resource Collection
This report provides some guidelines and discussion on how to evaluate complex ground-water flow models used in the investigation of ground-water systems. The important aspects to be included in a ...
Regional flow in the Dakota aquifer: a study of the role of confining layers part of SERC Print Resource Collection
This is a great paper describing the role of confining layers in regional flow systems using the historic work of N.H Darton in the Dakota Aquifer as a background to modern concepts and ...
Groundwater transport of arsenic and chromium at a historical tannery, Woburn, Massachusetts, U.S.A. part of SERC Print Resource Collection
This article from 'Applied Geochemistry' is an overview of the use and subsequent reduction of arsenic and chromium compounds in the tanning industry. The article also describes the transport of ... | <urn:uuid:2ed8c8f6-9f53-4e0b-8409-35d48827d6a4> | 3.265625 | 492 | Content Listing | Science & Tech. | 28.766094 |
Students compare known elemental spectra with spectra of Titan and Saturn's rings from a spectrometer aboard the NASA Cassini spacecraft. They identify the elements visible in the planetary and lunar spectra.
Prior Knowledge & Skills
AAAS Science Benchmarks
The Physical Setting
The Nature of Science
NSES Science Standards
- Science as inquiry: Abilities necessary to do scientific inquiry
- Physical science: Transfer of energy
- Earth and space science: Earth in the solar system, Structure of the earth system
- Unifying concepts and processes: Evidence, models and explanation
NCTM Mathematics Standards
- Data analysis and probability: Develop and evaluate inferences and predictions that are based on data
Teaching Time: One 45-minute period
Each student will need:
- A copy of the "Using Spectral Data" handout
Preparation Time: 20 minutes
- Copy handouts
- Review lesson plan
Why Do We Care?
The Ultraviolet Imaging Spectrograph (UVIS), which recorded the data used in this activity, is one of the instruments currently orbiting Saturn aboard the Cassini spacecraft. UVIS spectra show the intensity of ultraviolet light emitted by or reflected off an object over a range of light wavelengths. Astronomers use the distinctive pattern of peaks and valleys in each spectrum to uncover the chemical makeup of objects in the Saturn system, like its rings and moons.
Suggested background reading
The Instruments on UVIS
Cassini Mission to Saturn
Cassini Spacecraft and Huygens Probe
Cassini-Huygens Mission to Saturn
Activity Dependency Graphing the Rainbow
Group Size 1
Expendable Cost per Group $0
The instruments aboard Cassini were engineered to gather data about Saturn and Saturn's moons and rings. Mechanical and electrical engineers build these instruments to help advance our knowledge of planetary science.
Students should have some understanding of the nature of light i.e. rainbows are formed with light. Students should be familiar with graphical representations of data, such as line plots.
After this lesson, students should be able to:
- Explain that spectral data correlates to chemical compositions
- Match plots of real data to experimentally known data
- Describe how scientific data relates to scientific discovery
Introduction / Motivation
Show students the PowerPoint, "Spectrographs" from the CDrom
In 1997, NASA launched the Cassini spacecraft, the first spacecraft to orbit Saturn. Since June 30th of 2004, Cassini has been sending back images and data from Saturn, its rings, and its Moons, including Saturn's largest moon, Titan. Engineers
collaborated with scientists to create instrumentation that sits onboard Cassini. Mechanical, electrical, and aerospace engineers made sure the components of Cassini work properly and could withstand the launch and rigors of space travel. The spacecraft needs to be able to communicate with people on Earth, operate in very cold and harsh conditions, and be able to travel in the right direction! All of these things require appropriate engineering to make sure the spacecraft is healthy, going the right way, and able to send data back to Earth.
Cassini carries 12 different science instruments, including optical and microwave cameras and spectrometers. One of these instruments is the Ultraviolet Imaging Spectrograph (UVIS). Spectrographs measure the wavelengths and intensities of light coming from objects in space. Every chemical element emits light at a characteristic set of light wavelengths. By looking at the spectral 'fingerprints' of an object, like those generated from UVIS data, scientists can determine what the object's chemical composition is.
Today, you will look at two spectra from the Ultraviolet Imaging Spectrograph (UVIS) that traveled to Saturn aboard the Cassini spacecraft. After you look at these images on the first page, on the second page, you will find the known spectra of four elements, hydrogen (H), helium (He), nitrogen (N) and krypton (Kr).
Match the patterns of peaks and valleys you see in the known spectra with those you see on the spectra from UVIS to determine what elements UVIS is seeing in Saturn's rings and on Titan. Enter your answers on the worksheet provided.
| Spectrum (plural: spectra) || The pattern light produces as can be seen through a
| Spectrometer (also
Spectroscope, Spectrograph) || A tool that allows the components of light to be seen
easily with the eye. |
| Titan || A moon of Saturn that has an incredibly thick
| Microwave || A type of light that can be detected with a Microwave
| Ultraviolet || A type of light that can be detected with an ultraviolet
See also background from the "Graphing a Rainbow" Activity. It is highly recommended that you read the following article: http://www.pbs.org/wgbh/nova/space/how-to-get-an-atmosphere.html
Light is sometimes what scientists call the electromagnetic (E-M) spectrum, of which visible light is only a small portion. Other types of E-M radiation include Gamma Rays, X-Rays, UV, infrared, microwave and radio. Light can be thought of as both a wave and a particle in all cases. The more energetic the particle of light, the shorter wavelength, and hence, smaller frequency, it will have. Gamma rays are the most energetic, and radio are the least.
Spectral patterns of a gas can be shown on a plot such that the x-axis is the wavelength of the light, and the y-axis is the intensity of the light. Plotted in this way, scientists can determine if laboratory measurements of a gas match with data obtained elsewhere because every element has a unique signature. In this activity, students will compare the spectral lines in Titan's and Saturn's atmosphere with laboratory measurements of spectra.
Titan has a thick atmosphere consisting mostly of nitrogen, similar to the Earth's. The gravitational properties of a large moon like Titan are very different from those of a debris field like the rings. Titan's gravity captures atoms like nitrogen that would otherwise escape to space. Unlike Titan's atmosphere, Earth's atmosphere contains oxygen, mostly a result of photosynthesis. Before there were plants, we did not have oxygen in our atmosphere (see figure 1). We might speculate that Titan has no plant life (at least as we know it) because Titan's atmosphere lacks oxygen.
Severely vision-impaired and blind children will have difficulty with this activity. Students with corrective lenses will not have difficulty. Students can be paired to assist them with the activity.
Accessing prior knowledge: Ask students what they can tell you about light. Probe them for what they already know and understand. Ask students if they are familiar with any engineered devices that people use as tools to help them determine values that they cannot "see" i.e. thermometers, barometers, radon detectors, x-ray machines, etc.
Class discussion: Ask students why they think instrumentation is needed to get this type of data, and for what the data could be used. Ask students how they think engineers develop instrumentation. It is important to honor creative answers.
Review answers to questions aloud.
Complete the "Building a Fancy Spectrograph" activity.
Fisher, Diane. "Taking Apart the Light." "The Technology Teacher." March (2002).
Integrated Teaching and Learning Program and Laboratory, University of Colorado at
Laboratory for Atmospheric and Space Physics, University of Colorado at Boulder
Directions: Look at the data on page one and two. Page one shows the spectra of Titan and Saturn's rings. Page two shows known spectra of specific elements. Compare both pages and determine what elements are present in Titan's atmosphere and in Saturn's rings and answer the questions on page three.
a) Titan, October 26, 2004
b) Saturn's rings, June 30, 2004
1. Elements present in spectrum (a), Titan, are:
2. Elements present in spectrum (b), Saturn's rings, are:
3. Why is hydrogen so abundant in these spectra? (Hint: What do you know about the structure of hydrogen and about its
abundance in the universe?)
4. Why do you think nitrogen is present in the spectra from Titan, but not in the spectra of Saturn's rings?
5. Using the tables below, compare and contrast the composition of Titan's atmosphere and Earth's atmosphere. What are some reasons these differences might exist?
| Nitrogen || 95% || Nitrogen || 78% |
| Methane || 3% || Oxygen || 21% |
| Argon || 2% || Argon || 1% |
- Hydrogen and nitrogen
- Hydrogen is the simplest and most abundant element in the universe, so we expect to find it in high concentrations throughout the solar system. The hydrogen signature in the ring spectra, however, actually comes from hydrogen present in interplanetary space. The light shines through the rings and isn't actually emitted by the rings themselves. Supplemental question: What techniques could scientists use to remove the signature of interplanetary gas from their data? Answer: Scientists can compare the spectrum of "empty" space to the spectrum of the object being observed and subtract off the interplanetary "background."
- Titan has an atmosphere. The gravitational properties of a large moon like Titan are very different from those of a debris field like the rings. Titan's gravity captures atoms like nitrogen that would otherwise escape to space. Fun Fact: Nitrogen isn't always visible in Titan's spectrum: it can be seen only during a Titanian aurora, when electrons from the sun become trapped in Saturn's magnetic field and hit Titan's upper atmosphere. This energizes the nitrogen atoms and causes them to emit light.
- Earth's atmosphere reflects its inhabitants, as well as complex chemical processes. Oxygen is present in Earth's atmosphere as a result, among other things, of photosynthesis, the process that plants use to breath. It uses carbon dioxide and gives off oxygen as a by-product. The oxygen in the atmosphere forms our protective ozone layer that shields us from incoming solar radiation. | <urn:uuid:74609cb0-93be-477e-8bff-83c847675c08> | 3.859375 | 2,113 | Tutorial | Science & Tech. | 39.936392 |
Temperatures have increased both over land and water. Some of the heat from global warming gets stored in the world’s oceans causing higher water temperatures near the surface. This figure shows the trend in the heat content of the ocean between the surface and 700 meters deep. Warming of the oceans has many consequences, including sea level rise (warmer water expands), coral bleaching, loss of sea ice, and intensification of hurricanes.
Source: NOAA/NESDIS/NODC Ocean Climate Laboratory, Updated from Levitus et al. (2009) | <urn:uuid:b6b6a321-dc9f-4577-912c-06c973f846b8> | 3.765625 | 114 | Knowledge Article | Science & Tech. | 40.285882 |
The Binary Compatibility Problem
Again, there is no standard C++ ABI. Different compilers (and even different versions of the same compiler) produce different object files and libraries. The most obvious manifestation of this problem is the different name mangling algorithms implemented by different compilers. This means that in general you can only link C++ object files and libraries that were compiled using exactly the same compiler (brand and version). Many compilers don't even implement standard C++ features from the C++98
There are some partial solutions to this problem. For example, if you access a C++ object only through a virtual pointer and call only its virtual methods you sidestep the name mangling issue. However, it is not guaranteed that even the virtual table layout in memory is identical between compilers, although it is more stable.
If you try to load C++ code dynamically you face another issue -- there is no direct way to load and instantiate C++ classes from a dynamic library under Linux or Mac OS X (Visual C++ supports it under Windows).
The solution to this issue is to use a function with C linkage (not name mangled by the compiler) as a factory function that returns an opaque handle to the caller. The caller then casts the handle to the appropriate class (usually a pure abstract base class). This requires some coordination, of course, and works only if the library and the application were compiled with compilers that have a matching vtable layout in memory.
The ultimate in compatibility is to just forget about C++ and expose a pure C API. C is compatible in practice between all compiler implementations. Later I'll show how to achieve C++ programming model on top of C compatibility.
Plugin-Based System Architecture
A plugin-based system can be divided into three parts:
- The domain-specific system.
- A plugin manager.
- The plugins.
The domain-specific system loads the plugins and creates plugin objects via the plugin manager. Once a plugin object is created and the main system has some pointer/reference to it, it can be used just like any other object. Usually, there are some special destruction/cleanup requirements as we shall see.
The plugin manager is a pretty generic piece of code. It manages the life-cycle of the plugins and exposes them to the main system. It can find and load plugins, initialize them, register factory functions and be able to unload plugins. It should also let the main system iterate over loaded plugins or registered plugin objects.
The plugins themselves should conform to the plugin manager protocol and provide objects that conform to the main system expectations.
In practice, you rarely see such a clean separation (in C++-based plugin systems, anyway). The plugin manager is often tightly coupled with the domain-specific system. There is a good reason for that. Plugin managers need to provide eventually instances of plugin objects with certain type. Moreover, the initialization of the plugin often requires passing domain-specific information and/or callback functions/services. This can't be done easily with a generic plugin manager.
Plugin Deployment Models
Plugins are usually deployed as dynamic libraries. Dynamic libraries allow many of the advantages of plugins such as hot swapping (reloading a new implementation without shutting the system), safe extension by third-party developers (additional functionality without modifying the core system), and shorter link times. However, there are situations where static libraries are the best vehicle for plugins. For example, some systems simply don't support dynamic libraries (many embedded systems). In other cases, security concerns don't allow loading foreign code. Sometimes, the core system comes with pre-loaded with some plugins and it is more robust to statically link them to the main executable (so the users can't delete them by accident).
The bottom line is that a good plugin system should support both dynamic and static plugins. This lets you deploy the same plugin-based system in different environments with different constraints. | <urn:uuid:54809bd2-6806-47be-aeee-ca64d27b23cd> | 2.765625 | 804 | Documentation | Software Dev. | 37.577599 |
Source: http://www.popsci.com/science/articl...laws-space-yetOnly a few. Right now, the roughly 20,000 man-made objects orbiting the Earth are less regulated than the cars on a morning commute. Satellites are usually on a fixed path, so the traffic control comes prelaunch. Most can move slightly to maintain orbit, but only a few can maneuver on short notice to avoid a collision. Satellite operators make sure they know where other space objects are so that none come close enough to collide.
The International Telecom Union, a United Nations agency, assigns satellites slots in a geosynchronous orbit 22,000 miles above Earth. Operators must agree to follow ITU rules and to register the orbit, broadcast frequency and purpose of their satellite. Satellite owners also register an “end of life” plan, usually giving a nonfunctioning satellite a boost into an internationally recognized “graveyard orbit.”
Other launches, like those for space shuttles, don’t need any international body’s approval but often need national clearance, such as an FAA license. Most space agencies recognize the value of staying out of one another’s way, though, and register launches with the U.N. Office for Outer Space Affairs, which keeps track of an estimated 93.5 percent of all functional space objects, including about 3,600 active satellites. The current system usually works. The only satellite collision on record is a 2009 bang-up between Russian and American satellites in low Earth orbit. | <urn:uuid:6a2daff9-db19-4c3a-8e85-25f13d785e55> | 3.6875 | 320 | Comment Section | Science & Tech. | 43.974951 |
Have you read the Scanner class's API doc? Do you have any questions about the descriptions there of those two methods?
Please post your questions here.
A token is a string of non blank characters surrounded by white spaces.
The current line ends with a newline character.
Can you post the program you are having trouble with?
What I need is to be able to enter several words separated by space.
Use the nextLine method to read all of what is on the current line. It is possible for the current line to only have a newline character which would return an empty string. | <urn:uuid:9f66e6c0-c9b8-464a-a678-044f81ce5ebc> | 2.984375 | 124 | Q&A Forum | Software Dev. | 64.467619 |
Earth's forests are breathtaking. In fact, trees are effectively the greatest carbon dioxide warehouses to have ever evolved on Earth. For every metric ton of wood created, 1.5 metric tons of carbon dioxide are absorbed and 1 metric ton of oxygen released.
Frighteningly, Earth's forests are dying from a warming world. Will the delegates from 194 countries attending the Doha climate talks acknowledge this and what nature is unequivocally showing atmospheric, biologic and oceanic scientists?
Last week, researchers once again sent an SOS distress call to denizens of Earth -- drought conditions are placing deadly water-stress on forests around the globe. Moreover, Earth's forests and the myriad "ecosystem services" they provide are approaching an irreversible tipping point.
In 2009, the International Union of Forest Research Organizations came to a very bleak conclusion: "The carbon storing capacity of Earth's forests could be lost entirely if the planet heats up 4.5 F above pre-industrial levels." So far, we have increased by about 2 degrees Fahrenheit, which means we are already well on our way toward this fateful threshold. The result of crossing it would be an uninhabitable world.
Rising greenhouse gases are also wreaking unimaginable havoc in the tropical forests, more specifically in the Ferrari of jungles -- the Amazon. The heart of the Amazon has not evolved to contend with winds, never mind fierce winds, nor with drought.
Later the same year, a 100-year drought occurred. Not only did the Amazon fail to absorb 1.5 billion metric tons of carbon dioxide, but also over the next decade it's releasing approximately 5 billion metric tons of carbon dioxide from decomposing trees. If that isn't alarming enough, another mega-drought occurred across 1.16 million square miles in the Amazon in 2010, the second one-in-100-year event within five years. The enormous swath of dead jungle is releasing 8 billion metric tons of carbon dioxide over the next decade. And as the Amazon forests die, the Earth also loses its vast cloud-making machines, forcing it to absorb incoming solar radiation rather than reflect it.
In 2009, the United States alone emitted 5.4 billion metric tons of carbon dioxide from fossil fuel use. These emissions contribute to an equally disconcerting worldwide pattern that is beginning to emerge. Scientists have documented that greenhouse gas emissions have significantly altered global climate -- increasing the frequency, duration and/or severity of drought and heat stress in 88 forests on every wooded continent on planet Earth. If ever there were a clarion wake-up call, this is it, without exception.
All forest types are suffering from a lethal combination of at least three factors: insects and diseases associated with elevated temperatures; the drying out of plants; and carbon starvation, that is, water-stressed trees unable to photosynthesize, or make food. Every decade since 1970 has seen more than a tenth of a degree of additional warming, which has caused less snowfall, declining snowpack water content and longer summer drought periods. Both old and young trees are suffering.
Forests are dying all over the globe. Extreme droughts in North Africa are killing Atlas cedar from Morocco to Algeria. Heat and drought are battering the high-elevation tropical moist forests in Uganda, mountain acacia in Zimbabwe and centuries-old aloe plants in Namibia. Tropical forests of Malaysia and Borneohave also suffered significant death. Drought has also lambasted the tropical dry forests of northwest and southwest India, fir in South Korea, the junipers of Saudi Arabia, and pine and fir in central Turkey. Extensive areas of forest in southwestern and east-central China have now been recognized as being at a high threat of mortality in the ensuing years. Russia too has identified 187.8 million acres of high-threat southern forests, where drought is severely stressing trees. Australia has seen widespread death in acacia woodlands and eucalypt and Corymbia forests. New Zealand has documented drought-induced death in high- elevation beech forests. Oak, fir, spruce, beech and pines across Western Europe are dying too.
Rising greenhouse emissions are elevating temperatures and the occurrence of droughts across western North America. In turn, this is fueling the largest native bark beetle epidemic in modern or past times, dating back over 200 million years. Instead of absorbing carbon dioxide, about 30 billion mature trees are decaying and adding greenhouse gases to the ever-rising atmospheric pool.
Earth's forests are its life-support system. Around the globe they are clearly showing telltale signs of run-away carbon emissions and the effects of rising temperatures, prolonged droughts and massive insect infestations.
We need a carbon tax in America and worldwide. And we need it more than ever -- now!
Reese Halter is a broadcaster, writer and biologist. His latest books are "The Insatiable Bark Beetle" and "The Incomparable Honeybee." | <urn:uuid:63749515-cb25-4d07-86ae-cbce4d0f509a> | 3.609375 | 1,012 | Nonfiction Writing | Science & Tech. | 41.465783 |
Incorporating Climate Change into Conservation
The National Wildlife Federation (NWF) and Manomet Center for Conservation Sciences (Manomet), received funding from the Wildlife Conservation Society in September 2010 to help the conservation community in the Northeast implement on-the-ground climate-smart restoration and management projects.
With state fish and wildlife agencies, we are creating climate-smart projects in three ecosystems: coasts, freshwater and forests.
These pilot projects will test the effectiveness of climate-smart conservation strategies so that natural resource managers across the country have examples to learn from when designing their own climate smart projects.
Learn more: freshwater, forests, coasts
Restoring Freshwater Systems in Massachusetts
With the help of many partners including the Massachusetts Division of Ecological Restoration, Massachusetts Department of Fish and Game, Manomet Center for Conservation Sciences and A.D. Makepeace (among others), NWF is testing climate-smart restoration projects for freshwater systems. In Wareham MA, this partnership is restoring a cold-water fed cranberry bog to a trout stream with a functioning riparian system. The project has also created a monitoring program to record changes in the wetlands and stream that may result from climate change. With this monitoring data, partners will be able to make informed management decisions for the site as the climate continues to change.
Protecting Upland Forests in New York's Adirondacks
National Wildlife Federation will be testing guidance for upland forest ecosystems by working with the Shingle Shanty Preserve and Research Station (SSPRS) in Northern Hamilton and Eastern Herkimer Counties in New York State. New York State is located in the transition zone between northern temperate and boreal eco-zones, meaning that many wildlife species found here are at the edge of their range. In one of the remotest parts of the Adirondacks, the SSPRS has nine lakes and ponds, many miles of the headwater streams, 12,500 acres of upland northern hardwood forests and 2,000 acres of lowland boreal habitats, making it an ideal spot to test climate-smart adaptation strategies.
Protecting Delaware’s Coasts from Sea Level Rise
Delaware Division of Fish and Wildlife (DFW) is developing two climate-smart projects that will address the effects of sea-level on coastal impoundments. One project will repair a dyke in a coastal impoundment and restore a tidal wetland buffer on the seaward side of the impoundment. This project will help DFW maintain the impoundment in the short-term while enabling staff to monitor the effects of sea-level rise on the impoundment and plan longer-term management options. The second pilot project will create an upland impoundment as an alternative for an existing coastal impoundment that might need to be abandoned if sea levels continue to rise.
Learn more about NWF's climate-smart conservation work: | <urn:uuid:9ce7fdb4-aadf-423a-8df7-32cf2fe97b16> | 3 | 600 | Content Listing | Science & Tech. | 24.194172 |
When James Hack came to Oak Ridge National Laboratory in late 2007, he was given two hats: one as the director of ORNL's National Center for Computational Sciences and the other as leader of ORNL's laboratory-wide climate science effort.
In one role, he guides the world's foremost open science supercomputing center. As leader of ORNL's Climate Change Initiative, he is responsible for pulling together scientists and engineers from across the laboratory to address one of the nation's greatest scientific challenges. Hack is uniquely qualified to take on this role. Before coming to ORNL, he headed the Climate Modeling Section at the National Center for Atmospheric Research in Boulder, Colorado, and served as deputy director of the center's Climate and Global Dynamics Division.
We asked Hack about the future of climate science and the climate initiative at ORNL.
Q. How do you see climate research evolving in the coming years?
Climate science has largely been curiosity-driven research, but the growing acceptance that humans affect the evolution of atmospheric composition and land use, which in turn affects the climate state, provides more focus and greater urgency to taking a harder look at what new modeling tools are capable of providing in the form of specific consequences for society.
That to me is the transformation. There's a growing need for improvements in simulation fidelity and predictive skill. The potential consumers of that kind of simulation information will be leaning hard on the climate change community to provide answers to their questions. That's the change that's going to differentiate the next 10 years of climate change science from the previous 30.
Q. Give us an example of this information.
We know from observations over the last 50 years that the snowpack in the Pacific Northwest has been decreasing. At the same time, temperature in the same region has been increasing. If that trend continues, it raises lots of concerns for water resource managers who have counted on storing their water in the form of snow until a certain time of year when it starts melting.
If precipitation never comes down as snow or if it starts melting sooner than we need it, we may not able to meet water demands. This is a good example of an infrastructure that's vulnerable to specific changes in a region's climate state. Many of the solutions to this problem may also bring with them other environmental consequences.
Q. How accurate is climate prediction?
We think we might currently have sufficient skill to project climate change on regional scales about the size of the Southeast, Pacific Northwest, Rocky Mountain West or Farm Belt. As a scientific community we need to demonstrate the potential and quantify the uncertainties. Although thus far we haven't done a very good job with this challenge, climate researchers are starting to realize that we have an opportunity to take a step back and ask, "What can we do on regional scales and timescales that we think are predictable?"
For example, there's a belief that climate statistics have some predictive skill on decadal timescales. The driver for that is going to reside in the ocean, where motion scales have a very, very long time frame. There is a belief in the scientific community that the ocean's behavior can be predicted several decades into the future.
If we can solve the ocean part of the problem, given the fact that 70 percent of the planet is covered with water, we have a very strong constraint on the other parts of the system. The question then becomes, "Will the other component models follow?"
Q. How do you convince critics that you're getting it right?
We develop numerical experiments to assess whether the global model can produce useful information on the timescales and space scales of most importance to resource managers and planners. They may want to know where the temperature's headed locally, how the hydrological cycle is likely to behave, or how extreme events will change. Do the models provide us with the kind of predictive skill we need, and if not, how can they be improved?
Q. What is the role of computing in this effort?
fully evaluate the skill in our modeling tools, we need very large computer systems—petascale machines. Assimilating data streams that will be used in the evaluation of modeling frameworks requires very large computer and data systems.
Clearly, a significant computational piece is modeling—building models that have all the components they need to accurately predict the evolution of the earth's climate system. That's computationally very intensive. Incorporating the complexities of the carbon cycle in these models, using the expertise of ORNL's Environmental Sciences Division, contributes to the computational demands. And then mining the data to deal with questions of human impacts and climate extremes is also very computationally intensive.
So, computation in fact ties the whole effort together. It cuts across all the various climate science applications. There are certain areas of science where you need a virtual laboratory to explore the "what-if" experiments, which is what computation provides for the climate problem.
Q. You are leading a new multidisciplinary effort at ORNL focused on climate science. What is the goal?
ORNL has identified climate change as an opportunity that could very effectively exploit existing competencies, particularly high-performance computing and ORNL's long history in contributing to fundamental knowledge about carbon science and in global modeling. The lab also has expertise in evaluating impacts on societal infrastructure. Take rising sea levels. Most of the folks living around the world live close to coastlines, so if the sea level rises even a meter, it has a huge societal impact. The people who are displaced must go somewhere else, maybe moving into areas that were previously used for agriculture. That displaces agricultural activities. ORNL has a very strong geographic information systems group that can contribute to quantification of these scenarios.
We are looking at how we can bring these various competencies together to provide a capability that's unique among the laboratories. The goal is to provide stakeholders, resource managers and others with information they need to deal with the consequences of climate change.
Q. What will ORNL's climate initiative look like?
We're trying to engage people from across the laboratory to stretch the kind of work they're doing in such a way that it requires partnerships with other ORNL staff. So far, many of the more promising proposals include collaborations that cut across the directorates of Biological and Environmental Sciences and Computing and Computational Sciences.
As the initiative matures, I hope we'll begin to incorporate more people in the energy arena, another strong part of the ORNL scientific program. These things could include ways to link climate change and the hard questions we're facing in energy production, like bioenergy and renewable energy technologies, as well as energy consumption. Dealing directly with climate mitigation questions, such as strategies for the sequestration of carbon, is an opportunity for this initiative.
From an energy production point of view, planning has a multidecadal timeframe. Anyone planning investments in the energy infrastructure needs to understand what role the environment might play. That's the goal—to be able to say 20 years from now, "Here's what we anticipate will happen with environmental change on a regional scale."
Web site provided by Oak Ridge National Laboratory's Communications and External Relations | <urn:uuid:bb5bf013-07a4-4d9a-a643-481fc47e48dc> | 2.9375 | 1,457 | Audio Transcript | Science & Tech. | 35.02972 |
Basic Terminology and Concepts<
Learn about the wealth of natural resources associated with energy.Flickr Physics
Visit The Physics Classroom's Flickr Galleries and enjoy a visual overview of the topic of work, energy and power.Particle Physics
Learn about the energy of small particles like those studied by particle physicists.
Use this interactive Shockwave game to help your students understand the speed-KE relationshipCurriculum Corner
Learning requires action. Give your students this sense-making activity from The Curriculum Corner.Treasures from TPF
Need ideas? Need help? Explore The Physics Front's treasure box of catalogued resources for teaching about energy.Cosmic Collisions
Learn about asteroid collisions, impact cratering and the theory on dinosaur extinction.
Kinetic energy is the energy of motion. An object that has motion - whether it is vertical or horizontal motion - has kinetic energy. There are many forms of kinetic energy - vibrational (the energy due to vibrational motion), rotational (the energy due to rotational motion), and translational (the energy due to motion from one location to another). To keep matters simple, we will focus upon translational kinetic energy. The amount of translational kinetic energy (from here on, the phrase kinetic energy will refer to translational kinetic energy) that an object has depends upon two variables: the mass (m) of the object and the speed (v) of the object. The following equation is used to represent the kinetic energy (KE) of an object.
where m = mass of object
v = speed of object
This equation reveals that the kinetic energy of an object is directly proportional to the square of its speed. That means that for a twofold increase in speed, the kinetic energy will increase by a factor of four. For a threefold increase in speed, the kinetic energy will increase by a factor of nine. And for a fourfold increase in speed, the kinetic energy will increase by a factor of sixteen. The kinetic energy is dependent upon the square of the speed. As it is often said, an equation is not merely a recipe for algebraic problem solving, but also a guide to thinking about the relationship between quantities.
Kinetic energy is a scalar quantity; it does not have a direction. Unlike velocity, acceleration, force, and momentum, the kinetic energy of an object is completely described by magnitude alone. Like work and potential energy, the standard metric unit of measurement for kinetic energy is the Joule. As might be implied by the above equation, 1 Joule is equivalent to 1 kg*(m/s)^2.
Use your understanding of kinetic energy to answer the following questions. Then click the button to view the answers.
1. Determine the kinetic energy of a 625-kg roller coaster car that is moving with a speed of 18.3 m/s.
2. If the roller coaster car in the above problem were moving with twice the speed, then what would be its new kinetic energy?
3. Missy Diwater, the former platform diver for the Ringling Brother's Circus, had a kinetic energy of 12 000 J just prior to hitting the bucket of water. If Missy's mass is 40 kg, then what is her speed?
4. A 900-kg compact car moving at 60 mi/hr has approximately 320 000 Joules of kinetic energy. Estimate its new kinetic energy if it is moving at 30 mi/hr. (HINT: use the kinetic energy equation as a "guide to thinking.") | <urn:uuid:51462d98-b174-47c0-b266-5819ea5c9ba4> | 4.21875 | 720 | Tutorial | Science & Tech. | 47.279196 |
On 16-12-2010, in Picture stories, by phil
The wind and the general flow of air and ocean currents around our planet is of great importance to aviators and sailors alike. It is often hard to visualise exactly what is going on. Satellite pictures can show us a lot, not only for illustrating the weather forecasts we all see on TV, but sometimes also for helping us to visualise what is happening.
I was looking through a few satellite pictures recently and was struck by how similar fluid flow looks in different scales, whether it is in the atmosphere or in the oceans. We are all used to looking at the water in rivers and streams and seeing all the little eddies but we are not so familiar with what happens on a larger scale.
The first four satellite photos below show what is happening in the sea. In the first two the swirling currents are made visible by the plankton in the water, and in the second two by the drifting ice. For those of us who sail, it explains the odd changes of current a boat can be subjected to despite what the tide tables say.
The US Geological Survey has put together several collections called Earth As Art. They feature Landsat satellite images selected for their artistic quality, rather than for scientific reasons. The Landsat programme is a series of Earth-observing satellite missions jointly managed by NASA and the US Geological Survey. Since 1972, Landsat satellites have collected information about Earth from space. The images are presented in “false colour” – satellites use both visible and invisible parts of the electromagnetic spectrum. Near-infrared light is invisible to the human eye, but adding it to these images allows scientists to “see” the surface of the Earth in other than natural colours.
In the style of Van Gogh’s painting “Starry Night,” massive congregations of greenish phytoplankton swirl in the dark water around Gotland, a Swedish island in the Baltic Sea. Phytoplankton are microscopic marine plants that form the first link in nearly all ocean food chains. Population explosions, or blooms, of phytoplankton, like the one shown here, occur when deep currents bring nutrients up to sunlit surface waters, fuelling the growth and reproduction of these tiny plants.
Electric blue-coloured plankton blooms swirl in the North Atlantic ocean off Ireland. Plankton, the most abundant type of life found in the ocean, are microscopic marine plants that drift on or near the surface of the sea. While individually microscopic, the chlorophyll they use for photosynthesis collectively tints the surrounding ocean waters, providing a means of detecting these tiny organisms from space with dedicated ‘ocean colour’ sensors.
Like distant galaxies amid clouds of interstellar dust, chunks of sea ice drift through graceful swirls of ice in the frigid waters of Foxe Basin near Baffin Island in the Canadian Arctic.
Along the south-eastern coast of Greenland, an intricate network of fjords funnels glacial ice to the Atlantic Ocean. During the summer season, newly calved icebergs join slabs of sea ice and older weathered bergs in an offshore slurry that the southward-flowing East Greenland Current sometimes swirls into stunning shapes. Exposed rock of mountain peaks, tinted red in this image, hints at a hidden landscape.
But what is also interesting is that the same patterns can be found on a much smaller scale in a flame…
This image of a flame struggling for existence milliseconds before it is snuffed out by a blast of cold air has won a scientist a top award. It is the winning image in the Engineering photo competition at the University of Cambridge and was taken as part of a research project into the physics of flame extinction. Dr Rob Gordon, a Royal Society Newton International Fellow, was examining flame structures to prevent aircraft jet engines losing power due to flames suddenly going out. The photograph was taken using two high-speed cameras working at 5000 frames per second.
And for those of us who fly, the atmosphere is where we work, move and have our being. We are all used to the patterns created by fontal depressions that sweep across the temperate latitudes as seen in these pictures of the Earth.
Severe storm in California as seen from space.
But have you ever seen pictures of the vortices found downwind of island peaks and mountains?
Creating a striking design which looks a bit like a serpent swimming through clouds, curling patterns of eddies are formed as air flows around and over the island of Tristan de Cunha in the South Atlantic. These spiraling cloud patterns, caused when prevailing ocean winds encounter an island, are known as von Karman vortices or ‘vortex streets’. Home to about 275 people, Tristan de Cunha is considered to be the most remote inhabited island in the world, lying 2,816km (1,750 miles) from South Africa, the nearest land, and 3,360km from South America.
The steady south, southwest flow of bright white clouds on the Portuguese trade winds is dramatically interrupted by the island of Maderia and by the Canary Islands, resulting in swirls and eddies on the leeward side of each island. In the northeast corner of the image, the island of Maderia, Portugal, rises 1,862 meters (6,109 feet) above the ocean surface. On the day this image was captured, large fires were burning on the island and a wide plume of gray smoke can be seen trailing from the island.
Back on Earth, we poor souls, at the mercy of the elements, just see it all as chaotic weather, rain, winds, snow and turbulence. And when at sea, the unexpected ocean currents that set us towards the rocks.
Pictures from NASA and University of Cambridge | <urn:uuid:8ad4706e-b583-4b9e-ad7e-35011fc299a4> | 3.484375 | 1,211 | Personal Blog | Science & Tech. | 43.243735 |
Could nanomaterials hold the answer to reversing the effects of UV radiation?
By Sherrie Negrea
The link between sunlight and skin cancer is widely accepted — the absorption of ultraviolet radiation can damage skin cells. Exactly how the sun’s radiation breaks down the DNA within cells is a process that Changhong Ke, assistant professor of mechanical engineering, has spent the past six years trying to understand.
At first, Ke used an atomic force microscope with an extremely sharp tip to observe the single- or double-strand breaks that radiation causes in DNA molecules. More recently he has collaborated with Jie (Jayne) Wu, associate professor of electrical and computer engineering at the University of Tennessee, to use an electrical field to separate the DNA based on the impairment it has experienced.
“This can help us understand the damage caused by the radiation, and it can be used to study the repair of DNA,” Ke says. “You have to know how much damage occurred before you even consider repairing the DNA.”
Ke’s research on detecting DNA damage is one example of how he has integrated biology and physics with mechanical engineering at the nano level. While he is conducting foundational research, Ke says the tools he has developed to observe DNA molecules could be applied to evaluate new therapeutic drugs designed to rebuild impaired cells.
“Our tools can help determine how efficient the drug is,” Ke says. “If 50 percent of a cell’s DNA has been damaged and, after drug treatment, only 20 percent of the total DNA is still damaged, then the drug has fixed 60 percent of the damaged DNA.”
After earning a bachelor’s degree at Beijing Institute of Technology, Ke completed a doctoral degree in mechanical engineering at Northwestern University, where he focused on nanomechanics. It wasn’t until he began a post-doctoral fellowship at Duke University that he delved into biophysics, the study of the physical properties of biomolecular structures.
At Duke, Ke was part of a team of scientists who were the first to measure the force between the nucleotides in a single-stranded DNA molecule with an atomic force microscope. By quantifying a single strand of DNA, the Duke scientists could separate the effects of the two principal forces that characterize the double helix structures — the stacking force between base units along the length of the helix and the pairing force between opposing base units that form its rungs.
After arriving at Binghamton in 2007, Ke began a new area of research with many potential applications — nanotubes. These hollow structures form low-density, high-strength materials that can be used for tasks ranging from drug delivery to spacecraft development. When thousands of nanotubes are joined together, they’re still thinner than a single strand of hair.
In 2010, Ke was one of 43 researchers nationwide selected for the Air Force’s Young Investigator Research Program, which supports scientists and engineers who have received a PhD in the past five years and who show exceptional ability and promise for conducting basic research. With a grant of $120,000 annually for three years, Ke is investigating whether nanotubes, formed from either carbon or boron nitride, could enable the Air Force to reduce the weight of vehicles such as fighter planes and spacecraft.
In another angle of this research, Ke is combining the carbon nanotubes with DNA molecules to create a hybrid material that may have therapeutic applications. Working with Assistant Professor of Mechanical Engineering Pong-Yu “Peter” Huang, Ke is attempting to determine how strong the bond is between the DNA and the nanotubes and, conversely, how much force is required to separate the two materials after they interact. That question will have a bearing on potential applications because once the DNA wraps around these nanotubes, the DNA can no longer perform its chemical functions and is rendered useless.
“If you use these as some sort of drug delivery agents for gene therapy, you want to know exactly what kinds of impact they have when these carbon nanotubes are injected into cells,” says Huang, who has been collaborating with Ke since 2010.
In his nanomechanics laboratory, Ke works with three graduate and two undergraduate students, often conducting research late into the night. One of his students, Meng Zheng, who received his PhD in mechanical engineering in May 2012, has published nine journal articles with Ke and given four presentations at national and international conferences.
What impressed Zheng in the four years he worked for Ke was his dedication and his attitude toward his research. “I learned a lot from his research skills — how to define a problem, how to analyze a problem and how to solve a problem,” Zheng says. “He’s also a kind-hearted person and he can motivate people. He’s the best professor I’ve had in my life.” | <urn:uuid:b3132479-2c06-4804-81d2-311b8d98a5ff> | 3.25 | 1,010 | Nonfiction Writing | Science & Tech. | 32.642573 |
There are three resident killer whale populations found between Washington state and Alaska. These whales are called residents, because they spend about half of the year foraging in inland waters, and rely almost exclusively on salmon as prey. The southern resident killer whales (SRKW) are the most threatened population. They experienced an unexplained 20.4% population decline between 1995-2001. The population remained stable from 2001-2005. However, five individuals (5%) were lost in 2006 and seven (8%) were lost in 2008 (Center for Whale Research, pers. comm.). This is an alarming rate of decline for an already small population.
Three primary hypotheses have been proposed to explain the decline:
1) Decline in the whales’ primary prey, Chinook salmon;
2) Disturbance from private and commercial whale watching vessels; and
3) Exposure to high levels of toxicants (e.g. PCB, PBDE and DDT), which are stored in the whales’ fat.
Hypotheses 2 and 3 likely interact with Hypothesis 1 since the impacts of boats and toxicants may be exacerbated by the lack of prey.
Understanding the relative impacts of these three pressures is vital to mitigating further SRKW losses given the considerable economic and political impacts associated with any one of them. The Center for Conservation Biology is partitioning these pressures by using a combination of noninvasive measures of stress and nutrition hormones as well as toxicants from feces. Scat samples are located by Conservation Canines (specially trained scat detection dogs) that are able to locate samples floating on the water from as far away as a nautical mile from the whales and, therefore, from distances unlikely to disturb the whales.
We rely on Tucker, a Conservation Canine, to help us acquire enough scat samples to test these hypotheses. The boat moves perpendicular to the wind with Tucker and his handler secure on the bow of the boat. However, the specific orientation of the boat is varied with whale movements relative to wind direction so that the wind blows the scent from any scat in the water towards the dog: For whales moving in the direction of the wind-the boat moves immediately behind the whale(s) and conducts an upwind zigzag away from the whales. The width of the zigzag is the same as the area covered by the whales. For whales moving into the wind-the boat follows in a zigzag >100 meters behind the whales. For whales moving perpendicular to the wind-the boat positions at a 45° angle, again > 100 meters behind the group of whales.
Tucker indicates that he has detected a killer whale scat in the water by changing his behavior from passive (Figure 1a) to highly animated (Figure 1b). When this occurs, the handler directs the boat driver to steer into the wind. Tucker maintains his position for as long as the scent concentration is increasing. As as soon as the scent concentration begins to decrease, Tucker stands up and looks backwards, indicating the scent is behind him. We respond by turning the boat perpendicular to the wind until the dog’s animation returns. The boat again turns into the wind. We repeat this process until we arrive at the sample.
The dog is rewarded by a game of tug-o-war with his WestPaw ball as soon as the sample is collected. Once spotted, the sample (Figure 2) is collected with a net or specially designed poop scooper.
Each sample is extracted and assayed for stress, reproductive and nutrition hormones (glucocorticoids, GCs; tri-iodothyronine, T3, testosterone, estrogens and progestins), as well as for toxicants (PCB, PBDE and DDT congeners).
These physiological products are then examined over time and in relation to independent measures of Fraser River Chinook salmon abundance (the primary prey of the killer whales while in the study area) and boat densities over time. Scientists at the Northwest Fisheries Science Center also analyze our samples for prey DNA to see what the whale ate, and host DNA to determine the individual whale’s identity and sex.
Both prey and boat densities are low when the whales arrive in the study area during late spring. Prey and boat densities peak around the same time in August. Glucocorticoids (GCs; also known as cortisol) rise in response to both psychological and nutritional stress, increasing mobilization of glucose to provide quick energy to respond to the immediate emergency. Temporal changes in GCs indicate that lack of prey is having the greatest impact on killer whales since GCs are lowest in August when prey and boats are most abundant and highest in late fall when prey and boats are at their lowest (Figure 3).
Thyroid hormone also corresponds to nutritional stress. It declines in response to nutritional stress, lowering metabolism so that animals will more conservatively use their remaining resources. This response is slower and more sustained than is the GC response. Also, unlike GCs, thyroid hormone is unresponsive to psychological stress. Interestingly, thyroid hormone is at its highest when the whales arrive in late spring, despite the relatively low abundance of Fraser River Chinook salmon at that time. This suggests that the whales arrive in our study area after feeding on a rich food source earlier that spring. The data indicate that prey source to be early spring runs of Chinook salmon, known to have exceedingly high fat content to sustain them for their long spawning trips upstream. The Columbia River is one likely source of such fish, indicating that their protection may be critical to ensure killer whale population stability. Thyroid hormone begins to decline upon killer whale arrival in the study area, reaching a plateau when the Fraser River Chinook peak, and then continues to decline as the Fraser River Chinook run subsides in the fall. These responses further corroborate the nutritional impacts on this population. Note also the between year variation in all of these measures (Figure 3).
The toxin work is just getting underway. Thus far, we have validated our ability to acquire PCB, PBDE and DDT congeners from killer whale scat. The relative concentrations of these congeners are similar to those measured in killer whale biopsy samples.
Mitigation efforts to increase the abundance and quality of available prey to Southern resident killer whales will be an important first step towards assuring SRKW recovery. Toxin work will further contribute to understanding the effects of environmental pressures on this population.
Ayres, Katherine L., Rebecca K. Booth, Jennifer A. Hempelmann, Kari L. Koski, Candice K. Emmons, Robin W. Baird, Kelley Balcomb-Bartok, M. Bradley Hanson, Michael J. Ford, Samuel K. Wasser. 2012. Distinguishing the Impacts of Inadequate Prey and Vessel Traffic on an Endangered Killer Whale (Orcinus orca) Population. PLoS ONE 7(6): e36842.
This work is being conducted as part of the dissertation research of Katherine Ayres and Jessica Lundin in our Center. Collaborators include the Center for Whale Research, the Whale Museum , the Northwest Fisheries Science Center and Cascadia Research.
Support for this project is being provided by:
*The Washington Sea Grant, University of Washington, pursuant to NOAA Award No. NA10OAR417005
*NOAA, Northwest Fisheries Science Center
*The Canadian Consulate General
*The Center for Conservation Biology
*The Northwest Science Association | <urn:uuid:c26bd81b-0087-4cf5-a318-215af20ef96b> | 3.328125 | 1,532 | Academic Writing | Science & Tech. | 40.591014 |
Sticky and blunt ends
||This article relies largely or entirely upon a single source. (June 2009)|
DNA end or sticky end refers to the properties of the end of a molecule of DNA or a recombinant DNA molecule. The concept is important in molecular biology, especially in cloning or when subcloning inserts DNA into vector DNA. All the terms can also be used in reference to RNA. The sticky ends or cohesive ends form base pairs. Any two complementary cohesive ends can anneal, even those from two different organisms. This bondage is temporary however, and DNA ligase will eventually form a covalent bond between the sugar-phosphate residue of adjacent nucleotides to join the two molecules together.
Single-stranded DNA molecules
A single-stranded non-circular DNA molecule has two non-identical ends, the 3' end and the 5' end (usually pronounced "three prime end" and "five prime end"). The numbers refer to the numbering of carbon atoms in the deoxyribose, which is a sugar forming an important part of the backbone of the DNA molecule. In the backbone of DNA the 5' carbon of one deoxyribose is linked to the 3' carbon of another by a phosphate group. The 5' carbon of this deoxyribose is again linked to the 3' carbon of the next, and so forth.
Variations in double-stranded molecules
When a molecule of DNA is double stranded, as DNA usually is, the two strands run in opposite directions. Therefore, one end of the molecule will have the 3' end of strand 1 and the 5' end of strand 2, and vice versa in the other end. However, the fact that the molecule is two stranded allows numerous different variations.
Blunt ends
The simplest DNA end of a double stranded molecule is called a blunt end. In a blunt-ended molecule both strands terminate in a base pair. Blunt ends are not always desired in biotechnology since when using a DNA ligase to join two molecules into one, the yield is significantly lower with blunt ends. When performing subcloning, it also has the disadvantage of potentially inserting the insert DNA in the opposite orientation desired. On the other hand, blunt ends are always compatible with each other. Here is an example of a small piece of blunt-ended DNA:
Overhangs and sticky ends
Non-blunt ends are created by various overhangs. An overhang is a stretch of unpaired nucleotides in the end of a DNA molecule. These unpaired nucleotides can be in either strand, creating either 3' or 5' overhangs. These overhangs are in most cases palindromic.
The simplest case of an overhang is a single nucleotide. This is most often adenosine and is created as a 3' overhang by some DNA polymerases. Most commonly this is used in cloning PCR products created by such an enzyme. The product is joined with a linear DNA molecule with 3' thymine overhangs. Since adenine and thymine form a base pair, this facilitates the joining of the two molecules by a ligase, yielding a circular molecule. Here is an example of an A-overhang:
Longer overhangs are called cohesive ends or sticky ends. They are most often created by restriction endonucleases when they cut DNA. Very often they cut the two DNA strands four base pairs from each other, creating a four-base 5' overhang in one molecule and a complementary 5' overhang in the other. These ends are called cohesive since they are easily joined back together by a ligase. Also, since different restriction endonucleases usually create different overhangs, it is possible to cut a piece of DNA with two different enzymes and then join it with another DNA molecule with ends created by the same enzymes. Since the overhangs have to be complementary in order for the ligase to work, the two molecules can only join in one orientation. This is often highly desirable in molecular biology.
For example, these two "sticky" ends are compatible:
5'-ATCTGACT + GATGCGTATGCT-3' 3'-TAGACTGACTACG CATACGA-5'
They can form complementary base pairs in the overhang region:
GATGCGTATGCT-3' 5'-ATCTGACT CATACGA-5' 3'-TAGACTGACTACG
Frayed ends
Across from each single strand of DNA, we typically see adenine pair with thymine, and cytosine pair with guanine to form a parallel complementary strand as described below. Two nucleotide sequences which correspond to each other in this manner are referred to as complementary:
A frayed end refers to a region of a double stranded (or other multi-stranded) DNA molecule near the end with a significant proportion of non-complementary sequences; that is, a sequence where nucleotides on the adjacent strands do not match up correctly:
The term "frayed" is used because the incorrectly matched nucleotides tend to avoid bonding, thus appearing similar to the strands in a fraying piece of rope.
Although non-complementary sequences are also possible in the middle of double stranded DNA, mismatched regions away from the ends are not referred to as "frayed".
- Sambrook, Joseph; David Russell (2001). Molecular Cloning: A Laboratory Manual. New York: Cold Spring Harbor Laboratory Press. | <urn:uuid:9f37938d-51ad-4fdd-91bd-b408bda81be8> | 4.03125 | 1,150 | Knowledge Article | Science & Tech. | 38.543541 |
Brief SummaryRead full entry
North American Ecology (US and Canada)Polites origenes is a year-round resident in the eastern United States and into southern Canada (Scott 1986). Habitats are Gulf Coast to transition zone dry meadows (damp meadows eastward), open woodland and prairie. Host plants are grasses, with most known hosts Tridens flavus, Andropogon scoparius. Individuals overwinter as third and fourth instar larvae. In the northern part of their range there is one flight each year with the approximate flight time late June ? July 15 and in the southern part of their range two flights with approximate times between May 1-Oct. 31 (Scott 1986). | <urn:uuid:00caa329-7629-44f7-9bad-2ebb3f0640ac> | 2.75 | 145 | Knowledge Article | Science & Tech. | 50.198962 |
Magnetic Portals Found In Earth's Atmosphere
I almost posted this in another forum site because it opens up all kinds of interesting thoughts...
Magnetic Portals Found in Earth’s Atmosphere
July 3rd, 2012
– Science-fiction writers have toyed with the concept of a portal for many years, and scientists have been trying to discover such a structure in real life. A new study backed by NASA has revealed the existence of a so-called magnetic portal, connecting the atmospheres of the Earth and the Sun.
Usually, a portal is defined as an opening through spacetime that enables a traveler to move over great distances, or over time, instantly. In other words, it represents a shortcut, or maybe a guiding pathway to a particular destination.
Using funds provided by the American space agency, experts at the University of Iowa have recently been able to discover electron diffusion regions (X-points), where the magnetic field of Earth connects directly to the magnetic field of the Sun.
This link creates an uninterrupted path leading from our own planet to the Sun’s atmosphere,” more than 93 million miles (157 million kilometers) away,” says UI plasma physicist Jack Scudder.
The observations that led to this conclusion were carried out using the Cluster constellation – which is operated by the European Space Agency (ESA) – and the NASA Time History of Events and Macroscale Interactions during Substorms (THEMIS) mission.
The satellites indicate that the magnetic portals open and close several times per day, and that they are located around only a few tens of thousands of kilometers away from Earth. They prefer to appear at locations where the geomagnetic field meets incoming solar winds.
These portals can be either short-lived, or can last for a longer time, allowing highly energetic particles to flow right through. These particles can heat the planet’s upper atmosphere, create geomagnetic storms, and spawn very bright auroras.
NASA plans to study these magnetic portals in more detail, once it launches the Magnetospheric Multiscale Mission (MMS), in 2014. The constellation will feature four identical satellites.
All the vehicles will study magnetic reconnection, a process that occurs high above the planet, and which can provide telltale signs regarding the formation of magnetic portals. Each of the MMS spacecraft will have the ability to detect these clues, and then alert the others of the impending event.
"Happiness can only come from inside of you and is the result of your love. When you are aware that no one else can make you happy, and that happiness is the result of your love, this becomes the greatest mastery of the Toltecs: the Mastery of Love." ~~don Miguel Ruiz~~ | <urn:uuid:886fe09d-21e2-4932-a012-f304f5a9c8dd> | 2.828125 | 562 | Comment Section | Science & Tech. | 36.823622 |
5.5. Surface Brightness of Single and Double Galaxies
One of the general indicators of galactic structure is the mean surface brightness, B. This may be measured by various techniques depending on the chosen isophotal diameter system. The values of surface brightness presented in Appendix 2 are determined from
In other words, the integrated apparent magnitude of the galaxy mHoc is equivalent to the quantity BT0 in the RCBG catalogue, corresponding to the area within the standard isophote at 25m / sq.arc sec. The transformation from observed diameters and magnitudes to the (a25, mHoc) system was described in section 2.2. As usual, surface brightness is expressed in stellar magnitudes per square arcsecond.
The differentiation of galaxies by surface brightness, according to their location in pairs, groups, clusters or the field, has received insufficient attention in the literature. Bertola et al. (1971) noted that among 600 Zwicky (1971) compact galaxies, the percentage of double and multiple objects was noticeably higher than among single galaxies. The possibility of a relation between a galaxy's surface brightness and the location of its nearest neighbour was considered by Kormendy (1977), Zonn (1974) and Arakelyan and Magtesian (1981). These last two studies compared the catalogues of isolated (Karachentseva, 1973) and double (Karachentsev, 1972) galaxies, but their results appear contradictory. According to Zonn (1974), isolated and double spiral galaxies have the same mean surface brightness, while isolated ellipticals appear to be somewhat more compact. According to Arakelyan and Magtesian (1981), however, there is no significant difference between elliptical objects in both catalogues, but an excess surface brightness for the spiral components of double systems. A fresh and detailed comparison of the surface brightness for single and double galaxies was made by Karachentsev et al. (1985). In that study, the apparent magnitude and angular diameters of isolated galaxies were transformed to the common system (a25, mHoc) used for double galaxies. The following results are taken from that work.
Figure 38 shows the distribution of single galaxies (filled circles) and double galaxies (open circles) of all types, as a function of the surface brightness calculated according to (5.2). Both distributions follow a symmetric normal distribution very closely, with almost identical means (22.72 ± 0.02 for single galaxies, and 22.69 ± 0.02 for double galaxies), but with significantly different standard deviations, 0.82 and 0.60 respectively. Therefore, the presence of close neighbours to a galaxy does not change the maximum of the distribution but it is possible that the selection of objects for the catalogue may have excluded objects with extremely high or extremely low surface brightnesses.
Excluding contact pairs, for which the respective magnitudes of the galaxies were calculated from a total magnitude using (2.11), we constructed the bivariant distribution of B for the brighter and fainter components of double systems. It agreed excellently with the bivariant normal distribution, with the same mean and standard deviation, and a correlation coefficient of +0.37. The high degree of correlation between the surface brightnesses of pair members may probably be explained as due to their simultaneous formation. Thus, the correlation of B for components of close pairs is no higher than for wide pairs, since interactions as a cause of this correlation should not induce any particular value.
The dependence of the mean surface brightness of double and isolated galaxies on morphological and spectral types is shown in table 26, which lists the mean value of each quantity and the standard deviation of the mean. These data show that the mean surface brightness of double galaxies decreases monotonically on going from objects with absorption line spectra to objects with rich emission spectra. The amplitude of this effect is around 0.45 magnitudes and appears to be similar for galaxies of different morphological types. This trend is in agreement with the compendium by Arakelyan (1975) in that high surface brightness is anticorrelated with the presence of strong emission characteristics. This correlation between spectral types and compactness may have several causes, which we will now examine.
Figure 39 shows the distribution of 974 pair members by absolute magnitude and linear diameter. The straight line indicates the mean surface brightness, <B> = 22.69m / sq.arc sec. Dwarf galaxies are characterized by their greater mean compactness compared to giant systems. The quantitative relation between mean surface brightness and linear diameter is
where the diameter A25 is in kiloparsecs. It follows from table 27 that increasing richness in the emission line spectrum correlates with a decrease in both luminosity and linear diameter. This trend may be explained by postulating that the evolution of dwarf galaxies proceeds at a slower rate, so that they may normally retain their original levels of gas and therefore have the raw material for active star formation at the present epoch.
Consider again the data in table 26, showing the connection between surface brightness and morphological type. For components of double systems, the mean surface brightness is practically the same for all structural types, while isolated galaxies display a change on going from late types to early types. The greatest difference is observed for E and S0 galaxies, and isolated elliptical galaxies exceed pair components by a full magnitude in surface brightness. This agrees with Zonn (1974) but contradicts Arakelyan and Magtesian (1981). A detailed analysis shows that this last study is strongly affected by selection. Among isolated elliptical galaxies a considerable fraction are listed in the Zwicky catalogue as compact or very compact. Arakelyan and Magtesian used measurements of galaxy diameters from the MCG catalogue and therefore did not consider about 60% of the isolated E galaxies, predominantly the most compact ones, which has the effect of producing an artificially low estimate of the mean surface brightness. It is possible that field elliptical galaxies form a separate category of objects with structural properties not encountered among elliptical members of systems. Thus, Kormendy (1977) noticed the absence around isolated galaxies of the extended haloes characteristic of E galaxies with nearby massive companions. Kormendy ascribed this property to the recent operation of tidal effects.
Arakelyan and Magtesian (1981) demonstrated that the mean surface brightness of double galaxies decreases with increasing linear separation, asymptotically approaching the value for isolated galaxies for X 200 kpc. We show this dependence for the entire sample of 487 physical double systems in figure 40 by the filled circles, with error bars indicating the standard deviation of the mean. Excluding the single point in the interval 80 - 100 kpc, these values fall along the descending curve, which drops by B = 0.7m. Karachentsev et al. (1985) examined two effects which might produce such a dependence.
1. In tight pairs in which the mutual separation of the components is comparable to their diameters, tidal stripping of the outer regions of the disk will occur. The tidal effects increase with greater proximity of the galaxies to one another, so that members of contact pairs should have the highest surface brightness.
2. The decreasing number of compact objects on passing from tight pairs to wide pairs may be a selection effect. The inclusion of pairs in the catalogue depends on the angular diameters and apparent magnitudes of the galaxies, as much as on the angular separation. Two galaxies with a large separation will have a higher probability of satisfying the isolation criteria, the larger their angular diameter is compared to the surrounding field galaxies. Therefore, galaxies in wide pairs should be distinguished by lower surface brightness than members of tight pairs.
To estimate such selection we again used the results of the modelling of the apparent distribution of galaxies and the resulting selection of double systems (see section 3.1). The dependence of mean surface brightness in the model pairs on their linear separation is shown in figure 40 as diamonds whose height denotes the standard deviation of the mean (9) It follows from these results that selection effects in the catalogue can explain most of the effect observed for the real galaxy pairs. A small part (~ 0.2m) of the surface brightness for members of tight pairs with X < 30 kpc might also be explained by tidal effects during interaction. However, any dynamical changes in the structure of galaxies are not easy to distinguish from possible errors in measuring the diameters of galaxies which are extremely close and, perhaps, overlapping one another.
9 According to the adopted relation (3.3), the model galaxies have <B> = 23.63m/sq.arc sec., with standard deviation 0.8. In order to compare the observed and model means we shifted the model values to a fixed ordinal. Back. | <urn:uuid:000725e0-823f-4a22-8fbd-c1e9c11b2668> | 3.53125 | 1,800 | Academic Writing | Science & Tech. | 36.996355 |
Historically, the term Tesla principle was used to describe (amongst other things) certain reversible processes invented by Nikola Tesla.Electrical Experimenter, January 1919. p. 615. However, this phrase is no longer in conventional use. It was developed during Tesla's research in alternating currents where the current's magnitude and direction varied cyclically.
A reversible process in engineering is a process or operation of a system or device such that a net reverse in operation will accomplish the converse of the original function. The principle was that some systems could be reversed and operated in a complementary manner. During a demonstration of the Tesla turbine, the disks revolved and machinery fastened to the shaft was operated by the engine. If the turbine's operation was reversed, the disks acted as a pump."Tesla's New Monarch of Machines". New York Herald Tribune, Oct. 15, 1911. (Available online. Tesla Engine Builders Association. ) | <urn:uuid:57620529-03c1-45a1-9ce1-1d0fcaae7fdc> | 3.890625 | 188 | Knowledge Article | Science & Tech. | 34.140512 |
FEROCIOUS STORMS AND DROUGHT SEEN
December 07, 1988
Dr. Hansen cited a model prepared by another scientist, Dr. Kerry Emmanuel, showing that the global warming trend is likely to intensify the severity of storms. He said the warming of the ocean would speed evaporation, which would cause more active convection currents in the atmosphere. This increased atmospheric activity could produce storms with 40 percent to 50 percent more kinetic energy than the fiercest storms known today. Hurricanes packing winds up to 225 miles an hour are foreseen.
Their ingenious prediction had already happened in 1934
World Record Wind Gust: 408 km/h
Geneva, 22 January 2010 (WMO) – According to a recent review conducted by a panel of experts in charge of global weather and climate extremes within the WMO Commission for Climatology (CCl) the record of wind gusts not related to tornados registered to date is 408 km/h during Tropical Cyclone Olivia on 10 April 1996 at Barrow Island, Australia. The previous record was of 372 km/h, registered in April 1934 across the summit of Mount Washington, USA.
Eleven years later inn 1999, Hansen wrote this about droughts.
Empirical evidence does not lend much support to the notion that climate is headed precipitately toward more extreme heat and drought. The drought of 1999 covered a smaller area than the 1988 drought, when the Mississippi almost dried up. And 1988 was a temporary inconvenience as compared with repeated droughts during the 1930s “Dust Bowl” that caused an exodus from the prairies, as chronicled in Steinbeck’s Grapes of Wrath.
These “scientists” are completely useless spewers of propaganda, which is why the press trusts them. | <urn:uuid:fc81c539-72be-4de3-a54e-d36fbc9572c0> | 3.21875 | 369 | Personal Blog | Science & Tech. | 47.542755 |
In the http module HTTP exception classes and status codes are defined.
- exception Failure(message='Bad request', status=http.BAD_REQUEST)¶
A base class of errors which should be reported to a user by a HTTP response with the status code status and message in the content. Whenever your application faces a problem it has to report to a user, it should throw a Failure. The serve.catchingFailure() decorator will catch the error and convert it to a Response object.
- exception NotFound(message='Not found')¶
A resource was not found. Reported to a user by a 404 HTTP response. Subclass of Failure.
HTTP status code constants are properties of the http module. The most popular constants a described here. You are unlikely to need other constants, but if you do, see the source code and the List of HTTP status codes Wikipedia page.
This class of status codes indicates the action requested by the client was received, understood, accepted, and processed successfully.
Standard response for successful HTTP requests.
The request has been fulfilled and resulted in a new resource being created.
This class of status codes indicates that further action needs to be taken by the user agent in order to fulfill the request.
This and all future requests should be directed to the URI specified in the Location response header.
The response to the request can be found under the URI specified in the Location response header. This status code is used by the redirect() function to redirect the user agent after a successful fulfillment of a POST request.
The resource has not been modified since last requested. Typically, the HTTP client provides a header like If-Modified-Since or If-None-Match to identify the state of the resource possessed by the client.
This class of status codes is intended for cases in which the client seems to have erred.
The request contains bad syntax or cannot be fulfilled.
The application understood the request, but is refusing to fulfill it. The reason should be described in the content of the response.
The requested resource could not be found.
A request was made of a resource using a request method not supported by that resource. For example, using GET on a form which requires data to be presented via POST, or using PUT on a read-only resource.
These status codes indicate cases in which the application is aware that it has encountered an error or is otherwise incapable of performing the request.
The application has erred.
The application does not support the functionality required to fulfill the request.
The application is currently unavailable (because it is overloaded or down for maintenance). | <urn:uuid:996735d6-9c00-47ce-8b93-2721be2577cf> | 2.921875 | 537 | Documentation | Software Dev. | 47.923457 |
Is it possible to create a rocket with a variable blast diameter to achieve different levels of torque and power similar to a geared transmission?
I suppose the best analogy I have is the difference in power between a garden hose normally and when you plug it with your thumb, creating more pressure.
Would it be possible to have a rocket launch with maximum diameter, and slowly close up like a camera shutter to gain speed once in the air? Perhaps this shudder would be angled like a funnel to direct the blast easier. All the rockets I see have a fixed diameter and it just makes me curious.
Experts in the field are requested to answer via comments
How it is possible to double the momentum of a body by increasing the kinetic energy four times?at the time what happen to mass?
When we say, KE is increased, we mean to say by increasing speed alone unless otherwise specified.
Here mass remains constant.
Please note that the question says, KE of a body increased 4 times; which suggests that the body is the same and KE is increased by increasing the speed alone.
I just want to know how to easily solve problems related to kinematics and friction. I don’t know why i always face problem in these two topics a lot……
Please help and tell some tricks to solve these both…….
Categories: Force, How to, KINEMATICS Tags: ask, ask Physics, doubt, face, friction, kinematics, Online, physics, problem, project, solve, solved, solved paper, solved problems, solved questions, solving problems
In a circus show a clown who is sitting on a post with height,H drops an apple to the ground.At the same time another clown throw an orange vertically upward from ground with speed 11 m/s.If both fruits pass each other after 0.8s, (a) determine the height (b) where do the apple and orange meet? (c) what is the speed of each fruit when they meet each other?
[Asked nur zainun syafiqah ayob] | <urn:uuid:355c3750-de41-4975-a7c3-b2ea511d7924> | 2.78125 | 426 | Q&A Forum | Science & Tech. | 56.151471 |
For correctly rounded decimal to floating-point conversions, many open source projects rely on David Gay’s strtod() function. In the default rounding mode, IEEE 754 round-to-nearest, this function is known to give correct results (notwithstanding recent bugs, which have been fixed). However, in the less frequently used IEEE 754 directed rounding modes — round toward positive infinity, round toward negative infinity, and round toward zero — strtod() gives incorrectly rounded results for some inputs.
Articles from June, 2010
When a decimal number is converted to a binary floating-point number, the floating-point number, in general, is only an approximation to the decimal number. Large integers, and most decimal fractions, require more significant bits than can be represented in the floating-point format. This means the decimal number must be rounded, to one of the two floating-point numbers that surround it.
Common practice considers a decimal number correctly rounded when the nearest of the two floating-point numbers is chosen (and when both are equally near, when the one with significant bit number 53 equal to 0 is chosen). This makes sense intuitively, and also reflects the default IEEE 754 rounding mode — round-to-nearest. However, there are three other IEEE 754 rounding modes, which allow for directed rounding: round toward positive infinity, round toward negative infinity, and round toward zero. For a conversion to be considered truly correctly rounded, it must honor all four rounding modes — whichever is currently in effect.
I evaluated the Visual C++ and glibc strtod() functions under the three directed rounding modes, like I did for round-to-nearest mode in my articles “Incorrectly Rounded Conversions in Visual C++” and “Incorrectly Rounded Conversions in GCC and GLIBC.”. What I discovered was this: they only convert correctly about half the time — pure chance! — because they ignore the rounding mode altogether.
Visual C++ rounds some decimal to double-precision floating-point conversions incorrectly, but it’s not alone; the gcc C compiler and the glibc strtod() function do the same. In this article, I’ll show examples of incorrect conversions in gcc and glibc, and I’ll present a C program that demonstrates the errors. | <urn:uuid:a86569a7-a72e-43bb-a8e0-eae7ad6476b9> | 3.140625 | 489 | Personal Blog | Software Dev. | 39.7075 |
|Euclidean norm||computing dictionary|
<mathematics> The most common norm, calculated by summing the squares of all coordinates and taking the square root. This is the essence of Pythagoras's theorem. In the infinite-dimensional case, the sum is infinite or is replaced with an integral when the number of dimensions is uncountable.
(01 Sep 2004)
|Bookmark with:||word visualiser||Go and visit our forums| | <urn:uuid:cda7139a-76ba-451a-a6f7-8c6b61bb2c9e> | 3.21875 | 98 | Knowledge Article | Science & Tech. | 34.487917 |
Scientists at the Fish and Wildlife Research Institute (FWRI) have been developing habitat suitability models that predict spatial distributions and relative abundance of fish and invertebrate species in Florida estuaries.
Habitat Suitability Index (HSI) modeling was developed by the U.S. Fish and Wildlife Service (USFWS) in the early 1980s as part of the Habitat Evaluation Program. The models were used to support rapid decision-making in data-poor situations. Expert-opinion and literature sources were used to develop suitability indices (SI) indicative of habitat preferences across gradients. These indices were then combined to produce the index. The geometric-mean algorithm is most commonly used to determine the index.
In 1997, the Strategic Environmental Assessment Division of the National Oceanographic and Atmospheric Administration (NOAA) worked with USFWS to develop HSI models with geographic information systems (GIS) using qualitative methods to predict spatial distributions of estuarine species in Maine's Casco and Sheepscot Bays. Similar methods were used to predict the spatial distributions of American oyster, white shrimp, and spotted seatrout in Pensacola Bay, Florida.
In 1998, FWRI initiated studies to develop quantitative HSI models in collaboration with NOAA and the University of Miami (Rubec et al. 1998). FWRI's Fisheries-Independent Monitoring (FIM) data were analyzed by species life stages and season in Tampa Bay and in Charlotte Harbor (Rubec et al. 1999, 2001). Modeling was conducted initially with spotted seatrout (Cynoscion nebulosus), pinfish (Lagodon rhomboides), and bay anchovy (Anchoa mitchilli).
Methods were developed to average environmental data from FIM sampling and other agencies within sampling grids across each estuary on a monthly basis (Figure 1). Aerial photography is used to determine the distribution of submerged aquatic vegetation (SAV) for the creation of maps of bottom type. Soundings data obtained from NOAA were interpolated to create bathymetry maps. Data points for temperature, salinity, and dissolved oxygen were interpolated to produce monthly surface and bottom habitat layers. Then, monthly habitat layers were averaged using the ArcView GIS Spatial Analyst extension to create seasonal maps for each habitat type (Figure 2).
Habitat preferences for each species life stage were determined by fitting polynomial regressions to mean CPUEs across environmental gradients (Figure 3). Higher mean CPUEs indicate that the species is more abundant in parts of the gradient. For example, a peak in the suitability curve indicates that early juvenile spotted seatrout are most abundant at 28-32°C (Figure 3). Hence, the life stage has a habitat affinity for the peak in the suitability curve. Similar suitability curves for Tampa Bay and Charlotte Harbor indicate similar habitat preferences for the life stages of each species.
Mean suitability values from the curves (Figure 4) are used as input to habitat suitability models. The HSI model was used to calculate the geometric mean of the SIs associated with each habitat layer across grid cells to create a predicted HSI map in each estuary (Figure 5). The HSI model was used to create seasonal maps (spring, summer, fall, winter) depicting the spatial distribution of each species life stage.
Raw CPUE data were overlaid within four zones (Low, Moderate, High, and Optimum) of the predicted map (Figure 6) and mean CPUEs calculated to create a histogram (Figure 7). The model was verified when mean CPUEs were found to increase across the zones. Hence, the Optimal zone should have the highest mean CPUE.
Suitability indices from a nearby estuary were also used with the habitat layers from the first estuary to test transferability of the model. For example, Charlotte Harbor SIs were transferred to Tampa Bay to create a second map. Statistics were used to compare the similarity of each pair of seasonal maps within each estuary.
Figures 6 and 7
Suitability indices transferred from another estuary can be used to infer species distributions and relative abundance of species in estuaries lacking fisheries monitoring. For example, data from Tampa Bay has been applied to predict the distribution of juvenile pinfish in Charlotte Harbor (Figure 8).
The spatial modeling can be used to define which habitats are most important for each species. The Optimum zones have the potential of being designated Habitat Areas of Particular Concern (HAPC) associated with Essential Fish Habitat (Rubec et al. 1998). The approach can assist decision-making associated with habitat protection and fisheries management. This research was funded by USFWS through the Sport Fish Restoration Program.
Rubec, P. J., J.C.W. Bexley, H. Norris, M.S. Coyne, M.E. Monaco, S.G. Smith, and J.S. Ault. 1999. Suitability modeling to delineate habitat essential to sustainable fisheries. Pages 108-133, In: L.R. Benaka (ed.). Fish Habitat: Essential Fish Habitat and Restoration, American Fisheries Society Symposium 22.
Rubec, P.J., M.S. Coyne, R.H. McMichael, Jr., and M.E. Monaco. 1998. Spatial methods being developed in Florida to determine essential fish habitat. Fisheries 23(7):21-25.
Rubec, P.J., S.G. Smith, M.S. Coyne, M. White, A. Sullivan, D. Wilder, T. MacDonald, R.H. McMichael, Jr., M.E. Monaco, and J.S. Ault. 2001. Spatial modeling of fish habitat suitability in Florida estuaries. Pages 1-18, In: GH. Kruse, N. Bez, A. Booth, M.W. Dorn, S. Hills, R.N. Lipcus, D. Pelltier, C. Roy, S.J. Smith, and D. Witherell (eds.) Spatial Processes and Management of Marine Populations, Alaska Sea Grant College Program, Fairbanks Alaska, AG-SG-01-02. | <urn:uuid:e8dcaf08-6e0c-4355-a233-f4dac34592aa> | 3.3125 | 1,288 | Academic Writing | Science & Tech. | 44.01484 |
If is an idempotent in a ring (not necessarily with identity), then we can decompose as the direct sum of four components (subrings), each of them related to . Concretely,
note that here is just notation that means , and similarly for .
This decomposition is known as the Peirce decomposition of with respect to .
An important feature of this decomposition is that each of and is a subring of , and the former even has an identity, namely, the element , which does indeed lie in , since ; also, for all .
If does contain an identity , then is defined, and is again an idempotent, and one has (obviously), and since as is idempotent. One says that and form a pair of orthogonal idempotents. Furthermore, in this case, the subring as defined above, coincides with the set of products . (A similar remark applies to each of and .)
More generally, continuing to assume that contains an identity, if is a set of orthogonal idempotents for with the property that then
The basic idea of decomposing a ring via idempotents should be accessible to anyone knowing the basics of ring theory. Several of the examples below refer to contexts which require a more specialized degree of knowledge; in such cases, this is indicated at the beginning of the example.
If lies in the centre of (in particular, if is commutative), then , and Thus we obtain the simpler decomposition
This example requires a basic knowledge of the costruction of the spectrum of a commutative ring with identity.
If is commutative with and is an idempotent, then , as noted in Example 1. As remarked above, we may form the idempotent , and so in particular, both and are commutative rings with identity (namely and respectively). Thus , and are all defined, and the factorization induces a decomposition
of into a union of two open subsets. Conversely, any such decomposition of arises from an idempotent in this way.
In short, if we think of as being the ring of regular functions on , then idempotents in serve precisely as the indicator (or characteristic) functions of simultaneously open and closed subsets of . (In particular, is the indicator function of itself, while is the indicator function of the empty subset.)
Note that in the case that is a Boolean ring, so that every element is idempotent (by definition), the space is totally disconnected, and the above discussion specializes to the Stone representation theorem.
Suppose that is a topological group which admits a neighbourhood basis of the identity consisting of compact open subgroups. (A basic example of such a group is , the general linear group of invertible -matrices over the field of -adic numbers.) One consequence of this assumption is that is locally compact, and so we can choose a Haar measure on .
Let denote the -vector space of all compactly supported locally constant -valued functions on . We can make into a -algebra by defining a convolution product on its elements as follows:
for any two functions . The -algebra is then referred to as the Hecke algebraof the group .
If is any compact open subgroup of , then we may define an idempotent via the formula where is the indicator (or characteristic) function of . Since is open, the function is locally constant and compactly supported, and thus lies in , and hence so does .
In this situation, for any , the convolution is the function obtained by averaging on the left via the action of the compact open subgroup , and simililarly is the is the function obtained by averaging via the action of on the right. In particular if and only if for all and , and simililarly, if and only if for all K and . Thus the subalgebra of consists of those elements of that are bi-invariant under the action of , i.e. such that for all and .
Since any is compactly supported and locally constant, by virtue of our assumption on we may find some sufficiently small compact open subgroup such that is bi--invariant. Thus we find that
where the union is indexed by the collection of all compact open subgroups of . | <urn:uuid:2a18f2a0-df7a-4218-89df-958e63fcadee> | 3.046875 | 904 | Documentation | Science & Tech. | 37.177636 |
For nearly 30 years, jewel beetles (family Buprestidae) have been my primary research interest. While some species in this family have long been regarded as forest and landscape pests, my interest in the group has a more biosystematic focus. A faunal survey of Missouri was the result of my initial efforts (MacRae 1991), while later research has focused on distributions and larval host associations of North American species (Nelson & MacRae 1990; Nelson et al. 1996; MacRae & Nelson 2003; MacRae 2004, 2006) and descriptions of new species from both North America (Nelson & MacRae 1994, MacRae 2003b) and South America (MacRae 2003a). Research interest in other groups—especially longhorned beetles and tiger beetles, has come and gone over the past three decades; however, I always return to jewel beetles as my first and favorite group.
In recent years, one species in particular—the emerald ash borer (EAB, Agrilus planipennis) has garnered a huge amount of research, regulatory, and public interest after reaching North America from Asia and spreading alarmingly through the hardwood forests of Michigan and surrounding states. The attention is justifiable, given the waves of dead native ash trees that have been left in its wake. With huge areas in eastern North America still potentially vulnerable to invasion by this species, the bulk of the attention has focused on preventing its spread from infested areas and monitoring areas outside of its known current distribution to detect invasion as early as possible. One incredibly useful tool that has been adopted by survey entomologists is the crabronid wasp, Cerceris fumipennis. Like other members of the family, these solitary wasps dig nests in the ground, which they then provision with captured insect prey. The wasp uses its sting to paralyzed the prey but not kill it, and once inside the burrow the wasp lays an egg on the prey and seals the cell with a plug of soil. The eggs hatch and larvae develop by consuming the paralyzed prey (unable to scream!). After pupation the adult digs its way out of the burrow (usually the next season), and the cycle begins anew. However, unlike other members of the family (at least in North America), C. fumipennis specializes almost exclusively on jewel beetles for prey. So efficient are these wasps at locating and capturing the beetles that entomologists have begun using them to sample areas around known wasp populations as a means of detecting the presence of EAB. Philip Careless and Stephen Marshall (University of Guelph, Ontario) and colleagues have been leading this charge and have even developed methods for transporting wasp colonies as a mobile survey tool and developed a sizeable network of citizen scientists throughout eastern North America to expand the scope of their survey efforts. Information about this can be found at the excellent website, Working with Cerceris fumipennis (please pardon my shameless lifting of the title for this post).
I first became aware of the potential of working with C. fumipennis a few years ago when Philip sent me a PDF of his recently published brochure on use of this wasp for EAB biosurveillance (Careless et al. 2009). My correspondence with him and other eastern entomologists involved in the work suggested that ball fields with lightly vegetated, sandy soil would be the best places to look for C. fumipennis nests, but my cursory attempts to find the wasp at that time were unsuccessful. I reasoned that the clay-soaked soils of Missouri didn’t offer enough sand for the wasps’ liking and didn’t think much more about it until last winter when I agreed to receive for ID a batch of 500+ buprestid specimens taken from C. fumipennis wasps in Louisiana. What a batch of material! In addition to nice series of several species that I had rarely or never seen (e.g. Poecilonota thureura), three new state records were represented amongst the material. A paper is now in progress based on these collections, and that experience catalyzed a more concerted effort on my part to locate a population of the wasp in Missouri. Museum specimens were no help—the only records from Missouri were from old specimens bearing generic locality labels such as “St. Louis” and “Columbia.” Throughout the month of May, I visited as many ball fields as I could, but the results were always the same—regularly groomed, heavy clay, barren soil with no evidence of wasp burrows (or any burrows for that matter).
Near the end of May, however, I had a stroke of luck. I had switched to a flatter route through the Missouri River Valley to ride my bike to work because of knee pain (now thankfully gone) when I saw this:
Practice fields at Chesterfield Valley Athletic Complex | St. Louis Co., Missouri
Those are “practice” fields in front of regular fields in the background, and unlike the latter, this row of nine fields (lined up against the levee adjacent to the Big Muddy National Wildlife Refuge) showed no evidence of regular grooming or heavy human use. Only ten miles from my home, I made immediate plans to inspect the site at the first opportunity that weekend. Within minutes after walking onto the lightly vegetated, sandy-clay soil of the first field, I found numerous burrows such as this:
Cerceris fumipennis with circular, pencil-wide burrow entrance and symmetrical mound of diggings.
Only a few more minutes passed before I found an occupied nest, the wasp sitting just about an inch below the entrance to its pencil-wide burrow. The three yellow markings on the face indicated it was a female (males have only two facial markings), and in short order I found numerous other burrows also occupied by female wasps. Some were just sitting below the burrow entrance, while others were actively digging and pushing soil out of the burrow with their abdomen. I flicked a little bit of soil into one of the burrows with a female sitting below the surface, which prompted an immediate “cleaning out” of the burrow—this explains the dirty face of the female in the following photo, but the three yellow facial markings are clearly visible:
Cerceris fumipennis female removing soil from burrow entrance.
After finding the burrows and their occupants, I began to notice a fair number of wasps in flight—leaving nests, returning to nests, and flying about as if searching for a ‘misplaced’ nest. A few of these were males, but most were females, and I also caught a couple pairs flying in copula (or at least hitched, if not actually copulating). Despite the number of wasps observed during this first visit, I didn’t see a single wasp carrying a buprestid beetle. This puzzled me, because all of the Louisiana beetles I had determined last winter were taken by standing in the midst of nests and netting those observed carrying beetles. Finally, I had confirmation that I was truly dealing with this species when I found a couple of beetles lying on the ground near the entrance to a burrow. These would be the only beetles that I would find on this visit, but subsequent visits during the following few weeks would show “ground picking” to be the most productive method of collecting beetles. Across the nine fields, I found a total of nearly 300 nests, and the wasps showed a clear preference for some fields over others—one field (P-6) had about 150 nests, while a few others had less than a dozen. The photo shown in ID Challenge #19 shows a sampling of ground-picked buprestids from P-6 in a single day, and occasionally I would find a real prize like Buprestis rufipes:
Buprestis rufipes laying near Cerceris fumipennis nest entrance.
Coincident with the appearance of large numbers of beetles laying on the ground near nest entrances, I also began to see wasps carrying their prey. Wasps carrying large beetles are easily recognized by their profile, but even those carrying small beetles look a little more “thick-thoraxed” (they hold their prey upside down and head forward under their thorax) and exhibit a slower, more straight-line flight path compared to the faster, more erratic and repetitively dipping flight of wasps not carrying prey. Learning how to discern wasps carrying prey in flight from the more numerous empty-handed wasps prevents a lot of wasted time and effort netting the latter. Nevertheless, there does appear to be some bias towards larger beetles when netting prey-carrying wasps in flight, as evidenced in the photo below of beetles taken by this method, also in field P-6, on the same date as the ground-picked beetles shown in ID Challenge #19. This could be a result of visual bias towards wasps carrying larger beetles, as in later visits (and presumably with a more refined search image) I did succeed in catching larger numbers wasps carrying smaller beetles (primarily in the genus Agrilus).
Buprestid prey of Cerceris fumipennis: L–R and top to bottom 2 Dicerca obscura, 2 D. lurida, 3 Poecilonota cyanipes, 2 Acetenodes acornis, 1 Chrysobothris sexsignata, 1 Agrilus quadriguttatus, and 1 A. obsoletoguttatus
All told, I collected several hundred beetles during my twice weekly visits to the site from late May to the end of June. Beetle abundance and wasp activity began to drop off precipitously in late June, which coincides precisely with the end of the adult activity period for a majority of buprestid beetles in Missouri, based on my observations over the years. This did not, however, spell the end of my activities in using C. fumipennis to collect buprestid beetles, which will be the subject of Part 2 in this series.
Congratulations to Joshua Basham, whose efforts in ID Challenge #19 earned him 12 points and the win. Morgan Jackson and Paul Kaufman were the only others to correctly identify the Cerceris fumipennis connection and take 2nd and 3rd, respectively. In an unexpected turn of events, BitB Challenge Session #6 overall leader Sam Heads did not participate and was leapfrogged by Brady Richards, whose becomes the new overall leader with 59 points. Sam now trails Brady by 5 points, while Mr. Phidippus lies another 3 points back. With margins this tight, the overall standing can still change in a single challenge, and there will be at least one more in this current session before an overall winner is named.
Careless, P. D., S. A. Marshal, B. D. Gill, E. Appleton, R, Favrin & T. Kimoto. 2009. Cerceris fumipennis—a biosurveillance tool for emerald ash borer. Canadian Food Inspection Agency, 16 pp.
MacRae, T. C. 1991. The Buprestidae (Coleoptera) of Missouri. Insecta Mundi 5(2):101–126.
MacRae, T. C. 2003a. Mastogenius guayllabambensis MacRae, a new species from Ecuador (Coleoptera: Buprestidae: Haplostethini). The Coleopterists Bulletin 57(2):149–153.
MacRae, T. C. 2003b. Agrilus (s. str.) betulanigrae MacRae (Coleoptera: Buprestidae: Agrilini), a new species from North America, with comments on subgeneric placement and a key to the otiosus species-group in North America. Zootaxa 380:1–9.
MacRae, T. C. 2004. Notes on host associations of Taphrocerus gracilis (Say) (Coleoptera: Buprestidae) and its life history in Missouri. The Coleopterists Bulletin 58(3):388–390.
MacRae, T. C. 2006. Distributional and biological notes on North American Buprestidae (Coleoptera), with comments on variation in Anthaxia (Haplanthaxia) viridicornis (Say) and A. (H.) viridfrons Gory. The Pan-Pacific Entomologist 82(2):166–199.
MacRae, T. C., & G. H. Nelson. 2003. Distributional and biological notes on Buprestidae (Coleoptera) in North and Central America and the West Indies, with validation of one species. The Coleopterists Bulletin 57(1):57–70.
Nelson, G. H., & T. C. MacRae. 1990. Additional notes on the biology and distribution of Buprestidae (Coleoptera) in North America, III. The Coleopterists Bulletin 44(3):349–354.
Nelson, G. H., & T. C. MacRae. 1994. Oaxacanthaxia nigroaenea Nelson and MacRae, a new species from Mexico (Coleoptera: Buprestidae). The Coleopterists Bulletin 48(2):149–152.
Nelson, G. H., R. L. Westcott & T. C. MacRae. 1996. Miscellaneous notes on Buprestidae and Schizopodidae occurring in the United States and Canada, including descriptions of previously unknown sexes of six Agrilus Curtis (Coleoptera). The Coleopterists Bulletin 50(2):183–191.
Copyright © Ted C. MacRae 2012 | <urn:uuid:477a0210-1103-41f0-a397-59fe902b3056> | 2.796875 | 2,914 | Personal Blog | Science & Tech. | 51.32602 |
M-type asteroids were once known as metallic asteroids. Today their composition is in dispute, and many astronomers simply define the M type by a reflected spectrum and make no attempt to define a common composition for all of them. About 8% of all asteroids are of this type.
Characteristics and composition
Originally they were thought to be composed of pure nickel and iron, like the iron-nickel meteorites, or at most to have a small portion of silicates added. However, this definition has been in some dispute since 1982, when Lupishko et al. first reported an unusually high amount of silicates in the asteroid Kalliope. In 2000, Rivkin et al. reported that of 27 asteroids of this type that they and others had observed, 35% of them were hydrated and thus could not be composed primarily of iron and nickel. They thus urged their fellow astronomers to abandon the notion that M-type asteroids were metallic fragments of previously differentiated objects that were later struck and shattered. Instead they held that the smaller 10% of all M-type asteroids (likely to be anhydrous) were the likely sources of iron meteorites, and the rest were chondrites, including salt-rich carbonaceous chondrites. And in 2001, Magri et al. reported that many M-type asteroids have too weak a radar signature to have metallic surfaces. Today the definition of the M type depends strictly on the spectrum.
Observation and exploration
No spacecraft has reconnoitered an M-type asteroid yet. However, the Rosetta probe will make rendezvous with Lutetia on July 10, 2010.
- ↑ 1.0 1.1 1.2 Arnett, Bill. "Asteroids." The
Nine8 Planets, May 10, 2008. Accessed June 20, 2008.
- ↑ 2.0 2.1 2.2 "Asteroid Facts." The Planetary Society, n.d. Accessed June 20, 2008.
- ↑ 3.0 3.1 Lupishko D.F., Belskaia I.N., Tupieva F.A., and Chernova G.P. "UBV photometry of the M-type asteroids 16 Psyche and 22 Kalliope." Astronomicheskii Vestnik 16:101-108, April-June 1982. Translated into English and republished in Solar System Research 16(2):75-80, October 1982. Accessed June 21, 2008.
- ↑ 4.0 4.1 Rivkin A.S., Howell E.S., Lebofsky, L.A., et al. "The Nature of M-class Asteroids from 3-μm Observations." Icarus 145(2):351-368, June 2000. doi:10.1006/icar.2000.6354 Accessed June 21, 2008.
- ↑ 5.0 5.1 Magri C., Consolmagno G.J., Ostro S.J., et al. "Radar constraints on asteroid regolith compositions using 433 Eros as ground truth." Meteoritics and Planetary Science 36(12):1697-1709, December 2001. Full text as PDF. Accessed June 21, 2008.
- ↑ Bus S.J. and Binzel R.P. "Phase II of the Small Main-Belt Asteroid Spectroscopic Survey: A Feature-Based Taxonomy." Icarus 158(1):146-177, July 2002. doi:10.1006/icar.2002.6856 Accessed June 21, 2008. Bus and Binzel here rename the M type as X. | <urn:uuid:54d5dffe-5b60-4f02-ba1a-12767b4a3616> | 3.609375 | 751 | Knowledge Article | Science & Tech. | 76.456111 |
Let's see how this comes up.
Black holes are not black, they are actually invisible and the only way to "see" one is to look at how the stars around it shift.
Let me explain
A black hole bends any light that gets near it. If light from a star behind it is bent, it would appear as if the light came from a different direction. That change would make the black hole disapper hence, black holes are invisible. | <urn:uuid:393274bd-2266-42f5-bbc3-1dcc0939e0d5> | 2.90625 | 94 | Comment Section | Science & Tech. | 72.155 |
Floral signs go electric
Flowers' methods of communicating are at least as sophisticated as any devised by an advertising agency, according to a new study, published February 21 in Science Express by researchers from the University of Bristol. However, for any advertisement to be successful, it has to reach, and be perceived by, its target audience. The research shows for the first time that pollinators such as bumblebees are able to find and distinguish electric signals given out by flowers. Flowers often produce bright colours, patterns and enticing fragrances to attract their pollinators. Researchers at Bristol's School of Biological Sciences, led by Professor Daniel Robert, found that flowers also have their equivalent of a neon sign -- patterns of electrical signals that can communicate information to the insect pollinator. These electrical signals can work in concert with the flower's other attractive signals and enhance floral advertising power.
Plants are usually charged negatively and emit weak electric fields. On their side, bees acquire a positive charge as they fly through the air. No spark is produced as a charged bee approaches a charged flower, but a small electric force builds up that can potentially convey information.
By placing electrodes in the stems of petunias, the researchers showed that when a bee lands, the flower's potential changes and remains so for several minutes. Could this be a way by which flowers tell bees another bee has recently been visiting? To their surprise, the researchers discovered that bumblebees can detect and distinguish between different floral electric fields.
Also, the researchers found that when bees were given a learning test, they were faster at learning the difference between two colours when electric signals were also available.
How then do bees detect electric fields? This is not yet known, although the researchers speculate that hairy bumblebees bristle up under the electrostatic force, just like one's hair in front of an old television screen.
The discovery of such electric detection has opened up a whole new understanding of insect perception and flower communication.
Dr Heather Whitney, a co-author of the study said: "This novel communication channel reveals how flowers can potentially inform their pollinators about the honest status of their precious nectar and pollen reserves."
Professor Robert said: "The last thing a flower wants is to attract a bee and then fail to provide nectar: a lesson in honest advertising since bees are good learners and would soon lose interest in such an unrewarding flower.
"The co-evolution between flowers and bees has a long and beneficial history, so perhaps it's not entirely surprising that we are still discovering today how remarkably sophisticated their communication is."
The research was supported by the Leverhulme Trust.
Source: University of Bristol
- When flowers turn up the heatWed, 28 Jul 2010, 17:28:59 EDT
- Landing lights for bumblebeesMon, 11 Oct 2010, 20:31:15 EDT
- High-speed video and artificial flowers shed light on mysteries of hummingbird-pollinated flowersTue, 20 Nov 2012, 21:32:39 EST
- Frequent flower buyers seek product varietyThu, 5 Nov 2009, 6:54:42 EST
- Bees attracted to contrasting colors when looking for nectarThu, 21 Feb 2013, 22:05:07 EST
- Bees get a buzz from flowers' electrical fieldsfrom CBSNews - ScienceFri, 22 Feb 2013, 15:30:19 EST
- Flowers, bees have electrifying discussionsfrom MSNBC: ScienceFri, 22 Feb 2013, 14:41:29 EST
- Bumblebees Sense Electric Fields in Flowersfrom Scientific AmericanThu, 21 Feb 2013, 18:00:46 EST
- Bees and plants communicate via electric signals, say scientistsfrom The Guardian - ScienceThu, 21 Feb 2013, 16:01:36 EST
- Floral signs go electric: Bumblebees find and distinguish electric signals from flowersfrom Science DailyThu, 21 Feb 2013, 15:30:35 EST
- Bees sense flowers' electric signalsfrom BBC News: Science & NatureThu, 21 Feb 2013, 15:01:25 EST
- Bumblebees sense electric fields in flowersfrom News @ NatureThu, 21 Feb 2013, 14:31:05 EST
- Bees learn the electric buzz of flowersfrom Sciencenews.orgThu, 21 Feb 2013, 14:20:11 EST
- Bees and flowers communicate using electrical fields, researchers discoverfrom PhysorgThu, 21 Feb 2013, 14:00:35 EST
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Climate models are certainly improving, albeit more slowly than many would hope for. They are far from perfect.
Paul Valdes from Bristol University has an interesting paper in the last issue of Nature Geosciences about the reliability of climate models. He basically claims that climate models fail to reproduce past climate, in particular some abrupt climate change that happened in the deep past of Earth's history. This is not really a scoop, as Paul Valdes explains in this interview with Quentin Cooper in Material World, a BBC Radio 4 program. Does it mean that climate change will be worse than so far predicted by climate models ? Answer: we do not know. | <urn:uuid:a428c162-e6cc-4ec4-a21d-4a3e244ca4cc> | 2.90625 | 130 | Comment Section | Science & Tech. | 46.321786 |
It might surprise Western scientists to learn that there were periods in Korean history when the level of scientific achievement was the highest in Asia. This is the proposition that Dr. Sang-woon Jeon sets forth in the first comprehensive and systematic survey of Korean science to appear in any Western language. Dr. Jeon points up Korea's unique contributions to the history of science and technology as well as the country's role as a bridge between Japanese and Chinese science and civilization. Much of his discussion of Korean science focuses on instruments which he describes in great detail in chapters on astronomy, metereology, physics and physical technology, and geography and cartography.
Faced with the considerable difficulty of writing a history based on inadequate written records, Dr. Jeon has made use of available artifacts and other materials which have received little attention either in East Asia or the West. He has also summarized historical research in Korean science to the present and compiled an extensive bibliography. | <urn:uuid:ebcccffa-28e4-4338-a7c3-5156806a61ac> | 2.921875 | 191 | Academic Writing | Science & Tech. | 31.465782 |
I am confused about the concept of 'back emf'.
Have you got a clear, concise and logical explanation of just what it is?
Hi, Ben !!
Well, as you probably already heard before, the back-emf is
the same as counter emf (cemf). It is a voltage produced in
a conductor that tends to neutralize the present voltage. It is
a phenomenon that always tends towards the contrary of what happens!!
Lets suppose: if lines of a magnetic field are cut by a conductor,
than a voltage is generated in this conductor, which causes a
current of electrons to flow in one direction. At the same time,
like trying to avoid this, ANOTHER voltage is created that tends
to neutralize this effect, and it forces the electrons to flow in the
contrary direction. As you know, the back-emf is directly pro-
portional to the velocity of the magnetic field. It is proportional
to the relative motion between them.
I am sure that you know all of this. But, to give you an example,
think of a wire with a switch. Suppose the electrons are running
from a direction into another and suddenly, you open the switch.
What happens?? Well, when electrons run, they give rise to a magnetic
field. When you open the switch, the electrons should stop their
flow. But - as a kind of inertial action - they try to continue the flow,
and ionize the air, in an electric arc to find its way. Or let it be,
the originally initial magnetic field, in a circumference around
the wire, changes its sense, and try to avoid stopping the original
flow. It is possible to see this in an oscilloscope, as a negative
peak in certain experiences where you make use of a coil and
- abruptely - stops the electron flow.
I know you know all of this. But, that is it!!! It is the way things are.
Just try to answer this question: what is electrical charge?
Why is that we have positive and negative charges?? Answer :
nobody knows it!!! We must accept this condition!!! It belongs
to the laws of the universe, since the big bang created it like as it is.
Just to speak a little bit more about this subject, you know that
when an electrical induction "squirrel" motor runs, you have a
magnetic field that circulates around the squirrel. There is a
speed difference between them, what in turn generates a voltage
and a force appears, which drives the "squirrel". A back-emf
also appears, which lowers the net electric electron flow. The
current through a rotating electric motor is greatly reduced because
of this back-emf and if you avoid the moviment of the rotor, the
current should be so large that could damage the equipment.
And last but least, back-emf corresponds in a way to inertial
forces in the movement of a mass through space.
Inertia is a mass and has no intrinsic force.
The electron has a mass ( ca. 1/1840 of the mass of a proton ).
Just to compare, the Newtons first law states that a mass
will maintain its linear direction of movement, unless the resultant
of the forces applied on it be different from zero. When you
interrupt a current, the flow of electron tend to continue, like
having inertia (no voltage difference, no electrical pressure and
the flow should stop). Nevertheless, magnetic fields
appear alongside the current which act like forcing
electrons keep on their movement.
The short answer to your question is "No", but some words about it may
help. The universe is put together in such a way that whenever the
magnetic field through a loop changes, a voltage or emf is induced in
that loop. Now, in principle that emf could be in such a direction as
to oppose the change that produced it or, in the opposite direction
around that loop, to aid and increase the change that produced it.
Lenz's Law says the induced emf always opposes the change producing
it, leading to such terminology as "back emf". The argument, by the
way, is very simple. If the current aided the change that produced it,
the induced current would change the field more, producing more emf,
thereby producing more field, and so on to infinity, thereby blowing
up the universe. This does not happen!
To take a practical example, an electric motor running under no load
uses very little power. If the motor were frictionless and
superconducting, it would use no power. This is because the back emf
opposes the imposed voltage. As the load on the motor increases, the
back emf decreases as must be the case; the motor must be given energy
to produce energy. To see why the back emf decreases under load is
often complicated, having to do with the angle between coils in the
motor and the rotating magnetic field which is driving the coils.
Best, Dick Plano
Click here to return to the Physics Archives
Update: June 2012 | <urn:uuid:7fece38c-4fcb-4a0b-a284-487a94082195> | 3.25 | 1,090 | Q&A Forum | Science & Tech. | 58.437497 |
Electron vs Quark Size
Name: Tania N.
If a proton/neutron is very much larger than an electron,
is a quark bigger or smaller than an electron? -- Question from one of
my little year seveners. (grade~2)
A quark has never demonstrated any measurable size. Like an electron, it is
a "fundamental particle", one of the few particles from which all else is
made. The size of a proton or neutron comes from the motion of the quarks
as they orbit around each other, sending energy and particles(called mesons)
back and forth between each other. The three quarks are the primary
particles of a proton/neutron, the particles that identify the proton or
neutron for what it is. Still, the proton/neutron is essentially a cloud of
motion with low energy particles flashing in and out of existence all the
time. It is this cloud of motion that gives the proton/neutron its size.
Dr. Ken Mellendorf
Illinois Central College
It takes "seveners" to ask those questions we wish we had asked in graduate
The "size" of atomic and sub-atomic particles loses its meaning, because
these "particles" behave as though they are waves, or wave packets. So
"size" becomes kind of "squishy". However, with that caveat, the "classical"
radius of a "free" electron is taken to be about 3x10^-15 meters, and the
"classical" radius of a "free" proton is taken to be about 1x10^-15 -- only
about 1/3 the radius of the electron. However, the "classical" radius of a
hydrogen atom consisting of 1 proton and 1 electron, the Bohr radius, is
about 5x10^-9 meters about one million times the radius of either component
I do not know that anyone really thinks of quarks and other sub atomic
particles as having a particular "size", in fact their masses are usually
given in energy units of c^2 from the Einstein relation E = mc^2.
Click here to return to the Physics Archives
Update: June 2012 | <urn:uuid:072b32dd-5e6e-49de-92c1-97d3f8369d6d> | 3.21875 | 481 | Q&A Forum | Science & Tech. | 49.088182 |
The OMPS AI shows dust from the Sahara over northern Africa that is being blown over the Atlantic (with yellow, less opaque colors representing less dust and pink, more opaque colors representing more dust). Dust can also be seen over Saudi Arabia and parts of Iran, Afghanistan, and Pakistan. However, the aerosol index signal over the Western U.S. is due to dense smoke from wildfires, while smoke from agricultural biomass burning is visible over both South American and southern Africa. The sun glint in the middle of each swath shows the pattern of the satellite's view in orbit.
The second image from September 17, 2012 shows the smoke over the U.S. moving over the Midwest and stretching all the way to the Mid-Atlantic, with additional smoke appearing over Australia due to many wildfires burning there. → [web view] [hi-resolution] | <urn:uuid:a5ebf218-460b-45af-b956-1ae3e04acf05> | 3.171875 | 172 | Truncated | Science & Tech. | 49.904981 |
April 5, 1999
Eight years ago today NASA launched the Compton Gamma Ray Observatory. While the CGRO has revolutionized our understanding of cosmic gamma ray bursts, these distant explosions remain one of the biggest mysteries of modern astrophysics.
Aug. 10, 1999
Serious eclipse science is planned near home of legendary monster.
April 16, 1999
Science mimics science fiction as a Rensselaer Professor builds and tests a working model flying disc. The disc, or "Lightcraft," is an early prototype for Earth-friendly spacecraft of the future.
July 30, 1999
While professionals watch for a nearly transparent cloud of water vapor, amateurs will monitor the Moon's south pole for visible signs of Lunar Prospector's crash.
June 8, 1999
Scientists discuss what they know about lightning's effects on spacecraft and aircraft.
Dec. 19, 1999
A bigger, brighter Moon will herald the beginning of northern winter on Dec. 22, 1999 as lunar perigee, the winter solstice, and the full Moon all happen within a 10 hour period.
Feb. 26, 1999
As February winds down with no full moon at all, sky watchers are looking forward to two full moons in March and the second Blue Moon of 1999.
Jan. 12, 1999
An updated 20-year trend in atmospheric temperatures is unveiled at 1999 American Meteorological Society Meeting this week. These new results are corrected for orbital decay and drift of the nine satellites used to obtain the temperature measurements.
Aug. 18, 1999
The Cassini spacecraft has completed a highly accurate flyby of Earth, giving the spacecraft a velocity boost for its journey to distant Saturn.
Aug. 24, 1999
Who cares if it rains and the fish get wet? A Pacific Ocean rainfall experiment will have implications for global weather studies. | <urn:uuid:64f48a1a-4e75-41a4-8f12-434ef2a681cd> | 3.1875 | 371 | Content Listing | Science & Tech. | 59.380161 |
Indeed, every bit of your being, every gene in your genome, every base pair in your DNA, is no longer extant.
Or is it?
Well, scientists have recently taken a bit of DNA called Col2A1, gleaned from the extinct Tasmanian tiger (Thylacinus cynocephalus), extracted from 100 year-old museum samples, put that DNA in a mouse, and got it to function.
The DNA is a transcriptional enhancer. This is a bit of “non-coding” DNA that has an effect on the expression of other DNA. In this experiment, this worked. Extinct DNA of this type has been expressed in vitro, but this is the virst time in vivo.
(a) Young male thylacine in Hobart Zoo in 1928, photograph (Q4437). (b) One of the preserved pouch young specimens (head length 34 mm) from which DNA was extracted, from the Museum Victoria collection. (c-f) The skull of the thylacine (c,e) compared with that of the domestic dog Canis canis (d,f). The morphology of the head shows remarkable convergent evolution. However, there are some differences: in marsupials, the lacrymal extends outside the orbit and the angle of the dentary is medially inflected (c). The thylacine palatine has the vacuities characteristic of marsupial skulls (e). The teeth also show striking convergent evolution but the muzzle of the thylacine is quite narrow compared to that of the dog (e,f). Scale bar = 5cm.
In particular, the effects of the trancriptional enhancer was observed by watching the effects on a “reporter gene” (a gene that would be affected by it). The reporter gene predicted pretty much as expected. During the development of the mouse embryo, the reporter gene was expressed where and when, and roughly in the amount (though this varied) as expected.
The authors conclude, “Our method using transgenesis can be used to explore the function of regulatory and protein-coding sequences obtained from any extinct species in an in vivo model system, providing important insights into gene evolution and diversity.”
This assumes that the word “function” is used very carefully, of course. The exact effects of a gene may depend on context to the extent that one bit of DNA may function in one organism in a different way than other organism to the extent that we would normally assign the two outcomes to two different functions. It is that kind of context based functionality that makes genes a) really interesting and b) able to do so much work despite the fact that there are actually not that many different kinds of genes.
Pask, A.J., Behringer, R.R., Renfree, M.B., Svensson, E.I. (2008). Resurrection of DNA Function In Vivo from an Extinct Genome. PLoS ONE, 3(5), e2240. DOI: 10.1371/journal.pone.0002240 | <urn:uuid:d644df19-d63c-46d1-9423-b75e23dcd332> | 3.71875 | 647 | Personal Blog | Science & Tech. | 57.059912 |
Salt Marshes Under Siege
Agricultural practices, land development and overharvesting of the seas explain complex ecological cascades that threaten our shorelines
In North America, salt marshes once lined much of the Atlantic coast. Such a collection of salt-tolerant plants protects the shoreline from storms and filters pollutants from water flowing to the sea. Unfortunately, human activities, such as farming for desirable grasses and development, have destroyed many of the marshes—up to 70 percent of them along some stretches of coastline. Today, imbalances in nature—a foreign strain of reed, enormous flocks of geese and over harvesting of blue crabs—threaten salt marshes from Georgia to the Hudson Bay. Here, Bertness and his colleagues detail salt-marsh research and predict the loss of most Atlantic coast salt marshes, unless society fights back, and soon.
Go to Article | <urn:uuid:0645f765-671c-46a4-bdf5-26e678570279> | 3.265625 | 185 | Truncated | Science & Tech. | 28.625348 |
How did Pluto form (is it an asteroid or a planet?)
Written by Edo Loenen and Marco Westerkamp.
Pluto was discovered in 1930 by Clyde W. Tombaugh, who used a 33-cm photographic telescope at Lowell Obersvatory in Flagstaff, Arizona. The search for Pluto at Flagstaff had been initiated by the founder of the obervatory, Percival Lowell, who had estimated the ninth planet's position on the basis off its presumed gravitational pull on Uranus and Neptune. Scientist now know, however, that the mass of Pluto is insufficient to affect the orbits of Uranus and Neptune. The fact that Pluto was found relatively close to the position that had been predicted by Lowell was due to luck. After the discovery of Pluto, it was quickly determined that Pluto was too small to account for the discrepancies in the orbits of the other planets. The search for Planet X continued but nothing is found yet.
To answer the question about the formation of Pluto , it is necessary to know what Pluto is. Because the formation of a planet is different from the formation of, for example, an astroid.
Therefore the following subquestions must be answered:
What is a planet?
Officially Pluto is a planet. The IAU (International Astronomical Union) declared in a pressrelease that: "No proposal to change the status of Pluto as the ninth planet in the solar system has been made".
In what way does Pluto differ from the other eight planets?
We don't know the exact definition of a planet and the reason why the IAU made it's decision aren't known by us.
Inclination of it's orbit compared to the ecliptic is 17.148°Full article
Large orbital eccentricity: 0.248
Earth's eccentricity: 0.0167
Pluto is composed of:
core of hydrated rock (70% of mass)
mantle of water ice
atmosphere containing methane ice (and possibly: N2, CO, CO2)
This is very different from the other outerplanets, because they are mainly composed of gas.
Therefore Pluto's density is larger than the other outerplanets.
Pluto has a high albedo: ±0.5
Extraordinary is that it is irregular, Pluto has the largest global-scale contrast in the solar system. Which indicates that the planet is active.
Charon (Pluto's satellite) is extraordinary large compared to Pluto:
radius Pluto : radius Charon
1 : 0.5
in comparison with:
radius Earth : radius Moon
1 : 0.3
radius Mars : radius Phobos
1 : 0.003
Because of all the differences between Pluto and the other eight planets, it isn't hard to believe that Pluto belongs to an other group of objects. Pluto therefore might be formed in a different way. Because the size and composition of Pluto resemble the sizes and composition of Kuiper Belt Objects, science nowadays believes that Pluto might be formed as a Kuiper Belt Object.
What are Kuiper Belt Objects?
The Kuiper Belt is a large population (over 70,000) of small bodies orbiting the sun beyond Pluto.Full article
These Kuiper Belt Objects (or trans-Neptunians) are mostly confined within a few degrees of the ecliptic. This is why The Kuiper Belt is called Belt.
There are three types of KBO's: Plutino's, Classical and Scattered KBO's.
Plutino's are KBO's who revolve arround the sun in an orbit which has a 3:2 resonance with Neptune. This is the same resonance Pluto has. This is why the are called Plutino's (little Plutos).
CKBO's do not orbit in the 3:2 resonance with Neptune.
They are called "classical" because their orbits have small eccentricities, as is expected from bodies formed by quiet agglomoration in the early solar system.
Scattered KBO's are KBO's which possess large, eccentric, inclined orbits that have perihelion distances near 35 AU.
SKBO's are hard to detect due to theire large distance.
The SKBO's form a fat doughnut around the Classical KBO's and the Plutino's, extending to large distances.
It is likely that the Kuiper Belt Objects are extremely primitive debris from the formation of the solar system. The inner, dense parts of the proto-planetary disc condensed into the major planets, probably within a few millions to tens of millions of years. The outer parts were less dense, and accretion progressed slowly. Evidently, a lots of small objects were formed.
As far as we can tell little is known about the exact conditions of the formation of KBO's.We weren't able to find information about this subject.
How did Pluto end up in it's current orbit?
There are several models created to explain the orbit of Pluto:Full article
Dormand & Woolfson - 1977
Collision between major planets
Pluto (satellite of one of those planets) ejected at collision
Interacted with Triton (One of Neptune's satellite), reversing it's orbit.
Harrington & Van Flandern - 1979
Triton and Pluto natural satellites of Neptune
Object of mass 5 Mearth passed through system
Orbit Triton reversed, Pluto ejected
Farinella et. al. - 1979
Pluto natural satellite of Neptune
Triton captured from heliocentric orbit
Interaction between Pluto and Triton
Orbit Triton reversed, Pluto ejected
Charon formed due to tidal forces
Dormand & Woolfson - 1980
similar to Farinella et. al. but more precise
None of these models proved to be true.
The current model is one were Pluto was a natural satellite of Neptune and Triton was in a heliocentric orbit.
Their orbits were changed by a collision. This collision also created Charon.
The mechanism for producing Pluto in its present orbit accompanied by Charon and also Triton as a retrograde satellite cannot be uniquely defined by modelling. Nevertheless, the collision-model with Pluto as a natural satellite of Neptune and Triton as a body originally in a heliocentric orbit is strongly indicated.
In order to answer our subquestion, we have to answer two questions :
What is Pluto?:
Despite of all the differences between Pluto and the other planets, Pluto officially is a planet. However Pluto probably wasn't always a planet. Current models indicate that Pluto was formed as a KBO, became a satellite of Neptune, collided with Triton and then ended up in it's current orbit and became one of the nine planets.
How did Pluto form?:
Pluto didn't form exactly like the other planets. Because of the similarities between Pluto and KBO's it is most likely that Pluto was formed the way KBO's were formed. As far as we know little is known about the formation of KBO's. | <urn:uuid:8409277d-9ef2-4c3e-8603-afe465416762> | 3.796875 | 1,480 | Q&A Forum | Science & Tech. | 49.124638 |
|Themes > Science > Chemistry > Miscellenous > Help file Index > kinetics > Rate constants and order of a reaction|
If the power m or n is zero, then the reaction is 0th order in that species. m or n = 1 means the reaction is first order, 2 means 2nd order, and so on.
Example: a reaction has the rate expression rate = k[A]2[B]1. The reaction is 2nd order in A, 1st order in B and overall the reaction is third order.
To determine the order of a reaction from experimental data, simply vary the concentration of a species while holding everything else constant and look at the change in rate. If you double the concentration of A and the reaction rate doubles, then the reaction is first order; if the rate quadruples, then the reaction is 2nd order and so on. To see this, consider a general reaction of the form above and vary the concentration of [A] while keeping [B] constant
Example: Given the following data, what is the rate expression for the reaction between hydroxide ion and chlorine dioxide?
Solution: In the first and third reactions, the concentration of chlorine dioxide is varied while holding the concentration of hydroxide constant. In the first and second, hydroxide is varied while holding chlorine dioxide constant. To determine the order of the reaction in chlorine dioxide, divide the rate expression for the third experiment by the first.
For hydroxide, do the same thing with the first and second reactions
The overall rate expression is therefore | <urn:uuid:432065b3-fb55-43ac-b592-6ea57cc289d8> | 4.03125 | 324 | Tutorial | Science & Tech. | 45.059848 |
Logging is a critical technique for troubleshooting and maintaining software systems. It's simple, provides information without requiring knowledge of programming language, and does not require specialized tools. Logging is a useful means to figure out if an application is actually doing what it is supposed to do. Good logging mechanisms can save long debugging sessions and dramatically increase the maintainability of applications.
This article is a follow-up to Logging in C++. After having used the logging described therein for two years, I needed certain enhancements to it that improve logging granularity by a large margin: Each individual logging statement can be conveniently turned on and off without the need to recompile or even stop and restart the application.
The previous article presented a simple, yet powerful, logging framework in which each log statement has a specific level of detail associated with it. In that framework, the logging detail level depends on how important or interesting the logged information is. When the application runs, a log level is specified for entire application, so only the log statements at or below a specific detail level are enabled and displayed.
FILELog::ReportingLevel() = logINFO; FILE_LOG(logINFO) << "This log statement is enabled"; FILE_LOG(logDEBUG) << "This log statement is disabled";
The recommended use of the log level is to keep it at a high level of detail for as long as the code is not mature enough, or while you are hunting for a bug. For example, logging the content of some variables makes sense while you are still trying to figure out whether the application works fine, but it just generates logging noise after that. Once the code looks like is doing the right thing, you may want to progressively reduce the logging detail (i.e., level) to finally ship with a relatively sparse logging level that allows post-mortem debugging without slowing down the application.
Assume the application you released went into some bad state and doesn't do what it is supposed to do. You'd like to crank the debugging level up rapidly, but if that requires some static configuration change and the restart of the application, reproducing the problem may be difficult. Also, increasing the log level would dramatically increase the amount of total logged data (since there are so many other log statements on that level), possibly making the application unusable in a production environment.
In this article, I show how you can efficiently "hot-enable" exactly the log statements believed relevant without having to stop and rerun the program. Once you get from the log file the clues you need to track down the issue, you can disable back the logging so you keep the log file at normal size -- all while the application is running. The complete source code and related files are available here.
In this section I introduce some techniques used for achieving our goal: Efficiently enabling/disabling the log statements with line-level granularity:
- Sharing data between threads using simple variables and no locking. A simple and efficient way to communicate between different threads is to use a shared global variable. You have to satisfy certain conditions:
- The reading/writing of data has to be atomic (using native machine word size).
- Reading/writing should be done using memory barriers (compile time/run time). The code will use such shared global variables to signal whether a given log statement should be enabled or disabled. One thread will set the variable with the desired value, while another thread will read it. There is no locking involved in reading the variable, so sharing these variables can be done very efficiently.
- Declaring static local variable inside
forstatements. You can define a static local variable on-the-fly, inside a
forstatement. For example:
for (static int i = 0;;);
is legal in C++, and the variable is visible only inside the
forloop. By using these
forloops the log statements can read these variables very efficiently, without any lookup.
- Declare local variable inside
ifstatements. You can define a local variable on-the-fly, inside an
ifstatement. For example:
if (bool flag = false) ; else …
This variable is visible only inside the
if/elsestatement. The purpose of these
ifstatements is only to make sure that the inner
forloops are executed once at most. | <urn:uuid:56256b2c-4f36-4bc1-a706-1bb6ee4804f6> | 2.8125 | 895 | Documentation | Software Dev. | 31.651443 |
fundamentals of physics
THE LAW OF INERTIA
The tendency of a body to continue in its state of rest or of uniform motion in a straight line even when some external unbalanced force is applied is called Inertia. Mass is the measure of Inertia of a body.
Inertia is of two types namely:-
1. Inertia of rest
2. Inertia of motion
The force which a body possess due to combined effect of mass and velocity is callled the Momentum. It is defined as the product of mass and velocity. It is denoted by p . p=m*v
SI unit of Momentum is Kgm/sec
NEWTONs LAWS OF MOTION:-
NEWTON,s FIRST LAW OF MOTION
It states that a body will continue in its state of rest or of Uniform Motion in a straight line unless compelled by some applied unbalanced force to change of rest or of Uniform motion.
NEWTON,s SECOND LAW OF MOTION
The rate of change of Momentum of a body is directly proportional to the applied unbalanced force and takes place in the same direction in which the force acts.
NEWTON,s THIRD LAW OF MOTION
To every action, There is an equal and opposite reaction.
So, can u now answer,
1. How do we walk?
2. Why the gun recoils?
3. why is it difficult to alk on a sandy beach?
4. Can u tell the SI unit of Force?
Hope its all clear? | <urn:uuid:e9de5532-0fc4-471c-8cee-d7cfd839b0de> | 4.125 | 326 | Q&A Forum | Science & Tech. | 66.636406 |
Ryan Nichol, who works upstairs from me at UCL, gets together with NASA every now and then and flies a balloon around the Antarctic.
They are looking for the answer to one of the great questions in astrophysics. We know that there are really really high energy particles hitting the Earth all the time from outer space. We would really like to know where they are coming from. The aim of ANITA (Antarctic Impulsive Transient Antenna) is to address this by looking for neutrinos.
In their first flight, though, they found something else.
What they actually detect is short radio bursts. As part of what may become (along with coffee seen by neutrons) a series of weird ways to look at the world, here's the the image ANITA builds up of the continent in radio bursts.
They can measure the polarization of the radio waves - which direction the electromagnetic field oscillates in as the waves travels. Neutrino interactions produce vertically polarized pulses. They didn't see any of these. But they did see 16 pulses of horizontally polarized radio waves.
These turned out to be the signature of ultra high energy particles hitting the atmosphere and causing a cascade of particles - "cosmic-ray air-showers". In these showers, electron-positron pairs are produced and they spiral around the Earth's magnetic field lines, giving a characteristic radio signal seen by ANITA. As Ryan puts it:
The cosmic-ray air-shower radio signals were really unexpected and we only found them by checking a 'background' event sample for the neutrino search. It took us a long time to understand their significance to the point that for the second ANITA we removed the horizontal polarisation from the trigger to maximise neutrino efficiency. Whoops! Needless to say we will be reinstating it for the third flight.
These showers have been seen before, for example by the Auger experiment. But new ways of seeing them, and measuring where they come from, are valuable. ANITA has, serendipitously, demonstrated an important new technique with a lot of potential.
The paper was on the cover of Physical Review Letters this month. The images come from Ryan and Matthew Mottram. All the institutes in the ANITA collaboration are listed on the University of Hawaii site here.
NB Caption to the balloon picture modified 1/11/2010, to add credit and Wembley. | <urn:uuid:b57e7e57-3a44-4b33-b750-e0630d1f95f1> | 2.96875 | 507 | Personal Blog | Science & Tech. | 48.04926 |
Pure Appl. Chem., 2012, Vol. 84, No. 7, pp. 1669-1672
Published online 2012-06-26
INORGANIC CHEMISTRY DIVISION
Names and symbols of the elements with atomic numbers 114 and 116 (IUPAC Recommendations 2012)
Abstract: A joint IUPAC/IUPAP Working Party (JWP) has confirmed the discovery of the elements with atomic numbers 114 and 116. In accordance with IUPAC procedures, the discoverers proposed names as follows: flerovium with the symbol Fl for the element with Z = 114 and livermorium with the symbol Lv for the element with Z = 116. The IUPAC Inorganic Chemistry Division recommended these proposals for acceptance, and they were adopted on 23 May 2012 by the IUPAC Bureau as delegated to act by the IUPAC Council meeting on 3–4 August 2011. | <urn:uuid:34a2e219-1f2d-42df-a19f-0126bb229f45> | 2.703125 | 189 | Academic Writing | Science & Tech. | 61.030025 |
What is this DNA stuff?
If you've never heard of DNA, first read http://en.wikipedia.org/wiki/Dna and maybe pick up a textbook for the basics.
The critical things you should understand before trying to do this tutorial:
- DNA is a chemical entity, but we represent its sequence in the computer
- DNA is made of 4 deoxyribonucleotides, A, T, C, and G (casually called bases) in a specific sequence determined by covalent bonds
- DNA molecules have directionality; one end is the 5' terminus, the other end is the 3' terminus
- By convention, DNA sequences are always written out in the 5' to 3' direction unless stated explicitly with "5'-" and "3'-" Alternatively, DNAs can be represented in cartoon form as a line with a barb at one end. The barb refers to the 3' end.
- DNA can be circular or linear
- DNA can be single stranded or double standed
- The two molecules of a double standed DNA bond to each other by Watson-Crick base pairing
- The sequence of the complementary strand of a double standed DNA is the "reverse-complement" of the other strand
- The "reverse" and "complement" operations on a DNA sequence do not result in biochemically-meaningful sequences. You must always do both (reverse-complement) to get the sequence of the complementary strand
- With some exceptions, bacteria can only replicate double stranded circular DNAs. Genomic and plasmid DNA is therefore circular and double stranded.
- Oligonucleotides are linear single-stranded DNAs
- PCR products are linear double-stranded DNAs
- Even when DNAs are circular double stranded molecules, we represent them as linear single-stranded sequences using our software tools like ApE
Understanding the "reverse-complement" operation on a sequence is an essential concept that you will be using throughout this tutorial. If it isn't entirely clear yet, practice writing out a DNA sequences on a piece of paper, fill in what would be the complementary strand, and put in 5' and 3' ends to everything. Spin the piece of paper around and get used to the basic logic operations at play here. When you feel comfortable, proceed! | <urn:uuid:52ad8c44-f7fa-457e-a240-8dd90933c87b> | 4.3125 | 488 | Tutorial | Science & Tech. | 37.310446 |
Effects of fertilisation on phosphorus pools in the volcanic soil of a managed tropical forest
Meason, D. F., Idol, T.W., Friday, J.B. and Scowcroft, P.G. 2009. Forest Ecology and Management 258: 2199- 2206.
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Acacia koa forests benefit from phosphorus fertilisation, but it is unknown if fertilisation is a short or long term effect on P availability. Past research suggests that P cycling in soils with high P sorption capacity, such as Andisols, was through organic pathways. We studied leaf P and soil P fractions in a tropical forest Andisol for 3 years after fertilisation with triple super phosphate. Leaf P concentration and labile P remained high after fertilisation. Fertilisation had increased all the inorganic P fractions over the length of the study, while organic P fractions had not. The results suggested that the organic P fractions had a reduced role as a source of labile P after fertilisation. The size and dynamics of the sodium hydroxide- and hydrochloric acid-extractable P pools would suggest that either pool could be major sources of labile P. Because of the high level of poorly crystallineminerals in Andisols (allophone and imogolite), it would be expected that applied P would quickly lead to strong P sorption onto mineral surfaces and thus a rapid decline in P availability. We propose that the high organic matter present in these soils had masked some of the Al and Fe sorption sites, which allowed the sorption and desorption when large amounts of addition P were applied. | <urn:uuid:5b876b96-893e-4c04-8c21-137ba33fb1b9> | 2.703125 | 361 | Academic Writing | Science & Tech. | 54.33413 |
Written by Jonathan Wojcik
While commonly confused with the jellyfish and other Cnidaria, the comb jellies belong to their own distinct phylum, the Ctenophora, believed to be one of the planet's oldest and most basal forms of animal life. They are so named for their comb-like rows of beating cilia, which may appear brilliantly colored as they catch the light. This makes ctenophores the largest organisms to use cilia for swimming, like microscopic protozoa.
Like the jellyfish, ctenophores consist of little more than a gelatinous "pouch" lined inside and out with a thin layer of cells. Strictly carnivorous, they engulf microorganisms, other comb jellies or even small fish and crustaceans, rapidly liquefying prey with their digestive enzymes. Some comb jellies may eat several times their body weight in a day, and several species have become serious invasive pests.
Different orders of comb jelly exhibit highly diverse body types; the Cydippida are the largest and most common order, with simple pod-shaped body and a pair of long, trailing tentacles lined with smaller tentacles or tentilla. Though they lack the stinging cells or cnidoblasts of jellyfish, ctenophores often line their tentacles with colloblasts, explosive cells filled with a glue-like fluid. Some Cydippids may also devour stinging jellies and incorporate the cnidoblasts into their own tentacles, much like certain nudibranchs.
Cydippids of the family Lampeidae include the only known examples of parasitism in the ctenophores, their larvae latching onto the bodies of salps and slowly consuming their tissues. Salps continue to make up their entire diet as adults, but fully grown Lampea can devour them whole - even gobbling their way through entire connected salp chains or Blastozooids, as seen here.
Another unusual cydippid is Euplokamis dunlapae, whose bulbous, coiled tentilla have their own simple "muscles" and may be wriggled to attract small prey.
The Lobata are another large order, distinguished from the cydippids by two large lobes surrounding the mouth, which they can "clap" together when they need to swim quickly. Their tentacles are embedded in twisting grooves along their inner surface, trapping planktonic prey sucked inside by the cilia.
Thalassocalycida are often wider, rounder and more jellyfish-shaped than the other orders, lazily drifting in an open "bell" shape until they close shut around planktonic prey, as this one is demonstrating.
The two lone species of orderCestida may be the most beautiful and surreal of the ctenophores, often called "Venus' girdles" for their elongated, ribbon-like shape. With its mouth at the center, the rest of the girdle's serpentine form can be thought of as a pair of "arms" or "wings," which it can undulate rapidly to swim sideways in either direction.
Equally bizarre are the Platyctenida, combless comb jellies who live more like slugs or flatworms, creeping along what would normally be the interior lining and "mouth" of other ctenophores. Trailing their tentacles in the water to trap plankton, some species are domed and "horned" like these while many others are perfectly flat, often living harmlessly on the bodies of sea stars, cucumbers, corals or sponges where they look like little more than colorful patches of skin.
While by no means the weirdest or most elaborate, the Beroid comb jellies are my personal favorites, and I'm sure you can see why. Completely lacking tentacles or colloblasts, these swimming mouths prey exclusively on other comb jellies, swallowing them whole or taking bites out of of them with internal "teeth" formed from modified cilia. When not eating, they "zip shut" their mouths with adhesive cells and flatten out into a faster moving shape; sleek, ravenous sharks of the jelly world.
One of the most unusual ctenophores, and the last I'll be describing, is also one of the most recently discovered and still largely an enigma; it was captured on video in 2002, but its footage wasn't viewed until 2006, and no specimens have since been recovered. Still unnamed, we only know that this species seems to hold onto the seabed by a pair of long cables, drifting kite-like in the current with its feeding tentacles held out. | <urn:uuid:86f5fa66-c733-4715-b9b9-e09e6c817e92> | 3.90625 | 976 | Personal Blog | Science & Tech. | 31.293276 |
Drought 2008 (updated November 13, 2008)
As of November 11, the U.S. Drought Monitor placed many Minnesota counties in the D0 - Abnormally Dry category or worse (see map at right). Portions of the state, most notably southeastern Minnesota, were placed in the D1 - Moderate Drought classification.
The dry conditions were the result of a lengthy stretch of dry weather that commenced in mid-June and extended through the growing season. For the period mid-June through mid-November, many southeastern Minnesota communities received less than eleven inches of rainfall. This represents a negative departure from normal of five to eight inches in these areas. When compared with the same twenty one-week time span in previous years, mid-June through mid-November rainfall ranked below the 5th percentile (one year in twenty) in some southeastern Minnesota communities (see maps below).
Fortunately, summer temperatures were close to historical average and days with temperatures in the 90 were relatively rare. This kept evaporative demand near seasonal norms and mitigated the situation.
Previous week's weather:
The weekly rainfall map for November 4 through November 10 showed that precipitation totals were quite substantial in many areas. The heavy rains led the U.S. Drought Monitor authors to remove some sections of central Minnesota from drought designation. The authors also upgraded portions of north central and northeastern Minnesota from the "D1 - Moderate Drought" category to the "D0 - Abnormally Dry" category. Temperatures for the week were quite warm, averaging ten or more degrees above seasonal norms.
- Agriculture - The Agricultural Statistics Service reported that as of November 7, topsoil moisture across 6 percent of Minnesota's landscape was "Short" or "Very Short". Of greater concern are soil moisture supplies deeper in the soil profile, especially in south central and southeastern Minnesota. Subsoil moisture measurements taken at the University of Minnesota - Southern Outreach and Research Center in Waseca were below the long-term average in early November.
- Stream flow - Mid-November stream discharge in Minnesota rivers and streams was highly variable across the state. Some Minnesota streams reported flows that ranked below the 25th percentile in the historical distribution for the middle of November. By contrast, the Red River and many of its tributaries reported very high flows in response to heavy rains that fell in the late summer and autumn.
- Wildfire Danger - The Department of Natural Resources - Division of Forestry classified early-November wildfire danger as Low throughout Minnesota. | <urn:uuid:95cdc545-9f5e-4b9d-b76a-2f7370025d28> | 2.921875 | 510 | Knowledge Article | Science & Tech. | 30.695413 |