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Constructing an octahedron and Kepler's conjecture To make an interesting skeletal model of an octahedron, start with 12 identical squares of paper or light card.
Net for the octahedron Downloaded from http: // mathworld. wolfram. com / pdf / Octahedron. pdf For more information, see the MathWorld entry http: // mathworld. wolfram. com / Octahedron. html
Modular Structures for Manned Space Exploration: The Truncated Octahedron asa Building Block O. L. deWeck, W. D. Nadir †, J. G. Wong ‡, G. Bounova § and T. M. Coee ¶ Massachusetts Institute of Technology, Cambridge, MA, 02139, USA Modular space exploration systems have been built in the ...
octahedron isometric colorless to pale yellows, browns and grays non metallic white Yes octahedron Yes conchoidal 3.5 Galena 2 cube, octahedron isometric
Platonic Solids 2 A regular tetrahedron and a regular octahedron are two of the five known Platonic Solids. These five “special” polyhedra look the same from any vertex, their faces are
One might suppose that these forms are also infinite, but in fact they are, as Lewis Carroll once expressed it, "provokingly few in number."There are only five regular convex solids: the regular tetrahedron, hexahedron (cube), octahedron, dodecahedron, and icosahedron (see Figure 1).
Octahedron? Dodecahedron? Icosahedron? What'sthesolidwhose vertices are the midpoints of the edges of the tetrahedron? Cube? Octahedron? Dodecahedron?
17 Octahedron And Cuboctahedron We mentioned earlier that octahedron and cuboctahedron can be defined as transformed icosahedra. You can also imagine the 6 square faces of the cuboctahedron as diagonal connections (1*sqrt2) of two rectangular triangles.
When the device is switched 'on', the interior is isolated from its surroundings by the superluminal rotating magnetic field and octahedron antenna. | <urn:uuid:4609f201-efc1-4e08-8c9f-87ebe3e2ea74> | 3.8125 | 497 | Content Listing | Science & Tech. | 31.837121 | 1,900 |
Bangladesh capital has topped a list of cities facing the highest climate change risks in the coming years. Kolkata came seventh, Mumbai eighth while Delhi was in the 20th position.
The ranking of 50 cities was done by Maplecroft, a British firm specialising in risk analysis. The cities were chosen for their current and future importance in global business.Maplecroft’s Climate Change Vulnerability Index (CCVI) classified seven cities as facing “extreme risk”.
Manila was ranked second, while Bangkok, Yangon, Jakarta and Ho Chi Minh City came third, fourth, fifth and sixth, respectively. The report looked at exposure to extreme weather such as droughts, cyclones, wildfires and storms, which translate into water stress, loss of crops and land lost to the sea.
Chicago, London, St. Petersburg, Paris and Madrid are the only five cities classified as “low risk”.IANS | <urn:uuid:9390ef64-650e-4667-9143-3931f987acdb> | 2.703125 | 196 | News Article | Science & Tech. | 43.86968 | 1,901 |
But it isn't feasible to study every single species on the planet in depth- there are hundreds and thousands of types of insects alone! Fortunately, it has become clear that there are often many parallels between the biological systems at work in many types of creature, from yeast to humans. This had led to the establishment of a number of so-called "model organisms", which are studied consistently by investigators the world over. The consistent use of these particular critters allows us to make and test ideas about biology in a rapid and reproducible way. In the case of some very important mechanisms, the use of very simple animals has managed to tell us a great deal about humans. To do the same experiments with people would be very time-consuming (not to mention unethical).
The vast majority of model organisms used by scientists in the UK are small simple animals. The most common of these include microscopic nematode worms, fruit flies and African claw-toed frogs. Or to give them their official names, Caenorhabditis elegans, Drosophila melanogaster and Xenopus laevis. I'll stick with worms, flies and frogs to keep it simple. All these animals have the advantage of being available in large numbers, and are easy to breed. In the case of worms and flies, we have the complete sequence of their DNA. This makes it very easy to spot important genes and to use them for further study. As well as the breeding benefits, these animals have told us much about how animals develop from the egg. In particular, we have discovered how simple creatures work out which way is up, down, left and right when they are developing. Unfortunately, mammals such as mice and humans don't develop in the same way.
Plant biologists often use a specific type of cress as a model, although you probably wouldn't want to sprinkle Arabidopsis thaliana on your egg sandwiches. Many experiments are also performed on brewer's yeast, a.k.a. Saccharomyces cerevisiae. Let's hope the Campaign for Real Ale don't get too upset. This may seem unbelievable, but these yeasty beasties have huge similarities to the cells found in more complex animals, even humans. For example, the way that DNA is wrapped up to fit in the cell is the same in all these organisms, from yeast upwards. Similarly, the basic ways that genes are activated and turned off is preserved. Even the way that cells from yeast and animals multiply is the same. For me, one of the most breath-taking things about studying biology is finding that a gene that plays a particular role in the humble yeast is also of paramount importance in humans.
So why can't we just study yeast and flies to learn all about humans? The simple answer is that although many systems are the same in most cells, many are not- or have fundamental differences. As I mentioned before, mammals such as mice and humans don't make their embryos in the same way as flies, frogs or worms. The use of mammals in research is an emotive issue for some people, yet it is an inescapable fact that to study certain things only a mammalian model will do. In the UK, the use of such animals is very tightly regulated to ensure that only essential experiments are performed. There is a dazzling array of technology available to study the effects of genes in mice. This has led to the development of mice which model a wide range of human diseases, including diabetes, Down Syndrome, muscular dystrophy, obesity, deafness and many other inherited syndromes. The list goes on, as do the exploitable benefits to our understanding and treatment of human diseases. These "diseased" mice are created by the removal (or addition) of a particular gene by genetic engineering. Although the majority of disease models are mad in mice, there are a few syndromes which can be mimicked in other animals. For example, it's possible to breed fruit flies that have some of the symptoms of Alzheimer's disease.
One other technology which is developing into a model system in its own right is the growing of cells on plastic dishes in incubators, known as cell culture. Cultured cells can be taken from a wide range of sources. These may include human donors with particular diseases, such as cancers or inherited diseases. Cells can also be taken from animals such as the genetically engineered mice already mentioned. The only problem with devoting all our studies to cultured cells is the sad fact that the characteristics of these cells tends to change over time. This is because the cells pick up mutations from the culturing process. Some cell types, particularly the most popular ones, are now so mutated that they are like another organism altogether. So we must still always refer back to real animals to make sure our studies are really relevant and accurate. Scientists are therefore very lucky to have models that certainly will get out of bed for less than ten thousand pounds a day! It saves us a fortune on champagne as well | <urn:uuid:1b764e9b-78a1-4944-bcac-3edaaf9857f6> | 3.375 | 1,014 | Knowledge Article | Science & Tech. | 43.703782 | 1,902 |
NASA said Tuesday it has suspended use of one of the mineral-identifying tools on the Opportunity Mars rover due to a problem.
The robot's thermal emission spectrometer was acting up, and engineers are obtaining data from it while troubleshooting.
The problem might be related to a malfunctioning optical switch that tells a mirror in the instrument when to begin moving. Or the mirror might not be properly moving at a constant velocity.
"If it is the optical switch, we could use a redundant one built into the instrument," said Phil Christensen of Arizona State University, lead scientist for the miniature thermal emission spectrometers on both rovers.
In a statement released by NASA, Christensen added that if the root cause cannot be remedied, scientists could still get useful data from the instrument in its currently impaired condition.
The rovers have been on Mars since January 2004 and were guaranteed for only three months of work. Mission officials had always expected that if nothing unexpected cropped up, the rovers would operate longer.
Opportunity is continuing to operate, observing a crater called Vostok.
The problem dates back to March 3 and 4, when eight of 17 attempted readings by the instrument yielded incomplete data sets, according to the statement. The spectrometer sits high on the rover's mast and observes rocks and other targets from afar. It measures infrared radiation.
© 2013 Space.com. All rights reserved. More from Space.com. | <urn:uuid:88a20404-f043-4c74-b994-8711903632c8> | 3.015625 | 294 | News Article | Science & Tech. | 44.957763 | 1,903 |
Treading Heavily on the Environment: China's Growing Eco-Footprint Highlighted in New Report
photo by Sheila via flickr
We've written about the concept of Eco-Footprint a number of times--what it is, how to calculate it, and how to reduce yours--and with the Olympics upon us it comes as no surprise that China's environmental footprint might come into the spotlight.
A new report by the Global Footprint Network, WWF, and the China Council for International Cooperation on Environment and Development does just that. While China is the obvious focus, really this report highlights how humanity as a whole is increasingly overshooting the biological capacity of the planet. It also includes recommended steps that China can take to address the issue of its increasingly heavy environmental impact.China Has Low Individual Footprint, But High National FootprintWhat the report finds is that, per capita, China ranks 69th in the world, with each person requiring 1.6 hectares of biocapacity to support them. This is lower than the global average of 2.2 hectares per person, and quite a bit lower than the United States' world-leading 10 hectares per person.
However, because of the of the overall size of the country, China ranks 3rd in total global eco-footprint, trailing the United States and the entire European Union.
Footprint Grows Along With GDPThe result is that currently China requires the equivalent of two times its biocapacity to support its current population and current level of economic activity. As China's GDP grows the amount of resources it requires only increase. Therefore, it has to effectively import biocapacity from elsewhere.
Export Manufacturing Responsible To enable this, approximately 75% of China's total biocapacity imports are consumed by this process. Only slightly more than 25% of these remain in the country for domestic consumption. We recently highlighted a report that shows that roughly a third of China's carbon emissions are directly tied to manufacturing of consumer goods for export.
As of 2003, the nearest year for which data is available, China consumed 15% of the total biocapacity of the planet. The report points out that if China were to follow the lead of the United States, in terms of levels of natural resource consumption, it alone would require the entire biological capacity of the planet. Obviously this would be an impossibility, so something needs to change, both in China and in the rest of the world.
Where To Go From Here?The report recommends five areas that need to be addressed. This is where all nations should pay attention. These areas are:
Population -- Slow and reverse population growth by offering better family planning opportunities, increasing education and economic opportunity for women. This is probably the most uncomfortable aspect of our environmental problems, but also one most in need of action.
Consumption -- Essentially, we need to increase consumption at the bottom end of the scale to lift people out of poverty, while reducing (radically, I'd say) consumption at the top end. The report points out that the average Italian uses half as many resources to have a standard of living equal if not better than in some ways than the average US citizen. It is possible to do more with less when it comes to consumption and we must do that, particularly in the United States.
photo by Ruth LozanoTechnology -- Not a technological quick fix, but improvements in energy efficiency both in manufacturing and in the home, waste reduction and recycling increase, reduction of the distance which goods travel between factory and marketplace.
Area -- Reclaim and rehabilitate lands suffering from environmental degradation to increase biological capacity.
Productivity -- Increase the useful production per hectare of land through better land management. The report points out that while intensive agriculture can increase crop yields, this comes at the expense of biodiversity loss and increased fertilizer and energy usage, both which ultimately increase ecological footprint. As a recent UN report essentially said, we need a revolution in farming that takes a more holistic, ecosystems approach to agriculture, rather than the continued industrial viewpoint.
What Can You Do?Some of these steps really require large-scale action, but that can be led to some degree at the individual level. A good first step, as we've said many times, is to assess your own ecological footprint. I'll plug The Footprint Networks' Personal Eco-Footprint calculator as the report I've been referencing comes from them, though there are plenty of other good calculators on the internet.
From there you can look at ways you can reduce your own eco-footprint, keeping in mind that there is a line below which you can't go simply because of the structure of the society in which you live. That's where the heavy lifting has to come in and structural changes have to be made.
There's more on this report, and more on eco-footprints in general at :: The Footprint Network.
All charts: The Footprint NetworkEcological FootprintBrazil and India Top Greendex; USA, Canada and France Finish LastYour Ecological Footprint: Defining, Calculating and Reducing Your Environmental FootprintAfricans' Modest Eco-Footprint Still Has Negative Impacts in Some CountriesChinaChina Gets Dubious Honor of World's #1 CO2 EmitterIt's Not You, It's Me: 33% of China's CO2 Emissions From Export Manufacturing | <urn:uuid:a71cbc30-cd29-430f-8b78-f08c2763a387> | 2.78125 | 1,097 | Personal Blog | Science & Tech. | 31.015367 | 1,904 |
A Publication of
The University of Montana
UM researchers unearth Cinnabar
Scientists track Greenland meltwater
New UM center offers healing tools for Indian Country
New Directions: Combining health with research
View is published twice a year by the offices of the Vice President for
Research and Development and University Relations at The University of
Montana. Send questions, comments or suggestions to Rita
Munzenrider, managing editor, 327 Brantly Hall, Missoula, MT 59812,
or call 406-243-4824. Production manager and designer is Cary
Shimek. Contributing editors and writers are Brianne Burrowes, Brenda
Day and Shimek. The photographer is Todd Goodrich. Web design is by Shimek.
For more information about UM research, call Judy Fredenberg in the Office of the Vice President for Research and Development
An Icy Adventure
Scientists track Greenland meltwater
World oceans would rise 23 feet and flood many coastal areas if climate change melted the entire Greenland ice cap. And satellite images from 1980 onward reveal the surface of this vast ice sheet is warming, getting soggy and staying wet for longer periods every year.
However, preliminary research by UM and its partners suggests some of this meltwater does not reach the ocean to contribute to sea-level rise. Instead it infiltrates downward into colder snow and refreezes into ice layers that can be more than a foot thick. These layers are fragmented, so water can’t flow atop them for long before draining downward again and freezing in place.
“We are still working up our results, but so far this is good news concerning worries about Greenland’s role in the sea-level rise we see happening today,” says UM glaciologist Joel Harper. “Since many of the ice layers that form during a year of heavy melt are discontinuous, the next year’s melt can’t travel along the ice layers as a means of escaping the ice sheet.”
He says it’s so dark and cold during Greenland winters that even with some winter warming the snowpack is still extremely cold going into summer, “and summer melting always will have a hard time warming a snowpack laden with cold dense ice layers.”
Harper was part of a six-person scientific expedition that ventured onto the Greenland ice sheet for a month during June and July. They lived in tents high atop the ice cap at about 6,600 feet in a white, featureless landscape swept by endless wind. To do its work, the group made 60- to 70-mile journeys down into the melt zone closer to Greenland’s west coast, using snowmobiles to pull scientific gear and expedition members on skis.
Harper says their research was funded by a $524,000 National Science Foundation grant. His project collaborators are Tad Pfeffer of the University of Colorado and Neil Humphrey of the University of Wyoming. Each scientist brought one graduate student to complete the team.
The researchers drilled 21 35-foot-long ice cores during the course of their work. They also dug many snow pits and did numerous experiments with colored dye to track meltwater flow. In addition, they installed two meteorological stations and used radar to map ice layers beneath the snow.
In five boreholes located in sequentially lower elevations across a 25-mile span, the team also installed vertical strings of temperature sensors to note melting and freezing events in the snow up to 35 feet deep. (When water freezes it releases heat – a thermal signature that can be detected.) Harper says the sensors – called thermistors – have their own power source and will record data until researchers retrieve them next year.
He compared the Greenland ice cap to pancake batter. In its middle at higher elevations there is more snowfall than melting. As more snow is poured on, it compresses the vast sheet, which flows outward toward the warmer coasts where there is more melting.
The team had two snowmobiles to haul six people and their gear down to the melt zones to do their research. The landscape is utterly devoid of landmarks, so they used global positioning systems to navigate during the three-hour traverses. Two scientists drove, while the rest were towed behind the snowmobiles on skis.
“While skiing, we put on every bit of clothing we had and an iPod because you were standing behind these snowmobiles for three hours or more,” Harper says. “We would use a bike tire as a harness clipped to the rope. So we would just stand there and try not to fall asleep as we were pulled along.”
Harper, who was a competitive skier as a youth in Colorado, also tried using a sail to kite ski across the ice cap. His power source was Greenland’s endless katabatic winds, which are caused by dense cold air atop the ice sheet flowing downward toward the warmer coasts.
“A lot of times it was too windy – you could get up to 30 mph no problem,” he says. “I could get screaming along – and I’m used to speed – but this was on the edge. I found it was too hard to navigate long distances with GPS when you are trying to fly the kite and not crash. It just wasn’t compatible with the whole group, so in the end it was more for fun.”
He says some of the melt zone contained barely wet snow, while other areas were a “slush swamp” of super-saturated snow that a person without skis could sink into like quicksand. The expedition had to make the long traverses from base camp because members didn’t dare camp in the melt zone. Too much thawing could bog down their snowmobiles and leave the researchers stranded in an area where ski planes can’t land. They might be stranded in the soggy snow until the next freeze.
“And if the snow machines would break, you couldn’t possibly ski back in a day,” he says. “It’s too far.”
Harper says his group will return next year to study another 75-mile stretch of the ice cap. They will start at the lowest elevation examined last summer and continue downward toward the coastal melt zone. The expedition will begin earlier in the year so the snow won’t be as treacherous at lower elevations.
“This is one reason why our results are preliminary,” he says. “We only have half the story. I suspect things might really be moving down below, but so far in the upper part of the ice sheet, we have thrown that out. In that area we found the melt is increasing every year, but it isn’t going anywhere.”
Harper says they decided to study the west side of the ice cap because it is accessible from the town of Kangerlussuaq, which is the logistics headquarters for science in Greenland. The ice they studied also is the headwaters of Jakobshavn, one of Greenland’s big calving glaciers that has increased speed in recent years. Their base camp was a three-hour plane ride from Kangerlussuaq.
“There was nothing special about our camp,” he says. “It was just some GPS coordinates we selected in the middle of nowhere. We got nailed by a big storm right after we arrived, but after that temperatures stayed between about 10 and 35 degrees Fahrenheit.”
Harper says their work might partially explain why Greenland isn’t a larger player in current sea-level rises despite its enormous ice cap. A 2007 article in the journal Science contends Greenland contributes about 0.5 millimeters to ocean level rise annually, while smaller glaciers scattered around the globe contribute 1.1 millimeters to sea-level rise.
“Other recent work shows that ice loss from small glaciers and ice caps like those in Montana dominate current sea-level rise and will likely continue to dominate sea-level increases for at least the next 50 years,” he says. “Since there are several hundred thousand small glaciers around the world, the sea-level rise we expect from them is still very significant.
“I don’t know of any glaciologist who thinks anything like a 6-meter (19.8-foot) sea-level rise is in the cards by the end of the century,” Harper says, “but even 1 meter – which is at the upper end of what we currently think might be possible – would be a very big deal.”
— By Cary Shimek
Some days the researchers skied up to 70 miles per day behind snowmobiles. (Joel Harper photo)
|Wind-blasted UM researcher Joel Harper relaxes in a tent on the Greenland ice cap. (Tad Pfeffer photo)
|A map showing the extent of melting in 2005. The central black dot shows the expedition's base camp. (Graphic by Russell Huff and Konrad Steffen)
|UM glaciologist Joel Harper kite skis the Greenland ice cap. (Tad Pfeffer photo) | <urn:uuid:181f3c7a-cd04-45e9-b391-bd8c9d1af97c> | 2.953125 | 1,916 | News (Org.) | Science & Tech. | 54.664665 | 1,905 |
Classical General Relativity in more than four spacetime dimensions has been the subject of increasing attention in recent years. Among the reasons why it should be interesting to study this extension of Einstein’s theory, and in particular its black hole solutions, we may mention that
- String theory contains gravity and requires more than four dimensions. In fact, the first successful statistical counting of black hole entropy in string theory was performed for a fivedimensional black hole. This example provides the best laboratory for the microscopic string theory of black holes.
- The AdS/CFT correspondence relates the properties of a d-dimensional black hole with those of a quantum field theory in d − 1 dimensions.
- The production of higher-dimensional black holes in future colliders becomes a conceivable possibility in scenarios involving large extra dimensions and TeV-scale gravity.
- As mathematical objects, black hole spacetimes are among the most important Lorentzian Ricci-flat manifolds in any dimension.
And the translation:
Traditional general of relativity in more than four masses of that the time of the space was the subject of the increase attention these the slipped years. To the relations of transformation, so that he had that to being interesting, to this extension of the theory of Einstein to study and in the detail of the relative solutions to perforate black color, that we can we mentioned this
- The theory of the series of the characters will count the force of the gravity and it more has the necessity of the one of mass four. They executed the first guessed right statistical client of the entropy of the black color that really perforates in the theory of the series of the characters the end to perforate the black color of the fivedimensional. This better example releases the laboratory available for the microscopic theory of the series of the characters of the black color of the perforations.
- The correspondence of AdS/CFT connects the characteristics of a D dimensional schwarzen that the sacadores with those with a theory of the zone of the section of the time in the D without mass 1.
- The production of the perforations that the high-dimensional-black color in her the future transforms of colliders inside the great possibilities imaginable ones into the writing of the suggestion adds of the film and in the fairs of TeV the force of the gravity.
- As matemati of the messages those we belong spacetimes of the black color that the sacadores to the tubes the greatest piece of the important Stocherkaehne I gave curly Lorentzian in each possible measurement.
I hope that clarifies everything.
Makes me wonder why there is no requirement these translation maps be invertible. | <urn:uuid:152ce7f1-8d02-4546-a969-0b59a15efdeb> | 2.765625 | 560 | Personal Blog | Science & Tech. | 27.993433 | 1,906 |
We have now seen four common concurrency concepts that can be used for programming concurrent application logic. However, there are still other concurrency concepts and language primitives for concurrent programming. We will now introduce the more interesting ones briefly. We give hints how they relate to the former concepts and how they can be used in practice.
Promises [Fri76,Lis88] and futures [Bak77] generally describe the same idea of decoupling a computation and its eventual result by providing a proxy entity that returns the result, once available. In concurrent programming, promises and futures are often used for asynchronous background tasks. Once a task is dispatched, the proxy entity is returned and the caller's flow of execution can continue, decoupled from the new computation. The proxy entity can later be queried to return the result of the decoupled computation. If the result is not yet available, the proxy entity either blocks or provides a notification, when non-blocking.
Promises and futures also introduce a synchronization mechanism, as they allow to dispatch independent computations, but synchronize with the initial flow of control, once the result is requested and eventually returned. Futures and promises are available in many programming languages using threads for concurrency. In this case, the execution of the background task is scheduled to another thread, allowing the initial thread to continue its execution. Actor-based systems often use an actor as a proxy entity of a computation, which is essentially the same as a future [Hew73]. Sending a message to another actor and awaiting its eventual response is also often abstracted using futures. In event-driven systems, eventual results are represented by events, and handled by associated callbacks.
When programming web applications, promises or futures can be used to decrease latency. The scatter-gather pattern dispatches multiple independent operations (scatter) and waits for all operations to yield results (gather). For instance, multiple independent database queries can be parallelized using this pattern. This can be implemented by scattering all operations as background tasks yielding proxy entities, then gathering all results by accessing the proxy entities. In effect, this converts a sequence of operations into parallel execution of operations. Dataflow programming provides a similar execution strategy, but hides the notion of futures in the implementation.
Coroutines [Con63], and similarly fibers and green threads, are a generalization of subroutines. While a subroutine is executed sequentially and straightly, a coroutine can suspend and resume its execution at distinct points in code. Thus, coroutines are good primitives for cooperative task handling, as coroutines are able to yield execution. We have identified the advantages of cooperative task handling in chapter 4, especially in case of massive parallelism of asynchronous operations such as I/O.
Coroutines are often used as low-level primitives, namely as an alternative to threads for implementing high-level concurrency concepts. For example, actor-based systems and event-driven platforms may use coroutines for their underlying implementation.
There are also several programming languages and language extensions that introduce coroutines or their variants to high-level programming languages. For instance, greenlet is a coroutine framework for Python, that is heavily used by high performance event loop frameworks such as gevent.
Google Go is a general-purpose programming language from Google that supports garbage collection and synchronous message passing for concurrency (see below). Go targets usage scenarios similar to C/C++ by tendency. It does not supply threads for concurrent flows of executions, but a primitive called goroutine, which is derived from coroutines. Goroutines are functions that are executed in parallel with their caller and other running goroutines. The runtime system maps goroutines to a number of underlying threads, which might lead to truely parallel execution. In other circumstances, multiple goroutines might also be executed by a single thread using cooperative scheduling. Hence, they are more powerful than conventional coroutines, as they imply parallel execution and communicate via synchronous message passing, and not just by yielding.
Message passing is a theoretical model for concurrent systems that became well-known thanks to Hoare's CSP [Hoa78]. It is also the theoretical foundation for concurrent programming concepts.
There are two different flavors of message passing--synchronous and asynchronous. We have already got to know the latter one, because the actor model is essentially built on asynchronous message passing between actors. Asynchronous message passing decouples communication between entities and allows senders to send messages without waiting for their receivers. In particular, there is no synchronization necessary between senders and receivers for message exchange and both entities can run independently. On the other hand, the sender can not know when a message is actually received and handled by the recipient.
The other variant, synchronous message passing, uses explicit message exchanging. Both the sender and receiver have to be ready and block while the message is getting exchanged. As a consequence, synchronous message passing yields a form of synchronization, because message exchanges are explicit synchronization points for different flows of control.
There are several other differences between both models. In asynchronous message passing models, the communicating entities have identities, while their synchronous counterparts are anonymous. Synchronous messaging uses explicit, named channels for communication between entities, while asynchronous messaging does not have intermediaries.
Google Go makes heavy use of synchronous message passing for concurrent programming, very similar to the way pipes are used in Unix (also synchronous). Channels are first-level languages primitives that are used for data exchange between goroutines. As goroutines can be scheduled to multiple threads and might actually run in parallel, channels are also the main synchronization primitive assuring that multiple goroutines meet in a mutually known state.
Dataflow programming with declarative concurrency is a very elegant, yet rather uncommon approach to tackle concurrency. Imperative programming is based on the idea of describing a sequence of explicit operations to execute. Instead, dataflow programming defines the relations between necessary operations, yielding an implicit graph of dependencies, the flows of execution. This allows the runtime systems to automatically identify independent steps of operations and parallelize them at runtime. Coordination and synchronization are hidden in the runtime system, often by using channels in order to wait for multiple input data and then initiate the next steps of computation. Although this programming concept allows true parallelism, coordination and synchronization efforts are hidden due to the declarative style.
Mozart/Oz [Roy04] is a programming language that supports multiple paradigms and has strong support for dataflow programming with declarative concurrency. GPars is a Java concurrency library that also supplies a rich set of dataflow concurrency primitives.
Dataflow programming is also interesting for web application development. Application-level request handling can be defined as a flow of operations. Thanks to the implicit parallelization, independent operations are then executed in parallel and later synchronized without any locking. Hence, this style helps to decrease latencies. | <urn:uuid:d19f365f-2f0f-4abf-9d5c-13108b4eb3cd> | 3.125 | 1,435 | Academic Writing | Software Dev. | 13.799393 | 1,907 |
Panama’s San Lorenzo forest reserve is around the size of Manhattan. For two years, this small area was host to 102 scientists, working together to count everything that crept and crawled. They came from 17 countries, and converged upon a half-hectare of the forest, about the size of half a rugby pitch. They dug into the soil, and ascended into the 40-metre-tall treetops with ropes, balloons, and a giant crane. They unleashed fogs, set up sticky traps, and hacked into pieces of wood.
Together, they were part of the largest ever systematic attempt to answer a disarmingly simple question: in a patch of tropical rainforest, how many species of insects and other arthropods are there?
After collecting the critters in 2003 and 2004, and analysing the material for eight years, they got an answer: 6,144 species in that patch of forest. Using computer simulations to scale that up, they estimate that the entire 6,000-hectare Manhattan-sized forest is home to around 25,000 arthropod species.
When the fruit bat Pteropus allenorum was finally described by scientists, it was already extinct. One specimen of the bat was shot in Samoa in 1856, skinned, stored in alcohol, and shipped to the United States. It spent the next 153 years, inconspicuous and ignored, on a shelf in the Academy of Natural Sciences in Drexel University. When bat specialist Kristofer Helgen visited the museum, he immediately recognised that it was a new species. Sadly, it was too late. There are no fruit bats in Samoa nowadays, so the jar on the shelf represents our only encounter with this now-extinct animal.
The fruit bat’s story isn’t an original one. The beetle Meligethes salvan was collected from the Italian Alps in 1912 and sat in Frankfurt’s Senckenberg Museum until it was described in 2003. In the intervening time, the valley from which it came had been almost entirely destroyed in the process of building a hydroelectric power plant. Biologists searched in the nearby valleys but couldn’t find it. The beetle may be extinct.
These examples show that the shelves and drawers of the world’s museums are among the planet’s most diverse habitats—ecosystems brimming with different species, many of which have never been seen before.
People often think that discoveries are made when biologists see new species in the field, and immediately recognise them as such. That’s largely not true. Field biologists often collect their specimens en masse, taking them back to their respective institutions, and keeping them in storage until they get a chance to peer at them properly. This means that many of the planet’s new species are sitting pretty in jars and drawers, gathering dust while they wait to be formally described.
How long is this shelf life? For the bat, it was 153 years, and for the beetle, 92. On average, it’s around 21 years, according to a new study from Benoît Fontaine from the Natural History of Museum in Paris.
A.ervi attacks a pea aphid, by Alexander Wild
In a British lab, a wasp has become (locally) extinct. And then, another wasp follows it into oblivion. That’s odd because these two insects are not competitors. They don’t attack one another, and they don’t even eat the same food. They do, however, remind us that it’s very hard to predict how the decline of one species will affect those around it.
Some consequences are obvious. If an animal goes extinct, its loss will cascade up and down the food web, so that its predators will suffer but its prey will probably thrive. But food webs are webs for a reason, rather than a set of isolated linear “food chains”. Consequences can ripple across, as well as up and down.
If wasps didn’t exist, picnics would be a lot more fun. But the next time you find yourself trying to dodge a flying, jam-seeking harpoon, think about this: without wasps, many of your ingredients might not exist at all. Irene Stefanini and Leonardo Dapporto from the University of Florence have found that the guts of wasps provide a safe winter refuge for yeast – specifically Saccharomyces cerevisiae, the fungus we use to make wine, beer and bread. And without those, picnics would be a lot less fun.
S.cerevisiase has been our companion for at least 9,000 years, not just as a tool of baking and brewing, but as a doyen of modern genetics. It has helped us to make tremendous scientific progress and drink ourselves into stupors, possibly at the same time. But despite its significance, we know very little about where the yeast came from, or how it lives in the wild.
The wild strains do grow on grapes and berries, but only found on ripe fruits rather than pristine ones. And they’re usually only found in warm summery conditions. So, where do they go in the intervening months, and how do they move around? They certainly can’t go airborne, so something must be carrying them.
Stefanini and Dapporto thought that wasps were good candidates. They’re active through the summer, when they often eat grapes. Fertilised females hibernate through the winter and start fresh colonies in the spring, feeding their new larvae with regurgitated food. In the digestive tracts of wasps, yeasts could get a ride from grape to grape, from one wasp generation to the next, and from autumn to spring.
When Rachel Carson wrote her famous book Silent Spring, she envisioned a world in which chemical pollutants killed off wildlife, to the extent that singing birds could no longer be heard. Pesticides aside, we now know that humans have challenged birds with another type of pollution, which also threatens to silence their beautiful songs – noise.
A man-made world is a loud one. Between the din of cities and the commotion of traffic, we flood our surroundings with a chronic barrage of sound. This is bad news for songbirds. We know that human noise is a problem for them because some species go to great lengths to make themselves heard, from changing their pitch (great tits) to singing at odd hours (robins) to just belting their notes out (nightingales). We also know that some birds produce fewer chicks in areas affected by traffic noise.
Now, Julia Schroeder from the University of Sheffield has found one reason for this. She has shown that loud noises mask the communication between house sparrow mothers and their chicks, including the calls that the youngsters use to beg for food. Surrounded by sound, the chicks eat poorly. “City noise has the potential to turn sparrow females into bad mothers,” says Schroeder.
Even though most spiders are harmless to us, many people suffer from a crippling fear of them. Imagine then, what a grasshopper must feel. The threat of venomous fangs isn’t something that the insects can shrug off. It’s a perpetual danger that chemically alters their bodies, triggering changes that ripple through an entire ecosystem.
Now, Dror Hawlena from Yale University has found just how far-reaching these changes can be. In an elegant experiment, he showed that the fear instilled by spiders can extend into the very soil, affecting how quickly leaf litter decays.
Hawlena raised red-legged grasshoppers in outdoor enclosures, half a metre wide. Half the enclosures contained a single nursery-web spider, whose mouthparts had been glued shut, so they couldn’t actually kill any of the hoppers. Their presence, however, was felt.
Last September, I travelled to Peru to meet a fascinating scientist who is mapping the Amazon by plane. The piece was published in Wired UK earlier this year, and I’m reprinting it here now. This was one of the most enjoyably things I got to write last year. I hope you enjoy it too
A small, twin-propeller plane flies over the Amazon rainforest in eastern Peru. The scale of the vegetation is extraordinary. The tree canopy stretches as far as the eye can see — an endless array of broccoli florets bounded only by haze and horizon. Greg Asner, 43, has seen the rainforest from this vantage point many times before, but he still stares out of the window in rapt fascination.
This patch of forest in the Tambopata National Reserve is rich with life, even by the Amazon’s standards. A 50-hectare patch of forest — the size of as many rugby pitches — contains more plant species than the whole of North America. “We might as well be exploring Mars,” says Asner. “These are areas where no human has ever been. There’s no access.”
Access isn’t a problem for Asner. Behind him are three state-of-the-art sensors of his own devising which, as the plane flies along, take the forest’s measure. “We’re trying to do something really new,” He says. “This world is changing and it requires science that isn’t incremental.” Using the technology he’s developed, Asner is mapping the shape and size of the trees, down to individual branches, from two kilometres above. He can measure the carbon stored in trunks, leaves and soil. He can even identify individual plant species based on the chemicals they contain. With wings and lasers, Asner is conducting one of the most ambitious ecology studies ever staged. He accumulates more data in a single hour than most ecologists glean in a lifetime. With this data, he aims to influence governments, steer the course of climate-change treaties and save the forests over which he soars.
It turns out that if you unleash giant snakes into a place that didn’t previously have giant snakes, the other local animals don’t fare so well. That seems obvious, but you might be surprised at just how badly those other animals fare.
Since 2000, Burmese pythons have been staging an increasingly successful invasion of Florida. No one knows exactly how they got there. They normally live in south-east Asia and were probably carried over by exotic wildlife traders. Once in America, they could have escaped from pet stores or shipping warehouses. Alternatively, overambitious pet owners could have released when they got too large for comfort. Either way, they seem to be thriving.
With an average length of 12 feet (4 metres), the pythons are formidable predators. They suffocate their prey with powerful coils, and they target a wide variety of mammals and birds. The endangered Key Largo woodrat and wood stork are on their menu. So are American alligators (remember this oft-emailed photo?). Conservationists are trying to halt the spread of the giant snakes, out of concern that their booming numbers could spell trouble for local wildlife.
Michael Dorcas from Davidson College thinks they are right to be concerned. In the first systematic assessment of the pythons’ impact, Dorcas has found that many of Florida’s mammals have plummeted in numbers in places where the snakes now live.
A leaf falls from the rainforest canopy, but it never hits the ground. Instead, it becomes trapped by nets of sticky fungi. While other lost leaves litter the forest floor, this one has joined the jungle’s mezzanine level – a layer of litter suspended in mid-air and hanging by a thread.
The fungi belong to a single genus called Marasmius, which extend networks of root-like filaments through the air. They act like a web that catches falling matter from the branches above. They have gone unappreciated, but Jake Snaddon from the University of Oxford has found just how important they can be.
By snaring leaves, the fungi provide room and board to insects, spiders and other canopy creepy-crawlies that might otherwise be confined to the ground. When Snaddon removed the fungi, the numbers of these animals plummeted by 70 percent.
I’ve got a new piece in Nature about a newly discovered species of “yeti crab” that farms bacteria on its arms, then eats them. It lives in the deep ocean, near seeps that belch out methane. The bacteria living on its bristly arms (hence the name “yeti crab”) feed off the seeping gases, and the crab encourage the bacteria to grow by rhythmically waving their arms.
Go to Nature to read the full piece. Meanwhile, I loved this quote from lead author Andrew Thurber, which gets across how much there is left to discover about the oceans: “It was a big surprise. There’s a tonne of them, they’re not small, and they’re six hours off a major port in Costa Rica.”
(Photos by Andrew Thurber) | <urn:uuid:02aa08dd-851d-4e0d-b30a-d216d7782699> | 3.828125 | 2,756 | Personal Blog | Science & Tech. | 55.634264 | 1,908 |
Posted on 29/3/07 by Tim Koschützki
What are prototypes?
Prototypes are generally used to test an idea in an existing system or before a real system is established. The goal of the prototype is to prove whether the components that will also be in the final system will work together as expected. Think of car manufacturing. Most people use computer models to test things there, without the need to build the final product - the car. We build software prototypes due to the same reasons. On the one hand to fix problems with a lot less hassle and on the other hand to test things in advance. The real essence of prototypes lies in the things you learn building it.
Different forms of prototypes
When people think of software prototypes they think about source code. That is of course true, but only to a certain degree. A prototype in the php world could be a small script that checks whether the database, the php script and the Ajax request will work together as expected. You could also think of a typical Model View Controller setup. Your prototype could be a simple setup of the pattern to check if the controller, the model and the view operate together as expected and whether they are encapsulated as expected. You wouldn't want to build an entire application around your implementation of the Model-View-Controller-pattern only to decide after 6 months that your system is not flexible or scalable enough.
These two examples focus on prototypes being a source code product. However, prototypes need not be source code at all. When you do webdesign and you make a mock up of your website in Photoshop, then that's of course a prototype. When you are making a graphical user interface for another language, like java and not for php, you can use sketches on post-it-sheets, which will ultimately be a prototype of one form or the other too. CakePHP's scaffolding is a good example of prototypes used in php webdevelopment. The scaffolding in php is basically a source code generator - a prototype generator.
The goal of prototypes
Prototypes are required to answer questions only, that's why they are cheaper to produce. They can ignore unimportant details without which the actual product would be senseless. Details which aren't important for you now, but will be for the future users of your application. For example, when you are making a prototype for a website interface you don't need to have correct data. You can even live without that bad user interface when you are making prototypes for your performance tests.
The essence of using prototypes lies in what your learn building them.
What do prototypes investigate?
Put simply, prototypes need to investigate all risky things. Everything nobody has tried before and things that are absolutely critical to the final application. These things could be critical changes made to the database - something that I had to do last week - develop a password encryption system that encrypts all passwords in our current live database. Also I had to change all client code that operates on the passwords, like password resetting functionality.
Besides that, you can use prototypes on everything you feel uncomfortable with. Think of the following:
- New functionality in an existing system
- Buildup and contents of external data
- Tools, frameworks, libraries, etc. from external parties.
- Graphical User Interfaces
- Critical changes to the database
The value of prototypes is not in the source code you produce, but in the things you learn from it. That's the most important thing you need to remember about prototypes.
How to use prototypes
Which details can be ignored with prototypes (most of the time)?
- Correctness - you can use fictive data with prototypes
- Completeness - it could be that the prototype needs to work only with a specific input
- Error-checking - If you don't use the correct path, your prototype might explode. That's okay.
- Documentation - Yes, most prototypes don't need much documentation.
When using prototypes, make sure that everybody involved knows, that you are writing something for the trash bin.
You can skip to the end and add a comment.
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Published in Proceedings of the Symposium on Flow Measurement in Open Channels and Closed Conduits: Gaithersburg, MD, February 23, 1977, pages 471-477.
NOTE: At the time of publication, the author William Durgin was not yet affiliated with Cal Poly.
Laser doppler anemometers are non-invasive, linear, and inherently precise. Calibration, in the usual sense, is not necessary; length and frequency measurements suffice to establish velocity at a spatial point. Measurements were made at points in the cross-sections of two square ducts containing water flow. The points were selected in conformance with a numerical integration scheme to be used for volumetric flow rate determination from the velocity measurements. The experiments were performed in a primary calibration facility at flows up to 1.25 m3/sec using ducts with sides 46 and 92 cm. The anemometer, operating in forward scatter differential mode with a 15 mw He Ne laser, was positioned with a special traversing frame. Windows in the ducts allowed transmission of the beams into the flow and reception of scattered light. Two grid patterns, 4 x 11 and 11 x 11, were used so that 44 and 121 velocities were measured for each test. A total of eight tests were conducted covering a Reynolds number range from 1.1 to 3.9 X 108. After accounting for errors due to the discreet integration scheme of 0.61% and 0.13% for the 4 x 11 and 11 x 11 schemes, respectively, comparison with the calibration facility indicated extreme errors of +0.81/-0.16 and +0.84/-0.61. The major limitation of the set-up used was the time required to move the anemometer and obtain a new velocity value. It was pointed out that either better mechanical positioning or optical scanning could be employed to reduce the time required for a flow determination. | <urn:uuid:e6e5abc3-2225-4f82-8b81-7d9776397cbb> | 2.546875 | 393 | Academic Writing | Science & Tech. | 55.22637 | 1,910 |
Loggerhead sea turtle -
photographer DuBose Griffin
Sea turtles are among the largest reptiles in the world and inhabit almost every ocean. Fossil evidence indicates sea turtles shared the Earth with dinosaurs over 210 million years ago. Sea turtles are cold-blooded, air breathing, egg laying reptiles that deposit their eggs on dry, sandy beaches. Sea turtles differ from freshwater turtles because they have flippers instead of feet, cannot retract their heads and spend all of their life in salt water, except when females come ashore to lay eggs. There are seven species of sea turtles in the world. They are the loggerhead, Kemp's ridley, green, leatherback, Australian flatback, hawksbill and olive ridley. The loggerhead, Kemp's ridley, green and leatherback sea turtles can be found in South Carolina's near shore waters April through November or nesting on our beaches from May through October. Loggerheads are the most common sea turtle found in our state's coastal waters and nesting on our beaches. Sea turtle nests and strandings in South Carolina can be followed in real time on the SCDNR Sea Turtle Program web site: http://www.dnr.sc.gov/seaturtle/.
Loggerhead hatchling -
photographer Barbara Bergwerf
All sea turtles have a similar life history. Since loggerheads are the most common species found in South Carolina, the following life history information is specific to this species. The reproductive season begins when males and females mate in early spring. Females crawl onto the beach at night, 30 days after breeding, from May to August and deposit an average of 120 white, leathery eggs similar in appearance and size to a ping pong ball. They deposit these eggs in a nest cavity that is approximately 18 inches deep. The cavity is dug with their hind flippers in the dry sand above the high tide line. Each female will nest, on average, four times per season with two week intervals between each nesting event. The eggs incubate for approximately 60 days and during this time are susceptible to predation by raccoons, feral hogs, coyotes and ghost crabs. The temperature of the nest during the second trimester of incubation will determine the sex of the hatchlings. Hatchlings emerge from the nest at night and crawl towards the ocean using several cues, primarily celestial light reflecting off the ocean, to find their way.
Please click here for video footage of this emergence: http://www.dnr.sc.gov/seaturtle/videos/julyvideo_logger.wmv.
Once they reach the ocean, they swim continuously for about 36 hours to escape predators that may prey on them in coastal waters. They swim offshore in search of large clumps of Sargassum seaweed where they are camouflaged while feeding on a variety of small invertebrates. During the next 10 – 12 years they lead a pelagic existence and float actively and passively in the North Atlantic Ocean gyre. Once they reach approximately 20 inches in shell length, they move back into coastal waters along the Continental Shelf and begin feeding on bottom prey such as crabs and mollusks. They spend the rest of their juvenile and adult lives in these Shelf waters.
Sea turtles face many natural and human-caused threats during all stages of their life cycle. The primary natural predator of juvenile and adult sea turtles is the shark. A significant threat is accidental capture in commercial fisheries. Long line fishing, gill nets and bottom trawling can result in the lethal capture of sea turtles.
The use of Turtle Excluder Devices (TEDs) by shrimpers has reduced the occurrence of sea turtle deaths. However, these species still face many challenges for survival. Collisions with boats, including propellers, are becoming a significant problem as coastal areas continue to develop. Artificial light visible from the beach is harmful because it disorients adults and hatchlings, causing them to wander away from the ocean. Disoriented hatchlings are more susceptible to nocturnal predators. Pollution can cause sea turtle mortality. For example, plastic bags may be mistaken as food and ingested, and sea turtles can become entangled in monofilament line. Beachfront development interferes with the natural erosion and accretion along dynamic barrier islands which results in the loss of nesting habitat. Climate change is a threat to sea turtles, especially when coupled with beachfront development. Rising oceans move dynamic beaches landward. When this occurs on developed beaches, nesting habitat is lost when sand cannot migrate landward because of infrastructure or when beaches are armored to protect property. Warming temperatures can also alter the natural ratio of male to female turtles that are produced in a nest.
All four species of sea turtles found in South Carolina are protected by state and federal law, principally by the US Endangered Species Act of 1973. Additionally, all species of sea turtles are protected by the Convention on International Trade in Endangered Species (CITES). They are also listed as endangered or vulnerable by the International Union for the Conservation of Nature (IUCN).
Endemic Sea Turtles
Loggerhead sea turtle -
photographer Tom Murphy
Loggerheads (Caretta caretta) are the most widespread and commonly found sea turtle that nests in the southeastern United States. They were designated as the official South Carolina state reptile in 1988. Loggerheads are named for their massive heads and powerful jaws that enable them to feed on hard-shelled prey, such as whelks, crustaceans and conch. Loggerhead turtles have an oval-shaped carapace that is dark reddish-brown while their flippers and lower plastron are light yellow. Adult loggerheads can weigh as much 300 pounds and reach up to four feet in shell length. Loggerhead nesting has been well documented and has averaged 3,378 nests per year over the last 10 years in South Carolina. For more specific information on loggerhead sea turtles, please visit the following Web pages:
Kemp's ridley sea turtle -
photographers Phil and
Kemp's ridleys (Lepidochelys kempii) are the smallest and rarest of the seven sea turtle species, weighing approximately 100 pounds and as adults, growing to two feet in shell length. Adults have a round grayish-black to olive carapace (which lightens in color as the turtle ages) that is as wide as it is long. They feed on fast swimming crabs, such as blue crabs (Callinectes sapidus). Kemp's ridleys nest primarily near Rancho Nuevo, Mexico. They do not typically nest in South Carolina but can be found in inshore and near shore waters from April through November. However, a Kemp's ridley nest was recorded on Litchfield by the Sea in 1992 and South Litchfield in 2008 (less than a mile from the 1992 nest site). For more specific information on Kemp's ridley sea turtles, please visit the following Web pages:
Green sea turtle -
photographer Barbara Bergwerf
Green sea turtles (Chelonia mydas) are the largest hard-shelled sea turtle species. Their common name is derived from the green fat, or calipee, in their body due to their herbivorous diet. They have a serrated jaw for tearing grass, weigh approximately 300 - 350 pounds as adults and average five feet in shell length. In September 1996, the first documented green turtle nest was laid on South Island in South Carolina. Since 1996, green nesting has become more frequent. Although green turtles do not typically nest in South Carolina, juvenile turtles consistently utilize South Carolina’s inshore and near shore waters as foraging grounds from April through November. For more specific information on green sea turtles, please visit the following Web pages:
Leatherback sea turtle -
photographer Matthew Godfrey
Leatherbacks (Dermochelys coriacea) are the largest and widest ranging sea turtles. These sea turtles are unique because they do not have a hard shell, but a leathery shell with distinct longitudinal ridges. Although cold blooded, they can maintain a body temperature warmer than ambient. They range from 800 - 1,300 pounds and reach six feet in shell length. Leatherbacks feed on jellyfish in South Carolina near shore waters in the spring and fall while migrating between Nova Scotia feeding grounds to tropical nesting beaches. In 1996, the first South Carolina record for a leatherback nest was documented on St. Phillip’s Island. Since 1996, leatherback nesting has become more frequent. For more specific information on leatherback sea turtles, please visit the following Web pages:
- Sea turtles are revered in many cultures. Around the world there are numerous indigenous tales and legends that depict turtles as guardians or creators of life on Earth. In Hawaii, the turtle is a symbol of good luck and a Hindu symbol depicts the world as resting on the back of a turtle.
- Leatherbacks dive deeper than any other turtle species with recorded dive depths of up to 4,000 feet. Given the pressure and temperature at this depth, this is a remarkable dive for any air breathing vertebrate.
- Loggerhead hatchlings born on the beaches of South Carolina, North Carolina, Florida and Georgia live the first years of their lives in the pelagic environment off the west coast of Africa.
- It takes loggerheads 25 – 30 years to mature and reproduce. You cannot age a turtle and no one knows exactly how long they live.
- About 100 species of animals and plants have been recorded living on one single loggerhead, making them an entire mobile, living, breathing ecosystem.
- The smallest sea turtle is the Kemp’s ridley. The largest recorded leatherback was found stranded on the coast of Wales in 1988 and weighed roughly 2,020 pounds.
Biologists urge the public to assist with sea turtle conservation by reporting all dead or injured sea turtles to 1-800-922-5431. Additionally, the following tips are useful:
- Never disturb a sea turtle crawling to or from the ocean.
- Once a sea turtle has begun nesting, observe her only from a distance.
- Do not shine lights on a sea turtle or take flash photography.
- Turn out all lights visible from the beach, dusk to dawn, from May through October.
- Turn off all outdoor and deck lighting to reduce disorientation for nesting adults and hatchlings.
- Close blinds and drapes on windows that face the beach or ocean.
- Fill in holes on the beach at the end of each day as adults and hatchlings can become trapped.
- Do not leave beach chairs, tents etc. on the beach overnight.
- Never attempt to ride a sea turtle.
This publication was made possible in part with funds from SCDNR endangered species appropriations, SCDNR Check-off for Wildlife funds, SCDNR endangered species license plate sales, US Fish and Wildlife Service and NOAA Fisheries Endangered Species Act Section 6 funding.
- Carr, Archie. So Excellent a Fishe. The Natural History Press, Garden City, New York. 1967.
- Carr, Archie. The Windward Road. University of Florida Press, Tallahassee Florida. Republished 1979.
- National Research Council. Decline of the Sea Turtles: Causes and Prevention. National Academy Press, Washington, DC. 1990.
- Safina, Carl. Voyage of the Turtle: In Pursuit of the Earth’s Last Dinosaur. Henry Holt and Co., LLC, New York, New York. 2006.
For more information about sea turtles in South Carolina, visit the Web sites below:
- SCDNR Sea Turtle Conservation Program web site: http://www.dnr.sc.gov/seaturtle/
- Sea Turtle Outreach and Educational Materials: http://www.dnr.sc.gov/seaturtle/outreach.htm
- SCDNR Loggerhead State of the Resource: http://www.dnr.sc.gov/marine/pub/stateofloggerhead.pdf
Author credentials: Arturo Herrera and DuBose Griffin, Marine Turtle Conservation Program, Wildlife and Freshwater Fisheries Division of the South Carolina Department of Natural Resources.
The above information on the sea turtle is available in a brochure, please download the Sea Science - Sea Turtle information pamphlet which is in the Adobe PDF file format. Adobe® Reader® is required to open the files and is available as a free download from the Adobe® Web site. | <urn:uuid:c58f1c00-d007-4911-81a1-8c24b1ecf1d9> | 3.4375 | 2,579 | Knowledge Article | Science & Tech. | 49.184602 | 1,911 |
One of the things that makes Groovy different than most compiled languages is that you can create functions that are first class objects. That is you can define a chunk of code and then pass it around as if it were a string or an integer. Check out the following code:
The curly braces around the expression "it * it" tells the Groovy compiler to treat this expression as code. In the software world, this is called a "closure". In this case, the designator "it" refers to whatever value is given to the function. Then this compiled function is assigned to the variable "square" much like those above. So now we can do something like this:
and get the value 81.
This is not very interesting until we find that we can pass this function "square" around as a value. There are some built in functions that take a function like this as an argument. One example is the "collect" method on arrays. Try this:
This expression says, create an array with the values 1,2,3 and 4, then call the "collect" method, passing in the closure we defined above. The collect method runs through each item in the array, calls the closure on the item, then puts the result in a new array, resulting in:
For more methods you can call with closures as arguments, see the Groovy GDK documentation.
By default closures take 1 parameter called "it", you can also create closures with named parameters. For example the method Map.each() can take a closure with two variables, to which it binds the key and associated value:
More Closure Examples
Here are a few more closure examples. This first one shows a couple of things. First, the closure is interacting with a variable outside itself. That is, the closure's purpose is to put together the parts of a stock order held in the array orderParts, by adding (appending) it to the variable fullString. The variable fullString is not in the closure. The second thing that is different about this example is that the closure is "anonymous", meaning that it is not given a name, and is defined in the place where the each method is called.
You can probably guess what this prints out.
The next example is another anonymous closure, this time, summing up the values stored in a map.
Dealing with Files
Reading data from files is relatively simple. First create a text file, and call it myfile.txt. It doesn't matter what's in it, just type some random text into it and save it on your C: drive in the \temp directory. Then type the following code in the groovyConsole:
This should print out every line in the file prefixed with "File line: ". The first two lines of the code simply declare variables to specify where the file is located. The variable names don't have any special significance, and as you can see, all we do is combine them when we use them. Note that because the backslash character has special meaning in groovy, you have to use two of them to tell it that you '''really''' mean a backslash.
The next line that starts "myFile =" creates a new File object. An object is simply a collection of related methods and data. For example, a file object might have data describing its location, in this case "C:\temp\myfile.txt", and maybe a method to delete the file if it exists. In this case the only method we are going to use is the eachLine method, which we call in the last line of code. The line before that is a simple closure definition, that you have seen several times by this point.
Dealing with strings
Strings in Groovy have all the same functionality of Java strings. That is, a Groovy string is just a Java string with a few extra things added to it. Because of that, we can refer to the Java documentation for the String class to find out some of the interesting things we can do with it. For example, look in the section entitled '''Method Summary''' at the description for the '''split''' method. This method does something very useful, which is to split a string based on a regular expression. We will talk more about regular expressions later, but for now the only thing you have to know is that the simplest regular expression is a single character. So let's say that we want to split up the components of the date "2005-07-04", so that we can add one to the year to get the date of next fourth of July. We might:
This code brings together a bunch of things we have talked about before. There are two new things, first is the use of the split method on a String. Second is the call of toInteger() on a String. This call to toInteger simply tells Groovy that you want to treat that data as a number rather than a String. See what happens if you run the same code without ".toInteger()" at the end of the third line.
Another thing you might notice is that toInteger is not listed in the Java documentation for string. That is because it is one of the extra features that Groovy has added to Strings. You can also take a look at the documentation for the Groovy extensions to Java objects. | <urn:uuid:b6d33570-ad4d-40de-bc7a-34ae185c0b9b> | 3.53125 | 1,104 | Documentation | Software Dev. | 59.822762 | 1,912 |
- dotTech - http://dottech.org -
The 411 on Process Virtual Machines
Posted By Samuel On November 8, 2011 @ 12:20 PM In Computer Programming | 6 Comments
Most everyone uses ones of these every day and don’t know it. Some that do know either don’t understand it or, even worse, misunderstand it. Yet if anyone ever ran a Java program or a .NET based program they’ve used one.
At its most basic, a Process Virtual Machine (PVM) is somewhat like the Virtual Machines (think VirtualBox) that run whole operating systems. The main difference between the two being PVMs only virtualize processes, not whole operating systems. The main idea of a PVM is to simplify the creation of programs as well as making programs easy to use for the end user.
Java and .NET both have their own systems, but the basic idea remains the same: a coder can make a code once and the PVM deals with making it run on different computers. In Java’s case, this means that a programmer can make one code that will run on Windows, Mac, UNIX, Linux, and even mobile phones. In the case of .NET, a programmer can target any Windows based device and have the code work with little or no changes. This helps developers target very large groups of people with minimal expense in terms of time and money. Furthermore, PVMs makes programming easier since a lot of things that a programmer normally has to worry about, things they would usually have to code manually, can be easily called instead of created. Continuing on that trend, PVM based programs are also safer since the program is running in a virtual machine, making it harder to mess up the system (though not impossible, trust me, I know =D).
On the flip side not everything is rosy in PVM park. For starters you need to have the PVM installed on your computer, though in the case of .NET if you keep your computer up to date odds are you will have .NET (or, depending on what Windows you have, you may not even need to download it from anywhere because various versions of .NET come with Windows Vista and Win7). If you don’t have the PVM or even the correct version (in general having a new version is ok) the program won’t run. And the PVM is not always that small – the installer for .NET 3.5 SP1 is 250 MB. PVMs are also controversial. PVMs are considered to be cheating by some since the programmer has the PVM doing a lot of the work for him or her. However, that also hurts the programmer since if something is not in the PVM they have to access native (or non PVM) code to do it, which can be very hard sometimes. Finally, though this is more true with .NET than Java, a PVM program will only run if the PVM is supported on the OS in question.
I personally am a PVM programmer. My “native” programming language is Visual Basic (.NET PVM), but I know Visual C# (.NET PVM), and am in the process of learning Java (Java PVM). I also plan to learn to code natively in the future. Though I admit that using PVMs has some problems, I believe that just because a program uses them doesn’t make them any worse than a program that’s written natively. However, in the end I suppose that’s your call.
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DSSS: Determining chemical and microbial Fe(II) oxidation kinetics in situ: How well do organisms compete with chemical oxidation?
- Who: George W. Luther, Ph.D., University of Delaware
- What: Download the file (pdf)
- Where: Building 66, Auditorium
- When: 10:30 am to 12:00 noon, February 8, 2013
- Why: About the Distinguished Scientist Seminar Series
My interests cover a wide range of areas including redox reactions in the environment, trace element speciation in marine waters and sediments including metal-ligand complexes, biogeochemical processes, in situ electrochemistry and microelectrode technology. Our group also emphasizes research that interfaces chemistry with biology with the view that chemistry drives biology.
Abstract: The oxidation of aqueous Fe(II) to Fe(III) solids is of great significance to Earth history including banded iron formation (BIFs) and the rise of O2 in waters and the atmosphere. The chemical oxidation of aqueous Fe(II) in air saturated solutions is facile at circumneutral pH, but O2 arises mainly from photosynthetic activity. There are currently three theories on how microbes could have contributed to Fe(III) precipitation: (1) oxygenic photosynthesis, coupled to abiotic Fe oxidation, (2) aerobic (anerobic?) Fe oxidation by iron oxidizing bacteria (FeOB), and (3) anoxygenic photosynthesis, with Fe as an electron donor (photoferrotrophs). Using kinetic data obtained in the field as well as in the laboratory with in situ microelectrode techniques developed in our lab, it is now possible to discriminate between chemical Fe(II) oxidation and these microbially based processes in real time. Field data will be shown from diverse sites including Yellowstone National Park where groundwater, rich in Fe(II) and Mn(II) but with little or no O2, enter oxygenated systems. In the case of FeOB, their importance in Fe(II) oxidation increases at low O2 concentrations. Thermodynamic calculations for the first electron transfer between the metal ions, Fe(II) and Mn(II),with O2 over pH gives insight to the distribution of these metals in BIFs and their biogeochemical behavior. | <urn:uuid:f7b74ce6-7c20-4874-8bf3-085688534b2a> | 2.640625 | 478 | Academic Writing | Science & Tech. | 21.171537 | 1,914 |
Winter forecast, part I: the woolley bear prediction
According to legend, the severity of the upcoming winter can be judged by examining the pattern of brown and black stripes on woolly bear caterpillars--the larvae of Isabella tiger moths. If the brown stripe between the two black stripes on either end of the caterpillar is thick, the winter will be a mild one. A narrow brown stripe portends a long, cold winter. Some traditional forecasters say that the 13 segments on the caterpillar's body correspond to the 13 weeks of winter.
The Hagerstown, Maryland woolley bear forecast
The Hagerstown, Maryland Town and Country Almanack has been publishing weather forecasts and weather lore for 211 years. The Almanack sponsors an annual woolly bear caterpillar event, where local school children in Hagerstown collect woolly bears. A panel of judges examines the collected specimens and issues a woolly bear forecast for the upcoming winter. The results of this year's contest, which ended October 31: "From the small number of woolly bears, the consensus is that the winter will be very mild. The woolly bears predicted this by their three (3) bands of which the front band (representing the first half of winter and black in color) was shorter in length and normal. The back band (representing the second half of winter) was very small, thus indicating the mild winter prediction. As a result of those markings, which were similar in all woolly bears, the sponsors were able to make the predictions."
Oil Valley Vick
Naturally, this forecast only applies to the Hagerstown, Maryland area, so other locales will need to do their own woolly bear work to gauge the local winter forecast. In Oil City, Pennsylvania, just 150 miles northwest of Hagerstown, organizers of the Pumkin Bumkin Festival have located the lair of "Oil Valley Vick", a woolly bear caterpillar of unknown forecasting ability, but great potential. In his inaugural forecast on October 23 this year, Oil Valley Vick wowed the crowd at the Pumkin Bumkin Festival when he crawled out of his log. The black stripes covering fully 2/3 of Oil Valley Vick's body left no doubt that he expected a cold, severe winter for northwestern Pennsylvania.
Figure 1. Kelly the woolly bear caterpillar with her owner, six-year-old Kurstin Hartsell of Ansonville, NC. Image credit: Jim Morton, Avery County Chamber of Commerce.
The Banner Elk, North Carolina Woolly Bear forecast
In Banner Elk, NC it's the fastest woolly bear caterpillar which is judged to be the best forecaster. After successfully out-sprinting hundreds of other woolly bears, this year's winner of the 31st Annual Woolly Worm Festival race was Kelly the Woolly Worm, raced by six-year-old Kurstin Hartsell of Ansonville, NC. Kelly the Woolly Worm's official forecast for the winter of 2008-2009 calls for the first four weeks to be cold and snowy, followed by three weeks of seasonably cold weather, followed by six weeks of snowy and cold weather (severely cold in week 11, March 1-7). A study of the predictions of the Banner Elk woolly bears between 1978 and 2000 revealed that "woolly worm winter predictions were exactly on target eight times out of 23, or 34.8%. Woolly worm predictions were close (4.0-4.9) another five times (21.7%). Woolly worm predictions were right in some areas, wrong in others (3.0-3.9) six times (26.1%). Woolly worm predictions were wrong more than they were right (2.0-2.9) four times (17.4%). Put another way, the woolly worms were close or completely right 57% of the time, and more than half right 82.6% of the time".
Other studies of woolly bear forecast accuracy
Several scientific studies have been done on woolly bear caterpillar forecasts, including one by the American Museum of Natural History. None of these studies has shown any correlation between woolly bear markings and the severity of the upcoming winter. According to the Old Farmer's Almanac, Dr. Charles Curran, curator of insects at the American Museum of Natural History in New York City, studied woolly bear markings between 1948-1956 in Bear Mountain State Park, 40 miles north of New York City. He found some preliminary results that seemed to indicate that the thickness of the bands might indicate the severity of the upcoming winter. However, Dr. Curran gave up the study in 1955 after finding two groups of caterpillars living near each other that had vastly different predictions for the upcoming winter, according to science writer Ned Rozell.
So, two out of three woolley bear forecasts point to a colder than average winter for the Appalachian region of the U.S. In upcoming blog posts, I'll analyze what NOAA's computer models and the Old Farmer's Almanac have to say about the upcoming winter.
Portlight making keynote presentation at charity funding conference today
The Portlight.org charity is making the keynote presenation at a funding conference hosted by a coalition of state and federal agencies which work in the area of post-disaster relief involving people with disabilities. The presentation is this morning, November 20, at 9:15 am EST. You can follow the proceedings via the portlight webcam at stormjunkie.com. At the conference, they plan to discuss the Hurricane Ike relief efforts made possible by the Weather Underground community. Thanks for everyone's support for making all this possible! | <urn:uuid:8e8b145c-f474-45ec-9cf6-f8000160a666> | 2.65625 | 1,164 | Personal Blog | Science & Tech. | 54.575672 | 1,915 |
Synthetic biology is getting a boost. So far, most researchers have designed their synthetic circuits using transcription factors found in bacteria. However, these don’t always translate well to nonbacterial cells and can be a challenge to scale. Now, researchers have come up with a new method to design transcription factors for nonbacterial cells—specifically yeast. Their initial library of 19 new transcription factors should help overcome the existing bottleneck that has limited synthetic biology applications, says Timothy Lu, M.D., assistant professor of electrical engineering and computer science and a member of MIT’s Research Laboratory of Electronics.
The project is part of a larger, ongoing effort to develop genetic “parts” that can be assembled into circuits to achieve specific functions. Through this endeavor, Dr. Lu and his colleagues hope to make it easier to develop circuits that do exactly what a researcher wants.
“If you look at a parts registry, a lot of these parts come from a hodgepodge of different organisms. You put them together into your organism of choice and hope that it works,” says Dr. Lu.
Recent advances in designing proteins that bind to DNA gave the researchers the boost they needed to start building a new library of transcription factors. In many transcription factors, the DNA-binding section consists of zinc finger proteins, which target different DNA sequences depending on their structure. The researchers based their new zinc finger designs on the structure of a naturally occurring zinc finger protein. “By modifying specific amino acids within that zinc finger, you can get them to bind with new target sequences,” Dr. Lu says.
The researchers attached the new zinc fingers to existing activator segments, allowing them to create many combinations of varying strength and specificity. They also designed transcription factors that work together, so that a gene can only be turned on if the factors bind each other.
Such transcription factors should make it easier for synthetic biologists to design circuits to perform tasks such as sensing a cell’s environmental conditions. The researchers built some simple circuits in yeast, but they plan to develop more complex circuits in future studies. “We didn’t build a massive 10- or 15-transcription factor circuit, but that’s something that we’re definitely planning to do down the road,” Dr. Lu says. “We want to see how far we can scale the type of circuits we can build out of this framework.”
The researchers are also planning to try their new transcription factors in other species of yeast, and eventually in mammalian cells including human cells. “What we’re really hoping at the end of the day is that yeast are a good launching pad for designing those circuits,” Dr. Lu says. “Working on mammalian cells is slower and more tedious, so if we can build verified circuits and parts in yeast and then import them over, that would be the ideal situation. But we haven’t proven that we can do that yet.”
The study is called “A Synthetic Biology Framework for Programming Eukaryotic Transcription Functions”. It appears in the August 3 issue of the journal Cell. | <urn:uuid:55bb7b24-eee7-444d-99cc-c57087535dd1> | 3.484375 | 651 | News Article | Science & Tech. | 51.474598 | 1,916 |
If you want to make programs go faster on parallel hardware, then you need some kind of concurrency. Right?
In this article I’d like to explain why the above statement is false, and why we should be very clear about the distinction between concurrency and parallelism. I should stress that these ideas are not mine, and are by no means new, but I think it’s important that this issue is well understood if we’re to find a way to enable everyday programmers to use multicore CPUs. I was moved to write about this after reading Tim Bray’s articles on Concur.next: while I agree with a lot of what’s said there, particularly statements like
Exposing real pre-emptive threading with shared mutable data structures to application programmers is wrong
it seems that parallelism and concurrency are still being conflated. Yes we need concurrency in our languages, but if all we want to do is make programs run faster on a multicore, concurrency should be a last resort.
First, I’ll try to establish the terminology.
A concurrent program is one with multiple threads of control. Each thread of control has effects on the world, and those threads are interleaved in some arbitrary way by the scheduler. We say that a concurrent programming language is non-deterministic, because the total effect of the program may depend on the particular interleaving at runtime. The programmer has the tricky task of controlling this non-determinism using synchronisation, to make sure that the program ends up doing what it was supposed to do regardless of the scheduling order. And that’s no mean feat, because there’s no reasonable way to test that you have covered all the cases. This is regardless of what synchronisation technology you’re using: yes, STM is better than locks, and message passing has its advantages, but all of these are just ways to communicate between threads in a non-deterministic language.
A parallel program, on the other hand, is one that merely runs on multiple processors, with the goal of hopefully running faster than it would on a single CPU.
So where did this dangerous assumption that Parallelism == Concurrency come from? It’s a natural consequence of languages with side-effects: when your language has side-effects everywhere, then any time you try to do more than one thing at a time you essentially have non-determinism caused by the interleaving of the effects from each operation. So in side-effecty languages, the only way to get parallelism is concurrency; it’s therefore not surprising that we often see the two conflated.
However, in a side-effect-free language, you are free to run different parts of the program at the same time without observing any difference in the result. This is one reason that our salvation lies in programming languages with controlled side-effects. The way forward for those side-effecty languages is to start being more explicit about the effects, so that the effect-free parts can be identified and exploited.
It pains me to see Haskell’s concurrency compared against the concurrency support in other languages, when the goal is simply to make use of multicore CPUs (Edit: Ted followed up with a clarification). It’s missing the point: yes of course Haskell has the best concurrency support , but for this problem domain it has something even better: deterministic parallelism. In Haskell you can use multicore CPUs without getting your hands dirty with concurrency and non-determinism, without having to get the synchronisation right, and with a guarantee that the parallel program gives the same answer every time, just more quickly.
There are two facets to Haskell’s determinstic parallelism support:
- par/pseq and Strategies. These give you a way to add parallelism to an existing program, usually without requiring much restructuring. For instance, there’s a parallel version of ‘map’. Support for this kind of parallelism is maturing with the soon to be released GHC 6.12.1, where we made some significant performance improvements over previous versions.
- Nested Data Parallelism. This is for taking advantage of parallelism in algorithms that are best expressed by composing operations on (possibly nested) arrays. The compiler takes care of flattening the array structure, fusing array operations, and dividing the work amongst the available CPUs. Data-Parallel Haskell will let us take advantage of GPUs and many-core machines for large-scale data-parallelism in the future. Right now, DPH support in GHC is experimental, but work on it continues.
That’s not to say that concurrency doesn’t have its place. So when should you use concurrency? Concurrency is most useful as a method for structuring a program that needs to communicate with multiple external clients simultaneously, or respond to multiple asynchronous inputs. It’s perfect for a GUI that needs to respond to user input while talking to a database and updating the display at the same time, for a network application that talks to multiple clients simultaneously, or a program that communicates with multiple hardware devices, for example. Concurrency lets you structure the program as if each individual communication is a sequential task, or a thread, and in these kinds of settings it’s often the ideal abstraction. STM is vitally important for making this kind of programming more tractable.
As luck would have it, we can run concurrent programs in parallel without changing their semantics. However, concurrent programs are often not compute-bound, so there’s not a great deal to be gained by actually running them in parallel, except perhaps for lower latency.
Having said all this, there is some overlap between concurrency and parallelism. Some algorithms use multiple threads for parallelism deliberately; for example, search-type problems in which multiple threads search branches of a problem space, where knowledge gained in one branch may be exploited in other concurrent searches. SAT-solvers and game-playing algorithms are good examples. An open problem is how to incorporate this kind of non-deterministic parallelism in a safe way: in Haskell these algorithms would end up in the IO monad, despite the fact that the result could be deterministic. Still, I believe these kinds of problems are in the minority, and we can get a long way with purely deterministic parallelism.
You’ll be glad to know that with GHC you can freely mix parallelism and concurrency on multicore CPUs to your heart’s content. Knock yourself out | <urn:uuid:f25cf6db-310e-4606-bb3a-6a03073faf3d> | 3.3125 | 1,370 | Personal Blog | Software Dev. | 38.299249 | 1,917 |
Nonlinear Complex Resistivity
complex resistivity (NLCR) is a geophysical method of stimulating materials
with an electrical current sine wave of variable frequency and measuring
the voltage response. The ratio of the amplitudes of the voltage
to the current normalized by the geometry of the electrodes is the magnitude
of the resistivity. The shift in time between the stimulus current
and response voltage is a phase shift. Deconvolved response by stimulus
and summed root mean square harmonics are the total harmonic distortion.
Deviation of the real and imaginary parts of the complex resistivity transfer
function versus frequency from the Hilbert transform expectation are Hilbert
Distortions. Both distortions are measures of nonlinearity.
complex resistivity measurements as a function of frequency from 0.001
Hz to 1,000 Hz are useful in a variety of applications where remote measurements
of active chemical processes are important. As all chemical reactions
involve electron charge movement, NLCR can measure or observe nearly all
chemical processes (some are too fast or too slow). NLCR is used
in the laboratory, in boreholes, between boreholes or between holes and
the surface, from the surface and inside tunnels. It requires contact
with the ground to inject a current and has not been successfully employed
from airborne platforms. It has applications to the study of corroding
metals, ore exploration and delineation, clay-organic reactions for petroleum
exploration, environmental characterization and monitoring, ground water,
archaeology, and agriculture.
<more to come>
Copyright 1999 by Gary R. Olhoeft.
All Rights Reserved. | <urn:uuid:48c7089b-7243-45b2-9ab7-c054ed071daf> | 3.28125 | 339 | Knowledge Article | Science & Tech. | 20.921333 | 1,918 |
Download these brochures:
OASIS English OASIS French OASIS Inuktitut OASIS Cree
Not much is known about the chemistry in the air over the Arctic Ocean, and what happens to important chemicals is hardly studied by the scientific community because of the difficulty of working in this cold, inhospitable environment.
There is some evidence that many important processes occur right at the ice surfaces and ice/open water regions of the Arctic Ocean. This has to be confirmed and understood if we are to explain how chemicals are deposited from the air to the ice or water and how that might affect fish, marine mammals and eventually human health. For example, mercury (a toxic pollutant which can affect health) and ozone (an important gas causing chemical reactions) can change properties when exposed to salt from sea water in the Arctic. Carbon dioxide (CO2), one of the most important greenhouse gases can be trapped by the Arctic Ocean. Cloud covers the sky above the Arctic Ocean and this is influenced by chemicals emitted from the Ocean. It is clear that changes in these processes will affect the Arctic and those who live within it in many ways (e.g. clouds change the temperature which can change the ice cover). And change is happening: climate change is occurring at an accelerated rate in the Arctic, and this is especially evident over the Arctic Ocean. And there are many feedbacks between climate change and the Arctic System that we need to understand. The OASIS program was developed to face this challenge.
During the International Polar Year, the goal of OASIS is to collect information on the chemistry in the air over the Arctic Ocean itself. Buoys (floating platforms) will be used on the frozen ocean to make it possible, for the first time, to measure the chemicals in the air year round, and study what happens to them directly over the Arctic Ocean. Furthermore research vessels (ice breakers) will be joined providing the unique opportunity to collaborate with researchers from different fields of expertise (including social scientists) to study the air, ice, ocean, and the life they contain as a whole. These studies will permit us to better determine the future impacts of climate change to the Arctic Ocean and the life it contains, ultimately improving our ability to forecast the impact of climate change on those living in the North, and the rest of the planet.
What is IPY
Saturday, 30 December 2006 04:11
OASIS-IPY: Ocean-Atmosphere-Sea Ice Snowpack Interactions and connections to climate changeWritten by Administrator
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Date of Degree
MS (Master of Science)
Civil and Environmental Engineering
Michelle M. Scherer
Iron is ubiquitous in the environment mostly as stable iron hydr(oxides) such as hematite (α-Fe2O3) and goethite (α-FeOOH). The Fe(II)-Fe(III) redox couple plays a vital role in nutrient cycling, bacteria respiration, and contaminant removal. This redox couple, however, can be affected by external influences such as anion adsorption of sulfate, oxalate, and phosphate which can influence various goethite properties including the point of zero charge. This study attempts to determine the effect of phosphate sorption to a goethite surface and its subsequent influence on Fe(II) sorption. The objectives, specifically, were to quantify phosphate sorption on a goethite surface using colorimetric methods and to use Mössbauer spectrometry to determine if electron transfer occurred after a layer of phosphate was adsorbed to the goethite surface. The hypothesis of this study is as follows: an adsorbed layer of phosphate on a goethite surface will inhibit the electron transfer between the Fe(II) and Fe(III) phases at the surface.
The results of the study showed that phosphate follows typical anion sorption as seen in previous works, where more phosphate sorbed at lower pH values. In addition, with increasing aqueous phosphate concentrations there is increasing phosphate adsorption to the goethite surface. However, phosphate sorption was not significantly affected by reaction time after 20 hours or by changes in Fe(II) concentrations. Fe(II) sorption pH edges showed characteristic cation adsorption, where more Fe(II) sorbed at higher pH values. Fe(II) sorption was not affected by the presence or absence of phosphate, but was affected by an increase in the aqueous Fe(II) concentration. With increased Fe(II) there was a pH edge shift to a higher pH, which is consistent with Ca2+ sorption results on goethite. An Fe(II) isotherm was also conducted and showed that as Fe(II) concentration increased so did Fe(II) sorption, however the isotherm appeared to be approaching a plateau where the goethite surface sites would be saturated, below this limit the surface sites where not saturated.
Mössbauer analysis was conducted on a sample by Drew Latta, spectra showed that electron transfer was still occurring despite the adsorbed phosphate layer, disproving our initial hypothesis. It is possible that a higher concentration of phosphate could inhibit electron transfer, but at 500 μM PO43- and 100 μM Fe(II), electron transfer between the adsorbed Fe(II) and bulk phase Fe(III) still occurred.
Copyright 2010 Cristina Paola Fernández-Baca
Fernández-Baca, Cristina Paola. "Investigation of the effect of phosphate on iron(ii) sorption to iron oxides." thesis, University of Iowa, 2010. | <urn:uuid:7f27e322-47fd-41f0-9a8c-4431ed8fb676> | 2.625 | 648 | Academic Writing | Science & Tech. | 28.569501 | 1,920 |
I'm interested in learning the basics of nanotechnology, in particular, how nano-scale materials are constructed. What kinds of equipment are used? How are samples evaluated? etc. Does anyone have any recommendations?
asked Jul 27 '11 at 14:43
According to bestintrobook.com it's Fundamentals of Microfabrication and Nanotechnology, Third Edition by Marc J. Madou.
answered Aug 01 '11 at 19:41
Nanotechnology by far is a insanely complex science, borderline artform. I have two recommendations for books which you can find as pdf downloads around the place:
Title: Nano, The Essentials, Understanding Nanoscience and Nanotechnology By: T Paradeep Published: Tata McGraw-Hill Publishing, New Delhi
Title: Nano-Engineering in Science and Technology, An introduction to the world of Nano-Design By: Michael Rieth Published: World Scientific
The first book appears to touch on all points of 'nano' in some depth, however the second book does a really good job at explaining what is happening on the atomic level. Both books thus, talk about the machinery and applications of nanotech, but obviously there is no way they could tell you how to manufacture nanotech. Honestly though, it is simply a watch-in-awe kind of science as actually doing anything in nanotech is technically impossible without serious financial backing (and a degree :P)
answered Aug 03 '11 at 02:32
The book that really worked for me, although an older tome, now, was K. Eric Drexler's "Engines of Creation, The Coming Age of Nanotechnology".
In this volume, unlike some of his subsequent publications, Drexler gives a clear, and easy to understand background for Nanotech.
Drexler takes great pains to discuss both the benefits and (rather scary) possible negative side-effects of nanotechnology.
I've purchased this book six or seven times, and passed it on to others, in hopes of kicking around the ideas therein... but it's never been returned.
Clearly, I find this book worth reading, and have read it many times.
answered Aug 05 '11 at 11:48
Nanotechnology for Dummies??
I haven't read it, but the Dummies series books are generally good starter books.
answered Jan 19 '12 at 15:04 | <urn:uuid:69bc3fc4-e2a8-44b1-9957-0cad050f24ed> | 2.71875 | 495 | Q&A Forum | Science & Tech. | 49.128107 | 1,921 |
Provided by: manpages-dev_3.23-1_all
feclearexcept, fegetexceptflag, feraiseexcept, fesetexceptflag,
fetestexcept, fegetenv, fegetround, feholdexcept, fesetround, fesetenv,
feupdateenv, feenableexcept, fedisableexcept, fegetexcept - floating-
point rounding and exception handling
int feclearexcept(int excepts);
int fegetexceptflag(fexcept_t *flagp, int excepts);
int feraiseexcept(int excepts);
int fesetexceptflag(const fexcept_t *flagp, int excepts);
int fetestexcept(int excepts);
int fesetround(int rounding_mode);
int fegetenv(fenv_t *envp);
int feholdexcept(fenv_t *envp);
int fesetenv(const fenv_t *envp);
int feupdateenv(const fenv_t *envp);
Link with -lm.
These eleven functions were defined in C99, and describe the handling
of floating-point rounding and exceptions (overflow, zero-divide etc.).
The divide-by-zero exception occurs when an operation on finite numbers
produces infinity as exact answer.
The overflow exception occurs when a result has to be represented as a
floating-point number, but has (much) larger absolute value than the
largest (finite) floating-point number that is representable.
The underflow exception occurs when a result has to be represented as a
floating-point number, but has smaller absolute value than the smallest
positive normalized floating-point number (and would lose much accuracy
when represented as a denormalized number).
The inexact exception occurs when the rounded result of an operation is
not equal to the infinite precision result. It may occur whenever
overflow or underflow occurs.
The invalid exception occurs when there is no well-defined result for
an operation, as for 0/0 or infinity - infinity or sqrt(-1).
Exceptions are represented in two ways: as a single bit (exception
present/absent), and these bits correspond in some implementation-
defined way with bit positions in an integer, and also as an opaque
structure that may contain more information about the exception
(perhaps the code address where it occurred).
Each of the macros FE_DIVBYZERO, FE_INEXACT, FE_INVALID, FE_OVERFLOW,
FE_UNDERFLOW is defined when the implementation supports handling of
the corresponding exception, and if so then defines the corresponding
bit(s), so that one can call exception handling functions, for example,
using the integer argument FE_OVERFLOW|FE_UNDERFLOW. Other exceptions
may be supported. The macro FE_ALL_EXCEPT is the bitwise OR of all
bits corresponding to supported exceptions.
The feclearexcept() function clears the supported exceptions
represented by the bits in its argument.
The fegetexceptflag() function stores a representation of the state of
the exception flags represented by the argument excepts in the opaque
The feraiseexcept() function raises the supported exceptions
represented by the bits in excepts.
The fesetexceptflag() function sets the complete status for the
exceptions represented by excepts to the value *flagp. This value must
have been obtained by an earlier call of fegetexceptflag() with a last
argument that contained all bits in excepts.
The fetestexcept() function returns a word in which the bits are set
that were set in the argument excepts and for which the corresponding
exception is currently set.
The rounding mode determines how the result of floating-point
operations is treated when the result cannot be exactly represented in
the signifcand. Various rounding modes may be provided: round to
nearest (the default), round up (towards positive infinity), round down
(towards negative infinity), and round towards zero.
Each of the macros FE_TONEAREST, FE_UPWARD, FE_DOWNWARD, and
FE_TOWARDZERO is defined when the implementation supports getting and
setting the corresponding rounding direction.
The fegetround() function returns the macro corresponding to the
current rounding mode.
The fesetround() function sets the rounding mode as specified by its
argument and returns zero when it was successful.
C99 and POSIX.1-2008 specify an identifier, FLT_ROUNDS, defined in
<float.h>, which indicates the implementation-defined rounding behavior
for floating-point addition. This identifier has one of the following
-1 The rounding mode is not determinable.
0 Rounding is towards 0.
1 Rounding is towards nearest number.
2 Rounding is towards positive infinity.
3 Rounding is towards negative infinity.
Other values represent machine-dependent, non-standard rounding modes.
The value of FLT_ROUNDS should reflect the current rounding mode as set
by fesetround() (but see BUGS).
The entire floating-point environment, including control modes and
status flags, can be handled as one opaque object, of type fenv_t. The
default environment is denoted by FE_DFL_ENV (of type const fenv_t *).
This is the environment setup at program start and it is defined by ISO
C to have round to nearest, all exceptions cleared and a non-stop
(continue on exceptions) mode.
The fegetenv() function saves the current floating-point environment in
the object *envp.
The feholdexcept() function does the same, then clears all exception
flags, and sets a non-stop (continue on exceptions) mode, if available.
It returns zero when successful.
The fesetenv() function restores the floating-point environment from
the object *envp. This object must be known to be valid, for example,
the result of a call to fegetenv() or feholdexcept() or equal to
FE_DFL_ENV. This call does not raise exceptions.
The feupdateenv() function installs the floating-point environment
represented by the object *envp, except that currently raised
exceptions are not cleared. After calling this function, the raised
exceptions will be a bitwise OR of those previously set with those in
*envp. As before, the object *envp must be known to be valid.
These functions return zero on success and non-zero if an error
These functions first appeared in glibc in version 2.1.
IEC 60559 (IEC 559:1989), ANSI/IEEE 854, C99, POSIX.1-2001.
If possible, the GNU C Library defines a macro FE_NOMASK_ENV which
represents an environment where every exception raised causes a trap to
occur. You can test for this macro using #ifdef. It is only defined
if _GNU_SOURCE is defined. The C99 standard does not define a way to
set individual bits in the floating-point mask, for example, to trap on
specific flags. glibc 2.2 supports the functions feenableexcept() and
fedisableexcept() to set individual floating-point traps, and
fegetexcept() to query the state.
int feenableexcept(int excepts);
int fedisableexcept(int excepts);
The feenableexcept() and fedisableexcept() functions enable (disable)
traps for each of the exceptions represented by excepts and return the
previous set of enabled exceptions when successful, and -1 otherwise.
The fegetexcept() function returns the set of all currently enabled
C99 specifies that the value of FLT_ROUNDS should reflect changes to
the current rounding mode, as set by fesetround(). Currently, this
does not occur: FLT_ROUNDS always has the value 1.
This page is part of release 3.23 of the Linux man-pages project. A
description of the project, and information about reporting bugs, can
be found at http://www.kernel.org/doc/man-pages/. | <urn:uuid:94b93e3d-cde9-450b-8870-519677c7f27f> | 3.03125 | 1,801 | Documentation | Software Dev. | 38.007257 | 1,922 |
Send Your Name to Mars
For all those who submitted your names, Congratulations! Your name was successfully etched onto a microchip and is officially on Mars!
How did NASA collect the names? More than 1.2 million names were submitted on our web site over a one year period! Some 20,000 visitors to NASA’s Jet Propulsion Laboratory, Pasadena, Calif., and NASA's Kennedy Space Center, Cape Canaveral, Fla., wrote their names on pages that were scanned and reproduced at microscopic scale onto two chips the size of a dime.
How were the chips made? Engineers etched the names onto a silicon wafer or microchip. They used an electron beam “E-beam” machine at JPL that specializes in etching very tiny features (less than 1 micron, or less than the width of a human hair!). They normally use this machine to make high-precision microdevices in JPL's Microdevices Laboratory.
Leonardo da Vinci’s Codex on Bird Flight, a document from about 1505 was reproduced on a microscopic scale and fastened to the chip on Curiosity. Leonardo’s self-portrait is also on the rover, along with some essays, drawings, and other submissions from finalists and semi-finalists who participated in the “Send Your Name to Mars” rover naming contest opportunity. | <urn:uuid:391a9b61-a76c-451d-9921-dbca6e9262b5> | 3.59375 | 277 | News (Org.) | Science & Tech. | 46.834006 | 1,923 |
Search Journal of Online Mathematics and its Applications:
Journal of Online Mathematics and its Applications
Page 1 of 1
Dealing with Data: A 'Simple' Linear Fit
[Note: The activities in this module make reference to the computer algebra system (CAS) Maple. Any other CAS can be used instead (e.g., Mathematica, Mathcad, etc.) as long as the user is familiar with that CAS system. In other words, while preferred here, Maple is not required for the use of this module.]
The first true test of any scientific theory is whether or not people can use it to make accurate predictions. Calculus, being the study of quantities that change, provides the language and the mathematical tools to discuss and understand change in a precise, quantitative way. An important prerequisite to using calculus to analyze "real-world" situations is having a good understanding of the basic "elementary" functions: polynomials, logarithms, trigonometric functions, and all their compositions, inverses, etc.
With an understanding of the calculus of the basic functions, it is often possible to formulate a mathematical model of (an idealized version of) a phenomenon in one of two ways: First, enough might be understood about the phenomenon so that a mathematical formulation of it is directly attainable. For example, Newton's second law of motion -- force is the derivative of momentum, where momentum is the product of mass and velocity -- is such a model. At the other extreme are models which are derived purely empirically -- data are collected, and one searches for an appropriate formula to match the data with reasonable accuracy. Many economic models are derived in this manner.
More often, however, mathematical models are developed with a combination of the two approaches: one has some basic understanding of a phenomenon, enough to restrict the class of functions appropriate to model it. Very often, one knows enough so that the functions are determined except for a few parameters, such as the coefficients of a polynomial, or some other kind of multiplicative factor. Then, experimental data are used to determine the values of the missing parameters. Many of the "constants", "coefficients" and "numbers" one encounters in science (e.g., rate constants of chemical reactions, half-lives of radioactive elements, coefficients of thermal conductivity, the gravitational constant, etc.) started out as the last unknown parameters in a mathematical model, which had to be determined by collecting experimental data.
Linear fits: In many situations, researchers want to understand how some quantity will change when another quantity is varied. A simple example of this might be the following sports-physics experiment: A basketball is dropped from different heights, and the height of the first bounce is measured each time. What is the relationship between the height of the drop and the height of the bounce? We can try a simple mathematical experiment to look at the problem. Below is an interactive program that allows you to enter several data points (possibly non-physical) claiming to be data representing the starting height and subsequent bounce heights of a basketball. Enter the x,y values for any points you like, then use the mouse to click on any two positions inside the graph area. The program draws a line between the two points and indicates the endpoints and the midpoints with circles. By clicking near the center of any of the circles, you can drag the line around. As you do so, you will see a display of the distance between the closest approach of the line to each data point. You also see at the bottom a display of a number which characterizes how "badly" the line fits the points. The smaller the "badness" number, the better the line should appear to represent the points. Try it!
Dr. DeTurck collected the following data by dropping a basketball in his garage. After each drop, he measured the height of the first bounce:
To get ready for our subsequent analysis, we use Maple to make a list of the drop heights and the corresponding bounce heights:
#Make an ordered list of data points # drop:=[36,40,40,44,44,48,52,56,60]: bounce:=[25,29,28.5,31.5,32,35,38,42,46]:The square brackets indicate to Maple that the set of numbers is an ordered list. The two statements end with colons, rather than semicolons, so that there will be no output from them (because in this case, Maple would just parrot back the input).
It will be helpful to have Maple make what statisticians call a "scatter plot" of the data points. To plot points from a list, Maple expects an ordered list containing the x-coordinate of the first point followed by the y-coordinate of the first point, followed by the x-coordinate of the second point, etc. To transform our drop and bounce lists into ordered pairs, we enter the following command (this is pretty advanced Maple-speak, so don't worry if you wouldn't have thought of it):
This defines the variable points to be the list of points we want to plot. Be careful when you type this statement that you distinguish carefully between parentheses and square brackets.
The variable points has the drop height and the corresponding bounce height right next to each other, for use with plot. So try plotting the data ("style=POINT" and "symbol=cross" are to keep Maple from connecting the dots):
plot(points, style=POINT, symbol=cross);
The data look pretty linear, but how do we find the line that "best" describes it? There are several different definitions of "best" in use. We will be using the so-called "least-squares" fit. For our drop-bounce data, the least squares line is obtained as follows:
with(stats,fit); with(fit,leastsquare); leastsquare[[x,y],y=a*x+b]([drop,bounce]);
y = .8502604294 x - 5.567708941.
Now we can plot the data and the line to see how well Maple did with fitting the data. Since we want to combine two different kinds of plots, we will be using the display command.
First, let's assign a name to the equation Maple returned.
fitlin := .8502604294*x - 5.567708941;
Now we can plot both the line and data and store those plots as variables. The names stand for what Maple calls "plot structures", which are Maple's internal directions for making plots. It is very important to use colons at the end of statements that assign plots to names. You defnintely do not want to see the plot structures!
fitplot := plot(fitlin,x=35..60): pointplot := plot(points, style=POINT, symbol=cross):
We can display the plot commands we've saved. Before we do that, we have to have Maple load the display command.
Fit this data with a least-squares line. What interpretation do you give to the slope of your line? Using your linear model, predict the winning height in the 2000 Olympics... in the 2096 Olympics. According to your model, in what year will pole vaulters be able to "leap tall buildings in a single bound"? (The Empire State building is 1250 feet tall.)
Comment on the reasonableness of your model (including comments about the residuals).
Problem 2. In a physics experiment, students measure the period of a pendulum (i.e., the amount of time the pendulum takes to swing back and forth) as a function of its length. One group of students obtained the following data:
As you did in the first problem, find the least squares line that best fits this data. Compute and plot the residuals -- these are the differences between the measured values of the period and the value predicted by the least squares equation for each measurement. Explain why these indicate that a different model is needed.
Published July 2001
© 2001 by Larry Gladney and Dennis DeTurck | <urn:uuid:3afc882f-3743-40dc-b6ea-15777e6ec5c4> | 3.484375 | 1,704 | Documentation | Science & Tech. | 53.700603 | 1,924 |
History of Fractions
Date: 12/7/95 at 9:30:11 From: Anonymous Subject: History of Fractions I have several math classes coming to our school media center next week to research the history of fractions. The problem is, our media center does not have the right resources to help students with their assignment. They are trying to find out how fractions developed and how they have been used in history. For example, how did the Babylonians, Ancient Chinese, Egyptians, Greeks, or Hindus use fractions? How were fractions written? Which operations (addition, subtraction, multiplication, division), if any, could be carried out with fractions? How did they expand the use of fractions? We have a few books that cover what the numerals of these societies looked like, but nothing about the history of fractions in ancient cultures. Our public library and our district high school library didn't have anything either. Your help is greatly appreciated!
Date: 3/8/96 at 23:45:47 From: Doctor Jodi Subject: Re: History of Fractions Hi there! If you have access to a web browser, you'll find a detailed description of the Babylonian and Egyptian mathematical system, including some discussion of fractions, at http://www-groups.dcs.st-and.ac.uk/~history/HistTopics/Babylonian_and_Egyptian.html Briefly, the Babylonians used base 60, rather than base 10. Their fractional system survives in the hours minutes and seconds notation we still use. The Chinese system is described at http://aleph0.clarku.edu:80/~djoyce/mathhist/china.html Briefly, the Chinese used a symbol for the numbers 1-10, 100, 1000, and 10000. 2034 would be written 2, 1000, 3, 10, 4 (2 * 1000 + 3*10 +4) Small bamboo counting rods were used for calculations. Positions from left to right gave place value. Fractions, as far as I can tell from this description, were like ours. You might find a better description in the original sources, Development of Mathematics in China and Japan (Mikami) and Chinese Mathematics, A Concise History (Li Yan and DuShiran). Some of the resources from the bibliography at http://aleph0.clarku.edu:80/~djoyce/mathhist/numerals.html may also be useful. From my understanding of Greek mathematical history, I gather that Greeks emphasized the use of ratios. Euclid's ELEMENTS contains a book just on ratios and several others which depend heavily upon it. You may be particularly interested in exploring the golden ratio. I hope this will give you the information you're looking for. If you'd like more references or don't have access to a web browser, please mail us again. Thanks for your question! -Doctor Jodi, The Math Forum
Search the Dr. Math Library:
Ask Dr. MathTM
© 1994-2013 The Math Forum | <urn:uuid:10ea4a66-b38a-40ef-a43a-ed5049dfd923> | 3.5 | 632 | Comment Section | Science & Tech. | 62.218113 | 1,925 |
Arcs, Cevians, Tangents
Theorem 4.5 The lines tangent to the circumcircle of a triangle at its vertices cut the opposite sides in three collinear points.
The proof in the text is as follows: Let the tangent to the circumcircle at A meet line BC at L. Then Angle BAL is congruent to angle C since each angle is measured by half of arc AB. *****That would be fine, but I don't know how they determine this... *****. Also we have that angle LAC = 180 - angle ABC, since these angles are measured by halves of the two opposite arcs AC. *****Again, I am lacking the theorem which is used to deduce this******.... the rest of the proof is trivial and I don't need help with it.
Can someone please give me the theorems they use for those parts of the proof.
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It's elementary theorem that angles on the circumference of the circle 'looking' at the same arc of that circle are themselves equal. (the proof is a bit long but if necessary I can try to write it, try this Circumferential Angle Is Half Corresponding Central Angle ; the theorem works for any circumferential angle.)
BAL is 'looking' at the arc AB but is degenerated.
When you know this you can find the second part easily just observing the angles ABC and the angle at A 'looking' at arc AC.
Sorry if my English was bad. | <urn:uuid:a48c710c-cee8-4d73-8702-0f1548da2c2b> | 3.375 | 318 | Q&A Forum | Science & Tech. | 71.270484 | 1,926 |
|El NiƱo-Southern Oscillation
The most common way of monitoring the El NiƱo-Southern Oscillation phase is by looking at sea surface temperatures in the equatorial Pacific Ocean. The animated map below shows sea surface temperature anomalies over the past three months. Warm/positive anomalies are associated with the El NiƱo phase, while cool/negative anomalies are associated with the La NiƱa phase.
Several climate models also provide ENSO forecasts, again based on sea surface temperatures over a specific region in the equatorial Pacific Ocean. The graph below shows the observed ENSO phase for the previous three-month period (as a red circle near the left side of the image), along with computer model forecasts for the next year-and-a-half. The light blue square represents the model consensus forecast.
In North Carolina, a warm/positive phase (El NiƱo) event is often associated with cooler, wetter conditions and an increased chance of winter weather. Likewise, a cool/negative phase (La NiƱa) event often brings North Carolina warmer and drier conditions. The impacts of ENSO on North Carolina are most prominent during the winter.
Because ENSO conditions are generally slow to change, with a frequency on the order of months to seasons, we have some skill at issuing forecasts on a seasonal and even annual basis.
For more information about ENSO, visit our information page or the Climate Prediction Center's page that includes past, current and forecast conditions. | <urn:uuid:5e01c03d-a1e5-4b30-abfe-34ab14544b5c> | 3.28125 | 323 | Knowledge Article | Science & Tech. | 27.113896 | 1,927 |
Dog lovers in search for the right canine are often faced with the challenge of choosing between a mutt and a pure breed. Most of these people would never expect that their own curiosities are also shared by ecologists.
Hybrids are a symbol of complexity. For several decades these mixed species have challenged ecologists who study their role in ecological communities. Ecologists are still asking themselves the question: Are plant and animal hybrids viable contributors to ecosystems or just evolutionary blunders? The Special Feature in the March issue of Ecology focuses on hybridization and the current research encompassing this issue.
Indeed, researchers are intrigued by the unique genetic makeup of hybrid species that merit evolutionary distinction from their parental generations. Researchers at the University of Georgia, Department of Genetics conducted a study challenging the existing paradigms that minimize the importance of hybridization in ecological settings. Michael Arnold et al. in their paper "Natural Hybridization: How Low Can You Go and Still Be Important?" state that hybrids are in fact viable evolutionary components of communities, and in some cases, more fit than their parents. Because hybridization enhances genetic variation, Arnold states, "...hybrid genotypes can be more fit than parental genotypes in novel environments."
In contrast, Catherine Moulia from the Laboratoire de Parasiologie Compare in France presents a different scenario. Her research on hybrid mice reveals that they are more prone to parasite attack than their parental counterparts (Mus mus musculus and M. m. domesticus). Her review of the parasitism of animal hybrids not only suggests an evolutionary implication of parasites. It also stresses that this implication of parasites is very similar in animal and in plant hybrids.
According to some studies reviewed by Moulia, "By taking advantage of hybrid
susceptibility, parasites could enhance their range and
Contact: Alison Gillespie
Ecological Society of America | <urn:uuid:5e597cde-5bee-4b5c-ada7-9123d53ac027> | 3.203125 | 377 | News Article | Science & Tech. | 16.875419 | 1,928 |
Crab Pulsar emits light at highest energies ever detected in a pulsar system, scientists report
By Kim DeRose October 06, 2011 Category: Research
An international team of scientists has detected the highest energy gamma rays ever observed from a pulsar, a highly magnetized and rapidly spinning neutron star.
The VERITAS experiment measured gamma rays coming from the Crab Pulsar at such large energies that they cannot be explained by current scientific models of how pulsars behave, the researchers said.
The results, published today in the journal Science, outline the first observation of photons from a pulsar system with energies greater than 100 billion electron volts — more than 50 billion times higher than visible light from the sun.
"This is the highest energy pulsar system ever detected," said Rene Ong, a UCLA professor of physics and astronomy and spokesperson for the VERITAS collaboration. "It is a completely new and surprising phenomenon for pulsars."
Data were acquired for 107 hours over the course of three years by VERITAS's ground-based gamma ray observatory, which is part of southern Arizona's Whipple Observatory, a facility managed by the Harvard–Smithsonian Center for Astrophysics. VERITAS (Very Energetic Radiation Imaging Telescope Array System) observes gamma rays using a network of four telescopes, each 12 meters in diameter.
Ong noted that all previous observations of pulsars indicated that the radiation cuts off at the high energies the team observed.
"It means the radiation we detect must be a new component that was completely unexpected," he said.
Gamma rays, the most energetic type of electromagnetic radiation, cannot be directed by lenses or bounced off mirrors like ordinary visible light, Ong said. Because the rays are invisible to the human eye, the only way telescopes on Earth can detect them is by observing the path they take as they are absorbed in the planet's atmosphere.
Gamma rays are ejected from the Crab Pulsar, and they smash into Earth's atmosphere, causing "the electromagnetic equivalent of a sonic boom," Ong said. This collision creates a shower of visible light more than 6 miles above the ground that is recorded by VERITAS.
"The atmosphere is an integral part of our measurement system, which makes VERITAS different from conventional telescopes," Ong said.
One of the most widely studied astronomical objects in the northern hemisphere, the Crab Nebula, which is some 6,500 light-years from Earth, was formed when a massive star exploded in a supernova event that was observed on Earth in the year 1054. While it is most typical for pulsars to be ejected from the stellar wreckage during a supernova, in the case of the Crab system, the pulsar remained at its center, producing radiation that covers the entire electromagnetic spectrum, Ong said.
He calls the Crab system the "Rosetta Stone of astronomy," because astronomers and astrophysicists have observed this object at every conceivable wavelength of light.
"The Crab Pulsar is considered among the best understood systems in all of astronomy, yet here we have found something totally new," he said. "It is astronomy in a completely new light; we are seeing phenomena that you just can't explore with optical light or X-rays, or even low-energy gamma rays."
The Crab Pulsar is a highly magnetized neutron star with a surface magnetic field a trillion times stronger than that of the Earth. The star spins at the dizzying rate of about 30 times a second and emits gamma rays through "curvature radiation," an effect that creates a lighthouse-like beacon that winks on when the beam faces the Earth and off when the star pivots away.
Light detected by the VERITAS experiment cannot be explained by curvature radiation, however, and likely comes from regions well outside the high–magnetic field region close to the neutron star, Ong said. While such energetic gamma rays have been observed elsewhere in the galaxy, the actual mechanism of how they are created in a pulsar is not fully understood.
"The pulse duration of the radiation we see is almost three times shorter than that seen at other gamma ray energies," he said. "This was very surprising and means this new radiation is probably coming from a different physical region of the star's outer magnetosphere."
The VERITAS experiment looks for radiation emanating from celestial objects such as pulsars, active galaxies, the center of the Milky Way and supermassive black holes. It has collected data for nearly 1,000 hours every year since it began operating in 2007.
"We are trying to understand processes out in the cosmos that can create particles at these extreme energies, beyond what can be produced here on Earth," Ong said. "We are also very interested in seeing if these processes indicate some sort of new physics."
Ong hopes his research may shed some light on the mystery of cosmic rays.
"We are bombarded by high-energy particles from all over the cosmos that reach unimaginable energies," he said. "These cosmic rays are an important energy source in our galaxy, yet we have no clue where they are coming from.
"This measurement indirectly gives us clues to the highest energies in the cosmos, telling us about particles and energies that we can't generate here on Earth but that nature's accelerators are able to create for us."
Ong is currently helping to plan the next-generation ground-based gamma ray observatory, called the Cherenkov Telescope Array (CTA). Covering more than one-half square mile with dozens of telescopes, the CTA will be 10 times more sensitive than VERITAS, allowing radiation from fainter and more distant objects to be accurately resolved.
The 95 co-authors of the Science paper on the Crab Pulsar include scientists from 26 institutions in five countries who are part of the VERITAS collaboration. UCLA co-authors include Vladimir Vassiliev, an associate professor of physics and astronomy; Pratik Majumdar, a postdoctoral scholar in physics and astronomy; and Timothy Arlen, a graduate student.
This research is supported by the U.S. Department of Energy, the U.S. National Science Foundation, the Smithsonian Institution, the National Sciences and Engineering Research Council of Canada, the U.K.'s Science and Technology Facilities Council, and the Science Foundation Ireland.
UCLA is California's largest university, with an enrollment of nearly 38,000 undergraduate and graduate students. The UCLA College of Letters and Science and the university's 11 professional schools feature renowned faculty and offer 337 degree programs and majors. UCLA is a national and international leader in the breadth and quality of its academic, research, health care, cultural, continuing education and athletic programs. Six alumni and five faculty have been awarded the Nobel Prize. | <urn:uuid:48c1f916-0234-4f71-a55e-9fde92703c11> | 3.28125 | 1,382 | News Article | Science & Tech. | 32.874292 | 1,929 |
Can you design a new shape for the twenty-eight squares and arrange
the numbers in a logical way? What patterns do you notice?
In a square in which the houses are evenly spaced, numbers 3 and 10
are opposite each other. What is the smallest and what is the
largest possible number of houses in the square?
Exactly 195 digits have been used to number the pages in a book.
How many pages does the book have? | <urn:uuid:560d7182-0fc5-480e-856a-12c1b58c9970> | 3.234375 | 92 | Q&A Forum | Science & Tech. | 67.824615 | 1,930 |
The manned research submersible Alvin.
September 8 - October 1, 2001
The Deep East Expedition completed its field season on October 1. Scientists explored three regions of the Atlantic Ocean, from Maine to Georgia, including the submarine canyons of Georges Bank and Bear Seamount off the New England coast; Hudson Submarine Canyon, an ancient extension of the Hudson River Valley that extends more than 400 nautical mi seaward from the New York-New Jersey Harbor; and Blake Ridge off the Georgia coast. Even though these areas are very close to home, until now, little was known about the living and nonliving resources there.
Using the manned submersible Alvin, scientists ventured to the bottom of the Atlantic, collected video footage, measured the biological, geological, and chemical features of these areas, and collected biological and geological samples for further analysis. During the expedition, scientists examined deep-water corals and methane hydrates, and discovered previously unknown deep-sea resources and processes.
Background information about the expedition are found on the left side of this page. Daily updates are included below. Detailed daily logs of the expedition's activities are found on the right.
Read a summary of some of the preliminary findings from this fascinating expedition. On Dec 12, NPR Marketplace ran a special feature on the Deep East expedition. You can listen to it here (click on RealAudio link, then advance to 22:05).
Updates & Logs
Leg 3 Blake Ridge
Click images or links below for detailed mission logs.
The Deep East Expedition spanned 1,000 mi, from Georges Bank to the Blake Ridge off the U.S. Eastern Seaboard. Of the planned 15 dives, 11 descended to depths reaching 3,000 meters -- more than a mile and a half below the ocean surface. The expedition's accomplishments included the collection of eggs and sperm packets from two deep-water species of anemone and coral. Analysis of these samples will provide the first picture of invertebrate reproduction in deep-sea habitats.
The preliminary results of geological studies showed an elevated methane signal throughout the Hudson Canyon region, indicating that active methane vents occur in the area. Pending further analysis of samples collected at Blake Ridge, scientists expect to find several new species of sea creatures, including shrimps, worms, and clams. Some of these organisms may harbor new symbiotic relationships that could change our fundamental understanding of the global web of life.
Winds are sustained at 37 kts with higher gusts
and the seas are mess8 feet and continuing to build. Weather
predictions take the winds to 50 kts, and the Captain says that the
seas will probably reach 20 feet. The final Alvin
dive of the Deep East Voyage of Discovery has been cancelled. The underwater transponders that have navigated Alvin
again and again to the site of our deep sea finds have been retrieved. Dr. Carolyn Ruppel continues to gather the multibeam points to further expand our knowledge of the bathymetry at Blake Ridge.
Samples are being packed up and the Atlantis
has begun the task of getting her ready for the tours that will be
part of NOAAs Ocean Exploration Day in Charleston.
makes Dive 3712 on Area E on the
Blake Ridge, the weather report reads "Developing gale, 33 N 70W moving NE 30 kts. Forecast area of N winds 25-35 kt, seas 10-18 ft. within area S of 34Nw of 75W associated with the gale center south of the area." Although
is approximately 60 nautical miles east-southeast the affected area, there
is already an air of anticipation about whether tomorrows dive
will be affected by seas
kicked up by the developing system. Students from around the country have been participating in the Deep East Web Forum over the past four days. This online conversation concluded today with a very successful audio Deep East Web Chat with students from as far away as Washington and as close as South Carolina posing questions live via a satellite phone to scientists on board the Atlantis
It is an overcast day and the seas are calm. As Alvin makes Dive 3,711
the Blake Ridge, Dr. Joan Bernhard and graduate student Katie Knick
are experiencing the deep sea in a way that few of us ever will. Dr.
Carolyn Ruppel continues her work using the multibeam system to "fill in" details
of Blake Ridge bathymetry with 120 measurements that are sent back
to the ship with each ping of the multibeam instrument. And Dr. Joan
Bernhard discovers yet another new find on the Blake Ridge.
is making its second dive on the Blake Ridge. Dr. Barun Sen Gupta and Dr. Paul Aharon are in the submersible with pilot Dudley Foster as they explore for evidence of gas hydrates
. Dr. Joan Bernhard reported during the morning science meeting that microscopic examinations of sediment cores late last night revealed that, in fact, bacterial mats of Beggiatoa
were collected yesterday, the first chemoautotrophic (feeding on methane) bacteria to be collected at this site. Alvin
returns to us after a full day of diving and delivers incredible video tapes of gas hydrates, mussels that are larger than the ones collected yesterday, and live clams--yet another historic day of exploration on the deep seafloor of the Blake Ridge.
made its first dive on the Blake Ridge to a depth of 2,155 meters, almost a mile and a half under the surface of the ocean. Today will be a memorable one in deep sea research
as it goes down in history as being the first day that live samples were brought up from the deep ocean floor at Blake Ridge using the Alvin
. "Amazing, just amazing," says
Dr. Cindy Van Dover. These are by far the biggest mussels I have ever
arrived at the first station at approximately 1230 today. Transponders were released to aid the Alvin
underwater navigation for tomorrows dive. An expendable bathythermograph
(XBT) was deployed to measure temperature of the water column with
depth. A multibeam survey is underway to create a plot of the bathymetry
of the area. Seas are calm and scientists and crew are busy preparing for the first dive on Blake Ridge
scheduled to take place at 0800 tomorrow.
The R/V Atlantis
continues on her way to the Blake Ridge. We are currently 47 miles due east of Cape Hatteras, North Carolina. We have slowed in speed due to the presence of the Gulf Stream, which we are now crossing
as it makes an eastward bend off the coast of North Carolina. At the present speed of 11.1 kts, our estimated time of arrival on station is 1200 (noon) tomorrow. The seas are calm, despite the fact that the tropical depression has now been upgraded to Tropical Storm Humberto. Predictions continue to take it from its current northern track to a more northeastern track over the next 12 hours.
Leg 2 � Hudson Canyon
We have packed up our gear and are ready for departure. Much planning and organization went into our coming together for this leg of the Deep East Expedition, so in one sense, the trip was a culmination of the dreams and efforts of many people. In another way, the data we have collected, ideas we have exchanged, things we have learned, and questions we have raised make this a new beginning. We will leave the research vessel (R/V) Atlantis with a tremendous sense of accomplishment,
as well as new reasons and increased motivation to further explore the deep ocean and the dynamic ecosystems that characterize the Hudson Canyon.
Everyone woke to the excitement of having two Alvin
dives today.The first dive would carry a teacher, and the second, a graduate student. As teacher Holly Donovan approached her dive time, she was very nervous, but anxious to see the wonders of the sea.
While waiting for the second dive, graduate student Grant Law sat in the computer lab playing the guitar. As both dives came aboard, anxious scientists gathered around to hear the stories, collect their samples, and reminisce about the past week.
September 19 Today, Alvin dove to the northern edge of the Hudson Canyon.
This region is located on the outer edge of the continental shelf, near the head of the canyon. During this dive, scientists Fred Grassle and Ken Able were able to identify 21 species of fish. One of the most striking sights was a variety of predators (squid, hake, and crab) feeding feverishly on thousands of lantern fish near the bottom of the canyon at a depth of about 200 m.
The day started at 2:30 am, when the first box core was lowered into the ocean
then departed at 8:30 on its way to the plume site. As Alvin
returned, a rumor spread that a large animal had been captured. As Alvin
into its "garage," many scientists and others gathered
around to see the sight -- a huge anemone. Then the box cores,
niskin bottles, and Alvin
push cores were all unloaded. The evening came to an end with three box cores over the side at 8:30 and 11 pm, and finally at 1:30 am on Sept. 19. Mud was flying everywhere.
After our early morning attempt to launch the CTD rosette, which had been postponed due to weather conditions, we continued watching the wind speed and the size of the swells to determine whether our scheduled first dive with Alvin
would indeed occur. The initial launch time of 8 am was postponed until 9:30, at which time the launch was successfully completed
descended to the 106-mi Dumpsite. Box cores, water samples, and core samples were taken to study the evolution of the ecology and geology of the site since the last sampling in 1996. After dinner, the CTD rosette was successfully launched and retrieved. Its water samples will be tested later for methane.
Excitement was in the air as moving day approached. Scientists scurried around moving on board, while crew members busily loaded and tied down all the equipment needed for the trip. As the R/V Atlantis
pulled away from the dock, most of the scientists' paused to take one last look at land before heading out to sea
. Now they were ready to get to work.
Leg 1 Georges Bank Canyons
September 15 The first Leg of Deep East came to a close today, as we returned to dock in Woods Hole
at 9:15 am. The weather is getting rougher, and all those aboard are relieved that Leg 2 of Deep East will disembark from Woods Hole instead of from Staten Island, NY, as planned. Originally, the scientists participating in Leg 2 were to board a transfer boat on Staten Island and come out to sea to meet the Atlantis
. When the two boats rendez-voused, Leg 1 scientists would board the Staten Island transfer boat. When it became clear that the port of New York would be closed, however, Woods Hole became the exchange point.
At long last, the wind and waves subsided enough to allow Alvin
to dive safely into Hydrographer Canyon. The benthic substrate of this canyon was considerably different from that of Oceanographer Canyon. Instead of a rocky substrate, this canyon was steep and muddy. No corals were found in Hydrographer Canyon, but a rich community of fish and invertebrates was observed.
The science team wrapped up this leg of Deep East with an Alvin
ritual -- sending decorated Styrofoam cups down on the submersible. The crushing hydrostatic pressure shrinks them into tiny miniatures.
After four days at sea and only one dive day, the crew and science party once again woke to rough seas and high winds.
Some members of the science party kept busy editing digital video footage and still photos, while others caught up on missed sleep.The R/V Atlantis'
SeaBeam multibeam sonar system was pressed into service to map the depths of Bear and Physalia Seamounts. The Atlantis
crew set a course for Hydrographer Canyon, with high hopes for low winds and calm seas for Friday's planned Alvin
Weather conditions at sea have forced the cancellation of the dive at Bear Seamount. The swells from Hurricane Erin, approximately 150 mi southeast of the R/V Atlantis,
can be felt aboard ship, and the captain has ordered all hands to remain inside
until further notice. Work continues aboard the ship, while the crew and science staff monitor news updates from the U.S. mainland.
The R/V Atlantis
left Woods Hole at 12 noon and headed to Oceanographer Canyon, the first dive site. Shortly after departure, we encountered the WHOI vessel R/V Oceanus
to port. Once south of the Nantucket Shoals, the crew and science
staff participated in safety demonstrations and received advice on "getting their sea legs." An evening meeting for the science staff will discuss the next days dive, and the status of Hurricane Erin.
We'll also get to see slides of deep-sea coral species, courtesy of Dr. Barbara Hecker.
Prior to the cruise, preparations for the Deep East Expedition took place on the dock at Woods Hole Oceanographic Institution (WHOI) in Woods Hole, MA. Science equipment, food, and other supplies lined the dock as the crew, scientists, educators, and WHOI staff made a final inspection of the vessel and completed last-minute tasks.
A Deep East Professional Development Institute was provided for educators on Cape Cod, which included a tour of the R/V Atlantis
. As the excitement and anticipation began to build, a new element was added to the mix -- Hurricane Erin, whose path will be closely monitored as departure time approaches.
Sign up for the Ocean Explorer E-mail Update List. | <urn:uuid:25d2e1c4-c7e1-4ead-a970-89b1a6a25b89> | 3.40625 | 2,884 | Knowledge Article | Science & Tech. | 51.487519 | 1,931 |
As Saturn's rings orbit the planet, a section is typically in the planet's shadow, experiencing a brief night lasting from 6 to 14 hours. However, once approximately every 15 years, night falls over the entire visible ring system for about four days.
This happens during Saturn's equinox, when the sun is directly over Saturn's equator. At this time, the rings, which also orbit directly over the planet's equator, appear edge-on to the sun. During equinox, light from the sun hits the ring particles at very low angles, accenting their topography and giving us a three-dimensional view of the rings.
"The equinox is a very special geometry, where the sun is turned off as far as the rings themselves are concerned, and all energy comes from Saturn," said Dr. Michael Flasar of NASA's Goddard Space Flight Center in Greenbelt, Md.
During Saturn's latest equinox August 11, the rings reached a temperature of 382 degrees below zero Fahrenheit, the coldest yet observed, as seen by the Composite Infrared Spectrometer (CIRS) instrument on board the Cassini spacecraft in orbit around Saturn. CIRS was developed at NASA Goddard, and Flasar is the Principal Investigator for the instrument.
"The whole point of the CIRS observations of Saturn's rings, other than producing some cool pictures, is to learn something about the physical properties of the ring particles: their spin rates, how sluggish they are in storing and radiating heat (a diagnostic of size and composition), and their vertical distribution in the ring 'plane'," said Flasar.
Although the rings are wide, they are only about 30 feet thick. They are made of particles that are mostly water-ice. Scientists continue to debate the rings' origin and age. Some think they could be remnants of a shattered moon or captured comets, while others think they could have formed along with Saturn from the primordial disk of gas and dust that gave birth to our solar system.
"At first glance, Saturn's rings look broad and bland, but then we got close-up images from the Voyager flybys, and our reaction was: oh, my gosh, there's structure everywhere - what's going on?" said Dr. Linda Spilker, of NASA's Jet Propulsion Laboratory (JPL), Pasadena, Calif.
Researchers have discovered that while most of the ring particles are as small as dust and pebbles, there are a few chunks as big as mountains, and even some small moons several miles across embedded in the rings. Instead of orderly orbiting around Saturn, the particles clump together and drift apart, and the rings ripple and warp under the gravitational influence of Saturn's swarm of more than 60 moons.
"The closer we look at the rings, the more complex they get," says Spilker, Deputy Project Scientist for the CASSINI mission and a Co-Investigator on CIRS. She is leading the instrument team's investigation of the rings.
"Because Saturn's rings are so extended, going out to more than twice Saturn's radius (from the cloud tops), the furthest rings get less heat from Saturn than the innermost rings, so the ring temperatures at equinox tend to fall off with distance from Saturn's center," said Flasar.
However, the CIRS team discovered that the A-ring - the outermost of the wide, bright rings - did not cool off as much as expected during the equinox. This might give clues about its structure and evolution. "One possibility is that the gravitational influence of moons outside the A-ring is stirring up waves in it," said Spilker. "These waves could be much higher than the typical thickness of the rings. Since the waves rise above the ring plane, material in the waves would still be exposed to sunlight during the equinox, which would warm up the A-ring more than expected."
"But we have to carefully test this idea with computer models to see if it produces the temperatures we observed with CIRS," adds Spilker. "That's the challenge with CIRS. It's not like seeing a close-up picture of Mars, which can tell you something about its geology right away. We have to look at the CIRS data from different times and sun angles to see how the ring temperatures are changing, then make computer models to test our theories on what those temperatures say about the rings."
The effort to understand the rings could help us understand our origin. "Our solar system formed from a dusty disk, so by understanding the dynamics in a disk like Saturn's rings, we can gain insight into how Earth and the other planets in our solar system were made," said Spilker.
The equators of both Earth and Saturn are tilted compared to their orbit around the sun. This tilt makes the sun appear to rise higher and lower in the sky throughout the year as Earth progresses in its orbit, causing the seasons to change. Likewise, Saturn's tilt makes the sun appear higher and lower in the sky as Saturn moves in its orbit, which takes about 29.5 years to complete.
Saturn experiences two equinoxes per orbit, just as Earth does, when the planet's equator lines up edge-on to its orbital plane, causing the sun to appear directly over the equator. For a viewer on Saturn, the sun would seem to move from south to north around the time of the August 11 equinox.
Technically, the equinox is the instant when the sun appears directly over the equator, but Saturn's situation gives the rings an extended twilight. Saturn is about 10 times farther from the sun than Earth. Since Saturn is farther from the Sun's gravitational pull, it moves relatively slowly in its orbit compared to Earth, which makes it take longer for the sun to noticeably appear higher or lower in the sky. Also, even as far away as Saturn, the sun is large enough to appear as a disk, not a point, according to Spilker.
So, before the August 11 equinox, a viewer embedded in Saturn's rings would have seen sunlight fade as the top edge of the solar disk appeared to touch the rings first. This would be followed by darkness around the equinox as the solar disk slowly crossed the ring plane. Full sunlight would have returned when the sun's bottom edge rose above the ring plane, about four days from when the sunlight first began to fade.
Source: JPL/NASA (news : web)
Explore further: NASA launching experiment to examine the beginnings of the universe | <urn:uuid:a375f17c-fb83-4a04-8aad-e7f32ed9f6d1> | 3.96875 | 1,360 | News Article | Science & Tech. | 50.184288 | 1,932 |
Ion strings make brilliant beams
Aug 15, 2001
Physicists have long struggled to combat heating in the ion beams used in high-energy experiments. Laser cooling can be used to reduce collisions between the ions, which create heat and reduce the energy of the beam. Now Ulrich Schramm and colleagues at the University of Münich have created the first 'crystalline' ion beam, which is virtually free from collisions. "The crystalline beam is the ultimate state for an ion beam in terms of brilliance and stability", Schramm told PhysicsWeb. "It represents a different phase and has its own properties" (T Schätz et al 2001 Nature 412 717).
Collisions in high-energy ion beams reduce the beam intensity and can be remedied by extra focusing devices or the use of low-density beams. However, physicists predicted 20 years ago that in a sufficiently cool beam, the ions would not collide because their Coulomb repulsion would outweigh their kinetic energy.
Such 'crystallization' has been achieved before in ion traps - in which the ions are stationary - but it is more difficult in a circulating beam because of the motion of the ions and interactions between the beam and the storage ring. These problems affect both large storage rings - such as the Relativistic Heavy Ion Collider at Brookhaven - and smaller ones.
Schramm and co-workers injected magnesium ions into their 0.36-metre circumference storage ring, PALLAS - the Paul laser cooling acceleration system. The beam was laser-cooled and its fluorescence monitored. The team found that, at a certain laser wavelength, the diameter of the beam fell and the fluorescence peaked sharply. This pinpoints the transition to the crystalline state, during which the range of ion velocities drops by 75%.
The fluorescence measurements showed that the ring contained around 18 000 ions, and the temperature of the beam fell from 30 to 0.4 kelvin as the crystalline state emerged. In this new phase, the ions reach a speed of 2800 metres per second - corresponding to a beam energy of 1 electron volt - and resemble a one-dimensional thread. The beam can perform over 3000 revolutions of their storage ring without further cooling
According to Schramm, the technique could be used for a wide range of experiments. "Crystalline ion beams could aid inertial confinement fusion - which mimics stellar nuclear reactions - while precise experiments with relativistic beams could test special relativity", he says.
About the author
Katie Pennicott is Editor of PhysicsWeb | <urn:uuid:bc6e3879-d2fd-478e-832b-124df80bfc06> | 3.59375 | 529 | Truncated | Science & Tech. | 42.617974 | 1,933 |
Notes to Being and Becoming in Modern Physics
1. As translated in Wheelwright (1960). The quote by Parmenides in what follows is also from this volume.
2. Many recent papers on these issues are collected in Oaklander and Smith (1994). Gale (1967) has some good older papers and a useful bibliography.
3. There are many excellent non-technical introductions to the special theory. Two fine books that are currently available are Mermin (1968) and Born (1962). A more demanding introduction mathematically is Taylor and Wheeler (1963). An excellent philosophical discussion is Chapter IV of Friedman (1983).
All the concepts needed for the present discussion are outlined briefly in the opening paragraphs of section 4 of Shimony (1993), but there is no substitute for working through in detail at least one presentation of the special theory at whatever level of mathematical sophistication one is equipped to handle.
4. While most popular presentations of special relativity explicitly employ only these two assumptions, Friedman (1983) points out that another assumption of a more technical nature, the flatness of Minkowski spacetime, is needed in order to derive all the characteristic results of the theory. We will ignore this refinement here.
One should note, however, that the two assumptions explicitly made are assumptions concerning invariance — the invariance of the speed of light and the laws of physics. That certain other quantities classically thought to be invariant turn out not to be so in special relativity has sometimes obscured the fact that there is a fundamental invariant special relativisic four-dimensional quantity called the spacetime interval that will enter our considerations in due course.
5. Hans Reichenbach indicated the same view in 1925. See Grünbaum (1973, p. 318).
6. Whether this suggested distinction overlaps or is independent of the distinction between tensed and tenseless uses of ‘is’ invoked above in the section on Newtonian Spacetime is an open question. Questions about the viability of this distinction are connected to deep questions in ontology and philosophy of language on which Carnap, Quine, and Sellars differed. See the discussion in Jay Rosenberg's entry in this Encyclopedia, Wilfrid Sellars.
7. Minkowski spacetime is a time orientable manifold. If one chooses one of the two lobes of the light cone at a point O to be, say, future, that choice can be extended smoothly throughout the whole of the spacetime. We say nothing as to how this choice is to be made in this entry, but we assume that it has been, somehow, made.
8. The three are free to choose O as the origin of each of their coordinate systems and to assign it spatial coordinate (0,0,0) and temporal coordinate 0. But what position and time values are assigned by each of them to other spacetime points now follows rigorously from the rules, the Lorentz transformations, of special relativity.
9. It is the fact the Rietdijk-Putnam-Penrose argument for the fixity of the future does not rely on features of natural laws or causation that leads me to call the thesis chronogeometric fatalism rather than chronogeometric determinism. Determinist and fatalist arguments have the same conclusion, that the future is somehow fixed and not within our control, but the former do so from causal or nomological considerations while the later do not.
10. Briefly, Rxy iff (y < x or y << x). Clifton and Hogarth (1995) point out the relation betwen x and each point in (but not on) its past light cone also satisfies all the criteria of adequacy specified in the text.
11. This result is implicit in the proofs offered by Stein and by Clifton and Hogarth. It is made explicitly in Callender (2000).
12. Following Winnie (1977), I suggest calling this set ALEX(e0,e1), since it is an open subset in the Alexandrov topology. Richard Arthur, as far as I know, was the first philosopher to use these sets to account for temporal becoming. See Arthur (2006) and Savitt (2005). | <urn:uuid:5132acbb-61dc-4b6f-80ce-8fbdd21025ef> | 2.59375 | 869 | Academic Writing | Science & Tech. | 46.579159 | 1,934 |
A range of designs have been proposed for space habitats. Some appear to be mostly artistic concepts, others are much more serious. They include:
(From Wikipedia http://en.wikipedia.org/wiki/Space_habitat)
- Bernal sphere - "Island One", a spherical habitat for about 20,000 people.
- Stanford torus - A larger alternative to "Island One."
- O'Neill cylinder - "Island Three", the largest design.
- Lewis One A cylinder of radius 250m with a non rotating radiation shielding. The shielding protects the micro-gravity industrial space, too. The rotating part is 450 long and has several inner cylinders. Some of them are used for agriculture.
- Kalpana One, revisedA short cylinder with 250 m radius and 325 m length. The radiation shielding is 10 t/m2 and rotates. It has several inner cylinders for agriculture and recreation.
There are other well-known structures from science fiction literature, including
- Rama (a 20x50km rotating cylinder) from Arthur C. Clarke’s novel, Rendezvous With Rama
- Space Station V (from the movie 2001: A Space Odyssey)
- Babylon 5
Of these, the most complete design is “Kalpana One, Revised,” which properly accounts for issues such as shielding and rotational stability. Most designs presume that it is best to provide windows to admit natural sunlight, but there are many reasons to prefer artificial light sources, primarily involving heat, but also the need for shielding. For adequate shielding from radiation and meteors, the outer walls of the habitat must mass about ten tons per square meter. While transparent quartz windows could be built of this thickness, most designs involving natural sunlight use mirrors to deflect sunlight around shields of stone. But the admitted heat is the real problem (discussed below).
In my previous posts, including Our First Colonies In Space, Life in an Asteroid, and Our Homes, the Comets, I assumed that we would tunnel into asteroids and comets, enclose and spin them for gravity if they were small enough, or build spinning structures inside them if they were too large.
But while writing a sequel to my short story Apophis 2029, I realized that the best choice was simply to build one or more space habitats from the raw materials of the asteroids and comets. I came to this conclusion because of considerations for effective use of space, the stresses of spinning large objects for gravity, and (most importantly) thermal dissipation.
People consume energy in their homes, workplaces, and travel. Much more important, food requires a large amount of energy in the form of light for growing crops. After extensive research on plant needs, high-intensity farming, and lighting technologies, I concluded that the minimum light levels needed requires 4 kilowatts of very-high-efficiency LED lights to grow the food for one person (assuming a primarily vegetarian diet – you need more to grow additional crops for livestock). Add to that the per-capita electric consumption in the U.S.A. of about 1.5 kilowatts, add a little more for contingencies, and I realized we need to plan on 6 kilowatts of energy consumption for every human aboard the habitat.
That’s not too bad, especially considering that readily available solar power can easily provide such levels and at a modest cost.
But energy consumption turns into heat, and heat must be radiated away. The bottom line is that we must allot 19 square meters per person of surface area assuming black body radiation at a temperature of 0 degrees C. It does not help to plant little radiators all over the surface, as they interfere with each other. All that matters is the apparent size of the habitat from a distance, and how closely it approaches the ideals of a black body radiator. Of course, we could use active cooling to heat radiators to much higher temperatures while cooling the interior, but I prefer passive techniques so that a failure of the cooling system doesn’t rapidly result in cooking the inhabitants.
There goes my idea that a million people could thrive in a cubic kilometer of comet. There is plenty of room, more than enough materials. Unfortunately, their waste heat would rapidly boil their home away.
Also, solar light has a large content of heat – and that excess, too, must be radiated away. Sunlight is not energy efficient for growing crops in a thermos bottle (which is what a habitat in space effectively is).
So, my revised plan calls for 20 square meters of surface per person. Also, to provide radiation and meteor shielding equivalent to the Earth’s surface requires 10 tons of shielding per square meter of surface – and thus 200 tons of shield mass per person (regolith is fine, slag works well and is dense, ice is best as long as it doesn’t boil away). But the needed surface area and shield mass per person are constants.
My earlier thoughts on structure did not consider rotational stability, and the folks that designed Kalpana One came up with some very strong arguments that a spinning cylinder is best, and that the width of the cylinder should be 1.3 times the radius. Thus, a cylinder of radius 100 meters (spinning at 3 rpm for 1 G gravity along the outer rim) should be 130 meters wide. That gives a 1-G living area of a little over 80,000 square meters, a total surface area of over 144,000 square meters, and thus a maximum population of 7,200. This structure provides 11.25 square meters (121 square feet) per person of 1-G living space. Is that enough?
It’s comparable to the space provided (per person) in many hotel rooms and cruise ships. But few couples want to live in a 242 square foot efficiency for long, although 28 sm (300 sf) studio apartments are common in many expensive cities.
There is no need to live only on the outer 1-G surface. Assuming 3-meter intervals, the next level up provides 97% of a G. Surely that is adequate. And now we have 22.5 square meters per person of available living space, equivalent to 450 square feet per couple – or 900 square feet for a family of 4. A third living level raises the per-person space to over 33 square meters – 675 sf per couple – 1350 sf for a family of four. Not spacious, but certainly comfortable.
Humans need space for living, working, and of course for growing food. We must allot some space for office space, work space, schools. A single level should suffice (11 square meters per person), partly because some people will work in the farms, or in their homes, or outside the habitat entirely (such as in the mines, the smelters, the steel mills, the solar power satellites, etc.).
Each person requires approximately 64 cubic meters for crops, but crops don’t require 3-meter ceilings. Allocating 2 levels for agriculture may be tight, but 3 levels is more than enough and provides some excess capacity for the production of meat, milk, and eggs.
We need a little more space for overhead: storage, aisles, conduits for air, water, sewage. So we add an 8th level for good measure. That still leaves an interior cylinder with a radius of 75 meters as a park or recreation area. It has 3/4ths of a G of gravity. The opposite side is more than 500 feet overhead – it will feel spacious enough, and 15+ acres of playgrounds, hiking paths, trees, and grass will provide a little bit of Earth in space.
But there’s no need to leave the end caps – the walls of our cylinder – as bare metal. We should build offices, low-gravity facilities (perhaps hospitals), hotels, etc. along those walls. Allocating 15 meters of depth along each end-cap for such purposes still leaves a hundred-meter-wide park, now with only 12 acres of usable space, 100 meters wide by 470 meters around. The lowest level of the end caps is a perfect place for shops and restaurants.
The above ramble describes the capacity of a 100-meter radius cylinder, spinning at 3 rpm to provide Earth-normal gravity. This spin rate is often considered the maximum for a rotating space habitat, as most people (but not all) can adjust to it. More people can adjust to 2 rpm, and essentially everyone has no problem with 1 rpm. So how much room do we get with these and larger structures? Can they be built?
This table shows the size, possible population, and mass (in kilotons or kT) of the external steel shell, the internal steel infrastructure, and the shield (total mass of steel shell plus rock). Note that once the steel shell reaches a mass of 10 tons per square meter, additional shielding is not needed. For a reference point, the total mass of steel in a modern aircraft carrier is about 60,000 tons, about 20% less than the smallest habitat. The dimensions given are of the habitable volume; the outer walls are assumed to be an extra 5 meters in thickness to provide the volume needed to contain the shield mass (but that extra external area raises the maximum population as well). The thickness of the outer steel shell is also given, in meters, and it ranges from 3cm (1.2 inches) in the 100 meter cylinder to 1.31 meters (4 feet) in the largest. The table also shows the percentage of the asteroid Apophis needed to build this structure, or alternatively the minimum size of a rocky asteroid large enough to build it. *Note that the largest structure would require a nickel-iron asteroid, as there is no rocky shield mass needed.
|Steel Shell (kT)||38||105||385||2,092||23,258||129,560||3,154,722|
|Steel Structure (kT)||36||71||168||519||2,584||8,117||68,166|
|Total Mass (kT)||1,653||3,273||7,769||24,018||119,664||376,078||3,222,888|
|% Apophis (27 mT)||6.12%||12.12%||28.78%||88.95%||443.20%||1392.88%||11936.62%|
It is clear that Apophis contains enough raw materials to build habitats supporting 125,000 colonists in up to 16 structures. It is interesting that a 1-kilometer nickel-iron asteroid (of which there are approximately 50,000 in the main belt) provides enough iron that (adding the resources of a small carbonaceous chondrite for carbon, oxygen, and water) a 9x6 kilometer cylinder could be built, supporting over 15 million people. Still larger structures may be constructed; steel has adequate tensile strength for structures large enough to support a billion people, but they become wildly inefficient, requiring nearly 10 times the steel per person.
I plan additional posts providing details on farming in space, on solar power satellites, and on the economics of life in space. It is clear that space habitats are feasible, and that commerce based upon tourism and the construction and maintenance of solar power satellites can pay for it. The obstacles are the difficulty of the bootstrap process:
- capturing an asteroid such as Apophis into Earth orbit
- Launching the tools to mine the riches of the asteroid, the tools to smelt its ores into steel and other valuable materials, the tools to shape that steel into the plates, beams, and girders needed to build things
- Launching the people to make it possible with enough consumables to get past the bootstrap.
- Designing and implementing closed-system recycling facilities capable of efficiently converting human wastes (and crop residues) into food, oxygen, and water.
Once enough infrastructure is in place, the colony should not need the addition of oxygen, water, food, or structural materials. High tech tools will be needed, including whatever is needed to construct solar cells, but the raw materials would already be in place. The Earth will export technology, tools, vitamins, pharmaceuticals, and people. In exchange, the Earth will receive bountiful energy from the Sun, with zero carbon footprint.
But that, too, will take time, energy, and especially people. In the long run, the demand for people in orbit is likely to exceed our capabilities of putting them there. And that, too, is the subject of a future post. | <urn:uuid:6a270838-120e-4dc2-bbe9-cf890b8f9054> | 3.375 | 2,625 | Personal Blog | Science & Tech. | 55.352559 | 1,935 |
Layzej writes "Two new papers indicate that we are likely already seeing some of the predicted impacts of global warming. The first used Monte Carlo simulations to analyze how many new record events you expect to see in a time series with a trend. They applied the technique to the unprecedented Russian heat wave of July 2010, which killed 700 people and contributed to soaring wheat prices. According to the analysis, there's an 80 percent chance that climate change was responsible. The authors have described their methods and how they improved on previous studies. The second group studied wintertime droughts in the Mediterranean region. They found that 'the magnitude and frequency of the drying that has occurred is too great to be explained by natural variability alone. This is not encouraging news for a region that already experiences water stress, because it implies natural variability alone is unlikely to return the region's climate to normal.'" | <urn:uuid:346d42c8-2bb5-4cf2-a2d3-bddeacb77888> | 2.9375 | 175 | Comment Section | Science & Tech. | 36.036644 | 1,936 |
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The famous Cambrian Explosion- a rapid diversification of animal groups about 550 million years ago- assumes a rather diminished significance when mapped to the full Tree of Life.
update: yes, I made the diagram myself, by modifying this.
That’s a very nice illustration to put it in perspective. Thanks!
I have briefly seen videos on youtube about the subject of the cambrian explosion, And I had a question burning in my head. Why was the cambrian explosion a threat to the darwinian theory?
Maybe, the cambrian explosion is just a metaphor for the evolution and advancement of new forms with complex body parts that simply are modified ontogenetically through natural selection and mutation.
The reason why the Cambrian event may be problematic for Darwinian Evolution is that within canonical Darwinian theory is the assumption that phylotypic change occurs gradually, and is selected at each change. For the changes that occurred around the Cambrian Event, hundreds of millions of years would be required if later evolutionary changes scale linearly in time. Niles Eldridge et al proposed punctuated evolution which allows for rapid phylotypic change spaced with phylotypic stasis, one of the causes is hyppothesized to be geographical isolation which is often associated with an extinction event.
The systematics plot above is a bit misleading in that the large blue branch is all bacteria. I don’t think that it would come as a shock to anyone that there are many more species of bacteria than metazoa. The Cambrian event affected the multi-cell body plans, and in a very significant way. Its effect on bacteria is not preserved in the fossil record. Therefore, to indicate that the Cambrain even affected only the branch indicated is not positively supported in the fossil record.
After some consideration, I have decided to move Myrmecos back to its original location:
I apologize for…
I’ve posted all I’m going to say about Pepsigeddon here.
And while you’re doing that, I have answered the Monday Mystery back at my tried and…
Eristalis, the drone fly
Easily mistaken for a bee, Eristalis is in fact a clever mimic…
I would like to point out that when an Australian says “pot plant“, they mean house… | <urn:uuid:b490f88d-790e-4574-91e6-277481c04872> | 3.25 | 502 | Comment Section | Science & Tech. | 36.910476 | 1,937 |
SLOSH (Sea, Lake and Overland Surges from Hurricanes) is a computerized model run by the National Hurricane Center (NHC) to estimate storm surge heights and winds resulting from historical, hypothetical, or predicted hurricanes by taking into account pressure, size, forward speed, track and winds.
Graphical output (124kb or 348kb) from the model displays color coded storm surge heights for a particular area in feet above the model's reference level, the National Geodetic Vertical Datum (NGVD), which is the elevation reference for most maps.
The calculations are applied to a specific locale's shoreline, incorporating the unique bay and river configurations, water depths, bridges, roads and other physical features. If the model is being used to estimate storm surge from a predicted hurricane (as opposed to a hypothetical one), forecast data must be put in the model every 6 hours over a 72-hour period and updated as new forecasts become available.
The SLOSH model is generally accurate within plus or minus 20 percent. For example, if the model calculates a peak 10 foot storm surge for the event, you can expect the observed peak to range from 8 to 12 feet. The model accounts for astronomical tides (which can add significantly to the water height) by specifying an initial tide level, but does not include rainfall amounts, riverflow, or wind-driven waves. However, this information is combined with the model results in the final analysis of at-risk-areas.
The point of a hurricane's landfall is crucial to determining which areas will be inundated by the storm surge. Where the hurricane forecast track is inaccurate, SLOSH model results will be inaccurate. The SLOSH model, therefore, is best used for defining the potential maximum surge for a location.
For more information, visit NOAA Online.
St. Charles Parish SLOSH Models
(Click on each thumbnail to open a larger image in a new window. Please keep in mind the storm surge estimates do not take into account the elevation of particular areas. Storm surge predictions are made by taking this information into account.)
For more information, contact St. Charles Parish Public Information Officer Renee Allemand Simpson at (985) 783-5000 or firstname.lastname@example.org. | <urn:uuid:5e904fc9-0c1a-484f-87b9-b790d6416511> | 3.234375 | 462 | Knowledge Article | Science & Tech. | 35.896066 | 1,938 |
Sci. STKE, 12 September 2006
PLANT BIOLOGY Touché! Plants and Bacteria Battle at Leaf Pores
Plants have special openings on the surface of the leaf known as stomata, which allow gas exchange essential for respiration and osmotic balance. However, the stomata also provide a route by which infectious bacteria can gain access to internal tissues. The stomata are opened and closed in response to changes in exposure to light, humidity, and other stimuli, but new evidence shows that they can also be closed as part of the plants' immune defense against bacterial infection. Melotto et al. showed that Arabidopsis plants closed their stomata within 2 hours of exposure to the pathogenic bacterium P. syringae but then reopened them within a couple more hours. Microscopic observation of the bacteria showed that they were able to detect and migrate toward open stomata, perhaps sensing nutrients or other molecules released from the plant interior. The authors showed that flg22, a peptide derived from the bacterial flagellin protein, or lipopolysaccharide, a component of the bacterial outer cell wall, could also trigger stomatal closure. Plants are known to have immune receptors that recognize these molecules. The reopening of the stomata observed when leaves were exposed to whole bacteria led the authors to test whether the strain of P. syringae that they used produced a virulence factor to override the host plant's protective mechanism. Indeed, they found that the bacterially produced polyketide toxin coronatine was required to allow reopening of the stomata. The work reveals that plants have developed an innate immune mechanism to protect themselves from bacterial invasion and that, in response, some bacteria have developed a virulence factor that forces the pores open again to allow further infection.
M. Melotto, W. Underwood, J. Koczan, K. Nomura, S. Y. He, Plant stomata function in innate immunity against bacterial invasion. Cell 126, 969-980 (2006). [Online Journal]
Citation: Touché! Plants and Bacteria Battle at Leaf Pores. Sci. STKE 2006, tw315 (2006).
Science Signaling. ISSN 1937-9145 (online), 1945-0877 (print). Pre-2008: Science's STKE. ISSN 1525-8882 | <urn:uuid:5f6a3fc9-0fad-4906-89a7-fe02130381e2> | 3.515625 | 493 | Academic Writing | Science & Tech. | 43.048826 | 1,939 |
This, from the free daily UK paper called the Metro:
- "If you felt a bit soggy while walking through the snow this week, it's because your relatives were sponges. Well, your ancestors who lived 635 million years ago were.
Mankind is thought to have evolved from primitive sea sponges, according to a study of fossils found in rocks in Oman.
They are thought to date to the last ice age, according to the US research in Nature journal."
- Meet the ancestors: Earliest evidence of life suggests humans descended from sponges 635 million years ago
- "Now scientists say they have discovered the missing link in the chain of evolution. They have found evidence of the oldest animal life yet discovered on Earth – ancient sponges that lived 635 million years ago".
Anyone reading this on the 8.20 tube from Cockfosters would understand that the research is about discovering ancestors (i.e., missing links, a poriferan Adam & Eve). I had to see what Brocks & Butterfield (2009) wrote about 'ancestors':
- "So, what exactly were the organisms that produced these biomarkers? The most obvious answer, and the one that the authors plump for, is that demosponges had evolved and become ecologically prominent by at least the late Cryogenian. But this conclusion overlooks the evolutionary nature of biological taxa and the incremental assembly of defining characteristics along (now-extinct) 'stem lineages'. It is only with a full complement of such characteristics — in the last common ancestor of the extant 'crown group' — that modern taxonomic boundaries apply (...) Combined with new biomarker data and molecular phylo genomics, the identification of such signals promises to pinpoint the first appearance of our earliest animal ancestors." (Brocks and Butterfield, 2009: 673).
The Daily Mail Online however, do go on to publish a Reuters report by Michael Kahn that best summaries the research: "Chemical traces left in 635 million-year-old rocks in Oman provide the earliest evidence so far of animal life, researchers said Wednesday". Why the Mail didn't go with Reuter's original title Scientists find earliest evidence of animal life has more to do with sensationalism than with science journalism.
Jochen J. Brocks, Nicholas J. Butterfield (2009). Biogeochemistry: Early animals out in the cold Nature, 457 (7230), 672-673 DOI: 10.1038/457672a | <urn:uuid:6e02f333-c3d3-43c0-a9cc-020297cd2558> | 3.125 | 523 | Comment Section | Science & Tech. | 47.497408 | 1,940 |
WordCount Example in Python
The program reads text files and counts how often words occur. The input is text files and the output is text files, each line of which contains a word and the count of how often it occured, separated by a tab. To create some input, take your a directory of text files and put it into DFS.
bin/hadoop dfs -put my-dir in-dir
Each mapper takes a line as input and breaks it into words. It then emits a key/value pair of the word and 1. Each reducer sums the counts for each word and emits a single key/value with the word and sum.
As an optimization, the reducer is also used as a combiner on the map outputs. This reduces the amount of data sent across the network by combining each word into a single record.
To compile the example, build the Hadoop code and the python word count example:
ant cd src/examples/python ./compile cd ../../..
Note that you need to have jythonc and javac on your path for the compilation to work.
To run the example, the command syntax is:
bin/hadoop jar src/examples/python/wc.jar in-dir out-dir
The results of the word count will be in out-dir/part-*. | <urn:uuid:84d7d53e-7a88-4b17-817f-c836c9ec7b43> | 3.546875 | 288 | Documentation | Software Dev. | 76.271389 | 1,941 |
Bacteria's gold-making trick revealed
Eureka! Scientists say they have discovered how a bacteria turns water-soluble gold into microscopic nuggets of solid gold.
The bacteria Delftia acidovorans is frequently found on the surface of tiny gold nuggets.
Its presence led scientists to speculate it may be creating the particles from soluble gold - ions of gold that are dissolved in water.
But the puzzle was how D. acidovorans did this trick, as soluble gold is toxic.
The answer, suggests researchers from Canada, lies in a molecule excreted by the microbe that both shields the organism and transforms the poisonous ions into particles.
"This finding is the first demonstration that a secreted metabolite can protect against toxic gold and cause gold biomineralisation," the process by which living organisms produce minerals, they write in the journal Nature Chemical Biology.
The molecule, delftibactin A, is capable of achieving this feat within seconds in pH-neutral conditions at room temperature.
Study co-author Nathan Magarvey of Ontario's McMaster University says the study was not designed to show whether it would be viable to use the microbes to grow gold from water in the lab.
But such processes seem "distinctly possible," he says.
Previous research had shown that another bacteria found on gold, Ischiadicus metallidurans, deals with toxicity by storing the ions inside its cells.
Bacteria need some metals, such as iron, to grow, whereas others, like silver, will kill them.
Soluble gold, invisible in a glass of water, is found in the ocean, groundwater and other natural water sources.
Solid gold is mainly formed through geological processes in large veins underground.
Magarvey says the study may implicate D. acidovorans in secondary deposits such as nuggets found in rivers.
The bacteria, he adds, is not found only on gold but also in the soil and in water. Still unclear, though, is what the organism feeds on. | <urn:uuid:0ccb8fa3-3414-4eda-98ee-4883a37ef481> | 3.765625 | 422 | News Article | Science & Tech. | 41.996639 | 1,942 |
Fluid Thread Patterns
Thin threads of fluids show how conveyor belt speeds control fluid pattern behavior in both experiments and models. A thin thread of viscous fluid (translucent threads at left) is poured onto a moving belt, creating a dazzling array of intricate patterns. Simulations (gold threads at right) reproduce this rich and complex behavior, confirming the accuracy of a theoretical model developed to describe the phenomenon.
Reporters and Editors
Reporters may freely use this image. Credit format: Image courtesy of Columbia University (2011). | <urn:uuid:a6b79502-7ba7-46fb-a1c2-3dd995d5c3ea> | 3.421875 | 109 | Truncated | Science & Tech. | 34.683 | 1,943 |
Methane in the Earth's atmosphere is an important greenhouse gas, so far accounting for about 20 percent of the global warming caused by human activity — more than any other gas except CO2. It has a global warming potential of 25 over a 100-year period, meaning that a methane emission will have 25 times the impact on temperature of a CO2 emission of the same mass over the next 100 years. Methane has a big impact over a brief period — a lifetime of about 12 years in the atmosphere — whereas CO2 has a smaller impact for a far longer period of more than 100 years. An estimated 60 percent of the Earth’s methane emissions are attributable to human activity, with landfills, livestock husbandry, fossil fuel development, and rice agriculture as major causes.
Methane is also naturally released by the decay of organic matter in wetlands. Less significant natural sources include termites, oceans, and release from methane deposits buried deep within the Earth. Currently, the amount of methane released by those deposits is slight in comparison to other sources — but shifts in the planet’s stability, of the magnitude expected from continued rapid global warming, could cause massive releases of stored methane. In particular, Arctic methane could prove to be the linchpin for runaway global warming. Thousands of years ago, billions of tons of methane were created by decaying Arctic plants, which now lies frozen in permafrost and trapped in the ocean floor. As the Arctic warms, this methane will likely be freed, greatly accelerating warming.
Analysis of air bubbles trapped in ice sheets shows that methane is more abundant in the Earth’s atmosphere now than at any time during the past 400,000 years. Global average atmospheric concentrations of methane have increased from approximately 700 parts per billion by volume in 1750 — at the time of the Industrial Revolution — to roughly 1,800 parts per billion in 1998. Levels of the gas in the atmosphere had held steady since 1998, then suddenly spiked in 2007, when National Oceanic and Atmospheric Administration studies show they increased by 27 million tons. Researchers confirmed this finding in October 2008; they believe that unusually warm conditions over Siberia affected methane levels in the Northern Hemisphere by increasing the amount of methane produced by bacteria in Siberian wetlands.
Scientists are not sure whether the methane spike signals the beginning of a long-term, massive release or is a one-time blip, but say that given methane’s power to warm the climate, even a small increase is cause for concern.
Unleashing the methane reservoir could potentially warm the Earth tens of degrees; a violent opening of this “methane ice” (also known as clathrates), according to some scientists, may have triggered a catastrophic climate change and reorganization of the ocean and atmosphere around 635 million years ago.
The U.S. Environmental Protection Agency estimates that methane volumes equivalent to taking 90 million cars and light trucks off the road could be achieved globally by 2020 at a cost benefit or at no cost. In the United States alone, that would be the equivalent of taking more than 12 million cars and light trucks off the road. And the EPA analysis doesn’t even include the value of significant air-quality and health benefits that would accompany methane reductions: Studies have found that reducing global methane emissions by 20 percent would save 370,000 lives between 2010 and 2030, due to the decrease in ozone-related cardiovascular, respiratory, and other health impacts.
EPA may be underestimating available no-cost and low-cost methane mitigation options, but even its conservative analysis clearly demonstrates the opportunities available in methane control. Enormous reductions can be achieved with currently available technology, while mandatory greenhouse gas regulation would speed the development and deployment of new technology and mitigation options, making much deeper reductions feasible in the near future.
But the key is rapid action: Methane needs to be dealt with immediately through strong regulation to sharply restrict emissions. Because of the urgency of the problem, and the need to address methane now, longer-term attempts to address the crisis will not be sufficient.
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In this blog i have explained OOPS Features of C# in brief to help new comer's to crack an interview,i have explained these feature in brief because of focsing on new comer's to give them a idea how to answer thes questions which are often asked in an interview .
programming in which data is logically represented in the form of a class and
physically represented in the form an object is called as object oriented
programming (OOP). OOP has the following important features.
In OOP languages it is must
to create a class for representing data. Class contains variables for storing data
and functions to specify various operations that can be performed on data. Class
will not occupy any memory space and hence it is only logical representation of
Within a class variables are
used for storing data and functions to specify various operations
that can be performed on data. This process of wrapping up of data and functions
that operate on data as a single unit is called as data
encapsulation. Within a class if a member is
that member can
not be accessed from out side the class. I.e. that member is
hidden from rest of the program. This process of hiding the details of a class
from rest of the program is called as data abstraction. Advantage of data
abstraction is security.
Class will not occupy any
memory space. Hence to work with the data represented by the
class you must create a variable for the class, which is called as an object.
When an object is created by using the keyword new, then memory
will be allocated for the class in heap memory area, which is called as an
instance and its starting address will be stored in the object in stack memory
When an object is created without
the keyword new, then memory will not be allocated in heap I.e. instance will
not be created and object in the stack contains the value null.
When an object contains null, then it is not possible to access the members of
the class using that object.
Creating a new class from an
existing class is called as inheritance. When a
new class requires same
members as an existing class, then instead of recreating those members the new
class can be created from existing class, which is called as inheritance.
Advantage of inheritance is reusability of the code. During inheritance, the
class that is inherited is called as base class and the class that does the
inheritance is called as derived class.
Polymorphism means having
more than one form. Polymorphism can be
achieved with the help of
overloading and overriding concepts. Polymorphism is classified into compile
time polymorphism and runtime polymorphism.
I hope this blog is useful for all readers,if you have any suggestion then contact me. | <urn:uuid:886541f2-eb3a-4752-b999-da437f733bce> | 3.359375 | 587 | Personal Blog | Software Dev. | 49.700203 | 1,945 |
- PDF (411 kb)
- Full Text with Thumbnail Figures
- Full Text with Large Figures
- Cited by in Scopus (41)
- Request permission
- Size Selective Recognition of siRNA by an RNA Silencing Suppressor
Cell, Volume 115, Issue 7, 26 December 2003, Pages 799-811
Jeffrey M Vargason, György Szittya, József Burgyán and Traci M.Tanaka Hall
SummaryRNA silencing in plants likely exists as a defense mechanism against molecular parasites such as RNA viruses, retrotransposons, and transgenes. As a result, many plant viruses have adapted mechanisms to evade and suppress gene silencing. Tombusviruses express a 19 kDa protein (p19), which has been shown to suppress RNA silencing in vivo and bind silencing-generated and synthetic small interfering RNAs (siRNAs) in vitro. Here we report the 2.5 Å crystal structure of p19 from the Carnation Italian ringspot virus (CIRV) bound to a 21 nt siRNA and demonstrate in biochemical and in vivo assays that CIRV p19 protein acts as a molecular caliper to specifically select siRNAs based on the length of the duplex region of the RNA.
Summary | Full Text | PDF (677 kb)
- Effects and side-effects of viral RNA silencing suppressors on short RNAs
Trends in Plant Science, Volume 9, Issue 2, 1 February 2004, Pages 76-83
Dániel Silhavy and József Burgyán
AbstractIn eukaryotes, short RNAs play a crucial regulatory role in many processes including development, maintenance of genome stability and antiviral responses. These different but overlapping RNA-guided pathways are collectively termed ‘RNA silencing’. To counteract an antiviral RNA silencing response, plant viruses express silencing suppressor proteins. Recent results have shown that silencing suppressors operate by modifying the accumulation and/or activity of short RNAs involved in the antiviral response. Because RNA silencing pathways intersect, silencing suppressors can also inhibit other short-RNA-regulated pathways. Thus, suppressors contribute to viral symptoms. These findings fuel further research to test whether certain symptoms caused by animal viruses are also manifestations of altered RNA regulatory pathways.
Abstract | Full Text | PDF (249 kb)
- Crystal structure of p19 – a universal suppressor of RNA silencing
Trends in Biochemical Sciences, Volume 29, Issue 6, 1 June 2004, Pages 279-281
David C Baulcombe and Attila Molnár
AbstractRNA silencing in plants has an antiviral role and, consequently, plant viruses encode counter-defensive suppressor proteins that block this process. The recently reported crystal structure of two Tombusvirus suppressor proteins reveals a novel RNA-binding structure and illustrates precisely how the silencing mechanism is blocked. These suppressor protein structures, combined with molecular analyses of their effects in animal and plant cells, are informative about RNA silencing mechanisms. They also suggest various ways that Tombusvirus suppressors can be used to investigate RNA silencing in plants and animals.
Abstract | Full Text | PDF (211 kb)
Copyright © 2004 Elsevier Science Ltd All rights reserved.
Current Biology, Volume 14, Issue 5, R198-R200, 9 March 2004
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Plant RNAi: How aViral Silencing Suppressor Inactivates siRNA
- The three-dimensional structure of an siRNA bound to the tombusvirus p19 protein – a suppressor of gene silencing – provides a first glimpse into how plant viruses can defeat their host's anti-viral RNAi defenses. | <urn:uuid:524dab5e-865d-461a-a694-96cc87b1fb6d> | 2.609375 | 788 | Content Listing | Science & Tech. | 26.052679 | 1,946 |
Sea level is on the rise, which means my excellent day at the Jersey Shore might not be so much fun a few decades from now
On April 19th, 2012, Climate Central's Ben Strauss testified before the Senate committee on Energy and Natural Resources on the impact of sea level rise.
This NOAA animation shows the locations of each of the 7,793 daytime and 7,493 nighttime records (or tied records) in sequence over the 31 days in March.
Sample coverage of the national report called Surging Seas, which has recalculated the risk of flooding to coastal communities across America.
As the land loses its struggle with the sea, it's time for new tools to learn just how climate change and sea level rise will effect the coastal U.S.
An amazing 26-second video depicting how temperatures around the globe have warmed since 1880.
As Dr. Heidi Cullen reports, the suffocating heat comes on the heels of the government's release of the new climate "normals". Every 10 years, scientists from the National Oceanic and Atmospheric Administration calculate the 30-year averages for temperature and precipitation from thousands of U.S. locations.
National Hurricane Center scientist Jack Beven explains the technology used to forecast and track hurricanes as they happen. | <urn:uuid:0f3940ec-29ad-4d70-8fde-c1161d04beb8> | 3.21875 | 254 | Content Listing | Science & Tech. | 49.974354 | 1,947 |
Following the line of the article posted by A.Riazi, Solving engineering problem using MATLAB C API, I will show in this small example how to use M Functions inside our VC++ 6 project.
The project calculates the convolution of two vectors, and shows the resulting vector in the MsChart control. The function that performs the convolution is written in MatLab and then through the MatLab Add-in converted to C code ready to be used inside our app.
You need Visual Studio 6 and MatLab Release 12 installed with the MatLab C Library and Matlab Compiler.
Installing the MatLab Add-in
The add-in automates the integration of M-files into Visual C++ projects. The add-in for Visual Studio is automatically installed on your system when you run either mbuild -setup or mex -setup and select Microsoft Visual C/C++ version 6. In order to use the add-in you must follow these steps:
- Start MatLab, in the prompt type mbuild -setup
- Follow the menus and choose MS Visual C++6.0.
- Type the following commands in the matlab prompt :
These commands save the MatLab path to a file called mccpath in your user preferences directory (prefdir), ussually inside your documents and settings file. The path is used by the add-in because it runs outside Matlab and there is no other way for it to determine your Matlab path. If you add new directories to your Matlab path you will have to rerun this command if you want the add-in to see them.
- Configure the Matlab Add-in for Visual Studio 6 to work within MSVisual C++.
- Open MSVisualC++.
- Select Tools -> Customize from the MSVC menu.
- Click on the Add-ins and Macro Files tab.
- Check MATLAB for Visual Studio on the Add-ins and Macro Files list and click Close.
The floating MATLAB add-in for Visual Studio toolbar appears. The checkmark directs MSVC to automatically load the add-in when you start MSVC again.
Calculating the convolution in Matlab
We will write a simple function in MatLab that will perform the convolution of two vectors:
In2 and store the result in
We actually can use any matlab built-in function or toolbox function inside our function here we use only the function conv for simplicity.
%Returns the convolution of vector IN1 and IN2
Save the function with the name MyFunc.m
Writing the Application
Use the MFC AppWizard (exe) option to generate a Dialog Based Application and call it conv. Create a Button which will calculate the convolution of two given vectors.
Add the code below to the button's Message Handler.
Copy MyFunc.m into your VC++ project directory. Now go to the MatLab Add-in and click the .m++ (Add m-files to current project) button:
Select Windows Console Exe from the Combo Box and check Generate main file and debug mode. Press OK.
Then select the MyFunc.m file and click Open. After a while you will see new files added to your project.
Under MATLAB M-files you will see our MyFunc.m, you can even edit it from inside Visual C++. Under MATLAB C/C++ are MyFunc.c and MyFunc_main.c, generated by the MatLab Compiler. And all the headers needed by the compiler.
We can't build the app yet, we must add the following lines to convDlg.cpp:
Now the project should be built without any problem.
Points of Interest
The steps described here don't include the MSChart part, you can see it from the source code, but you can see that the calculation is done by placing a breakpoint inside the button message handler and checking the value of the
res vector after the line:
Well I hope this simple article be interesting for MatLab lovers, this is the first article I wrote, so I apologize if it is not clear enough. I will be glad to explain anything if you ask me. Greetings.
Daniel Cespedes is now working on his final project to get the Electrical Engineering degree at the National University of Technology in Cordoba Argentina. He is developing a Computerized system for the study of Human Echolocation, the ability to detect obstacles with the echoes of self generated sounds.(yes like bats!!) at the CINTRA (Centro de Investigación y Transferencia Acústica).He uses MsVisual C++ 6 as a developing tool. He also work at the Software Research Lab at the University.
He comes from Sta.Cruz de la Sierra-Bolivia a paradise in SouthAmerica´s heart, where you can find pure air, nature contact, happy people, beautiful women etc. | <urn:uuid:617eaeb4-cee8-4db0-8024-0a783be0d3f3> | 2.546875 | 1,040 | Documentation | Software Dev. | 59.724506 | 1,948 |
Tag Archives: About Energy
What is the largest source of renewable energy in the United States? Hydropower accounted for 63% of the electricity generated from renewable sources and 6% of total U.S. electricity in 2001. Learn more about the largest, and one of the oldest, sources of renewable energy with information and resources from Conservation Conversations.
It’s hard to ignore the power of the sun, especially as the seasons change from winter to spring and spring into summer. Many of us appreciate the warmer temperatures and additional hours of sunlight during spring and summer months, but households, businesses and buildings with solar panels have even more to be thankful for. Learn more about the benefits of solar power, the ways solar power is converted into electricity and the impacts of solar energy with information and resources from Conservation Conversations.
As schools, neighborhoods and communities prepare to celebrate Earth Day and take action to reduce their environmental impact Conservation Conversations will explore the connection between natural resources and energy production. American used renewable energy sources to meet about 8% of our total energy needs in 2009. Learn more about the use of natural resources and renewable energy with Conservation Conversations! | <urn:uuid:760221e9-1874-4ca1-b68a-a850b83c63b3> | 2.5625 | 234 | Content Listing | Science & Tech. | 24.138928 | 1,949 |
Boreal Tree Growth Slows as Climate Warms
It appears that climatic warming in boreal forests has pushed many trees beyond the limits of their optimal growing conditions. In recent decades, the growth rates of northern conifers often slowed down when temperatures got abnormally high.
American scientists examined widths of tree growth rings laid down between 1902 and 2002 at 269 northern sites distributed across North America and Eurasia. They then matched the tree growth data with local historical temperatures and precipitation.
The ten major species of boreal conifers analyzed all showed instances during the 20th century of slower tree growth under higher temperatures. This phenomenon, which the study's authors term "browning", appeared in nearly all areas of Canada, Alaska, Europe and Asia that they sampled.
Notably, browning occurred much more frequently after 1942. Browning has been particularly prevalent in jack pine and four species of spruce: Norway, Siberian, black and white spruces.
Scots pine and Siberian spruce had stalled growth during hot years more frequently on some drier sites with relatively low precipitation compared with moister locations. They, along with white spruce and Siberian larch also experienced browning most often in the warmer portions of their range. For instance, sites where growth rates slowed in Siberian larch were on average 2 °C warmer in summer than sites that never exhibited browning.
One other factor showed up in the intercontinental tree-ring analysis, that of pollution. Tree browning occurred more frequently in eastern Europe and northwestern Russia, regions prone to heavy air pollution, than in undeveloped areas.
The effect of temperature was widespread, though, as even unpolluted forests showed browning. The study's authors conclude that warmer temperatures have dampened tree growth in two ways. Both the direct effect of rising growing-season temperatures and the indirect effect of water stress induced by greater evapotranspiration under warm conditions have hindered boreal tree growth.
Andrea H. Lloyd and Andrew G. Bunn. 2007. Responses of the circumpolar boreal forest to 20th century climate variability. Environmental Research Letters. 2: 045013. | <urn:uuid:ae1beab5-445d-450f-ae96-39d5ad2ada81> | 3.84375 | 441 | Academic Writing | Science & Tech. | 35.566011 | 1,950 |
Indications of volcanic activity on Venus
8 April 2010
DLR scientists evaluate data from the VIRTIS infrared spectrometer
3-D radar image of the Maat Mons volcano on Venus
Although some uncertainty remains, the most recent infrared data from VIRTIS (Visible and Infrared Thermal Imaging Spectrometer) seem to confirm it. "We are pretty sure that Venus still has volcanic activity," say Jörn Helbert and Nils Müller from the DLR Institute of Planetary Research (Institut für Planetenforschung) – members of the VIRTIS team.
The European Space Agency's (ESA) Venus Express orbiter has been circling the planet, which is constantly obscured by thick cloud cover, since 11 April 2006. The spacecraft travels around the planet in an elliptical orbit at an altitude that varies from 300 to 66 000 kilometres. It carries VIRTIS, the only instrument that can look through the atmospheric windows onto the surface of Venus and record its infrared radiation patterns at a variety of heights. "At certain infrared ranges we can clearly see that the surface is glowing," says planetary physicist Helbert.
Solidified lava flows radiate heat
According to the VIRTIS data, there are nine hotspots, areas over underground magma chambers, which are very likely volcanically active. "The solidified lava flows, which radiate heat from the surface, seem hardly weathered. So we can conclude that they are younger than 2.5 million years old – and the majority are probably younger than 250,000 years," added Helbert. "In geological terms, this means that they are practically from the present day." It is also possible that there are smaller volcanic vents and lava flows that cover very restricted areas. Nils Müller and Jörn Helbert are co-authors of a paper on volcanic hotspots that appears in the latest edition of Science.
Volcanic peak Idunn Mons
Like on Earth, Venus's valleys are warmer than its mountains. But the venusian atmosphere is so dense that it completely determines the temperature of the planet's surface. This enabled the scientists to predict surface temperatures with computer models. Data obtained from VIRTIS last year shows that certain areas deviate from the predictions by as much as two or three degrees. "This may because there are different types of rock, which have different thermal properties." VIRTIS has shown that the Imdr, Themis and Dione region are hotspots, which rise 0.5 to 2.5 kilometres above the plain and are the most likely candidates for the presence of active volcanism. But it is not easy to evaluate the data: "the cloud coverage obstructs the view of the surface, and we have to include its effect in our calculations. Even then, it’s like looking through frosted glass."
Research in the Planetary Emissivity Laboratory
The DLR planetary emissivity laboratory: Measurements at 500° Celsius
The researchers are still unable to say which materials are responsible for the radiation emitted from Venus's surface. The next step will be for Jörn Helbert to build a special laboratory – the Planetary Emissivity Laboratory – at the DLR Institute of Planetary Research, in which a variety of rocks will be heated to venusian temperatures of 500 to 600 degrees Celsius. He will then measure their emissions at a range of wavelengths, just as VIRTIS does from space. By comparing the results with the VIRTIS data, the researchers will be able to answer the open question about the composition of the planet's surface.
About 25 missions have surveyed Venus before Venus Express, so researchers have been able to rely in part on tried-and-tested systems. For instance, they incorporated technologies from ESA's Mars Express spacecraft. VIRTIS itself was originally constructed at DLR Berlin for ESA's Rosetta comet chaser. One important predecessor mission was NASA's Magellan probe, which mapped Venus with its radar, indicating the presence of hundreds of volcanoes. But it was thought that they were all extinct. Along with VIRTIS, another six instruments on Venus Express are studying the planet to determine the composition of its atmosphere and its temperature, among other things.
Learning from Venus
If further analysis confirms that Venus is volcanically active, making it the first geologically active planet after Earth itself, it would certainly affect our understanding of our own planet. While Earth and Venus are very similar in size and structure, they have had very different histories. So when and why did their development take such distinct paths, such that waterless Venus, at 500 degrees Celsius, is completely hostile to life, and Earth is so suited to it? "Perhaps Venus can tell us why Earth is so special," added Jörn Helbert. | <urn:uuid:88586543-1d41-4451-ad77-dfe6569a192d> | 3.234375 | 975 | Knowledge Article | Science & Tech. | 37.825036 | 1,951 |
In a recent breakthrough, researchers at the Massachusetts Institute of Technology (MIT) have made great strides into what could be the future of solar power.
Their methods have replicated a process from the natural world that is so basic and universal as to almost beg the question why someone didn’t come up with it before. That process is photosynthesis. It is how all plants derive energy from sunlight. The scientists captured an essential element of the photosynthesis process, simply called PS-I, and combined it with other “designer” chemicals to construct a solar cell.
However, it was not a “simple” matter of harnessing photosynthesis. The scientists also used sophisticated nanotechnology to improve the performance of their cells. By mounting the cells on an array of nanocrystals and nanowires, they increased the surface area and exposure of their cells to sunlight.
To be fair, this is not the first attempt at so-called biophotovoltaics. However, with their innovative materials, geometry and design, the scientists claim to have solved problems with previous experiments that made them cumbersome and expensive. They assert their methods led to a simple device of “unprecedented performance.” More specifically, they calculate the output of their cells to be more than 10,000 times greater than that of any other plant-based cell previously constructed.
Like most scientific breakthroughs, the promise of its usefulness far exceeds any practical use at this stage. In other words, it will be years before plant-based cells start popping up, or growing for that matter, on rooftops across American suburbia.
But one of the great things about renewable power and science in general is to constantly challenge accepted notions of what and how things can be done. The scientists note that PS-I, which is the “central molecule” in photosynthesis, is an abundant raw material that promises “ultra-low-cost” solar cells. It could be a boon for the solar industry, which has always been challenged by its high upfront costs. The scientists noted that these cells could be constructed from abundant sources, such as discarded clippings from agriculture and timber operations.
The results of this experiment were included in the February 2012 issue of Scientific Reports. | <urn:uuid:56ac33c4-65e9-4086-9457-3004c8aa6d26> | 4.09375 | 465 | News Article | Science & Tech. | 38.533028 | 1,952 |
Nematodes are nonsegmented roundworms that are abundant in freshwater lakes. Nematodes often comprise 15% of the total biomass on lake bottoms. This reflects the incredible abundance of these organisms, since most only grow to a maximum length of a centimeter.
Life stages of these species are often as complex as they are abundant. Some are free living their entire lives while others are only free living as adults or juveniles. At other stages some are parasitic on invertebrates, vertebrates, or even plants.
Most freshwater free-living nematodes are about 1 mm in length though parasitic forms are often even smaller. Their body wall is covered by a cuticle that is four layers thick. As the worm grows it moults, sloughing off the outer layer. At the same time another layer is created on the inside. The pseudocoel is small in the free-living forms but tends to be much larger in the parasitic forms. All freshwater nematodes bear a spinneret at the tip of their hind end that secretes a sticky mucous which anchors the worm in place whether it be a on rock or inside an intestine.
Non-parasitic roundworms are adapted to swimming along lake and stream bottoms. In fact "swimming" may not be an accurate word to describe their motion. Nematodes have only longitudinal muscles for movement, unlike segmented worms (like earthworms) that also have circular muscles to help with locomotion. Movement is therefore limited to a side-to-side flailing that pushes them forward.
Nematodes have a pair of amphids (one on each side of the body) which are structures at the anterior end of the worm that were once considered to aid in equilibrium. Now, they are seen as chemosensory structures, perhaps for the purpose of detecting food. Due to the wide variation their structure, amphids are also used to classify horsehair worms taxonomically. Some freshwater species have separate light sensors referred to as ocelli or pseudocelli. They are seen as pigmented spots also situated at the anterior end.
Most nematode species are aerobic, meaning that they need oxygen to survive. However, some species can survive short periods of anoxia, and a few can live without oxygen indefinitely. There are not any specialized systems for acquiring oxygen for any member of this phylum. Because they are small animals with a large surface area, they can exchange gases through the skin surface with enough efficiency to survive.
Nitrogenous waste is eliminated though the body wall in the form of ammonium ions. Osmoregulation, and excretion of other metabolites is controlled either by excretory gland cells, an excretory canal system, or a combination of both. These structures are unique to the nematodes.
Nematodes usually possess separate sexes and all fertilization is internal. In most freshwater species the males have spicules that enter the female's vagina where the sperm is released Other species specialize in "traumatic fertilization" in which the male simply punctures the cuticle of the female with his spicules and releases the sperm directly into her body cavity.
Feeding structures and strategies are determined by the lifestyle of the nematode. Species parasitic on plants have stylets within the stoma (mouth) that can be extended outward and into the plant tissues. These stylets are used like straws to suck out nutritious plant juices. Species parasitic on invertebrates have a slightly modified stylet of the same nature to pierce the cuticle of their prey, for the purpose of feeding on haemolymph. Nematodes that feed on microorganisms need only a small tubular stoma to engulf their prey. Finally, the predators have an enlarged stoma with either a spear-like structure or rows of pointed teeth.
Predaceous nematodes are often the worst enemies of other nematodes. This is understandable since both have roughly the same oxygen and pH requirements, so they therefore live in the same places on the lake bottom. Other predators include crayfish, turbellarians, and nemertean worms. Freshwater nematodes are often infected with protozoan diseases and microsporidia.
Freshwater nematodes survive in very diverse environments. Many species that exist in Canada are apparently found all over the world. Some species can survive in snow pools while others occur in hot springs. Aphelenchoides sp. can survive in a temperature of 61.3°C, the highest temperature tolerance by any multi-celled animal on the planet. Most nematodes have drought-resistant stages in which the roundworm becomes inactive. This attribute is most common in the juvenile stages as this is the most sensitive period for many freshwater species. A steady supply of food and oxygen are necessities for health and growth and when these become unavailable the quickest defense is to dry down until conditions improve. Some species have been known to survive in a dried state for up to 25 years before being reanimated in water. These dessication-resistant stages are the primarily means of dispersal. Flash floods or high winds can carry these nematodes to different areas. There is even the possibility of transport in mud that is attached to animals that frequent different water bodies for drinking or bathing.
Eutely is a phenomenon found in a few organisms, including nematodes, wherein each member of a species has exactly the same number of cells. For example, males of the species Caeonorhabditis elegans have exactly 1031 cells, while females have 959 cells, almost half of which are designated to the nervous system. | <urn:uuid:692fb250-5513-48d8-9012-6601c442388e> | 4.21875 | 1,162 | Knowledge Article | Science & Tech. | 32.649554 | 1,953 |
Predation Did Not Come from Evolution
by Daniel Criswell, Ph.D. *
Although the origin of predation is poorly understood, it is incorrect to attribute to young-earth creation the assertion that predatory animals quickly and recently evolved the physical features necessary for predation. It is a common fallacy that carnivores evolved from a change in form and function. No physical evolution was required to change herbivores to predators--it was merely a change in behavior.
The view that an alteration of genomes and phenotypes, such as sharp teeth and claws, would have been required to supply the physical features for predation from herbivorous features common in plant-eating animals is not correct. The shape of the teeth, the ability to run fast for short distances, and all the other physical attributes given to predators can be used for acquiring plant food sources as well. A few examples of mammal diets will verify this quite well.
Large, sharp teeth are not used solely for killing and ripping flesh from other animals. Fruit bats have sharp, pointed teeth, similar to those in cats, designed to quickly tear flesh from fruit. These teeth easily could remove flesh from an animal, but the fruit bat does not use them for this purpose. The same teeth in many kinds of predatory animals used to shred meat can also be used to shred plant material.
Large canine teeth are also used in communication. Many animals--including chimpanzees, dogs (wild and domestic), big cats, and other predators--expose their canines to communicate ownership of mates, animal groups, food resources, and territory. Teeth are vital to the success of animals, both for communication as well as for feeding.
Bears of the American northwest provide the best example in the wild of how behavior determines diet. Grizzly bears and black bears are well-equipped to destroy the life of other animals. But they also use their physical tools to eat fruits and vegetables. As a biologist, I have personally witnessed bears clean apples out of an apple tree, consume large quantities of clover, and strip all the berries from wild raspberry, huckleberry, and choke cherry plants. These activities are also well documented in the scientific literature. Although classified as carnivores, bears are actually opportunistic omnivores and are quite capable of living off a vegetarian diet if the food source is available. Many "meat-eating" animals fall into this category. This "predatory" animal, like others, will eat the most nutritious meals that are the most easily obtainable.
Domesticated animals also provide an excellent example of how the behavior of an animal can be altered to utilize a specific food source. Dogs and cats have the same tooth structure as wild wolves and lions, respectively, yet these animals are able to change their behavior and eat processed food (cereal) made mostly from corn meal, soybean meal, and rice.
The ability and desire to eat prepared cereal or "chow" emphasizes another misconception concerning social predators. Most people are under the impression that these animals are after the same meat that we would use for roasts and steaks. They aren't. The choice portions of a killed herbivore are the internal organs that are rich in vitamins and other nutrients acquired from a vegetarian diet. This is what social predators, like wolves and lions, are after. The lower ranking animals are left with the steaks, roasts, and bones, while the higher ranking animals enjoy the benefits of a more nutritious, "vegetarian" diet found in the gut. The need for predation by these animals clearly results from a change in behavior, not from a change in form and function. It is also interesting to note that, typically, predators have to learn to kill. Social predators are not born with the knowledge of how to hunt and kill. They must learn these skills from the other animals in their group.
A change in form and function implies evolution has occurred through new genetic information, while a change in behavior requires no new genetic information. The latter is what we clearly observe, and it is perfectly consistent with a literal rendering of Genesis 1:30: "And to every beast of the earth, and to every fowl of the air, and to every thing that creepeth upon the earth, wherein there is life, I have given every green herb for meat: and it was so."
* Dr. Daniel Criswell has a Ph.D. in Molecular Biology.
Cite this article: Criswell, D. 2009. Predation Did Not Come from Evolution. Acts & Facts. 38 (3): 9. | <urn:uuid:7c3ae2d6-280f-4242-becc-3823e717b85e> | 3.453125 | 931 | Truncated | Science & Tech. | 43.610463 | 1,954 |
This is part 1 of 2. Part 2 is my Guide to the use of Semantic HTML Elements
I’ve seen a lot of articles discussing the importance of HTML and XHTML semantics. I’ve seen articles describing what it means for a document to be semantic. Most of these articles, however, don’t provide a serious overview of what HTML elements actually may be considered semantic — and what those semantic elements actually mean.
And, even more particularly, why it matters.
Semantics is an erudite area of study. Literally, semantics can be fairly defined as the study of meaning in communication. Communication can readily be extended to cover symbolic notations, representations of language, organization of language, body language and information structures. In developing a web page, we are organizing a means to communicate the content of that page: ideally, we are organizing the page in such a manner that it will be understood regardless of the method by which the page is accessed. It should be equally understandable whether seen, heard, or felt.
The semantics of HTML structure, then, are clearly an important part of web design. Sending mixed signals to the user agent or the user by using a
blockquote purely for it’s native indentation is an abuse of semantics: even the visual impact is dependent on the assumption that user agents will consistently render a
blockquote in an indented manner.
It’s not precisely an issue that you’ve used a semantic element for presentational means, because, in fact, you’ve done more than that: you’ve presented a block of text which is not quoted material as if it were.
Semantic elements of HTML carry meaning regardless of your knowledge of that meaning. The result is that the misuse of an element creates the potential to mislead or confuse an end-user.
The most obvious examples in common use are those which make use of elements with semantic meaning which also offer a browser-contributed default presentation in order to use that presentational style. The
blockquote example above is not uncommon; similarly, the use of empty
p elements to create extra white space or heading elements used as a questionable SEO technique in substitution for normal paragraphs.
Now, you may point to the following paragraph, from the HTML 4.01 specifications, as a response to my opinion:
Authors may also create an A element that specifies no anchors, i.e., that doesn’t specify href, name, or id. Values for these attributes may be set at a later time through scripts.
The fact that it is allowed by the specification does not make it a best practice. With all due respect to the W3C, this should not be permitted. For reference, the HTML 5 specification currently reads:
If the a element has no
hrefattribute, then the element is a placeholder for where a link might otherwise have been placed, if it had been relevant.
In addition, although I won’t quote everything, the specification states that an anchor which does have the
href attribute must specify a URI as the value of that attribute. It appears to essentially state that an anchor element should have no semantic meaning if the
href attribute is not set and valid. But I could be wrong.
The best means to avoid the misuse of elements is to have a clear understanding of when and why a given element should be used in web development. To hopefully expand on your knowledge in that respect, I’m attempting to provide a semantic guide to HTML elements for your reference and rich disagreement.
Be aware, however, that semantics are largely a matter of opinion. It’s not a question of blindly following the guidelines set by a group; it’s a question of interpreting those guidelines to the best of your ability and belief. This guide reflect how I think HTML elements should be used; and I welcome your opinions.
Other HTML Semantics Articles
- Guidelines from WCAG 2.0 on the use of HTML for semantic structure
- Traditional HTML Semantics (Part I of a three-part series on web semantics by John Alsopp)
- HTML: The Foundation of the Web – Niels Matthijs
- Semantic HTML and Search Engine Optimization – From the Opera Developer Community, by Joost de Valk
- Who will read your semantic HTML? – Jesse Skinner
- When semantic markup goes bad – Matthew Paul Thomas
- Semantics – why bother? – Mel Pedley at Accessites
- HTML Semantics from Western Civilization, Pty.
- Graph the Semantic HTML Structure of your Web Page – Joe Dolson | <urn:uuid:3e87c193-01d3-467a-90b8-dfb6ef04243d> | 3.21875 | 950 | Personal Blog | Software Dev. | 42.369613 | 1,955 |
MoEDAL (the Monopole and Exotics Detector At the LHC) is the newest of the experiments that will investigate particle collisions at the Large Hadron Collider. Approved by the CERN Research Board in December 2009, the MoEDAL experiment will search for very specific exotic particles.
The experiment is relatively small, cheap and quick to install but its physics potential is huge. The MoEDAL detector will consist of layers of plastic attached to the walls and ceiling of the cavern that houses the VELO detector of the LHCb experiment. Physicists will look for tell-tale collinear 'etch-pits' created by a stable particle such as a magnetic monopole or a massive stable supersymmetric particle crossing through the plastic.
The international MoEDAL collaboration, made up of physicists from Canada, CERN, the Czech Republic, Germany, Italy, Romania and the US, is preparing to deploy the MoEDAL detector during the next long shutdown of the LHC, which will start late in 2011. The full detector comprises an array of approximately 400 nuclear track detectors (NTDs). Each NTD consists of a 10-layer stack of plastic and altogether they have a total surface area of 250 m2. The detectors are deployed at the intersection region at Point-8 on the LHC ring around the VErtex LOcato (VELO) of the LHCb detector. | <urn:uuid:6ffea5e4-250a-4692-b981-b5819cd5cbb3> | 2.5625 | 290 | Knowledge Article | Science & Tech. | 39.751499 | 1,956 |
NASA appears to have resolved problems with a new urine recycling system on the International Space Station, bolstering hopes it will be able to expand the research outpost's crew next year, officials at the space agency said on Tuesday.
Reusing wastewater is essential for doubling the size of the crew living aboard the station from three members to six, especially since the space shuttles, which produce water as a by-product of their electrical systems, are to be retired in two years.
The device, part of a $250 million new life-support system aboard the station, shut down during three previous attempts to purify urine. NASA wants the visiting shuttle Endeavour crew to bring home processed samples for analysis before declaring the water purification system suitable for use.
Two rounds of modifications to stabilise the device's centrifuge appear to have worked, flight director Brian Smith said on Tuesday. It completed a full five-hour run on Monday and was nearing completion of a second full run early on Tuesday.
Engineers planned to keep the device operating all day in hopes of producing enough processed urine before Endeavour's departure on Friday. The device was ferried into orbit and installed in the station's Destiny laboratory after the shuttle arrived on 16 November.
The shuttle's stay at the station was extended a day to wait for the samples.
"We're going to try to keep it going all day and have the crew just reload the (urine) tank as it gets low," Smith said.
Also Tuesday, NASA tested the station's newly repaired solar wing rotary joint, which was cleaned and restored during four spacewalks by Endeavour astronauts.
The joint had been contaminated by metal filings, prompting NASA to lock it in place to prevent damage. Immobilising the wing, however, prevented panels from tracking the Sun for full power.
While the crews slept, engineers on the ground watched as the joint automatically pivoted to track the Sun for the first time in a year.
"There's months worth of testing left to go before we can really determine what impact all four (spacewalks) had on that joint," Smith said.
Endeavour is due back at the Kennedy Space Center in Florida on Sunday after 16 days in orbit.
NASA plans eight more flights to the station, a $100 billion project of 16 nations, before the shuttles are retired in 2010.
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Have your say
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Only personal subscribers may leave comments on this article
Tue Nov 25 23:37:32 GMT 2008 by Andos
So, the stabilising and vibration dampening rubber stand that the water recycler was originally attached to actually amplified vibrations and made the centrifuge unstable? Damn.
It's good that they got it working. I wonder why the original design worked out so counter-actively? I guess with these things you just have to get them up there and try them out to find out what works best.
Quote Of The Week
Wed Nov 26 02:01:59 GMT 2008 by Dann
ABC News (Australia) covered this story recently. I quote:
"A spokesman said their number one priority was to get a sample of recycled water back to Earth for testing."
'Number one' priority indeed... :-)
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SWADDLED in a cloud of dust and gas, a baby solar system 450 light years away offers one of the best peeks yet at what our sun may have looked like in its infancy. The star is surrounded by enough raw material to build at least seven Jupiter-sized planets.
But it was unclear from previous studies whether the disc of debris swirling around developing star L1527 IRS was moving in the necessary way to spawn planets.
John Tobin of the National Radio Astronomy Observatory in Charlottesville, Virginia, and colleagues found that the disc's motion mirrors the way planets orbit stars, hinting that it has all the right moves for planet formation (Nature, doi.org/jxm).
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Air Pressure and Resistance
Name: Loretta H.
Is there a relationship between air pressure and air
resistance? Recently, I had said that the air resistance acting on a
falling object is actually the air pressure that is acting on the object.
This did not sound right. Air pressure that is acting on an object is I
know a constant value per square area. However, what I was trying to say
was that since air resistance is actually a force that is acting on the
falling object and it is acting on every area of the object, and since we
know that Pressure = Force divided by Area, therefore, air resistance is
somehow related to the pressure of air acting on that object. Please do
enlighten me on this. Thanks.
Air resistance is due to the force exerted on the air by the falling
object to push the air aside to let the object proceed through the
air. By Newton's third law (for every force there is an equal and
opposite reaction) the air pushes on the object with an equal and
opposite force. The air comes together behind the object, of course,
but the resulting pressure there is less that the pressure in front of
the object. The difference in these pressures (times an area, as you
mention) is the cause of the air resistance.
Since, for a stationary object, the air pressure is equal on all sides
of the object, it exerts no net force on the object. If the air
pressure is increased, the net force on a stationary object is still
zero. The net force on a moving object will increase due to the fact
that the air is denser and the object has to push more air aside.
The detailed calculation of air resistance is complicated, but the
basic idea, as stated here, is simple.
Best, Dick Plano
Hi, Loretta !!!
I can only understand this problem by considering
that the bigger the pressure, the more resistance
there will be against the movement of a body.
And that because there will be more air to be
crossed. The behavior of the limit layer surely
will show us that at the front the pressure will
be greater than behind, where greater turbulence
should be expected. If there were no movement
the only force acting on the body is that due to
pressure differences, vertical, from the bottom to
the top. This force is independent from the value
of pressure. If the body moves across the air,
there will be a greater pressure ahead and vacuum
at the tail ( depending upon how big is the speed ).
If a body falls, the resistance will be increasingly
bigger, till it reaches a value where there will be no
more acceleration, or be, constant speed. On the
other extreme, without air, there always will be
acceleration, what means increasing velocity.
When comets reach the earth atmosphere - as
you know - the friction is so high that the tempe-
ture increases and oxygen starts a chemical
reaction and burns the comet. In a planet where
the gravity is bigger than at the earth, there will
be more gases present, and the friction will be
You are ok in this as long as you are careful about what you mean by air
pressure. The pressure that acts to oppose an object moving through
air is not the ambient air pressure. That pressure exerts the same
force on all sides of the object, so the net force from it is zero.
When an object moves through the air, its motion causes the air
pressure in front to increase while the pressure behind decreases, and
this pressure difference produces a net force on the object. If the
object suddenly stops moving, it will take a while for the higher
pressure air in front to leak around to the back, and while this is
happening, the object will still feel a net force from the pressure
difference. So it is the pressure that causes the force.
But drag is more complicated than this because there are other things
that happen as the object moves. The air and the object are heated,
there is turbulence, jets make a condensation trail, etc. All of these
things must be "paid for" out of the momentum (and energy) of the
moving object, and any time momentum changes, there is by definition a
force of some kind.
There is a relation between air pressure and air resistance, but air
resistance and air pressure are not the same thing. If air pressure were
zero, air resistance would also be zero. Still non-zero air pressure does
not mean any air resistance is being felt.
Air pressure is from all directions. Air pressure can be different on
different parts of an object, but in most cases it is quite large all
around. Air pressure is due to molecules crashing into the object from all
Air resistance is due to the motion of an object through the air. The
object pushes the air molecules out of the way. The molecules push back.
Because the air molecules in front get squeezed together more tightly,
pressure in front is greater. Air molecules in back get a little spread
out, so air pressure in back is less. The net effect is a force opposite
the direction of motion.
Just as important to air resistance is the shape of the moving object. A
narrow, pointed object pushes the molecules aside quite easily. A flat
front must push the molecules harder to get them to the side. It is like
hammering a sharp nail versus a dull peg into a piece of wood. For an
arrow, the air molecules in front do not get so tightly squeezed together as
for the dull peg.
Air pressure may be viewed as part of why air resistance exists, but it is
not air resistance itself.
Dr. Ken Mellendorf
Illinois Central College
Air pressure does act on all (exposed) surfaces of an object. The presence of
air pressure does not depend on the state of motion of an object, or even the
presence of an object. It is a property of the air alone.
Wind resistance can only be talked about in terms of the resistance to motion
of an object in the air. The presence of a body to be acted on and the motion
of the air around it creates an increase in the air pressure in front of the
object compared to the air pressure behind the object. This DIFFERENCE in air
pressure results in a new force resisting the motion of the object, which we
call wind resistance.
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Non-Luminary World Classification Scheme
The Non-Luminary World Classification Scheme, or NoLWoCS, is a near standard classification method used to identify the many different forms of planetary bodies, minor worlds, and artificial structures that have evolved naturally or that have been created by the many societies and cultures of the Terragen Sphere. While every world or megastructure is, in its own way, unique, there are certain characteristics that can be used to identify and classify these places. The purpose of NoLWoCS is to provide an easy, "at a glance" platform for the common User, whereby he might find the navigation of the Sphere, virtual or real, a little easier.
- NoLWoCS is divided into three tiers of classification: Class, Type, and Subtype. The different Classes of worlds are dependent on size, overall characteristics, and status of a planet. For instance, Planetoidal and Terrestrial world Classes are divided according to size, just as Terrestrial and Jovian worlds are different Classes because of their general characteristics, and of course, artificial worlds are different from all of these because they are not naturally occurring.
- World Types are dependant on a variety of factors, but generally the compositional elements, which often lead to different planetary features and behaviors, are of sufficient difference to separate these worlds. Subtypes are much more specific, and often are the result of what would normally be considered minor planetary features. For instance, Gaian worlds are divided into several different Subtypes based on items such as the amount of surface water, atmospheric composition, and so on.
Orbital and Rotational Parameters
Eccentric worlds and Tilted Worlds Worlds of any class that have unusually high tilts or unusual orbits are classed as Skolian, Janusian or Ikarian worlds.
- Skolian Type Worlds Worlds with axial tilts greater than 45 degrees; any class of world can have Skolian characteristics. More information here
- Janusian Type Worlds Worlds in resonant orbits which regularly exchange momentum. More Information here
- Ikarian type worlds Worlds with eccentric orbits, with an eccentricity greater than 0.35. Any class of world can have an Ikarian type orbit. More Information here.
Image from John Dollan
ASTEROID CLASS: non-spherical worlds of extremely low mass The Asteroidal Class is the most basic, and the most numerous, of all the classes in the NoLWoCS. There are, of course, even more numerous smaller objects, namely meteoroids and space dust, and these are the ultimate building blocks of any solar system. But only asteroids can be considered worlds in their own right. By NoLWoCS definition, these are worlds from 50 meters to 50 kilometers in diameter. More Information here.
Types of Asteroid
- Carbonic: Almost exclusively of carbon compound construction, resulting in the formation of bodies from pockets of high carbon material around later generation stars choked with heavier elements; common near the galactic core. They may also form in systems where two white dwarfs have spiralled together, and the resulting circumstellar disk coalesces into bodies high in carbon.
- Metallic: More Information here
- Carbonaceous: More Information here
- Silicaceous: More Information here
- Hydronic: Located close to the system's snow-line, these are silicaceous bodies with high instances of subsurface volatiles, typically in the form of water ice. Polar deposits in permanently shadowed regions may also be present.
- Gelidic: Located beyond the snow line of their system, these are bodies with high instances of ice, ranging from water to methane to carbon dioxide, and many other compounds besides, surrounding a core of silicate rock. The smaller bodies may be a nearly homogeneous mixture of ice and rock, due to the lack of a mass great enough to have caused layer differentiation early in the formative period. See also Centaurian Type
- Oortean: More Information here.
- Vulcanian: More Information here.
PLANETOID CLASS: worlds with enough mass to pull themselves into spherical or near-spherical shapes Generally, rocky (more rarely metallic or icy) bodies, either irregular or regular in shape, mostly large asteroids, some small moons, about 51 to 1,000 km along the longest axis. More information here.
Types of Planetoid
- Carbonean type: Carbon worlds of this mass have a chance to form around stars whose proto-stellar disks have developed carbon pockets within them, but they are far more common about late generation, high metal stars or even as the results of secondary planetary formation around high carbon stars such as white dwarfs. However, worlds of this size and mass also experience some differentiation during their formation. The cores of such worlds are dense masses of condensed graphite, though the planetoids at the higher mass range could form cores of partially crystallized diamond.
- Hadean Type: More Information here.
- Hygiean: These bodies are typically quite dark, with albedos ranging from 0.03 to 0.1. While there can be deposits of water ice or other volatiles beneath the surfaces of these planetoids, the surfaces are more often marked by craters and large boulders. These worlds are less dense and more easily disrupted by major impacts. The larger bodies, however, will have been differentiated through the formation process, and can have small cores of iron, with a dense mantle or rock and a crust of lighter silicates. The smaller worlds, though, may be a relative even mixture of sparse metals and the far more common silicate rock.
- Cerean Type: More Information here.
- Chronian type: Named after the plethora of such bodies orbiting the planet Saturn, these can be a highly varied lot. Typically, these worlds are small and heavily cratered bodies untouched by time, save for the numerous impacts that they have suffered. Their low mass and composition of primarily ice, with small rocky cores, are simply too small for sustained geological activity. As such, there is an absence of atmosphere, or related surface features. However, certain disruptions, such as through tidal flexing or other massive external forces may initiate geological forces that can completely resurface a planetoid, as well as form a minor atmosphere. If such active worlds are positioned properly in a gas giant system, an impressive ring system may even be formed.
- Vestian Type: More Information here.
- Kuiperian Type: More Information here.
Image from John M Dollan
TERRESTRIAL CLASS: worlds with an active internal geology that lasts one million years or more: 0.05 to 2.5 x Earth's mass
- Adamaean: Carbon Worlds. Carbon-rich terrestrials. More information here
- Ferrinian: Iron-rich, dense worlds. More information here
- Hermian: Dense, inner system worlds. More information here
- Selenian: Worlds with little or no metallic core.More information here
- Cytherean: Hot, greenhouse worlds. More information here.
- PelaCytherean: Terrestrial sized hot ocean worlds with thick atmospheres. More information here.
- LithicGelidian: Worlds with a mixed rock and ice composition. More information here.
- Europan: Icy worlds with a subcrustal ocean. More information here.
- Titanian: Icy worlds with thick atmospheres. More information here.
- Ymirian: Worlds made almost entirely of ices. More information here.
- Vesperian: Tidally locked terrestrial worlds. More information here.
- Hephaestian: These are the most active of planets, with surfaces that are almost entirely molten and a geology that changes on a yearly basis. The atmospheres of these planets vary greatly according to the world's size and mass, from having thick, Cytherean-like atmospheres to almost non-existent ones, where the feeble gravity loses any elements almost as soon as they are released from the surface. These worlds are generally heated by tidal flexing, by proximity to a star or as a moon of a gas giant. Example: Io.
- Amunian Type: Cold, dry worlds with high levels of ammonia in the atmosphere but little water. May develop an ammonia-based biosphere (see the Soft Ones xenosophonts for one example).
- Vitriolic Type: Worlds with lakes, seas or oceans of sulphuric acid; often with life, More information here.
Image from John M Dollan
- Arean type: Mars-like worlds where the atmosphere and hydrosphere has largely disappeared due to the cessation of magnetic activity. .More information here.
- EoArean subtype Young Mars-like Type planet with substantial atmosphere and surface water. More information here
- AreanLacustric subtype: Young Mars-like worlds with moderate amounts of ocean cover . More information here.
- AreanXeric subtype Mature, unusually hot and dry Arean type worlds. More information here.
- AreanTundral subtype Cold Arean type worlds, often with considerable reserves of ice More information here.
- EuArean Subtype Typical mature Mars-like world with minimal atmosphere and hydrosphere More information here.
- Gaian Type: Any Earth-like terrestrial world, of which there are many diverse forms depending on water content, composition and temperature. More information here
- EoGaian Subtype: Young terrestrial worlds; these may develop into Gaian, Cytherean or Arean worlds later More information here
- MesoGaian Subtype: Earth-like worlds with primitive biospheres More information here
- Eugaian Subtype A mature Gaian world with life, also known as a Garden World More Information Here
- GaianTundral Subtype: Cold Gaian worlds with periodic, or persistent, ice ages More Information Here
- Campian Subtype: Dry Gaian worlds with 25% to 50% ocean cover More Information Here
- Paludial Subtype: Humid Gaian worlds with 25% to 50% ocean cover More Information Here
- Lacustric Subtype:Humid Gaian worlds with low topography and 50-80% ocean coverage; some of these worlds have extensive rainforest-type biomes More Information Here.
- Chlorogaian (Halogenic) type: Gaian worlds with high levels of atmospheric chlorine. More: Chlorine Worlds.
- To'ul'hese Worlds: These worlds are essentially Gaian versions of the Cytherean worlds. Thick and dense atmospheres, as well as a large amount of water, create high surface pressures and high temperatures. Life arises and adapts to these conditions, and can become quite diverse indeed. In one known instance, it has lead to an independent form of sapient life. More: To'ul'hian Worlds.
- Pelagic Subtype Gaian worlds where oceans cover the surface anywhere from 85 to 100%. More Information here
- EuPelagic Subtype Gaian worlds where shallow oceans cover the surface anywhere from 85 to 100%. More information here
- BathyPelagic Subtype: Gaian worlds where deep oceans cover the surface anywhere from 85 to 100%. More information here.
- PelaGelidic Subtype, ice covered ocean worlds More information here.
- TundralPelagic subtype, partially ice covered ocean worlds More information here.
- Xeric subtype Dry worlds with less than 25% ocean cover More information here.
- HyperXeric subtype Very dry worlds with less than 10% ocean cover More information here.
- PostGaian subtype: Old Gaian Worlds that are losing their biosphere and hydrosphere More information here.
SUPER-TERRESTRIAL CLASS: worlds that are moderately massive, intermediate in mass between Terrestrial worlds and Gas Giants More details here.
This class of worlds is both numerous and varied; most types of terrestrial worlds also exist as superterrestial types, but with higher gravity and greater mass which can profoundly affect the conditions on the surface.
Among the most common types of superterrestrial are SuperHermian, SuperCytherian and SuperGaian types, as well as the more unusual types listed below.
- Pyrothalassic Type: Hot superterrestrials More information here
- Pyrohydrothallasic Type - Hot waterworlds More information here
- Panthalassic Type: Giant Waterworlds More information here
- Nebulous Type: Superterrestrials with thick, helium-rich atmospheres. Helium worlds of this kind often have superrotating atmospheres; those which are tidally locked often have wildly assymetric weather patterns.
- Gas Dwarfs. Example Kepler 11b
- Other types of superterrestrial planets include certain hyperbarian and chthonian worlds, some of which have very sparse atmospheres indeed.
Image from John M Dollan
Gas Giants (also known collectively as Jovian worlds) form beyond the snow line, and have very large fluid envelopes compared to their cores. Some rare, and very ancient gas giants formed around the first generation of very low metallicity stars and have almost no rocky or metallic component. Gas giants are classified in two ways- by temperature, which affects the composition of the cloud layers of the giant in a number of significant ways, and by mass. Examples of each of the temperature classes can be found in any of the size classes, and vice versa, although some size classes are more common at certain temperatures and vice versa.
A typical gas giant may be classified using both size and temperature types to create a subtype, so the full classification might be Meso-EuJovian Subtype(This is the full classification for Jupiter) or Super-HyperthermalJovian Subtype (the full classification for Behemoth, Hat-P-1B).
Gas Giant Size Classes
Neptunian Class: 0.03 to 0.2 Jupiter masses
- MicroJovian Type Small gas giants, with minimal solid core. More information Here .
- SubJovian Type Medium sized gas giants, 0.08 to 0.2 Jupiter Masses. Many worlds of this type are outer system cryojovian worlds like Neptune and Uranus. More information here.
- Hot Neptunes - a numerous class of world, which may be MicroJovian or Subjovian in mass, and EpiStellar or Hyperthermal in temperature More information here.
Jovian Class: 0.2 to 13.0 Jupiter masses
- Mesojovian Type Major Type of Jovian Class of planet. Masses from 0.21 to 8.0 that of Jupiter More information here
- SuperJovian Type Jovian worlds with masses from 8.1 to 13.0 that of Jupiter, the theoretical upper limit of planets. Objects more massive than this are classed as Brown Dwarfs. More information here.
Gas Giant Temperature Types
- HyperthermalJovian Type: Very hot gas giants, with temperatures above 1400 Kelvin. Includes so=called 'Puffy worlds' and 'Comet worlds'. More Information here.
- EpiStellar Jovian Type: Hot, dark gas giants with temperatures between 900 Kelvin and 1400 Kelvin. More information here
- AzuriJovian Type Warm clarified blue gas giants with temperatures between 350K and 800K. More information here.
- HydroJovian Type: Temperate gas giants with clouds predominantly consisting of water vapour. More information here.
- EuJovian Type: Cool gas giants, with clouds predominantly consisting of ammonia. More information here.
- CryoJovian Type: Cold gas giants in the outer reaches of a planetary system, generally too cold for clouds to form at all. More information here.
Other World Classes
- HyperBarian Class: Very dense planets with cores up to 100 x Earth's mass. More information here.
- Chthonian Class: Gas giant worlds, formerly HyperthermalJovians, which have lost their volatiles through evaporation. More information here.
- Stevensonian Class Planetary mass objects which are found in interstellar space. More information here.
ARTIFICIAL CLASS The artificial worlds found within the Terragen Sphere have almost all been constructed by humans and their mind-children; some, such as the Black Acropolis, are much older. Artificial worlds fall into two broad categories- those that rotate to produce artificial gravity, and those that do not.
- Rotating Space Habitats Habitats constructed using conventional materials - includes Paired Habitats, Stanford Tori, O'Neill Cylinders, Bernal Spheres, Bishop Rings. More information Here.
- Banks Orbitals and Ringworlds - Rotating habitats made from exotic materials (see Banks Orbitals).
- Non Rotating Space Habitats - often used by space adapted clades; can be very large, but they are limited by their density- if they are too dense they will undergo self-gravitational collapse. More information here.
- Ederworlds More information here.
- Supermundane Worlds -worlds dynamically suspended above planets and stars. More information here
- Freespheres - microgravity balloons containing atmosphere -can be very large indeed. More information here.
- Dyson Swarms and Spheres Many variants of this type of construct are described here. | <urn:uuid:ff3f3ca9-0abe-46d5-8983-695a17f99e41> | 2.96875 | 3,644 | Knowledge Article | Science & Tech. | 29.490865 | 1,960 |
CORRECTED-Warming temperatures could multiply Katrina-like hurricanes -study
(Corrects that IPCC assesses but does not run computer simulations, and expands range of warming, paragraph 5)
* Extreme storms most sensitive to rising temperatures
* Number of strong hurricanes could increase seven-fold
By Environment Correspondent Deborah Zabarenko
WASHINGTON, March 18 (Reuters) - The number of Atlantic storms with magnitude similar to killer Hurricane Katrina, which devastated the U.S. Gulf Coast in 2005, could rise sharply this century, environmental researchers reported on Monday.
Scientists have long studied the relationship between warmer sea surface temperatures and cyclonic, slowly spinning storms in the Atlantic Ocean, but the new study attempts to project how many of the most damaging hurricanes could result from warming air temperatures as well.
The extreme storms are highly sensitive to temperature changes, and the number of Katrina-magnitude events could double due to the increase in global temperatures that occurred in the 20th century, the researchers reported in the journal Proceedings of the National Academy of Sciences.
If temperatures continue to warm in the 21st century, as many climate scientists project, the number of Katrina-strength hurricanes could at least double, and possibly rise much more, with every 1.8 degree F (1 degree C) rise in global temperatures, the researchers said.
Computer projections assessed by the U.N. Intergovernmental Panel on Climate Change suggest that global temperatures could rise by between 1.8 degrees and 10.8 degrees F (1 degree and 6 degrees C) by century's end.
To figure out how many of the most extreme hurricanes these higher temperatures might spawn, Aslak Grinsted of the Centre for Ice and Climate at the University of Copenhagen and his co-authors looked at storm surges, which are often the most damaging aspect of these monster storms.
A storm surge is the abnormal rise in water, over and above normal high tide, pushed toward shore by the winds whipping around a big cyclonic storm. Much of the damage from Hurricane Katrina, an estimated $108 billion, was caused by high storm surges across a wide area of the Gulf of Mexico coast, according to the National Oceanic and Atmospheric Administration (NOAA).
Superstorm Sandy, which plowed into the northeastern U.S. coast with hurricane-strength winds last year, cost an estimated $75 billion, NOAA said.
The researchers looked at storm surges going back to 1923, and related those to how warm air temperatures were when the surges occurred. Then, using computer models, they projected how storm surges might be influenced by future warming.
Storm surges can be a more accurate gauge of a hurricane's severity than wind speed, like those on the Saffir-Simpson hurricane wind scale, Grinsted said by phone from Denmark.
"When people talk about (hurricane) intensity normally, then they mean wind speed," he said. "But that is not what is causing the most damage only. Sometimes it's about how fast it is traveling."
He said that was the case with Sandy, which traveled so slowly and stretched over such a wide area that its impact was intense, even though wind speeds abated somewhat by landfall.
Previous research on the link between climate change and hurricanes has suggested that there may be fewer hurricanes overall but more stronger ones as global temperatures rise.
This study indicates there will be an increase of hurricanes of all magnitudes, but the increase will be greatest for the most extreme events. (Reporting by Deborah Zabarenko; Editing by Ros Krasny, Jackie Frank and Eric Beech)
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Cicada wing surface biomimicry could lead to anti-bacterial surfaces
While many research groups throughout the world seek for better ways to fight bacteria, an international research group of researchers Australia’s Swinburne University of Technology and Spain’s Universitat Rovira i Virgili investigated cicada insect and came up with a discovery that may lead to a surface able to destroy bacteria solely through its physical structure.
The clanger cicada (Psaltoda claripennis) is a locust-like insect whose wings are covered by a vast hexagonal array of nanopillars which aid in insect’s fight against bacteria – one of the first natural surfaces found to do so. Although it seems as the texture layout could be puncturing bacteria, this bed of nails made of nanopillars actually does not puncture the bacterial cells on first contact.
When a bacterium settles on the wing surface, its cellular membrane gets “grabbed” by these nanopilars, thus sticking to the surface. After sticking to the surface of nanopillars, the surface of bacterium stretches into the gaps between them. As you can see in the video bellow, bacteria membrane ruptures if its surface is soft and thin enough.
“The rupturing effect is more like the stretching of an elastic sheet of some kind, such as a latex glove. If you take hold of a piece of latex in both hands and slowly stretch it, it will become thinner at the center, [and] will begin to tear”, said Elena Ivanova, Professor of Bionanotechnology at the Swinburne University of Technology and lead author of the study.
Ivanova and her team irradiated bacteria with microwaves to generate cells that had different levels of membrane rigidity in order to test their hypothesis that the more rigid bacteria would be less likely to rupture between the nanopillars. The results confirmed the model and demonstrated that the cicada’s nanopillar defense couldn’t be used for general fight against bacteria, but rather a fight against bacteria with sufficiently soft membranes.
Swinburne University of Technology researchers claim that they need to study cicada’s wing before its physical-defense properties can be mimicked in man-made materials. These materials could be used on public surfaces that commonly harbor disease, such as bus railings, thus significantly cutting costs for maintenance and environmental impact of detergents uses during their cleaning.
Once further researched and perfected to become more efficient against tougher membranes, the surface could act as be combined with coatings which don’t allow bacteria to stick to surfaces. The surface with nanopillars could be used as “drains” where bacteria unable to stick to coated surfaces can stick to. Aside acting as passive bacteria-killing surface for bacteria with suitable membranes, it could be replaceable and cleaned with microwaves and sterilized for reuse.
For more information, read the paper published in the Biophysical Journal: “Biophysical Model of Bacterial Cell Interactions with Nanopatterned Cicada Wing Surfaces” | <urn:uuid:c116f962-cf40-4972-917c-36bf4d532447> | 3.53125 | 647 | News Article | Science & Tech. | 16.61125 | 1,962 |
Jan. 22, 2005 Taking stock of the stuff between the stars - the all-important dust and gases that are the building blocks of new stars - has never been easy.
The interstellar medium, as scientists know it, is a murky, nebulous place that defies easy measurement. Yet probing the space between the stars and the star-building materials that reside there is increasingly important as astrophysicists seek to add precious detail to their pictures of how stars are born, live and die.
Now, with help from a novel new device, a team of astrophysicists has successfully developed a method for sampling the interstellar medium, specifically to take the temperature of and explore the pockets of ionized oxygen interspersed between the stars of the Milky Way.
"This is a first for studies of our galaxy," says Ron Reynolds, a professor of astronomy and an authority on the chemical soup of elements that permeates the space between the stars.
With colleagues John Harlander of St. Cloud State University and Edwin Mierkiewicz, UW physics Professor Fred Roesler constructed and deployed a new type of instrument capable of sampling wide swaths of the sky and exploring the vast clouds of ionized oxygen that well up from the plane of the galaxy. The new device was built with support from the National Science Foundation (NSF).
Data from the first observations using the new spectrometer, which is attached to a small telescope at UW-Madison's Pine Bluff Observatory, were presented by Merikiewicz here today (Jan. 13, 2005) at a meeting of the American Astronomical Society (AAS).
The new observations, taken by Mierkiewicz during the past year, reveal enormous chimneys of ionized gas that rise from the galactic plane into the far corners of the Milky Way.
"The galaxy seems to be full of channels or chimneys of ionized hydrogen, oxygen and nitrogen gas," says Reynolds. "The source is down in the muck where stars are born, but these channels seem to extend into the nooks and crannies of the galaxy."
That discovery, according to Mierkiewicz and Roesler, is intriguing because it provides insight not only to the patchwork of elements that make up the interstellar medium, but also to a class of rare stars that seems to be primarily responsible for the heating and churning that creates the chimneys of gas.
The stellar culprits, known as "O stars," are the most massive and luminous of stars, shining as much as a million times brighter than the sun.
"O stars are the only known stars that can create that much ionization," says Reynolds. "These are very rare stars - one in 10 million stars is an O star - but we see that they have a large influence on the interstellar medium. At this point, if there were other objects creating that much ionization, we'd know about them."
The picture that is emerging, according to Roesler, is that the O stars, which tend to occur in clusters near stellar nurseries, act as galactic blenders of sorts: "They are responsible for the ionization - the stripping of electrons from atoms - and the stirring up of the oxygen."
The Spatial Heterodyne Spectrometer, the new spectrometer developed by the Wisconsin team, looks at ultraviolet light, which is invisible to the unaided eye, but is laden with information for astrophysicists. The new technique, says Mierkiewicz, is especially useful as a temperature probe, and gives scientists a new way to take the temperature of the invisible clouds of gas that permeate space.
Teasing out the details of the interstellar medium is important, the scientists say, because each new finding helps fill in the picture of the life cycle of stars and, ultimately, of galaxies like the Milky Way.
In addition to Mierkiewicz, Roesler, Harlander and Reynolds, K.P. Jaehnig of UW-Madison contributed to the work presented at the AAS meeting. The new Wisconsin spectrometer was developed with support from NSF's Advanced Technology Instrumentation Program.
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NASA Airborne Science Campaign Begins Antarctic Sequel
Greenbelt MD (SPX) Oct 27, 2010
Scientists returned this week to the Southern Hemisphere where NASA's Operation IceBridge mission is set to begin its second year of airborne surveys over Antarctica. The mission monitors the region's changing sea ice, ice sheets and glaciers.
Researchers will make flights from Punta Arenas, Chile, on NASA's DC-8, a 157-foot airborne laboratory equipped with a suite of seven instruments. The focus is on re-surveying areas that are undergoing rapid change and embarking on new lines of investigation.
"We are excited to learn how the glaciers and sea ice have changed since last year's campaign," said Michael Studinger, IceBridge project scientist at NASA's Goddard Space Flight Center in Greenbelt, Md. "We also are going to be mapping uncharted regions that will allow us to better assess future behavior of the Antarctic ice sheets and sea ice."
IceBridge science flights are scheduled to begin this week and continue through mid-November. Flights will take off from Punta Arenas and cross the Southern Ocean to reach destinations including West Antarctica, the Antarctic Peninsula and coastal areas. Each flight lasts about 11 hours.
Instruments for the 2010 Antarctic campaign are the same as those flown in 2009. A laser instrument will map and identify surface changes. Radar instruments will penetrate the snow and ice to see below the surface, providing a profile of ice characteristics and also the shape of the bedrock supporting it. A gravity instrument will measure the shape of seawater-filled cavities at the edge of some major fast-moving glaciers.
Using these tools, researchers will survey targets of on-going and potential rapid change, including the West Antarctic Ice Sheet, which is the area that has the greatest potential to rapidly increase sea level. Another concern is that the ice sheet is below sea level, adding to its instability.
Revisiting previously flown areas, scientists can begin to quantify the magnitude of changes to land ice. Pine Island Glacier, the largest ice stream in West Antarctica with significant potential contribution to sea level rise, has long been a primary target for sustained observations.
Satellite data, most recently from NASA's Ice, Cloud and land Elevation Satellite (ICESat) have shown dramatic thinning there of up to 10 meters per year in places. Previous IceBridge flights mapped the surface of the glacier and unusual features beneath it, providing clues to the glacier's rapid retreat and ice loss.
In addition to flying previous lines over the glacier, the IceBridge team plans to fly a new horseshoe pattern to sample the tributaries feeding into Pine Island Glacier's main trunk. Other new flight lines will further explore the Antarctic Peninsula to map new targets, including the George VI Ice Shelf, above and below the ice.
Three high-priority flights are aimed at measuring sea ice, including a plan to map and measure sea ice across the Weddell Sea. Scientists want to know why sea ice in Antarctica is growing in extent, unlike sea ice in the Arctic, which is declining in extent. Current theories range from ozone depletion to changing ocean dynamics.
Other flights are being planned to be coordinated with existing space and ground-based missions, such as the European Space Agency's ice-observing Cryosat-2 satellite and European ship-based research. Overlapping measurements help researchers calibrate instruments and boost confidence in the resulting observations.
"A concerted effort like this will allow us to produce long time series of data spanning from past satellite missions to current and future missions," Studinger said. "This is only possible through international collaboration. We are excited to have many opportunities to work with our international partners during the upcoming campaign."
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Beyond the Ice Age
UBC Underwater Robot To Explore Ice-Covered Ocean And Antarctic Ice Shelf
Vancouver, Canada (SPX) Oct 26, 2010
Researchers at the University of British Columbia are deploying an underwater robot to survey ice-covered ocean in Antarctica from October 17 through November 12. Scientists predict that the sea ice area around Antarctica will be reduced by more than 33 per cent by 2100, accelerating the collapse of ice shelves. Up to hundreds of metres thick, ice shelves are floating platforms of ice that ... read more
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Unveiling the hidden universe: infrared observatory clears up dusty tales.Peek in any apartment window, it's said, and you'll discover a unique story.
The same is true of the heavens, except that skywatchers face a special challenge. The windows through which they view the cosmos are often clouded by dust. An observer peering through a telescope in visible or ultraviolet light misses much of the drama in the universe, from a stellar nursery teeming teem 1
v. teemed, teem·ing, teems
1. To be full of things; abound or swarm: A drop of water teems with microorganisms.
2. with newborns to the fireworks fireworks: see pyrotechnics.
Explosives or combustibles used for display. Of ancient Chinese origin, fireworks evidently developed out of military rockets and explosive missiles and accompanied the spread of military explosives westward to generated by the collision of two galaxies.
Infrared telescopes can penetrate this dust, revealing much more of the story. They can also record emissions from heavenly bodies too cool to radiate light at shorter wavelengths and higher energies.
For 28 months, the European Space Agency's Infrared Space Observatory Infrared Space Observatory: see infrared astronomy.
Infrared Space Observatory (ISO)
European Space Agency satellite that from 1995 to 1998 observed astronomical sources of infrared radiation. The satellite, which carried a 60-cm (24-in. (ISO (1) See ISO speed.
(2) (International Organization for Standardization, Geneva, Switzerland, www.iso.ch) An organization that sets international standards, founded in 1946. The U.S. member body is ANSI. ) has scanned the heavens from its vantage point in Earth's orbit. The mission, which ended in early April, generated remarkable new views of several familiar objects. It also examined the composition of these bodies by analyzing the intensity of light at wavelengths from 3 to 240 micrometers. Such a feat isn't possible with ground-based telescopes, which are hampered by water vapor and other molecules in Earth's atmosphere that both emit and absorb infrared light.
ISO scientists presented a roundup of the observatory's discoveries last month at a press briefing in London. Some of the most intriguing finds came relatively late in the mission, when the observatory examined a region of Orion, the nearest birthplace of massive stars.
In visible light, Orion's well-known Horsehead nebula looks like a dark dust cloud. Viewed with a camera aboard the observatory, however, the Horsehead silhouette vanishes and young stars shine through. Areas rich in dust appear as bright filaments.
The space observatory paints a portrait of two other star-forming clouds within Orion, NGC NGC New General Catalogue (of Nebulae and Star Clusters; astronomy)
NGC National Geographic Channel (TV)
NGC National Guideline Clearinghouse 2068 and NGC 2071. In the infrared, clutches of young stars dot the landscape. ISO also detected the bright glow of polycyclic aromatic hydrocarbons in these nebula nebula (nĕb`ylə) [Lat.,=mist], in astronomy, observed manifestation of a collection of highly rarefied gas and dust in interstellar space. . These organic compounds have been found in the Martian meteorite ALH ALH Advanced Light Helicopter
ALH Amplitude of Lateral Head (Displacement)
ALH Alpha Hospitality Corporation (former stock symbol; now ALHY)
ALH Advanced Liquid Hydrogen 84001 and in other interstellar clouds. Astronomers have suggested that these chemicals could provide some of the raw materials of life.
While observing the intensity of the stars at several infrared wavelengths, Lennart Nordh and Goran Olofsson of Stockholm University and their colleagues identified groups of stellar objects so young that they are still lying inside placentas of gas and dust. As many as 20 percent of these objects have insufficient mass to qualify as bona fide, hydrogen-burning stars, says Gerry Gilmore of the University of Cambridge in England. With less than 8 percent of the mass of the sun, these cool, infrared-emitting objects will become brown dwarfs, fizzling out after they exhaust their supply of deuterium deuterium (dtēr`ēəm), isotope of hydrogen with mass no. 2. The deuterium nucleus, called a deuteron, contains one proton and one neutron. .
The space observatory uncovered other new features of Orion. The long-wavelength spectrometer revealed that a cloud near the sword of Orion Sword of Orion is a Big Finish Productions audio drama based on the long-running British science fiction television series Doctor Who. This audio drama was broadcast on BBC 7 in four weekly parts starting from 3 September 2005, and was repeated in 2006. contains a massive concentration of water vapor--enough to fill Earth's oceans 10 million times.
By volume, that's about 1 part in 2,000, or roughly 20 times the concentration detected in other gas clouds in the Milky Way. Nonetheless, "an enhanced concentration of water is precisely what we expected in this gas cloud," notes ISO astronomer Gary J. Melnick of the Harvard-Smithsonian Center for Astrophysics The Harvard-Smithsonian Center for Astrophysics (CfA) is located in Cambridge, Massachusetts. It consists of the Harvard College Observatory and the Smithsonian Astrophysical Observatory. The Center is located at 60 Garden Street. in Cambridge, Mass.
Astronomers had theorized that water vapor is abundant in stellar nurseries like Orion. Water provides a means of cooling such regions--and a cloud of gas and dust must cool in order to contract and form stars.
In Orion, as in other star-forming regions, winds from hot, young stars send out shock waves into the surrounding gas, notes Melnick. At temperatures above a few hundred kelvins, molecular hydrogen, which is abundant in the clouds, radiates most of the heat away. Below those temperatures, however, molecular hydrogen can no longer cool the region. At this point, water vapor radiates the surplus heat, allowing the cloud to grow denser and contract.
"It's in the critical region where the gas has partially cooled itself but is still too hot to collapse that the water vapor cooling becomes very significant," says Martin Harwit, an ISO researcher and former director of the National Air and Space Museum The National Air and Space Museum (NASM) of the Smithsonian Institution is a museum in Washington, D.C., United States, and is the most popular of the Smithsonian museums. It maintains the largest collection of aircraft and spacecraft in the world. in Washington, D.C.
The vapor itself is generated by the shock waves, says Melnick. The waves cause unbound unbound
said of electrolytes, e.g. iron and calcium, and other substances which are circulating in the bloodstream and are not bound to plasma proteins so that they are available immediately for metabolic processes. See also calcium, iron. oxygen atoms to team up with molecular hydrogen and form water vapor. A similar process may have generated water in the solar system.
Harwit, Melnick, and their colleagues describe their study in the April 20 Astrophysical Journal Letters. Melnick notes that NASA's Submillimeter Wave Astronomical Satellite, now scheduled for launch in January 1999, will continue the studies of water vapor in Orion and search other parts of the Milky Way.
Near the Milky Way's dusty core, the space observatory examined several cold, dark clouds that seem to resemble Orion in its earliest stages of formation. The patches appear to have "just condensed out of the interstellar medium," says Gilmore. "They're just in the throes throe
1. A severe pang or spasm of pain, as in childbirth. See Synonyms at pain.
2. throes A condition of agonizing struggle or trouble: a country in the throes of economic collapse. of condensing into star-forming units, but they haven't [yet] got stars to warm them up. So unlike the Horsehead nebula, these things are still black."
Their very existence in the inner region of the galaxy, where they are buffeted by stellar winds and ultraviolet light, "is a great puzzle," Gilmore adds. Michel Perault of the National Center for Space Studies in Paris suggests that the density of the clouds, which is greater than that of the clouds in Orion, may offer protection. Ultraviolet radiation from neighboring stars may evaporate the outer layers of these clouds, leaving the cores intact, he speculates. The cores may even be able to snare additional material.
"It's likely that [these clouds] could become an, Orion and may even get brighter than Orion," says Perault. "If these things are on the verge On the Verge (or The Geography of Yearning) is a play written by Eric Overmyer. It makes extensive use of esoteric language and pop culture references from the late nineteenth century to 1955. of starting to collapse, it wouldn't take much more than a million years until you get the [formation of] young, bright stars."
Follow-up observations with IRAM Iram (ī`răm), in the Bible, duke of Edom. , a 30-meter radio telescope in Pico Veleta veleta
same as valeta , Spain, attest to the chilliness and high density of the clouds, he notes. A second infrared spacecraft, the U.S. Air Force's Midcourse Space Experiment Mission
The Midcourse Space Experiment (MSX) is a Ballistic Missile Defense Organization satellite experiment (unmanned space mission) to map bright infrared sources in space. , has also confirmed the cold, dark nature of these compact objects. M.P. Egan of the Air Force Research Laboratory in Bedford, Mass., and his colleagues described the study in the Feb. 20 Astrophysical Journal Letters.
Mark R. Morris of the University of California, Los Angeles UCLA comprises the College of Letters and Science (the primary undergraduate college), seven professional schools, and five professional Health Science schools. Since 2001, UCLA has enrolled over 33,000 total students, and that number is steadily rising. says that the evolution of the clouds will depend on their exact location in the galaxy. At the core of the galaxy, intense magnetic fields are common, he notes. They thread through gas clouds and act as springs, which may prevent the clouds from collapsing immediately and forming stars. In addition, differences in gravitational grav·i·ta·tion
a. The natural phenomenon of attraction between physical objects with mass or energy.
b. The act or process of moving under the influence of this attraction.
2. forces across the clouds are amplified at the core. Such stresses could also prevent collapse. In that case, only a particularly energetic shock could get star formation going.
The space observatory's findings on the Antennae, two galaxies that smashed into each other about a million years earlier, reveal that their "most massive stars are completely hidden in the widely publicized images" taken in visible light by the Hubble Space Telescope Hubble Space Telescope (HST), the first large optical orbiting observatory. Built from 1978 to 1990 at a cost of $1.5 billion, the HST (named for astronomer E. P. Hubble) was expected to provide the clearest view yet obtained of the universe. , says I. Felix Mirabel of the Centre d'Etudes de Saclay in Gif-sur-Yvette, France.
Fifteen to 20 percent of the luminosity luminosity, in astronomy, the rate at which energy of all types is radiated by an object in all directions. A star's luminosity depends on its size and its temperature, varying as the square of the radius and the fourth power of the absolute surface temperature. of these galaxies originated from a tiny region--roughly 150 light-years across--that looks dark in visible light. Its intense glow in infrared light comes from massive newborn stars "that have not yet cleared out all the dust and gas around them," says Mirabel. "The placenta clouds are still there."
The findings, he says, have implications on a truly cosmic scale.
Astronomers estimate the history of star formation in the universe by studying distant galaxies in visible light. If visible-light images fail to capture a substantial amount of star formation in relatively nearby galaxies like the Antennae, they are likely to miss even more in a distant galaxy, he asserts.
That's because the expansion of the universe lengthens, or reddens, light from distant galaxies. Ultraviolet light emitted by a faraway galaxy is shifted to visible light by the time it reaches Earth. Thus, a distant galaxy viewed in visible light reveals what the galaxy looked like billions of years earlier in the ultraviolet. Since dust obscures ultraviolet light even more effectively than it does visible wavelengths, a visible-light image can scarcely reveal the true nature of a faraway galaxy, Mirabel says.
"We are missing the grand design of galaxies," he says. He and his colleagues describe their findings in the May 1 Astronomy and Astrophysics Astronomy and astrophysics may refer to:
Astronomy and Astrophysics (abbreviated as A&A .
ISO depended on a tank of liquid helium to maintain its temperature at a frigid 2 kelvins--cold enough to reduce sharply the infrared emissions from the satellite's telescope and prevent it from interfering with observations. Engineers expected the helium to run out 18 months after ISO was launched.
During those months, the position of the observatory did not allow it to view Orion without running the risk of letting light from such bright sources as the sun or Earth enter its aperture and boil off precious helium. Fortunately, the helium lasted an additional 10 months. During that time, ISO's orbit moved the observatory into a location from which it could view Orion safely. This confluence of circumstances enabled ISO to examine Orion for several weeks in October 1997 and March 1998.
ISO's temperature began to climb on April 8, and the craft took its last set of observations about a month later. Now, researchers are looking ahead to 2001, when two new infrared observatories, devoted entirely to astronomical studies, are scheduled to begin operation.
Featuring a 2.5-meter telescope nearly five times the size of ISO's, the Stratospheric Observatory for Infrared Astronomy Stratospheric Observatory for Infrared Astronomy: see infrared astronomy. is housed permanently in an airplane that will cruise 45,000 feet above Earth. At this altitude, the flying telescope can avoid 99 percent of water vapor's emissions and absorptions, which can interfere with observations.
Scheduled for launch the same year, the Space Infrared Telescope Facility Space Infrared Telescope Facility: see observatory, orbiting. will orbit Earth well above the atmosphere, providing astronomers with an even cleaner window through which to view the heavens. | <urn:uuid:43ece1f0-99e6-4cc7-be9e-0d2b704844c1> | 3.34375 | 3,088 | Truncated | Science & Tech. | 42.183281 | 1,965 |
Posted on Mar 08, 2011 | Comments 0
The U.S Department of Defense has teamed up with the Department of Energy for a great green idea, which will develop energy storage. It may sound odd for many but the U.S military is already involved in many environmental initiatives.
Nowadays these two Departments have shown a real green signal that they are ready to be involved in new energy storage projects. Of course the new projects will need to be funded.
According to the Secretary of the Navy Raymond Mabus, these projects can be developed only with a funding of $50 million. The idea came out after it was said that the U.S. military was unable to pioneer the alternative power sources on their missions around the globe. The reason was one – they couldn’t find batteries with enough storage capacity, as well as adequate solar-power storage.
The U.S. mission in Afghanistan, Pakistan and other places can use the green power alternative only if there is a better battery. For instance, some foot patrols of the 3rd Battalion in Afghanistan were already using roll-up solar panels on their missions, but they had to ditch 700 pounds of batteries. The waste was unavoidable, simply because the soldiers don’t have enough storage capacity, not to mention that the waste can be dangerous for people in there.
The idea for creating new energy storage projects isn’t new, but this time the two Departments are going to launch two projects in this matter. The first project is about creating new hybrid modules for energy storage.
The project will try to improve and create better batteries as it uses only light weighted materials. The batteries will be capable to store huge amounts of energy. The batteries will be very important for the U.S. military, for they will be able to store the energy for use without any waste. The second project that will be funded by the two Departments is going to be a project that will develop energy storage only in military power grids.
It is a well known fact that U.S. has military bases all over the world. The military needs for energy storage have been growing. Therefore, the second project will aim to boost the energy reliability, as well as finding an adequate prevention of an eventual energy supply disruption.
The energy projects will be launched with a certain goal: the expectations are that by 2020 the energy consumption of half of the U.S. bases will be reduced to zero. Using renewable energy sources in all of the U.S. bases is also one of the goals of the green military projects.
Filed Under: Green News | <urn:uuid:1fa668f5-d873-4c64-b38f-6e2d7210b0b1> | 3.203125 | 530 | News Article | Science & Tech. | 54.19204 | 1,966 |
Next: 8.7 Input
Up: 8.6 Output
Previous: 8.6.4 Boxes and Lines
- void bkgdset(ch)
void wbkgdset(win, ch)
Set the background character and attribute for the screen or a window.
The attribute in ch will be ORed with every non blank
character in the window. The background is then part of the window
and will not be changed with scrolling and in- or output.
- int bkgd(ch)
int wbkgd(win, ch)
Will change the background character and attribute to ch.
Fri Mar 29 14:43:04 EST 1996 | <urn:uuid:5586ee43-d409-410f-bcba-8c08b6dca9d0> | 2.6875 | 144 | Documentation | Software Dev. | 98.608152 | 1,967 |
American Burying Beetle Conservation Centre
To survey existing populations and reintroduce captive-bred American burying beetles into their former range in the USA
American burying beetles, Nicrophorus americanus, just about 3 cm long, are master scavengers, cleaning the environment as they bury dead small mammals and various insects for future consumption.
American burying beetles were once plentiful in 35 states and south eastern parts of Canada. Quite suddenly in the 1920’s sharp declines were noticed in the range of this large colourful Silphid species. Its decline may be due to several factors. Fragmentation of habitat has increased accessibility for other carrion consumers such as fox, raccoon, small mammals, and some raptors. Thus, the American burying beetle often finds less and less to bury and then eat. Another reasons is the increased lighting in developed areas. This diminishes the abundance of night use insects and curbs another food source for the beetles. Also, certain genetic changes may alter reproduction on some level.
By 1989 the beetle could be found in only one state, Rhode Island, on an island known as Block Island. They were listed as Endangered by the federal government during the same year. Since 1989 small populations have been found in five other states, Oklahoma, South Dakota, Kansas, Nebraska and Arkansas. Successful breeding colonies can be found in Roger Williams Park Zoo, Ohio State University and the Saint Louis Zoo. Reintroduction has been tried in Ohio, and Nantucket (Massachusetts). Further surveying is going on in Missouri in hopes of finding a wild colony and research on the beetles continues in hopes of finding answers to questions about its swift disappearance and if reintroduction will be successful.
The Saint Louis Zoo's Invertebrate Department acts as the Center of Conservation of the American Burying Beetle. Surveys are carried out throughout the State of Missouri every summer to try to find wild populations of the American burying beetles. The Center is working with Government agencies to determine the status of the American burying beetles to determine if they are extant from the state and if it will be possible to work with the Nature Conservancy on a site they own to try a reintroduction within the next two years.
WAZA Conservation Project 05002 is operated by the Saint Louis Zoo in cooperation with the Missouri Department of Conservation, The Nature Conservancy, Department of Natural Resources, and the United States of Fish and Wildlife.
> a vista general Proyecto | <urn:uuid:0f4fc096-9aaa-4ccf-9de2-c1f2ea4c8e9b> | 3.515625 | 498 | Knowledge Article | Science & Tech. | 31.898037 | 1,968 |
This image shows a subsurface explorer on the surface of Mars (this is an artist's rendition). Such subsurface explorers would help us look for water and organic material below the surface of Mars. A "robotic mole" like this one would also test to see what minerals make up the Martian interior. One of the proposals does involve a subsurface explorer that would dive through the Martian polar ice caps.
Click on image for full size
Courtesy of NASA/JPL
News story originally written on June 18, 2001
43 Scout missions were proposed to NASA. 10 were selected. These 10 are competing to see which missions will be included as future Scout missions to Mars. May the best robots, gliders, rovers, orbiters or landers win!
The 10 proposals that made it this far will receive 6 months of funding to do further investigation for their proposed mission. The Scout missions that are sent to Mars in the coming years (the first being launched in 2007) will join the Martian fleet including the 2001 Mars Odyssey, twin rovers which will land on Mars in 2003, a science orbiter, a mobile laboratory and a return sample mission.
The 10 proposals are really different! One mission would involve three gliders that would investigate the walls of Valles Marineris. Another would place 24 weather stations across the surface of Mars. Still another would have a probe that could dive down through the Martian polar ice caps!
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The Mars Odyssey was launched April 7, 2001, from Florida. After a six-month, 285 million-mile journey, the Odyssey arrived at Mars on October 24, 2001. The Odyssey is in its aerobraking phase right now....more
It was another exciting and frustrating year for the space science program. It seemed that every step forward led to one backwards. Either way, NASA led the way to a great century of discovery. Unfortunately,...more
The Space Shuttle Discovery lifted off from Kennedy Space Center on October 29th at 2:19 p.m. EST. The weather was great as Discovery took 8 1/2 minutes to reach orbit. This was the United States' 123rd...more
A moon was discovered orbiting the asteroid, Eugenia. This is only the second time in history that a satellite has been seen circling an asteroid. A special mirror allowed scientists to find the moon...more
Will Russia ever put the service module for the International Space Station in space? NASA officials want an answer from the Russian government. The necessary service module is currently waiting to be...more
A coronal mass ejection (CME) happened on the Sun early last month. The material that was thrown out from this explosion passed the ACE spacecraft. The SWICS instrument on ACE has produced a new and very...more
J.S. Maini of the Canadian Forest Service called forests the "heart and lungs of the world." This is because forests filter air and water pollution, absorb carbon dioxide, release oxygen, and maintain...more | <urn:uuid:bec0cb6b-14ef-4a14-89d3-b9a0d5fb7b4c> | 3.578125 | 646 | Content Listing | Science & Tech. | 58.232221 | 1,969 |
In 1989 a space weather storm caused an electrical blackout in Canada. The black area on this map shows where people lost their electrical power for many hours.
Click on image for full size
Image courtesy of M. A. Shea, Geophysics Directorate, Phillips Laboratory.
Power Blackout Caused by Space Weather Storm
In 1989 a space weather storm caused an electrical blackout over a large area. Six million people in eastern Canada lost electrical power for 9 hours or longer.
In March 1989 a large space weather storm struck Earth. The storm generated strong electrical currents in our atmosphere. Some of that electricity caused currents to flow in wires in our electrical power system. That extra surge of electricity damaged some kinds of equipment. A major transformer was destroyed. That caused the whole electrical system to "go down". Lots of people lost power for many hours.
The blackout in Canada cost a lot of money and was dangerous. Scientists are trying to learn how to predict big space weather storms better. That could help prevent blackouts like the one in Canada.
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Space weather causes electricity to flow in our atmosphere. Sometimes that electricity lights up the sky by causing the aurora (the Southern and Northern Lights). Electric currents in the atmosphere can...more
Our electrical power system supplies our homes and businesses with electricity. Space weather storms can mess up the power system, leaving us without electricity. A transformer is a piece of equipment...more
Space weather "storms" can cause problems on Earth. They can even mess up our systems that make electricity and that deliver electricity to peoples' houses. Sometimes really big space weather storms can...more
In 1989 a space weather storm caused an electrical blackout over a large area. Six million people in eastern Canada lost electrical power for 9 hours or longer. The blackout of the HydroQuebec power grid...more
Sometimes a whole electric power system shuts down. This can happen after a strong space weather storm. It is hard to get the whole system running again after it has been shut down all the way. The main...more
There is a giant magnetic "bubble" in space around the Sun. That "bubble" is called the heliosphere. In a sense, we Earthlings live within the outer atmosphere of our Sun. The solar...more
Earth's magnetosphere shields our planet from most of the solar wind. Some solar wind particles do leak in and combine with ions escaping from the top of Earth's atmosphere to populate the magnetosphere...more | <urn:uuid:fcc08313-76f5-4bca-9b28-7794e729c83b> | 3.484375 | 561 | Knowledge Article | Science & Tech. | 54.207723 | 1,970 |
Mathematica Notebook for This Page.
All trignometric functions sine, cosine, tangent, secant, cosecant, cotangent can all be simply defined in terms of a single function sine. Sine, as associated with trigonometry, began in early civilization as a very important measuring science. When the function concept and calculus and analytic geometry were introduced in about 1700, sine became a function and has little to do with triangles. The sine function appears unexpectedly throughout analysis, because in essence it captures the idea of a wave, a fundamental concept in physics.
From Robert Yates:
Trigonometry seems to have been developed, with certain traces of Indian influence, first by the Arabs about 800 as a aid to the solution of astronomical problems. From them the knowledge probably passed to the Greeks. Johann Müller (c.1464) wrote the first treatise: De triangulis omnimodis; this was followed closely by others.
See also: History of trigonometric functions.
Sine curve is the curve of the sine function. It is also known as sinusoid. Sine is sometimes called circular function because the essential feature of the sine function can be thought of as a point moving around a circle in constant speed, and the value of sine being the height of the point.
Step by step description:
In the formula y == a*Sin[x/p+s], a is the amplitude, p the period, and s the phase shift. sine_plot.gcf
All trig functions is defined in terms of sine.
If a right triangle is placed in a standard position (That is: in the Cartesian coordinate system such that it lies in the first quadrant, and the right angle vertex lies on the x-axes, and the hypotenuse touches the origin), and if r denote (the length of) the hypotenuse, x the bottom side, y the vertical side, θ the angle of x and r, then we have the following formulas:
|Sin[θ] == y/r|
|Cos[θ] == x/r|
|Tan[θ] == y/x|
See: List of trigonometric identities.
Sine curve is the development of a obliquely cut right circular cylinder. (the edge of the cylinder rolled out is a sinusoid). graphics code..
Tracing Sinusoid Sinusoid Fun Animation
Robert Yates: Curves and Their Properties.
Trigonometric functions.blog comments powered by Disqus | <urn:uuid:045fd621-b315-45a4-b532-be448460ba76> | 4.125 | 544 | Tutorial | Science & Tech. | 48.515928 | 1,971 |
Classifying North Atlantic Tropical Cyclone Tracks by Mass Moments
Jennifer A. Nakamura; Upmanu Lall; Yochanan Kushnir; Suzana J. Camargo
- Classifying North Atlantic Tropical Cyclone Tracks by Mass Moments
Nakamura, Jennifer A.
Camargo, Suzana J.
- Lamont-Doherty Earth Observatory
- Permanent URL:
- Book/Journal Title:
- Journal of Climate
- A new method for classifying tropical cyclones or similar features is introduced. The cyclone track is considered as an open spatial curve, with the wind speed or power information along the curve considered to be a mass attribute. The first and second moments of the resulting object are computed and then used to classify the historical tracks using standard clustering algorithms. Mass moments allow the whole track shape, length, and location to be incorporated into the clustering methodology. Tropical cyclones in the North Atlantic basin are clustered with K-means by mass moments, producing an optimum of six clusters with differing genesis locations, track shapes, intensities, life spans, landfalls, seasonal patterns, and trends. Even variables that are not directly clustered show distinct separation between clusters. A trend analysis confirms recent conclusions of increasing tropical cyclones in the basin over the past two decades. However, the trends vary across clusters.
- Atmospheric sciences
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Today marks a major milestone in the development of the Go programming language. We're announcing Go version 1, or Go 1 for short, which defines a language and a set of core libraries to provide a stable foundation for creating reliable products, projects, and publications.
Go 1 is the first release of Go that is available in supported binary distributions. They are available for Linux, FreeBSD, Mac OS X and, we are thrilled to announce, Windows.
The driving motivation for Go 1 is stability for its users. People who write Go 1 programs can be confident that those programs will continue to compile and run without change, in many environments, on a time scale of years. Similarly, authors who write books about Go 1 can be sure that their examples and explanations will be helpful to readers today and into the future.
Forward compatibility is part of stability. Code that compiles in Go 1 should, with few exceptions, continue to compile and run throughout the lifetime of that version, even as we issue updates and bug fixes such as Go version 1.1, 1.2, and so on. The Go 1 compatibility document explains the compatibility guidelines in more detail.
Go 1 is a representation of Go as it is used today, not a major redesign. In its planning, we focused on cleaning up problems and inconsistencies and improving portability. There had long been many changes to Go that we had designed and prototyped but not released because they were backwards-incompatible. Go 1 incorporates these changes, which provide significant improvements to the language and libraries but sometimes introduce incompatibilities for old programs. Fortunately, the go fix tool can automate much of the work needed to bring programs up to the Go 1 standard.
Go 1 introduces changes to the language (such as new types for Unicode characters and errors) and the standard library (such as the new time package and renamings in the strconv package). Also, the package hierarchy has been rearranged to group related items together, such as moving the networking facilities, for instance the rpc package, into subdirectories of net. A complete list of changes is documented in the Go 1 release notes. That document is an essential reference for programmers migrating code from earlier versions of Go.
We also restructured the Go tool suite around the new go command, a program for fetching, building, installing and maintaining Go code. The go command eliminates the need for Makefiles to write Go code because it uses the Go program source itself to derive the build instructions. No more build scripts!
Finally, the release of Go 1 triggers a new release of the Google App Engine SDK. A similar process of revision and stabilization has been applied to the App Engine libraries, providing a base for developers to build programs for App Engine that will run for years.
Go 1 is the result of a major effort by the core Go team and our many contributors from the open source community. We thank everyone who helped make this happen.
There has never been a better time to be a Go programmer. Everything you need to get started is at golang.org. | <urn:uuid:f4d90a6a-5c98-4f34-93a6-86c8c8f0db15> | 2.6875 | 623 | News (Org.) | Software Dev. | 44.150903 | 1,973 |
During each day of January 2013, I am creating a new video showing you how to use the new C++Builder XE3 compilers for Win32, Win64 and OSX to create multi-platform, database, multi-tier, HD and 3D applications. In this twenty-second video you will learn how to include inline assembly language code using the C++Builder 64-bit compiler for Windows. Big thank you(s) go out to Peter Evans and Tomohiro Takahashi for their help in the research and preparation of the programs used in this inline assembler video. The first inline assembler example is taken from the Intel assembler article at http://software.intel.com/sites/products/documentation/doclib/stdxe/2013/composerxe/compiler/cpp-lin/GUID-5100C4FC-BC2F-4E36-943A-120CFFFB4285.htm. There is also a great article, by Sandeep S., about the AT&T syntax/GCC inline assembler (which Clang supports) at http://www.ibiblio.org/gferg/ldp/GCC-Inline-Assembly-HOWTO.html. There are additional links in my December 18, 2012 blog post on C++Builder 64-bit compiler inline assembler at http://blogs.embarcadero.com/davidi/2012/12/21/42152 (also includes the source code for the C++Builder version of the Intel inline assembler example). Stay tuned to my blog for additional C++ programming videos each day.
January 22, 2013 - Adding Inline Assembler to your C++Builder 64-bit applications
Watch on YouTube: http://www.youtube.com/watch?v=9hhGMzxpJyE
Duration: 4 minutes and 15 seconds
Watch/Download the C++Builder 64-bit Compiler Preview Video
Additional details about the 64-bit C++Builder compiler are available in the preview video. Watch the C++ 64-bit compiler preview video on YouTube at http://www.youtube.com/watch?v=PwwMpBUoR6Y. You can also download the MP4 video file at http://cc.embarcadero.com/item/29197. The preview video is 9 minutes long.
Try the C++Builder 64-bit compiler
The C++Builder XE3 and RAD Studio XE3 free trial downloads have been updated to include the new C++Builder 64-bit compiler. Trial downloads are available at https://downloads.embarcadero.com/free/c_builder | <urn:uuid:0ca1e42e-ffef-4111-9323-421d246797d8> | 2.515625 | 563 | News (Org.) | Software Dev. | 70.167323 | 1,974 |
February 20, 2013 | 14
When a 17-meter asteroid barreled into Earth’s atmosphere over central Russia on February 15, releasing a powerful shock wave that injured more than 1,000 people, many observers wondered how such a momentous event could arrive unheralded. The fact is, the object that exploded in a fireball over Chelyabinsk, releasing hundreds of kilotons of energy, was small potatoes. There may be millions of comparably sized objects in the inner solar system, only a small fraction of which have been discovered. The searches to date have been focused on tracking much larger dino-killers and other potentially catastrophic asteroids and comets—those objects larger than about one kilometer. So the door has been open to unpleasant but ultimately survivable asteroid surprises.
Several new and forthcoming projects will amass reams of new data about the near-Earth asteroid (NEA) population, but a comprehensive catalogue of Chelyabinsk-scale objects remains beyond the technological horizon. The asteroids are too numerous, and too faint, to be systematically tracked. Below is a rundown of some of the best tools that researchers currently have for asteroid detection and defense:
The Catalina Sky Survey discovers about 600 NEAs every year from telescope sites in Arizona and Australia. Since the mid-2000s Catalina has been the leading NEA-detection project in existence, helping NASA to reach its goal of cataloguing 90 percent of all near-Earth asteroids larger than one kilometer in diameter. But its pace of discovery is too slow to make a significant dent in the much larger populations of smaller objects. Near-Earth asteroids larger than 100 meters likely number in the tens of thousands, whereas nearby asteroids 10 meters and up number in the millions.
The first of four planned Pan-STARRS telescopes in Hawaii recently came online and is now the second-leading NEA search in existence, in terms of objects detected per year. In 2012, its second full year of operation, Pan-STARRS discovered 251 near-Earth asteroids, according to NASA statistics. It should help discover many asteroids with diameters in the hundreds of meters, but the bulk of smaller objects will remain out of reach.
The Large Synoptic Survey Telescope, which should come online toward the end of the decade in Chile, will be a survey telescope of astonishing capability. The 8.4-meter telescope, equipped with a 3-gigapixel digital camera, will scan the skies every few nights to pick up moving objects or transient events. But even the LSST will have trouble picking up asteroids as small as the one that impacted the atmosphere over Russia last week. It will take decades of work (right) before the LSST has catalogued the vast majority of much larger objects—those 140 meters and up—thereby meeting NASA’s next asteroid-detection goal.
If an asteroid were detected years in advance, the world’s governments could take corrective action—detonating, nudging or tugging a hazardous object onto a safer orbit. The Asteroid Terrestrial-Impact Last Alert System (ATLAS) has a much simpler goal: detect asteroids just weeks before impact so as to warn or evacuate the threatened areas. ATLAS, which will comprise several small telescopes in Hawaii, is in development with financial assistance from NASA and may be operational by 2015. Its planners estimate that a 50-meter “city killer” could be detected one week ahead of impact.
The nonprofit B612 Foundation recently unveiled its plans to build the Sentinel Space Telescope, an asteroid spotter that would scan the inner solar system in the infrared from an orbit similar to the planet Venus. If the foundation can raise the hundreds of millions of dollars needed to build Sentinel, the spacecraft would launch in 2018 and make quick work of the truly dangerous asteroids out there. The Sentinel mission design calls for a telescope that would catalogue 90 percent of NEAs bigger than 140 meters over its 6.5-year mission. According to a recent statement from B612, the Sentinel would also spot more than half of the currently undiscovered asteroids larger than about 50 meters.
With limited resources, asteroid spotters have naturally focused on the largest asteroids that could cause the most mayhem. But the smaller, more frequent arrivals to our planet are likely to remain unpredictable for the foreseeable future. On the bright side, no deaths have been reported as a result of the Chelyabinsk incident, and the odds of the next significant meteor exploding over such a populous area are slim.
And, fortunately, impacts on the scale of the Chelyabinsk meteor are predicted to occur only once a century. So perhaps humankind will have figured out better techniques for discovery and tracking by the time the next one comes our way. | <urn:uuid:cfbc9939-5a4f-4402-b670-6de67ebb0dfd> | 3.96875 | 969 | News Article | Science & Tech. | 35.309164 | 1,975 |
Serving wine usually involves a rather elaborate ceremony in which the host tastes the wine before pouring it for the guests. One reason for this is the possibility that the wine may have been spoiled by exposure to air.
Certain bacterial enzymes are capable of converting ethanol to ethanoic acidIn Arrhenius theory, a substance that produces hydrogen ions (hydronium ions) in aqueous solution. In Bronsted-Lowry theory, a hydrogen-ion (proton) donor. In Lewis theory, a species that accepts a pair of electrons to form a covalent bond. (acetic acid) when oxygen is present:
The same reaction occurs when cider changes into vinegar, which contains 4 to 5 percent acetic acid. Acetic acid gives vinegar its sour taste and pungent odor and can do the same thing to wine.
Acetic acid, CH3COOH, is an example of the class of compounds called carboxylic acids, each of which contains one or more carboxylThe functional group consisting of a carbon atom bonded to a hydroxyl group and doubly bonded to an oxygen atom; found in carboxylic acids: -C(=O)OH. groups, COOH. The general formula of a carboxylic acid is RCOOH. Some other examples are
Formic acid (the name comes from Latin word formica meaning “ant“) is present in ants and bees and is responsible for the burning pain of their bites and stings. Butyric acid, a component of rancid butter and Limburger cheese, has a vile odor. Adipic acid is an example of a dicarboxylic acid—it has two functional groups—and is used to make nylon.
Since the carboxyl group contains a highly polarDescribes a molecule that has separated, equal positive and negative charges that consitute a positive and a negative pole; such a molecule tends to assume certain orientations more than others in an electric field. as well as an OH group, hydrogen bonding is extensive among molecules of the carboxylic acids. Pure acetic acid is called glacial acetic acid because its melting pointThe temperature at which a solid becomes a liquid. Also called freezing point. of 16.6°C is high enough that it can freeze in a cold laboratory. As you can see from the table below, acetic acid boils at a higher temperatureA physical property that indicates whether one object can transfer thermal energy to another object. than any other organic substance whose molecules are of comparable size and have but one functional group. It is also quite thick and syrupy because of extensive hydrogen bonding.
Boiling Points of Some Organic Compounds Whose Molecules Contain 32 or 34 Electrons.
Below is a Jmol model of acetic acid. In the general menu to the left, click on partial charges. Each atom in the molecule will be assigned a partial charge. It is clear that the oxygen atomsThe smallest particle of an element that can be involved in chemical combination with another element; an atom consists of protons and neutrons in a tiny, very dense nucleus, surrounded by electrons, which occupy most of its volume. are sharing electrons unequally and causing other parts of the molecule to gain a partial positive charge in the carboxyl carbon and hydrogen. Further, this induces a partial negative charge on the methyl carbon, leading to positive charges on the methyl hydrogen atoms.
An even better way to view the electron distribution is with the Molecular Electrostatic Potential (MEP) Surface options. One can look at "MEP on isopotential surface", which show surfaces where electrostatic potential is the same, but the most informative option here is the "MEP on Van der Waals Surface" radio button. This shows the potential along the van der Waals surface of the molecule. The closer to red on the color spectrum, the more negative the potential at that surface is, the closer to blue, the more positive. One can see that both oxygen atoms are centers of partial negative charge, while the acidic hydrogen atom has a substantial partial positive charge, and the methyl group is also has a partial positive charge. One more way to look at the molecule, is to use the "MEP on a plane" button. Choose the XY plane, and then click "Set Plane Equation." This will show the electrostatic potential along the axis of symmetry for the molecule. While two hydrogen atoms on the methyl group are out of the plane, this view still allows one to see how partial charge is distributed along the backbone of the molecule in a way the van der Waals surface does not. From this modeling of the acetic acid molecule, hopefully it is becoming clear how the macroscopic properties we discussed arise.
Acetic acid is synthesized commercially according to the reaction shown above, but silver is used as a catalystA substance that increases the rate of a chemical reaction but that undergoes no net change during the reaction. instead of bacterial enzymes. It is also prepared by reading air with propane separated from natural gasA state of matter in which a substance occupies the full volume of its container and changes shape to match the shape of the container. In a gas the distance between particles is much greater than the diameters of the particles themselves; hence the distances between particles can change as necessary so that the matter uniformly occupies its container.. The liquidA state of matter in which the atomic-scale particles remain close together but are able to change their positions so that the matter takes the shape of its container acetaldehyde obtained in this reaction is then combined with oxygen in the presence of manganese(II) acetate to make acetic acid. About half the acetic acid produced in the United States goes into cellulose acetate from which acetate fibers are made. | <urn:uuid:e66e40a8-9165-40c0-9c90-f4295980351d> | 3.515625 | 1,194 | Knowledge Article | Science & Tech. | 32.01548 | 1,976 |
Biodiversity's Ticking Time Bomb: Understanding and Addressing the Problem of Invasive Species in Europe
28 January 2013 | News story
On 21 February 2013, IUCN and BirdLife, with the support of the European Habitats Forum, will organize a high-level debate at the European Parliament in Brussels to discuss the issue of invasive alien species in Europe and the development of a EU policy instrument to tackle them. The event is hosted by MEP Pavel Poc, Group of the Progressive Alliance of Socialists & Democrats (S&D).
NATURE Invasive alien species are acknowledged as a serious threat to biodiversity in Europe, and the first cause of documented extinctions at the global scale. Today, Europe hosts over 11,000 alien species and invasions are growing at exponential speed, with a recorded increase of 76% in the last 30 years.
MONEY The economic costs of invasions are estimated at more than 12 billion Euros per year in Europe only. This affects many economic sectors, from forestry to agriculture, and to the shipping industry.
ACTION Following the EU Biodiversity Strategy to 2020, the EU Council Conclusions, the opinion of the European Economic and Social Committee and the European Parliament Resolution, IUCN and BirdLife urge the European Union to adopt a legislative instrument on invasive alien species early in 2013. IUCN and BirdLife call for more stringent policies and measures to prevent and mitigate the impacts of invasions.
YOU Participate in a high-level discussion on Thursday 21 February 2013 to better understand the challenges posed by invasive alien species, bring in your experience and join IUCN and BirdLife in the call for action. European policy-makers, scientists and NGOs will discuss together the best solutions to combat invasions in Europe.
Intervening at the event:
- MEP Pavel Poc, Member of Committee on Environment, Public Health and Food Safety, European Parliament
- Julia Marton-Lefèvre, Director General, International Union for Conservation of Nature (IUCN)
- Janez Potočnik, Commissioner for the Environment, European Commission
- Dr Piero Genovesi, Institute for Environmental Protection and Research (ISPRA) and Chair of IUCN SSC Specialist Group on Invasive Alien Species
- Patrick ten Brink, Senior Fellow, Head of Brussels office and Environmental Economics Programme, Institute for European Environmental Policy (IEEP)
- Pia Bucella, Director of Nature Unit, DG Environment, European Commission
- Ladislav Miko, Deputy Director General, DG Health & Consumers, European Commission
- Dr Joe Caffrey, Senior Research Scientist, Inland Fisheries Ireland
- Dr Paul Walton, Head of Habitats and Species, Royal Society for the Protection of Birds (RSPB), BirdLife Europe, European Habitats Forum (EHF)
See the agenda here.
Register by 13 February at biodiversitystickingtimebomb.eventbrite.co.uk.
For more information, contact Ana Nieto at email@example.com. | <urn:uuid:49ffdf31-da2f-4812-a163-ea3ab51e79ca> | 2.609375 | 625 | News (Org.) | Science & Tech. | 17.59086 | 1,977 |
Just to clear up a common misconception, one that seems to be at the root of every newcomer's approach to coding for standards, you do not use divs instead of tables. That's important enough to repeat, "you do not use divs instead of tables".
What do you use? You use well structured, semantic and well formed html instead of table layouts. A non-trivial table layout cannot be well structured nor semantic, though it can contain well formed (valid) html.
The div element is a non-semantic structural container that lets you form groupings of other, semantic, elements. Notice, I said elements. A div should never contain bare nekkid content, only elements.
These groupings provide independent styling contexts. Think of the div as a drawer in a chest. You can arrange and re-arrange the socks, handkerchiefs and underwear in one drawer (div) without affecting the contents of other drawers. Further, you can arrange and re-arrange the positioning of the drawers in the chest without affecting the contents of the drawers.
Keep in mind that the div is semantically neutral. It says nothing about what its %flow element contents are. Use the div only for its proper structural purposes. Replacing tables is not it. | <urn:uuid:9d2852e2-12ae-406e-8b2b-a3c32618f5e4> | 2.765625 | 267 | Personal Blog | Software Dev. | 58.425177 | 1,978 |
|Back to . . .
Clerk Maxwell ( 1831-1879 )
14 India Street
epoch ended and another began with James Clerk Maxwell."
"The special theory
of relativity owes its origins to Maxwell's
equations of the electromagnetic field."
James Clerk Maxwell was one of the greatest scientists and
mathematicians of the 19th century. With talents rarely united
today, he made landmark
contributions to both theoretical and experimental science.
Maxwell published phenomenal work in two areas. First, building
upon the experimental data of Michael
Faraday, and applying highly sophisticated mathematical methods,
he predicted the existence of electromagnetic waves (1864).
Moreover, he calculated the waves would travel at the speed of
Later, Heinrich Hertz discovered these waves (1887) thereby
paving the way for radio, television, radar, and even the boom in
computer science. For Maxwell, the great mental
breakthrough came in thinking of electricity as an electromagnetic
not some sort of mechanical process.
"The true logic of
this world is in the calculus of probabilites."
James Clerk Maxwell
Maxwell's other spectacular contribution was in the dynamical theory of
gases. His first great paper in the field was published in
1859. Today this subject is part of thermodynamics.
Willard Gibbs, on the other side of the Atlantic at Yale University,
would join Maxwell in opening the door for exploration of the
physical and chemical properties of gases and other states of matter.
As is evident by his place of birth, Maxwell was the son of prosperous
parents. He was educated across town at the University of
Edinburgh, entering at the age of 16, and then Trinity College,
Cambridge. Eventually he became Cambridge University's first
teacher of experimental physics. He left retirement to serve as
the founding director of the Cavendish Laboratory of Cambridge
He is buried with his family in the church yard of
Parton Kirk, Galloway, Scotland.
| The house
where Maxwell was born is in a nice neighborhood near a park close to
the center of Edinburgh. The house now serves as a meeting place
for mathematicians and scientists and is home of the Foundation.
|Feynman on Maxwell's Contributions
the most dramatic moment in the development of physics during the 19th
century occurred to J. C. Maxwell one day in the 1860's, when he
combined the laws of electricity and magnetism with the laws of the
behavior of light. As a result, the properites of light were partly
unravelled -- that old and subtle stuff that is so important and
mysterious that it was felt necessary to arrange a special creation for
it when writing Genesis. Maxwell could say, when he was finished
his discovery, 'Let there be electricity and magnetism, and there
Feynman in The Feynman
Lectures on Physics, vol.
of the JCM Foundation at 14 India Street . . . .
"To promote, encourage, and advance the study of, research into, and
the dissemination of knowledge of and relating to physics, chemistry
and physical chemistry in all their aspects and in particular, but
without prejudice to the foregoing generality, colloids and interfaces."
Scotland has honored Maxwell
in a number of significant ways . . .
and at Yale
|Maxwell himself on how to visualize a
single center of electrified force . . . .
"I am anxious that these diagrams should
be studied as illustrations of the language of Faraday in speaking of
'lines of force,' the 'forces of an electrified body,' etc. . . .
Now the quantity of electricity in a body is measured, according to
Faraday's ideas, by the number
of lines of force, or rather of induction, which proceed from it.
These lines of force must all terminate somewhere, either on bodies in
the neighborhood, or on the walls and roof of the room, or on the
earth, or on the heavenly bodies, and wherever they terminate there is
a quantity of electricity exactly equal and opposite to that on the
part of the body from which they proceeded. By examining the
diagrams this will be seen to be the case.
These diagrams are constructed in the following
manner:- First, take the case of a single centre of
force, a small electrified body with a charge E. The potential at a
is V = (E/r); hence, if we make
r = (E/V), we shall find r, the radius of the sphere for
which the potential is V
If we now give to V the
values 1, 2, 3, etc., and draw the corresponding spheres, we shall
obtain a series of equipotential surfaces, the potentials corresponding
to which are measured by the natural numbers. The sections of
these spheres by a plane passing through their common centre will be
circles, which we may mark with the number denoting the potential of
each. These are indicated by the dotted circles on the right
James Clerk Maxwell, "An elementary treatise on electricity,"
of this material will join the National
Bank - A MATH Archive in thanking the Huntington Library, San
Marino, CA, for permitting us to enjoy Maxwell's explanation and
assuming there is no
or magnetic material (free space).
Note #4 is the same equation as
on the San Marino stamp.
Hertz on the left with Maxwell
on the right. | <urn:uuid:944e23b5-e2d2-48db-9603-b8e7fe4abc96> | 3.203125 | 1,160 | Knowledge Article | Science & Tech. | 47.083809 | 1,979 |
Penguins on a treadmill - the latest (and most bizarre) way to save the planet
Scientists put monitors on birds in expirement to chart global warming
Last updated at 21:17pm on 7th April 2007
They may look absolutely bizarre ... but these king penguins struggling on a treadmill could help to save the planet.
Scientists from Birmingham University have fitted 50 of the birds with special heart-rate monitors in an experiment designed to measure global warming.
They will record how much energy the birds are using in order to feed themselves. If the data shows they are making longer trips further into the oceans to find fish, it may prove waters are warming up and climate change is taking place.
Dr Lewis Halsey, of the university's School of Biosciences, said: "We are fairly confident that there have been changes in the southern oceans where these penguins live. We expect they will also have to change what they are doing when they go into the sea to feed.
"The lantern fish the penguins eat are going to be moving further south into colder waters as the southern oceans increase in temperature due to global warming.
"The penguins are going to have to go further afield - and burn more calories - to find them.
"We use the heart-rate monitors to find out how hard the penguins are working. Over time they will be working harder to find the fish."
The 'guinea pig' penguins live on the Crozet Islands, in the southern Indian Ocean, about 1,500 miles north of the Antarctic.
The monitors record each penguin's heart rate, location, the surrounding pressure and hence water depth, and the temperature at the back of its throat, telling the scientists when it has swallowed a cold fish.
The birds, famously awkward and ungainly on land, are released back into the wild to go on their usual diving expeditions and caught again a few months later when they return to land to breed.
The data from all their fishing trips can then be downloaded to a computer for study, and the penguins return to the colony.
The problem for the scientists was working out the relationship between the penguins' heart rates and how much energy they were expending.
To do this, ten penguins were placed on treadmills so their heart rates could be measured at the same time as breathing rate - calculated by putting the treadmill in a sealed, clear plastic box and monitoring how much oxygen they used.
The treadmill was speeded up and slowed down to find out how the penguin's heart rates changed at different levels of activity.
Then their height, weight and flipper length were compared to the heart rate and energy use.
This can be compared with birds living in the wild to see how much energy they use.
King penguins are the second largest penguins after the emperor species. They are about 3ft tall and can dive to 700ft, staying under water for up to 15 minutes. | <urn:uuid:aa5c3569-450b-4592-8c24-b4da2a5d538f> | 2.984375 | 613 | News Article | Science & Tech. | 55.960647 | 1,980 |
#include <stdlib.h>char *getpass(const char *prompt);
#include <unistd.h>char *getpass(const char *prompt);
The getpass() function opens the process's controlling terminal, writes to that device the null-terminated string prompt, disables echoing, reads a string of characters up to the next newline character or EOF, restores the terminal state and closes the terminal.
The getpassphrase() function is identical to getpass(), except that it reads and returns a string of up to 256 characters in length.
Upon successful completion, getpass() returns a pointer to a null-terminated string of at most PASS_MAX bytes that were read from the terminal device. If an error is encountered, the terminal state is restored and a null pointer is returned.
The getpass() and getpassphrase() functions may fail if:
The function was interrupted by a signal.
The process is a member of a background process attempting to read from its controlling terminal, the process is ignoring or blocking the
SIGTTIN signal or the process group is orphaned.
OPEN_MAX file descriptors are currently open in the calling process.
The maximum allowable number of files is currently open in the system.
The process does not have a controlling terminal.
The return value points to static data whose content may be overwritten by each call.
See attributes(5) for descriptions of the following attributes:
|ATTRIBUTE TYPE||ATTRIBUTE VALUE| | <urn:uuid:1960dbfd-a7c7-471a-bfcb-14f2049c3a7a> | 3.015625 | 323 | Documentation | Software Dev. | 43.052737 | 1,981 |
|Skip Navigation Links|
|Exit Print View|
|man pages section 3: Curses Library Functions Oracle Solaris 11 Express 11/10|
- get a single-byte character from the terminal
cc [ flag... ] file... -I /usr/xpg4/include -L /usr/xpg4/lib \ -R /usr/xpg4/lib -lcurses [ library... ] c89 [ flag... ] file... -lcurses [ library... ] #include <curses.h> int getch(void);
int wgetch(WINDOW *win);
int mvgetch(int y, int x);
int mvwgetch(WINDOW *win, int y, int x);
Is a pointer to the window associated with the terminal from which the character is to be read.
Is the y (row) coordinate for the position of the character to be read.
Is the x (column) coordinate for the position of the character to be read.
These functions read a single-byte character from the terminal associated with the current or specified window. The results are unspecified if the input is not a single-byte character. If keypad(3XCURSES) is enabled, these functions respond to the pressing of a function key by returning the corresponding KEY_ value defined in <curses.h>
Processing of terminal input is subject to the general rules described on the keypad(3XCURSES) manual page.
If echoing is enabled, then the character is echoed as though it were provided as an input argument to addch(3XCURSES), except for the following characters:
The input is interpreted as follows: unless the cursor already was in column 0, <backspace> moves the cursor one column toward the start of the current line and any characters after the <backspace> are added or inserted starting there. The character at the resulting cursor position it then deleted as though delch(3XCURSES) were called, except that if the cursor was originally in the first column of the line, the user is alerted as though beep(3XCURSES) were called.
The user is alerted as though beep() were called. Information concerning the function keys is not returned to the caller.
If the current or specified window is not a pad, and it has been moved modified since the last refresh operation, then it will be refreshed before another character is read.
The following is a list of tokens for function keys that are returned by the getch() set of functions if keypad handling is enabled (some terminals may not support all tokens).
Upon successful completion, these functions return the single-byte character, KEY_ value, or ERR. When in the nodelay mode and no data is available, ERR is returned.
No errors are defined.
Applications should not define the escape key by itself as a single-character function.
When using these functions, nocbreak mode (cbreak(3XCURSES)) and echo mode (echo(3XCURSES)) should not be used at the same time. Depending on the state of the terminal when each character is typed, the application may produce undesirable results.
See attributes(5) for descriptions of the following attributes: | <urn:uuid:a4abd555-36c3-4526-a217-f59c4fc072a3> | 2.828125 | 699 | Documentation | Software Dev. | 54.870903 | 1,982 |
The Application Programmer's Interface to Python gives C and C++ programmers access to the Python interpreter at a variety of levels. The API is equally usable from C++, but for brevity it is generally referred to as the Python/C API. There are two fundamentally different reasons for using the Python/C API. The first reason is to write extension modules for specific purposes; these are C modules that extend the Python interpreter. This is probably the most common use. The second reason is to use Python as a component in a larger application; this technique is generally referred to as embedding Python in an application.
Writing an extension module is a relatively well-understood process, where a ``cookbook'' approach works well. There are several tools that automate the process to some extent. While people have embedded Python in other applications since its early existence, the process of embedding Python is less straightforward than writing an extension.
Many API functions are useful independent of whether you're embedding or extending Python; moreover, most applications that embed Python will need to provide a custom extension as well, so it's probably a good idea to become familiar with writing an extension before attempting to embed Python in a real application. | <urn:uuid:da5fb3b0-48cd-4024-9047-45131b2274e3> | 2.96875 | 244 | Documentation | Software Dev. | 28.808571 | 1,983 |
Partition function (statistical mechanics)
In physics, a partition function describes the statistical properties of a system in thermodynamic equilibrium. They are functions of temperature and other parameters, such as the volume enclosing a gas. Most of the aggregate thermodynamic variables of the system, such as the total energy, free energy, entropy, and pressure, can be expressed in terms of the partition function or its derivatives.
There are actually several different types of partition functions, each corresponding to different types of statistical ensemble (or, equivalently, different types of free energy.) The canonical partition function applies to a canonical ensemble, in which the system is allowed to exchange heat with the environment at fixed temperature, volume, and number of particles. The grand canonical partition function applies to a grand canonical ensemble, in which the system can exchange both heat and particles with the environment, at fixed temperature, volume, and chemical potential. Other types of partition functions can be defined for different circumstances; see partition function (mathematics) for generalizations.
Canonical partition function
As a beginning assumption, assume that a thermodynamically large system is in constant thermal contact with the environment, with a temperature T, and both the volume of the system and the number of constituent particles fixed. This kind of system is called a canonical ensemble. Let us label with s = 1, 2, 3, ... the exact states (microstates) that the system can occupy, and denote the total energy of the system when it is in microstate s as Es. Generally, these microstates can be regarded as analogous to discrete quantum states of the system.
The canonical partition function is
where the "inverse temperature", β, is conventionally defined as
with kB denoting Boltzmann's constant. The exponential factor exp(−βEs) is known as the Boltzmann factor. (For a detailed derivation of this result, see canonical ensemble). In systems with multiple quantum states s sharing the same Es, it is said that the energy levels of the system are degenerate. In the case of degenerate energy levels, we can write the partition function in terms of the contribution from energy levels (indexed by j ) as follows:
where gj is the degeneracy factor, or number of quantum states s which have the same energy level defined by Ej = Es.
The above treatment applies to quantum statistical mechanics, where a physical system inside a finite-sized box will typically have a discrete set of energy eigenstates, which we can use as the states s above. In classical statistical mechanics, it is not really correct to express the partition function as a sum of discrete terms, as we have done. In classical mechanics, the position and momentum variables of a particle can vary continuously, so the set of microstates is actually uncountable. In this case we must describe the partition function using an integral rather than a sum. For instance, the partition function of a gas of N identical classical particles is
- pi indicate particle momenta
- xi indicate particle positions
- d3 is a shorthand notation serving as a reminder that the pi and xi are vectors in three dimensional space, and
- H is the classical Hamiltonian.
The reason for the factorial factor N! is discussed below. For simplicity, we will use the discrete form of the partition function in this article. Our results will apply equally well to the continuous form. The extra constant factor introduced in the denominator was introduced because, unlike the discrete form, the continuous form shown above is not dimensionless. To make it into a dimensionless quantity, we must divide it by h3N where h is some quantity with units of action (usually taken to be Planck's constant).
where Ĥ is the quantum Hamiltonian operator. The exponential of an operator can be defined using the exponential power series. The classical form of Z is recovered when the trace is expressed in terms of coherent states and when quantum-mechanical uncertainties in the position and momentum of a particle are regarded as negligible. Formally, one inserts under the trace for each degree of freedom the identity:
where |x, p⟩ is a normalised Gaussian wavepacket centered at position x and momentum p. Thus,
A coherent state is an approximate eigenstate of both operators and , hence also of the Hamiltonian Ĥ, with errors of the size of the uncertainties. If Δx and Δp can be regarded as zero, the action of Ĥ reduces to multiplication by the classical Hamiltonian, and Z reduces to the classical configuration integral.
Meaning and significance
It may not be obvious why the partition function, as we have defined it above, is an important quantity. First, let us consider what goes into it. The partition function is a function of the temperature T and the microstate energies E1, E2, E3, etc. The microstate energies are determined by other thermodynamic variables, such as the number of particles and the volume, as well as microscopic quantities like the mass of the constituent particles. This dependence on microscopic variables is the central point of statistical mechanics. With a model of the microscopic constituents of a system, one can calculate the microstate energies, and thus the partition function, which will then allow us to calculate all the other thermodynamic properties of the system.
The partition function can be related to thermodynamic properties because it has a very important statistical meaning. The probability Ps that the system occupies microstate s is
The partition function thus plays the role of a normalizing constant (note that it does not depend on s), ensuring that the probabilities sum up to one:
This is the reason for calling Z the "partition function": it encodes how the probabilities are partitioned among the different microstates, based on their individual energies. The letter Z stands for the German word Zustandssumme, "sum over states". This notation also implies another important meaning of the partition function of a system: it counts the (weighted) number of states a system can occupy. Hence if all states are equally probable (equal energies) the partition function is the total number of possible states. Often this is the practical importance of Z.
Calculating the thermodynamic total energy
In order to demonstrate the usefulness of the partition function, let us calculate the thermodynamic value of the total energy. This is simply the expected value, or ensemble average for the energy, which is the sum of the microstate energies weighted by their probabilities:
Incidentally, one should note that if the microstate energies depend on a parameter λ in the manner
then the expected value of A is
This provides us with a method for calculating the expected values of many microscopic quantities. We add the quantity artificially to the microstate energies (or, in the language of quantum mechanics, to the Hamiltonian), calculate the new partition function and expected value, and then set λ to zero in the final expression. This is analogous to the source field method used in the path integral formulation of quantum field theory.
Relation to thermodynamic variables
In this section, we will state the relationships between the partition function and the various thermodynamic parameters of the system. These results can be derived using the method of the previous section and the various thermodynamic relations.
As we have already seen, the thermodynamic energy is
The variance in the energy (or "energy fluctuation") is
The heat capacity is
The entropy is
Partition functions of subsystems
Suppose a system is subdivided into N sub-systems with negligible interaction energy, that is, we can assume the particles are essentially non-interacting. If the partition functions of the sub-systems are ζ1, ζ2, ..., ζN, then the partition function of the entire system is the product of the individual partition functions:
If the sub-systems have the same physical properties, then their partition functions are equal, ζ1 = ζ2 = ... = ζ, in which case
However, there is a well-known exception to this rule. If the sub-systems are actually identical particles, in the quantum mechanical sense that they are impossible to distinguish even in principle, the total partition function must be divided by a N! (N factorial):
This is to ensure that we do not "over-count" the number of microstates. While this may seem like a strange requirement, it is actually necessary to preserve the existence of a thermodynamic limit for such systems. This is known as the Gibbs paradox.
Grand canonical partition function
We can define a grand canonical partition function for a grand canonical ensemble, which describes the statistics of a constant-volume system that can exchange both heat and particles with a reservoir. The reservoir has a constant temperature T, and a chemical potential μ.
The grand canonical partition function, denoted by , is the following sum over microstates
Here, each microstate is labelled by , and has total particle number and total energy . This partition function is closely related to the Grand potential, , by the relation
This can be contrasted to the canonical partition function above, which is related instead to the Helmholtz free energy.
It is important to note that the number of microstates in the grand canonical ensemble may be much larger than in the canonical ensemble, since here we consider not only variations in energy but also in particle number. Again, the utility of the grand canonical partition function is that it is related to the probability that the system is in state :
An important application of the grand canonical ensemble is in deriving exactly the statistics of a non-interacting many-body quantum gas (Fermi-Dirac statistics for fermions, Bose-Einstein statistics for bosons), however it is much more generally applicable than that. The grand canonical ensemble may also be used to describe classical systems, or even interacting quantum gases.
See also
- J. R. Klauder, B.-S. Skagerstam, Coherent States --- Applications in Physics and Mathematical Physics, World Scientific, 1985, p. 71-73.
- Huang, Kerson, "Statistical Mechanics", John Wiley & Sons, New York, 1967.
- A. Isihara, "Statistical Physics", Academic Press, New York, 1971.
- Kelly, James J, (Lecture notes)
- L. D. Landau and E. M. Lifshitz, "Statistical Physics, 3rd Edition Part 1", Butterworth-Heinemann, Oxford, 1996.
- Vu-Quoc, L., Configuration integral, 2008 | <urn:uuid:2d23088a-355c-4d5a-89fb-97e7d23e4b29> | 3.453125 | 2,195 | Knowledge Article | Science & Tech. | 30.677008 | 1,984 |
sth is right. You can also use os.popen(), but where available (Python 2.4+) subprocess is generally preferable.
However, unlike some languages that encourage it, it's generally considered bad form to spawn a subprocess where you can do the same job inside the language. It's slower, less reliable and platform-dependent. Your example would be better off as:
baz is a directory and I'm trying to get the contents of all the files in that directory
? cat on a directory gets me an error.
If you want a list of files:
If you want the contents of all files in a directory, something like:
for leaf in os.listdir('/tmp/baz'):
path= os.path.join('/tmp/baz', leaf)
or, if you can be sure there are no directories in there, you could fit it in a one-liner:
foo= ''.join(open(os.path.join(path, child), 'rb').read() for child in os.listdir(path)) | <urn:uuid:ce066de4-b043-45a7-a206-5c651d394563> | 3.09375 | 228 | Q&A Forum | Software Dev. | 73.124533 | 1,985 |
Our Solar System: In Order From the Sun
7 of 10
The sixth planet from the Sun is the majestic Saturn. It takes 29 years for Saturn to make one trip around the Sun. Orbiting this giant, gas-filled planet are its famous rings. The rings are a collection of billions of boulder-sized chunks of ice. Saturn's intense gravitational field keeps its icy rings from clumping together.
Fun Fact: Saturn rotates rapidly, making each day only 10 hours long.
Photo source: NASA | <urn:uuid:b13dd7f6-d747-409d-9fd4-1edc25b78540> | 3.015625 | 104 | Listicle | Science & Tech. | 66.732143 | 1,986 |
See also the
Dr. Math FAQ:
Browse High School Sequences, Series
Stars indicate particularly interesting answers or
good places to begin browsing.
Selected answers to common questions:
Strategies for finding sequences.
- Adding Arithmetic Sequences [07/10/1998]
How do you add the numbers from 1 to 5000 without actually doing it or
using a calculator? What if you were adding just the odd numbers?
- Calculating the Fibonacci Sequence [11/28/1996]
Is there a formula to calculate the nth Fibonacci number?
- Decimal To Fraction Conversion [06/25/1998]
I am trying to find a method (one that can be programmed on a PC) to
convert the decimal part of a real number to a fraction represented by
integers for the numerator and denominator.
- Describing Patterns in Sequences [04/16/2002]
My students are able to identify the number patterns corresponding
to number sequences, but are having difficulty explaining them in
- Doubling Grains of Wheat [10/7/1996]
A man asked for 1 grain of wheat for the 1st square on a chess board, 2
grains for the 2nd square...
- Doubling Sequence [8/24/1996]
On Jan 1st it snowed one centimeter; on Jan 2, 2cm; on Jan 3, 4 cm...
- Fibonacci and Incoming Bits [09/08/99]
Given a transmitter sending 100 bits of random data over an ideal
communication channel, what is the probability that there will be three
consecutive 1's at least once in the sequence?
- Finding a Pattern [11/11/2001]
Give the next four numbers in the sequence: 2, 8, 7, 28.
- Finding a Rule for a Sequence [07/24/2003]
What is the next number in this sequence? 1, 3, 11, 67, ?
- Finding Sum Formula using Sequences of Differences [06/28/1998]
Finding a formula for the sum of the first n fourth powers using
sequences of differences.
- Finding the Pattern in a Series of Numbers [11/14/1995]
What is the pattern for 1, 8, 27...?
- Infinite square root [6/4/1996]
If y= sqrt(2+ sqrt(2+ sqrt(2+ sqrt(2+ ..., y=2,... how can I prove that
this is true, using normal properties of roots?
- Look-and-Say Sequence [02/14/2002]
I can't find the next six numbers: 1, 11, 21, 1211, 111221, ...
- Mean Proportionals and Geometric Means [01/06/1999]
How do you find the mean proportional of two numbers? What about two mean
proportionals? n mean proportionals?
- Next Number in a Sequence [03/13/2002]
Given any sequence, one can construct an infinite number of n-degree
polynomials that satisfy the sequence, hence discern an infinite number
of answers. What is the proof for this?
- Sequence Differences [06/24/2003]
The third and fourth terms of a sequence are 26 and 40. If the second
differences are a constant 4, what are the first five terms of the
- Strategies for Tests on Sequences [7/9/1996]
I have a problem answering test questions about number sequences.
- Sum of n Odd Numbers [7/11/1996]
Why is the sum of the first n odd numbers the square of n?
- The Traveling Bee [09/18/1998]
If a bee travels between two trains that are moving at 30 and 20 mi/hr
respectively, starting from 50 mi apart, how far does the bee travel?
- Unsolvable Equations [11/10/2001]
If I have an equation in the form of x^n+y^n=z, how do I solve for n?
- Why is Zero the Limit? [02/25/2002]
Why is zero called the limit of the terms in the sequence the limit of 1
over n, as n approaches infinity, equals zero?
- 121, 111211, 311221 Puzzle (Look and Say Sequence) [10/23/2001]
121, 111211, 311221 - what's the next number?
- 1, 7, 23, 55, 109, 191, ___ [10/03/2002]
My family is stumped on this number pattern: 1,7,23,55,109,191,___ ...
- 21^100 - Last Two Digits [09/04/1997]
What are the last two digits of 21 to the 100th power?
- 22/7 as an Approximation for Pi [04/01/1998]
Approximating pi by simple continued fractions.
- Activities to Find Pi [10/07/1998]
Can you suggest any classroom activities to find pi, other than the
standard way of measuring the circumferences and diameters of circles?
- Advanced Algebra [09/23/1997]
My teacher gave us this problem: 1+1/(1+1/(1+1/(1+1/1+...)))
- Alternating Harmonic Series [11/18/1997]
I am trying to find the proof for the sum of the alternating harmonic
series. I did find out that it is ln(2), but please tell me why?
- Alternating Sequence [01/27/1997]
Find a pattern and the next three numbers in the sequence: 0, 8, 27...
- Ant Walking in a Squared Spiral [06/02/1999]
An ant walks out a distance of 1 from the origin, down the x-axis. It
then turns left and goes up 1/2. If it continues turning left and going
the half the previous distance, where does the ant end up?
- Are All Infinitely Long Repeating Numbers Even? [06/06/2000]
Given an infinitely long repeating series, x = 12341234..., then 10000x =
123412341234... Since 9999 is odd and 12340000... is even, can we say
that x is even, and therefore all infinitely long repeating series are
- Arithmetical Progression [7/7/1996]
An arithmetical progression has a common difference of 1/1/2. The sum of
the first n terms is 365 and the sum of the first 2n terms is 1330.
Calculate the value of n and the first term.
- Arithmetic and Geometric Progressions [03/23/1998]
Given a set of conditions, can you find a specific term in an arithmetic
or geometric progression?
- Arithmetico-Geometric Series and Polylogarithms [07/06/2006]
Is there a closed form expression for the sum of the series
e^(-x) + 1/9 * e^(-3x) + 1/25 * e^(-5x) + 1/49 * e^(-7x) + ... ?
- Arithmetic Progression [12/19/1996]
If (b+c-a)/a, (c+a-b)/b and (a+b-c)/c are in arithmetic progression, show
that 1/a, 1/b and 1/c are also in arithmetic progression.
- Arithmetic Sequence Conundrum [10/11/2002]
For some real number T, the first three terms of an arithmetic
sequence are 2T, 5T - 1, and 6T + 2. What is the numerical value of
the fourth term?
- Arithmetic Sequences as Lines [09/05/2003]
In a sequence like -40, -25, -10, 5, ... is there a sure-fire way to
find the the general term?
- Arithmetic Series [5/19/1996]
How do you calculate a series like 2,4,6,8... for say 3 terms starting
anywhere in the series not by adding 3 specific terms together, but by
using the first term and the number 3?
- Arithmetic vs. Exponential Increases [05/06/1999]
What does "....the work produced... will increase exponentially rather
than arithmetically" mean?
- Average Yearly Depreciation [06/07/2002]
I'm trying to figure out the average depreciation per year for an
automobile, given its price history over several years. | <urn:uuid:63a82a0f-0053-44f2-bc7c-2f070a650f26> | 3.484375 | 1,866 | Q&A Forum | Science & Tech. | 86.677548 | 1,987 |
July 17, 2012
Sea ice extent in June since 1979. Graph courtesy of NOAA.
Worldwide, temperatures were 0.63 degrees Celsius (1.13 degrees Fahrenheit) above the average temperature of the 20th Century. In the Northern Hemisphere—where much of Russia and North America sweltered under heatwaves—the temperature was 1.3 degrees Celsius (2.34 degrees Fahrenheit) above normal. Meanwhile, the Arctic has also been significantly warmer than normal resulting in a record drop in sea ice during the month. Sea ice is now at its second lowest extent recorded for this time of year.
The first six months of 2012 have put it on track to be the eleventh warmest year on record, though that is likely to change depending on the next six months. As La Nina conditions dissipated in the Spring, the year has increasingly seen more abnormal warmth. Currently, the world remains in a neutral phase, yet El Nino could start soon.
Overall, the world is warming due to climate change with global temperatures up 0.8 degrees Celsius (1.44 degrees Fahrenheit) since the early 20th Century. | <urn:uuid:8bef5cc8-07c4-4ea9-8ee7-a0fdf992094a> | 3.53125 | 229 | News Article | Science & Tech. | 60.698069 | 1,988 |
WASHINGTON, D.C.--The Opportunity rover has found strong evidence that eons ago water flowed across Mars, pooled on the surface, and then returned to the atmosphere, leaving behind a thick layer of minerals leached from the land. "We've found our ancient water on Mars," says rover science team member Harry McSween of the University of Tennessee, Knoxville.
At a press conference at NASA headquarters here today, rover principal investigator Steven Squyres of Cornell University ticked off the evidence for a soaking wet Mars he and his team had developed from Opportunity observations of the previous weeks. The new findings don't prove that Mars ever sustained life or even that Mars was ever as warm and wet as Earth has been. However, they do mean that at least in one patch the size of Oklahoma, water soaked the rock for age upon age, which is all that life could ask for.
Part of the evidence involves the structure of the outcrop. The round balls 2 or 3 millimeters in diameter seen weathering out of the rock, they decided, resemble "concretions" that grow as mineral-laden water lays down salts in the rock pores. Also indicative are vugs, "very weird-looking, tabular holes" that riddle the rock, in Squyres's words. They are probably the voids left by now vanished crystals of gypsum--to judge by their shape--that grew from mineral-laden water.
The mineralogy is telling, too. The rover's spectrometer found high concentrations of jarosite, an iron-rich mineral "you have to have water around to make," said Squyres. Another sign of water was chemical. The rover's alpha particle x-ray spectrometer found "an enormous quantity of sulfur in this rock," said Squyres. "It must be full of sulfate, a telltale sign of liquid water." The rover's minithermal emission spectrometer also saw abundant signs of sulfate in the infrared colors of the rock, much of it probably magnesium sulfate, the familiar epsom salts. "This is an astonishing amount of salt," said Benton Clark, a science team member at Lockheed Martin in Denver. On Earth, such an abundance of salts most often forms when water carrying dissolved material pools and then evaporates.
All this salty water on early Mars tells team members that water soaked the subsurface or, more likely, the bottom of a lake or ocean. "We may never know which," said Squyres, "but we're going to give it our best shot."
Background and news about the Mars rovers | <urn:uuid:3778b983-fc58-4e01-8c12-3a9e91bf6a06> | 3.71875 | 538 | News Article | Science & Tech. | 49.049968 | 1,989 |
Even for the lucky few creatures that are preserved in the fossil record, soft tissues such as skin and feathers typically disappear over time. But a newly developed technique has found a way to bring them back to life in some cases. Researchers have now used the approach to resurrect the teeth and recognize the carcass of a 50-million-year-old fossil of a lizard, long thought to be merely preserved remnants of skin shed from the reptile.
"This is incredibly uncharted territory," says Gregory Erickson, a vertebrate paleontologist at Florida State University in Tallahassee. "This technique reveals that there's literally more to fossils than meets the eye."
Discovered in the 1980s, the lizard fossil is one of only two known examples of reptile skin unearthed from the Green River Formation of the western United States, a finely layered mudstone best known for its exquisite fish fossils. Even though soft tissues are incredibly rare in the fossil record, being preserved only in unusual environmental circumstances, this lizard fossil survived the ages, says Phillip Manning, a vertebrate paleontologist at the University of Manchester in the United Kingdom. It's easy to see the remnants of individual scales in the skin, but the rock doesn't include any visible remains of bones or other hard tissue—a combination that led researchers to believe that the skin had been shed by a living creature and then preserved.
But recently, to learn more about the fossil, Manning and his colleagues turned to a relatively new x-ray analysis technique—dubbed synchrotron rapid scanning x-ray fluorescence—with surprising results. Instead of enabling scientists to see inside or through rock, he notes, the intense x-rays produced by this technique cause particular elements or compounds to fluoresce, revealing previously unrecognized chemical remnants that are invisible to the naked eye but persist in the rocks at very low concentrations.
When the researchers illuminated the fossil with x-rays that cause sulfur and copper to fluoresce, the skin remnants showed up in remarkable detail. But when they lit the fossil with x-rays that cause phosphorus to glow, the technique revealed many small spots in the lizard's head where that element was concentrated—regularly spaced spots that appear where the creature's jaws would have been. The arrangement prompted the researchers to interpret the traces of phosphorus as the chemical remnants of teeth. Because lizards don't shed their teeth when they molt their skin, the technique reveals the unusual fossil to be the partially preserved remnants of a full carcass, the researchers report online this month in Applied Physics A: Materials Science & Processing.
The fossil's state of preservation reveals a lot about the environmental conditions where the carcass ended up, presumably after being washed into the lake soon after it died. Lake-bottom waters at this particular spot likely had little or no oxygen, enabling preservation of the skin. But the waters apparently were also acidic, which totally dissolved the creature's bones and left only scant traces of its teeth. The chemical vestiges of the teeth were most likely preserved because tooth enamel typically has a low concentration of organic matter and large crystals of phosphate minerals, both of which render the teeth more resistant to decay.
The x-ray technique the team used "will open the curtain to a whole new way of studying extinct animals and the conditions in which they lived and died," Manning says. Another benefit of the approach, he notes, is that it's nondestructive.
Previous studies using the technique have revealed the chemical residues of pigments in feathers, providing insight into the color patterns that ancient birds might have sported. The technique also offers the opportunity to discern remnants of soft tissues that are only rarely preserved, such as the pigment-filled retinas of eyes, the ink sacs of ancient squid, and possibly other tissues such as muscles—at least as far as the naked eye is concerned.
Results of the new study "are fantastically interesting," says Mark Norell, a vertebrate paleontologist at the American Museum of Natural History in New York City. "There's a whole lot more preserved with fossils than we ever thought there was."
Erickson agrees. "This technique will prompt paleontologists to revisit a lot of classic fossils," he says. "Who knows what got missed during the first 150 years of paleontology?" | <urn:uuid:a6de1d41-a1d3-4d41-85bc-bf3da2402612> | 3.890625 | 881 | News Article | Science & Tech. | 31.796675 | 1,990 |
Several oil slicks occurred on Lake Maracaibo in northwestern Venezuela between December 2002 and January 2003, and were observed by various satellite instruments. These images from the Multi-angle Imaging SpectroRadiometer (MISR) provide new information relating to one such event near the center of Lake Maracaibo on December 26, 2002.
In unpolluted areas, the water surface is "ruffled" by wind and the resulting wave facets divert reflected rays into many directions. An oil film dampens the presence of small wind-driven "capillary" waves, resulting a smoother, more mirror-like surface. Also, oil is more strongly absorbing than the surrounding water. Therefore, at most viewing angles, a surface slick will appear darker than the surrounding unpolluted areas, whereas near the specular angle (the angle at which a perfect mirror reflects light) it will appear brighter. Simultaneous observation at multiple view angles therefore enhances the reliability of oil-slick detection using optical imaging.
An example of how the optical contrast of an oil film on a water surface changes as a function of viewing angle is illustrated by these false-color MISR images, comprised of near-infrared, red and blue spectral data at three different angles, using the vertical-viewing camera (left), the 26°-forward-viewing camera (center) and the 46°-forward-viewing camera (right). A swirly area in the middle of the lake appears darker than the surrounding waters at both the nadir and 46° views, but brighter than the surrounding waters at the 26° view. Of the three images, only the 26° camera observes close to specular reflection angle.
Lake Maracaibo is the largest lake in South America. The lake is somewhat saline, since it is connected to the Gulf of Venezuela by a narrow strait in the north. Venezuela is the largest oil producing nation in the Western Hemisphere, and the Lake Maracaibo basin includes the largest oil fields and almost a quarter of this nation's population.
The Multi-angle Imaging SpectroRadiometer observes the daylit Earth continuously from pole to pole, and every 9 days views the entire globe between 82 degrees north and 82 degrees south latitude. These data products were generated from a portion of the imagery acquired during Terra orbit 16081. The panels cover an area of 72 kilometers x 225 kilometers, and utilize data from blocks 81 to 83 within World Reference System-2 path 8.
MISR was built and is managed by NASA's Jet Propulsion Laboratory, Pasadena, CA, for NASA's Office of Earth Science, Washington, DC. The Terra satellite is managed by NASA's Goddard Space Flight Center, Greenbelt, MD. JPL is a division of the California Institute of Technology. | <urn:uuid:2e9cc51d-c5e6-4e53-83c3-01dbbdcf5254> | 3.34375 | 568 | Knowledge Article | Science & Tech. | 33.261518 | 1,991 |
The public and scientists have helped create the first 150,000 species pages in the Encyclopedia of Life (EOL), the global online project to create a page for each of the 1.8 million known species on the planet.
It may be less than one tenth of the way there, but the response of people who have uploaded more than 30,000 images and videos, has been huge say EOL, especially since new tools have been installed to make it easier to add to the site.
It isn't only experts who can contribute to the site. People with an interest in nature but no special scientific training, known as citizen scientists, can add information. For example, images can be uploaded through the EOL's Flickr page.
Each EOL page is verified by experts, and scientists from all over the world can add species information, from physical descriptions to details of habitat, diseases, look-alikes and even DNA barcodes.
The information will shed light on things such as conservation strategies for endangered species, or climate change and the movements of disease-bearing or invasive pests.
David Lees, is an expert on moths and butterflies at the Natural History Museum and at INRA (French National Institute for Agricultural Research), France.
He has created an EOL species page to mark the 25th anniversary of the discovery in Europe of an invasive moth called the horse chestnut leafminer, Cameraria ohridella. It is ravaging the leaves of the white-flowered horse chestnut tree, popular not only for its flowers in spring but for the game of conkers.
'Like the opening of Pandora's box, this moth, first discovered at Lake Ohrid in Macedonia in 1984, has spread like wildfire after a probable accidental release near Vienna in 1989,' says Lees.
Representing a genus not known before in Europe, its origins had been a mystery, but this year entomologists at INRA working on the diversity of its DNA have shown it originated in the Balkans, the source of the horse chestnut tree itself.
The moth does not kill the tree, but can completely brown the leaves by summer, causing councils to replace the trees with other species. In some parts of Europe, it is starting to infest nearby sycamores as well.
'This moth is now more or less throughout Europe and poses a threat to ecosystems in Southeast Asia, North America and elsewhere - wherever the beautiful horse chestnut trees occur,' says Lees.
EOL will help raise awareness of invasive species through detailed species descriptions to help with identification, and regularly updated maps to show their spread. Hopefully, this will allow effective control measures to be carried out more quickly.
Encyclopedia of Life (EOL) -- www.eol.org/
EOL page in Flickr -- www.flickr.com/groups/encyclopedia_of_life
Provided by Natural History Museum
Explore further: Bittersweet: Bait-averse cockroaches shudder at sugar | <urn:uuid:139eca28-c244-4ae0-94ec-7844eca4df50> | 3.609375 | 614 | News Article | Science & Tech. | 41.110667 | 1,992 |
This is a case of an unwisely chosen simile taken waaaay too far. This idea, that the entire universe could be inside the event horizon of not a supermassive, but rather a superduperultrahypermegastupendouslymassive black hole, is usually introduced in introductory classes about general relativity. The instructor in this case is trying to make clear that, contrary to a fairly popular misconception, the event horizon of a black hole is locally flat. That is, there are no CGI-fireworks, nor any kind of hard "surface", nor anything else particularly special, in the immediate vicinity of the event horizon. The only special thing that happens is a long distance effect, like noticing that every direction now points off in the distance towards the singularity.
The simile is also used to point out that, at the event horizon, even second-order, nearly local effects (that is, curvature of spacetime, or tidal effects in other words) become less pronounced the more massive the black hole is. (As an aside, this also explains why Hawking radiation is more intense for smaller black holes) So... as the simile suggests, if the black hole were massive enough, we might not even be able to detect it.
The key, though is massive enough. First of all, the whole beauty of the Einstein curvature tensor (the left side of Einstein's equation) is that it is Lorentz invariant, so it can be calculated in any reference frame, including one that is hypothetically based inside an event horizon.
The curvature can still be unambiguously calculated, so when you suggest that it may be only an optical illusion, you are also suggesting that all the scientists who do that type of large-scale curvature calculation (not me personally) are totally incompetent. Just so you know. I would suggest not mentioning that at any conferences on cosmology. One of the enduring mysteries of modern cosmology is that the large-scale curvature of the Universe seems to be open (like the 3-space-plus-one-time dimensional analog of a saddle or Pringle potato chip) and not flat (like Euclidean geometry) or closed (like a sphere). The last is what we would calculate if the visible Universe were inside a black hole.
So, for the visible Universe to be inside an event horizon, the Cosmic Acceleration we have seen thus far would have to actually just be one small, contrarian region inside an even larger event horizon of globally closed curvature. Just to make the event horizon radius 13.7 giga-lightyears (a bare minimum starting point that excludes all manner of things that make the real situation many orders of magnitude worse*), you would need over 8E52 kg of mass in the singularity. This would require over 5E79 protons, where I have heard that the entire visible Universe only has about 10^80 particles, total, and I think I heard that there are about 10^18 photons for every proton, or maybe even all other particles. Somebody can look that up if they want to, but it's definitely a big number. The upshot is that there would have to be an amount of mass, all crammed into one singularity, that would render the total mass of every single thing we can see a barely detectable rounding error. Monkeying with all those dark matter and even dark energy theories is less of a leap than that.
Your prediction doesn't actually predict anything, since you account for either its presence or its absence.
Speculation 1: Olber's Paradox is already solved for accepted theories of cosmology, so pointing out that your theory can also resolve it is nice but doesn't score any points.
Speculation 2: Are you suggesting that the singularity is where all the antimatter to match the Universe's matter went? Remember the singularity dwarfs the visible Universe. That still doesn't explain the asymmetry, it only pushes the question back by one logical step: Why did the antimatter go into the big singularity and not the matter?
Speculation 3: Hawking radiation for the big singularity's event horizon lends whole new meaning to the term negligible. See my previous aside. Also, we can't observe matter being destroyed at the singularity. That's information flowing the wrong way. Also, that negates the previous assertion that the sky is black because it's towards the singularity.
*Like cosmic expansion, just how small our contrarian region is, compared to the whole event horizon, and probably some other, subtler things. | <urn:uuid:25ce42b8-4cc2-4cf1-9891-c2a28713ea4b> | 2.53125 | 941 | Q&A Forum | Science & Tech. | 35.906256 | 1,993 |
|Spend the time||outdoors|
All you need is a camera or a camera trap so that you can photograph African mammals. The quality of the photographs needs to be good enough to allow us to identify the animal in the image.
A handheld GPS device is useful, but not essential as we have a link to Google Maps on our website that allows citizen scientists to identify the location of their photographs.
|Help update the distribution records of African mammal species.|
|Add your recent photos of animals photographed in Africa.|
THE BROAD PICTURE: The aim of MammalMAP is to update the distribution records of all African mammal species. Through collaborations with professional scientists, conservation organisations, wildlife authorities and citizen scientists across Africa, we consolidate all reliable and identifiable evidence (camera trap records, photographs) of current mammal locations into an open-access digital database. The database software automatically generates online distribution maps of all recorded species which are instantly visible and searchable. The information consolidated within MammalMAP will not only yield crucial information for species conservation policies and landscape conservation policies, but provides an excellent platform for educating the public about African mammals and their conservation challenges.
WHY MAMMALMAP IS NECESSARY: In Africa, our knowledge of mammal distribution patterns is based largely on historical records. However, the last three centuries have seen extensive human-modification of African landscapes with the associated conversion, compression and fragmentation of natural land. With further land development presenting a likely reality for the future, the effectiveness of mammal conservation efforts depends on ecological records being updated so that they accurately reflect mammal distribution patterns in the 21st Century. With MammalMAP we plan to conduct these ecological updates over the coming years, by mapping the current distribution of mammal species (including marine mammals and small mammals) across Africa.
HOW MAMMALMAP CONTRIBUTES TO CONSERVATION: The conservation benefits of this research are multiple. First, the comparison of these updated distribution records with both historical and future records will enable the detection of species’ distribution changes in response to human-related and climate-related habitat changes. These change detections will assist the guidance of continent-wide conservation policies and decision making processes. Second, the research will promote and facilitate interdisciplinary and international collaboration amongst scientists and conservation practitioners, with potential benefits to the advancement of conservation science. Finally, both the project input stage (data collection) and output stage (data dissemination) will offer interactive, dynamic and widely applicable education tools suitable for both formal and informal education sectors.
THE WHERE AND THE HOW OF MAMMALMAP: The area of interest for MammalMAP is the whole of Africa. To achieve this we collaborate with scientists, conservation organisations, wildlife authorities and citizen scientists across the continent. Our methods involve consolidating evidence of mammal occurrence in a given location (camera trap records, photographs and other reliable records) into a digital database hosted by the Animal Demography Unit (ADU) at the University of Cape Town. In time, we will use the records in the database to generate distribution maps for all recorded species, in the same way that the ADU has done for birds, reptiles, frogs and butterflies. | <urn:uuid:7c83764a-53a6-45af-88ad-b5b6c2ba98de> | 2.90625 | 645 | About (Org.) | Science & Tech. | 3.665611 | 1,994 |
A reentrant lock is one where a process can claim the lock multiple times without blocking on itself. It's useful in situations where it's not easy to keep track of whether you've already grabbed a lock. If a lock is non re-entrant you could grab the lock, then block when you go to grab it again, effectively deadlocking your own process.
Reentrancy in general is a property of code where it has no central mutable state that could be corrupted if the code was called while it is executing. Such a call could be made by another thread, or it could be made recursively by an execution path originating from within the the code itself.
If the code relies on shared state that could be updated in the middle of its execution it is not re-entrant, at least not if that update could break it.
A use case for re-entrant locking
A (somewhat generic and contrived) example of an application for a re-entrant lock might be:
You have some computation involving an algorithm that traverses a graph (perhaps with cycles in it). A traversal may visit the same node more than once due to the cycles or due to multiple paths to the same node.
The data structure is subject to concurrent access and could be updated for some reason, perhaps by another thread. You need to be able to lock individual nodes to deal with potential data corruption due to race conditions. For some reason (perhaps performance) you don't want to globally lock the whole data structure.
You computation can't retain complete information on what nodes you've visited, or you're using a data structure that doesn't allow 'have I been here before' questions to be answered quickly.
An example of this situation would be a simple implementation of Dijkstra's algorithm with a priority queue implemented as a binary heap or a breadth-first search using a simple linked list as a queue. In these cases, scanning the queue for existing insertions is O(N) and you may not want to do it on every iteration.
In this situation, keeping track of what locks you've already acquired is expensive. Assuming you want do the locking at the node level a re-entrant locking mechanism alleviates the need to tell whether you've visited a node before. You can just blindly lock the node, perhaps unlocking it after you pop it off the queue.
A simple mutex is not re-entrant as only one thread can be in the critical section at a given time. If you grab the mutex and then try to grab it again a simple mutex doesn't have enough information to tell who was holding it previously. To do this recursively you need a mechanism where each thread had a token so you could tell who had grabbed the mutex. This makes the mutex mechanism somewhat more expensive so you may not want to do it in all situations.
IIRC the POSIX threads API does offer the option of re-entrant and non re-entrant mutexes. | <urn:uuid:c78af1d7-ca10-4975-a938-d2dea12b4a6b> | 3.0625 | 622 | Q&A Forum | Software Dev. | 50.108782 | 1,995 |
Editors: Rainer Beck, Heinz Hilbrecht, Klaus Reinsch and Peter Völker
Hardcover: 546 pages
This book is not so much about the Sun, but about the opportunities for amateur astronomers to observe the Sun. Compared with other areas of astronomy solar observing has a number of advantages:
• Observation can be carried out during the day. You do not have to stay up all night and arrive at work the next day exhausted!
•There is an abundance of light. Unlike "Deep Sky" astronomy you actually have to discard much of the light reaching your telescope.
• You can set up your observatory in your own backyard - even in the city -there is no need to escape light pollution at remote locations.
• Observations can be made practically every clear day and some simple programs like sunspot counts can be done in just a few minutes.
• You do not need a monster telescope, even a small telescope will show an amazing amount of detail.
• The view is constantly changing, the Sun's appearance has never been, nor will it ever be exactly the same as today.
This book was conceived and written by a group of German amateur observers. Each section was the responsibility of the amateur who had made that aspect of solar astronomy his specialty. The emphasis was on the practical and covers the kind of solar astronomy within the reach of most amateurs. Soon after publication it was declared by many reviewers as the "standard work" and much correspondence reached the authors from abroad requesting an English translation. In terms of content the basic information in the original German edition will be found here. Where necessary, updating has taken place and errors have been corrected. Numerous passages were revised taking into account the larger, inter-national circle of readers, many pictures have been added and references to German-language literature have been changed, where possible, to appropriate English-language works. The book is divided into four major parts. Part A describes instruments used in solar astronomy, offers help in making decisions with regard to buying, and provides instructions for those who might build their own instrument. Part B deals with the many different amateur observation possibilities. Part C gives encouragement and help in planning and carrying out expeditions to observe solar eclipses and gives details on observation. Part D is an extensive bibliography especially tailored for the amateur solar astronomer. Each chapter of the book is self-contained in terms of contents and the reader can turn to those subjects which interest him or her the most. Numerous cross-references are embedded within the text to point the reader to related sections. | <urn:uuid:d470a64c-439a-425d-8ff0-cd5f2c188cbb> | 2.921875 | 526 | Product Page | Science & Tech. | 38.598518 | 1,996 |
Characters of Permutation Representations
Let’s take to be a permutation representation coming from a group action on a finite set that we’ll also call . It’s straightforward to calculate the character of this representation.
Indeed, the standard basis that comes from the elements of gives us a nice matrix representation:
On the left is the matrix of the action on , while on the right it’s the group action on the set . Hopefully this won’t be too confusing. The matrix entry in row and column is if sends to , and it’s otherwise.
So what’s the character ? It’s the trace of the matrix , which is the sum of all the diagonal elements:
This sum counts up for each point that sends back to itself, and otherwise. That is, it counts the number of fixed points of the permutation .
As a special case, we can consider the defining representation of the symmetric group . The character counts the number of fixed points of any given permutation. For instance, in the case we calculate:
In particular, the character takes the value on the identity element , and the degree of the representation is as well. This is no coincidence; will always be the degree of the representation in question, since any matrix representation of degree must send to the identity matrix, whose trace is . This holds both for permutation representations and for any other representation. | <urn:uuid:9ac5eacd-bf7d-47ac-8347-1bfd2b5cef0c> | 2.875 | 296 | Knowledge Article | Science & Tech. | 49.679185 | 1,997 |
Coastal & Marine Geology InfoBank
Our Mapping Systems
The USGS and Science Education
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ground penetrating radar
Comment: 11:53 - 13:06 (01:13)
Source: Annenberg/CPB Resources - Earth Revealed - 4. The Sea Floor
Keywords: subduction, "Grand Canyon", vessel, instrument, "camel-grab", "box corer", "James Sadd"
Our transcription: Subduction begins at enormous underwater trenches, some of them several times deeper than the Grand Canyon.
Because of the great depth, marine geologists have had to come up with a host of ingenious ways of exploring the deep sea floor.
The primary tool used by Earth scientists to study the ocean floor is a research vessel like this one, outfitted with a variety of oceanographic sampling instruments.
Mounted on the stern of the vessel, is this A-frame, which is a hydraulically movable rack used to lift and deploy the instruments.
The oceanographic sampling instruments are tethered to the vessel with this steel cable wound around a revolving drum.
Scientists can take a bite of sediment or rock from the ocean bottom using a sampling instrument like this "camel-grab".
It takes sediment samples very quickly but only of the upper few centimeters of ocean bottom.
Often times, an undisturbed sample of the deeper layers is required to examine variations in the accumulated sediment on the ocean bottom with time.
This "box corer" takes an entire column of sediment, which later can be split open and the individual layers analyzed like pages in a book.
Geology School Keywords | <urn:uuid:42b1e945-abcd-4ae4-9b84-8465df6d50b2> | 4.03125 | 343 | Knowledge Article | Science & Tech. | 37.567739 | 1,998 |
PARIS – Scientists have made an incredible discovery on an asteroid that may prove a highly debated theory!
An asteroid has provided evidence of water ice, as well as organic compounds which bolster a leading theory for the origins of life on Earth. Scientists made their findings by studying 24 Themis, an asteroid about 479 million kilometers from the sun, which is one of the largest asteroids in the solar system.
“Up until now there was no sign that asteroids had any abundant organics or ice on them,” said Joshua Emery, an astronomer at the University of Tennessee and one of the authors of the studies. His discovery, along with other scientists, may provide the evidence for the possibility that the essential building blocks for life came from asteroids.
Asteroids have mostly been known to be devoid of water due to their proximity to the sun, with comets being the ones to contain water because they form farther out in space.
“We had previously thought that only the comets could have brought a lot of water to Earth,” said Andrew Rivkin, researcher at John Hopkins University and one of the lead authors of the studies. “But we now have more reasons to think that the asteroid impacts may also have brought a significant amount, especially if each one might have 20 to 30 percent water.”
Scientists now plan to scan the asteroid belt for more evidence of water and organic materials, hoping to determine if 24 Themis is just a comet that got stuck in the asteroid belt or an actual water-bearing asteroid. | <urn:uuid:77e6c6a4-77b6-45ae-b865-e56d51d812bc> | 3.859375 | 314 | News Article | Science & Tech. | 36.603342 | 1,999 |