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Study alters Greenland glacier melt view
Leeds, England (UPI) Jan 26, 2011
Warm summer temperatures may not melt the Greenland ice sheet as fast as previously feared and may actually slow the flow of glaciers, British researchers say.
Scientists at the University of Leeds say they believe increased melting in warmer years causes the internal drainage system of the ice sheet to adapt and accommodate more melt-water without speeding up the flow of ice toward the oceans, a university release said Wednesday.
The Greenland ice sheet covers roughly 80 percent of the island and contains enough water to raise sea levels by 22 feet if it were to melt completely.
Rising temperatures in the Arctic in recent years have caused the ice sheet to shrink, prompting fears that it may be close to a tipping point of no return.
The Leeds researchers used satellite observations of six landlocked glaciers in southwest Greenland to study how ice flow develops in years of markedly different melting.
"It had been thought that more surface melting would cause the ice sheet to speed up and retreat faster, but our study suggests that the opposite could in fact be true," Professor Andrew Shepherd from the university's School of Earth and Environment said. "If that's the case, increases in surface melting expected over the 21st century may have no affect on the rate of ice loss through flow.
"However, this doesn't mean that the ice sheet is safe from climate change, because the impact of ocean-driven melting remains uncertain," he said.
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Beyond the Ice Age
Santa Barbara CA (SPX) Jan 27, 2011
A new scientific study shows that debris coverage - pebbles, rocks, and debris from surrounding mountains - may be a missing link in the understanding of the decline of glaciers. Debris is distinct from soot and dust, according to the scientists. Melting of glaciers in the Himalayan Mountains affects water supplies for hundreds of millions of people living in South and Central Asia. Expert ... read more
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MSYNCSection: Linux Programmer's Manual (2)
Index Return to Main Contents
NAMEmsync - synchronize a file with a memory map
DESCRIPTIONmsync() flushes changes made to the in-core copy of a file that was mapped into memory using mmap(2) back to disk. Without use of this call there is no guarantee that changes are written back before munmap(2) is called. To be more precise, the part of the file that corresponds to the memory area starting at start and having length length is updated.
The flags argument may have the bits MS_ASYNC, MS_SYNC, and MS_INVALIDATE set, but not both MS_ASYNC and MS_SYNC. MS_ASYNC specifies that an update be scheduled, but the call returns immediately. MS_SYNC asks for an update and waits for it to complete. MS_INVALIDATE asks to invalidate other mappings of the same file (so that they can be updated with the fresh values just written).
RETURN VALUEOn success, zero is returned. On error, -1 is returned, and errno is set appropriately.
- MS_INVALIDATE was specified in flags, and a memory lock exists for the specified address range.
- start is not a multiple of PAGESIZE; or any bit other than MS_ASYNC | MS_INVALIDATE | MS_SYNC is set in flags; or both MS_SYNC and MS_ASYNC are set in flags.
- The indicated memory (or part of it) was not mapped.
AVAILABILITYOn POSIX systems on which msync() is available, both _POSIX_MAPPED_FILES and _POSIX_SYNCHRONIZED_IO are defined in <unistd.h> to a value greater than 0. (See also sysconf(3).)
B.O. Gallmeister, POSIX.4, O'Reilly, pp. 128-129 and 389-391. | <urn:uuid:b08500ca-0756-47db-9541-dff77bf8d4d7> | 2.78125 | 433 | Documentation | Software Dev. | 55.864624 |
Features formed from those igneous rocks that have reached or nearly reached the Earth's surface before solidifying. [Adapted from Glossary of Geology, 4th ed.]
Alexandria Digital Library Feature Type Thesaurus
Earth tides and volcano monitoring [ More info] Article in the May 28, 1998 issue of Volcano Watch describing of correlation of earth tides to volcanic eruptions and value in monitoring underground magma movement with deformation measurement instruments including tiltmeters and strainmeters.
Encounters of aircraft with volcanic ash clouds; A compilation of known incidents, 1953-2009 [ More info] Of 129 reported incidents, 94 are confirmed ash encounters, 79 of which entailed airframe or engine damage; 20 are low-severity events involving suspected ash or gas clouds; for 15 the data are insufficient to assess severity.
Eruptions from the Inyo chain about 600 years ago: sequence of events and effects in the Long Valley Area [ More info] Describes the volcanic activity that occurred along the southern part of the Mono-Inyo Craters volcanic chain in California about 600 years ago.
Eruptions in the Cascade Range during the past 4,000 years [ More info] Chart showing 13 volcanoes on a map of Washington, Oregon, and northern California, along with time lines for each volcano showing the ages of their eruptions.
Eruptions of Hawaiian volcanoes - past, present, and future [ More info] Originally published in 1987, this general-interest booklet has been revised in anticipation of the Centennial of the Hawaiian Volcano Observatory (HVO) in January 2012.
Eruptions of Lassen Peak, California, 1914 to 1917 [ More info] Summary of the most recent eruption of Lassen Peak, Cascades (1914-1917)
Eruptions of Mount St. Helens: past, present, future [ More info] Online booklet on the 1980 eruption of Mount St. Helens, past history, and future hazards.
Geologic hazards at volcanoes [ More info] Poster diagram showing the various hazards that accompany volcanic activity as they relate to the structure of the volcano.
Geologic history of Long Valley Caldera and the Mono-Inyo Craters volcanic chain, California [ More info] Summarizes the geologic and volcanic activity of the Long Valley Caldera and Mono-Inyo Craters volcanic chain in east central California.
Hawaiian Volcano Observatory [ More info] Hawaiian Volcano Observatory's latest news with links to information on Kilauea, Mauna Loa, and other volcanoes, earthquakes, volcanic hazards, photo archive, and general information about the center.
Alphabetical Index of Topics
a b c d e f g h i j k l m n o p q r s t u v w x y z | <urn:uuid:5b0c8445-e142-499d-bdcc-20231a3c1ca4> | 3.40625 | 577 | Content Listing | Science & Tech. | 23.172354 |
Meitnerium: the essentials
Element 109, meitnerium, is a synthetic element that is not present in the environment at all. There is no dispute concerning the name meitnerium for element 109.
The interested reader should consult the on-line version of The Wonderful World of Atoms and Nuclei for a fascinating insight into research on "super-heavy" atoms.
Meitnerium: historical information
In August 1982 the first atom of the element meitnerium with atomic number 109 was detected at the Gesellschaft für Schwerionenforschung (GSI) in Darmstadt, Germany. The isotope of element 109 which was discovered has an atomic mass number of 266 (that is, 266 times heavier than hydrogen). The new element was produced by fusing an iron (58Fe) and a bismuth atom (209Bi) together in a reaction that produces a neutron. This was achieved by accelerating the iron atoms to a high energy in the heavy ion accelerator UNILAC at GSI.
Meitnerium: physical properties
Meitnerium: orbital properties
Isolation: only a few atoms of element 109, meitnerium, have ever been made. The first atoms were made through a nuclear reaction involving fusion of an isotope of bismuth, 209Bi, with one of iron, 58Fe.
209Bi + 58Fe → 266Mt + 1n
Isolation of an observable quantity of meitnerium has never been achieved, and may well never be. This is because meitnerium decays very rapidly through the emission of α-particles.
WebElements now has a WebElements shop at which you can buy periodic table posters, mugs, T-shirts, games, molecular models, and more. | <urn:uuid:9783b886-409e-4c36-a0ea-87626c9a7fc5> | 3.796875 | 378 | Knowledge Article | Science & Tech. | 37.117744 |
Last year, researchers reported that radar mapping of Titan by the Cassini spacecraft had found a peculiar shift in landmarks on the moon's surface of up to 19 miles (30 kilometers) between October 2004 and May 2007.This last bit about the theory being testable makes this more interesting to me. It's a great example to share with students. My 6th grade class is beginning a unit on geology today after finishing a unit on astronomy. We'll be spending a good deal of time asking, "How do we know what is inside of Earth?" It's fascinating to observe scientists piecing together a model for another body in our solar system.
Now investigators say the best explanation is a moon-wide underground ocean that disconnects Titan's icy crust from its rocky interior.
"We think the structure is about 100 kilometers of ice sitting atop a global layer of water … maybe hundreds of kilometers thick," says Cassini scientist Ralph Lorenz of Johns Hopkins University Applied Physics Laboratory in Laurel, Md.
If confirmed, Titan would be the fourth moon in the solar system thought to contain such an internal water ocean, joining Jupiter's satellites Ganymede, Callisto and Europa. Researchers believe that heat from radioactivity in a moon's core or gravitational squeezing may melt a layer of frozen water.
Luckily, the group's model is testable. It predicts a quickening of Titan's rotation rate in the coming year or two followed by a slowdown—something that can be measured on succeeding Cassini flybys.
Monday, March 24, 2008
Possible ocean under Titan's crust | <urn:uuid:a3d23f16-9e4d-4255-a979-2c8b1e668df7> | 4.15625 | 321 | Personal Blog | Science & Tech. | 45.469228 |
It is known that all sensory information is input to the brain as neural spike sequences. Now, to distinguish between the spike sequences generated by retinal red/blue/green cone cells from each other, and these from the cochlear (inner ear) hair cells, and so on, some sort of encoding scheme must be used.
To further clarify, in the case of retinal cone cells, the rate of incident light quanta in a given energy range, is the primary information that is coded. But, if all 3 types of cone cells generated identical responses for a given rate-of-incidence, like the CCD pixels in our digital cameras do, then there would be no way for upstream neurons to tell what type of cone cell a spike sequence came from. Instead, my guess is that, each type of cone cell encodes the rate-of-incidence in its own characteristic way, similar to how different types of musical instruments sound differently, even when playing the same pitch at the same intensity, via timbre.
Is there evidence that each sensory neuron type has a characteristic spike sequence pattern?
Why message type must be encoded in the message itself
During the development of the visual system, the retina, the LGN and the visual cortex develop separately initially and sometime later, axons from the retinal ganglions grow into LGN, and optic radiations from the LGN grow and reach into the cortex. As far as we can tell it is not guaranteed that a specific ganglion will project its axon to a specific neuron in the LGN. All that is guaranteed by the growth process is that ganglions close together will project to LGN neurons that are also close together.
Given this development process, when a higher region say in the V1 receives a spike stream from a neuron somewhere lower, the question arises: how does it know that this spike stream means, red, blue or green? A simple idea that occurred to me from information theory is that the message type could somehow be encoded in the message itself.
Evidence for characteristic spike patterns for each sensory neuron type would take us one more step towards understanding qualia, the hard problem of consciousness. My speculation is that qualia are the neuronal analogs of timbre in musical instruments.
Erwin Schrödinger thought we'd never get there. He said, "The sensation of color cannot be accounted for by the physicist's objective picture of light [as] waves [or as quanta]. Could the physiologist account for it, if he had fuller knowledge than he has of the processes in the retina and the nervous processes set up by them in the optical nerve bundles and in the brain? I do not think so."
I guess he's right in the sense that we will never be able to fully wrap our minds around the mysterious and ineffable nature of qualia.
However, evidence of characteristic spike patterns would offer resolutions to qualia related thought experiments, such as Is there something about Mary?, that philosophers seem to be pulling their hair out over. | <urn:uuid:fa87f4bc-f34c-4dc3-87ac-c93d4783a6ad> | 3 | 623 | Q&A Forum | Science & Tech. | 40.130075 |
I’m sure you’ve noticed by now how much the media loves tug-on-the-heartstrings images of oiled birds, dead fish and mile-wide slicks. But have you heard about the millions of casualties in every square foot of mud? The news reports overwhelmingly fail to mention how this oil disaster is affecting a keystone group in marine ecosystems—nematode worms. Ok, so they’re not quite as cute and cuddly (unless you have a certain fondness for minute specs on a microscope slide), but this large and diverse phylum pretty much runs the show in marine sediments. Nematodes account for 85-95% of the organisms inhabiting deep-sea ooze (Gage & Tyler, 1992) and are hugely abundant, with 100,000 (abyssal plains) to 84 million (intertidal mud) worms living in every square meter (Lambshead, 2004).
There’re also quite cool to look at, with lots of interesting morphology—don’t you dare let anyone tell you that they “all look the same”:
Why should we worry about things we can’t see?
Well, nematodes underpin ecosystem function. The diversity of feeding habits amongst species (eating everything from bacteria, fungi, alage, diatoms and even other nematodes) coupled with sheer numbers makes them important primary consumers at the base of countless food webs. Diverse meiofauna communities play important roles in bioturbation (vertical oxygen movement), nutrient release and cycling (Snelgrove et al., 1997). Most importantly, the deep-sea benthos is directly dependent on productivity and organic flux from the overlying surface waters. Translation: an oil slick larger than Rhode Island equals very unhappy nematodes.
The precise impacts of the Gulf Spill on meiofaunal communities are unclear, but the few facts don’t look promising. Nematodes (shockingly!) don’t like oil; tar particles cause significant mortality and community abundances show an immediate, sharp decline in response to hydrocarbon stress (Danovaro et al. 1995). Chronically polluted sites have distinct community structures, and long-term exposure appears to reduce both the trophic diversity (feeding types) and number of genera present (Wang et al 2009). Meiofaunal communities after the Amoco Cadiz (a “measly” 1.6 million barrels, compared to probably 3 million barrels and counting in the Gulf) were still depauperate 2½ years later, with the strongest lasting effects seen in estuarine mud (Boucher 1985). There is no data on how deep-sea benthic communities might be affected, but all those dispersants are great for bringing oil down through the water column. The deep-sea doen’t have the same high-energy hydrodynamics as intertidal habitats, and decomposition processes occur much slower with increasing depth—meaning oil will continue to stagnate in this ecosystem for much longer.
What I find most sickening is that we don’t even know what we’re losing. At least we can name the species of dead fish, count the losses, and use our extensive biological knowledge to study impacts and recovery. For smaller organisms, no such luck—we don’t know anything about their biology, life cycles or reproduction. Out of an estimated 1 million to 100 million nematode species a mere 5% of total estimated diversity has been described, representing the largest taxonomic deficit for any group of animals (even bigger than for insects, Hugot et al. 2001). Nematodes don’t have any obvious means of dispersal and many species are regionally restricted (De Mesel et al., 2006). Any given deep-sea region may harbor a trove of endemic species and unique genetic diversity—it’s a horrifying thought, but the Gulf spill may be silently erasing thousands of years of nematode evolution.
So next time you see a picture of an oiled vertebrate, spare a thought for the worms. Nematodes might be uglier, tinier, and in desperate need of a PR specialist, but the marine ecosystem can’t function without them.
Boucher G (1985) Long term monitoring of meiofauna densities after the Amoco Cadiz oil spill. Marine Pollution Bulletin 16:328-333
De Mesel I, Lee HJ, Vanhove S, Vincx M, Vanreusel A (2006) Species diversity and distribution within the deep-sea nematode genus Acantholaimus on the continental shelf and slope in Antarctica. Polar Biology 29:860-871
Danovaro R, Fabiano M, Vincx M (1995) Meiofauna response to the Agip Abruzzo oil spill in subtidal sediments of the Ligurian Sea. Marine Pollution Bulletin 30:133-145
Gage JD, Tyler PA (1991) Deep-Sea Biology: A natural history of the organisms at the deep-sea floor, Vol. Cambridge University Press, Cambridge
Hugot JP, Baujard P, Morand S (2001) Biodiversity in helminths and nematodes as a field of study: an overview. Nematology 3:199-208
Lambshead PJD (2004) Marine Nematode Biodiversity. In: Chen ZX, Chen, S.Y., and Dickson, D.W. (ed) Nematology: Advances and Perspectives, Vol 1. CABI Publishing, Wallingford, p 439-468
Snelgrove PVR, Blackburn TH, Hutchings P, Alongi D, Grassle JF, Hummel H, King G, Koike I, Lambshead PJD, Ramsing NB, Solis-Weiss V, Freckman DW (1997) The importance of marine sediment biodiversity in ecosystem processes. Ambio 26:578-583
Wang Y, Chen H, Wu J (2009) Influences of chronic contamination of oil field exploitation on soil nematode communities at the Yellow River Delta of China. Frontiers in Biology in China 4:376-383 | <urn:uuid:0a38b7da-98de-4b1d-acac-3e52b6d3afbf> | 3.265625 | 1,318 | Personal Blog | Science & Tech. | 44.414814 |
See Also: Container Members
A Gtk# user interface is constructed by nesting widgets inside widgets. Gtk.Container widgets are the inner nodes in the resulting tree of widgets: they contain other widgets. So, for example, you might have a Gtk.Window containing a Gtk.Frame containing a Gtk.Label. If you wanted an image instead of a textual label inside the frame, you might replace the Gtk.Label widget with a Gtk.Image widget.
The first type of Gtk.Container widget has a single child widget and derives from Gtk.Bin. These containers are decorators, which add some kind of functionality to the child. For example, a Gtk.Button makes its child into a clickable button; a Gtk.Frame draws a frame around its child and a Gtk.Window places its child widget inside a top-level Gtk.Window.
The second type of Gtk.Container can have more than one child; its purpose is to manage layout. This means that these containers assign sizes and positions to their children. For example, a Gtk.HBox arranges its children in a horizontal row, and a Gtk.Table arranges the widgets it contains in a two-dimensional grid.
To fulfill its task, a layout Gtk.Container must negotiate the size requirements with its parent and its children. This negotiation is carried out in two phases, size requisition and size allocation. | <urn:uuid:b736aefb-680e-4646-a5f2-16a27eb914f1> | 3.59375 | 299 | Documentation | Software Dev. | 64.066162 |
The one important task that only embedders (as opposed to extension writers) of the Python interpreter have to worry about is the initialization, and possibly the finalization, of the Python interpreter. Most functionality of the interpreter can only be used after the interpreter has been initialized.
The basic initialization function is
This initializes the table of loaded modules, and creates the
fundamental modules __builtin__
sys It also initializes the module
search path (
Py_Initialize() does not set the ``script argument list''
sys.argv). If this variable is needed by Python code that
will be executed later, it must be set explicitly with a call to
argv) subsequent to the call to
On most systems (in particular, on Unix and Windows, although the details are slightly different), Py_Initialize() calculates the module search path based upon its best guess for the location of the standard Python interpreter executable, assuming that the Python library is found in a fixed location relative to the Python interpreter executable. In particular, it looks for a directory named lib/python2.1 relative to the parent directory where the executable named python is found on the shell command search path (the environment variable PATH).
For instance, if the Python executable is found in /usr/local/bin/python, it will assume that the libraries are in /usr/local/lib/python2.1. (In fact, this particular path is also the ``fallback'' location, used when no executable file named python is found along PATH.) The user can override this behavior by setting the environment variable PYTHONHOME, or insert additional directories in front of the standard path by setting PYTHONPATH.
The embedding application can steer the search by calling
Py_SetProgramName(file) before calling
Py_Initialize(). Note that PYTHONHOME still
overrides this and PYTHONPATH is still inserted in front of
the standard path. An application that requires total control has to
provide its own implementation of
defined in Modules/getpath.c).
Sometimes, it is desirable to ``uninitialize'' Python. For instance, the application may want to start over (make another call to Py_Initialize()) or the application is simply done with its use of Python and wants to free all memory allocated by Python. This can be accomplished by calling Py_Finalize(). The function Py_IsInitialized() returns true if Python is currently in the initialized state. More information about these functions is given in a later chapter.
See About this document... for information on suggesting changes. | <urn:uuid:2eb0a641-c3c3-4313-a043-b8cced12b317> | 3.078125 | 545 | Documentation | Software Dev. | 26.811959 |
I am Trying to write a program that does the following:
Write a program that simulates the rolling of two dice. The program should use rand to roll the first dice and should use rand
again to roll the second dice. The sum of the two values should then be calculated. [note: each dice can show an integer value from 1-6, so the sum of the two values will vary from 2-12, with 7 being the most frequent sum and 2 and 12 being the least frequent sums] Your program should roll the dice 36,000 times. use a single array to tally the numbers of times each possible sum appears. Print the results in a tabular format. Also, determine if the totals are reasonable (i.e. there are six ways to roll a 7, so approximately one sixth of the rolls should be 7).
Please help me.
Thank you in advance. | <urn:uuid:57ffab9f-ef75-4e29-acc2-c10059182ff5> | 3.140625 | 183 | Comment Section | Software Dev. | 77.261364 |
By Deja Dragovic
With the BP Oil Spill trial starting, here is a recap of the environmental impact caused by the Deepwater Horizon disaster and oil spill in April 2010.
Due to a delicate ecosystem that exists in the Gulf, of the many different species of flora and fauna interacting perfectly in their natural environment, the disruption of their regimen brought many disruptions to the entire chain of species.
These types of disasters limit the growth principle of ecological and environmental systems, restraining the species in their natural habitat, their supply of food, water and other essentials for their survival. This way the supply of resources changes and causes major drawbacks to the already established patterns in the area.
The damages may include direct impact on food stocks and fisheries, their economic and tourism losses due to environmental constraints such as contamination and pollution of waterways and land.
The habitat, already fragile and subject to varying climate change forces has been hit with unexpected sludge of oil – a substance that is poisonous, hard to sponge, and which leaves physical residue on the surrounding ecosystem.
The marine ecosystem, the coastal territory, the conditions of the physical and inbred activities—are all at stake following such a disaster. Oftentimes the media and the industry are quick to analyze only the tangible effects such as the oil smudges in the sea and their washing up along the coast. However, the cleanup is only an immediate resolution, the true impact is seen and felt only after the emergency steps have been implemented. In the long run, the spilled oil may produce oxidized compounds which exposure the ecosystem to high levels of toxicity
Oil spills of many types have remarkably persistent effects, and they reflect a multitude of factors, such as the overall magnitude of the disaster, the time it takes for emergency services to react and implement solutions, and for the area affected.
The delayed and prolonged emergency response and the drawn-out cleanup have contributed to heightened toxicity of the area, as the fresh oil loaded with toxic substances hit wildlife and marsh grasses, washed onto beaches and killed fish and turtles in the deep sea.
The impacts on the coast, on the ocean surface, on the sea floor were predicted to be severe. Even before the spill, the land was under enormous environmental stress, including sea level rises due to global warming, wind and water currents adjusting to climate change, and human activities adapting to these and many upcoming transformations.
The extent of the incident will be only visible when the damages can be measured and recorded. At the rate the oil is breaking down, some of it could still be there a century from now.
The final impact will depend on many factors, including the distance between the oil spill location and the potential impact sites along the Gulf Coast, the sea conditions, and the residual level of contamination of oil, however none of it is likely to be positive.
Recovery can take years or decades, based on not only man-made response, but also the biological response.
Restoring the state of the region and the oil that has spread, carried by the currents and the species to the land and further, is going to take time, dedication and resources. | <urn:uuid:1f650ea0-6c2d-4774-b761-694ec8f1309d> | 3.390625 | 636 | Truncated | Science & Tech. | 26.093893 |
Question: determine whether the points lie on straight lines
- A(2,4,2), B(3,7,-2), C(1,3,3)
- D(0,-5,5), E(1,-2,4), F(3,4,2)
Answer: first one no, second one yes
My work: only the one of the variables would be changing and it would be by a constant factor (e.g. 3,6,9,12...). I think this because a line has a constant slope.
Is it possible to plot 3d graphs by hand? If yes, how? | <urn:uuid:2dad97dc-e8ee-408d-8f5d-569551799b23> | 2.796875 | 135 | Q&A Forum | Science & Tech. | 116.312989 |
Programming is the act of creating new software for use on a computer system. This is often categorized into two broad types - system software and application software. Programming is the art of creating the instructions that tell a computer what to do. Without these instructions, the source code of an application, the computer would be a useless chunk of metal and plastic. What confuses some people is that computers do quite a bit even if they don't have access to a hard disk in the system or other storage device. This is because there is already source code burned into chips inside the computer, that run programs of their own. The BIOS (Basic Input Output System) is a program that is run from these chips when a computer is first powered on, before the computer ever touches any of its disk drives.
There are literally hundreds of different programming languages. This is because there are a countless number of tasks to be solved and each language has its strengths and weaknesses. Some programming languages are much better for one set of tasks than another. PHP (Hypertext Preprocessor) is an open source scripting language that is excellent for running while embedded in HTML web pages. It is used by millions of web servers world-wide. Prolog is a language particularly well suited for programming tasks that involve the heavy use of logic. For extremely fast execution time and the ability to access very low-level devices on a computing system, the ubiquitous C programming language is used. There are many more major languages such as LISP, Java, C++, Basic, and others. The future will most definitely bring many more.
Programming is done using a variety of tools, depending on the exact system being used and what it must interface with.
Various tools can be used in the creation of software, regardless of what the end result of the program is meant to be. | <urn:uuid:0678282f-5868-437a-98b9-13f5964fdaf1> | 4.0625 | 371 | Knowledge Article | Software Dev. | 45.0895 |
Exotic life beyond Earth? Looking for life as we don't know it
Scientists at a new interdisciplinary research institute in Austria are working to uncover how life might evolve with "exotic" biochemistry and solvents, such as sulphuric acid instead of water. Their research ...
USF Study Shows First Direct Evidence of Ocean Acidification
(PhysOrg.com) -- Seawater in a vast and deep section of the northeastern Pacific Ocean shows signs of increased acidity brought on by manmade carbon dioxide in the atmosphere -- a phenomenon that carries with ...
More asteroids could have made life's ingredients
(PhysOrg.com) -- A wider range of asteroids were capable of creating the kind of amino acids used by life on Earth, according to new NASA research.
One Sponge-Like Material, Three Different Applications
(PhysOrg.com) -- A new sponge-like material that is black, brittle and freeze-dried (just like the ice cream astronauts eat) can pull off some pretty impressive feats. Designed by Northwestern University chemists, it can ...
Scientists sound acid alarm for plankton
The microscopic organisms on which almost all life in the oceans depends could be even more vulnerable to increasingly acidic waters than scientists realised, according to a new study.
Scientists sound alarm at Arctic Ocean's rapid acidification
Scientists expressed alarm on Monday over the rapid acidification of the Arctic Ocean caused by carbon dioxide emissions, which could have dire consequences on the region's fragile ecosystem.
Arctic studies show dire effect of ocean acidity
The icy Arctic waters around Norway's archipelago of Svalbard may seem pristine and clear, but like the rest of the world's oceans they are facing the threat of growing acidity.
One sponge-like material, three different applications
A new sponge-like material that is black, brittle and freeze-dried (just like the ice cream astronauts eat) can pull off some pretty impressive feats. Designed by Northwestern University chemists, it can remove mercury from ...
Team identifies proton pathway in photosynthesis
(Phys.org) —A Purdue University-led team has revealed the proton transfer pathway responsible for a majority of energy storage in photosynthesis. Through photosynthesis, plants, algae and bacteria convert sunlight, carbon ...
Geographic isolation drives the evolution of a hot springs microbe
Sulfolobus islandicus, a microbe that can live in boiling acid, is offering up its secrets to researchers hardy enough to capture it from the volcanic hot springs where it thrives. In a new study, researchers report that p ...
Earth is having a bad acid trip, study finds
Earth may be overdosing on acid - not the "turn on, tune in, drop out" kind, but the "kill fish, kill coral, kill crops" kind. And it's shaping up to be a very bad trip.
Molecules wrestle for supremacy in creation of superstructures
(PhysOrg.com) -- Research at the University of Liverpool has found how mirror-image molecules gain control over each other and dictate the physical state of superstructures.
Key piece of puzzle sheds light on function of ribosomes
(PhysOrg.com) -- When ribosomes produce protein in all living cells, they do so through a chemical reaction that happens so fast that scientists have been puzzled. Using large quantum mechanical calculations of the reaction ...
Pharmaceutical substances found in waters of Donana
Researchers from the University of Seville (US) have detected active pharmaceutical substances for the first time in the waters of the Doñana National Park and its surrounding areas. The results suggest eco-toxicological ... | <urn:uuid:a41036b9-a0d7-453b-906b-18fbad01f78e> | 2.734375 | 753 | Content Listing | Science & Tech. | 39.11589 |
Optical tweezers have been used by biophysicists since their invention at Bell Labs in the 1980s, and are typically used to study cellular components. But they have a few drawbacks, not least of which are overheating and inefficiency.
So engineers at Harvard have been working on a next-gen model they call plasmonic nanotweezers to solve those and other issues with traditional optical tweezers so that tiny particles such as viruses can be isolated, observed, and manipulated.
Back at Bell Labs, scientists had shined a laser through a microscope lens to focus it tightly. They found that light, made of electromagnetic waves, creates a gradient force at the point of focus that is capable of attracting a tiny particle and holding it in that beam of light until random motion or some other force knocks it out.
The basic limitation of this approach is that a lens cannot focus that beam beyond half the wavelength of light, so if the particle the researchers hope to trap is smaller than the focal spot, they might have trouble trapping it.
Meanwhile, that focal size limit also places an upper limit on the gradient force generated, and yet a stronger force is required to trap nanoscale particles. So for a conventional optical tweezer to capture nanoscale particles, a high-powered laser is required.… Read more | <urn:uuid:dab9a986-de3d-48a2-ad2e-f208d5171d63> | 4.15625 | 274 | Truncated | Science & Tech. | 33.476858 |
Looks can deceive…
A South American sabertooth-lookalike, Thylacosmilus was in fact a marsupial – at roughly the size of a jaguar, one of the largest marsupial carnivores.
Looks a great deal like a saber tooth tiger, huh?
The similarity between Thylacosmilus and Smilodon is an excellent example of convergent evolution - two distantly relating forms converging upon a simular morphology and life habitat. There are an three other examples of mammals that have developed saber-teeth- in fact most of the last 65 million years had some large cat-like saber-toothed mammal present, the modern biota is the outlier.
Thylacosmilus went extinct roughly 3 million years ago, closely coinciding with the formation of the land bridge linking the Americas. Animals from North America emigrated south and those from South America journeyed north; this fauna exchange is referred to as the Great American Interchange. It is at this time we start to find Smilodon fossils in South America. It is thought that the arrival of this relatively larger predator (the largest Smilodon was twice the size of the largest Thylacosmilus) may have been what drove the only known marsupial saber-toothed form to extinction.
Here’s a cool example of convergent evolution the kids can understand:
“CONVERGENT EVOLUTION occurs when two or more groups that are not closely related come to resemble each other more and more as time passes. This is usually the result of occupation of similar habitats and the adoption of similar environmental roles..” | <urn:uuid:ee0a7d77-285f-4640-9af3-5022a1b0e3ab> | 3.34375 | 351 | Personal Blog | Science & Tech. | 27.316397 |
Using Command Line using Visual C++ 2008
- Select Start >> All Programs >> Microsoft Visual C++ 2008 Express Edition >> Visual Studio Tools >> Visual Studio 2008 Command Prompt (Run with administrator privileges)
- Once you are in the command line, you can use any editor such as edit to write a C program.
C:> edit myprogram.c
- After written the program, to compile it, issue the command cl
C:> cl myprogram.c
- During the compilation and linking, myprogram.obj and myprogram.exe will be created.
- To run the program:
Using Visual C++ 2008 IDE
- Create an empty project by select File >> New >> Project. Select General >> Empty Project and type in the project name.
- Under folder Source, right-click Select Add >> New Item.
- Under Code, Select C++ File (.cpp), however, when you type in the name use a program name with extension .c, such as myprog.c and click Add
- You can program to type your C program. Click Save icon to save your file.
- To compile the program select Build >> Compile (Ctrl+F7).
- Please note that you cannot run the program until you have build solution.
- To build solution select Build >> Build Solution (F7)
- Running the program:
- Select Debug >> Start without debugging (Ctrl+F5)
- For any runtime error, you can debug the program as follows:
- Select Debug >> Start debugging (F5)
- Please note that during debugging, the program will show and close the console display immediately.
- To see the console display, you must run without debugging.
- The problem using Visual Studio is that many files will be created even for a simple program. All files are created inside the project folder.
- Under the project name of your program, the source code and object file is located at sub folder similar to your project name, the executable file is under sub folder debug.
Using Borland C++ Compiler Command Line Tools
- Installing and running the Command Line Tools
- Run freecommandlinetools.exe; choose the drive and folder into which you want to install the free C++Builder 5 command line tool development system.
- From the bin directory of your installation: Add “c:\Borland\Bcc55\bin” to the existing path
- Create a bcc32.cfg file which will set the compiler options for the Include and Lib paths (-I and –L switches to compiler) by adding these lines:
- Create an ilink32.cfg file which will set the linker option for the Lib path by adding this line:
- Compiling the program: | <urn:uuid:ec3508db-4b08-4f7e-8437-ae121afce79c> | 3.109375 | 575 | Tutorial | Software Dev. | 57.9845 |
Wearing diamonds on the inside – to monitor biochemistry
Diamonds are biocompatible and cheap enough to be considered for use as sensors inside the body. Some cancer treatments require regular monitoring of blood. David Hoxley is investigating the use of diamond as a sensor of blood chemistry. The area is known as microfluidics. The challenge is to sensitise diamond so it responds to biological reactions occurring at the surface of the diamond. This field of research sees the combined application of biology and physics.
Robyn Williams: A final piece of carbon, though not quite nano, is in the form of diamond. And to hear about it we leap to Melbourne.
David Hoxley: Hi, my name is David Hoxley and I'm a physicist from La Trobe University down in Victoria, and like to talk to you briefly today about my plans for making implantable diamond biosensors, microfluidic biosensors for testing the blood of cancer patients. First of all you might ask yourself, why diamonds? Surely no one can afford to have an implantable diamond sensor?
The great thing about diamonds is that they are incredibly biocompatible and they are a lot cheaper than they used to be. About five or ten years ago we started being able to make these beautiful pure optical semiconductor-grade diamonds that cost maybe a couple of hundred dollars for a sample that's a couple of millimetres by a couple of millimetres. They're better than gems if you want to make sensors out of them.
A sensor is something that takes a chemical or a biological reaction and turns it into an electrical signal. And my particular interest is in how do you test the blood of a cancer patient without having to stick a needle into them and pull the blood out? There are so many different ways that we can test for things by looking at a person's blood. Pathology tests are very, very sophisticated, and almost every single disease involves a blood test these days. But for cancer patients, especially blood cancer patients like multiple myeloma or leukaemia, they need to have a lot of blood tests because the way that the cancer is fought primarily is with chemotherapy. Cancer patients, particularly ones that have bone marrow transplants, find themselves walking a knife edge of having too much chemo and having an immune system crash and getting an infection and ending up in intensive care, or not having quite enough chemotherapy and the cancer not being quite completely killed and coming back. So for a lot of cancer patients on chemo, their lives involve a constant round of blood tests and trips to the hospital.
What I'd really like to achieve is a sensor that you could put inside a person's body that would effectively email you when it was time to stop giving this particular sort of chemo or time to give a different sort of chemo. How in practice can we achieve that? Well, one way we could do that is to use a microfluidics. Microfluidics a particular branch of engineering that involves taking very, very small channels in a substrate, in this case diamond, about the size of a human hair, probably a little bit bigger in the case of something that's going to have blood flowing through it, because blood has fairly large cells in it.
When the channel is very, very small, the surface area to volume ratio is very, very, very large, so your walls of your channel can be coated with a sensitive compound and they can access a very large amount of the fluid flowing through it. This is not a new idea, it's been very, very popular in biosensing engineering for a long time. For example, people have tried to develop ways to measure the tears coming from a person to try and find out what their kidneys are doing.
But what I'm interested in is implanting this. And the advantage of having such tiny channels is that if you can get your assays, the reactions that detect the presence of particular chemicals or biological products, if you can have those assays very, very small, then they can line the walls of this microfluidic system.
So why diamonds? Diamond is very, very biocompatible, it's unreactive biologically, unless you want it to be. Diamond is normally an electrical insulator, which is actually a good thing to have in the bulk of a sensor because that way you don't get any leakage currents or cross talks. But the surface can be made very conducting by applying atomic hydrogen to it. In fact, if you put other molecules on top of the hydrogen you get even greater conductivity. What I would like to do is find out ways that conductivity can change in response to the biological reactions that are happening at that surface.
I'm not the first person to have thought of this, but I'm very excited about the possibility of doing this in a combined package. My research when I finished my doctorate was to look at sensors made out of diamond to try and find out where a charged particle had moved. So, particle detection. But I had my own particular brush with cancer and I was diagnosed with multiple myeloma in my first postdoctoral fellowship. That threw everything into chaos.
I was very, very lucky and I had a bone marrow transplant that was relatively successful. Those of you who know something about multiple myeloma realise that it has a tendency to come back eventually, but after eight years I'm still in fairly good shape. But in all of the panic of the cancer and everything, I had a couple of ideas about trying to make some sort of implantable biosensor so that I could really know where my levels were at so I could get the treatment just right.
Then I went back to work and the idea faded just a little bit. Then my son was diagnosed with leukaemia. The thing about young people is that they don't always understand what's happening to them, and any medical procedure that is invasive is quite traumatic, and getting blood out of a three-year-old is tricky. Usually you have to prick their finger, and you can only deal with a very small amount of blood. So being able to implant a sensor into a kid, that would be great.
So that's my motivation, it is a very personal one for trying to make these implantable biosensors. However, the practicalities of making these devices is quite complex. I don't think that I'm going to be engineering a device like this any time in the near future. But my particular passion is to try and look at the ways that I can sensitise the diamond surface so that it is sensitive to these biological reactions.
I think that growing the diamonds or tunnelling into the block of diamond is not the hardest problem, I think that we can actually do that. Connecting the diamonds to the circuits so that it can be read out to the outside world is not the hardest problem either. I am particularly interested in that fundamental problem of how do we detect a biological reaction when it's happening at the diamond's surface. And this is the basic problem of all biosensing.
So I've decided that I need to reach out to biologists, and a physicist often find themself in an odd position when they want to talk to biologists because there's quite a gulf that separates the two. I guess what I'm partly doing is trying to reach out a little bit to the biological community and look for partners who can help me with the biological reaction part of what I'm trying to do. And the potential gains for doing this are enormous. We're just on the edge of an explosion in medical technology, and I think it's just in time, because medical technology is also getting more expensive. Any way that we can minimise the number of hospital stays and the amount of expense involved in treating patients, especially with cancer, is a really good thing. But in order to do so, we need to use technology, and I think that implantable sensors are a really, really big part of the future. I don't find anything sinister in them, I think that they will just be very, very positive indeed, particularly for people who are older and people who are younger, like my son. So, hopefully in a not too distant future we will be able to wear our diamonds on the inside.
Robyn Williams: Dr David Hoxley at La Trobe University in Melbourne. And you're listening to The Science Show on RN, from Geelong to Vancouver.
- David Hoxley
La Trobe University
- Robyn Williams
- Robyn Williams | <urn:uuid:aaf6cbdb-3cd6-4c22-bad6-9354368f964d> | 3.453125 | 1,754 | Audio Transcript | Science & Tech. | 48.920896 |
More than 3,050 species of invertebrates inhabit the benthos of the Barents Sea (Sirenko, 2001). Total fauna biomass, including benthic species, generally increases near the Polar Front, in shallow regions, and near the edges of banks. The richest species diversity is found on sandy silts, and silty-sand floors. Lower biomass occurs in areas with limited upwelling, low primary production, reduced vertical flux, and areas with less suitable substrata caused by heavy sedimentation (e.g. inner parts of glacial fjords). | <urn:uuid:b17bd043-0236-442d-92ae-21eb5aff043d> | 3.0625 | 120 | Knowledge Article | Science & Tech. | 45.865833 |
Mulvaney, R., Abram, N.J., Hindmarsh, R.C.A., Arrowsmith, C., Fleet, L., Triest, J., Sime, L.C., Alemany, O. and Foord, S. 2012. Recent Antarctic Peninsula warming relative to Holocene climate and ice-shelf history. Nature 489: 10.1038/nature11391.
The authors write that "the Antarctic Peninsula is at present one of the most rapidly warming regions on Earth (Vaughan et al., 2003)," noting that "historical observations since 1958 at Esperanza Station document warming equivalent to 3.5 ± 0.8°C per century."
What was done
In an attempt to determine just how unprecedented this warming might have been compared to the rest of the Holocene, Mulvaney et al. drilled an ice core to the bed of the ice cap on James Ross Island, which lies just off the northeastern tip of the Antarctic Peninsula, next to an area that has experienced a series of recent ice-shelf collapses. And based on deuterium/hydrogen isotope ratios of the ice (δD), they developed a temperature history of the region that spans the entire Holocene and extends into the last glacial period.
What was learned
The nine researchers report that "the Antarctic Peninsula experienced an early Holocene warm period followed by stable temperatures, from about 9200 to 2500 years ago, that were similar to modern-day levels [these italics and those following added for emphasis]." They also found that "the high rate of warming over the past century is unusual (but not unprecedented) in the context of natural climate variability over the past two millennia." More specifically, they state that "over the past 100 years, the James Ross Island ice-core record shows that the mean temperature there has increased by 1.56 ± 0.42°C," which ranks as one of the fastest (upper 0.3%) warming trends since 2000 years before present, according to a set of moving 100-year analyses that demonstrate that "rapid recent warming of the Antarctic Peninsula is highly unusual although not outside the bounds of natural variability in the pre-anthropogenic era." And even though the temperature of the northern Antarctic Peninsula has risen at a rate of 2.6 ± 1.2°C over the past half-century, they say that "repeating the temperature trend analysis using 50-year windows confirms the finding that the rapidity of recent Antarctic Peninsula warming is unusual but not unprecedented."
What it means
Even for what Mulvaney et al. describe as "one of the most rapidly warming regions on Earth," recent warming there has not been unprecedented within the context of the past two millennia.
Vaughan, D.G., Marshall, G.J., Connolley, W.M., Parkinson, C., Mulvaney, R., Hodgson, D.A., King, J.C., Pudsey, C.J. and Turner, J. 2003. Recent rapid regional climate warming on the Antarctic Peninsula. Climatic Change 60: 243-274. | <urn:uuid:e06a8694-4bf8-4769-97d6-2964abb22c8b> | 3.390625 | 643 | Knowledge Article | Science & Tech. | 59.936411 |
Milkweed is a challenging plant to eat. It is covered with hairs, contains a sticky, gummy latex, and is highly toxic. Yet there are a variety of insects that are specialists on feeding on milkweed. The caterpillar of the monarch butterfly is the most famous.
Anurag Agrawal shares his research on the relationship between milkweed and the insects that rely on it.
Agrawal is an associate professor in the Department of Ecology and Evolutionary Biology and the Department of Entomology. He is also the director of the Cornell Chemical Ecology Group and an associate director of the Cornell Center for a Sustainable Future. | <urn:uuid:7f581c8b-c855-4d80-89f2-4febc96696e8> | 2.875 | 130 | Truncated | Science & Tech. | 35.841748 |
Researching the ancient bristlecone pines with Google Earth
— John Muir
Since the days of Charles Darwin, biologists have struggled with ways to represent our planet's incredible biological diversity on maps that convey both meaningful information and a realistic sense of scale. In recent years, this challenge has morphed into a search for mapping platforms that are available to help educate the general public, are easily accessible to both novice and established scientists, and are powerful enough to track and display biological data. Our research focuses on the population ecology of ancient bristlecone pine trees in California's White Mountain range, and we have found that Google Earth is an important tool for both expediting the everyday process of fieldwork and for educating the public about our projects. Since 2004, Google Earth has made it much easier for our team to share spatial data, to quickly view this data overlaid on aerial imagery, and has helped us discover key ecological patterns in the bristlecone pine forests.
The White Mountains of eastern California receive less attention and fewer visitors than the nearby High Sierra Range, yet they are similarly spectacular mountains capped by high peaks over 14,000 feet in elevation. Only a few dirt roads cross this surprisingly rugged terrain, where the rolling, sagebrush covered hills are populated with abundant wildflowers and where the valleys support herds of bighorn sheep. This environment is home to Earth's most ancient trees, the bristlecone pines (Pinus longaeva), and is also the site of North America's highest elevation research station, the University of California's White Mountain Research Station.
In 1953, several trees over 4500 years old were discovered in the "Methuselah Grove" area by biologist Edmund Schulman, yet older trees probably exist undiscovered throughout the range. For many scientists, the most interesting attribute of the bristlecone pines is not their extreme age, but the persistence of their dead wood. Due to slow growth in a dry, high elevation mountain range, bristlecone wood is extremely dense and filled with resin, and can thus remain un-decomposed on the ground for up to 10,000 years after a tree has died. For over 50 years, researchers from the University of Arizona's Laboratory of Tree-Ring Researchh and others have used the bristlecone tree-ring record as an important tool in studying past and present climatic changes. In 2004, we began a project (based out of the UC Santa Cruz Department of Ecology and Evolutionary Biology) to better understand the population ecology of Bristlecone pines. This project specifically seeks to examine how certain ancient bristlecone groves have grown or shrunk over the last several millennia, and how these populations may react to a changing climate. To this end, we are studying many different bristlecone groves across the White Mountain range, including both old and young trees, as well as examining aspects of cone production and wood development.
One of the greatest challenges of conducting scientific field research in a rugged mountain environment is locating sites of interest, figuring out how to get there, and communicating this information to a team of people. Before the Google Earth imagery for the White Mountains was updated, obtaining aerial imagery that clearly showed individual bristlecone pine trees for a large area was difficult and expensive. However, with the updated Google Earth imagery, each tree can be distinguished from others, the major rock types are clearly identifiable, and it is easy to tell whether the trees are located in sparse or dense groves.
How they did it
Google Earth has become invaluable for our research on several levels. Initially, we used it as a tool to view the range of these trees and to examine characteristics of different stands before hiking out into the field. Using the Google Earth polygon feature, we drew boundaries around groups of trees that were obviously large bristlecone or limber pine trees as opposed to smaller pinyon pines or bushes of mountain mahogany (see example video). To our knowledge, this is the first complete map produced of bristlecone stands in the White Mountains. Immediately, some important overall patterns emerged, such as the higher densities of trees on north-facing slopes and the locations of the rare stands that were growing on quartzite or granitic substrates as opposed to the preferred dolomite. This preliminary mapping has helped us identify promising field sites that are within a day's hike from the nearest road.
As our project grew, we began to use Google Earth on a daily basis during the field season. Our basic strategy is to keep a "master" KML file of all points or paths that we are tracking, including thousands of individual trees, that can be accessed by any member of our team or other individual at the research station. A recent improvement has been to link each point to a photograph of the tree for easy identification. To do this, we first create a text file with a list of tree names, GPS coordinates, picture names, and the data associated with each tree (such as tree age, number of cones, etc). We then use a PHP script that creates a KML file with placemarks at the location of each tree; the bubble for each placemark contains a photograph and the data associated with that tree.
In the morning before heading out into the field, we might use this master KML file to print out a map of survey points that represent one day's work for several people while at the same time uploading the coordinates of a different transect onto GPS units for a separate team. In the evening, any new data collected can be downloaded and entered into this KML so that we can plan the next day's work.
Laying out transects
One perplexing aspect of bristlecone pine biology is that there are very few young trees within the groves of ancient and dead trees. Bristlecone seeds may germinate and survive only about 1 year out of every 50 years, and this might only happen in certain areas. Therefore, part of our project involves "walking transects" through bristlecone forests of different elevations, slopes, and substrates, and measuring all small trees within 20 meters of where the observer is walking. This method of sampling young trees will help us determine the conditions that are required for bristlecone germination and survival.
For this part of our project, we first used Google Earth to identify promising areas. The video below shows an example of a transect at an elevation of 10,400 to 10,700 feet, crossing both dolomite and granite rock-types (other transects were laid out at different elevations, slopes, and rock types). We measured this path to be about a mile on Google Earth, which is approximately the distance our team could cover over an 8-hour day. Before hiking out to this area, we first examined this path using the Google Earth tilt feature to ensure that it did not cross any areas of loose dolomite that were too steep for safety, we also printed out several views of the aerial photographs so that different team members could locate the area. We then saved the file as a KML and used MacGPS Pro to export this path to several Garmin GPS units. In the field, we were able to roughly follow this path on the GPS units while searching for and measuring all small trees within 20 meters of the centerline. During the day's data collection, we recorded the point location of each tree and used the tracking feature on the GPS to record the actual transect we walked (which has small variations from the one laid out on Google Earth). Upon returning from the day's hike, we uploaded the actual path walked straight into Google Earth and used our PHP script to link the placemarks with photographs and data. As a result, we can click on each placemark to get an image of the tree and see the data associated with it (e.g., estimated age, height, diameter at base, and reproductive status). Therefore, if we want to return to a particular tree on this transect, any member of the team could click on the point, get a picture of the tree and return to that location.
Finding Isolated Trees
Another part of our project involves examining the growth patterns and cone production of trees that are growing at least 50 meters away from all other bristlecones as opposed to those located in dense groves. We first used Google Earth to find what appeared to be isolated trees and then to measure the distance between these trees and others. These trees are tracked in our master KML file, and linked to pictures and data in our online database.
Keeping track of individual trees within a stand
A core part of our project involves aging a set of several hundred living and dead trees within a stand. This requires us to document several hundred points within a small area, and keep each point associated with a unique number and identifying photograph. As we continue surveying each area, the number of points increases daily. We keep a list of points in our master KML file and similarly have each point linked to a picture on our online database. If a question regarding the data or age of a particular tree comes up, we can click on the point to get an image of the tree, upload that point to our GPS, and return to the site.
We created a KML with several different types of information for other scientists, educators, and the general public.The first section, labeled "For Travelers", has placemarks over key visitor sites such the campground and visitors center. The second section, "Learn About the Bristlecone Pine", is an educational tour of the bristlecone ecosystem. Here, interested parties can learn about the discovery of bristlecone pines, the science of dendrochronology, examine differences between bristlecone groves, and explore the upper tree line. This is a good example of how a KML file can be used to transmit a variety of information about the natural history of particular species. The third section, "A Week of Field Research" details a week's worth of fieldwork with our team and demonstrates how Google Earth is critical to our everyday field operations. Here, we provide layers that contain links to many pictures of our trees, show a sample vegetation transect, and provide an outline of the range of bristlecone pines across California, Nevada, and Utah. Finally, the last section is about the White Mountain Research Station, users can explore the four different substations and find links to some of the many projects based here.
For our team, Google Earth has made the process of daily fieldwork much easier, and enables us to keep track of a large amount of spatial data in a way that is accessible to many different people. Here are a few lessons that we've learned:
- Use many different levels of folders to organize your data. If you have hundreds of points, paths and polygons to keep track of, this will help keep everything organized and will keep the scroll bar in the display window short when you expand folders.
- Import custom icons to mark points that are in close proximity to each other if the standard Google Earth icons are too large and appear crowded.
- Google Earth Pro has great features like the ability to draw polygons and import shapefiles, but the free version can do many of the things described above as well.
- Explore 3rd party programs that import and export KML files. Both MacGPS Pro and KMLer are simple and inexpensive programs that have helped us manage data, but there are many, many others.
- Don't be afraid to mark a couple of points, save them as a KML and email the file to colleagues when trying to describe field locations.
In summary, if you are new to using computer-based mapping programs, then you won't find an easier method of managing and sharing your spatial data. Alternatively, for those that are familiar with more traditional GIS platforms, I recommend trying Google Earth as a way to expedite displaying and sharing your data.
Google Earth was invaluable for our research and used on a daily basis. The advantage of using Google Earth was the ease of use by different people, including undergraduate students and volunteers. As well, using KML files gave the team the ability to trade data easily between Mac and PC operating systems. They also had the flexibility to quickly print out maps, photos, or transfer the constantly growing sets of waypoints to and from different GPS units.
The Bristlecone Pine Research KML lets the public explore the White Mountains and these unique trees.
WWF & Eyes on the Forest
Mapping forests and wildlife ranges in Sumatra with Google Maps Engine
Living Oceans Society
Conserving British Columbia's coastline with Google Maps Engine
The HALO Trust
Clearing landmines with Google Earth Pro
Chief Almir and the Surui
Mapping indigenous culture in Google Earth and monitoring the Surui Carbon Project with Open Data Kit
Amazonas Sustainable Foundation
Collecting Street View imagery of the Amazon for sustainable development
Using Google Maps API for Business for the Tajikistan Stability Enhancement Program Monitoring and Evaluation System
Grameen Foundation AppLab
Bringing market information to Ugandan farmers with the help of Open Data Kit and Google Maps API
Defenders of Wildlife
Showing impacts of the 2010 Gulf of Mexico oil spill with Google Maps API
Mapping slums in India with Google Earth
Tracking their North Pacific Gyre expedition with Google Earth and Maps
Borneo Orangutan Survival
Visualizing donor's adopted acreage on Google Earth.
Save the Elephants
Protecting elephants from poaching by tracking them on Google Earth
Appalachian Mountaintop Removal
Transporting the public to mountaintop removal coal mine sites and their impacts using Google Earth and Maps.
Edge of Existence
Showcasing the world's threatened species with Google Earth and Spreadsheet Mapper
Jane Goodall Institute
Monitoring chimpanzees and their forest habitat using Google Earth and Open Data Kit
Neighbors Against Irresponsible Logging
Sparking grassroots activism with Google Earth
UNEP: Atlas of Our Changing Environment
Exploring the changes in the world's landscape over time with Google Earth.
United States Holocaust Memorial Museum: Crisis in Darfur
Illuminating the genocide in Darfur with satellite imagery, data and multimedia in Google Earth
Sierra Club and the Arctic National Wildlife Refuge
Protecting the Arctic National Wildlife Refuge from oil and gas drilling with Google Earth
Planning ancient bristlecone pine research with Google Earth | <urn:uuid:a793f3e6-7021-443e-aaec-a9d425ada7f7> | 3.859375 | 2,976 | Knowledge Article | Science & Tech. | 31.327249 |
Our universe’s shortest algorithm has 3 lines and computes all possible universes, not just ours.
To predict we need more: a plausible prior measure
1. Weak assumption on this measure: the universe is sampled from a formally describable prior. Then futures with lots of randomness and without short descriptions are necessarily unlikely. Occam!
2. Stronger assumption: the universe is deterministic a la Zuse and created under resource constraints reflected by the Speed Prior. Then much stronger nontraditional predictions about beta decay etc. Let us test them!
Back to J. Schmidhuber's Theory of Everything page | <urn:uuid:9dfb0850-f84b-43b7-8318-16f8fab2ef5d> | 2.78125 | 128 | Academic Writing | Science & Tech. | 43.7535 |
Asteroids are rocky objects. There are many different types of asteroid, consisting of different amounts of metal, silicate and carbon. They also have different histories. Some of them have completely melted like the planets, whereas others have not melted but have been altered by water. This means there are a wide variety of structures both inside and on the surface of asteroids, formed by their turbulent existence.
The asteroid Ida is about 55km long. It is one of thousands of asteroids in the asteroid belt. © NASA
Rather than one solid mass, asteroids are groups of several rocks, or rubble piles, held together by their own gravity. The largest and oldest asteroids are nearly spherical and are made up lots of smaller rocks. These are known as mature rubble piles. The largest asteroid, Ceres, is 933 kilometres in diameter, about the length of England. Asteroids this big are called minor planets. Newer asteroids may only contain a couple of large rocks and are known as contact binaries. These asteroids are about 10 metres across.
Most asteroids are found in a belt orbiting the sun between Mars and Jupiter, 300,000,000 kilometres away. There are maybe millions of asteroids in the main belt. They are thought to be debris from a planet that failed to form when the solar system was created. These asteroids have, however, changed a lot from when they were first created due to billions of years of collisions. During these collisions, fragments can break away. It is these fragments that make up most of the meteorites that fall to Earth.
Some asteroids get pushed out of the main asteroid belt by the massive planet Jupiter. As they pass Jupiter, its gravity tugs on the asteroid, causing their orbit to wobble. This happens each time the asteroid travels around the sun until eventually the wobble gets so big the orbit breaks and the asteroid shoots away. Sometimes these new paths cross the orbits of the terrestrial planets, including Earth. These asteroids, typically up to 10 kilometres in diameter, can come very close to Earth, so are known as near-earth asteroids. They have even been known to crash into Earth, generating craters hundreds of kilometres across. | <urn:uuid:fd674259-5534-441c-8e71-31dcb6b241d3> | 4.21875 | 436 | Knowledge Article | Science & Tech. | 48.786781 |
Extratropical Water Level Guidance
What is a datum?
In the context of this site, datum refers to a vertical tidal datum.
The four datums used by this site are defined as follows. For more on
tidal datums, please see
NOAA's National Ocean Service (NOS) tidal datum definition page.
Highest Astronomical Tide|
| "The [height] of the highest
predicted astronomical tide expected to occur ... over the National Tidal
Datum Epoch (NTDE). The present NTDE is 1983 through 2001." HAT is
an estimate of the highest tide predictable strictly from the
effects of gravity.
Mean Higher High Water|
| "The average of the higher high
water height of each tidal day observed over the NTDE."
Mean Sea Level|
| "The arithmetic mean of the hourly water
heights observed over the NTDE."
Mean Lower Low Water|
| "The average of the lower low water
height of each tidal day observed over the NTDE."
Each datum has its uses:
provides an estimate of where the "grass line" is. Crossing HAT
is an indication that flooding will occur as people tend to build to the grass
line, thus it has direct human impact.
is an estimate of how high water gets each day; however it is
exceeded by the tidal cycle alone for approximately half the month. This site
uses it as a warning that waters are likely to be high, so please pay attention.
is the average water surface. Deviations from MSL provide a
precise description of unexpected amounts of water, but it is
difficult to directly tie it to human impacts due to the variability of
the tide range centered on MSL.
is an estimate of how low water gets each day and is the
standard datum used by NOS tide stations. It is useful for mariners
concerned with running aground.
What do the Datum buttons do?
The buttons allow the graphs or text to be displayed in other datums.
The reasons for this specific choice of datums were:
- HAT the datum which best approximates the grass line and
hence flooding. (Note: MHHW was omitted as HAT serves
this purpose better.)
- MSL the datum most familiar to the general public.
- MLLW to be consistent with NOS and earlier versions of this site.
NOTE: "Surge Guidance" and "Anomaly" values are changes in water
level, so are "datumless". This means that while they appear to move on the
graph when toggling datums, they actually continue to be centered on 0. | <urn:uuid:11311976-8e2d-4298-8fa8-5278485060af> | 3.6875 | 581 | Documentation | Science & Tech. | 53.65903 |
Puppis ( Latin: poop deck) is a southern constellation. It is the largest of the four parts into which Argo Navis was split.
Notable deep sky objects
As the milky way runs through Puppis, there are a large number of open clusters in the constellation. Messier 46 (M46) and Messier 47 (M47) are two open clusters in the same binocular field. M47 can be seen with the naked eye under dark skies, and its brightest stars are 6th magnitude. Messier 93 (M93) is another open cluster somewhat to the south. NGC 2451 is a very bright open cluster containing the star c Puppis.
On November 14, 2007, Nova Puppis 2007, or V597 Pup, was discovered about 1 degree northeast of RS Puppis, a Cepheid variable. The coordinates are RA = 8:16.3, DEC = -34°15', J2000.0 standard. On the Puppis map at right, that is approximately two thirds the distance from ρ Pup to ζ Pup.
Several extrasolar planet systems have been found around stars in the constellation Puppis, including:
* On April 18, 2006, HD 69830 (the nearest star of this constellation) was discovered to have three Neptune-mass planets, the first multi-planetary system without any Jupiter-like or Saturn-like planets. The star also hosts an asteroid belt at the region between middle planet to outer planet.
* On July 4, 2007, the first extrasolar planet found in the open cluster NGC 2423, was discovered around the red giant star NGC 2423-3. The planet is 10.6 times the mass of Jupiter and orbits at 2.1 AU distance.
* Ian Ridpath and Wil Tirion (2007). Stars and Planets Guide, Collins, London. ISBN 978-0007251209. Princeton University Press, Princeton. ISBN 978-0691135564.
* Richard Hinckley Allen, Star Names, Their Lore and Legend, New York, Dover.
Retrieved from "http://en.wikipedia.org/" | <urn:uuid:a70effe7-19a7-4699-ac73-a9d13653a228> | 2.96875 | 443 | Knowledge Article | Science & Tech. | 75.07047 |
Renewable Energy Sources
One of the most common uses of renewable energy is to heat the water of outdoor swimming pools using solar collectors.
While solar energy is a familiar terminology these days, many people don’t know much about any of the other renewable energy sources yet? These are wind, geothermal heat, and rain.
In this article all different types of renewable energy sources and there applications will be explained.
When you have a better understanding of what renewable energy is and that it is naturally replenished you can make more informed decisions. With that heightened environmental awareness you can start to make changes to your lifestyle by consuming less traditional forms of energy.
Today, solar energy has received the most media attention because it is one of the most used renewable energy sources worldwide.
The term solar energy refers to the conversion of energy from the sun into power for all kinds of appliances.
There are already many everyday devices on the market that use solar energy technology. The list includes solar lights, calculators and many items used for hiking and camping.
Anybody who is interested in helping to protect our environment could, for example, use solar power in their house.
You could choose to have your solar power equipment installed by one of the many solar energy providers that are available all over the country. Be aware though, the initial set up can be a little bit expensive with the unit costing approximately $20,000.
Another one of the renewable energy sources that is already being used in this country is wind energy.
Wind turbines are the most common technology to convert wind power into electricity. The wind spins the blades of the turbine around a hub and the main body then spins a generator around.
These days small wind turbines can be found on farms and ranches and they already produce approximately 2,500 megawatts (mw) of energy.
The further expansion of wind energy as one of the major renewable energy sources has been hindered by the high initial installation costs, the fact that wind does not blow every day or everywhere. Therefore, wind energy is more applicable in some states and during specific times of the year.
Geothermal heating is the next of the renewable sources of energy that we discuss in this article.
In principle, geothermal heat takes advantage of the energy/heat found underground below the earths crust.
Geothermal heat pumps are currently the most commonly used type of geothermal technology. Geothermal heat pumps have replaced the older air source heat pumps as the new “in” product in the area of renewable energy sources.
While most people have probably heard of solar energy and some have heard of geothermal energy hardly anybody has heard anything about rain energy, yet.
Scientists have proven that it is possible to generate electricity from falling water drops.
The idea is still very new and lot’s of research and development is needed to get this latest addition to the family of renewable energy sources off the ground but new technologies are being developed almost on a daily basis.
Once the technical challenges are overcome rain energy will be as popular as other renewable energy sources.
We hope this article could assist you in deepening your understanding of the renewable energy sources that are already available today.
New technologies are being constantly introduced that offer new ways to solve our current energy crisis using renewable energy sources and thereby eliminating our dependence on other forms of energy such as fossil fuels or nuclear power. | <urn:uuid:4bf9fc24-3891-464d-b075-4175395d5b91> | 3.171875 | 689 | Knowledge Article | Science & Tech. | 29.124329 |
The Fourier transform is a fundamental tool in many parts of mathematics. This is even more so when one looks at various natural generalizations of it. This article contains brief descriptions of the Fourier transform in various contexts and links to articles about its use.
Basic analysis, complex numbers.
Different kinds of Fourier transform
Periodic functions and functions defined on . Let be a function such that for every . Then the th Fourier coefficient is given by the formula . The function is called the Fourier transform of . Periodic functions are naturally thought of as functions defined on the circle. If we write for the unit circle and have a function , then the formula for becomes .
In the other direction, let be a function from to . We can create a periodic function by defining it to equal . Under some circumstances, and with suitable notions of convergence, one can show that this inverts the previous operation: that is, the sum converges to the function . If we express as a function defined on , then this says that we can write as a doubly infinite power series , defined when .
Functions defined on the group of integers mod . Let be a function from to . Write for . Then the discrete Fourier transform of is the function given by the formula
Functions defined from to .
Functions defined on finite Abelian groups.
Functions defined on locally compact Abelian groups.
Basic facts about the Fourier transform
To be included: Parseval/Plancherel identity, inversion formulae, convolution identities. | <urn:uuid:3ab8b4a8-8168-41e1-ba54-d1a8c0ca820b> | 3.6875 | 319 | Knowledge Article | Science & Tech. | 48.098659 |
Climate change is fast becoming one of the most important issues of our time. Not to dismiss the political discussions going on across the U.S., but a recent analysis of public opinion sponsored by the National Science Foundation indicates that 75 percent of the American public believes the earth’s climate is warming and human activities are responsible (1). The Stanford University study also found that about the same percentage of Americans think the United States government should be passing regulations limiting emissions of greenhouse gases that are causing the problem and moving towards energy savings and green technologies. No one can predict how fast the political process will respond but because of our dependence on the fossil fuels, oil and coal, it’s fair to say that significant changes are coming.
The earth is in an inter-glacial period when cooling would be expected, yet temperatures are increasing (2). Scientists estimate that with current trends, temperature increases of at least seven to 12 degrees Fahrenheit seem likely over the next 50 to 100 years, which will increase sea levels and change weather patterns in unpredictable ways. The heightened awareness of the American public leads to many asking the question- ‘How can we help control carbon dioxide(CO2) emissions and do our part to prevent climate change?’
Most strategies being proposed to mitigate global climate change include increasing carbon storage in plant systems (3). This is often referred to as ‘terrestrial carbon sequestration’. If large amounts of CO2 are removed from the atmosphere by photosynthesis and then held in stable plant material or soil organic matter, it could help offset CO2 generated by fossil fuel use.
The potential benefit of carbon sequestration provides an opportunity for the turfgrass industry to become involved in efforts to control global warming. Turfgrasses comprise 16.4 million hectares in the U.S., the largest irrigated agricultural crop. In addition to offsetting CO2 generation, carbon storage may be of monetary value. A carbon credit/trading market is beginning to develop.
One of the challenges for university scientists is to come up with accurate estimates for amounts of carbon that can be sequestered under turfgrasses. In this study we are examining carbon storage under different turfgrass species receiving differing inputs. It can act as a guide for how to maximize soil carbon levels. Bermudagrass, zoysiagrass, and fescue are receiving low or high amounts of fertilizer and pesticides.
1. Krosnick J. 2009 The Climate Majority, NY Times op-ed June 8, 2009. Refer to woods.stanford.edu
2. Hansen J. 2009. Storms of My Grandchildren. Bloomsbury publishers, 304 pp. ISBN 978-1-60819-200-7 | <urn:uuid:17263ba3-e51e-4312-8d03-520720bf10b7> | 3.6875 | 555 | Academic Writing | Science & Tech. | 42.632652 |
The Tusi-couple is a mathematical device in which a small circle rotates inside a larger circle twice the diameter of the smaller circle. Rotations of the circles cause a point on the circumference of the smaller circle to oscillate back and forth in linear motion along a diameter of the larger circle.
The couple was first proposed by the 13th-century Persian astronomer and mathematician Nasir al-Din al-Tusi in his 1247 Tahrir al-Majisti (Commentary on the Almagest) as a solution for the latitudinal motion of the inferior planets, and later used extensively as a substitute for the equant introduced over a thousand years earlier in Ptolemy's Almagest.
Original description
Some modern commentators also call the Tusi couple a "rolling device" and describe it as a small circle rolling inside a large fixed circle. However, Tusi himself described it differently:
- if two coplanar circles, the diameter of one of which is equal to half the diameter of the other, are taken to be internally tangent at a point, and if a point is taken on the smaller circle—and let it be at the point of tangency—and if the two circles move with simple motions in opposite direction in such a way that the motion of the smaller [circle] is twice that of the larger so the smaller completes two rotations for each rotation of the larger, then that point will be seen to move on the diameter of the larger circle that initially passes through the point of tangency, oscillating between the endpoints.
Other sources
The term "Tusi couple" is a modern one, coined by Edward Kennedy in 1966. It is one of several late Islamic astronomical devices bearing a striking similarity to models in De revolutionibus orbium coelestium, including his Mercury model and his theory of trepidation. Historians suspect that Copernicus or another European author had access to an Arab astronomical text, but an exact chain of transmission has not yet been identified, although the 16th century scientist and traveler Guillaume Postel has been suggested.
There are other sources for this mathematical model for converting circular motions to reciprocating linear motion. It is found in Proclus's Commentary on the First Book of Euclid and the concept was known in Paris by the middle of the 14th Century. In his questiones on the Sphere (written before 1362), Nicole Oresme described how to combine circular motions to produce a reciprocating linear motion. Oresme's description is unclear and it is not certain whether this represents an independent invention or an attempt to come to grips with a poorly understood Arabic text.
Since the Tusi-couple was used by Nicolaus Copernicus in his reformulation of mathematical astronomy, there is a growing consensus that he became aware of this idea in some way. It has been suggested both by a historian of Medieval European astronomy and by a historian of Arabic astronomy that the idea of the Tusi couple may have arrived in Europe leaving few manuscript traces, since it could have occurred without the translation of any Arabic text into Latin. One possible route of transmission may have been through Byzantine science, which translated some of al-Tusi's works from Arabic into Byzantine Greek. Several Byzantine Greek manuscripts containing the Tusi-couple are still extant in Italy.
- George Saliba (1995), 'A History of Arabic Astronomy: Planetary Theories During the Golden Age of Islam', pp.152-155
- "Late Medieval Planetary Theory", E. S. Kennedy, Isis 57, #3 (Autumn 1966), 365-378, JSTOR 228366.
- Craig G. Fraser, 'The cosmos: a historical perspective', Greenwood Publishing Group, 2006 p.39
- Vatican Library, Vat. ar. 319 fol. 28 verso math19 NS.15, fourteenth-century copy of a manuscript from Tusi
- Translated in F. J. Ragep, Memoir on Astronomy II.11 , pp. 194, 196.
- E. S. Kennedy, "Late Medieval Planetary Theory," p. 370.
- E. S. Kennedy, "Late Medieval Planetary Theory," p. 377.
- Saliba, George (1996), "Writing the History of Arabic Astronomy: Problems and Differing Perspectives", Journal of the American Oriental Society 116 (4): 709–18, JSTOR 605441, pp. 716-17.
- Whose Science is Arabic Science in Renaissance Europe? by George Saliba, Columbia University
- I. N. Veselovsky, "Copernicus and Nasir al-Din al-Tusi", Journal for the History of Astronomy, 4 (1973): 128-30
- Claudia Kren, "The Rolling Device," pp. 490-2.
- Claudia Kren, "The Rolling Device," p. 497.
- George Saliba, "Whose Science is Arabic Science in Renaissance Europe?"
- George Saliba (April 27, 2006). "Islamic Science and the Making of Renaissance Europe". Retrieved 2008-03-01.
- Di Bono, Mario. "Copernicus, Amico, Fracastoro and Tusi's Device: Observations on the Use and Transmission of a Model." Journal for the History of Astronomy 26 (1995):133-154.
- Kennedy, E. S. "Late Medieval Planetary Theory." Isis 57 (1966):365-378.
- Kren, Claudia. "The Rolling Device of Naṣir al-Dīn al-Ṭūsī in the De spera of Nicole Oresme." Isis 62 (1971): 490-498.
- Ragep, F. J. "The Two Versions of the Tusi Couple," in From Deferent to Equant: A Volume of Studies in the History of Science in Ancient and Medieval Near East in Honor of E. S. Kennedy, ed. David King and George Saliba, Annals of the New York Academy of Sciences, 500. New York Academy of Sciences, 1987. ISBN 0-89766-396-9 (pbk.)
- Ragep, F. J. Nasir al-Din al-Tusi's "Memoir on Astronomy," Sources in the History of Mathematics and Physical Sciences,12. 2 vols. Berlin/New York: Springer, 1993. ISBN 3-540-94051-0 / ISBN 0-387-94051-0.
- Dennis W. Duke, Ancient Planetary Model Animations includes two links of interest:
- George Saliba, "Whose Science is Arabic Science in Renaissance Europe?" Discusses the model of Nasir al-Din al-Tusi and the interactions of Arabic, Greek, and Latin astronomers. | <urn:uuid:dff3df46-e4c5-4cb0-a22b-71d7fd758bb5> | 3.640625 | 1,423 | Knowledge Article | Science & Tech. | 52.402231 |
Specifies the type of key container access allowed.
This enumeration has a FlagsAttribute attribute that allows a bitwise combination of its member values.Namespace: System.Security.Permissions
Assembly: mscorlib (in mscorlib.dll)
|No access to a key container.|
|Create a key container.|
Creating a key container also creates a file on disk. It is very important that any key container that is created is removed when it is no longer in use.
|Open a key container and use the public key.|
Open does not give permission to sign or decrypt files using the private key, but it does allow a user to verify file signatures and to encrypt files. Only the owner of the key is able to decrypt these files using the private key.
|Delete a key container.|
Deleting a key container can constitute a denial of service attack because it prevents the use of files encrypted or signed with the key. Therefore, deletion is a privileged operation.
|Import a key into a key container.|
The ability to import a key can be as harmful as the ability to delete a container because importing a key into a named key container replaces the existing key.
|Export a key from a key container.|
The ability to export a key is potentially harmful because it removes the exclusivity of the key.
|Sign a file using a key.|
The ability to sign a file is potentially harmful because it can allow a user to sign a file using another user's key.
|Decrypt a key container.|
Decryption is a privileged operation because it uses the private key.
|View the access control list (ACL) for a key container.|
|Change the access control list (ACL) for a key container.|
|Create, decrypt, delete, and open a key container; export and import a key; sign files using a key; and view and change the access control list for a key container.|
This enumeration is used by members of the KeyContainerPermissionAccessEntry class.
Many of these flags can have powerful effects and should be granted only to highly trusted code.
The most powerful of the flags are , , , , , , and . For specific threats that the use of these flags can present, see the member descriptions.
The following code example shows the use of the enumeration. This code example is part of a larger example provided for the KeyContainerPermission class.
Windows 7, Windows Vista, Windows XP SP2, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP Starter Edition, Windows Server 2008 R2, Windows Server 2008, Windows Server 2003, Windows Server 2000 SP4, Windows Millennium Edition, Windows 98
The .NET Framework and .NET Compact Framework do not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements. | <urn:uuid:5390c993-1c08-4e6d-9528-3bf3c96ed60e> | 2.921875 | 609 | Documentation | Software Dev. | 47.574495 |
Water and Solution Evaporation Rates
Date: Winter 2011-2012
After researching many sites including yours, my son attempted an experiment to determine what would evaporate quicker: tap water, bottled purified water, or a homemade solution of salt water. All of the research dictated that the tap water should evaporate first. He conducted the experiment 3 separate times and came up with different results every time. The variables for all three experiments were the same every time. He used 8 ounces of each specific type of water in the same size plastic container each time and allowed it to sit for 48 hours in a controlled area of the house (a dark dining room). He then measured the amount of water left in the container. During the first experiment the tap water evaporated the quickest followed by the salt water and lastly the bottled water. After 48 hours the results were 6 oz (tap), 6.125 oz (salt), 6.25 oz (bottled). In the second experiment the salt water evaporated the quickest then the bottled water and lastly the tap water. The results were 7oz (tap), 6.5 (salt) and 6.75 (bottled). In the third attempt the salt water evaporated quickest, followed by the tap water and lastly the bottled water. The results were 7 oz (tap), 6.75 oz (salt), and 7.125 oz (bottled). Please help explain these findings, we are at a loss trying to explain this. Unfortunately time isn't on our side as this needs to be turned in this Friday the 10 of Feb.
Did your son have a hypothesis (which water did he predict would evaporate more quickly)?
Were the containers steam cleaned before each experiment?
Was each container exactly like the others?
Were they located in the exact same place (and in the same order)?
How were the measurements made? By weight or volume?
What techniques were used?
Were air vents in the area?
Was shade an issue?
It is OK to be at a loss and unable to explain your results. One of the many great things about science is that often the results raise more interesting questions that need exploration.
Your son could say that the inconclusive results require further experimentation. This type of conclusion would be appropriate.
Leslie Kanat, Ph.D.
Professor of Geology
Johnson State College
First, please allow me to applaud you and your child for attempting to do experimental science.
The inconsistency of the results indicate that there must be other factors at play. These might be called experimental errors. Experimental errors are not necessarily a bad thing. They can be due to unforeseen environmental factors. It may also be that your data indicate a flaw in the prevailing theories about evaporation rate, which would be especially exciting!
In looking over your results, the lack of consistency would seem to infer that there is some kind of experimental error. Identifying the source of the error can be difficult. Some critical areas that come to my mind that would affect results include: surface area, water temperature, humidity, air flow above the water sample. Another thing that you did not include in your write-up was the amount of salt in your salt water sample.
It is really important to control all the variables except those that we are changing and testing for. I am wondering why you though that bottled water would evaporate at a different rate than tap water? A lot of bottled water is just filtered tap water. Any differences in rate could be due to the concentration of mineral content in either the bottled or the tap water.
To control for all these factors may require equipment that is more sophisticated than the apparatus that you have.
A better test would be to obtain distilled water and test that against various concentrations of salt water. To control for environmental factors, you should run multiple sets at the same time. For example, several containers of distilled water, several containers of low concentration salt water, several containers of slightly higher concentration salt water, several containers of even higher concentration salt water, several containers of even higher concentration salt water, and so forth. All the containers should remain in the same environment. The salt water should be made from table salt and distilled water. The results should be averaged and compared.
Ray Tedder, NBCT
I think you should think the experiment through with this idea:
A little liquid evaporates and makes water vapor. The air holds rather little of that.
The water vapor has to go away somewhere for more liquid to evaporate,
and the motion of the air is what moves that vapor.
In any one run of your experiment I'm not convinced that all 3 dishes experienced the same amount of airflow and heat input.
I also can't know whether the relevant things were the same between one trial and the next.
The typical dish of water will evaporate faster if there is a fan blowing over it, than if the air is left to it's own spontaneous motions.
There is almost always some rate of motion, due to convection or breezes or whatever.
If the rate was zero, evaporation would pretty distinctly stop.
When something that matters like this airflow is so subtle you do not see it, but it still matters,
then mysterious things just keep on happening.
It is a variable and you must eliminate or measure the variables.
If the room is totally closed, the fan will not help much.
the whole room gets humid, then there is no more room in the air for more water vapor.
Or maybe the walls drip if they are held cooler than the dishes.
But the usual exhaust path for water vapor is out of the room through some window or door.
Then the world at large can worry about getting rid of it.
Someday It will condense in a cloud somewhere and rain onto the ground or into the ocean.
Evaporation requires heat input.
That is _not_ the same as saying the temperature has to be higher.
The water can be a little colder than the room and still keep evaporating.
When it is cold, it tries to suck in heat from the surroundings.
If it can get that heat, it keeps evaporating.
If you had a perfect thermos bottle of water with no way for heat to get in,
some evaporation would happen, and that would make the water cooler,
and that would slow down the evaporation.
It would keep getting cooler, and slower, until evaporation pretty much stopped.
So all 3 dishes need to have the same heat-sinking to have a fair experiment.
Be sure they have identical containers,
and you don't have a lamp pointing right at one dish more than the others,
or sunlight with moving shadows.
Plastic cups are probably the best identical containers you can get.
Maybe put all three on a common aluminum plate or pan,
and maybe even have an opaque roof, elevated a few inches over the pan.
I think you need to do a control run.
put 3 identical containers filled with the same liquid into your setup.
They should go down at about the same rate, but maybe they are up to 30% different.
Measure how fast or how far in a given time, for each. The ratios between them are what matters.
If one has a better position than the others, it shows up clearly here.
Do it one more time, and hope the ratios of rates are the same as the first time.
If they are, you can start doing assorted various liquids and know you are measuring the right thing.
If you do the same 3 liquids three times, but rotate the positions so that each liquid gets to be in each position once,
and then you average the rates of those three times for each liquid,
that can be a pretty fair answer.
But it is important to know that the relative advantages of the 3 positions are repeatable.
That is what the control runs are for.
I would use bottled water for control runs.
It has the least solids, and solids can precipitate at the surface and affect the exposure to moving air,
either by blocking or by wicking.
I would probably do this by making a big box with two 4" holes
or getting a large pot and propping the lid up 1" on one side.
then have a fan point at one hole of the box or tangent to the open side of the pot-lid.
Keep the fan at a fixed and fairly large distance.
Air is really going to swirl around inside the pot. I think that helps all 3 cups get equal air exposure.
Having a fan in the room you used, next to the wall on the opposite side of the room,
blowing parallel to the wall, probably would have helped. (I know, who would have guessed that...)
It would make sure the air was moving at a fair (non-zero) pace, the same pace each time,
and about the same speed for all three cups, if all three were the same distance from the wall they were near.
You could let the liquids take turns being the upwind cup.
There are several issues that need to be resolved. The first is “units”. Unfortunately, in English units (ounces = oz) can be either volume, or weight (mass), if gravity is take into account. Although you assert that the samples were evaporated in a controlled area (a dark dining room), how do you “know” that this is a controlled area? For example, how do you “know” that the humidity was the same in the various conditions. Both temperature and humidity would have to be carefully a controlled constant. This is not so easy as it may seem. The presence or absence of light would be much less important than small changes in temperature and humidity. Small changes in the flow of air above the samples would be a much more important factor. How do you know these variables were controlled? Were the three test samples tested simultaneously or sequentially? From your description, it is not clear what the order of operations is. You did not mention the percent change of the various weight. It would be important if the relative change was 0.1% or 10.0%, because then “experimental” error would become a large factor.
Your experiment is not a loss, not at all! You are not getting the result you “expected”. That is probably your most important observation. What you “expected” is not what happened. That is far MORE IMPORTANT than the getting the “right answer”. Analyzing what may have happened is far more interesting!!
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Update: June 2012 | <urn:uuid:ad2acc8b-ffa9-497c-bfa0-02775df4b7b9> | 3.234375 | 2,223 | Q&A Forum | Science & Tech. | 58.184403 |
Can you each work out the number on your card? What do you notice?
How could you sort the cards?
I am thinking of three sets of numbers less than 101. They are the
red set, the green set and the blue set. Can you find all the
numbers in the sets from these clues?
If you have ten counters numbered 1 to 10, how many can you put
into pairs that add to 10? Which ones do you have to leave out?
A case is found with a combination lock. There is one clue about the number needed to open the case. Can you find the number and open the case?
This is a game in which your counters move in a spiral round the snail's shell. It is about understanding tens and units.
Skippy and Anna are locked in a room in a large castle. The key to that room, and all the other rooms, is a number. The numbers are locked away in a problem. Can you help them to get out?
Here is your chance to investigate the number 28 using shapes,
cubes ... in fact anything at all.
I am thinking of three sets of numbers less than 101. Can you find
all the numbers in each set from these clues?
Can you find ways of joining cubes together so that 28 faces are
Guess the Dominoes for child and adult.
These spinners will give you the tens and unit digits of a number. Can you choose sets of numbers to collect so that you spin six numbers belonging to your sets in as few spins as possible?
Nearly all of us have made table patterns on hundred squares, that
is 10 by 10 grids. This problem looks at the patterns on
differently sized square grids.
Bernard Bagnall recommends some primary school problems which use
numbers from the environment around us, from clocks to house
This investigates one particular property of number by looking closely at an example of adding two odd numbers together.
This article introduces the idea of generic proof for younger children and illustrates how one example can offer a proof of a general result through unpacking its underlying structure.
What would you do if your teacher asked you add all the numbers from 1 to 100? Find out how Carl Gauss responded when he was asked to do just that.
Look at three 'next door neighbours' amongst the counting numbers. Add them together. What do you notice?
This problem looks at how one example of your choice can show something about the general structure of multiplication.
Mr Gilderdale is playing a game with his class. What rule might he have chosen? How would you test your idea?
Can you find any perfect numbers? Read this article to find out more...
This article gives you a few ideas for understanding the Got It! game and how you might find a winning strategy.
Find out about palindromic numbers by reading this article.
Marion Bond recommends that children should be allowed to use
'apparatus', so that they can physically handle the numbers
involved in their calculations, for longer, or across a wider
ability band,. . . .
Each light in this interactivity turns on according to a rule. What
happens when you enter different numbers? Can you find the smallest
number that lights up all four lights?
This task depends on learners sharing reasoning, listening to
opinions, reflecting and pulling ideas together.
Work out how to light up the single light. What's the rule?
Ranging from kindergarten mathematics to the fringe of research
this informal article paints the big picture of number in a non
technical way suitable for primary teachers and older students. | <urn:uuid:874fa1a7-2528-4120-a755-2c8abe351e22> | 3.75 | 758 | Content Listing | Science & Tech. | 70.299195 |
To have threading supported at the language level means that the language provides first-class support for multi-threading, as opposed to just providing second-class support via class libraries.
In Java, threading is supported at the language level with the
volatile keywords. Using monitors and volatile fields are relatively low-level threading constructs - higher level constructs, such as generic Locks, Barriers, ThreadPools, Concurrent collections are found in the
java.util.concurrent package, along with low level atomic operations.
Threading in Java is more than a few keywords in the language. The Java Memory Model mandates the results of multi-threaded memory access, such as when changes by one thread are visible to other threads. This ensures correctly written threaded programs function as intended regardless of the underlying architecture (instruction re-ordering, cache-coherence polices etc..)
The original java class library provides threading support with
java.lang.Thread, representing a thread, and since JDk 1.2,
java.lang.ThreadLocal, representing thread-local variables. The original JDK also includes an abstract notion of an executable object -
java.lang.Runnable. The concurrency utils extend this with
Future, which make creating asynchronous results much simpler than it would be coding with just the low level constructs.
While you can make do with
Runnable (as many did prior to JDK 1.5) the classes provided by the concurrency utils make writing threaded programs much easier and with a greater chance of them being correct. | <urn:uuid:30cb8a1f-56f2-4969-9f89-ab4a6e7156a1> | 3.234375 | 328 | Q&A Forum | Software Dev. | 42.25 |
The grey-faced sengi is a relative newcomer to the elephant shrew family. The journey of discovery began in 2005, when a unfamilar species of giant elephant shrew was caught on a camera trap in the Udzunga mountains of Tanzania. An expedition the following year confirmed this as the first new elephant shrew species identified for over 120 years and by far the biggest. The only place on Earth they can be found is in this African mountain range, where the population is estimated to be fewer than 100.
Scientific name: Rhynchocyon udzungwensis
Grey-faced elephant shrew
The Grey-faced sengi can be found in a number of locations including: Africa. Find out more about these places and what else lives there.
The following habitats are found across the Grey-faced sengi distribution range. Find out more about these environments, what it takes to live there and what else inhabits them.
Discover what these behaviours are and how different plants and animals use them.
Additional data source: Animal Diversity Web
The grey-faced sengi (Rhynchocyon udzungwensis) is a species of elephant shrew that is endemic to the Udzungwa Mountains of south-central Tanzania. The discovery of the species was announced in January 2008; only 15 species of elephant shrew were known until then, and the last discovery was made more than 120 years ago. As the name implies, the species is characterised by a distinctive grey face and a black rump, as well as being larger than the other species of elephant shrews.
This page is best viewed in an up-to-date web browser with style sheets (CSS) enabled. While you will be able to view the content of this page in your current browser, you will not be able to get the full visual experience. Please consider upgrading your browser software or enabling style sheets (CSS) if you are able to do so. | <urn:uuid:3c4e4cc2-e8b5-4236-a1d0-c307011fd033> | 3.390625 | 402 | Knowledge Article | Science & Tech. | 45.325714 |
Despite the increasing knowledge of amphibians and reptiles in Guyana, the southern part of the country has yet to be explored. Southern Guyana has been noted as a high research priority because it harbors large, contiguous forests, and a high diversity of habitats. The reptiles and amphibians of the Acarai Mountains and the upper Essequibo River had never been surveyed before this expedition.
Sampling for reptiles and amphibians took place in the rivers and tributaries and in the nearby vegetation, with the exception of occasional findings by the other RAP team members (usually the insect team). Adult and juvenile amphibians and reptiles were captured by hand once seen, while tadpoles were collected using fine mesh nets (occasionally by the fish team).
|Blue poison dart frog |
The team also interviewed local field guides informally, who were able to provide information especially about medium-to-large reptiles.
The study area yielded 26 species of amphibians and 34 species of reptiles. Most of the amphibians were of the order Anura, of which over half were tree-frogs. Toads and poison arrow frogs were found in smaller numbers. Within reptiles, the team recorded two species of crocodilians, three turtles, 14 lizards, and 16 snakes. All of the large reptiles, including two species of crocodiles and three of turtles, are part of the Wai-Wai diet.
Most of the sampling effort was devoted to areas of importance to the Wai-Wai, or near to their village. Overall, the results showed only a fraction of the amphibians and reptiles found in the area and more work should be undertaken to determine its true richness. Many of the amphibians found were species generally associated with habitat affected by human activity.
IN DEPTH: Learn more about reptiles and amphibians of the Konashen, Guyana.
|Schneider's dwarf caiman (Paleosuchus trigonatus) young, this species |
prefers more turbid waters than other species of the genus.
This includes such species as the common cane toad Chaunus marinus
, the smooth sided toad Rhaebo guttatus
, the black spotted skink Mabuya nigropuntata
, the bridled gecko Gonatodes humeralis
, and turnip tailed gecko Thecadactylus rapicauda
These species were found in the houses, and whiptail lizards Ameiva ameiva and Kentropix calcarata were found at sites nearby.
|Worm lizard |
is legless and without
The blind snake Typhlophis ayarzaguenai
represents the first record of this species for Guyana. An aquatic lizard, the snake Helicops
sp., and the caecilian may also represent new records for Guyana, once taxonomic review is completed. The caecilian was found only in the non-flooded forest of the Acarai Mountains. Monkey frogs of the genus Phyllomedusa
were also found in this area.
In the Kamoa River area, two species were found that were unique to that area; the crested forest toad (Bufo margaritifera) and the chicken frog (Leptodactylus knudseni).
What it Means
|Emerald tree boa (Corallus caninus) coiled in a tree.|
Since the expedition was conducted only during the dry season, there are undoubtedly many more species to discover in this region. The Acarai Mountains and Sipu River area is likely the richest in the Konashen COCA for reptiles and amphibians.
The elevation ranges and unique habitats, including non-flooded forest and mountain streams, probably harbor many endemic and undescribed species, making it very important for future research.
Although the area of Konashen closest to the villages showed much less abundance of medium-to-large reptiles, many of which are part of the Wai-Wai diet, the other reptile and amphibian communities appeared to be in good shape.
| Ant Team | Dung Beetle Team | Katydid Team | Fish Team |
| Reptile and Amphibian Team | Bird Team | Mammal Team | | <urn:uuid:14b23082-e1c2-445c-be6b-bb1262aa9658> | 3.171875 | 895 | Knowledge Article | Science & Tech. | 33.293203 |
Pacific Rocky Intertidal Monitoring: Trends and Synthesis
Click here for Long-Term trends
Click here for Biodiversity Survey findings
Paradise Cove is located in the South Coast region of California. The site is located in an Area of Special Biological Significance (Mugu Lagoon to Latigo Point ASBS), within the Point Dume State Marine Conservation Area. There is at least one storm water discharge in the vicinity of this site, and this site is 1.2 miles northeast of the Point Dume Mussel Watch site. This moderately sloping site consists of moderately uneven terrain, containing few cracks and folds.
Paradise Cove is dominated by a mixture of consolidated sandstone bedrock and sandy beach, and the area surrounding the site is comprised of a mixture of consolidated bedrock and sandy beach. The primary coastal orientation of this site is southeast.
Long-Term Monitoring Surveys at Paradise Cove were established in 1994, and are done by University of California Los Angeles. Long-Term MARINe surveys currently target the following species: Chthamalus/Balanus (Acorn Barnacles), Mytilus (California Mussel), Endocladia (Turfweed), Phyllospadix (Surfgrass), and Pisaster (Ochre Star). In addition, motile invertebrates, barnacle recruitment, and mussel size structure are monitored at this site. Click here to view Long-Term trends at this site.
Biodiversity Surveys were done by University of California Santa Cruz in 2001, 2006, and 2010. The Biodiversity Survey grid encompasses two sections that are approximately 12 meters (along shore) x 10 meters (seaward), and 15 meters (along shore) x 10 meters (seaward). Click here to view Biodiversity Survey findings at this site.
For more information about Paradise Cove, please contact Rich Ambrose. | <urn:uuid:3bd9f76e-d711-4e97-b11a-c52049499f75> | 2.828125 | 388 | Knowledge Article | Science & Tech. | 24.779135 |
April, 2013. Scheyvens, Henry; Sagara, Miho and Ibarra Gené, Enrique. Institute for Global Environmental Strategies (IGES), Japan. 133 pages. ISBN: 978‐4‐88788‐133‐4
Curious about REDD?
Want to learn more about REDD?
If you want to learn more about REDD, than read on this page...
Some external reading
MUST READ! June 2012 - REDD+ status after RIO+20:
The Status of REDD: An interesting and informative collection of articles
Recarbonizing the earth
The case for reducing emissions of greenhouse gases is more compelling than ever. But it's also past time to begin drawing carbon out of the air...
WWF REDD Library
It's from WWF, nothing more to say, just follow the link!
REDD training materials
Reducing Emissions from Deforestation and forest Degradation (REDD) is a concept that has been gaining momentum in climate change policy negotiations both internationally and at the national level in capitals around the world. Yet despite the increasing levels of interest and activity in REDD, there is a great deal of confusion that still surrounds the concept...
New proposals to use international financial mechanisms to reduce carbon emissions from deforestation and degradation (REDD) have radical implications for the ways in which tropical forests...
The Little REDD+ book
Launched at the UNFCCC climate summit in December 2008 The Little REDD Book is a guide to the UN negotiations on Reducing Emissions from Deforestation and Degradation (REDD)...
The Eliasch Review
The Review aims to provide a comprehensive analysis of international financing to reduce forest loss and its associated impacts on climate change. It does so with particular reference to the international efforts to achieve a new global climate change agreement in Copenhagen at the end of 2009...
AMONG THE MANY NASTY things that humans are doing to the environment, few rank worse than destroying tropical forests. Rainforests sustain an astonishing diversity of species and keep our planet liveable by limiting soil erosion, reducing floods, maintaining natural water cycles, and stabilising...
As time goes by, site has envolved, therefore we do offer two different texts for users who have been brought to our site and this link:
September/October 2012 - a note by the Editor of ForestIndustries.EU: We wrote this article more than two years ago. Many significant events happened since then and a huge amount of new knowledge has been collected by the global community.
In 2007, more than 50,000 fires raged through the Brazilian Amazon, reducing what were once lush rainforests to charred plains stretching to the horizon. Meanwhile, on the other side of the world, fires on the island of Borneo consumed millions of hectares of old-growth forests. | <urn:uuid:8f162c26-252c-43b5-be99-12fb98ec717e> | 3.296875 | 582 | Content Listing | Science & Tech. | 46.409762 |
This first edition was written for Lua 5.0. While still largely relevant for later versions, there are some differences.
The third edition targets Lua 5.2 and is available at Amazon and other bookstores.
By buying the book, you also help to support the Lua project.
|Programming in Lua|
|Part II. Tables and Objects Chapter 14. The Environment|
Lua keeps all its global variables in a regular table,
called the environment.
(To be more precise,
Lua keeps its "global" variables in several environments,
but we will ignore this multiplicity for a while.)
One advantage of this structure is that it simplifies the internal
implementation of Lua,
because there is no need for a different data structure for global variables.
The other (actually the main) advantage is that we can manipulate this
table as any other table.
To facilitate such manipulations,
Lua stores the environment itself in a global variable
_G._G is equal to
the following code prints the names of
all global variables defined in the current environment:
for n in pairs(_G) do print(n) end
In this chapter, we will see several useful techniques to manipulate the environment.
|Copyright © 2003–2004 Roberto Ierusalimschy. All rights reserved.| | <urn:uuid:64d5c808-1df6-4de3-bfa6-ea375ea69c39> | 2.9375 | 275 | Documentation | Software Dev. | 47.3665 |
The science of a solar eclipse
Total solar eclipse to occur over northeastern Australia
A total solar eclipse occurred over the northeastern Australian coast early in the morning of November 14 local time.
Clueless about this spectacular astronomical event? No worries, we've got you covered. We're here to explain what causes this remarkable act of nature, what skygazers see and how those outside of Australia can join in the experience.
What exactly is a total solar eclipse?
A solar eclipse happens when the moon, as it orbits Earth, passes directly in front of the sun, obscuring its rays and casting a shadow on Earth's surface. Sometimes referred to as a "happy accident of nature," a total solar eclipse occurs when the moon is perfectly aligned with both the sun and Earth, so it appears from our perspective that the sun is completely blocked.
When is this happening and who can see it?
The total solar eclipse became visible in the far north of Australia about an hour after sunrise local time on November 14 (afternoon of November 13 in the United States and evening of November 13 in Europe).
A total eclipse of the sun can only be seen from within what's known as the path of totality, a narrow path the moon's inner shadow travels as it glides across the Earth. The most populated areas within that path are in the Cairns and Great Barrier Reef region.
It estimated to take about three hours for the moon's shadow to travel the entire path of totality. What time total darkness occurred, and how long it lasted, depended on location. Totality was expected to begin in Cairns at 0638 local time and was to last nearly two minutes. By contrast, totality was estimated to only last just about 20 seconds in the small town of Innisfail.
What's all the fuss about? Don't these happen frequently?
According to NASA, a full solar eclipse happens, on average, every 18 months. The last one happened in July 2010, crossing Chile's Easter Island, and one will occur over equatorial Africa in November 2014. But for any given region, a total solar eclipse only happens, on average, once every 375 years.
Solar eclipses were shrouded in superstition in ancient times -- in China, for example, viewing total solar eclipses was important for divining the future success of an emperor. However, as scientific knowledge deepened, these events became opportunities for conducting important experiments. It was during a total solar eclipse in 1919 that Einstein's theory of general relativity was tested and confirmed for the first time.
What's it like to experience a solar eclipse and what do you see?
A solar eclipse is often described as one of nature's most awe-inspiring events. Some people are so moved by the experience of watching an eclipse that they travel around the world chasing them.
About an hour leading up to totality, all sorts of things begin to happen. There are changes in the color of the sky, the temperature drops, birds and animals behave in a peculiar manner and shadows sharpen, according to Rick Brown, an eclipse chaser from New York who is viewing his 14th total solar eclipse. "I never really expected to be moved the way I was. It's a phenomenal thing to see," he said, recalling his first experience.
As the moon's shadow sweeps across the Earth, the sun turns into a crescent in the sky. Just before totality, so-called Baily's beads --- bright spots of sunlight shining through the moon's craggy surface --- can appear around the moon. Then the moon completely blots out the sun, leaving only a halo of light visible. After the brief period of darkness, Baily's beads might appear again as the sun comes back into view.
I missed it. Where can I see this eclipse?
You can watch the video here on CNN.
On Twitter, there was a tweet-up devoted to the event and you can always get first-hand accounts of the event on iReport, where we asked people to share their solar eclipse photos and experiences.
Do I need special glasses to watch a solar eclipse?
Yes! Permanent eye damage can occur if you look directly at the sun. That means when viewing any partial phase of a total eclipse, you need to wear proper solar eclipse glasses. Regular sunglasses won't offer enough protection, and forget about using telescopes or binoculars unless you've attached special filters to them. Only during totality can you remove filters and glasses. If you're feeling crafty, you can create your own pinhole projector.
Any tips for first-time viewers?
If you're keen to capture some good photos, you need to be prepared. Eclipse Chasers, a website devoted to solar eclipses, has several pointers for photographers. Among them:
-- Leave your flash attachment at home -- Don't forget to remove your filter during totality -- Use a telescope or telephoto lens with a focal length of 400 millimetres or more -- Opt for manually focusing over auto focus -- Keep your setup as portable, light and easy to assemble as possible in case you need to relocate in a hurry to escape clouds.
Veteran eclipse watchers all had the same advice for first-timers: don't waste time fiddling with cameras and telescopes that you miss soaking up that fleeting moment of complete darkness.
Copyright 2012 by CNN NewSource. All rights reserved. This material may not be published, broadcast, rewritten or redistributed. | <urn:uuid:c0151c56-b689-4662-9181-4e70f320cd84> | 3.703125 | 1,116 | Audio Transcript | Science & Tech. | 49.004485 |
Report an inappropriate comment
Thu Jan 17 14:37:39 GMT 2013 by Eric Kvaalen
"About 300,000 years after the big bang, the charged hydrogen that filled the universe became neutral and opaque, creating a cosmic fog that blotted out visible light for a billion years."
That's not right. When the hydrogen became neutral it became transparent! That's why we can still see the light that was emitted at that time. | <urn:uuid:d58aeceb-1609-43ee-b59a-695d25764063> | 3.375 | 91 | Comment Section | Science & Tech. | 69.160203 |
Water Proof Neoprene
I am trying to explain to my class why Neoprene is
waterproof, but I lack the in-depth knowledge to do so. Please assist me
Neoprene is a trade name for a class of synthetic rubber. Most
rubbers are polymers built up from butadiene (H2C=CH-CH=CH2).
Isoprene replaces the H of the second carbon with CH3, chloroprene
replaces that H with Cl. In any case, there are two main reasons why
rubbers are waterproof. The first being that the polymer does not
form intermolecular attractive interactions with water. Most rubbers
are only capable of either London Forces (LF) or Dipole-dipole (DD)
interaction whereas water forms Hydrogen Bonding (HB) intermolecular
forces with itself. The HB forces in water are so strong and makes
the interaction so stable that in order for anything to interact
with water that something must be capable of replacing the HB forces
within water with an interaction that is equally as strong. Since LF
and some DD forces are weaker than HB, the replacement does not
happen. The other reason is that in order for water molecules to
penetrate a sheet of rubber, the water molecule must be able to
migrate through the gaps in between the polymer strands. The
molecular strands in a rubber sample do form gaps that are large
enough for a single water molecule to pass through. However, since
water forms very strong interactions with itself, one does not find
a single molecule of water by itself. Rather it is droplets of
water, an agglomeration of water molecules that is trying to migrate
through a sheet of rubber. Since the water does not interact with
the rubber molecules, it will tend to have a high surface tension,
retain its droplet size and as such is too big to pass through the
gaps between the rubber molecule strands in the rubber sample.
Since you are teaching K-3 students, it might be better to forego
the above explanation and try to let the students formulate their
own conceptions that may not be founded on the more involved
chemistry just explained.
I would try a more exercise driven discussion. Here is what I think.
You will need some nail polish remover (mostly acetone and water).
Some foamed pressed polystyrene (those take-out boxes from fast food
places), some polystyrene sheets (cut out the plastic windows from
envelopes and mailers), a few glasses or beakers, and some water.
Let the students discover that the foamed boxes do not dissolve in
water but readily dissolve in acetone. They can then come to the
conclusion that a bead of water on the surface of the polystyrene
windows will not be able to penetrate the window. However, a drop of
acetone on this same window will eventually push through and
actually punch a hole. This could bring home the idea that
controlling solubility properties is one of the factors in water-proofing.
For the permeability lesson, you can inflate a rubber balloon so
that the skin is very tight and come back the next day to find that
the balloon is not quite as inflated as it was before. A balloon
filled with water on the other hand should remain just as inflated
and should indicate to the students that the ability of a molecule
to migrate through a skin controls whether the skin is proof against
Hope this helped.
Greg (Roberto Gregorius).
Update: June 2012 | <urn:uuid:a5b91f73-9a10-4b35-b494-847a46bc043b> | 3.265625 | 763 | Q&A Forum | Science & Tech. | 45.680621 |
The New Caledonian crow is a member of the corvid family, which also includes ravens, jays, and magpies. Corvids are considered the most intelligent bird species, and their tool-making abilities rival or surpass those of great apes--in fact, their puzzle-solving skills are about on par with a 5-year-old human child. Crows are the only non-primates to consistently complete the "stick and tube" puzzle, in which a piece of food is placed halfway down the length of a clear tube. A long stick is placed nearby. To get the food, the animal has to use the stick to poke the food out of the tube. Crows complete this task easily and spontaneously, without having to watch another crow do it first--and even without having seen a clear tube before.
The New Caledonian crow is also the only non-human species to invent new tools by modifying existing tools. It then passes those new creations onto other crows in its social group. The crow is able to use tools to retrieve other tools, and it can create tools out of materials it has never seen in the wild--again, the only non-human to do so. In an experiment at the University of Oxford, two crows were presented with two types of wire, one hooked and one straight. The hooked wire was needed to retrieve a tiny pail containing food from a tube. But when one of the crows grabbed the hooked wire and "made off," the second crow bent the straight wire into a hook and snagged the food. These crows had never seen wire before. | <urn:uuid:e3597fb4-b7be-4945-ae83-50c80e613b3c> | 3.46875 | 333 | Knowledge Article | Science & Tech. | 57.14293 |
Nowadays, electron microscopes are an essential tool, especially in the field of materials science. At TU Vienna, electron beams are being created that possess an inner rotation, similarly to a tornado. These "vortex beams" cannot only be used to display objects, but to investigate material-specific properties - with precision on a nanometer scale. A new breakthrough in research now allows scientists to produce much more intense vortex beams than ever before.
Quantum Tornado: the Electron as a Wave
In a tornado, the individual air particles do not necessarily rotate on their own axis, but the air suction overall creates a powerful rotation. The rotating electron beams that have been generated at TU Vienna behave in a very similar manner. In order to understand them, we should not think of electrons simply as minuscule points or pellets, as in that case they could at most rotate on their own axis. Vortex beams, on the other hand, can only be explained in terms of quantum physics: the electrons behave like a wave, and this quantum wave can rotate like a tornado or a water current behind a ship's propeller.
"After the vortex beam gains angular momentum, it can also transfer this angular momentum to the object that it encounters", explained Prof. Peter Schattschneider from the Institute of Solid State Physics at TU Vienna. The angular momentum of the electrons in a solid object is closely linked to its magnetic properties. For materials science it is therefore a huge advantage to be able to make statements regarding angular momentum conditions based on these new electron beams.
Beams Rotate - With Masks and Screens
Peter Schattschneider and Michael Stöger-Pollach (USTEM, TU Vienna) have been working together with a research group from Antwerp on creating the most intense, clean and controllable vortex beams possible in a transmission electron microscope. The first successes were achieved two years ago: at the time, the electron beam was shot through a minuscule grid mask, whereby it split into three partial beams: one turning right, one turning left and one beam that did not rotate.
Now, a new, much more powerful method has been developed: researchers use a screen, half of which is covered by a layer of silicon nitride. This layer is so thin that the electrons can penetrate it with hardly any absorption, however they can be suitably phase-shifted. "After focusing using a specially adapted astigmatic lens, an individual vortex beam is obtained", explained Michael Stöger-Pollach.
This beam is more intense by one order of magnitude than the vortex beams that we have been able to create to date. "Firstly, we do not split the beam into three parts, as is the case with a grid mask, but rather, the entire electron stream is set into rotation. Secondly, the grid mask had the disadvantage of blocking half of the electrons - the new special screen does not do this", said Stöger-Pollach.
Thanks to the new technology, right and left-rotating beams can now be distinguished in a reliable manner - previously this was only possible with difficulty. If we now add a predetermined angular momentum to each right and left-rotating beam, the rotation of one beam is increased, while the rotation of the other beam decreases.
Electron microscopes with a twist
This new technology was briefly presented by the research team in the "Physical Review Letters" journal. In future, the aim is to apply the method in materials science. Magnetic properties are often the focus of attention, particularly in the case of newly developed designer materials. "A transmission electron microscope with vortex beams would allow us to investigate these properties with nanometric precision", explained Peter Schattschneider.
More exotic applications of vortex beams are also conceivable: in principle, it is possible to set all kinds of objects in rotation - even individual molecules - using these beams, which possess angular momentum. Vortex beams could therefore also open new doors in nanotechnology. | <urn:uuid:2a0ae20e-9e35-4c91-ba0d-12fd656c4087> | 3.9375 | 816 | Knowledge Article | Science & Tech. | 32.231131 |
What has global warming done since 1998?
What the science says...
|Select a level...||Basic||Intermediate|
For global records, 2010 is the hottest year on record, tied with 2005.
No, it hasn't been cooling since 1998. Even if we ignore long term trends and just look at the record-breakers, that wasn't the hottest year ever. Different reports show that, overall, 2005 was hotter than 1998. What's more, globally, the hottest 12-month period ever recorded was from June 2009 to May 2010.
Though humans love record-breakers, they don't, on their own, tell us a much about trends -- and it's trends that matter when monitoring Climate Change. Trends only appear by looking at all the data, globally, and taking into account other variables -- like the effects of the El Nino ocean current or sunspot activity -- not by cherry-picking single points.
There's also a tendency for some people just to concentrate on air temperatures when there are other, more useful, indicators that can perhaps give us a better idea how rapidly the world is warming. Oceans for instance -- due to their immense size and heat storing capability (called 'thermal mass') -- tend to give a much more 'steady' indication of the warming that is happening. Here records show that the Earth has been warming at a steady rate before and since 1998 and there's no signs of it slowing any time soon.
Land, atmosphere, and ice heating (red), 0-700 meter ocean heat content (OHC) increase (light blue), 700-2,000 meter OHC increase (dark blue). From Nuccitelli et al. (2012).
Last updated on 10 January 2013 by dana1981. View Archives | <urn:uuid:a93e058c-554f-4b96-9543-7a640f0243ac> | 3.328125 | 362 | Personal Blog | Science & Tech. | 67.106966 |
There are ethical guidelines that have to be followed when conducting experiments. They keep experimenters from committing acts of pointless waste or extreme destruction. That's fair. But if those ethical limitations were ever swept aside, I know what unholy acts of scientific mayhem I'd like to see.
10. Chimpanzees with human vocal cords.
Project Nim has hit theaters. It's the story of a chimpanzee raised among humans as an experiment to see if chimps can learn language as well as humans when raised in the right environment. The experiment was hampered by, among other things, the fact that chimps can't speak and his human family didn't know sign language. At the time, there was nothing to be done but have humans learn sign language while teaching a chimp to learn sign language as well. Now, if we can put an ear on a mouse, we can put some vocal cords in a chimpanzee. Or a gorilla.
9. Make everything huge.
We've seen that when lions and tigers mate, the offspring gets a combination of the growth genes from each, growing to gigantic size. There are genetic ways to make animals enormous. There needs to be an entire branch of science that does nothing but work out how to make various animals gigantic. I picture it as being called The International Cool-Ass Center for Embiggening, and it should make chinchillas the size of ponies, ponies the size of SUVs, and elephants the size of houses.
8. Also make everything tiny.
Obviously, this goes both ways. I should be able to ride my three-story elephant back to my house to play with my cat-sized pony, and all while keeping a pocket-panda in my coat at all times in case I get depressed.
7. Fire things into the sun, or the moon.
We've got no shuttles. We're not going to the moon. We're not going to Mars. Let's just fire things into the sun and splatter things across the moon. It will be like the bit where Letterman threw things off a roof, only better. We don't need to be particularly precise or ambitious. Just lob things, a freighter full of watermelons, a player piano, balloons full of jello, at the sun or the moon with a camera just good enough to observe the splash/inferno.
6. Make some zombies
This would be a multidisciplinary attempt at apocalypse. It has been shown that various creatures can be zombified through parasites, through neurotoxins and other chemicals, and someday probably through nanotechnology. It's time to see if we can make some honest-to-god zombies. And if they get out of the lab and start wrecking civilization? Well, that's been shown on TV and in movies, so it must be desirable. Let the wildly unscrupulous experimentation with inadequate safeguards begin!
5. Do massive, sustained sociological experiments.
Remember the Milgram Experiment, in which people were made to believe that they were shocking a fellow human being to death? Or the Stanford Prison Experiment, during which some students were assigned the roles of 'prisoners' and others were assigned the roles of 'guards,' and which had to be stopped after six days when the guards and the prisoners participated in torture? Those seem almost quaint, in the era of reality shows that dunk anorexic aspiring models in ice water until they need to be rushed to the hospital or make people eat spiders. Not only would these new experiments be fascinating to watch, they'd be readily funded. Get an unscrupulous psychologist, or a social engineer, and have a TV crew haul them and a bunch of people, who either believe in the cause or will do anything to be famous, out to the middle of nowhere for the most elaborate and cruel sociological experiments ever. Hell, if the shows are profitable enough, and private space travel works out, we might get lunar colonies after all.
4. Bliss brain jacks
Scientists are finding ways to manipulate the various chemicals that make the brain happy. They might start working towards finding a way to keep it happy, or even brain modifications that make people happy all the time. Yes, it's all scary and dystopian. But if you believe the idea saying that, "Most men lead lives of quiet desperation," real life is even more dystopian. If the future looks bleak, maybe it would be a good idea to let people march into it artificially happy.
3. Isolate and reproduce the neurochemical soup that makes people feel love.
The potential for abuse is right there on the surface, and even if it weren't abused it would be creepy. But I like the idea that not only could people isolate and reproduce these chemicals, but they could make different 'flavors' of love. So those who wanted to experience all different types of love during their time on earth, could go with their partner and pick out angry, conflicted love one weekend, and obsessive love the next, and even chaste, courtly love if they needed a couple of days off. Those accustomed to their lovers could pick out 'first love' or 'new love' again and again. It would be a time saver. A horrific, soul-cheapening time saver.
2. Develop human intelligence for everything.
Artificial intelligence is getting good. Scientists are investigating the genetic sequences that might switch on human brain development in apes. They're also finding out about collective intelligence in animals like ants and bees. On film we've seen an uprising of the machines. We're going to see an uprising of the apes. What we need to see is a fight between the apes and the machines. Meanwhile, sentient sharks could fight sentient seaweed and algae in the ocean, and superintelligent colonies of ants could fight the encroaching flocks of intelligent birds. Enough uprising. It's time for a free-for-all.
1. Brain transplants.
I have to admit, this one would end not just the credibility of science but life as we know it. The rich would be farming the poor for bodies before anyone even thought of the appropriate twitter hashtag for the story. But I'd love to see if it would work. | <urn:uuid:bbdbc173-f468-4446-abe2-6fc1b39e10db> | 2.875 | 1,275 | Listicle | Science & Tech. | 57.462539 |
The Eastern Steppes of Mongolia are some of the largest and last remaining temperate grasslands in the world. They are also home to the Mongolian gazelle (Procapra gutturosa), or zeer, which migrate annually in herds ranging from 35,000 to 80,000 between winter and calving grounds spread throughout the steppes. Although the Eastern Steppes are still relatively undisturbed, the overall geographic range of zeer has declined dramatically from 1.2 million km2 in 1950 to less than 400,000 km2 in the late 1990s. Gazelles have experienced a corresponding decline in population.
|Historic and present distribution of Mongolan gazelles|
Peter Leimgruber and other researchers at the Conservation and Research Center used a normalized difference vegetation index (NDVI), derived from coarse-resolution satellite imagery to map relative primary productivity of steppes between April 1992 and December 1995. Although productivity varied during these years, winter and calving grounds had the highest NDVI scores during periods of use by the gazelles. In fact, gazelle movements to these areas followed shifts in primary productivity across the steppe. By mapping productivity "hotspots" used by gazelles during critical periods in their life cycle, researchers hope to identify which areas should be priorities for conservation.
|Relative differences in aboveground net primary productivity (ANPP) between calving, summer and winter grounds.| | <urn:uuid:eb9ba7e8-6018-439d-a6ce-3358e6510b63> | 3.796875 | 301 | Knowledge Article | Science & Tech. | 22.767613 |
Science Fair Project Encyclopedia
Lanthionine is a non proteinogenic amino acid found in peptides of microbial origin. It is a sulfide bridged alanine dimer (HOOC-CH(NH2)-CH2-S-CH2-CH(NH2)-COOH) which is synthesized from cysteine and dehydroalanine by posttranslational modifications of peptides.
The contents of this article is licensed from www.wikipedia.org under the GNU Free Documentation License. Click here to see the transparent copy and copyright details | <urn:uuid:43fa54ac-200d-4000-8bb4-3a7354bf27fd> | 2.796875 | 116 | Knowledge Article | Science & Tech. | 33.594 |
With the astounding growth of the Internet over just the last few years has come a concomitant increase in the number of environmental information resources available on the Net. These resources come in a bewildering array: mailing lists, Usenet newsgroups, gopher servers and World Wide Web (WWW) servers, among others.
While this article will focus on Usenet newsgroups and some WWW
resources, a broader overview of environmental information sources is
contained in A Guide to Environmental Resources on the Internet, by
Carol Briggs-Erickson and Toni Murphy. Last updated in October 1994,
the guide is available via the following URL:
Subscribers to a group "post" articles (messages) which can then be commented on ("followed up") by other subscribers. An original message, along with all of its follow-ups, is called a thread. Anyone may read the accumulated threads in a newsgroup. Due to the sheer volume of Usenet news postings, older messages are normally deleted. Although message life varies from group to group, it is typically about two weeks.
To read newsgroups, users need access to a news server, which is often available through Internet Service Providers (ISP). The server maintains a database of Usenet articles and "serves up" groups, threads and articles as they are requested. Every news server maintains its own database of Usenet articles, generally accessible only by the clientele of the particular ISP. Not all ISPs carry all the newsgroups; in fact, some are quite selective. It is not unusual for an ISP to decline to carry any of the massive "alternative" (alt.*) hierarchy.
In addition to a news server, users need a newsreader to access Usenet. The reader interacts with the server by translating user requests into a form that can be understood by the server. It also formats for screen display the information returned by the server. Internet service provided by a shell account generally uses a UNIX-based reader, such as "rn," "nn," "trn" or "tin." When service is provided through a direct network connection, a SLIP account or TIA software, a desktop reader, such as NewsExpress, Trumpet Newsreader or WinVN, can be used.
Many newsgroups deal with environmental issues to varying extents. Some groups most directly related to the environment are listed below. The number of postings (messages) in each group on the server the authors used in late December 1994 is given in parentheses.
To provide a flavor for the kinds of discussions that take place, the following list shows a few of the current threads in the group sci.environment. Numbers following the asterisks indicate the number of articles (original posting plus follow-ups) in the thread. Where no asterisk exists, only an original article has been posted.
*15 We get no oxygen from trees! Nuclear Waste Disposal: A Reality Any urban environ. quality indexes? *2 ACGIH *3 CFC substitutes McDonalds on trial Good news about Kuwait *2 plaster of paris or gypsum reuse/recycling Radioactive smoke Question About Grazing On Public Lands *5 HELP ozone in lower vs. upper atmosphere Env vs Solar or Nuclear energy was Nuclear Waste Disposal *4 Radioactive smoke News for NIRS *7 Nuclear Waste Disposal: A Reality in Canada *2 RACHEL: Chemical Safety, Pt. 1 *8 Nuclear/Solar comparison (was Nuclear Waste Disposal) Internet connections on the Environment *2 GlobalWarming=CO2 UN Climate Change Bulletin #5 Laboratory Contaminants Top Soil Loss (Was: McDonalds on trial) *3 Nuclear Ship Lawsuit - Factum *10 Chernobyl Health Effects *2 Recycling Exclusions and exemptions, HAZMAT environmentally sound camping
Among the currently popular WWW viewers are Mosaic and Netscape. The viewers require "TCP/IP to the desktop," which can be achieved through a direct network connection, a SLIP or PPP account, or TIA software with a shell account. WWW information can be accessed through a shell account using a character-based (VT100) viewer known as Lynx, which delivers the textual portion of WWW pages, but the graphical component is always difficult, and sometimes impossible, to configure.
Resource discovery is perhaps the most tenuous aspect of WWW use.
There are so many server sites available that it is often difficult to
find the ones that deal with a specific category of information.
Fortunately, some Web sites have tackled the problem by categorizing and
grouping Web information resources. "Yahoo - A Guide to WWW"
http://akebono.stanford.edu:80/yahoo/) provides an
excellent entree to environmental information, with 191 sources
currently listed in its "Environment and Nature" category. Yahoo also
lets its users search WWW-space by keyword.
Among other environmentally oriented indexes are the following:
For those interested in federal law and policy regarding the
environment, the League of Conservation Voters maintains a service
detailing information about how Congressional representatives vote on
key environmental legislation, a summary rating of each representative's
environmental voting record and an explanation of each of the issues
considered. The site can be found at URL:
New Web resources come online daily, further complicating navigation of the network. But users who remain in touch with newsgroups often stay on top of the new products and services. Two groups which do a good job of announcing many of the new and interesting sites on the Net are comp.internet.net-happenings and comp.infosystems.announce. | <urn:uuid:a55316c7-7125-4b34-ba01-cd5b2d56c2d5> | 2.765625 | 1,183 | Knowledge Article | Science & Tech. | 37.044572 |
|Version||0.2 - Friday, 23 February 2007|
|Source code repository|
The library is a set of macros tries to emulate python's generators functionality in lisp.
One difference from the python's generators it is impossible to save a generator to a variable and call 'next' method manually. Only 'foreach' syntax is supported.
The reason of missed 'next' method is that pygen does not use real continuations to implement generators (as python does). It uses continuations idea only. Library's macros perform CPS transformation for FOREACH and YIELD forms.
(defgenerator gen1() (yield 1) (yield 2) (yield 3)) (defun use-generator () (foreach x in gen1() (print x)))
Normal thinking of the code is: OK, call gen1(), save the return value into a variable 'x' and call print(x); call gen1() again and do the same; cal gen1() again, again, again... In short, 'foreach' is a master and 'generator' is a slave - master calls slave while slave has a job to do.
But we can thing a little bit different: OK, we know what we are going to do with the generator's value - run the body of FOREACH form ((print x) in our case). So, it is possible to pass that code to a generator and the generator will call it when needed. The generator becomes a master and foreach becomes a slave. We can think about a generator as a normal function that receives additional parameter - what to do with the result value aka continuation. By pygen's macros the code above is transformed into something like this:
(defun gen1 (*cont*) (funcall *cont* 1) (funcall *cont* 2) (funcall *cont* 3)) (defun use-generator () (gen1 #'(lambda (x) (print x))))
If a generator function is simple that means it is relatively easy to save and and restore the function's state in a closure it might be more appropriate to use series package or some other lazy-lists package. For someone it could be more convenient to pass a functional parameter represented a continuation to a generator directly. Pygen is doing well when a generator function is a quite complex, e.g. there are several inner loops or when it is needed to work with 'unwind-protect' resources such as files. For example, SAX and pull XML parsers could be implemented using generators.
Generators are an abstraction. If it is suitable for you - pygen is here :)
You must be logged to add a note
You must be logged to add a comment | <urn:uuid:e84dacd8-3b41-45eb-b1cd-466d2fe585ec> | 3.046875 | 572 | Documentation | Software Dev. | 51.733725 |
The True Rotational Symmetry of Space
The following deep, elegant, and beautiful explanation of the true rotational symmetry of space comes from the late Sidney Coleman, as presented to his graduate physics class at Harvard. This explanation takes the form of a physical act that you will perform yourself. Although elegant, this explanation is verbally awkward to explain, and physically awkward to perform. It may need to be practised a few times. So limber up and get ready: you are about to experience in a deep and personal way the true rotational symmetry of space!
At bottom, the laws of physics are based on symmetries, and the rotational symmetry of space is one of the most profound of these symmetries. The most rotationally symmetric object is a sphere. So take a sphere such as a soccer—or basket-ball that has a mark, logo, or unique lettering at some spot on the sphere. Rotate the sphere about any axis: the rotational symmetry of space implies that the shape of the sphere is invariant under rotation. In addition, if there is a mark on the sphere, then when you rotate the sphere by three hundred and sixty degrees, the mark returns to its initial position. Go ahead. Try it. Hold the ball in both hands and rotate it by three hundred and sixty degrees until the mark returns.
That's not so awkward, you may say. But that's because you have not yet demonstrated the true rotational symmetry of space. To demonstrate this symmetry requires fancier moves. Now hold the ball cupped in one hand, palm facing up. Your goal is to rotate the sphere while always keeping your palm facing up. This is trickier, but if Michael Jordan can do it, so can you.
The steps are as follows:
Keeping your palm facing up, rotate the ball inward towards your body. At ninety degrees—one quarter of a full rotation—the ball is comfortably tucked under your arm.
Keep on rotating in the same direction, palm facing up. At one hundred and eighty degrees—half a rotation—your arm sticks out in back of your body to keep the ball cupped in your palm.
As you keep rotating to two hundred and seventy degrees—three quarters of a rotation—in order to maintain your palm facing up, your arm sticks awkwardly out to the side, ball precariously perched on top.
At this point, you may feel that it is impossible to rotate the last ninety degrees to complete one full rotation. If you try, however, you will find that you can continue rotating the ball keeping your palm up by raising your upper arm and bending your elbow so that your forearm sticks straight forward. The ball has now rotated by three hundred and sixty degrees—one full rotation. If you've done everything right, however, your arm should be crooked in a maximally painful and awkward position.
To relieve the pain, continue rotating by an additional ninety degrees to one and a quarter turns, palm up all the time. The ball should now be hovering over your head, and the painful tension in your shoulder should be somewhat lessened.
Finally, like a waiter presenting a tray containing the pi'ece de resistance, continue the motion for the final three quarters of a turn, ending with the ball and your arm—what a relief—back in its original position.
If you have managed to perform these steps correctly and without personal damage, you will find that the trajectory of the ball has traced out a kind of twisty figure eight or infinity sign in space, and has rotated around not once but twice. The true symmetry of space is not rotation by three hundred and sixty degrees, but by seven hundred and twenty degrees!
Although this excercise might seem no more than some fancy and painful basketball move, the fact that the true symmetry of space is rotation not once but twice has profound consequences for the nature of the physical world at its most microscopic level. It implies that 'balls' such as electrons, attached to a distant point by a flexible and deformable 'strings,' such as magnetic field lines, must be rotated around twice to return to their original configuration. Digging deeper, the two-fold rotational nature of spherical symmetry implies that two electrons, both spinning in the same direction, cannot be placed in the same place at the same time. This exclusion principle in turn underlies the stability of matter. If the true symmetry of space were rotating around only once, then all the atoms of your body would collapse into nothingness in a tiny fraction of a second. Fortunately, however, the true symmetry of space consists of rotating around twice, and your atoms are stable, a fact that should console you as you ice your shoulder. | <urn:uuid:5501c0de-6ffb-4f47-bb1c-0326f12325c2> | 3.234375 | 962 | Knowledge Article | Science & Tech. | 48.305342 |
Yes, I am aware that this is the temperature change that a doubling of CO2 would have in a scenario with no feedbacks- a blackbody.
It is likely that there are negative feedbacks that act to supress the warming even further.
There is only one negative feedback that has been clearly demonstrated and that is the simple fact that objects at higher temperatures radiate very much faster than those at lower temperatures. In other words the hotter something is the faster it cools down. For example you might want to claim that clouds are a negative feedback, but if we look at Venus which has a 100% more cloud cover, and lower a total for incoming radiation, yet it has a much higher surface temperature than earth.
On the other hand there are numerous positive feedbacks. Particularly that higher temperatures increase the amount of water vapour in the air (7% per 1 deg C) which is again a stronger GHG than CO2. Loss of ice cover over the sea changes the surface from reflecting 90% of the radiation to absorbing in excess of 80%.
Higher temperatures of themselves also increase the amount of carbon based GHGs in the atmosphere EG forest fires, increased methane emission's from tundra and peat areas
You are a bit confused here cell phones generate heat due to potential energy being released in to the cell phone circuits. All objects that are above 0 Deg K radiate and absorb radiation, an equilibrium is reached with its neighbours, when the radiation in is in balance with the radiation out.
You missed my point.
The point is, just because that we know something impacts the surroundings, does not mean it is a large factor by any means.
No you don't get it that just because the size of something is small does not mean that it can't have a big impact for example a catalyst can completely change the outcome and speed of chemical reactions even though they may be present in very small quantities. On the other side of the coin nitrogen has fairly minor effects on the atmosphere despite being the largest component.
In the case of your cell phones if the heat from them is not allowed to escape the room, the temperature will rise, but the reality is this becomes harder and harder as the temperature rises. As a simpler example buildings have been designed which are heated only by the heat from the occupants.
This is quite correct but unfortunately the minor effect of CO2 causing 3 or 4 deg C increase in temperature is going to be a major problem for nearly all life on earth.
I still can not believe how some people can believe sensitivities that high.
In order to believe a 4 Degree sensitivity, you would have to believe that the increase in CO2 has caused a 1.6 Degree C temperature change over the 20th Century, which we haven't even come close to.
The figure is 1.3 deg C based on sensitivity of 3 deg C.
The equivalent of 0.4 Deg C ended up in the oceans and 0.9 Deg C in the atmosphere. Bear in mind that the ocean increase in temperature is in fact much less as water has a much higher heat capacity than air. Just be patient we are getting there.
If you do not accept that level of sensitivity then how are you going to explain the ice ages of the last 4 million years or for that matter how the earth was much hotter than today, 100s of millions of years ago, despite the fact that the sun was not emitting as much heat as today.
You would then need to prove that something is so strong that it would create a cooling of 0.8-0.9 Degrees C to give us the 0.7-0.8 Degrees C of warming we have observed during the 20th Century.
Ah you don't understand that the warming caused by other GHGs in the atmosphere such as methane and NO2 etc are balanced by the aerosol cooling effect.
If it were aerosoles, we would see the Northern Hemisphere warming the slowest, and the cities would be seeing enormous temperature drops to get the global value of nearly 1 Degree C cooling, since the impacts of aerosoles are short lived and very local.
We don't see either of these.
The southern hemisphere is warming faster than the northern hemisphere when you take into account the deference in proportions of land and sea.
The temperature of a city is strongly influenced by local weather conditions ie how windy it is and its latitude. The major effect of Aerosols is to increase cloud cover and to make clouds more reflective therefore it is reasonable to assume that the effect lasts several days by which time the airmass may well have gone 1/4 of the way round the globe.
You can argue as much as you like but the people who thoroughly understand the science say you are wrong.
There are many people who are skeptical who would argue that you were mistaken yourself.
There is nothing wrong with being skeptical but it must be tempered by the current state of our knowledge and the level of understanding of those people making various claims.
I am not wrong or right I simple accept that the vast majority of climate scientists have made a convincing case that the current and future levels of GHGs will lead to higher surface temperatures. Whereas those who claim this is not the case have not, and is best summed up by the saying " The devil can quote scripture for his own purposes" | <urn:uuid:fbf90794-3df8-4314-8462-61753796de10> | 3.171875 | 1,093 | Comment Section | Science & Tech. | 53.460705 |
Sub Exercise() Dim Tracks As Integer End Sub
Instead of using As Integer, you can use the % type character. Therefore, the above declaration could be done as follows:
Sub Exercise() Dim Tracks% End Sub
After declaring the variable, you can assign the desired value to it. If you assign a value lower than -32768 or higher than 32767, when you decide to use it, you would receive an error.
If you have a value that needs to be converted into a natural number, you can use CInt() using the following formula:
Number = CInt(Value to Convert)
Between the parentheses of CInt(), enter the value, text, or expression that needs to be converted. | <urn:uuid:9b723c88-2324-4cae-8ae9-cf4ae610fc29> | 2.765625 | 147 | Tutorial | Software Dev. | 40.94 |
Metamorphic Rock Process III
Written for the KidsKnowIt Network by:
Scientists call the third way metamorphic rocks form a tectonic process. Sometimes I think scientists like to use long words to make it harder for non-scientists to figure out what they are talking about. Here's what they are talking about: The large plates that make up the crust of the earth are always moving. Sometimes they slam into each other. Sometimes they grind past each other. Sometimes the plates are pulling apart forming large cracks called rifts. When plates pull apart it is called a divergent boundary. On some boundaries one plate dives under another plate. Geologists call this type of boundary a convergent boundary. When the plates bump and grind past each other, the geologists call this boundary a transform fault boundary. A famous example of this type of fault in the United States is called the San Andres Fault. At that plate boundary, the North American plate is moving mostly south and the Pacific plate is moving mostly north, which means that in 15 million years Los Angeles and San Francisco will be neighbors. I wonder if that will solve the debate about which is the better town. In any case, metamorphic rocks are formed from the pressure and heat caused by the plates crashing into each other.
The San Andreas Fault in California.
So what rocks are metamorphic rocks? Examples of these rocks are marble, schist, slate, gneiss (pronounced "nice"). All of these rock types are formed by heat and pressure. So what makes them different? The answer is simple. Metamorphic rocks are formed from different rocks. Marble is made from sedimentary rock called limestone and sometimes dolomite. Gneiss is formed from ingenious rock, like granite. Schist is formed from sedimentary rocks like mudstone or siltstone. Slate is formed from shale. As a matter of fact, slate and shale look so much like each other, the best way to tell them apart is to lightly tap them with a metal object like a coin. Slate and shale make different sounds when tapped. When tapped, slate has a slightly more metallic sound than shale. Shale makes a kind of hollow thumping sound.
Because of its beauty, marble is used for many purposes.
Metamorphic rocks are one of the three main types of rocks and are the most common of rock on the continental plates. Fossils may be found in metamorphic rocks, but only if the metamorphic rock was formed from a sedimentary rock that already had the fossil in it. However, the fossil is most likely going to be crushed, warped, or somehow changed because the process that changes sedimentary rock into metamorphic rock will change the fossil, too. Marble is a metamorphic rock used by artists to create sculptures and to decorate buildings and other things. Slate was used to make chalkboards and is still used to make pool tables. Keep your eyes open! Metamorphic rocks are everywhere. | <urn:uuid:1d1ec831-9cdb-449e-b509-151c54bcc473> | 4.1875 | 613 | Knowledge Article | Science & Tech. | 52.596815 |
If a rough surface is illuminated by a coherent lightwave of wavelength λ1, it is not possible to determine the surface profile from the phases of the speckle field formed by the scattered light. If the rough surface is illuminated, however, by an additional coherent wave of wavelength λ2, the phase differences between the two speckle fields do contain information about the macroscopic surface profile even if subject to a statistical error. It is shown that (1) the macroscopic surface profile may be determined from the phase differences if the effective wavelength Λ = λ1λ2/|λ1 - λ2| is sufficiently larger than the standard deviation of the microscopic profile of the illuminated surface, and (2) the statistical error is reasonably small if the phase measurements are obtained from speckles of sufficient intensity. Using a heterodyne interferometer we demonstrate the feasibility of this technique. In the first experiment we determine the radius of curvature of a rough spherical surface. In the second experiment the macroscopic surface contour on two ophthalmic lenses of the same power variation, one with a grounded surface and the other with a polished surface, was determined.
© 1985 Optical Society of America
A. F. Fercher, H. Z. Hu, and U. Vry, "Rough surface interferometry with a two-wavelength heterodyne speckle interferometer," Appl. Opt. 24, 2181-2188 (1985) | <urn:uuid:96b5d49d-375c-4ba3-bbc0-3bc2ca0e1411> | 2.703125 | 306 | Academic Writing | Science & Tech. | 28.879404 |
Earth in the Solar System
The planet earth is the 3rd planet from the sun: A solar system consists of the moon, seven more planets and the sun. Our sun is certainly an average dimension star. Many objects inside the solar system happen to be in regular, predicable movement. These kinds of motions describe our time, the entire year, phases from the eclipses and moon. Gravity is a force which maintains planets inside orbit across the sun. Also gravity holds us towards the planet's surface and generates the tides. So sun is a main source of energy around the earth's surface. Periods result from various amounts of natural light which visits the earth.
The Solar System
A solar system is composed of nine planets and the sun. The image above displays an order by which individual planets orbit a sun (nevertheless the sizes and ranges are never to scale
Explaining the planets given that 'chunks of a matter' is surely an over simplification. Although a few of those, just like the planet Mercury, tend to be small greater than big rocks, many are quite intricate. We need to look our existence towards the fact how the Earth is really an intricate system with numerous layers. The earth by itself has three layers: core, crust and mantle.
Earth was shaped 4.54 Thousands of years back and life made an appearance upon its surface in 1 Thousand years. The earth gives shelter for Thousands of species, which includes Human beings. Earth's biosphere has substantially changed the ambiance and some other biotic circumstances on the earth, permitting the expansion of aerobic creatures as well as the development from the ozone layer that, along with Earth's permanent magnetic field, blocks dangerous solar radiation, making it possible for life to sustain on Earth.
The physical characteristics of the earth and its geological orbit hold permitted life to remain during this period of time. Earth's external surface is separated into numerous rigid sectors, or perhaps tectonic plates, which migrate around the surface for many Thousands of years. Around 71% of the earth’s surface is coated with oceanic masses sodium water, with the rest containing of locations and island destinations which collectively have numerous lakes and also other water resources which add up to the hydrosphere. | <urn:uuid:f8861e14-8db6-4732-a179-e095a1e444d2> | 3.484375 | 452 | Knowledge Article | Science & Tech. | 45.222702 |
Discover the cosmos! Each day a different image or photograph of our fascinating universe is featured, along with a brief explanation written by a professional astronomer.
November 11, 1998
Explanation: On some nights the sky is the most interesting show in town. This picture captures a particularly active and colorful display of aurora that occurred a month ago high above Alaska. Auroras are more commonly seen by observers located near the Earth's poles. Aurora light results from solar electrons and protons striking molecules high in the Earth's atmosphere. Planetary aurora activity can sometimes be predicted after particularly active solar coronal mass ejections.
Authors & editors:
NASA Technical Rep.: Jay Norris. Specific rights apply.
A service of: LHEA at NASA/ GSFC
&: Michigan Tech. U. | <urn:uuid:31ef45df-0c90-4475-ae5c-6b100b798e81> | 2.78125 | 163 | Knowledge Article | Science & Tech. | 30.557957 |
In what has become an annual tradition here at BA Central, literally the day I post my gallery of best pictures of the year, something comes along that really would’ve made it in had I seen it even a few hours earlier. In this case, it’s a combined Chandra X-Ray Observatory and optical Very Large Telescope image of galaxy clusters colliding that’s so weird that at first I thought for sure it was Photoshopped! But it’s real, so check this out:
What you’re looking at is a collision on a massive scale: not just two galaxies, but two clusters of galaxies slamming into each other, forming this object, called Abell 2052. The total mass of this combined cluster is almost beyond imagining: something like a quadrillion times the mass of the Sun — 1,000,000,000,000,000 Suns! Note that our galaxy has about a hundred billion stars in it, so Abell 2052 is about 10,000 more massive. Yikes.
No, don’t fret: I’m not betraying everything I know to be true and suddenly supporting astrology! I’m just having a little joke at the expense of NGC 4435 and 4438, two galaxies in the Virgo Cluster known as "The Eyes", and seen in lovely detail by the Very Large Telescope:
[Click for orbus giganticus, and you really should; the details are beautiful.]
Clearly, these guys know each other. NGC 4438 (upper left) is distorted and drawn out, which is a sure bet that it’s undergone a collision with another galaxy in the recent past. Given how close NGC 4435 (lower right) is to it, that seems like the culprit (though M86, not seen in this shot, is also close by and may be to blame). They may have actually passed right through each other as recently as 100 million years ago! Direct hits between galaxies aren’t like car accidents where the vehicles stop dead; galaxies are mostly empty space, and stars are so small compared to the galaxies themselves that a direct impact between two stars is incredibly unlikely.
But the gravitational pulls from the opposing galaxies can affect each other, teasing out long tails of material just like the one streaming from NGC 4438 . The scattering of dust is also another clue. Although stars don’t collide, gas clouds are much larger, some dozens of light years across. Those do in fact slam into each other, causing them to collapse and form stars (though there’s some evidence that’s not always the case). Vigorous star formation can cause lots of dust to be created, and that’s what we’re seeing in NGC 4438. And it’s all weird and distorted too, clinching the case.
You may notice NGC 4435 is a bit featureless. That’s actually common in disk galaxies that live in clusters. As they move through the cluster at high speed, the intergalactic medium — thin gas expelled from the galaxies — can strip away the gas and dust in a galaxy, like opening a car window can blow out stale air inside.
Galaxy collisions are pretty cool, and a rich field for study. And if you’re patient, you’ll get a great view of one: our galaxy is headed for a close encounter with the Andromeda Galaxy. Given that it and the Milky Way are among the biggest and most massive spiral galaxies in the local Universe, it’ll be a spectacular show. Better reserve your seats now, though. You only have a billion or two years to wait!
Astronomers are like forensic investigators. We have all this data taken from the scene of some sort of event, and have to piece together what happened. But those folks on CSI have it easy: they get to actually walk around the scene, poke and prod it, examine various stains, and even take physical evidence back to the lab. Astronomers are stuck standing a quintillion kilometers away, and we only get to see things at one angle.
But oh, what an angle. If it pleases the court, I’d like to enter this evidence for your consideration:
That’s my kind of evidence (click to embiggen). It’s an image of the lovely grand-design spiral galaxy M81, one of the nearest major galaxies to our own. At about 12 million light years away it’s bright enough to be seen in binoculars (and in fact some extremely keen-eyed observers have been able to see it with their unaided eyes). That means it’s close enough to study in detail… and what detail!
Every now and again I think I’ve pretty much seen it all when it comes to astronomical images, and I’m getting jaded.
And then I see a picture like this:
Yeah, I still get a thrill from seeing things like this! Click to massively embiggen.
The image shows what’s called the Hickson Compact Group 31, a small collection of galaxies. It’s a combination of images from Hubble (visible light, shown in red, green, and blue), Spitzer (infrared, shown as orange), and the Galaxy Explorer or GALEX (ultraviolet, seen here as purple).
If I saw this picture with no caption, I’d know I was seeing dwarf galaxies colliding; the shape and the glow from newly-forming stars is a dead giveaway. But I’d also guess that the galaxies were young; old galaxies tend not to have much gas in them, and there’s clearly plenty of that in those galaxies! But in fact the galaxies here are very old; there are globular clusters (spherical collections of perhaps a million stars each that tend to orbit outside of galaxies) in the group that can be dated to being 10 or so billion years old. That means these are old objects, reinvigorated by their collision.
In fact, star clusters inside the galaxies can be dated as well, and appear to be only a few million years old. Oddly, the gas content of the galaxies is very high, with about five times as much as the Milky Way has. That’s pretty weird; it should’ve been used up a long time ago. Apparently, these galaxies have lived very sedate lives until very recently. I’ll note that they are relatively close to us, about 166 million light years away. Usually, colliding dwarf galaxies like this are seen billions of light years away, so we really are seeing them as they appeared recently.
Apparently, the lower-case g-shaped object on the left is the result of two galaxies smashing into each other, and the longer galaxy above them is separate. The spiral to the right is part of this as well and may be involved in the gravitational dance; you can see a splotchy arm of material pointing right at it from the collision on the left. Typically in collisions the gravity of one galaxy draws matter out of the other, and that can collapse to form stars. The red glow is from gas excited by newly born stars, and the blue glow is from these stars themselves. The galaxies are pouring out ultraviolet light (the purple glow) which is another dead giveaway of vigorous star formation.
The background galaxies are gorgeous, too. There’s a phenomenal distant open spiral on the bottom, to the left of center, and what looks like yet another pair of interacting galaxies at the bottom left, obviously much farther away than the Hickson group. Take a minute to look around the high-res version to see what else you might find!
Yup. I guess you can teach old galaxies new tricks… and even sometimes jaded astronomers, too. | <urn:uuid:1be9cb51-382c-4537-8104-9421c7a76f04> | 3.09375 | 1,627 | Personal Blog | Science & Tech. | 57.467139 |
Multiple adjacent string literals (delimited by whitespace), possibly using different quoting conventions, are allowed, and their meaning is the same as their concatenation. Thus, "hello" 'world' is equivalent to "helloworld". This feature can be used to reduce the number of backslashes needed, to split long strings conveniently across long lines, or even to add comments to parts of strings, for example:
re.compile("[A-Za-z_]" # letter or underscore "[A-Za-z0-9_]*" # letter, digit or underscore )
Note that this feature is defined at the syntactical level, but implemented at compile time. The `+' operator must be used to concatenate string expressions at run time. Also note that literal concatenation can use different quoting styles for each component (even mixing raw strings and triple quoted strings). | <urn:uuid:fd6c9fe4-3919-4ac9-953f-bb4f3601ab09> | 2.984375 | 190 | Documentation | Software Dev. | 29.348367 |
Reflection: mirror, mirror on the wall
Reflection of light is how we ‘see’ things at all, regardless of color. Light waves from the sun--which, as it emanates its own light, is known as a luminous source—are reflected by all the objects in their path. All objects, that is, except those that allow light to pass through them, like glass, for example. These objects are called transparent, but the vast majority of matter obstructs light waves, and is called opaque. As these objects obstruct the path of light, it is forced to deviate, i.e. it is forced to change its path as it bounces of the obstruction. This “bouncing off” is known as reflection, and when light bounces off opaque objects and enters our eyes, which are then able to “see” things once the light sensed is processed and analyzed by the brain.
For this demonstration of reflection of light, you will need a laser pointer, a room with no windows with a mirror on the wall and any type of spraying device (ask mom for some room freshener or window cleaner or use deodorant!). Turn off the lights in the rooms. It is very important to make sure no light enters the room from outside. Once it is nice and dark and creepy, take the pointer in your hand and point it towards the mirror.
You will find that you can only see the red dot of the pointer at two places—where it hits the mirror, and where it is reflected onto the wall. Note that these are the two opaque objects the light has encountered.
Now equip yourself with the spray can and spray away into the darkness, keeping the laser pointed at the mirror. What do you see?
Magic? Not at all. You have just proved that sight depends on the reflection of light. The spray in the air obstructed the light from the laser, enabling you to see the path of the beam. This is exactly how we see our surroundings! The wall behind you is obstructing sun rays and reflecting them back towards your eyes, and eureka! You can see the wall! (Although that may not seem such a brilliant achievement on your resume)
Reflection, however, does follow a set of principles, which explains why you and I when standing in the same position see exactly the same image (given that our eye lenses are properly functional!). It is easiest to demonstrate these laws using a plane mirror, as it is a leveled, flat surface.
There are a few terms we use to describe reflection of light in optical physics. To make things simpler to understand, we choose to demonstrate the reflection of light by a single light ray, although there are thousands in reality. This ray of light which falls on a surface (in this case, the mirror) is known as the incident ray. At the point where the incident ray hits the surface, a perpendicular line to the surface is drawn, which we call the normal. The angle formed between the incident ray and the normal is called the angle of incidence. When the incident ray of light hits the mirror, it will be reflected in a specific direction. The resultant ray is known as the reflected ray. The angle that this particular ray forms with the normal is known as the angle of reflection.
Now that we’ve enhanced our vocabularies, let’s get down to the hands on part—we’re now going to try and prove the law of reflection.
You’ll need a few supplies for this experiment. First, of course, a plane mirror, then a black surface, a dark room, a lamp, a few pins and a piece of black paper with a white colored pencil to write on it. First take the mirror and place it on top of the black paper, near the edge. You may need a stand for the mirror if it is not thick enough to support itself. With the white pencil, mark the position of the mirror carefully.
Set up the lamp opposite the mirror, and use thick paper to create a shield around the lamp. Cut a slit in the shield so that only a thin line of light escapes. Now turn off the lights and turn on the lamp. Carefully mark the incident ray’s path with two pins on the black paper, and do the same for the reflected ray. Then turn on the lights, remove the mirror and the lamp and use the white pencil to connect the pins so that two lines represent the incident and reflected ray. At the point where the incident ray intersects the line marking the position of the mirror, draw a perpendicular with a dotted line. This is your normal. Identify the angle of incidence and the angle of reflection, and measure them with a protractor. What do you find?
Precisely. The angle of incidence is always of the same magnitude as the angle of reflection. This is the law of reflection, and at each point where light is obstructed and reflected, this law is obeyed.
For our convenience here, we have used a flat, regular surface. However, most objects are not regular, so how do we see them?
If you experiment further, you will find that when using a plane mirror, all the rays of incidence are parallel to each other, as are the rays of reflection. However, when an irregular object is used, irregular or diffuse reflection takes place, where the reflected rays are not parallel to each other. But you will still find that at each point, the law of reflection is obeyed, although the reflected rays are irregular.
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Authors: H.-J. Hochecker
I stick metal foil on an a 1 square meter large and 10 kilograms heavy dielectric so that a condenser is build. By putting a tension of 10 kV on the condenser or by short-circuiting it I measure a real reduction of the weight of about 0.1 grams each time. This result confirms my theoretical conclusion which says that the weight of a body is related with the movements of its charges (protons and electrons). Keywords: Gravitation, movement of electrical charges, relativity
Comments: 3 Pages.
[v1] 3 Aug 2010
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Tests of general relativity are difficult to come by. The curvature of space time that is central to the theory is only strong around black holes and neutron stars. Around the Sun, the effects of space-time curvature are of order GM/Rc2 = 2 × 10−6 or less, where G is the gravitational constant, M is the mass of the binary system, R is the radius of the Sun, and c is the speed of light. Farther out from the Sun, such as at the orbit of Mercury, the effects are weaker by the ratio of the distance from the Sun to the radius of the Sun. Tests based on the drift in the perihelion of Mercury's orbit are measuring a value of only 43 arc seconds per century. Tests based on the time delay of light passing by the Sun are measuring a value of order 0.2 milliseconds.
Testing general relativity outside of our own Solar System is difficult. While neutron stars and black hole candidates have strong gravitational fields that should produce strong general relativistic effects, these effects are generally mixed in with the physics of energy generation and light production. Especially in x-ray binaries, where gas is flowing to the compact object from a companion star, the environment is much too complex to definitively test general relativity.
Nature does, however, provide us with several very nice systems for testing general relativity. These are the binary pulsars that contain two neutron stars. These double-neutron-star systems, which now number 8, contain a radio pulsar in orbit with another neutron star. The stars in most of these systems are in close orbit. For instance, the original Binary Pulsar, PSR B1913+16, has an orbit with a 7×105 km projected semimajor axis (the length of the semimajor axis projected on the sky), making the system about the size of the Sun. The binary period for this system is 7 hours 45 minutes. A more compact binary system, PSR J0737−3039, has a projected semimajor axis of 4.2×105 km and a binary period of only 2 hours 27 minutes. The neutron stars in these systems are generally around 1.4 solar masses, and the environment surrounding these stars is clean of gas that would affect the propagation of radio waves from the pulsar to the observer. These properties ensure that the observable effects of general relativity are stronger within these systems without the complicating factor of a solar wind or accretion disk that can alter the propagation of light.
But the crucial feature that makes these systems valuable for testing general relativity is that the radio pulsar is a superb clock. In accurately measuring time over years, pulsars surpass atomic clocks in accuracy. This feature allows astronomers to measure precisely the changes in light travel time from Earth to the pulsar as it orbits its companion.
Two of the basic tests of general relativity within our Solar System—the modification of the propagation time of light by the gravitational field and the perihelion drift of Mercury—can be performed with the double-neutron-star double pulsars. These effects, along with the Gravitational redshift and the Doppler shift of radio waves from the pulsar and the propagation time across the binary system, appear to observers as changes in the arrival times of radio pulses from the pulsar.
The modification of the pulse arrival time is quite small, of order (GM/ac2)3/2 (a is the semimajor axis), which is of order 10−9 for PSR B1913+16. Despite being 3 orders of magnitude smaller than the shift in arrival time caused by the Gravitational redshift and the Doppler shift, which are of order GM/ac2, the effect is seen by observers.
The other test, the periastron drift of a binary pulsar's orbit, is a rather large effect, because while the shift per orbit is only of order GM/ac2 = 10−6, the binary pulsar completes of order 1,000 orbits per year. The periastron of PSR B1913+16 drifts by 4 degrees per year. The periastron drift of a binary pulsar's orbit is much more impressive than that of Mercury's orbit.
Beyond providing better tests of general relativistic effects seen in our own Solar System, binary pulsars provide us with our only unambiguous confirmation of gravitational radiation.
All orbiting systems, whether galaxies, planetary systems, or binary stars, radiate gravitational waves. The gravitational waves carry energy and angular momentum from a system, causing the orbits within the system to decay. In most instances, this effect effect is too small to observe. The exception is in compact binary stars. Gravitational radiation drives the orbital decay of x-ray binary stars, causing the mass transfer that enables us to see them as brilliant x-ray sources. But this is an indirect and somewhat theoretical way of seeing the effect of gravitational radiation, because binary systems can lose energy and angular momentum through mechanisms other than gravitational radiation. In the close double-neutron-star binary pulsars, we can see the effect of gravitational waves on the system directly, because these binary pulsars can only lose orbital and angular momentum by radiating gravitational waves.
When a binary pulsar emits gravitational radiation, it loses orbital energy and angular momentum, which causes the orbit to shrink and the period to decrease. This is a tiny effect, but the precision of the pulsar as a clock allows us to see it. In the case of the original binary pulsar, PSR B1913+16, the period decreases by 2.3×10−12 seconds every second, or 1 second every 14,000 years. This decrease is what is predicted by general relativity. So we know that gravitational radiation is being emitted; the question remains whether we can detect it. | <urn:uuid:83781076-b08e-4021-b5d3-2335313262bf> | 3.984375 | 1,203 | Knowledge Article | Science & Tech. | 42.944771 |
School: SANTA FE SCHOOL FOR THE ARTS
Area of Science: Ecology
Abstract: Problem: How the breeding cycle of the Leatherback Sea Turtle is affected by natural and human causes. The Leatherback is an endangered species due to poaching and nesting habitat destruction. By modeling these affects we hope to gain information to help us preserve the future of the Leatherback Sea Turtle.
Sponsoring Teacher: David Bailey | <urn:uuid:70ec3d67-1f92-465c-8759-ae04e9d3c693> | 3.1875 | 83 | Academic Writing | Science & Tech. | 34.532273 |
Forest Pests: Insects, Diseases & Other Damage Agents
Identification of Gypsy Moth Larval Color Forms
United States Department of Agriculture
Since 1991, Asian gypsy moths (AGM) have been introduced into North America on commercial and military vessels and their cargo, from the Far East and more recently from Europe. AGM and the gypsy moths already present in North America (NAGM) differ in many ways, most notably in female flight capability and host plant acceptance. Many of the traits which make AGM potentially a more serious pest are retained when NAGM and AGM hybridize. Unfortunately, positive visual identification of trapped male moths or other intercepted stages of AGM, NAGM or their hybrids is almost impossible. DNA analysis has been the primary means of positive identification. Recently completed research on larval color and its inheritance suggest that this trait may be useful in detecting North American sites where AGM or its hybrids from Asia or Europe have been introduced.
Three principal characteristics are used to distinguish the five larval color forms when larvae are 4th or early 5th instars (i.e., they have lighter head capsule with eye spots visible):
Each body segment may have spots (three anterior and three posterior) on the dorsal surface. The color of the spots on the dorsal surface can be white, yellow, orange or red (especially near the posterior end of the abdomen). The median spots may extend longitudinally forming the median stripe. When the spots on the 4th and 5th body segments are large and fused, they form the thoracic spot between the 3rd and 4th pair of blue verrucae (warts). The genital spot occurs when the spots on the 9th body segment fuse between the 3rd pair of brick red warts. The side stripes can be white to yellow in color. The dorsal body surface between the warts can be almost all white or yellow, varying shades of mottled gray, or black. The key on the back can be used to identify the five larval color forms: bright yellow, yellow, black, yellow-gray and gray (Fig. 2).
Color analysis must be done on 4th or early 5th instar larvae. In the early instars, larvae of most of the color forms appear black. Near the end of the 5th instar, much of the dorsal spot pattern is not discernable. Only the bright yellow and black forms show their true color patterns before the 4th instar and late in the 5th instar. The blue and brick red warts do not appear until the 4th instar.
NAGM are predominantly of the gray form with a few individuals that fall into the yellow-gray category, especially in Southern areas. All of the five color forms are present in AGM larvae. Larvae from the Far East of Russia are predominantly of the bright yellow or yellow forms, and those from Central Siberia are predominantly of the gray form. The exact proportions of each color form present in a population can vary from year to year. In laboratory hybridization experiments between Far East Russian and NAGM, about 50% of first generation hybrids are of the yellow-gray form. Larvae from Western Europe, reared from egg masses collected in September 1993, were predominantly of the gray form. Areas in Europe where AGM has hybridized with the resident population (e.g., Germany) all color forms are present, including the bright yellow form. In parts of Europe, where no apparent hybridization has occurred (e.g., Austria), larvae of the black, yellow and yellow-gray forms are present.
Larval Color Form Key | <urn:uuid:9e007b0a-09fb-4a9b-8b23-8d713f0e167d> | 3.265625 | 749 | Knowledge Article | Science & Tech. | 49.2241 |
Table of Contents
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Flexibility in large component based systems raise questions on how to organize a project for easy development and maintenance while protecting your data and reputation, especially from new developers and unwitting users. The answer is in using the Model, View, Control (MVC) architecture. An architecture such as MVC is a design pattern that describes a recurring problem and its solution where the solution is never exactly the same for every recurrence.
To use the Model-View-Controller MVC paradigm effectively you must understand the division of labor within the MVC triad. You also must understand how the three parts of the triad communicate with each other and with other active views and controllers; the sharing of a single mouse, keybord and display screen among several applications demands communication and cooperation. To make the best use of the MVC paradigm you need also to learn about the available subclasses of View and Controller which provide ready made starting points for your applications.
In the MVC design pattern , application flow is mediated by a central controller. The controller delegates requests to an appropriate handler. The controller is the means by which the user interacts with the web application. The controller is responsible for the input to the model. A pure GUI controller accepts input from the user and instructs the model and viewport to perform action based on that input. If an invalid input is sent to the controller from the view, the model informs the controller to direct the view that error occurred and to tell it to try again.
A web application controller can be thought of as specialised view since it has a visual aspect. It would be actually be one or more HTML forms in a web application and therefore the model can also dictate what the controller should display as input. The controller would produce HTML to allow the user input a query to the web application. The controller would add the necessary parameterisation of the individual form element so that the Servlet can observe the input. This is different from a GUI, actually back-to-front, where the controller is waiting and acting on event-driven input from mouse or graphics tablet.
The controller adapts the request to the model. The model represents, or encapsulates, an application's business logic or state. It captures not only the state of a process or system, but also how the system works. It notifies any observer when any of the data has changed. The model would execute the database query for example.
Control is then usually forwarded back through the controller to the appropriate view. The view is responsible for the output of the model. A pure GUI view attaches to a model and renders its contents to the display surface. In addition, when the model changes, the viewport automatically redraws the affected part of the image to reflect those changes. A web application view just transforms the state of the model into readable HTML. The forwarding can be implemented by a lookup in a mapping in either a database or a file. This provides a loose coupling between the model and the view, which can make an application much easier to write and maintain.
By dividing the web application into a Model, View, and Controller we can, therefore, separate the presentation from the business logic. If the MVC architecture is designed purely, then a Model can have multiple views and controllers. Also note that the model does not necessarily have to be a Java Servlet. In fact a single Java Servlet can offer multiple models. The Java Servlet is where you would place security login, user authentication and database pooling for example. After all these latter have nothing to do with the business logic of the web application or the presentation.
Now that we have a convenient architucture to separate the view, how can we leverage that? Java Server Pages (JSP) becomes more interesting because the HTML content can be separated from the Java business objects. JSP can also make use of Java Beans. The business logic could be placed inside Java Beans. If the design is architected correctly, a Web Designer could work with HTML on the JSP site without interfering with the Java developer.
The Model/View/Controller architecture also works with JSP. In fact it makes the initial implementation a little easier to write. The controller object is master Servlet. Every request goes through the controller who retrieves the necessary model object. The model may interact with other business entities such as databases or Enterprise Java Beans (EJB). The model object sends the output results back to the controller. The controller takes the results and places it inside the web browser session and forwards a redirect request to a particular Java Server Page. The JSP, in the case, is the view.
The controller has to bind a model and a view, but it could be any model and associated any view. Therein lies the flexibility and perhaps an insight to developing a very advanced dynamic controller that associates models to a view.
The prior sections have concentrated on their being one controller, one model, and one view. In practice, multiple controllers may exist - but only one controls a section of the application at a time. For example, the administrator's functions may be controlled by one controller and the main logic controlled by another. Since only one controller can be in control at a given time, they must communicate. There may also be multiple models - but the controller takes the simplified view representation and maps it to the models appropriately and also translates that response back to the view. The view never needs to know how the logic is implemented.
Decoupling data presentation and the program implementation becomes beneficial since a change to one does not affect the other. This implies that both can be developed separately from the other: a division of labor. The look and feel of the web application, the fonts, the colours and the layout can be revised without having to change any Java code. As it should be. Similarly if the business logic in the application changes, for instance to improve performance and reliability, then this should not cause change in the presentation.
A model-view-controller based web application written with only Java Servlets would give this decoupling. If the presentation changed then the Java code that generates the HTML, the presentation, in the view object only has to change.
Similarly if the business logic changed then only the model object has to change. A web application built with MVC and Java Server Pages would be slightly easier if the business logic is contained only in Java Beans. The presentation (JSP) should only access these beans through custom tag libraries. This means that the Java Beans did not have Java code that wrote HTML. Your beans would only concern themselves with the business logic and not the presentation. The JSP would get the data from the Beans and then display the presentation (the "view"). Decoupling is therefore easy. A change to the implementation only necessitates changes to the Java Beans. A change to the presentation only concern changes to the relevant Java Server Page. With Java Server Pages a web designer who knows nothing about Java can concentrate on the HTML layout, look and feel. While a Java developer can concentrate on the Java Beans and the core logic of the web application.
The following persons have contributed their time to this chapter:
David Lloyd (JGroup Expert)
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of what used to be called Pelvetia, now
Silvetia compressa (J. Agardh)
Serrão, Cho, Boo et
Silvetia compressa grows primarily in the Northern Hemisphere on the west coast from Coos Bay, Oregon to Lower California (Ensenada.) It is found either isolated or in aggregations forming thick beds on top of somewhat protected rocks in the mid-littoral belt. The ability of the fertilized egg to settle and germinate under the environmental conditions present determine its geographical distribution and location on shore; movement of water may affect the attachment process. (See Demography.) It can withstand freezing temperatures and summer highs; its level above the high tide line is proportional to the amounts of fucoidan present--the more it has, the higher it can survive.
Silvetia's habitat at high tide:
Silvetia's habitat at low tide:
S. compressa plays an important role in intertidal ecology due to its interactions with animals and other algae. F.C. Gunnill has performed many studies on these interactions. At Hopkins Marine Station at Cabrillo Point on the Monterey Peninsula, California, USA, qualitative observations of the S. compressa beds around Hopkins show that there seems to be more invertebrates living on the plants on protected beaches and fewer out at more exposed beaches.
Below are some images of these invertebrates and epiphytes. If the species mentioned in the captions are not readily apparent, click on the image to see a labeled picture.
This image illustrates epiphytes on a Silvetia thallus. The darker red spots are epiphytes while the green spots are cellular debris from Silvetia. On certain thalli Silvetia lie dark spots. By using a razor blade and scraping the surface, one may prepare a slide of the epiphytes. This one is probably a red alga, perhaps Erythrotrichia.
In this aggregation of Silvetia, another member of the order Fucales may be seen. At the lower side of the image lies Fucus which tends to grow near Silvetia but in smaller density.
Many gastropods make their homes under SIlvetia fronds at low tide. Here, the fronds trap moisture and provide protection against the sun and wind. Many gastropods are grazers upon the epiphytes growing on SIlvetia. In this image are limpets and the black turban snail, Tegula funebralis.
Chitons are another type of mollusc which inhabit Silvetia. Next to the chiton in this image are small structures made of sand. These are the tubes of a tube worm, Phragmatopoma californica. This polychaete worm makes its tube out of sand grains which it first inspects and then cements down to form a small tube. Though the group of tubes looks like a colony, each tube is the result of one individual worm settling near other worms and building its home; the group is not formed by any asexual reproduction as many metazoan colonies are.
Other gastropods are predatory like this tiny Nucella or Acanthina. These prey upon barnacles and limpets.
© 1996 R. H. Lin | <urn:uuid:23bd0172-e2ba-4619-838c-842570ce357c> | 3.65625 | 689 | Knowledge Article | Science & Tech. | 39.381741 |
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Copepods (Temora)—Douglas P. Wilson
Any of the 10,000 known species of crustaceans in the subclass Copepoda. Copepods are widely distributed and ecologically important, serving as food for many species of fish. Most species are free-living marine forms, found from the sea's surface to great depths. Some live in freshwater or in damp vegetation; others are parasites. Most species are 0.02–0.08 in. (0.5–2 mm) long. The largest species, a parasite of the fin whale, grows to a length of about 13 in. (32 cm). Unlike most crustaceans, copepods have no carapace. Nonparasitic forms feed on microscopic plants or animals or even on animals as large as themselves. Members of the genus Cyclops (order Cyclopoida) are called water fleas. See alsoguinea worm.
This entry comes from Encyclopædia Britannica Concise. For the full entry on copepod, visit Britannica.com. | <urn:uuid:bab50d6d-98da-4159-8be5-2ed3df370fa2> | 3.6875 | 238 | Knowledge Article | Science & Tech. | 58.605902 |
FEELING a little dull? Follow the lead of flamingos, which apply make-up to brighten their feathers. This touch-up allows the healthiest birds to continue looking their best, and so helps them signal their status as high-quality mates.
The bright pink colour of flamingos comes from pigments called carotenoids, which the birds acquire from their diet. Only healthy birds can gather enough carotenoids through their food to make bright feathers, but carotenoids fade quickly in sunlight, so feathers bleach over time.
To combat this, the flamingos turn to cosmetics. Juan Amat of the Doñana Biological Station in Seville, Spain, and colleagues found that greater flamingos, Phoenicopterus roseus, secrete the same carotenoid pigments via a gland near their tail.
When they preen, the flamingos spread the pigment over their feathers, brightening their colour. The team found this behaviour ...
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Deepwater and shallow water coral reef communities are rich in diversity and provide habitat for many species. Shallow water coral reef systems have been well-studied partly due to their accessibility. Deepwater corals and associated habitats can only be studied with technologically advanced methods such as manned submersibles, remote operated vehicles (ROV) and autonomous underwater vehicles (AUV). Only a small percentage of deepwater reefs have been described.
Photo credit: S. Ross et al., UNCW
Unlike reef-building tropical corals, deepwater corals are found beyond the reach of sunlight and are adapted to the dark environment. As opposed to shallow water corals, deepwater coral polyps do not contain the symbiotic algae that provide their tropical cousins with energy via photosynthesis. Instead, deepwater corals rely on catching passing food in the water column. As a result, deepwater corals grow very slowly, from less than one centimeter to up to two centimeters per year. Deepwater coral colonies tend to be found in areas where there are strong water currents, which supply food and remove sediments that would otherwise smother the coral polyps. They are also typically found along rocky ledges or in narrow regions. Deepwater coral systems are receiving increased attention worldwide. Click on the thumbnails below to learn more about Oculina and other deepwater coral communities in the region.
Learn more at NOAA's Coral Reef Information System and Coral Reef Conservation Program.
Visit the global coral information system ReefBase to explore coral resources, threats, and photos from around the world.
Life on the Edge 2004: Exploring Deep Ocean Habitats - click on the following links to learn more about this cruise:
USGS Florida Integrated Science Center
North Carolina Museum of Natural Sciences
Research on Deepwater Ecosystems
Megafaunal-habitat associations at a deep-sea coral mound off North Carolina, USA, Quattrini et al.
This site raises awareness of the UK's deep-sea habitats:
Deep-sea Corals in Atlantic Canada
Photos of Norwegian reefs
Deep-sea Coral Reseach and Conservation in Offshore Nova Scotia
Coral Reefs in Norway | <urn:uuid:7034a33a-ea12-41c0-a531-35a250e75c52> | 3.875 | 445 | Knowledge Article | Science & Tech. | 27.229947 |
Riding the atomic waves: with the magic of quantum mechanics, an atom goes two ways at once.Physicists have added a new trick to their experimental repertoire. In their latest feat, called atom interforometry, they paradoxically divide and recombine re·com·bine
To undergo or cause genetic recombination; form new combinations. single atoms, aided by a beautiful but enigmatic assistant known as quantum mechanics quantum mechanics: see quantum theory.
Branch of mathematical physics that deals with atomic and subatomic systems. It is concerned with phenomena that are so small-scale that they cannot be described in classical terms, and it is .
Four teams have recently performed atom interferometry, each using a different technique to accomplish this same bit of seeming magic. Unlike real magicians, however, these physicists eagerly explain the mysteries of their craft. In the past few months, all four groups have shared the secrets of their atom interferometers.
Interferometers are highly sensitive Adj. 1. highly sensitive - readily affected by various agents; "a highly sensitive explosive is easily exploded by a shock"; "a sensitive colloid is readily coagulated" instrument that provide exact measurements of extremely small distances and physical properties such as wavelength. Scientists use them mainly for experimentation, but the devices have several commercial applications as well. Laser interferometers, for instance, play a vital part in advanced gyroscopes.
In the past, interferometers accomplished their precise measurements by manipulating electrons, neutrons or light. Researchers have now made even more sensitive instruments that extend those manipulations to atoms.
In the paradoxical world of quantum mechanics, an atom--like a photon--can be thought of as both a particle and a wave. But atoms have a great advantage over photons when it comes to interferometry. The wavelenth of an atom, known as its de Broglie de Broglie. For persons thus named use Broglie. wavelenth, is based on its momentum and can be 10,000 times shorter than that of visible light. The smaller the wavelength used, the greater an interferometer's precision.
With the new atom interferometers, physicists plan to conduct difficulties tests of atomic properties, general relatively and quantum mechanics. One such device shows promise for measuring gravitational acceleration In physics, gravitational acceleration is the acceleration of an object caused by the force of gravity from another object. An interesting fact is that any object will accelerate towards a large object at the same rate, regardless of the mass of the object. with record-breaking precision.
The key to all types of interferometry lies in quantum mechanics' wave-particle duality wave-particle duality
Principle that subatomic particles possess some wavelike characteristics, and that electromagnetic waves, such as light, possess some particlelike characteristics. . The instruments take a particle and break the single wave that represents it into multiple (usually two) distinct components. In an atom interferometer, for example, "each atom has been split and is going both ways at once," explains David E. Pritchard of the Massachusetts Institute of Technology Massachusetts Institute of Technology, at Cambridge; coeducational; chartered 1861, opened 1865 in Boston, moved 1916. It has long been recognized as an outstanding technological institute and its Sloan School of Management has notable programs in business, in Cambridge. Yet an observer attempting to witness this counterintuitive coun·ter·in·tu·i·tive
Contrary to what intuition or common sense would indicate: "Scientists made clear what may at first seem counterintuitive, that the capacity to be pleasant toward a fellow creature is ... split will see only one wave--a phenomenon arising from the quirks of quantum mechanics. With quantum mechanics, notes Pritchard "you beat your intuition into submission."
After traveling their divergent paths, the wave components recombine at an awaiting detector. If their path difference is exactly the particle's wavelength or an integer multiple of it, the waves are "in phase" and harmoniously merge with each other--an effect known as constructive interference. In other words Adv. 1. in other words - otherwise stated; "in other words, we are broke"
put differently , the crests and troughs of each wave coincide and reinforce one another.
But at other spots on the detector, the path difference amounts to only a fraction of the wavelength, and the components are out of phase. The waves still recombine, but with destructive interference. At these places, where the merging waves are out of alignment, probability dictates that fewer particles will appear.
Ligth interferometers, for example, often produce an interference pattern interference pattern
An overall pattern that results when two or more waves interfere with each other, generally showing regions of constructive and of destructive interference. consisting of a series of dark strips, where few photons emerge, and light strips, where many photons are detected. Atom interferometers show similar patterns based on the number of atoms at each spot on the detector. In effect, "you get ligth and dark spots of atoms," Pritchard says.
Careful examination of these interference patterns can reveal the minute fraction of a wavelength by which the atom's paths differed (the phase shift) and can even reveal the particle's wavelength.
Pritchard's team and a German group unveiled their atom interferometers in the May 27 PHYSICAL REVIEW LETTERS Physical Review Letters is one of the most prestigious journals in physics. Since 1958, it has been published by the American Physical Society as an outgrowth of The Physical Review. . The German researchers, led by Jurgen Mlynek of the University of Konstanz The University of Konstanz (German: Universität Konstanz) is a university in the city of Konstanz in Baden-Württemberg, Germany. It was founded in 1966, and the main campus on the Gießberg was opened in 1972. , created their device by adapting the classic double-slit experiment “Slit experiment” redirects here. For other uses, see diffraction.
In the double-slit experiment, light is shone at a solid thin plate that has two slits cut into it. A photographic plate is set up to record what comes through those slits. of English physicist Thomas Young Noun 1. Thomas Young - British physicist and Egyptologist; he revived the wave theory of light and proposed a three-component theory of color vision; he also played an important role in deciphering the hieroglyphics on the Rosetta Stone (1773-1829)
Young , who in 1802 used photons to demonstrate interference.
In Mlynek's atom interferometer, a supersonic beam of helium atoms passes through a 2-micrometer-wide opening in a thin gold foil. This "spreads" the atom into a wider wave before it travels through two smaller slits. While passing through the two smaller slits, the waves scatter again and eventually recombine into the original atom's single wave. Mlynek and co-worker Olivier Carnal carnal adjective Referring to the flesh, to baser instincts, often referring to sexual “knowledge” suggest the device can resolve a phase shift equal to 0.053 of the atom's wavelength. Since an atom's wavelength is known, the researchers can translate that phase shift into the minute distance by which the wave paths differed.
Pritchard's device--which uses a thin silicon-nitride membrane with a series of extremely fine slits cut into it for a diffraction grating--is even more sophisticated. A beam of sodium atoms must travel through three of these diffraction gratings before yielding an interference pattern. This instrument can resolve a phase shift of 0.016 wavelength, a significant improvement over Mlynek's device, Pritchard says. Moreover, the use of sodium allows additional precision, since sodium atoms are heavier than helium atoms and therefore have a shorter de Broglie wavelength De Broglie wavelength
The wavelength γ = h/p associated with a beam of particles (or with a single particle) of momentum p; h = 6.626 × 1034 joule-second is Planck's constant. .
That precision wasn't easy to achieve. To preserve the instrument's sensitivity, the MIT MIT - Massachusetts Institute of Technology researchers had to incorporate a number of features merely to eliminate vibrations and maintain the alignment of the three diffraction gratings. They even included a laser interferometers to continuously monitor the gratings' alignment.
Physicists have long used atoms--in the form of solid objects such as diffraction gratings, mirrors and lenses--to manipulate light. Some of the new interferometers do just the opposite: Light -- in the form of laser pulses -- manipulates atoms. In the July 8 PHYSICAL REVIEW LETTERS, two groups describe atom interferometers that accomplish this reversal.
In one such device, a calcium atomic beam Atomic beam or atom laser is special case of particle beam; it is the collimated flux (beam) of neutral atoms. The imaging systems using the slow atomic beams can use the Fresnel zone plate (Fresnel diffraction lens) of a Fresnel diffraction mirror as focusing element. is divided into four wave paths by two laser beams perpendicular to the atoms. A second pair of lasers, aimed in the opposite direction of the first pair of laser beams, redirects the waves to either of two detection areas, where the atoms are counted. Both detectors reveal interference patterns, although chance determines which detector will tally a given atom.
This complex instrument is sensitive to rotational changes, report Jurgen Helmcke of the Federal Agency for Technical and Scientific Research in Braunschweig, Germany, and his colleagues. By rotating their instrument on a turntable at different speeds, the researchers can influence the paths of the wave components, thereby shifting the resulting interference patterns. The laser gyroscopes on many of today's airplanes work by a similar principle, but theory indicates that an atom-based system would offer 10 billion times as much sensitivity, useful for general-relatively experiments.
At Stanford University Stanford University, at Stanford, Calif.; coeducational; chartered 1885, opened 1891 as Leland Stanford Junior Univ. (still the legal name). The original campus was designed by Frederick Law Olmsted. David Starr Jordan was its first president. , Steven Chu Steven Chu (Chinese: 朱棣文; Pinyin: Zhū Dìwén), born 1948 in St. Louis, Missouri, is an American experimental physicist. and his colleagues manipulate atoms of a slightly different sort. While other research teams work with fast-moving atomic beams, Chu slowly pumps laser-cooled atoms through his interferometer interferometer: see interference under Interference as a Scientific Tool. See also virtual telescope.
An instrument that measures the wavelengths of light and distances. with an "atomic fountain" (SN:8/19/89, p.117). The languid atoms spend up to 0.5 second within the device--an important consideration in measurements of minute effects. "The sensitivity [of an interferometer] increases when you use slow atoms," Chu explains.
Pritchard agrees and says he plans to try slower atoms in his own devices. He adds, however, that the "brightness" of such sources needs improvement. Chu's fountain can deliver atoms much more slowly than an atomic beam, he says, but it cannot yet match the beam's intensity--the number of atoms delivered.
In Chu's interferometer, lasers not only precool pre·cool
tr.v. pre·cooled, pre·cool·ing, pre·cools
To reduce the temperature of (produce or meat, for example) by artificial means before packaging or shipping. atoms but also lie at the heart of the device. Two lasers--one on each side of the atom's path--provide an initial pulse that splits the atom into a super-position of two different energy states. The higher energy state, recoiling from the laser pulse, moves away from the lower energy state so that the atom appears to be in two places at once. A second pulse reverses the action, causing the atom to reconverge. A third laser pulse ultimately reads the interference pattern.
For another experiment, Chu directed the lasers along, rather than across, the path of the crawling atoms. As a result, an atom's components actually travel the same path at slightly different speeds, so that they move apart from each other in space. This setup should allow the most precise measurement yet of a single atom's gravitational acceleration, potentially achieving a resolution of 1 part in 10 billion, the Stanford researchers assert.
With further refinement, atom interferometers could compete with the laser technology now used in gyroscopes, says Pritchard. But these new devices will shine their brightest in probing the minute details of physics, he maintains. For experimental physicists, improving measurements by a single decimal place can represent a life's goal--a goal now achievable with atom interferometers.
This added precision should help to test the predictions of general relatively and might finally lay to rest the controversial issue of a fifth force, physicists say. It might also dispel any remaining doubts about the charge neutrality of atoms. To confirm atomic neutrality, experimenters would apply an electric field to only one wave component of an atom. If the atom is not neutral, the field will create a discernible change in the interference pattern.
While the new interferometers provide a powerful tool for unveiling atomic properties, "we're not going to find that quantum mechanics is wrong," cautions Pritchard. That's fortunate--because without the perplexing per·plex
tr.v. per·plexed, per·plex·ing, per·plex·es
1. To confuse or trouble with uncertainty or doubt. See Synonyms at puzzle.
2. To make confusedly intricate; complicate. theory, physicists could never have performed their latest show-stopping trick. | <urn:uuid:30fc437f-f6d3-4a6d-a83f-404a87326608> | 3.265625 | 2,914 | Truncated | Science & Tech. | 33.906857 |
This month’s picturing science image, from University Research Fellow Dr Hugh Tuffen, is just four millimeters across. It shows the remarkable microscopic textures within obsidian, or volcanic glass, formed in an Icelandic eruption twenty-five thousand years ago. Obsidian forms from cooling of magma with a high silica content, which makes it very viscous.
This high viscosity also means that crystal growth is sluggish and the few crystals that do form include rounded masses called spherulites that are rich in the mineral cristobalite, a mineral hazardous to human health. Some of these enigmatic crystals are captured in the image, along with dark bands picked out by micron-scale crystals. These bands record how the magma flowed and folded around a perfectly circular bubble of trapped gas.
Dr Tuffen is a volcanologist who investigates the processes that control hazardous eruptions. He is currently using a combination of field studies on active volcanoes and experimental approaches in the lab to address how gases escape from magma and how crystals such as spherulites grow. He was one of the lucky few to witness an obsidian lava flow when he visited Puyehue-Cordon Caulle volcano in Chile and the second image here shows the setting sun lighting up the plume as Puyehue-Cordon Caulle erupts.
During his 10 day trip in January 2012 he collected samples, videos and images, providing a rich resource for future research. If being there to witness the eruption wasn’t exciting enough, he also shot a film of the expedition that was featured in the BBC Volcano Live series. The clip can be found here and is definitely worth a watch. | <urn:uuid:f839fff2-7d01-45c8-bcc9-373ce800d830> | 4.15625 | 349 | Knowledge Article | Science & Tech. | 36.545948 |
The ocamldep command scans a set of OCaml source files (.ml and .mli files) for references to external compilation units, and outputs dependency lines in a format suitable for the make utility. This ensures that make will compile the source files in the correct order, and recompile those files that need to when a source file is modified.
The typical usage is:
ocamldep options *.mli *.ml > .depend
where *.mli *.ml expands to all source files in the current directory and .depend is the file that should contain the dependencies. (See below for a typical Makefile.)
Dependencies are generated both for compiling with the bytecode compiler ocamlc and with the native-code compiler ocamlopt.
The ocamlbuild compilation manager (see chapter 18) provide a higher-level, more automated alternative to the combination of make and ocamldep.
The following command-line options are recognized by ocamldep.
filename: Module1 Module2 ... ModuleNwhere Module1, …, ModuleN are the names of the compilation units referenced within the file filename, but these names are not resolved to source file names. Such raw dependencies cannot be used by make, but can be post-processed by other tools such as Omake.
Here is a template Makefile for a OCaml program.
OCAMLC=ocamlc OCAMLOPT=ocamlopt OCAMLDEP=ocamldep INCLUDES= # all relevant -I options here OCAMLFLAGS=$(INCLUDES) # add other options for ocamlc here OCAMLOPTFLAGS=$(INCLUDES) # add other options for ocamlopt here # prog1 should be compiled to bytecode, and is composed of three # units: mod1, mod2 and mod3. # The list of object files for prog1 PROG1_OBJS=mod1.cmo mod2.cmo mod3.cmo prog1: $(PROG1_OBJS) $(OCAMLC) -o prog1 $(OCAMLFLAGS) $(PROG1_OBJS) # prog2 should be compiled to native-code, and is composed of two # units: mod4 and mod5. # The list of object files for prog2 PROG2_OBJS=mod4.cmx mod5.cmx prog2: $(PROG2_OBJS) $(OCAMLOPT) -o prog2 $(OCAMLFLAGS) $(PROG2_OBJS) # Common rules .SUFFIXES: .ml .mli .cmo .cmi .cmx .ml.cmo: $(OCAMLC) $(OCAMLFLAGS) -c $< .mli.cmi: $(OCAMLC) $(OCAMLFLAGS) -c $< .ml.cmx: $(OCAMLOPT) $(OCAMLOPTFLAGS) -c $< # Clean up clean: rm -f prog1 prog2 rm -f *.cm[iox] # Dependencies depend: $(OCAMLDEP) $(INCLUDES) *.mli *.ml > .depend include .depend | <urn:uuid:0f35a136-6d49-4a1d-b732-e89bbe7380a0> | 2.75 | 685 | Documentation | Software Dev. | 49.463105 |
View Full Version : Neutron Stars have charge...waa?
2008-May-24, 01:54 AM
Pardon me if this has already been asked, but since neutrons don't have charges, how can a neutron star have a magnetic field?
The composition of a neutron star is known only via theory, and theoretical details are not complete. However, a neutron star is believed to contain not only neutrons but also quarks, electrons, protrons, and nuclei of elements heavier than hydrogen, so there is plenty of charge present to account for a magnetic field. For more details, Google "neutron star" and go to "Structure" in the Wikikpedia article.
Powered by vBulletin® Version 4.2.0 Copyright © 2013 vBulletin Solutions, Inc. All rights reserved. | <urn:uuid:fb5a9e78-8f60-4663-bd69-0fbed68f077e> | 3.015625 | 176 | Comment Section | Science & Tech. | 63.44 |
Class #11 (Feb. 12) Reading Questions - The Dark Side of the Universe
1. Current observational results constrain to the total matter (plus energy) density of the universe to the range 0.1<Omega<10 where Omega=Mtotal/Mcritical. Explain why this result strongly implies that Omega actually equals exactly one and thus, that the universe is "flat".
2. Explain the "horizon problem" (giving the experimental evidence for this "problem") and describe how the Inflationary Model solves this problem.
3. Explain the connection between the Standard Model of particle physics and the Inflationary Model of the universe.
4. Explain how detailed measurement of temperature variations in the cosmic background radiation (CMB) provide direct experimental evidence that the universe is "flat".
5. What is "dark energy" and what is the observational/experimental evidence for its existence.
6. What is a type Ia supernova and why do these objects provide nearly "ideal standard candles"?
7. What "shocking" result was deemed the 1998 "Science Breakthrough of the Year" and what is the observational evidence for this result?
Your Question: Please give a well formulated question that you have regarding the material covered in this reading assignment. | <urn:uuid:5a9d025f-972e-4241-87fd-bb5ce24a2833> | 3.390625 | 263 | Q&A Forum | Science & Tech. | 41.789583 |
See also the
Dr. Math FAQ:
Browse High School Discrete Math
Stars indicate particularly interesting answers or
good places to begin browsing.
Selected answers to common questions:
Four-color map theorem.
How many handshakes?
Squares in a checkerboard.
- Graph Theory [09/29/2001]
Why is a graph with five vertices, each having a degree of 3, impossible?
- Graph Without Crossing Lines [7/19/1996]
There are three houses and three utilities: how do you connect each of
the houses individually to the three utilities without crossing your
- Greatest Integer Functions [09/27/1998]
Can you help me solve for the graph of [y]=[x], where is the greatest
- How Many are in the Group? [10/17/1996]
Everyone in the group had been to at least one of the parks...
- How Many Balls Would Be Used? [5/8/1995]
Consider a knock-out tournament, say tennis or ping-pong, with n
participants. The winner of any game goes on to the next round and the
loser retires...How many balls have been used in the tournament?
- How Many Distinct Patterns? [01/15/2001]
Given a large equilateral triangle divided into four smaller equilateral
triangles, if two edges are painted white and the rest are painted black,
how many distinct patterns are possible?
- How Many Factors? [7/14/1996]
How do you find the number of factors for a number?
- How Many Games in the Tournament? [01/15/2002]
There are eight teams in a single-elimination tournament. Each team gets
to play until it loses. How many games will be played in the tournament?
- How Many Threes? [06/12/1999]
If all the numbers from 1 to 333,333 are written out, how many times will
the digit 3 be used?
- Infinity Hotel Paradox [09/15/1999]
How can a hotel with an infinite number of rooms, all already occupied,
accommodate the passengers of an infinite number of buses without
doubling them up?
- Integer Solutions of ax + by = c [04/03/2001]
Given the equation 5y - 3x = 1, how can I find solution points where x
and y are both integers? Also, how can I show that there will always be
integer points (x,y) in ax + by = c if a, b and c are all integers?
- Inverse, Product of Permutations [04/27/2002]
I don't understand how to calculate the inverse or the product of
- Josephus Problem [04/18/2003]
Every other person at a table is eliminated until there is only one
person left. Who is the survivor?
- Karnaugh Maps [05/07/2000]
What are Karnaugh maps? How are they used?
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If x knights are sitting at a round table, and every other one is
removed, who is the last one left sitting at the table?
- The Königsberg Bridge [5/20/1996]
Do you have information on Konigsberg's bridge?
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What is an interior lattice point and a boundary lattice point of a given
shape (triangle, circle, rectangle, etc.)?
- Line Drawn through Lines Puzzle [10/18/2001]
Given a box made up of 16 lines, with two rectangles above and three
squares below, draw a line through each line without crossing any line
- Lines determined by 5 points [11/13/1994]
How many lines are determined by 5 points, no three of which are
- Locker Problem [11/21/1997]
There are 1,000 lockers numbered from 1 through 1,000. The first student
opens all the doors; the second student closes all the doors with even
- Math Games Involving Forcing an Opponent into an Outcome [06/19/2004]
A very challenging math game provides the background for a discussion
of how to find the winning strategy in 'reduced state' games, where
players attempt to force a final outcome after a series of moves.
- Math Logic - Determining Truth [04/13/1999]
A number divisible by 2 is divisible by 4. Find a hypothesis, a
conclusion, and a converse statement, and determine whether the converse
statement is true.
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Why does matrix multiplication work? Why are the rows multiplied and
added with the columns?
- Meaning of '-ominoe' [11/07/2001]
We are drawing pictures of dominoes, triominoes, tetrominoes, and
pentominoes. What is the meaning of the root "ominoe"?
- Minimum Number of Cuts to Slay the Dragon? [01/14/2007]
A magic dragon has 3 heads and 3 tails. A knight with a magic sword
can make four types of cuts--one head, two heads, one tail, or two
tails. For each type of cut, the dragon regrows one head, nothing,
two tails, or one head respectively. The knight must remove all
heads and tails to slay the dragon. What's the fewest number of cuts
he can make?
- Moving Knights on a Chessboard [01/27/1999]
Given 4 knights at the 4 corners of a 3-by-3 chessboard, can the knights
exchange places if they can move only in the following way?
- Multi-Dimensional Four-color Theorem [08/08/1997]
Has any work been done on theorems like the four-color theorem for
- The N-Color Theorem? [07/27/2002]
What happens if we try to generalize the Four Color Theorem to other
numbers of dimensions?
- New School Lockers [01/28/2001]
Which locker was touched the most?
- Nim [09/26/2000]
What is the principle of Nim and what is its application?
- No Three Red Beads Together [09/16/2001]
Given 10 beads on a necklace, 6 white and 4 red, how many ways can the
beads be arranged so that no three red beads are together?
- Number/Color Cube [09/13/2001]
You want to make a number cube by putting the numbers 1,2,3,4,5,6 on the
face. 1/5, 3/6, and 2/4 must be on opposite faces. Each face is a
different color. How many ways can you make the cube?
- Number of Unordered Partitions [08/18/1999]
Is there a formula for the number of unordered partitions of a positive
- Number of Ways to Move [1/30/1996]
I have a group of squares which together form a larger square. In how
many ways can you travel from the upper left corner of the large square
to the lower right corner by only going down or to the right?
- Number Systems: Two Points of View [06/30/1998]
What are the number systems?
- Number Theory Proofs [06/24/1999]
How can I prove that the equations (x,y) = g and xy = b can be solved
simultaneously if and only if g^2|b for integers g, b?
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Objects are stacked in a triangular pyramid... how many objects are in
the nth layer from the top?
- Occupancy Problem [08/06/2001]
Given n bins and m (indistinguishable) balls, how many arrangements are
possible such that no bin has greater than r balls?
- Odd and Even Vertices [1/30/1996]
We are trying to trace networks without crossing a line or picking up our
pencils, but how can we know if a vertex is odd or even?
- Odd Number of Hands, Even Number of People [08/31/2001]
Every person on earth has shaken a certain number of hands. Prove that
the number of persons who have shaken an odd number of hands is even. | <urn:uuid:ba4e41fe-e2b0-4ab4-b780-81205bbc7a1b> | 3.0625 | 1,844 | Q&A Forum | Science & Tech. | 73.597802 |
The direction flag is a CPU flag specific to Intel 80x86 processors. It applies to all assembly instructions that use the REP (repeat) prefix, such as MOVS, MOVSD, MOVSW, and others. Addresses provided to applicable instructions are increased if the direction flag is cleared.
The C run-time routines assume that the direction flag is cleared. If you are using other functions with the C run-time functions, you must ensure that the other functions leave the direction flag alone or restore it to its original condition. Expecting the direction flag to be clear upon entry makes the run-time code faster and more efficient.
The C Run-Time library functions, such as the string-manipulation and buffer-manipulation routines, expect the direction flag to be clear. | <urn:uuid:c65ff48a-714c-47fa-bbd9-c2f02e9b360d> | 2.734375 | 163 | Documentation | Software Dev. | 45.199528 |
Gets the collection of controls contained within the control.
Assembly: System.Windows.Forms (in System.Windows.Forms.dll)
A Control can act as a parent to a collection of controls. For example, when several controls are added to a Form, each of the controls is a member of the Control.ControlCollection assigned to the property of the form, which is derived from the Control class.
When adding several controls to a parent control, it is recommended that you call the SuspendLayout method before initializing the controls to be added. After adding the controls to the parent control, call the ResumeLayout method. Doing so will increase the performance of applications with many controls.
Use the property to iterate through all controls of a form, including nested controls. Use the GetNextControl method to retrieve the previous or next child control in the tab order. Use the ActiveControl property to get or set the active control of a container control.
The following code example removes a Control from the Control.ControlCollection of the derived class Panel if it is a member of the collection. The example requires that you have created a Panel, a Button, and at least one RadioButton control on a Form. The RadioButton control(s) are added to the Panel control, and the Panel control added to the Form. When the button is clicked, the radio button named removeButton is removed from the Control.ControlCollection. | <urn:uuid:28d81b3e-fca4-46d9-ae8c-d94938c25e45> | 3.046875 | 294 | Documentation | Software Dev. | 50.036667 |
The Medieval Warm Period in Northeast China
Wang, L., Rioual, P., Panizzo, V.N., Lu, H., Gu, Z., Chu, G., Yang, D., Han, J., Liu, J. and Mackay, A.W. 2012. A 1000-yr record of environmental change in NE China indicated by diatom assemblages from maar lake Erlongwan. Quaternary Research 78: 24-34.
Focusing on Lake Erlongwan, one of eight maar lakes in the Long Gang Volcanic Field of Jilin Province, NE China (42°18'N, 126°21'E) - which they describe as a closed dimictic lake that occupies an area of 0.3 km2 and has a small catchment (0.4 km2) with no natural inflows or outflow - Wang et al. retrieved a 66.5-cm-long sediment core from its central, deepest region in 2001, which they dated with the help of radiometric 210Pb, 137Cs and 14C analyses, and which they analyzed for diatom species and quantities. Although they note, in this regard, that diatoms "are generally not known to be very sensitive to water temperature," they indicate that "climate affects the physical properties of the lake water column, especially as it controls the seasonal durations of ice cover, water column mixing and stratification, which all have profound effects on the availability of nutrients and light necessary for algal photosynthesis and growth," so that "climate has an indirect influence on the composition and productivity of phytoplankton, especially non-motile organisms such as diatoms," which thus allows them to undertake "a detailed qualitative paleolimnological interpretation of the Lake Erlongwan sediment sequence based mainly on the growing body of literature that focuses on the ecology of planktonic diatoms, especially their responses to climate-driven changes in limnology."
The ten researchers report that "three intervals were identified by their diatom assemblages and correspond within dating uncertainties to the Medieval Warm Period, the Little Ice Age and the 20th century warming trend." During the MWP, they further indicate that "the duration of the summer was longer while the spring and autumn were shorter than the 20th century." And they unequivocally declare that "the period between ca. AD 1150 and 1200 was the warmest interval of the past 1000 years."
In view of the fact that, prior to the time of their study, there was no record of mean annual temperatures from NE China covering the past 1000 years with the same resolution as their diatom record, Wang et al.'s work demonstrates - for yet another part of the planet - that late-20th-century warmth, even with the help of an extra 100 ppm of CO2, was less than that of the MWP, which makes it extremely difficult to believe that Earth's current level of warmth largely owes its existence to anthropogenic CO2 emissions, as the world's climate alarmists continue to claim it does.
Battarbee, R.W., Jones, V.J., Flower, B.P., Cameron, N.G., Bennion, H., Carvalho, L. and Juggins, S. 2001. Diatoms. In: Smol, J.P., Birks, H.J.B. and Last, W.M. (Eds.). Tracking Environmental Change Using Lake Sediments. Kluwer Academic Publishers, Dordrecht, The Netherlands, pp. 155-201.
Mackay, A.W., Jones, V.J. and Battarbee, R.W. 2003. Approaches to Holocene climate reconstruction using diatoms. In: Mackay, A.W., Battarbee, R.W., Birks, H.J.B. and Oldfield, F. (Eds.). Global Change in the Holocene. Arnold, London, United Kingdom, pp. 294-309.
Smol, J.P. and Cumming, B.F. 2000. Tracking long-term changes in climate using algal indicators in lake sediments. Journal of Phycology 36: 986-1011.
Zolitschka, B., Brauer, A., Negendank, J.F.W., Stockhausen, H. and Lang, A. 2000. Annually dated late Weichselian continental paleoclimate record from the Eifel, Germany. Geology 28: 783-786. | <urn:uuid:4e71d045-b508-41ce-b787-6bbabce7c2d2> | 2.796875 | 950 | Academic Writing | Science & Tech. | 69.364463 |
The Compact Reconnaissance Imaging Spectrometer for Mars (CRISM) took this image of the Nili Fossae region at 0643 UTC (2:43 a.m. EDT) on June 21, 2007, near 21.15 degrees north latitude, 74.24 degrees east longitude. CRISM's image was taken in 544 colors covering 0.36-3.92 micrometers, and shows features as small as 20 meters (66 feet) across. The region covered is just over 10 kilometers (6.2 miles) wide at its narrowest point, and is one of several dozen that CRISM has taken to map the minerals at candidate landing sites for the Mars Science Laboratory (MSL) mission, which will launch in 2010.
The Nili Fossae region is critical to understanding the history of water on Mars and whether water ever formed environments suitable for life, because the region is underlain by a layer of phyllosilicate (clay) minerals. This type of mineralogy formed where water was in contact with Mars' crustal rocks for very long periods, altering the silicates in volcanic rocks. In addition, phyllosilicates can encapsulate and preserve organic chemicals associated with life (if life was present). Its rocky record of an ancient wet environment makes Nili Fossae a top contender among the 30-plus landing sites being considered for MSL, whose objectives include measuring the chemistry preserved in an ancient wet environment.
This series of four different versions of the same 544-color image illustrates the mineral-mapping capability that comes from moving beyond the wavelength range of the human eye, and into infrared wavelengths where minerals leave distinct "fingerprints" in reflected sunlight. At upper left, more than three dozen of the distinct wavelengths measured by CRISM were combined to mimic how the human eye would see the image. The subtle shading comes from the Sun's position high in Mars' sky when the image was taken, creating few shadows. The bland, butterscotch color comes from the dust coating nearly all of the Martian surface to some degree. At upper right, three infrared wavelengths (2.53, 1.50 and 1.08 micrometers) replace the red, green and blue image planes. These wavelengths are less sensitive to dust, and begin to show the spectral variations in the underlying rocks.
The two bottom versions combine different wavelengths to show strength of absorption due to the different minerals that are present, providing indications of the minerals' presence and distribution. The lower left version combines measurements of the strength of iron mineral absorptions at 0.53, 0.86 and 1.0 microns in the red, green and blue image planes. Bluer areas have more pyroxene, a mineral found in volcanic basaltic rock, whereas reddish and especially orange areas have more oxidized iron minerals. The lower right version combines measurements of mineral absorptions at 1.0, 1.9 and 2.3 microns in the red, green and blue image planes. Redder areas are richer in pyroxene, and green and blue areas contain more phyllosilicate minerals. The combination of basaltic rocks and highly altered phyllosilicates in close proximity would allow MSL to make detailed measurements of rocks formed in two distinct environments.
The Compact Reconnaissance Imaging Spectrometer for Mars (CRISM) is one of six science instruments on NASA's Mars Reconnaissance Orbiter. Led by The Johns Hopkins University Applied Physics Laboratory, the CRISM team includes expertise from universities, government agencies and small businesses in the United States and abroad. | <urn:uuid:6da7a36b-e587-4861-b511-0bf4a1e04b62> | 3.796875 | 733 | Knowledge Article | Science & Tech. | 44.64751 |
Some high-energy experiments (RHIC, LHC) use ion-ion collisions instead of proton-proton collisions. Although the total center-of-mass energy is indeed higher than p-p collisions, it might happen that the total energy per nucleon is actually lower. What are the advantages of using ion-ion collisions (e.g. gold-gold or lead-lead) instead of proton-proton collisions, considering the same accelerator?
As a clarification the energy per nucleon is always lower: for example, currently in the LHC the proton top energy is 3.5 TeV. Now the Pb energy is 3.5 TeV times Z so the energy per nucleon is 3.5*Z/A and A is greater than Z for every nucleus (except the proton where it is equal to one).
But the goal of ion-ion collision is not to increase the total energy or the energy per nucleon: it is to obtain a different type of collision.
It should be noted than in a proton-proton collision, the energy involved in the real collision process is variable: each quark and gluon carry a fraction of the energy of the proton, and hard collision involve a collision between a quark/gluon of one proton against a quark/gluon of the other.
In the case of ion-ion collision you have the same process: the energy is shared by the protons/neutrons and they can have different energies.
The goal of such collision is also to obtain a volume (bigger than in a p-p collision) with a very high energy density. In such a volume, a "state of matter" called quark-gluon-plasma is believed to be possibly created. The study of this QGP is one of the main goal of the ALICE experiment at the LHC.
A few references: | <urn:uuid:e169a27d-af4a-46af-ba2f-3cefd4cfff6e> | 3.328125 | 402 | Q&A Forum | Science & Tech. | 57.907806 |
Compiled/interpreted is hardly a meaningful distinction nowadays; IDE's such as Eclipse completely hide away the compile step, interpreted languages are sometimes compiled transparently to improve performance. The really interesting metric is "how much time I need to start my program while developing", really. With today's processors, even compiled heavyweight Java + Tomcat starts in my box in less than two seconds, which hardly bothers me.
Again, most languages are Turing complete, meaning they are all "equivalent" wrt. to the capabilities of the programs you can make with them. What matters normally is:
- Bindings/ability to use the libraries/framework you need. If you are developing a GUI app, you will need to be able to use a GUI library from the language you want. There are loads of GUI libraries (GTK, QT, the couple of Windows frameworks, Cocoa for OS X, etc.)- some are a platform's native GUI library, some are multiplatform- and they all support different sets of languages (and within that, there are often first-class citizens; Objective C is Cocoa's first-class citizen, for instance)
- General language quality and suitability to the task at hand
The latter is more complicated, and fairly subjective.
I would say that PHP is ill-suited to GUI app development- the main GUI binding I know is PHP-GTK and it seems to be pretty much inactive. Also, PHP's programming model is fairly tied to the request-response/HTML generating nature of web applications, which doesn't really fit nicely with GUI development.
Python is generally OK to develop GUI apps. Bindings exist for a variety of toolkits, and while Python isn't a particularly fast language, that hardly matters for most desktop apps- unless your application does something particularly CPU-intensive, you're not gonna notice any performance difference between any languages.
In general, GUI applications are more chosen by your target platform. If you target a single platform, often the least-effort/best-results approach is choosing the first-class citizen in that platform. If you are coding an OS X app, Objective-C + Cocoa is probably the way to go. If you develop a Gnome/Linux app, GTK + (Python|Vala|C) are probably the best options, likewise C++/QT for KDE, and C# + one of the official Windows toolkits (I've lost track now). Funnily enough, the "official way" is muddled- what you want here is something with plenty of documentation and maintained by the same people who develop the platform- languages/bindings by third-parties often lag behind or miss features.
But if you can choose the native "first-class" toolkit/language combination, you'll normally be able to deliver an application which looks and behaves like the rest of applications in the platform and which provides the most natural experience.
If you want to develop cross-platform apps, it gets slightly more complicated. There exist cross-platform toolkits- GTK, QT, Java's Swing and SWT, etc.- but you must realize that often they do not provide as good an experience as native toolkits- maybe the widgets do not look like the native widgets, or stuff like that, but even the best cross-platform toolkit cannot fix that different platforms have different conventions (standard shortcuts, menu arrangement and naming, dialogs, etc.)- think of iTunes on Windows- it looks and behaves definitely foreign and different to regular Windows applications, although it looks perfectly at home at OS X: same application, different platforms; means no native experience.
You might be OK with this- or even you want one of those custom-looking applications which look like no regular apps.
If you aren't, prepare for a road of pain. Probably the best solution is to develop separate applications for each platform you target, and if you are lucky, you might be able to reuse a good chunk of code from platform to platform (particularly, if you can use a common language- for instance you might develop your core app in Python and develop several GUIs for different platforms using different toolkit bindings- if you are lucky and they exist). Another way would be to use a multiplatform toolkit and work hard to adapt your program to the different platforms you target, but that might be a lot of effort or maybe even outright impossible to achieve completely. | <urn:uuid:ec5b640c-d989-49f9-8742-20cbab922bbb> | 2.796875 | 917 | Q&A Forum | Software Dev. | 37.091763 |
Map of the cosmic microwave background radiation, c. 2006
This beach ball shows a full-sky map of the microwave radiation left over from the Big Bang—a snapshot of what the early Universe was like, 13.7 billion years ago. Many scientists believe that temperature fluctuations observed in the microwave background are a result of Hawking radiation. This map is the best proof of Hawking’s theories about black holes and the origins of the Universe.
Source: The Hawking Family Archive. CMB image: NASA.
- Currently on display in:
- Stephen Hawking: A 70th birthday celebration | <urn:uuid:bcb499b7-f1b9-47b8-965c-f69df0789159> | 3.15625 | 120 | Knowledge Article | Science & Tech. | 53.247368 |
n: The letter "n" when used as a prefix
before a unit symbol indicates a multiplier of 10-9. Abbreviation of "nano".
E.g., nV = 10-9 volt, one nanovolt, one billionth of a volt.
nA: Symbol and abbreviation of nanoampere
(= 10-9 ampere, one billionth of an ampere).
nano: When used as a prefix before a
unit name it indicates a multiplier of 10-9. E.g., nanovolt = 10-9 volt, one
billionth of a volt. Symbol: "n".
nanoampere: 10-9 ampere,
symbol: "nA" (one billionth of an ampere).
Nanometer: abbreviated "nm", a unit
of length equal to one thousandth of a micrometer.
nanovolt: 10-9 volt, symbol:
"nV" (one billionth of a volt).
Negatively charged electrode, usually of a secondary cell; acts as
anode during discharge and cathode during charge.
Nernst equation: An equation defining
the equilibrium potential of an electrode. The potential is the sum of the standard
electrode potential and a correction term for the deviation from unit concentrations
of the reactant and the product of the electrode reaction in the solution; if
the "reduced" form is a metal, a pure metal (not alloyed with other metals)
is considered to be at unit concentration. The correction term is the product
of the "Nernst slope" and the logarithm of the ratio of the concentrations (strictly
speaking, activities) of the oxidized species and the reduced species. At room
temperature, the Nernst slope is 0.05916 volt divided by the number of electrons
transferred during the reaction. E.g., for a simple metal deposition/dissolution
reaction the slope is 0.05916 for a single charged metal cation, 0.00296 volt
for a double charged ion, etc.
Nernst slope: See Nernst equation. It
is equal to the change of equilibrium electrode potential when the concentration
(strictly speaking, activity) of a species involved in the electrode reaction
changes by ten fold.
Nernstian behavior: An electrode is
said to behave "nernstially" if the equilibrium electrode potential obeys the
Nernst equation when the concentration (strictly speaking, activity) of a species
involved in the electrode reaction changes. Opposite: non-nernstian behavior.
Nernstian (or Nernst's) hypothesis:
See diffusion layer.
Nernstian reaction: See reversible electrode
Neutralization: (1) The reaction of
an acid and a base to form a "neutral" (pH = 7) solution. (2) The removal of
electrical charge to produce a "neutral" (electrically uncharged) particle or
Neutron: See atomic structure.
NHE: Stands for "normal hydrogen electrode,"
which is an alternative name for the standard hydrogen electrode.
Noble metal: A metal that resists oxidation
(corrosion) in air, and therefore retains its metallic luster. Examples are
platinum and gold. These metals have high positive standard electrode potentials
and are the lowest ones on the electromotive series. Contrast with active metal.
Non-aqueous solution: A solution with
the solvent anything but water (e.g., organic or inorganic liquid, molten salt).
Non-faradaic current (density): See
capacitive current (density).
Non-nernstian behavior: An electrode
is said to behave "non-nernstially" if the equilibrium electrode potential does
not obey the Nernst equation when the concentration (strictly speaking, activity)
of a species involved in the electrode reaction changes. Opposite: nernstian
Non-ohmic resistance (behavior): A system
or system element is behaving "non-ohmically" if it does not follow Ohm's law.
That is, the value of the resistance depends on the current or the potential.
Opposite: ohmic behavior. The resistance can be formally defined as the differential
of the potential with respect of the current. In the case of Ohm's law, this
is the constant value of the resistance. In electrochemistry, a typical "non-ohmic"
element is the charge-transfer resistance. The charge-transfer reaction can
be considered a circuit element because it requires a certain amount of overpotential
to force through a current. However, the pertinent relation here is the Tafel
law (at least at relatively large overpotentials), and the differential of the
current (that is the resistance) is a function of the current itself.
Non-polarizable electrode: An electrode
that is not easily polarizable. That is, the potential of the electrode will
not change significantly from its equilibrium potential with the application
of even a large current density. The reason for this behavior is that the electrode
reaction is inherently fast (has a large exchange current density). See also
overpotential. Opposite: polarizable electrode.
Non-rechargeable battery: A battery
in which the chemical reaction system providing the electrical current is not
easily "chemically" reversible. It provides current until all the chemicals
placed in it during manufacture are used up. It is discarded after a single
discharge. Also called "primary" battery or cell. Contrast with rechargeable
battery. This battery always operates as a galvanic cell. Consequently, the
anode is the negative electrode, while the cathode is the positive electrode.
Normal electrode potential: Alternative
name for standard electrode potential.
Normal hydrogen electrode: Alternative
name for standard hydrogen electrode. Abbreviated as "NHE."
Nucleus: See atomic structure.
nV: Symbol and abbreviation of nanovolt
(= 10-9 volt, one billionth of a volt). | <urn:uuid:de6ae0c5-8442-4fad-bc99-b4a87a1858dd> | 3.390625 | 1,317 | Structured Data | Science & Tech. | 34.695766 |
Methyl mercaptanMethyl mercaptan is a colorless gas with a smell like rotten cabbage. It is a natural substance found in the blood, brain, and other tissues of people and animals. It is released from animal feces. It occurs naturally in certain foods, such as some nutss and cheese. The chemical formula for methyl mercapatan is CH3SH.
Methyl mercaptan is released from decaying organic matter in marshes and is present in the natural gas of certain regions in the United States, in coal tar, and in some crude oils. It is manufactured for use in the plastics industry, in pesticides, and as a jet fuel additive. It is also released as a decay product of wood in pulp mills. | <urn:uuid:cbe96730-eee3-447f-ae0f-fb926b6c6839> | 3.203125 | 151 | Knowledge Article | Science & Tech. | 49.907818 |
so i was reading the article about primitive data types and i came across litterals. so i understand the uses of the 8 primative types but i dont understand why you would do this below
float pi = 3.1415F;
long pi2 = 3141L;
does adding the extra 'F' / 'L' onto the value do anything ? i have been struggling to find infomation that I understand. also where would i use these in a program. thanks, hope you understand what im trying to get at :S massive learninng curve, SO MUCH TO LEARN !!
if there are any articles you could link me to that would be great, just trying to save you time on explaining. | <urn:uuid:31630c68-228a-4ecb-9f1d-5bd917816ca7> | 3.3125 | 149 | Q&A Forum | Software Dev. | 70.257143 |
Show that the work required to assemble
four identical point charges of magnitude q on the corners of a square of
side a is
To calculate the work to assemble any number of point charges you can proceed as follows:
- Numerate each charge.
- Assume charges are brought from an infinite distance.
- Charge 1 is brought first and placed on corner 1. This charge does not requires any work because there is no electric field present.
- Charge 2 is brought then and placed on corner 2, charge 3 is brought and placed on corner 3 and so on.
Charge 2 requires a work keq2/a.
Charge 3 requires a work keq2/a + keq2/(a21/2) (work due to charges 1 and 2 already present).
Charge 4 requires a work keq2/a + keq2/(a21/2) + keq2a (work due to charges 1, 2 and 3 already present).
The work needed to get the desired configuration is obtained adding each required work:
keq2/a + keq2/a + keq2/(a21/2) + keq2/a + keq2/(a21/2) + keq2/a. = (keq2/a)(1 + 1 + 2-1/2 + 1 + 2-1/2 + 1) = 5.41 keq2/a.
The axis x is the axis of symmetry of a ring uniformly charged of radius R and total charge q. A point charge q with mass m is placed at the center of the ring. When the ring is slightly displaced to the left the point charge moves along the x axis towards infinity. Show that the final speed v of the point charge is v = (2keq2/mR)1/2.
The charge potential energy at the center of the ring can be calculated using the relation for the potential in differential form, dV = kedq/R, where dq is an infinitesimal charge on the ring and R is the distance to the center of the ring. The total potential at the center of the ring is the integral of dV, V = keq/R.
Then, the point charge energy is Vq = keq2/R.
At infinity, V = 0 and the energy is zero.
The change in potential energy is 0 - keq2/R = - keq2/R.
The change in kinetic energy is ½ mv2 - 0 = ½ mv2.
As ( Ufinal - Uinitial) + (Kfinal - Kinitial) = 0
- keq2/R + ½ mv2 = 0
½ mv2 = keq2/R or v = (2keq2/mR)1/2.
A small sphere of mass 0.2 g hangs by a thread between two parallel vertical plates 5 cm apart. The charge on the sphere is 6x10-9 C. What is the potential difference between the plates if the thread assumes an angle of 10º with the vertical? Assume a uniform electric field between the plates.
From the sphere free body diagram, we have:
(A) Tsin10º = F, F = qE, where E is the electric field assumed uniform. Tsin10º = qE.
Also, Tcos10º = mg or T = mg/cos10º =
0.0002 kgx(9.8 m/s2)/cos10º = 0.00199 N
Replacing in (A) and solving for E,
E = Tsin10º/q = 57.6 x103 N/C or 57.6x103 Volts/m.
As in a uniform field E = potential difference (V)/plates separation (d), the potential difference is Ed = (57.6x103 Volts/m)(0.05m) = 2.88 kV.
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· Free Fall Exercises, Part Three | <urn:uuid:59d49671-1dc7-467d-a99c-99d4d19ba321> | 3.328125 | 1,081 | Tutorial | Science & Tech. | 75.260201 |
It is being said by the end of this year the underground South Dakota laboratory in the US will start collecting data with a good chance to discover dark matter.
Dark matter is an elusive matter known only by its gravitational pull and is so far undetected. By discovering dark matter, scientists could explain how the world as we know it came to be.
The most popular citizen journalists' reports on merinews chosen automatically on the basis of views and comments
View more jobs | <urn:uuid:f1d477f1-849c-40cf-a761-305972c6ed53> | 2.6875 | 95 | Truncated | Science & Tech. | 40.436429 |
For some time, biologists have known that ecological communities made up of many species are particularly resistant to invasion by new species. The most obvious explanation is that the communities are stable because all the niches are filled and so there is no room for new species. But the obvious answer is wrong, according to an American ecologist.
Ted Case of the University of California, San Diego, has developed a theoretical model of the invasion process. He finds that interactions between species in a large community create an 'invisible protective network', and it is this that underlies a community's resistance to invasion.
According to Case, the obvious explanation for stability in species-rich communities ignores an important fact. The invading species is adapted to one niche only, so whether or not other niches are empty or filled in a community is really of no consequence to it.
If the availability of ...
To continue reading this article, subscribe to receive access to all of newscientist.com, including 20 years of archive content. | <urn:uuid:bdd6927a-076d-4132-864b-cafe697879ab> | 3.25 | 204 | Truncated | Science & Tech. | 30.956434 |
We have been reading much about droughts, excessive rainfall and explanations of global warming, but another unpublicized factor enters the story of climatic change. Recall that several years ago an Icelandic volcano erupted and put so much ash into the sky that European air travel was disrupted for several days.
What seems to be unknown to metro residents is that in the winter of 1783-84 the Laki Volcano in Iceland erupted and spread a mass of ash so great that it caused crop failure and famine in Europe. The volume of ash so completely occluded the sun that the Mississippi River was iced over as far south as New Orleans. Ice masses were floating in the Gulf of Mexico.
The greatest recorded volcano eruption was in 1815 in Mount Tambora, an Indian Ocean island in Indonesia. It was called "The year without a summer." The largest documented volcanic eruption occurred on the island of Krakatoa between Sumatra and Java.
In August 1883 the volcano erupted and was recorded on barographs around the world. It was estimated to be 13,000 times greater force than the A-bomb released on Hiroshima, Japan. Estimates of the number of people killed range from 38,000 to 120,000, and it destroyed hundreds of villages and towns. It caused tsunamis 100 feet high and reduced global temperature by a little more than 2 degrees F. Global temperature did not return to normal until 1888.
The fossil record shows many major climatic changes but Mother Nature can also affect climate on short term. When I took an ecology course in the late 1940s the professor told us that U.S. climate had 51-year cycles. Despite the present cache of data, we still remain mystified to explain the unusual weather of the past few years.
Harold A. Dundee, Ph.D. | <urn:uuid:1f1b7be6-67b4-4cc6-b5b7-ce3674c54ed6> | 3.953125 | 372 | Nonfiction Writing | Science & Tech. | 54.915588 |
Consider the polarity of the ions released when the water decomposed.
Which gas collected at the cathode? Why?
(Oxygen. Oxygen ions are positive and the cathode is negative.
were there more hydrogen bubbles than oxygen bubbles? (Water
contains twice as many hydrogen atoms as oxygen atoms.)
did the chlorine gas generated in step 10 come from?
(Ions of chlorine that had formed when table salt (NaCl) was
dissolved in water.)
In addition to generating free chlorine gas, how
might adding a "pinch" of salt affect the decomposition of water?
(The salt would make the water more conductive and therefore
increase the rate of electrolysis.) | <urn:uuid:cd44f6e9-b78e-451f-ade5-0468937ffc20> | 3.59375 | 152 | Tutorial | Science & Tech. | 40.240559 |
The polar bear has become the poster child of global warming, but there’s more to the Arctic than ice and polar bears. Beyond these two famous and prominent features of the Arctic environment, there is an entire intricate ecosystem of wildlife and plant life that will be profoundly affected by a prolonged warming trend in the Arctic.
There’s no doubt the Arctic is warming. In fact, this extreme region has warmed faster than any other on earth, with the Arctic temperature increasing three to five times faster than the Earth as a whole over the past 100 years. Climate models predict that the Arctic will become an additional 7 to 12 degrees Fahrenheit warmer during the next century.
Experts predict these rising temperatures are likely to cause the melting of at least half the Arctic sea ice by the end of the century. Melting ice is expected to lead to even higher Arctic temperatures as bright white ice plays a significant role in reflecting the sun’s radiation. As ice melts, more of the dark ocean and land are exposed to absorb the radiation, thus further warming the climate. Research has found that over a major portion of the ice-covered Arctic Ocean, sea ice is 40 percent thinner than it used to be. And some climate models predict that by 2070, there may be no summer ice cover in the Arctic at all.
The disappearance of sea ice is a particularly dire threat to the polar bear, a super specialist in the Arctic environment. Polar bears rely on the ice to hunt seals, their main food source, and also to rest between hunts out on the ice. Trapped, drowning and starving bears have become such a concern that in September 2007, the U.S. Geological Survey (USGS) released a series of studies that led its scientists to conclude that “future reduction of sea ice in the Arctic could result in a loss of two-thirds of the world’s polar bear population within 50 years.” As sad as such a fate for this majestic creature would be, the consequences would extend far beyond the bear. A polar bear decline could trigger what biologists call a “trophic cascade,” or a complete uncoupling of the Arctic food chain.
As much attention as the effects of melting sea ice on polar bears has drawn of late, it is important to understand that the thaw will have immediate effects on everything in the marine food chain, from benthic invertebrates to marine mammals. What will be the fate of the ringed seal, bearded seal, bowhead, beluga, and walrus — all creatures that depend on the ice for habitat or food?
Warming not only affects sea ice, it alters the Arctic’s terrestrial landscape. Melted permafrost means a proliferation of low-lying shrubs. These northern-spreading shrubs establish a new order of plant life, shading out low-growing lichens and plants like ground willow and cotton grass, all favorite foraging items for grazers like caribou. Without their main summer and winter foods, caribou are vulnerable to starvation.
Another species affected by changing Arctic vegetation is the lemming. Drastic changes in its food supply of sedges and mosses, along with a lack of snow tunnels to burrow in, will challenge the survival of these rodents and may cause their populations to crash beyond repair. When lemming numbers drop, so do the numbers of predators like snowy owls and Arctic foxes. Researchers have already observed warning signs in the Arctic fox population in the form of an invasion of red foxes into the traditional range of Arctic foxes.
With a warming Arctic comes an earlier spring and a proliferation of parasitic insects such as flies and mosquitoes. For Arctic dwellers as disparate as caribou and guillemots, a population explosion of insects is at best a nuisance, and at worst, life-threatening. Grazers spend less feeding time and more energy just trying to escape these pests. Arctic-nesting Brunnich’s guillemots in Canada have been such victims of relentless mosquito attack, they have been observed abandoning their nests.
A changed season for insects also has a different effect on some other species of birds, which time their migrations to coincide with insect swells. Northern Alaska dunlins, for example, migrate from Asia and lay their eggs to take advantage of peak insect populations in order to feed their young. Warmer temperatures may cause the insects to hatch earlier, throwing off the carefully timed breeding and nesting season of the dunlins.
With the Arctic experiencing the most rapid and severe climate change on Earth, the plants and animals that have evolved to survive in this extreme habitat come increasingly under threat. Like the canary in the coal mine, the Arctic can serve as our early warning sign of impending climate change. Observing the tumultuous change its inhabitants are experiencing can be a lesson to us about the changes in store for the rest of the world. | <urn:uuid:bbb2f7f8-cfb7-403e-a6cd-1e00bd64f464> | 3.984375 | 1,005 | Knowledge Article | Science & Tech. | 44.000857 |
libpq is the C application programmer's interface to PostgreSQL. libpq is a set of library routines that allow client programs to pass queries to the PostgreSQL backend server and to receive the results of these queries. libpq is also the underlying engine for several other PostgreSQL application interfaces, including libpq++ (C++), libpgtcl (Tcl), Perl, and ecpg. So some aspects of libpq's behavior will be important to you if you use one of those packages.
Three short programs are included at the end of this section to show how to write programs that use libpq. There are several complete examples of libpq applications in the following directories:
Frontend programs that use libpq must include the header file libpq-fe.h and must link with the libpq library. | <urn:uuid:aaa06f7f-40ad-46e6-b44b-83912be1fd71> | 2.875 | 176 | Documentation | Software Dev. | 51.460938 |
How do Z pinches contribute to a variety of scientific research projects?
Z provides the fastest, most accurate, and cheapest method to determine how materials will react under high pressures and temperatures, characteristics that can then be expressed in formulas called “equations of state.” Equations of state tell researchers how materials will react if basic conditions like pressure and temperature are changed by specific amounts. Dovetailing theoretical simulations with laboratory work, Sandia researchers have been able to perform equation-of-state measurements more precisely than ever before. Exposing targets to the high power levels of Z also allows scientists to study extreme states of matter, such as plasmas, and it may produce unexpected reactions and generate responses of great interest to many areas of science.
Fusion research on Z, too, contributes to broader scientific insight. Because near-perfect symmetry is necessary to ignite fusion (so the imploding particles will be forced to collide by not having room to escape), a persistent challenge in fusion science has been to heat the target evenly, so it will implode symmetrically. The capsule and container holding the target have to work together to produce the desired outcome, and their configurations and interactions have been the focus of intense theory and experimentation.
Diamond, for example, has been the object of much study as a potential capsule material. In melting diamond to a puddle, Z scientists have been able to understand the material’s various states – from solid to liquid, with a mixed state in-between. Thanks to Z, researchers now have a better understanding of the mixed state, which is not ideal to ignite a fusion reaction, and they can avoid it as they continue to experiment with diamond. In this and other ways, research on Z provides a roadmap for potential problems and opportunities on the path to fusion.
Beyond the fabrication of fusion pellets and the careful design of targets, achieving fusion requires work on many other interdependent elements including the machines, the mechanisms for delivering power onto a target, implementing detailed diagnostics for experiments, and creating computer codes to understand and then predict what the diagnostics revealed. Fusion is conducted in extremely complicated systems that involve complicated radiation dynamics as well as densities and temperatures not otherwise seen in nature. Trying to understand all the elements involved requires large computer codes, and tests conducted on the Z machine are very useful for testing and refining those codes. All of this work is crucial especially in conjunction with the National Ignition Campaign, which is the program to reach ignition of an inertial confinement fusion target at the National Ignition Facility.
How do Z pinches work?
The Z machine uses electricity to create radiation and heat, which are both applied to a variety of scientific purposes ranging from weapons research to the pursuit of fusion energy.
The process starts with wall-current electricity, which Z uses to charge up large capacitors (structures designed to store an electric charge). The electricity is supplied by a local utility company, and in every shot the machine consumes only about as much energy as it would take to light 100 homes for a few minutes. Metal cables arranged like the spokes of a wheel connect the capacitors to a central vacuum chamber, 10 feet in diameter and 20 feet high. The cables, some insulated by water and some by oil, are each as big around as a horse and 30 feet long.
When the accelerator fires, powerful electrical pulses strike a target at the center of the machine. Each shot from Z carries more than 1,000 times the electricity of a lightning bolt, and it finishes 20,000 times faster. The target is about the size of a spool of thread, and it consists of hundreds of tungsten wires, each thinner than a human hair, enclosed in a small metal container known as a hohlraum (German for hollow space). The hohlraum serves to maintain a uniform temperature.
The flow of energy through the tungsten wires dissolves them into a plasma and creates a strong magnetic field that forces the exploded particles inward. The speed at which the particles move is equivalent to traveling from Los Angeles to New York – about 3,000 miles – in slightly less than one second. The particles then collide with one another along the z axis (hence the name “Z pinch”), and the collisions produce intense radiation (in physics terms, 2 million joules of X-ray energy) that heats the walls of the hohlraum to approximately 1.8 million degrees Celsius.
As fast and powerful as the implosion is, the instruments that measure it must be even faster in order to record the details of the process. This is an added challenge for researchers who rely on the accuracy of these measurements to understand Z results and nuclear events in general. Accurate measurements also allow scientists to experiment with a variety of target arrangements to create conditions useful for many different purposes. | <urn:uuid:1c9cf1d1-d505-41d1-ac40-4ebd58a3e6fe> | 4 | 985 | Knowledge Article | Science & Tech. | 30.301988 |
This document has the following sections:
What is an Indexer?
Goal of an indexer
The main goal of an indexer is to create and setup some resource
automatically. The resources can be created depending on their
name or their extension. Once the resource has been created, the
indexer is also in charge of attaching the right frames to this
resource, like the HTTP frame, the filters and so on.
DirectoryResource (and subclasses) is associated to an indexer,
if no indexer is specified the DirectoryResource is associated
to the "default" indexer.
Description of an indexer
- Class and attributes of an indexer
- Usually, the indexer's class is
- The name of the indexer, ex: "icons"
- Last Modified
- Unused, but resent as, internally, it is a resource.
- Super Indexer
- The name of the parent indexer used when the current indexer
fails to index. By default, the super indexer is the "default"
- The sons of an indexer
- Used to index files matching exactly a name, mainly used to
index directories. You can specify that an "Icons" directory
will always be negotiable, for example. The default name (ie:
matching all directory names) is "*default*"
- Used to index files with a specific extension. For example,
"html" is a FileResource with an HTTPFrame set to give the
"text/html" content type to this file. Then all the "foo.html"
files will be indexed as "text/html" type object when accessed
by HTTP. The default extension (ie: matching all the extension
names) is "*default*". To index files with no extensions, you
must use the name "*noextension*".
- content-types (only for the Content Type Indexer)
- In some cases the file extension is not the only criteria,
for example when a PUT request occurs the indexer should use
the Content-Type header coming with the request (if there is
a content-type header). This is the job of the Content Type
Indexer. The Content Type Indexer
(org.w3c.jigsaw.indexer.ContentTypeIndexer), has one more
child, the content-types node. The associations between mime
types and resources are stored in this new child.
Since 2.0.2 the ContentTypeIndexer accept generic mime
types like text:*, *:xml or even
*:*. For example, if you define text:* as a
FileResource using a HTTPFrame (with a content-type set to
*none*) all content types like text/html, text/plain,
text/xml will be accepted.
Note: The mime types stored in the indexer are not
"real" mime types, the '/' has been replaced by a ':'. We
decided that because the '/' can create some conflicts with
the URLs in Jigsaw.
You can find a sample indexer configuration in this page.
Indexers in JigAdmin
The Indexers Space is exactly the same thing than the Documents Space except that
indexers classes are available in the "Available Resources"
window. You are still able to add, delete, configure resources
and frames but only in the indexers nodes (directories,
extensions and sometimes content-types). Of
course, you can also create new indexers (under the | <urn:uuid:a8f70524-9f68-4fbf-8df3-b1e0cb52d1bc> | 2.78125 | 757 | Documentation | Software Dev. | 45.149485 |
HTML 4.0 (the predecessor of 4.01) introduced something called frames, which split the browser's viewport up into different sections, each displaying a different webpage.
It was a good idea in concept, but the execution left a few things to be desired. Amongst the litany of woes:
Using the back button on a browser in frames tended to be unpredictable, depending on what frame was loaded when.
You could not bookmark a specific set of pages in the frameset's, only the default set.
Accessibility for the disabled was severely compromised.
Printing frames could also wasteful, as you might find yourself printing all pages displayed in the browser.
Viewers would have to download multiple pages: the page defining the frames, and all pages displayed by the frames.
Not all browsers during frames' heyday supported frames, so you had to code a no-frames version of your webpage.
So why were they ever used?
If you had a part of a webpage (usually the navigation) that you used over and over again, a frameset allowed you to put that code in its own webpage and display it apart from everything else. While server-side processing—explained in Server-Side Scripting—also was used for this, in many cases (such as website hosts at the time and websites that come on a CD, like this one), that simply wasn't available.
Speaking of navigation lists, they could be quite long, and frames allowed the list and the page proper to scroll seperately.
They were a means of arranging a page before CSS really came into its own.
For someone unused to programming, frames (which are HTML) were easier to work with than server-side scripts, which (for the most part) require some knowledge of a programming language.
The search engines have been able to read and follow <frameset>s for over ten years now, but that's not to say there are no issues. Google will often/usually just link to the <frameset> page now, even if it was an internal page that actually ranked for the user's query. Heaven knows what Bing does now, but its probably something similar.
My errors: Yes, typo HTML. Well, server-side PHP etc. is not too easy. The results you get by chopping up the browser window [replacing <BODY> tag] makes the whole page overly complicated and unwieldy.
Up until a year or so (when HTML5 became a hot topic), one of the professors teaching basic/beginner HTML where I tutor made students use <FRAMESET>. Made me so angry that he complicated HTML that way and students ended up with Web sites that did not function properly.
What effect do you want to achieve with <FRAMESET>? Do you have an online example to share? Maybe someone can suggest an alternative approach.
I for one don;t have the attitude or aptitude for AJAX coding.
P.S. -- Re-reading note your purpose is an HTML "tutorial." Imagine a very brief "footnote" reference to <FRAMESET> would suffice. Think it would be more helpful to point out how <FRAMESET> worked than whether or not it was "easier" than server-side scripting.
Last edited by auntnini; 01-09-2013 at 05:55 PM. | <urn:uuid:f15693ab-521a-48d7-b149-f9c82782f321> | 2.953125 | 700 | Comment Section | Software Dev. | 56.87876 |
The Chemical Abstracts Service
is part of the American Chemical Society
and maintains a database of chemical compounds and sequences. The CAS database currently contains over 55 million different organic and inorganic chemical compounds. Each CAS entry is identified by their CAS Registry Number, or CAS RN for short.
CAS Numbers themselves are up to 10 digits long using the format xxxxxxx-yy-z. They are assigned to a compound as the CAS registers a new compound. The number has no significance to the chemistry, structure or chemical nature of the molecule.
The CAS Number of a compound is a useful way to identify a chemical over its name. For example, the compound CAS 64-17-5 refers to ethanol. Ethanol is also known as ethyl alcohol, ethyl hydrate, absolute alcohol, grain alcohol, hydroxyethane. The CAS number is the same for all these names.
The CAS Number can also be used to distinguish between stereoisomers of a compound. Glucose is a sugar molecule that has two forms: D-glucose and L-glucose. D-glucose is also called dextrose and has CAS number 50-99-7. L-glucose is the mirror image of D-glucose and has a CAS Number of 921-60-8. | <urn:uuid:805c1377-d92d-49a3-a40e-cf01f2de3b76> | 3.375 | 272 | Knowledge Article | Science & Tech. | 52.089914 |
The codecs defines a set of base classes which define the interface and can also be used to easily write you own codecs for use in Python.
Each codec has to define four interfaces to make it usable as codec in Python: stateless encoder, stateless decoder, stream reader and stream writer. The stream reader and writers typically reuse the stateless encoder/decoder to implement the file protocols.
The Codec class defines the interface for stateless encoders/decoders.
To simplify and standardize error handling, the encode() and decode() methods may implement different error handling schemes by providing the errors string argument. The following string values are defined and implemented by all standard Python codecs:
||Raise ValueError (or a subclass); this is the default.|
||Ignore the character and continue with the next.|
||Replace with a suitable replacement character; Python will use the official U+FFFD REPLACEMENT CHARACTER for the built-in Unicode codecs.| | <urn:uuid:b49e9300-7a5b-4564-b569-8f045480a69e> | 3.625 | 211 | Documentation | Software Dev. | 26.880849 |
This module provides regular expression matching operations similar to
those found in Perl. Regular expression pattern strings may not
contain null bytes, but can specify the null byte using the
\number notation. Both patterns and strings to be
searched can be Unicode strings as well as 8-bit strings. The
re module is always available.
Regular expressions use the backslash character ("\") to
indicate special forms or to allow special characters to be used
without invoking their special meaning. This collides with Python's
usage of the same character for the same purpose in string literals;
for example, to match a literal backslash, one might have to write
'\\\\' as the pattern string, because the regular expression
must be "\\", and each backslash must be expressed as
"\\" inside a regular Python string literal.
The solution is to use Python's raw string notation for regular
expression patterns; backslashes are not handled in any special way in
a string literal prefixed with "r". So
r"\n" is a
two-character string containing "\" and "n",
"\n" is a one-character string containing a newline.
Usually patterns will be expressed in Python code using this raw | <urn:uuid:9d8eae3e-d2bc-470b-b1ac-bc0791fa2ede> | 2.765625 | 267 | Documentation | Software Dev. | 39.354013 |
Special & General Relativity Questions and Answers
Does anyone really understand general relativity well enough to have an intuitive grasp of the universe?
It is all a mater of perspective. Physicists and astronomers who spend all of their professional lives amass an enormous amount of intuition about the mathematics of relativity, and through constant contact with the technical details develop, perhaps, the best intuition that is humanly possible. Those who see relativity and cosmology as a recreation, and who never grapel with any of the mathematical details, probably never acheive an intuitive grasp of relativity. Like learning an instrument, there is a wide gulf between the kind of experiences many of us have had in grade school just learning how to sound the notes, and the kind of proficiency enjoyed by professional musicians who practice 4-8 hours EVERY DAY.
To the extent that general relativity is showing us the right way to think about the physical universe, yes, there are in fact many people who have an intuitive grasp of what the universe looks like. How they choose to 'visualize' this world-view may differ from individual to individual, but they all agree about the underlying mathematics.
Return to the Special & General Relativity Questions and Answers page.
All answers are provided by Dr. Sten Odenwald (Raytheon STX) for the NASA Astronomy Cafe, part of the NASA Education and Public Outreach program. | <urn:uuid:c11a9cb5-3054-43d9-b693-7329c165494e> | 2.875 | 284 | Q&A Forum | Science & Tech. | 26.640448 |
|Navigate Language Fundamentals topic:)|
The previous chapter "Getting started" was a primer course in the basic of understanding how Java programming works. Throughout the chapter, we tackled with a variety of concepts that included:
- Objects and class definitions;
- Abstract and data types;
- Class-level and method-level scopes;
- Keywords; and,
- Access modifiers, etc.
From this point on, we would be looking into the above mentioned concepts and many more in finer detail with a deeper and richer understanding of how each one of them works. This chapter on Language fundamentals introduces the fundamental elements of the Java programming language in detail. The discussions in this chapter would use the concepts we have already gathered from our previous discussions and build upon them in a progressive manner.
The Java programming syntax
In linguistics, the word syntax (which comes from Ancient Greek σύνταξις where σύν [syn] means "together", and τάξις [táxis] means "an ordering") refers to "the process of arranging things". It defines the principles and rules for constructing phrases and sentences in natural languages.
When learning a new language, the first step one must take is to learn its programming syntax. Programming syntax is to programming languages what grammar is to spoken languages. Therefore, in order to create effective code in the Java programming, we need to learn its syntax — its principles and rules for constructing valid code statements and expressions.
Java uses a syntax similar to the C programming language and therefore if one learns the Java programming syntax, they automatically would be able to read and write programs in similar languages — C, C++ and C# | <urn:uuid:11f2776d-fdd2-4921-9709-187c87581a3d> | 4.15625 | 357 | Truncated | Software Dev. | 32.581113 |