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For the following code (Java):
double d = (double) m / n; //m and n are integers, n>0 int i = (int) (d * n); i == m
Is the last expression always true? If it's not is this always true?:
i = (int) Math.round(d * n); i == m
The second question you ask concerns how large an ulp is in Java.
If the ulp exceeds
The following program tests all the positive integer values of
The output is:
Rounding that using Math.round, then casting to int should recover the original int.
This is false for m=1, n=49.
My intuition tells me it should be true, but it may be hard to prove rigorously.
Mathematically it should be true. However you're likely going to get floating point rounding errors that will make it false. You should almost never compare floating point precision numbers using
You're much better off comparing them using a threshold like this:
Note that the two statements should be equivalent
However for example, if
The first on is definitely not always true. The second one I would say yes it's true, but only because I can't think of a counterexample.
If n is very large, it could possibly be false, I'm not sure really. I know it will be true at least 99% of the time though. | <urn:uuid:92a66715-a1a7-4fa8-b21a-8c811190980d> | 2.953125 | 299 | Q&A Forum | Software Dev. | 75.0905 |
The Hubble Space Telescope image at the bottom of the page centers on the 100-million-solar-mass black hole at the hub of the neighboring spiral galaxy M31, or the Andromeda galaxy, the only galaxy outside the Milky Way visible to the naked eye and the only other giant galaxy in the local group. This is the sharpest visible-light image ever made of the nucleus of an external galaxy. The event horizon, the closest region around the black hole where light can still escape, is too small to be seen, but it lies near the middle of a compact cluster of blue stars at the center of the image.
The blue stars surrounding the black hole are no more than 200 million years old, and therefore must have formed near the black hole in an abrupt burst of star formation. Massive blue stars are so short-lived that they would not have enough time to migrate to the black hole if they were formed elsewhere.
Astronomers are trying to understand how apparently young stars were formed so deep inside the black hole's gravitational grip and how they survive in an extreme environment.
The fact that young stars are also closely bound to the central black hole in our Milky Way galaxy suggests this may be a common phenomenon in spiral galaxies.
Tod R. Lauer of the National Optical Astronomy Observatory in Tucson, Ariz., assembled the image below of the nuclear region by taking several blue and ultraviolet light exposures of the nucleus with Hubble's Advanced Camera for Surveys high-resolution channel, each time slightly moving the telescope to change how the camera sampled the region. By combining these pictures, he was able to construct an ultra-sharp view of the galaxy's core.
The Daily Galaxy via NASA's Goddard Space Flight Center
Image Credit: This image of the Andromeda galaxy was taken on Jan. 13, 2001, with the WIYN/KPNO 0.9-meter Mosaic I by T. Rector, University of Alaska in Anchorage. | <urn:uuid:61ce33ac-5e69-40cc-b0c2-878d8fe39ada> | 3.96875 | 396 | Nonfiction Writing | Science & Tech. | 45.299761 |
. "14 Phylogenetic Trees and the Future of Mammalian Biodiversity--T. JONATHAN DAVIES, SUSANNE A. FRITZ, RICHARD GRENYER, C. DAVID L. ORME, JON BIELBY, OLAF R. P. BININDA-EMONDS, MARCEL CARDILLO, KATE E. JONES, JOHN L. GITTLEMAN, GEORGINA M. MACE, and ANDY PURVIS." In the Light of Evolution, Volume II: Biodiversity and Extinction. Washington, DC: The National Academies Press, 2008.
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In the Light of Evolution: Volume II—Biodiversity and Extinction
FIGURE 14.3 Strength and significance of clumping in extinction risk within WWF ecoregions. Scale bar below the map indicates clumping strength. A value of 1 indicates randomness, and clumping is stronger for lower values. Circle size indicates the p value [radius is proportional to −ln(p)]; circle size for P = 0.05 is shown at the lower left.
than the significance) of the clumping is high in most realms apart from the Nearctic (Fig. 14.3). It also appears to be stronger in ecoregions with high disparity (Spearman’s ρ = 0.316) and with relatively old diversity (Spearman’s ρ = 0.195). These correlations should not be taken as evidence of a functional syndrome unless confirmed at more local scales: Some of the signal probably derives from differences among, rather than within, major biogeographic realms. The prevalence of clumping of risk implies that, faced with approximately equal pressures, species differ in their ability to persist because of lineage-specific characteristics. This finding invites a search for biological correlates of extinction risk.
COMPARATIVE ANALYSES OF MAMMALIAN EXTINCTION RISK
Perhaps the most obvious proposed risk factor for extinction is large body size. The end-Pleistocene mass extinction of mammals removed mostly large species (Barnosky, Chapter 12, this volume), and declining mammals are an order of magnitude heavier, on average, than are non-threatened species (Cardillo et al., 2005). There are several possible reasons: Large-bodied species are more tempting targets than small ones for hunters; they are, on average, less abundant; and they take longer to reach sexual maturity, have smaller litters of larger offspring, and have larger individual home ranges. Narrow ecological tolerances are also a plausible risk factor—habitat specialists may be more at risk than generalists from | <urn:uuid:55cab3b1-1212-4892-bff8-7c0c11fabf06> | 3.21875 | 597 | Academic Writing | Science & Tech. | 39.620324 |
Where have all the barn swallows gone?
My mother used to predict the weather by looking at the flight patterns of barn swallows. "Low flies the swallow, rain to follow." I have childhood memories of growing up with the "hirondelles" in the South of France, and I remember the excitement we felt when we spotted a swallow nest under the roof of our house. I loved listening to the high-pitched sounds the swallows made in the warm summer nights. Over thirty years later, every time I return to my parents' house, I look for the swallows, but sadly I am now looking at empty skies. The swallows are gone, and the pigeons have taken up residence under our roof.
The barn swallow is one of the world's most widely and common bird species. Yet for decades now, swallows are declining at an alarming rate. And Canada is no exception. Canadian Breeding Bird Survey data has shown that in the last 20 years, the population of barn swallows has fallen by 70 percent. This year, the Committee on the Status of Endangered Wildlife in Canada has assessed the barn swallow as Threatened.
In July of this year, videographer Mike McKinley and myself went to check out barn swallow nests with Derek Matthews, master bander at the Vancouver Avian Research Centre, a non-profit organization he founded to monitor bird populations in the Lower Mainland region.This field trip resulted in “Plight of the Barn Swallow,” a video we put together to support our campaign to obtain legislation for species at risk in British Columbia.
Derek Matthews has always been passionate about birds. He started banding birds in England when he was 10, and continued to do so after he moved from London to Vancouver. In the last ten years, Matthews has noticed that less and less barn swallows (Hirundo rustica) come back to his banding station. "For all of us growing up, barn swallows were just basically a way of life," he says. Today, the barn swallow cannot be taken for granted anymore. Researchers have examined several explanations to explain the decline, including agricultural practices, urbanization, loss of nesting sites, and foraging habitat. They are now turning to the decline in abundance of aerial (flying) insects as the main culprit for the massive bird losses. Barn swallows belong to the "guild" of aerial insectivores which feed on flying insects and include such species as whip-poor-wills, nighthawks, swifts, martins, and flycatchers. Like swallows, other aerial insectivores have suffered dramatic declines.
Watch the video, learn about these amazing creatures, and if you feel strongly about keeping barn swallows around, please sign our petition to ask for endangered species legislation in BC.
-- Isabelle Groc for the Wilderness Committee -- | <urn:uuid:fde81580-a95a-45ab-af87-ace368979eb8> | 3.296875 | 589 | Personal Blog | Science & Tech. | 48.37415 |
Global Electric Circuit of Mars
Even though several missions to Mars have passed through the Martian atmosphere and have had extended research programs on the surface, to date there have been no measurements of the vertical profiles of atmospheric conductivity, electric field, or current density. Therefore, any conclusions made concerning the global electric circuit of Mars must be made by using what is known of Earth's global electric circuit and applying it to Mars through analogy or by reproducing conditions found at Mars in a laboratory setting.
On Earth it is generally accepted that the global electric circuit is driven by thunderstorms [Wilson, 1920]. In this circuit model, thunderstorms act as electrical generators that drive currents upward. As a result, the upper atmosphere becomes positively charged with respect to Earth's surface. In the steady state, charge in the upper atmosphere leaks back to the ground through the finitely conducting atmosphere. Near Earth's surface, the atmospheric conductivity is large enough to dissipate any field on the order of minutes. Therefore, the average global electric field must be maintained by some almost continuous current source. For Earth, the dominant generator is believed to be thunderstorms [Krider and Roble, 1986]. Other sources also play a role in driving Earth's global electric circuit, but it is thought that thunderstorms are the dominant contributor.
How can knowledge of Earth's global electric circuit be applied to Mars? In order for a global electric circuit similar to Earth's to exist in the Martian atmosphere, a constant current source, or current generator must be located in a finitely conducting atmosphere. Over decades of visual observations by both orbiting spacecraft and landers, no thunderstorms have been detected on Mars. Most likely, the Martian environment is too dry and too cold for such phenomena to form. Therefore, alternate current sources must be found in order to drive the global electric circuit. Alternate current sources on Earth and their applications to the Martian environment will be investigated later. First, we will look at the possibility of the presence of a conducting atmosphere and some of the sources of atmospheric conductivity. | <urn:uuid:c0a53ff6-c167-4c10-a83a-7eb010061be6> | 4.125 | 411 | Comment Section | Science & Tech. | 29.546454 |
In the right light, everything casts a shadow—even an atom. A large object creates a shadow by physically blocking the light flying past it, and even a miniscule atom or ion can prevent photons with specific wavelengths from reaching their destinations.
Australian researchers from Griffith University captured a relatively large ytterbium atom in an ion trap, and then hit it with light of a wavelength the ytterbium could absorb. When the light reached the detector, the missing photons that the atom had gobbled up left this negative space: the shadow of a single atom, less than a millionth of a meter in length.
Image courtesy of Kielpinski group, Griffith University / Nature Communications | <urn:uuid:ef9d1360-68e9-4c44-8819-53d1253d5910> | 4.0625 | 143 | Truncated | Science & Tech. | 29.175409 |
|Cambodian kukri. Photo credit: Neang Thy/FFI.|
The Cambodian kukri (Oligodon kampucheaensis) snake has curved rear teeth to hold and help swallow eggs.
July 16, 2012
A new species of egg-eating snake has been discovered in the Cardamom Mountains in south west Cambodia. The snake, named the Cambodian kukri (Oligodon kampucheaensis) was named after the country in which it was found. Neang Thy, a Cambodia Ministry of Environment officer who works with Fauna & Flora International (FFI) discovered the snake with Dr. Lee Grismer and Dr. Jenny Daltry.
“Cambodian science was smashed under the Pol Pot regime, and only now are we picking up the pieces. It gave me a great sense of pride to both discover and describe this species, and to name it in honor of my country,” Thy said in a statement released by FFI. “Most kukri snakes are dull-colored, but this one is dark red with black and white rings, making it a beautiful snake.”
The kukri snake is a rainforest species that eats eggs as its principle food source. It has rear curved teeth that apparently are similar in shape to a Nepalese knife known as the kukri, hence the name. According to FFI, the snake is under threat due to habitat loss and land conversion, and is the second reptile FFI has described in Cambodia in 2012. | <urn:uuid:b0c54ade-b47e-4882-8060-7514682bb336> | 3.09375 | 326 | Personal Blog | Science & Tech. | 55.008393 |
Not going to write out the whole question but here's the basics:
h = -0.5t^2g + d
h = height
t = time
g = gravity
d = starting height (which is 100m)
Find how long it takes a rock to fall to a height of 25m on each planet.
gravity for mars is g = 3.7m/s^2, gravity for venus is g = 8.9m/s^2
so I've got 25 = -0.5t^2(3.7) + 100
and that's as far as I can get lol, all the previous questions have been in the form of y = ax^2 + bx + c, and I'm find with those, I'm just not sure what to do when there's multiplication. Can I multiply a number by a squared number? Do I do something to the squared number first? Maybe just multiply it by -0.5t to get t (bx)? | <urn:uuid:664d5622-d7d8-44e8-a2e3-a350efe06902> | 3.453125 | 212 | Q&A Forum | Science & Tech. | 109.72188 |
eldavojohn writes "A new paper presented at NASA's Goddard Space Flight Center in Maryland shows the rapid heating of the atmosphere directly above the fault days before the devastating earthquake hit. This is theorized to be the Lithosphere-Atmosphere-Ionosphere Coupling mechanism that occurs when large amounts of radon are released due to massive stress in the fault right before the quake. This can be detected with satellites analyzing infrared waves: 'The radioactivity from this gas ionizes the air on a large scale and this has a number of knock on effects. Since water molecules are attracted to ions in the air, ionization triggers the large scale condensation of water. But the process of condensation also releases heat and it is this that causes infrared emissions.' This is a shift from the Haiti earthquake where DEMETER was used to monitor ultra low frequencies. The presence of radon could also possibly explain erratic wildlife behavior prior to an earthquake." | <urn:uuid:72b9084a-538a-4d52-82ac-180e17928b46> | 3.375 | 192 | Comment Section | Science & Tech. | 28.946038 |
In turn 4 people throw away three nuts from a pile and hide a
quarter of the remainder finally leaving a multiple of 4 nuts. How
many nuts were at the start?
Factorial one hundred (written 100!) has 24 noughts when written in full and that 1000! has 249 noughts? Convince yourself that the above is true. Perhaps your methodology will help you find the number of noughts in
10 000! and 100 000! or even 1 000 000!
Prove that if a^2+b^2 is a multiple of 3 then both a and b are multiples of 3. | <urn:uuid:db566095-870b-4cb7-96da-ad55c838e61c> | 3.078125 | 129 | Tutorial | Science & Tech. | 96.011 |
In a study published in British science weekly Nature today, a US team has extracted a light-sensing gene from a germ called a cyanobacterium to make the film.
They have stitched it into the cell membranes of Escherichia coli (E coli) bacteria so exposure to red light switches off a gene that controls the production of the bug's black pigment.
As a result, black-and-white images can be "stencilled" onto a mat of the engineered bacteria grown on a plate of protein-rich lab gel.
The resolution and tone scale are extraordinarily good because the screen's definition is on bacterial scale, at up to 100 million pixels per square inch.
The authors from the University of California say their invention could spur "bacterial microlithography" and the creation of new materials made from living organisms.
They say their study could also help unlock fundamental knowledge about how bacteria use gene switches to send signals to each other. abc | <urn:uuid:5c3c9141-30fe-426b-8552-2c19f82ee54b> | 3.75 | 200 | Personal Blog | Science & Tech. | 35.621527 |
In the fields of Brunei Darussalam in North Borneo, once a crown colony of Great Britain, lies the pitcher plant. The pitcher plant is carnivorous, capturing and devouring insects that seek to harvest its nectar.
The pitcher plant is beguiling, attractive, and has evolved many ways to seduce its predator. Insect prey is captured within the wells of its pitcher-shaped leaves, when insects crawling along it slip on the wax crystals of the inner wall, and fall into the digestive fluid at the bottom. A dense layer of platelet-shaped wax crystals, orientated perpendicularly to the surface for a reason — to essentially make it difficult for insects to grip — especially when wet.
The wax crystal layer is a common feature to many species of the pitcher plant. One such species, Nepenthes gracilis, is unusual in the fact that the crystals are also present on the underside of the pitcher lid.
This was the observation that led to recently published research describing a new way the pitcher plant captures its prey.
The lead author of the paper, published today in PLoS ONE, Dr Ulrike Bauer from the University of Cambridge’s Department of Plant Sciences, said: “It all started with the observation of a beetle seeking shelter under a N. gracilis lid during a tropical rainstorm. Instead of finding a safe — and dry — place to rest, the beetle ended up in the pitcher fluid, captured by the plant. We had observed ants crawling under the lid without difficulty many times before, so we assumed that the rain played a role, maybe causing the lid to vibrate and ‘catapulting’ the beetle into the trap, similar to the springboard at a swimming pool.”
In effect, it’s a clever strategy on the part of the pitcher plant. At times, mostly when the weather is dry, insects have no problem gathering nectar from the plant. This allows “scout” insects and ants to report back and ultimately means a larger number of insects are on their way back to the plant.
The trap is set.
In that field in Borneo it was a Coccinellid beetle that fell for the trap, being flicked into the well of the pitcher by a raindrop that bounced off the lid of the plant. The beetle had sought shelter from the rain but had found its ultimate demise instead. Researchers posited that the wax crystal layer, while providing a secure foothold under normal conditions, causes insects to detach more easily under sudden impacts.
Researchers replicated and simulated rain in the lab and its effect on ant colonies trying to gather nectar. Comparing this to real in-the-field settings showed that the lid itself goes a long way to contributing to prey capture.
In the fields of northern Borneo the rains are brief, heavy and intermittent. And the pitcher plant — with its canopy-like lid — makes an attractive refuge from the deluge. But the most interesting part suggests that N. gracilis uses much more than its simple lid to capture insects — but has also re-upped its nectar secretion in a way that increases attraction of its prey to the lower lid surface.
Dr Bauer added: “Scientists have tried to unravel the mysteries of these plants since the days of Charles Darwin. The fact that we keep discovering new trapping mechanisms in the 21st century makes me curious what other surprises these amazing plants might still have in store!”
A version of this appears in Australian Science Mag
Photo credit: Ulrike Bauer
Bauer, U., Di Giusto, B., Skepper, J., Grafe, T., & Federle, W. (2012). With a Flick of the Lid: A Novel Trapping Mechanism in Nepenthes gracilis Pitcher Plants PLoS ONE, 7 (6) DOI: 10.1371/journal.pone.0038951 | <urn:uuid:d154c88e-a442-467d-b74e-e4d4f5b06d39> | 4.46875 | 814 | Personal Blog | Science & Tech. | 56.723477 |
Science Fair Project Encyclopedia
A Hill sphere approximates the gravitational sphere of influence of one astronomical body in the face of perturbations from another heavier body around which it orbits. It was defined by the American astronomer George William Hill. It is also called the Roche sphere because the French astronomer Édouard Roche independently described it.
- gravity due to the central body
- gravity due to the second body
- the centrifugal force in a frame of reference rotating about the central body with the same angular frequency as the second body (Jupiter)
The Hill sphere is the largest sphere within which the sum of the three fields is directed towards the second body. A small third body can orbit the second within the Hill sphere, with this resultant force as centripetal force.
The Hill sphere extends between the Lagrangian points L1 and L2, which lie along the line of centers of the two bodies. The region of influence of the second body is shortest in that direction, and so it acts as the limiting factor for the size of the Hill sphere. Beyond that distance, a third object in orbit around the second (Jupiter) would spend at least part of its orbit outside the Hill sphere, and would be progressively perturbed by the tidal forces of the central body (the Sun) and would end up orbiting the latter.
Formula and examples
If the mass of the smaller body is m, and it orbits a heavier body of mass M at a distance a, the radius r of the Hill sphere of the smaller body is
For example, the Earth (5.97×1024 kg) orbits the Sun (1.99×1030 kg) at a distance of 149.6 Gm. The Hill sphere for Earth thus extends out to about 1.5 Gm (0.01 AU). The Moon's orbit, at a distance of 0.370 Gm from Earth, is comfortably within the gravitational sphere of influence of Earth and is therefore not at risk of being pulled into an independent orbit around the Sun. In terms of orbital period: the Moon has to be within the sphere where the orbital period is not more than 7 months.
An astronaut could not orbit the Space Shuttle (mass = 104 tonnes), if the orbit is 300 km above the Earth, since the Hill sphere is only 120 cm in radius, much smaller than the shuttle itself. In fact, in any low Earth orbit, a spherical body must be 800 times denser than lead in order to fit inside its own Hill sphere, or else it will be incapable of supporting an orbit. A spherical geostationary satellite would need to be more than 5 times denser than lead to support satellites of its own; such a satellite would be 2.5 times denser than iridium, the densest naturally-occurring material on Earth. Only at twice the geostationary distance could a lead sphere possibly support its own satellite; the moon itself must be at least 3 times the geostationary distance, or 2/7 its present distance, to make lunar orbits possible.
The Hill sphere is but an approximation, and other forces (such as radiation pressure) can make an object deviate from within the sphere. The third object must also be of small enough mass that it introduces no additional complications through its own gravity. Orbits at or just within the Hill sphere are not stable in the long term; from numerical methods it appears that stable satellite orbits are inside 1/2 to 1/3 of the Hill radius (with retrograde orbits being more stable than prograde orbits).
Within the solar system, the planet with the largest Hill sphere is Neptune, with 116 Gm, or 0.775 AU; its great distance from the Sun amply compensates for its small mass relative to Jupiter (whose own Hill sphere measures 53 Gm). An asteroid from the main belt will have a Hill sphere that can reach 220 Mm (for 1 Ceres), diminishing rapidly with its mass. In the case of (66391) 1999 KW4, a Mercury-crosser asteroid which has a moon (S/2001 (66391) 1), the Hill sphere varies between 120 and 22 km in radius depending on whether the asteroid is at its aphelion or perihelion!
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:f81d57af-26b0-417d-a3da-623b0520f487> | 4.09375 | 901 | Knowledge Article | Science & Tech. | 55.514798 |
One of the great missions for the 21st century could be FOCAL — a space probe sent to the Sun’s gravity lens some 550 AU out. Gravitational lensing is becoming a major tool for astronomers, and we’ve even seen planetary detections using microlensing, looking at targets in the direction of galactic center and the faint changes in light that indicate a planet’s passage. The gravity lens concept, harking back to a 1936 Einstein paper, came to the fore in 1978, when Dennis Walsh and team spotted a twin quasar image, the result of the lensing caused by an intervening galaxy as it bends light around it.
So we know that lensing works. As far as I know, the first person to apply the notion to spacecraft was Von Eshleman (Stanford University), who considered a space probe to 550 AU to exploit the potential magnifications available there. And such missions have also been considered, by Frank Drake among others, as SETI experiments, using the Sun’s ability to magnify the hydrogen line at 1420 MHz, the so-called ‘waterhole’ frequency for interstellar communications.
But no one has put more thought into a FOCAL mission than Claudio Maccone. The Italian physicist led a 1992 conference that investigated mission concepts, and submitted a proposal to the European Space Agency the following year. Since then, he has followed up this work with a series of papers in Acta Astronautica and the Journal of the British Interplanetary Society, investigating among other things the uses of the gravity lens for cosmology (detailed imaging of a small slice of sky to study the cosmic microwave background), communications (using gravity lenses around nearby stars to boost signals from interstellar probes) and astronomy. His 1997 book The Sun As a Gravitational Lens: Proposed Space Missions (Colorado Springs: IPI Press) is an exhaustive analysis of the topic now in its 3rd edition.
Image: Gravitational lensing at work. A space probe at 550 AU and beyond could exploit such effects to make detailed studies of other solar systems, among numerous other scientific targets. Credit: Martin Kornmesser & Lars Lindberg Christensen, ST-ECF.
In a presentation he will make today at the New Trends in Astrodynamics and Applications conference in Princeton, Maccone notes that the use of stars as gravitational lenses is a logical next step for astronomers. “As each civilization becomes more knowledgeable, they will recognize, as we now have recognized, that each civilization has been given a single great gift: a lens of such power that no reasonable technology could ever duplicate or surpass its power. This lens is the civilization’s star. In our case, our Sun.”
A fascinating aspect of the Sun’s gravity lens is that we do not need to park a spacecraft at 550 AU to utilize it. As the spacecraft pushes past this distance, effects created by the Sun’s corona diminish and imaging only becomes better. We have an opportunity to see images the likes of which could not be produced by ground-based or conventional space-based telescopes, assuming we can find a way to propel a spacecraft to the needed distance in a reasonable amount of time.
If we try to sketch out a rational pattern for exploration beyond Pluto, FOCAL should be front and center in our thinking. New Horizons reaches the Pluto/Charon system in 2015. After that there is active work on Innovative Interstellar Explorer, a probe that would carry instrumentation beyond the heliosphere and become the first mission specifically targeting the interstellar medium. A well-equipped FOCAL probe, driven perhaps by solar sail with close solar flyby, is a logical goal after IIE or as part of a combined mission concept.
But such a mission, the groundbreaker for space-based gravity lens studies, would be the first of many. In particular, as we learn to push spacecraft to truly interstellar speeds, FOCAL becomes a needed precursor that can tell us much about target solar systems. As Maccone notes in The Sun As a Gravitational Lens:
I anticipate that there will be a host of FOCAL space missions launched in all directions around the Sun, each probe launched in the direction exactly opposite to the star to explore with respect to the Sun position….A FOCAL space mission could be used to magnify anything of interest outside the Solar System. One should then say that FOCAL will be used to magnify the nearby planetary systems, meaning not just the nearby stars themselves, but also their planets, halo disks, Oort clouds, etc.
The range of targets is vast if FOCAL-style missions become routine through breakthroughs in our propulsion technologies. In the interim, deep space probes to the required distances offer the possibility of numerous scientific investigations, many of which were first examined by NASA in its studies for the TAU (Thousand Astronomical Units) mission in the 1980s. What Maccone continues to argue forcefully is that any probe into regions beyond the heliosphere will be in position to exploit the gravity lens, and that our designs for such probes should incorporate the needed instrumentation to show us how best to use this tremendous natural tool. | <urn:uuid:67333be5-020d-425f-91a3-bab86f9e54a6> | 3.75 | 1,072 | Knowledge Article | Science & Tech. | 32.564517 |
Role of nitrite and nitric oxide in the processes of nitrification and denitrification in soil: Results from 15N tracer experiments
Recent research has proven soil nitrite to be a key element in understanding N-gas production (NO, N2O, N2) in soils. NO is widely accepted to be an obligatory intermediate of N2O formation in the denitrification pathway. However, studies with native soils could not confirm NO as a N2O precursor, and field experiments mainly revealed ammonium nitrification as the source of NO. The hypothesis was constructed, that the limited diffusion of NO in soil is the reason for this contradiction. To test this diffusion limitation hypothesis and to verify nitrite and NO as free intermediates in native soils we conducted through-flow (He/O2 atmosphere) 15N tracer experiments using black earth soil in an experimental set up free of diffusion limitation. All of the three relevant inorganic N soil pools (ammonium, nitrite, nitrate) were 15N labelled in separate incubation experiments lasting 81 h based on the kinetic isotope method. During the experiments the partial pressure of O2 was decreased in four steps from 20% to about 0%. The net NO emission increased up to 3.7 μg N kg−1 h−1 with decreasing O2 partial pressure. Due to the special experimental set up with little to no obstructions of gas diffusion, only very low N2O emission could be observed. As expected the content of the substrates ammonium, nitrate and nitrite remained almost constant over the incubation time. The 15N abundance of nitrite revealed high turnover rates. The contribution of nitrification of ammonium to the total nitrite production was approx. 88% under strong aerobic soil conditions but quickly decreased to zero with declining O2 partial pressure. It is remarkable that already under the high partial pressure of 20% O2 12 % of nitrite is generated by nitrate denitrification, and under strict anaerobic conditions it increases to 100%. Nitrite is present in two separate endogenous pools at least, each one fed by the nitrification of ammonium or the denitrification of nitrate. The experiments clearly revealed that nitrite is almost 100% the direct precursor of NO formation under anaerobic as well as aerobic conditions. Emitted N2O only originated to about 100% from NO under strict anaerobic conditions (0–0.2% O2), providing evidence that NO is a free intermediate of N2O formation by denitrification. To the best of our knowledge this is the first time that NO has been detected in a native soil as a free intermediate product of N2O formation at denitrification. These results clearly verify the “diffusion limitation” hypothesis. | <urn:uuid:b196782e-e8c8-4a10-b069-be7de0350e9b> | 3.078125 | 571 | Academic Writing | Science & Tech. | 30.901399 |
How Does Microwave Radiation Affect Different Organisms?
Grade Level: 9th to 12th; Type: Biology
This experiment will determine how microwave radiation affects fungi, bacteria, and plant life.
- Does microwave radiation destroy all life?
- Will varying lengths of radiation affect organisms differently?
Microwave ovens blast food with high levels of energy. This results in heating up certain fats and other ingredients in food. The energy simply passes through other substances without damage. Through this experiment, we will see how this energy affects simple organisms of different types.
- Packet of radish seeds
- Paper towels
- Four small containers filled with sterilized potting soil
- Four packets of bakers’ yeast
- Four small bowls
- Four prepared Petri dishes with agar (available from biological supply companies)
- Sterilized swabs
- Notepad and pen
- Plant several radish seeds in a small container. Put them in a sunny, warm location. This is the control sample.
- Place several more radish seeds on a paper towel. Microwave the seeds for five seconds.
- Plant these seeds in another pot and place in the same location as the control group.
- Repeat Step 2 and 3 for two more samples, except microwave one group of seeds for fifteen seconds and the other for thirty seconds.
- Tend the samples by watering the pots once a day and ensuring they get enough sunlight.
- Take pictures everyday and note if and how quickly the samples grow.
- Dump a packet of bakers’ yeast into a small bowl of warm water. Stir. This is the control sample.
- Take note of how long it takes for the yeast to bubble up and how vigorous the reaction is. Take photos.
- Dump another packet of bakers’ yeast onto a plate. Microwave for five seconds.
- Mix this yeast into another bowl of warm water. Repeat Step 8.
- Repeat steps 9 and 10 for the other packets of yeast, except microwave one sample for fifteen seconds and the other for thirty seconds.
- Wearing gloves, use the sterilized swab to collect a sample of bacteria and swab it on a prepared Petri dish. Good places to find bacteria are areas where lots of people touch something, like doorknobs or faucets. Seal the dish and label it “control.” Put it in a warm, dark place. This is your control sample.
- Swab another sample from the exact location as the control sample. Smear it on another Petri dish. Seal and label the dish. Place it in a warm, dark place.
- Repeat Step 13 for the other two samples.
- Let the samples alone overnight.
- Take one sample out (not the control) and microwave it for five seconds. Place it back in the warm, dark place.
- Repeat Step 16 for the other two samples, except microwave one for fifteen seconds and the other for thirty seconds.
- After another day, take out all the samples. Note how many colonies of bacteria are growing and their size.
- Analyze all this data. Does microwave radiation affect all life equally? Does time matter? How does each type of organism respond to the radiation?
Terms/Concepts: Microwaves, microbiology, radiation
References: Wikipedia article on microwaves
Warning is hereby given that not all Project Ideas are appropriate for all individuals or in all circumstances. Implementation of any Science Project Idea should be undertaken only in appropriate settings and with appropriate parental or other supervision. Reading and following the safety precautions of all materials used in a project is the sole responsibility of each individual. For further information, consult your state’s handbook of Science Safety. | <urn:uuid:6f7ddad6-eaaa-4fe2-91a7-f33b14e29931> | 3.515625 | 781 | Tutorial | Science & Tech. | 50.343943 |
STEP 2: Respond to the request.
Ask " How Would I Find Out ? "
STEP 3: Generate the result.
Ask " What does the result tell me? "
Problem Source: http://www.lincoln.ac.nz/educ/tip/39.htm
Solution presentation copyright Howard C. McAllister, 1998.
Given two intersecting straight lines and a point P marked on one of them, show how to construct a circle that is tangent to both lines including point P.
The problem asks for the location of the center of a circle that fulfills the stated conditions. The center of the circle will lie on a perpendicular drawn through P.
We are now asked to located a particular point on the perpendicular.
1) Draw a circle of radius X-P with center at X.
2) Construct a perpendicular at P'. The intersection of this with the previously drawn perpendicular defines the center of the circle sought.
3) Draw the circle of radius P-C with center at C.
Start a problem by responding to what is asked for. In the present case we are asked to draw a particular circle. To draw a circle the first thing one needs to know is the location of the center.
The concept involved is that a tangent to a circle is perpendicular to a diameter of the circle.
The example is one of those presented by A. Schoenfeld to illustrate his well developed theory of Mathematical Problem Solving. | <urn:uuid:654ae97b-b206-4c2f-9900-6f648e1b912d> | 4.21875 | 304 | Tutorial | Science & Tech. | 72.463489 |
A new era of discovery in particle physics has opened in November 2009 with the start-up of the Large Hadron Collider (LHC) at CERN, the European Organization for Nuclear Research, in Geneva, Switzerland. The LHC, a circular proton-proton synchrotron, will operate at the highest energies any particle accelerator has ever achieved. The International Linear Collider will explore the same energy range using a different approach. By colliding electrons with positrons, the International Linear Collider would provide results with extraordinary precision, enabling the exploration of unknown regions of science – the "Terascale", so named after energies approaching Tera –electronvolts (trillions of electronvolts or TeV).
Based on experiments and discoveries over the last decades, physicists believe that the Terascale will yield evidence for entirely new forms of matters, and possibly even extra dimensions of space. The new matter might include the Higgs particle, as well as an extended family of elementary 'superparticles', the heavier cousins of the particle we already know. On 4 July 2012, the ATLAS and CMS experiments presented their latest preliminary results in the search for the long-sought Higgs particle. Both experiments observe a new particle in the mass region around 125-126 GeV. As the evidence grows, we are beginning to uncover the new physics territory being opened up by the LHC. These discoveries will tell us about the nature of the universe and how the laws of physics came to be.
The great precision of its electron-positron collisions would allow the ILC to act as a telescope to explore energies far beyond those that any accelerator could ever directly achieve.
For now, though, our view is obscure by a lack of knowledge of Terascale physics. Data from ILC would bring the Terascale into focus and give us a telescope to the beyond. The ILC would provide a view of energies trillion times beyond its own – into the ultrahigh-energy realm where nature's force might become unified. | <urn:uuid:93d844b2-0499-48c6-8c77-d3706c01f856> | 3.359375 | 411 | Knowledge Article | Science & Tech. | 27.837314 |
|Sep4-06, 01:10 AM||#1|
vague question about polar coordinate basis
I hae a kind of strange, vague question. We know that any vector in R^2 can be uniquely represented by unique cartesian coordinates (x, y). If we wish to be more rigorous in our definition of "coordinates" we consider them to be the coefficients of the linear combination of the standard basis vectors [itex]e_1[/itex] and [itex]e_2[/itex]
Now, we know that every vector in R^2 can also be uniquely represented by unique polar coordinates ([itex]r[/itex], [itex]\Theta[/itex]), except for the zero vector. Does this mean that we can consider those "coordinates" to be coefficients with respect to some basis vectors?
I would think no, but it seems odd that one coordinate system can be considered to have a "basis" and the other cannot.
My only linear algebra text I have is Strang, who is vague on coordinate representations in general, and barely brings up polar coordinates at all.
|Sep4-06, 08:36 AM||#2|
I'm afraid my explanation is very coherent - sorry.
Usually, coordinates are associated with manifolds. Sometimes, a manifold is also a vector space. In this case, coodinates are sometime associated with a basis for the vector space, but they don't have to be.
The surface of the Earth is a 2-dimensional manifold that has lattitude and longitude as one coordinate system. The surface of the Earth is not a vector space, but it can, locally, be approximated by a vector space. The surface at any point can be approximated by a 2-dimensional plane that is tangent to the surface at that point. These tangent spaces are vector spaces, and coordinate systems give rise to particular bases for these vector spaces.
In general, an n-dimensional (topological) manifold is something that, for a myopic observer, looks like a piece of R^n, i.e., any point of the manifold is contained in an open neighbourhoood from which which there is a continous map (with continuous inverse) onto an open subset of R^n. The image (under any such map) of any point p of an n-dimensional manifold is an element of R^n - the coordinates of p.
R^2 is both a manifold and a vector space. (r, theta) coordinates use the manifold structure of R^2, but not the vector space structure. Cartesian coorinates are related of R^2 to both the manifold and vector space structures of R^2.
(r, theta) coordinates do give rise, at point, to tangent vectors, though.
|Sep4-06, 02:42 PM||#3|
that makes a lot of sense, thanks. not sure why I didn't think of that :)
LOL, now that I think about it, I remember that I was once asked to derive the radial and tangent basis vectors,a s a function of time, for a rotating reference frame on a physics quiz. Somehow never made the connection! :)
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Anyone who has ever bought or sold a home knows the three most important factors in real estate: location, location, location. Traditionally, geneticists did not think this principle had much to do with the variability of biological traits, but recent research now suggests otherwise. In fact, it looks as if a gene’s location is more important than its identity when it comes to the variability of biological traits. 1
Knowing the relationship between gene location and trait variability will help researchers understand the genetic basis of diseases and will also help breeders develop economically useful plants and animals. This relationship also has implications for the creation/evolution controversy. Moreover, this new research makes it possible to account for a genetic feature, long touted as evidence for biological evolution, from a creation model perspective.
Genes and Biological Traits
Some biological traits, such as height, weight, etc., vary continuously within a population. These traits, determined by several <a href="http://www.bioinformaticstutorials.com/?p=6">genes</a>, are called quantitative traits. Researchers want to understand where the genes that influence quantitative traits are located within chromosomes. They also want to understand the source of the genetic variability. The expectation is that the location of a gene within the chromosome should have limited influence on trait variability. Rather, natural selection and genetic drift should be the key factors that create this variation.
Location, Location, Location!
To test these ideas, a team of scientists from Princeton University determined the location of several thousand quantitative traits in the nematode Caenorhabditis elegans. They discovered that the variable traits tend to reside at the ends of chromosomes and, to a much lesser extent, near chromosomes’ center. It turns out that the identity of the gene had little to do with whether or not it displayed genetic variability. What seemed to be the most important was the gene’s location along the chromosome.
In other words, whether or not a particular biological trait varies within a population depends on its location on the chromosome, more so than anything else. This result has important implications, one of which relates to the case for biological evolution.
Gene Location and the Case for Biological Evolution
Proponents of biological evolution claim that if evolutionary processes created life’s diversity, then organisms that share a common ancestor would also share similar genomes. This similarity would not only include gene types and gene sequences, but also the physical arrangement, or ordering, of genes along a chromosome.2 But this new work suggests an alternative explanation. It could very well be that the shared ordering of genes may not reflect common ancestry but common design.
1. Matthew V. Rockman et al., “Selection at Linked Sites Shapes Heritable Phenotypic Variation in C. elegans,” Science 330 (2010): 372–76.
2. Dennis Venema and Darrel Falk, “Signature in the Synteny,” The Biologos Forum, http://biologos.org/blog/signature-in-the-synteny/, accessed October 22, 2010. | <urn:uuid:ae62ecbd-86a8-43b6-9c93-b135943e4e3c> | 3.46875 | 641 | Knowledge Article | Science & Tech. | 31.28423 |
Ship in a bottle catalysts
by David Bradley
Zeolites, porous catalytic minerals are commonly used in refining crude oil and as molecular sieves. Chemists would like to be able to use them for more varied reactions but they come only with pores of a limited range of sizes and shapes. Writing in Chemical Communications (1997, 901) Thomas Bein and Steven Ogunwumi of Purdue University in Indiana describe how they have trapped another catalyst - an asymmetric manganese-containing organic compound - in the pores of a zeolite (EMT) to make a hybrid material.
The hybrid is made using starting materials that can enter the pores of the zeolite but once assembled inside the product cannot get out "like a ship in a bottle", Bein explains. "One of the advantages of encapsulating a catalyst in a zeolite is the convenient recovery of the products from the reactor, compared to reactions in solution," he added.
They have tested their hybrid and found that it produces just excess of one mirror image form of the two possible products (enantiomers) in a so-called alkene epoxidation. In this reaction a bridging oxygen atom is added across an alkene double bond. Epoxides are important precursors to materials from drugs to agrochemicals and making them selectively is important as often one enantiomer of a drug for instance is safer and more effective than the other. For instance, the common painkiller ibuprofen is three times more effective in one form than the other.
choose frozen juice for a vitamin C boost
In research funded not surprisingly by the Florida Citrus Growers scientists have found that frozen concentrated orange juice generally has the highest vitamin C levels compared with other commercial orange and grapefruit juice products, but regardless which one you drink you are probably getting your daily requirement of the vitamin.
Hyoung S. Lee and Gary A. Coates of the Florida Department of Citrus in Lake Alfred, Florida conducted a ten-year study - described in the July 16 issue of the Journal of Agricultural and Food Chemistry - to look at vitamin C levels in some 2299 samples of orange and grapefruit juices collected from 21 Florida processors. They found that 95.7% of the samples provided more than 100% of the daily amount set out by US laws. Overall, an eight ounce serving of frozen concentrated orange juice had the highest vitamin C content (173%), with orange juice from concentrate coming in second (161.2%) and pasteurised orange juice third (138.4%).
worth its salt
Salts are used in almost every cuisine as flavouring agents from the simple table salt of boiled beef and carrots to the monosodium glutamate in a vegetable spring roll. The effects of salt on taste have puzzled most flavour scientists, however, psychophysical studies show that sodium chloride either suppresses or has no effect on flavours rather than enhancing anything, as most people would feel.
Paul Breslin and Gary Beauchamp of the Monell Chemical Senses Center in Philadelphia believe they have found a solution to the paradox (Nature, 1997, 387, 563). They used mixtures of a bitter substance, urea, unpleasantly enough, a sweetener sucrose and almost tasteless sodium acetate to test their idea that salts selectively filter tastes.
Twenty-one volunteers were asked to judge the bitterness of the urea and the sweetness of the sugar of various combinations of solutions of the three ingredients.
The volunteers reported exactly what the scientists predicted that the sodium acetate suppressed the bitterness of the urea much more than enhancing the sweetness of the sucrose. The scientists admit, howf, that the study does not mimic all the possible flavour combinations of food the taste test does show that as well as adding "saltiness" to food (which many people like) salts also filter other tastes suppressing unpalatable bitterness and boosting sweetness.
They hint that this could be why low sodium foods - often recommended for people with high blood pressure - tend to be rather bland tasting.
channel no 5
The surface of every cell in your body is pitted with tiny holes - a worrying thought? It should not be because each hole is formed from a natural channel protein there to control the molecular traffic in and out of the cells controlling sodium, potassium, calcium and chloride ions.
Understanding exactly how they work is, according to George Gokel of the Department of Molecular Biology and Pharmacology at Washington University School of Medicine in St. Louis, Missouri, "One of the hottest areas of modern biology because channels are important in neural transmission as well as in controlling ion concentrations and in communication between cells."
Scientists know what they do but not a lot about how they accomplish it and how they control which ions pass which way in the channel. Gokel and his team have devised a simple synthetic channel which they hope will work in the same way as a protein channel so they can use chemical methods to analyse form and function.
They recently reported results in Chemical Communications (1997, 1145) that show they can indeed mimic natural channels using ring-shaped molecules - macrocycles - stacked together.
The long-term goal is to develop new drugs based on artificial channels. For example, if a channel mimic could be made to get into a cell wall selectively, perhaps by adding a targeting peptide, fatty acid, or steroid it would effectively punch a hole in the cell, which might cause a deleterious flood of ions either in or out. If the cell is a cancer cell then it would be killed therefore potentially halting tumour growth.
Gokel points out that cystic fibrosis is intimately linked to chloride ion transport and that making a chloride-conducting channel could be used to redress the balance in patients although this is a very distant goal.
Gokel's team is currently trying to control selectivity; since publishing in Chem Comm they have achieved about 3:1 transport through the channel of potassium over sodium and are now altering the size of the macrocycles with further success.
ever so sensitive
A super-sensitive detector for brain chemicals has been designed and built by David Parker and Ritu Kataky at Durham University. The sensor is based on a ring of sugar molecules known as a cyclodextrin (CD)
and can detect quantities of the neurotransmitter acetylcholine down to 10-14 molar. More exciting , says Parker, is that it can be used to "watch" changes in the concentration of molecules that inhibit the enzyme that breaks down acetylcholine after it has passed on its signal. These enzyme inhibitors include various organophosphorus pesticides and also chemical warfare agents such as Sarin.
The sensor works by trapping the target molecule in the central cavity of the cyclodextrin rings, which are held in a thin plastic membrane. The presence of a molecule in the CD cavity then triggers a series of chemical changes in a ferrocene molecule also embedded in the membrane that is then detected by an electrochemical connection through an enzyme. Parker says the sensing unit is simply a disposable, coated screen printed electrode costing less than a pound each.
The team reported results earlier in the year in Chemical Communications (1997, 141) and having patented the work, are now considering exploiting its use in pesticide analysis. The work was funded by the BBSRC and the EPSRC in the UK.
the root of all evens?
Conscientious readers might like to check back to a previous issue of elemental discoveries to read up on the odd-even disparity found in the organic world by Desiraju and colleagues. They claimed to have found a far larger number of even numbered carbon compounds than odd and were at a loss to explain the result. Several readers came up with suggestions as to what might be going on and indeed a follow up paper was published in Nature, 1997, 385, 782.
The various explanations seemed to hinge on ideas such as there being more natural products than non-natural molecules (based on acetate units for instance) and benzene and hexose sugar rings and the like. Desiraju, however, is not convinced by any of them having delved a little deeper. He and his colleagues are fairly sure that the disparity is not of biosynthetic origin. "If the acetate origin of organic compounds were paramount, the even-odd effect should taper off with time as synthesis became increasingly diverse," explains Desiraju, "this, however, is not the case." He adds that if it were the origin there would be a preference for compounds with 4n carbon atoms as compared to those with 2n, say after C20 or so but this again does not happen.
He admits that for limited classes of natural products where the acetate route is important, say steroids, the even-odd effect may be rationalised but not for the entirety of organic compounds. It might also be worth looking again at the illustration we used. It is just as easy to have an extra methyl group to upset the numbers.
Suspecting that money might be the root of all evens, they did an analysis of the Aldrich and Acros catalogues by cost. There is no preference for the evens!
We look forward to further suggestions...
Finally, this is not exactly chemistry but because I play guitar this piece of research caught my eye.
Engineers at Cornell University in New York have used electron-beam lithography, to build what they say is the world's smallest guitar. With a Fabry-Perot interferometer they carved a piece of crystalline silicon no larger than a single cell into a guitar to demonstrate the potential for making microscale mechanical devices. The strings are about 4000 times thinner than a human hair but make no sound. I bet they still cannot get it to stay in tune when they use the whammy bar! | <urn:uuid:a1c33fb0-a687-4ae8-9975-e66aac25a683> | 3 | 2,015 | Content Listing | Science & Tech. | 36.563609 |
Observations of eight distant clusters of galaxies, the furthest of which is around 10 thousand million light years away, were studied by an international group of astronomers led by David Lumb of ESA's Space Research and Technology Centre (ESTEC) in the Netherlands. They compared these clusters to those found in the nearby Universe. This study was conducted as part of the larger XMM-Newton Omega Project, which investigates the density of matter in the Universe under the lead of Jim Bartlett of the College de France. Clusters of galaxies are prodigious emitters of X-rays because they contain a large quantity of high-temperature gas. This gas surrounds galaxies in the same way as steam surrounds people in a sauna. By measuring the quantity and energy of X-rays from a cluster, astronomers can work out both the temperature of the cluster gas and also the mass of the cluster.
Theoretically, in a Universe where the density of matter is high, clusters of galaxies would continue to grow with time and so, on average, should contain more mass now than in the past.
Most astronomers believe that we live in a low-density Universe in which a mysterious substance known as 'dark energy' accounts for 70% of the content of the cosmos and, therefore, pervades everything. In this scenario, clusters of galaxies should stop growing early in the history of the Universe and look virtually indistinguishable from those of today.
In a paper soon to be published by the European journal Astronomy and Astrophysics, astronomers from the XMM-Newton Omega Project present results showing that clusters of galaxies in the distant Universe are not like those of today. They seem to give out more X-rays than today. So clearly, clusters of galaxies have changed their appearance with time.
In an accompanying paper, Alain Blanchard of the Laboratoire d'Astrophysique de l'Observatoire Midi-Pyrénées and his team use the results to calculate how the abundance of galaxy clusters changes with time. Blanchard says, "There were fewer galaxy clusters in the past."
Such a result indicates that the Universe must be a high-density environment, in clear contradiction to the 'concordance model,' which postulates a Universe with up to 70% dark energy and a very low density of matter. Blanchard knows that this conclusion will be highly controversial, saying, "To account for these results you have to have a lot of matter in the Universe and that leaves little room for dark energy."
To reconcile the new XMM-Newton observations with the concordance models, astronomers would have to admit a fundamental gap in their knowledge about the behaviour of the clusters and, possibly, of the galaxies within them. For instance, galaxies in the faraway clusters would have to be injecting more energy into their surrounding gas than is currently understood. That process should then gradually taper off as the cluster and the galaxies within it grow older.
No matter which way the results are interpreted, XMM-Newton has given astronomers a new insight into the Universe and a new mystery to puzzle over. As for the possibility that the XMM-Newton results are simply wrong, they are in the process of being confirmed by other X-ray observations. Should these return the same answer, we might have to rethink our understanding of the Universe. | <urn:uuid:7f5a06f3-523e-4465-bafd-32f7904e8b88> | 3.828125 | 689 | Knowledge Article | Science & Tech. | 34.741751 |
Halldor Bolbeins/AFP/Getty Images
The Fimmvorduhals volcano near the Eyjafjallajokull glacier in Iceland
There have been countless earthquakes around the globe. Now the volcanic eruption in Iceland leads many to wonder if California could be next. California is better known for its earthquakes, but there are volcanoes around, like Mammoth Mountain. Patt talks to a geologist to find out whether or not an eruption is in sight.
Margaret Mangan, scientist-in-charge of the Long Valley Observatory for the United States Geological Survey, which looks at volcanoes in the northern Owens Valley-Mono Basin region. | <urn:uuid:89e88c7c-d1a6-4796-b14b-283e82d9ae05> | 2.953125 | 136 | Truncated | Science & Tech. | 32.247 |
An array is a data structure consisting of a group of elements that are accessed by indexing. In most programming languages each element has the same data type. However, ColdFusion, as we will see, is not strictly typed and therefore allows any data type to be stored in combination. This allows strings, integers, booleans and other complex data types all to be stored in the same array. However, doing this certainly isn't a good practice as it causes signification complication when accessing the stored data.
Variables of a simple data type commonly only store a single value but, in some situations, it is useful to have a variable that can store a series of related values - using an array. Arrays are described as complex data types because they can hold data in a structured, complex way. Read more – ‘Implicit Arrays in ColdFusion 8’. | <urn:uuid:c864d9ba-9b57-4461-bbe2-72c6df016777> | 3.5 | 180 | Personal Blog | Software Dev. | 38.7525 |
by Jim Algar
Washington DC (UPI) Jul 16, 2012
When a huge solar flare Thursday sent a magnetic storm heading toward earth, Americans heard the usual warnings of possible power outages, disruption of satellite communications and other effects -- and for the most part ignored them.
The warnings seem to come with every such event. "Heard it all before." "They always say that." Familiarity breeds contempt.
And yet Canadians in Quebec Province probably felt the same way on March 13, 1989, complacent and happily going about their business -- until the lights went out in the early morning hours, the start of a 12-hour blackout that left people stranded in dark office buildings by stalled elevators, or waking up to up to cold homes.
Schools and businesses were closed by the blackout, and the Montreal Metro commuter system was shut down during the morning rush hour.
The entire province of Quebec had suffered a loss of electricity.
The cause? A solar storm.
Six days earlier, astronomers had witnessed a powerful solar flare, resulting three days later in a so-called coronal mass ejection, a burst of matter and electromagnetic radiation into space.
This solar storm of electrically charged particles, when it reached the Earth, began creating extremely intense auroras at the earth's poles, with some in the Northern Hemisphere visible as far south as Texas.
Satellites in polar orbits did not respond to signals from the ground and tumbled out of control for several hours, and weather satellites stopped sending images to Earth.
The intense magnetic disturbance actually created electrical currents in the ground beneath much of North America, and at 2:44 a.m. on March 13, those currents found a weakness in the electrical power grid of Quebec, tripping circuit breakers on Hydro-Quebec's system.
The entire grid went down in less than 2 minutes.
In a cascade effect, U.S. utility companies found themselves dealing with problems of their own. Across the United States more than 200 power grid problems erupted within minutes of the start of the outage, although fortunately none caused a blackout.
Quebec was particularly vulnerable because it sits on a large geological shield of igneous rock.
Such areas are the most vulnerable to the effects of intense geomagnetic activity because the high resistance of the igneous rock prevents current from the storms flowing through the earth, and in the Quebec blackout it found a less-resistant path by travelling through Hydro-Quebec's long-distance transmission lines, eventually overloading them and tripping the system's breakers.
In the wake of the outage, Hydro-Quebec implemented various strategies to prevent such events in the future, including raising the breaker trip level, installing protections on ultra high voltage lines and upgrading various monitoring and operational procedures.
Other utilities took note, and in North America, Northern Europe and elsewhere they implemented programs to reduce the risks associated with geomagnetically induced currents.
Could such a thing happen again?
Scientists say solar storms of the magnitude of the 1989 event are rare, and it would require an enormous flare and coronal mass ejection to create conditions that would trigger a Quebec-style blackout.
Still, the sun, for all we've learned about it, remains something less than predictable in its behavior.
Which is why they issue those warnings about which perhaps we shouldn't be quite so complacent.
Solar Science News at SpaceDaily
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Solar storm protection
Newark, DE (SPX) Jul 13, 2012
Massive explosions on the sun unleash radiation that could kill astronauts in space. Now, researchers from the U.S. and South Korea have developed a warning system capable of forecasting the radiation from these violent solar storms nearly three hours (166 minutes) in advance, giving astronauts, as well as air crews flying over Earth's polar regions, time to take protective action. Physici ... read more
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Natural Gas: The Transitional Energy Source Against Climate Change?
Natural gas holds a composition of different gases, but it is primarily composed of hydrocarbons. However unlike other fossil fuels such as petroleum, the chemical reactions involved in extracting energy from natural gas is quite different, thus producing far less carbon emissions than most non-renewable energy sources.
Despite being a lot cleaner, cheaper and easier to find than oil and coal however, the fact that it still produces a small amount of emissions when used still places it in the dirty fuels category. New study and research however, seems to encourage the use of natural gas anyway, if we ever want to mitigate the effects of climate change on our planet at the earliest time possible.
The conclusion of using natural gas to fight global warming was a result of the research made by Cornell University’s Professor Lawrence Cathles. The main point of his research explains the urgency of quickly phasing coal and oil out of use in favor of natural gas to quickly reduce global carbon emissions. The calculations in the report elaborates with an explanation that if our civilization could make the switch right now, natural gas could yield at least 40% of the positive effect on carbon-emissions and global warming that a renewable green energy source could make. All in all, the research generally considers natural gas as the most important “stabilization wedge” that we could ever use to quickly mitigate the effects of global warming.
The study specifically pointed out that transitional speed is the more important element in its proposition, logically because our green energy technologies are currently still behind schedule. We are still uncertain whether these green technologies would actually be developed efficiently in time before permanent climate changes occur. With natural gas as the transitional fuel, we can at least slow down climate change and extend the ultimate deadline, providing the much needed development window for alternative energy to catch up.
Increased leakage rates would perhaps be one of the problems that critics would point out when it comes to natural gas extraction, especially if it were to become the next primary source of non-renewable energy. However, the study carefully points out that leakage rates are actually lower now that what the data has shown a few years ago. And even with slightly higher leakage rates, we would still be ultimately better off using natural gas than the dirtier oil and coal.
It should be noted that, as indicated earlier, the study simply showed that alternative green energy cannot be the solution right at this exact moment. It has never made the importance of green renewable energy look inferior in any way. It is just that in terms of proliferation, application, and development speed, they are still not what we would need right now at this moment to significantly reduce carbon emissions. Of course, the decision to actually adopt the use of natural gas over oil and coal is still at the hands of the higher economic authorities.
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Materials Analysis Using New X-ray Microbeams
Materials ranging from massive steel girders to the microscopic aluminum wires in computer chips are made of grains - tiny crystals with diameters measured in millionths of a meter (microns). If scientists could "see" these individual grains, they could determine their orientation, as well as the effects of stress and chemical activity on them. They might also be able to determine how best to jam more circuits together in microelectronic components, making them smaller and faster, so computers could perform complex functions - such as speech recognition - more quickly. They could also find out to what extent grains of a superconducting material mimic the alignment of the substrate on which the material is grown; discovery of such orientation replication involving deposited thin films is essential to the design of effective high-temperature superconductors.
Figure: Schematic drawing of an x-ray microbeam experiment. Curved mirrors focus the synchrotron x rays down to a diameter of less than one micron on the sample. The microbeam penetrates each layer of the sample, and an area detector measures the directions of the scattered x rays. Here, the sample consists of a roll-textured nickel substrate covered with two epitaxial films: a buffer layer and a superconductor (YBCO). The detector image provides a grain-by-grain description of the atomic structure, orientation, and strain of each layer.
Scientists are now able to study the fine details of grain behavior in materials, thanks to new x-ray beamlines at the Advanced Photon Source (APS), an intense synchrotron x-ray source at DOE's Argonne National Laboratory. Oak Ridge National Laboratory (ORNL) is a leader in efforts to develop microbeams at the APS. Microbeams are x-rays that are focused down to beam diameters smaller than one micron, allowing researchers to see a material's microstructural features within individual grains. The instrumented beamlines now enable researchers to perform micro-diffraction x-ray scattering using beams of submicron dimensions. These microbeams will provide access for the first time to the mesoscale, the length scale that determines the macroscopic properties of many materials.
ORNL scientists have also performed experiments using microbeam analysis with a resolution of <1 µm. They are studying strain in integrated circuit wires, a major source of electrical problems in developing smaller, denser microelectronic components for the next generation of computers. They are also investigating the epitaxy of oxide films on nickel foils and the defects introduced by ion-implantation processing in silicon to help in understanding and improving materials properties.
The initial design, microbeam optics, and associated techniques for materials analysis are being developed by ORNL and Howard University at the APS on the MHATT-CAT beamline constructed by the University of Michigan, Howard University (a historically black university), and Lucent Technologies Collaborative Access Team. To exploit microbeam capabilities fully, ORNL is developing a dedicated microbeam facility directed toward 0.1 µm resolution on the recently commissioned UNI-CAT synchrotron beamline. (UNI-CAT stands for University National Laboratory Industry Collaborative Access Team.) UNI-CAT is a $10-million collaboration involving ORNL, the University of Illinois, the National Institute of Standards and Technology, and UOP Research, Inc. UNI-CAT provides access to the nation's most intense x-ray beams for a wide range of studies of the structure and properties of materials. ORNL has received funding through the new-initiative competition of the Division of Materials Science in DOE's Office of Basic Energy Sciences to develop a mesoscale-materials program at the APS using microbeams.
From "Facilitating Science: ORNL Research at User Facilities" Oak
Ridge National Laboratory Review Volume 32, Number 2, 1999.
The full text of this article is available at: http://www.ornl.gov/ORNLReview/v32_2_99/fac.htm | <urn:uuid:5dc98c9e-6b80-437a-9dd4-f8c1067fccad> | 3.890625 | 842 | Academic Writing | Science & Tech. | 22.616504 |
We were fortunate to have hosted three species of giant silkmoths (family Saturniidae) in Butterfly Magic this year. They are spectacular insects, but so unique and short-lived that one cannot generalize to moths as a whole from their life cycle and behavior.
Estimates differ as to how many species are in the Saturniidae, but somewhere between 1,300 and 1,500 is fairly accurate. Gene sequencing could result in more or fewer species than currently recognized. Giant Silkmoths are found the world over in forest habitats, but are especially diverse in the neotropics (Mexico, Central and South America). You are probably already familiar with some U.S. species: the Luna Moth, Cecropia Moth, Polyphemus Moth, Royal Walnut Moth, Imperial Moth, and Cynthia Moth. Not all the silkmoths are giants. Buck moths (genus Hemileuca) are much smaller, and fly during the day.
The adult moths do not feed. They have vestigial mouthparts at best and fuel their flight on fat reserves accumulated as caterpillars. Consequently, the caterpillars of giant silkmoths are large and heavy at maturity. The “hickory horned devil,” larva of the Royal Walnut Moth, approaches the size of a frankfurter. It looks menacing but is harmless.
Meanwhile, the larvae of other silkmoths are studded in venomous spines. Beware the caterpillars of buck moths (I can attest from personal experience!), the io moth, and especially the South American Lonomia (see also more recent articles in medical journals).
The Forbes Moth, Rothschildia lebeau forbesi, is frequently mistaken for an Atlas Moth by our visitors. Both species have “windows” in their wings that are devoid of scales. The Forbes Moth ranges from the Lower Rio Grande Valley through much of eastern Mexico and south to Brazil. Relatives of this moth figure prominently in the culture of indigenous peoples. Bushels of cocoons are harvested to make rattles worn on the ankles during ceremonial dances.
The African Moon Moth, Argema mimosa, occurs over most of sub-Saharan Africa. Their cocoons are distinctive: compact, and made of dense silk with numerous small perforations. The adult moths are spectacular: a wingspan averaging 125 mm, yellowish green in color with long, streaming “tails” on the hindwings. What purpose those tails serve is open to speculation, but perhaps it further camouflages the insect when it is at rest among foliage.
Last but not least is the Atlas Moth, Attacus atlas, a real giant with a wingspan of 240 mm (compare that to the Forbes Moth, only 90-100 mm from wingtip to wingtip). The Atlas Moth is widely distributed, from India to Hong Kong, tropical Asia in general, plus Taiwan and Indonesia. The front wings have a conspicuous lobe with markings that suggest the head of a serpent, but whether this is real mimicry or not is debatable.
The adult females of all the silkmoths rarely stray far from their cocoons after emerging. They invest most of their energy in egg production, so instead of exerting calories in flight, they simply sit and emit a species-specific sexual attractant called a pheromone. This scent, while usually imperceptible to us, is potent when it comes to drawing males. The males, with broad wings and streamlined bodies, use their sensitive antennae to home in on the pheromones, following the scent trail up to a mile or more to find its source. Females, once mated, will then finally fly to appropriate host trees and deposit their eggs. Even unmated females will dump their eggs in great quantities, as is often seen in our greenhouse. Both genders live only a few days, assuming they can avoid predation by bats.
Breeding silkmoths in captivity is becoming quite the hobby and cottage industry. My friend Liz Day has a web page devoted to helpful hints for rearing common eastern U.S. species. Considering the threats faced by these magnificent moths, from suburban sprawl and light pollution to introduced parasites, our domestic species could use some help.
I would like to conclude by recommending Wings of Paradise by John Cody, published by University of North Carolina Press, 1996. Cody renders giant silkmoths in stunning watercolor paintings. He features all three species in the greenhouse, plus scores more. The art is complemented with anecdotes and factual information. | <urn:uuid:0ce2a6b5-4335-4fcf-9b4c-53ae4a8c42fa> | 3.21875 | 952 | Personal Blog | Science & Tech. | 45.645217 |
NASA scientists say a rise in black soot concentrations on the Tibetan Plateau has caused increases in temperature and has accelerated glacial melting since the 1990s. This September 2009 NASA image — based on weather and air chemistry models that used satellite and ground observations of soot and other air pollution — depicts levels of air pollution as measured by how much incoming sunlight is absorbed by soot particles. Areas where the air was thick with soot are white, while lower soot concentrations are purple. The highest levels of soot can be seen on the right, over China’s coastal plain, and over much of India. India’s black carbon pollution often circulates at high concentrations against the base of the Himalaya Mountains, spilling over onto the Tibetan Plateau and depositing the soot on glaciers.
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Simple aromatic ring
Simple aromatic rings, also known as simple arenes or simple aromatics, are aromatic organic compounds that consist only of a conjugated planar ring system with delocalized pi electron clouds. Many simple aromatic rings have trivial names. They are usually found as substructures of more complex molecules ("substituted aromatics"). Typical simple aromatic compounds are benzene, indole, and cyclotetradecaheptaene.
Simple aromatic rings can be heterocyclic if they contain non-carbon ring atoms, for example, oxygen, nitrogen, or sulfur. They can be monocyclic as in benzene, bicyclic as in naphthalene, or polycyclic as in anthracene. Simple monocyclic aromatic rings are usually five-membered rings like pyrrole or six-membered rings like pyridine. Fused aromatic rings consist of monocyclic rings that share their connecting bonds.
Heterocyclic aromatic rings
- In the basic aromatic rings, the lone pair of electrons is not part of the aromatic system and extends in the plane of the ring. This lone pair is responsible for the basicity of these nitrogenous bases, similar to the nitrogen atom in amines. In these compounds the nitrogen atom is not connected to a hydrogen atom. Examples of basic aromatic rings are pyridine or quinoline. Several rings contain basic as well as non-basic nitrogen atoms, e.g., imidazole and purine.
- In the non-basic rings, the lone pair of electrons of the nitrogen atom is delocalized and contributes to the aromatic pi electron system. In these compounds, the nitrogen atom is connected to a hydrogen atom. Examples of non-basic nitrogen-containing aromatic rings are pyrrole and indole.
In the oxygen- and sulfur-containing aromatic rings, one of the electron pairs of the heteroatoms contributes to the aromatic system (similar to the non-basic nitrogen-containing rings), whereas the second lone pair extends in the plane of the ring (similar to the basic nitrogen-containing rings).
Criteria for aromaticity
- Molecule must be cyclic.
- Every atom in the ring must have an occupied p orbital, which overlaps with p orbitals on either side (completely conjugated).
- Molecule must be planar.
- It must contain an odd number of pairs of pi electrons; must satisfy Huckel's rule: (4n+2) pi electrons, where n is an integer starting at zero.
In contrast, molecules with 4n pi electrons are antiaromatic.
See also
- Clayden Jonathan, Nick Greeves, Stuart Warren, Peter Wothers (2001). Organic chemistry. Oxford, Oxfordshire: Oxford University Press. ISBN 0-19-850346-6.
- Eicher, T.; Hauptmann, S. (2nd ed. 2003). The Chemistry of Heterocycles: Structure, Reactions, Syntheses, and Applications. Wiley-VCH. ISBN 3-527-30720-6. | <urn:uuid:baf5fc9d-6545-43b4-876f-3042aced01b7> | 3.828125 | 649 | Knowledge Article | Science & Tech. | 32.303571 |
|Name, Symbol, Number||Darmstadtium, Ds, 110|
|Chemical series||Transition metals|
|Group, Period, Block||10[?], 7 , d|
|Appearance||unknown; probably metallic,|
silvery white or gray
|Atomic weight|| amu|
|Electron configuration||probably [Rn] 5f14 6d9 7s1|
a guess based upon platinum
|e- 's per energy level||2, 8, 18, 32, 32, 17, 1|
|State of matter||Presumably a solid|
Darmstadtium (formerly Ununnilium) is a chemical element in the periodic table that has the symbol Ds and atomic number 110. It has an atomic weight of 271 making it one of the super-heavy atoms[?]. It is a synthetic element and decays in thousandths of a second. Due to its presence in Group 10 it is believed to be likely to be metallic and solid.
History It was first created on November 9, 1994 at the Gesellschaft für Schwerionenforschung (GSI[?]) in Darmstadt, Germany. It has never been seen and only a few atoms of it have been created by the nuclear fusion of isotopes of lead and nickel in a heavy ion accelerator[?] (nickel atoms are the ones accelerated and bombarded into the lead).
Scientists are not always serious, so some suggested the name policium for the new element, because 110 is the telephone number of the German police. The element was named after the places of its discovery, Darmstadt (actually, the GSI is located in Wixhausen, a small suburb north of Darmstadt). The new name was given to it by the IUPAC in May 2003. | <urn:uuid:59e106d8-94de-42a3-8f1a-c29d655a9e8b> | 3.34375 | 384 | Knowledge Article | Science & Tech. | 53.128974 |
- Gosselin, Louis and Bejan, Adrian, Constructal heat trees at micro and nanoscales,
Journal of Applied Physics, vol. 96 no. 10
pp. 5852 - 5859 [1.1782278] .
(last updated on 2007/04/06)
We consider the problem of cooling a two-dimensional heat generating conducting volume with one heat sink, such that the smallest features of the internal structure are so small that the conventional description of conduction breaks down. The effective thermal conductivity exhibits the "size effect," and is governed by the smallest structural dimension, which is comparable with the mean free path of the energy carriers. According to the constructal method, the development of the internal cooling structure proceeds from small to large, in steps of geometric optimization and assembly. This starts at the elemental level, where there is only one high-conductivity layer for collecting and evacuating the heat. The shape of the smallest volume can be optimized for minimal thermal resistance. Next, a first construct is formed by optimizing the number of assembled elements and the internal geometric features of the assembly. The method is repeated at the second construct level, where several first constructs are grouped so that their global thermal resistance is minimal. The construction reveals an internal multiscale structure shaped as a tree, where the spaces between the smallest branches are ruled by nanoscale heat transfer. It is shown that the transition from regions with nanoscale heat transfer to regions with conventional heat transfer is governed not only by the smallest dimensions, but also by heterogeneity (relative amounts of high- and low-conductivity materials). © 2004 American Institute of Physics.
Heat transfer;Cooling;Heat conduction;Heat resistance;Electrons;Fractals;Optimization; | <urn:uuid:b9e21808-32b8-4c54-b1fb-6ac2853b43c0> | 2.828125 | 360 | Academic Writing | Science & Tech. | 33.914771 |
The USGS Water Science School
The ground beneath our feet is not just rock, or at least, not just one kind of rock. Many different types of rock exist, and they have very different properties. Often, different types of rocks exist in horizontal layers beneath the land surface. Some layers are more porous than others, and at a certain depth below ground the pores and fractures in these rocks can be totally filled with water (an aquifer). When precipitation falls and seeps into the ground, it moves downward until it hits a rock layer, which is so dense and unfractured that it won't allow water to easily move through it. When this happens it is easier for the water to start moving horizontally across the more porous rock layer. Sometimes when building a road, the layers are cut into and revealed, and water can be seen dripping out through the exposed layers.
Ground water Aquifers Ground-water seepage | <urn:uuid:fd37c377-92f6-4a55-8986-65ce196746c0> | 4.09375 | 188 | Knowledge Article | Science & Tech. | 52.357358 |
Count the triangles of any size. Extend the sequence. Find a formula for the number of triangles corresponding to v dividing lines from the vertex and h horizontal dividing lines.
Construct a matrix to generate general formulas for each row and column. What would the formula be for h horizontal lines and v lines from the vertex?
How would you prove it? | <urn:uuid:c8a7e93e-7706-47c0-b836-e6d4c394c061> | 3.359375 | 70 | Q&A Forum | Science & Tech. | 59.895054 |
Solve the following:
b) a bacterial culture starts with 1500 bacteria. After 5h, the estimated count is 35 000. What is the doubling period?
c) When the function f(x)=ax3+7x2+bx-8 is divided by (x+1) it has a remainder of 18; and (x-2) is a factor. Determine a and b. | <urn:uuid:017c2b7a-627f-428b-8b55-4682a0c7db8d> | 2.8125 | 85 | Tutorial | Science & Tech. | 100.302727 |
How scientists use DNA
Name: Peter and Edmund
We would like to know some ways that scientists use DNA.
For instance, we have heard that scientists used DNA to
change fruits and vegetables, such as tomatoes, so they
don't spoil so fast.
We appreciate your help with this investigation, because
we have found a lot of information on how the police use
DNA to help identify criminals, but we need to find out
about other uses of DNA.
We are in the first grade.
Thank you for your help.
Scientists use DNA is many ways. Some of those ways will show up
in the news, like the police work or the tomatoes. Most often, though,
scientists use DNA (and the ways they can work with DNA) to try to
find out how things work - like how plants or animals grow and develop,
or why bone cells are different than muscle cells, or how the brain
works. Sometimes scientists and physicians (doctors) used DNA to help
figure out what disease is making someone sick, and can even use DNA
to help make some people well. I'll be glad to tell you more, if you
want to hear more!
Steve J Triezenberg
DNA is being used my medical doctors in an attempt to cure some human disease.
One strategy is to replace the mutant (non-functioning) gene with a normal gene.
This strategy can be used when the cell is constantly dividing. One form of genetic
immunodeficiency disease is caused by a defective gene in a bone marrow cell and has
been cured by this approach. Some cells are not in a state of constant division
but the cells can be infected with a virus that has been engineered not to cause
disease and also to contain the normal gene. Cystic fibrosis is a lung disease
caused by a mutant gene. Scientists have placed the normal gene in a disabled
virus and infected kids and restored partial normal lung function. One problem
is that all the cells that need to be infected are not and the procedure needs
to be repeat I think another problem is the children develop antibodies
(resistance) to the infection. Another problem is that the defective gene
also causes other organs to function abnormally. There are other strategies
that you may be able to read about. DNA has may other uses. One of the
most far-fetched uses (at least in my mind because I don't understand it!) is to
uses DNA molecules as the basis for the development of molecular computing chips!
Michael B Lomonaco
Click here to return to the Biology Archives
Update: June 2012 | <urn:uuid:e9e6cc39-e0df-45c8-8b41-472d3e1c8894> | 3.109375 | 551 | Comment Section | Science & Tech. | 53.347447 |
Okay, some textbooks I came across, and a homework assignment I had to do several years ago, suggested that the reason we can skate on ice is the peculiar $p(T)$-curve of the ice-water boundary. The reasoning is that due to the high pressure the skates put on the ice, it will melt at temperaturs below $273 K$ and thus provide a thin film of liquid on which we can skate. It was then mentioned as fun fact that you could ice-skate on a planet with lakes of frozen dioxide because that gas has the $p(T)$-curve the other way round.
My calculations at that time told me that this was, pardon my french, bollocks. The pressure wasn't nearly high enough to lower the melting point to even something like $-0.5$ degrees Celsius.
I suppose it is some other mechanism, probably related to the crystal structure of ice, but I'd really appreciate if someone more knowledgeable could tell something about it. | <urn:uuid:b56c835e-8a22-4246-bae8-5dce68557ee3> | 2.796875 | 210 | Q&A Forum | Science & Tech. | 54.567857 |
5.3.4 Classes and functions
Instances of the TestCase class represent the smallest
testable units in a set of tests. This class is intended to be used
as a base class, with specific tests being implemented by concrete
subclasses. This class implements the interface needed by the test
runner to allow it to drive the test, and methods that the test code
can use to check for and report various kinds of failures.
setUp[, tearDown[, description]]])|
This class implements the portion of the TestCase interface
which allows the test runner to drive the test, but does not provide
the methods which test code can use to check and report errors.
This is used to create test cases using legacy test code, allowing
it to be integrated into a unittest-based test
This class represents an aggregation of individual tests cases and
test suites. The class presents the interface needed by the test
runner to allow it to be run as any other test case, but all the
contained tests and test suites are executed. Additional methods
are provided to add test cases and suites to the aggregation. If
tests is given, it must be a sequence of individual tests that
will be added to the suite.
This class is responsible for loading tests according to various
criteria and returning them wrapped in a TestSuite.
It can load all tests within a given module or TestCase
class. When loading from a module, it considers all
TestCase-derived classes. For each such class, it creates
an instance for each method with a name beginning with the string
Instance of the TestLoader class which can be shared. If no
customization of the TestLoader is needed, this instance can
always be used instead of creating new instances.
A basic test runner implementation which prints results on standard
output. It has a few configurable parameters, but is essentially
very simple. Graphical applications which run test suites should
provide alternate implementations.
A command-line program that runs a set of tests; this is primarily
for making test modules conveniently executable. The simplest use
for this function is:
if __name__ == '__main__':
In some cases, the existing tests may have be written using the
doctest module. If so, that module provides a
DocTestSuite class that can automatically build
unittest.TestSuite instances from the existing test code.
New in version 2.3.
See About this document... for information on suggesting changes. | <urn:uuid:397b8e92-4508-4edf-95e7-4afadec61c13> | 3.265625 | 531 | Documentation | Software Dev. | 49.896721 |
If one side of a triangle is extended beyond the vertex, an exterior angle is formed. This exterior angle is supplementary with its adjacent, linear angle. Since the angle sum in a triangle is also 180 degrees, the exterior angle must have a measure equal to the sum of the remaining angles, called the remote interior angles.
When we talk about exterior angles and the remote interior angles it helps that we think about what in English what do they mean do they mean? Exterior means outside, so this is angle 1 outside of our triangle. The angles that are inside the triangles are the interior but there's only two that are remote. Remote means far away which is why when you're trying to use your TV you use a remote because your far away, so the remote interior angles are 3 and 4 so again 1 is your exterior angle because it's outside and the two angles that are not adjacent to angle 1 are your remote interior angles.
There's a special relationship that exists here and that is angle 1 is equal to angle 3 plus angle 4 but you're not just going to take my word for it you're going say "Mr. McCall you need to prove that," so what I'm going to do is I'm going to say angle 1 and angle 2 must sum to 180 degrees because if I add those two angles up we get a straight line. The second thing I'm going to say is that these 3 angles 2, 3, 3. 2, 3 and 4 must sum to 180 degrees because they make a triangle.
If I solve this equation for 2, I'm sorry that 2 is a little messy, then I can substitute in to my first equation, so I'm going to subtract angle 3 and I'm going to subtract angle 4 so what I'm doing is just moving everything to the other side of that equation so subtract angle 3 subtract angle 4 and I find that angle 2 must equal 180 minus those two angles, so 180 degrees minus angle 3 minus angle 4 so I know angle 2 in terms of angle 3 and 4 and I'm going to substitute that in right over there, so we're going to shift and I'm going to say angle 1 plus angle 2 which we said was 180 minus angle 3 minus angle 4 if we go back to our original equation here that has to equal 180 degrees. I see I have 180 degrees on both sides so I'm just going to minus 180 and then that will make them disappear and if I move negatives angle 3 and negative angle 4 to the other side by adding angle 3 and angle 4 then all I have left is angle 1 is equal to 180 and negative 180 is 0 so we have angle 3 plus angle 4 which has proven that the remote exterior angle excuse me the exterior angle is equal to the sum of the remote interior angles. | <urn:uuid:228e8bd0-d92b-4e9d-8abe-ef4145427a6a> | 4.09375 | 563 | Tutorial | Science & Tech. | 52.785616 |
Shrinking sea ice cover
Sea ice cover has been shrinking in the Barents Sea and the Arctic generally over the past 30 years. In 2012, a record level of ice melt was recorded in the Arctic. There had never been so little ice cover since satellite measurements started in 1979. The Greenland ice sheet and glaciers in Svalbard are melting, and the temperature of the permafrost is rising. Researchers are also warning of accelerating ocean acidification as a result of CO2 emissions.
This satellite image from NASA (NASA/Goddard Scientific Visualization Studio) shows the extent of the sea ice on 16 September 2012. The yellow line shows the average minimum for the last 30 years.
The Arctic is also being affected by pollution. Although levels of several hazardous substances have declined, there are still alarmingly high concentrations in a number of species, including polar bears, ivory gulls, glaucous gulls and fulmars.
The impacts of climate change are much less marked in the Antarctic, and pollution levels are considerably lower.
Shrinking ice cover a threat to many species
The loss of sea ice in the Arctic poses a threat to many species. Harp seals and hooded seals will lose their habitat and polar bears their hunting grounds, and populations of fish, plankton and algae that are dependent on the ice edge are expected to decline steeply.
Impacts of human activity in the polar regions
Greenhouse gas emissions and pollution originating in distant parts of the world are having impacts in the polar regions. In addition, there is increasing human activity within these regions, and growing pressure to exploit oil, gas and coal reserves and biological resources.
Tens of thousands of tourists visit Svalbard every year, the population of the islands is growing, and research activity is expanding. An ice-free Barents Sea will open up new areas of interest for fisheries, oil and gas activities and research.
In the Antarctic, the fisheries, research and tourism are all expanding considerably. This may be harmful to the vulnerable environment of the Southern Ocean and more accessible land areas of Antarctica.
Protection, regulation and emission cuts
Cuts in greenhouse gas emissions are needed to safeguard the polar environment. It is also important to protect large continuous areas of habitat and to regulate tourism, mineral exploitation and research activities.
In the Arctic, stricter national and international legislation can help to reverse negative trends. Information on how to avoid damage to the vulnerable environment is also important. In the Antarctic, there is already a strict international regime that regulates potentially harmful activities. | <urn:uuid:733d3c7e-64a1-4d97-81b9-70361c31da3d> | 3.90625 | 522 | Knowledge Article | Science & Tech. | 31.148111 |
Chatham / Challenger project - Voyage 2 Sea-bed Ecology - Chatham Rise
Planning for the biological sampling voyages in 2007 was complex and required a rigorous approach to designing a sampling programme that would result in measures of biodiversity and characterisation of habitats in the survey area. A pragmatic approach also had to be developed because of the logistics of sampling the sea-bed in relatively deep water.
Using the multibeam data from Voyage 1, scientists at NIWA were able to identify 9 areas with distinct acoustic or environmental signals on the Chatham Rise. These areas or ‘strata’ were used as a basis for allocating biological sampling stations in Voyage 2.
Each colour in the map represents a stratum, and the small lines mark the approximate location of a sampling station. A trade-off between achieving broad coverage across the whole survey area and detailed sampling at individual locations had to be made.
A range of sampling tools are being deployed. Some of the stations will get ‘the works’ (sediment corer, sled, beam trawl, cameras and videos, all replicated twice). Others will be sampled with just the sled and camera system, and some will just be viewed by the camera system.
As the Voyage progresses [see weekly Voyage diary from the ship] stations will be added or dropped depending on how kind the weather is and how long it takes to process the samples.
It can take hours to sieve through mud samples and select out every creature for identification counting and weighing. There is a team of 21 scientists on board the ship. They are split into 2 groups so that sampling and processing can proceed 24-7.
The Chatham Rise survey is for 30 days. | <urn:uuid:b0df2211-d661-43f6-96e1-c85e0234ed25> | 3.1875 | 353 | Knowledge Article | Science & Tech. | 45.766184 |
When the geometry of the part is relatively uncomplicated and
the orientation of a flaw is well known, the length (a)
of a crack can be determined by a technique known as tip diffraction.
One common application of the tip diffraction technique is to
determine the length of a crack originating from on the backside
of a flat plate as shown below. In this case, when an angle beam
transducer is scanned over the area of the flaw, the principle
echo comes from the base of the crack to locate the position of
the flaw (Image 1). A second, much weaker echo comes from the
tip of the crack and since the distance traveled by the ultrasound
is less, the second signal appears earlier in time on the scope
Crack height (a) is a function of the ultrasound
velocity (v) in the material, the incident
and the difference in arrival times between the two signal
(dt). Since the incident angle and the thickness of the
material is the same in both measurements, two similar right triangle
are formed such that one can be overlayed on the other. A third
similar right triangle is made, which is comprised on the crack,
the length dt and the angle Q2.
The variable dt is really the difference
in time but can easily be converted to a distance by dividing
the time in half (to get the one-way travel time) and multiplying
this value by the velocity of the sound in the material. Using
trigonometry an equation for estimating crack height from these
variables can be derived as shown below.
Solving for "a" the equation becomes
The equation is complete once distance dt is calculated by dividing
the difference in time between the two signals (dt) by two and
multiplying this value by the sound velocity. | <urn:uuid:0a0f59ff-fe3e-4b62-b189-0fcaee7b3d1a> | 4.1875 | 386 | Tutorial | Science & Tech. | 36.689076 |
Report an inappropriate comment
Larger Drops Fall Faster Than Smaller Drops, Due To Their Greater Mass.
Sun May 17 04:55:48 BST 2009 by Evil Rocks
Small drops have lower terminal velocities because there's a non-linear relationship to surface area (which determines drag) and weight, meaning that as drops fragment their daughter drops have less mass relative to their surface area than the parent drop did.
However, they maintain the speed of the parent drop until they decelerate to their new terminal velocity as determined by their new mass:drag ratio.
I'd hold off on making any judgements about the effect this has on Doppler stats until I saw the relevant math, though. I'm sure that *someone's* calculated the error between its predictions and actual rainfall and those error bars are already accounted for by meteorologists.
But hey, sell the scare not the story. | <urn:uuid:cf96f3dd-56d3-427b-b7f4-c8f8102a8964> | 3.0625 | 186 | Comment Section | Science & Tech. | 48.92 |
Although dispersed over a wide geographical area in the Holoarctic Region since the Late Pliocene, the Alceini group is difficult to study today because remains are typically few and sparsely distributed, as the social organisation of these animals was probably non-gregarious.
Cervalces latifrons never reached the southernmost regions of Europe probably because of the warmer and drier climate. Notably, it has never been recorded from Spain, the peninsular portion of Italy (south than the Appennine chain), Dalmatian coast and Greece.
In Britain Cervalces latifrons is recorded only from the Forest Bed Formation, outcropping along the Norfolk and Suffolk coast.
The amazing morphological stability in teeth, oral apparatus and limb bones within the Alceini tribe (extinct Cervalces and living Alces), and the numerous morphological peculiarities that the Alceini share with respect to other deer, suggest Cervalces latifrons and living moose are adapted to a similar diet, and lived in similar marshy habitats, with bushes and strewn debris.
Like living moose, Cervalces probably moved along flood valleys to range from the taiga, to both the tundra and steppe environments, and so was subject to a wide range of temperature.
These valley biotopes survived during the abrupt Pleistocene climatic variations when the forest degraded to a tundra-steppe association and vice versa. This may explain why the Alceini morphology remained, antlers apart, unvaried during the Quaternary.
Palaeobotanical and palaeontological data from European sites bearing remains of Cervalces latifrons indicate that it could have lived either in boreal forests and in mixed conifer and deciduous forests, and in meadow steppes. Warm-temperate deciduous forests seem to be excluded, probably because the wide antler span would have hampered movements in a closed forest.
A detailed reconstruction of the palaeoenvironment of Cervalces latifrons from a locality in Northern Italy has been performed through the pollen analysis of sediment adhering to its remains. It consists of:
Cervalces latifrons probably browsed mainly on telmatic vegetation and high forbs in this locality, as observed today for Alces alces in some areas.
Palaeoenvironmental reconstruction along a topographic transect through Ranica (Bergamo region, Italy) at the time of Cervalces latifrons occupancy, as inferred by detailed pollen analysis of the sediment extracted from a moose skull.
Drawing modified from: Ravazzi 2003 - Gli antichi bacini lacustri e i fossili di Leffe, Ranica e Pianico Sellere.
Portion of the phalanx bearing the nails/claws which articulates to the previous finger/toe bones.
A group of organisms that is derived from its ancestor (and/or develops into its descendant) by a process of slow, steady, evolutionary change and is not regarded as a member of the same species as its ancestor and/or descendant.
Bones of the ankle.
Scientific study of animal behaviour.
Herbaceous flowering plants that are not graminoids (grasses, sedges and rushes). The term is used in vegetation ecology to represent a guild of grassland plant species with broadly similar growth form, which in ecology is often more important than taxonomic relationship.
The single specimen designated by an author to formally describe a new species.
Main bone of the ankle of Ruminant animals.
Hand and foot bones between the fingers/toes and the wrist/ankle.
Living in a marsh or swamp.
Bones of the fingers and toes.
Ancestor-descendent populations that undergo morphological change over time.
Vegetation living in the swamp zone of a lake developing into a bog. | <urn:uuid:bc51be9a-3fe5-4a2b-a7ec-cbb8f227c56f> | 3.71875 | 825 | Knowledge Article | Science & Tech. | 21.404364 |
This is undoubtedly the most popular physics equation ever. Its like even fuckin’ junkies out there know about it, but few actually understand it. My understanding goes as follows (the bold part is the answer to your question, the remaining part is for better understanding) :
E represents energy
M represents mass
c represents the speed of light
We know that,
Energy can neither be created nor be destroyed it can only be converted from one form to another. This is still true, but Einstein added that mass can also be converted into energy. And if you convert a mass M into energy, the energy obtained is equal to that mass M multiplied by the square of the speed of light. This energy is usually pretty huge even for little masses, do the math, you are multiplying mass with , this makes the resultant value i.e. the energy, really BIG. You can have a better understanding of it if you know how this equation is applied. Here are a few interesting instances:
- It can be used to proof that nothing can travel at the speed of light as follows: When a body moves it gains energy and due to the previously mentioned equivalence of mass and energy, after a point the extra gained energy is converted to mass as per , so when it reaches the speed of light, its mass must have reached a very high value so it can no more be accelerated and it slows down thus failing to reach the speed of light.
- It accounts for the stability of nucleus and as to why protons inside the nucleus despite being likely charged stick together and don’t fall apart: After a radioactive decay if we see the initial and final values of the decaying isotope and the resulting nuclei, we find an unexpected difference, according to the law of conservation of energy the initial masses should be equal to the final masses thus it was concluded that the difference in the masses is because the “missing” mass was converted to energy. Thus energy was released and this is what stabilizes the whole process, makes it feasible and hence the nucleus is stable.
I know that was some real nerd-lish but, well, who are we taling about here? Einstein, right? The terra-nerd.
There are a real bunch of such uses out there just fiddle around the links in the below Google search and slowly your understanding will grow. You really can’t understand it at once.
If you are asking for a mathematical proof, I wrote one here:
P.S: I typed all this myself, i didn’t copy-paste it. So, vote me up :D | <urn:uuid:148d2cf9-d632-487e-b46d-c107cd39610b> | 3.078125 | 536 | Personal Blog | Science & Tech. | 51.709526 |
7.3.3 Buffer Objects
Python objects implemented in C can export a group of functions called
the ``buffer interface.'' These functions can
be used by an object to expose its data in a raw, byte-oriented
format. Clients of the object can use the buffer interface to access
the object data directly, without needing to copy it first.
Two examples of objects that support
the buffer interface are strings and arrays. The string object exposes
the character contents in the buffer interface's byte-oriented
form. An array can also expose its contents, but it should be noted
that array elements may be multi-byte values.
An example user of the buffer interface is the file object's
write() method. Any object that can export a series of bytes
through the buffer interface can be written to a file. There are a
number of format codes to PyArg_ParseTuple() that operate
against an object's buffer interface, returning data from the target
More information on the buffer interface is provided in the section
``Buffer Object Structures'' (section 10.7), under
the description for PyBufferProcs.
A ``buffer object'' is defined in the bufferobject.h header
(included by Python.h). These objects look very similar to
string objects at the Python programming level: they support slicing,
indexing, concatenation, and some other standard string
operations. However, their data can come from one of two sources: from
a block of memory, or from another object which exports the buffer
Buffer objects are useful as a way to expose the data from another
object's buffer interface to the Python programmer. They can also be
used as a zero-copy slicing mechanism. Using their ability to
reference a block of memory, it is possible to expose any data to the
Python programmer quite easily. The memory could be a large, constant
array in a C extension, it could be a raw block of memory for
manipulation before passing to an operating system library, or it
could be used to pass around structured data in its native, in-memory
This subtype of PyObject represents a buffer object.
- PyTypeObject PyBuffer_Type
The instance of PyTypeObject which represents the Python
buffer type; it is the same object as
types.BufferType in the Python layer.
- int Py_END_OF_BUFFER
This constant may be passed as the size parameter to
PyBuffer_FromReadWriteObject(). It indicates that the
new PyBufferObject should refer to base object from
the specified offset to the end of its exported buffer. Using
this enables the caller to avoid querying the base object for
|int PyBuffer_Check(||PyObject *p)|
Return true if the argument has type PyBuffer_Type.
|PyObject* PyBuffer_FromObject(||PyObject *base,
Py_ssize_t offset, Py_ssize_t size)|
Return a new read-only buffer object. This raises
TypeError if base doesn't support the read-only
buffer protocol or doesn't provide exactly one buffer segment, or it
raises ValueError if offset is less than zero. The
buffer will hold a reference to the base object, and the
buffer's contents will refer to the base object's buffer
interface, starting as position offset and extending for
size bytes. If size is Py_END_OF_BUFFER, then
the new buffer's contents extend to the length of the base
object's exported buffer data.
|PyObject* PyBuffer_FromReadWriteObject(||PyObject *base,
Return a new writable buffer object. Parameters and exceptions are
similar to those for PyBuffer_FromObject(). If the
base object does not export the writeable buffer protocol,
then TypeError is raised.
|PyObject* PyBuffer_FromMemory(||void *ptr, Py_ssize_t size)|
Return a new read-only buffer object that reads from a specified
location in memory, with a specified size. The caller is
responsible for ensuring that the memory buffer, passed in as
ptr, is not deallocated while the returned buffer object
exists. Raises ValueError if size is less than
zero. Note that Py_END_OF_BUFFER may not be
passed for the size parameter; ValueError will be
raised in that case.
|PyObject* PyBuffer_FromReadWriteMemory(||void *ptr, Py_ssize_t size)|
Similar to PyBuffer_FromMemory(), but the returned
buffer is writable.
|PyObject* PyBuffer_New(||Py_ssize_t size)|
Return a new writable buffer object that maintains its own memory
buffer of size bytes. ValueError is returned if
size is not zero or positive. Note that the memory buffer (as
returned by PyObject_AsWriteBuffer()) is not specifically
See About this document... for information on suggesting changes. | <urn:uuid:7ae674e6-a01d-4433-b923-1f19f739f973> | 3.375 | 1,067 | Documentation | Software Dev. | 36.098331 |
Data Entry in ProgressThis describes a final project that consists of a poster session and a written report on a student-chosen topic related to chemistry in everyday life. The students are asked to describe the chemistry of something in the world around us, relate it to at least one chemical concept we learned about in class and then include a description of the "life cycle" of their topic. Additionally, the students are asked to describe which of the 12 Principles of Green Chemistry apply or how they might be used in their topic's case. They then present a poster in a traditional "poster session" format and finally, write a scientific-style report on their findings with references.
This exercise is written for an undergraduate general chemistry course, but could be modified for other classes, including engineering, sustainability or environmental studies courses. Students benefit by making a simple scientific poster and discussing it with others and also by practicing both their scientific writing and research skills beyond simple lab reports. The link to the Course Module includes student handouts and grading rubric.
Summary prepared March 2012 by Dr. Amber Wise at the UC Berkeley.
Wise, A. The Chemistry All Around Us: A Final Project Outline for Chemistry, Chemistry, UC Berkeley, 2012 | <urn:uuid:344139e3-c306-4669-aac9-50f8df7191de> | 3.765625 | 249 | Knowledge Article | Science & Tech. | 35.271717 |
Early sample of Fleming’s mould, 1935/1936
Alexander Fleming discovered penicillin with the help of the arts. He was a self-taught painter, creating art from microbial cultures — a hobby that triggered a breakthrough in antibiotics. Fleming’s lab was cluttered with petri dishes of bacteria in search of natural pigments to use in his germ paintings. He eventually found a green fungus killing the bacteria in the cultures. This would become the first effective antibacterial drug. Interestingly, Fleming coined the word penicillin from Penicillium (its latin root meaning “painter’s brush”) because, under the lens of a microscope, it resembles a paintbrush.
Read more about how he uncovered the effects of Penicillium in Smithsonian magazine.
(via Science Museum) | <urn:uuid:c39b5658-6047-443b-9eb1-f139c285ac3d> | 3.859375 | 171 | Knowledge Article | Science & Tech. | 40.68 |
why 360 degrees?
See also the
Dr. Math FAQ:
segments of circles
Browse High School Conic Sections, Circles
Stars indicate particularly interesting answers or
good places to begin browsing.
Selected answers to common questions:
Find the center of a circle.
Is a circle a polygon?
Volume of a tank.
Why is a circle 360 degrees?
- 1/4 Tank Dipstick Problem (from Car Talk) [12/04/2002]
The gauge on Rick's 18-wheeler is broken, so he uses a dowel to
measure the diesel in his tank, which is cylinder-shaped, 20 inches in
diameter, and sits on its side. How can he mark the dipstick to show
1/4 of a tank of fuel?
- Hands of a Clock [10/10/1997]
How many times do the hour and minute hands cross in a 12-hour period of
- One Circle Revolving Around Another [05/26/1999]
How many revolutions will a smaller circle make while rotating around the
perimeter of a larger circle?
- Accuracy in Measurement [02/08/2002]
Since pi is irrational, either the circumference or the diameter of a
circle must be irrational. How is that possible?
- Accurate Drawing of an Ellipse [02/14/1999]
Draw an ellipse accurately using simple tools.
- Algebraic Spirals [5/19/1995]
I have read about "algebraic" spirals called "cissoid" and "conchoid," which Descartes deemed more exact than the "transcendental" logarithmic and Archimedean spirals, but I have not been able to find any other information on these figures.
- Analytic Geometry [08/31/1997]
How do I find the standard equations of the circles that pass through
(2,3) and are tangent to both the lines 3x - 4y = -1 and 4x + 3y = 7?
- Analytic Proof that Midpoints Form a Circle [03/10/1998]
Analytic proof that midpoints between a point within a circle and its
circumference form a circle.
- Angle Inscribed in a Semicircle [11/07/2001]
Prove that any angle inscribed in a semicircle is a right angle.
- Angle Measurements of Triangles inside Semicircle [11/26/1998]
If the area of a triangle inside a semicircle is equal to the area
outside the triangle within the semicircle, then find the values of the
acute angles in the triangle.
- Another Grazing Cow [6/7/1995]
A man has a barn that is 20 ft by 10 ft. He tethers a cow to one corner
of the outside of the barn using a 50-ft rope. What is the total area
that the cow is capable of grazing?
- Applications of Parabolas [10/24/2000]
How are parabolas used in real life?
- Approximating Pi using Geometry [08/12/1998]
I need to know a simple method to find the approximate value of pi using
- Arbelos Construction [03/10/2000]
Is there a Euclidean construction for the circles that are sandwiched in
- Arc Formulas [05/08/2003]
I am trying to determine the angle of an arc from the radius and arc
length. The radius is 630 and the arc length is 66.82.
- Archimedes and the Area of a Circle [09/17/1997]
How do you find the area of a circle without pi?
- Archimedes' Method of Estimating Pi [5/29/1996]
What was Archimedes' method for estimating pi using inscribed and
circumscribed polygons about a circle?
- Arcs Inside a Square [07/25/1999]
What is the area of the figure created by the intersection of two arcs
drawn in a square of sidelength 5 units?
- Area and Perimeter in Polygons [06/24/1999]
How can I prove the formula A = (a^2n)/(4tan(180/n)) for computing the
area of a regular n-gon with sidelength a? How does this compare to the
area of a circle?
- Area, Angle of Chords of a Circle [7/25/1996]
Calculate the angles PAB and POB, the area of the sector bounded by OP,
OB and the minor arc PB.
- Are Angles Dimensionless? [08/31/2003]
If you look at the dimensions in the equation arc length = r*theta, it
appears that angles must be dimensionless. But this can't be right.
Or can it?
- Area of a Circle Segment [04/18/1999]
What are the steps for figuring out the area of a segment of a circle?
- Area of a Circle with Radius less than 1 [02/18/2002]
If the radius is less than 1 it just gets smaller and you get a smaller
- Area of a Crescent [11/10/2000]
What is the formula for the area of a crescent?
- Area of a Curved Figure [07/26/1997]
How can you find the area of a curved figure without using calculus?
- Area of an Annulus [10/13/2001]
How can I find the area of an annulus?
- Area of an Ellipse [08/18/1999]
How do you calculate the area of an ellipse?
- Area of an Ellipse Cut by a Chord [05/26/2000]
How can you calculate area of the part of an ellipse cut off by a chord,
if you know the major and minor axes, and the chord?
- Area of an Ellipse using Integral Calculus [11/4/1996]
How do you find the area of an ellipse?
- Area of an Ellipse without using Calculus [11/28/1997]
How do you find the area of an oval without using calculus?
- Area of an Oval [11/30/2001]
How do I figure out the area of an oval 17" x 38"?
- Area of a Parabola [09/05/1997]
How do you find the area of a parabola? (I just finished Algebra 2.)
- Area of A Sector of An Ellipse [02/28/1998]
Finding the area of a sector of an ellipse, given the semiminor and major
axes and the angles of the 2 vectors bounding the sector.
- Area of a Segment from Arc and Chord Length [11/27/2000]
How do you find the area of a segment of a circle if you know only the
arc length and chord length?
- The Area of a Square Inscribed in a Circle [12/23/1995]
What is the area of a square inscribed in a circle whose circumference is
- Area of Inscribed Circle [12/01/1998]
Find the area of the circle inscribed in a triangle ABC using Heron's
- Area of Intersection of Two Circles [12/1/1995]
My teenage son asked me for the formula for the area of intersection of
two arbitrary circles.
- Area of Part of an Ellipse [04/07/2001]
Given an ellipse with a line bisecting it perpendicular to either the
major or minor axis of the ellipse, what is the formula for the area of
the ellipse either above or below that line?
- Area of Union of Two Circles [6/10/1996]
If the effective length of a rope tied to a goat is L, and the goat can
eat exactly half of the grass in a field, express L in terms of R.
- Areas of N-Sided Regular Polygon and Circle [02/24/2005]
The area of an n-sided regular polygon approaches the area of a circle
as n gets very large. | <urn:uuid:208ab689-1499-4d45-9ef9-a6d21aef4b93> | 3.71875 | 1,780 | Q&A Forum | Science & Tech. | 67.187904 |
GHCN Temperature Adjustments Affect 40% Of The Arctic
By Paul Homewood
There has been much discussion recently about temperature adjustments made by GHCN in Iceland and Greenland, which have had the effect of reducing historic temperature levels, thereby creating an artificial warming trend. These can easily be checked at the GISS website, where both the old and new datasets can be viewed as graph and table data, here and here.
It has now been identified that similar adjustments have been made at nearly every station close to the Arctic Circle, between Greenland and, going East,via Norway to Siberia, i.e 56 Degrees West to 86 Degrees East, about 40% of the circumference.
So it is perhaps time to recap where we are now.
The NCDC has produced the Global Historical Climatology Network (GHCN), a dataset of monthly mean temperatures, since the 1990’s. Version 2 was introduced in 1997 and included “Methods for removing inhomogeneities from the data record associated with non-climatic influences such as changes in instrumentation, station environment, and observing practices that occur over time “. The GHCN datasets are used by both GISS and HADCRUT for calculation of global temperatures, as well as NCDC themselves.
In May 2011, NCDC brought out Version 3, which “enhanced the overall quality of the dataset”, but made little difference in overall terms. However, only two months later in July, a Google Summer Student, a graduate called Daniel Rothenberg, was brought in to convert some of the GHCN software and make modifications to “correct software coding errors”. The result was Version 3.1, which went live in November 2011. (The full technical report is here).
It is this latest version that has thrown up the Arctic adjustments we are now seeing.
Until December, GISS used Version 2 unadjusted temperatures. Since then, they have changed to using Version 3.1 adjusted temperatures.
Basis of Homogeneity Adjustments
It is worth taking time to be clear why temperature adjustments are made (or should be). As far as GHCN are concerned, they explain their logic thus :-
Surface weather stations are frequently subject to minor relocations throughout their history of operation. Observing stations may also undergo changes in instrumentation as measurement technology evolves. Furthermore, observing practices may vary through time, and the land use/land cover in the vicinity of an observing site can be altered by either natural or man-made causes. Any such modifications to the circumstances behind temperature measurements have the potential to alter a thermometer’s microclimate exposure characteristics or otherwise change the bias of measurements relative to those taken under previous circumstances. The manifestation of such changes is often an abrupt shift in the mean level of temperature readings that is unrelated to true climate variations and trends. Ultimately, these artifacts (also known as inhomogeneities) confound attempts to quantify climate variability and change because the magnitude of the artifact can be as large as or larger than the true background climate signal. The process of removing the impact of non-climatic changes in climate series is called homogenization, an essential but sometimes overlooked component of climate analysis.
It is quite clear. Their algorithms should look for abrupt changes that are not reflected at nearby stations. It has nothing to do with “averaging out regional temperatures” as is sometimes claimed.
GISS also make homogeneity adjustments, but for totally different reasons. In their case, it is to make an allowance for the Urban Heat Island Effect (which is not spotted by GHCN because it is a slow change).
Effect of The Adjustments
Appendix A lists every current GHCN station with records back to 1940,that lie between Greenland, at a latitude of 56 W, around to a point about midway across Siberia at 86 E and which are situated close to the Arctic Circle. The table shows the adjustment made by GHCN for 1940 data. Out of 26 stations, the adjustment has reduced actual temperatures in 23 cases, many substantially. In contrast, 2 remain unchanged and only one has a positive adjustment (and this is insignificant). As a crude average, the adjustment works out at a reduction of 0.70 C.
These adjustments typically extend back to the beginning of the station records (though Reykjavik is an exception) and most continue at the same level till about 1970. ( Some of the Russian stations last longer – e.g. Ostrov Dikson’s disappears in 2009).
By 2011, however, the adjustments disappear at ALL of these sites. In other words, an artificial warming trend has been manufactured.
It is worth spelling out two points :-
1) Within this arc of longitude, there are no other stations within the Arctic Circle.
2) With the exception of Lerwick and Vestmanneyja, I can find no stations, in the region, below a latitude of 64 North with similar adjustments. Why is 64 North significant? GISS produce zonal temperature data, and their “Arctic” zone goes from 64 North to the Pole. Coincidence?
Is there any justification for adjusting?
Trausti Jonsson, a senior climatologist at the Iceland Met Office, has already confirmed that he sees no reason for the adjustments in Iceland and that they themselves have already made any adjustments necessary due to station moves etc before sending the data onto GHCN.
Clearly the fact that nearly every station in the region has been adjusted disproves the idea that these sites are outliers, which give biased results not supported by nearby stations.
GHCN were asked in January to investigate this issue and so far have failed to come up with any explanation. Unless they can do this, the assumption must be that the adjustments have been created by faulty software.
In global terms, these few stations make no tangible difference to overall temperatures. However, they do make a significant difference to temperatures in the Arctic, which are derived from a small number of stations such as these and then projected over hundreds of miles.
Across much of the Arctic, temperatures were as high in the years around 1940 as they are now. History should not be revised at the whims of an algorithm.
What should happen next? In my view, GHCN should immediately revert to Version 3.0 until the matter is properly investigated and any issues resolved. They maybe just need to put Version 3.1 down as a bad experience and start from scratch again. I believe they also need to seriously review their Quality Control procedures and question how these anomalies were allowed to arise without being flagged up.
It should not be up to independent observers to have to do this.
1) GISS still archive the Version 2.0 data here. (Also GISS, following requests by me and others, have included a link to Version 2.0 on their main site).
2) And can be compared with Version 3.1 here.
3) The adjustments can also be seen in graph format at GHCN here. (The station numbers can be obtained at GISS)
Annual Mean Temperature Centigrade in 1940
|Station||Country||Actual Temperature||Adjusted Temperature||Difference||Longitude/
|Upernavik||Greenland||-3.97||-5.94||-1.97||56 W / 72 N|
|Jakobshavn||Greenland||-2.77||-3.07||-0.30||51 W / 69 N|
|Nuuk||Greenland||-0.07||-1.17||-1.10||51 W / 64 N|
|Angmagssalik||Greenland||-0.82||-1.02||-0.20||37W / 65 N|
|Stykkisholmur||Iceland||3.72||3.62||-0.05||22 W / 65 N|
|Reykjavik||Iceland||5.08||2.88||-2.20||21 W / 64 N|
|Vestmannaeyja||Iceland||5.43||3.63||-1.80||20 W / 63 N|
|Akureyri||Iceland||3.90||2.80||-1.10||18 W / 65 N|
|Teigarhorn||Iceland||4.88||3.98||-0.90||14 W / 64 N|
|Lerwick||Shetland Isles||7.46||6.96||-0.50||1 W / 60 N|
|Jan Mayen||Norway||-0.06||-0.34||-0.28||8 W / 70 N|
|Bodo||Norway||4.14||3.94||-0.20||14 E / 67 N|
|Tromso||Norway||2.23||2.23||NIL||19 E / 69 N|
|Karasjok||Norway||-2.76||-3.36||-0.60||25 E / 69 N|
|Vardo||Norway||0.88||0.88||NIL||31 E / 70 N|
|Kandalaksa||Russia||-0.31||-1.01||-0.70||32 E / 67 N|
|Murmansk||Russia||-0.40||-0.77||-0.37||33 E / 68 N|
|Archangel||Russia||0.00||-0.60||-0.60||40 E / 64 N|
|Kanin Nos||Russia||-1.38||-1.74||-0.36||43 E / 68 N|
|Ust Cilma||Russia||-2.36||-2.29||+0.07||52 E / 65 N|
|Malye Karmaku||Russia||-4.51||-5.11||-0.60||52 E / 72 N|
|Narjan||Russia||-3.24||-3.88||-0.64||53 E / 67 N|
|Salehard||Russia||-5.96||-7.06||-1.10||66 E / 66 N|
|Tarko||Russia||-6.30||-7.50||-1.20||77 E / 64 N|
|Ostrov Dikson||Russia||-11.10||-11.39||-0.29||80 E / 73 N|
|Dudinka||Russia||-9.71||-10.81||-1.10||86 E / 69 N|
I originally set this table up yesterday, 9th March. Today I noticed a few had changed slightly, presumably at the monthly update, so have amended them. It appears GHCN are still fiddling with their algorithms as the same thing occurred last month. | <urn:uuid:886b6c76-3303-460e-8aea-43de863a45a1> | 3.21875 | 2,308 | Personal Blog | Science & Tech. | 71.183102 |
Does anyone know ......
lemstra at worldonline.nl
Mon Feb 23 04:23:23 EST 1998
Actually, even at the most deepest point of the ocean there is life. This
point is called the Mariana depth and is located east off the phillipines,
close to the island of Guam. (Please look up for correct depth and name)
The deepest part is called the challenger depth and was discovered by the
Challenger expedition in 1951. A weight of one kilo takes an hour to sink
from the surface to the bottom. It4s close to 11 kilometers deep. There are
organisms here that depend on chemicals and heat generated by vulcanic
action. There are quite a number of different species there. All of them
are white (or red because the blood shows through the skin). There are
crustations, shellfish and spungelike animals. Many of these animals have
the ability to create light. Either they glow or pulse.
Over this closed of environment supported by vulcanic heat and chemicals
there is a portion almost 10 kilometers of water that is virtually
richard.taylor at utas.edu.au schreef in artikel <6cjju6$2dn at net.bio.net>...
> Can any one help me please - my son is trying to find answers to the
> following questions:
> How deep in the ocean can living organisms exist?
> What organism holds the record for the deepest habitat?
> He's tried encyclopeadias, searched the net, but to no avail.
Magnus L. Johnson, Department of Biology, University of Leicester,
Leicester, LE1 7RH, U.K.
see : http://www.le.ac.uk/biology/research/blpgs.html#magnus
email : mlj2 at le.ac.UK
Tel : 0116 252 3353/2
\\\ /----<==>-----\ / / /
/ / / \----<==>-----/\\\
More information about the Deepsea | <urn:uuid:4ef3b490-5ba6-4361-a50d-c36e5e71dc74> | 2.84375 | 446 | Comment Section | Science & Tech. | 70.20857 |
Positrons, Alpha Particles, and Gamma Rays
That's the case with beryllium 7, 7Be4.
Click on it in the applet and see what happens.
It decays to lithium 7--so a proton turns into a neutron. That makes sense...but how do you deal
with the electric charge problem now? Going from Be to Li, you lose charge; emitting an
electron would just make things worse.
Right...so instead you emit a positron--a particle that's just like an electron except
that it has opposite electric charge. In nuclear reactions, positrons are written this way:
So the reaction looks like this:
Good. The applet will show you many other decays that produce either electrons or positrons;
it's easy to tell which, by the "direction" in which the decay moves. Sometimes it even takes
more than one decay to arrive at a stable isotope; try 18Ne or 21O, for
So all radioactive isotopes decay by giving off either electrons or positrons? | <urn:uuid:913b4da6-4bad-410a-844c-25cda56081b4> | 3.671875 | 223 | Tutorial | Science & Tech. | 63.228556 |
It's fun to toss around theories about how there might be other universes out there, and there may even be some evidence that at least four of them have smashed headlong into our universe. You'd think proving that this is the case would be tricky, but neutrons may be taking trips to other universes all the time.
A few years ago, physicists showed that it might be theoretically possible for neutrons (particles of zero charge and one of the basic constituents of atoms) to make the leap from our universe to a different one if the gravitational potential of an entire galaxy were involved. Lucky for us, we happen to live in a galaxy (yay!) so if we look closely enough, it should be possible to spot these neutrons jumping out of our galaxy.
The odds of any one neutron pulling this trick are very, very low: worse than one in a million, if it happens at all (and that's a big if). But by watching a bunch of neutrons all at once, we might be able to experimentally verify whether any of them are disappearing off to alternate universes.
The way we'd do it is by filling up a bottle with ultracold neutrons, sealing it up, and then letting it sit there for a year and watching what happens. Neutrons undergo beta decay at a rate that we're familiar with, and if there's no other way for them to get out of the bottle but we notice that some extras are missing, there has to be an explanation as to where they went, and another universe might just fit the bill. Furthermore, since the gravitational potential changes as we orbit the sun, we should notice annual changes in the number of neutrons that vanish.
We're the first to admit that this theory seems a little, um, exotic, but it's also something that we're able to go and test with current technology. And if it does show something suggesting that neutrons are taking vacations off to alternate universes, well If nothing else, it would be one of the most conceptually mind-blowing discoveries ever made ever. | <urn:uuid:b9af9da4-18ec-41ef-9edd-b4943fdd626a> | 3.109375 | 424 | Personal Blog | Science & Tech. | 42.224549 |
Spinner Dolphins, Stenella longirostris
Taxonomy Animalia Chordata Mammalia Cetacea Delphinidae Stenella longirostris
Description & Behavior
Spinner dolphins, Stenella longirostris (Gray, 1828), aka long-snouted spinner dolphins, measure about 2 m in length and weigh about 90 kg. They have small, pointed flippers and curved dorsal fins at the center of their bodies. Spinner dolphins are dark gray on their dorsal (top) sides with a lighter gray area that runs from their eyes to their tails. Their ventral (under) side is white.
Common names for the geographic varieties of Stenella longirostris found in the Pacific include: the Costa Rican, Eastern, whitebelly, and Hawaiian or Gray's dolphins. A dwarfed form of this species is found in the Gulf of Thailand. The regional populations vary in size. Eastern spinner dolphins are slightly smaller than the Costa Rican spinner dolphins measuring between 1.65-1.8 m in length and weighing about 61 kg, compared to the Costa Rican spinner's length of about 2 m and 91 kg weight.
There are four subspecies of spinner dolphins:
- Gray's (Hawaiian) spinners, S. longirostris longirostris
- Eastern spinners, S. longirostris orientalis
- whitebelly spinners (probable hybrid form of eastern and Gray's)
- Central American or Costa Rican spinners, S. longirostris centroamericana
- Dwarf spinner dolphins, S. longirostris roseiventris
Body shape and color also vary regionally, but in general spinner dolphins are small cetaceans with slender bodies. Most have long thin beaks with the exception of Clymene dolphins (Atlantic short-snouted spinners). This species has more teeth than other dolphins; between 45-65 sharp, pointed teeth are found in each side of both the upper and lower jaws. They have small pointed flippers, and are variations of gray in color with white ventral (under) sides.
Spinner dolphins are a very gregarious species frequently traveling together in schools and with other species, such as spotted dolphins and humpback whales. In the eastern tropical Pacific, spinner dolphins swim with yellowfin tuna, which has resulted in great numbers of spinner dolphins caught as bycatch in purse-seines.
The characteristic spinning of this species is thought to be used for communication as it is often observed when a school is scattered. Another theory is that the spinning may be related to the removal of parasites or of remoras.
World Range & Habitat
Spinner dolphins, Stenella longirostris, are found all over the world.
Hawaiian or Gray's spinners are found throughout the Hawaiian Islands traveling in somewhat smaller groups of >200, and in the Gulf of Mexico, Caribbean, and mid-Atlantic to the northwest coast of Africa.
Eastern spinners also inhabits the waters off the west coast of Central America, but farther offshore in deeper waters than Costa Rican spinners. Eastern spinners is also found in deep waters off the coast of Mexico. This subspecies also travels in very large schools of >1,000.
Costa Rican spinner dolphins are found in large schools of >1,000 in coastal waters off the west coast of Central America.
Whitebelly spinners are also found off the coast of Mexico, but farther out in the open sea than Eastern spinners. Whitebellies also inhabit the northern Pacific coast of South America in large schools of >1,000.
Dwarf spinner dolphins are found in the Gulf of Thailand.
Feeding Behavior (Ecology)
Spinner dolphins, Stenella longirostris, feed at night on small fish and squid. Known predators are sharks, orca (killer whales), and possibly false killer whales, pygmy killer whales, and pilot whales.
Female spinner dolphins, Stenella longirostris, reach sexual maturity at about 4-7 years, males at about 7-10 years. The gestation period lasts about 10.5 months, and calves are nursed for 1-2 years. The calving interval is between 2-3 years.
Conservation Status & Comments
Spinner dolphins, particularly whitebelly and eastern spinner dolphins in the eastern tropical Pacific, have significantly decreased in population size due to their entanglement in the purse-seine nets used by the tuna fishing industry. They are commonly found swimming in large schools above schools of yellowfin tuna, and are therefore used by fishermen to target yellowfin schools. Purse seines capture marine life indiscriminately and have caused declines in spinner dolphin populations as large as 80% since the 1960s when the use of purse seines began. Spinner dolphins are often found in aquariums because they survive in captivity.
References & Further Research
Research Stenella longirostris » Barcode of Life ~ BioOne ~ Biodiversity Heritage Library ~ CITES ~ Cornell Macaulay Library [audio / video] ~ Encyclopedia of Life (EOL) ~ ESA Online Journals ~ FishBase ~ Florida Museum of Natural History Ichthyology Department ~ GBIF ~ Google Scholar ~ ITIS ~ IUCN RedList (Threatened Status) ~ Marine Species Identification Portal ~ NCBI (PubMed, GenBank, etc.) ~ Ocean Biogeographic Information System ~ PLOS ~ SCIRIS ~ SIRIS ~ Tree of Life Web Project ~ UNEP-WCMC Species Database ~ WoRMS
Feedback & Citation
Find an error or having trouble with something? Let us know and we'll have a look!
Help us continue to share the wonders of the ocean with the world, raise awareness of marine conservation issues and their solutions, and support marine conservation scientists and students involved in the marine life sciences. Join the MarineBio Conservation Society or make a donation today. We would like to sincerely thank all of our members, donors, and sponsors, we simply could not have achieved what we have without you and we look forward to doing even more. | <urn:uuid:b6759d84-a0f0-408a-8fa8-587dbc792175> | 3.15625 | 1,284 | Knowledge Article | Science & Tech. | 39.770552 |
Teen scientist Priyanka Satpute is using her scientific prowess and research skills to come up with a way to benefit communities in developing countries. With help from her classmates, the Nashua High School North student is designing a new electrical source: a battery powered entirely by bacteria.
A 50-gallon tub stored underground would be filled with soil and bacteria, which would create energy as the bacteria multiplied that would be converted into electricity. According to Satpute, this process would also produce methane gas, which could be used for cooking and heating.
Click "source" to read the entire article. | <urn:uuid:31f23041-a734-45e4-829b-418ac89aa492> | 2.796875 | 122 | Truncated | Science & Tech. | 37.192545 |
Simplified DNA Extraction from Cell or Tissue
|Author: Long-Cheng Li|
|Source: Protocol Online|
|Date Added: Tue May 14 2002|
|Date Modified: Thu Apr 29 2004|
|Abstract: This method doesn't require organic extraction and centrifugation. It's the most simplest way of preparing DNA and works great.|
DNA extraction without phenol extraction and centrifugation.
1. Lysis: the lysis buffer (usually 0.5ml) is added to the tissue or cell ( for a 75cm2 flask, add 5ml directly to the cell). Digestion is complete within several hours at 37C (cell, 2-3h) or 55C (tissue) with agitation.
100mM Tris Hcl pH 8.5 5ml
0.5M EDTA 0.5ml
10% SDS 1ml
5M NaCl 2ml
20mg/ml Proteinase K 0.25ml
Bring up to 50ml with dd water
2. isopropanol precipitation: one volume of isopropanol is added to the lysate and the samples are mixed or swirled until precipitation is complete ( about 10-20 min ) (viscosity completely gone).
3. Recovery of precipitate: the DNA is recovered by lifting the aggregated precipitate from the solution using a disposable yellow tip. Excess liquid is dabbed off and the DNA is dispersed in a prelabeled Eppendorf tube containing, depending on the size of the precipitate, 20 to 500ul to 10mM Tris HCl, 0.1mM EDTA, pH 7.5. complete dissolution of the DNA may requires several hours of agitation at 37C or 55C (may need overnight). It is important that the DNA is completely dissolved to ensure the reproducible removal of aliquots for analysis.
Adopted from Laird PW, Nucleic Acids Research 1991,19:4293 | <urn:uuid:d57d41e2-02ae-489d-83f0-cb282f25e3f3> | 3.0625 | 418 | Truncated | Science & Tech. | 65.763846 |
Web edition: August 8, 2012
Print edition: September 8, 2012; Vol.182 #5 (p. 10)
A handful of thirsty countries are guzzling their groundwater reserves much faster than those resources can be renewed.
India, Pakistan, Saudi Arabia, Iran, Mexico, and the United States lead the global pack of water-thirsty nations, researchers report online August 8 in Nature. Irrigation for agriculture drives much of the demand, says hydrogeologist and study coauthor Tom Gleeson of McGill University in Montreal.
He and colleagues devised a new “groundwater footprint” measure to evaluate the sustainability of withdrawals from the world’s aquifers. The analytic tool balances water coming in with water going out, and gauges how large an aquifer would have to be to accommodate current withdrawals. A groundwater footprint larger than its aquifer means people are sucking down water faster than it can be replenished — treating it as a nonrenewable resource, Gleeson says.
Though 80 percent of the world’s aquifers have sustainable footprints, people drawing on other aquifers are draining the world’s water supply. For these overtapped reservoirs, groundwater footprints vastly exceed aquifer areas. “It’s not sustainable,” Gleeson says. “We don’t know how long the aquifers will last.”
T. Gleeson et al. Water balance of global aquifers revealed by groundwater footprint. Nature. Vol. 488, August 9, 2012, p. 197. doi:10.1038/nature11295.
D. Powell. Groundwater dropping globally. Science News. Vol. 181, January 14, 2012, p. 5. Available online: [Go to]
J. Raloff. Warming is accelerating global water cycle. Science News Online. October 5, 2010. [Go to]
S. Perkins. Crisis on Tap? Science News, Vol. 162, July 20, 2002, p. 3.
Available online: [Go to] | <urn:uuid:4c1ec6b8-475b-452c-b5a3-17f71ef07782> | 3 | 430 | Knowledge Article | Science & Tech. | 58.958445 |
Call a large company these days, and you will probably start by having a conversation with a computer. Until recently, such automated telephone speech systems could string together only prerecorded phrases. Think of the robotic-sounding "The number you have dialed ... 5 ... 5 ... 5 ... 1 ... 2 ... 1 ... 2...." Unfortunately, this stilted computer speech leaves people cold. And because these systems cannot stray from their canned phrases, their abilities are limited.
Computer-generated speech has improved during the past decade, becoming significantly more intelligible and easier to listen to. But researchers now face a more formidable challenge: making synthesized speech closer to that of real humans--by giving it the ability to modulate tone and expression, for example--so that it can better communicate meaning. This elusive goal requires a deep understanding of the components of speech and of the subtle effects of a person's volume, pitch, timing and emphasis. That is the aim of our research group at IBM and those of other U.S. companies, such as AT&T, Nuance, Cepstral and ScanSoft, as well as investigators at institutions including Carnegie Mellon University, the University of California at Los Angeles, the Massachusetts Institute of Technology and the Oregon Graduate Institute. Like earlier phrase-splicing approaches, the latest generation of speech technology--our version is code-named the IBM Natural Expressive Speech Synthesizer, or the NAXPRES Synthesizer--is based on recordings of human speakers and can respond in real time. The difference is that the new systems can say anything at all--including natural-sounding words the recorded speakers never said.
This article was originally published with the title Conversational Computers. | <urn:uuid:b9928216-044d-41e2-82a1-7c3ff2a53cd6> | 2.796875 | 347 | Truncated | Science & Tech. | 41.566796 |
What causes or triggers the earths auroras (the Northern and Southern Lights)? The Earths fast plasma jet causes spacequakes and these trigger the aurora, also known as the Northern Lights (Southern Lights are called the Aurora Australis). Although the Solar plasma wind is part of the process, the solar wind is not the the only cause of auroras being seen in our skies.
Earths natural Neon light show
The cause of the aurora is electrically excited or charged atoms, molecules and ions emitting photons (light). It is a natural version of Neon lights. How the aurora creating atoms get electrically charged and are accelerated towards earth (against the solar plasma wind) is due to the process that creates earths spacequakes. | <urn:uuid:02c3b92a-5ccf-4835-8d67-9be509285e0b> | 3.71875 | 152 | Knowledge Article | Science & Tech. | 46.945 |
Mercury’s high density has been a longstanding puzzle in planetary science. Its density means that it must have a significantly higher iron abundance than Venus, Earth, Mars, or the asteroids, probably in the form of a large iron core. NASA’s MESSENGER mission has challenged many of the hypothesized ways to create an iron-rich Mercury; a new hypothesis is required.
Two years ago this month, I wrote my very first astrobite about the puzzlingly cloudy atmosphere of the outermost planet, HR 8799b; today I’m revisiting the system and looking at a recent paper which measured spectra of not just one planet, but the entire planetary system. This is the first comparative spectroscopic study of any multi-planet system (other than our own Solar System of course).
The census of planets for smaller stars—M dwarfs—is now basically complete. In this paper, Courtney Dressing and Dave Charbonneau use this M dwarf advantage to determine the occurrence rate of small planets around M dwarfs.
The holy grail for exoplanet science would be to find an inhabited planet. Not just habitable, but actually inhabited. But where are we most likely to find those planets? Only around Sun-like stars, or could life thrive around other types of stars? Could evolved stars like white dwarfs or neutron stars harbor life? Could brown dwarfs, the so-called failed stars, have inhabited planets?
Do planets form in place, or migrate?
How planets form is still a remarkably open question. We haven’t even figured out definitively whether planets formed in the places they are now, or formed in different places and then migrated to their present locations.
As a young astronomer, I’m excited to learn as much as I can about observing process. So when the chance to observe with a collaborator Sandy Leggett at Gemini North came up, I couldn’t pass it up! I spent a week in Hawaii learning about queue observing.
Astronomers don’t stop after discovering planets in systems near and far from our own solar system. The next big step is to characterize the planets. We want to understand what they’re made of, what their atmospheres look like, whether they have clouds, how massive they are, how old they are, etc. As it turns out characterizing exoplanets is really, really challenging for both observers and modelers. The challenges encountered are well illustrated by the saga of WASP-12b.
Astronomers have started trying to understand how to organize classes of exoplanets based on their physical characteristics. As it has turned out over the last ten years, exoplanets are considerably more complicated to classify than stars. The evolution of star is based (almost) exclusively on how massive it is at birth. Instead, this paper classifies hot exoplanets by their level of irradiation from their host star and their chemical composition.
It took homo sapiens hundreds of thousands of years on the planet to understand a fundamental, simple-sounding, question: how old is the Earth? The answer to this question has gone down in the history books as one of the most important geophysical and astrophysical discoveries of the past century. This paper, by Clair Patterson in 1956, is credited with providing the first accurate, measured age of the Earth. | <urn:uuid:52cc15ca-5132-449e-80e1-148f1eb206fc> | 3.46875 | 691 | Personal Blog | Science & Tech. | 44.784306 |
Things in Boo but Not Python
- quickly compile boo script to standalone cross-platform exe
- easy super(), and constructor automatically calls super() for you. If you don't have a constructor, one is created for you.
- set class properties via the constructor (constructor doesn't have to handle them explicitly):
x = MyClass(Property1:"value1", Property2:"value2")
- Anonymous Closures - including multi-line closures:
b = Button(Text:"Press Me") b.Click += def(): MessageBox.Show("you clicked me")
- Events, Callable Types
- unless statement: print "good job" unless score < 75
- built-in support for Regular Expressions
- timespan literals (example: t = 10ms)
- extensible compiler pipeline
- custom Syntactic Macros
since boo is statically typed, you get:
- static typing: "x as int" but you can just say "x" (x is an object)
- Interfaces, Enums
- private,public,protected,final,etc. variables & methods
- speed increases - without having to convert your code to a different language like C
- easier interoperability since boo uses standard CLI types (e.g. string is System.String, int is a System.Int32...)
- convert C# and VB.NET to boo code (part of the Boo AddIn For SharpDevelop)
other C#/.NET features you get:
- "lock" (like java's synchronized). See the lock* examples under tests/testcases/semantics/.
- property getters and setters
- using: (automatically disposes of object when you are done using it)
//in this example you can also use the simpler // "for line in StreamReader("filename"):" using f = System.IO.StreamReader('using0.boo'): while line = f.ReadLine(): print line
- parameter checking
def foo([required(value > 3)] value as int): pass
- [attributes] for functions, fields, classes...
- asynchronous execution, see Asynchronous Design Pattern.
- XML Serialization | <urn:uuid:606e0ed4-90eb-4136-90f8-85e196fb30cb> | 3.046875 | 466 | Documentation | Software Dev. | 47.255485 |
Shakarad, M and Gadagkar, R (1997) Do Social Wasps Choose Nesting Strategies Based on Their Brood Rearing Abilities? In: Naturwissenschaften, 84 (2). pp. 79-82.
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Download (72Kb) | Request a copy
Primitively eusocial wasp nests may be founded by one or a group of females. The solitary foundress builds a nest, lays eggs, defends her brood from parasites and predators, and forages to feed her growing larvae, all by herself, at least until the eclosion of her first daughter. In multiple-foundress nests, only one individual normally assumes the role of dominant queen or egg layer while the remaining cofoundresses act as subordinate workers, building the nest and foraging for food and building material and laying few or no eggs [1, 2].
|Item Type:||Journal Article|
|Additional Information:||Copyright of this article belongs to Springer.|
|Department/Centre:||Division of Biological Sciences > Centre for Ecological Sciences|
|Date Deposited:||06 Feb 2007|
|Last Modified:||19 Sep 2010 04:32|
Actions (login required) | <urn:uuid:4351aca8-ee3c-4729-9299-7ff8cab59b13> | 2.734375 | 264 | Truncated | Science & Tech. | 42.104329 |
When a large outlet glacier of North Greenland (Petermann Gletscher) discharged an ice island four times the size of Manhattan in August of 2010, the United States’ Congress held formal inquiries on its cause within days of the event. Congressmen, scientists, and the global media speculated that this event and concurrent severe droughts in Russia and floods in Asia were tied to record-breaking air temperatures and global warming. Reviewing available data, Johnson et al. (2011) cautioned that most melting of floating ice shelves such as Petermann Gletscher is dominated by physical ocean processes below, not above the ice (Reeh, 2001, Rignot and Steffen, 2008). The National Journal asked me to write an essay to answer the question: “Is Climate Change Causing Wild Weather?” which I answered with a nerdy No, but …. Motivated by questions asked during the congressional hearing, I showed that waters in Petermann Fjord (a) originate from the Arctic Ocean to the north, (b) contain heat of Atlantic origin, and (c) have warmed significantly since 2003 (Muenchow et al., 2011).
When I reported here that the same glacier discharged yet another ice island in July 2012, this one “only” twice the size of Manhattan, I was not so sure anymore, that this was merely another extreme event caused by natural processes. Furthermore, only 4 weeks later I was aboard the CCGS Henry Larsen working in Petermann Fjord and Nares Strait to recover instruments that we had deployed in 2009. Witnessing dramatic change off North Greenland from my first visit in 2003 to my last in 2012, I will send NASA a proposal on monday. If suported, it would enable me to test the idea, that a changing sea ice cover off North Greenland over the last 30 years or so relates to the retreat and decay of glaciers north of 76 N latitude. Most of these glaciers connect the Greenland Ice Sheet to the ocean via floating ice shelves as does Petermann.
This is an image that shows land-fast ice in Nares Strait next to Petermann with the large ice-arch blocking all flow of ice to the south where we see open water or thin ice:
Contrast the conditions in June 2012 above with in April of 2009 below. The southern ice-arch failed to form in 2009, there is much open water and loose, thin ice next to Petermann Fjord, but a northern ice-arch formed and prevented all flow of thick ice from the Arctic Ocean into Nares Strait or Petermann to glue it all together as it did in 2012 (or right now for that matter):
My main question is this: Has the changing sea ice cover next to glaciers anything to do with the break-up of many large glaciers all around North Greenland that we have observed the last few years? Is the removal of the summer sea ice from the many fjords of North Greenland a normal occurrence or is this a new regime that flushes many fjords free of ice in summer? Does the available record of air and ocean observations allow us to explain observed change? I believe that the public has all the data (MODIS, SSM/I, ICESat, etc) to answer these questions, but it will need a little work to actually provide quantifiable answers with error bars to pass academic peer review. Anyone is more than welcome to help and maybe even learn or apply skills for a graduate degree and well-paying jobs in physics or engineering.
ADDENDUM (16:33 EDT): As a result of Greenland losing so much mass and ice, the geographic North Pole started in 2005 to move abruptly towards Greenland. This was reported earlier this week by Nature after the research was accepted for publication at Geophys. Res. Let.
Johnson, H., Münchow, A., Falkner, K., & Melling, H. (2011). Ocean circulation and properties in Petermann Fjord, Greenland Journal of Geophysical Research, 116 (C1) DOI: 10.1029/2010JC006519
Münchow, A., Falkner, K., Melling, H., Rabe, B., & Johnson, H. (2011). Ocean Warming of Nares Strait Bottom Waters off Northwest Greenland, 2003–2009 Oceanography, 24 (3), 114-123 DOI: 10.5670/oceanog.2011.62
Reeh, N., H. H. Thomsen, A. K. Higgins, and A. Weidick (2001). Sea ice and the stability of north and northeast Greenland floating glaciers Annals of Glaciology, 33, 474-480
Rignot, E., & Steffen, K. (2008). Channelized bottom melting and stability of floating ice shelves Geophysical Research Letters, 35 (2) DOI: 10.1029/2007GL031765 | <urn:uuid:441a14d7-016b-443a-8d54-917c22f86c57> | 3.265625 | 1,029 | Comment Section | Science & Tech. | 63.46259 |
PDB EDUCATION CORNER: EARLY PROTEIN STRUCTURES
Part of the RCSB-Rutgers Open House (described in this newsletter's
Message from the RCSB PDB) was a celebration marking the opening of
the Molecular Art Mural. Painted by local artist Jessica Milazzo onto
the walls of RCSB-Rutgers, this mural depicts some of the earliest
structures solved by X-ray crystallography.The mural's accompanying text notes, reprinted here, are from the RCSB
PDB's Molecule of the Month series and RCSB PDB staff.
Lysozyme protects biological organisms from the ever-present danger
of bacterial infection. This small enzyme attacks the protective cell
walls of bacteria. Bacteria build a tough skin of carbohydrate chains
to brace their delicate cell membranes against changes in osmotic
pressure. Lysozyme breaks these carbohydrate chains, which destroys
the structural integrity of the bacterial cell wall. The bacteria
then burst under their own internal pressure.
Lysozyme is present in many places that are rich with potential food
for bacterial growth. The lysozyme pictured here is from hen egg
white, where lysozyme serves to protect the proteins and fats that
will nourish the developing chick.
Lysozyme was the first enzyme structure solved.
PDB ID: 2lyz. Blake, CCF, Koenig, DF, Mair, GA, North, ACT, Phillips,
DC and Sarma, VR (1965) Structure of hen egg-white lysozyme. A three
dimensional Fourier synthesis at 2 Angstrom resolution. Nature, 206,
757-761. Blake, CCF, Johnson, LN, Mair, GA, North, ACT, Phillips, DC
and Sarma, VR (1967) Crystallographic studies of the activity of hen
egg-white lysozyme. Proc. R. Soc. London Ser. B, 167, 378-388.
Myoglobin was the first reported protein structure. It represented a
milestone in structural biology for which John Kendrew shared the
Nobel Prize in Chemistry in 1962. This structure, along with the work
on hemoglobin being carried out by Max Perutz, set the stage for
developing our emerging understanding of biology at the atomic level.
Myoglobin is a small, bright red protein. It is very common in muscle
cells, and gives meat much of its red color. Its biological function
is to store oxygen obtained from hemoglobin that is carried in the
blood for use when muscles are hard at work. The myoglobin used in the
structure shown was taken from sperm whale muscles. Marine whales and
dolphins have a great need for myoglobin, so that they can store extra
oxygen for use in their deep dives undersea.
PDB ID: 1mbn. Kendrew, JC, Bodo, G, Dintzis, HM, Parrish, RG and
Wyckoff, H (1958) A three-dimensional model of the myoglobin molecule
obtained by X-ray analysis. Nature, 181, 662-666. Watson, HC (1969)
The stereochemistry of the protein myoglobin. Prog. Stereochem., 4,
The structure of ribonuclease was the third protein - after myoglobin
and lysozyme - that was determined by X-ray crystallography. Two
independent ribonuclease structures were reported in 1967.
Ribonucleases are small enzymes that catalyze the breakdown of
single-stranded ribonucleic acid (RNA) by cleaving a phosphodiester
bond. Ribonucleases have many biological functions, such as cutting
harmful RNA into smaller components in order to remove them from the
cell. Ribonuclease's structure contains a cleft in which the RNA is
held during cleavage.
Kartha, G, Bello, J and Harker, D (1967) Tertiary structure of
ribonuclease. Nature, 213, 862-865. Wyckoff, HW, Hardman, KD,
Allewell, NM, Inagami, T, Tsernoglou, D, Johnson, LN and Richards, FM
(1967) The structure of ribonuclease-S at 6 Angstrom
resolution. J. Biol. Chem., 242, 3749-3753.
The science of protein structure began with the structure of
hemoglobin. After years of arduous work, Max Perutz and his coworkers
determined its atomic structure. Perutz's pioneering work in X-ray
crystallography of proteins - including his study of hemoglobin - won
him the Nobel Prize in 1962.
Hemoglobin is the protein that makes blood red. It is composed of four
protein chains - two alpha chains and two beta chains, each with a
ring-like heme group containing an iron atom. Oxygen binds reversibly
to these iron atoms and is transported through blood. Each of the
protein chains is similar in structure to myoglobin, the protein used
to store oxygen in muscles and other tissues.
PDB ID: 2dhb. Bolton, W and Perutz, MF (1970) Three-dimensional
Fourier synthesis of horse deoxyhaemoglobin at 2.8 Angstrom units
resolution. Nature, 228, 551-552. Perutz, MF, Rossmann, MG, Cullis,
AF, Muirhead, G and Will, G (1960) Structure of haemoglobin: a
three-dimensional Fourier synthesis at 5.5 Angstrom resolution. Nature, | <urn:uuid:91854a5c-9bb0-4b50-8bcd-0930adaab1b8> | 3.390625 | 1,202 | Knowledge Article | Science & Tech. | 56.045843 |
Respiration—gas exchange between blood and an outside medium (air or water)—always takes place across a wet membrane whether the organ hosting the blood is a gill or a lung. There is no fundamental difference between gills and lungs. Their essential anatomy is the same: a large surface area overlaying blood vessels. To further increase the surface area for efficient gas exchange, gills are usually branched or filamentous and lungs may be invaginated or branchiate.
A gill is not necessarily restricted to an aquatic medium: if it can stay erect and wet, it will also function in the air. Likewise, a lung can also function in water. In fact, in certain habitats animals with gills can live side by side with animals with lungs.
Here is an example. In this picture are 2 species of tiny snails that I found on a rock that I had pulled out of the sea during the high tide at a Florida beach. The 4 snails with shiny shells are Assiminea succinea, a species in the superfamily Rissooidea. They have small rudimentary gills. The snail with the duller shell near the center-left is Pedipes ovalis in the family Ellobiidae. Like its distant relatives the pulmonate land snails, Pedipes ovalis obtains its oxygen via a lung.
We see that in transitionary seashore habitats snail species with gills and lungs live alongside each other, creating an evolutionary mosaic. | <urn:uuid:fdba3b96-f5e2-4a8b-b711-469805834f36> | 3.9375 | 304 | Personal Blog | Science & Tech. | 44.531538 |
This section describes six possible topics on ocean life that can be incorporated into your science curriculum.
Origins and evolution of life: History of Marine Life
In certain areas, the Hall takes an historical approach to our knowledge about marine life, a kind of study known as phylogenetic evolution. All life on Earth shares a common ancestor and originated in the ocean; evidence suggests that marine life was already present about 3.5 billion years ago. Students can find examples of the history of marine life throughout the Hall.
- Ancient Oceans — Compare three views of ocean life at different points in time: 450 million years ago, 270 million years ago, and 70 million years ago; observe a 1.5-billion-year-old filament of a photosynthetic marine bacteria called cyanobacteria; and touch a stromatolite, a structure formed by communities of microorganisms.
- Tree of Life — The cladograms found here show how groups of organisms relate to each other. Search the touchscreen interactives for detailed information on the species displayed.
Physical setting: Living in Water
The properties of water, such as density (the amount of substance found within a specific volume) and viscosity (the resistance to flow exhibited by a liquid), influence the fundamental structures and ways of life of all marine organisms. For example, locomotion is influenced by the fact that water is denser and more viscous than air. In addition, feeding, respiration, and sensory perception are influenced by other marine characteristics. Food, for instance, is extremely scarce in some areas, water contains less "free" oxygen than air, and areas of the ocean can be completely dark.
- Life in Water — Explore the displays adjacent to the Tree of Life Walls that illustrate biological features, such as breathing, feeding, moving, and reproduction, of different aquatic vertebrates and invertebrates.
- Ecosystem Displays — Study the label text of the eight ecosystems, which provides information on the implications of living in water.
Many marine species possess special adaptations. These are characteristics resulting from the evolutionary process in response to environmental and biological changes. Adaptations permit organisms to live in particular ocean habitats, such as the deep sea or mangrove forests. Some organisms have adaptations that allow them to move from one habitat to another. Certain whales and sharks, for example, can overcome changes in pressure and move from the surface to the deep sea.
- Ecosystem Displays and Marine Mammal Dioramas — These cases suggest some of the challenges that exist for plants and animals and their adaptations for survival. For example, the deep sea ecosystem case highlights adaptations involving bioluminescence (light produced by living organisms), big mouths, and the ability to detect red light. Investigate how these adaptations help animals.
- Diving for Pearls Diorama — Consider how the human body lacks adaptations for life in water.
The displays in the Hall illustrate the amazing diversity of marine ecosystems and reveal the variety of species within each. The health of an ecosystem is related to the ecological balance between its species and the physical environment. This balance is the result of the relationships among the ecosystem species. Each ecosystem is also connected to both surrounding marine ecosystems and some to those on land.
- Mangrove Forests Display — One of the eight ecosystem displays, this example depicts the connection between the mangrove ecosystem and seagrass beds. For example, baraccuda live in mangroves as juveniles and move to seagrass when they mature.
- Comparison of Ecosystem Displays — Ask students to compare two different displays, such as estuaries and the polar sea. What species live in these two ecosystems? What do they eat? What are the morphological (relating to the form, structure, or anatomy of an organism) characteristics of a particular organism living in each ecosystem? How have they adapted?
Conservation: Human Impacts on the Ocean
A complex interrelationship exists between humans and the ocean. Each ecosystem display contains text entitled "Critical Connections," detailing many examples of human-related threats to the ocean, such as pollution, overfishing, and mining. Consider the impact humans have on the ocean based on information found throughout the Hall.
- Open Ocean Label Text — These panels indicate such ongoing threats to marine life such as the overfishing of shark species, the effects of global warming, and the mobility of "long-distance" pollutants like oil, plastic bags, and chemicals such as DDT.
- Video Wall — Watch this video montage for examples of human interaction with and impact on the ocean.
Ocean Impacts on Humans
More than half the world's population—2.7 billion people—lives within 60 miles (100 kilometers) of a coast. The ocean and its resources influence the cultures of communities worldwide, affecting livelihoods, diet, transportation, mythology, and art.
Ask students to consider the following:
- Various ocean resources—marine mammals, birds, fish, and marine plants—may be available to a coastal community but not to a landlocked community. These marine resources serve and influence coastal communities in different ways. Encourage students to extend their investigation beyond the Hall to compare and contrast the use of resources in two different coastal communities.
- Coastal residents benefit from their proximity to the ocean, but may also contend with dangers such as hurricanes, typhoons, and tsunamis. Examine how the ocean affects the weather in different coastal regions around the globe.
- Different countries have different coastlines, or none at all. Coastlines have always been areas where goods and ideas are exchanged. Ask students to explore how bordering the ocean might affect a country. | <urn:uuid:75e0d8ed-00a4-4fce-b559-e6fdc0e2afe0> | 3.78125 | 1,164 | Tutorial | Science & Tech. | 26.800979 |
Solving Triangles by Reflection
A 5ft ladder leans against a wall as shown.
What is the angle between the ladder and the wall?
This is surprisingly easy to solve by using Reflection:
Here is the triangle with its reflection
Together they make an equilateral triangle (all sides equal).
|The angles in an
are all 60°
So the angle between the ladder and the wall is half of 60º
We can use the same idea to find an unknown length.
Alex has a laser that measures distance.
By standing some distance from the tree Alex measures 42m to the top of the tree at an angle of 30º.
What is the height of the tree?
Here is the triangle and its reflection:
Once again the triangle and its reflection make an equilateral triangle.
So, we know the height of the tree must be half of 42m
These examples show that the same triangle can occur in many different situations! | <urn:uuid:cfd3443e-80f8-42aa-a812-27a48f711820> | 3.25 | 200 | Tutorial | Science & Tech. | 64.793326 |
World's Fastest Road
Today, I'm going to get into a car and drive faster than I've ever driven before.
What is special, is not the car, but the road I'm going to be driving on. It may look like a perfectly normal road, but it's got two particular features. It's location and the direction it's heading.
This road is right on the equator and it's heading due east. The speedometer of the car is reading about 96 kilometres an hour. As we travel around the sun, the Earth's surface is spinning through space. And the place where it moves fastest is the equator. The road is spinning at over a 1,000 miles an hour, and because I'm heading due east, the same direction as the Earth's rotation I am travelling at over 1,060 miles an hour! Making this, quite probably, the world's fastest road.
High Speed Road
The Earth moves fastest at the equator, because this is where it's circumference is greatest, so it has the longest distance to travel in a single day.
But this also means that the further away from the equator you go, the slower you turn. Until, if you stood at the poles, you'd barely be moving at all, just rotating gently on the spot in a 24-hour pirouette.
These different speeds create an atmospheric force that has global significance. You can see it in action at one very particular time of the year, when it helps create the most destructive weather event on the planet. | <urn:uuid:ff53844d-eb4f-4efc-aa2d-0d2c2925273c> | 2.796875 | 317 | Personal Blog | Science & Tech. | 69.692124 |
ICESat has provided a critical look at ice thickness at Earth's polar regions over the course of its seven-year life. That mission has now ended.
02.24.10 - ICESat has provided a critical look at ice thickness at Earth's polar regions over the course of its seven-year life. That mission is now coming to an end.
10.19.06 - NASA scientists have found that ice losses now far surpass ice gains in the shrinking Greenland ice sheet.
03.08.06 - NASA scientists confirm climate warming is changing how much water remains locked in Earth's largest storehouse of ice and snow.
12.05.05 - Thanks to satellites, NASA has the best maps to help researchers get around the huge land of ice and snow.
11.18.05 - ICESat fired its one billionth laser shot earthward to obtain elevations from objects on the land, sea and in the air.
12.13.04 - Investigating ice, glaciers, forests, rivers, clouds and pollutants
09.30.04 - Changes in glacier flow surprises researchers.
12.09.03 - Satellite views of Earth's polar ice sheets, clouds, mountains, and forestlands are helping scientists understand how life on Earth is affected by changing climate.
10.06.03 - The principal mission of ICESat is to measure the surface elevation of the large ice sheets covering Antarctica and Greenland.
ICESat will collect data about the Earth using the lasers on the GLAS instrument.› View This Video
Scientists Eager to Study Ice.› View This Video
The newest addition to NASA's fleet of Earth observing satellites has only one scientific instrument called GLAS.› View This Video | <urn:uuid:376d4651-19a0-4b78-8a4d-985c26720709> | 3.734375 | 356 | Content Listing | Science & Tech. | 71.874403 |
Vincent J. Abreu, Paul B. Hays, and Wilbert B. Skinner
The distributions of most chemical species in the stratosphere are affected by both dynamical and chemical processes. Conversely, the distribution of certain photochemical species, such as ozone, can influence the radiative budget of the stratosphere, affecting temperatures and motions. Satellite remote observations of the stratosphere to date have provided only temperature and constituent measurements. The horizontal winds on a global basis have been deduced from temperature fields by using the thermal wind relationships, which relate the vertical shear of the geostrophic wind components to horizontal temperature gradients.
Access to the full text of this article is restricted. In order to view this article please log in. | <urn:uuid:847e10f0-9d8e-4e2a-9e0b-30e00f832315> | 3.203125 | 150 | Truncated | Science & Tech. | 23.823467 |
Sylon hippolytes M. Sars, 1870
|Sylon hippolytes on a Pandalus goniurus shrimp captured at 75 m depth, San Juan Channel.|
|(Photo by: Dave Cowles, August 2008 )|
How to Distinguish from Similar Species: This may be the only Sylon species. Its characteristic sack-like shape is distinctive.
Geographical Range: Arctic, Bering Sea, Chukchi Sea, North Pacific, Sea of Okhotsk, Sea of Japan, North Atlantic, Iceland, Greenland, Shetland Islands, Spitzbergen
Habitat: Parasitic on shrimps from families Hippolytidae (Hippolyte, Heptacarpus, Spirontocaris, Caridion, Eualus, Lebbeus), Pandalidae (Pandalus), and Crangonidae (Sclerocrangon, Crangon, Metacrangon)..
Biology/Natural History: Rhizocephalan barnacles such as this species are bizarrely distorted parasitic barnacles. It was not even known that they were barnacles until the cypris larva in their life cycle was discovered. The eggs of Rhizocephalans usually hatch as a nauplius larva which metamorphoses into a cypris larva. Members of order Akentrogonida, however, such as Sylon hippolyte, apparently pass the nauplius stage in the egg and hatch as a cypris. The female cyprid settles onto a recently molted host or attaches to the host gill. She attaches to the host using a glue gland on her antennae. She then metamorphoses, losing her legs and eyes. She extrudes her tissue through the antenna or through her mouth through the host carapace into the host internal tissue. At that point she may be called a "kentrogon" if she is in order Kentrogonida. The injected barnacle grows into a ramifying rootlike structure called an "interna". The interna begins growing by sending out rootlike projections through the body of the host. These projections absorb nutrients from the host, and typically destroy the gonads (a parasitic castrator). The interna may grow very large and may actually become heavier than the host tissue. When she matures, a part of her body called the "externa" erupts through the exoskeleton of the host, usually on the ventral side of the abdomen near the gonads. The externa has a cavity for eggs and a place for males to attach. Male cyprids settle into the externa and metamorphose into a wormlike structure.
Female shrimp which have this parasite species do not bear eggs, so
the parasite is probably a parasitic castrator as are many Rhizocephalans.
|Main Page||Alphabetic Index||Systematic Index||Glossary|
Butler, 1980 (this is the main reference)
Lamb and Hanby, 2005
O'Clair and O'Clair, 1998
Boschma, H., 1928. Rhizocephala of the north Atlantic region. Danish Ingolf Exp. 3(10). 49 pages.
Boschma, H., 1931. Papers from Dr. Th. Mortensen's Pacific Expedition 1914-1916. LV. Rhizocephala. Viden. Medd. Dan. Naturhist. Foren. Kobenhavn 89: 297-380
Calman, W.T., 1898. On a collection of Crustacea from Puget Sound. Ann. N.Y. Acad. Sci. II: 259-293
Hoeg, J. and J. Lutzen, 1985. Crustacea Rhizocephala.--Marine Invertebrates of Scandinavia 6: 1-92. Norwegian University Press, Oslo, Norway
Hoeg, J. and A.V. Rybakov, 1992. Revision of the Rhizocephala Akentrogonida (Cirripedia), with a list of all the species and a key to the identification of familes. Journal of Crustacean Biology 12(4) 600-609
Smith, G.W., 1906. Rhizocephala. Fauna Flora Golfes Neapel (Berlin) Monogr. 29. 123 pages.
General Notes and Observations: Locations,
abundances, unusual behaviors:
I have not often seen this parasite.
Ventral view of the parasite. The host's thorax is to the left.
The parasite externa is erupting from the ventral side of the hosts first
abdominal segment. The second pair of host pleopods partly overlap
the externa. The texture of the externa looks as if it is packed
with small eggs. | <urn:uuid:93fc102a-fcfe-4a48-a039-699aefc29143> | 3.125 | 1,027 | Knowledge Article | Science & Tech. | 51.048788 |
This is an image showing the cratered surface of the planet Mercury.
Click on image for full size
In addition to being hot, the surface of the Earth was being cratered.
Even though the solar system was finished forming, there were still probably a lot of smaller planetesimals
debris around, too.
gravity of the large planets would attract nearby planetesimals,
which would hit the planets and leave a crater on the planet's
When we look at images of many of the planets such as Mercury, shown here, we see all sorts of
circular craters on the planet surfaces. Most of these craters
were probably formed at this period of history. The cratering eventually tapered off, even though craters are still formed on planetary surfaces today.
Subsequent evolution of a planet's surface, driven by activity within the
planet itself (if the planet were still active), would wipe out any
evidence of this period of cratering. Thus scientists can often trace a planet's age by counting the amount and size of the craters on the surface.
This is page 3 of 10
Shop Windows to the Universe Science Store!
Our online store
includes issues of NESTA's quarterly journal, The Earth Scientist
, full of classroom activities on different topics in Earth and space science, ranging from seismology
, rocks and minerals
, and Earth system science | <urn:uuid:d929a63d-464f-47da-932d-0f4677c47132> | 4.5 | 288 | Knowledge Article | Science & Tech. | 38.204 |
In electron microscopy, scientists bounce electrons off of objects and track their rebound to form images, including 3D models, of the objects in very fine detail, down to picometer scales. While these highly detailed pictures can tell us a lot about how things are, they say somewhat less about how they got that way. To rectify this, several methods are now being developed to watch in a fourth dimension—time. It's now possible to obtain videos at frame rates several orders of magnitude higher than what most other methods can capture, allowing scientists to see processes never before observed in real time and space. A recent review in Science discusses progress in the area.
The more detailed a picture you want to capture, the finer your medium needs to be; for example, you can get a better fingerprint with ink or Silly Putty than with sand. Since electrons are one of the tiniest items we know how to handle, we can bounce them off surfaces and detect their rebound to produce detailed photos of many things on the atomic scale.
Where electron microscopes fall short, though, is tracking changes over time. The electrons in transmission and scanning electron microscopy are sent out in discrete packets and are not continuous like waves of light, so they can only detect shapes to produce one image at a time.
Light, and especially lasers, would seem to be much better suited to producing video of tiny, fast-moving objects. When using light, scientists don't have to account for the Pauli exclusion principle, which limits how many electrons can occupy the same state and creates complications when you'd like to calculate where exactly electrons are. However, light can't image the locations of all the atoms of a complex structure, because the wavelength of the light is too long. Since the wavelength of an electron is much shorter, it should be capable of taking much more detailed video.
To make an electron microscope take video, scientists realized they needed to track the packets they sent out very carefully, timing the intervals between them down to femtoseconds. That means the electron pulses have to be very short. To get the timing right, you need to send out an initial probe pulse to set a reference point of zero time (t = 0), then send pulses of coherent single-electron packets. This process is called "ultrafast electron microscopy," and takes video at frame rates as high as 1012 images every second.
Scientists have used UEM in many ways, including watching sheets of graphene getting jolted off chunks of graphite. Shocking graphite distorts the structure and liberates a sheet of graphene. With four-dimensional electron microscopy, scientists could watch this process happen in very high detail, and see exactly how the graphene sheet separates. They noted that the separation is the result of the carbon lattice expanding for a very short period of time before the graphene sheet pops away.
UEM can also be used to observe very fine, high-frequency and low-amplitude oscillations that scientists have never seen before. When larger pieces of graphite experience heating over longer times, the microscopy videos showed that a strain propagated though it at very high frequencies, up to 30GHz. Since the technique doesn't involve time averaging like other microscopy approaches, it showed several areas where the amplitude and phase of the oscillations varied slightly.
Some materials undergo small, almost undetectable transformations when they are in use. Scientists used UEM to look at nanoscale cantilevers, and were able to see that they vibrated at very high frequencies when in use, sometimes expanding up into the micrometer scale. The microscope also allowed researchers to watch phase changes in much better detail, like the crystallization of silicon.
While the electron packets can now be used to measure changes over time, they can still only take one angle, falling in a sheet on the object that's being observed. To see additional angles, scientists can create a tomograph, which uses electron pulses from multiple angles that can then be patched together to provide a 360-degree view of the object in question.
The possible uses for such detailed video are broad, and we've outlined only a few from the review paper here. The authors mention in particular that the ultrafast electron microscopes could also be used in biological systems, or at least those systems that don't require extensive labeling or freezing. The authors suggest targets might include circulating fluid within cells, imaging proteins in real space, and determining how cryogenic freezing alters the structure of cells in real time. While even one electron microscope is still expensive, the advent of UEM will let scientists pinpoint more complete answers to the how's and why's of their research.
Listing image by NIH | <urn:uuid:b35eb37a-3c69-4030-836d-ab21a115fd95> | 3.75 | 961 | Knowledge Article | Science & Tech. | 34.476805 |
We can see because neurons in our eyes take in visible light and relay electric signals to the brain. But some of the neurons in our retinas detect light that we cannot actually see. In fact, people who lose all their other retinal cells except these neurons are blind. If you shine a light in their eyes and ask them to guess the color, however, they guess very well. It turns out these neurons feed this invisible light to many parts of the brain. In my latest column for Discover, I take a look at this hidden light. Check it out.
Links to this Post
- Podemos Detectar Luz Invisible con Nuestros Ojos. | Pablo Della Paolera | February 17, 2012 | <urn:uuid:5b25c20d-eb3f-4a12-984f-7159e3302081> | 3.046875 | 149 | Personal Blog | Science & Tech. | 66.397648 |
This module implements a file-like class, StringIO, that reads and writes a string buffer (also known as memory files). See the description of file objects for operations (section File Objects). (For standard strings, see str and unicode.)
When a StringIO object is created, it can be initialized to an existing string by passing the string to the constructor. If no string is given, the StringIO will start empty. In both cases, the initial file position starts at zero.
The StringIO object can accept either Unicode or 8-bit strings, but mixing the two may take some care. If both are used, 8-bit strings that cannot be interpreted as 7-bit ASCII (that use the 8th bit) will cause a UnicodeError to be raised when getvalue() is called.
The following methods of StringIO objects require special mention:
import StringIO output = StringIO.StringIO() output.write('First line.\n') print >>output, 'Second line.' # Retrieve file contents -- this will be # 'First line.\nSecond line.\n' contents = output.getvalue() # Close object and discard memory buffer -- # .getvalue() will now raise an exception. output.close()
The module cStringIO provides an interface similar to that of the StringIO module. Heavy use of StringIO.StringIO objects can be made more efficient by using the function StringIO() from this module instead.
Return a StringIO-like stream for reading or writing.
Since this is a factory function which returns objects of built-in types, there’s no way to build your own version using subclassing. It’s not possible to set attributes on it. Use the original StringIO module in those cases.
Unlike the StringIO module, this module is not able to accept Unicode strings that cannot be encoded as plain ASCII strings. Calling StringIO() with a Unicode string parameter populates the object with the buffer representation of the Unicode string instead of encoding the string.
Another difference from the StringIO module is that calling StringIO() with a string parameter creates a read-only object. Unlike an object created without a string parameter, it does not have write methods. These objects are not generally visible. They turn up in tracebacks as StringI and StringO.
The following data objects are provided as well:
There is a C API to the module as well; refer to the module source for more information.
import cStringIO output = cStringIO.StringIO() output.write('First line.\n') print >>output, 'Second line.' # Retrieve file contents -- this will be # 'First line.\nSecond line.\n' contents = output.getvalue() # Close object and discard memory buffer -- # .getvalue() will now raise an exception. output.close() | <urn:uuid:849ddf84-9bbd-4596-9111-26d14f3d39a4> | 3.171875 | 597 | Documentation | Software Dev. | 52.0125 |
The illumination from a bulb varies directly as the intensity of the light and Intensity varies inversely as the square of the distance from the source. Two bulbs are placed 54 feet apart. The intensity, Ia, of bulb A is 64cd, and the intensity, Ib, of bulb B is 125cd. At how many feet from bulb A along the line between the two bulbs is the total illumination the least?
I have no idea how to start this problem...I thought about using optimization but I'm not sure where to start | <urn:uuid:cbffcca7-aabb-4730-8895-b0d4e15e737f> | 3.28125 | 108 | Q&A Forum | Science & Tech. | 67.514565 |
ASP.NET books Page2 Posted on: February 14, 2008 at 12:00 AM
ASP.NET is a web programming platform developed by Microsoft. It is the successor to Active Server Pages.
ASP.NET books Page2
Introduction of ASP.NET ASP.NET is a web programming platform developed by Microsoft. It is the successor to Active Server Pages. The term "classic ASP" is often used to distinguish previous versions of Active Server Pages with the .NET
versions. This wikibook is an introduction to ASP.NET. It assumes no prior experience with web programming or with any particular web programming language or platform (including classic ASP), though we will often compare ways of doing things in ASP.NET with ways of doing them in other languages, especially PHP. We believe the differences between classic ASP and ASP.NET are substantial enough to merit separate treatment.
Introduction of ASP.NET database
The Microsoft. NET framework comes with several namespaces to manage data in databases. .NET also comes with SQL Server and Oracle native providers. A native provider will only work with one database product, and uses the native database more efficie
ntly. There are several generic database classes, however if you are using a database that has a native provider, use it.
A database is essentially a place to store data. However the key to understanding the term "database" is that a database is an electronic warehouse for storing data.
The Application: Microsoft.NET and J2EE This book gives you the best information available about how to ensure that enterprise applications based on J2EE work in harmony with components based on Microsoft .NET and vice versa. If you are developer with responsibility for implementing interoperability between these two platforms in an enterprise environment, then this book is for you.
The information in this book is both practical and prescriptive. Rather than discuss every possible interoperability technique in detail, it focuses on the three most likely scenarios and shows how to solve those specific challenges. | <urn:uuid:a155225e-a562-4b85-bb57-377d2b88302f> | 2.765625 | 407 | Truncated | Software Dev. | 38.637604 |
Specify the font of text:
The face attribute is supported in all major browsers.
The <font> tag is not supported in HTML5. Use CSS instead.
The face attribute of <font> is deprecated in HTML 4.01.
The face attribute specifies the font of the text inside a <font> element.
Tip: The value of the face attribute can hold several font names as a "fallback" system. List the font that you want first, followed by any fonts that can fill in for the first, if it is unavailable. You should end the list with a generic font (serif, sans-serif, monospace, cursive or fantasy), to let the browser pick a font that is in the generic family, if no other fonts are available.
The face attribute of <font> is deprecated in HTML 4.01. Use CSS instead.
CSS syntax: <p style="font-family: verdana">
In our CSS tutorial you can find more details about the font-family property.
|font_family||The font of the text. To specify a prioritized list of several fonts, separate the names with a comma (like this <font face="verdana,arial,sans-serif">|
Your message has been sent to W3Schools. | <urn:uuid:a9893c15-9ef0-4036-8d20-cb19bcbab06c> | 2.6875 | 275 | Documentation | Software Dev. | 63.418 |
Science subject and location tags
Articles, documents and multimedia from ABC Science
Thursday, 26 July 2012
About half the protected tropical forest areas in the world are losing biodiversity due to pressures both within and from outside the reserves, according to a new study.
Thursday, 15 September 2011
There's no substitute for old growth forests when it comes to protecting tropical species from extinction.
Thursday, 14 July 2011
The more carbon dioxide goes into soil, the more the soil releases other, more potent, greenhouse gases.
Monday, 20 June 2011
Schemes to regrow forests will make almost no inroads against global warming this century.
Wednesday, 30 March 2011
Large-seeded trees rely on native birds for their survival, New Zealand biologists have confirmed.
Friday, 22 October 2010
Plants, especially some trees under stress, are even better than expected at scrubbing certain chemical pollutants out of the air, researchers report.
Thursday, 11 February 2010
Commercial logging of moist native forests creates conditions that increase the severity and frequency of bushfires, an international study claims.
Friday, 4 December 2009
A program aimed at protecting forests in developing countries to save on carbon emissions could be used to also help slow down the rapid loss of the planet's species, say researchers.
Tuesday, 16 June 2009
Mountain ash forests in Australia are the best in the world at locking up carbon, a new study has found.
Thursday, 11 September 2008
Old-growth forests remove carbon dioxide from the atmosphere, helping to curb the greenhouse gases that drive global warming, according to a new study.
Wednesday, 20 August 2008 6
Green Guru Is non-recycled paper the answer to our environmental problems???
Thursday, 14 August 2008
Game Can you save a water catchment in distress? Play Catchment Detox to see if you can repair a damaged river catchment and create a sustainable and thriving economy.
Monday, 11 August 2008
A hormone that can literally stop trees branching out has been discovered by an international research team, who say the find could improve productivity of crops around the world.
Friday, 27 June 2008 3
Green Guru Some bits of paper weren't meant for recycling ...
Wednesday, 11 June 2008
Gels or sprays infused with the scent of dingo could one day offer a humane way of keeping kangaroos and other marsupials out of places they're not wanted, researchers say. | <urn:uuid:2c562245-8c10-4f14-8b34-ed5bb697ce23> | 3.171875 | 499 | Content Listing | Science & Tech. | 48.430269 |
Science Fair Project Encyclopedia
Once a local coordinate system xi is chosen, the metric tensor appears as a matrix, conventionally denoted G. The notation gij is conventionally used for the components of the metric tensor (i.e. the elements of the matrix). In the following, we use the Einstein notation for implicit sums.
The length of a segment of a curve parameterized by t, from a to b, is defined as:
- G = JTJ
The Euclidean metric
Given a two-dimensional Euclidean metric tensor:
The length of a curve reduces to the familiar calculus formula:
The Euclidean metric in some other common coordinate systems can be written as follows.
Polar coordinates: (x1,x2) = (r,θ)
Cylindrical coordinates: (x1,x2,x3) = (r,θ,z)
Spherical coordinates: (x1,x2,x3) = (r,φ,θ)
Flat Minkowski space: (x1,x2,x3,x4) = (t,x,y,z)
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Adding a tree parser stage
In the section about the token parser we revealed the structure of an XML document to be a tree. You did not see pretty much of it, though. The reason is that you did not actually build up any data structure from what you revealed. Such a data structure usually is described as an AST (abstract syntax tree), a tree structure that mimics the structure of the parsed input. In this section you will see how to build up such a structure and also how to traverse it using tree parsers.
Tree parsers do not consume flat streams of tokens, both rather structured trees of tokens generated by the token parser. Usually, all redundant data is stripped from those trees and their internal structure is most natural. One example of redundant data is an end tag. Its purpose in a flat stream is to indicate where an element ends. Such structure can, however, be expressed in a two dimensional tree. No need for an end tag. An example of a token that can be completely skipped is the equal sign (=) between attribute name and value. It is there for better human readability, but actually does not carry any meaning. Finally, there is good reason to consider an empty element equivalent to a start tag directly followed by an end tag. This can be unified.
Even though this is not a common approach, let us start with the tree grammar that looks most natural and simple. Later you can find out how tree construction must look like to produce a tree matching this grammar. To achieve this, let us remember that an XML document is a representation of a tree structure. Leaf nodes are either empty elements or text data. Non-leaf nodes are always elements that enclose other elements or text. Additionally, there are attributes and finally names that are associated to elements. It turns out that you can easily write all this in a single rule:
Cute, isn't it? This rule expresses the whole stammering above. The ^ symbol before an opening bracket indicates a hierarchical tree structure with the first item after the bracket being the root of the tree and the rest being the children. In this case we have a token called ELEMENT that tells us what follows actually is an element. The first child is GENERIC_ID which is the name of the element, then we have a list of attributes and finally the element's sub elements potentially mixed with text. All attributes are again structured as a tree.
To complete the tree grammar we just need to add the header that tells the tree parser to use the same token vocabulary as the lexer and the parser and we are done:
For real processing of the tree you certainly would want to access the text of the tokens. In ANTLR 3 you do this by
where name is the label of a tree element like name=GENERIC_ID. You need to tell ANTLR about the type of your tree and also need to introduce a start rule. This is the complete tree grammar that simply dumps the whole AST back to XML:
You now have to augment the parser you have already seen above with tree construction statements. In ANTLR 3 tree creation and matching syntax is very similar. You can actually declare how the constructed tree is supposed to look like by duplicating the grammar fragment that matches the tree. E.g. for the tree construction of the attribute part we could write:
where the tree construction part that comes after the -> is exactly the same as the fragment seen in the tree grammar above. Isn't that cool? It, however, turns out that tree construction declaration by example isn't sufficient in all scenarios. For example we want our end tag to be omitted completely. That's what the ! operator is for. You can either apply it to a full rule by placing it behind a rule name like in
or to a single item (endTag again) in a rule like in
You will notice that this is the element rule you already are familiar with. Next to the ! we can see the double ^ here. This operator declares startTag to be the root of the generated tree. As you can see, this does not only work for a single token, but also for complete sub trees! Additionally, we make use of the automatic tree construction feature already known from ANTLR 2. Left hand items without declaration will simply result in a flat tree node.
Finally, we have the two rules for start tags and empty elements
which generate a unified tree for both complete as well as for empty elements. As you might have noticed, we are using new token names which we have to declare. This results in this grammar head:
That's our complete parser grammar that actually creates an AST:
Never has tree construction been easier! Finally, the glue code:
When you feed in an example that is a bit more complex, like:
This is what your parser spits out:
The first part of the output is the result of the toStringTree() method call from our glue code. The formatted XML is printed by the actions inside our tree parser. And, wow! So, what you have built is an XML unifier and pretty printer.
As you have now mastered this complete trail through all ANTLR parser types you may ask yourself where to go from here. A good idea is to have a look at the examples provided with ANTLR3. Another good starting point is the ANTLR3 main page and of course the Wiki documentation which this tutorial is part of. If you have any questions concerning ANTLR or this tutorial or any fixes or enhancements to this tutorial feel free to contact the ANTLR mailing list. Obvious corrections to this tutorial can be applied directly to the Wiki.
My siblings (including me): | <urn:uuid:16ef81ad-52f4-4d48-bd17-3b271455cc7d> | 3.1875 | 1,172 | Tutorial | Software Dev. | 57.711686 |
Over a period of time the perception of building
applications is changing very rapidly whatever it may be either desktop
applications, web applications or distributed applications. Now a days it has
become the practice to build applications as set of components that are
distributed across a network of machines and work together as if all the sets of
components are available from the single machine. Traditionally, distributed
application logic known for DCOM, CORBA or RMI, laid reliable and scalable
platform to meet the growing needs of applications.
technologies work very well in an intranet environment. Only thing is we cannot
use this technology over the internet because the technologies do not
pinch over Webservices Vs Remoting.
applications, in contrast, are loosely coupled and remarkably interoperable.
They communicate using HTTP to exchange MIME-typed data in a wide range of
formats. Web services adapt the traditional Web programming model for use from
all sorts of applications, not just browser based ones. They exchange SOAP
messages using HTTP and other Internet protocols. Because web services rely on
industry standards, including HTTP, XML, SOAP and WSD, to expose applications
functionality on the Internet, they are independent of programming language,
platform and device.
Thanks to Microsoft
inventing of ASP.NET Web services and .NET Remoting. Web services infrastructure
provides a simple API for Web services based on mapping SOAP messages to method
invocations. This is achievable by providing a very simple programming model
based on mapping SOAP message exchanges to individual method invocations. The
clients of Web services do not have to know anything about the platform, object
model, or programming language used to build them and vice versa (i.e. the
services also unaware of the clients sending them messages). Only thing is both
the parties should follow a protocol on the format of the SOAP message being
produced and consumed.
.NET Remoting provides
an infrastructure for distributed objects. It exposes full object semantics of
.NET to remote processes using plumbing that is both flexible and extensible.
.NET Remoting offers much more complex functionality, including support for
passing objects by value or by reference, callbacks, and multiple-object
activation and lifecycle management policies. In order to use .NET Remoting, a
client needs to be built using .NET.
To put in simple words
using object references to communicate between server objects and clients is the
heart of Remoting. The Remoting architecture, however, provides the programmer
with an even simpler procedure. If anyone configures the client properly, we
need only to create a new instance of the remote object using new keyword, then
client receives a reference to the server object and rest of the things are as
usual ( like invoking methods) as the object were in your process though it is
running on a separate computer.
Suppose we have an
application running on one computer, and we want to use the functionality
exposed by a type that is stored on another computer, below depicted is typical
How the data is getting marshaled. We
discuss the same in below:
Serialization and Metadata:
communication plumbing ultimately does two things:
1. marshals instances
of programmatic data types into messages that can be sent across the network is
accomplished using some form of serialization engine or marshaller.
2. provides a
description of what those messages look like is achieved through some form of
For instance, for most DCOM interfaces, the serialization engine was the Type
Library Marshaler and type libraries provides the metadata.
The key difference
between ASP.NET web services and .NET Remoting is in how they serialize data
into messages and the format they choose for metadata.
.NET Remoting Marshals Data
.NET Remoting relies
on the pluggable implementations of the IFormat interface used by the
System.Runtime.Serialization engine to marshal data to and from messages. .NET
Framework provides two standard formatters:-
and SoapFormatter as the name suggest marshal types in binary and SOAP format
respectively. For metadata .NET Remoting relies on the CLR assemblies, which
contain all the relevant information about the data types they implement and
expose it via reflection. The reliance on the assemblies for metadata makes it
easy to preserve the full runtime type-system reliability. As a result, when the
.NET Remoting marshals data, it includes all of a class's public andprivate members.
However, as we
mentioned above relying on runtime metadata for marshalling also limits the
reach of a .NET Remoting system - as Client has to understand .NET constructs in
order to communicate with a .NET Remoting endpoint.
As an addition to the
flavor, the .NET Remoting layer supports pluggable channels how messages are
sent. There are two standard channels for the message transfer, independent of
format (i.e. Binary format or Soap format) both TCP
Channel and HTTP
Channel provides an
implementation for a sender-receiver channel that uses the HTTP protocol to
As mentioned above in
the state management options, there are three types of objects that can be
configured to serve as .NET remote objects. Choose the type of object depending
on the requirement of the application.
- Single Call : Single Call objects service one and only one request coming in. Single Call objects are useful in scenarios where the objects are required to do a limited amount of work. Single Call object are not required to store state information, in fact they cannot hold state information between method calls.
- Singleton Objects : These objects service multiple clients and hence share data by storing state information between client invocations. They are useful in cases in which data needs to be shared explicitly between clients.
- Client-Activated Objects : These objects are server-side objects that are activated upon request from the client. When the client submits a request for a server object using "new" operator, an activation request message is sent to the remote application. The server then creates an instance of the requested class and returns an ObjRef back to the client by using which proxy is then created. These objects can store state information between method calls for its specific client. Each invocation of "new" returns a proxy to an independent instance of the server type.
Life Time of Remote Object.
In typical, for
the objects that have object references that are transported outside the
application, a lease is created. The lease has a lease time; when the lease
reaches zero it expires and the object is disconnected from the .NET Remoting
Framework. Once all the references to the object within the AppDomain have been
freed, the object will be collected when the next garbage collection occurs. The
lease controls the lifetime of the object.
To sum up points:
- .NET Remoting favors the runtime type system and provides a more complex programming model with much more limited reach.
- .NET Remoting gives the flexibility to host remote objects in any type of application including a Windows Form, a managed Windows Service, a console application or the ASP.NET worker process. Both the channels (TCP and HTTP) provide communication between sending and receiving processes using sockets.
- .NET Remoting infrastructure is extensible. It can be possible to filter inbound and outbound message, control aspects of type marshaling and metadata generation. It is possible to implement custom formatters and channels using .NET Remoting.
- .NET Remoting, hosted in IIS with ASP.NET can leverage all the security features available to ASP.NET Web Services. If we use TCP or HTTP channel hosted in processes other than aspnet_wp.exe, we have to implement authentication, authorization and privacy mechanisms by our own.
- .NET Remoting supports a range of state management options (depends on object lifetime scheme SingleCall or Singleton objects).
- In terms of performance .NET Remoting provides the fastest communication when we use TCP channel and the binary formatter.
Building the sample application:
In the below example
we consider an example, the remote object which exposes two methods adding and
subtracting given two numbers.
application that uses .NET Remoting to communicate across application domain
boundaries is very straightforward:
1. You must have an
implementation of a remotable type.
2. A listening or host application domain.
3. A client or calling application domain.
4. And you must configure the remoting system in each application domain to use
remote activation for the remotable type.
The above process
applies no matter how complex or simple the remoting scenario becomes.
We discuss each of the
above in following:
- Building Remotable Type: We discuss in brief about how to build the remotable type. To enable objects in other application domains to use an instance of the class, the class must inherit from MarshalByRefObjet. The following code example shows a simple object that can be created and invoked from objects executing in another application domain.
Public Class MathLibrary
: Inherits MarshalByRefObject
Private result As Integer
Public Function AddTwoNumber(ByVal num1 As Integer, ByVal num2 As Integer) As Integer
result = num1 + num2
Public Function SubtractTwoNumber(ByVal num1 As Integer, ByVal num2 As Integer) AsIntegerresult
= num1 - num2
End FunctionEnd Class
Store the above file as
MathLibrary.cs in your own directory. Compile this file as dll from the command
prompt as below:
/noconfig /t:library MathLibrary.cs.
Building a Host Application.
job is not over by simply creating MathLibrary. To create instances of this
object remotely, you must build a host or listener application which does two
- Choose and register a channel, which is an object that handles the networking protocols and serialization formats.
- Register your type with the .NET Remoting system so that it can use your channel to listen for requests for your type.
remote configuration is done on a per-application-domain basis, the application
domain must be running to listen for requests.
important thing is that unlike COM, Remoting does not start the host or server
application by its own.
following code implements a simple MathLibrary host application domain that uses
a configuration file.
Public Class Listener
Public Shared Sub Main()
Console.WriteLine("Listening for requests. Press Enter to exit")
Store the above code as
Listener.cs in the same directory as where MathLibrary.dll is created. Compile
Listener.cs with reference to MathLibrary.dll as below:
Since the above code snippet
uses Listener.exe.config file to listen to it's remotable type we need to create
the Listener.exe.config file in the same directory where we created the Listener.exe.
<wellknown mode="Singleton" type="MathLibrary,
MathLibrary" objectUri="MathLibrary.rem" />
<channel ref="http" port="8989"/>
Building a Client Application:
now we have created MathLibrary, Host Application for the Remoting. Our
application must register itself as a client for the remote object and then
invoke it as residing in the client application domain. The .NET Remoting system
intercepts the client calls, forward them to the remote object, and return the
results to your client.
Public Class Client
Public Shared Sub Main()
'INSTANT VB NOTE: The
local variable lib was renamed since it is a keyword in VB:
Dim lib_Renamed As MathLibrary
= New MathLibrary
Dim num1 As String =
Dim num2 As String =
Store the above code as
Client.cs in the same directory as where Client.exe is created. Compile
Client.cs with reference to MathLibrary.dll as below:
/noconfig /r:MathLibrary.dll Listener.cs.
Since the above code snippet
uses Client.exe.config file to listen to its remotable type, we need to create
the Client.exe.config file in the same directory where we created the
MathLibrary" url="http://localhost:8989/MathLibrary.rem" />
Now every thing
is ready to run your application:
the command prompt(from the directory where you created the Client.exe and
Listener.exe) type Listener.exe.
From the command prompt(from
the directory where you created the Client.exe and Listener.exe) type
sure that while you are running your Client, Listener should be running to
accept the requests from the client. | <urn:uuid:69873a97-58c6-429e-bf68-6d0de914cbc7> | 2.75 | 2,708 | Documentation | Software Dev. | 38.046426 |
There are a huge number of effects of climate change.
Already, millions of people are dying each year.
The latest reports predict that over 100 million people could die by 2030 if the world fails to take action.
Each year, an increasingly larger amount of people will be affected with over 90 % of victims living in developing countries.
Climate change will not solely cause an increase in the average surface temperatures across the globe, a phenomenon known as global warming.
In reality, it will cause an increase in both the number and ferocity of
Even more alarming, the ten hottest years on record all occurred since 1998. The hottest of all was 2010.
In that year, hundreds of wildfires swept through Siberia and British Columbia, Canada.
It is clearly not a coincidence that the warmest years on record have brought forth the worst hurricane seasons, wild fires and heat waves ever seen.
The Internal Displacement Monitoring Centre reports that there were over 42 million environmental refugees in Asia and the Pacific during 2010 and 2011.
These people were displaced because of rising sea levels, drought, storms, floods, and heat and cold waves.
There are now more environmental refugees than political and war refugees combined.
Unfortunately, experts predict that there will be over 150 million refugees by 2050.
However, the effects of climate change include a change in weather patterns, precipitation, sea level rise, and wildlife.
A combination of changes in precipitation and weather patterns will bring forth droughts in one sector and great floods in a neighbouring areas.
This has drastic consequences on human life as well as ecosystems. It will even have a large impact on agriculture.
From National Geographic
The intensity, frequency, and duration of tornadoes are increasing due to climate change.
In the United States, they cause billions of dollars in damages annually.
In passing, it should be noted that all the effects of climate change combined will cause hundreds of billions of dollars in damages in the upcoming decades.
Dust storms, also known as sandstorms, will have tremendous consequences on agriculture.
Moreover, it will spread disease and pollution to hundreds of thousands of people around the world.
Floods cause devastating damage and affect millions of people each year. With climate change, they are getting more destructive.
An example would be events that have unfolded in Zhejang province, China in June 2011.
The worst drought in 50 years has been followed by deadly floods. Over half a million people have been evacuated and a great number of crops have been destroyed.
Sadly, over a hundred people were killed in landslides. These extreme weather events are repeating themselves across the world and are getting worst each year.
Incredible floods in Pakistan and Australia have occurred not too long ago. In the 2010 Pakistan floods, there was an estimated 43 billion dollars in damages.
By the end of it, 20 million people were affected. In Australia, several incredible floods have occurred.
Yet another of the effects of climate change is the shrinking of lakes.
A decrease in precipitation caused by climate change has caused lakes to decrease in size.
A combination of the effects of climate change and population pressures has caused Lake Chad in Africa to shrink by over 90% since 1963.
As a result, 30 million people living in the region are now competing over scarce water resources.
Even worse, although Lake Chad was once one of the largest lakes in the world, it could disappear in about 20 years.
This has caused millions of
people to immigrate to new locations. In many cases, children are forced
to travel several kilometers on a daily basis in order to obtain drinking water.
Mass desertification is occurring at an increasing rate and is one of the least known effects of climate change.
Millions of square kilometers of once agricultural land have become barren. Any lakes or rivers in its path have disappeared.
There are over a 100 countries, primarily in Africa, Asia and Latin America that are currently affected by desertification.
Shortages of food and water will become commonplace in the future.
As the world population is growing, there is a higher demand for these vital resources.
However, agricultural output in many regions of the world is depleting because of drought, desertification, heat waves, wildfires, and changes in precipitation.
The mass extinction of species is one of the most troubling effects of climate change.
We humans have the technology to help us adapt to drastic changes in weather patterns but animals do not stand a chance.
Do not be mistaken, the climate has changed for millions of years. However, in the last few decades it has changed at such a rate that animal life could not adapt to it.
Evolution is a process that requires millions of years and life has a remarkable ability to adapt.
However, when it changes in mere decades as opposed to millions of years, all life on Earth is severely affected.
In fact, some experts predict that over 1 million species could become extinct by 2050.
Ocean acidification is yet another effect of climate change.
The increasing PH of oceans due to carbon dioxide being absorbed will affect marine life at the bottom of the food chain.
As a result, the entire food chain is being affected and eventually, land animals that are dependent on fish will suffer as well.
In the worst case scenario, it is possible that ocean acidification will wipe out almost all ocean life.
The polar ice caps as well as glaciers around the world play an important role in regulating temperature by not only absorbing heat, but also by reflecting the sun's light (see albedo).
Moreover, glaciers play an integral role in forming the world's perennial rivers which are responsible for agriculture that much of the world population is dependent on.
Hence, if these glaciers melt, millions of people will have to struggle for water, and wars over natural resources may occur in the far future.
Additionally, when ice in Antarctica or glaciers in Greenland melt, they will contribute to rising sea levels.
Rising sea levels will inundate millions of acres of agricultural land which will just add to the declining food supply caused by desertification.
Furthermore, rising sea levels will inundate some of the largest cities in the world such as New York City, Shanghai and Amsterdam. Needless to say, Venice will be in hot water.
Nearly 100 million people live within 1 meter (nearly 3 feet) from average sea level and thus will potentially lose their homes.
Malaria alone could spread to millions of people in the near future and will have devastating consequences.
Moreover, it will increase salmonella outbreaks.
As aforementioned, climate change will increase the frequency and intensity of dust storms which will also spread disease.
The spread of disease and food poisoning is among the least known effects of climate change.
The effects of climate change are extremely important in today's society and will have a large impact on human life across the world.
In the future, wars over natural resources could result in millions or even billions of casualties.
Indisputably, climate change is mankind's greatest challenge and we cannot afford to ignore it any longer.
Please, do your part to help stop climate change.
Have your say about what you just read!
Please, leave a comment below. I started my website over a year ago and will do my best to improve it for you, my visitors. Truly, I would love to hear from you and I strongly appreciate any feedback :)
Sincerely, Laurent Cousineau
Founder of Climate-Change-Guide.com
My site now receives hundreds of visitors a day from over 160 countries, and I want to thank each and every one of you.
Together, we can make a difference. Together, we can help build a better future.
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The patterns of anomalous ocean temperatures,
atmospheric circulation and precipitation are consistent in indicating La Niña
conditions in the tropical Pacific.
During January negative equatorial SST anomalies less than –0.5ºC were
observed at most locations between the date line and the South American
coast, while anomalies greater than +0.5ºC were restricted to the region
between Indonesia and 160ºE (Fig. 1). Negative SST
departures increased in magnitude in the Niño 4 and Niño 3.4 regions (Fig.
2), as the oceanic cold tongue strengthened in the central equatorial Pacific.
During January above-average precipitation (negative OLR anomalies, Fig.
panel) was observed over Indonesia, the Philippines and northern Australia, while
below-average precipitation (positive OLR anomalies) was observed
over the central equatorial Pacific. Stronger-than-average low-level
(850-hPa) easterly winds (Fig. 3, middle panel) persisted over the central
equatorial Pacific, and anomalous upper-level (200-hPa) cyclonic circulation
centers were observed in both hemispheres (Fig. 3, bottom panel). These
patterns are similar to those observed during previous La Niña episodes.
past several months most of the statistical and coupled model forecasts have
trended towards cooler conditions in the tropical Pacific through mid-2006.
The spread of the most recent statistical and coupled model forecasts (weak La Niña
to ENSO-neutral) indicates some uncertainty in the outlooks.
However, current conditions (stronger-than-average easterly winds over the
central equatorial Pacific) and recent cooling trends in observed oceanic
conditions support continuation of La Nina conditions in the tropical Pacific
during the next 3-6 months.
Based on current conditions in the tropical Pacific, the most recent SST
predictions, and on results from historical studies on the effects of cold
episodes, we expect wetter-than-normal (drier-than-normal) conditions to
prevail over Indonesia/Philippines (central equatorial Pacific) during the
remainder of the NH winter. That pattern of tropical precipitation favors a
northward shift in the position of the jet stream over the eastern North
Pacific during winter, which is usually accompanied by drier-than-normal
conditions over southern California and Arizona. The recent patterns of anomalous
temperature and precipitation for the United States (Fig.
4) are similar to
wintertime patterns observed during previous La Niña
episodes (Fig. 5), except for temperature over the northern Plains and in the
Pacific Northwest, which are normally colder than average.
This discussion is a consolidated effort of NOAA and its funded institutions. Weekly updates for
SST, 850-hPa wind, OLR and features of the equatorial subsurface thermal structure are available on the Climate
Prediction Center web page at http://www.cpc.ncep.noaa.gov (Weekly Update). Forecasts for the evolution of El Niño/La Niña are updated monthly in the
Forecast Forum section of CPC's Climate
Diagnostics Bulletin. The next ENSO Diagnostics Discussion is scheduled for | <urn:uuid:0a742f85-526a-483b-b485-f0bfc6244e5d> | 2.71875 | 687 | Academic Writing | Science & Tech. | 26.180756 |
April 15, 2011
Insects have a highly sensitive sense of smell. Extremely low concentrations of odour molecules in the air are sufficient to be detected by receptor neurons on their antennae. Specific proteins, so-called receptor proteins, expressed in these neurons recognize the odours. The odour molecules bind to the receptors and produce chemical and electrical signals that are processed in the insect brain and eventually affect the insect’s behaviour.
Apart from the receptors, further proteins involved in olfaction, including enzymes and chemosensory proteins, come into play. Based on these molecular principles, all insects follow their innate and elementary survival formula: finding food, recognizing mates, and − in case of females − identifying adequate oviposition sites that guarantee nutritious and easily digestible food for their offspring.
Moths (Lepidotera) are popular research objects in addition to fruit flies. The genome of the silkworm Bombyx mori has been fully sequenced. This insect, however, has been domesticated by humans for thousands of years, therefore its native conspecifics can no longer be found. On the other hand, the “habits” of the tobacco hornworm Manduca sexta, a moth species native to North America, have been the subject of intense physiological investigations to study the insect olfactory system, and recently also because its host plant, wild tobacco Nicotiana attenuata, has advanced to an important model plant in ecological research.
Genetic analysis of the Manduca sexta antennae closes a gap in the search after the insect’s odour-directed behaviour: The release of stress-induced odour molecules by tobacco plants is well studied, as is the pollination of the flowers by the moths. “But how does the plant odour – metaphorically speaking − end up in the insect’s brain?”, asks Bill Hansson, director of the Department of Evolutionary Neuroethology founded in 2006 at the Max Planck Institute.
The scientists identified the antennal transcriptome as an important basis for studying olfactory function of the insect and sequenced all active genes in the antennae completely. Additionally, they determined the amount of individual messenger RNAs (mRNAs) that belong to each gene. Sequence information which involved more than 66 million nucleotides was analyzed. Basically, the results can be summarized as follows:
i.) Manduca sexta has 18 specific odorant binding proteins (OBPs) and 21 chemosensory proteins (CSPs).
ii.) Manduca males possess 68 different odorant receptors, each expressed in a specific type of neuron coupled to a corresponding glomerulus in the brain, whereas females have 70 of these “response units”. Most of the receptors could be identified in the course of these studies.
iii.) 69% of the transcripts could not be assigned to a specific gene function: their role in the antennae is so far unknown. Presumably there are many more neural mechanisms of stimulus processing in the antennae that are yet to be elucidated. Some mRNAs imply that there is intense enzymatic activity, esterases for instance; there is also a larger amount of transcripts that regulate gene expression, indicating that the antenna can react to new situations by gene regulation.
iv.) Antennal genetics do not seem particularly complex: For comparison: there are almost twice as many active genes in the larval midgut as in the antennae of an adult moth. Only 348 genes are exclusively expressed in males; females, after all, claim 729 genes as their own. This may be due to their life sustaining formula to lay their fertilized eggs in ideal places, such as wild tobacco leaves, where young larvae can feed. | <urn:uuid:c9b249b5-351e-4111-81b0-077fbdf26506> | 3.953125 | 779 | Knowledge Article | Science & Tech. | 25.848158 |
Simple Harmonic Motion
All of the statements in Section B, aside from those dealing
with the terminology utilized in this work, can be deduced directly from
the postulates. Hereafter, the deductions will be cumulative; that is,
each statement may be a consequence, wholly or in part, of some conclusion
or conclusions previously stated.
- While the progression is normally outward (positive), it is possible,
within the limits imposed by the postulates, for certain motions to
take place in the inward (negative) scalar direction. One such possibility
is a single negatively directed unit of translational motion. This
makes possible the existence of simple harmonic motion, in
which the scalar direction of movement reverses at the end of a unit
of space, or time. In such motion, each unit of space is associated
with a unit fo time, as in unidirectional translational motion, but
in the context of a stationary, three-dimensional spatial (or temporal)
reference system, the motion oscillates back and forth over a single
unit of space (or time), and from the standpoint of such a system
of reference, this is a vibratory motion in which one unit of space
(or time) is associated with n units of time (or space).
- At this stage of the development, no mechanism is available whereby
changes can take place, and only continuous processes are
possible. At first glance, therefore, it might appear that the reversals
of scalar direction at each end of the basic unit are inadmissable.
However, the changes of direction in simple harmonic motino are actually
continuous, as can be seen from the fact that such motion is a projection
of circular motion on a diameter. The algebraic sum of hte positive
and negative motions varies continuously from +1 at the midpoint of
the forward movement to zero at the positive end of the path of motion,
and then to -1 at the midpoint of the reverse movement and zero at
the negative and of the path.
- As indicated in Section B, the inherent scalar direction (positive
or negative) of a motion in space (or in time) has a direction with
reference to any stationary coordinate system, a vectorial direction,
we may call it. This vectorial direction is independent of the scalar
direction, except to the extend that the same factors may, in some
instances, affect both. As an analogy, we may consider a motor car.
The motion of this car has a direction in three-dimensional space,
while at the same time, it has a scalar direction, in that it will
be moving either forward or backward. As a general proposition, the
vectorial direction of this vehicle is independt of its scalar direction.
The car can run forward in any vectorial direction, or backward in
any direction. However, if it is traveling on a very narrow road,
and going forward when it moves south, then it must reverse the scalar
direction and travel backward in order to move north. Similarly, the
simple harmonic motion reverses both the scalar and the vectorial
directions at each end of its one-unit path. This unit of space (or
time) therefore remains stationary in the dimension of the motion
when viewed in the context of a stationary three-dimensional coordinate
- But the linear motion of the vibrating unit has no component in
the dimensions perpendicular to the line of oscillation, and the normal
progression of space-time is therefore operative in these dimesions.
The absolute location of the vibrating unit consequently moves outward
at unit speed in a direction perpendicular to the line of vibration.
The combination of a vibratory motion and a linear motion perpendicular
to the line of vibration results in a path which has the form of a
sine curve. The vectorial direction of the progression is purely a
matter of chance, and if a substantial number of these vibrating units
originate coincidentally, it will be observed that they move outward
in all directions from the point of origin. traveling at unit speed,
and following a wave-like path.
- Inasmuch as the theoretical phenomena emerge from the development
without labels it is necessary to identify the physical phenomenon
corresponding to a theoretical derivation before the two can be compared.
However, this identification is easily accomplished by comparing the
characteristics of the physical and theoretical phenomena. In most
cases, the correlation is obvious, and in any event, the verification
of the identification is automatic, as any error will quickly show
up as a discrepancy.
- The identity of the physical counterpart of the theoretical vibrating
unit is obvious. This unit is a photon. The process of emission
and movement of the photons is radiation. The space-time
ratio of the vibrations is the frequency of the radiation,
and the unit outward speed of movement is the speed of radiation,
more familiarly known as the speed of light.
- One of the most difficult problems with respect to radiation has
been to explain how it can be propagated through space without some
kind of a medium. This problem has never been solved other than by
what has been described as a "semantic trick"; that is, assuming,
entirely ad hoc, that space has the properties of a medium.
In the theoretical universe this problem does not arise, as the photon
remains in the same absolute location in which it originates. With
respect to the natural system of reference it does not move at
all, and the movement that is observed in the context of a stationary
reference system relative t othe stationary system, not a movement
of the photon itself.
- Another serious problem has been to provide an explanation for the
fact that the photon behaves in some respects as a particle, whereas
in other respects it behaves as a wave. Here, again, there is no problem
at all in the theoretical universe. The theoretical photon acts as
a particle in emission or absorption because it is a particle
(that is, a discrete unit). It travels as a wave because the combination
of its own inherent oscillating motion and the forward progression
of space-time has the form of a wave. | <urn:uuid:96266945-9336-4d6e-9a7c-899300d5ee51> | 3.609375 | 1,314 | Academic Writing | Science & Tech. | 26.903189 |
Problem : If triangles JGS and RPC are congruent, to which segment is segment SJ congruent?
Problem : If triangles JHF and TLG are congruent, which angle is congruent to angle L?
Problem : Why aren't two triangles with three pairs of congruent angles necessarily congruent?
Problem : When the lengths of the sides of two triangles are the same, those triangles are congruent. Using symbols and the correct correspondence, write that the two triangles below are congruent.
Problem : Is it possible for five parts of a triangle to be congruent to five corresponding parts of another triangle, and the triangles aren't congruent? | <urn:uuid:7aa1c6ec-0ad1-48f4-ba58-a2a96cceddc3> | 2.859375 | 144 | Q&A Forum | Science & Tech. | 60.755107 |
Polymer chemistry or macromolecular chemistry is a multidisciplinary science that deals with the chemical synthesis and chemical properties of polymers or macromolecules.1 According to IUPAC recommendations,23 macromolecules refer to the individual molecular chains and are the domain of chemistry. Polymers describe the bulk properties of polymer materials and belong to the field of polymer physics as a subfield of physics.
Polymer chemistry is that branch of one, which deals with the study of synthesis and properties of macromolecules.
Polymers are formed by polymerization of monomers. A polymer is chemically described by its degree of polymerisation, molar mass distribution, tacticity, copolymer distribution, the degree of branching, by its end-groups, crosslinks, crystallinity and thermal properties such as its glass transition temperature and melting temperature. Polymers in solution have special characteristics with respect to solubility, viscosity and gelation.
The work of Henri Braconnot in 1777 and the work of Christian Schönbein in 1846 led to the discovery of nitrocellulose, which, when treated with camphor produced celluloid. Dissolved in ether or acetone, it is collodion, used as a wound dressing since the U.S. Civil War. Cellulose acetate was first prepared in 1865. In 1834, Friedrich Ludersdorf and Nathaniel Hayward independently discovered that adding sulfur to raw natural rubber (polyisoprene) helped prevent the material from becoming sticky. In 1844 Charles Goodyear received a U.S. patent for vulcanizing rubber with sulfur and heat. Thomas Hancock had received a patent for the same process in the UK the year before.
In 1884 Hilaire de Chardonnet started the first artificial fiber plant based on regenerated cellulose, or viscose rayon, as a substitute for silk, but it was very flammable.4 In 1907 Leo Baekeland invented the first synthetic polymer, a thermosetting phenol-formaldehyde resin called Bakelite. Around the same time, Hermann Leuchs reported the synthesis of N-carboxyanhydrides and their high molecular weight products upon reaction with nucleophiles, but stopped short of referring to these as polymers, possibly due to the strong views espoused by Emil Fischer, his direct supervisor, denying the possibility of any covalent molecule exceeding 6,000 daltons.5 Cellophane was invented in 1908 by Jocques Brandenberger who squirted sheets of viscose rayon into an acid bath.6
In 1922 Hermann Staudinger (of Worms, Germany 1881-1965) was the first to propose that polymers consisted of long chains of atoms held together by covalent bonds. He also proposed to name these compounds macromolecules. Before that, scientists believed that polymers were clusters of small molecules (called colloids), without definite molecular weights, held together by an unknown force. Staudinger received the Nobel Prize in Chemistry in 1953. Wallace Carothers invented the first synthetic rubber called neoprene in 1931, the first polyester, and went on to invent nylon, a true silk replacement, in 1935. Paul Flory was awarded the Nobel Prize in Chemistry in 1974 for his work on polymer random coil configurations in solution in the 1950s. Stephanie Kwolek developed an aramid, or aromatic nylon named Kevlar, patented in 1966.
There are now a large number of commercial polymers, including composite materials such as carbon fiber-epoxy, polystyrene-polybutadiene (HIPS), acrylonitrile-butadiene-styrene (ABS), and other such materials that combine the best properties of their various components, including polymers designed to work at high temperatures in automobile engines.
In spite of the great importance of the polymer industry, it took a long time before universities introduced teaching and research programs in polymer chemistry. An "Institut fur Makromolekulare Chemie was founded in 1940 in Freiburg, Germany under the direction of Hermann Staudinger. In America a "Polymer Research Institute" (PRI) was established in 1941 by Herman Mark at the Polytechnic Institute of Brooklyn (now Polytechnic Institute of NYU). Several hundred graduates of PRI played an important role in the US polymer industry and academia. Other PRI's were founded in 1961 by Richard S. Stein at the University of Massachusetts, Amherst, in 1967 by Eric Baer at Case Western Reserve University, in 1982 at The University of Southern Mississippi, and in 1988 at the University of Akron.
Association theory is a discredited theory which tried to explain molecular structures of macromolecules.
Some other theories related to polymers include
They are produced by living organisms:
- structural proteins: collagen, keratin, elastin…
- chemically functional proteins: enzymes, hormones, transport proteins…
- structural polysaccharides: cellulose, chitin…
- storage polysaccharides: starch, glycogen…
- nucleic acids: DNA, RNA
- thermoplastics: polyethylene, Teflon, polystyrene, polypropylene, polyester, polyurethane, polymethyl methacrylate, polyvinyl chloride, nylon, rayon, celluloid, silicone…
- thermosetting plastics: vulcanized rubber, Bakelite, Kevlar, epoxy…
- Ravve, Abe (2000). Principles of Polymer Chemistry (Second ed.). Plenum Publishing. ISBN 978-0-306-46368-6.
- "Macromolecule". IUPAC. Retrieved 2011-09-05.
- "Polymer". IUPAC. Retrieved 2011-09-05.
- "The Early Years of Artificial Fibres". The Plastics Historical Society. Retrieved 2011-09-05.
- Kricheldorf, Hans, R. (2006), "Polypeptides and 100 Years of Chemistry of α-Amino Acid N-Carboxyanhydrides", Angewandte Chemie International Edition 45 (35): 5752–5784, doi:10.1002/anie.200600693
- "History of Cellophane". about.com. Retrieved 2011-09-05. | <urn:uuid:55a89ae6-f028-4553-a2cf-0c1c80ad2959> | 3.21875 | 1,319 | Knowledge Article | Science & Tech. | 25.97752 |
Definition: A string matching algorithm which builds a deterministic finite state machine to recognize the search string. The machine is then run at each location in turn. If the machine accepts, that is a match.
If you have suggestions, corrections, or comments, please get in touch with Paul E. Black.
Entry modified 16 November 2009.
HTML page formatted Tue Dec 6 16:16:32 2011.
Cite this as:
Paul E. Black, "deterministic finite automata string search", in Dictionary of Algorithms and Data Structures [online], Paul E. Black, ed., U.S. National Institute of Standards and Technology. 16 November 2009. (accessed TODAY) Available from: http://www.nist.gov/dads/HTML/determFinitAutSrch.html | <urn:uuid:ac3a7c68-1e3a-45c3-8e90-1696858b6d07> | 3.140625 | 173 | Structured Data | Software Dev. | 65.304944 |
|San José State University|
& Tornado Alley
the Nucleons of Nuclei are, Where Possible,
Organized into Alpha Particles: The Proton Data
An alpha particle, composed of two neutrons and two protons, is an amazing structure. It is relatively compact and has an extraordinary level of binding energy compared with smaller nuclides such as a deuteron or triteron. Binding energy is like, and perhaps is identical with, potential energy. Energetically it would be difficult for nucleons in a nucleus not to come together and form alpha particles wherever possible. This suggests that the binding energies of larger nuclei are composed of that due to the formation of alpha particles and that due to the arrangement of alpha particles and the extra nucleons. This latter binding energy will be called the excess binding energy. It is computed for a nuclide by subtracting from its binding energy the possible number of alpha particles it could contain times 28.29567 million electron volts (MeV), the binding energy of an alpha particle. The plot of the excess binding energies for the alpha nuclides shows a shell structure. The plot of this excess binding energy for the nuclides which could contain exactly an integral number of alpha particles is shown below.
It might appear that the graph above indicates the existence of only three shells: 1 to 2, 3 to 14 and 15 to 25. The upper limits of those shells correspond to filled shells. Fourteen alpha particles means there are 28 neutrons and 28 protons. Twenty five alpha particles correspond to 50 neutrons and 50 protons. Fifty and 28 are nuclear magic numbers.
The alpha nuclides only go up to 25 alpha particles. The range can be extended by including extra neutrons. The analysis for extra neutrons has been carried out The Neutron Data. This material covers the case of extra protons. When extra protons are included the range does not even reach 25 alpha particles, but the results are of interest anyway.
The incremental binding energy of a nuclide with a alpha particles is the excess binding energy of that nuclide less the excess binding energy of the nuclide with (a-1) alpha particles. An inspection of the graph for the incremental excess binding energies of the alpha nuclides, shown below, reveals that the 3 to 14 shell is composed of subshells. The end points of those subshells are levels of neutrons and protons that correspond with the nuclear magic numbers.
The numbers of alpha particles where there is a sharp drop; 3, 7, 10 and 14 correspond to 6, 14, 20 and 28 neutrons, all magic numbers. At points of sharp drops in the IXSBE the numbers of protons are 7, 15, 21 and 29, none of which are magic numbers. This indicates some dominance of the neutron numbers.
The graphs for the case of the two, four and six extra protons are shown below.
The sharp drops at 3, 7 and 14 alpha particles and corresponding to 6, 14 and 28 neutrons are maintained for the two and four extra protons cases.
According to the theory developed previously the increments in the incremental excess binding energies of alpha particles (the second differences in excess binding energy) should be negative, reflecting the net repulsion of alpha particles for each other, and constant within a shell. The graphs of the data for the cases considered above are shown below.
For this case there are the spike associated with a transition between shells the other values are generally near zero with some above and some below.
Except where the spikes occur for transitions from one shell to another the values are generally negative and roughly constant.
As in the previous cases the alpha-plus-four-protons and alpha-plus-six-protons nuclides give the interaction energies for the alpha particles in the same shell as negative.
According to the theory the cross differences of excess binding energy is equal to the interactive binding energy of the last alpha particle with the last extra proton. According to another development the alpha particle has a nucleonic (strong force) charge that is a fraction of that of the proton. This means that protons should be repelled by alpha particles and thus the interactive binding energy should be negative when the increments are computed from the binding energy of nuclides in the same shell. The following graphs give the results of that computation.
In each case when the spikes associated with a change in shell the data points are predominantly negative. According to the conventional theory both protons and neutrons should be strongly attracted to alpha particles. Results here and a previous study indicate that alpha particles and neutrons are attracted to each other but alpha particles and protons are repelled by each other.
The incremental excess binding energy of alpha particles for various numbers of extra protons displays sharp drops at particular numbers of alpha particles. These drops occur at the numbers of neutrons correspond to the number of neutrons reach a level where a neutron shell is filled and additional neutrons must go to a higher shell.
The previous theoretical analysis that the increments in the incremental excess binding energies of alpha particles should be negative and roughly constant within a shell is confirmed.
HOME PAGE OF Thayer Watkins | <urn:uuid:30c32df9-8be5-4520-b8fa-ab4bea888fb7> | 3.78125 | 1,073 | Knowledge Article | Science & Tech. | 41.806385 |
Before you begin
Before you can use the Administration Console to install, start, and configure WebLogic Web Services, you must create one.
The WebLogic Web Services programming model centers around JWS
files and Ant tasks that execute on the JWS files. JWS files are
Java files that use Java Web Service (JWS) metadata annotations (a new
JDK 5.0 feature) to specify the shape and behavior of the Web Service.
Programmers begin creating a Web Service by either programing the JWS
file from scratch, or generating a stubbed-out version from an existing
WSDL file (public contract of the Web Service) and updating it with
their business logic Java code. Programmers then use the
jwsc Ant task to generate, from the JWS file, a
deployable J2EE application or module that represents the Web Service.
These tasks are iterative; programmers keep coding and generating the
Web Service until it works as they want.
As part of this iterative process, programmers also use the Administration Console to test that the generated Web Service deploys and works correctly. Later, administrators perform similar tasks on the completed Web Service, such as installing, starting, and further configuring the Web Service, as described in the sections below.
For detailed information and procedures about creating a WebLogic Web Service, see:
A Web Service is a Java class or a stateless session EJB that contains additional artifacts so that it can be invoked using SOAP. The additional artifacts include Web Service-specific deployment descriptors, a WSDL file (public contract of the Web Service) and data binding components to convert data between its internal Java representation and its external XML representation used in the request and response SOAP messages.
Web Services are deployed as either Web applications or EJBs, depending on their implementation. The Web applications or EJBs can be deployed on their own, or as part of an Enterprise Application. See View installed Web Services for instructions on viewing the Web Services that are currently installed on this Administration Server.
You perform this task only if the Web Service has been previously programmed to use the reliable SOAP messaging or buffering features. See Using Reliable SOAP Messagingand Creating Buffered Web Services for information about programming these features for your Web Service.
When programmers created the Web Service, they might have used
@WssConfiguration JWS annotation to associate a
Web Service security configuration to the service. This associated
Web Service security configuration is used to configure security
features (in addition to those specified in any associated WS-Policy
files), such as whether to use X.509 certificates to establish
identity or use a password digest in a SOAP message.
See the following tasks: | <urn:uuid:82ab5226-0726-4777-9eb1-b82eb36da3a7> | 2.859375 | 574 | Documentation | Software Dev. | 24.47286 |
The tuatara Sphenodon punctatus is one of the real treasures of the zoology museum. Tuataras (from the Maori word for peaks on the back) are only found in New Zealand and are seriously endangered.
Tuatara Sphenodon punctatus
Photograph: Martyn L Gorman
Tuataras may be grey, olive, or brickish red in color. They range in adult length from about 40 cm (female) to 60 cm (large male), with the male generally reaching larger proportions. They lack external ears, have a diapsid skull (two openings on either side), and posses a "parietal eye" on the top of their head. This "third-eye," contains a retina and is functionally similar to a normal eye, though the function has not been clearly recognized and a scale grows over it in adult tuataras. The male tuatara displays a striking crest down the back of the neck, and another down the middle of the back. The female has a less developed version of this. Unlike all other living toothed reptiles, the tuatara's teeth are fused to the jaw bone (acrodont tooth structure). The tuatara has a very slow metabolism and is a very long-lived species. It's not uncommon for an individual to live for over 100 years.
Despite their appearance, tuataras are not lizards, they are the last remaining member of an ancient group of reptiles known as the Sphenodontia which was well represented by many species during the age of the dinosaurs, some 200 million years ago. All the species in the group, apart from the tuatara, declined and eventually became extinct about 60 million years ago.
Originally the tuatara was thought to be a lizard but in 1867, Dr Albert Gunther, the curator at the British Museum in London examined a bottled tuatara specimen and linked it to the land-based group of reptiles called Rhynchocephalia, a group thought to have been extinct for millions of years (Rhynchocephalia is now known as Sphenodontia). In 1989 Dr Charles Daugherty, of Victoria University in Wellington, discovered that there were two species of tuatara, Sphenodon punctatus and Sphenodon guntheri.
The two recognized species of tuatara are found on some 30 small, relatively inaccessible, islands off the coast of New Zealand. The species were once widely distributed throughout New Zealand, but became extinct on the mainland before the arrival of European settlers.
Our specimen probably dates from the early 1900s; is now Illegal to export tuataras from New Zealand. In 1895, New Zealand awarded the tuatara strict legal protection. It is currently considered a CITES (Convention on the International Trade in Endangered Species) Appendix I species. This is the most restricted classification for a species. | <urn:uuid:d4e77875-dd22-4423-829a-427951aacf07> | 3.703125 | 597 | Knowledge Article | Science & Tech. | 40.594697 |
Long-term consequences for Northern Norway of a hypothetical release from the Kola nuclear power plant
Howard, B.J.; Wright, S.M.; Salbu, B.; Skuterud, K.L.; Hove, K.; Loe, R.. 2004 Long-term consequences for Northern Norway of a hypothetical release from the Kola nuclear power plant. Science of the Total Environment, 327 (1-3). 53-68. 10.1016/j.scitotenv.2004.01.007Full text not available from this repository.
The spatial and temporal variation in radiocaesium and 90Sr doses to two population groups of the two Northernmost counties of Norway, Troms and Finnmark, following a hypothetical accident at the Kola nuclear power plant (KNPP)have been estimated using a model implemented within a geographical information system.The hypothetical accident assumes a severe loss of coolant accident at the KNPP coincident with meteorological conditions causing significant radionuclide deposition in the two counties.External doses are estimated from ground deposition and the behaviour of the different population groups, and internal doses from predicted food product activity concentrations and dietary consumption data.Doses are predicted for reindeer keepers and other Norwegian inhabitants, taking account of existing 137Cs and 90Sr deposition but not including the remedial effect of any countermeasures that might be used. The predicted doses, arising mainly from radiocaesium, confirm the Arctic Monitoring and Assessment Programme assessment that residents of the Arctic are particularly vulnerable to radiocaesium contamination, which could persist for many years.External doses are predicted to be negligible compared to ingestion doses. Ingestion doses for reindeer keepers are predicted to exceed 1 mSv yy1 for several decades primarily due to their high consumption of reindeer meat.Other Norwegians would also be potentially exposed to doses exceeding 1 mSv yy1 for several years, especially if they consume many local products.Whilst reindeer production is the most important exposure pathway, freshwater fish, lamb meat, dairy products, mushrooms and berries are also significant contributors to predicted ingestion doses.Radionuclide fluxes, defined as the total output of radioactivity in food from an area for a unit time, are dominated by reindeer meat.The results show the need for an effective emergency response, with appropriate countermeasures, should an accident of the scale considered in this paper occur at the KNPP.
|Programmes:||CEH Programmes pre-2009 publications > Biogeochemistry > SE01B Sustainable Monitoring, Risk Assessment and Management of Chemicals > SE01.4 Monitoring and predicting the distribution of chemicals in terrestrial and freshwater ecosystems|
|CEH Sections:||_ Environmental Chemistry & Pollution|
|NORA Subject Terms:||Ecology and Environment|
|Date made live:||25 Apr 2012 10:22|
Actions (login required) | <urn:uuid:b31c25a0-1424-473f-9e69-abde681a8aca> | 2.703125 | 602 | Academic Writing | Science & Tech. | 30.883899 |
During all the recent discussion around Neandertals and modern humans, it’s often pointed out that Homo sapiens is the sole extant representative of the genus Homo. I began to wonder “how unusual is this?” in a FriendFeed comment thread. What resources exist that could help us to answer this question?
Genera that contain only one species are termed monotypic. Wikipedia even has a category page for this topic but their lists are limited, since Wikipedia is not a comprehensive taxonomy resource.
Taxonomy is not my specialty but once in a while, I enjoy challenging myself with unfamiliar resources and data types. I figured initially that we could get some way towards an answer using BioSQL and the NCBI taxonomy database. As it turned out I was completely wrong, but it was an interesting educational exercise. I turned instead to a “real” taxonomy resource, the Integrated Taxonomic Information System, or ITIS.
First, I set up the ITIS database:
# fetch and unpack wget http://www.itis.gov/downloads/itisMySQL012710_v3.TAR.gz tar zxvf itisMySQL012710_v3.TAR.gz # Problem - 2 versions of the SQL setup file cp dropcreateloaditis.sql itisMySQL020210/ cd itisMySQL020210 # and load into MySQL mysql -u root -p --enable-local-infile < dropcreateloaditis.sql
A couple of minor issues here. First, ITIS, if your tarball name contains TAR in upper-case, Linux tab-completion doesn’t work. Second, confusingly, unpacking the tarball generates two files named dropcreateloaditis.sql: one inside the directory itisMySQL020210 and another one directory level up. The former does not work properly, the latter does.
OK, a brand new database with an unfamiliar schema. Some poking around in the MySQL console shows 24 tables. To make a long story short, the table taxon_unit_types contains a field named rank_id, which shows that “species” have a rank_id value of 220. The table taxonomic_units contains lots of fields, including the rank_id and a field called unit_name1 which for species records, appears to indicate the genus. There’s also a field in taxonomic_units called name_usage which takes values of “invalid”, “valid”, “accepted” or “not accepted”. I assume that it’s best to stick with “valid” or “accepted”.
So, to count species per genera, we can try something like this:
SELECT unit_name1, count(*) AS species FROM taxonomic_units WHERE rank_id = 220 AND (name_usage = 'valid' OR name_usage = 'accepted') GROUP BY unit_name1 ORDER BY species DESC INTO OUTFILE '/tmp/itis.txt';
Here are the first few lines of the resulting output file:
head /tmp/itis.txt Lasioglossum 1740 Megachile 1522 Andrena 1495 Camponotus 965 Hylaeus 709 Nomada 701 Rhyacophila 647 Perdita 631 Pheidole 549 Chimarra 537
A quick cross-check using a few genus names at the ITIS website seems to confirm that we are counting species per genera correctly. So, how many did we retrieve and how many have only one species?
# total records wc -l /tmp/itis.txt 41723 itis.txt # records with number 1 in second column grep -P "\t1$" itis.txt | wc -l 16786 # one of those is Homo, right? grep -P "^Homo\t" itis.txt Homo 1
It seems then that around 40% of valid or accepted genera, as retrieved from ITIS, contain one species – assuming that I have not made an error in my SQL query. This raises some questions. Does this mean that humans are not particularly unusual in being the sole extant representative of Homo? How complete a resource is ITIS? 40% seems high – are there really so many monotypic genera, or is it more likely that many genera contain as-yet undescribed species?
I venture back onto safe ground and leave these questions to the experts. | <urn:uuid:0f37e09a-ea77-4cf6-81a9-f1c074397f29> | 3.28125 | 960 | Personal Blog | Science & Tech. | 49.729525 |
Classification of Differential Equations
While differential equations have three basic types—ordinary (ODEs), partial (PDEs), or differential-algebraic (DAEs), they can be further described by attributes such as order, linearity, and degree. The solution method used by DSolve and the nature of the solutions depend heavily on the class of equation being solved.
The order of a differential equation is the order of the highest derivative in the equation.
This is a first-order ODE because its highest derivative is of order 1.
Here is the general solution to a fourth-order ODE.
A differential equation is linear if the equation is of the first degree in and its derivatives, and if the coefficients are functions of the independent variable.
This is a nonlinear
second-order ODE that represents the motion of a circular pendulum. It is nonlinear because Sin[y[x]]
is not a linear function of
warning message appears because Solve
(the inverse of EllipticF
) to find an expression for
This plots the solutions. The discontinuity in the graphs at
results from the choice of inverse functions used by Solve
It should be noted that sometimes the solutions to fairly simple nonlinear equations are only available in implicit form. In these cases, DSolve returns an unevaluated Solve object.
This nonlinear differential equation only has an implicit solution. The
messages can be ignored; they appear because Solve
cannot find an explicit expression for
because non-algebraic functions (ArcTan
) are involved.
When the coefficients of a linear ODE do not depend on , the ODE is said to have constant coefficients.
This is an ODE with constant coefficients.
The previous equation is also homogeneous: all terms contain or derivatives of and its right-hand side is zero. Adding a function of the independent variable makes the equation inhomogeneous. The general solution to an inhomogeneous equation with constant coefficients is obtained by adding a particular integral to the solution to the corresponding homogeneous equation.
is added to the right-hand side of the previous equation, making the new equation inhomogeneous. The general solution to this new equation is the sum of the previous solution and a particular integral.
When the coefficients of an ODE depend on , the ODE is said to have variable coefficients. Since equations with variable coefficients that are rational functions of have singularities that are easily classified, there are sophisticated algorithms available for solving them.
The coefficients of this equation are rational functions of
There is a close relationship between functions and differential equations. Starting with a function of almost any type, it is possible to construct a differential equation satisfied by that function. Conversely, any differential equation gives rise to one or more functions, in the form of solutions to that equation. In fact, many special functions from classical analysis have their origins in the solution of differential equations. Mathieu functions are one such class of special functions. Mathieu was interested in studying the vibrations of elliptical membranes. The eigenfunctions for the wave equation that describes this motion are given by products of Mathieu functions.
This linear second-order ODE with rational coefficients has a general solution given by Mathieu functions.
The presence of ArcCos[t]
in the previous solution suggests that the equation can be given a simpler form using trigonometric functions. This is the form in which these equations were introduced by Mathieu in 1868.
This plots the surface for a particular product of solutions to this equation.
The degree of a differential equation is the highest power of the highest-order derivative in the equation.
This is a first-order ODE of degree 2.
The higher degree leads to non-uniqueness of the solution.
The examples in this tutorial have focused on the classification of ODEs. The classification of PDEs is similar but more involved. PDEs can also be classified by linearity or nonlinearity, order, degree, and constant or variable coefficients. More important is the classification that identifies a PDE as hyperbolic, parabolic, or elliptic. These classifications are discussed in further detail in "Second-Order PDEs". | <urn:uuid:a1e29adf-d453-4c0d-9364-e6a558a63121> | 3.1875 | 874 | Tutorial | Science & Tech. | 29.686169 |
SOHO's unique view of a comet that fell to pieces
18 May 2001When Spain's Instituto de Astrofisica de Canarias reported on 28 July 2000 that an ordinary-looking comet was breaking up, some of the world's top telescopes watched its subsequent disintegration till nothing was left. The French-Finnish SWAN instrument on the SOHO spacecraft had already been observing Comet LINEAR by ultraviolet light for two months, and continued to watch it till the remnants faded from view in mid-August. Today the SWAN team reports, in the journal Science, that their observations showed four major outbursts in June and July.
The fragmentation seen by SWAN began on 21 July, almost a week before observers on the ground noticed it. Between 25 May and 12 August, the dying comet released altogether 3.3 million tonnes of water vapour into space, as its ice evaporated in the warmth of the Sun. The data also suggest that the density of Comet LINEAR was extremely low.
"Only SWAN on SOHO saw the entire drama of this self-destroying object," comments Teemu Mdkinen of the Finnish Meteorological Institute, lead author of the report in Science. "The ice on the surface of the comet's nucleus did not simply vaporize as in a normal comet, but came away in large chunks. We saw 90 per cent of the ice falling off before the complete fragmentation of the remainder began."
Comet LINEAR, known more formally as Comet 1999 S4, was discovered by the LINEAR asteroid-hunting telescope in the USA, and may have been making its first visit to the Sun. It disappointed amateur astronomers by not becoming bright enough to see with the naked eye. The break-up occurred near the time of the comet's closest approach to the Sun on 26 July, when it was moving across the sky from Ursa Major towards Leo.
In early August the NASA-ESA Hubble Space Telescope and the European Southern Observatory's Very Large Telescope in Chile both saw about 16 fragments in the form of mini-comets, which faded away by the middle of the month. These observations by visible light indicated that the pieces were about 100 metres in diameter. A prominent dust tail still visible in early August corresponded with the onset of fragmentation seen by SWAN on 21 July.
SWAN's unique capability in observing comets comes from its continuous scanning of the whole sky, at just the right ultraviolet wavelength to see the cloud of hydrogen atoms that surrounds every moderately active comet. The hydrogen comes from the break-up of water molecules released from the comet by the Sun's warmth. SWAN also benefits from its location on the ESA-NASA SOHO spacecraft 1.5 million kilometres from the Earth, well clear of a hydrogen cloud that surrounds the Earth itself.
"Our primary aim is to study the interaction of the solar wind with interstellar hydrogen," explains Jean-Loup Bertaux of France's Service d'Aironomie, the principal investigator for SWAN. "But we always knew that we'd have an excellent view of comets too. They are quite often traceable in our records even before their formal discovery by others."
Lessons from the SWAN song of Comet LINEAR
Complete fragmentation provides a rare opportunity for scientists to learn about the internal make-up of a comet. Members of the SWAN team believe that their newly published results compel them and their fellow scientists to think afresh about Comet LINEAR's construction, and to consider that different parts of the young Solar System may have produced comets of different sorts.
"Comets do not usually blow themselves to smithereens," says lead author Mdkinen. "So we should not be surprised if Comet LINEAR was peculiar in composition and structure compared with other comets."
The character of the comet did not change throughout the months of observation by SWAN, even when deep layers inside the nucleus were being laid bare. Comet scientists usually have to consider the possibility that the surface of the nucleus is different in composition from the interior. One lesson from the 'SWAN song' of Comet LINEAR seems to be that, in this case at least, the surface exposed at the outset was representative of the whole nucleus.
The SWAN team also suspects that Comet LINEAR was as flimsy and light as the expanded polystyrene used for packing fragile equipment. The density of its water ice may have been as low as 15 kilograms per cubic meter, compared with 917 kg/m3 for familiar non-porous ice on the Earth. Even allowing for a possibly equal mass of dust grains within the comet, a total density of 30 kg/m3 would be far less than the 500 kg/m3 often assumed by comet scientists. By this reckoning, the initial diameter of Comet LINEAR on its approach to the Sun was about 750 metres.
"Our opinion about the low density is tentative and controversial," says Jean-Loup Bertaux. "We expect plenty of arguments with our colleagues when we put all the observations of Comet LINEAR together. But we start with the advantage of having seen the whole course of events, which no one else did."
The break-up of Comet LINEAR gave a small-scale impression of the disintegration, many centuries ago, of a far larger comet into an enormous swarm of mini-comets. LASCO, another instrument on SOHO, has observed hundreds of the fragments from that event falling into the Sun.
For more information please contact:
Dr. Paal Brekke, ESA-SOHO Deputy Project Scientist
Dr. Teemu Mdkinen, SWAN scientist, Finnish Meteorological Institute
Dr. Jean-Loup Bertaux, Service d'Aeronomie du CNRS
Last Update: 10 June 2003For further information please contact: SciTech.email@example.com
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pycrc provides a CRC reference implementation in Python and a source code generator for C.
The used CRC variant can be chosen from a fast but space-consuming implementation to slower but smaller implementations suitable especially for embedded applications.
The following functions are implemented:
- generate the checksum of a string
- generate the C header and source files for a client implementation. The algorithm can be chosen from fast but big implementation to slower but smaller implementations suitable especially for embedded applications.
The following variants of the CRC algorithm are supported:
- bit_by_bit: the basic algorithm which operates individually on every bit of the augmented message (i.e. the input data with width 0-bits attached to the end). This algorithm is the easiest one to understand, because it's a direct implementation of the basic polynomial division, but it is also the slowest among all possible variants.
- bit_by_bit_fast: a variation of the simple bit_by_bit algorithm, which doesn't need the augmented message. This algorithm might be a good choice for embedded platforms, where code space is a major concern.
- table_driven: the standard table driven algorithm. This algorithm works only on models with multiples of 8 as width. This is the fastest variant, because it operates on bytes as opposed to bits, and uses a look-up table of 256 elements, which might not be feasible for small embedded systems, though. Anyway, the number of elements in the look-up table can be reduced by means of the --table_idx_with command line switch. By using 4 bits (16 elements in the look-up table) a significant speed-up can be measured with respect to the bit-by-bit algorithms. | <urn:uuid:6c2baf0c-563d-40f4-a14c-f98ad2c3e048> | 2.796875 | 358 | Documentation | Software Dev. | 38.882913 |
Peter Seligmann, Chairman and CEO of Conservation International.
You may have read last week's news of a ‘lost world' harboring scores of rare and previously unknown animals and plants, unearthed in a remote Indonesian rainforest, or the recent announcement of exciting undersea discoveries in the Caribbean off the Saba Bank. They reinforce the fact that while pristine regions on our increasingly crowded and exploited planet are becoming a true rarity, much of our world remains to be explored, and amazing new creatures are waiting to be found.
This rare feat of unearthing an uncharted pocket of wilderness and a trove of natural treasures captures the public's imagination. The hunger for discovering and crossing new frontiers is an elemental force that has driven humans for centuries. In the quest for new discoveries, the first place we often look to is space, which is why the Bush administration wants to send Americans back to the moon.
But it's time to concentrate on our own Earth more closely. Unknown places and creatures are still being found to remind us how little we really know about the biodiversity that shares the planet with us. Last year, for example, Africa's first new species of monkey in 20 years was found in Tanzania . The American ivory-billed woodpecker – last spotted 60 years ago and thought to be extinct – turned up in an Arkansas swamp.
This week comes news of fascinating new marine discoveries at Saba Bank Atoll, a coral-crowned undersea mountain peak in the Caribbean . In a short, two-week scientific survey, divers found scores more fish species than were previously known in the area, including two believed to be new to science, and vast, luxurious “seaweed cities” containing at least a dozen new algae species.
Yet these exciting discoveries are tempered with regret. We are losing ‘lost worlds' before they are even surveyed. Rainforests in the Amazon, Central Africa, and Asia harbor the greatest varieties of plant and animal species. They may contain the next miracle drug, the next agricultural wonder. Yet they are being destroyed and developed for short-term economic gain from timber, minerals, and other natural resources before their long-term value can be recognized.
The same is true for our oceans. In fact, we've never made a serious effort to learn about the 95 percent of Earth that we've never seen, the world beneath the waves. We owe our very existence to the ocean, yet our knowledge of the deep seas is scant at best.
The earth's oceans, covering more than 97 percent of the planet, drive climate and weather, generate more than 70 percent of the oxygen in the atmosphere, absorb carbon dioxide, and replenish our fresh water through the clouds. Yet oceans are vulnerable and in deep trouble.
Each year, close to 100 million tons of fish and other marine wildlife are caught by industrial fleets. Ninety percent of large predators like swordfish, tuna, and sharks have been wiped out by over-fishing. Three-fourths of all commercial fisheries are exploited to capacity, or beyond.
Ancient deep ocean habitats are scraped and ruined by the heavy gear of bottom trawls. Coral reefs and coastal mangrove forests, vital nurseries for young fish and natural buffers to flooding and tsunamis, are destroyed to build shrimp farms or commercial development.
Over the decades, we've released billions of tons of noxious materials into the seas. Dozens of massive “dead zones” blight coastal areas. Gigantic swaths of toxic algae are fueled by high levels of nitrates and phosphates from fertilizer and animal-waste runoff from farms.
Indonesia 's ‘lost world' and the Caribbean 's undersea mountain teeming with new discoveries is big news around the globe. These remnants of Eden remind us of what Earth used to be before humans began exploiting the lands and the seas with little thought of the consequences for this exceptional place we call home. Do we not owe our future generations the legacy of a natural world that we have explored, understood, and protected -- above and beneath the oceans? | <urn:uuid:29d9f66e-58e3-4097-af51-5978fb8ab4e1> | 3.203125 | 836 | Nonfiction Writing | Science & Tech. | 44.33926 |
Ursi's Eso Garden
Your Competent Esoteric Guide
Friday, 26. October 2007
Comet Holmes Undergoes Huge OutbursOn Oct. 24, 2007, Comet Holmes shocked sky watchers with a spectacular eruption, brightening almost a million-fold from 17th to 2.5th magnitude in a matter of hours. The comet is now visible to the naked eye - even from light polluted cities - high in the northern sky. Look for a golden 2.5th magnitude fuzzball in the constellation Perseus after sunset.
The golden hue of Holmes' core is probably the color of sunlight scattered by comet dust, while the green fringe likely signifies an atmosphere rich in diatomic carbon and cyanogen (substances found in many green comets). There are reports that the fuzzball is expanding and taking on a lopsided shape - the first signs of a tail? Amateur astronomers are encouraged to monitor developments.
Comet 17P/Holmes Photo Gallery by SpaceWeather.
Comet Holmes, named for its 1892 discoverer, Edwin Holmes, is not your typical comet with a tail, said Tulsa Air and Space Museum planetarium director Chris Pagan. "Originally, the comet was nothing impressive," Pagan said. "It was pretty faint, but suddenly, it became very bright." Such a change is unusual for comets, and could have been caused by a large fracture, a breakup or a collision with an asteroid, Pagan said.
Comet Holmes gets an unexpected glow by Tulsa World.
A comet usually too faint to be seen with the naked eye has brightened by a factor of a million since Tuesday, suggesting its surface may have cracked open and expelled clouds of dust and gas. Astronomers are scrambling to observe the strange object, which is likely to fade in the coming days and weeks.
Comet 17P/Holmes, which orbits the Sun every seven years on a path that takes it from the distance of Jupiter's orbit to about twice that of Earth's, is usually 25,000 times too dim to be seen with the naked eye. But since 23 October, it has brightened by a million times and now resembles a bright yellow star.
Comet brightens mysteriously by a factor of a million by New Scientist Space.
From Florian Boyd, Palm Springs, California: "I think this is about the most amazing thing I've ever seen in the sky!"
Sudden Naked-Eye Comet Shocks the Astronomy World by Sky & Telescope.
Over the past three weeks, Comet Holmes' cloud of haze has spread out to a diameter of 900,000 miles (1.4 million kilometers), which is wider than the diameter of the sun, astronomers at the University of Hawaii Institute for Astronomy noted this week. That's not unprecedented for a comet, but this cloud has such a spherical shape that it's easy to imagine the comet as an insubstantial, ghostly star haunting the constellation Perseus.
And Hubble Zooms In on Heart of Mystery Comet by Hubblesite.
See also: Incredible Comet Bigger than the Sun by Space.com.
A comet that has delighted backyard astronomers in recent weeks after an unexpected eruption has now grown larger than the sun.
The sun remains by far the most massive object in the solar system, with an extended influence of particles that reaches all the planets. But the comparatively tiny Comet Holmes has released so much gas and dust that its extended atmosphere, or coma, is larger than the diameter of the sun.
Category: Astrology & Astronomy
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Android Programming with App Inventor
Drag and drop your way to Android programming.
MIT App Inventor, re-released as a beta service (as of March 5, 2012) by the MIT Center for Mobile Learning after taking over the project from Google, is a visual programming language for developing applications for the Android mobile computing platform. It is based on the concept of blocks, and applications are designed by fitting together blocks of code snippets. This may sound like a very childish way of programming, especially for seasoned readers of Linux Journal. But then again, App Inventor will tickle the child programmer in you and make you chuckle at the ease with which you can develop applications for your Android device. In this article, I describe how to use the camera on the Android device, develop e-mail and text-messaging-based applications and also show how to use location sensors to retrieve your current geographical location. Let's get started.
App Inventor has minimum setup requirements and is completely browser-based. You need a working Java installation on your system, as it uses Java Web Start for its functioning. Point your browser to http://appinventor.mit.edu, and once you sign in with your Google account, you should see a screen as shown in Figure 1. This is called the Projects Page where you can see your existing projects and create new ones.
Figure 1. App Inventor's Projects Page
Now, let's develop and deploy an Android application using App Inventor and in the process learn the basic development-deployment cycle. Create a New Project using the New Project button, and enter a name for your project, say "Project1". Now you should see the Designer window for your project. The Designer window is composed of four sub-components. The Palette on the leftmost side of the window is the placeholder for all the available components for your project. The Viewer is where the application will be designed by placing together various components (this is where you design the user interface for your application). The Components show the currently used components in your project, and the Properties column is where you assign the properties of the components.
First, let me briefly explain the notion of components. An App Inventor project is made up of building blocks called components, such as a text label to display text, a text box to take user inputs, a camera component to click pictures and so on. Currently, you will see a few categories of components—basic components, such as those for user input and display of text to more specialized components, such as those for displaying media and animations, and components acting as an interface to the device sensors. A complete reference for all the components is available at http://appinventor.mit.edu/learn/reference/index.html. Components have associated behavior, methods and properties. Some of the properties can be set; whereas others can be only read.
In this first project, let's use the following components: Camera, Button and Image. The code usually shows it better, but briefly here is what you're going to do: clicking the button starts the camera on your device, which you use to click a picture, which then is displayed using the Image component. Here are the steps:
Drag a Camera component from the palette to the Viewer. It should show up under Non-visible components below the Viewer. By default, it will be named as Camera1, which you can, of course, change to something else.
Drag a Button to the Viewer, and from the Properties, change its Text to "Click".
Drag an Image component onto the Viewer.
You can play around with the Screen properties to set things like title, background color and orientation. For the purpose of this project, set the Title to "Click!".
Figure 2. User Interface for Project1
That completes the design of the user interface (Figure 2). Next, let's program the components using Blocks.
Open the Blocks Editor, which should start downloading the JAR file for the editor. It will ask you for the location of the App Inventor setup commands if you have not installed them in the standard location under /usr/google. The Blocks Editor for the current project will look like Figure 3. Going back to the description for this project, the goal is to activate the device camera when the button is clicked. This is done with the code block "When Button1.click", which you dragged from the Blocks pane on the left. When the button is clicked, you want the device's camera to be activated, so drag the "call Camera1.TakePicture" block inside the previous block. Once the picture is taken, you will want it to be displayed using the Image component. So, insert the block "when Camera1.AfterPicture" into the editor, and then set the "Image1.Picture" to the location of the saved image.
Figure 3. Blocks Editor for Project1
Now that you have designed the user interface and programmed the application's logic, you're ready to test it. Go back to the Designer window, and on the right, click on Package for Phone→Download to this Computer. That should initiate the download of the Android package (.apk file) for your project. Now, transfer this file to your Android device, and install it. Then, try it out.
A Peek under the Hood
Now you have designed and deployed your first Android application, and you have used components (the camera component and the image components), assigned them behavior and set properties. If you are familiar with the idea of event-driven programming, you already will have realized that App Inventor is an event-driven programming framework. The event can be the user clicking a button or the reception of a text message. For example, when the button is clicked, an event is said to have occurred, and in response to this event, the camera is activated. Again, when the camera finishes capturing a picture and saving it, the response code uses the image location to display it using an image component.
Earlier, I mentioned that components have associated behavior, methods and properties. You can find these for a component by clicking the component in the Blocks Editor. For example, Figure 4 shows the method available for the Camera component (Camera1.TakePicture) and the behavior (Camera1.AfterPicture).
Figure 4. Blocks Available for the Camera Component
Besides the blocks associated with components, more fundamental programming blocks are available: Math blocks, Logic blocks, Control blocks and others. (I'll demonstrate using a few of these in one of the projects later in this article.)
Now that you have a basic idea of developing applications using App Inventor, let's look under the hood a bit, starting from the source. Download the source code for "Project1" by going to the Projects Page and selecting Project1 and clicking on More Actions→Download Source. That should start downloading the sources in a zip file. When you unzip the file, you will have two directories: src and youngandroidproject. Under the src directory, you will have a subdirectory called appinventor, which houses the subdirectories, and then ai_droidery/Project1 (note that "droidery" is my Google user name). In this directory, you will see the source files Screen1.blk, Screen1.scm and Screen1.yail. Screen1.blk is an XML-based representation of the visual blocks that was created earlier; Screen1.yail is an intermediate language based on the Scheme language used by App Inventor, which is then fed to Kawa to create the Android package for installation on Android devices. The Screen1.scm file is a JSON representation of the components used in the project with details about the components, such as the version information. If you are keen to understand how App Inventor really works, you also may want to check out App Inventor's source code (see Resources).
Next, let's move on to becoming familiar with sensors and some of the other components available in App Inventor.
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Enter to Win an Adafruit Pi Cobbler Breakout Kit for Raspberry Pi
It's Raspberry Pi month at Linux Journal. Each week in May, Adafruit will be giving away a Pi-related prize to a lucky, randomly drawn LJ reader. Winners will be announced weekly.
Fill out the fields below to enter to win this week's prize-- a Pi Cobbler Breakout Kit for Raspberry Pi.
Congratulations to our winners so far:
- 5-8-13, Pi Starter Pack: Jack Davis
- 5-15-13, Pi Model B 512MB RAM: Patrick Dunn
- 5-21-13, Prototyping Pi Plate Kit: Philip Kirby
- Next winner announced on 5-27-13!
Free Webinar: Hadoop
How to Build an Optimal Hadoop Cluster to Store and Maintain Unlimited Amounts of Data Using Microservers
Realizing the promise of Apache® Hadoop® requires the effective deployment of compute, memory, storage and networking to achieve optimal results. With its flexibility and multitude of options, it is easy to over or under provision the server infrastructure, resulting in poor performance and high TCO. Join us for an in depth, technical discussion with industry experts from leading Hadoop and server companies who will provide insights into the key considerations for designing and deploying an optimal Hadoop cluster.
Some of key questions to be discussed are:
- What is the “typical” Hadoop cluster and what should be installed on the different machine types?
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- How do I plan for expansion if I require more compute, memory, storage or networking? | <urn:uuid:08a024bb-2671-4b73-a537-951a5d93cb31> | 3.109375 | 2,430 | Content Listing | Software Dev. | 51.721129 |