text large_stringlengths 148 17k | id large_stringlengths 47 47 | score float64 2.69 5.31 | tokens int64 36 7.79k | format large_stringclasses 13 values | topic large_stringclasses 2 values | fr_ease float64 20 157 |
|---|---|---|---|---|---|---|
A programming model found on many modern 32 bit systems.
It means that integers, longs, and pointers are all represented as 32 bit quantities.
That means if you wrote the following program in C:
printf("int: %d\n", sizeof (int));
printf("long: %d\n", sizeof (long));
printf("pointer: %d\n", sizeof (void *));
Compiling and executing the program on an ILP32 system would
result in the following output:
Meaning that the default size of those C data types are all
4 bytes long, or 32 bits in size.
Reliance upon ILP32 assumptions in your code can break if
you port your code to something like Windows 3.1 or
the Macintosh, because both of those are LP32, and not
ILP32. In LP32, the size of an integer is 16 bits and | <urn:uuid:e6d9508f-b07c-437f-8efd-919efde00fdc> | 3.484375 | 190 | Knowledge Article | Software Dev. | 65.909615 |
The dream of nanotechnology includes unbelievably tiny electronic devices — including medical devices that could work at the microscopic level. But how do you assemble nanoparticles into larger systems, like nanocrystals? You can't exactly use a pair of tweezers.
Instead, researchers create a solution of dissolved nanoparticles, which self-assemble into crystal structures. These nanocrystals –- which have a uniform structure and properties that can vary depending on their size –- may have a variety of applications. But to customize them, researchers need to be able to control their growth. And a good first step is figuring out how they assemble in the first place.
As the researchers write in their paper, published in the journal Science, "Understanding the mechanism of…nanocrystal growth using nanoparticles as building blocks provides a link between the world of single molecules and hierarchical nanostructures, and paves the way to rational design of nanomaterials with controlled properties."
How can you observe a nanocrystal as it grows? While any traditional optical microscope would fail miserably if it tried to focus at this scale, there are other imaging methods, such as transmission electron microscopy, or TEM. In TEM, the device sends a beam of electrons through an object and measures how the electrons interact with the sample. Then, an image of these interactions can be focused onto a film or measured by a camera.
But TEM needs its electron beam to travel through a vacuum, which means placing the sample under vacuum conditions. Meanwhile, nanoparticles need to be in solution in order to assemble into nanocrystals. Placing a liquid sample in the TEM vacuum would cause the solution to evaporate, destroying the assembly process rather than capturing its image.
Researchers at Lawrence Berkeley National Laboratory solved the problem by sealing their solution in a liquid cell. The scientists were studying platinum-iron nanorods, which can act as catalysts in electrochemical reactions. This makes them good candidates for inclusion in devices that store energy and convert it from one form to another. The nanorods self-assemble from a "growth solution" of platinum and iron nanoparticles dissolved in a solvent.
To create a liquid cell that could protect the solution from evaporation in a TEM's vacuum, the researchers stacked two thin transparent membranes of silicon nitride atop one other, leaving a gap only 120 nm thick between them. This gap was the right size to allow capillary action to suck the growth solution into the cell, leaving the solution sandwiched between the membranes. Finally, epoxy sealed the sandwich edges shut to close up the cell.
Another study in the same issue of Science used a similar technique to image nanocrystals assembling, but they were observing how two iron oxyhydroxide nanoparticles can attach to each other after they rotate to align their crystal lattices.
When the liquid cell of platinum-iron nanoparticles went into a TEM, this is what the scientists saw. These videos are sped up to run 30 times faster than real time. As time went on, the structures growing out of the solution became more and more organized. The nanoparticles began by forming long chains with multiple crystal orientations. Then the chains aligned, latching on to each other to form nanowires. Finally, the nanowires straightened out into long nanorods, 40 times longer than they were wide, with uniform crystal structures and orientations.
The paper describes in detail how the mess of nanoparticles grew more and more organized, eventually forming nanorods with a consistent crystalline structure:
"The nanoparticle chains formed during the early stage are winding and markedly flexible. The relative position of the nanoparticles within the chain changes and the orientation of individual nanoparticles also alters…During the final stage of growth, adjacent nanoparticles within the chain contact each other, forming a neck…Subsequently, mass redistribution eliminates the neck, and a smooth nanowire is formed. The diameter of the nanowire is slightly smaller (about 4.0 nm) than that of the individual nanoparticles before attachment (5.3 nm). A bent polycrystalline nanowire can straighten and transform into a singlecrystal nanorod with well-defined shape. This final stage of structural relaxation sometimes proceeds in parallel with the second stage of nanoparticle attachment. Notably, most of the nanowires remain twisted and polycrystalline for an extended period of time."
Knowing how these rods form will help scientists design nanomaterials with specific properties for a more effective, and perhaps tinier, future. | <urn:uuid:e98ceba5-6177-4f49-8baa-4bb3ce8fcad4> | 4.375 | 936 | Truncated | Science & Tech. | 27.679076 |
Jane N. Shields
Hi Again! You've just finished the lesson on radiation and the nuclear particles that are released from nuclides. Did you know that nuclear particles release usable energy? This energy source comes uranium pellets that are inserted into rods that undergo fission when bombarded by a neutron starter. So, put on your seat belt and open up your notepad (brain) to a trip that explains the intricate details of nuclear energy as source of energy (electricity).
What is Nuclear Power? Well, to get a better understanding click on this site what explains how nuclear is a viable, realistic means of producing heat that is transferred to water that turns a generator to produce electricity to millions of people.
Uranium Now, that you know what nuclear is, lets discuss what is in the reactor vessel those fuels rods that have pellets.
So, a nuclear reactor has atoms that undergo fission. This reaction is continuous unless it is controlled. To control the reaction, borate water is used to prevent overheating may come from lakes, rivers, and the ocean to remove the generated heat.. Another method of controlling the heat generated is manipulating the fuel rods in and out of the reactor.
Inside A Nuclear Power Plant
Types of Reactors
Heat Exchangers As the reactor heats up the primary water, it moves into heat exchangers (steam generators) that remove the heat. This pressurized steam is referred to a the primary heat that spins a turbine to generate electricity. The secondary steam is condensed and returns to a steam generators.
Outside A Nuclear Power Plant
Now that you have seen what the inside of nuclear power plant looks like, check out this site for the outside.
What Bad things can happen at a nuclear power plant?
Well, on March 28, 1979, Three Mile Island had a mishap. Lots of mistakes were made my operators which lead to a nuclear meltdown. Click on this site to learn more.
As a result of all the mistakes that caused the Three Mile Island accident. Many people became anti-nuclear power activist. There fears were silenced for not quite a decade when the Worlds' worst accident occurred. http://www.world-nuclear.org/info/chernobyl/inf07.html
Do you have more questions about nuclear power?
This site will answer some of the frequently asked questions. For example, in 1993 there were 109 operable nuclear power plants. These power plants supply 20% of the energy requirement of the United States. This does not included the large number of naval reactors.
Interested in a career in nuclear energy, link to this site.
Click on the site below to test you knowledge about energy.
Schedule a fun "Power Trip".
Clipart from http://www.google.com | <urn:uuid:00defd09-2794-4bd2-b59e-035e66eb2665> | 3.6875 | 566 | Tutorial | Science & Tech. | 54.953684 |
Poyang Lake is situated in Jiangxi Province, around 50 kilometres north of the city of Nanchang. The Lake's basin is one of the People's Republic of China's most important rice-producing regions, but local inhabitants must contend with massive seasonal changes in water level, topped by regular severe floods.
Poyang Lake is connected to the Yangtze (Chiang Jiang) River through a narrow channel. In the dry season of a normal year, the area of the Lake shrinks to less than 1000 square kilometres, but by the end of the rainy season its size can grow up to 3500 square kilometres.
Improved understanding of Poyang Lake's annual dynamic could help with flood mitigation as well as improved ecological characterisation of the surrounding landscape. Accordingly a radar sensor aboard Envisat was used to regularly monitor the Lake during 2004 to 2005.
Envisat's Advanced Synthetic Aperture Radar (ASAR) instrument records the signal reflectivity of the Earth's land, sea and ice surfaces, and works on even through clouds, rain or local darkness. ASAR functions in various different modes Global Monitoring Mode (GMM) data being acquired continuously over the land as part of the satellite's background mission.
GMM images have a comparatively low spatial resolution of one kilometre, but with a swath of 400 kilometres they have very wide coverage and a frequent revisit time, useful for tracking dynamic features.
Up until now GMM has mainly been utilised for monitoring icebergs but Strasbourg-based rapid mapping specialists SERTIT began investigation of its potential for following seasonal water level changes on Poyang Lake as part of the Flood Rapid Mapping element of the Dragon Programme, a joint und
Contact: Mariangela D'Acunto
European Space Agency | <urn:uuid:d2f8d1e7-8c1d-470e-a188-7b7b5f7351e3> | 2.96875 | 363 | Knowledge Article | Science & Tech. | 23.720416 |
Major Section: GUARD
The discussion of guards concludes here with a few miscellaneous
remarks. (Presumably you found this documentation by following a
link; see guards-for-specification.) For further information
related to guards other than what you find under ``guard,'' see
any of the following documentation topics: guard-example,
Defun can be made to try to verify the guards on a function.
This is controlled by the ``defun-mode'' of the
see defun-mode. The defun-mode is either as specified with the
xarg of the
defun or else defaults to the default
defun-mode. See default-defun-mode. If the defun-mode of the
logic and either a
guard is specified or
t is specified in the
xargs, then we attempt to
verify the guards of the function. Otherwise we do not.
It is sometimes impossible for the system to verify the guards of a
recursive function at definition time. For example, the guard
conjectures might require the invention and proof of some
inductively derived property of the function (as often happens when
the value of a recursive call is fed to a guarded subroutine). So
sometimes it is necessary to define the function using
:verify-guards nil then to state and prove key theorems about the
function, and only then have the system attempt guard verification.
defun guard verification is achieved via the event
verify-guards. See verify-guards.
It should be emphasized that guard verification affects only two things: how fast ACL2 can evaluate the function and whether the function is executed correctly by raw Common Lisp, without guard violations. Since ACL2 does not use the raw Common Lisp definition of a function to evaluate its calls unless that function's guards have been verified, the latter effect is felt only if you run functions in raw Common Lisp rather than via ACL2's command loop.
Guard verification does not otherwise affect the theorem prover or the semantics of a definition. If you are not planning on running your function on ``big'' inputs and you don't care if your function runs correctly in raw Common Lisp (e.g., you have formalized some abstract mathematical property and just happened to use ACL2 as your language), there is no need to suffer through guard verification. Often users start by not doing guard verification and address that problem later. Sometimes you are driven to it, even in mathematical projects, because you find that you want to run your functions particularly fast or in raw Common Lisp.
certify-book is used to compile a file, and the file contains
functions with unverified guard conjectures, then you will be warned
that the compiled file cannot be loaded into raw Common Lisp with
the expectation that the functions will run correctly. This is just
the same point we have been making: ACL2 and Common Lisp agree only
on the restricted domains specified by our guards. When guards are
violated, Common Lisp can do anything. When you call a compiled
function on arguments violating its guards, the chances are only
increased that Common Lisp will go berserk, because compiled
functions generally check fewer things at runtime and tend to be
more fragile than interpreted ones. | <urn:uuid:4a81d301-65c4-4f02-8ffb-f6ef3c0eb9b0> | 2.71875 | 684 | Documentation | Software Dev. | 43.38768 |
Scientists Refute Argument Of Climate Skeptics
ScienceDaily (Jan. 10, 2009) — Scientists at the GKSS Research Centre of Geesthacht and the University of Bern have investigated the frequency of warmer than average years between 1880 and 2006 for the first time. The result: the observed increase of warm years after 1990 is not a statistical accident.
Between 1880 and 2006 the average global annual temperature was about 15°C. However, in the years after 1990 the frequency of years when this average value was exceeded increased.
The GKSS Research Centre asks: is it an accident that the warmest 13 years were observed after 1990, or does this increased frequency indicate an external influence?
With the help of the so called "Monte-Carlo-Simulation“ the coastal researchers Dr. Eduardo Zorita and Professor Hans von Storch at the GKSS-Research Centre together with Professor Thomas Stocker from the University of Bern estimated that it is extremely unlikely that the frequency of warm record years after 1990 could be an accident and concluded that it is rather influenced by a external driver.
"Our study is pure statistical nature and can not attribute the increase of warm years to individual factors, but is in full agreement with the results of the IPCC that the increased emission of greenhouse gases is mainly responsible for the most recent global warming“, says Zorita in summary.
Full article here: | <urn:uuid:aac3a2c7-ccfb-4a61-9fd5-0cdda4d3f8fb> | 2.765625 | 291 | Comment Section | Science & Tech. | 37.443937 |
Written by John Power
The Aleutian volcanic arc is comprised of at least 75 volcanic centers that extend more than more than 2500 km from Mount Spurr to Kiska (Fig. 1). The arc is the result of the subduction of the Pacific plate beneath the North American plate. Within historic times 40 of these volcanoes have produced more than 265 documented eruptions (Miller et al., 1998). Based on historic rates of activity over the last 100 years1 to 2 eruptions within the Aleutian arc each year. The high rate of volcanic activity is thought to be related to the rapid rate of plate convergence (~7 cm/year maximum) along much of the arc. Aleutian arc volcanoes cover the entire range in eruptive style and magma composition. The principal hazards from Aleutian volcanic eruptions are airborne volcanic ash, which is extremely dangerous for aircraft. The Aleutian volcanoes lie beneath the heavily traveled North Pacific air routes, Local communities, oil production facilities and land based sea food processing plants are also exposed to hazards from mudflows, ash fall, and pyroclastic flows.
The Alaska Volcano Observatory (AVO) a joint program of the U.S.G.S., the Geophysical Institute of the University of Alaska, and the Alaska Division of Geological and Geophysical Surveys is presently involved in monitoring Aleutian arc volcanoes and provides warnings to local communities and affected industries. AVO presently monitors seismic activity in real-time at 25 Aleutian arc volcanoes in real-time and plans to extend seismic monitoring to all 41 historically active centers within the next 10 years.
Many of the Aleutian volcanoes are located on small islands that greatly restrict the geometry and aperture of AVO’s seismographic networks. Location of seismic stations is often further restricted by strong mircoseismic noise generated by ocean waves. The effects of mircoseismic noise are often amplified by the unconsolidated pyroclastic deposits that frequently makeup the flanks of many Aleutian arc volcanoes. The limited extent of many of AVOs seismographic networks often restricts the accuracy of earthquake hypocenter determination and frequently precludes the detection and tracking of volcano induced seismicity in the mid- to lower crust. The addition of Ocean Bottom Seismometers (OBS) would greatly strengthen AVOs existing seismic networks and would allow improved locations of volcano related seismicity such as Long-Period events and Volcano-Tectonic earthquakes as well as improved determination of velocity and attenuation structures using tomographic techniques. These measurements would provide for a greatly improved understanding of the subsurface components of the magmatic system and the processes that proceed and lead to eruptions.
The Aleutian arc volcanoes that are most likely to benefit from deployment of OBS systems would be Augustine, Westdahl, Akutan, Makushin, Okmok, Great Sitkin, Kanaga, Tanaga, and Gareloi (Fig. 2). These volcanoes have a combined total of 64 eruptions within the last 100 years, suggesting that an eruption could be expected at one or more of these volcanoes within the next 5 years. Other Aleutian volcanoes could certainly benefit from OBS deployments but these are not currently monitored by AVO. Volcanic eruptions are frequently preceded by weeks to months of increased earthquake activity. Once the AVO seismic network identified significant unrest we would deploy OBS systems surrounding the target volcano within 1 to 2 weeks. The OBS would be deployed from a contract vessel based in Homer, Dutch Harbor or Adak (Fig. 2).
ReferencesMiller, T.P., McGimsey, R.G., Richter, D.H., Riehle, J.R., Nye, C.J., Yount, M.E., Dumoulin, J.A., 1998, Catalog of the active volcanoes of Alaska, U.S. Geological Survey Open-file Report 98-582. | <urn:uuid:1a418c92-8897-4cad-8496-3ac10663c973> | 3.328125 | 817 | Academic Writing | Science & Tech. | 38.204652 |
Gonochoristic- fish that maintain the same sex throughout their entire lifespan.
Induction- When one member changes sex due to lack (or removal) of the other sex; often when that individual is placed in a new environment.
Polygyny- a single, dominant male reproducing with a group of females (a harem).
Protandry- beginning life as a male and then changing to female.
Protogyny- beginning life as a female and then switching to male.
Secondary Male- A male that began life as a female (protogynous in origin).
Simultaneous Hermaphroditism- the sex organ is partitioned into both male and females (only seen in the Serranidae, genus Hypoplectrus, the Hamlets)
Size advantage model (Ghiselin 1969)- if an individual of a certian sex could significantly increase its reproductive success after reaching a certain size, it would be to their advantage to switch to that sex.
For example, a female with a larger body cavity can produce and more eggs per reproductive episode, and the more eggs produced increases her potential reproductive success. In such an instance, it would me beneficial for males after reaching a certain size to change to female. Such circumstances would predict protandry within a species.
Conversely, if a male above a certain size were to have greatly increased reproductive success (i.e. gain control of a harem), females would switch to males. This scenario would predict protogyny.
The size advantage model can be more clearly illustrated in the following figures:
Sneaker Male (also known as initial phase males, primary males, streaker males)- Born as males in a protogynous species, and stay as males. In fact, they will pretend to be females, and through this behavior, they can get close enough to a harem of females without being percieved as a threat, and fertilize the females eggs before the dominant secondary male has a chance to. Some of the most violent interactions on reefs are between secondary and primary males.
Suppression- In protogyny, when the presence of a male prevents females from changing sex. The females will then change sex upon removal of the male.
Main Page Social Determinants Physiology Future Directions References About the Author | <urn:uuid:f6579910-2627-4755-8f01-0bcf53e66ff8> | 3.03125 | 476 | Knowledge Article | Science & Tech. | 28.363771 |
G327.1-1.1 is the aftermath of a massive star that exploded and left behind a highly magnetic, rapidly spinning neutron star called a pulsar. This pulsar is producing a wind of relativistic particles, seen in X-rays by Chandra and XMM-Newton (blue) as well as in the radio data (red and yellow). The large red circle shows radio emission from the blast wave, and the composite image also contains infrared data from the 2MASS survey (red, green, and blue) that show the stars in the field. The X-ray observations allow scientists to estimate the energy released during the supernova explosion and the age of the remnant, as well as the amount of material being swept up as the blast wave from the explosion expands.
View Page | View Handout | More Images | <urn:uuid:f433b2db-2690-4e5e-b6f9-5b14dc87e3ae> | 3.125 | 169 | Knowledge Article | Science & Tech. | 54.10995 |
The Effect of an Electromagnetic Field on Single-Celled Organisms
Purpose or Problem
The purpose is to determine if there is any effect in the behavior (the movement) of common one-celled organisms when in the presence of a static electromagnetic field.
There has been a great debate over the years as to whether or not magnetism has an effect on living cells. People on one side of the debate believe that living under high-power electric lines causes harmful electromagnetic radiation that damages farmers' crops and is unhealthy for their bodies. The magnetic field created by alternating current traveling through electric power lines is a moving field; the field expands and collapses many times each second. On the other side of the debate are those people who believe that static fields of magnetism (unlike those generated by high-power electric lines) may be beneficial to health. They place magnets on parts of their body to aid in healing various ailments and injuries.
No doubt, you have at some time placed a magnet underneath a piece of paper or cardboard, sprinkled iron filings on top, and tapped it to see a pattern as the filings form lines, showing the otherwise invisible magnetic lines of force.
Magnetism is a phenomenon that is intimately related to electricity. Early scientists realized this when they placed a compass next to a wire through which electricity was flowing. The compass needle was deflected when electricity was flowing in the wire.
When direct current (DC), which is the type of current flow that comes from a battery, travels through a wire, a magnetic field extends out from the wire. Do common
single-celled organisms respond to this field by moving toward or away from the wire?
Hypothesize that several common one-celled organisms will not show any response (to move away from or to move toward the source) to a static electromagnetic field.
- Model train DC transformer
- Small 12-volt light bulb and socket
- Hook-up wire
- Wire cutters
- Small slotted screwdriver
- 40x or 50x microscope
- Microscope slide
- Petroleum jelly
- Adhesive or masking tape
- Live single-celled organisms (euglena, paramecium, flagellum, amoeba, and so forth)
Using hook-up wire, connect a model train DC transformer to a 12-volt light bulb to make a complete circuit. Any variable power supply or DC power transformer is appropriate, including one designed for model HO racing car sets. One piece of wire should be very long, so it can be draped across a slide on a microscope. The train power supply has a variable control on it, so the amount of electricity that flows in the circuit can be changed from zero to its full potential.
Position a microscope slide under the microscope and lay the wire across the slide. Use adhesive or masking tape to secure the wire in place. Be sure the wire is flat against the slide.
In the middle of the slide, squeeze a tube of petroleum jelly to form a "donut-shaped" circle. This will act as a wall to contain a tiny liquid pool of microorganisms. If your petroleum jelly is in a jar, use an ice-pop stick or a toothpick to form the petroleum dam.
From a science supply house or your high school biology teacher, obtain live single-celled microorganisms. They must be active organisms that are able to move on their own. These include euglena, paramecium, flagellum, and amoeba. Place a few small drops of the liquid medium containing the organisms in the "petroleum pool." The petroleum will not harm the organisms.
Set the microscope with a large-enough field of view so the wire and organisms around it can be seen.
Observe the organisms to be sure they are alive and moving around. Turn on the power supply and watch to see if any response occurs by the organisms to the wire that now has an electromagnetic field surrounding it. Try varying the amount of electricity supplied through the wire. The light bulb will give a visual indication that current is flowing, and its dimness or brightness is also a relative gauge indicating the amount of current.
Write down the results of your experiment. Document all observations and data collected.
Come to a conclusion as to whether or not your hypothesis was correct.
- Electromagnetic fields are also present in a wire carrying alternating current (AC). With AC, the electromagnetic field builds and collapses many times each second. Repeat the experiment using AC rather than DC. An AC power supply can be obtained from your local electronics store. An AC doorbell transformer, available at your local hardware store, will also work.
- Increase the magnetic field by exposing single-celled organisms to the strong alternating magnetic field from a bulk tape eraser (available at electronic stores) used to erase audio and video tapes. Observe the organisms.
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:f68a2938-aa1e-4a0a-b51f-8f313b5fabd9> | 3.484375 | 1,087 | Tutorial | Science & Tech. | 39.719523 |
By Jon Miller | Post Date: August 31, 2009 12:45 PM | Comments: 5
Can you guess what the small squares on this map indicate? This is an image that has been distributed on science news websites during the past week. The picture has been cropped to hide some information. This map and the tiny squares offer a lot of hope for our future. They also illustrate several important kaizen principles. Take a moment to think about what these squares could be before scrolling down the page or reading the next few paragraphs.
These tiny squares on the map are in very large in life size. These squares represent the surface are of the planet required to supply our power needs by energy from the sun. How does this map illustrate lessons in kaizen?
Get rid of fixed ideas and paradigms. Our energy comes from oil, coal, hydro and those green energy sources aren't technologically feasible. That's an old fixed idea. While it may have been true in the past, whenever we try to renew ourselves and do kaizen we need to challenge existing paradigms.
Visualize the ideal situation. Free, unlimited, universal, clean energy. Wouldn't that be great? We'll, it's just 8 minutes away and shiny.
Go get the facts. This map is a good visualization of the facts. I haven't "gone to see" for myself, so it could be just processed information and not facts. It did come off the internet after all... but for the sake of this illustration, and assuming they are facts, the map points us towards a possible way to bust paradigms and achieve the ideal.
Reduce waste. What is it about our current solution or process that is wasteful. Try until you can remove as many of those as you can and the result is kaizen (continuous improvement). There is still a lot we can do with kaizen in every field including energy. Sometimes it's kaikaku (revolution) when you invent or enable a totally new process or technology, such as shifting from non-renewable to renewable energy.
Think of ways to make it possible. Don't make excuses why it can't be done. Whether it is converting from non-renewable fossil fuels to renewable clean energy or simply changing how we work from individual work to team work, the people who have a stake in the status quo will fight change and give every reason why the idea won't work, why the ideal will never be reached. If we believe in the ideal, we should listen to these objections but not accept them as truth, only problems to be solved. If we had believed even half of the powers-that-be and their reasons for why it could not be done, humanity would never have made any progress.
Get input and ideas from many people. But it will be easier said than done. Unless you live in a benevolent dictatorship, massive efforts to install solar panels can be met with NIMBY (not in my back yard) sentiments as well as lobbying from interest groups, or simply stagnation due to bureaucratic process and government waste. People need to get engage in giving ideas on how to make it happen (not excuses).
I am not saying that solar is the answer. I'm in favor of less energy waste and making use of whatever free energy resources we have whether it be wind, algae, solar or other. We need a combination of kaizen and kaikaku and this map is encouraging for both.
Comments are moderated to filter spam and inappropriate content. There may be a delay before your comment is published. | <urn:uuid:8459bb35-f768-4042-8bd9-0529a08ef523> | 3.015625 | 728 | Personal Blog | Science & Tech. | 58.495855 |
I witnessed this explosive breeding spectacle in two consecutive years (both times mid-December - see http://www.inaturalist.org/observations/36714) at Montagne d'Ambre. There were thousands of bright yellow frogs mating noisily in a very shallow pool (video clip with audio available on request).
What puzzles me is that in all the literature concerning all species of Aglyptodactylus, it says that breeding MALES turn yellow (to a greater or lesser degree depending on species) yet in the population I observed clearly BOTH sexes turn yellow.
A. madagascariensis and A securifer are both known from Montagne d'Ambre. My justification for identifying these specimens as the latter is that Glaw & Vences (2007) say the breeding males are 'bright yellow', whereas in the former species they are only described as 'partly yellowish'. However, they were observed in rainforest habitat, which is not typically the domain of A. securifer. I am wondering if these could represent an undescribed species of Aglyptodactylus.
For further information, to see additional images or to enquire about using my photos, feel free to contact me via www.madagascar-photography.com | <urn:uuid:bbf7504b-e08b-468f-a8aa-bcd5aac962c8> | 2.78125 | 268 | Personal Blog | Science & Tech. | 37.98189 |
8. Shapes of Small Molecules and Proteins
Michael L. Connolly
Basically different methods have been used to study the shapes of small molecules and proteins. Tony Hopfinger has developed a method for small molecules that he calls "molecular shape analysis" and which involves comparing electrostatic fields (Hopfinger, 1980; Tokarski and Hopfinger, 1994). Stouch and Jurs (1986) measured small molecule similarity by superposing the two molecules and identifying the volumes that do not match using a spatial grid of points. Arteca and Mezey (1988) applied homology theory to study the shape of small molecules. They call their method "molecular shape descriptors" (Arteca, 1996). Meyer and Richards (1991) have developed a method to measure the similarity of molecular shape. Hermann and Herron (1991) have developed a pair of programs, OVID and SUPER, for studying small molecule shape. The latter program superposes two molecules. Masek, Merchant and Matthew (1993ab) have developed a method for measuring shape matching they call "molecular skins". Instead of maximizing the overlap of the whole interior volume, they consider only a shell or skin. It has particular advantage when attempting to match molecules of substantially different size. Bemis and Kuntz (1992) have developed methods for molecular shape description based upon considering distances between all possible triplets of atoms. Molecular shape has been used to screen databases of small molecules for the purpose of identifying molecules of possible pharmaceutical use (Good, Ewing, Gschwend and Kuntz, 1995). A fast method for shape characterization has been developed by Nilakantan, Bauman and Venkataraghavan (1993). Petitjean (1995) has defined a metric on the mathematical space of small molecule shapes based upon the volume of the symmetric difference when the molecules as superposed for maximum overlap. Blaney, Edge and Phippen (1995) have compared small molecules by comparing their electrostatic vector fields.
The shape of the protein as a whole have been studied several methods. Gates (1979) and Janin (1979) has studied the protein surface area to volume ratio. Peter Bladon (1989) has used the symmetries of the regular dodecahedron. Fourier analysis and spherical harmonics have been applied by Leicester, Finney and Bywater (1988, 1994), Max and Getzoff (1988), Max (1988), and Duncan and Olson (1993a). Malhotra, Tan and Harvey (1994) have combined spherical harmonics with electron microscopy and molecular mechanics.
The shapes of regions of the protein surface have been studied by different methods. Lee and Rose (1985) have made topographic maps of proteins. A topographic contouring method based upon depth below the convex hull has also been developed (Badel-Chagnon, Nessi, Buffat and Hazout, 1994). A method for measuring local curvature has been developed by (Connolly, 1986a). It is based upon centering a sphere at the protein surface and measuring the fraction of the sphere inside the solvent-excluded volume of the protein. If more than half of the sphere is inside the protein, the region is concave, if less than half of the sphere is inside the protein, the shape is convex. Either the solid sphere or the sphere surface may be used. A two-dimensional example is shown below.
The chymotrypsin surface below has been colored according to convexity or concavity. A sphere of radius six angstroms was centered at several points on each surface face, and the solid angle of the sphere lying inside the protein's molecular surface was computed and averaged over the face. Each face was colored according to where its average solid angle fell in the range between zero and four pi steradians. Convex regions are yellow, concave regions are blue, and regions of intermediate curvature are orange, red, and purple. The surface has been clipped, and the inner side of the molecular surface has been colored grey. The substrate-binding pocket is at the center of the image and can be seen to be blue.
This method has been further developed to distinguish between regions of equal curvature, but different shape (Connolly, 1992). Instead of simply measuring the amount of sphere area lying inside the protein's surface, one classifies its shape by comparing it to several thousand different template shapes.
One way to describe a protein surface is to identify the critical points, that is maxima and minima of some function akin to elevation that identifies knobs and holes (Fischer, Norel, Wolfson and Nussinov, 1993; Lin, Nussinov, Fischer and Wolfson, 1994). Other methods of studying protein topography have been developed by the Darmstadt group (Zachmann, Heiden, Schlenkrich and Brickmann, 1992; Zachmann, Kast, Sariban and Brickmann, 1993; Heiden and Brickmann 1994). Methods for measuring protein surface shape have been developed by Duncan and Olson (1993b).
Besides general methods for analysing protein surface shape, which apply also to convex and flat regions, there have also been developed specific methods for identifying clefts, crevices, and ligand-binding pockets in protein surfaces. Arthur Lesk has called this molecular speleology (1986). Voronoi polyhedra have been used to find clefts and possible drug binding sites in protein surfaces: (David, 1984; Boulu, Crippen, Barton, Kwon and Marletta, 1990; Crippen, 1991; Srivastava, and Crippen, 1993; Bradley and Crippen, 1993; Bradley, Richardson and Crippen, 1993). Blaney and Dixon (1991) describe the application of distance geometry in modeling receptor pockets. Some methods try to find the largest sphere that can be placed tangent to a particular surface atom without overlapping any other atom (Kuhn, Siani, Pique, Fisher, Getzoff and Tainer, 1992; Yeates, 1995). Parsons and Canny (1994) have written an interesting comparison of protein docking to robotics. Herbert Edelsbrunner (1993) and his colleagues at the University of Illinois and the National Center for Supercomputing Applications (NCSA) have applied methods from computational geometry and algebraic topology to characterizing protein surface concavities. Edelsbrunner and MŸcke (1994) have used a generalization of the convex hull called a 3D Alpha Shape to identify depressions and pockets on protein surfaces. These ideas have been applied to gramacidin A, HIV-I protease and the heme pocket of apomyoglobin (Edelsbrunner, Facello and Liang, 1995). Peters, Fauck and Fršmmel (1996) have developed an algorithm (APROPOS) for finding possible ligand-binding sites on protein surfaces using alpha shapes. They note that ligand-binding regions are concave, while protein-protein interfaces are generally rather flat.
[ 1. Introduction ] [ 2. Physical Molecular Models ] [ 3. Electron Density Fitting ] [ 4. Molecular Graphics ] [ 5. Solvent-Accessible Surfaces ] [ 6. Molecular Surface Graphics ] [ 7. Molecular Volume and Protein Packing ] [ *** 8. Shapes of Small Molecules and Proteins *** ] [ 9. Structure-based Drug Design ] [ 10. Protein-Protein Interactions ] [ 11. Surface Biology, Chemistry and Physics ] [ 12. Bibliography ]
All material in ths article Copyright © 1996 by Michael L. Connolly
NetSci, ISSN 1092-7360, is published by Network Science Corporation. Except where expressly stated, content at this site is copyright (© 1995 - 2010) by Network Science Corporation and is for your personal use only. No redistribution is allowed without written permission from Network Science Corporation. This web site is managed by:
- Network Science Corporation
- 4411 Connecticut Avenue NW, STE 514
- Washington, DC 20008
- Tel: (828) 817-9811
- E-mail: TheEditors@netsci.org
- Website Hosted by Total Choice | <urn:uuid:f0209059-68c9-40da-9945-b597f09e1527> | 3.1875 | 1,724 | Knowledge Article | Science & Tech. | 33.117575 |
3.1. Creating UML Diagrams The following example will create a class diagram with the UML2 tools. Create a new java project "de.vogella.uml2.first" and a new folder "uml2". Right-click on the folder "uml2", select New-> Other. Select UML 2.1 Diagrams and then the "class diagram" as the type.
The TechRepublic CIO50 list celebrates the most influential and innovative tech chiefs, voted by their fellow CIOs To effectively use the Unified Modeling Language (UML) when developing Java applications, developers must have a thorough understanding of the UML elements and how these elements map to Java. For now, I'll focus on one aspect of UML: the elements of a class diagram. Arguably, class diagrams are the most often used UML diagrams. The purpose of a class diagram is to specify the structural makeup of the system.
Copyright © 2007, 2008, 2009, 2010, 2011, 2012, 2013 Lars Vogel Eclipse Java IDE This tutorial describes the usage of Eclipse as a Java IDE. It describes the installation of Eclipse, the creation of Java programs and tips for using Eclipse. This tutorial is based on Eclipse 4.2 (Juno). This tutorial is part of this Kindle book: | <urn:uuid:00778733-4dd1-47e1-98a4-d3c09c1335d2> | 3.09375 | 273 | Tutorial | Software Dev. | 62.170044 |
This entry illustrates the intricate mineral structures that are formed by organisms (biomineralization). Biominerals are a composite of mineral and an organic component called the organic matrix. The organic matrix is believed to influence the architecture of the mineral aggregates and results in a vast array of beautifully intricate structures throughout the plant and animal kingdom. Biominerals are a perfect example of “life imitating art.” Oysters deposit two distinct shell layers composed of calcium carbonate. The submitted picture shows the deposition of folia crystals (look like the picket of a fence) from the inner shell layer which coalesce to form folia sheets. In this picture, the folia sheets converged to form a “rosette” structure at their boundaries. You can also see the organic matrix in between crystals which appears like “glue.” How the organic matrix “glue” affects the mineral type, shape and orientation continues to be at the heart of studies of biomineralization. Understanding how organic matrix is regulated by the cells that secrete it and how it influences mineral structure and growth has implications both in the human health realm of bone and teeth formation as well as nanotechnology applications that seek to create novel ceramic coatings. In this particular experiment, metal implants were placed into the oyster which resulted in the deposition of natural shell onto a removable surface. In this way, we can isolate and study key events that occur during shell formation.
Funding sources for research represented by the image:
AFOSR-UDRI subcontract; DOD | <urn:uuid:8f71e519-8a6f-4ffb-bf0f-6c08e089145f> | 3.109375 | 322 | Knowledge Article | Science & Tech. | 23.822043 |
Energy & Climate Change
Our modern society depends on affordable, reliable supplies of energy, both distributed for industrial and in-home use, and for transport. Developing countries most of which have been relatively energy-poor until recently are rapidly increasing their use of energy as their economies grow. The world depends for its current needs primarily on fossil fuels: coal, oil and gas. But concern about the effect of increasing levels of carbon dioxide in the atmosphere on global climate has focussed attention in recent years on replacement of fossil fuels by non-CO2 emitting energy sources, such as solar, wind and nuclear. Policies designed to reduce CO2 emissions are not necessarily the best ones to promote energy security or help developing countries to prosper. There are important decisions to be taken which will affect the lives of all of us. It is vital that the evidence for human influence on climate is debated openly and that all viable approaches to energy security are properly considered. | <urn:uuid:8204dd10-99dc-43bd-925f-bb4a74d6732a> | 2.921875 | 188 | Knowledge Article | Science & Tech. | 21.913636 |
geckzilla wrote:You could always cool off like a kangaroo. Dig a little hole to lay in under a bush or tree and lick your forearms all over.
Hah, meteors are like cockroaches, then. You see one, there must be more lurking... Expert Chris Peterson dispels the myth! Well, sort of, anyway.
http://www.kktv.com/news/headlines/Poss ... 95025.html
For the past 10 days I was camping with Troop 199 in the Boy Scouts of America and others in the Heart of America Council at H. Roe Bartle Scout Reservation. The only time it rained was on the morning of June 22, and only that morning. For the rest of the time the heat index was at least 100 degrees with the added humidity. The inside of the tents were like ovens.
The heat was in tents?
http://earthobservatory.nasa.gov/IOTD/view.php?id=78394 wrote:<<On June 28, 2012, wildfires raged across the western United States. The Waldo Canyon fire in Colorado attracted the most attention after spreading into Colorado Springs and charring hundreds of homes, but large wildfires also burned throughout Utah, Wyoming, Montana, New Mexico, and Arizona.
A lack of winter snow cover and ongoing drought primed vegetation in these states for ignition. But in recent weeks, another ingredient for extreme wildfire emerged: heat. High temperatures dry out vegetation and decrease the relative humidity, making it easier for fires to ignite and spread.
Land surface temperatures (LST) are distinct from the air temperatures that meteorological stations typically measure. LSTs indicate how hot the surface of the Earth would feel to the touch. From a satellite vantage point, the “surface” includes a number of materials that capture and retain heat, such as desert sand, the dark roof of a building, or the pavement of a road. As a result, daytime land surface temperatures are usually higher than air temperatures.
This heat wave, like all extreme weather events, has its direct cause in a complex set of atmospheric conditions that produce short-term weather. However, weather occurs within the broader context of the climate, and there’s a high level of agreement among scientists that global warming has made it more likely that heat waves of this magnitude will occur.>>
http://earthobservatory.nasa.gov/IOTD/view.php?id=78389 wrote:<<Along the Rocky Mountain range, there has been a dearth of snow cover, insect stress in the forests, and a hot spring that has turned into a hot summer. The result by late June 2012 was a surplus of smoke from many dangerous fires raging across the western United States.
The map above depicts the relative concentration of aerosols in the skies above the continental United States on June 26, 2012. The map was assembled from data acquired by the Ozone Mapper Profiler Suite (OMPS) on the new Suomi National Polar-orbiting Partnership (S-NPP) satellite. Aerosol are tiny solid and liquid particles that have an outsized impact on weather and climate. Their concentrations are represented above in shades of red and yellow, with the highest concentrations in deep red and the lowest in light yellow. Grays represent clouds or areas where no reliable data were available.
In addition to measuring ozone levels in the atmosphere, OMPS can track aerosols (such as smoke particles) as they are lofted and transported by winds. The instrument measures the light scattered and reflected by the atmosphere. Specifically, it observes the difference between the amount of ultraviolet (UV) light the smoke- and dust-filled atmosphere scatters back to the satellite compared to the amount of UV the atmosphere would scatter back if skies were clear.
In the image, the aerosol signal is strong to the north and east of the North Schell, Dump, and Wood Hollow fires in Nevada and Utah. Thick smoke plumes from wildfires across Colorado moved east and south into the plains states. Further south in Texas, New Mexico, and Mexico, it is unclear if the aerosols were blown in from distant fires, if there is local burning, or if they are dust storms, which are also a result of hot, dry, and windy weather.>>
Users browsing this forum: CommonCrawl [Bot] and 7 guests | <urn:uuid:6a572d54-029f-4df9-b923-3eb297e8dfa3> | 2.796875 | 906 | Comment Section | Science & Tech. | 52.917901 |
#include <stdio.h>char *cuserid(char *s);
The cuserid() function generates a character-string representation of the login name under which the owner of the current process is logged in. If s is a null pointer, this representation is generated in an internal static area whose address is returned. Otherwise, s is assumed to point to an array of at least L_cuserid characters; the representation is left in this array. The constant L_cuserid is defined in the <stdio.h> header.
In multithreaded applications, the caller must always supply an array s for the return value.
If the login name cannot be found, cuserid() returns a null pointer. If s is not a null pointer, the null character `\0' will be placed at s.
See attributes(5) for descriptions of the following attributes:
|ATTRIBUTE TYPE||ATTRIBUTE VALUE| | <urn:uuid:a762e88d-b7dc-4c2c-8017-2572b600aaeb> | 2.796875 | 203 | Documentation | Software Dev. | 50.289869 |
A number of survey stations are in use in the Ross Sea Region by both the USAP and NZAP. All of the survey stations have been visited to connect and unify all current survey datums in use in the area to establish a network of survey stations surveyed with GPS. In 2000, Land and Information New Zealand (LINZ) implemented the Ross Sea Region Geodetic Datum 2000 (RSRGD2000) - a multi purpose geodetic ... referencing system. This new datum is consistent with New Zealand Geodetic Datum 2000, meets SCAR requirements and is aligned to the International Terrestrial Reference System (ITRS). This work is carried out in association with the US Geological Survey (USGS)/Ohio State University TransAntarctic Deformation Monitoring Project (TAMDEF 1). The data from the TAMDEF project is used to extend the RSRGD2000. LINZ continues to installed and observed new survey marks in the Ross Sea Region to strengthen the geodetic datum. These survey marks extended the network to cover an area south of the Shackleton Glacier to northern Victoria Land. A high accuracy continuous Global Positioning System tracking station was also installed at Scott Base (SCTB - LINZ Geodetic Code) and was operational as of 29 October, 2004. A second GPS station was established at Butcher Ridge on 7 December, 2007. The aim of the TAMDEF project is to predict crustal movement as a result of variations in the ice volume and loading of the East and West Antarctic Ice Sheets through time. In addition, active tectonics are suspected in association with the Terror Rift, an offshore fault zone that is nearby. There are also active volcanoes in the region that may also be responsible for a measureable amount of crustal deformation. GPS measurements separated by several years are used to test the predicted rates of motion.
The Scott Base GPS Continuous Tracking Station provides hourly and daily 30
second GPS Rinex files. Files are downloaded hourly and daily and are
available through the LINZ web site http://www.linz.govt.nz/positionz . GPS
data from this site can be used with data collected at remote sites to
determine the precise position at the remote site. | <urn:uuid:49d44370-f27c-4b5f-9577-6e3f94809c7b> | 3.09375 | 459 | Knowledge Article | Science & Tech. | 47.345029 |
Carbon Molecular Sieve and Producing Nitrogen Lasers
First invented in 1960 the laser was first called the solution looking for a problem. More than fifty years later lasers have become an invaluable part of human technology. Today uses for lasers range from being used in material processing endeavors such as laser cutting, welding, and bending, to reading bar-codes when you purchase something at a store, to being used by the military as a targeting sight, and even being used to do surgery (laser eye surgery being the one of the most common).
As technology has improved many different types of lasers have been developed. One of the more common types of lasers developed was the nitrogen laser. This laser uses nitrogen as a medium and an electrical discharge to create its beam.
Nitrogen lasers are particular useful in handling material processing functions for example they are good at cutting metal. However material processing functions require that lasers be efficient and cost effective and that is where nitrogen generation systems play an important role.
In order for the laser to function it needs pure nitrogen (between 97%-99.99%). The most common type of technology used in purifying nitrogen is membrane technology. This method is able to produce nitrogen up to 99%. However if that amount of nitrogen purity is not enough to generate a laser. Depending on what you are using the laser for the nitrogen may not be purified enough.
In order to get the purest form of nitrogen a PSA system and a carbon molecular sieve is needed. The PSA system, air compressor, and carbon molecular sieve work when the air compressor forces compressed air into the PSA system. Naturally compressed air is composed of 78% nitrogen, 21% oxygen, and less than 1% of various other gases, the same air that makes up the air in our atmosphere.
Once this air enters the PSA system the carbon molecular sieve adsorbs all of the oxygen and other gases, the nitrogen is able to pass by because it is not attracted to the carbon molecular sieve and it is then guided into a storage tank (See our earlier article on adsorption with carbon molecular sieve). Once the carbon molecular sieve reaches its adsorption capacity it can be regenerated so that it can be used over and over again.
The end result of this is process is that you have now produced nitrogen that is between 99%-99.99% pure. This highly pure form of nitrogen is useful for cutting through tougher and thicker metals. | <urn:uuid:ae087005-5ba5-4cad-aa4f-07165c8ee4d4> | 3.625 | 501 | Knowledge Article | Science & Tech. | 40.520693 |
ev_async_send() not trigerring corresponding async handler in target loop ?
py.kerembellec at gmail.com
Tue Dec 29 16:29:59 CET 2009
> Your experience is interesting, but I have a question: why do you need
> threads in event-driven machine? I just tested my app based on libev,
> it works as followed:
> for (i = 0; i < 4; ++i)
> switch (fork())
> case -1: /* epic fail */ break;
> case 0: return run_loop();
> default: /* manage worker (ev_child_init, ev_child_start etc) */
> * Watch workers
> int run_loop(void)
> * Ignore all signals as master process will manage them itself.
> * Do accept() which is managed by kernel instead of master
> * process.
> With this model I get about 17k req/s (including HTTP/1.0 protocol
> parsing) on 4 CPU server.
These threads are "worker threads", and there are several of them because a single threaded program would
only use one core on a multi-way server. In your example above, you replaced thread by processes (which is
barely the same on Linux for instance).
Also, the small HTTP server stub was just an example of code to pinpoint concurrency problems, understand
where the fds were being lost and get an estimation of performance (and most importantly use "ab"). My worker
threads will in fact perform much more operations at each request, including memory structure manipulation
and disk I/O (which may block a little). Threading (or forking) is then necessary to avoid one particular client
processing to stuck the entire clients stack.
Hope this answers your question,
More information about the libev | <urn:uuid:773143be-0dc1-48ab-8c45-3ab4dc890fcf> | 2.78125 | 396 | Comment Section | Software Dev. | 52.202473 |
I have an elementary question about the history of $\pi$. I thought the answer would be easy to find. But, to the contrary, after quite a bit of searching and after consulting math historians, I have been unable to find a satisfactory answer.
Who first proved that $C/d$ is independent of the choice of circle ($C$ and $d$ are the circumference and diameter, respectively)?
Who first proved that given two circles with circumferences $C_1$ and $C_2$ and diameters $d_1$ and $d_2$, that $C_1/C_2=d_1/d_2$? (Or, as I imagine Euclid would have written it: the circumferences of circles are to one another as their diameters.)
Most accounts of the history of $\pi$ spend a lot of time talking about how this fact has been "known" for a long time (giving Egyptian, Babylonian, biblical, etc. approximations to the value). But they never say who first proved it. I expected it to be in Euclid's Elements, but was surprised to find that it isn't. Can I take that to mean that it hadn't been proved by then? I would be very surprised if the proof was known to Euclid and he had not included it in Elements.
Note: Euclid does contain Eudoxus's proposition that $A_1/A_2=d_1^2/d_2^2$, where the $A_i$ are the areas of the two circles (Elements XII.2: Circles are to one another as the squares on their diameters.). This implies that the value of $A/d^2$ is independent of the choice of circle.
If we jump ahead a few years from Euclid we find the fact that $C/d$ is constant given implicitly in Archimedes's Measurement of the Circle. First of all, he finds bounds for $C/d$ (it being between $223/71$ and $22/7$). So presumably he knew that it was a constant. But also, it follows logically from his result that $A=rC/2$, where $r$ is the radius of the circle (Archimedes says that the area of a circle is equal to the area of a triangle with height $r$ and base $C$): if we take Eudoxus's proposition as saying $A=kd^2$ (for some constant $k$) and Archimedes's result as $A=dC/4$, then setting them equal we get $kd^2=dC/4$, or equivalently $C/d=4k$ (i.e., $k=\pi/4$).
So, my question is: who first prove this fact? Was it Archimedes? I've read that the version of the Measurement of the Circle that we have may be only a part of what Archimedes actually wrote. Do people conjecture that it was proved and stated explicitly in the missing part of this document?
This all seems very mysterious to me. I would be a little surprised to discover that the answer to this question is lost to history since it is such a major mathematical result (but maybe that is so). I would be surprised if it took until Archimedes to get a proof of this; if it was "known" empirically for the entire Greek period (which I assume it was), one would imagine that a rigorous proof would be highly sought after. One imagines a proof would have been within Eudoxus's reach. Finally, whether the answer the answer to the question is known or not known, I have been very surprised that no one has written about this fact (or at least not that I've found). | <urn:uuid:17fe8528-3c45-4076-81a7-9ab052a000f1> | 2.875 | 802 | Q&A Forum | Science & Tech. | 68.601718 |
2.2.3. Photoionization Modeling
Photoionization modeling is a necessary component of any abundance analysis. We have seen that the bright line method relies on calibrations from photoionization models as do ionization correction factors in the direct method. Thus, it might be misleading to give modeling a separate category. I do so to point out that with a high signal/noise spectrum, rich in emission lines, it is possible to derive more accurate abundances and to deduce properties of the exciting stars and the nebular geometry. Often, abundance studies deal with surveys of many objects intended to uncover underlying patterns, but in some cases, the accurate abundances of an individual object are critical for a particular problem. In the latter case, a direct abundance analysis can be put on firmer ground by developing a detailed photoionization model of the nebula.
Really wonderful things can be done when spatially resolved observations are combined with detailed photoionization models. I think a great example of this is the work of Baldwin et al. (1991) on the Orion nebula; this is a real treat with regard to getting the most out of one's observations. In this study it is possible to identify geometrical effects (the relative positions of the exciting stars and the bounding molecular clouds), but the most impressive aspect of this work is the detailed investigation of the possible effects of dust within the nebula. Their appendix C is a valuable monograph on the potential effects of dust on HII regions.
Photoionization modeling also allows us to explore different physical processes which may affect abundance derivations. As mentioned above, Shields & Kennicutt (1995) looked at the effects of dust in high metallicity HII regions. They discovered that the dust acts as an additional heating agent, strengthening the collisionally excited optical forbidden lines, which is why one never observes pure Balmer line optical spectra from high metallicity HII regions (even though they are easy to produce in photoionization models without dust). They also confirmed the suggestion by Henry (1993) that the depletion of refractory elements onto grains (specifically Si and Fe) could lead to hotter nebula as the efficiency of particular fine structure lines as coolants was diminished. From the conclusions of Shields & Kennicutt one can take away the following rule of thumb: HII region abundances are generally more secure for low metallicity regions with high temperature exciting stars and generally less secure for high metallicity regions with low temperature exciting stars. | <urn:uuid:6f9a2feb-8d14-4ff6-bb80-adc340d86e40> | 2.703125 | 514 | Academic Writing | Science & Tech. | 22.611706 |
The IRC protocol doesn’t define a specific encoding that should be used, nor does it provide any information on which encodings are being used.
At the same time, lots of different encodings have become popular on IRC. This presents a big problem, because, if you’re using a different encoding than someone else on IRC, you’ll receive their text as garbage.
Cinch tries to work around this issue in two ways, while also keeping the usual Ruby behaviour.
By setting the
encoding option, you
set your expectations on what encoding other users will use. Allowed
values are instances of Encoding, names of valid encodings (as
strings) and the special
:irc encoding, which will be explained
If set, Cinch will automatically convert incoming messages to the
encoding defined by
Encoding.default_internal, unless the special
:irc is being used as the
As mentioned earlier, people couldn’t decide on a single encoding to use. As such, specifying a single encoding would most likely lead to problems, especially if the bot is in more than one channel.
Luckily, even though people cannot decide on a single encoding, western countries usually either use CP1252 (Windows Latin-1) or UTF-8. Since text encoded in CP1252 fails validation as UTF-8, it is easy to tell the two apart. Additionally it is possible to losslessly re-encode CP1252 in UTF-8 and as such, a small subset of UTF-8 is also representable in CP1252.
If incoming text is valid UTF-8, it will be interpreted as such. If it
fails validation, a CP1252 → UTF-8 conversion is performed. This
ensures that you will always deal with UTF-8 in your code, even if
other people use CP1252. Note, however, that we ignore
Encoding.default_internal in this case and always present you with
If text you send contains only characters that fit inside the CP1252 code page, the entire line will be sent that way.
If the text doesn’t fit inside the CP1252 code page, (for example if you type Eastern European characters, or Russian) it will be sent as UTF-8. Only UTF-8 capable clients will be able to see these characters correctly.
Invalid bytes and unsupported translations
If Cinch receives text in an encoding other than the one assumed, it can happen that the message contains bytes that are not valid in the assumed encoding. Instead of dropping the complete message, Cinch will replace offending bytes with question marks.
Also, if you expect messages in e.g. UTF-8 but re-encode them in
CP1252 (by setting
Encoding.default_internal to CP1252), it can
happen that some characters cannot be represented in CP1252. In such a
case, Cinch will too replace the offending characters with question | <urn:uuid:da1692d8-3474-4b8b-be91-675f710fa743> | 2.765625 | 626 | Documentation | Software Dev. | 50.631579 |
If we could look at a nearby black hole, we would see that it wraps around itself an infinite series of annuli, each containing a complete and distorted image of the sky. This is quite different from the image of the sky produced by the gravitational lens of a star, which creates at most two images of the sky immediately behind the star. Passing starlight can orbit a black hole many times before escaping to an observer, which creates an infinite number of images of any object in the sky. The simulator on this page calculates our view of the sky around a black hole.
The simulator shows two sets of maps. The map on the left-hand side of the page, which is labeled “Lens Image,” shows the appearance of the sky around the black hole. The two maps on the right-hand side, which as a pair is labeled ”Source Positions,” show the appearance of the full sky in the absence of a black hole. The buttons below the maps permit the reader to rotate the sky to any desired position.
The Lens Image map is centered on the black hole, which is located at the zenith of the sky. The two red circles on this plot show the Einstein rings. The outer ring corresponding to the Einstein ring of a star, marking the image on the sky of light traveled around the black hole from the zenith. The inner ring marks the image on the sky of light traveling from the nadir. There are an infinite number of Einstein rings nested inside the inner red circle that alternate between the zenith image and the nadir image. Each pair of Einstein rings mark the boundaries of an annulus that contains a complete image of the sky. Because each annulus is exponentially smaller than the annulus that surrounds it, most annuli are too close together to show on the Lens Image map.
The black circle on the Lens Image map shows the region bounded by the Einstein rings. The boundary of this region is the black hole's last stable orbit; light at precisely this boundary can orbit the black hole indefinitely. The region inside the last stable orbit is black because light from a distant star that passes inside the last stable orbit inevitably falls onto the black hole's event horizon. The event horizon is smaller that the black region on the map, but it is not visible through any effect on passing starlight.
The Source Positions map shows the full sky. The half hemisphere map centered on the zenith is plotted above the half hemisphere map centered on the nadir. The zenith map shows the two Einstein rings and the disk inside the last stable orbit. The sources are shown as they would appear in the absence of the black hole.
The sky is mapped onto the plane in all of the plots through the stereographic projection. This projection has the properties that a circle on a sphere projects to a circle on the plane and angles on the sphere are preserved when projected to the plane.
The observer is situated at 12.5 Schwarzschild radii in the simulation. This distance defines the size of the Einstein rings and the last stable orbit on the sky. The angle by which light is deflected is approximated under the assumption that the observer is at infinity.
While only the two images resulting from less than a full rotation of the black hole are readily visible on the Lens Image, the two images resulting from more than a full rotation but less than two full rotations of the black hole are also calculated and plotted. These extra images lie within the inner Einstein ring, and at times appear as slight smudges of color inside the inner red circle.
The orientation of the sky relative to the black hole can be changed using the four buttons at the bottom of the simulator. These buttons can be activated with either the mouse or the keyboard. The buttons labeled “Left” and “Right” rotate the sky to the left and the right, changing the zenith angle between the black hole and the image sources. The buttons labeled “Clockwise” and “Counterclockwise” rotate the sky clockwise and counterclockwise around the zenith, changing the azimuthal angle of the image sources.
When a button is clicked using the right mouse button, the map rotates a fixed interval. If the mouse button is held for more than half a second, the map rotates continuously until the mouse button is released. To increase the rate of rotation, press the control key along with the mouse button.
The space key controls the rotation of the sky in precisely the same manner as the mouse button. If the space key is pressed for less than half a second, the sky rotates a fixed interval. If the space key is held for more than a half second, the sky rotates continuously. Pressing the control key along with the space key increases the rate of rotation.
I would appreciate hearing from you if you encounter an error while running the simulator or if you have suggestions for improvement. Send your e-mail to the editor of the website. | <urn:uuid:5d15e1e1-fd63-4df1-a26d-f1d384f66546> | 4.0625 | 1,030 | Knowledge Article | Science & Tech. | 51.290341 |
Quantum mechanics must be one of the most successful theories in science. Developed at the start of the twentieth century, it has been used to calculate with incredible precision how light and matter behave – how electrical currents pass through silicon transistors in computer circuits, say, or the shapes of molecules and how they absorb light. Much of today’s information technology relies on quantum theory, as do some aspects of chemical processing, molecular biology, the discovery of new materials, and much more.
Yet the weird thing is that no one actually understands quantum theory. The quote popularly attributed to physicist Richard Feynman is probably apocryphal, but still true: if you think you understand quantum mechanics, then you don’t. That point was proved by a poll among 33 leading thinkers at a conference in Austria in 2011. This group of physicists, mathematicians and philosophers was given 16 multiple-choice questions about the meaning of the theory, and their answers displayed little consensus.
That’s because quantum theory poses all sorts of strange questions that stretch the limits of our imagination – forcing us, for example, to conceive of objects like electrons that can, in different circumstances, be either waves or particles.
One of the most controversial issues concerns the role of measurements. We’re used to thinking that the world exists in a definite state, and that we can discover what that state is by making measurements and observations. But quantum theory (“quantum mechanics” is often regarded as a synonym, although strictly that refers to the mathematical methods developed to study quantum objects) suggests that, at least for tiny objects such as atoms and electrons, there may be no unique state before an observation is made: the object exists simultaneously in several states, called a superposition. Before measurement, all we can say is that there is a certain probability that the object is in state A, or B, or so on. Only during the measurement is a “choice” made about which of these possible states the object will possess: in quantum-speak, the superposition is “collapsed by measurement”. It’s not that, before measuring, we don’t know which of these options is true – the fact is that the choice has not yet been made.
This is probably the most unsettling of all the conundrums posed by quantum theory. It disturbed Albert Einstein so much that he refused to accept it all his life. Einstein was one of the first scientists to embrace the quantum world: in 1905 he proposed that light is not a continuous wave but comes in “packets”, or quanta, of energy, called photons, which are in effect “particles of light”. Yet as his contemporaries, such as Niels Bohr, Werner Heisenberg and Erwin Schrodinger, devised a mathematical description of the quantum world in which certainties were replaced by probabilities, Einstein protested that the world could not really be so fuzzy. As he famously put it, “God does not play dice.” (Bohr’s response is less famous, but deserves to be better known: “Einstein, stop telling God what to do.”)
Wonderful, wonderful Copenhagen
Schrodinger figured out an equation that, he said, expressed all we can know about a quantum system. This knowledge is encapsulated in a so-called wavefunction, a mathematical expression from which we can deduce, for example, the chances of a quantum particle being here or there, or being in this or that state. Measurement “collapses” the wavefunction so as to give a definite result. But Heisenberg showed that we can’t answer every question about a quantum system exactly. This is Heisenberg’s uncertainty principle: the more precisely you determine an electron’s momentum (as measured by mass multiplied by velocity), the less you can know about its position in space, and vice versa. In other words, there are some pairs of properties for which an increasingly accurate measurement of one of them renders the other ever fuzzier. | <urn:uuid:9d5d60ef-feb0-4552-905e-376baa12a047> | 3.28125 | 844 | Nonfiction Writing | Science & Tech. | 35.407997 |
Australian Water Information Dictionary
Describes a landscape within the GDE Atlas that is wetter than surrounding areas either seasonally or permanently, because it receives water from inflows in addition to rainfall. IDs include groundwater dependent ecosystems as well as ecosystems which use sources of water other than rainfall (e.g. surface water, soil water, irrigation).
The layer that shows IDs is derived from the remote sensing layer, in which only pixels that have inflow dependence likelihoods of between 6 and 10 are included. The pixels are a combination of MODIS and Landsat data and are at a resolution of 25m2.
This definition applies to: | <urn:uuid:3a654c4c-60e5-4ed1-9742-8f78bbf82b46> | 2.953125 | 130 | Knowledge Article | Science & Tech. | 31.430128 |
SpirogyraArticle Free Pass
Spirogyra, genus of green algae, found only in fresh water and usually free-floating. The slippery unbranched filaments are composed of cylindrical cells containing one or more beautiful spiral green chloroplasts, from which the genus gets its name. The nucleus is suspended in the central vacuole by fine cytoplasmic filaments. Vegetative reproduction is by fragmentation of the filaments. In sexual conjugation, cells of two strands lying side by side are joined by the outgrowths, or conjugation tubes, and the contents of one cell pass into and fuse with the contents of the other. The resulting fused cell (zygote) becomes surrounded by a thick wall and overwinters, while the vegetative filaments die.
On bright spring or fall days, there might be masses of Spirogyra floating near the surface of streams and ponds, buoyed by oxygen bubbles released during photosynthesis. During the night, when photosynthesis decreases, the masses tend to sink.
What made you want to look up "Spirogyra"? Please share what surprised you most... | <urn:uuid:b19d01ad-c805-4a28-a6eb-83601feedc31> | 3.546875 | 240 | Knowledge Article | Science & Tech. | 39.9026 |
In this age of rapidly evolving technology, DNA sequences can be analysed by computers, and machines can separate hundreds of proteins at once. This makes it is easy to forget that the genetic code isn’t simply a series of letters, and that proteins aren’t just what we get out of eating poultry. They are physical and chemical structures that build and care for our bodies.
The building blocks of DNA are known as nucleotides, and are comprised of three main parts: a phosphate group, a sugar, and a highly-charged unique nitrogenous base. Of the four bases, adenine (A) and guanine (G) are both purines, which consist of an aromatic ring attached to an imidazole group. The other two bases, cytosine (C) and thymine (T) are pyrimidines, made up of a single aromatic ring. It is widely known that in DNA, A pairs with T and G pairs with C, but why is this? Read more » | <urn:uuid:b12c06f0-8987-492e-aee6-b54b10be60c3> | 3.921875 | 210 | Truncated | Science & Tech. | 48.457911 |
The Sun is our closest star. It is a member of the Milky Way galaxy. The diameter of the Sun is 1,392,000 kilometers.
It is believed to be over 4 billion years old. The Sun is a medium
sized star known as a yellow dwarf. The
Sun spins slowly on its axis as it revolves around the galaxy.
The Sun is a large ball of gas consisting mostly
of hydrogen and helium. The Sun is about 109 times larger
The center, or core, of the Sun is very hot. The
temperature in its core is estimated to be over 15,000,000 degrees
Celsius. A process called "nuclear fusion"
takes place there. Nuclear fusion produces a lot of energy. Some of this
energy travels out into space as heat and light. Some of it reaches the
We can see storms on the Sun's surface called as "sunspots"
because they look like dark spots on the Sun's surface. The Sun also produces
big explosions of energy called solar flares. These flares shoot fast moving
particles off the Sun's surface. These particles can hit the Earth's atmosphere
and cause a glow called an Aurora.
The Sun has several layers: the core, the radiation zone, the convection zone, and the photosphere
(which is the surface of the Sun). In addition, there are two layers of gas
above the photosphere called the chromosphere and the corona. The following are
the events that occur on the Sun frequently: sunspots, solar flares, solar wind,
and solar prominences.
Without the Sun, the Earth would be a lifeless ball of rock
and ice. The Sun warms our planet, creates our weather, and gives energy to
plants providing food and energy to support life on Earth. The Sun is a large
ball of gas consisting mostly of hydrogen and helium. The Sun is about 109 times
larger than the Earth. Scientists estimate that the temperature at the center of
the Sun is about 15 million degrees Celsius. This is similar to exploding a
hydrogen, or nuclear, bomb. Large explosions on the Sun's surface cause solar
flares that shoot up high into space. The surface temperature is about 4000
degrees Celsius. Energy released from the Sun radiates in all directions,
reaching the Earth and other planets. The further the planet is from the Sun,
the less energy it receives. | <urn:uuid:135ea8b1-3969-4039-9c39-b61e5b865ecc> | 3.890625 | 505 | Knowledge Article | Science & Tech. | 62.443182 |
THE rare discovery of a fossil embryo has cleared the name of a dinosaur called "egg stealer". Oviraptor, first discovered apparently making a meal of another dinosaur's eggs, was, it now turns out, simply trying to hatch its own offspring.
In 1923, an expedition from the American Museum of Natural History in New York found the first Oviraptor skeleton on a nest of eggs in the Mongolian desert. The scientists thought the elongated eggs belonged to Protoceratops, a plant-eating dinosaur whose fossils were common in the area. They chose the name Oviraptor because they assumed the animal, a predator with sharp claws and a parrot-like beak, was trying to eat the eggs when it was caught in a sandstorm and died.
No one could confirm that a Protoceratops had definitely laid the eggs, however. The contents of fossil eggs are hardly ever preserved. But in the latest issue of the ...
To continue reading this article, subscribe to receive access to all of newscientist.com, including 20 years of archive content. | <urn:uuid:33c057b0-5f5f-407b-b636-e8e604d1b2a1> | 3.546875 | 225 | Truncated | Science & Tech. | 50.876072 |
Measuring Surface Tension
Date: May 2006
What are the measurements you use to find the
surface tension of a liquid?
There are many methods for measuring the surface tension of liquids.
Each has its advantages and limitations. There is a reason why there
are different methods -- surface tension is a very complicated
property of a liquid. It depends upon many variables, some of which
are: temperature, composition of the liquid (it may be a solution or
contain small amounts of substances that affect the surface
tension), measurement time (surface tension depends on time), the
material of construction of the apparatus, the viscosity of the
liquid: And this is the short list!! Realistically, one should refer
to the surface "tensionS" (plural) of a liquid because the answer
you get can be very different depending upon the method used.
One category of methods is based on the angle of contact a
liquid makes to a solid surface. The solid may be a flat horizontal
plate, a tilted plate, a vertical plate, or the walls of a thin
tube (capillary). Assuming the variables above are all under
control, all these methods have a common limitation that the angle
of contact is difficult to measure accurately. Everybody "sees" the
angle a bit differently and this results in a different value of
the surface tension. In each case the liquid solid contact may be
stationary or may be moving.
A second category of methods is based on the shape of a drop of
the liquid. The drop may be hanging stationary, or it may be
dripping, or it may be resting on a flat plate. The "problem" with
this class of methods is that the mathematical analysis of the
shape of a drop and the surface tension of the liquid is very
complicated (in fact the relation between the shape and surface
tension must be solved numerically because the formulas don't have
a direct solution).
Each of these methods also comes in "flavors". One "flavor" is a
static measurement in which the liquid is not moving. The other
"flavor" is a dynamic measurement in which the liquid is moving.
Often the "static" and "dynamic" surface tension have quite
different values that are real, and not just experimental error. In
fact the difference between the "static" and "dynamic" value can be
very useful in understanding the surface properties of the liquid.
An interesting side light for any of these surface tension
measurements is that most all the experimental setups now use video
cameras to record the basic interface. So there is a permanent
record of the experimental results. This allows the scientist the
opportunity to review the result and refine its analysis.
Click here to return to the General Topics Archives
Update: June 2012 | <urn:uuid:a8495798-643f-4d98-a847-c86600d6ae79> | 3.921875 | 598 | Knowledge Article | Science & Tech. | 35.994817 |
An international team of scientists today published the first analysis of the genome sequence of Glennie, a female duck-billed platypus from Australia. Because the platypus occupies a unique branch on the tree of life, Glennie's genome could provide important clues about how humans and other mammalian species evolved.
Like all mammals, the platypus nourishes its young with milk. But platypus babies hatch from eggs, a characteristic usually associated with birds and reptiles.
By comparing the platypus genome with the genomes of other animals—including the human, mouse, dog, chicken and green anole lizard—the scientists hope to pinpoint which genes are common to all mammals, and when various traits have appeared or disappeared in the mammalian lineage. | <urn:uuid:93580ee4-5bdc-41d9-b88b-0edb765a60f3> | 3.46875 | 152 | Knowledge Article | Science & Tech. | 24.85279 |
It is built to peer farther into space than the Hubble can and measure and observe objects in space from the early Universe. Since it's mission is to study objects farther into space, the size, its orbit and the mirrors of the telescope, the instruments on the James Webb Space Telescope are different from those in the Hubble.
The mirror of the JWST is 6.5 meters in diameter and will have a five layer sunshield the size of a tennis court. It will be positioned around 1.5 million kilometers (930,000 miles) from the Earth and is designed to work primarily in the infrared range of the electromagnetic spectrum.
Compared to JWST, the Hubble Space Telescope is positioned 353 miles away from the Earth.
Four scientific instruments will be placed on the JWST. These are the:
- The Near InfraRed Camera (NIRCam)
- The Near InfraRed Spectrograph (NIRSpec)
- The Mid-InfraRed Instrument (MIRI)
- The Fine Guidance Sensor/ Near InfraRed Imager and Slitless Spectrograph (FGS-NIRISS)
By having the JWST able to study farther objects, astronomers can study objects from the early universe and peer through dust covered stars and galaxies that the Hubble is not able to do.
Video: The James Webb Space Telescope
There are four mission themes of the JWST.
- The End of the Dark Ages: First Light and Reionization
- The Assembly of Galaxies
- The Birth of Stars and Protoplanetary Systems
- Planetary Systems and the Origins of Life
The James Webb Space Telescope was named after the NASA Administrator who crafted the Apollo program, and who was a staunch supporter of space science.
The James Webb Space Telescope
National Aeronautics and Space Administration (NASA)
The European Space Agency (ESA)
Canadian Space Agency
James Webb Space Telescope Getting Ready To Launch and Replace The Hubble
Globular Star Cluster NGC 6362 Shown To Have Young Stars As Well As Ancient Ones
Hubble Telescope Reveals Galaxy NGC 922 Collided With Smaller Galaxy 330 Million Years Ago
Galaxy Pair Arp 116 Imaged By Hubble Space Telescope
Massive Galactic Filament of Dark Matter Imaged By Hubble Space Telescope In 3D
Binary Stars Discovered Orbiting Center Of Fleming 1 Nebula By ESO's Very Large Telescope (VLT) | <urn:uuid:ea2d0a96-f809-4ea7-a03c-62c381142ea9> | 3.96875 | 505 | Knowledge Article | Science & Tech. | 27.986738 |
FOSSIL BATS OF THE AMERICAS
SB 1A/Live Oak
The SB 1A/Live Oak LF was collected from a limestone mine just north of Live Oak in Suwannee County, northern Florida. Arikareean fossils were derived from fine-grained sediments filling a solution feature developed in marine Oligocene limestone (Frailey 1978). Frailey (1978) reported seven species of mammals from the SB 1A/Live Oak LF: four carnivores (the amphicyonid Mammacyon cf. M. obtusidens, the canids ?Mesocyon and Phlaocyon, and the mustelid Paroligobunis frazieri), the sciurid rodent Protosciurus, a horse, and the small camelid Nothokemas waldropi. Subsequent screenwashing led to the recovery of a diverse fauna of amphibians, reptiles, and small mammals. New additions to the SB 1A/Live Oak mammalian fauna include: the marsupial Herpetotherium, a vespertilionid bat, the small musteloid carnivores Palaeogale minuta and Arikarictis chapini, an undescribed entoptychine rodent, the large eomyid rodent Arikareeomys, and several species of the heteromyid rodent Proheteromys. Only two bat fossils have been recovered from this site, a lower molar of a small vespertilionid and an unidentified distal radius.
Frailey (1978) considered SB 1A/Live Oak to be late Arikareean and Tedford et al. (1987) and Albright (1998) placed this fauna in the early late Arikareean (Ar3), whereas Hayes (2000) thought this site was late early Arikareean (Ar2). The rodents Protosciurus and Arikareeomys and the tiny camelid Nothokemas waldropi are restricted to early Arikareean faunas in Florida. Protosciurus is found in Chadronian through early Arikareean faunas in the western US. Arikareeomys occurs in three other Florida Arikareean faunas, Cow House Slough, White Springs, and Buda. The only non-Florida record of this genus is from the McCann Canyon LF in Nebraska, originally placed in Ar3 (Korth 1992), but now thought to correlate with the Ar2 Monroe Creek Fauna (Tedford et al. 1996). SB 1A/Live Oak shares three species with the early Ar2 Brooksville 2 LF, the small carnivores Palaeogale minuta and Arikarictis chapini, and an undescribed entoptychine rodent. SB 1A/Live Oak LF is here placed in the late early Arikareean (late Ar2, 24-26 Ma), and is considered correlative with the White Springs LF, younger than Brooksville 2 and older than Buda. | <urn:uuid:39122837-5946-4e31-804e-a045b77cb292> | 2.71875 | 631 | Knowledge Article | Science & Tech. | 30.26 |
Swimming in the rain: novel untethered vehicle catches 'marine snow' falling through the sea.Twilight zones, witch hunts, and crossbows usually don't find their way into tales about new oceanographic instruments. This story isn't typical, but it does start in the usual way, with oceanographers striving to coax secrets out of inscrutable oceans.
In this case, scientists were investigating a fundamental but still mysterious process: How do tiny particles--comprised of dead phytoplankton phytoplankton
Flora of freely floating, often minute organisms that drift with water currents. Like land vegetation, phytoplankton uses carbon dioxide, releases oxygen, and converts minerals to a form animals can use. , dead zooplankton zooplankton: see marine biology.
Small floating or weakly swimming animals that drift with water currents and, with phytoplankton, make up the planktonic food supply on which almost all oceanic organisms ultimately depend (see , and zooplankton feces--sink from sunlit sun·lit
Illuminated by the sun.
Adj. 1. sunlit - lighted by sunlight; "the sunlit slopes of the canyon"; "violet valleys and the sunstruck ridges"- Wallace Stegner
sunstruck surface waters where they are produced, through the ocean's "twilight zone" where light penetrates weakly, and into the dark abyss? The rain of this so-called "marine snow" provides the food supply for organisms in the depths. It also has a major impact on Earth's climate by transporting carbon to the deep sea and preventing it from re-entering the atmosphere as a greenhouse gas. (See "A journey to the ocean's twilight zone," page 42.)
To collect the rain of particles, scientists built devices called sediment traps--cones or tubes that hang beneath buoys or float up from seafloor anchors. That, said Ken Buesseler, a biogeochemist at Woods Hole Oceanographic Institution Woods Hole Oceanographic Institution, at Woods Hole, Mass.; est. 1930. In addition to oceanographic research, it conducts important work in meteorology, biology, geology, and geophysics. (WHOI), "is like putting out a rain gauge in a hurricane."
Here's the problem: While particles descend slowly, perhaps 10 to a few hundred meters per day, they are swept sideways by ocean currents traveling at 3 to 27 nautical miles (5 to 50 kilometers) per day. (Imagine a balloon carried away by proportionally high winds from the top of the Empire State Building; it would be in Pennsylvania before it landed on a sidewalk.) "Particles do not fall vertically but 'sink' nearly horizontally, pushed by ocean currents," explained Dave Siegel, an oceanographer at the University of California, Santa Barbara History
The predecessor to UCSB, Santa Barbara State College, focused on teacher training, industrial arts, home economics, and foreign languages. Intense lobbying by an interest group in the City of Santa Barbara led by Thomas Storke and Pearl Chase persuaded the State .
In the late 1980s, Buesseler developed a technique to track marine snow by using thorium-234, a naturally occurring radioactive element in seawater that sticks to the particles. In a provocative 1991 paper in Nature, he pointed out that his chemical measurements of falling particles did not jibe with those measured by sediment traps.
"That got me into a lot of trouble early in my career," said Buesseler, who is now chair of the Marine Chemistry and Geochemistry Department at WHOI. "I was a junior scientist and was yelled at by some very important scientists for saying that their methods weren't working well. Some said I was off on a witch hunt."
For several years, Buesseler couldn't get peer-reviewed funding to go beyond the "classic 'put-out-a-coffee-cup-and-see-what-falls-in' sediment trap methods," he said. "It took a little while from putting out the idea to getting some movement."
In 1994, Buesseler, WHOI physical oceanographer Jim Price, and WHOI engineer Jim Valdes received a Cecil H. and Ida M. Green Technology Innovation Award from WHOI, which provided seed money to try a new idea. They wanted to cut the cord and go with the flow--to build a particle collector that would not be attached to a mooring. Instead, it would sink to a programmed depth and remain neutrally buoyant--that is, neither rise nor sink--at a depth between 450 and 1,500 feet (150 to 500 meters) in the twilight zone. It would be swept along with the currents for several days, collecting particles, and then return to the surface.
"Think of a hot air balloon This article is about hot air balloons themselves. For the associated activity, see Hot air ballooning.
The hot air balloon is the oldest successful human-carrying flight technology, dating back to its invention by the Montgolfier brothers in Annonay, being carried by the wind with a rain gauge attached," Buesseler said.
The team piggybacked on new technology by attaching particle-collecting tubes to floats being developed for physical oceanographers to measure currents, water temperature, and salinity. The floats pump oil into and out of an internal bladder to adjust their volume and regulate their buoyancy.
"The key to the whole endeavor," Valdes said, "is to accurately predict what the instrument will weigh in seawater." Extremely accurately.
"It may sound simple, but it is quite a balancing act to get these Neutrally Buoyant Sediment Traps (or NBSTs) to sink to the exact depth we need," Buesseler said. "If we are off in our weight calculations by the weight of a 1A-inch washer, it can send the instrument down another 100 meters, or more than 300 feet. Imagine if you were swimming and having a few coins in your pocket meant the difference between sinking or swimming."
Over the years, more evidence of the limitations in conventional traps mounted. As Buesseler's most vigorous opponents left the field or died, support for new traps rose. The researchers' work on a prototype NBST NBST Naruto Bunshin Scanlation Team (gaming)
NBST Narrowband Secure Terminal
NBST Narrow Band Subscriber Terminal earned them a grant from the National Science Foundation.
The team spent more than seven years designing the NBST--testing different instrument configurations in pressurized tanks; precisely estimating how pressure would compress materials in the depths and how this would shift weights; adding or removing items; making tradeoffs; trimming weight by adding small bottles of lead shot; changing glass tubes to aluminum because they were less fragile (though heavier); estimating the density of the water the instrument would travel through; calculating and recalculating the weight of every adjustment.
"It's all in the details," Valdes said. "But when you put an instrument over the side and it's untethered Unattached to any data or power source by wire or fiber; in other words: wireless. Contrast with tethered. , it has to work the first time, every time, or you'll never get it back."
That's what happened on a 2003 test. The team tracked the loss to a color-coding error in a resistor. "A small error in a 2-cent part resulted in the loss of the instrument," Valdes said.
So with trepidation, Valdes sent seven NBSTs overboard in 2004 in the Pacific Ocean near Hawaii. They sank, gauged and maintained their depths using a microprocessor that measures water temperatures and pressure, collected particles, and then surfaced a few days later and 10 to 20 nautical miles away. Here's where the crossbow comes in. (See article on next page.)
On their first scientific mission, "seven NBSTs went in the water and all seven came back with their precious cargo--a first in ocean sciences history," Buesseler said. A year later, the NBSTs proved their mettle again on another expedition in the northwest Pacific.
Based on their success, the National Science Foundation in July awarded Buesseler and Valdes a $2 million grant to build the next generation, which they call the Twilight Zone Explorer, or TZEX. It would be able to stay out for longer missions--initially for one month--so that scientists can sample particle fluxes over longer time periods without returning to sea.
The researchers are looking at a rotating carousel in TZEX that can open and close and segregate previous samples. They are also contemplating how to keep track of TZEXs that can be swept far and wide the longer they are at sea.
The team also wants to add more sensors to measure chlorophyll and light levels in the oceans, for example. Every addition requires recalculation re·cal·cu·late
tr.v. re·cal·cu·lat·ed, re·cal·cu·lat·ing, re·cal·cu·lates
To calculate again, especially in order to eliminate errors or to incorporate additional factors or data. of the instrument's buoyancy.
Finally, they seek a solution for what Buesseler called "the bane BANE. This word was formerly used to signify a malefactor. Bract. 1. 2, t. 8, c. 1. of particle trapping"--zooplankton that swim into sampling tubes in pursuit of food. Scientists call them "swimmers."
"Collection tubes are like pie plates for all the critters out there that want a free meal," Valdes explained. Swimmers sometimes "eat my data," Buesseler said, and other times mistakenly become data.
"They're carbon, too," Valdes said, and it's difficult to distinguish whether swimmers died and sank, or died after pursuing food into the trap. Researchers spend tedious hours peering through microscopes, picking out swimmers from their samples with tweezers tweezers An instrument with pincers used to grasp or extract. See Optical tweezers. .
"There's a whole art--or Zen--of swimmer picking," Buesseler said, and it creates bias depending on who is doing the picking. Valdes is designing a device with 5-inch rotating dimpled balls that look like golf balls, which shunt To divert, switch or bypass. smaller particles into bottles while preventing entry by larger swimmers.
"There are going to be challenges," Valdes said, "and it's not clear where it'll take us. We have a lot of concepts that we need to test in the lab and in open water, but we certainly have a destination in mind."
RELATED ARTICLE: Have crossbow, will travel to track down ocean devices.
When a Neutrally Buoyant Sediment Trap surfaces after a three- to five day particle-collecting mission in the ocean depths, "only its orange cap is visible, about the size of a 2-liter bottle of Coke," said Jim Valdes, an engineer at WHOI, "a proverbial needle ill a haystack."
"Couple this with a 6- to 10-foot swell and a wind of 35 or more knots producing whitecaps and blowing water, and you'll have some idea of how daunting a task finding an NBST call be," he said.
"The engineers at Woods Hole, with years of seagoing sea·go·ing
Made or used for ocean voyages.
built for travelling on the sea
Adj. 1. experience, designed a number of recovery aids into our NBSTs," Valdes said. "They knew that locating an NBST after deployment would not be trivial."
Scientists use an Acoustic Doppler Current Profiler An Acoustic Doppler Current Profiler (ADCP or ADP), is a type of sonar that attempts to produce a record of water current velocities over a range of depths.
Depending on the field application, ADCP may use 2, 3, 4, or more ceramic transducers, which work in water onboard ship to monitor the speed and direction of subsurface currents that have carried the NBST. They estimate where the NBST will surface and steer the ship in that direction.
At the surface, the NBST turns on an internal Global Positioning System Global Positioning System: see navigation satellite.
Global Positioning System (GPS)
Precise satellite-based navigation and location system originally developed for U.S. military use. receiver and then sends its position to the ship via a series of satellite relays. The NBST also transmits a radio signal that a sophisticated Radio Direction Finding Radio-location in which only the direction of a station is determined by means of its emissions. receiver on the ship picks up at a range of 5 to 7 nautical miles (9 to 13 kilometers).
During daylight, it's difficult to see small submerged objects in the water, so recoveries are made at night, when the crew can spot an NBST's flashing light up to 2 nautical miles (3.7 kilometers) away in good conditions. The crew shines a spotlight on it (left) and maneuvers the big research ship within yards of the NBST. The scientists use a crossbow (bottom left) to shoot a line with a grappling hook to reel in the instrument.
"So the crossbow became standard equipment," Valdes said. "But it's not a carry-on item," he said with a smile. "You ship them in advance, so you don't get stopped at Customs." | <urn:uuid:9fced92f-bc4a-420b-924d-8685b5591d70> | 3.234375 | 2,873 | Truncated | Science & Tech. | 50.811786 |
Source: Underwater Times
December 17, 2012
BUFFALO, New York -- Coral colonies that suffered tissue damage in The Bahamas were still producing low numbers of eggs four years after the injuries occurred, according to new research by University at Buffalo scientists. Tiny sperm-producing factories called spermaries were also in short supply. The slow recovery was a surprise, said UB geology professor Howard Lasker, PhD, who led the study on the coral species Antillogorgia elisabethae.
"The really interesting finding was that four years later, these colonies were still displaying an effect," Lasker said. "They don't necessarily look damaged anymore, but it takes some time to get back to where they were in terms of reproduction."
"This research has broader repercussions," Lasker said. "When you start talking about damage to reefs from events like hurricanes, you might say that the coral survived, that it lost some tissue, but it's still reproducing. That's true, but we now know the corals are not quite as healthy as we thought."
To read the full text of this article, click here . | <urn:uuid:f960c41f-ecfd-4f82-a53a-b4ffde828126> | 2.890625 | 237 | Truncated | Science & Tech. | 42.750443 |
Not something you see everyday — a snow-covered desert. The Taklimakan Desert in western China, the country’s largest desert, was covered with snow after a storm swept through the area in late December 2012 and continued into early January (the area also received snow in 2008). The cold wave hit different parts of China including Xinjiang Uygur Autonomous Region, Inner Mongolia Autonomous Region, north China and northeast China. Could it be attributed to the melting of arctic sea ice pushing colder weather south? This seems a question worth further exploration. Clearly, extreme weather events of this kind are not limited to certain geographic areas as last year’s cold snap in Europe also demonstrated.
References and Further Reading
Storm turns Taklimakan Desert White. Earth Observatory
Temperature continues to drop as cold snap lingers. Xinhua News Agency
China’s ice weather shatters records. Mother nature network | <urn:uuid:fe43426e-8b7f-4849-a636-975e8de9c0bb> | 2.90625 | 188 | Knowledge Article | Science & Tech. | 38.553006 |
a1 United Nations Environment Programme World Conservation Monitoring Centre, 219 Huntingdon Road, Cambridge, CB3 0DL, UK.
a2 Geographic Information Science Center of Excellence, South Dakota State University, Brookings, USA
a3 Program on Food Security and the Environment, Stanford University, Stanford, USA
Forest loss and degradation in the tropics contribute 6–17% of all greenhouse gas emissions. Protected areas cover 217.2 million ha (19.6%) of the world’s humid tropical forests and contain c. 70.3 petagrams of carbon (Pg C) in biomass and soil to 1 m depth. Between 2000 and 2005, we estimate that 1.75 million ha of forest were lost from protected areas in humid tropical forests, causing the emission of 0.25–0.33 Pg C. Protected areas lost about half as much carbon as the same area of unprotected forest. We estimate that the reduction of these carbon emissions from ongoing deforestation in protected sites in humid tropical forests could be valued at USD 6,200–7,400 million depending on the land use after clearance. This is > 1.5 times the estimated spending on protected area management in these regions. Improving management of protected areas to retain forest cover better may be an important, although certainly not sufficient, component of an overall strategy for reducing emissions from deforestation and forest degradation (REDD).
(Received December 14 2009)
(Reviewed February 08 2010)
(Accepted March 26 2010)
p1 Also at: Department of Zoology, University of Cambridge, Cambridge, UK
p2 Also at: WWF-US, Washington, DC, USA, and Department of Biology, University of Copenhagen, Copenhagen, Denmark | <urn:uuid:959b0076-1446-4154-9ce1-cb8fef0ba3ec> | 3.5625 | 350 | Academic Writing | Science & Tech. | 45.870481 |
The author takes us on an aerial view of the mighty Colorado River, providing water to 30 million people but running almost dry when it reaches the sea.
From the seat of a small jet plane I can place my hand against the window and parts of the Colorado River disappear. This isn’t like anytime I’ve flown before. There are no crying babies, peanuts or bathrooms.
I am with a pilot and a couple other college students dipping and turning at 10,000 feet. In four days we will traverse Colorado, Arizona and New Mexico. We’ll touch down in each state and speak with different groups about their work and lives as they relate to the Colorado River.
It’s the most disputed water source on planet earth, and we want to know why.
I’m flying courtesy of Eco Flight, a non-profit based in Aspen, Colorado. The founder Bruce Gordan has flown all around the world. He’s so good a pilot, in fact, that I spotted him reading the newspaper at a casual 9,000 ft above the ground.
He spoke of seeing the landscape change drastically in a short period of time. It inspired him to fly politicians and other decision makers, so they could be better informed on how their policies affect the environment. He said he became discouraged because nothing changed. That’s when he decided to fly students.
From an aerial perspective, the Colorado River looks like veins cursing through the thirsty body of the arid West.
It provides water for 30 million people, and is allocated for agriculture, the energy extraction industry, and domestic use. What’s left provides habitat to rapidly disappearing populations of fish and birds.
See Alexandra Cousteau’s Video “Death of a River: The Colorado River Delta”
After flowing to meet the Gulf for six million years, the Colorado River no longer reaches its delta. It hasn’t since 1998. The veins are drying up, and it’s leaving a strong battle in its wake.
Unfortunately, it’s often the oppressed communities that suffer the most from environmental exploitation. And with native populations, the story is all too common.
“I taste oil in the river by my school,” said Leo, a 14-year-old Navajo boy who spoke to us for hours about his love of running and basketball, his culture, and what it’s like to have a parent work at the coal plant.
We toured the Four Corners coal processing plant. A fellow student asked Nathan, our tour guide and a Navajo, what he thought about the future of coal. “We need to transition to renewables,” he said. And that it was just a matter of time before the plants were shut down.
The plant operates 24 hours a day sending its electricity to Las Vegas, San Francisco and New Mexico. It uses water to cool the potash (coal waste) that it gets from the San Juan river.
To read more and see the beautiful photographs from the trip, go to http://www.elephantjournal.com/2012/10/flying-the-colorado-river-our-rapidly-disappearing-life-source/
Environmental News from Living Green Magazine - Where Green Is Read | <urn:uuid:c05e83bb-de51-4b9c-b393-3d68d0bd0e2e> | 2.796875 | 680 | Truncated | Science & Tech. | 59.457612 |
Three points have coordinates o(0,0), A(5,0) and B(7,6). If P is the point (x,y) where y>0, calculate the value of x and y given that AP=BP and that the area of the triangle AOP is 10sq. units.
Three points have coordinates: .
If where , calculate the value of and.
given that and that the area ofCode:| (x,y) (7,6) | P o * B | o * * | o * * | * o * | * o | * * o | * * o | * * - - * - - - - - - - - - - - * - - - - - - (0,0) (5,0) O A
Since is equidistant from and
. . lies on the perpendicular bisector of
. . which has the equation: .
Code:| P | o (x,y) | * :* | * : * | * : * | * :y * | * : * | * : * O| * : * A - - * - - - - - - - + - - - * - - (0,0) (5,0)
The area of is 10 units
Its base is 5 and its height is . | <urn:uuid:876dd860-2ad5-4359-a8d8-434cba0ffa0c> | 3.21875 | 281 | Tutorial | Science & Tech. | 102.606085 |
Woodley, Jeremy D.; De Meyer, K.; Bush, P.G.; Ebanks-Petrie, G; Garzon-Ferreira, J.; Klein, E.; Pors, L.; Wilson, C.
Author Affiliation, Ana.
Centre for Marine Sciences
Status of coral reefs in the south-central Caribbean
Status of coral reefs of the world
Place of Publication
Australian Institute of Marine Sciences
Date of Publication
Series Editor Role
Series Volume Identification
Series Issue Identification
Caribbean corals have suffered from bleaching, diseases, and Diadema die-off. Reefs on narrow shelves adjacent to large human populations with many fishers (Columbia, Curacao, Jamaica, Venezuela) suffer from runoff of sediment and pollutants, over-fishing, and now show signs of degradation (fewer fish, more algae, less coral cover). Where shelves or banks are wide, or far from human populations, reefs are less disturbed. Islands with fewer people and little fishing pressure (Bonaire, Cayman) have good reefs. Here, diving tourism is economically important, and there is greater awareness of reef conservation. Cayman has the best-developed national coastal area management plan, while most other countries have marine protected areas. These are stimulating improved coastal management, aided by increasing numbers of nongovernmental organizations (NGOs)..... | <urn:uuid:d6d4ca19-8ad1-4681-bece-de5345573904> | 2.984375 | 283 | Structured Data | Science & Tech. | 30.406782 |
Problem 305Published on Sunday, 10th October 2010, 04:00 am; Solved by 402
Let's call S the (infinite) string that is made by concatenating the consecutive positive integers (starting from 1) written down in base 10.
Thus, S = 1234567891011121314151617181920212223242...
It's easy to see that any number will show up an infinite number of times in S.
Let's call f(n) the starting position of the nth occurrence of n in S.
For example, f(1)=1, f(5)=81, f(12)=271 and f(7780)=111111365.
Find f(3k) for 1k13. | <urn:uuid:e6e58ab3-d23a-47fa-92e1-4d52eda984b9> | 3.171875 | 160 | Tutorial | Science & Tech. | 102.20875 |
As has been hinted in many previous posts, many facts about algebraic number theory tell us about geometric objects like elliptic curves. For instance, if you are working on a problem which primarily uses the affine geometry of a curve like the semistable reduction theorem for elliptic curves, the scheme you’re working on is opposite to what’s called a Dedekind Domain. We begin a series of posts on Dedekind Domains, beginning today with the very abstract and progressing to the concrete(which would of course be terrible for teaching this material but I mean these posts as more of a reference work).
Definition: A Dedekind Domain is an integral domain which is:
- Krull Dimension 1
- Integrally Closed(Normal)
Many equivalent criteria exist for characterizing Dedekind domains among one-dimensional noetherian domains, two of which are:
- For each prime , the localization is a DVR
- Every nonzero ideal admits a unique factorization into a product of prime ideals
Then an affine ring of an elliptic curve (or any reasonable nonsingular curve) corresponds to a Dedekind domain as they are irreducible(integral) nonsingular(normal) curves(1-dimensional and noetherian). This is already enough to be of interest to any number theorist, but rings of integers of number fields are also Dedekind domains.
Definition: A number field is a finite algebraic extension of . The ring of integers is the integral closure of in . This is sometimes also called the maximal order of , in reference to the fact that we call subrings of that are also free -modules of rank contained in orders of .
These are 1-dimensional since any prime ideal of an order intersects with in an integral prime ideal so is a finite extension of so is a finite integral domain and thus a field. They are clearly noetherian since they are finitely generated -modules.
From this we can already see that rings of integers are Dedekind domains, but much more is true. The following theorem shows that starting from any order (or affine ring of a geometrically integral algebraic curve which could even be singular) the integral closure is a Dedekind domain. It also holds independent interest regarding the valuative criteria for properness and seperatedness (Hartshorne exercise II.4.11).
Theorem[Krull-Akizuki]:If is a one dimensional noetherian domain with field of fractions and is a finite extension of then the integral closure of in is a Dedekind domain.
For a proof consider first that we can simplify by taking by letting be a basis of contained in the integral closure and considering . This is noetherian because it is a finitely generated module and is noetherian. It is one dimensional because is one-dimensional and if is a chain of primes in then their intersections with give a chain of primes in . Since are nonzero ideals we could say about either of them that they contain a nonzero element and thus the principal ideal generated by . Since every element of is integral over (since ), satisfies an irreducible monic polynomial over so . Thus (respectively for ) and so are nonzero primes of so they must be equal by dimensionality. On the other hand consider that since is a finite integral extension so is also a finite integral extension, or more to the point since is a maximal ideal, a finite algebraic field extension. We thus arrive at a contradiction under the supposition that there is a chain of primes of length greater than 1 since has the nonzero prime ideal . On the other hand, cannot be dimension zero because contains nonzero primes and is contained in . Since a dimension zero domain is a field, if then . This is in contradiction to the fact that is integral over whereas the minimal polynomial for over is .
Thus we have reduced ourselves to the case that and to the following statement, which is sometimes itself called the Krull-Akizuki Theorem. Let be a one dimensional noetherian domain with field of fractions . Then any ring such that is also a one dimensional noetherian domain.
The idea of the proof is that if is a nonzero ideal of and is a nonzero element of then we can find an integer such that and so as an submodule (something), and thus is finitely generated over so is finitely generated over and so over . Thus by adding to the list of generators, is finitely generated over . For the gritty details of the proof of this statement, I refer the reader to Theorem 4.9.2 in http://books.google.com/books?id=APPtnn84FMIC&lpg=PA83&ots=2L9MiWbIYZ&dq=krull%20akizuki&pg=PA85
Note that I make no claims as the the finite generation of over . If is a separable field extension this holds true, but it’s quite possible to cook up an example of an integral closure which is not finitely generated if the field extension is inseparable(see Theorem 100 of Kaplansky’s book on Commutative Rings, where the example is actually a pair of DVRs). If this happens you’re typically stuck and can’t really do any algebra or geometry, but if we have finite generation( or a finite type morphism if that’s the terminology you prefer) of then we can have much of what we could possibly want to be true.
For instance, take the case that we have a degree morphism of curves over an algebraically closed field . Then if are the preimages of with multiplicities in it is well-known that . We have a corresponding result once we allow for non-closed points.
Theorem: Let be a Dedekind Domain with fraction field . Let be a finite field extension and the integral closure of in . Then if is finitely generated over if a prime ideal of factors in as
For a detailed proof we refer the reader to either Dino Lorenzini’s Invitation to Arithmetic Geometry Theorem III.3.5. The idea is that if is a P.I.D. then we can use classical techniques, like the structure theorem on finitely generated modules over a PID to get and the chinese remainder theorem to decompose into a product of finite field extensions of . Then we can reduce to the case of a PID by localization.
Having considered ideals and how they factor, we come to fractional ideals: a key point in algebraic number theory. An -module contained in the fraction field is called a fractional ideal if it is finitely generated over or equivalently if there is a denominator such that .
A fractional ideal is called invertible if there exists another fractional ideal such that the module product for some . We call ideals of the form for principal fractional ideals. Note that invertible fractional ideals are projective -modules of rank 1 and any projective -module of rank 1 is isomorphic to a fractional ideal. Also note that two fractional ideals are isomorphic as -modules iff there is such that . By definition the invertible fractional ideals of a ring form a group, and likewise after we mod out by the normal subgroup of principal fractional ideals. We call this quotient group the Picard Group and if the reader proves the above claims about projective modules of rank 1 this name makes sense in a wider context.
The Picard Group of a Dedekind Domain(which we sometimes call the ideal class group to distinguish how nice it is) is particularly nice because of the following characterization:
- A one dimensional noetherian domain is Dedekind if and only if every fractional ideal is invertible.
This is easy enough to prove with the following lemma.
Lemma: A fractional ideal of a one-dimensional noetherian domain is invertible if and only if for all , is a principal ideal of .
For a proof, see page 17 of http://math.uga.edu/~pete/8430notes2.pdf or else Neukirch’s book, section I.12.
We bring this up because if is a one-dimensional noetherian domain with field of fractions and is the integral closure of in and is finitely generated over then we can relate the Picard group of (which might not be so easy to understand) with the Picard group of (which by the above is easier to understand).
Theorem: If we let , there is an exact sequence
To prove this first note that surjects onto the group of principal fractional ideals in the obvious way and that if then for some . Thus the principal fractional ideals are isomorphic to .
Moreover by the above Lemma, the invertible fractional ideals are isomorphic to the direct sum over all primes of the principal ideals of . Thus the group of invertible fractional ideals is isomorphic to .
Thus we have the exact sequence
Likewise if we do the same for we get the sequence
Now consider that consists only of (the finitely many) primes lying above . It is not hard to prove that the localization of a Dedekind domain is Dedekind, and to use the Chinese Remainder Theorem to prove that a Dedekind domain with finitely many primes is a PID. If we let denote the group of principal fractional ideals of a ring , we have:
and thus since every prime of lies over a prime of , . Therefore our sequence for becomes the following:
Then we also have natural (surjective) quotient maps and which commute and thus give a natural surjective quotient map . Then we just apply the snake lemma for our result.
Next time we see what we can do with Dedekind Domains in separable extensions. | <urn:uuid:8a5aee80-305d-4d5b-aec6-15daf2c6c63b> | 2.703125 | 2,081 | Academic Writing | Science & Tech. | 40.211847 |
This week, animal rights group PETA announced the group would offer a million-dollar prize for the development of commercially-viable 'test-tube meat' -- real meat grown through a lab process, not from a live animal. The prize money would be awarded to the contest participant able to make the first in vitro chicken meat and sell it to the public by June 30, 2012. To win, the lab-grown meat must also have a taste and texture indistinguishable from real chicken flesh, be produced in large enough quantities to be sold commercially, and successfully sold at a competitive price in at least 10 states.
The process would likely invove some of the same techniques used now by medical researchers to grow tissue for medical procedures -- but would also need special conditions to produce tastes and textures similar to those fo natural meat. Earlier this month, researchers met in Norway for the 'First International In Vitro Meat Symposium.' Can a prize for the development of artificial meat spur research innovation in the same way that prizes have sparked competition in human space flight and robotic vehicles research? In this segment, we'll talk about the possibility, and how close science is to being able to grow a lab-made steak for your weekend cookout.
Produced by Karin Vergoth | <urn:uuid:bcf0c105-71bb-493d-9415-d9429c5b4fd6> | 2.96875 | 255 | Truncated | Science & Tech. | 33.966284 |
NET talk => F# language => Topic started by: Patriiick on November 19, 2010, 01:23:39 PM
F# (pronounced F Sharp) is a multi-paradigm programming language, targeting the .NET Framework, that encompasses functional programming as well as imperative and object-oriented programming disciplines. It is a variant of ML and is largely compatible with the OCaml implementation. F# was initially developed by Don Syme at Microsoft Research but is now being developed at Microsoft Developer Division and is being distributed as a fully supported language in the .NET Framework and Visual Studio as part of Visual Studio 2010.
(* print a list of numbers recursively *)
let rec printList lst =
match lst with
| -> ()
| h :: t ->
printf "%d\n" h
source: F Sharp (programming language). (2010, November 16). In Wikipedia, The Free Encyclopedia. Retrieved 12:23, November 19, 2010, from http://en.wikipedia.org/w/index.php?title=F_Sharp_(programming_language)&oldid=397032758
For more information, see Microsoft F# developer centre (http://msdn.microsoft.com/en-us/fsharp/default.aspx). | <urn:uuid:f467deae-39c8-4911-8bbe-de41909c4906> | 2.703125 | 270 | Comment Section | Software Dev. | 61.250158 |
An Aerospace Simulation Scenario
The Aerospace simulation uses initial resource deposits as estimated by British Petroleum (BP). Total initial deposits were 1.3 × 1012 tons of coal, 1.2 × 1012 barrels of oil, and 3.3 × 106 tons of uranium ore at the end of 2006. When the simulation is run, shortages of essential resources develop in some areas from changing rainfall patterns or the depletion of energy sources. These shortages may be met byexchanges of food or industrial production, or by shifting water and energy resources to food production. Where
shortages cannot be mitigated, the portion of the population affected is flagged as either migrating or in conflict. If the population moves to a new cell but still does not have sufficient resources, it decreases to the minimally supportable number of individuals. The simulation records the difference between the population growth and decrease on a monthly basis. Cell populations suffering from resource shortages have the option of migrating to a neighboring cell if it has sufficient food and water (the simulation assumes that such cells will accept refugees), or randomly competing with either the population within its cell or a neighboring cell. Competition with another cell involves migrating into a target cell without sufficient resources to support the new combined population. In cases where spreading shortages occur with energy in short supply, the area is labeled as a low-intensity conflict. In areas of water or food shortages, where energy resources and production are not in short supply, the area is labeled as a high-intensity conflict. | <urn:uuid:baf287e3-a215-4f6b-a925-69ef46d9b659> | 3.34375 | 300 | Knowledge Article | Science & Tech. | 33.685814 |
A magpie with yellow mark used in a mirror self-recognition experiment. Magpies can recognize themselves in a mirror, highlighting the mental skills of some birds and confounding the notion that self-awareness is the exclusive preserve of humans and a few higher mammals.
(Institute of Psychology, Goethe University, Frankfurt/Handout/Reuters)
It had been thought only chimpanzees, dolphins and elephants shared the human ability to recognize their own bodies in a mirror.
But German scientists reported on Tuesday that magpies -- a species with a brain structure very different from mammals -- could also identify themselves.
"It shows that the line leading to humans is not as special as many thought," lead researcher Helmut Prior of the Institute of Psychology at Goethe University in Frankfurt told Reuters.
"After finding this kind of intelligence in apes, many people thought it had developed once in one evolutionary line with humans at the end. The bird studies show it has developed at least twice."
The discovery of self-awareness in magpies follows a 2002 study in which a crow stunned researchers with its tool-making skills, by twisting a wire into a hook to lift food from a tube.
Prior and his colleagues tested their magpies by marking the birds' bodies with a red or yellow dot that could only be seen in a mirror. They found the birds regularly scratched the mark on their body, proving they recognized the image in the mirror as themselves and not another animal.
To ensure they were actually seeing and reacting to the mark, and not just investigating what had been done to them, a "sham" black mark was used as a control that was invisible on the birds' dark feathers.
The result throws into question some basic ideas about how our brains work.
In particular, it had been thought that the neocortex brain area found in mammals was crucial to self-recognition. Yet birds, which last shared a common ancestor with mammals 300 million years ago, do not have a neocortex, suggesting that higher cognitive skills can develop in other ways.
Prior believes parrots, too, may yet show hidden mental skills -- but it is the crow family, which includes magpies and jays, that is the smartest.
"Crows have really huge brains compared to other birds," he said in a telephone interview.
The research was published in the Public Library of Science journal PLoS Biology and is available online at http://biology.plosjournals.org/perlserv/?request=get-document&doi=10.1371/journal.pbio.0060202
(Editing by Mary Gabriel) | <urn:uuid:906d94cc-9584-4f92-95a7-92f13ebffbed> | 3.578125 | 538 | Truncated | Science & Tech. | 47.952208 |
Six-spot burnet moth (Zygaena filipendulae)
|Size||Wingspan: 25-40 mm (2)|
The six-spot burnet moth is not threatened (2).
The six-spot burnet moth (Zygaena filipendulae) is a brightly coloured day-flying moth. Its bright colours warn potential predators that it is poisonous. The blackish forewings have a metallic sheen and feature red spots that earn the species its common name (3). Despite the name, however, the number of spots can vary between individuals, and may be fused in some cases (4). The red hind wings have a fine bluish border and the antennae are club-shaped (3). A colour form known as f. flava has yellow spots in place of the normal red ones. Very occasionally, specimens with brown spots are also seen (5).
The six-spot burnet moth has a wide distribution in Britain and is fairly common. In Scotland it becomes more of a coastal species (2).
Found in a range of habitats including meadows with plenty of flowers, chalk downland, sea-cliffs, woodland rides, railway cuttings, disused quarries, and sand hills (2) (1). The six-spot burnet moth seems to prefer sites that have a mix of short and long grass, where there are sheltered sunny patches (3). The larvae need long grasses on which to pupate (1).
The six-spot burnet moth lives in colonies, and flies in sunshine from June to August (2). It feeds on the nectar of a large range of flowers, with wild thyme being a particular favourite (3). On overcast days it tends to retreat deep into grasses and can be difficult to spot (4). It is a single-brooded species, and the eggs are laid on bird’s-foot-trefoil. The caterpillars overwinter once, and occasionally twice, before pupating in paper-like cocoons on grass stems before emerging in June (4).
Although the six-spot burnet moth is not threatened at present, it seems likely that the widespread loss and agricultural improvement of semi-natural grasslands that has taken place will have impacted on this beautiful moth. Loss of ancient grasslands continues to date, while scrub encroachment is also a problem. Furthermore, colonies are vulnerable to drought (3).
The burnet study group has been formed to promote the conservation of burnet moths in Scotland (6).
For more on butterflies and moths see Butterfly Conservation:
- Larvae: stage in an animal’s lifecycle after it hatches from the egg. Larvae are typically very different in appearance to adults; they are able to feed and move around but usually are unable to reproduce.
- Pupate: the process of forming a pupa, the stage in an insect’s development, when huge changes occur that reorganise the larval form into the adult form. In butterflies the pupa is also called a chrysalis.
- Pupating: the process of becoming a pupa.
- Single brooded: (also known as ‘univoltine’). Insect life cycle that takes 12 months to be complete, and involves a single generation. The egg, larva, pupa or adult over winters as a dormant stage.
National Biodiversity Network Species Dictionary (January 2004):
- Skinner, B. (1984) Colour identification guide to the moths of the British Isles. Penguin Books, Harmondsworth.
Edinburgh Biodiversity partnership: Six-spot burnet (January 2004):
Habitas.org (January 2004):
- Young, M. (2004) Pers. comm.
The Burnet Study Group (January 2004): | <urn:uuid:c5d379d4-a276-4742-8d0b-e6cd9e743713> | 3.5625 | 798 | Knowledge Article | Science & Tech. | 54.434093 |
As everyone in the world knows by now, the U.N.'s IPCC, its Climategate scientists, other consensus-only "scientists", and the mainstream media have put all their money on the human CO2-horse that "causes" global warming. Unfortunately, the IPCC political agenda of proving human CO2 emissions are the cause of global warming and/or climate change has not proven terribly effective or convincing (google Copenhagen failure). Why?
The IPCC chose a pseudo, non-scientific approach that was unable to explain the actual real-world (non-model) physical science and the actual climate observable conditions since 1880, as this chart indicates -- human CO2 emissions are not a major, primary driver of temperatures, nor the climate. Instead, the IPCC science focus should be on solar, land-use and aerosol (soot, dust, etc.) forcings. The 5% increase in global temperatures is more likely due to black soot, solar/cosmic and land-use factors than CO2. (click on image to enlarge)
Note: The IPCC climate science assumes that all human CO2 emissions remain in the atmosphere for 100 to 200 years. The vast majority of peer-reviewed research finds, though, that human CO2 emissions remain in the atmosphere less than 10 years. The IPCC assumes this without any physical evidence and it has been a major reason why IPCC climate models have been absolute failures in predicting major climate trends, like the recent global cooling.
The adjacent chart shows the cumulative growth percentage in human fossil fuel CO2 emissions since 1880, versus the cumulative growth percentage for both the atmospheric CO2 levels and the NCDC global average temperature. If human CO2 has a global warming impact, it's not significant based on the actual evidence, i.e., human CO2 emissions have a low correlation with global temperature increases. (The 'Human CO2 Emissions' bar is based on assumption that total human fossil fuel CO2 emissions prior to 1880 was a cumulative 20 gigatons.) | <urn:uuid:ed13ee71-7625-46e2-b342-53cacc807e0b> | 3.078125 | 409 | Personal Blog | Science & Tech. | 39.150368 |
As shown, rod AB is subjected to the loading of two blocks, each of weight W (and where we neglect the mass of the pulley). The loading creates a normal strain in the rod given by , where z is measured in inches. This strain corresponds to the total deformation in the rod given by ΔB = 2.00 in.
a. Determine the initial length of the rod, L, measured before the loading is applied. (three sig figs, units in) | <urn:uuid:41e7f55e-d4bb-4984-8104-c4cba4fbb6d4> | 3.125 | 100 | Q&A Forum | Science & Tech. | 79.755385 |
Looking Beyond Ethanol
Researchers are trying to domesticate Mother Nature and use "super bugs" like E. coli microbes for fuel.
October 23, 2008
Researchers are trying to domesticate Mother Nature and use “super bugs” like E. coli microbes for fuel.
"Nature is stubborn. It doesn't like to be tampered with,” the Wall Street Journal (WSJ) said in an Oct. 14 article. “Train it to give up an ancient habit, and soon it reverts to its old ways. For instance, how do you make prairie grass more amenable to being turned into sugar? How do you mutate E. coli microbes so that they gleefully turn that sugar into fuel? How, in short, do you liquefy shredded plants into jet fuel to power a flight to Paris? Dozens of private firms and government-funded labs are now trying to answer those questions.”
"This year's oil-price shock and fears over global warming have reinvigorated the quest for the ultimate liquid fuel -- one that is clean, cheap, easy to make, and doesn't compete with food stocks,” the article continued. “Nature took millions of years to turn dead microorganisms into oil and gas. Scientists now want to trick nature into reducing that to a day or so.
Jay Keasling, a noted microbiologist who directs the new government-funded Joint BioEnergy Institute in the San Francisco Bay area, describes the challenge to WSJ succinctly: “We need to find a way to domesticate nature so we can create energy from waste.”
WSJ noted that “success will require scientific breakthroughs at every step, from designing the perfect feedstocks to hitting on the ideal microbe for turning that roughage into fuel. The federal government wants biofuel production to replace a quarter of all gasoline consumed in the U.S. by 2025. The nation's corn-based ethanol factories are now churning out around 6.5 billion gallons a year -- just over 2 percent of the country's gasoline intake.
“But ethanol's drawbacks are well known -- not least of which that it takes huge amounts of energy to produce,” the WSJ article continued. “Keasling's lab is shooting for something far superior: a newfangled hydrocarbon made from biomass. The advantages of a pure biofuel are numerous. The government estimates that the U.S. could harvest 1.3 million tons of biomass feedstocks a year, ranging from special grasses to wood chips. Unlike ethanol, the fuel would also be a direct alternative to gasoline and sold through the same pumps. Making it happen, though, requires some serious doctoring."
(Source: Wall Street Journal) | <urn:uuid:ec329d23-f8e1-45dd-89bd-5a167c7b0fcd> | 2.984375 | 569 | Truncated | Science & Tech. | 57.08901 |
Found 10 - 20 results of 44 programs matching keyword "model of the atmosphere of saturn"
Dr. Stephen H. Schneider joins us to discuss climate change. Dr. Schneider was honored in 1992 with a MacArthur Fellowship for his ability to integrate and interpret the results of global climate research through public lectures, seminars, classroom teaching, and research collaboration with colleagues. Join Exploratorium physicists Paul Doherty and Stephanie Chasteen as they examine the past, present, and future of climate change. Watch as Paul and Stephanie demonstrate how you can look at a slice of climate from the past, what a sediment core might look like, and the secrets hidden in an ice balloon! A year and a half after entering Saturn's orbit, the Cassini spacecraft continued to gather exciting new information. Dr. Paul Doherty and Dr. Eric Weygren bring us up to date on the Cassini Mission and show stunning images of Saturn and its ever-growing assortment of moons. On the occasion of Hubble's 15th birthday we unveil two spectacular mosaic images from the telescope, discuss the amazing accomplishments of Hubble during the past 15 years, and look at some of the images from space. After a week of analyzing the data from the Huygens probe, do scientists think of Titan differently? What were the unexpected findings? Which hypotheses were wrong? Which were correct? Join us as we talk to mission scientists at NASA's Jet Propulsion Laboratory and get the latest on this enigmatic moon. After yesterday's historic mission to the surface of Titan, what happens next? What do the new pictures of Saturn's largest moon tell us, and what does it mean for our understanding of earth? After its long journey to Saturn's largest moon, Titan, the Huygens probe is released from the Cassini spacecraft. The Huygens probe completes its descent to Titan, capturing hundreds of images on its way. Join Senior Scientist Paul Doherty as he gives us background on this incredible mission and sets the stage for the first close-up images of this mysterious moon. Join Senior Scientist Paul Doherty as we receive the first images of Titan, Jupiter's largest moon, from the European Space Agency headquarters in Darmstadt, Germany. The Huygens probe, released from the Cassini spacecraft, descended to Titan and captured hundreds of images of this mysterious moon. Paul Doherty and Eric Wegryn explore the latest photos of Titan, Saturn’s largest moon, taken from only 750 miles away by the Huygens probe. Paul Doherty and Ron Hipschman discuss the clouds and atmosphere of Saturn. Learn how to make a cloud in your kitchen or an atmosphere in a soda bottle! | <urn:uuid:9aecb121-62a6-48d1-a7d8-75ca762e0fee> | 3 | 542 | Content Listing | Science & Tech. | 50.390962 |
This image depicting the porosity of the lunar highland crust was derived using bulk density data from NASA's GRAIL mission and independent grain density measurements from NASA's Apollo moon mission samples.SA/JPL-Caltech/ IPGP
This map shows the gravity field of the moon as measured by NASA's GRAIL mission. The viewing perspective, known as a Mercator projection, shows the far side of the moon in the center and the nearside (as viewed from Earth) at either side.NASA/ARC/MIT
LOS ANGELES – The moon took quite a beating in its early days, more than previously believed, scientists reported Wednesday.
This surprising new view of the moon comes from detailed gravity mapping by twin spacecraft, which slipped into orbit around the celestial body earlier this year.
Evidence of a highly fractured lunar interior just below the surface suggests that other rocky planets including Earth would have suffered similar bombardment from space rocks early in their history.
Measurements by the NASA spacecraft called Ebb and Flow also found that the moon's crust, or outermost layer, is much thinner than scientists thought — only about 25 miles thick.
The findings were presented Wednesday at a meeting of the American Geophysical Union meeting in San Francisco and published online in the journal Science.
Though past missions have measured lunar gravity — about one-sixth Earth's pull — Ebb and Flow are the first spacecraft dedicated to this pursuit.
To collect data, the washing machine-size spacecraft flew in formation, orbiting about 35 miles above the moon's surface. Their positions allowed them to peer deep into the moon.
The spacecraft also managed to see landforms on the moon in greater detail than before including volcanoes, basins and craters.
The mission is scheduled to end later this month when Ebb and Flow crash into the moon. | <urn:uuid:7db54518-1a32-49ed-90fd-deb5dfb80af0> | 4.21875 | 373 | Truncated | Science & Tech. | 41.728563 |
A turn can be subdivided in many different ways: into half turns, quarter turns, centiturns, milliturns, binary angles, points etc.
A turn can be divided in 100 centiturns or 1000 milliturns, with each milliturn corresponding to an angle of 0.36°, which can also be written as 21'36". A protractor divided in centiturns is normally called a percentage protractor.
Binary fractions of a turn are also used. Sailors have traditionally divided a turn into 32 points. The binary degree, also known as the binary radian (or brad), is 1/256 turn. The binary degree is used in computing so that an angle can be efficiently represented in a single byte (albeit to limited precision). Other measures of angle used in computing may be based on dividing one whole turn into 2n equal parts for other values of n.
The notion of turn is commonly used for planar rotations. Two special rotations have acquired appellations of their own: a rotation through 180° is commonly referred to as a half-turn ( radians), a rotation through 90° is referred to as a quarter-turn. A half-turn is often referred to as a reflection in a point since these are identical for transformations in two-dimensions.
The word turn originates via Latin and French from the Greek word τόρνος (tornos – a lathe).
In 1697 David Gregory used (pi/rho) to denote the perimeter of a circle (i.e. the circumference) divided by its radius, though (delta/pi) had been used by William Oughtred in 1647 for the ratio of diameter to perimeter. The first use of on its own with its present meaning of perimeter/diameter was by William Jones in 1706. Euler adopted the symbol with that meaning in 1737, leading to its widespread use.
In 2001, Robert Palais proposed using the number of radians in a turn as the fundamental circle constant instead of , in order to make mathematics simpler and more intuitive, using a "pi with three legs" symbol to denote the constant (). In 2010, Michael Hartl proposed to use the Greek letter τ (tau) to represent the number instead. His Tau Manifesto gives many examples of formulas that are simpler if tau is used instead of pi.
One turn is equal to 2π (≈6.28) radians.
In kinematics a turn is a rotation less than a full revolution. A turn may be represented in a mathematical model that uses expressions of complex numbers or quaternions. In the complex plane every non-zero number has a polar coordinate expression z = r cos a + r i sin a where r > 0 and a is in [0, 2π). A turn of the complex plane arises from multiplying z = x + i y by an element u = eb i that lies on the unit circle:
Frank Morley consistently referred to elements of the unit circle as turns in the book Inversive Geometry (1933) that he coauthored with his son Frank Vigor Morley.
The Latin term for turn is versor, which is a quaternion that can be visualized as an arc of a great circle. The product of two versors can be compared to a spherical triangle where two sides add to the third. For the kinematics of rotation in three dimensions, see quaternions and spatial rotation.
Here you can share your comments or contribute with more information, content, resources or links about this topic. | <urn:uuid:1ac2723c-20d5-4244-b721-62c3c11bf9fa> | 3.921875 | 747 | Knowledge Article | Science & Tech. | 54.705277 |
Kinematic Self-Replicating Machines
© 2004 Robert A. Freitas Jr. and Ralph C. Merkle. All Rights Reserved.
Robert A. Freitas Jr., Ralph C. Merkle, Kinematic Self-Replicating Machines, Landes Bioscience, Georgetown, TX, 2004.
Prions have been described by Prusiner as “the only known example of infectious pathogens that are devoid of nucleic acid. All other infectious agents have genomes composed of either RNA or DNA that direct the synthesis of their progeny.” In mammals, prions (Figure 4.12) replicate by recruiting normal cellular prion protein and stimulating its conversion to the disease-causing prion isoform (e.g., “scrapie prion”) . Modified (pathogenic) prion protein acts as a template upon which normal prion protein is refolded into a nascent modified protein through a process facilitated by another protein .
The normal cellular prion protein is converted into modified protein through a post-translational process during which it acquires a high beta-sheet content . In particular, the polypeptide chains of normal prion and scrapie prion are identical in composition but differ in their 3-dimensional folded structures: normal prion is rich in alpha helices (spiral-like formations of amino acids) with few beta sheets (flattened strands of amino acids), whereas scrapie prion is poorer in alpha-helices and has many more beta-sheet domains . This structural transition from alpha-helices to beta-sheet in prion protein is apparently the fundamental event underlying prion disease .* Since scrapie prions can induce ordinary prion protein to refold into more scrapie protein, they represent an example of a self-replicating molecule [1368, 1736-1738] that employs a self-replicating geometry roughly analogous to the Penrose blocks (Section 3.3). The fastest-reported prion refolding event measured to date is for mPrP(121-231), the ~15.7 kD structured 111-residue domain of the murine cellular prion protein PrPC (a strongly conserved cell surface glycoprotein totaling 231 amino acids in size), and occurs without kinetic intermediates at an extrapolated rate at 4 oC of 4000 sec-1 (~170 microsec half-life).
* The abnormal isoform also differs physically from the normal cellular isoform by its insolubility in detergents, its propensity to aggregate, and its relative resistance to breakdown by hydrolysis . Limited proteolysis of scrapie prion produces a smaller and protease-resistant molecule of approximately 142 amino acids which polymerizes into amyloid . Prions also appear to encode strain-specific properties in the tertiary structure of the modified prion protein .
Prions are responsible for the transmissible spongiform encephalopathies (TSEs) including mad cow disease, scrapie, and the human Creutzfeldt-Jakob disease.
Last updated on 1 August 2005 | <urn:uuid:39e1dcde-15fe-4cd0-85ce-cc783c9418ab> | 2.96875 | 643 | Academic Writing | Science & Tech. | 34.133333 |
Information on Photosynthesis
by Suzanne McCullough White
The word "photosynthesis" means "put together by light." It is the chemical process by which green plants and certain types of algae convert light energy into food and oxygen. Photosynthesis is one of the most important chemical processes on Earth.
All green plants contain "chlorophyll," a green pigment used in the process of photosynthesis. Within the plant's cells are "organelles" (so named because they are a tiny equivalent of the organs inside the body) called "chloroplasts," which are filled with chlorophyll and are the site of photosynthesis. In a plant, chloroplasts are only found in the stems and leaves, and photosynthesis occurs mainly in the upper surfaces of the leaves.
Green plants (and some algae) contain a pigment called "chlorophyll," which is used to trap the sun's energy in a process called "photosynthesis." During this reaction, the plant takes in this light energy, plus water, plus carbon dioxide from the atmosphere and converts them into chemical energy, in the form of sugars. These sugars are then used by the plants as its food source.
The exact equation for photosynthesis is that six molecules of water, plus six molecules of carbon dioxide use energy from the sun to yield one molecule of sugar and six molecules of oxygen. The reaction is a two-part one, with one stage occurring in the light, and the other in the dark. The plant converts energy during the light reaction and stores it during the dark one.
Pigments are defined as substances that absorb light. The darker the color, the greater the range of colors that it can absorb. Chlorophyll absorbs all frequencies of light except green, which is why it looks green to our eyes. It is the red and blue pigments that do all the work.
Photosynthesis by plants is necessary in the environment to get rid of excess carbon dioxide. "Global warming" is a direct result of the increase of carbon dioxide in the atmosphere. Human activity is responsible for this increase, caused by such things as our use of fossil fuels and fertilizers. Plants act as carbon dioxide "sinks" and without them, the atmosphere would not be able to support life. | <urn:uuid:d45dee47-d1e0-4ee9-988f-49d69420a4f5> | 4.0625 | 460 | Knowledge Article | Science & Tech. | 46.420445 |
Standard State: Presumably a solid at 298 K
Color: Unknown, but probably metallic and silvery white or gray in appearance
Bohrium is a synthetic element that is not present in the environment at all. The
German discoverers at GSI proposed the name Nielsbohrium (symbol Ns) after Niels Bohr.
IUPAC is happy to name an element after Bohr, but it suggested Bohrium
on the grounds that the first name of a person does not appear in the names of any other
element named after a person. This seems to have been accepted by all concerned.
Only a few atoms of element 107, Bohrium, have ever been made. The first atoms were
made through a nuclear reaction involving fusion of an isotope of lead with one of | <urn:uuid:b4f5875a-a3be-492b-b9bf-8f54e0e17697> | 3.296875 | 166 | Knowledge Article | Science & Tech. | 43.3928 |
For those whose curiosity has been piqued by the Himalayan glacier error in the IPCC’s report, Nature magazine has a great article on the real holes in climate science. Far from undermining climate science, though, it underlines the importance of continuing research.
The story notes that the IPCC highlights 54 ‘key uncertainties’ in its 2007 report, but it picks out four key areas of concern:
Regional climate prediction: “To plan for the future, people need to know how their local conditions will change, not how the average global temperature will climb. Yet researchers are still struggling to develop tools to accurately forecast climate changes for the twenty-first century at the local and regional level.” This makes it difficult for countries to make specific adaptation plans – and simply extrapolating from global forecasts risks enhancing weaknesses in the broader model.
Precipitation: Knowing how rising temperatures will affect the hydrological cycle – more simply, evaporation and rain – is another challenge. Different models agree that subtropical areas will be dryer, increasing precipitation at higher altitudes. But beyond that, they tend to diverge. Robust predictions were particularly problematic for winter precipitation, which is most important for water supplies. And, worryingly, the models appear to underestimate the changes that have already occurred.
Aerosols, or airborne liquid or solid particles, are also a big source of uncertainty. Exactly how aerosols interact with sunlight and clouds to affect the temperature, and how extensive their effects are, is not clear. Actual data on the presence of aerosols is lacking too. (Bad news, we suspect, for those putting hope in geo-engineering based on aerosols.)
Tree rings: The subject of much of the controversy over the climategate emails, and the Michael Mann/Stephen McIntyre debate. In short, tree rings are one of several ‘proxy’ records used to estimate temperatures pre-1850, or before more reliable records were kept. While they mostly reflect known changes in temperature, tree rings from a few sites began to diverge from the recorded temperatures in recent decades. Why this happens isn’t known – “It may be that when temperatures exceed a certain threshold, tree growth responds differently,” writes Nature. In any case, the ‘trick’ referred to by Phil Jones in the most famous climategate email involved substituting actual temperature data for those trees when they did begin to diverge.
However as the story concludes, the IPCC’s recommendations were based on the totality of research, and not on any one particular observation.
Nature also takes a look at the six most enduring climate myths, featuring all the classics such as ‘global warming stopped 10 years ago’ and ‘temperatures were higher in pre-industrial times’.
Himalayan glaciers – another climategate? Not quite (FT Energy Source, 19/01/10)
Top 10 questions for 2010: Climate change and clean tech edition (FT Energy Source, 23/12/09) | <urn:uuid:aea87325-d458-456b-bcb4-2e59d136c6fe> | 2.9375 | 627 | Personal Blog | Science & Tech. | 29.706214 |
Note: If you're not sure what a dialog box is then have a read of What Is a Dialog Box?
A message box is a simple pop-up window that displays a message to the user and is dismissed with the click of a button. To avoid having to build your own dialog box from scratch, the JOptionPane class provides methods to make a variety of dialog boxes by simply feeding them some parameters to determine the appearance of the dialog box.
Note: If you're looking to get a specific input from a user then have a look at Building an Input Dialog Box. It still uses a method from the JOptionPane class but it's worth distinguishing it from a simple message box as the options the user can choose are more varied.
The JOptionPane Class
To create a simple message dialog box you have a choice of three
showMessageDialog- This method is the most basic. It allows you to set the message, a title for the dialog box, a message type (e.g., warning message, error message), and only has an OK button.
showConfirmDialog- Again, you can set the message, a title, a message type, but you can also choose between a selection of button combinations (e.g., YES/NO, OK/CANCEL). It returns an int representing which button was clicked.
showOptionDialog- This is the most flexible method. In addition to setting the message and title, you have the choice of how to customize the dialog box. You can pick a message type and button combination, or you can provide a specific icon and an
Objectarray for the button options. The
Objectarray gives the flexibility to make the button names from an String array or even give them all images using an Icon array. It returns an int representing the user's choice of button.
Using the showMessageDialog Method
To create a simple message box use the
JOptionPane.showMessageDialog(this, "This is the dialog title" ,"This is the dialog message", JOptionPane.PLAIN_MESSAGE);
This will create a dialog with no icon - just a message, a title and an OK button.
That sounds like a pretty plain message box and that's because I've passed the static field
JOptionPane.PLAIN_MESSAGE as the message type. The message type tries to give the dialog box a certain feel by determining the icon that will be used. A
PLAIN_MESSAGE has no icon but the other fields do:
JOptionPane.ERROR_MESSAGE uses a red octagon with an exclamation mark in the middle to try and give the feel that something unexpected has happened.
Have another look at the first parameter in the above example. I'm using
this to refer to the
JFrame object as the parent of the dialog box. The first parameter of any of the three
JOptionPane methods is always the parent component (e.g.,
JPanel) of the dialog box. This allow the dialog box to determine its position on the screen relative to its parent. This parameter can be null if you want to create a dialog box without a container like a
The final thing to note about the
JOptionPane.showMessageDialog method is it does not return the user's response. There is only an OK button for them to click. As their options are so limited it's not worth trying to capture a response.
Read Creating a Message Dialog Box - Part II to see how the other JOptionPane methods are used. | <urn:uuid:f0333b75-662a-448e-bed2-5ece614be8d4> | 3.140625 | 751 | Tutorial | Software Dev. | 52.971419 |
The crystallography restriction states that any 2-dimensional lattice can have rotational symmetry of degree 1, 2, 3, 4 or 6 - and that's it. A simple proof of I've heard of this is: the magnitude of $rot_\theta(x)-x$ is less than the magnitude of $x$ if $\theta$ is less than $\pi / 3$. (So if there's a rotation by less than $\pi/3$, it will fail to be a lattice, since we can always get smaller and smaller elements.)
That sounds fine to me, and I get why real crystals would have the requirement that all atoms be some epsilon away from each other. I don't understand why nature requires the lattice to be closed though - obviously real crystals aren't completely closed under addition, or else they would be infinitely large.
So why does the crystallography restriction limit the symmetries of real crystals? (Or does it not, and this application of the theorem is made up by math teachers to convince their students that math is useful?) | <urn:uuid:71d64d88-ea47-472a-a1a8-8343878bff87> | 2.734375 | 222 | Q&A Forum | Science & Tech. | 56.072543 |
Geoengineering To Mitigate Climate Change
The American Meteorological Society recently issued a statement regarding the feasibility of geoengineering our climate to mitigate climate change.
Geoengineering could lower greenhouse gas concentrations, provide options for reducing specific climate impacts, or offer strategies of last resort if abrupt, catastrophic, or otherwise unacceptable climate-change impacts become unavoidable by other means. However, research to date has not determined whether there are large-scale geoengineering approaches that would produce significant benefits, or whether those benefits would substantially outweigh the detriments. Indeed, geoengineering must be viewed with caution because manipulating the Earth system has considerable potential to trigger adverse and unpredictable consequences.
Geoengineering proposals fall into at least three broad categories: 1) reducing the levels of atmospheric greenhouse gases through large-scale manipulations (e.g., ocean fertilization or afforestation using non-native species); 2) exerting a cooling influence on Earth by reflecting sunlight (e.g., putting reflective particles into the atmosphere, putting mirrors in space, increasing surface reflectivity, or altering the amount or characteristics of clouds); and 3) other large-scale manipulations designed to diminish climate change or its impacts (e.g., constructing vertical pipes in the ocean that would increase downward heat transport).
The American Meteorological Society recommends:
1. Enhanced research on the scientific and technological potential for geoengineering the climate system, including research on intended and unintended environmental responses.
2. Coordinated study of historical, ethical, legal, and social implications of geoengineering that integrates international, interdisciplinary, and intergenerational issues and perspectives and includes lessons from past efforts to modify weather and climate.
3. Development and analysis of policy options to promote transparency and international cooperation in exploring geoengineering options along with restrictions on reckless efforts to manipulate the climate system.
Geoengineering will not substitute for either aggressive mitigation or proactive adaptation, but it could contribute to a comprehensive risk management strategy to slow climate change and alleviate some of its negative impacts.
SF writers Niven and Pournelle had an interesting idea in their 1974 classic The Mote in God's Eye. To mitigate climate problems on a recently settled planet, natural vulanism was harnessed to achieve atmosphere control.
Potter was doing most of the talking and all the pointing. "Those twin volcanoes; d'ye see them, Mr. Renner? D'ye see yon boxlike structures near the peak of each one? They're atmosphere control. When yon volcanoes belch gas, the maintenance posts fire jets of tailored algae into the air stream. Without them our atmosphere would soon be foul again."
The earliest sfnal proposal that I know about for radically altering our climate for the better comes from the 1894 story A Journey in Other Worlds by John Jacob Astor IV.
"GENTLEMEN: You know that the objects of this company are, to straighten the axis of the earth, to combine the extreme heat of summer with the intense cold of winter and produce a uniform temperature for each degree of latitude the year round.
(Read more about Global Climate Control)
Scroll down for more stories in the same category. (Story submitted 7/23/2009)
Follow this kind of news @Technovelgy.
| Email | RSS | Blog It | Stumble | del.icio.us | Digg | Reddit |
you like to contribute a story tip?
Get the URL of the story, and the related sf author, and add
Comment/Join discussion (Back On) ( 2 )
Related News Stories -
Swiss HCPVT Giant Photovoltaic 'Flower'
'...leaning against one of the slender stalks of a sunshade-photocell collector.'- David Brin, 1990.
Peel And Stick Thin Film Solar Cells
'It turns sunlight into electricity, just like any solar power converter, but you spray it on.'- Larry Niven, 1995.
Microbattery Extreme High Performance
'To this Foyle affixed a power pack the size of a pea and switched it on.'- Alfred Bester, 1956.
Speeding Ticket Robots To Cite Autonomous Cars?
'There is no danger of a vehicle's speed exceeding that allowed in the section in which it happens to be...'- John Jacob Astor IV, 1894.
Technovelgy (that's tech-novel-gee!)
is devoted to the creative science inventions and ideas of sf authors. Look for
the Invention Category that interests
you, the Glossary, the Invention
Timeline, or see what's New.
Sweat Be Gone! Non-Wetting Fabric
'The skin-contact layer is porous.'
German Firm Seeks To Recruit Autistics
Not a deficit, but a strength.
NASA Supports Pizza Printer
Is it extra with printed pepperoni?
Could Ground-Based Lasers De-Orbit Space Junk?
'Then their lasers vaporized the smaller satellites...'
'Hello, Computer!' Google Now Highlighted at IO13
MIT Robot Cheetah Video Shows Gait Transition
'The legs are long, curled way up to deliver power, like a cheetah's.'
TrackingPoint Smart Rifle
Not your typical 'smart bullet' approach.
Sky City's 220 Stories Are Go
'It rested among green parklands and... stood in total isolation, a glittering block of whites and flashing windows dotted with colors.'
CARMAT Bioprosthetic Total Human Heart Replacement
'George Walt's corporate existence proved the workability of wholly mechanical organs...'
Personal Sniffer Robots
'...The ticking combinations of the olfactory system of the hound.'
Physical Exam? We've Got Apps
See the future of handheld, personal medical devices.
The Interplanetary Internet, Vint Cerf Speaking
'This was the center of Interplanetary Communications.'
Drosophila Robotica, The Mechanical Fly
'... the Scarab [flying robot] buzzed into the great workroom as any intruding insect might...'
Robo-Raven Flapping Wing Robot Bird
'When he had first built them, they had been crude indeed, flying mechanisms with little more than a reflex-response unit.'
Japan's Nursing Home Robot Plan
Let's make the Roujin Z-0001 Robotic Bed!
Samsung Smart TVs With Gesture Control
'He waved his hand and the circuit switched abruptly.'
More SF in the News Stories
More Beyond Technovelgy science news stories | <urn:uuid:b216d6b7-36da-429e-bff8-6aaf5ae57dee> | 3.125 | 1,354 | Content Listing | Science & Tech. | 38.263849 |
The mission objective of the Voyager Interstellar Mission (VIM) is to extend the NASA exploration of the solar system beyond the neighborhood of the outer planets to the outer limits of the Sun's sphere of influence, and possibly beyond. This extended mission is continuing to characterize the outer solar system environment and search for the heliopause boundary, the outer limits of the Sun's magnetic field and outward flow of the solar wind. Penetration of the heliopause boundary between the solar wind and the interstellar medium will allow measurements to be made of the interstellar fields, particles and waves unaffected by the solar wind.
The VIM is an extension of the Voyager primary mission that was completed in 1989 with the close flyby of Neptune by the Voyager 2 spacecraft. Neptune was the final outer planet visited by a Voyager spacecraft. Voyager 1 completed its planned close flybys of the Jupiter and Saturn planetary systems while Voyager 2, in addition to its own close flybys of Jupiter and Saturn, completed close flybys of the remaining two gas giants, Uranus and Neptune.
At the start of the VIM, the two Voyager spacecraft had been in flight for over 12 years having been launched in August (Voyager 2) and September (Voyager 1), 1977. Voyager 1 was at a distance of approximately 40 AU (Astronomical Unit - mean distance of Earth from the Sun, 150 million kilometers) from the Sun, and Voyager 2 was at a distance of approximately 31 AU.
It is appropriate to consider the VIM as three distinct phases: the termination shock, heliosheath exploration, and interstellar exploration phases. The two Voyager spacecraft began the VIM operating, and are still operating, in an environment controlled by the Sun's magnetic field with the plasma particles being dominated by those contained in the expanding supersonic solar wind. This is the characteristic environment of the termination shock phase. At some distance from the Sun, the supersonic solar wind will be held back from further expansion by the interstellar wind. The first feature encountered by a spacecraft as a result of this interstellar wind/solar wind interaction was be the termination shock where the solar wind slows from supersonic to subsonic speed and large changes in plasma flow direction and magnetic field orientation occur.
As of March 2012, Voyager 1 was at a distance of 17.9 Billion Kilometers (119.9 AU) from the sun and Voyager 2 at a distance of 14.7 Billion kilometers (98.3 AU).
Voyager 1 is escaping the solar system at a speed of about 3.6 AU per year, 35 degrees out of the ecliptic plane to the north, in the general direction of the Solar Apex (the direction of the Sun's motion relative to nearby stars). Voyager 2 is also escaping the solar system at a speed of about 3.3 AU per year, 48 degrees out of the ecliptic plane to the south.
Passage through the termination shock ended the termination shock phase and began the heliosheath exploration phase. Voyager 1 crossed the termination shock at 94 AU in December 2004 and Voyager 2 crossed at 84 AU in August 2007. Since passage through the termination shock, the spacecraft has been operating in the heliosheath environment which is still dominated by the Sun's magnetic field and particles contained in the solar wind. The heliosheath exploration phase ends with passage through the heliopause which is the outer extent of the Sun's magnetic field and solar wind. The thickness of the heliosheath is uncertain and could be tens of AU thick taking several years to traverse. Passage through the heliopause begins the interstellar exploration phase with the spacecraft operating in an interstellar wind dominated environment. This interstellar exploration is the ultimate goal of the Voyager Interstellar Mission.
Both Voyagers are headed towards the outer boundary of the solar system in search of the heliopause, the region where the Sun's influence wanes and the beginning of interstellar space can be sensed. The heliopause has never been reached by any spacecraft; the Voyagers may be the first to pass through this region, which is thought to exist somewhere from 8 to 14 billion miles from the Sun. This is where the million-mile-per-hour solar winds slows to about 250,000 miles per hour—the first indication that the wind is nearing the heliopause. The Voyagers should cross the heliopause 10 to 20 years after reaching the termination shock. The Voyagers have enough electrical power and thruster fuel to operate at least until 2020. By that time, Voyager 1 will be 12.4 billion miles (19.9 billion KM) from the Sun and Voyager 2 will be 10.5 billion miles (16.9 billion KM) away. Eventually, the Voyagers will pass other stars. In about 40,000 years, Voyager 1 will drift within 1.6 light years (9.3 trillion miles) of AC+79 3888, a star in the constellation of Camelopardalis. In some 296,000 years, Voyager 2 will pass 4.3 light years (25 trillion miles) from Sirius, the brightest star in the sky . The Voyagers are destined—perhaps eternally—to wander the Milky Way. | <urn:uuid:da48153c-0b28-4a18-9430-4dc06e57aa7e> | 3.46875 | 1,056 | Knowledge Article | Science & Tech. | 54.275684 |
We can make this one easier by finding the volume within the sphere
but above the cone and subtracting the result from the volume of
the upper hemisphere. Since the sphere has radius 2, it's volume is
4/3 pi (2)^3 = 32pi/3. Hence the hemisphere volume is 16pi/3. Now
we compute the part we have to subtract. The differencein height
between the 2 surfaces is sqrt(4-x^2-y^2) - sqrt(3x^2+3y^2). The
circle of intersection is 4-x^2-y^2=3x^2+3y^2 or 4=4x^2+4y^2 so
that x^2+y^2 = 1. Thus we integrate over this region. This is
suited well for polar coordinates. We take x=rcos t, y=rsint so
that dydx=rdrdt. Then we have int (0,2pi) int (0,1) [sqrt(4-r^2) -
r sqrt(3)]rdrdt. Since eah integral is independent in this case, we
have 2pi * int (0,1) [r sqrt(4-r^2) - r ^2sqrt(3)]dr which is
2pi* [(-1/2)(2/3)(4-r^2)^(3/2) - r^3*sqrt(3)/3] from 0 to 1.
=2pi[-sqrt(3)- sqrt(3)/3 - [-8/3]]=2pi[ -(4/3)sqrt(3) +(8/3)]
So we should have 16pi/3 - 2pi[-(4/3)sqrt(3) +(8/3)]
if an error did not ceep into my calculations. | <urn:uuid:2b097671-7ef0-4f2a-8625-291231da0d05> | 3.609375 | 418 | Q&A Forum | Science & Tech. | 111.36236 |
In a discovery that could promise a quick fix to the common hangover a team of researchers led by UCLA engineers has identified a method for speeding up the body's reaction to the consumption of ... - Read More
In the search for renewable alternatives to gasoline heavy alcohols such as isobutanol are promising candidates Not only do they contain more energy than ethanol but they are also more compatible with existing gasoline based ... - Read More
How green algae produce hydrogen in the dark is reported by biologists at the Ruhr Universität Bochum in the Journal of Biological Chemistry Biologists have uncovered a mechanism for the production of the gas which ... - Read More
An innovative technique which pinpoints protein locations and helps researchers unravel the protein's functions has been developed by the researchers from the Massachusetts Institute of Technology MIT researchers who recently moved from MIT to the ... - Read More
MIT engineers have created genetic circuits in bacterial cells that not only perform logic functions but also remember the results which are encoded in the cell's DNA and passed on for dozens of generations Share ... - Read More
The discovery that sea urchins use nickel particles to harness carbon dioxide from the sea could be the key to capturing tons of carbon dioxide CO2 from the atmosphere Share This See Also Nature Biology ... - Read More
Scientists studying an enzyme that naturally produces alkanes long carbon chain molecules that could be a direct replacement for the hydrocarbons in gasoline have figured out why the natural reaction typically stops after three to ... - Read More
There's a wobbly new biochemical structure in Burckhard Seelig's lab at the University of Minnesota that may resemble what enzymes looked like billions of years ago when life on earth began to evolve long before ... - Read More
Enzymes workhorse molecules of life that underpin almost every biological process may have a new role as intelligent micro and nanomotors with applications in medicine engineering and other fields That's the topic of a report ... - Read More
With projections of 9.5 billion people by 2050 humankind faces the challenge of feeding modern diets to additional mouths while using the same amounts of water fertilizer and arable land as today Share This See ... - Read More
Jan 22 2013 — While working out the structure of a cell killing protein produced by some strains of the bacterium Enterococcus faecalis researchers stumbled on a bit of unusual biochemistry They found that a ... - Read More
The rise of antibiotic resistant bacteria has initiated a quest for alternatives to conventional antibiotics One potential alternative is PlyC a potent enzyme that kills the bacteria that causes strep throat and streptococcal toxic shock ... - Read More
Released 1 15 2013 10 45 AM ESTSource University of Medicine and Dentistry of New Jersey UMDNJ Investigators probe mechanisms of RNA synthesis Jan 16 2013 NEWARK N J – One of the most extraordinary ... - Read More
Tell us what you think of Chemistry 2011 -- we welcome both positive and negative comments. Have any problems using the site? Questions?
Chemistry2011 is an informational resource for students, educators and the self-taught in the field of chemistry. We offer resources such as course materials, chemistry department listings, activities, events, projects and more along with current news releases.
The history of the domain extends back to 2008 when it was selected to be used as the host domain for the International Year of Chemistry 2011 as designated by UNESCO and as an initiative of IUPAC that celebrated the achievements of chemistry. You can learn more about IYC2011 by clicking here. With IYC 2011 now over, the domain is currently under redevelopment by The Equipment Leasing Company Ltd.
Are you interested in listing an event or sharing an activity or idea? Perhaps you are coordinating an event and are in need of additional resources?
Within our site you will find a variety of activities and projects your peers have previously submitted or which have been freely shared through creative commons licenses.
Here are some highlights: Featured Idea 1, Featured Idea 2.
Ready to get involved? The first step is to sign up by following the link: Join Here. Also don’t forget to fill out your profile including any professional designations. | <urn:uuid:602122a1-6753-4824-b156-b7a21ed61534> | 2.734375 | 842 | Content Listing | Science & Tech. | 42.058075 |
Particle Worldline Model Documents
This material has 2 associated documents. Select a document title to view a document's information.
The Particle Worldline model computes and displays the trajectory of a test particle in the vicinity of a black hole using Schwarzschild coordinates. It was created for the study of Einstein's theory of general relativity and the Schwarzschild metric.
The model has input fields displaying the Schwarzschild coordinates and their rates of change as well as the energy E and and angular momentum L of the particle. Conservation laws and the speed of light impose restrictions on the dynamical variables and these restrictions are enforced when entering values or dragging the particle. For example, if a user changes the default value of dr/dt to 10, the model automatically reduces the value to 0.685 because the particle speed cannot exceed the speed of light c=1.
The Particle Worldline model a supplemental simulation for the article "When action is not least for orbits in general relativity" by C. G. Gray and Eric Poisson in the American Journal of Physics 79(1), 43-55 (2011) and has been approved by the authors and the American Journal of Physics (AJP) editor. The simulation was developed using the Easy Java Simulations (EJS) modeling tool and is distributed as a ready-to-run (compiled) Java archive. Double clicking the ejs_gr_ParticleWorldline.jar file will run the program if Java is installed.
- Download ejs_gr_ParticleWorldline.jar - 813kb Java Archive File
Last Modified October 31, 2010
This file has previous versions. | <urn:uuid:197f80e9-47cf-4ffd-ae44-3becdbbbb9d9> | 2.734375 | 334 | Knowledge Article | Science & Tech. | 43.023143 |
A Swedish company wants to make burials more eco-friendly, and they're doing it by freezing dead people in liquid nitrogen, shattering them into dust with focused sound waves, and then sucking all the leftover moisture out with a vacuum.
Traditional funerals are apparently pretty bad for the environment. Embalming fluid is toxic stuff. Coffins are often made of metal, which doesn't biodegrade, or wood finished with nasty chemicals. Tons of concrete are often poured into the ground to create a stable vault and protect against zombies. And even the cremation route uses scads of energy and releases mercury into the atmosphere.
A Swedish company called Promessa has come up with a crazy new way of handling the remains of the deceased, and it's straight out of science fiction. First, a body is chilled down to 18 degrees Celsius. Then it's entirely submerged in liquid nitrogen, which freezes it solid, and makes it brittle enough that it can be shattered and pulverized into dust using high power sound waves. Next, the dust (which is still about the same mass as the body was) is exposed to a vacuum which boils off all the moisture contained in the dust, reducing its mass by 70% or so. Lastly, all of the inorganic stuff that may be left over is removed with an electromagnet, and the dust is placed in a coffin made of corn starch, all ready for a shallow burial that'll turn everything into compost within a year.
Of course, this whole process is fairly complicated and certainly takes some amount of energy to perform on its own, but at the very least the end product is a bit better for the planet than some more traditional methods. Plus, unlike burial or cremation, it's also guaranteed to destroy killer robots. | <urn:uuid:b2aa371e-627d-4be4-b25d-4f8b9fec3675> | 2.796875 | 360 | Personal Blog | Science & Tech. | 47.384161 |
Michael J. Tyler
with the assistance of the Editorial Advisory Committee
Wildlife Australia, April 1997
ISBN 0 642 21400 X
Recovery Outline No. 2: Yellow-Spotted Tree Frog
2. Scientific Name
Litoria castanea (L. flavipunctata)
3. English Name
Yellow-Spotted Tree Frog
4. Intraspecific taxa:
None recognised, but it is conceivable that an allopatric population in the ACT and adjacent NSW may merit sub-specific recognition.
5. Species survival status
Endangered. The species has not been the subject of detailed study since its description in 1975. Observation on the New England Tableland of NSW suggests that the population there has diminished significantly, because it has not been located there for several years despite extensive searches. Because of its close relationship to the allopatric south eastern species L. aurea and
L. raniformis (each of which has declined significantly), the future of this species is regarded with concern.
6. Former distribution
Confined to the Great Dividing Range, concentrated upon the New England Tableland. A further population in the ACT and the adjacent portion of NSW almost certainly represented this species (but note there have been no studies to determine the genetic similarity of the isolates).
7. Current distribution
The ACT and Southern Tablelands population has disappeared entirely. Despite intensive survey the New England Tableland population has not been detected in the last ten years.
Associated with marshes, ponds, small lakes etc., principally around permanent waters.
9. Reasons for decline
Unknown. No significant physical change has been observed in the environment but it may be significant that this and closely related species bask in the sun.
10. Conservation reserves on which species occurs
11. Other public lands on which species occurs
12. Other lands on which species occurs
Extensive areas of grassland used for grazing.
13. Is knowledge about species adequate for objectives and actions to be defined accurately?
No. Even the most fundamental biological information has not been published.
14. Recovery Plan objectives
14.1. Determine the geographic range and status of the species.
14.2. Determine the identity of the isolated population which until recently existed in the ACT and the adjacent portion of NSW (this is or was an allopatric population of L. castanea, or an undescribed species or sub-species).
15. Management actions completed or under way
The following actions have been completed as part of a project funded by the Endangered Species Program of Environment Australia and the NSW National Parks and Wildlife Service:
15.1. Search for New England Tableland population.
15.2. Production of a brochure and transportable display to assist the public (in particular landholders and amateur naturalists) in identifying L. castanea. Subsequent community information program.
16. Management actions required
16.1. Continue survey effort for the species in northern NSW.
16.2. Complete surveys undertaken in the southern tablelands.
16.3. Visit each of the localities from which the type series was taken, and supplement this using any records of additional sites derived from databases of State museum and other comparable collections, to determine the distribution of the species.
16.4. Compare the advertisement calls that have been obtained to determine the identity of the isolated population which until recently existed in the ACT and the adjacent portion of NSW.
17. Organisations responsible for conservation of species
NSW National Parks and Wildlife Service, ACT Parks and Conservation Service.
18. Other organisations involved
Frog and Tadpole Study Group of NSW Inc, University of Newcastle, University of Canberra.
19. Can recovery be carried out with existing resources?
Costs: Extraction of museum data and physical verification of specimen $4K. Field surveys at each locality = salaries (2 people) $20K, allowances $3K, field travel $12K. Materials etc for comparison of calls $0.5K.
Herpetological authorities consulted
M.J. Mahony, W.S. Osborne | <urn:uuid:2dac16e9-6b96-4d03-b860-1328cc704a4f> | 2.796875 | 861 | Knowledge Article | Science & Tech. | 41.780031 |
Lightword Theme by Andrei Luca
This website is titled how does wind energy work and it's aim is to discuss ways in which wind energy has been used, is currently used and is likely to be utilized to generate power through the coming years, well in to the future, for whether we like it or not wind power is certainly here to stay.
As the global population continues to grow, we are constantly faced with a number of key problems...
How to house this growing increase of people, how to feed them and how to generate the power to supply the services and needs of this ever expanding world.
There are a number of energy forms leading the fray, including solar power and water or wave power.
But the subject we're here to discuss is 'WIND ENERGY'
Wind energy is an especially 'GREEN' way to generate electricity...
It's virtually silent...
Tirelessly works all year round and...
Is not particularly intrusive, certainly not when compared to other more traditional ways of generating electricity such as nuclear or coal fueled power stations, not to mention the polution they churn out.
There are however a couple of factors that hold wind energy back in the fight against traditional fuels as our sources of energy.
Firstly, if you live an area where there is little or no wind, then you simply can't use this form of energy generation.
Secondly there are many people that complain about the appearance of wind farms or simply the odd solitary windmill.
So let's get down to the real facts and discuss how does wind energy work?
Firstly wind energy is harnessed by the use of wind turbines or windmills as they were known in the past. In fact wind power is nothing new, we have been using it in a very primitive way for grinding our grains for hundreds of years.
Wind turbines are the medium by which the wind is used to convert wind energy into electricity. The way they work is that a turbine is placed on to a tall mast or stand and this turbine has generally 3 large propeller blades which are connected to a rotor.
The blades of the windmill generate energy by turning a shaft in a gearbox that increases the speed of revolutions to power a generator.
This generator uses magnetic fields to convert the energy in to electrical energy.
This generated power is transformed in to the correct voltage for use in our homes, businesses and general everyday life.
If the wind generator is connected to the main power supply then this generated electricity then enters the general network and can be used by everybody. It is generally charged out to the public by a network of electrical companies, who buy electricity off the national grid and charge it out to their own customers for a slight profit.
Please stay on how does wind power work .org and look around a while. We have links to a range of wind power resources where you can find out more about this exciting subject. | <urn:uuid:8452fe01-c8eb-43ef-8894-1a81831ca4c9> | 3.0625 | 593 | Knowledge Article | Science & Tech. | 52.000043 |
Sponges regain their tag of most primitive animal on Earth
There was a mad rush to get to the base of animal tree of life in the past twelve months, in order to establish most primitive animal on our planet, with many phylogenomics studies contradicting each other. In April 2008, Cassey dunn et el published their famous phylogenomics work in Nature, which placed Ctenophores at the base of the tree making them most primitive animal on Earth. Before that work Sponges were considered as first animals to branch off from rest of the animals and hence occupied a most basal position in the tree of animals for long time. However, some months later another phylogenomics study carried out by Bernd Schierwater et al ; changed things dramatically by placing Trichoplax as most primitive animal replacing Ctenophores. Now a new phylogenomic study published in online section of Current Biology is making headlines , where Sponges regain their position as most primitive animal on Earth. This work is lead by famous Harvey Philippe in association with the group of Michael Manuel in paris and many other support labs.
So what makes this work from Micheal Manuel and colleagues different from other phylogenomics studies done earlier ? What makes it more credible? But before getting answers to these questions, we will try to understand a general view of what phylogenomics is all about ?
A phylogenetic tree is a graphical representation of the evolutionary relationship between taxonomic groups.The term phylogeny refers to the evolution or historical development of a plant or animal species, or even a human tribe or similar group. The idea of phylogenetic tree is not something of modern era,in fact it is used for the first time by Charles Darwin in his most famous book “On the origin of species” .The diagram of Tree of life happens to be only illustration in his famous book ,to represent evolutionary relationships among species, in the form of a phylogenetic tree.
As all the extant species on earth share a similar history in terms of their common ancestry and this makes understanding of phylogenetic trees becomes a prerequisite of almost any evolutionary
study. In today’s molecular era thanks to revolutionizing progress in DNA sequencing technology,there is ever increasing numbers of whole genome sequences and collections of ESTs.The wealth of generated by sequencing various species from different phyla lead to the origin of new branch in “Phylogenomics”(portmanteau word for phylogenetics and genomics) ,which is considered as intersection of evolution and genomics , using phylogenetic principles to make sense of genomic data. The first use of word phylogenomics can be traced back to writings of Jonathan A. Eisen @ The Institute of Genome Research (TIGR) in the context of an “approach to the prediction of gene function” for genome-scale data. The contribution of Phylogenomic studies in the use of data at the genomic scale to reconstruct the phylogeny of organisms is immense.
Anyhow coming to the main story of the day regarding phylogenomics study by Harvey.P. et al involving 128 gene data set including newly generated sequence data from ctenophores, cnidarians, and all four main sponge groups. Prior phylogenomics studies provided valuable insights for for intrabilaterian relationships,but things related to basal phyla still remain a puzzle. Deciphering true relationships among early branching animals is extremely vital in understanding origins of defining features of animal body plans, such as symmetry, nervous system, and the mesoderm.
So what makes this study different ?
Authors are of the opinion that previous phylogenomics studies of basal metazoan relationships are supported by poor supported trees and produced contradicting results.This study is mainly done to clarify the basal metazoan relationships, involving more comprehensive sampling of all the major early branching animal lineages and the effort is seen in as they used 128 different protein-coding genes (30,257 unambiguously aligned positions) for 11 outgroup species and 44 metazoans, including 9 sponge species, 3 ctenophores, 9 cnidarians, the placozoan Trichoplax.
The two important outcomes from the study are:
1) Sponges (Porifera) are monophyletic and not paraphyletic as repeatedly proposed , thus undermining the idea that ancestral metazoans had a sponge-like body plan. (This is the first phylogenomic data set to include all four main sponge lineages)
2) Ctenophora is together with the cnidarians.
3) Sponges is the earliest diverging animal group(most primitive animal) and followed by Placozoa (Trichoplax).
Phylogenomics and the reconstruction of the tree of life.
Delsuc F, Brinkmann H, Philippe H.
Nat Rev Genet. 2005 May;6(5):361-75.
Phylogenomics: intersection of evolution and genomics.
Eisen JA, Fraser CM.
Science. 2003 Jun 13;300(5626):1706-7.
Philippe H, Delsuc F, Brinkmann H, Lartillot N:
Annu Rev Ecol Evol Syst 2005, 36:541-562.
Curr Biol. 2007 Nov 20;17(22):R945-6.
Phylogenomics Revives Traditional Views on Deep Animal Relationships.
Philippe H, Derelle R, Lopez P, Pick K, Borchiellini C, Boury-Esnault N, Vacelet J, Renard E, Houliston E, Quéinnec E, Da Silva C, Wincker P, Le Guyader H, Leys S, Jackson DJ, Schreiber F, Erpenbeck D, Morgenstern B, Wörheide G, Manuel M.
Curr Biol. 2009
I am thankful to Jonathan Eisen for pointing out that its not correct to use the word “PRIMITIVE” for organisms , should only be used for characters.
This is simply wrong as the term primitive, which I avoid at all costs because it is so frequently misused, should only be used to refer to features of organisms not to the branching pattern in an evolutionary tree.
So in the article it should be “Sponges are the deepest branching in the group.” or “most basal” instead of primitive. sponges are typically considered to represent descendants of the earliest branching lineage. To be more clear, first animals probably were not very similar to sponges as we see them today , as representatives of a lineage that branched off first from those of other major animal groups and has been evolving for millions of years since diverging. Its quite possible that sponge evolved its simpler form from the more complex form during the course of hundred million years of evolution. To have more insights into the morphological changes ,its is very important to have data from fossil , as molecular information can only tell us about order of branching in tree of life.
calling organisms that branch deeply in a tree “primitive” is wrong not only because it is referring to an organism not a feature but also because deep branching does not imply ancestral features.
I found a very nice post by Ryan Gregory explaining the “Phylogenetic Fallacies: Early Branching Must Mean Primitive” -a post regarding cassey dunn work showing ctenophores as deepest branching group or most basal group
Specifically, it draws the false conclusion that a modern member of an early branching lineage is very similar to the distant ancestor that it shares with other lineages. In actuality, the species under consideration are all modern species whose lineages have been evolving for exactly the same amount of time since their divergence from a common ancestor. The comb jelly lineage may have branched first, but the common ancestor from which it and the other animals lineages diverged probably looked nothing like a comb jelly. It is entirely possible that comb jellies are highly derived (i.e., very different from their early ancestor), just as other animal lineages are…………….
“one cannot assume that a modern representative of an early branching lineage is the same as the ancestor from which it is descended” — RYAN GREGORY
For better understanding of phylogenetic trees read :
Understanding evolutionary trees.
Gregory, T.R. 2008b.
Evolution: Education and Outreach 1: 121-137. | <urn:uuid:f1e30a0e-6a57-45c8-99ec-fb2d6ae26042> | 3.46875 | 1,766 | Personal Blog | Science & Tech. | 35.123628 |
As Discharge increases, does bed load increase?
Suspended loads increase dramatically with discharge, so I would expect that the bed load would increase as well. Bed loads are difficult to observe and measure though, so we have few data on the subject. Measurements on the Niobrara River near Cody, Nebraska, however, have shown that at discharges between 6 and 30 cubic metres per second, the bed load averaged about 50% of the total load. One variable affecting discharge rate is of course velocity, and as velocity increases, so does the streamís capacity to erode and move the larger particle that make up the bed load.
Dr. Craig Glenn, Professor
Department of Geology and Geophysics
University of Hawaii, Honolulu, HI 96822 | <urn:uuid:19a4a550-53f3-4567-8225-1d9eb6d63648> | 2.6875 | 158 | Q&A Forum | Science & Tech. | 38.485 |
This was posted on another list by Herbert Borteck. It is reposted
here with permission. It seems to pertain very strongly to how the
Scientific method and peer review work.
All humans have social and psychological problems which interfere
with their attempts to be objective. When new ideas and
modifications of old theories are presented, people will react to
them depending on how these ideas will affect them. Science is an
error correcting process. Science thrives on open and free debate
about the merits of rival hypotheses. Sometimes many rival
hypotheses are considered before the best is found. It's the nature
of scientific inquiry that scientists publish hypotheses that may
later be disproved by new evidence and replaced by a better rival.
Eventually some hypotheses receive sufficient positive evidence.
They become accepted as theories with the understanding that even
the best theories may be revised in the light of new evidence. No
method exists to take data as input and produce true scientific
theories as output. Linus Pauling said: "A student once asked me,
'Dr Pauling, how do you go about having good ideas?' and I answered:
You have a lot of ideas and you throw away the bad ones."
This method works both for individual scientists and for the
scientific community. Plausible ideas need to be published,
subjected to debate, challenged with new evidence. If a hypothesis
turns out to be bad, science throws it away. If it stands up in the
face of further evidence, then the scientist who first published it
receives the credit. Scientific inquiry is an on-going process of
In one of the major scientific undertakings of his life, Lord Kelvin
was in error. His calculations of the age of the earth were made
obsolete by the discovery of radioactivity. Lord Kelvin had based
his mathematics on the earth's cooling from a molten mass. The two
questions were what is the source of the sun's heat and how old is
the earth? The earth was assumed to have cooled with only the sun
for an additional energy source. Lord Kelvin seriously considered
the collision with meteors as a source of fuel for the sun and as
impact energy for the earth. But calculations showed that even the
highest estimates of meteors hitting the sun would only sustain it
for a few thousand years. He suggested that the sun was slowly
contracting and in that way produced heat.
Beginning in 1862, and for thirty years after, Lord Kelvin published
papers arguing that, according to his calculations of the rate of
the earth's cooling, the earth could not possibly be old enough for
either Darwin's evolution by natural selection or for the
uniformitarian scenario for the formation of the earth's features.
He said that a fundamental assumption of uniformitarianism was
contrary to natural laws. According to principles of thermodynamics,
since the earth was a cooling body, it could not have been at the
present temperature and with the present conditions for hundreds of
millions of years. As Lord Kelvin refined his calculations, his
estimates of the age of the earth went down, from 400 my to 100 my
to 50 my to 20-40 my.
What Lord Kelvin lacked was radioactivity. Ernest Rutherford
discovered that the source of radioactivity is disintegration of
the atomic nucleus. As a radioactive element disintegrates it ejects
particles and releases heat. Upon receiving this NEW information,
Lord Kelvin would not be convinced but most other physicists were.
Rutherford was about to give a speech on radioactivity in which he
disagreed with Lord Kelvin's estimates of the age of the earth when
he realized Kelvin was in the audience. "I… realized I was in
for trouble at the last part of the speech… Then a sudden
inspiration came and I said Lord Kelvin had limited the age of the
earth, PROVIDED NO NEW SOURCE OF HEAT WAS DISCOVERED." That
prophetic utterance refers to what we are now considering tonight,
radium! The old boy beamed upon me." Rutherford concluded his
speech, before the Royal Society, with… "The discovery of the
radio-active elements, in which their disintegration liberate
enormous amounts of energy, thus increases the possible limit of
the duration of life on this planet, and allows the time claimed by
the geologist and biologist for the process of evolution."
Lord Kelvin never published any acknowledgment that radioactivity
was supplying heat to the earth's crust and that thus his
calculations of the age of the earth were not accurate.
J.J. Thompson, related in his own memoirs that "in private
conversation Kelvin did concede that his theories had been
I am aware that the conclusions arrived at in this work will be denounced by some as highly irreligious; but he who denounces them is bound to shew why it is more irreligious to explain the origin of man as a distinct species by descent from some lower form, through the laws of variation and natural selection, than to explain the birth of the individual through the laws of ordinary reproduction.
This archive was generated by hypermail 2b29 : Tue Oct 17 2000 - 15:54:38 EDT | <urn:uuid:70663a9f-90cd-4504-9a0b-4b640c52885f> | 2.890625 | 1,097 | Comment Section | Science & Tech. | 44.879186 |
Endangered Plants of Antarctica
Corals, Jellyfish, and Sea Anemones
Click on the species name to view all info that is currently available.
|Borneo Teak||Africa, Asia, Australia, Europe, Oceanic|
|Cycas spp. (3)||Asia, Australia, Oceanic|
|Podocarpus spp. (2)||Oceanic|
|Zanthoxylum spp.||Central America, North America, Oceanic, South America|
More endangered creatures in Antarctica:|
Corals, Jellyfish, and Sea Anemones | Plants
***What plants are listed here?:The Antarctica section of this site lists the folllowing plants appearing on select endangered species lists:
- Plants that dwell in or migrate to Antarctica.
- Plants of the oceans that travel to the Antarctic (Southern) Oceans.
In some cases, the creatures listed in this section may also be found on other continents or in other areas, which is why you may see additional
areas noted in the range column.
This list combines species from several endangered species lists.
Using the total count of species found on this site as an official count of
endangered species of the world is not recommended
. For more information on
what creatures are listed on this site, please visit our | <urn:uuid:f7781875-abcb-4715-9153-cd9009afdd18> | 2.953125 | 279 | Content Listing | Science & Tech. | 34.776989 |
El Modelo de Objetos de Gambas
1. Objetos y clases
es una estructura de datos que provee propiedades
Esta estructura de datos se describe a través de una clase
Cada objeto de Gambas
dispone de una clase
que describe todas sus propiedades públicas, métodos y eventos.
Esta clase a su vez es un objeto también, cuya clase es la clase llamada Class
A static class
is a class whose all members are static
(see below). In Gambas
, a static clase
is also named a module
A virtual class
is an hidden pseudo-class that you cannot explicitely manipulate.
1.2. Properties, methods and variables
Properties and methods allow to manipulate the data structure.
A property, a method or a variable can be static
- A static variable will be shared by all instances of the same class.
- A static property or método can only modify static variables.
A method or a variable can be either public
. A property is always public.
Private symbols can only be used from the class inside.
Public symbols can be used everywhere, provided you have a reference pointing at the object.
Events are signals sent by an object when something happens on it.
If an object raises events, it will hold a reference on its observer
, or parent object
This observer is another object that implements event handlers
. An evento handler
is just a public método
that is called each time the evento
By default, the observer is the current object where the newly instanciated object is declared.
To raise events, an object must have an event name
. This event name is assigned at object instanciation, when using the NEW
instruction, and is the prefix of all event handler methods.
If no event name is specified, then the objeto
won't raise events.
An object can be locked so that it stops raising events, and can be unlocked so that it raises them again.
See the Object.Lock
Some events can be cancelled by the event handler, by using the STOP EVENT
The effect of this cancellation depends on the evento
There is no garbage collector
. So each object has a reference counter
that is incremented each time the object is referenced by any variable
, array, collection or other object, and decremented when it is released.
This reference counter is zero at object creation, and when it becomes zero again after a reference release, the object is freed.
1.5. Invalid objects
An object can become invalid
. Because, for example, it is linked to an internal object not managed by Gambas
that was destroyed.
Trying to use an invalid object raises an error.
1.6. Special methods
Special methods are methods declared in classes, whose name begins with an underscore character, and that are called by the interpreter in the following situations:
- When an object is created.
- When an object is freed.
- When the object class is loaded.
- When the object class is unloaded.
- When using an object as if it is an array.
- When enumerating the object.
- When using an object as if it is a function.
- When trying to use an unknown object método or propiedad.
for more information.
Inheritance is the way for a class to become a specialized version of another class.
2.1. What is inherited?
The class inherits from its parent every método
2.2. Which class can be a parent class?
You can inherited any class, even a native one!
For example, you can create
a custom MyListBox class that inherits ListBox
but allows to associate a tag with each list item.
Note that you cannot use INHERITS
in a form class file, because forms already
inherits the Form
2.3. Virtual dispatching
When calling a método
or accessing a propiedad
from an object reference, Gambas
uses virtual dispatching
It means that the real class of the object is always used, and
not the type of the variable
that references the object - As it was in Gambas
2.4. Inheritance and constructor
Contrary to all the object language I know, each class in the inheritance
hierarchy consumes the parameters passed to the constructor.
Let's suppose we have the following inheritance tree:
MyListBox ---inherits--> ListBox ---inherits---> Control
- Control._new() does not exist.
- ListBox._new() takes one parameter: the parent control.
- MyListBox._new() takes one parameter: a name - It is just an example.
So NEW MyListBox
will take two parameters.
- The first will be sent to MyListBox._new().
- The second to ListBox._new().
Be careful: the ListBox
._new() will be called first,
so that you are sure that the ListBox
when you are in MyListBox._new().
So arguments must be specified in reverse order.
Then you will create a MyListBox control this way:
hMyListBox = NEW MyListBox("Name", hContainer)
are external shared libraries written in C, C++ or in Gambas
that add new functions and/or classes to the Gambas
are grouped according to the component they come from.
3.1. Default internal component
The interpreter includes an internal component named gb
that defines all standard classes of the language.
This component is always loaded by default, and can be considered as part of the language.
3.2. Symbol tables
Each component has its own private class symbol table, so that class names do not conflict.
3.3 Global symbol table
So that components can work together, there is a global symbol table, where all classes exported by components and all classes exported by the current project are stored.
If there is a name conflict in this global symbol table, the last loaded class overrides the
previous loaded class with the same
name, by using inheritance. In other words, the overriding class extends the overriden one.
This last feature can be used for:
- Extending an already declared class by adding new methods or properties to it. For example, the gb.qt Application class reimplements the gb Application class.
- Overriding the methods of an already declared class. For example, the gb.form.dialog component replaces most of the static methods of the Dialog class.
3.4 Project symbol table
Your project has its own private symbol, like any componente
, and can export any of its classes to the global symbol table
by using the EXPORT
The project classes are loaded after all components. So your exported clase
can override any exported classes declared in any componente | <urn:uuid:94ecd07d-79c0-43a3-b513-90e098aecbc8> | 3.84375 | 1,506 | Documentation | Software Dev. | 51.995091 |
I have read that Marconi, aboard his yacht called “Electra” (or something like that) was known to do strange experiments such as “anti-gravity” experiments and sending signals into space.
I also read that Marconi might have formed a secret group of scientists in South America working for peace and science. Apparently alot of their technology was based on Nikola Tesla’s and Marconi’s work.
Does anyone know any similar strange experiments Tesla or Marconi did? I am asking about the science, not conspiracy theories.
How did building a radio (I know Tesla did it first) lead to anti-gravity experiments (even if anti-gravity does not exist)?
I have heard of these experiments, but have yet to see a single one of them actually demonstrated or any papers that would lead to a real experiment being conducted. I am inclined to think either one of two things:
1) Telsa needed funding for his experiments do lied or exaggerated to the public or financiers to get more money;
2) He ended up doing work on superconductors; they expel magnetic field, and hence repel magnets. This repulsion can be stronger than gravity, which leads to levitation. This could be misunderstood for anti-gravity.
If you think of gravity the way we understand it . . . a warping of spacetime caused by mass . . . it would be hard to see how a genuine anti-gravity machine could exist, except in the sense of something that overcomes gravity in the manner of a plane. That’s my opinion anyway.
on: 30th June 07 | <urn:uuid:01ed8057-3cb9-46e8-b8ce-2559a4d5d3bd> | 2.6875 | 338 | Comment Section | Science & Tech. | 50.95876 |
Young Chimps' Photographic Memory Better than Adult Humans
"In a memory competition of man versus chimp, Japanese researchers found that chimpanzees performed better than humans.
"No one could imagine that chimpanzees -- young chimpanzees at the age of 5 -- have a better performance in a memory task than humans," Kyoto University researcher Tetsuro Matsuzawa said in a statement.
In the first test, the chimps successfully counted sequentially from one to nine in return for a peanut or other tasty reward.
In the second test, researchers flashed just some of the nine numerals, then blocked them. The chimps remembered, with mixed success, where each numeral was -- in the right order, even though some were missing.
Though far from perfect, the results surprised the Japanese researchers, who reported their results in the journal Current Biology.
See a video here and here
One chimp, Ayumu, distinguished himself from the other chimps in mental ability. He was included in a second round of tests, which included him and 9 college students.
Five numbers were flashed on a screen for 7/10 of a second, before they became white squares. The participants were required to touch the squares in their correct numerical sequence. When the numbers were shown, Ayumu and the college students succeeded in guessing the correct sequence about 80 percent of the time." | <urn:uuid:f2987cc7-8878-41ec-9224-f7ac65f4fe13> | 3.234375 | 278 | Personal Blog | Science & Tech. | 38.673848 |
The <body> is where the bulk of your web page is. Almost everything
you've seen on web pages is done in between two body tags. But there are
also a few things that are set within the actual <body> tag. You'll
see what I mean in a little bit. Within the <body> tag you can set the
background picture, background color, text color, link color, visited link
color, and active link color. The background picture is
background="filename.gif". The background color is bgcolor="white".
The text color is text="black". The link color is link="blue". The
visted link color is vlink="green". The active link color is
alink="red". The background picture is any picture that you want to
be loaded behind the text. You can only have one picture, and it will
repeat. Be sure that the text color you choose contrasts with the
picture, or the text will be unreadable. The background color is used
if you do not wish to put a picture in the background. The text color
is the color of the words on that particular document. The link color
is the color of the words that are links. The visited link color is
the color that links turn if you've already visited a particular site.
The active link color is the color that the link turns when you click
on a link. If you click on a link really fast, it will (if alink
isn't the same as link or vlink) flash another color. To test what
the alink color is, click and hold on a link.
Color can also be set using the RGB code. The code is in hexadecimal
format. So, black would be #000000. White would be #FFFFFF. Red would
be #FF0000. Green would be #00FF00. Blue would be #0000FF. The code is
a six digit number. The first two digits are the red value. The seconde
two digits are the green value. The last two digits are the blue value.
So, if you want a page with a white background, black text, blue links,
green visited links, and red active links, you'd put
<body bgcolor="white" text="black" link="blue" vlink="green"
alink="red"> and to end it, </body>. So everything between those two
tags would recieve the properties of the first tag. An equivalent would
be <body bgcolor="#FFFFFF" text="#000000" link="#0000FF"
vlink="#00FF00" alink="#FF0000">. If you wanted a picture in the
background, you'd remove the bgcolor="white" and add
background="filename.jpg". So a file with the htmlcolor.gif picture as a
background, and all other properties the same, would be <body
background="htmlcolor.gif" text="black" link="blue" vlink="green"
alink="red">. Want to see this in action? Click
here. If you clicked
on that link, you'd notice how busy it appears, and how hard it is to
read the text. So try to keep that in mind. Don't use images that
are too busy. | <urn:uuid:f7f9baf7-7161-4503-996a-9c641b13f15c> | 2.796875 | 704 | Tutorial | Software Dev. | 79.561991 |
Hi, I need some help on this question.
A unifom lamina ABCEF is obtained from a rectangle ABCD with AB = CD = 8cm and BC = AD = 6cm, by removing the triangle EDF, where E and F lie on CD, AD respectively, with CE = 2cm and AF = 3cm.
1. Find the distance of the centre of mass of the lamina ABCEF from AB and AD.
2. The lamina is suspended freely from F and hangs in equilibrium under gravity. Find the angle which AF makes with the vertical.
I'm stuck and don't know how to start. | <urn:uuid:fdb04fc5-3976-4c30-b43d-fd68975fa609> | 2.796875 | 132 | Q&A Forum | Science & Tech. | 86.26125 |
Like any other form of matter gas molecules feel the gravitational pull of the planet they surround, so they're attracted to the planet by gravity. At any temperature above absolute zero the atoms/molecules in a gas have a velocity distribution known as the Maxwell-Boltzmann distribution. As long as their velocities remain well below the escape velocity of the planet the atmosphere will be bound to it.
Although this gives the basic idea it's an oversimplification for several reasons. For example the escape velocity decreases as you move up through the atmosphere, however the temperature changes as well so the average gas atom/molecule velocity also changes with height. Also even if the average is well below the escape velocity a small fraction of molecules will have high enough velocities to escape. However even then only molecules near the top of the atmosphere are likely to escape as the mean free path near the ground is too short for even an energetic molecule to escape. Finally radiation from the Sun is an important factor in removing gas molecules from planets. On Earth the magnetic field keeps most of the radiation out, but on Mars gas loss due to solar radiation is important.
For more info you might want to have a look at the Wikipedia article on atmosphere loss.
I'm not sure what your second question is asking as it doesn't seem relevant to atmosphere loss. If you're asking why planets generally have a non-zero tilt this should be posted as a separate question. In brief, for most planets the tilt is chaotic and varies contnuously, and the planet may even flip over completely. Earth's tilt is stabilised by the moon and varies only slightly with time.
Re the revised question: At any given temperature the average velocity of lighter gas molecules is greater than heavier gas molecules, so it's the ligher gas molecules that escape most easily. For example the Earth loses a few kg of hydrogen per second but almost no oxygen or nitrogen.
However if the rate of loss of a light gas is very fast it can carry molecules of heavier gases along as well by colliding with them and transferring momentum to the heavier molecules. This is known as hydrodynamic escape. Note that this only happens when there is a rapid loss rate of the lighter gas, so it isn't happening to any significant extent on any of the planets in the solar system. | <urn:uuid:45a6f037-7e44-4b48-b256-225ddb35373f> | 3.96875 | 475 | Q&A Forum | Science & Tech. | 38.673059 |
There's a natural cause that may account for much of the Arctic warming, which has melted sea ice, ice sheets and glaciers, according to a study published Thursday in the journal Nature. New research points a finger at a natural and cyclical increase in the amount of energy in the atmosphere that moves from south to north around the Arctic Circle.This article represents a significant change in tone for Borenstein. Just over three weeks ago, Borenstein produced this panicked piece on the very same subject, entitled "'The Arctic is screaming' — summer sea ice could be gone in five years".
"If we didn't have the little extra kick from global warming then we wouldn't have gone past the threshold for the change in sea ice," said Overland, of the National Oceanic and Atmospheric Administration's lab in Seattle.
"The Arctic is often cited as the canary in the coal mine for climate warming," said Zwally, who as a teenager hauled coal. "Now as a sign of climate warming, the canary has died. It is time to start getting out of the coal mines."Coupled with John Tierney's skeptical New York Times piece earlier this week, this has been a watershed week for climate skepticism in the mainstream media. This hysteria's long crumbling process has clearly begun.
It is the burning of coal, oil and other fossil fuels that produces carbon dioxide and other greenhouse gases, responsible for man-made global warming. For the past several days, government diplomats have been debating in Bali, Indonesia, the outlines of a new climate treaty calling for tougher limits on these gases. | <urn:uuid:858652f5-b19a-44b2-b2de-18bdb1fdf30d> | 3.015625 | 326 | Personal Blog | Science & Tech. | 46.462431 |
Science Fair Project Encyclopedia
- The pound (avoirdupois).
- The troy pound.
- The metric pound, no longer officially sanctioned but still in informal use in some places.
Standards bodies define the pound as a unit of mass, which are the pounds most people in everyday usage use as a unit of weight.
The Latin word libra describes a Roman unit of weight similar to a pound, and the abbreviation "lb" for the unit of weight and the signs £ and ₤ (crossed-out L's) for the currency derived from this. The word "pound" itself comes from the Latin pendere, to weigh, while libra meant "scales, balances".
In the Imperial system (often referred to as the pound-inch system, or the British system in the United States) there are two basic pounds defined, and also an obsolete definition of one variant of the pound.
Pound (avoirdupois) or international pound
Main article: avoirdupois
The avoirdupois pound was invented by London merchants in 1303.
The pound (avoirdupois) or international pound, abbreviation "lb" or sometimes # in the United States, is the mass unit defined as exactly 0.45359237 kilograms (or 453.59237 grams). This definition has been in effect since a 1959 agreement among the national standards laboratories of the United States, Canada, the United Kingdom, South Africa, Australia, and New Zealand. It is part of the avoirdupois system of mass units.
In the United States, the pound has been officially defined as a unit of mass and defined in relation to the kilogram since 1893, but its value in relation to the kilogram was altered slightly in 1894, and again to its current value in 1959 (which only differs from the 1894 definition by approximately one part in 10 million).
In the United Kingdom, the avoirdupois pound was defined as a unit of mass by the Weights and Measures Act of 1878, but having a very slightly different value (in relation to the kilogram) than it does now, of approximately 0.453592338 kg. (This was a measured quantity, with the independently maintained artifact still serving as the official standard for this pound.) This old value is sometimes called the imperial pound, and this definition and terminology are obsolete unless referring to the slightly-different 1878 definition.
There are 16 ounces in a pound (avoirdupois). This pound is equal to exactly 7000 grains, where a grain is exactly 0.06479891 gram. This relationship between avoirdupois pounds and troy grains has held true since the avoirdupois pound was redefined in terms of the troy units in the reign of Henry VIII, abandoning independent standards which had been measured as about 7002 grains troy. Since then, the grain has often been considered as a part of the avoirdupois system as well, even though it does not fit very well in that system.
Main article: Troy weight
A troy pound is a unit of mass in the United States, Canada, Australia, the United Kingdom, and other places. The troy pound is a unit of mass equalling exactly 0.3732417216 kilograms. There are 12 troy ounces in a troy pound. A troy pound is equal to exactly 5760 grains, making a troy pound equal to exactly 144/175 pounds avoirdupois.
The troy pound is now used only for measurements of precious metals such as gold, silver, and platinum, and sometimes gems such as opals. Most weight measurements of precious metals using pounds and ounces use troy pounds and ounces, even though it is not always explicitly stated that this is the case. Some notable exceptions are Encyclopędia Britannica (a U.S. encyclopedia for about a century now) which uses either avoirdupois pounds or troy ounces, likely never both in the same article (which would make a weird system with 14 7/12 ounces to a pound), and King Tut's sarcophagus lid, which is often stated to have been 242 or 243 pounds (avoirdupois; when it is, much less commonly, stated as 296 pounds, then the pounds are troy).
One troy pound = 12 troy ounces = 240 pennyweight = 5760 grains.
Main article: kilogram
In many countries that use the SI or metric system, the pound (or its translation, for example, the German Pfund, the French livre, or the Dutch pond) is used as an informal term for half of a kilogram, therefore for this case the pound is 500 grams. In many cases, this was an official redefinition back in the 19th century, but its use is generally no longer officially sanctioned. These replaced hundreds of older pounds, for example, one of around 459 to 460 grams in Spain, Portugal, and Latin America; 498.1 g in Norway; and several different ones in what is now Germany. In the case of the Dutch pond, this was officially redefined as 1 kg, with an ounce of 100 g; the former has fallen out of use, and if the pound is used today it is likely the 500 g variety, but the 100 g ounce remains in limited use.
Pound as a unit of weight
When a pound is called a "unit of weight", it is usually a unit of mass. This is always true for the term net weight, for example.
Pounds are also used for the force definitions of weight, in which the pound force is a unit of force equal to 4.448 newtons. That is the force due to gravity of a pound (avoirdupois) where the acceleration of gravity is 32.17405 ft/s². The troy units of weight are never units of force. Pounds-force are never used for net weight, nor are they used for body weight in the medicial sciences, in zoology, or in sports. Main article: pound-force
Which one is meant?
If neither "avoirdupois" nor "troy" is specified, the international pound (avoirdupois) is meant and is by law the only proper definition in the United States, United Kingdom, and Canada; the troy pound has been officially abandoned in the United Kingdom. The valuation of precious metals on U.S. exchanges is specified as dollars per troy ounce, although the fact that the troy ounce is used is usually implied. In the context of vegetable and meat sales within metric countries, a metric pound (500 g) is usually implied.
Force, weight, and mass
Historically, the pound predates the understanding of the distinction between force and mass. Once that distinction became clear, it was natural to ask whether the pound should be construed as a unit of mass, or a unit of force (and weight, which is defined as the gravitational force acting on an object). But because the foot-pound-second systems are no longer used in science (and are gradually approaching extinction even in U.S. engineering work), many scientists today would be as bemused by this question as by the question of whether the shekel is a unit of mass or of force.
In many contexts, there is a long history of considering the pound to be a unit of mass:
- Pounds were primarily a measure of how much stuff people had, for the purposes of trade. We know what we use for those purposes today--the only pounds legal for trade anywhere in the world are those defined as units of mass exactly equal to 0.45359237 kg.
- Mass-measuring balances were the only weighing instruments anybody ever used before the 19th century.2
- Over time, the various keepers of the standards redefinedpounds in terms of the metric system (which has happened in case of the avoirdupois and troy pounds as well as the metric pounds), they were defined in terms of the kilogram, not the dyne or the newton.
- When units such as the British thermal unit are defined based on the pound, those pounds are units of mass just like the grams or kilograms used as the basis of the definition of calories.
- On labels of products sold in the U.S., the pounds and ounces are units of mass, like the grams and kilograms which appear right alongside them.
On the other hand, pounds are always to be construed as a unit of force in contexts such as these:
- Thrust of rocket or jet engines in pounds-force.
- Torque in foot-pounds or pound-feet.
- Pressure in pounds per square foot or pounds per square inch.
- Energy in foot-pounds.
There are some contexts in which the word "weight" is customarily used in a misleading way:
- In commerce, the terms "net weight," troy weight, and carat weight actually refer to mass rather than weight. The pounds used for this purpose are units of mass.
- The scientific terms "molecular weight," "atomic weight," and "formula weight" all actually refer to mass, which is why some now refer to "molecular mass," etc. If a "pound mole" is used, it is based on the pound as a unit of mass.
There are three practical ways of doing calculations with mass and force in the fps systems (and other systems such as inch-pound-second systems not discussed here), which the following table summarizes and compares with the SI.
|unit of time||s||s||s||s||unit of distance||m||ft||ft||ft||unit of mass and weight||kg||slug||pound||pound||unit of force and weight||N||pound-force||pound-force||poundal||Newton's second law||F = ma||F = ma||F = ma/gc||F = ma||weight of an object||W = mg||W = mg||W = mg/gc||W = mg|
The absolute and gravitational fps systems are coherent systems of units which both share with the SI the advantage of avoiding needless complication in several of the formulas used, whereas the engineering fps system requires the introduction of the factor gc, which is a dimensionless constant, defined as 32.17405 lb ft/(lbf s2) and approximately equal to the typical acceleration of gravity on Earth, in ft/s2. This must be distinguished from the actual local value of g.
No one of the three fps systems is more correct than the other two. None of our ordinary measurements are made in the context of any of these specialized subsets of mechanical units, used only in calculations.
Although the U.S. National Bureau of Standards has defined the pound as a unit of mass, and the pound-force as a unit of force, this distinction is not widely recognized among working physicists, because the fps system has not been used in physics, even in the U.S., since the early 20th century. When giving data to be used in calculations, it is not a good idea to use the term pound without clarifying whether mass or force is intended. If force is what is meant, the symbol "lbf" or the term "pounds-force" can be used for clarification. For mass, one can specify "pounds-mass."
NotesIt is primarily the United States which uses them today, though other places such as livestock markets in Canada do still sell cattle in cents per pound, even though they sell hogs in cents per kilogram (actually, it is most often quoted as dollars per hundred pounds and dollars per hundred kilograms).
Note 2: Copies of the standard pound in London were distributed to other locations, where they served as the local standard. These copies have the same mass at the new location, even though they exert a (slightly) different amount of force due to regional variations in the Earth's gravitational field. The standards for pounds always were standards of mass, not standards of force.
- History of the pound as a unit of mass: U.S. National Institute of Standards and Technology Official Definition, showing history
- Official abbreviations and definitions: U.S. National Institute of Standards and Technology Special Publication 811
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:9f07b6b7-9c9a-45c7-a6cb-0e9b8b6f1027> | 3.625 | 2,605 | Knowledge Article | Science & Tech. | 55.389421 |
Piecing Together Life’s Potential
Interview with Carol Stoker
Carol Stoker, a planetary scientist at NASA’s Ames Research Center, is a team member for the upcoming Phoenix Lander. This mission, launching in 2007, aims to land in the high northern latitudes of Mars to search for frozen water and any indications of past habitable conditions.
|Carol Stoker of NASA’s Ames Research Center
In this interview with Astrobiology Magazine’s Leslie Mullen, Stoker describes what Phoenix can expect to find when it lands on the northern plains of Mars, and why astrobiologists have high hopes for finding the signs of life there.
Astrobiology Magazine (AM): You’ve outlined three things that any place on Mars would need to be considered habitable: liquid water, an energy source, and the chemical building blocks of life.
Carol Stoker (CS) : That strategy for assessing the habitability of a site was laid out by MEPAG: the Mars Exploration and Payload Analysis Group. They’ve developed a program for the exploration of Mars over the next decade, and they appointed a committee to devise a strategy for the astrobiology field laboratory. That’s the mission after Mars Science Laboratory which is supposed to try to detect life. The committee recommended how to pick a landing site for that mission, and also what are the precursor things that need to be done before you can fly a mission to look for life.
To some extent, this was informed by the 1970s Viking missions to look for life, which we sort of did in the blind. At that time, our understanding of Mars was very primitive compared to what it is now. We had a Lowellian view where we thought Mars was a warm, wet, habitable planet. So we had optimistic assumptions that we would find life wherever we landed.
For the astrobiology field lab, the working group at MEPAG recommended a strategy to evaluate three probabilities: the probability that an environment has or had liquid water in the past, the probability of there being an energy source to support life, and the probability of there being a chemical environment that’s conducive to supporting life. The product of those three probabilities creates a habitability index.
|This MARCI image from MRO is a composite mosaic of the north polar cap. The image shows the mostly water-ice perennial cap (white area), sitting atop the north polar layered materials (light tan immediately adjacent to the ice), and the dark circumpolar dunes.
Image Credit: NASA/JPL/MSSS
We’ll use the observations from Phoenix to evaluate those three parameters, and see what kind of a score we get. The selection of the landing site for Phoenix and the choice to explore the northern plains was based on theoretical modeling that suggests we should get a high habitability score there.
AM: Have they picked a site yet for Phoenix, or do you mean that the northern high latitudes generally look promising in terms of habitability?
CS: You would expect anywhere in the northern plains to be pretty good. Selecting the landing site is largely based on finding places where it will be safe to land, but another key factor has been selecting a site where there’s ground ice. Mars Odyssey discovered there’s near-surface ground ice virtually everywhere in the northern plains north of 60 degrees, and to a large extent the choice of a landing site for the Phoenix mission is driven by that discovery. The actual landing site will be chosen to optimize both the amount of ice and the depth below the surface at which that ice occurs.
AM: Do all three qualities –- water, organics, energy -- need to be present for a site to be considered habitable? What if we only find two out of the three?
CS: Well, of the three, liquid water is the one that has the most discrimination between different landing sites. Sunlight is the dominant energy source for most places where one would look for evidence of life on Mars, and sunlight is going to be available pretty much equally anywhere.
While the chemical building blocks of life is certainly an issue, they also are available nearly everywhere. We have measurements from four landing sites on Mars which show basically the same global uniform soil unit, and the soils contain those elements. So the presence of liquid water is going to be the big difference between sites on Mars.
|Mars Reconnaissance Orbiter HiRISE image of a potential Mars Phoenix landing site. The polygonal patterned ground looks similar to permafrost regions of Earth. The diameters of these martian polygons are dominantly 10 to 20 meters, but some are a few meters or less wide. Rocks protruding above the surface soil cast shadows, which can aid in the determination of the rock's size and height.
Click image for larger view.
In the MEPAG analysis, they stated that unless you have a high habitability index -- in other words, that these three probabilities combined suggest there was ever a habitable environment -- you shouldn’t send a life detection mission. But a factor they didn’t consider is the detectability of biosignatures. One of the things you need to know is whether biosignatures are preserved in that environment, or whether there are processes that destroy biosignatures. A model based on the non-detection of organic compounds at the Viking landing sites says there are oxidants in the soil that destroy organics. So that factor would take away from your probability of detecting life.
Another factor to consider is time. The Mars Exploration Rover sites are both in locations that have a high habitability index, but the factors of habitability, like liquid water, occurred 3 billion years ago or more. That’s really a long time ago. If you look at the history of life on Earth, the further back in time you go, the harder it gets to prove you’ve found evidence of life. In fact, the only evidence scientists have accepted as definitive about ancient life on Earth is by having a modern analogue to compare to. You’re not going to get that on Mars.
So my argument is that you’ve got a much higher probability of finding a detectable form of life if that habitable environment was recent -- actually happening right now or in the recent past. I think the habitable conditions in the northern plains are likely to be more modern, and don’t rely on something that happened 3 or 4 billion years ago. So for that reason, the biological potential of the northern plains, from the point of view of detectability, is higher.
AM: So you think the northern plains had liquid water in a more modern time period? Maybe there’s liquid water even today underneath the surface ice?
CS: It’s not modern in the sense that it’s happening today; it’s modern in the sense that it has happened in the last million years. The climate conditions on Mars change as a function of the cycling of solar insulation due to several orbital parameters that vary over time.
The orbit of Mars is eccentric. It makes a difference if you’re close to the sun or far from the sun in the summer. Currently, in the northern summer, Mars is furthest from the sun, and in the southern summer, Mars is closest to the sun. That amounts to a 50 percent difference in the solar insulation between the southern hemisphere in the summer and the northern hemisphere in the summer.
|The orbit of Mars is not as circular as the orbit of Earth. Changes in the orbit over time have affected the martian climate and distribution of the ice.
Click image for larger view.
The southern hemisphere in the summer is warm enough that water should be rapidly evaporating out of the southern high latitudes. But because the mean elevation of the southern hemisphere of Mars is 2 kilometers higher than it is in the north, the atmospheric pressure never gets high enough for there to be liquid water in the south.
In order to get liquid water, you need to have pressure and temperature above a certain threshold called the triple point. The triple point conditions are never exceeded in the southern hemisphere in the summer, even though it’s very warm, because the pressure is too low.
In the north, during periods when Mars happens to be closest to the sun during northern summer, solar insulation is 50 percent higher so it also gets very warm. The lower elevation of the north means the atmospheric pressure is higher, so it is possible to have liquid water during the north’s warm periods.
Right now, we’re in a period where the solar insulation in the northern plains in the summer is at a historically low point. But 25,000 years ago, it was 50 percent higher. And 500,000 years ago it was 300 percent higher. So the triple point conditions were exceeded in the north during that warmer climate epic.
That climate epic happens on 50,000 year time scales, which is a long time by our experience. But you could have habitable conditions where life grows in those periods when conditions are good, and then freezes and remains frozen for 50,000 years. Life is perfectly adapted to doing that on Earth. We have many examples of permafrost sediments that have been frozen and metabolism-prohibited for hundreds of thousands of years, and even in some cases millions of years, and life has survived and can be revived the next time it gets warm. That kind of environment is not happening in the northern plains of Mars today, but in the last 50,000 years liquid water could have been periodically available.
|Model of the Mars Phoenix lander. Click image for larger view.
Photo credit: University of Arizona.
AM: Phoenix has a rotor to grind up the ice, and those ice crystals will go into a scoop for analysis. Can we tell from that sample if there’s any life present?
CS: Phoenix can’t actually detect life, but it can tell you if there are organic compounds. The presence of organic compounds is another one of those factors that goes into detectability. Finding out if biosignatures are preserved has to do with finding out if they are being destroyed faster than they’re being produced. If life has to sit around for 3 billion years, it doesn’t have to be destroyed very fast to not be preserved. But if life only sits around for 50,000 years between growing periods, then you may have a chance.
The availability of solar energy cuts both ways, because on the one hand, solar energy is by far the most plentiful and attractive energy source. But on the other hand, it’s highly laden with ultraviolet light, which can destroy biological signatures. You need solar energy for life to metabolize and create organics, but then you want to bury those organics so they’re not being destroyed by the solar energy. You want the organics to be buried faster than they’re destroyed.
The other factor comes from the Viking results. Viking poured soil into different instruments and added water, and then reactive chemistry occurred. Although the results duplicated many of the features of a biological reaction, it was interpreted as not being biological but instead as active chemistry resulting from oxidants.
There was a big difference between the reactions for the Viking 1 and the Viking 2 landing sites. Viking 1 was at low latitudes, while Viking 2 was within about 10 degrees of latitude of where Phoenix is going to land. So Viking 2 might have been sitting on ground ice, but that ice would have been under a thicker blanket than what Phoenix will be sitting on. The Viking 2 lander saw less evidence of oxidants.
|Trapped mineral fragments associated with microbial communities appear in ice on Earth. Could we find such evidence for life in the ice on Mars?
Credit: Kjell Ove Storvik/AMASE.
Models have shown that many candidate oxidants react with water vapor, and so the more water vapor you have, the less oxidants you’ll have. That’s one line of evidence that suggests there won’t be oxidants at the Phoenix site, or at least they won’t be as dominant.
So the Phoenix site not only may have habitable conditions, it also could have conditions that will preserve biological signatures. The problem Phoenix will face is we don’t know the deposition rate of sediments that might have buried the surface when it had habitable conditions.
AM: We don’t know how far down 50,000 years is.
CS: Exactly. Hopefully 50,000 years is not very far down. But we’d really like to go back a million years, or 10 million years, so we’d get a record of a lot of these climate cycles. For that, we’d probably have to drill down at least a few meters.
Related Web Pages
Martian Poles in the Swiss Alps
Managing Mars Missions
Future Missions to Mars
Life Below the Limit
Sunning Frozen Soil
Divining Ice on Mars Through Time
The Changing Face of Mars
Drilling for Weird Life | <urn:uuid:4e260806-c517-48c0-b791-2c8587d5883f> | 2.75 | 2,713 | Audio Transcript | Science & Tech. | 47.456454 |
Simply begin typing or use the editing tools above to add to this article.
Once you are finished and click submit, your modifications will be sent to our editors for review.
use in nuclear reactors
...of this policy is the Canada Deuterium Uranium (CANDU) reactor—a line of natural uranium-fueled reactors moderated and cooled by heavy water. A reactor of this kind consists of a tank, or calandria vessel, containing a cold heavy water moderator at atmospheric pressure. The calandria is pierced by pressure tubes made of zirconium alloy in which the natural uranium fuel is placed and...
What made you want to look up "calandria"? Please share what surprised you most... | <urn:uuid:1502c728-5705-4781-97ad-531e34627fb2> | 3.390625 | 149 | Knowledge Article | Science & Tech. | 48.907987 |
hi.. i have a question regarding Swapping of characters in a string that uses stringbuffer.. like StringBuffer codestring="abcdefghijkl"..how do i swap the char 'a' with 'd' in the string so that final string is like.. codestring="dbcaefghijkl"..
how do i swap the char 'a' with 'd' in the string this sentence.Poster does not say about vice versa
I'm not a native English-speaker, but I think swap is not the same as replace, which is what you are referring to. Swap indeed means that the two items in questions switch their places, so there really is no "vice versa" - both happen at the same time.
One possibility would be to replace 'a' by a completey different character -which you can be sure does not otherwise occur in the string-, then replace 'd' by 'a', and then the other character by 'd'.
Here's a replace based on REXX syntax. Note how it can be used to rearrange a string. You could use that to swap characters based on position. I bet it would not give correct results on translate AD to DA.
This is very old code with a semi-hungarian prefix naming thing that I outgrew ...
The left() method pads or truncates as necessary to left justify.
A good question is never answered. It is not a bolt to be tightened into place but a seed to be planted and to bear more seed toward the hope of greening the landscape of the idea. John Ciardi | <urn:uuid:a3298996-d6af-42b8-b27f-9e1fa4ebf1ab> | 3.15625 | 332 | Q&A Forum | Software Dev. | 71.510628 |
The programming language should handle the business logic – get the stuff out of the database, make some decisions about it based on the other known factors, and end up with the data you want to display, described in a way which is comprehensible and reusable to the programming language, retaining the metadata obtained through the business logic. (for instance, pageTitle = “You’re Doing It Wrong”; bunchOfArrays = commentID, commentText, userID, userName, commentDate, gravatarID, gravatarCategory) There should be no HTML here (other than perhaps any originally embedded in commentText itself) because *at this stage you don’t even know whether you want to output it as HTML*. Here you are deciding on the data to output and how to describe it.
The data and its descriptors should then be handed over to a module which is capable of transforming it into the output language. Usually for our purposes, this is HTML, but it could easily be a CSV download, an RSS feed, or a bunch of emails. (well, why not?) This can be a templating engine which has templates for different output types, and the only logic it should really engage in is looping through arrays provided to it, i.e. foreach, and what to do when data has not been provided (e.g. a null gravatarID should mean that no img tag is output). There should be no decision making because your first stage has already provided you with all the information needed. If you are a template and are given a single variable, you output it once within the template definition. If you are given an array, you output it several times within the template definition. Here you get to define the order in which the data should be displayed, and the method (markup) you’re using to describe it. (for instance, whether it is *semantically* better to output the userName before or after the commentText, regardless of how you want it to be visually displayed.)
The final stage is presentational, usually in the form of CSS, and takes the structured markup and tells the device how to display it. Here you get to choose the color of the text, whether the userName should visually appear before or after the commentText (not the best example: think of a sidebar and body text; far too many developers output the sidebar and then the body text because the sidebar is being displayed on the left, when it is more accessible to output the body text then the sidebar, and style it so that they’re the other way round) and so on.
The first stage is defined by business logic and turns raw data into parsed data. (database -> decisions -> data+metadata)
The second stage is defined by semantic rules and usability-led, accessibility-led, platform-specific definitions and turns parsed data into structured data. (data+metadata -> output definition -> structured data)
The third stage is defined by presentational rules (design) and turns structured data into “displayed” data. (structured data -> style definition -> output data)
With embedded HTML all this is too difficult so you only offer one output stream, severely limiting your own options in the future. Also, with well designed output, the designer should never need to come back to “ask for another class”. The structured data should already contain enough semantic information in the form of the tag used and the id/class provided, to be able to hang any design elements off a set of CSS selectors.
If you are not designing your application in such a discrete way that a new “corporate image” or a print stylesheet decision only affect the presentational stage, or that a new usability issue only affects the second stage, or that a business decision only affects the first stage, then you are always going to run into trouble. | <urn:uuid:9691b230-8ddb-4bbc-9a83-1dae5de9e317> | 2.78125 | 803 | Documentation | Software Dev. | 36.526669 |
Discussion about math, puzzles, games and fun. Useful symbols: ÷ × ½ √ ∞ ≠ ≤ ≥ ≈ ⇒ ± ∈ Δ θ ∴ ∑ ∫ • π ƒ -¹ ² ³ °
You are not logged in.
A common misconception (I think) is that if you've got a set of permuatuations (which are open to variation that could mean that they're not all distinct) the simple way to find out how many there are (ignoring what they are) is to take the number of permuations P (where variation are classed as different) and divide by the number of variations V :these could be "rotations and reflections" (for shapes) cyclic combinations of colours (for couloured patturns etc)
Why did the chicken cross the Mobius Band?
To get to the other ...um...!!!
Re: combination misconception
Maybe Burnside's Lemma will help for some of these examples.
Imagine for a moment that even an earthworm may possess a love of self and a love of others. | <urn:uuid:981d1763-8928-4f0d-99f0-e911b2e696e3> | 2.75 | 235 | Comment Section | Science & Tech. | 69.06 |
LAST winter, Florida got so cold that torpid iguanas fell from trees, pythons froze to death, crops were damaged and corals in the seas around the Florida Keys died in greater numbers than ever recorded before. Further north, heavy snowstorms caused chaos across much of the US.
Across the pond in the UK, it got pretty nippy too - and it stayed cold for much longer than usual. The average temperature of the country in December 2010 was -1 °C, well below the long-term December average of 4.2 °C. It was the second coldest December in central England since records began back in 1659. Here too, heavy snowfalls brought cars, trains and planes to a standstill.
This extreme weather followed on from similar conditions in parts of Europe, the US and Asia the winter before (2009-10) and, to a lesser extent, the winter before ...
To continue reading this article, subscribe to receive access to all of newscientist.com, including 20 years of archive content. | <urn:uuid:6f35b029-c9a8-4e03-af94-844c3ea8171b> | 2.765625 | 215 | Truncated | Science & Tech. | 62.836335 |
Modern imaging technology has widened our knowledge and appreciation of the world more than we could have ever imagined.
Scientists can now explore far beyond the reaches of the human eye, without damaging the specimens they study. Microscopes and X-ray technology enable us to see down to the molecular if not atomic level, and satellites give us perspectives of our planet from thousands of miles above the ground.
Not only can we examine the natural world over a wide range of magnifications, we can also model it in 3-dimensions, and even four, if you add time as well.
Explore some examples below of what modern imaging techniques can reveal.
Why do sharks have such a good sense of smell? Investigate how a team of scientists used the Museum’s CT scanner to find out.
Take a much closer look at 12 familiar species as seen through the Museum’s state-of-the-art scanning electron microscope.
Journey back in time to see images of 100-million-year-old microscopic animals called ostracods, made using revolutionary X-ray technology at the European Synchrotron Radiation Facility in France.
Zoom in to see images of the natural world ranging from those taken 1,000s of kilometres away to those magnified by more than 100,000 times.
Find out about the Museum’s state-of-the-art imaging technologies, including electron and confocal microscopes and the micro- and nano-CT scanners. | <urn:uuid:4ea3bc59-3947-43b6-aac3-742fbea5c2eb> | 3.9375 | 303 | Knowledge Article | Science & Tech. | 41.77596 |
Pages: 1, 2
Now What do I do With It?
There are two approaches you can take to your SOAP education. One is to regard SOAP simply as a featureful, remote-procedure mechanism. It's useful in that role. Many organizations are rolling out internal applications that rely on SOAP as a public programming interface. SOAP's portability plays nicely in this game. It's convenient to write servers in systems programming languages including Java and extended SQL while rapidly developing clients in languages like Visual Basic, Python, and Delphi. You can also use PySOAP to write servers in Python with as little code as
import SOAP def echo(s): return s + "\n " + s server = SOAP.SOAPServer(("localhost", 8080)) server.registerFunction(echo) server.serve_forever()
You'd access this in Python with
import SOAP server = SOAP.SOAPProxy("http://localhost:8080") print server.echo("Hello, there ...")
Notice what the SOAP module achieves:
echo, is defined on the server side but is exposed as a method available for use in the client. The PySOAP distribution includes a
SOAPpy095/README with salient examples of client and server use.
You can also use SOAP to communicate across an organizational boundary. In this model, SOAP is part of a larger, emerging standard called Web Services. Web Services provide computer-to-computer information and communications similar to the way the Web currently mediates between computers and humans. Think of it this way: the Weather Channel delivers pages humans can read, with information about temperature and other conditions. The XMethods service demonstrated above renders similar information, in a form that's handy for further automated computations.
If you're a public utility, for example, you might use public Web Services for temperature, humidity, fuel prices, and other variables to calculate improved management of power generation and distribution.
XML-RPC vs. SOAP
One of the best-documented Web Services is the Meerkat syndication service. Meerkat uses XML-RPC to communicate content and information about content. How does SOAP compare to XML-RPC? Which should you use?
As of June 2001, XML-RPC remains more mature and simpler to implement. However, there are several reasons I favor SOAP for my own development work. XML-RPC's easier implementation matters little to me in application programming because PySOAP wraps up SOAP's difficulty. With a good SOAP binding in hand, I find SOAP's scalability, extensibility, transaction-awareness, and transport flexibility make it easier to use than XML-RPC for typical problems. XML-RPC is only a remote-procedure technology, with a fixed set of data types and XML element names. SOAP adds to these the ability to marshal objects (in the sense of an object-oriented language like Python) and messages, and it can also communicate named parameters and attributes.
As convenient as I find PySOAP, I exaggerated when I wrote, "PySOAP wraps up SOAP's difficulty." The SOAP specification defines many variations and options, only a fraction of which PySOAP 0.95 implements. It's the most important fraction, though, and even the 0.95 release is an adequate base for plenty of useful development.
If you're a consumer of a public SOAP service, like one of those listed on XMethods, you'll need to use SOAP rather than XML-RPC. Moreover, industry heavyweights including IBM and Microsoft have sent clear signals that they've decided SOAP is their long-term preference as a remote-procedure protocol.
Return to the Python DevCenter. | <urn:uuid:6ad508ad-2eb4-4ceb-90c2-ac905b2d21b9> | 3.09375 | 790 | Documentation | Software Dev. | 43.218386 |
|The heliosphere is the region of space governed by the Sun. It is filled with plasma from the Sun in the form of the solar wind. Outside the heliosphere is plasma from other stars (interstellar space). The heliopause marks the division between the solar plasma and the interstellar plasma. This is where the pressure of the solar wind equals the pressure of the interstellar medium.||
Before reaching the heliopause the solar wind is slowed from supersonic to subsonic velocity, and this creates a shockwave shown on the above diagram as the termination shock. The exact positions of both the heliopause and the termination shock vary with time as the pressure of the solar wind changes. At sunspot minimum, the density of the solar wind is reduced and these boundaries contract inward toward the Sun. Conversely, during times of intense coronal mass ejection (CMEs), the density, velocity and magnetic field strength of the interplanetary medium increase. The increased dynamic pressure and the magnetic pressure of the solar wind during these times pushes the heliopause away from the Sun.
The Voyager spacecraft have crossed the termination shock several times as it moves in and out from the Sun.
The heliopause has been found to generate high power VLF radio waves (2 - 3 kHz), particularly when CMEs crash against it. However, these signals can only be detected beyond Saturn because only then does the interplanetary plasma frequency (proportional to the square root of the plasma density) drop low enough to allow signal propagation at these very low frequencies.
|The International Heliophysical Year (2007 - 2009) is a United Nations sponsored scientific program to promote studies of physical phenomena within the heliosphere. Following 50 years after the very successful International Geophysical Year, it expands the domain of study from the Earth to the extended solar system. More details can be found at the official IHY website.|
Australian Space Academy | <urn:uuid:76abf699-fa8a-444e-893b-2dc0ac762870> | 4.125 | 397 | Knowledge Article | Science & Tech. | 32.534096 |
Want to stay on top of all the space news? Follow @universetoday on Twitter
Object Name: Messier 73
Alternative Designations: M73, NGC 6994
Object Type: Four Star Asterism
Right Ascension: 20 : 58.9 (h:m)
Declination: -12 : 38 (deg:m)
Distance: 2.5 (kly)
Visual Brightness: 9.0 (mag)
Apparent Dimension: 2.8 (arc min)
Locating Messier 73: When visiting M72, it’s only about a degree and a half starhop east to pick up M73, or alternately you can start about a fistwidth southeast of Epsilon Aquarii. Although this small grouping of four stars averages 9th magnitude, don’t be fooled into believing it would be an easy binocular target, because the stars themselves range between 10th to 12th magnitude and the large field of view makes it difficult. Even a telescope will require that you double check a reference to be sure you have the right stellar pattern!
What You Are Looking At: Messier 73 has long been referred to as an asterism – a group of stars which only seem related by their proximity to each other. But, is that truly the case? The arguments have been on both sides of the fence for years. The four stars might be fairly widely separated in some respects – but they are very close to each other in other ways. All are bright, evolved giants or subgiants, above the main sequence in the Hertzsprung-Russell diagram and all fit into a color-magnitude diagram of an old cluster of age 2 or 3 billion years. So what do the scientists have to say?
“We present the results of BV(RI)_KC CCD photometry down to V=21 mag in the region of NGC 6994. To our knowledge, no photometry has previously been reported for this object and we find evidences that it is a poor and sparse old open cluster, with a minimum angular diameter of 9 arcmin, i.e. larger than the 3 arcmin originally assigned to it. We obtain a color excess E(B-V) = 0.07 +/- 0.02 mag by means of the BVI_(C) technique.” says L. P. Bassino (et al), “Based on the theoretical isochrones from VandenBergh (1985) that are in better agreement with our data, we estimate for this cluster a distance from the Sun of 620 pc (Vo-Mv = 9 +/- 0.25 mag) and an age lying within the range of 2 – 3 Gyr, adopting solar metallicity. Thus, the corresponding cluster’s Galactocentric distance is 8.1 kpc and is placed at about 350 pc below the Galactic plane. According to this results, NGC 6994 belongs to the old open cluster population located in the outer disk and at large distances from the Galactic plane, and must have suffered significant individual dynamical evolution, resulting in mass segregation and evaporation of low mass stars.”
Then, on the other side of the coin we have this evidence:
“We report on CCD photometry in the Johnson B,V and I passbands for 146 stars in a 9′ \times 9′ region around the southern aggregate NGC 6994 (C 2056-128), which appears in the Lynga (1987) catalogue of open star clusters. We argue that this object is not really an open cluster, but simply a random enhancement of four bright stars above the background level.” says Giovanni Carraro, “This stars sample includes HD 358033 and GSC 05778-0082, together with M 73, which is referred to as a binary star, but actually represents the whole asterism. Since NGC 6994 is not the first case (see for instance Carraro and Patat 1995), this raises the possibility that other open clusters may have been misclassified. We also suggest that NGC 6994 is unlikely to be an open cluster remnant (OCR).”
So who is right and who is wrong? The debate may be as old as the stars themselves!
History: M73 was discovered by Charles Messier on the night of October 4/5, 1780. In his notes he writes: “Cluster of three or four small stars, which resembles a nebula at first sight, containing a little nebulosity: this cluster is situated on the same parallel as the preceding nebula: its position was determined from the same star Nu Aquarii.”
Although many shake their heads at Messier’s log of four stars, other historical astronomers continue to follow suit and observe it. On September 28, 1783, Sir William Herschel notes: “Consists of a few stars arranged in triangular form. No nebulosity among them.” Later, his son John would catalog this same “nothing” group as GC 4617, noting that they were a “Cluster ??; extremely poor; very little compressed; no nebulosity.” If that were not enough, even Emil Dreyer would catalog them as NGC 6994! Not bad for a group of stars that isn’t a group, huh?
Observe them… I dare you.
Top M73 image credit, Palomar Observatory courtesy of Caltech, Messier 73 courtesy of 2MASS and M73 color image courtesy of REU program/NOAO/AURA/NSF. | <urn:uuid:33c57ea7-d5f6-442f-80ff-a080ec47070c> | 2.828125 | 1,169 | Knowledge Article | Science & Tech. | 63.782825 |
Graduate Student Michael McDonald Studies Herbivores as Architects: Moose and Black-throated Blue Warblers in Northeastern Forests
- By Michael McDonald
In the course of a single year, the temperate hardwood forests of New Hampshire’s White Mountains and foothills transition from a quiet, leafless winter corn maze of grey bark and deep snow to a bud-breaking spring mud-scape rich with spring ephemerals. As the season progresses, a multi-story network of niche patches develops and bustles with the energy of songbirds finding mates, building nests, foraging, and rearing young. As summer becomes fall, the transition back to winter’s relative slow takes hold.
Annual chronological dynamics create an often overlapping succession of seasonal niches for the organisms found therein. The low growing deciduous shrub hobblebush (Viburnum alnifolium) is the focus of one such overlap. At Hubbard Brook Experimental Forest in Grafton County, New Hampshire, the shrub is utilized by moose (Alces alces), a large mammalian herbivore, as winter browse (food) and as nesting substrate for some understory nesting birds including Black-throated Blue Warbler (Setophaga caerulescens). The large, heart shaped leaves of hobblebush are among those first to leaf out in spring capitalizing on greater light transmission through the canopy and providing early cover to spring migrants. Some people recognize hobblebush by the big, unprotected, “praying hands” buds that make this early leaf-out possible. These buds are also what make the plant so appealing to a moose during a nutrient-poor New England winter. Building on the existing understanding of these three species one can imagine the effects of a single lone moose in winter, pruning terminal buds and interrupting apical dominance and somewhat like a bonsai artist, changing the architecture of the understory.
My research questions are as follows: 1) Through the act of browsing, do moose affect the morphology of hobblebush and how? and 2) Do these moose-induced changes have an effect on nest-site selection in Black-throated Blue Warbler?
To answer these questions, I utilized field data gathered by myself and other field technicians over the course of three summers at Hubbard Brook on the distribution of understory shrub/sapling species, the distribution of moose browse and scat, the morphology of individual hobblebush plants, and the collective architecture of a hobblebush patch. These “patches” were established as pairs, and each pair was selected within a single Black-throated Blue Warbler territory. Each pair consisted of a “nest patch” and a randomly selected “non-nest” patch within 30 meters of the nest and meeting a minimum plant density threshold.
Although preliminary, our results suggest that a moose browsed hobblebush will have more branches than an un-browsed plant of the same height. Perhaps more interestingly, it appears that moose forage strategy concentrates this effect in patches. In our comparison of paired hobblebush patches, it appears that patches containing nests are more representative of the aforementioned moose affected condition than non-nest patches and have greater incidence of moose browse.
Moose returned from extirpation to New Hampshire within the last 35 years. Although Black-throated Blue Warbler was successful in the absence of moose, an interaction such as I hope to describe may explain the selective pressures leading to its success. It is my hope that this research will help further our understanding of terrestrial, multi-trophic species interactions in the northern hardwood forests and the web of connections that comprise this particular ecosystem as we know it now. | <urn:uuid:bb9e7498-73bd-4362-beef-fd399bed166b> | 3 | 783 | Academic Writing | Science & Tech. | 27.351855 |
Partial Derivatives of Functions (continued)
Physical Interpretation of the partial derivative ∂f(x,y)/ ∂y
Consider a surface S given by z = f(x,y). The intersection of the plane, PL,
x = constant with the surface, S, defines the curve of intersection, C. Let the
tangent line to C at point P with coordinates (a, b, c) be T.
Then the slope of the line tangent to the curve C at the point (a,b,c) in the y-direction is:
fy(x,y) = ∂f(x,y)/ ∂y evaluated at the point P (a,b,c)
Similarly one can imagine a plane, y = constant, intersecting the surface z
along a curve D (not shown).
The slope of the line tangent to the curve D at the point (a,b,c) in the x-direction is:
fx(x,y) = ∂f(x,y)/ ∂x evaluated at the point P (a,b,c)
Copyright © 2011 Richard C. Coddington
All rights reserved | <urn:uuid:393b0f5a-4e5c-4cb7-91a5-3e86c9936822> | 3.40625 | 256 | Academic Writing | Science & Tech. | 67.136949 |
By Tushna Commissariat
Earlier this week, NASA’s $1bn Curiosity rover landed on Mars and successfully started sending back data. The mission has taken a mammoth team of hundreds of scientists and engineers more than eight years to build and it promises to provide new insights into the Martian landscape while looking for conditions that could host life as we know it.
The rover can travel about 200 m per day and the current mission is expected to last about 687 Earth days or one Martian year. Being much heavier than previous rovers sent to Mars, Curiosity was lowered to the planet’s surface using a retro-rocket-firing “sky crane” that slowly deposited the car-sized rover. The unique and ultimately successful landing had people worldwide excited by the idea of travelling to other worlds once more.
Around the same time, it was revealed (albeit unofficially) that the Indian government has approved the country’s first ever mission to Mars, with a launch planned for November 2013 from the country’s spaceport at the Satish Dhawan Space Centre on the island of Sriharikota using the Polar Satellite Launch Vehicle. The £70m mission would follow just four years after India’s Chandrayaan-1 lunar mission and the expected 500 kg orbiter would study Martian geology and climate. The mission has already been allocated £26m in the country’s science budget.
In the light of the current interest in sending robots or travelling to other planets in our solar system, this week we are asking you which planet you find the most captivating. Please let us know your opinion by taking part in this week’s Facebook poll.
Which is the most scientifically interesting planet in our solar system, apart from the Earth?
None of the above – exoplanets are more interesting
Have your say by visiting our Facebook page, and please feel free to explain your response or give us more suggestions by posting a comment below the poll.
In last week’s poll we asked you what would be the most beneficial way of spending $27m on physics, were you feeling very generous, in light of the newly established Fundamental Physics Prize. Of the 216 of you who voted, almost 60% thought that the money would be best spent by investing in a research institute, with another 21% supporting high-school education, 11% voting for funding numerous PhDs, 4% voting for funding goal-oriented competitions and 1% voting for awarding the money to high-achieving scientists – the category that the money is actually used for!
Thank you to everyone who took part and we look forward to hearing from you again in this week’s poll. | <urn:uuid:a2f3176d-4376-4b5b-8302-1eb49b728d7b> | 3.046875 | 553 | Listicle | Science & Tech. | 42.926967 |
common name: alligatorweed thrips (suggested)
scientific name: Amynothrips andersoni O'Neill (Insecta: Thysanoptera: Phlaeothripidae)
Introduction - Distribution - Description - Life Cycle - Hosts - Economic Importance - Selected References
Alligatorweed, Alternanthera philoxeroides (Mart.) Griseb. (Amaranthaceae), is an aquatic weed native to South America that began threatening Florida's waterways in the early 1900s (Langeland et al. 2008). This rooted perennial herb reproduces vegetatively from stem fragments and forms dense floating mats. The floating mats impede navigation, block drains and water intake valves, reduce light penetration, and displace native species (Langeland et al. 2008).
The alligatorweed thrips, Amynothrips andersoni O'Neill, was the second South American natural enemy of this aquatic weed imported into the United States. The alligatorweed flea beetle was the first one. The alligatorweed thrips was released in Florida, Georgia, South Carolina, and California for biological control of alligatorweed in 1967. Subsequent releases occurred in Texas and Mississippi in 1968 (Center et al. 2002, Grodowitz and Whitaker 2005).
Figure 1. A short-winged (brachypterous) adult alligatorweed thrips, Amynothrips andersoni O'Neill. Photograph by U.S. Army Engineer Research and Development Center, Vicksburg, MS.
Native to South America, the alligatorweed thrips is established across the southern United States, including Alabama, Florida, Georgia, Louisiana, Mississippi, South Carolina, and Texas. Establishment in California has not been confirmed (Center et al. 2002, Grodowitz and Whitaker 2005).
Adults: Alligatorweed thrips adults are shiny and black in color. Females are only about 2.1 mm long, whereas males are about 1.7 mm long. Two forms exist, a brachypterous (short-winged) form and a macropterous (long-winged) form. Only the macropterous form is capable of flight (Center et al. 2002, Grodowitz and Whitaker 2005).
Eggs: The eggs are laid singly and are yellowish or amber in color when deposited, but turn red as the embryos mature. Egg development is completed in about seven days (Center et al. 2002).
Figure 2. Second instar (deep red in color with black legs) and yellowish eggs (foreground) of the alligatorweed thrips, Amynothrips andersoni O'Neill. Photograph by U.S. Army Engineer Research and Development Center, Vicksburg, MS.
Larvae: There are two distinct larval instars. The first instar (length 0.6 to 0.7 mm) is light gray at first, becoming amber as it matures. The second instar (length 1.3 to 1.9 mm) is deep red with black legs (Center et al. 2002).
Figure 3. Second instar (deep red in color with black legs) of the alligatorweed thrips, Amynothrips andersoni O'Neill. Photograph by USDA ARS, Bugwood.org.
Pupae: As with other species of thrips in the family Phlaeothripidae, development of the alligatorweed thrips progresses through three pupal instars; a propupa, followed by pupal instars 1 and 2 (Center et al. 2002).
Females undergo a 4-day preovipositional period after which they deposit their eggs on or behind hairs present in leaf axils on stem nodes of alligatorweed. Each female lays an average of 200 eggs (Center et al. 2002, Grodowitz and Whitaker 2005).
Larvae are active feeders, piercing the meristematic tissues (new growth) of the alligatorweed plant with stylets (rod-like structures) formed from the mandibles and maxillae (mouthparts). The total generation time is about 28 days, and the adults live up to four months. Females probably are facultatively parthenogenetic, i.e., unmated females will produce haploid males (Center et al. 2002, Grodowitz and Whitaker 2005).
The thrips feeds only on alligatorweed, Alternanthera philoxeroides (Mart.) Griseb. (Amaranthaceae).
Figure 4. Dense stand of alligatorweed, Alternanthera philoxeroides (Mart.) Griseb. Photograph by Kerry Dressler, Center for Aquatic and Invasive Plants, University of Florida.
On floating alligatorweed, the thrips has difficulty competing with the alligatorweed flea beetle which rapidly defoliates the plants. However, the thrips thrives on rooted alligatorweed, that is usually not heavily attacked by the flea beetle.
Thrips damage is restricted primarily to new growth, e.g., leaf buds, new leaves, and young flowers. Scarified lesions are produced along the margins of the young leaves, causing the leaves to distort and curl. The larvae often aggregate within these curled leaves, which provide excellent hiding and feeding sites. The feeding activity of the larvae causes stunting of leaf growth, but thrips populations are sporadic and their distribution seems limited. Of the three insects (alligatorweed thrips, alligatorweed flea beetle, and stem boring moth) released for biological control of alligatorweed, the thrips is the most cold tolerant. Some evidence indicates that predators may suppress thrips populations, as does resource competition from flea beetles (Center et al. 2002, Grodowitz and Whitaker 2005).
Infested plants exhibit damage similar to plants that have been treated with the herbicide 2,4-D: the leaves appear to be curled and highly folded. Because feeding by alligatorweed thrips is almost entirely on the newest portion of the plant, they continually prevent the production of healthy functional leaves. This in turn reduces the ability of the plant to produce photosynthate (food), significantly weakening it over time. However, the effect of this insect on alligatorweed, particularly the rooted form, has never been fully evaluated (Grodowitz and Whitaker 2005).
Figure 5. Leaf distortion on alligatorweed, Alternanthera philoxeroides (Mart.) Griseb. is characteristic of feeding by adults and larvae of the alligatorweed thrips, Amynothrips andersoni O'Neill. Photograph by Gary Buckingham, USDA Agricultural Research Service, retired; Bugwood.org.
- Center TD (retired), Dray Jr FA, Jubinsky GP, Grodowitz MJ. 2002. Insects and Other Arthropods That Feed on Aquatic and Wetland Plants. U.S. Department of Agriculture, Agricultural Research Service, Technical Bulletin No. 1870.
- Grodowitz MJ, Whitaker, SL. (2005). Amynothrips andersoni - Alligatorweed Thrips, Aquatic Plant Information System (APIS), Engineer Research and Development Center, U.S. Army Corps of Engineers, Vicksburg, MS. (4 April 2013).
- Langeland KA, Cherry HM, McCormick CM, Craddock Burks KA. 2008. Identification and Biology of Nonnative Plants in Florida's Natural Areas, 2nd Edition. SP 257. University of Florida/IFAS, Gainesville. 210 pp.
- [UF/IFAS] University of Florida/IFAS. (2009). Alligator weed, Alternanthera philoxeroides. Center for Aquatic and Invasive Plants. (4 April 2013). | <urn:uuid:7171fbc9-e489-4dbb-9a84-4002e9f464f3> | 3.40625 | 1,634 | Knowledge Article | Science & Tech. | 39.241968 |
Read the full story from the University of Missouri.
Carbon nanotubes (CNTs) are some of the strongest materials on Earth and are used to strengthen composite materials, such as those used in high-performance tennis rackets. CNTs have potential uses in everything from medicine to electronics to construction. However, CNTs are not without risks. A joint study by the University of Missouri and United States Geological Survey found that they can be toxic to aquatic animals. The researchers urge that care be taken to prevent the release of CNTs into the environment as the materials enter mass production. | <urn:uuid:493368a6-d654-41ff-b3fa-132db979da50> | 3.484375 | 122 | Truncated | Science & Tech. | 34.868912 |
Gilbert Martínez has his work cut out for him. A reef ranger for the Belize Department of Fisheries, he spends his days patrolling a 87,000-acre Marine Protected Area called Glover’s Reef, an azure paradise of an atoll about 28 miles from the country’s mainland. I met him while reporting for an article in Tuesday’s Science Times about a reef-monitoring project in the atoll that is sponsored by the Bronx-based Wildlife Conservation Society.
Beneath the white hull of Mr. Martínez’s patrol boat was a system of some 800 patch reefs teeming with diverse life. Robust corals, sponges the size of oil barrels, spiny lobsters and a dizzying array of multihued tropical fish all call this place home.
The ranger’s job to protect these animals from overfishing and other damage. Within just three hours on a recent afternoon on which I accompanied him, he encountered at least three men illegally collecting conch, a local favorite that can fetch $15 a pound in local markets.
One of these men was just outside the so-called no-take zone, where no fishing of any kind is allowed. It is legal for him to collect conch here so long as they weigh three ounces or more. The fisherman’s bag was swollen with the slimy reef-dwellers, which are cut from their shells by using a short blade.
One by one, Mr. Martínez had the man weigh the conch; 24 of them proved to be undersize, and he wrote a citation that will cost the man almost $500 — not a small sum in a country where fishermen often earn less than $4,000 a year.
“That’s really a lot,” Mr. Martínez said of the undersize conch he found in the man’s bag. “if you take 10 a day, that can cause a lot of damage.”
Scientists say that overfishing has wreaked havoc throughout the Caribbean, which is why marine reserves like Glover’s are so important. Belize’s government has imposed strict limits on what can be caught, and although there are definitely gaps in enforcement, some scientists here say the efforts to preserve important species like sharks are working.
“I know a lot of people were skeptical, and even I was surprised at first, that a small marine reserve could make a difference in the longevity and the population size sharks,” said Ellen K. Pikitch, a marine biologist with Stony Brook University who is a force behind a study of sharks here. “What we’ve learned after a 10-year period is parks do work for sharks they are actually effective at keeping populations stable.”
Keeping populations stable might not sound like much, but some shark populations are in severe decline throughout the world, in part because of the broad demand for their meat and a growing demand for shark fin soup in China.
(Here is a video I prepared of shark fishermen cutting fins from sharks and dumping their bodies back into the water.)
Ms. Pikitch and other scientists and conservationists are now trying to push Belize to create more reserves like Glover’s that allow some fishing in specified zones but maintain others where no fishing is allowed so that species can grow back and be replenished. | <urn:uuid:6d95f3ce-b065-4597-afac-0c5b02d99489> | 2.75 | 709 | Personal Blog | Science & Tech. | 54.203664 |
A charged particle in a magnetic field is spiralling along a path defined in cylindrical coordinates by
r = 1 m and
Theta = 2z rad (z is in meters).
The speed along the path is constant at V km/s with the value of V as given below.
Find the angular velocity, w. Give your answer in rad/s. | <urn:uuid:6400193b-13a3-4f2b-8aac-d4fbf1862115> | 3.453125 | 77 | Q&A Forum | Science & Tech. | 79.803707 |
Present observations do provide some precise quantitative information. For example, we have good estimates of the gas mass as a function of radius. We have a good estimates for the mean iron abundance in clusters with the best value around 20% for Coma. We have high quality images of a large sample of clusters and good integrated temperatures for the brighter clusters.
The most poorly known cluster properties are those which require spatially resolved spectroscopic information. For example, the radial distribution of the heavy elements is very poorly known and better observations could provide information relating to the enrichment mechanism and the epoch of enrichment. Similarly, temperature profiles are not known for many systems and hence virial mass determinations (based on gas density and gas temperature profiles) still have large uncertainties. Optical estimates are subject to contamination and sub-structure and X-ray observations seem to provide the most direct method for obtaining detailed mass distributions.
Future missions will provide the missing information to expand our understanding of clusters. Questions we can address with future missions like ASTRO-D, AXAF, XSPECT, and XMM, include:
where is the gas density and r is the radial distance from the cluster center. Only M87 and Centaurus (NGC4696) have measured density and temperature gradients (Fabricant and Gorenstein 1983, Matilsky et al. 1985). For most clusters Tgas(r) remains unknown (or very uncertain). Thus, ASTRO-D, AXAF, and XMM can add immeasurably to our present knowledge of the gravitating mass distributions which can be directly compared to formation models of clusters.
In conclusion, while considerable advances have been made in understanding clusters through their X-ray emission, the potential of X-ray observations has yet to be fully achieved and awaits the application of spatially resolved spectroscopic observations and studies of clusters at high redshifts. | <urn:uuid:76c6f65f-1cd4-4977-a1e7-d526b19129ef> | 3.234375 | 386 | Academic Writing | Science & Tech. | 26.641 |
This problem in geometry has been solved in no less than EIGHT ways
by a pair of students. How would you solve it? How many of their
solutions can you follow? How are they the same or different? Which
do you like best?
Follow hints using a little coordinate geometry, plane geometry and
trig to see how matrices are used to work on transformations of the
Given probabilities of taking paths in a graph from each node, use
matrix multiplication to find the probability of going from one
vertex to another in 2 stages, or 3, or 4 or even 100. | <urn:uuid:152d5bb5-2bf7-418d-a903-0e203f45b977> | 3.125 | 125 | Tutorial | Science & Tech. | 61.592731 |