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By Alexander Villafania INQUIRER.NET In the aftermath of perhaps the worst typhoon that struck Metro Manila in recent years, environmental groups are blaming climate change for the effects of âOndoyâ (international name âKetsanaâ). In different statements, the World Wildlife Fund (WWF) and Greenpeace warned that such a disaster could be repeated unless comprehensive measures are taken immediately. Greenpeace, in their statement , reiterated their call for industrialized countries to put in money to fund climate change measures especially in disaster-prone countries, including the Philippines. Greenpeace Climate and Energy Campaigner Amalie Obusan said in a statement that the disaster in the Philippines had to happen in between two international climate change meetings, the recently concluded G20 Summit and the upcoming United Nations Framework Convention on Climate Change (UNFCCC) Summit. âWhile world leaders are pussyfooting on their commitments, countries like ours are left to experience the ravages of climate change,â Obusan said. In a separate statement, WWF-Philippines Vice Chair Jose Lorenzo Tan is calling for the reduction of fossil fuel consumption, which is being blamed for contributing to climate change. Tan said the country is not equipped to take the brunt of another similar disaster and so measures must be taken to help mitigate its effects. âPlanning must start from scenarios of the future, rather than from the present. Collectively, we must identify 'next practices', because today's 'best practice' will no longer suffice. We must start small, learn fast and scale rapidly,â Tan said. The Philippine Atmospheric, Geophysical and Astronomical Services Administration (PAGASA) reported that Ondoy dropped the heaviest rainfall in Metro Manila in recent history, a record 34.1 centimeters (13 inches) of water in less than six hours. The previous record was in 1967 with 33.4 centimeters of rainwater over the course of 24 hours.
September 2009 Archives
By Dennis Posadas THERE are interesting developments in Chinese cleantech, and I will discuss some headlines of interest that have been reported recently. While I will continue to write about Philippine cleantech efforts in renewables and energy efficiency, it is also important to take note of what is happening in the region, and maybe some implications for us. The first is a news report in the New York Times that First Solar, a company that makes thin film solar photovoltaics, bagged a contract to build the world’s largest solar installation in Mongolia. The rated capacity of the solar plant will be 2GW (or 2,000 MW if you prefer), and will be built using the non-silicon technology of First Solar. Thin films like Cadmium Telluride are typically deposited on surfaces like glass, and do not require silicon. The upside of thin films is that you can make it into windows and basically coat a building with it, at a cheaper price. The downside is it is only around 7% efficient, as compared to 11% efficiency of silicon-based solar photovoltaics, which means you need more cells and you need more space (e.g. land). Another is that Cadmium is poisonous, and so while there is no danger of leaching for the active life of the solar cell, the cells have to be disposed of properly once these are past their useful life of around 25 years. The implication for us is that this particular project, because the winner was a thin-film solar technology (which we do not make here as far as I know) did not result in additional business for the local Philippine operations of SunPower and Solaria, which make silicon-based photovoltaics. However, if the 2GW China project is an indication of future opportunities, maybe it will be good for the industry as a whole. The second, featured in both in MIT Technology Review and the New York Times, is what the Chinese are doing with clean coal. It appears that most of the plants being built in China these days are advanced technology clean coal plants, which do not burn the coal directly (which releases carbon dioxide) but instead, using an old pre World War II process, converts coal into synthetic gas (similar to natural gas). China has the world’s third largest coal reserves, after the US and Russia. US Energy Secretary and Nobel Laureate Steven Chu has promised to prioritize its adoption in the US as well. It is important to stress that while the carbon dioxide emissions have been cut by a large percentage, these new plants still emit carbon dioxide. The Chinese have even built a small experimental plant to remove the carbon dioxide from power emissions, and use it for softdrinks carbonation. What a creative way to do carbon capture and storage! Store it in our bodies when we drink it. Of course, we will eventually release it back to the atmosphere. But seriously, the Chinese are also looking at Carbon Capture and Storage (CCS), although I have not seen any major advances yet in China in this arena. The implication here for us is that if the Chinese can develop a better way, or an alternative to CCS that cuts carbon emissions of coal, then maybe coal can have a second life, particularly since we have a lot of it. But that is, in my opinion, still in the realm of research. I do not expect to see carbon capture and storage in the Philippines for a long time; it is still very, very expensive, unless someone comes up with a breakthrough. In wind, China has doubled its capacity in the past few years and will become the world’s largest market for wind equipment. Interestingly enough, India, through a company called Suzlon Energy (you may have seen their commercials on CNN) is now giving US and European wind players like GE and Vestas a run for their money. Locally, I think we should pursue the development of micro-wind and micro-hydro systems. In electric vehicles, Fortune recently did a profile on a company called BYD (Build Your Dreams) which Warren Buffett recently invested in. In solar photovoltaics, Suntech, a Wuxi-based company which was started by local government funds is now one of the largest solar cell manufacturers in the world. The key learning for us here is that Suntech was started by Chinese local government funds, not even national government funds. The figure mentioned in Fortune was $4m, which is doable even here. Maybe that is a learning we can use, but I am not sure if local laws will permit that. Finally, the UK Guardian recently reported that US President Barack Obama may be in China this November to sign a major US-China cleantech alliance accord, prior to the December Copenhagen climate summit. While it is hard to convince the US Senate, which has to contend with a strong oil, gas and coal industry lobby, to go green, it appears that the Chinese see green as a way, not just to improve their worldwide image in the climate arena, but to actually make some serious green (as in greenbacks) out of it. The question there is where does that leave us? __________________________________________________________________________ Dennis Posadas is the editor of Cleantech Asia Online, and the author of Jump Start: A Technopreneurship Fable (Singapore: Pearson Prentice Hall, 2009)
By Dennis Posadas While I appreciate the enthusiasm that groups like Greenpeace and WWF about enabling as much clean/renewable energy as we can put into the system, given that we have a new renewable energy law, there are also a few mindset changes we need to put into place. I am all for renewable energy; however, as a trained engineer, I also realize that there are some hurdles that need to be overcome. First is, some renewable energy sources, like solar and wind, while abundant, are also intermittent. The sun doesn’t always shine, and the wind doesn’t always blow. On the other hand, cogeneration and biomass plants, which are clean sources, can be stable if enough heat or biomass material is forecast and planned. For solar and wind, if we want to use it for 24x7 use, we need to make sure that there is an energy storage mechanism of some type. The most common energy storage device is of course a battery. For bigger solar and wind systems, running in the megawatt range, batteries would have to be connected together, so it probably won’t be practical. Concentrated Solar Plants (CSPs) that employ banks of mirrors in the desert use some type of liquid like molten salt. Another possibility is to use pumped storage, like in Lake Caliraya. When power is available, it is used to pump water up an elevated lake. During nighttime, the lake water can be released to drive a generating turbine. Other schemes involve compressed air (in the US), or as in the case of some wind systems, natural gas turbines. But for many systems, the storage technique they employ is to simply connect the renewable energy system to the grid. Now as we increase the percentage of renewable energy systems that connect directly to the grid, we have to remember again that these are intermittent. You can’t exactly tell the sun to shine exactly at 6:00am, or the wind to start blowing at 9:00pm. So there has to be a way to prevent blowups of circuit breakers or fuses, a way to plan when each energy source will come on stream. There is a role for software and intelligent grid systems that work with meteorological information to determine that there is a high/low likelihood that the wind/sun will be available at a certain time. The grid itself, and components will have to be redesigned to take into account the higher occurrence of intermittent turn-on and turn-off of power sources, many of them being renewable. Appliances may need to have chips in them, telling them that the power at a given hour is mostly coming from renewable sources, or not. Meralco’s plan, for example, to offer Internet over broadband lines, is indicative of this. The common perception is that they plan to mainly utilize this to offer broadband services to the public through their power lines. Actually, it is not as simple as that. The Internet over power lines can also be used to command and control equipment, such as chillers in malls, to turn on or to idle at a certain time. The grid needs to be intelligent, to handle the intermittent nature of clean/renewable energy systems. There will be a lot of new capabilities, already being experienced in places like California and Europe, that we will soon have here. Our electric meters (“kontadors”) for example, will run backwards and forwards. So if we decide to install solar panels or wind turbines on our roofs, not only can we be consumers, we can also be mini power producers supplying to Meralco. The amount we sold, is then subtracted from the amount we consumed. The more citizens and private industry, as well as government, invest in these mini and private renewable energy systems, the less need there will be for big, and often carbon emitting power plants. In other words, power generation will be decentralized to many small renewable power producers, as opposed to a few large ones. Now who will pay for that? Some cities in the US consider solar panels as part of the house (roof) and allow citizens to simply add a little extra to their real estate tax, and amortize the solar panels over 25 years. The payment can actually be taken from the savings generated by the panels, so in effect a no-cash out scheme is feasible. Are we ready for that? We all want reduced carbon emissions. But we don’t get there by simply joining token Earth Hour or Earth Day celebrations. We also need to do some work, and take the time to educate ourselves. ___________________________________________________________ Dennis Posadas is the editor of Cleantech Asia Online, and the author of Jump Start: A Technopreneurship Fable (Singapore: Pearson Prentice Hall, 2009)
By Alexander Villafania INQUIRER.NET After over 50 years, mathematical genius Alan Turing could get the justice he deserves after being prosecuted as a homosexual. Two separate online petitions for an apology by the British government were set up by supporters of Alan Turing, the British cryptanalyst who broke the codes of the legendary German Enigma machines during World War II. The first petition was created by computer scientist John Graham-Cumming. In his blog Cumming said he wanted all records about Turing to be released by the British government. He also said he wanted Turing to get a posthumous knighthood. So far, his petition has gathered about 22,800 supporters. The deadline for the end of signing the online petition is on January 20, 2010. The second petition demanded an apology from the British government for Turing, who was alleged to have been prosecuted because of his homosexuality. The second petition was started by Cameron Buckner in support of Cummingâs first petition. So far, Bucknerâs petition has 8,700 signatories. Based on the records of the British National Archives British National Archives Turing joined the British governmentâs Government Code and Cypher School during World War II specifically to decipher the Enigma machine used by the Germans. His paper, âOn Computable Numbersâ led to the creation of the âTuring machine,â a thought process experiment that simulated the logic of a computer algorithm. Turingâs work on computational algorithms thus led to future development of computer science concepts, as well as the modern computer. But in 1953 Turing was arrested for being a homosexual and was subjected to chemical castration using estrogen injections. He died by consuming a cyanide-laced apple the following year. | <urn:uuid:02304444-c95f-4f31-9bf8-87f611ecbc3f> | 2.71875 | 2,828 | Comment Section | Science & Tech. | 40.463503 | 200 |
Our Changing Ocean
Vast and powerful though the ocean is people have changed it. It’s a different ocean now.
The ocean’s enduring surface beauty hides its plight. But the ocean today is a diminished version of a much healthier ocean of not so long ago.
The ocean is the source of about half the oxygen we breathe, much of the water we drink, and much of the food we eat. (If you don’t eat fish, consider this: about a third of the world fish catch gets made into feed for chickens, pigs, and other livestock.) Changes to the ocean undermine the health and well-being of people and wildlife worldwide.
These changes include depletion from overfishing, warming, ocean acidification caused by the same carbon dioxide that is warming the atmosphere and the upper sea, chemical pollution, plastic debris, loss of wetlands, coastal mangrove forests, and coral reefs, and invasive species.
Each of these alone is serious.
Can any particular part of the oceans survive these things happening all at once? The answer is: “it depends.”
There is still time to reverse course and restore the ocean to a healthy balance. Many dedicated people and organizations, including Blue Ocean Institute, are working actively to solve the oceans’ problems.
Be a part of this hopeful work. Jump in and help save the oceans!
Dive into our Issues section to learn more. Being knowledgeable will help you decide what part of the solution is just for you.
Why the Oceans?
Simple: the ocean supports life on this planet. It feeds us, produces the oxygen we breathe, maintains our climate, cycles vital nutrients through countless ecosystems and provides food and medicines. The ocean provides jobs, food, energy, and recreation. As if that weren’t enough, the ocean is beautiful and inspiring. And that would be enough. People
Climate change is the defining environmental issue of our time and our children’s time. Into one crowded elevator go conservation of nature, human health, the prospects for agriculture, international stability, national security, and of course energy policy and technology. Climate change reflects our intensifying presence on the surface of this planet. It wraps together everything
Carbon dioxide from burning fossil fuels is changing the oceans’ chemistry. This is ocean acidification. The head of the National Oceanic and Atmospheric Administration calls ocean acidification global warming’s equally evil twin. The oceans are absorbing up to a million tons of carbon dioxide every hour. The good news: less carbon dioxide in the air
Carbon dioxide from burning fossil fuels is not only changing the oceans’ chemistry and warming the atmosphere, it is also warming the oceans. There’s a third more carbon dioxide in the air than at the start of the Industrial Revolution. The carbon acts like insulation in the atmosphere, or like glass in a greenhouse —
Overfishing is depleting the world’s oceans and having a negative impact on marine biodiversity and on human health, welfare, and prosperity. Links to more complete info in our Fish as Food section.
In the ocean, little fish play a big role. Small fish like sardines and anchovies are some of the most important fish in the sea. Fish such as herring, anchovies, menhaden, and sardines feed mostly on plankton all their lives. They supply calories and nourishment (food!) for many top predators including cod, tuna, salmon, and
Invasive Marine Species
Invasive species are animals and plants that hitchhike or ride along to places where they are not normally found. In their new homes, invasive species can sometimes create big problems for native species and ecosystems. The main source of marine invasive species is the global shipping industry, specifically through ballast water. Species can also be
Marine debris comes from everyone and every source that makes every kind of garbage. Tons of trash from both land – up to 80 percent — and ships constantly finds its way to the sea. Much of this marine debris does not go away; it cannot dissolve and it lasts in the oceans for many
Coastal Habitat Loss
Homes, jetties, seawalls, canals, and other structures built on beaches or wetlands often destroy habitat for sea turtles, birds, fish, and other sea life. Salt and tidal marshes, wetlands, mangroves, and coral reefs also suffer when development is unsustainable. Wetlands, mangroves and sea grasses are valuable natural resources as they hold sediment and nutrients, filter
In addition to carbon dioxide, mercury, and marine debris, which are types of pollution, other man made pollutants constantly enter the oceans from a range of sources. These include oil, fertilizers, toxic chemicals, and sewage. OIL & CHEMICALS Oil spills may be the most infamous pollutant because popular media often vividly shows dramatic damage. The
Aquaculture – Farmed Seafood
Aquaculture can impact many aspects of ocean life. Visit Aquaculture in our Fish as Food section which also includes sustainable seafood choices plus discussions about genetically modified fish, seafood fraud, bycatch, and more. | <urn:uuid:37813f25-88c4-46b8-a404-67d7ad70dc62> | 3.0625 | 1,062 | Knowledge Article | Science & Tech. | 39.662902 | 201 |
Chandra "Hears" a Supermassive Black Hole in Perseus
A 53-hour Chandra observation of the central region of the Perseus galaxy cluster (left) has revealed wavelike features (right) that appear to be sound waves. The features were discovered by using a special image-processing technique to bring out subtle changes in brightness.
These sound waves are thought to have been produced by explosive events occurring around a supermassive black hole (bright white spot) in Perseus A, the huge galaxy at the center of the cluster. The pitch of the sound waves translates into the note of B flat, 57 octaves below middle-C. This frequency is over a million billion times deeper than the limits of human hearing, so the sound is much too deep to be heard.
The image also shows two vast, bubble-shaped cavities, each about 50 thousand light years wide, extending away from the central supermassive black hole. These cavities, which are bright sources of radio waves, are not really empty, but filled with high-energy particles and magnetic fields. They push the hot X-ray emitting gas aside, creating sound waves that sweep across hundreds of thousands of light years.
The detection of intergalactic sound waves may solve the long-standing mystery of why the hot gas in the central regions of the Perseus cluster has not cooled over the past ten billion years to form trillions of stars. As sounds waves move through gas, they are eventually absorbed and their energy is converted to heat. In this way, the sound waves from the supermassive black hole in Perseus A could keep the cluster gas hot.
The explosive activity occurring around the supermassive black hole is probably caused by large amounts of gas falling into it, perhaps from smaller galaxies that are being cannibalized by Perseus A. The dark blobs in the central region of the Chandra image may be fragments of such a doomed galaxy. | <urn:uuid:7c5032f8-872f-474b-bda7-8c70bc31adaa> | 4.34375 | 389 | Knowledge Article | Science & Tech. | 43.14427 | 202 |
Declares a cursor definition.
A cursor is declared in accordance with the select-statement or the result set procedure call specified in procedure-call-statement.
The select-statement may be specified explicitly in ordinary embedded SQL applications or by the name of a prepared select-statement, identified by statement-name, in dynamic SQL statements, see the Mimer SQL Programmer's Manual, chapter 11, Dynamic SQL.
The cursor is identified by cursor-name, and may be used in FETCH, DELETE CURRENT and UPDATE CURRENT statements. The cursor must be activated with an OPEN statement before it can be used.
A cursor declared as REOPENABLE may be opened several times in succession, and previous cursor states are saved on a stack, see OPEN. Saved cursor states are restored when the current state is closed, see CLOSE.
A cursor declared as SCROLL will be a scrollable cursor. For a scrollable cursor, records can be fetched using an orientation specification. See the description of FETCH for a description of how the orientation can be specified.
A cursor will be non-scrollable if NO SCROLL is explicitly specified. The cursor will be non-scrollable and not reopenable by default.
select-statement, see SELECT Statements.
procedure-call-statement, see CALL.
If an execute-statement-command is used, the precompiled statement must be a select or a result-set procedure.
If a procedure-call-statement is specified, it must specify a result set procedure.
The following restrictions apply to procedural usage:
- The cursor cannot be declared as REOPENABLE
- The select-statement cannot be in the form of a prepared dynamic SQL statement, i.e. specifying statement-name is not allowed
- If the cursor declaration contains a select statement, the access-clause for the procedure must be READS SQL DATA or MODIFIES SQL DATA, see CREATE PROCEDURE.
The DECLARE CURSOR statement is declarative, not executable. In an embedded usage context, access rights for the current ident are checked when the cursor is opened, not when it is declared.
In a procedural usage context, access rights for the current ident are checked when the cursor is declared, i.e. when the procedure containing the declaration is created.
The value of cursor-name may not be the same as the name of any other cursor declared within the same compound statement (Procedural usage) or in the same compilation unit (Embedded usage).
The select-statement is evaluated when the cursor is opened, not when it is declared. This applies both to select-statement's identified by statement name, and to host variable references used anywhere in the select statement.
The execution of the result set procedure specified in a CALL statement is controlled by the opening of the cursor and subsequent fetches, see the Mimer SQL Programmer's Manual, chapter 12, Result Set Procedures.
REOPENABLE cannot be used if evaluation of select-statement uses a work table, or if the cursor declaration occurs within a procedure.
If the declared cursor is a dynamic cursor, the DECLARE statement must be placed before the PREPARE statement.
A reopenable cursor can be used to solve the 'Parts explosion' problem. Refer to the Mimer SQL Programmer's Manual, chapter 8, The 'Parts explosion' Problem for a description.
ExampleDECLARE cur1 CURSOR FOR EXECUTE STATEMENT seltaba
EXTENDED The EXECUTE STATEMENT command is a Mimer SQL extension.Support for the keyword REOPENABLE is a Mimer SQL extension.
Note: See also standard compliance for SELECT.
Upright Database Technology AB
Voice: +46 18 780 92 00
Fax: +46 18 780 92 40 | <urn:uuid:b1993193-d6e1-462e-bd4a-4801beb1522b> | 2.84375 | 803 | Documentation | Software Dev. | 36.165247 | 203 |
Examples of Python source code or interactive sessions are represented as \verbatim environments. This environment is a standard part of LaTeX. It is important to only use spaces for indentation in code examples since TeX drops tabs instead of converting them to spaces.
Representing an interactive session requires including the prompts and output along with the Python code. No special markup is required for interactive sessions. After the last line of input or output presented, there should not be an ``unused'' primary prompt; this is an example of what not to do:
>>> 1 + 1 2 >>>
Within the \verbatim environment, characters special to LaTeX do not need to be specially marked in any way. The entire example will be presented in a monospaced font; no attempt at ``pretty-printing'' is made, as the environment must work for non-Python code and non-code displays. There should be no blank lines at the top or bottom of any \verbatim display.
Longer displays of verbatim text may be included by storing the example text in an external file containing only plain text. The file may be included using the standard \verbatiminput macro; this macro takes a single argument naming the file containing the text. For example, to include the Python source file example.py, use:
Use of \verbatiminput allows easier use of special editing modes for the included file. The file should be placed in the same directory as the LaTeX files for the document.
The Python Documentation Special Interest Group has discussed a number of approaches to creating pretty-printed code displays and interactive sessions; see the Doc-SIG area on the Python Web site for more information on this topic.
See About this document... for information on suggesting changes. | <urn:uuid:8e8afdb8-adcd-4d41-a263-cdcb0e2a135e> | 3.203125 | 365 | Documentation | Software Dev. | 39.90125 | 204 |
The modules described in this chapter support storing Python data in a persistent form on disk. The pickle and marshal modules can turn many Python data types into a stream of bytes and then recreate the objects from the bytes. The various DBM-related modules support a family of hash-based file formats that store a mapping of strings to other strings. The bsddb module also provides such disk-based string-to-string mappings based on hashing, and also supports B-Tree and record-based formats.
The list of modules described in this chapter is: | <urn:uuid:9658ddde-001b-43ce-b86a-c2ce800a0eb2> | 2.546875 | 116 | Documentation | Software Dev. | 49.149803 | 205 |
Scientists have long projected that areas north and south of the tropics will grow drier in a warming world –- from the Middle East through the European Riviera to the American Southwest, from sub-Saharan Africa to parts of Australia.
These regions are too far from the equator to benefit from the moist columns of heated air that result in steamy afternoon downpours. And the additional precipitation foreseen as more water evaporates from the seas is mostly expected to fall at higher latitudes. Essentially, a lot of climate scientists say, these regions may start to feel more like deserts under the influence of global warming.
Now scientists have measured a rapid recent expansion of desert-like barrenness in the subtropical oceans –- in places where surface waters have also been steadily warming. There could be a link to human-driven climate change, but it’s too soon to tell, the scientists said.
[UPDATED below, 3/6, 1 p..m] Read more… | <urn:uuid:71855304-2f8a-4425-8945-02a9b90be1ae> | 3.078125 | 203 | Truncated | Science & Tech. | 46.19395 | 206 |
The Seine, the scenic river running through Paris, has inspired artists, attracted tourists and served as the soul of the city, and now it will also be a source of renewable energy. Paris officials have announced a plan to place river turbines beneath four bridges on the Seine.
The Pont du Garigliano, Pont de la Tournelle, Pont Marie and Pont au Change will each have two turbines installed underwater at their base. These bridges were chosen because the speed of the current accelerates in those locations. While river currents don't produce the kind of electricity that wave power can, the current-harvesting technology has come a long way and more devices are being introduced that can generate energy from even the slowest moving waters.
City officials have put a call out to power companies to come up with the best plan for installing the turbines, with a winner being chosen in January and installations starting next spring.
via The Guardian
written by Quiet-Environmentalist, June 29, 2010
written by David Brockes, July 08, 2010
|< Prev||Next >| | <urn:uuid:e338e7ab-37e4-40ee-98f0-254c81baa630> | 2.953125 | 220 | News Article | Science & Tech. | 33.024703 | 207 |
Many people are confused about the concepts in DBus. This page gives an analogy to the web which should help to explain things.
- unique bus name
- well-known bus name
- object path
- method name
- in parameters
- out parameters
Web Server Analogy
- unique bus name is like an IP address. In particular it is dynamic.
- well-known bus name is like a hostname. It can be held by different programs at different times, but they should all implement the same API
- object path is like the path on the server
- interface/method name is like GET or POST
- in parameters are like like GET/POST variables
- out parameters are like the page which is returned.
Object-Oriented Language Analogy
- an object path refers to an object, such as a java.lang.Object
- an interface is exactly like a Java interface
- in parameters are method arguments
- out parameters are method return values
- unique bus name identifies the running process or application uniquely (these bus names are never re-used by a different process)
- well-known bus name is a "symlink" that points to the process providing a particular API
- an API is made up of objects that are expected to exist, which are expected to implement certain interfaces
- see also http://log.ometer.com/2007-05.html#17 | <urn:uuid:cb0bcce9-2024-41cc-84bb-9ebb601e44b8> | 3.03125 | 295 | Knowledge Article | Software Dev. | 39.245758 | 208 |
The effect of UVR on biological systems is wavelength dependent. Action spectrum for DNA damage is an essential component of understanding the effects of increased UVB on a range of Antarctic invertebrate larvae. The wavelength dependency is quantified using spectral weighting functions which provide information such as the target organelles/molecules of the UVR, the degree that organisms are ... influenced by wavelengths that are enhanced by the process of ozone depletion and the activity of sunscreening and anti-oxidant compounds. Biological weighting functions (BWFs) were made for 3 embryonic stages of Sterechinus (eggs, blastula, 4 armed larvae) and embryos of Acodantaster, Perknaster and Parbolarsis. The embryos and larvae were exposed to artificial lights for 3 days. Three filter treatments with 50% nominal cut-off at 280, 305, 320, 375 and 400nm wavelengths were used. DNA was analysed for cyclobutane pyrimidine dimers (CPDs). Using the species specific BWF and spectral irradiance data, biological effective irradiances were calculated for a given ambient light environment. Modelling of the species specific and stage specific effects of ozone depletion on larval stage were made using the BWFs and the change in ambient light field during ozone depletion. | <urn:uuid:8aa7e8f1-43dd-4954-ad12-56a69e48c91b> | 3.078125 | 263 | Academic Writing | Science & Tech. | 29.766875 | 209 |
Active RNA polymerase (RNAP) somehow remains both stable and mobile. In the 28 July Science Korzheva et al. combine the X-ray crystal structure of Thermus aquaticus (Taq) core RNAP with their own crosslinking data to derive a model of a functioning bacterial core RNAP (Science 2000, 289:619-625). At the front, a 20° hinged movement closes the RNAP "jaws" around the downstream DNA. At the back of the RNAP, the rudder region is positioned to separate the exiting RNA from the DNA template strand. Termination probably comes when an RNA hairpin disrupts interactions with the rudder, triggering collapse of the transcription bubble. | <urn:uuid:ffba1cfb-3e1a-45eb-a491-fe3036ab3deb> | 2.625 | 147 | Academic Writing | Science & Tech. | 49.326282 | 210 |
Author Contact: email@example.com
Biocatalysis and biotransformations are important alternatives to consider when one is looking to substitute a conventional method with a greener one. One of the many advantages of using biotransformation as a synthetic method is that they are usually done in water and at ambient conditions. In addition, the reagents themselves are readily available, safe, and inexpensive to both buy and dispose of.
This experiment uses shredded carrots to enantioselectively reduce benzofuran-2-yl methyl ketone, yielding the optically pure alcohol. This lab illustrates the topics of green chemistry, biocatalysis, biotransformations, reductions, carbonyl chemistry, stereochemistry, stereoselectivity, optical activity, thin-layer chromatography, liquid-liquid extractions, and column chromatography.
The authors also suggest that students perform the sodium borohydride reduction of the ketone to compare and contrast the ease, safety, "greenness" and stereoselectivity of the two reactions.
The supplemental materials include lab procedures, lab report outline, lab questions, instructor notes, a list of necessary lab equipment, and CAS numbers.
Summary prepared October 2008 by Douglas M. Young at the University of Oregon.
Ravía, S.; Gamenara, D.; Schapiro, V.; Bellomo, A.; Adum, J.; Seoane, G.; Gonzalez, D. J. Chem. Educ., Print 2006, 83, pp 1049-1051. | <urn:uuid:0623dac4-742f-4aad-ba41-e19e30324d0a> | 2.5625 | 323 | Knowledge Article | Science & Tech. | 22.530592 | 211 |
How LCLS X-ray pulses can be used to determine the atomic structure of a complicated molecule.
A New Kind of Laser
SLAC's two-mile-long linear accelerator (or linac) has begun a new phase of its career, with the creation of the Linac Coherent Light Source (LCLS).
For nearly 50 years, SLAC's linac has produced high-energy electrons for cutting-edge physics experiments. Now, scientists continue this tradition of discovery by using the linac to drive a new kind of laser, creating X-ray pulses of unprecedented brilliance.
LCLS produces pulses of X-rays more than a billion times brighter than the most powerful existing sources, the so-called synchrotron sources which are also based on large electron accelerators.
The ultrafast X-ray pulses are used much like flashes from a high-speed strobe light, enabling scientists to take stop-motion pictures of atoms and molecules in motion, shedding light on the fundamental processes of chemistry, technology, and life itself.
Probing the Ultrasmall
The diameter of a human hair is about 1/1000 of an inch. The wavelength of visible light is about 50 times smaller than this, so ordinary microscopes can easily resolve a hair. But a molecule, about 10,000 times smaller than a hair, is too small to be resolved with visible light. X-rays, with wavelengths that are even smaller than a molecule, are ideal for imaging at the atomic scale.
Capturing the Ultrafast
The atomic and molecular world is abuzz with frenetic motion. Because they are so small and light, molecules and atoms react incredibly quickly to forces that act on them. Chemical reactions, in which molecules join or split, can take place in mere quadrillionths of a second.
The ultrafast LCLS X-ray flash captures images of these events with a “shutter speed” of less than 100 femtoseconds (100 femtoseconds = 1/10 of a trillionth of a second).
A Long History of Imaging Breakthroughs
The LCLS photographs atomic motion much as a “strobe” flash is used to photograph the motion of a bullet in flight. This latest advance in stop-action imaging at Stanford has roots going back more than 100 years. Around 1872, Eadweard Muybridge started making stop-motion photographs of people, animals, and trains in motion on Leland Stanford’s farm. He is famous for showing that all four of a horse’s feet leave the ground during a gallop. To be able to click a shutter fast enough to show each stride a horse makes when galloping required tremendous engineering ingenuity. The LCLS provides X-rays of such shortness and precision that stroboscopic experiments can be done with materials on the nanoscale, and even with individual molecules and atoms.
How Fast Is a Femtosecond?
2.4 seconds: The time it takes light to travel the distance to the moon and back—about 480,000 miles.
100 femtoseconds: the time it takes light to travel the width of a human hair. | <urn:uuid:84a9f46f-4fe6-4a19-8045-3dd7ce4c44f6> | 3.859375 | 663 | Knowledge Article | Science & Tech. | 50.014085 | 212 |
Properties of Water
Life would not have existed on earth without water. Water molecules
are composed of one oxygen atom and two hydrogen atoms. Together, the
hydrogen and oxygen molecules form a shape that resembles the head of
While water molecules seem to be simple compounds, their properties
have profound impact on life. Because of the arrangement of hydrogen
and oxygen atoms, water molecules have polarized charges (one end is
positive and the other end is negative). Due to their polarized nature, 2
adjacent water molecules can form a linkage via a hydrogen bond.
The polarized nature of water causes other molecules to be either
hydrophilic (like water) or hydrophobic (afraid of water). This
property allows certain molecules to dissolve in water while preventing others from entering the cell. For example, hydrophobic
interaction can hold molecules together.
Another important property of water is its ability
to facilitate the transfer of molecules through osmosis. When 2
aqueous solutions are separated by a membrane that only allows the
passage of water molecules, water will move from the less concentrated
to the more concentrated side (Shown in the diagram below).
Hydrophobic interactions can hold molecules together: 2 or more
hydrophobic groups surrounded by water will tend to coalesce since
they thereby cause less disruption to the hydrogen-bonded structure of
water (Shown in the diagram below. Red hexagons represent hydrophobic
material and blue dots represent water molecules.). | <urn:uuid:3bc65f9d-b881-45f5-a3f1-3d957eeccb92> | 3.96875 | 309 | Knowledge Article | Science & Tech. | 18.641923 | 213 |
Sketch the graph of the following.
Any help would be appreciated!
You know that there are two vertical asymptotes at x = 5 and x = -3, then the graph also tends to the line y = x as x becomes large.
Since there are two asymptotes, the graph is in three parts and as similar graphs, the central part is fairly similar to the numerator, that is a cubic.
Now what you can do is try out what is the value of y slightly to the left and slightly to the right of the asymptotes to know the shape of the graph, whether it's ascending or descending. | <urn:uuid:b6dc6fda-e814-45bf-8df1-b4f612a1c966> | 2.796875 | 136 | Q&A Forum | Science & Tech. | 69.590585 | 214 |
leafscale gulper shark
Today the European Commission proposed new catch limits for 2013 and 2014 that will allow fishermen to exploit some little-known but important deep-sea fishes against the advice of scientists. As this video of the European deep-sea prepared by our European office demonstrates, even though light doesn’t penetrate to the ocean bottom, it's still thriving with life. It's a strange world and the animals themselves often have fittingly strange names, like the Mediterranean slimehead, greater forkbeard, and conger, to name a few.
Some species, like the roundnose grenadier, blue ling and red seabream, need special protection. Executive Director of Oceana Europe, Xavier Pastor explains why:
“Due to their biological characteristics, like low reproduction, slow growth rate and late maturity, deep sea species are highly vulnerable to overexploitation. Their management must, now more than ever, follow the precautionary approach.”
European fishermen have increasingly turned to scouring the deep-sea for fish as more traditional stocks have fallen and pirate fishermen have been able to hammer stocks of threatened deep-sea sharks through the sale of shark liver oil in the EU.
Right now Oceana’s research vessel, the Oceana Ranger, is sailing off of the picturesque Algarve section of Portugal using an underwater robot, known as an ROV, to explore and document the scarcely seen world of seamounts, deep-sea coral reefs and seafloor habitat. It’s an effort that will help scientists develop conservation proposals and better protect this vital ecosystem--one that can be obliterated in an instant by bottom trawlers. Keep up with the Ranger expedition online and check out the latest pictures and video. | <urn:uuid:4935bb1d-38d3-421d-b9fd-780da26f16ef> | 3 | 362 | News (Org.) | Science & Tech. | 28.795955 | 215 |
You have an empty container, and an infinite number of marbles, each numbered with an integer from 1 to infinity.
At the start of the minute, you put marbles 1 - 10 into the container, then remove one of the marbles and throw it away. You do this again after 30 seconds, then again in 15 seconds, and again in 7.5 seconds. You continuosly repeat this process, each time after half as long an interval as the time before, until the minute is over.
Since this means that you repeated the process an infinite number of times, you have "processed" all your marbles.
How many marbles are in the container at the end of the minute if for every repetition (numbered N)
A. You remove the marble
numbered (10 * N)
B. You remove the marble numbered (N)
(In reply to My ideas?
Well... to be specific, I think you said that you can't multiply or divide infinity (not dividing BY infinity).
I'm not sure what dividing by infinity means, unless you're implying dividing by a variable as the variable grows towards infinity. In which case, you are talking about the "normal" limit described by calculus.
You said in your first post "so it's infinity times 9 divided by 10... Wait, we can't divide or multiply infinity".
I don't see why not. But an infinity multiplied by, divided by, added to, or lessened by a constant is the same infinity.
Again, I would refer you to studies about what infinities mean and that they are normally dealt with as sets of elements and operations (often mappings) ON those sets. | <urn:uuid:d185d41e-eca2-40cb-80e0-525a863d830c> | 2.921875 | 350 | Comment Section | Science & Tech. | 60.809695 | 216 |
Ingenious fishing method may be spreading through dolphinsAugust 24th, 2011 in Biology / Plants & Animals
(PhysOrg.com) -- Researchers from Murdoch University believe a recently documented method of fishing may be spreading throughout a population of dolphins.
Indo-Pacific bottlenose dolphins (Tursiops aduncus) in Shark Bay were photographed engaging in conching in 2007 and 2009.
The dolphins would trap small fish in large conch shells with their rostrums (beaks), then bring the shells to the surface and shake them, causing the water to drain out and the fish to fall into their mouths.
Murdoch Cetacean Research Unit Researcher Simon Allen says this previously rarely witnessed phenomenon might be on the increase, suggesting that the technique is spreading.
In the last four months alone, the research team have seen and photographed the behaviour no less than six times, possibly even seven.
If and that is a big if we are witnessing the horizontal spread of this behaviour, then I would assume that it spreads by an associate of a conching dolphin closely observing the behaviour and then imitating it, Mr. Allen said.
It is a tantalising possibility that this behavior could spread before our very eyes over a field season or two and that we could track that spread.
The prospect of observing a learned behavior spreading through a population over a short period of time is exciting in itself, but the behavior also raises new questions about how exactly dolphins engage in conching.
As yet, we dont know if dolphins simply pursue fish into the refuge of the large, empty conch/bailer shells or whether they actually manipulate the shells prior perhaps turning them over so that the opening is facing up in order to make them appealing to fish as a place to hide from the jaws of death, Mr. Allen said.
If we were to set up a few shells opening down in a known location and either witness dolphins turning them over, see evidence of them having been turned over when we werent around, or better still get some video footage of dolphins manipulating them in some way, then that would be priceless, since that implies forward planning on the dolphins part.
I wouldnt be too surprised to find such cunning and devilish ploys being adopted by Shark Bays bottlenose dolphins.
Until such observations are recorded though, Mr. Allen says it is too early to rush to any conclusions.
Members of the Murdoch Cetacean Unit, with colleagues from the University of Zurich, spend roughly four months of the year studying western Shark Bays dolphin population in the field.
The Unit operates with the assistance of a partnership with Shark Bay Resources, who provide accommodation, office space and mess facilities for the research teams.
Provided by Murdoch University
"Ingenious fishing method may be spreading through dolphins." August 24th, 2011. http://phys.org/news/2011-08-ingenious-fishing-method-dolphins.html | <urn:uuid:c652dec2-1f35-4e79-9f2d-a10ce480f310> | 3.640625 | 608 | News Article | Science & Tech. | 46.509545 | 217 |
The steps by which molecules in the primordial soup came together to form the genetic backbone of life are largely unknown. One approach to finding out is to artificially create basic life functions in the laboratory and consider if such conditions might have been possible in the Earth’s past. Writing in Physical Review Letters, Hubert Krammer and colleagues at the Ludwig Maximilian University of Munich in Germany show they are able to drive the replication of segments of tRNA (transfer ribonucleic acid), the molecule responsible for translating genetic code into the production of specific proteins, using a purely thermal process.
Krammer et al. begin by rapidly cooling a solution of four halves of tRNA from high temperatures to so that the molecules form hairpins—a state where the strand forms a closed loop on itself, except for a snippet of a sequence of bases, called a “toe hold.” It is this toe hold, which, in principle, carries enough information to encode a protein, that the authors try to protect and replicate by using a thermal process to coax the hairpins to open and pair to a complementary strand. When Krammer et al. thermally cycle the solution between and , the energy stored in the hairpin (which prefers it to bind to a complementary pair instead of itself) compensates for the loss of entropy associated with the molecules pairing up with their partners.
This thermally driven process occurs on a relatively fast time scale of about seconds, an important factor since molecules need to replicate faster than they degrade. According to the authors, convection currents in prebiotic liquids could have provided the necessary quenching and thermal cycling. – Jessica Thomas | <urn:uuid:4667167f-2026-4584-834a-5892652dce7e> | 4.15625 | 339 | Academic Writing | Science & Tech. | 27.06836 | 218 |
What is API?
API is an interface that allows software programs to interact with each other. It defines a set of rules that should be followed by the programs to communicate with each other. APIs generally specify how the routines, data structures, etc. should be defined in order for two applications to communicate. APIs differ in the functionality provided by them. There are general APIs that provide library functionalities of a programming language such as the Java API. There are also APIs that provides specific functionalities such as the Google Maps API. There are also language dependent APIs, which could only be used by a specific programming language. Furthermore, there are language independent APIs that could be used with several programming languages. APIs needs to be implemented very carefully by exposing only the required functionality or data to the outside, while keeping the other parts of the application inaccessible. Usage of APIs has become very popular in the internet. It has become very common to allow some of the functionality and data through an API to the outside on the Web. This functionality can be combined to offer an improved functionality to the users.
What is SDK?
SDK is a set of tools that can be used to develop software applications targeting a specific platform. SDKs include tools, libraries, documentation and sample code that would help a programmer to develop an application. Most of the SDKs could be downloaded from the internet and many of the SDKs are provided free to encourage the programmers to use the SDK‘s programming language. Some widely used SDKs are Java SDK (JDK) that includes all the libraries, debugging utilities, etc., which would make writing programs much easier in Java. SDKs make the life of a software developer easy, since there is no need to look for components/ tools that are compatible with each other and all of them are integrated in to a single package that is easy to install.
What is the difference between API and SDK?
API is an interface that allows software programs to interact with each other, whereas a SDK is a set of tools that can be used to develop software applications targeting a specific platform. The simplest version of a SDK could be an API that contains some files required to interact with a specific programming language. So an API can be seen as a simple SDK without all the debugging support, etc. | <urn:uuid:7cf35450-4a45-4a04-92c2-84c70317cbd0> | 3.40625 | 462 | Q&A Forum | Software Dev. | 39.488346 | 219 |
Download chapter 3: 'Basic SOA Using REST'
This chapter is excerpted from the book titled, SOA Using Java Web Services, authored by Mark Hansen, published by Prentice Hall Professional, May, 2007, ISBN 0130449687, Copyright 2007 Pearson Education, Inc. For more information please visit: www.prenhallprofessional.com
3.1.1 What Is REST?REST-style services (i.e., RESTful services) adhere to a set of constraints and architectural principles that include the following:
- RESTful services are stateless. As Fielding writes in Section 5.1.3 of his thesis, "each request from client to server must contain all the information necessary to understand the request, and cannot take advantage of any stored context on the server."
- RESTful services have a uniform interface. This constraint is usually taken to mean that the only allowed operations are the HTTP operations: GET, POST, PUT, and DELETE.
- REST-based architectures are built from resources (pieces of information) that are uniquely identified by URIs. For example, in a RESTful purchasing system, each purchase order has a unique URI.
- REST components manipulate resources by exchanging representations of the resources. For example, a purchase order resource can be represented by an XML document. Within a RESTful purchasing system, a purchase order might be updated by posting an XML document containing the changed purchase order to its URI.
These are the basic principles behind REST. However, when people talk about the benefits of RESTful systems today, they usually are not strictly applying these principles. For example, among REST advocates, keeping shopping cart data on the server and maintaining a session related to the shopping process that is using the cart is acceptable.2 In fact, the XML/HTTP Binding provided by JAX-WS for implementing RESTful services provides for session management capabilities using cookies, URL rewriting, and SSL session IDs.
More significant deviations from Fielding's definition of REST involve getting around the "uniform interface" constraint by embedding verbs and parameters inside URLs. The Amazom.com REST interface, for example, includes verbs in query strings and doesn't have unique URIs for each resource. Systems like this, although labeled as RESTful, are really starting to look very much like RPC using XML over HTTP without SOAP.
For the purposes of this book, I am not going to wade into a debate on what is or isn't RESTful. I simply define RESTful Web Services in contrast to SOAP Web Services. Table 3–1 illustrates the principal differences.
a. Some would argue that XML Schema could be used as an interface definition for RESTful services. Not only is that approach possible, but it is used in many practical cases. However, it is not a complete interface solution because many, if not most, RESTful services incorporate HTTP parameters (e.g., URL query strings) in addition to XML as part of their invocation interface. Chapter 9 looks at the Yahoo! Shopping RESTful interface, which uses HTTP parameters in this manner.
This is consistent with common usage in the REST versus SOAP debates. REST uses simple XML over HTTP without a WSDL interface definition.
3.1.2 Topics Covered in This ChapterIn addition to introducing RESTful Web Services, this chapter introduces and reviews some basic techniques for integrating Enterprise Information Systems (EISs) using XML, XSLT, HTTP, and Java. For each example, I demonstrate how to implement it with and without JWS. The versions of the examples without JWS use basic Java HTTP and XML techniques. Both approaches are provided to give you a sense of what is really happening, under the covers, when a Web service is consumed or deployed using JWS. This should give you a better understanding of the mechanisms underlying JWS and when to use them. For simple Web services, often it is easier to work with the basic Java tools than to pull out all the power of JWS. On the other hand, you will see from these examples how things can quickly get complicated and require the power of the JWS technologies.
Since one focus of this book is on SOA-style development for the enterprise, many of the examples deal with EIS—the basic infrastructure of most corporate computing environments. This chapter describes
- Structuring EIS Records as XML documents
- Getting EIS records from a REST service (with and without JWS)
- Posting EIS records to a REST service (with and without JWS)
- Basic SOA-style integration of REST services using XSLT for data transformation
- Deploying a REST service to be used for getting EIS records—in other words, an HTTP GET service (with and without JWS)
- Deploying a REST service to be used for posting EIS records—in other words, an HTTP POST service (with and without JWS)
3.2 XML Documents and Schema for EIS RecordsThe first step toward implementing an SOA component that consumes or provides EIS records involves formatting the EIS records that need to be exchanged as XML documents. This process is formalized by creating an XML Schema to represent the structure of an XML document for a particular EIS record. This section introduces some simple examples that are used throughout this chapter to illustrate the role of XML and XML Schema in SOA-style applications development based on Web Services. Understanding these examples requires a basic knowledge of XML and XML Schema. If you are new to XML, you should get an introductory text such as Beginning XML by David Hunter et al. [Hunter]. For the necessary background on XML Schema, I suggest Definitive XML Schema by Priscilla Walmsley [Walmsley]. Alternatively, if you know basic XML, but need to brush up on XML Schema, you can probably find all you need to know for this book by reading through the W3C's "XML Schema Part 0: Primer" [XSD Part 0].
To illustrate how XML is used, I employ an example based on the fictitious XYZ Corporation. The example illustrates real SOA challenges faced by many companies. XYZ Corporation has an Order Management System (OMS) that needs to be integrated with a Customer Service System (CSS). The OMS should be thought of as an EIS, such as SAP, for taking customer orders and tracking them through delivery. The CSS should be thought of as an EIS, such as Oracle's Siebel Customer Relationship Management Applications, that is used by customer service employees as a tool for handling customer inquiries.
XYZ Corporation would like to build an SOA application bridging the OMS and the CSS. Every time a new order is entered in the OMS (or an existing order is updated), the new SOA application should transfer that information to the CSS and add it to the relevant customer's history log. The purpose of this SOA application is to ensure that customer service representatives have fast access, through the CSS, to basic customer order information. If customer service representatives need access to more detailed order information from the OMS, the CSS will contain the keys within the customer history log (updated via the SOA application) to query the OMS and access that detailed information.
Figure 3–1 illustrates what an OMS order record looks like as it might appear on a user interface.
Visit the Prentice Hall
Professional website for a detailed description and to learn how to purchase this title.
This was first published in May 2007 | <urn:uuid:dfca6006-bdf3-4e2c-951f-26755b764c06> | 2.5625 | 1,550 | Truncated | Software Dev. | 47.177085 | 220 |
Matter in the corona and solar wind is derived from the outer convective zone (OCZ) of the Sun. Isotopic abundances of the less volatile elements in the solar atmosphere are probably very similar to terrestrial, lunar and meteoritic abundances. From such elements it is possible to infer the amount of isotopic fractionation under varying conditions in the solar wind source region. For many species, the solar wind provides the only source of information, which is important for many cosmochemical and astrophysical applications. Knowledge of the isotopic composition of the OCZ will yield information on the early solar nebula and the history of the solar system. The CELIAS solar wind mass spectrometer (MTOF, Mass Time-of-Flight sensor) has unprecedented mass resolution for solar wind composition studies, and has already measured rare elements and isotopes that were previously not resolvable from more abundant neighboring species, or were not previously observable at all. The MTOF sensor is routinely measuring isotopic abundance variations for several elements (neon, magnesium, silicon, sulfur, argon, calcium, iron, and nickel), some of which have never been previously observed in either the solar wind, solar energetic particles, or spectroscopically. Among the new solar wind isotopes are those of silicon, sulfur, calcium, chromium, iron, and nickel. Other isotopes are being measured with a much finer temporal resolution than previously available (on the order of minutes/hours instead of months/years). Previously, neon and argon solar wind isotopic measurements were available only from foil measurements collected during the Apollo lunar landings - clearly a limited data set! The first magnesium isotope measurements have been reported by MTOF's sister sensor WIND/SMS/MASS. This image shows isotopes of Chromium, Iron, and Nickel. | <urn:uuid:9e86d6d1-7844-4d1f-a3f1-0319fa1e4405> | 3.546875 | 377 | Knowledge Article | Science & Tech. | 13.649524 | 221 |
Marine science students at Tates Creek High School are raising largemouth bass and growing vegetables without soil in a new three-level aquaponics station, which recycles water in a sustainable food-production model.
In the simple setup, water from the fish barrel trickles into the grow beds, which routinely drain so the roots get some air and the plants aren’t overly saturated. The water then is pumped back into the barrel of bass.
“Throughout generations, it’s been done. It’s the whole idea of being sustainable and increasing your output with low input,” said teacher Diana Mullins. “In this closed system, the plants are taking less time to grow, so you’ve got a faster turnaround. In six months, the fish will be about plate-size.”
The project is a collaboration with FoodChain, a local nonprofit run by Becca Self.
“The great thing is the fish and the plants have a symbiotic relationship. The fish waste is used by the plants as food, and they filter the water so it’s clean to go back to the fish,” Self said. “It uses less than 10 percent of the water that conventional agriculture uses, so it’s a really environmentally friendly way of producing food.” | <urn:uuid:1764129b-73fc-4231-8edb-5beff6b03fe3> | 3 | 275 | News Article | Science & Tech. | 58.052061 | 222 |
In Python, for a binary file, I can write this:
buf_size=1024*64 # this is an important size... with open(file, "rb") as f: while True: data=f.read(buf_size) if not data: break # deal with the data....
With a text file that I want to read line-by-line, I can write this:
with open(file, "r") as file: for line in file: # deal with each line....
Which is shorthand for:
with open(file, "r") as file: for line in iter(file.readline, ""): # deal with each line....
This idiom is documented in PEP 234 but I have failed to locate a similar idiom for binary files.
I have tried this:
>>> with open('dups.txt','rb') as f: ... for chunk in iter(f.read,''): ... i+=1 >>> i 1 # 30 MB file, i==1 means read in one go...
I tried putting
iter(f.read(buf_size),'') but that is a syntax error because of the parens after the callable in iter().
I know I could write a function, but is there way with the default idiom of
for chunk in file: where I can use a buffer size versus a line oriented?
Thanks for putting up with the Python newbie trying to write his first non-trivial and idiomatic Python script. | <urn:uuid:49c7c0b6-a2ce-4617-b05c-a6e4bae21e61> | 2.78125 | 319 | Q&A Forum | Software Dev. | 85.561623 | 223 |
'Global Warming is real' declares new scientific work from an independent group of researchers called the Berkeley Earth Surface Temperature Study. The research team is at least partially funded by the Koch Brothers who fund several climate denial groups. The team was setup to identify flaws in the climate science of global average temperature trends, but has confirmed the analysis undertaken by NASA, NOAA and the Hadley Centre that about 1 degree Celsius of global warming has occurred since 1950.
The study confirmed that "We are seeing substantial global warming" and subtantially eliminated arguments that heat island effects, temperature station quality, and the risk of data selection bias had more than a very modest or marginal impact on the trend for increasing global average temperatures.
Related Commentary: Nature Different method, same result: global warming is real | Climate Progress Hot Dog Bites Skeptical Man: Koch-Funded Berkeley Temperature Study Does “Confirm the Reality of Global Warming”
Four research papers have been released for public discussion with a view for them all to be submitted for peer review and eventually published. The research team was lead by Professor Richard Muller, a physicist at the University of California at Berkeley and included Saul Perlmutter who was recently announced as a winner of the 2011 Nobel Prize in Physics (for his work in cosmology). Muller criticised the global temperature trend during 2004 in an article in Technology Review, alledging that the "hockey stick" of global temperatures was broken.
"Our biggest surprise was that the new results agreed so closely with the warming values published previously by other teams in the U.S. and the U.K.,” Muller said. “This confirms that these studies were done carefully and that potential biases identified by climate change skeptics did not seriously affect their conclusions."
The study ruled out of contention the urban heat island effect and poor station quality in terms of bias in the results by NASA, NOAA and the Hadley Centre. Robert Rohde, lead scientist for Berkeley Earth, noted that "the Berkeley Earth analysis is the first study to address the issue of data selection bias, by using nearly all of the available data, which includes about 5 times as many station locations as were reviewed by prior groups."
In a related study published this week - Effects of Urban Surfaces and White Roofs on Global and Regional Climate - Stanford University researchers have quantified the contribution of the heat islands on a global basis for the first time, showing that the contribution to global warming from urban heat islands is very modest compared with what greenhouse gas emissions contribute. The study also ran a simulation for the geoengineering solution of painting roofs white in urban areas to enhance local cooling. The cooling effect does work, but it also marginally increases warming on a global scale. Professor Jacobson advised it was better to Install solar panels to combat Global Warming rather than paint roofs white.
On the urban heat island effect the BEST study reported "The urban heat island effect is locally large and real, but does not contribute significantly to the average land temperature rise. That’s because the urban regions of the Earth amount to less than 1% of the land area".
On temperature sites the BEST study detailed "About 1/3 of temperature sites around the world reported global cooling over the past 70 years (including much of the United States and northern Europe). But 2/3 of the sites show warming. Individual temperature histories reported from a single location are frequently noisy and/or unreliable, and it is always necessary to compare and combine many records to understand the true pattern of global warming."
"The large number of sites reporting cooling might help explain some of the skepticism of global warming,” Rohde commented. “Global warming is too slow for humans to feel directly, and if your local weather man tells you that temperatures are the same or cooler than they were a hundred years ago it is easy to believe him."
The research looked in some depth into the allegations by Anthony Watts that temperature results were skewed in the US due to "poor" station data. The research identified that these stations showed the same pattern of global warming as stations ranked “OK”. "Absolute temperatures of poor stations may be higher and less accurate, but the overall global warming trend is the same, and the Berkeley Earth analysis concludes that there is not any undue bias from including poor stations in the survey."
The website explains in depth the methodology of the research and also publishes full datasets which required combining data from different sites and formats and building from scratch a statistical analysis of the data.
While the research identifies that the same degree of global warming is ocurring as other well known analyses, it hasn't made an independent assessment of how much of the observed warming is due to human actions according to Richard Muller.
Scientists from Australian and the UK have commented on the release of these papers. Several commented that the papers need to undergo the peer review process. “I think it would be very unwise to comment until the peer review process has completed. If we have learned anything over the last couple of years it is surely that ensuring the rigour of the science is paramount - however good the "scoop" might seem." said Professor Chris Rapley, Professor of Climate Science at UCL
Professor Neville Nicholls from the School of Geography and Environmental Science at Monash University, Melbourne said "Only those most desperate to dismiss global warming have tried to blame urbanization for the observed warming. But I guess it is always good to have yet another group confirm decades of work by climate scientists. Perhaps this will finally put to rest the furphy that the warming is caused by urbanization. I won't hold my breath though. I guess those spreading misinformation about warming will just move on to another one of their furphies."
Professor Dave Griggs, CEO of ClimateWorks Australia and Director of the Monash Sustainability Institute, Melbourne said that: "The paper confirms previous work that the observed warming of the Earth since the beginning of the 20th Century cannot be attributed to the urban heat island (UHI) effect."
"This comes as no surprise to climate scientists who take great care to take account of this effect in their work. It also confirms findings from other studies using very different methods. For example, looking at temperature trends on windy days and calm days also show no difference contrary to what you would expect from the urban heat island as the heat would build up more on calm days. So, hopefully this paper will help to put this urban (heat island) myth to bed." said Dave Griggs.
Professor Simon Tett, Head of Global Change Research Institute School of Geosciences at the University of Edinburgh, said:
"Earlier analysis, including that from the [Hadley] Climatic Research Unit, using a restricted set of temperature records, to avoid urban warming, show large scale warming. Comparison of that data with climate models leads to the conclusion that anthropogenic drivers are responsible for the late 20th century warming. The BEST study, assuming its results are similar after peer review, would not change that view."
Bob Ward, Policy and Communications Director, Grantham Institute for Climate Change and the Environment at the London School of Economics (LSE), said:
"This new study confirms what we already knew. The warming of the land areas of the Earth since the 19th century cannot be explained by the impact of cities growing to engulf rural weather stations. So-called 'sceptics' should now drop their thoroughly discredited claims that the increase in global average temperature could be attributed to the impact of growing cities, which create an urban heat island effect. This claim was always dubious as oceans also show the same level of warming as land areas."
"The warming of the Earth is unequivocal and, as every major scientific organisation in the world has pointed out, the overwhelming evidence indicates that this warming is being driven by the unarguable increase in greenhouse gas concentrations in the atmosphere."
"More broadly this study also proves once again how false it was for 'sceptics' to allege that the e-mails hacked from the University of East Anglia proved that the Climatic Research Unit's land temperature record had been doctored. Several independent inquiries, and now this study, have shown that allegation to be entirely untrue. It is now time for an apology from all those, including US Presidential hopeful Rick Perry, who have made false claims that the evidence for global warming has been faked by climate scientists." concluded Bob Ward.
- Berkeley Earth Summary of Findings, 20 October, 2011 - Cooling the Warming Debate -
Berkeley Earth Releases Global Land Warming Analysis (PDF)
- Australian Science Media Centre, 21 October 2011 - RAPID REACTION: New data on climate change from the Berkeley Earth Surface Temperature (BEST) project – experts respond
- Image - Decadal Land-Surface Average Temperature from Berkeley Earth | <urn:uuid:8f8897c6-a03e-4bf4-ab03-1f6c22eaccaf> | 2.8125 | 1,805 | Comment Section | Science & Tech. | 30.976811 | 224 |
Explanation: Please wait while one of the largest mobile machines in the world crosses the road. The machine pictured above is a bucket-wheel excavator used in modern surface mining. Machines like this have given humanity the ability to mine minerals and change the face of planet Earth in new and dramatic ways. Some open pit mines, for example, are visible from orbit. The largest excavators are over 200 meters long and 100 meters high, now dwarfing the huge NASA Crawler that transports space shuttles to the launch pads. Bucket-wheel excavators can dig a hole the length of a football field to over 25 meters deep in a single day. They may take a while to cross a road, though, with a top speed under one kilometer per hour. | <urn:uuid:7e88181f-71be-4790-9182-7f6015ab60d7> | 3.265625 | 155 | Personal Blog | Science & Tech. | 49.371154 | 225 |
Laura formed as a slightly unusual sub-tropical storm in the northern mid-Atlantic on September 29, 2008. Subtropical storms are hybrids of tropical storm systems and extratropical storms, forming in cooler waters farther north (or south) of the usual hurricane formation regions. Laura formed quite far north, well away from major land masses. As of September 30, the National Hurricane Center predicted that the storm could hit Scotland by October 4. With peak sustained winds of around 95 kilometers per hour (55 miles per hour), Laura was a powerful storm, but not hurricane strength. It was unlikely that the storm would ever become a hurricane, but forecasters expected the storm to remain near its September 30 strength for several days.
This data visualization was made with observations from the QuikSCAT satellite taken on September 30, 2008, at 5:39 a.m. local time (7:39 UTC). It shows Laura as a tight ball of circular winds around a calmer core. The image depicts wind speed in color and wind direction with small barbs. White barbs point to areas of heavy rain.
QuikSCAT measurements of the wind strength of Laura and other cyclones (the generic term for typhoons, hurricanes, and similar storms) can be slower than actual wind speeds. QuikSCAT’s scatterometer sends pulses of microwave energy through the atmosphere to the ocean surface and measures the energy that bounces back from the wind-roughened surface. The energy of the microwave pulses changes depending on wind speed and direction.
To relate the radar signal to actual wind speed, scientists compare measurements taken from buoys and other ground stations to data the satellite acquired at the same time and place. Because the high wind speeds generated by cyclones are rare, scientists do not have corresponding ground information to know how to translate data from the satellite for wind speeds above 50 knots (about 93 km/hr or 58 mph). Peak winds in Laura measured in other ways are near this extreme limit, so values from QuikSCAT may not be reliable near the core of the storm system.
Also, the unusually heavy rain found in a cyclone distorts the microwave pulses in a number of ways, making a conversion to exact wind speed difficult. Instead, the scatterometer provides a nice picture of the relative wind speeds within the storm and shows wind direction. | <urn:uuid:9ed34bc9-0835-4317-a6cc-92f905d09392> | 3.8125 | 480 | Knowledge Article | Science & Tech. | 48.08331 | 226 |
|Direct Imaging of Asymmetric Magnetization Reversal|
The phenomenon of exchange bias has transformed how data is read on magnetic hard disks and created an explosion in their information storage density. However, it remains poorly understood, and even the fundamental mechanism of magnetic reversal for exchange-biased systems in changing magnetic fields is unclear. By using x-ray photoemission electron microscopy at the ALS to directly image the magnetic structure of an exchange-biased film, a team from the University of Washington and the Stanford Synchrotron Radiation Laboratory has identified separate magnetic-reversal mechanisms in the two branches of a hysteresis loop. This advance in fundamental understanding will provide new insights for developing the next generation of information storage and sensing devices where exchange bias is expected to play a critical role.
There are two basic energies involved in the manipulation and control of the magnetic properties of materials. Exchange controls magnetic order, and anisotropy controls magnetic orientation. A soft ferromagnet such as iron has a large exchange parameter but a small anisotropy, making ferromagnetic order stable at higher temperatures but with an unpredictable orientation of the magnetization, especially in structures of nanoscale dimensions. On the other hand, many antiferromagnets have weak exchange interactions (low ordering or Néel temperatures) but large anisotropies that result in very stable orientations.
Exchange bias arises when a thin ferromagnetic film is grown on an antiferromagnet and the resulting heterostructure is cooled in a magnetic field through the Néel temperature of the antiferromagnet. As a result of exchange coupling between the layers, the ferromagnet both retains a stable order and gains a higher anisotropy at room temperature. Moreover, the unidirectional character of the anisotropy results in a shifted hysteresis loop that is now centered on a non-zero magnetic field. This exchange bias makes the ferromagnet an excellent magnetic reference layer in modern nanolayer magnetic devices because it is very difficult to demagnetize it.
More than fifty years of research has provided varying insight into the exchange-bias phenomenon but not yet a comprehensive description of all its salient features. To gain more insight, the Washington–Stanford team resorted to x-ray photoemission electron microscopy (PEEM) imaging of high-quality single-crystal ferromagnetic iron epitaxially grown on antiferromagnetic MnPd (all on an MgO substrate), samples that had been previously well-characterized magnetically and structurally.
At an iron absorption resonance, absorption of circularly polarized x rays at ALS Beamline 184.108.40.206 is sensitive to the angle between the magnetization within a ferromagnetic domain and the polarization vector. With the PEEM-2 microscope, this x-ray magnetic circular dichroism (XMCD) effect allows an exact determination of the direction of the local domain magnetization at the surface of ferromagnets with a spatial resolution of 50 nm or less.
By means of XMCD measurements taken at points in hysteresis loops with the applied field in different crystallographic directions of the iron ferromagnet, the team has accumulated the first direct imaging evidence for an asymmetry in the magnetic-reversal mechanism in exchange-biased systems, evidence that until now has only been inferred indirectly by measurements such as neutron scattering.
Normally, magnetic reversal in ferromagnets occurs either by coherent rotation of magnetic moments in the domain or by nucleation and growth of reverse domains. Generally, the mechanism is determined by the material microstructure and is symmetric with respect to the applied field, i.e., it is the same in both branches of the hysteresis loop. However, the team found that in exchanged-biased ferromagnetic iron, the magnetization reversal occurs by moment rotation for decreasing fields, while it proceeds by domain nucleation and growth for increasing fields. The observed domains are also consistent with the crystallography of the bilayers and favor a configuration that minimizes the overall magnetostatic energy of the ferromagnetic layer.
Research conducted by P. Blomqvist and K.M. Krishnan (University of Washington) and H. Ohldag (Stanford Synchrotron Radiation Laboratory).
Research funding: U.S. Department of Energy, Office of Basic Energy Sciences (BES). Operation of the ALS is supported by BES.
Publication about this research: P. Blomqvist, K.M. Krishnan, and H. Ohldag, "Direct imaging of asymmetric magnetization reversal in exchange-biased Fe/MnPd bilayers by x-ray photoemission electron microscopy," Phys. Rev. Lett. 94, 107203 (2005). | <urn:uuid:6303857f-0867-4589-b8d6-612b9491697c> | 2.84375 | 999 | Academic Writing | Science & Tech. | 21.16189 | 227 |
TAU Researchers Part of Team of International Scientists to Uncover the "God Particle" Wednesday, July 25, 2012
Higgs boson particle crucial for explaining how the universe was built
Tel Aviv University's Prof. Yaron Oz, dean of TAU's Faculty of Exact Sciences, and Prof. Aharon Levy of TAU's School of Physics and Astronomy were among the theoretical and experimental physicists who made the groundbreaking discovery of a particle known as the Higgs boson or "God particle," a key to understanding how the universe was built. The discovery was made at Geneva's European Laboratory for Particle Physics (CERN) and announced in early July.
First proposed in 1964 by a team of six physicists, including University of Edinburgh Professor Peter Higgs, the particle is said to explain the existence of mass. In particle physics, bosons are one of the two fundamental classes of subatomic particles. The Higgs boson is the final building block, missing until now from the "Standard Model," which describes the structure of matter in the universe. The model is to physicists what the theory of evolution is to biologists.
Prof. Yaron Oz
Albert Einstein would have been "very happy" at the discovery, Prof. Oz noted.
The term "God particle" originated with Prof. Max Lederman, an American experimental physicist who won the Nobel Prize in physics for his work with neutrinos. Prof. Lederman wrote a book using the term, "by which he meant the mysterious particle that's part of everything," Prof. Levy says. "Particle physics aims at understanding what conditions created the Big Bang that created the Universe, to look backwards as much as possible at that event."
Prof. Oz congratulated the group of researchers not only on their scientific achievement but also on their ability to put political considerations aside and work together for the good of humanity. Calling the huge CERN facility "what the UN should be," he said that "everybody is devoted to making the discovery as a team, without any politics or vested interests. I even worked with Iranians there, and there was never a harsh word between us. We all just want to understand. It was has already been proven that the nationals of the world can function together harmoniously for joint targets." | <urn:uuid:3395d913-9a54-4e42-8af6-a4b4a5198506> | 2.765625 | 463 | News (Org.) | Science & Tech. | 43.505575 | 228 |
July Rendezvous with Vesta
"We often refer to Vesta as the smallest terrestrial planet," said Christopher T. Russell, a UCLA professor of geophysics and space physics and the mission's principal investigator. "It has planetary features and basically the same structure as Mercury, Venus, Earth and Mars. But because it is so small, it does not have enough gravity to retain an atmosphere, or at least not to retain an atmosphere for very long.
"There are many mysteries about Vesta," Russell said. "One of them is why Vesta is so bright. The Earth reflects a lot of sunlight — about 40 percent — because it has clouds and snow on the surface, while the moon reflects only about 10 percent of the light from the Sun back. Vesta is more like the Earth. Why? What on its surface is causing all that sunlight to be reflected? We'll find out."
Dawn will map Vesta's surface, which Russell says may be similar to the moon's. He says he expects that the body's interior is layered, with a crust, a mantle and an iron core. He is eager to learn about this interior and how large the iron core is.
Named for the ancient Roman goddess of the hearth, Vesta has been bombarded by meteorites for 4.5 billion years.
"We expect to see a lot of craters," Russell said. "We know there is an enormous crater at the south pole that we can see with the Hubble Space Telescope. That crater, some 280 miles across, has released material into the asteroid belt. Small bits of Vesta are floating around and make their way all the way to the orbit of the Earth and fall in our atmosphere. About one in every 20 meteorites that falls on the surface of the Earth comes from Vesta. That has enabled us to learn a lot about Vesta before we even get there."
Dawn will arrive at Vesta in July. Beginning in September, the spacecraft will orbit Vesta some 400 miles from its surface. It will then move closer, to about 125 miles from the surface, starting in November. By January of 2012, Russell expects high-resolution images and other data about surface composition. Dawn is arriving ahead of schedule and is expected to orbit Vesta for a year.
Vesta, which orbits the Sun every 3.6 terrestrial years, has an oval, pumpkin-like shape and an average diameter of approximately 330 miles. Studies of meteorites found on Earth that are believed to have come from Vesta suggest that Vesta formed from galactic dust during the Solar System's first 3 million to 10 million years.
Dawn's cameras should be able to see individual lava flows and craters tens of feet across on Vesta's surface.
"We will scurry around when the data come in, trying to make maps of the surface and learning its exact shape and size," Russell said.
Dawn has a high-quality camera, along with a back-up; a visible and near-infrared spectrometer that will identify minerals on the surface; and a gamma ray and neutron spectrometer that will reveal the abundance of elements such as iron and hydrogen, possibly from water, in the soil. Dawn will also probe Vesta's gravity with radio signals.
The study of Vesta, however, is only half of Dawn's mission. The spacecraft will also conduct a detailed study of the structure and composition of the "dwarf planet" Ceres. Vesta and Ceres are the most massive objects in the main asteroid belt between Mars and Jupiter. Dawn's goals include determining the shape, size, composition, internal structure, and the tectonic and thermal evolution of both objects, and the mission is expected to reveal the conditions under which each of them formed.
Dawn, only the second scientific mission to be powered by an advanced NASA technology known as ion propulsion, is also the first NASA mission to orbit two major objects.
"Twice the bang for the buck on this mission," said Russell, who added that without ion propulsion, Dawn would have cost three times as much.
UCLA graduate and postdoctoral students work with Russell on the mission. Now is an excellent opportunity for graduate students to join the project and help analyze the data, said Russell, who teaches planetary science to UCLA undergraduates and solar and space physics to undergraduates and graduate students.
After orbiting Vesta, Dawn will leave for its three-year journey to Ceres, which could harbor substantial water or ice beneath its rock crust — and possibly life. On the way to Ceres, Dawn may visit another object. The spacecraft will rendezvous with Ceres and begin orbiting in 2015, conducting studies and observations for at least five months.
Russell believes that Ceres and Vesta, formed almost 4.6 billion years ago, have preserved their early record, which was frozen into their ancient surfaces.
"We're going back in time to the early solar system," he said. | <urn:uuid:62f9a0fe-badd-43cc-ae00-acdb6adf5f1a> | 3.640625 | 1,015 | Knowledge Article | Science & Tech. | 53.927142 | 229 |
Why does this galaxy have so many big black holes?
No one is sure.
What is sure is that
NGC 922 is a ring galaxy created by the collision of a large and small galaxy about
300 million years ago.
Like a rock thrown into a pond, the
ancient collision sent ripples of
high density gas out from the impact point near the center that partly condensed into stars.
Pictured above is NGC 922 with its beautifully complex ring along the left side, as imaged recently by the
Hubble Space Telescope.
Observations of NGC 922 with the
Chandra X-ray Observatory, however, show several glowing X-ray knots that are likely large black holes.
The high number of massive black holes was
somewhat surprising as the gas composition in
NGC 922 -- rich in heavy elements -- should have discouraged almost anything so massive from forming.
Research is sure to continue.
spans about 75,000 light years, lies about 150 million light years away, and can be seen with a small telescope toward the constellation of the furnace (Fornax).
Acknowledgement: Nick Rose | <urn:uuid:3231bdb9-63f9-4af7-ba27-fa67dc6013bb> | 4.0625 | 241 | Knowledge Article | Science & Tech. | 53.525 | 230 |
Scientists identified seven new species of bamboo coral discovered on a NOAA-funded mission in the deep waters of the Papahānaumokuākea Marine National Monument. Six of these species may represent entirely new genera, a remarkable feat given the broad classification a genus represents. A genus is a major category in the classification of organisms, ranking above a species and below a family. Scientists expect to identify more new species as analysis of samples continues.
"These discoveries are important, because deep-sea corals support diverse seafloor ecosystems and also because these corals may be among the first marine organisms to be affected by ocean acidification," said Richard Spinrad, Ph.D., NOAA's assistant administrator for Oceanic and Atmospheric Research. Ocean acidification is a change in ocean chemistry due to excess carbon dioxide. Researchers have seen adverse changes in marine life with calcium-carbonate shells, such as corals, because of acidified ocean water.
"Deep-sea bamboo corals also produce growth rings much as trees do, and can provide a much-needed view of how deep ocean conditions change through time," said Spinrad.
Rob Dunbar, a Stanford University scientist, was studying long-term climate data by examining long-lived corals. "We found live, 4,000-year-old corals in the Monument meaning 4,000 years worth of information about what has been going on in the deep ocean interior."
"Studying these corals can help us understand how they survive for such long periods of time as well as how they may respond to climate change in the future," said Dunbar.
Among the other findings were a five-foot tall yellow bamboo coral tree that had never been described before, new beds of living deepwater coral and sponges, and a giant sponge scientists dubbed the "cauldron sponge," approximately three feet tall and three feet across. Scientists collected two other sponges which have not yet been anal
|Contact: Christine Patrick| | <urn:uuid:ad26ba98-1713-48a2-a39f-70743debf943> | 3.8125 | 405 | News Article | Science & Tech. | 31.986071 | 231 |
March 22, 2000
UPTON, NY - Painting a bridge can be a costly and time-consuming undertaking, especially if the paint job doesn't last. So scientists have been working on ways to test paint durability before the brushes even get wet. At a March 22 session at the American Physical Society meeting in Minneapolis, scientists from the University of Missouri at Kansas City, who worked in collaboration with physicist Bent Nielsen of the U.S. Department of Energy's Brookhaven National Laboratory, will present findings that could lead to the development of an extremely sensitive and quick durability test.
The technique is called positron annihilation. Essentially, the scientists bombard small painted samples of metal with a beam of positrons, or positively charged electrons. When these "antielectrons" interact with the electrons in the molecules of the paint, they annihilate one another and send out gamma rays that give the scientists information about the molecules in the paint. The technique can detect nanometer-scale holes and defects in the paint molecules; free radicals, which indicate the presence of broken chemical bonds; and cross linking, which may make the paint brittle.
"These experiments show that this technique is extremely sensitive to detecting damage early," says Brookhaven's Nielsen - well before the formation of any visible cracks in the paint. "So you can test the paint on a much shorter time scale - a day instead of half a year. That's a big advantage," Nielsen says.
The scientists typically test the paint samples before and after exposure to ultraviolet (UV) light, one of the components of sunlight known to damage bridge coatings. The more sensitive the paint is to UV damage, the less durable the paint would be on a bridge exposed to sunlight day after day. They've also exposed samples to UV light during the positron annihilation test to see if they could detect the damage as it occurred. In both cases, the damage increased with UV exposure time, and was most severe near the surface of the paint.
In addition to laying the foundation for a quick paint durability test, the detailed observations made possible by positron annihilation may also help scientists learn more about the fundamental mechanisms of paint degradation. That knowledge, in turn, may eventually lead to the development of more durable paints.
Brookhaven was a pioneer in developing positron beams in the late 1970s and early 1980s. Positron emission tomography (PET) scanning, a medical technique used to learn about the function of body organs such as the brain, works on a similar principle, Nielsen says.
This paper will be presented at session L36 on March 22, 2000, at 10 a.m. in the Exhibit Hall of the Minneapolis Convention Center.
The U.S. Department of Energy's Brookhaven National Laboratory creates and operates major facilities available to university, industrial and government personnel for basic and applied research in the physical, biomedical and environmental sciences and in selected energy technologies. The Laboratory is operated by Brookhaven Science Associates, a not-for-profit research management company, under contract with the U.S. Department of Energy.
Note to local editors: Bent Nielsen lives in Port Jefferson, New York.
Last updated 5/28/99 by Public Affairs | <urn:uuid:40761850-51ad-4c6c-8255-6eef07767cd1> | 3.515625 | 648 | News (Org.) | Science & Tech. | 38.193606 | 232 |
Exponential growth refers to an amount of substance increasing exponentially. Exponential growth is a type of exponential function where instead of having a variable in the base of the function, it is in the exponent. Exponential decay and exponential growth are used in carbon dating and other real-life applications.
I want to talk about exponential growth, I have an example here the population of mice in the Duchy of Grand Fenwick grows at a rate of 6% per year. How long will it take for the population to double or quadruple? I have a table of values here I wanted to show you why this is exponential growth. Increasing at 6% per year means very year we're multiplying by 1.06 and so we get p sub 0 when t=0, p sub 0 times 1.06 when t=1 and p sub 0 times 1.06 squared when t=2 and so on.
This would suggest the formula p sub t equals p sub 0 times 1.06 to the t and that's an exponential growth formula. Now to find the doubling time I need to plug in twice the initial population here. I don't know what the initial population is but twice the initial population is 2 times p sub and after you plug in you can see that the actual initial population doesn't matter it's going to cancel out. So now I have the equation 2=1.06 to the t, this is an exponential equation and the way we solve exponential equations is to take the log of both sides. I'm going to take that natural log of both sides, it doesn't matter what log you use as long as it's on your calculator so you can use either the common log or the natural log.
Okay before I calculate I actually need to use the property of the logs, natural log of 1.06 to the t this is the log of a power so the exponent can come out in front t times ln of 1.06 and then we have a simple linear equation to solve this all we need to do is divide both sides b y natural log of 1.06. So ln 2 over ln of 1.06 now I'd like a numerical answer so I'm going to calculate this value ln2 divided by ln 1.06 enter, I get t, t is approximately 11.89566 and that would be in years. Because the population growth rate was given as 6% per year, I want to round this off let's say your teacher likes you to round off to the nearest hundredth then when I calculate quadrupling time a reason like this in order for a population to quadruple, it's got to double and then double again. So we're going to have 2 doubling times in a row. So it stands to reason that the quadrupling time is twice the doubling time. Twice this, but if I write 23.80 years my answer is not quite right let me multiply in my calculator answer times 2. it's actually 23.79 years.
You have to be really careful when you're using rounded values to do calculations. These values rounded to the nearest hundredth and when I double it I double whatever round off error there was. So the best way to get my final answer for quadrupling time is to double this value which is still stored in the calculator so multiply this times 2 and you get the correct value to the nearest hundredth. This is my answer. | <urn:uuid:d2dd73a6-860a-4d35-a21c-b746c236c544> | 3.46875 | 695 | Tutorial | Science & Tech. | 75.162048 | 233 |
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Family Megalopygidae ( flannel moths)240 species in Central and South America; larvae similar to those of Limacodidae, but with normal prolegs and traces of additional ones; setae very toxic and...
What made you want to look up "flannel moth"? Please share what surprised you most... | <urn:uuid:1468355c-3c1f-45db-ae94-69b998b5c0c8> | 2.53125 | 104 | Knowledge Article | Science & Tech. | 49.100731 | 234 |
Enumerators in C#
In this article I will explain you about Enumerators in C#.
This article has been excerpted from book "The Complete Visual C# Programmer's Guide" from the Authors of C# Corner.
As explained earlier, C# has a new iteration syntax called foreach. The foreach statement can only be applied to objects of classes that implement the IEnumerable interface. The IEnumerable interface exposes the enumerator, which supports a simple iteration over a collection. Enumerators are intended to be used only to read data in the collection and cannot be used to modify the underlying collection. The enumerator does not have exclusive access to the collection. To understand what happens in the background, consider the code snippet in Listing 5.57.
Listing 5.57: Enumerator Example 1
foreach (int i in a)
This code functions just like the while loop used in Listing 5.58.
Listing 5.58: Enumerator Example 2
a = x.GetEnumerator();
Please refer to the C# Language Specification (http://msdn.microsoft.com/en-us/library/aa645596(VS.71).aspx) for more details and recent updates to the C# language.
Before entering the statement block, the compiler generates the code to call the method GetEnumerator of the object passed as the second parameter in the foreach statement. The GetEnumerator method must return an object, having a property named Current, of type similar to the first argument of the foreach statement. Also this object must have a MoveNext method of return type bool. This method informs the runtime when to terminate the loop.
When an enumerator is instantiated, it takes a snapshot of the current state of the collection. If changes are made to the collection, such as the addition, modification, or deletion of elements, the snapshot gets out of sync and the enumerator throws an InvalidOperationException. Two enumerators instantiated from the same collection simultaneously can have different snapshots of the collection.
If the enumerator is positioned before the first element in the collection or after the last element in the collection, the enumerator is in an invalid state. In that case, calling Current throws an exception.
The enumerator is positioned before the first element in the collection initially. The Reset function brings the enumerator back to this position. The MoveNext method must be called to advance the enumerator to the first element of the collection before reading the value of Current, after an enumerator is created or after a Reset. The Current property returns the same object until either MoveNext or Reset is called.
Once the end of the collection is passed, the enumerator is in an invalid state and calling MoveNext returns false.
Calling Current throws an exception if the last call to MoveNext returned false. With this information under your belt, you should insert your enumerating code inside a try-catchfinally block to prevent unexpected exits.
Hope this article would have helped you in understanding Enumerators in C#. See other articles on the website on .NET and C#.
| ||The Complete Visual C# Programmer's Guide covers most of the major components that make up C# and the .net environment. The book is geared toward the intermediate programmer, but contains enough material to satisfy the advanced developer.| | <urn:uuid:587448ab-7956-49b2-82c3-cfc1cc2935bb> | 3.09375 | 702 | Documentation | Software Dev. | 38.987817 | 235 |
In all modern languages like C# and Java, we gain benefits of garbage collection. What about implementing our own. In this article, I will try to explain how to implement garbage collector for C language.
What is Garbage Collection?
In C language, dynamic memory management operations are done with
free() functions. When a piece of memory area is required, programmer calls the
malloc() function and receives a pointer of this area, and releases this area using
free() function when it is not used anymore. This is really a very easy task, you create memory area using
malloc() and release it using
free(). What if the programmer forgets to call the
free() function or application breaks before the
free() function is executed? If
free() function is not called, operating system cannot use this area and still thinks that it is in use. Large chunks of unreleased memory areas can affect system performance vitally.
Need for an automated garbage collection mechanism is born at this point. Automated garbage collection mechanism guarantees that all allocated memory during program run are released at the end.
There are a lot of garbage collection algorithms such as mark and sweep, copying, generational, reference counting, etc. In this article, I will try to explain mark and sweep algorithm.
What about Conservation?
Garbage collectors (abbreviated GC from now on) should not force developers to tag data or force to use special
datatype as pointers. GC also should work on existing source code. Working on existing code without compilation would be a more elegant solution. GC should not force to change on compilers. Conservative garbage collection approach provides GC solution preserving the above mentioned tasks.
In order to work properly, GC should have knowledge about the following tasks:
- Variables actively in use
- Which variable is a pointer and which is not
- Information of the allocated memory
Information about the allocated memory can be collected while GC allocates memory.
In C language collection about variables in use can be done with a special scanning on heap, stack and static data of the application. This solution is highly hardware dependent.
Also in C language, we do not have knowledge of a type at runtime. This means, at runtime phase it is not an easy task to distinguish pointers from non-pointers. Again we receive no assistance from the compiler. Once we have information about variables actively in use, we can scan this list with a special pointer identification algorithm to distinguish pointers. This step has some shortcomings but efficiency can be provided with elegant algorithms.
Conservative approach allows developers to use GC in their already written codes without any change on it. Developers call
malloc() function and never call
free() again inside the code. The rest is handled by GC as a smart servant.
Stop the World Approach
I mentioned that we scan memory areas of the application. We also need to release unused memory areas. These operations take additional CPU cycles. So when garbage is being collected, we need to use CPU. At this point, there are two main approaches for use of the CPU. These are stop the world and concurrent approaches.
Concurrent approach handles GC cycles on different threads. For this approach, complex locking mechanisms are needed. As a result, it benefits high performance which is desirable by most of the modern architecture. For further information, you can search on Tri-Color Marking Algorithm.
Stop the world approach stops program execution, does garbage collection and resumes program execution. This has a completely big disadvantage, it does not allow the application to use CPU while garbage is collected. This can cause the application to pause while garbage is being collected. Also we cannot use multi processor even if hardware has more than one CPU which can be a big performance gap. Although it has a lot of disadvantages, it is really very easy to implement so in this article we will use this approach.
Mark and Sweep Algorithm
Mark and Sweep Algorithm is the first algorithm which handles cyclic references. This algorithm is one of the most commonly used garbage collectors with combination of some other techniques.
Mark and sweep algorithm is a tracing collector so it traces through all available pointers to distinguish used and unused memory areas. It consists of two phases. The first phase is the marking phase. In marking phase, GC traces through all available variables and finds pointers using pointer identification algorithm. Once pointers are determined, marking phase finds the heap area of the pointers and marks them as used. In the second phase, GC traces through the heap and picks unmarked areas. Unmarked areas are the memory areas which are not currently used. These areas are reclaimed.
As mentioned, mark and sweep can handle cyclic references. Moreover, it includes no overhead on variables.
Conservative GC faces two main difficulties, the first is for identifying where to find root set and the second is how to identify pointers.
Root set can be described as the variables which are in use at time(t). Finding root sets without the assistance of the compiler is a highly system and hardware dependent issue. Root sets can be found on stack, registers and static area of the application. In order to implement our GC, we should find base addresses of these memory areas.
GC should discover the bottom and top of the stack. Stack is the main stack of the application. If we take a closer look into the CPU architecture, we can see that there is a dedicated stack which holds addresses of execution points, passed parameters to functions and local variables. Stack grow direction may change in each architecture. When a new item is pushed into the stack in some architectures, the stack grows downward and in some, it grows upward. GC should be aware of this. Stack bottom and top addresses can be found by combination of EBP, ESP and DS register values of 32bit architecture. Also there are alternative ways.
Static areas are held in the data segment register in 32Bit CPUs and stored in the heap of the running application. Static areas are the memory block where local static and global variables are held. In a realworld application, we can have some global and static local variables which hold pointers. GC should be aware of these variables.
Registers are CPU registers of the hardware. These memory areas are highly system dependent. GC should be aware of the root sets held in the registers before GC takes place. Reclaiming of the memory areas which are in use could cause severe bugs.
The second difficulty that Conservative GC faces is identification of the pointers. In C and C++ languages, pointers can be held inside the integer variables. In some cases, it is not an easy task to distinguish a pointer with a 32 bit integer value. As GC has no assistance from the compiler, it has to handle identification of the pointers by itself. In general, the approach for conservative garbage collector is that "GC must treat any word (integer) that it encounters as a potential pointer unless it can prove otherwise"¹.
While in this step, GC should be aware of pointers to pointers. In this project, I implemented depth first search as pointer traversal algorithm. In order to identify pointers, GC should have some test steps to filter pointers with non-pointers. Some of the tests are mentioned below:
- Does a potential pointer refer to the atom pointer.
- Does a potential pointer refer to application heap
- Does a potential pointer refer to root sets. If so, execute pointer traversal algorithm to find which portion of the heap it refers.
- If potential pointer refers to heap, traces through allocated block to find exact block that it points.
Atom pointers are the pointers which are used by GC itself. GC should distinguish these pointers from actual application pointers. Also GC should give the ability to the developer to identify custom atom pointers. Atom pointers are being skipped at pointer identification phase and they are not recognized as pointers by GC. GC never touches the memory areas of these pointers.
If a potential pointer passes these tests, it is treated as a pointer and marked as in use at mark phase. Pointer identification has some deficiencies such as false pointers. False pointers are the integer values which hold heap addresses. Assume that we have an integer
i which holds random 32bit value, also assume that this value is
0x003932e8. When GC takes place, we have also a pointer
p which points to
0x003932e8 heap address with size in MBs.
p is set to NIL and not used anymore. Application requests new memory block but having less memory GC cannot allocate free space and steps into collection phase. In collection phase,
p should be reclaimed so it is not used anymore but
i can be recognized as a pointer actually which is not. This type of situations can be troublesome. Boehm reports that certain classes of data, such as large compressed bitmaps, introduce false references with an excessively high probability [Boehm, 1993].
After a lot of theoretical information, let's take a look at how we can implement that type of automated memory manager.
As mentioned, the GC we will design will be highly system and hardware dependent. We will use IA32 architecture and Windows Operating system.
The first thing GC should do is to find root sets. Stack top can be found by retrieving address of the last created variable. In Windows environment, the address of the last created variable can be used to query active memory block using
VirtualQuery function. This function tells the base address and other properties of the related memory area². After calling
VirtualQuery function with top of the stack, we can retrieve full set of stack roots. This root set gives us the variables currently in use. Defining
static root sets requires another call to
VirtualQuery function. This time we query memory area using a created
static local variable. Register roots can be retrieved using
When developer calls
malloc function of GC, our code should add additional header information to this memory block. This block is linked to doubly linked list. Using this list, we can store and query which memory areas are allocated by GC. In my implementation, allocation does not invoke collection step which it should do when system gets low on memory, it does only create new memory area using low level
malloc and returns address of this block. In future releases, my implementation of
gc_malloc should work in a smarter and elegant way.
In our implementations, the developer should be able to call
collect function of GC. Calling this function is not recommended but for flexibility we can allow developers to call our
Collect function should invoke the following steps. First it should determine root sets, then it should invoke mark and sweep phases respectively.
In mark phase, GC should trace through whole root sets. Code should invoke pointer identification step for each possible pointer in the root set. Once possible pointer is passed identification step code should mark it as in use (in my current implementation, I have two lists. The first list holds used areas, and the second holds free areas. When I mark a pointer as used, I remove it from the used area and link it to a free area which decreases CPU use on sweep phase).
In sweep phase, GC should trace through the whole heap. In this step, only marked areas are not reclaimed and the rest is reclaimed. (In my current implementation, I free the memory area when it is not used anymore. This can cause performance penalties. A more advanced approach can be used at this step.)
The last thing GC should do is reclaiming the whole heap when the application quits. We can use
atexit() function of standard C. In this function, we will trace through the whole heap to reclaim all used memory.
Source Code and Last Words
This project is an open source project. Please feel free to join this project. If you wish to work on this project, please let me know. Source repository of this project can be found here.
Please note that this project is actively in development. Also the current version supports a fully working GC mechanism and it has a lot of deficiencies on performance issues.
- Garbage Collection - Algorithms for Automatic Dynamic Memory Management 1996, Richard Jones, Rafael Lins
- An introduction to garbage collection part II, Richard Gillam
- Mark-and-Sweep garbage collection
- Why conservative garbage collectors
- Automatic garbage collection
- Fast multiprocessor memory allocation and garbage collection, Hans-J.Boehm, HP Laboratories
- Composing high-performance memory allocators, Emery D. Berger, Benjamin G.Zorn, Kathryn S. McKinley
- Hoard: a scalable memory allocator for multithreaded applications, Emery D. Berger, Kathryn McKinley, Robert D. Blumofe, Paul R. Wilson
- Managing heap memory in win32
- Heap pleasures and pains
- The measured cost of conservative garbage collection, Bejamin Zorn
- Conservative garbage collection for general memory allocators, Gustavo Rodriguez-Rivera, Charles Fiterman
- Conservative garbage collection for C, Christian Höglinger
Yasin has more than 10 years of professional experience. He has several published articles includes graphics programming, robotics and application development in academic resources and national press. He is now working as a software developer for semi-governmental organization in Turkey. | <urn:uuid:ce19234a-ce21-4e12-b5cb-ff091e5c29bd> | 3.671875 | 2,722 | Documentation | Software Dev. | 44.768218 | 236 |
Introduction and Installation of Php
What is PHP?
PHP is an acronym for Hypertext Preprocessor. It is a dynamic server side scripting language that allows an application developer to create very simple to very complex mechanisms for the web. Think of PHP as the brain and central nervous system behind your applications. PHP code can be directly mingled in with your HTML page content as long as the page has a .php extension ( myPage.php ). Or it can be scripts and class files placed on server and connected to your front-end files. Any HTML file you have can be turned into a PHP file and PHP script will run inside it.
Why Learn PHP?
- Relatively easy to learn and understand
- Processes data fast and dynamically
- Most dynamic web applications being made today have a PHP core (brain)
- Free Open Source Technology
- Sports over 700 Built-In functions that are ready to automate your programming tasks
- Works very well with MySQL Databases (PHP+MySQL are married)
- Create and populate XML files using PHP
- Communicates with Flash (back and forth)
- Time and date functions
- Mathematics to cover any need
- Can be used to create complete social networks, and online forums
- Parse file uploads
- Processes online forms and sends emails
- Imaging Libraries
- Resize Images on the fly, create shapes and colors on the fly out of nowhere
- Create files and directory folders out of thin air
- Create multidimensional data arrays, data looping, and deep data parsing
- Huge Free online resource databases for classes and functions
- The list goes on and on and on…….
Who Is Using PHP In the Programming of Their Website or Applications?
• Develop PHP
• Zen Cart
• Web Intersect
And Hundreds of Thousands More
Usually any time you can interact with a website in any way, PHP is doing its thing behind the scenes there.
PHP blends well into other useful programming languages
You have two options to enable yourself to work with PHP.
1. Build and test on your web server (easy)
Most people starting in PHP development already have a web server online. Simply create your .php files, FTP them into your web directory and the server will parse them for you automatically. Most web hosts offer PHP support, and if your host does not, consider switching to a better one.
If you do not have a web server online yet, buy a Domain Name for about $10 and set up a free or paid hosting account for that domain name. Be sure to choose PHP and not ASP if given a choice. Then you can FTP files to the server and test online.
2. Create a local testing environment (complicated for beginners)
To install a web server on your PC you should research and install these 3 things.
you can configure these three, Bu Installing WAMP server
3. What is WAMP server and how to Install it
WAMP stand for Windows Appache Mysql Php, in order to setup a Local testing server you should use this.
You can see Video tutorial on how to Install WAMP Server here.. http://hostinpakistan.com/learnjoomla/?p=13 | <urn:uuid:93e7568d-ea00-4e99-a8f3-b4d699a610e4> | 3.40625 | 674 | Product Page | Software Dev. | 57.943167 | 237 |
Algae plus salt water equals … fuel? Bilal Bomani wants to create a biofuel that is "extreme green"— sustainable, alternative and renewable. At NASA's GreenLab Research Facility, he uses algae and halophytes to create a self sustaining, renewable energy ecosystem that doesn't consume arable land or fresh water.
Bilal Bomani currently serves as the lead scientist for NASA's biofuels research program focusing on the next generation of aviation fuel. The intent is to use algae and halophytes with the goal of providing a renewable energy source that does not use freshwater, arable land or compete with food crops. | <urn:uuid:eed9527c-7d8a-4dfb-812f-9c0597ec971d> | 3.296875 | 129 | Nonfiction Writing | Science & Tech. | 31.717 | 238 |
Exploring Nonlinear Mechanical Behaviour of Rocks at LANCE
SMARTS - Spectrometer for Materials Research at Temperature and Stress
Atomic-scale stress-strain information obtained from the neutron Rietveld data indicate that the strain experienced by the crystalline quartz is ~1/5 of the macroscopic strain (the rest taken up by the grain contacts and bonds in the rock). No hints of nonlinearity whatsoever are evident in the neutron data.
Conclusion? The grain bond system (a small fraction of the total rock) is responsible for all the peculiar quasi-static nonlinearity we see.
Beamlines at the LANSCE (Los Alamos Neutron Science Center)/Lujan Center - LANSCE produces intense sources of pulsed protons and spallation neutrons from a tungsten target. Proton beam currents during all the experiments varied from 100 to 110 µA.
The Neutron Powder Diffractometer has the unique capability of simultaneous high-Q Rietveld and pair-density function analyses, enabling determination of the average and local structures of complex materials with high accuracy. The questions these experiments are designed to answer are (1) can neutrons "see" the grain bond system and if so, (2) can neutrons help to ascertain the role(s) of intergranular bonds vs. the bulk crystalline volume in the nonlinear behaviour of rocks? Results below show evidence of non-crystalline silica in a pure quartz sandstone.
Above - Rietveld analysis shows an excellent match with crystalline quartz; there are no other crystal phases in Fontainebleau sandstone.
Above - A revised model adding ~7% amorphous silica to the crystal model makes a greatly improved fit.
Above - When the PDF data (red crosses) is compared to a perfect quartz model, there is a large discrepancy in the nearest neighbor peaks.
Above - PDF data (red) of amorphous silica shows that only the nearest neighbor peaks are sharp and correspond with those of the crystal (blue).
HIPPO's proximity to the neutron spallation source and its numerous detectors mean it can watch atomic plane structures change in real time. Counting for 1 minute or less is sufficient for a Rietveld analysis of the scattering data. Scattering experiments were performed to observe the crystalline structure of sandstone samples undergoing periodic temperature changes. Modulus (resonance frequency) and temperature was tracked as a function of time. Neutron results -unit cell volume- show none of the peculiar macroscopic nonlinear behavior.
History - Modulus drop observed after a temperature change IN either direction for a sample of Berea sandstone
Sandstone sample in holder, thermocouples, and a piezoelectric source and receiver all mounted in an isothermal temperature chamber and mylar thermal radiation shielding.
Corresponding shift of frequency as temperature changed.
Plot of temperature and unit cell volume during the experiment.
Work supported by Office of Basic Energy Sciences, DOE, with Los Alamos National Laboratory Institutional Support.
HTML conversion by Jeff Simpson. | <urn:uuid:cc2dd5ff-dead-495c-b3ab-c30e87bf94c3> | 2.90625 | 652 | Academic Writing | Science & Tech. | 26.517243 | 239 |
Cosmogenic Nuclide Group
Humans live on the earth’s surface and Earth Surface Processes (ESP) are cornerstones defining fundamental boundaries for civilization. Many of these processes occur so rapidly and unexpectedly that they have daunting consequences. We are poorly equipped to predict their nature and possible impacts due to the lack of scientific understanding. In particular, the impact of current environmental change on the nature of Earth Surface Processes is hardly predictable. It is a high priority challenge for modern earth sciences to better understand such processes. One of the most promising approaches to this task is the quantitative investigation of ESP from the past to the present, and to apply the insight to current and future environmental challenges. The leading technique to realize this is the application of terrestrial cosmogenic nuclide.
The LDEO Cosmogenic Nuclide Group develops terrestrial cosmogenic nuclide techniques and applies those as chronometers and tracers in the Earth Sciences. Terrestrial cosmogenic nuclides are produced by interactions between secondary cosmic rays and near surface rocks. Our research interests cover a wide spectrum of earth scientific disciplines and include timing of ice ages, subglacial erosion rates, uplift rates of Pleistocene terraces, and a better understanding of the production systematics of cosmogenic nuclides. We apply the full spectrum of cosmogenic nuclides, including the routine extraction of 10Be, 26Al, and 36Cl. In cooperation with the LDEO noble gas group (Gisela Winckler, link), we also routinely measure cosmogenic 3He. Recently, we have pioneered the terrestrial 53Mn technique as new monitor of earth surface processes, and we also have established an extraction line for in situ 14C from quartz (LINK TO 14C LINE). | <urn:uuid:35e2c8bf-09be-4668-9037-dfb92cc9d874> | 3.15625 | 364 | About (Org.) | Science & Tech. | 18.661394 | 240 |
Kroto is now one of several prestigious individuals, including the groundbreaking Chemist Linus Pauling, who have enriched the Linfield community at an Oregon Nobel Laureate Symposium.
“The lecture-symposium was scheduled two years ago,” Director of Communications Mardi Mileham.
She mentioned that Kroto was selected to participate in the symposium by Dr. Fred Ross who retired from Linfield last spring.
Kroto is well-known for the co-discovery of the form of carbon now known as Buckminsterfullerene, or, “buckyballs” in 1985. This molecule is a spherical arrangement of 60 carbons in a pattern that resembles the stitching on soccer balls.
Up until its discovery, only two stable forms of carbon, graphite and diamond, were known to exist, Professor of Chemistry Thomas Reinert said.
He said this third stable form of carbon changed the way chemists thought about carbon and the bonds between atoms. Chemists learned that this form of carbon occurs in the universe, naturally. “It’s not just made up in a lab,” Reinert said.
Kroto discussed the importance of science and scientific education in his lecture that was interspersed with humorous remarks.
Kroto based his lecture on a quote that says science is the only thing we have to determine the truth to any degree of reliability.
“Science, for me, is a way of life,” Kroto said. He applied his scientific philosophy to several matters such as sustainability and indoctrination. Kroto stressed the importance of questioning everything and seeking evidence to support claims. He considers the acceptance of facts without evidence dangerous.
Kroto explained his “four out of five method.” He stated if you make an observation, make a hypothesis; if four out of five observations are in line with the hypothesis, you are “almost certainly right.”
Kroto’s current project is to try to teach science globally by using the Internet to share educational videos.
Professor of English Lit David Sumner commented on Kroto’s scientific emphasis saying that the sciences and humanities should work hand in hand. “A combination of the two is essential,” he said.
Senior Craig Geffre praised Kroto for his call to the researchers of natural sciences to be mindful of ethics and the outcome of their research. Kroto cited atomic bombs as examples of weapons that should not be further researched.
“Anthropologists and sociologists are careful in deliberating what the outcome of our research will be. I thought it was great that he emphasized ethics,” said Geffre.
For more information about Dr. Sir Harold Kroto and the discovery of buckminsterfullerene visit www.nobelprize.org.
Michele Wong/For the Review
Michele Wong can be reached at firstname.lastname@example.org. | <urn:uuid:dfc2156e-6208-4bc8-820a-c377aeb8d85e> | 2.546875 | 615 | Nonfiction Writing | Science & Tech. | 42.165211 | 241 |
tree-equal tree-1 tree-2 &key test test-not => generalized-boolean
Arguments and Values:
test---a designator for a function of two arguments that returns a generalized boolean.
test-not---a designator for a function of two arguments that returns a generalized boolean.
generalized-boolean---a generalized boolean.
tree-equal tests whether two trees are of the same shape and have the same leaves. tree-equal returns true if tree-1 and tree-2 are both atoms and satisfy the test, or if they are both conses and the car of tree-1 is tree-equal to the car of tree-2 and the cdr of tree-1 is tree-equal to the cdr of tree-2. Otherwise, tree-equal returns false.
tree-equal recursively compares conses but not any other objects that have components.
The first argument to the :test or :test-not function is tree-1 or a car or cdr of tree-1; the second argument is tree-2 or a car or cdr of tree-2.
(setq tree1 '(1 (1 2)) tree2 '(1 (1 2))) => (1 (1 2)) (tree-equal tree1 tree2) => true (eql tree1 tree2) => false (setq tree1 '('a ('b 'c)) tree2 '('a ('b 'c))) => ('a ('b 'c)) => ((QUOTE A) ((QUOTE B) (QUOTE C))) (tree-equal tree1 tree2 :test 'eq) => true
Side Effects: None.
Affected By: None.
The consequences are undefined if both tree-1 and tree-2 are circular.
equal, Section 3.6 (Traversal Rules and Side Effects)
The :test-not parameter is deprecated. | <urn:uuid:0dff129e-b6b0-4cf2-aef9-9316f348a147> | 3.234375 | 402 | Documentation | Software Dev. | 73.98829 | 242 |
Did a Comet Really Chill and Kill Clovis Culture?
A 130-foot-meteor created the mile-wide Meteor Crater in Arizona. The comet proposed to have impacted life in North America was significantly larger, but no crater indicating its collision has been found.
CREDIT: Dan Durda
A comet crashing into the Earth some 13,000 years ago was thought to have spelled doom to a group of early North American people, and possibly the extinction of ice age beasts in the region.
But the space rock was wrongly accused, according to a group of 16 scientists in fields ranging from archaeology to crystallography to physics, who have offered counterevidence to the existence of such a collision.
"Despite more than four years of trying by many qualified researchers, no unambiguous evidence has been found [of such an event]," Mark Boslough, a physicist at Sandia National Laboratories in New Mexico, told LiveScience.
"That lack of evidence is therefore evidence of absence."
Almost 13,000 years ago, a prehistoric Paleo-Indian group known as the Clovis culture suffered its demise at the same time the region underwent significant climate cooling known as the Younger Dryas. Animals such as ground sloths, camels and mammoths were wiped out in North America around the same period. [Wipe Out: The 10 Most Mysterious Extinctions]
In 2007, a team of scientists led by Richard Firestone of the Lawrence Berkeley National Laboratory in California suggested these changes were the result of a collision or explosion of an enormous comet or asteroid, pointing to a carbon-rich black layer at a number of sites across North America. The theory has remained controversial, with no sign of a crater that would have resulted from such an impact.
"If a four-kilometer [2.5-mile] comet had broken up over North America only 12.9 thousand years ago, it is certain that it would have left an unambiguous impact crater or craters, as well as unambiguous shocked materials," Boslough said.
Boslough, who has spent decades studying the effects of comet and asteroid collisions, was part of a team that predicted the visibility of plumes from the impact of the 1994 Shoemaker-Levy 9 comet with Jupiter.
"Comet impacts may be low enough in density not to leave craters," Firestone told LiveScience by email.
He also points to independent research by William Napier at the University of Cardiff in the United Kingdom that indicates such explosions could have come from a debris trail created by Comet Encke, which also would not have left a crater.
A large rock plunging into the Earth's atmosphere may detonate in the air without coming into contact with the ground. Such an explosion occurred in Siberia in the early 20th century; the explosive energy of the so-called Tunguska event was more than 1,000 times more powerful than the atomic bomb dropped on Hiroshima.
"No crater was formed at Tunguska, or the recent Russian impact," Firestone said.
But Boslough said this math doesn't add up. The object responsible for the Tunguska event was very small, about 130 to 160 feet (40 to 50 meters) wide, while the recent explosion over Russia was smaller, about 56 feet (17 meters). The proposed North American space rock linked with the Clovis demise is estimated to have been closer to 2.5 miles (4 kilometers) across.
"The physics doesn't support the idea of something that big exploding in the air," he said, noting that the original research team doesn't provide any explanation or models for how such a breakup might occur. [The 10 Greatest Explosions Ever]
If such a large object crashed into the Earth, the resulting crater would be too large to miss, particularly when it was only a few thousand years old, Boslough said. He pointed to Meteor Crater in Arizona, which is three times as old and formed by an object "a million times smaller in terms of explosive energy."
"Meteor Crater is an unambiguous impact crater with unambiguous shocked minerals," Boslough said. If a 2.5-mile comet had broken into pieces, it could have made a million Meteor Craters, he added.
Firestone argued that water or ice could have absorbed the impact, possibly leaving behind no crater.
Boslough disagreed. Even if the comet had plunged into the ice sheet covering much of North America, the crater formed beneath it would still be sizable. "We wouldn't be able to miss that right now — it would be obvious," Boslough said.
The arguments and evidence against the impact were published in the December 2012 American Geophysical Union monograph.
"Extraordinary claims require extraordinary evidence"
Powerful impacts are Boslough's field, but the other 15 scientists working on the paper offered up other sources of counterevidence for the existence of a collision.
"We all independently came to the conclusion that the evidence doesn't support a Younger Dryas impact," Boslough said. [Asteroid Basics: A Space Rock Quiz]
"We all came to this based on our own very narrow piece of the puzzle."
For instance, the initial team studying the event announced the discovery of a carbon-rich black layer, colloquially known as a "black mat," at a number of sites in North America. Containing charcoal, soot and nanodiamonds, such material could be formed by a violent collision.
But this isn't the only possible source.
"The things they call impact markers are not necessarily indicators of high-pressure shocks," Boslough said. "There are other processes that potentially could have formed them."
Speaking of the black mat found in central Mexico, Firestone said, "Boslough is correct that there are other black mats, but these are dated to 12,900 years ago at the time of impact." He points to independent research published this fall that located hundreds to thousands of samples.
However, radiocarbon dating of one of the sites in Gainey, Mich., suggested its samples were contaminated.
Melted rock formations and microscopic diamonds found in a lake in Central Mexico last year were also suggested as evidence for the collision, but Boslough's team disagrees with the age of the sediment layer in the region.
Boslough said the standard for indicating a strong shock occurred is pretty high in the impact community, and the findings by the original team don't meet them. Nor do they offer up any physical models that propose how an impact or airburst would have occurred — and the ones Boslough has run just don't pan out.
"It's really a stretch to claim that there was this large impact event with no crater and no unambiguous shock material, because large impacts are such rare events," Boslough said.
"When somebody is making a claim that something extraordinary happened, something out of the ordinary and with a very low probability, and they have ambiguous evidence, then the default is that it didn't happen," he continued.
"Extraordinary claims require extraordinary evidence."
Firestone stands firm.
"All the evidence has now been confirmed by others," he said.
"Boslough has no data supporting his arguments, and ignores the counter arguments of Bill Napier."
MORE FROM LiveScience.com | <urn:uuid:f3aa90d9-f56f-428a-a0b4-cef450a9b830> | 3.65625 | 1,523 | News Article | Science & Tech. | 42.966301 | 243 |
Texas Dust Storms
The same weather system that brought snow and ice to the American Midwest just after Thanksgiving 2005 also kicked up significant dust in western Texas and eastern Mexico. The winds associated with this cold front also fanned the flames of grass fires in the region, adding smoke to the mixture of aerosols. The most obvious dust cloud is a pale beige dust plume swirling through Texas and Mexico. However, a second, more orange-colored cloud of dust blows across northern Texas. Parts of northern Texas saw wind speeds around 60 miles per hour. Resulting dust storms reduced visibility to just 2.5 miles in some areas, and swamped local fire departments with calls regarding both fires and downed power lines.
Image Credit: NASA/GSFC/MODIS Land Rapid Response Team/Jeff Schmaltz | <urn:uuid:2091f67c-e700-47ea-81fd-57c4320514bc> | 3.421875 | 164 | Knowledge Article | Science & Tech. | 49.772164 | 244 |
Spider silk can be scary enough to insects to act as a pest repellant, researchers say.
These findings could lead to a new way to naturally help protect crops, scientists added.
Spiders are among the most common predators on land. Although not all spiders weave webs, they all spin silk that may serve other purposes. For instance, many tiny spiders use silk balloons to travel by air.
Science news from NBCNews.com
Researchers suspected that insects and other regular prey of spiders might associate silk with the risk of getting eaten. As such, they reasoned silk might scare insects off.
The scientists experimented with Japanese beetles (Popillia japonica) and Mexican bean beetles (Epilachna varivestis). These plant-munching pests have spread across eastern North America within the past half-century. [ Ewww! Nature's Biggest Pests ]
The beetles were analyzed near green bean plants (Phaseolus vulgaris) in both the lab and a tilled field outdoors. The investigators applied two kinds of silk on the plants — one from silkworms (Bombyx mori) and another from a long-jawed spider (Tetragnatha elongata), a species common in riverbank forests but not in the region the researchers studied.
Both spider and silkworm silk reduced insect plant-chewing significantly. In the lab, both eliminated insect damage entirely, while in the field, spider silk had a greater effect — plants enclosed with beetles and spider silk experienced about 50 percent less damage than leaves without spider silk, while silkworm silk only led to about a 10 to 20 percent reduction. Experiments with other fibers revealed that only silk had this protective effect.
"This work suggests that silk alone is a signal to potential prey that danger is near," researcher Ann Rypstra, an evolutionary ecologist at Miami University in Ohio, told LiveScience.
Rypstra was most surprised that the effect occurred even though the species involved do not share any evolutionary history together as predator and prey. This suggests "herbivores are using the silk as some sort of general signal that a spider — any ol' spider — is around and responding by reducing their activity or leaving the area," she said.
While more work will need to be done before this research might find applied use, the fact that the presence of silk alone reduced damage caused by two economically important pest insects "suggests that there could be applications in agricultural pest management and biological control," Rypstra said.
Rypstra is also interested in the chain reaction of events that silk might trigger in an ecosystem.
"For example, if an herbivore encounters a strand of silk and alters its behavior in a particular manner, does that make it more susceptible to predation by a non-spider?" Rypstra asked. "Do spiders that leave lots of silk behind have a larger impact in the food web, and how does it vary from habitat to habitat? These are just a couple of questions that we might be exploring in the near future."
Rypstra and her colleagues detailed their findings online Wednesday in the journal Biology Letters.
- Gallery: Spooky Spiders
- What Really Scares People: Top 10 Phobias
- Gallery: Dazzling Photos of Dew-Covered Insects
© 2012 LiveScience.com. All rights reserved. | <urn:uuid:2bf9f9b2-3cdc-4ce4-979e-a8d74b24efa5> | 3.96875 | 690 | News Article | Science & Tech. | 41.406379 | 245 |
SETI Pioneers by David Swift, University of Arizona Press, pp 434, $35/£32.50
The scientist at the sensitive radio receiver was baffled by the strange signals apparently coming from deep space. 'The thought flashed through my mind that the disturbances I had observed might be due to intelligent control . . . The feeling is constantly growing on me that I had been the first to hear the greeting of one planet to another.'
No, this is not a piece of science fiction. Nor is it an account of a contemporary NASA researcher into SETI (the search for extraterrestrial intelligence). The scientist was Nikolas Tesla, tuning into 'the ether' back in 1899.
Despite a few suspicions of this kind, no one pursued SETI seriously until 1959, when interest in the subject suddenly exploded. Since then, hundreds of radio telescopes around the world have been pressed into service to scan the sky ...
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DID shrinking guts and high-energy food help us evolve enormous, powerful brains? The latest round in the row over what's known as the "expensive tissue hypothesis" says no. But don't expect that to settle the debate.
The hypothesis has it that in order to grow large brains relative to body size, our ancestors had to free up energy from elsewhere - perhaps by switching to rich foods like nuts and meat, which provide more calories and require less energy to break down, or possibly by learning to cook: cooked food also requires less energy to digest.
Kari Allen and Richard Kay of Duke University in Durham, North Carolina, turned to New World monkeys to explore the hypothesis. Previous studies offer a wealth of data on the monkeys' diets and show that their brain size varies greatly from species to species. But when the pair controlled for similarities between related species, they found no correlation between large brains and small guts (Proceedings of the Royal Society B, DOI: 10.1098/rspb.2011.1311).
As Robin Dunbar at the University of Oxford points out: "It is one thing to say that the hypothesis doesn't apply to New World monkeys, and another to extrapolate that to humans."
If you would like to reuse any content from New Scientist, either in print or online, please contact the syndication department first for permission. New Scientist does not own rights to photos, but there are a variety of licensing options available for use of articles and graphics we own the copyright to.
Have your say
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Virginia Tech's Bill Hopkins holds a female wood duck, as part of the studies he and his colleagues are conducting to determine how the physiology and behavior of female amphibians, turtles and birds affect their offspring, and the consequences these interactions may have for population health. See more images and read more about wood ducks.
Credit: Photo by Kate Hasapes; courtesy Bill Hopkins, Virginia Tech
Gail Patricelli, an animal behaviorist at the University of California, Davis studies animal communication and sexual selection, with a focus on understanding the amazing diversity and complexity in animal signals. Check out the story in this Science Nation video. Credit: Science Nation, NSF
Research conducted by biologists at the University of Maryland, College Park shows that when two neighboring termite families meet within the same log, one or both families' kings and queens are killed and a new, merged, cooperative colony results. Check out the story in this audio slideshow and news release.
Credit: Zina Deretsky, National Science Foundation
According to a study by scientists at the University of Arizona, female house finches are able to change their hormonal makeup to ensure male birds hatch later, grow faster and spend less time in the nest than their sisters. Read more in this news release.
Credit: Alex Badyaev
The Integrative Organismal Systems Division (IOS) in NSF's Directorate for Biological Sciences supports research aimed at an integrative understanding of organisms. The goal is to predict why organisms are structured the way they are and function as they do. The division particularly encourages research projects that innovatively apply systems biology approaches and that lead to new conceptual and theoretical insights and predictions about integrated organismal properties that may be experimentally verified.
Scientists studying the relationship between testosterone and natural selection in an American songbird, the dark-eyed junco, reported that extreme testosterone production puts male dark-eyed juncos at a disadvantage.
A University of California, San Diego study shows that increased environmental variation causes birds to lay more eggs at a time. In addition, increased predation pressure experienced by open-nesting birds causes them to lay smaller clutches than cavity-nesting birds, literally having fewer eggs in one basket to spread the risk.
August 23, 2010
Make Way for Ducklings
What wood ducks are revealing about threats to our fine feathered friends
Parent birds know best when it comes to taking care of their babies. But, when food gets scarce and they are forced to fly longer distances to grab a bite, "egg sitting" time drops off. What impact does this have on their brood?
"I guess everybody, from a human health perspective, knows that what a mother does during pregnancy can have all sorts of effects on her babies," says Bill Hopkins, an associate professor in the Department of Fisheries and Wildlife Sciences at Virginia Tech. He is holding a duckling in his hand. It's one of many he and his team are studying. "We study how these little guys can be affected by the things that mom does."
A member of his research team, Sarah DuRant, examines an egg. "If you look really closely," she says, "you can see the embryo moving."
With the support of the National Science Foundation (NSF), ecologists Hopkins and DuRant are studying wood ducks to better understand the impact of mom's nesting behavior on her ducklings and their ability to survive.
"How much time a female spends on her nest is going to influence the temperature that the nest is at," notes DuRant. The researchers incubate eggs at different temperatures to simulate warmer and cooler nesting conditions. "What we're interested in are very, very subtle changes in temperature, maybe a degree Celsius at most," adds Hopkins.
DuRant says they already see differences in the developing embryo. "Our embryos in the lowest temperature are going to develop a little bit slower than embryos in our higher temperatures," she says.
And once the ducklings are hatched, researchers are finding that just a slightly cooler nest can dramatically alter the health and vitality of an individual.
"They may look healthy, but if you actually dig a little deeper, we see a number of physiological deficits. Their immune systems aren't developing as rapidly. They appear to be almost developmentally stunted," explains Hopkins. "We see that they have changes in terms of endocrine function; in terms of stress hormones. We see changes in thermoregulatory capacity and locomotor performance. They swim slower than the same individuals from the same clutch. Swimming is a critical part of their early survival. They've got to avoid predators."
This research is not just about wood ducks. It has implications for many birds living in conditions where their nesting behaviors and habitats are disrupted.
"If their immune system isn't functioning as well as it needs to be and disease wipes through, then those guys aren't going to make it," says DuRant. "For many species that are breeding earlier in the year, those young are going to be exposed to colder temperatures so if they can't regulate their body temperature, then they're also going to die."
Hopkins hopes these findings will improve future conservation strategies.
"If you have an area, say, that's subjected to ecotourism, where you may have a lot of disturbance around nesting areas, those sorts of areas may actually come at a cost," he says.
That could adversely affect the health and vigor of future generations. Hopkins and his team want to learn all they can about what it will take to keep these little guys thriving--and following in mom's footsteps. | <urn:uuid:488601a4-8dd1-4d73-b45b-dba4021c1e67> | 3.296875 | 1,146 | News (Org.) | Science & Tech. | 37.633754 | 248 |
S-1. Sunlight & Earth
S-1B. Global Climate
S-3.The Magnetic Sun
S-4. Colors of Sunlight
Optional: Doppler Effect
S-4A-1 Speed of Light
S-4A-2. Frequency Shift
S-4A-3 Rotating Galaxies
and Dark Matter
S-5.Waves & Photons
Optional: Quantum Physics
Q3. Energy Levels
Q4. Radiation from
One widely used property of waves is the shift in frequency when the source approaches or recedes. If the engine of a train blows its whistle as it passes by, a listener standing near the track cannot help but notice that the tone of the whistle drops as it passes.
Actually, the tone is already raised above its normal note as the engine approaches, and then drops below it as it recedes. This shift in frequency, also noted in electromagnetic waves such as light or radio, is named the Doppler Effect after its discoverer, the Austrian Christian Doppler, born in 1803.
Earlier, a somewhat similar phenomenon was discovered by the Dane Ole Roemer in 1676. The story deserves to be told because it also led to the first determination of the velocity of light.
Those were the times when the sailing ships of seafaring nations – especially, France, Spain, Britain and the Netherlands (Holland) – fought to dominate the oceans and to establish (and protect) trade routes and distant bases. In such a struggle, one technology was crucial: commanders of ships had to somehow know at all times their position in mid-ocean, that is, their latitude and longitude.
Latitude was relatively easy: the elevation of the celestial pole above the horizon (deduced, for instance, from the position of the pole star) gave that. Or else, the elevation of the Sun when it was most distant from the horizon ("solar noon"), i.e. made the greatest angle between it and the horizon, gave the latitude (after being adjusted for the day of the year). The cross staff, or a later more accurate instrument, the marine sextant (or the octant) allowed "shooting the Sun," i.e. finding its elevation above the horizon, and by combining several timed observations, its greatest elevation for that day could be derived.
Longitude was much harder. It required knowledge of the time at Greenwhich (longitude zero) when a cross staff or sextant determined that the Sun was passing local noon. For example, if the Sun passed local noon when it was 1 p.m. at Greenwich, the ship was 15° west of Greenwich, because
To get this information, the captain needed a clock which kept accurate time for a many months: it could be set in Greenwich (or set to Greenwich time at a location of known longitude), and used later to give "Greenwich time" of local noon. Such clocks ("chronometers") were in fact developed in the 1700s, but clocks of the 1600s were not accurate enough, especially on a ship that rolled and pitched, and their errors accumulated rapidly.
A less precise clock may be used, if somehow it can be constantly corrected, reset to the correct "Greenwich time" at frequent intervals. In a later era this was done using time signals obtained by radio, but in the 1600s accurately timed celestial phenomena held the greatest promise. One class of such phenomena were the eclipses of the four large moons of Jupiter, discovered by Galileo and easily seen through even a small telescope.
In particular, Io, the innermost moon of Jupiter, seemed suitable: being closest to Jupiter, Kepler's 3rd law assured that it had the fastest motion, making its entry into eclipses and out of them particularly rapid. With an orbital period of 1.77 days, Io also offered the largest number of eclipses, and every one of its orbits crossed Jupiter's shadow. (In the satellite age Io was found to have other unique features, such as sulfur volcanoes.)
Giovanni Domenico Cassini, an Italian astronomer who headed of the Paris Observatory, therefore assigned Roemer to make a table of the predicted times of Io eclipses, allowing sailors at sea to set their clocks (within a minute or so, deemed accurate enough). Roemer did so, but soon discovered that the period was not constant. When Earth (which moves faster than Jupiter) was approaching Jupiter, the observed period was shorter, and when it was receding, longer.
He guessed the reason: light did not spread instantly, but (like sound) did so at a certain speed. If Earth and Jupiter maintained a constant distance, the eclipses would have been spaced at regular intervals, equal to the orbital period of Io. When Earth is approaching, however, the return trip is shortened, compared to the time it would have taken if the distance stayed constant. When Earth is receding, the return trip is longer, and the time between eclipses is longer too
That gave Roemer convincing evidence that light spread in space with a certain velocity--later denoted by the letter c (lower case, not capital). However, he and his contemporaries had only a vague idea how big c was, because the dimensions of the solar system were uncertain. About that same time, the French astronomer Jean Richer used a telescope to estimate of the distance of Mars, and gradually, the value of c was obtained with increasing accuracy. Today it is known to an accuracy of 9 decimals, and has therefore been used to define the metre, the unit of length, replacing optical wavelengths or scratches on a metal bar kept in a vault (supposedly derived from the size of our globe).
And the problem of longitude?
It turned out that observing the eclipses of Io from a constantly moving ship, even in a calm sea, was a difficult task. Even a small telescope magnifies all motions tremendously, and early telescopes in particular showed only a small patch of the sky. Also, the method required a sky free of clouds. On the other hand, the method proved very useful for determining the longitude of ports, capes, islands and other features on land.
Consistent determinations of longitude from a moving ship had to wait for sophisticated clocks, using a balance wheel compensated for changes due to variation of temperature. One early model of such a "chronometer" accompanied Captain James Cook on his journey around the world.
(S-4A-2) The Frequency Shift and the Expanding Universe
(S-5) Waves and Photons
Timeline Glossary Back to the Master List
Author and Curator: Dr. David P. Stern
Mail to Dr.Stern: stargaze("at" symbol)phy6.org .
Last updated: 9 December 2006 | <urn:uuid:9268091d-e08f-49a1-9c2a-bfdc6d447834> | 3.859375 | 1,410 | Knowledge Article | Science & Tech. | 46.500109 | 249 |
Mechanics: Circular Motion and Gravitation
Circular Motion and Gravitation: Audio Guided Solution
A loop de loop track is built for a 938-kg car. It is a completely circular loop - 14.2 m tall at its highest point. The driver successfully completes the loop with an entry speed (at the bottom) of 22.1 m/s.
a. Using energy conservation, determine the speed of the car at the top of the loop.
b. Determine the acceleration of the car at the top of the loop.
c. Determine the normal force acting upon the car at the top of the loop.
Audio Guided Solution
Click to show or hide the answer!
b. 30. m/s/s
c. 1.9 x 104 N
Habits of an Effective Problem Solver
- Read the problem carefully and develop a mental picture of the physical situation. If necessary, sketch a simple diagram of the physical situation to help you visualize it.
- Identify the known and unknown quantities in an organized manner. Equate given values to the symbols used to represent the corresponding quantity - e.g., m = 61.7 kg, v= 18.5 m/s, R = 30.9 m, Fnorm = ???.
- Use physics formulas and conceptual reasoning to plot a strategy for solving for the unknown quantity.
- Identify the appropriate formula(s) to use.
- Perform substitutions and algebraic manipulations in order to solve for the unknown quantity.
Read About It!
Get more information on the topic of Circular Motion and Gravitation at The Physics Classroom Tutorial.
- Mathematics of Circular Motion
- Newton's Second Law - Revisited
- Situations Involving Energy Conservation
Return to Problem Set
Return to Overview | <urn:uuid:1d779db4-f950-4006-9a69-5785000fcf08> | 3.671875 | 380 | Tutorial | Science & Tech. | 64.747194 | 250 |
Should I write: [itex](1-t)[(1-t)(2-t)-2 = -(t-3)(t-1)(t)[/itex]. This is the characteristic polynomial. Thus, the roots are 3,1,0. These are the eigenvalues. If I have equations,
(1-t)x + 2y = 0
1x + (2-t)y = 0
(1-t)z = 0,
and I plug in for t=0,1,3, I find for t=3 that eigenvectors are multiples of (1,1,0). For t=1, eigenvectors are multiples of (0,0,1). For t=0, eigenvectors are multiples of (-2,1,0). The matrix is diagonalizable because T has three linearly indep. eigenvectors.
Because these vectors are linearly independent, and because the number of vectors = dim(R3), these vectors span R3. Thus, R3 is the eigenspace of T (???)
How does that look? | <urn:uuid:42c86bf5-494c-4912-bdda-c646595625e6> | 2.875 | 247 | Q&A Forum | Science & Tech. | 100.506786 | 251 |
|Oct17-07, 09:45 PM||#1|
p value (stats)
1. The problem statement, all variables and given/known data
Measurements o the percentage of enrichment of 12 fuel rods used in a nuclear reactor were reported with a sample mean of 3.26. Test the hypothesis H_0: [tex]\mu[/tex]=2.95 versus H_1: [tex]\mu\neq[/tex]2.95, and draw appropriate conclusions. Use the p-value approach.
2. Relevant equations
3. The attempt at a solution
I honestly don't know where to begin since the variance is unknown. Can someone help me out?
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Many years ago if you wanted to design something that used a microprocessor, you pretty much had to use some standard package provided by a vendor who had specialized software specific for that processor. You would use a non-standard interface to generate non-standard code to do the non-standard things that your product needed to do.
If you were to upgrade your product to use a different processor, you would start all over again. The typical product lifetime of a processor-based piece of equipment is three years, and the typical software development cycle may exceed a year. If you were trying to keep three products in the manufacturing pipeline, this would require the undivided attention of a dedicated software engineer just to keep up.
POSIX to the rescue
Every software based product requires a basic set of code plus some special code that uniquely defines your product. Most of the unique code consists of drivers and some product-specific routines. Everything else duplicates what has already been done for previous products. To help prevent duplication, a set of rules has been developed by the software community. It’s called POSIX (Portable Operating System Interface). Once code has been written to this standard, it can be reused in many other products. Linux, even at the kernel level, provides a POSIX interface for the basic functions. This is further enhanced by a runtime library which is linked with your software.
Linux and POSIX
Because of Linux and POSIX, not all of your code has to be changed if you change the hardware. Let me give you an example. Suppose you were making a weigh-scale. It is a box that is connected to a strain-gage. It has some calibration, tare, linearization, and temperature-compensation routines. It is nearly identical to last year’s model but you couldn’t get the processor anymore and, since it was a new product, you decided to change the display.
Just some drivers
If you had used Linux and the POSIX interface with the old product, you’d need to write a new display driver, and new hardware interface to the strain-gage. That’s it. Perhaps there might be a few code changes to take advantage of the new display, but otherwise major portions of last year’s code could be reused.
This might not work
If the code for the last product isn’t available anymore, isn’t documented, or was poorly written, you can’t reuse it. That’s where Route 495 Software can be helpful. We know how to write reusable code. We also know how to document it so it will not only pass your QC department’s inspection, but also use the methods, words, and interfaces about which the software community has been trained. This makes it appealing to the software engineer who is expected to reuse significant portions of it.
This webpage copyright © 2009, Route 495 Software, LLC | <urn:uuid:81fe85b6-ef5e-42a1-bb40-f3e72cc93571> | 2.984375 | 603 | About (Org.) | Software Dev. | 46.307737 | 253 |
This Site is
ICRA and SafeSurf
For All Ages!
Descriptions of the Fields of Science
Chemistry is the science of matter at or near the atomic scale. (Matter is the substance of which all physical objects are made.)
Chemistry deals with the properties of matter, and the transformation and interactions of matter and energy. Central to chemistry is the interaction of one substance with another, such as in a chemical reaction, where a substance or substances are transformed into another. Chemistry primarily studies atoms and collections of atoms such as molecules, crystals or metals that make up ordinary matter. According to modern chemistry it is the structure of matter at the atomic scale that determines the nature of a material.
Chemistry has many specialized areas that overlap with other sciences, such as physics, biology or geology. Scientists who study chemistry are called chemists. Historically, the science of chemistry is a recent development but has its roots in alchemy which has been practiced for millennia throughout the world. The word chemistry is directly derived from the word alchemy.
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IN THE TANK: The Daya Bay experiment currently employs six detectors, with a total of 120 metric tons of liquid detector material, to register passing neutrinos. Image: Roy Kaltschmidt, Lawrence Berkeley National Laboratory
Neutrinos are devious little particles. Only in the late 1990s were they shown to have mass, after decades of head-scratching hints to that effect. They can oscillate between three neutrino types, or "flavors," changing their identity on the fly. And, perhaps most famously, they were accused just last year of breaking cosmic law by traveling faster than light. (The jury is out, but an acquittal appears imminent.)
Now investigators are just a bit closer to figuring out the neutrino's modus operandi. A collaboration of physicists says it has measured one of the key descriptors of the neutrino's flavor-changing behavior—a number called theta 13 (pronounced "theta one three"). That number, known as a mixing angle, describes the probability that an electron neutrino's antiparticle, the electron antineutrino, will oscillate into another flavor over a relatively short distance. (Each of the three neutrino flavors—electron, tau and muon—has its own antiparticle partner.) Two other neutrino oscillation parameters, or mixing angles, have already been measured, but theta 13 is relatively small compared with the other two and has proved harder to pin down.
Since last year a group of physicists has been trying to measure theta 13 by tracking antineutrinos given off by a large Chinese nuclear power plant. The Daya Bay Reactor Neutrino Experiment collaboration built a series of six detectors, some near the reactors and some more than a kilometer farther away, to track how electron antineutrinos morph into other flavors as they travel through space. Because the detectors are tuned to identify only electron antineutrinos, any oscillation means that the neutrinos will escape detection—that is, they will seem to disappear. Other experiments have taken the opposite tack, looking for the appearance of electron neutrinos in a beam carrying other types of neutrinos.
In just two months of data, the distant set of detectors registered more than 10,000 hits by electron antineutrinos. But that is only 94 percent as many as would be naively expected by extrapolating from the detectors closest to the nuclear reactors. That means that a substantial fraction had oscillated to another flavor on their relatively short journey. "What we're seeing now is this disappearance of [electron antineutrinos] is at the 6 percent level," says neutrino physicist Karsten Heeger of the University of Wisconsin–Madison, a member of the Daya Bay collaboration. "It's a fairly large effect." Heeger presented the experimental results March 8 at a symposium at Duke University, and the group has submitted its study to Physical Review Letters.
The experiment is not even fully built yet—a seventh and eighth detector are in the works—but already the Daya Bay team has observed enough disappearances to quantify how the process works. The new estimate, which falls within previous limits set by other experiments, establishes that theta 13 is not equal to zero, and in fact is relatively large compared with what was plausible in light of other recent results. A zero value for theta 13 would mean that electron neutrinos would not appear in beams of muon neutrinos or, in the Daya Bay case, that electron antineutrinos would not disappear by the time they reached the far detectors. Another reactor experiment, called KamLAND, has also registered the disappearance of antineutrinos over much larger distances, where the oscillation is described by the mixing angle theta 12, rather than theta 13.
"We are the first experiment that measures it and shows that it is nonzero," Heeger says of theta 13. "There have been recent indications, but none of the other results were significant enough to match what we physicists call a discovery." The Daya Bay group claims better than 5-sigma evidence in support of a nonzero value for theta 13. 5 sigma, or five standard deviations, implies that the finding has only a one-in-several-million chance of being caused by a statistical fluke. | <urn:uuid:47264ba4-bbe4-4982-b518-14319bf1a0b8> | 3.578125 | 909 | News Article | Science & Tech. | 32.496085 | 255 |
"World Must Plan For Climate Emergency: Report"
"LONDON -- Humans may have to reset the Earth's natural thermostat and develop new technologies like reflecting sunlight back into space if climate talks fail, Britain's top science academy said on Tuesday.
So-called geoengineering was not a quick fix but may be needed to head off planetary catastrophe and so deserved more research as an insurance policy, the Royal Society said in a report, "Geoengineering the climate."
Such technologies were not an alternative to cutting emissions, however, the report stressed.
Political efforts to curb greenhouse gases are in the spotlight three months before a U.N-led meeting meant to clinch a new climate treaty to replace the Kyoto Protocol.
"Nothing should divert us from the priority of reducing global carbon dioxide emissions and ensuring that the December meeting in Copenhagen does lead to real progress," said Royal Society President Martin Rees.
"But if such reductions achieve too little too late there will be surely pressure to contemplate a plan B," he told an audience at the launch of the report in central London."
Source: Reuters, 09/02/2009 | <urn:uuid:088ff32c-3590-441a-9d16-aae6ab063d69> | 2.53125 | 230 | News Article | Science & Tech. | 33.775 | 256 |
A group of researchers at DTU Space is developing an observatory to be mounted on the International Space Station. Called ASIM, the observatory will among other things photograph giant lightning discharges above the clouds. The objective is to determine whether giant lightning discharges affect the Earth’s climate.
The question is whether giant lightning discharges, which shoot up from the clouds towards space, are simply a spectacular natural phenomenon, or whether they alter the chemical composition of the atmosphere, affecting the Earth’s climate and the ozone layer.
In recent years, scientists at DTU Space have studied giant lightning using high-altitude mountain cameras. From time to time, the cameras have succeeded in capturing low-altitude lightning flashes which have shot up from a thundercloud. The International Space Station provides a clear view of these giant lightning discharges, and the opportunity to study them will be significantly improved with the introduction of the observatory.
The researchers will also use ASIM to study how natural and man-made events on the ground – such as hurricanes, dust storms, forest fires and volcanic eruptions – influence the atmosphere and climate. | <urn:uuid:64609457-8d80-4c2f-9854-ad43579b4866> | 3.90625 | 231 | Knowledge Article | Science & Tech. | 24.952379 | 257 |
Want to stay on top of all the space news? Follow @universetoday on Twitter
Currently, astronomers have two competing models for planetary formation. In one, the planets form in a single, monolithic collapse. In the second, the core forms first and then slowly accretes gas and dust. However, in both situations, the process must be complete before the radiation pressure from the star blows away the gas and dust. While this much is certain, the exact time frames have remained another matter of debate. It is expected that this amount should be somewhere in the millions of years, but low end estimates place it at only a few million, whereas upper limits have been around 10 million. A new paper explores IC 348, a 2-3 million year old cluster with many protostars with dense disks to determine just how much mass is left to be made into planets.
The presence of dusty disks is frequently not directly observed in the visible portion of the spectra. Instead, astronomers detect these disks from their infrared signatures. However, the dust is often very opaque at these wavelengths and astronomers are unable to see through it to get a good understanding of many of the features in which they’re interested. As such, astronomers turn to radio observations, to which disks are partially transparent to build a full understanding. Unfortunately, the disks glow very little in this regime, forcing astronomers to use large arrays to study their features. The new study uses data from the Submillimeter Array located atop Mauna Kea in Hawaii.
To understand how the disks evolved over time, the new study aimed to compare the amount of gas and dust left in IC 348′s disc to younger ones in star forming regions in Taurus, Ophiuchus, and Orion which all had ages of roughly 1 million years. For IC 348, the team found 9 protoplanetary disks with masses from 2-6 times the mass of Jupiter. This is significantly lower than the range of masses in the Taurus and Ophiuchus star forming regions which had protoplanetary clouds ranging to over 100 Jupiter masses.
If planets are forming in IC 348 at the same frequency in which they form in systems astronomers have observed elsewhere, this would seem to suggest that the gravitational collapse model is more likely to be correct since it doesn’t leave a large window in which forming planets could accrete. If the core accretion model is correct, then planetary formation must have begun very quickly.
While this case don’t set any firm pronouncements on which model of planetary formation is dominant, such 2-3 million year old systems could provide an important test bed to explore the rate of depletion of these reservoirs. | <urn:uuid:dd183d74-6efe-4b52-a5fd-55d21cf5c3b4> | 4.09375 | 545 | Truncated | Science & Tech. | 42.653072 | 258 |
In a city of tweeting food trucks and Michelin-star restaurants, it was only a matter of time before San Francisco’s fusion-food culture found a way into a chemistry class.
After all, chemistry is what we taste when we bite into a chocolate-drizzled double scoop of destabilized fat globules and Fragaria ananassa. We just call it a strawberry ice cream sundae.
Tami Spector, professor of chemistry, introduced the class, called Molecular Gastronomy, in spring 2011. It focuses on the physical and chemical processes of food and drink preparation.
The idea of the course is to introduce non-science students, many of whom find memorizing chemical formulas and reactions mind-numbing, to the intricacies of molecular chemistry using an accessible and interactive approach. Michelle Cancellier ’12, an English major, said the class helped her and other humanities majors understand the abstract concepts that underlie chemistry—such as polymers, ionic charge, and chemical bonds—which can make the subject so challenging.
Spector incorporates common foods into the science lessons, including an in-class experiment that separates caffeine from tea to illustrate solubility and extraction. Another lesson has students whip up a batch of mayonnaise to learn about emulsions. Working with a palette of flavors from sweet to savory, students have isolated clove oil, created ice cream, pickled vegetables, and baked soufflés.
And they walk away from the course with a scientifically educated palate. | <urn:uuid:54bd4fa6-9d20-4541-87b9-baddceea04f3> | 2.78125 | 314 | News Article | Science & Tech. | 28.33549 | 259 |
Comparison of water in two adjacent watersheds before and after implementing a brush management strategy in one of the watersheds helps us see what water resource characteristics are sensitive to brush management and how.
Changes in the way communities address potential problems with stormwater runoff may affect surface waters. This study combines geographic with hydrologic analyses to better understand the effects of the management strategies.
Study of the effects of the practice of cycling municipal nutrient-enriched wastewater from holding ponds through forested wetlands. Studies were in the Cypiere Perdue Swamp, Louisiana, and the Drummond Bog, Wisconsin.
Reviews how coal fires occur, how they can be detected by airborne and remote surveys, and, most importantly, the impact coal-fire emissions may have on the environment and human health, especially mercury, carbon dioxide, carbon monoxide, and methane.
The USGS reviews and prepares technical comments on environmental impact statements and establishes policies to implement the National Environmental Policy Act (NEPA). Site has links to environmental laws and regulations including NEPA.
Wetlands and oil wells shouldn't mix, but in some areas they do. This explains what problems may arise and how we study the effects of highly salty water produced by oil wells when it leaks into nearby wetlands and streams. | <urn:uuid:bfd6d5a9-0ff7-493f-be13-62a7869b0cf1> | 2.890625 | 257 | Content Listing | Science & Tech. | 23.707624 | 260 |
During the week of May 13th, the CO2 level at the Mauna Loa Observatory in Hawaii topped 400 ppm repeatedly. Daily levels of CO2 can vary due to weather, and there are seasonal trends as well. The level of atmospheric greenhouse gases continues to increase, now over 120 ppm since the Industrial Revolution began. For more on the Keeling Curve, see http://keelingcurve.ucsd.edu/. Find out more about greenhouse gases and warming.
The week of May 19 brings dozens of tornadoes to Tornado Alley in the states of Oklahoma, Kansas, Iowa, Illinois and Missouri. On May 20th, a massive tornado struck Moore, Oklahoma, devastating communities - destroying over 100 homes and hitting two elementary schools and a hospital - with many casualties and deaths. Our thoughts are with our friends and colleagues suffering from these storms. For more on the May 20th storms, see the NOAA Storm Prediction Center Storm Report.
Did you know that individuals donít evolve, but populations do?
Did you know that the Japanese god Susanowo was the god of the sea and storms, and that he had a terrible temper?
Earth and Space Science Concept of the Day
Do you know what this word or phrase means?
xDip-slip fault : Dip-slip faults are inclined fractures where the blocks have mostly shifted vertically. If the rock mass above an inclined fault moves down, the fault is termed normal, whereas if the rock above the fault moves up, the fault is termed reverse.
Tiny variations in the isotopic composition of silver in meteorites and Earth rocks are helping scientists put together a timetable of how our planet was assembled, beginning 4.568 billion years ago. Results...Read more | <urn:uuid:9316d379-1f75-4e3f-992c-57d24c0b89af> | 3 | 353 | Content Listing | Science & Tech. | 57.035238 | 261 |
The heaviest known insects are the Goliath beetles of equatorial Africa. One fully grown male was found to weigh 3.5 ounces. (almost as much as a handful of quarters)
The heaviest human in medical history was Jon Brower Minnoch, who weighted 392 lbs. in 1963, 700 lbs. In 1966, and 975 lbs. in 1976. After being admitted to a hospital in 1978 from heart and respiratory failure, a doctor estimated that Jon weighted over 1300 pounds. When he died in 1978, he weighed more than 798 pounds.
The larva of the Polyphemus moth consumes an amount equivalent to 86,000 times it own birth weight in the first 56 days of life. In human terms, this would be like a 7 pound baby taking in 301 tons of nourishment. That is a lot of baby food!
Highest g Force
The click beetle averages 400g when "jack-knifing" into the air to escape predators. One specimen that jumbed to a height of 11.75 inches was calculated to have endured a peak brain deceleration of 2300g by the end of the movement. A recorded human example is that of David Purley, a race car driver who survived a deceleration from 108 mph to 0 in 26 inches in England in 1977. His g force was estimated to 179.8g. He suffered 29 fractures, 3 dislocations, and 6 heart stoppages!
Female mosquitoes hold the record in this category. They need a lot of protein in order to lay eggs. They obtain this protein by drinking the blood of reptiles, birds, or mammals. Sometimes a mosquito will triple her body weight with just one meal of blood. For a 100 pound human to imitate this feat, he would have to consume 36 gallons of liquid at one sitting.
The fastest moving insects are certain large tropical cockroaches. The record is 3.36 mph, or 50 body lengths per second. Tiger beetles are also quite fast, as they scurry after their prey. They can often be seen zipping across a road, their bright metallic colors flashing in the sun. The fastest human ever recorded was Carl Lewis, who ran 100 meters in 9.86 seconds in 1991 in Tokyo, Japan.
The champion jumper among insects is the common flea. In one experiment, a flea performed a long jump of 13 inches, and a high jump of 7.75 inches. If a human could jump like a flea, we would be able to jump 853 feet, which would be like jumping from street level to the 70th floor of the Empire State Building. The champion human high jumper is Javier Sotomayor of Cuba, who jumped 8 ft. 0 in. in San Juan, Puerto Rico.
The ant may be tiny, but for his size he is one of the "giants" of the insect world. With his strong jaws he is able to carry 50 times his own weight. That would be like a human trying to carry a baby elephant. Among human strongmen, the record is held by Leonid Taranenko of Russia, who lifted a whopping 1,047 pounds in Australia in 1988.
The monarch butterfly is capable of flying 2,000 miles from Canada to Mexico and parts of California. Millions migrate every autumn, often stopping in the same rest spots each year. In early spring and summer, returning females travel north in relays, new generations replacing old, laying their eggs along the way. In comparison, the longest human-powered flight ever documented was when Kanellos Kanellopoulos averaged 18.5 mph in his 112 foot wingspan machine from Crete to the island of Santorini, Greece, flying 74 miles.
Other Interesting Tid-bits
Loudest Insect - The loudest of all insects is the male cicada. At 7,400 pulses per minute, its tymbal organs produce a sound detectable over a quarter of a mile away.
Best Stunt Flyer - Large dragonflies are not only super fast flyers, they are also masters of maneuverability! Many kinds of dragonflies can hover, fly backward, turn around quickly in mid-air, and land in an instant.
Longest Insect - The longest insect in the world is the tropical walking stick. Females have been measured at 13 inches in body length. It looks just like a slender twig, which is how it blends in with its surroundings.
Fastest Flyer - Modern experiments have established that the highest maintainable air speed of any insect, including the deer bot-fly, hawkmoths, and horseflies is 24 mph, rising to a maximum of 36 mph for short bursts by some large dragon flies.
Official State Insects and Butterflies of the United States
Many states have adopted official state insects and/or butterflies in recent years. They have done this to remind citizens of the vital role that insects play in our lives. As of December 31, 1995, 34 states have officially designates state insects and/or butterflies, and this information is summarized below. You will find an alphabetic list of the states that have official state insects and/or butterflies (along with the name of the insect), as well as a list of insects (and the states that have adopted them s their official symbols).
State Insects and Butterflies Listed by States
Alabama monarch butterfly Arkansas honey bee California California dogface butterfly Colorado Colorado hairstreak butterfly Connecticut European praying mantis Delaware convergent ladybird beetle Florida giant swallowtail butterfly Georgia honey bee (insect); tiger swallowtail (butterfly) Illinois monarch butterfly Iowa ladybug Kansas honey bee Kentucky viceroy butterfly Louisiana honey bee Maine honey bee Maryland Baltimore checkerspot butterfly Massachusetts ladybug Mississippi honey bee (insect); spicebush swallowtail (butterfly) Missouri honey bee Nebraska honey bee New Hampshire Ladybug New Jersey honey bee New Mexico tarantula hawk wasp New York nine-spotted ladybird beetle North Carolina honey bee Ohio ladybug (insect); tiger swallowtail (butterfly) Oregon Oregon swallowtail butterfly Pennsylvania firefly South Carolina Carolina mantis South Dakota honey bee Tennessee ladybug and firefly Utah honey bee Vermont monarch butterfly Virginia tiger swallowtail butterfly Wisconsin honey bee Wyoming western swallowtail butterfly
State Insects and Butterflies Listed by Species
Baltimore checkerspot butterfly Maryland California dogface butterfly California Carolina mantis South Carolina Colorado hairstreak butterfly Colorado European praying mantis Connecticut Firefly Tennessee and Pennsylvania Honey bee Arkansas, Georgia, Kansas, Louisiana, Maine, Missouri, Nebraska, New Jersey, North Carolina, South Dakota, Utah and Wisconsin Ladybird beetles/ladybugs Delaware (convergent), Iowa, Massachusetts, New York (nine-spotted). and Ohio Swallowtail butterflies Florida (giant), Georgia (tiger), Mississippi (spicebush), Ohio (tiger), Oregon (Oregon), Virginia (tiger), and Wyoming (western) Tarantula hawk wasp New Mexico Viceroy butterfly Kentucky
Is your state on the list? If not, you might want to help initiate a campaign to have a representative insect and/or butterfly designated as one of your official state symbols.
The first step is to collect "nominations" from friends, family, and classmates. Have them think of an insect and/or butterfly that would make a good symbol for your state. After a while you should have a list of possible candidates and an idea of how popular each nominee is. Now comes the hard part - selecting one candidate to present to state legislators. Perhaps you might narrow the field to two or three of the most popular nominees and have a run off "election."
Once you have the possibilities narrowed down to a single candidate you will need to begin building a rationale for designating your insect candidate as the official state insect (or butterfly). Why is your insect candidate the best choice? How does it fit into your state's history or culture? How popular is the choice (collect signatures on a petition). All of this information will be useful to you when you go looking for a legislative sponsor or sponsors to help you introduce a commemorative bill into the house and senate (start with the representative for your district first). The commemorative bill will most likely go to a committee first, at which time you (and others will have an opportunity to speak for or against the bill), but if you are persistent and well prepared you might be responsible for your state adopting an official state insect or butterfly!
The Amazing Animal Quiz
Introduction - Insects and their relatives (arthropods) are some of the most amazing animals that inhabit our world, yet most of us rarely give them credit for their incredible abilities. The "Amazing Animal Quiz" can help you and your students "tune in" to the incredible world of arthropods and open their eyes and minds to learning more about them. Hopefully after students complete this exercise they will have a better appreciation for the amazing abilities of arthropods.
Getting started - This quiz is really quite simple and makes a great introduction to a unit on insects and other arthropods. Before starting, have students number a piece of paper from 1-25 down the left-hand side. Tell the students that you are going to read a series of statement that describe animal activities (don't bias them by mentioning insects or arthropods at this time) and that you want them to right down the name of any one animal that they can think of that fits the description you have given.
Name An Animal That...
- ...raids the garbage
- ...is cold blooded
- ...hides from other animals by using camouflage
- ...changes shape as it grows
- ...is poisonous and covered with scales
- ...lives in the ground
- ...is capable of flying
- ...attacks and devours (eats) other animals
- ...migrates long distances
- ...gathers and stores food
- ...sings to attract a mate
- ...hibernates as an adult
- ...eats wood
- ...lives longer than 40 years
- ...is striped
- ...lives on another animal
- ...spends part of its life cycle in the water
- ...drinks nectar from flowers
- ...lays eggs
- ...has big back legs and is a good hopper
- ...catches their prey with traps
- ...is active mostly at night
- ...is brightly colored
- ...is covered with hairs
- ...gives off a foul odor
Scoring the quiz. After administering the quiz, have the students score themselves in the following manner: 1 point for each mammal named, 3 points for each bird, reptile, amphibian, or fish names, and 5 points for each arthropod (insect, spider, etc.) names. As you can see in this exercise you get more points when you answer with arthropod names. A few of the possible arthropod (insect/spider) answers are:
- fly/maggot, carrion beetle
- any insect or other arthropod
- walkingstick, underwing moth, crab spider
- any insect or other arthropod
- monarch butterfly
- ant, yellowjacket, white grub/beetle
- fly, bee, wasp, ant, moth, butterfly, beetle, bug, grasshopper, dragonfly, mayfly, caddisfly, in fact most adult insects.
- Praying mantis, ladybird beetle, aphidlion, wolf spider, tarantula, centipede
- Monarch butterfly, painted lady butterfly, green darner dragonfly, leafhopper
- Ant, honey bee
- Cicada, cricket, katydid
- Morning cloak butterfly, ladybird beetles
- Termite, wood-boring beetle (not ants)
- Queen termite
- Bee, monarch (caterpillar), swallowtail (caterpillar), beetle
- Louse, flea, tick
- Dragonfly, damselfly, mosquito, stonefly, mayfly, caddisfly
- Butterfly, moth, bee, fly
- Any insect or other arthropod (except a few aphids and roaches)
- Grasshopper, cricket, leafhopper, flea, flea beetle
- Antlion, spider
- Moth, most beetle
- Many butterflies and beetles
- Mosquito, caddisfly, and many caterpillars
- Stink bug, bombardier beetle, black swallowtail caterpillar
Source:Young Entomologists' Society, Inc., Minibeast World of Insects and Spiders, by Gary A. Dunn, M.S., F.R.E.S., Director of Education
- During a single meal, a female mosquito can drink her own weight in blood.
- Some mayflies live 24 hours or less as adults.
- The smallest insect ever discovered is a hairy-winged beetle from the tropics. It measures 1/100 of an inch (.25 mm) in length.
- The longest insect ever found is a tropical stick insect from Asia. Some of the females get to be over a food (30cm) in length.
- Over one million different kinds of insects have been discovered. This is twice the total of all other kinds of animals put together.
- A swarm of desert locusts (of the grasshopper family), containing over 1000 million insects, has covered an estimated area of 2000 square miles (5200 KM2). Swarms of locusts have been seen at sea 1200 miles from land (1920 km).
- Bombardier beetles can shoot a hot, smelly liquid from their abdomen that is 212 ° F (100° C).
- Fireflies aren't the only light-producing insects. Some click beetles, springtails, and gnats also light up.
- There is a fly in California called the petroleum fly that lives and breeds in petroleum.
- The largest animal in Antarctica that lives strictly on land is a wingless fly less than 1/4 of an inch (6 mm) long.
- The color a head louse will be as an adult can depend on the color of the person's hair is living in. For example, a louse living in blond hair would most likely be alight color; one living in black hair would be dark.
- A cockroach can live nine days without its head.
- Fleas can jump 200 times the length of their bodies.
- Some queen termites live as long as 50 years.
- The atlas moth of India is one of the world's largest insects. It measures 12 inches (30 cm) from wingtip to wingtip.
- A tiny insect called a biting midge can beat its wings 1000 times a second.
- How many flowers must honey bees tap to make one pound of honey?
- Two million
- How far does a hive of bees fly to bring you one pound of honey?
- Over 55,000 miles
- How much honey does the average worker honey bee make in her lifetime?
- 1/12 teaspoon
- How fast does a honey bee fly?
- About 15 miles per hour
- How much honey would it take to fuel a bee's flight around the world?
- About one ounce
- Why are honey bees sometimes called "white man's flies?"
- North American natives called honey bees this because they were brought to North America by European colonists.
- What is mead?
- Honey wine
- How long have bees been producing honey from flowering plants?
- 10-20 million years
- What Scotch liqueur is made with honey?
- How many sides does each honeycomb cell have?
- What is the U.S. per capita consumption of honey?
- What state is known as the beehive state?
- How many wings does a honey bee have?
- How many beekeepers are in the United States?
- An estimated 211,600
- How many honey-producing colonies of bees are there in the United States?
- The USDA estimates that there are approximately 3 million honey producing colonies. This estimate is based on beekeepers who manage five or more colonies.
- Hall of Fame Trivia Bugs
- How many flowers does a honey bee visit during one collection trip?
- 50 to 100
- How do honey bees communicate with one another?
- "Dancing." Honey bees do a dance which alerts other bees where nectar and pollen was located. The dance explains directions and distance. Bees also communicate with pheromones.
- What does "super" mean to a beekeeper?
- The super is the hive box in which honey is stored.
Source:National Honey Board | <urn:uuid:db38593a-4cb9-4b79-b9fe-f2dffe4b9b4b> | 3.171875 | 3,480 | Knowledge Article | Science & Tech. | 56.895535 | 262 |
Evidence from caves in Siberia indicates that a global temperature increase of 1.5° Celsius may cause substantial thawing of a large tract of permanently frozen soil in Siberia. The thawing of this soil, known as permafrost, could have serious consequences for further changes in the climate.
Permafrost regions cover 24 percent of the land surface in the northern hemisphere, and they hold twice as much carbon as is currently present in the atmosphere. As the permafrost thaws, it turns from a carbon sink (meaning it accumulates and stores carbon) into a carbon source, releasing substantial amounts of carbon dioxide and methane into the atmosphere. Both of these gasses enhance the greenhouse effect.
By looking at how permafrost has responded to climate change in the past, we can gain a better understanding of climate change today. A team of international researchers looked at speleothems, such as stalagmites, stalactites, and flowstones. These are mineral deposits that are formed when water from snow or rain seeps into the caves. When conditions are too cold or too dry, speleothem growth ceases, since no water flows through the caves. As a result, speleothems provide a detailed history of periods when liquid water was available as well as an assessment of the relationship between global temperature and permafrost extent.
Using radioactive dating and data on growth from six Siberian caves, the researchers tracked the history of permafrost in Siberia for the past 450,000 years. The caves were located at varying latitudes, ranging from a boundary of continuous permafrost at 60 degrees North to the permafrost-free Gobi Desert.
In the northernmost cave, Lenskaya Ledyanaya, no speleothem growth has occurred since a particularly warm period around 400,000 years ago—the growth at that time suggests water was flowing in the area due to a melt in the permafrost. The extensive thawing at that time allows for an assessment of the warming required globally to cause a similar change in the permafrost boundary. Global temperatures at that time were only 1.5°C warmer than today, suggesting that we could be approaching a critical point at which the coldest permafrost regions would begin to thaw.
Not only will increasing global temperatures cause substantial thawing of permafrost, but it may also create wetter conditions in the Gobi Dessert, based on data from the southern-most cave obtained for the same time period. This suggests a dramatically changed environment in continental Asia.
Aside from changes in temperature and precipitation, thawing permafrost enables coastal erosion and the liquefaction of ground that was previously frozen. This poses a risk to the infrastructure of Siberia, including major oil and gas facilities. | <urn:uuid:867e4ca7-5a93-4c6d-b021-8088aa153645> | 4.625 | 570 | News Article | Science & Tech. | 33.777143 | 263 |
NASA’s Solar Dynamics Observatory has had virtually unbroken coverage of the sun’s rise toward solar maximum, the peak of solar activity in its regular 11-year cycle. This video shows those three years of the sun at a pace of two images per day.
These noteworthy events appear at the following times in the video:
00:30;24 Partial eclipse by the moon
00:31;16 Roll maneuver
01:11;02 August 9, 2011 X6.9 Flare, currently the largest of this solar cycle
Video description: The Sun unleashed a medium-sized solar flare that is visually spectacular. The large cloud of particles mushroomed up and fell back down looking as if it covered an area of almost half the solar surface.
Two NASA spacecrafts observed this event from three different view-points.
Image description: At the end of August, a filament from the sun suddenly erupted into space. The filament had been held up for days by the Sun’s ever changing magnetic field and the timing of the eruption was unexpected. Learn more about the eruption.
Image from the Solar Dynamics Observatory at NASA’s Goddard Space Flight Center
Image description: Should you put sunscreen on infants? Not usually. The best approach is to keep infants under 6 months out of the sun, especially between 10:00 AM and 2:00 PM.
But when you are outside together, here are some of the most important ways to protect your infant from the harmful rays of the sun: an umbrella and brimmed hat for shade, a cooler for liquids, a bottle for hydration, and clothing for covering the skin.
Image description: These images show a solar flare as observed on January 23. You can see the sun’s surface brighten as gas was superheated and magnetically supercharged. In the far right image, there is a stream of solar material flowing into space, likely solar protons and a coronal mass ejection.
Solar flares and coronal mass ejections are not a danger to humans on Earth. The planet’s magnetic field and atmosphere deflect and absorb the energy. Sun storms can pose some risks to astronauts, and upset science, military, and communications satellites. | <urn:uuid:520aab0d-fde8-4b8b-abbf-fde142a3feea> | 3.40625 | 454 | News (Org.) | Science & Tech. | 51.193034 | 264 |
Over 4 billion years ago the young and barren Earth was being buffeted by meteor strikes, and that violent bombardment could have created the first amino acids that then gave rise to the origin of life on the planet, a new study suggests. The hellish temperatures and pressures generated when an extraterrestrial object strikes Earth at speeds of several kilometers per second are enough to shatter and vaporize rock…. Yet part of such an immense burst of energy can trigger chemical reactions that generate complex organic substances from basic inorganic ingredients, says Takeshi Kakegawa [Science News].
Previously, researchers have suggested that organic molecules may have been created elsewhere in the universe and were brought to Earth by meteors. But the new study, in which researchers simulated the impact of meteorites in the primordial ocean, argues that the organic molecules could have been synthesized from the inorganic molecules already present on the planet when the meteorites crashed into the ocean. Other researchers have suggested similar processes for the creation of organic molecules on Earth, including lightning strikes or chemical reactions surrounding hot, volcanic vents in the deep sea.
In the study, published in Nature Geoscience [subscription required], the researchers fired meteorite-like balls of iron and carbon into a mixture of water and ammonia, meant to resemble the oceans billions of years ago. In the experiment, the researchers found that the iron and carbon were heated by the impact and reacted with hydrogen and nitrogen to form biomolecules, including fatty acids, amines and the amino acid glycine [Cosmos Online]. Amines are the building blocks for more complex amino acids, and fatty acids are found in cell membranes.
While experts describe the results as plausible, the research hasn’t won over everyone. “It’s neat to show that you could harness the energy of impacts to create organic bonds,” says Jennifer Blank, an astrobiologist at the SETI Institute in Mountain View, Calif. But she fears that theories of life’s origin may never move beyond the hypothetical. “As someone in the general field, one of the frustrations, of course, is that we’re never going to know the answer,” she says. “But as another mechanism for contributing to the inventory of organic compounds, this is cool” [Scientific American].
80beats: New Results from a 1953 Experiment Offer Hints to the Origin of Life
80beats: The Earth’s Oldest Diamonds May Show Evidence of Earliest Life
DISCOVER: Life’s Fifth Element Came From Meteors | <urn:uuid:5bf43055-b25f-4836-87bd-ac23a3404a0b> | 3.8125 | 528 | News Article | Science & Tech. | 24.417317 | 265 |
Douglass Jacobs, an associate professor of forestry and natural resources, found that American chestnuts grow much faster and larger than other hardwood species, allowing them to sequester more carbon than other trees over the same period. And since American chestnut trees are more often used for high-quality hardwood products such as furniture, they hold the carbon longer than wood used for paper or other low-grade materials.
"Maintaining or increasing forest cover has been identified as an important way to slow climate change," said Jacobs, whose paper was published in the June issue of the journal Forest Ecology and Management. "The American chestnut is an incredibly fast-growing tree. Generally the faster a tree grows, the more carbon it is able to sequester. And when these trees are harvested and processed, the carbon can be stored in the hardwood products for decades, maybe longer."
At the beginning of the last century, the chestnut blight, caused by a fungus, rapidly spread throughout the American chestnut's natural range, which extended from southern New England and New York southwest to Alabama. About 50 years ago, the species was nearly gone.
New efforts to hybridize remaining American chestnuts with blight-resistant Chinese chestnuts have resulted in a species that is about 94 percent American chestnut with the protection found in the Chinese species. Jacobs said those new trees could be ready to plant in the next decade, either in existing forests or former agricultural fields that are being returned to forested land.
"We're really quite close to having a blight-resistant hybrid that can be reintroduced into eastern forests," Jacobs said. "But because American chestnut has been absent from our forests for so long now, we really don't know much about the species at all."…
Douglass Jacobs examines a young hybrid of the American chestnut. He expects the trees could be reintroduced in the next decade. (Purdue University file photo/Nicole Jacobs) | <urn:uuid:ade2c38d-a45b-4987-9c84-8d2fc184da53> | 3.84375 | 396 | Personal Blog | Science & Tech. | 35.308634 | 266 |
int WidthInInches(int feet);
// Initialize variables by calling functions.
int feet = WidthInFeet();
int wd = WidthInInches(feet);
// Display results.
std::cout << "Width in inches = " << wd;
std::cout << "Enter width in feet: ";
std::cin >> feet;
int WidthInInches(int feet)
return feet * 12;
I'm a new to C++ and I understand that it reads up to down. However, I don't understand how the last part could return a number and then that number is returned to the out line in the main function. Can someone please explain this? | <urn:uuid:a1a9e390-3568-45d2-be7e-695120f07aa9> | 3.15625 | 150 | Documentation | Software Dev. | 73.456759 | 267 |
First tropical depression of the season may form from 92L
An unusually large and well-developed African tropical wave for so early in the season has developed midway between the coast of Africa and South America. The storm was designated Invest 92L by the National Hurricane Center yesterday, and has a good chance of becoming the first tropical depression of the Atlantic hurricane season. Surface winds measured by the 8:23am EDT pass of the European ASCAT satellite revealed that 92L already has a closed surface circulation, though the circulation is large and elongated. Top winds seen by ASCAT were about 25 mph. METEOSAT visible satellite loops show a large and impressive circulation that is steadily consolidating, with spiral bands building inward towards center, and upper-level outflow beginning to be established to the northwest and north.
Figure 1. Morning satellite image of Invest 92L.
Climatology argues against development of 92L, since only one named storm has ever formed between Africa and the Lesser Antilles Islands in the month of June--Tropical Storm Ana of 1979 (Figure 2). However, sea surface temperatures (SSTs) underneath 92L are an extremely high 28 - 30°C, which is warmer than the temperatures reached during the peak of hurricane season last year, in August - September. In fact, with summer not even here, and three more months of heating remaining until we reach peak SSTs in the Atlantic, ocean temperatures across the entire Caribbean and waters between Africa and the Lesser Antilles are about the same as they were during the peak week for water temperatures in 2009 (mid-September.) While 92L will cross over a 1°C cooler patch of water on Monday, the storm will encounter very warm SSTs of 28-29°C again by Tuesday.
The disturbance doesn't have to worry about dry air--Total Precipitable Water (TPW) loops show a very moist plume of air accompanies 92L, and water vapor satellite loops show that the center of 92L is at least 300 - 400 miles from any substantial areas of dry air. The 60-day cycle of enhanced thunderstorm activity called the Madden-Jullian Oscillation is currently favoring upward motion over eastern tropical Atlantic, and this enhanced upward motion helps create stronger updrafts and higher chances of tropical cyclone development.
Figure 2. Tropical Storm Ana of 1979 was the only June named storm on record to form between Africa and the Lesser Antilles Islands.
The forecast for 92L
A major issue for 92L, like it is for most June disturbances, is wind shear. The subtropical jet stream has a branch flowing through the Caribbean and tropical Atlantic north of 10° N that is bringing 20 - 40 knots of wind shear to the region. Our disturbance is currently located at 7°N, well south of this band of high shear, and is only experiencing 5 - 15 knots of shear. This moderate amount of shear should allow for some steady development of 92L over the next few days as it tracks west-northwest at 10 - 15 mph. The National Hurricane Center is giving 92L a medium (30% chance) of developing into a tropical depression by Tuesday morning. Based on visible satellite imagery over the past few hours, I believe this forecast is not aggressive enough, and that 92L has a 50% chance of developing into a tropical depression by Tuesday morning. Another factor holding 92L back is its proximity to the Equator. I would give 92L higher chances of developing if it were not so close to the Equator. The system is organizing at about 7°N latitude, which is so close to the Equator that it cannot leverage the Earth's spin much to help it get spinning. It is quite unusual for a tropical depression to form south of 8°N latitude.
The farther south 92L stays, the better chance it has at survival. With the system's steady west-northwest movement this week, 92L should begin encountering hostile wind shear in excess of 30 knots by Thursday, which should be able to greatly weaken or entirely destroy the storm before it gets to the Lesser Antilles Islands. However, residents of the islands--particularly the northern Lesser Antilles--should follow the progress of 92L closely, and anticipate heavy rains and high winds moving through the islands by Saturday or Sunday next weekend. The GFDL and HWRF models are predicting that 92L will develop into a moderate strength tropical storm that will then be weakened or destroyed by the end of the week, before it reaches the islands. This looks like a reasonable forecast.
Figure 3. The departure of sea surface temperature (SST) from average for June 10, 2010. Image credit: NOAA/NESDIS.
Oil spill wind forecast
There is little change to the oil spill wind forecast for the coming two weeks. Light winds of 5 - 10 knots mostly out of the south or southeast will blow in the northern Gulf of Mexico all week, according to the latest marine forecast from NOAA. These winds will keep oil near the coast of Louisiana, Alabama, Mississippi, and the extreme western Florida Panhandle, according to the latest trajectory forecasts from NOAA and the State of Louisiana. The long range 8 - 16 day forecast from the GFS model indicates a typical summertime light wind regime, with winds mostly blowing out of the south or southeast. This wind regime will likely keep oil close to the coastal areas that have already seen oil impacts over the past two weeks. | <urn:uuid:6de7ce61-5b96-4eb5-aa7f-7fe832fa5540> | 2.515625 | 1,120 | Personal Blog | Science & Tech. | 46.113158 | 268 |
Special & General Relativity Questions and Answers
If a photon travels at the speed of light, why isn't its mass infinite?
Because the photon is one of those handful of particles ( photon, graviton, gluon) which has 'zero rest mass'. The special relativistic formula that shows mass increasing with speed only applies to particles with non-zero rest mass such as neutrinos, electrons, quarks and so on.
Return to the Special & General Relativity Questions and Answers page.
All answers are provided by Dr. Sten Odenwald (Raytheon STX) for the NASA Astronomy Cafe, part of the NASA Education and Public Outreach program. | <urn:uuid:7b69a7b7-162d-4061-84c4-c0b93d50fd95> | 3.140625 | 142 | Q&A Forum | Science & Tech. | 45.252333 | 269 |
Introduction to Physical Science/Energy
Many Forms of Energy
By 9th grade (U.S. system) some students can identify potential energy (energy stored in objects due to their position - snow on a steep slope) and kinetic energy (displayed by snow when it breaks loose and an avalanche falls down the steep slope.) Some students recognize the heat is a form of energy as well. In fact, depending on the context of the discussion, students may identify many forms of energy, such as: Potential, Kinetic, Thermal, Chemical, Electrical, Magnetic, Sound, Nuclear and so on. | <urn:uuid:0da88be6-9328-444a-9744-daffe374e829> | 3.359375 | 122 | Knowledge Article | Science & Tech. | 40.588258 | 270 |
Sivaram, C and Sinha, KP and Lord, Eric A (1974) f Gravity and gravitational singularities. In: Nature, 249 (5458). pp. 640-641.Full text not available from this repository. (Request a copy)
TRAUTMAN has postulated1 that the usual space−time singularity occurring in classical cosmological models and in the gravitational collapse of massive objects could be averted if intrinsic spin effects are incorporated into general relativity by adding torsion terms to the usual Einstein field equations, that is through the Einstein−Cartan theory. Invoking a primordial magnetic field for aligning all the individual nuclear spins he shows that his universe consisting of 1080 aligned neutrons collapses to a minimum radius of the order of 1 cm with a corresponding matter density of 1055 g cm-3.
|Item Type:||Journal Article|
|Additional Information:||Copyright of this article belongs Nature Publishing Group.|
|Department/Centre:||Division of Physical & Mathematical Sciences > Physics|
|Date Deposited:||17 Dec 2009 11:27|
|Last Modified:||17 Dec 2009 11:27|
Actions (login required) | <urn:uuid:388b7d44-3929-43c2-b847-7a2656985dfe> | 2.5625 | 250 | Truncated | Science & Tech. | 34.133352 | 271 |
The theory behind fossil fuels is actually quite simple. Burning coal, natural gas, and petroleum releases energy stored in the fuel as heat. The energy contained by the fuels is derived from the energy of the sun. For more detailed explanations of the origins of the different fossil fuels, visit the coal, natural gas, and petroleum pages.
The heat that is recovered upon combustion of the fuel can be used by us in several ways. Industrial processes that require extremely high temperatures may burn a great deal of very pure coal known as "coke" and use the energy released to directly heat a system. Some people make use of clean burning natural gas to heat their homes. Combustion of fossil fuels can also be used to generate electricity; the fuel is burned to heat water, and the steam from the boiling water spins turbines that power a generator, thereby manufacturing electricity:
Next Page: "Pollution" | <urn:uuid:9af8df0e-8b5a-4355-b5f1-b4a57327a9fb> | 3.984375 | 181 | Knowledge Article | Science & Tech. | 35.081623 | 272 |
phhttpd uses an XML config file format to express how it should behave while running. More information on XML may be found near http://www.w3.org/XML/
phhttpd's configuration centers around the concept of virtual servers. For us, a virtual server may be thought of as the merging of a document tree and the actions phhttpd takes while serving that content.
phhttpd.conf may be thought of as having two main sections. The global section, which defines properties that are consistent across the entire running phhttpd server, and multiple virtual sections that describe properties of that only apply to a virtual server. There will only be one global section while multiple virtual sections are allowed.
The global section defines properties of the running server that don't apply to a single virtual server. It should be enclosed in
Global config entities
Sets the maximum number of cached responses that will be held in memory. Each cached responses holds a minimal amount of memory. More importantly, each cached response holds an open file descriptor to the file with real content and an mmap()ed region of that content. phhttpd will start pruning the cache when it notices either of these two resources coming under pressure, but has no way to easily deduce that its running low on memory. The administrator may set this value to set an upper bound on the number of responses to keep in memory.
This specifies the file that will be used to talk with phhttpd_ctl.
This specifies the file to which global messages will be logged.
This specifies the file that contains the mapping of file extensions to MIME types. It should be of the form:
text/sgml sgml sgm video/mpeg mpeg mpg mpe
Controls various network connection timeouts. 'inactivity' sets the amount of time that a connection can be idle before phhttpd will forcibly disconnect it. inactivity defaults to 0, which lets the connections idle until TCP timeouts take effect.
Enabling this option tells phhttpd to use sendfile() rather than write()ing from an mmap()ed region. Avoiding calling mmap() will shorten the amount of time it takes to build cached responses.
A Virtual Server can be thought of as the abstraction serving up a content tree ( "docroot" in Apache speak). There are a set of attributes that are used to define a virtual server. These attributes are used to decide which virtual server will process a client's request. Then there are attributes which define how the content is served.
A virtual server must have a docroot. The virtual tag in the config file has a docroot attribute that must be set.
<virtual docroot=PATH> ... </virtual>
Global Config Entities
This enables the generation of the Content-MD5: header. This greatly increases the cost of creating a cached response for this virtual, because the MD5 function must be applied to the entire content of the response. Once the response is created, though, there is no per-request overhead.
This will cause phhttpd to traverse the entire docroot at initialization time and prepare cached responses for all the files it finds. This happens in the back ground during normal operation, so there is no dramatic increase in the time it takes for phhttpd to start serving connections.
This tag surrounds the string that will be used to identify the server. This string will be compared to the Host: header given in the request from the client, or will be compared to the 'host part' of the full URL if that was given. This will be used in combination with the network address and port pair to determine if a request should be served by a virtual server.
This virtual server will be chosen to serve an incoming request if that request was made to the network address specified in this entity. There can be as many of these as one likes in a given virtual server, and '*' may be specified for either parameter to indicate that all addresses or ports should match.
The logs section of the virtual server define the per virtual log files that should be written to during operation. See the following section on logging. | <urn:uuid:93efbaf0-bd69-4425-b2ff-1cbec9d2c17c> | 2.828125 | 855 | Documentation | Software Dev. | 57.511966 | 273 |
The Power of One
In 1987 Brazilian-born Canadian, Marcelo da Luz saw a news clip about the World Solar Challenge race and it inspired him to design a super cool solar vehicle of his own - XOF1, which he calls The Power of One.
When the model was completely, he set out on a record-breaking trip. This visionary trip began in Buffalo, N.Y., in June 2008, and went through Canada, Alaska and down the West Coast to Los Angeles, where pilot Marcelo da Luz and his solar-powered car made a pit stop Friday.
"Hopefully this won't be the end of the journey for me," said da Luz, 40, whose UFO-like car broke the world's 9,000-mile distance record for travel by a solar vehicle.
His journey came to a halt this past Friday, however, because the funding for his project ran out. The solar team traveled more than 11,500 miles to break the previous record.
The 470-pound, 14-foot vehicle took 10 years and more than 50,000 man hours to build and $50,000 to build, da Luz said.
To read lots more on da Luz’s journey and the fascinating technology involved click here. | <urn:uuid:30735313-761e-4b5e-a93f-3436c3f96f5d> | 2.515625 | 260 | News Article | Science & Tech. | 69.238232 | 274 |
Is Zero Even?
Date: 03/28/2001 at 02:59:56 From: John Matousek Subject: Zero odd/even At numerous sites across the Internet the answer to the question whether zero is odd or even seems to be totally subjective, and the proofs used to justify 'even' (zero can be divided by two, therefore it is even), sound reasonable. But zero can't really be divided by two since the result is zero - neither a positive or negative integer. Q: How many times does 2 go into 0? A: Zero times. Or to rephrase, two doesn't go into zero. The question arose when a retired math teacher stated "2/20/2000, the first day ever with seven even numerals in its date." Of course he is wrong, 2/20/2000 BC being the most obvious example - if you accept zero as even. But there are also thousands of dates from the astronomical, Hebrew, Chinese, Hindu lunar, old Hindu solar and lunar calendars where zero would not even need to be considered. 'Ever' is such a big word. Thanks.
Date: 03/28/2001 at 09:18:35 From: Doctor Rick Subject: Re: Zero odd/even Hi, John. Thanks for writing! I hope I can clear up some confusion. Our archives sometimes say that zero is neither positive nor negative, not that it is neither even nor odd. That's very different. The question of evenness or oddness is based on definitions. There may be variations on how "even" is defined, just as there are on how "natural numbers" are defined; but once you have established your definition, the question can be answered objectively based on that definition. An even number, as our archive pages say, is defined as one that is divisible by 2. Divisibility by 2 is defined as giving an integer quotient when divided by 2. The only matter open to debate is whether this last statement should say "integer," "natural number," or "whole number." If integer, then the even numbers are ..., -6, -4, -2, 0, 2, 4, 6, ... If natural number (0, 1, 2, 3, ...), then the even numbers are 0, 2, 4, 6, ... If whole number (1, 2, 3, ...), then the even numbers are 2, 4, 6, ... There is no reason to be restrictive in our definition of divisibility: the definition introduces no contradictions or special cases when it is extended to all integers. If you have found places on the Web where a restrictive definition is used, I'd like to see them. You state that the problem you have with zero being even is that zero can't really be divided by 2, because the quotient is 0, which is neither positive nor negative. Putting this in my terms, you are defining "divisible" as meaning "giving a quotient that is a positive or negative (that is, non-zero) integer." I could accept one of the alternative definitions I gave above before I would accept yours. If we say that zero cannot be divided by anything, then this introduces lots of special cases to our mathematical properties. For example, the sum of two even numbers is even. You are telling me that the 4 and -4 are even, but that the sum of 4 and -4 is *not* even. We'd need to change the rule to "The sum of even numbers is even, UNLESS it is zero." It's so much simpler to define our terms in a way that does not require such special cases. Defining evenness and divisibility as we do does not introduce special cases. Before zero was introduced to our number system, negative quantities were treated as an entirely separate kind of entity from positive numbers. Different rules were needed for lots of different cases, depending on whether a quantity was added (positive) or subtracted (negative). The history of quadratic equations illustrates this. A big part of the genius of introducing zero in the first place was that it unified all these special cases into one. I am asking you now to see that you do not need to treat zero as special; and when you treat it like every other integer, it follows that zero is even. For related answers in our archives, see: Zero is even: Are these numbers odd or even? http://mathforum.org/library/drmath/view/57062.html Is Zero Even, Odd, or Neither? http://mathforum.org/library/drmath/view/57104.html Is Zero Odd or Even? http://mathforum.org/library/drmath/view/57132.html FAQ: Integers, Rational and Irrational Numbers http://mathforum.org/dr.math/faq/faq.integers.html Even and odd numbers enumerated, start with 1: Infinity, Zero http://mathforum.org/library/drmath/view/52400.html Neither positive nor negative: Why Zero is Neither Positive nor Negative http://mathforum.org/library/drmath/view/58735.html What is 0? http://mathforum.org/library/drmath/view/58743.html Is Zero Positive or Negative? http://mathforum.org/library/drmath/view/60300.html - Doctor Rick, The Math Forum http://mathforum.org/dr.math/
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© 1994-2013 The Math Forum | <urn:uuid:406d6832-8e5c-4eb8-936a-5c22bc09e887> | 2.90625 | 1,150 | Comment Section | Science & Tech. | 65.148556 | 275 |
Snow Pit Data from Greenland Summit, 1989 to 1993
Chemistry and isotope information from snow pits dug at the Summit area of Greenland, 1989-1993 includes major ions (Na, K, Mg, Ca, Cl, NO3, SO4), oxygen isotopes (18O) and H2O2. Four snow pits were dug and sampled in 1989, three snow pits in 1990, two in 1991, one in 1992 and one in 1993. All snow pits had a 3 cm sampling interval except the snow pits in 1990, which had either a 3 cm or 5 cm sampling interval. Chemistry and isotope information were obtained from each of the snow pits.
The pits and surface snow samples were collected by the Glacier Research Group (GRG), using established protocols to prevent contamination. The samples collected in 1991 were analyzed at the GISP2 drilling camp. All data except the oxygen isotope data, which is from the University of Washington, were generated by GRG at the University of New Hampshire.
The following example shows how to cite the use of this data set in a publication. For more information, see our Use and Copyright Web page.
Paul A. Mayewski and Sallie Whitlow. 1999. Snow Pit Data from Greenland Summit, 1989 to 1993. [indicate subset used]. Boulder, Colorado USA: National Snow and Ice Data Center. | <urn:uuid:af970009-66d7-4642-ad4b-4597cf766f40> | 2.59375 | 279 | Knowledge Article | Science & Tech. | 63.99344 | 276 |
Lamp Shell Terebratulina septentrionalis
It would be easy to mistake a lamp shell for a small bivalve mollusk, as both have a hinged shell in two parts and live attached to the sea floor. Lamp shells, however, have a very thin, light shell and the two parts are different sizes, with the smaller one fitting into the larger. The shell valves cover the dorsal and ventral surfaces of the animal whereas in bivalve mollusks they are on the left and right side of the body. Lamp shells attach their pear-shaped shell to hard surfaces by means of a fleshy stalk that emerges from a hole in the ventral shell valve. With the shell valves gaping open, the animal draws in a current of water that brings plankton with it. Taking up most of the space inside the shell is a feeding structure called the lophophore, which consists of two lateral lobes and a central coiled lobe covered in long ciliated tentacles. The beating of the cilia creates the water current. Lamp shells are found worldwide, but they are especially abundant in colder waters. In the northeastern Atlantic, Terebratulina septentrionalis is mostly found in deep water, while along the east coast of North America, it commonly occurs in shallow water. This species is very similar to Terebratulina retusa. | <urn:uuid:0c979112-e58f-46d8-980b-de289ead7025> | 4.15625 | 289 | Knowledge Article | Science & Tech. | 45.001578 | 277 |
(Washington, DC • 11/6/06) – The second of five Special Sensor Ultraviolet Limb Imager (SSULI) remote sensing instruments, developed by the Naval Research Laboratory, was launched on November 4, 2006 on board the DMSP F-17 satellite. SSULI is the first operational instrument of its kind and provides a new technique for remote sensing of the ionosphere and thermosphere from space. SSULI's measurements will provide scientific data supporting military and civil systems and will assist in predicting atmospheric drag effects on satellites and reentry vehicles.
A Boeing Delta 4 vehicle launched the Air Force's Defense Meteorological Satellite Program (DMSP) F-17 satellite and the SSULI sensor into low earth orbit from Vandenberg Air Force Base, California. SSULI will be powered on and start initial sensor checkout 30 days after launch.
"Characterization of the Earth's upper atmosphere and ionosphere is a critical goal for Department of Defense (DoD) and civilian users," said Andrew Nicholas, the SSULI Principal Investigator at NRL. He discussed the significance of the planned SSULI observations, saying, "The upper atmosphere affects many systems from global to tactical scales. These systems include GPS positioning, HF radio communications, satellite drag and orbit determination, and over-the-horizon radar. Both the neutral atmosphere and the ionosphere are driven by solar and geomagnetic forcing that occur on many timescales ranging from short (minute, hours) to medium (days to months) to long (years). Real-time global observations that yield altitude profiles of the ionosphere and neutral atmosphere, over an extended period of time (DMSP through the year 2016) will fill a critical need."
SSULI measures vertical profiles of the natural airglow radiation from atoms, molecules, and ions in the upper atmosphere and ionosphere from low earth orbit aboard the DMSP satellite. It builds on the successes of the NRL High Resolution Airglow/Aurora Spectroscopy (HIRAAS) experiment recently flown aboard the Space Test Program (STP) Advanced Research and Global Observations Satellite (ARGOS). SSULI makes measurements from the extreme ultraviolet (EUV) to the far ultraviolet (FUV) over the wavelength range of 80 nm to 170 nm with 2.4 nm resolution. SSULI also measures the electron density and neutral density profiles of the emitting atmospheric constituents. SSULI uses a spectrograph with a mirror capable of scanning below the satellite horizon from 10 degrees to 27 degrees every 90 seconds. These observations represent a vertical slice of the Earth's atmosphere from 750 km to 50 km in depth. Use of these data enables the development of new techniques for global ionospheric remote sensing and new models of global electron density variation.
Commenting on the practical application of the instrument, Mr. Ken Weldy, the Program Manager at NRL said, "Since natural atmospheric phenomena can disrupt day-to-day operations in the military use of space, we look forward to providing SSULI operational products to feed into the Global Assimilation of Ionospheric Measurements (GAIM) model. This will provide an important piece of the characterization of the Earth's upper atmosphere and ionosphere."
An extensive data processing suite was developed to support on-orbit observations and flight operations. It includes data reduction software using unique science algorithms developed at NRL, comprehensive data validation techniques, and graphical interfaces for the user community. After launch, the SSULI sensor, software, and derived atmospheric specification will under go an extensive validation. After validation, SSULI products will be distributed by the Air Force Weather Agency to support operational DoD systems.
Additional information about the SSULI instrument and its data processing software is available at http://www.nrl.navy.mil/tira/Projects/ssuli/.
The Defense Meteorological Satellite Program (DMSP) is a Department of Defense (DoD) program run by the Air Force Space and Missile Systems Center (SMC). The program designs, builds, launches, and maintains several near-polar orbiting, sun synchronous satellites monitoring the meteorological, oceanographic, and solar-terrestrial physics environments. Additional information is available at the DMSP web site (http://dmsp.ngdc.noaa.gov/dmsp.html).
NRL is the Department of the Navy's corporate laboratory. NRL conducts a broad program of scientific research, technology, and advanced development. The Laboratory, with a total complement of approximately 2,500 personnel, is located in southwest Washington, DC, with other major sites at the Stennis Space Center, MS; and Monterey, CA.
Last reviewed: By John M. Grohol, Psy.D. on 21 Feb 2009
Published on PsychCentral.com. All rights reserved. | <urn:uuid:a168bd55-6030-4ce8-bdae-e503fe05ec37> | 2.90625 | 990 | News (Org.) | Science & Tech. | 31.048096 | 278 |
Roland Piquepaille points out a news release from the University of Michigan where researchers are looking to birds and bats for insights into aerospace engineering. Wei Shyy and his colleagues are learning from solutions developed by nature and applying them to the technology of flight. A presentation on this topic was also given at the 2005 TED conference. From the news release: "The roll rate of the aerobatic A-4 Skyhawk plane is about 720 degrees per second. The roll rate of a barn swallow exceeds 5,000 degrees per second. Select military aircraft can withstand gravitational forces of 8-10 G. Many birds routinely experience positive G-forces greater than 10 G and up to 14 G. Flapping flight is inherently unsteady, but that's why it works so well. Birds, bats and insects fly in a messy environment full of gusts traveling at speeds similar to their own. Yet they can react almost instantaneously and adapt with their flexible wings." | <urn:uuid:057cd66a-5444-47c4-a917-238fea363035> | 3.15625 | 194 | News Article | Science & Tech. | 55.136444 | 279 |
Greenhouse Effect Basics: Warm Earth, Cold Atmosphere
Posted on 29 February 2012 by Tom Curtis
Heating and Heat Flow
Some physics, everyone knows. In our daily lives we encounter the effects of physics all the time, and as a result, we know what physics predicts in those circumstances at a gut level. We may not be able to put it into numbers. We may not be able to apply it in novel situations. But we know it all the same.
One example is as simple as putting on a blanket. We know that if we want warm something up, we can increase the supply of heat - or we can reduce the escape of heat. Either is effective. If you have a pot that is simmering and you want to bring it to the boil, you can turn the heat up, or you can put on the lid. If we put on the lid, the pot will go nicely from simmering to boiling, and we don't need to turn up the heat even slightly. Indeed, if we are not careful to turn down the heat, the pot may well boil over.
Likewise, if you have two identical motors running with an identical load and speed (Revolutions Per Minute), one with the water pump working and one without, we are all physicist enough to say that the second one will run hotter. It does not matter that the energy supplied as fuel is identical in both cases. The fact that heat escapes more easilly with water circulating through the radiator will keep the first cooler. The consequence is that stopping the the water from circulating will lead second motor to disaster.
Nor do we find people who doubt this. Suppose somebody told us their water pump was broken, but that the Second Law of Thermodynamics prohibited transfer of heat from a cooler place (the water) to a hotter place (the engine block), so they'ld be fine so long as they didn't rev any faster than normal, we'ld look at them in complete disbelief. Or we would if we were too polite to burst out laughing. And if they set out cross country confident in their belief, it doesn't matter what destination they claim they're heading for. Rather, as we all know, they're really heading for a breakdown!
(Image copyright to iStock, and not to be reproduced without their permission.)
Heat Flow to Space
This physics that everyone knows is not only true of pots and radiators. It is true of the Earth as well. The Earth is warmed by our remarkably stable Sun. As a result, the Earth's surface radiates energy to space, and over time the incoming energy balances the outgoing energy. The process is made more complicated, however, by the existence of Infra Red (IR) absorbing molecules in the atmosphere.
Without those molecules, Infra Red radiation from the Earth's surface would travel directly to space, cooling the Earth quickly and efficiently. At certain wavelengths of Infra Red radiation, however, those molecules absorb many, or all, of the photons emitted from the Earth's surface. That energy is often redistributed among other molecules by collision, but eventually some of the redistributed energy will be reradiated by the Infra Red absorbing molecules. This process absorption, redistribution and then re-emission may occur many times before the energy escapes the atmosphere, but eventually it will either by being emitted to space, or back to the surface.
Intuitively, the energy that goes through multiple stages of absorption, redistribution and re-emission will not escape to space as fast that which is emitted directly to space from the surface. This intuition is sound, but it depends essentially on one factor, the temperature of the atmosphere.
We can see this by considering a fundamental law that governs the radiation of energy, the Stefan-Boltzmann Law:
In words, that is J-star equals epsilon sigma T to the fourth power, but we don't need to worry about that. What we need to notice is that J-star, which is the energy radiated over a given time from a given area, is proportional to the fourth power of T, ie, temperature. If the temperature doubles, the energy radiated increases sixteen-fold. If it triples, it increases eighty-one- fold. And so on. So, if the temperature of the atmosphere is different from that of the surface, the absorption, redistribution and re-emission of IR radiation by molecules in the atmosphere will certainly change the rate at which heat escapes to space.
Higher is Colder
There is another piece of physics everyone knows. It is that as you go higher in the atmosphere, the atmosphere gets colder. That is the reason why some mountain peaks are snow covered while their bases are still warm. This is not a universal law. It is not true, for example, in the stratosphere where the absorption of UltraViolet radiation from the Sun causes temperatures to rise with increased height. But eighty percent of the Earth's atmosphere is in the troposphere (the lowest layer of the Earth's atmosphere), and most radiation leaving the top of the troposphere escapes to space. And in the troposphere, as you get higher, the temperature gets lower. On average, the temperature drops by 6.5 degrees C for every thousand meters of altitude you climb. That means, for example, that the temperatures fall by about 24.5 degrees C as you climb to the summit of Mount Fuji, and by 50 to 100 degrees as you rise to the top of the troposphere.
We have already seen that temperature significantly effects the radiation of heat. Colder objects radiate less energy, and the Infra-Red absorbing molecules in the atmosphere are colder than the surface. Therefore it is no surprise that the Infra-Red absorbing molecules in the atmosphere radiate less energy to space than they absorb from the warmer surface. That difference is the essence of the greenhouse effect.
No More Arm Waving
It would be helpfull to recapitulate at this point. So far we have noted four simple facts:
- That if you reduce the escape of heat, but do not reduce the incoming heat, things warm up;
- That the atmosphere contains molecules that absorb Infra-Red radiation;
- That radiated energy depends on the temperature of the radiating object; and
- That the atmosphere gets cooler as you get higher, so that the Infra-Red absorbing molecules in the atmosphere radiate less energy to space than they absorb from the surface.
These four facts imply the existence of an atmospheric greenhouse effect, ie, that the presence of Infra-Red absorbing molecules in the atmosphere results in the surface being warmer than it otherwise would be.
In science, however, purely verbal reasoning like this is considered suspect. The reason is that sometimes odd effects occur that render verbal reasoning moot. So in science, there is no substitute for putting the theory into a mathematical form. It gets rid of the arm waving.
Fortunately for us, scientists have already put this theory into mathematical form, at a very detailed level. We can access this work, free of charge, by using the Modtran Model. The Modtran Model shows the radiation up or down over a column of atmosphere under particular conditions. By changing the conditions, you can explore the predicted effects of those changes on upward or downward radiation at any level of the atmosphere from 0 to 70 kilometers altitude. Setting the altitude to 70 kilometers effectively shows the radiation upward to space from the top of the atmosphere, or downward from space at the top of the atmosphere. Setting the altituded to 0 kilometers effectively shows the radiation upward, or downward at the surface.
Using Modtran, I determined the energy output looking downwards from an altitutude of 70 kilometers using the US Standard Atmosphere (1). The result can be seen on the following graph as the green shaded area. I repeated the model run, but this time with the altitude set at 0 km. The result is shown by the outer curve defining the red area in the graph below. That means that the red area itself, which is the upwards radiation from the surface minus the upward radiation to space, is the reduction in energy radiated to space because of the presence of Infra-Red absorbing molecules in the atmosphere. That is, it is the greenhouse effect.
We have all heard how inaccurate models can be. Therefore the fact that a particular model predicts this difference in radiation only shows what the theory predicts. It does not show what is actually happening.
Scientists are not happy with theories whose only support is a model. So in 1969, Conrath and associates compared the results of model calculations of radiation to space with the actually observed radiation using the IRIS instrument on the Nimbus 3 Satellite. The following graph shows the result of their comparison. The dotted line shows the modelled values, while the solid line shows the observed values:
The effect of a particular Infra-Red absorbing molecule, Carbon Dioxide, is clearly visible. With the publication of this data in 1970, the greenhouse effect ceased to be theoretical. It was an observed fact.
(1) Default settings except for adjusting surface temperatures (Ground T offset, c) to approximately match the Earths Global Mean Surface Temperature (about -10 degrees C offset). | <urn:uuid:cf658369-b75c-4945-b276-042f88282485> | 3.234375 | 1,893 | Personal Blog | Science & Tech. | 45.790763 | 280 |
Cicadas: Superfamily Cicadoidea
The drone of cicadas is one of Sydney's most recognisable sounds of summer. Cicadas are the loudest insects in the world and there are more than 200 species in Australia.
It is thought that the sound produced by some communal species can act as a defence against predatory birds and some are even loud enough (120 decibels) to be painful to the human ear. Cicadas also often sing in chorus, which makes it more difficult for a predator to locate an individual.
Cicadas are so conspicuous that many of their common names were initially given to them by children. As a result cicadas probably have the most colourful common names in the insect world. Some of these include: Black Prince (Psaltoda plaga), Double Drummer, Floury Baker, and the Green Grocer or Yellow Monday, Cyclochila australasiae.
- Only male cicadas sing. They do this in an attempt to find a mate.
- Different species have different songs to attract only their own kind.
- Adult cicadas have short lives, usually only a few weeks.
- Most of their lives are spent as nymphs underground. For some species this can be up to several years.
- Cicadas feed only on plant sap using their piercing, sucking mouthparts.
- Cicadas feed on a huge range of plants, including eucalypts and grasses.
- Birds, bats, spiders, wasps, ants, mantids and tree crickets all prey on cicadas.
What are cicadas?
They are classified in the order Hemiptera, which includes all insects with piercing and sucking mouth-parts. (Other insects in this order are bugs, aphids and scale insects). There are more than 200 Australian species of cicadas, most of which belong to the one large family, the Cicadidae. Cicadas are sometimes known as locusts in Australia, but that term is more correctly applied to certain migratory species of grasshopper.
What do cicadas look like?
Adult cicadas have stout bodies with two pairs of wings. The wing spans of the different species range from about 2.5 cm - 15 cm. When not in use, the wings fold back along the sides of the body. The longer fore wing covers the short hind wing, but the wings of each side do not overlap. The fore wing is usually glassy and transparent although in a few species it is dull and opaque. The wings are strengthened by a number of thin, firm veins.
Adult cicadas have three pairs of legs all about the same length. The femur (thigh joint) of the fore leg is thicker than that of the other legs.
Cicadas have large compound eyes situated one on each side of the head They also have three very small glistening simple eyes (ocelli) on the top of the head. The cicada's antennae (feelers) are quite small and bristle-like.
The mouth parts of the cicada are enclosed in a long, thin, beak-like sheath. The sheath (labium) passes backwards from the lower surface of the head between the legs when the insect is not feeding. It contains four fine, needle-like stylets used in feeding.
Cicadas feed by piercing the surface of plants with their mouth stylets. They then suck up the sap through a tube formed by the concave surfaces of two of the stylets. This piercing and sucking kind of feeding apparatus can be contrasted with the biting and chewing kind found in grasshoppers, cockroaches, beetles and caterpillars.
Cicadas may cause some slowing of the growth of trees from the amount of sap that they consume, but the effects are not very noticeable. They do not bite, though they may cling to the skin with their sharp claws when handled. They are considered harmless to people, despite the fact that their high-pitched call may annoy some people.
The adults of larger kinds of cicadas can be found on the trunks or branches of trees in summer. They are often wary and fly away when approached. Smaller kinds often live on low shrubs, or even on long grass.
Cicadas are eaten in large quantities by birds. They are also carried off by wasps as food for their young, and undoubtedly serve as food for many other animals Even the nymphs beneath the ground are parasitised by the larvae of Feather-horned Beetles (family Rhipiceridae).
Cicadas are notorious singers. The song is a mating call produced by the males only. Each species has its own distinctive call and only attracts females of its own kind even though rather similar species may co-exist.
Cicadas are the only insects to have developed such an effective and specialised means of producing sound. Some large species such as the Greengrocer/Yellow Monday and the Double Drummer produce a noise intensity in excess of 120 dB at close range (this is approaching the pain threshold of the human ear). In contrast, some small species have songs so high in pitch that the noise is beyond the range of our hearing.
The apparatus used by cicadas for singing is complex and research is still continuing on the mechanisms involved. The organs which produce sound are the tymbals, a pair of ribbed membranes at the base of the abdomen. Contracting the internal tyrnbal muscles causes the tymbals to buckle inwards and produces a pulse of sound. By relaxing these muscles, the tymbals pop back to their original position. In some cicada species, a pulse of sound is produced as each rib buckles.
Both male and female cicadas have organs for hearing. A pair of large, mirror-like membranes, the tympana, receive the sound. The tympana are connected to an auditory organ by a short tendon. When a male sings, it creases the tympana so that it won't be deafened by its own noise.
Many species of cicada sing during the heat of the day. The loud noise produced by some day-singing cicadas actually repels birds, probably because the noise is painful to the birds' ears and interferes with their normal communication. The males of many cicada species, including the Greengrocer/Yellow Monday, and the Double Drummer, tend to group together when calling which increases the total volume of noise and reduces the chances of bird predation.
Some cicada species only sing at dusk. Often these species are weak fliers (as in the case of the Bladder Cicada). They gain some protection from predatory birds by confining their activity to dusk.
Cicadas spend most of their life underground. It has been suggested that some of the large, common Australian species of cicada may live underground as nymphs for around 6-7 years. This would explain why adult cicadas are much more abundant during some seasons that others, with peaks occurring every few years. The periodical cicadas of North America spend 13 or 17 years underground.
In contrast to that of the nymph, the life of adult cicadas is very short, lasting only a few weeks. After mating, the adult female cicada lays its eggs. It does this by piercing plant stems with its ovipositor (egg-laying spike at the tip of the abdomen) and inserting the eggs into the slits it has made. The eggs hatch into small wingless cicadas which are known as nymphs. They fall to the ground and burrow below the surface. Here they live on the sap from plant roots for a period which may last several years. They shed their skin at intervals as they grow.
When the nymph reaches full size it digs its way to the surface with its front legs, which are specially adapted for digging. It generally surfaces about nightfall in late spring or early summer. The nymph then climbs on to a tree trunk or other object and sheds its skin for the last time. The fully-winged adult cicada which emerges leaves its old empty nymphal skin behind.
For enquiries relating to these insects in the Australian Museum collection please contact the Collection Manager
- Moulds, M.S. 1990. Australian Cicadas. New South Wales University Press. 217 pp., 24 pls.
Dr Dave Britton , Collection Manager, Entomology | <urn:uuid:dc87789c-562f-43b0-bfee-0dee44be1fec> | 3.484375 | 1,770 | Knowledge Article | Science & Tech. | 56.365563 | 281 |
Locating thermophiles in other parts of the universe could very well aid in the search for extraterrestrial life. Most people have agreed that if life is found among the stars, it will be microbial (at least in the near-term future). Many individuals have also suggested that intelligent life forms might very well be extinct in other parts of the universe. If scientists could locate thermophile microbes, they could piece together an archaeological picture of once powerful civilizations.
Taiwan is well known for its hot springs. Most tourists that visit the island end up visiting at least one. Many people like to take relaxing baths in them. Hot springs can be great for people with arthritis. New research is proving that they can also be a great place to find astrobiological data.
Photosynthetic thermophiles that live in hot springs may potentially be removing significant amounts of industrially produced carbon dioxide from the atmosphere. They’ve thrived because of fundamental changes to the atmosphere caused by humanity. In fact, there are some scientists who feel that these microbes could play a vital role in regulating the planet’s climate. That role might become increasingly important in the future.
Planets that were once inhabited by industrially developed civilizations that have since passed might be teeming with life similar to these. If a planet was sufficiently changed by another race of beings, it could have ultimately favored the development of these tiny beings. They could indicate that intelligent lifeforms once inhabited a planet, and that planet could be different today than it was in the past.
While discovering a planet full of microbes would be initially interesting, in the future it could be a relatively common occurrence. Therefore, news services of the future might very well pass by such stories after a few weeks – much like they do today with the discovery of new exoplanets. Finding sufficient numbers of photosynthetic thermophiles would be telling about the history of a world, but it would also require a great deal of geological activity. Then again, there’s nothing to say that other civilizations wouldn’t also have the ability to increase the amount of geological activity on other planets. They might even do it on purpose, as a way of terraforming for instance.
For that matter, humans might want to give that a try. Venus is superheated because of thermal runaway as a result of excess carbon dioxide in the atmosphere. If water were transported to that very hot world, colonists could use the resulting geysers to grow bacteria that would absorb the atmospheric gas.
Leu, J., Lin, T., Selvamani, M., Chen, H., Liang, J., & Pan, K. (2012). Characterization of a novel thermophilic cyanobacterial strain from Taian hot springs in Taiwan for high CO2 mitigation and C-phycocyanin extraction Process Biochemistry DOI: 10.1016/j.procbio.2012.09.019 | <urn:uuid:fb936873-c4b3-4301-85c5-1bd5eb0d9a9c> | 3.8125 | 601 | Truncated | Science & Tech. | 43.368302 | 282 |
Santa's magic based on science
Ever wondered how Santa Claus can travel around the world in just one night on his reindeer-pulled sleigh and deliver toys to all the children?
"He exploits the space-time continuum," says Larry Silverberg, a professor of mechanical and aerospace engineering at North Carolina State University.
Santa's magic may go far beyond merely travelling across 322 million square kilometres to visit hundreds of millions of homes of children in just one night, Silverberg says.
"He understands that space stretches, he understands that you can stretch time, compress space and therefore he can, in a sense, actually have six Santa months to deliver the presents," says Silverberg.
"In our reference frame it appears as though he does it in the wink of an eye and in fact there have been sightings of Santa, quick sightings, and that's in our reference frame, but in Santa's reference frame he really has six months".
Building on demand
Silverberg says his research has established that Santa does not, as commonly thought, carry enough presents for each child in his sleigh. "How could he?" he says.
"We believe that he uses nanotechnology to grow the presents under the tree and really, what he's done, is he's figured out how to turn what we call irreversible thermo-dynamic properties into reversible ones and so he really starts with soot, candy, other types of natural materials, he puts them under the tree and he actually grows them in a reverse process to create the presents, wrapping and all."
And then there's the age-old question that Santa has to address every year - who's been naughty and who's been nice?
"We believe, that there are large antennas miles long under the snow up at the north pole and we think the grid-spacing is in the order of millimetres so that you can receive radar-type signals," says Silverberg.
Santa's trip takes in all continents and all time zones. Silverberg says his sleigh is equipped with an onboard sleigh guidance system.
He says the reindeer are genetically bred to fly, balance on rooftops and see in the dark.
Silverberg has been researching Santa for more than a decade.
"It's certainly a worthy thing to spend time on and it has all sorts of ramifications in everyday life," he says. | <urn:uuid:0a2bf733-f75c-48c6-9d08-3984c48079a9> | 3.40625 | 488 | News Article | Science & Tech. | 48.890111 | 283 |
Is Seaweed the Future of Biofuel? Monday, March 5, 2012
TAU scientist takes the search for alternative energy sources to the sea
As scientists continue the hunt for energy sources that are safer, cleaner alternatives to fossil fuel, an ever-increasing amount of valuable farmland is being used to produce bioethanol, a source of transportation fuel. And while land-bound sources are renewable, economists and ecologists fear that diverting crops to produce fuel will limit food resources and drive up costs.
Now, Prof. Avigdor Abelson of Tel Aviv University's Department of Zoology and the new Renewable Energy Center, and his colleagues Dr. Alvaro Israel of the Israel Oceanography Institute, Prof. Aharon Gedanken of Bar-Ilan University, Dr. Ariel Kushmaro of Ben-Gurion University, and their Ph.D. student Leor Korzen, have gone to the seas in the quest for a renewable energy source that doesn't endanger natural habitats, biodiversity, or human food sources.He says that marine macroalgae — common seaweed — can be grown more quickly than land-based crops and harvested as fuel without sacrificing usable land. It's a promising source of bioethanol that has remained virtually unexplored until now.
The researchers are now developing methods for growing and harvesting seaweed as a source of renewable energy. Not only can the macroalgae be grown unobtrusively along coastlines, Prof. Abelson notes, they can also clear the water of excessive nutrients — caused by human waste or aquaculture — which disturb the marine environment.
A man-made "ecosystem"
While biomasses grown on land have the potential to inflict damage on the environment, the researchers believe that producing biofuel from seaweed-based sources could even solve problems that already exist within the marine environment. Many coastal regions, including the Red Sea in the south of Israel, have suffered from eutrophication — pollution caused by human waste and fish farming, which leads to excessive amounts of nutrients and detrimental algae, ultimately harming endangered coral reefs.
Encouraging the growth of seaweed for eventual conversion into biofuel could solve these environmental problems. The system that the researchers are developing, called the "Combined Aquaculture Multi-Use Systems" (CAMUS), takes into account the realities of the marine environment and human activity in it. Ultimately, all of these factors function together to create a synthetic "man-made ecosystem," explains Prof. Abelson.
Man-made fish feeders, which produce pollution in the form of excess nutrients and are generally considered harmful to the marine environment, would become a positive link in this chain. Used alongside an increased population of filter feeders such as oysters, which suck in extra particles and convert them food that the microalgae can consume, this "pollution" could be used to sustain a much greater yield of seaweed, which is needed for seaweed to become a sustainable source of fuel.
"By employing multiple species, CAMUS can turn waste into productive resources such as biofuel, at the same time reducing pollution's impact on the local ecosystem," he says.
Turning waste into opportunity
The researchers are now working to increase the carbohydrate and sugar contents of the seaweed for efficient fermentation into bioethanol, and they believe that macroalgae will be a major source for biofuel in the future. The CAMUS system could turn seaweed into a sustainable bioethanol source that is productive, efficient, and cost-effective.
For more environment and ecology news from Tel Aviv University, click here. | <urn:uuid:4d27543d-0ab3-44f3-99cf-bf2174b9b1f7> | 3.109375 | 741 | News (Org.) | Science & Tech. | 25.5499 | 284 |
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Proceedings of Symposia in Applied Mathematics
1998; 275 pp; hardcover
List Price: US$60
Member Price: US$48
Order Code: PSAPM/55
There exists a history of great expectations and large investments involving Artificial Intelligence (AI). There are also notable shortfalls and memorable disappointments. One major controversy regarding AI is just how mathematical a field it is or should be.
This text includes contributions that examine the connections between AI and mathematics, demonstrating the potential for mathematical applications and exposing some of the more mathematical areas within AI. The goal is to stimulate interest in people who can contribute to the field or use its results.
Included is work by M. Newborn on the famous Deep Blue chess match. He discusses highly mathematical techniques involving graph theory, combinatorics and probability and statistics. G. Shafer offers his development of probability through probability trees with some of the results appearing here for the first time. M. Golumbic treats temporal reasoning with ties to the famous Frame Problem. His contribution involves logic, combinatorics and graph theory and leads to two chapters with logical themes. H. Kirchner explains how ordering techniques in automated reasoning systems make deduction more efficient. Constraint logic programming is discussed by C. Lassez, who shows its intimate ties to linear programming with crucial theorems going back to Fourier. V. Nalwa's work provides a brief tour of computer vision, tying it to mathematics--from combinatorics, probability and geometry to partial differential equations.
All authors are gifted expositors and are current contributors to the field. The wide scope of the volume includes research problems, research tools and good motivational material for teaching.
Graduate students and research mathematicians interested in artificial intelligence; possibly those interested in philosophy.
"Although this book was written to introduce mathematicians to AI, the book is also likely to be a valuable resource for cognitive scientists and mathematical psychologists."
-- Journal of Mathematical Psychology
"Seven excellent papers are included, covering important AI topics."
-- Mathematical Reviews
Table of Contents
AMS Home |
© Copyright 2012, American Mathematical Society | <urn:uuid:2f973b63-67de-47d4-94bc-6d8aa7463c01> | 2.546875 | 458 | Product Page | Science & Tech. | 22.921429 | 285 |
Many, see text.
Hummingbirds (family Trochilidae) are small birds capable of hovering in mid-air due to the rapid flapping of their wings (15 to 80 beats per second, depending on the size of the bird). They are named for the characteristic hum of this rapid wing motion. They are the only birds that can fly backwards.
Hummingbirds bear the most glittering plumage and some of the most elegant adornments. Male hummingbirds are usually brightly coloured, females duller. The males take no part in nesting. The nest is usually a neat cup in a tree. Two white eggs are laid, which are quite small, but large relative to the bird's size. Incubation is typically 14-19 days.
The names that admiring naturalists have given to hummingbirds suggest exquisite, fairylike grace and gemlike refulgence. Fiery-tailed Awlbill , Ruby-topaz Hummingbird, Glittering-bellied Emerald , Brazilian Ruby , Green-crowned Brilliant --are some of the names applied to the 233 species of the hummingbirds briefly described in Meyer de Schauensee's scientific Guide to Birds of South America.
Iridescent colors are common among hummingbirds. By changing position, the direction of the reflected light might give the effect of two completely different colors of the same plumage parts.
On the hummingbird's glittering throat or crown, the exposed surfaces of the barbules resemble tiny flat mirrors, which send forth their resplendence in the favored direction. This mechanism plays an important role in social interaction and species recognition.
All the metallic colours of hummingbirds are caused by interference.
Source (Skutch, 1973
Hummingbirds have the highest metabolism of all animals except insects in flight, a necessity in order to support the rapid beating of their wings. Their heartbeat can reach 500 beats per minute. They also typically consume more than their own weight in food each day, and to do that, they have to visit hundreds of flowers every day. But at any given moment, they're hours away from starving. Fortunately, they are capable of slowing down their metabolism at night, or any other time food is not readily available. They enter a hibernation-like state known as torpor. During torpor, the heartrate and rate of breathing are both slowed dramatically, reducing their need for food.
Studies of hummingbirds' metabolism are highly relevant to the question of whether a migrating ruby-throated hummingbird can cross 500 miles of Gulf of Mexico on a nonstop flight, as field observations suggest it does. The ruby-throated hummingbird like other birds preparing to migrate, stores up fat to serve as fuel, thereby augmenting its weight by as much as 40 to 50 per cent--this would increase the bird's flying time. (Skutch, 1973) --Ccson 10:06, 18 Mar 2005 (UTC)
Hummingbirds of the U.S. and Canada generally migrate to warmer climates, though some remain in the warmest coastal regions. In addition, there is an increasing trend for Rufous Hummingbirds to migrate east to winter in the eastern United States, rather than south to Central America, this trend being the result of increased survival with the provision of artificial feeders in gardens. In the past, individuals that migrated east would usually die, but now they survive, and their tendency to migrate east is inherited by their offspring. Provided sufficient food and shelter is available, they are surprisingly hardy, able to tolerate temperatures down to at least -20°C.
Hummingbirds owe their wide distribution to their great power of flight and wandering habits no less than to their hardiness.
Hummingbirds and People
Hummingbirds will use feeders, particularly red ones. A suitable artificial nectar consists of one part sugar to four parts water. It is easiest to dissolve the sugar in boiling water, then cool it completely before putting it out for the birds. Sweet foods other than white sugar, such as honey, ferment too quickly and can injure the birds. Some commercial hummingbird foods are available, but they contain red dyes which are unnecessary and have been anecdotally reported to poison the birds. They also contain small amounts of nutrients, but hummingbirds apparently get their nutrients from the insects they eat, not from nectar, so the nutrients are also unnecessary. Thus plain white sugar and water make the best nectar.
The feeder should be rinsed and the water changed weekly, or more often in warm weather. At least once a month, or whenever black mold appears, it should be soaked in a solution of chlorine bleach. Hummingbirds tend to avoid feeders that have been cleaned with soap, possibly because they dislike the smell.
Much more detailed information is available at .
Hummingbirds sometimes fly into garages and become trapped. It is widely believed that this is because they mistake the hanging (usually red-colored) door-release handle for a flower, although hummingbirds can also get trapped in enclosures that do not contain anything red. Once inside, they may be unable to escape because their natural instinct when threatened or trapped is to fly upward. This is a life-threatening situation for hummingbirds, as they can become exhausted and die in a relatively short period of time, possibly as little as an hour. If a trapped hummingbird is within reach, it can often be caught gently and released outdoors. It will lie quietly in the space between cupped hands until released.
The Ohlone tells the story of how a Hummingbird brought fire to the world.
Traditionally hummingbirds were placed in the order Apodiformes, which also contains the swifts. In the modern Sibley-Ahlquist taxonomy, hummingbirds are separated as a new hummingbird order Trochiliformes.
There are between 325 and 340 species of hummingbird, depending on taxonomic viewpoint, divided into two subfamilies, the hermits (subfamily Phaethornithinae, 34 species in six genera), and the typical hummingbirds (subfamily Trochilinae, all the others).
Hummingbirds have been thought by evolutionists to have evolved in South America, and the great majority of the species are found there. All the most familiar North American species are thought to be of relatively recent origin, and are therefore (following the usual procedure of lists starting with more 'ancestral' species and ending with the most recent) listed close to the end of the list.
Genetic analysis has indicated that hummingbirds diverged from other birds 30 to 40 million years ago, but fossil evidence has proved elusive. Fossil hummingbirds have been found as old as a million years, but older fossils had not been securely identifiable as hummingbirds. Then, in 2004, Dr. Gerald Mayr of the Senkenberg Natural History Museum in Frankfurt-am-Main identified two 30-million-year old German hummingbird fossils and published his results in Nature. The fossils of the extinct hummingbird species, Eurotrochilus inexpectatus ("unexpected European hummingbird") had been sitting in a museum drawer in Stuttgart. They had been unearthed in a claypit in Frauenweiler, south of Heidelberg. | <urn:uuid:10898cf8-af56-42f3-863a-7a402ec5c489> | 3.96875 | 1,502 | Knowledge Article | Science & Tech. | 40.922178 | 286 |
(S.D.)-Search For Radioactive Decay Continues In SD Lab
LEAD, S.D. (AP) - Physicists in South Dakota have started assembling "detector units" in the search for a rare form of radioactive decay that could help explain how the universe evolved.
The Majorana Demonstrator Experiment is under construction in the Davis Campus of a shuttered gold mine in Lead in the Black Hills. It's next door to another experiment meant to detect dark matter.
Both experiments are housed nearly a mile beneath the earth in the former Homestake Gold Mine. Officials with the Sanford Underground Research Facility say that the first detector units were built through Monday when physicist Ryan Martin "attached a polished germanium-crystal detector the size of a hockey puck to a wafer-thin glass electronics board."
The experiment will need about 70 such units to search for neutrinoless double-beta decay.
(Copyright 2012 The Associated Press)
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18 Feb 2009 Corn starch/water on
an audio speaker. There is a very interesting video at this link
of oobleck dancing on an audio speaker:
Subject:University of Iowa Hydraulics
Center Films on Youtube (six films)
Introduction to the study of fluid
motion (1961, 25 minutes) http://youtu.be/EIuU9Q8CGDk
The first in a widely used series of films on fluid mechanics, produced
at IIHR under the direction of Hunter Rouse.
This introductory program, designed to orient engineering students,
shows examples of flow phenomena from a host of everyday experiences.
Empirical solutions by means of scale models are illustrated. The
significance of the Euler, Froude, Reynolds, and Mach numbers as
similitude parameters is illustrated.
Dr. Hunter Rouse served as Director of IIHR from 1944 to 1966. During
this time, he was instrumental in strengthening IIHRs fundamental
research emphasis and in developing teaching programs for hydraulic
engineers. Through his writings, research, and global travels, he
established IIHR as an internationally acclaimed innovative research
and teaching laboratory.
Fundamental Principles of flow (23 min)
Second in the series, this video departs from the essential generality
of the first by explicitly illustrating, through experi ment and
animation, the basic concepts and physical relation ships that are
involved in the analysis of fluid motion. The concepts of velocity,
acceleration, circulation, and vorticity are introduced, and the use of
integral equations of motion is demonstrated by a simple example.
Fluid Motion in a gravitational field
(24 min) http://youtu.be/-xoyLhiEOus
In this third video of the series, which proceeds from the intro
ductory and the basic material presented in the first two videos,
emphasis is laid upon the action of gravity. Principles of wave
propagation are illustrated, including aspects of gen eration,
celerity, reflection, stability, and reduction to steadiness by
relative motion. Simulation of comparable phenomena in the atmosphere
and the ocean is considered.
Characteristics of laminar and
turbulent flow (26 min) http://youtu.be/eIHVh3cIujU
The fourth video deals with the effect of viscosity. Dye, smoke,
suspended particles, and hydrogen-bubbles are used to reveal the
Various combinations of Couette and plane Poiseuille flow introduce the
principles of lubrication. Axisymmetric Poiseuille flow and development
of the flow around an elliptic cylinder are related to variation in the
Reynolds number, and the growth of the boundary layer along a flat
plate is shown.
Instability in boundary layers and pipe flow is shown to lead to
turbulence. The eddy viscosity and apparent stress are intro duced by
hotwire-anemometer indications. The processes of turbulence production,
turbulent mixing, and turbulence decay are considered.
Form, drag, lift, and propulsion (24
In the fifth video of the series, emphasis is laid upon the role of
boundary-layer separation in modifying the flow pattern and producing
longitudinal and lateral components of force on a moving body. Various
conditions of separation and methods of separation control are first
illustrated. Attention is then given to the distribution of pressure
around typical body profiles and its relation to the resulting drag.
The concept of circulation introduced in the second film is developed
to explain the forces on rotating bodies and the forced vibration of
cylin dri cal bodies. Structural failure of unstable sections is
Effects of fluid compressibility (17
The last in the six-video series makes extensive use of the analogy
between gravity and sound waves and illustrates, through laboratory
demonstrations and animation, the con cepts of wave celerity, shock
waves and surges, wave reflec tion and water hammer.
Two-dimensional waves are produced by flow past a point source at
various speeds relative to the wave celerity to illus trate the effect
of changing Mach number, and the principle is applied to flow at curved
and abrupt wall deflections. Axisymmetric and three-dimensional wave
patterns are then portrayed using color Schlieren pictures. | <urn:uuid:58bbc3a2-2cca-4aac-975b-6a2a183c1e45> | 2.890625 | 923 | Content Listing | Science & Tech. | 25.221004 | 288 |
Nitrate vs Nitrite
Both nitrate and nitrite are oxy anions of Nitrogen. Although they both seem to look alike, there are differences between them. These differences can be with respect to their structure, bonding, geometrical shape, oxidation state of Nitrogen, chemical reactivity, uses of them and etc. These differences are mainly discussed here.
NO3- ion is the conjugate base of HNO3 (nitric V acid) which is a strong acid. It is a planer molecule with sp3 hybridization in Nitrogen atom. All three oxygen atoms are equivalent. There are 24 electrons in the valence shells. NO3- ion has the molecular weight of 62.004 g mol-1.
NO2- ion is the conjugate base of HNO2 (nitric III acid) which is a weak acid (pKa=3.5). It is also a planer molecule with sp2 hybridization. In the valence shells, there are only 18 electrons. NO2- ion has the molecular weight of 46.006 g mol-1.
When the bonding in both the ions are considered, in NO3- ion the pi bonding involves four 2pz atomic orbitals (one orbitla from N and three orbitals from 3 oxygen atoms). These four atomic orbitals form 4, four-centred pi molecular orbitals. The molecular orbital with the lowest energy is the bonding orbital. The orbital with the largest energy is the anti-bonding orbital. Other two orbitals are degenerate (equal in energy) which are non-bonding orbitals. In the case of NO2- ion, the pi bonding involves only three 2pz atomic orbitals. Here, the orbital with the lowest energy is the bonding orbital, the middle one is the non-bonding orbital, and the other one is the anti-bonding orbital. In both the ions, the bonding orbitals involve in making the σ-bond (sigma-bond) and non-bonding orbitals involve in making π-bonds (pi-bonds). Therefore, in NO3- ion each bond has a bond order of 11/3. 1 from σ-bond and 1/3 from the π-bonds. In NO2- ion, the bond order is 11/2. 1 from σ-bond and 1/2 from the π-bonds.
Although, both the ions are from the same electronic geometry, as the bond order is different, their geometrical shapes are also different. The NO3- ion has a shape of planer triangular and the NO2- ion has an angular shape (or V shape). The bond angles are also different. ONO bond angle of NO3- ion and NO2- ion are 1200 and 1150 respectively. The oxidation state of Nitrogen in both NO3- ion and NO2- ion are +5 and +3 respectively. Because of these reasons (especially the difference in bonding), the chemical reactivity (such as basicity, oxidizing/reducing ability, products of thermal decomposition of the compounds consist of these ions) is also different.
In practice, NO2- ion is a weaker base while NO3- ion is a very weaker base. When the oxidation state of Nitrogen atom in these ions is taken in to consideration, NO2- ion can act as a reducing agent as well as an oxidizing agent while NO3- ion can only act as an oxidizing agent.
The examples for products obtained from thermal decomposition of NO3- and NO2- ions containing compounds are given below to show the difference in reactivity.
Even, when they form complexes with metal ions they behave in a dissimilar manner. That is, NO2- ion acts as a monodentate ligand while NO3- ion acts as a bidentate ligand.
These differences in chemical reactivity help us to differentiate the uses of them. For example, nitrites are generally used in the processing of meat (sometimes nitrates are also used), and nitrates are used for producing of explosives. Nitrates are naturally occurring and are cancerous. But Nitrites are not cancerous. | <urn:uuid:f6a548ac-b4b1-4ef4-b26e-802eaf6fc2cc> | 3.59375 | 877 | Knowledge Article | Science & Tech. | 51.455701 | 289 |
Famous Women in Astronomy
Part of the Astronomy For Dummies Cheat Sheet
When you’re studying astronomy don’t forget the women that made an impact in the field. Check out this list of amazing achievements by women astronomers and astrophysicists:
Caroline Herschel (1750–1848) Discovered eight comets.
Annie Jump Cannon (1863–1941) Devised the basic method for classifying the stars.
Henrietta Swan Leavitt (1868–1921) Discovered the first accurate method for measuring great distances in space.
Sally Ride (1951–2012) A trained astrophysicist, she is the first American woman in space.
Jocelyn Bell Burnell Discovered pulsars in her work as a graduate student.
E. Margaret Burbidge Pioneered modern studies of galaxies and quasars.
Wendy Freedman Leader in measuring the expansion rate of the universe.
Carolyn C. Porco Leads the Cassini imaging science team in the study of Saturn and its moons and rings.
Nancy G. Roman As NASA’s first chief astronomer, she led the development of telescopes in space.
Vera C. Rubin Investigated the rotation of galaxies and detected the existence of dark matter.
Carolyn Shoemaker Discovered many comets, including one that smashed into Jupiter.
Jill Tarter Leader in the search for extraterrestrial intelligence. | <urn:uuid:c1a9e1d0-9350-465a-a08c-c188f4ed1b70> | 3.859375 | 306 | Listicle | Science & Tech. | 42.766321 | 290 |
Go ahead and punch me in the face for being such a dweeb, but seeing Terrence Mallick’s Tree of Life really did have a fairly profound effect on my relationship with Mother Nature. It was apparent pretty much from the moment I walked out of the theater; something about the director’s vision just put me a bit more in tune with the natural world--especially, for some reason, birds. It’s kind of like the arrow in the FedEx logo: Once you start paying attention to birds, you can’t stop seeing them. But unlike the shipping company’s satisfying but straightforward visual gag, birds reward your attention over time with their incredible diversity. This graphic shows how all those dazzling species came to be.
The chart was created in conjunction with a groundbreaking new paper outlining avian evolution, published recently by an international team of biologists in the journal Nature. Using fossil records and DNA data, the group traced the speciation of all 9,993 species of birds known to man in unprecedented detail. Essentially, the dense circle you’re looking at is one of the most epic family trees ever created. Dr. Gavin Thomas, a postdoctoral fellow at the University of Sheffield, in England, was responsible for making the graphic, so I turned to him for a little help in decoding it.
You can think of the radial display like a typical top-down family tree, just wrapped up like a burrito to fit in as much data as possible. Each gray, concentric ring, Thomas explained, represents an interval of 20 million years, so the ancestor found in the circle’s center is roughly 110 million years old.
The colors correspond to the rate of speciation: Red indicates a high rate, green is moderate, and dark blue shows species that were slowest to mutate. Look at the Paleognaths at roughly 3 o’clock; they have a "fairly direct path to the centre," Dr. Thomas points out, meaning there are "relatively few speciation events" separating the 100-million-year-old birds from the ones living today. Among other species, the Paleognath superorder includes ostriches, which seem like a not-so-distant relative of dinosaurs, so that all checks out. Just below that you’ll find cardinals, conebills, and tanagers, all of which, in contrast, are products of far more significant speciation.
The team’s exhaustive work has already yielded some surprising insights. Whereas it was generally thought that biodiversity, in recent history, was slowing down across the board, speciation in birds is actually speeding up. Dr. Arne Mooers, a biologist from Simon Fraser University in Canada and one of the paper’s co-authors, speculated about the phenomenon in a statement. "Perhaps birds are special," he says. "Maybe they’re so good at getting around they can escape local competition from relatives and start anew elsewhere, producing bursts of new species at different times and in different parts of the globe."
It seems like a reasonable theory. Now can’t we get a bit closer the bull’s-eye to see where the dinos fit into all this?
[Hat tip: Yale News] | <urn:uuid:49895bfa-08fa-460f-9548-79d451ec3c43> | 2.6875 | 675 | News Article | Science & Tech. | 49.515429 | 291 |
Fire and Invasive Plants -- Combustibility of Native and Invasive Exotic Plants
Alison C. Dibble, U.S. Department of Agriculture, Forest Service, Northern Research Station, 686 Government Rd., Bradley, ME 04411
William A. Patterson III, Department of Forestry and Wildlife Management, University of Massachusetts, Amherst, MA 01003
Robert H. White, U.S. Department of Agriculture, Forest Service, Forest Products Laboratory, Madison, WI 53705-2398
The ease with which a plant fuel catches fire – its combustibility, or flammability, might differ between native plants versus invasive exotic plants that overtake their habitat. By comparing combustibility in these two groups of plants, we are seeking to improve the effectiveness of prescribed fire and the assessment of fire hazards in the Northeastern U.S. Risk of wildfire could be greater in the wildland-urban interface if invasive plants are dense and have higher combustibility than the native species. Conversely, a fire-prone ecosystem invaded by exotics might have less frequent fire return and lower severity, with consequences for fire-dependent species, e.g., federally endangered Karner Blue butterfly and its host plant, a native lupine of pitch pine forests.
With support from the Joint Fire Science Program (JFSP) we, with Mark J. Ducey
of University of New Hampshire, are modifying the Rothermel fuel models to
better represent conditions in the Northeast. Heat content is a missing link,
especially regarding common shrubs and herbs, and some invasive exotic plants.
These combustibility data can be used in BEHAVE Plus, FARSITE, and the
Emissions Production Model (EPM) so that models better represent the local
vegetation, and will added to the Fuel Characteristic Classification System
(Cushon et al 2002), which is a clearinghouse of fuels information.
We sampled flammability of plants in a cone calorimeter (ASTM 2002, see Fig. 1)
to quantify effective heat of combustion (HOC) as a measure of heat content in
dried (60°C), unground leaves and twigs. We compared 14 invasives, 12 of
which are exotic, to 13 native species which might be displaced in disturbed
habitats. Based on five replicates per species, we found a range from 6-17
Mj/kg, which is overall lower than for green and dry plant fuels from
California and Colorado.
|Fig. 1 Cone calorimeter apparatus used to measure heat content in oven dried, unground leaves and twigs of 27 native and exotic plants that grow in the Northeastern U.S.|
Highest average heat content was in speckled alder. Among shrubs and vines, it was relatively high in highbush blueberry, purple nightshade, common barberry, and Japanese honeysuckle, and lowest in smooth buckthorn and Oriental bittersweet. Among six herbs, rough-stemmed goldenrod had the highest heat content while Japanese stiltgrass and Japanese knotweed were lowest. Quaking aspen had higher heat content than invasive trees, while Norway maple and apple were lower than the others.
Overall, invasive plants tended to have lower heat content than native species (Fig. 2).
|Fig. 2. Notched box plot summarizing effective heat of combustion in six tree species, half of which are invasive in northeastern North America and half native. Because the notched portions of the two boxes do not overlap on the horizontal plane, the groups are significantly different.|
When broken out as a subset, three invasive trees (black locust -- Robinia
pseudoacacia, which is native only as far north as Pennsylvania; apple
-- Malus sp., and Norway maple -- Acer platanoides) are
significantly LESS flammable than three native trees (Fig. 2).
Our sample is small. In January 2003 Dibble, Ducey and White applied to the JFSP
to conduct a nation-wide combustibility survey of native and invasive exotic
We conclude that (1) use of fire to control undesirable vegetation can be more effective if a species-by-species approach is taken to meet management objectives in a particular stand; (2) flammability also involves leaf surface to volume ratio and moisture content (which is being measured in another study), and these should be quantified to improve modeling fire behavior; and (3) comparison of combustibility data from other regions will increase our understanding of fuels in the Northeast.
ASTM International. 2002. Standard test method for heat and visible smoke
release rates for materials and products using an oxygen consumption
calorimeter. Designation E 1354-02. West Conshohocken, PA: ASTM International.
Cushon, G. H., R. D. Ottmar, D. V. Sandberg, J. A. Greenough and J. L. Key. In
press. Fuel characteristic classification: characterizing wildland fuelbeds in
the United States. In A. Brennan, et. al. (eds.) National Congress on Fire
Ecology, Prevention and Management Proceedings, No. 1. Tall Timbers Research
Station, Tallahassee, FL. http://www.fs.fed.us/pnw/fera/jfsp/fcc/FCCpaper.pdf
Richburg, J. A., A. C. Dibble, and W. A. Patterson III. 2001. Woody invasive species and their role in altering fire regimes of the Northeast and Mid-Atlantic states. Pp. 104-111 in K.E.M. Galley and T. P. Wilson (eds.). Proceedings of the Invasive Species Workshop: the Role of Fire in the Control and Spread of Invasive Species. Fire Conference 2000: the First National Congress on Fire Ecology, Prevention and Management. Misc. Publ. No. 11, Tall Timbers Research Station, Tallahassee, FL.(Top) | <urn:uuid:edc43201-bbe0-4879-8f31-cc11f5f812ab> | 2.828125 | 1,256 | Academic Writing | Science & Tech. | 47.401774 | 292 |
Hyped Arsenic Bacteria Research 'Should Not Have Been Published'
by Brian Thomas, M.S. *
NASA recently issued a series of press releases and arranged a press conference to promote research claiming that life was possible in outer space.1, 2 However, the research drew heavy criticism from scientists around the world, and the interest-generating tactics that the space agency employed have been called into question.
The study, which appeared in the journal Science, focused on microbes found in a California lake, not in materials from space.3 The study's authors concluded that certain bacteria could actually incorporate the element arsenic—a well-known poison—into the structure of their DNA molecules. However, critics quickly noted that the testing procedure was flawed. The research results could have come from arsenic that was on or near the DNA, but not in it. It would have been quite simple for the researchers to have "washed" the DNA and then searched for the arsenic in a clean sample of pure DNA—but they didn't.
In addition, "it turns out the NASA scientists were feeding the bacteria salts which they freely admit were contaminated with a tiny amount of phosphate," science writer Carl Zimmer wrote for the online news magazine Slate. This could have supplied the phosphorous the bacteria needed, rather than having it completely replaced by arsenic. The University of Colorado's Shelley Copley added, "This paper should not have been published."4
The report in Science did not address the additional conundrum that DNA has physical size constraints on its elemental building blocks. Arsenic atoms are much larger than those of phosphorus and would undoubtedly yield warped and misshapen DNA that would be inaccessible to the many DNA-binding proteins upon which cellular life depends.
The NASA authors have so far refused to engage these issues, pointing to the more proper scientific procedure of publishing in a peer-reviewed journal. Critical letters to Science are currently in the mail.4
In the meantime, other scientists are not staying silent. Jonathan Eisen, University of California, Davis genomicist and Academic Editor of the online science journal PLoS Biology, called the NASA authors' lack of response "absurd." He told Slate, "They carried out science by press release and press conference. Whether they were right or not in their claims, they are now hypocritical if they say that the only response should be in the scientific literature."4
These events have a familiar tone. When media hyped the fossil primate "Ida" as a "missing link" in human evolution, rebuttals appeared in journals and news stories. Analysis of the details showed that the claim had absolutely no substance. Ida was merely an extinct variety of lemur.5,6,7
The same can be said of NASA's 1996 work-up of a meteorite, which supposedly contained intact fossils of Martian bacteria.8 A subsequent report from earlier this month, not accompanied by a press conference, demonstrated how these kinds of "fossil" markings are made by ozone gas interacting with minerals.9
ICR News has reported that the practice of doing "science" by press release serves an agenda other than presenting scientific data. For instance, since science could not show that the much-hyped "Ardi" was a human ancestor, that message was instead broadcast through the press.10 And since NASA needed federal funding at the time, the agency promoted the Martian germs.
So, did a press conference substitute for quality science when NASA proclaimed its arsenic bacteria find? Perhaps the government agency needs more public support again. At any rate, these cases and others show that the science often does not match the headlines, and it pays for readers to dig a little deeper.
- Brown, D. and C. Weselby. NASA-Funded Research Discovers Life Built With Toxic Chemical. NASA Feature. Posted on nasa.gov December 2, 2010, accessed December 9, 2010.
- Brown, D. and C. Weselby. NASA Sets News Conference on Astrobiology Discovery; Science Journal Has Embargoed Details Until 2 p.m. EST On Dec. 2. NASA press release, November 29, 2010.
- Wolfe-Simon, F. et al. A Bacterium That Can Grow by Using Arsenic Instead of Phosphorus. Science. Published onlineDecember 2, 2010.
- Zimmer, C. "This Paper Should Not Have Been Published"; Scientists see fatal flaws in the NASA study of arsenic-based life. Slate. Posted on slate.com December 7, 2010, accessed December 9, 2010.
- Thomas, B. New Fossil Hype Fits Old Pattern. ICR News. Posted on icr.org May 27, 2009, accessed December 9, 2010.
- Thomas, B. 2009. The Ida Fossil: A Clever Campaign for a Lackluster "Link." Acts & Facts. 38 (7): 17
- Thomas, B. More Scientists Say 'Ida' Is Not a Missing Link. ICR News. Posted on icr.org March 19, 2010, accessed December 9, 2010.
- Thomas, B. Meteor Crystals Spark Latest 'Life on Mars' Hype. ICR News. Posted on icr.org December 15, 2009, accessed December 9, 2010.
- Choi, C. Q. Martian Meteorite Not Evidence of Extraterrestrials, Scientists Say. Space.com. Posted on space.com December 2, 2010, accessed December 9, 2010.
- Thomas, B. Scientists Back off Ardi Claims. ICR News. Posted on icr.org December 4, 2009, accessed December 9, 2010.
* Mr. Thomas is Science Writer at the Institute for Creation Research.
Article posted on December 17, 2010. | <urn:uuid:8e873607-c3da-4b12-bc38-7bf5699c4af9> | 3.1875 | 1,184 | News Article | Science & Tech. | 58.001149 | 293 |
Mars has a striking red appearance, and in its most favorable position for viewing, when it is opposite the sun, it is twice as bright as Sirius, the brightest star. Mars has a diameter of 4,200 mi (6,800 km), just over half the diameter of the earth, and its mass is only 11% of the earth's mass. The planet has a very thin atmosphere consisting mainly of carbon dioxide (95%) with some nitrogen, argon, oxygen, and other gases. Mars has an extreme day-to-night temperature range, resulting from its thin atmosphere, from about 80°F (27°C) at noon to about - 100°F ( - 73°C) at midnight; however, the high daytime temperatures are confined to less than 3 ft (1 m) above the surface.Surface Features
A network of linelike markings first studied in detail (1877) by G. V. Schiaparelli was referred to by him as canali, the Italian word meaning "channels" or "grooves." Percival Lowell, then a leading authority on Mars, created a long-lasting controversy by accepting these "canals" to be the work of intelligent beings. Under the best viewing conditions, however, these features are seen to be smaller, unconnected features. The greater part of the surface area of Mars appears to be a vast desert, dull red or orange in color. This color may be due to various oxides in the surface composition, particularly those of iron. About one fourth to one third of the surface is composed of darker areas whose nature is still uncertain. Shortly after its perihelion Mars has planetwide dust storms that can obscure all its surface details.
Photographs sent back by the Mariner 4 space probe show the surface of Mars to be pitted with a number of large craters, much like the surface of Earth's moon. In 1971 the Mariner 9 space probe discovered a huge canyon, Valles Marineris. Completely dwarfing the Grand Canyon in Arizona, this canyon stretches for 2,500 mi (4,000 km) and at some places is 125 mi (200 km) across and 2 mi (3 km) deep. Mars also has numerous enormous volcanoes—including Olympus Mons (c.370 mi/600 km in diameter and 16 mi/26 km tall), the largest in the solar system—and lava plains. In 1976 the Viking spacecraft landed on Mars and studied sites at Chryse and Utopia. They recorded a desert environment with a reddish surface and a reddish atmosphere. Experiments analyzed soil samples for evidence of microorganisms or other forms of life; none was found, but a reinterpretation (2010) of the results in light of data collected later suggests that organic compounds may have been present. In 1997, Mars Pathfinder landed on Mars and sent a small rover, Sojourner, to take soil samples and pictures. Among the data returned were more than 16,000 images from the lander and 550 images from the rover, as well as more than 15 chemical analyses of rocks and extensive data on winds and other weather factors. Mars Global Surveyor, which also reached Mars in 1997 and remained operational until 2006, returned images produced by its systematic mapping of the surface. The European Space Agency's Mars Express space probe went into orbit around Mars in late 2003 and sent the Beagle 2 lander to the surface, but contact was not established with the lander. In addition to studying Mars itself, the orbiter has also studied Mars's moons. The American rovers Spirit and Opportunity landed successfully in early 2004 and have explored the Martian landscape ( Spirit's last transmission was in 2010). In 2008 NASA's Phoenix lander touched down in the planet's north polar region; it conducted studies for five months. Curiosity, another NASA rover, landed on Mars near its equator in 2012.
Analysis of space probes' data indicates that Mars appears to lack active plate tectonics at present; there is no evidence of recent lateral motion of the surface. With no plate motion, hot spots under the crust stay in a fixed position relative to the surface; this, along with the lower surface gravity, may be the explanation for the giant volcanoes. However, there is no evidence of current volcanic activity.
There is evidence of erosion caused by floods and small river systems as well as evidence of ancient lakebeds. The possible identification of rounded pebbles and cobbles on the ground, and sockets and pebbles in some rocks, suggests conglomerates that formed in running water during a warmer past some 2–4 billion years ago, when liquid water was stable and there was water on the surface, possibly even large lakes or oceans. Rovers have identified minerals believed to have formed in the presence of liquid water. There is also evidence of flooding that occurred less than several million years ago, most likely as the result of the release of water from aquifers deep underground or the melting of ice. However, other evidence suggests that the water would have been extremely salty and acidic. Data received beginning in 2002 from the Mars Odyssey space probe suggests that there is water in sand dunes found in the northern hemisphere, and the Mars Reconnaissance Orbiter, which went into orbit around the planet in 2006, collected radar data that indicates the presence of large subsurface ice deposits in the mid-northern latitudes of Mars. Most of the known water on Mars, however, lies in a frozen layer under the planet's large polar ice caps, which themselves consist of water ice and dry ice (frozen carbon dioxide); the lander Phoenix found and observed frozen water beneath the soil surface in the north polar region in 2008.
Because the axis of rotation is tilted about 25° to the plane of revolution, Mars experiences seasons somewhat similar to those of the earth. One of the most apparent seasonal changes is the growing or shrinking of white areas near the poles known as polar caps. These polar caps, which are are composed of water ice and dry ice (frozen carbon dioxide). During the Martian summer the polar cap in that hemisphere shrinks and the dark regions grow darker; in winter the polar cap grows again and the dark regions become paler. The seasonal portion of the ice cap is dry ice. When the ice cap is seasonally warmed, geyserlike jets of carbon dioxide gas mixed with dust and sand erupt from the ice.
Sections in this article:
The Columbia Electronic Encyclopedia, 6th ed. Copyright © 2012, Columbia University Press. All rights reserved.
See more Encyclopedia articles on: Astronomy: General | <urn:uuid:0b209998-4433-4b7d-8629-dc91f68d4b69> | 4.0625 | 1,348 | Knowledge Article | Science & Tech. | 44.253885 | 294 |
Science of the Quake
Developments in the wake of Japan's triple disasters: earthquake, tsunami, nuclear.
The US Geological Survey upgraded Japan's 11 March earthquake today to 9.0 from 8.9.
Based on Japan's huge network of 1,200 GPS monitoring stations, the quake shifted the country's coastline some 4 meters / 13 feet to the east, and knocked Earth of its axis by 16.5 centimeters / 6.5 inches, shortening Earth's days by about 1.8 millionths of a second.
The BBC reports that geographical shift will require that GPS-based driving maps be updated, and nautical charts, too, since water depths have been changed. Furthermore, much of the flooded coastline appears to have subsided permanently—or as permanently as anything ever is on this restless planet—and will not be dry land again anytime in the near future.
Here are before and after images of the the city of Ishinomaki in Miyagi Prefecture near the quake's epicenter. The "after" shot, above, was taken three days after the quake. Water still inundated the city. The "before" shot was from August 2008. Both are false color images: water is dark blue; vegetated land is red; dirt is tan; buildings are silver.
You can see how much of the vegetation in the agricultural fields has been stripped away. This is sure to have an impact on Japan's food production, perhaps for a while, since saltwater inundation is tough on farmlands. If people in the area depend on aquifers for fresh water, those could be affected by saltwater flooding too.
You can also see the extensive flooding around the Matsushima Air Base in the lower left corner of the image. It's not at all clear, at this point, just what pollution or toxins may have been unleashed from the air base and nearby industries.
Meanwhile much of Japan's chemical industry is still nonoperational due to power shortages. More worrisome is that fate of chemical plants in the tsunami zone. According to Chemical & Engineering News, there aren't many chemical manufacturing plants in this hardest hit region of northeastern Japan. But there are some. The effects on them of fires, earthquakes, tsunamis, and continued flooding remains largely unknown and/or undisclosed:
A raging fire at the Cosmo Energy refinery in Chiba that began March 11 touched off an overnight fire at the neighboring Chisso polyethylene and polypropylene plant. Chisso says that none of its workers were injured and that damage to the facility is relatively light. Polysilicon producer Tokuyama has a subsidiary... located in [an area] devastated by the tsunami. Tokuyama says it is assessing damage to the subsidiary and to its facilities elsewhere in Japan. Chemical manufacturer Tosoh says its staff in the Tohoku area is safe, including the staff of a plant in the town of Ishinomaki, which was largely destroyed by the tsunami. This facility was flooded and Tosoh says the extent of the damage is unclear.
In the images above you can see fires at several oil refineries and industrial complexes, including facilities in the Port of Sendai and a petrochemical facility in Shiogama, where a large explosion was reported. On the left is a natural-color image showing a large brown smoke plume extending about 85 kilometers / 53 miles southeast from the coastline. The image on the right was used to confirm that the brown plume was actually something in the air and not something on the ground/water. Here's an explanation of the technology used to ascertain that information from far away:
[T]he right-hand image is a stereoscopic "anaglyph" created from data in MISR’s [Multi-angle Imaging SpectroRadiometer aboard NASA’s Terra spacecraft] red spectral band, and generated by displaying the 46-degree backward view in red and 60-degree backward view in cyan. The separation between the red and cyan images is known as stereo parallax, and is related to the height of the observed features above the surface. Viewing the anaglyph with red-cyan glasses (red filter over the left eye) gives a perception of height. No separation is visible for the coastline, which is at sea level, but the clouds and plume are distinctly elevated. The height of the plume is estimated to be about 2 kilometers (1.2 miles), at a similar altitude as the nearby clouds.
As for efforts to avert disaster at Japan's imperiled nuclear power plants, the New York Times reports near chaos among those running the show:
"They're basically in a full-scale panic" among Japanese power industry managers, said a senior nuclear industry executive. "They're in total disarray, they don't know what to do."
Most alarming of all is what's happening at the Fukushima Daiichi's reactor number 3 that exploded yesterday. In the current catalogue of bad possibilities, this one is the Mother of all Bad Possibilities, since the reactor uses a mixed oxide fuel, known as MOX, made with reprocessed plutonium and uranium oxides. If any of that gets out, the situation gets much worse faster, since inhaling plutonium is lethal, even tiny bits of it. | <urn:uuid:b8cbac5b-a324-484f-919c-ed2222fbcc74> | 3.734375 | 1,084 | News Article | Science & Tech. | 45.18859 | 295 |
Joined: 16 Mar 2004
|Posted: Thu Aug 06, 2009 11:24 am Post subject: Nanotubes Could Aid Understanding of Retrovirus Transmission
|Recent findings by medical researchers indicate that naturally occurring nanotubes may serve as tunnels that protect retroviruses and bacteria in transit from diseased to healthy cells — a fact that may explain why vaccines fare poorly against some invaders.
To better study the missions of these intercellular nanotubes, scientists have sought the means to form them quickly and easily in test tubes.
Sandia National Laboratories researchers have now learned serendipitously to form nanotubes with surprising ease.
“Our work is the first to show that the formation of nanotubes is not complicated, but can be a general effect of protein-membrane interactions alone,” says Darryl Sasaki of Sandia's Bioscience and Energy Center .
The tunnel-like structures have been recognized only recently as tiny but important bodily channels for the good, the bad, and the informational.
In addition to providing protected transport to certain diseases, the nanotubes also seem to help trundle bacteria to their doom in the tentacles of microphages. Lastly, the nanotubes may provide avenues to send and receive information (in the form of chemical molecules) from cell to cell far faster than their random dispersal into the bloodstream would permit.
Given the discovery of this radically different transportation system operating within human tissues, it was natural for researchers to attempt to duplicate the formation of the nanotubes. In their labs, they experimented with giant lipid vesicles that appeared to mimic key aspects of the cellular membrane .
Giant lipid vesicles resemble micron-sized spherical soap bubbles that exist in water. They are composed of a lipid bilayer membrane only five nanometers thick.
The object for experimenters was to create conditions in which the spheres would morph into cylinders of nanometer radii.
But researchers had difficulties, says Sasaki, perhaps because they used a composite lipid called egg PC that requires unnecessarily high energies to bend into a tubular shape.
Egg PC is inexpensive, readily available, and offers good, stable membrane properties. It is the usual lipid of choice in forming nanocylinders via mechanical stretching techniques.
But Sandia postdoctoral researcher Haiqing Lui instead used POPC — a single pure lipid requiring half the bending energy of egg PC.
She was trying to generate nanotubes by a completely different approach that involved the use of motor proteins to stretch naturally occurring membranes into tubes.
Working with Sandia researcher George Bachand, she serendipitously found that interaction of the POPC membrane with a high affinity protein called streptavidin alone was enough to form the nanotubes.
“Perhaps this information — linking membrane bending energy with nanotube formation — may provide some clue about the membrane structure and the cell's ability to form such intercellular connections,” Sasaki says.
The formation was confirmed by Sandia researcher Carl Hayden, who characterized the nanotube formation through a confocal imaging microscope. The custom instrument allows pixel-by-pixel examination of the protein interaction with the membranes comprising the nanotubes by detecting the spectrum and lifetimes of fluorescent labels on the proteins.
Nanotube formation had been noticed previously by cell biologists, but they had dismissed the tiny outgrowths as “junk — an aberration of cells growing in culture,” says Sasaki. “The reason they were only noticed recently as trafficking routes is because of labeling studies that marked organelles and proteins. This allowed a focused look at what these nanostructures might be used for.”
It became clear, says Sasaki, that the organelles were being transported with “specific directionality” on the backs of motor proteins within the tubes, rather than randomly.
Three-dimensional networks of nanotubes also are found to be created by macrophages — part of the police force of the body — grown in culture, says George. The tubes in appearance and function resemble a kind of spider web, capturing bacterium and transporting them to the macrophages, which eat them.
Other paper authors include postdoc Hahkjoon Kim and summer intern Elsa Abate.
The lipid work is supported by Sandia's Laboratory Directed Research and Development office. Motor protein work is supported by DOE's Office of Basic Energy Sciences.
Results were published in the American Chemical Society's Langmuir Journal in mid-March.
Source: Sandia.gov /... | <urn:uuid:8be1c3e2-ea54-459f-83ce-a0fd4be35a9f> | 3.03125 | 950 | Comment Section | Science & Tech. | 23.619571 | 296 |
Emerging Explorer, National Geographic Blackstone Innovation Challenge Grantee
Photograph by Dino Martins
Photograph by C. Lewis
Do you like chocolate? Coffee? Pollinating insects make these and hundreds of other foods possible. The threatened habitats that support those insects may often be out of sight and out of mind, but Dino Martins brings their importance home. “Pollinators are one of the strongest connections between conservation and something everyone needs—food.” With his infectious enthusiasm and practical solutions, Martins acts as a pollinator himself, carrying crucial information to Kenya’s isolated farmers, schoolchildren, and a larger world of travelers and scientists.
“Insects are the invisible, behind-the-scenes workers that keep the planet going,” Martins observes. “They do incredibly complicated things but are never recognized for it. I’m privileged to be their messenger.” Growing up in rural Kenya, Martins saw the most basic interface between farms, food, and nature every day. “In the developing world, subsistence farmers are on the front lines of poverty, hunger, and either saving or destroying forests. Africa is especially vulnerable since so many of the crops that provide nutrition are 100 percent dependent on wild insects.”
Examples abound. In a shrinking fragment of forest, some of the last remaining African violets cling to a hillside and fight to survive. Long-tongued bees grasp the fragile flowers in their teeth, fold back their wings, and vibrate with unimaginable intensity to buzz-pollinate the blossoms. Energized, the same bees then travel to pollinate crops in nearby farm fields. But for how long? If the violets vanish, so could the bees, and ultimately acres of crops.
Elsewhere, a community of farms struggles on land degraded by deforestation, charcoal burning, and high pesticide use. Yet when passion fruit trees produce poor yields, what is blamed? Bees. “Farmers look at the big scary carpenter bees swarming around their trees and rush to kill them,” says Martins. “In fact, they need more bees, not fewer. Passion fruit nectar lies concealed below a lid in the plant. It takes a big hefty bee to lift the lid, extract the nectar, and pollinate the flower. A little honeybee could never do it.” Martins helps create a nesting habitat that will attract the big bees and allow pollinators and crops to flourish again.
Down the road, hawk moths flit from male to female papaya trees, their brief evening commute entirely responsible for the trees’ pollination and survival. “Papaya is such an important crop for many rural communities because it’s incredibly rich in vitamins, can be used medicinally, and survives drought,” Martins notes. “We help farmers recognize and protect its major pollinators.”
All across East Africa, Martins works to identify the most useful plants and pollinators, return them to their habitats, and help both ecosystems and local communities thrive. He stresses that “farmers need to understand why leaving a little space for nature isn’t a luxury, but a necessity for productive, sustainable agriculture. Farmers everywhere are conservative and skeptical. So I make one or two of them my champions in the community, demonstrating the success of our techniques. When others see the proof, they all want to try it.”
If you can’t find Martins with farmers in the field, try looking in an outdoor classroom. One school he’s involved with meets under a tree that’s buzzing with 400 species of bees. “The biodiversity is overwhelming,” Martins exclaims. He works with schoolchildren to start pollinator gardens; collect bugs; examine hairy, eight-eyed wonders under magnifying glasses; and identify the most relevant crops and pollinators in their community. “In largely illiterate areas, these kids are often the first in their families to go to school. They may be resource-poor, but they’re nature-rich. You couldn’t ask for better, more enthusiastic young scientists.”
Technology is transforming his efforts. “Now that rural Kenya has Internet and mobile phone connections, I can email the farmers and field scientists I work with. Eventually I want farmers to be able to take pictures with phones and send them to bee taxonomists on the other side of the world. I want Kenyan school kids to talk with U.S. kids about pollinators and crops where they live.” Martins’s blog links him with scientists across the globe. One recent entry about mango pollination prompted responses from the U.S., Italy, Nepal, Pakistan, India, and Ghana within just one day. His magazine articles, illustrations, and guidebooks are widely published. “Sharing information opens our eyes to the fact that the problems of the world are not unique to any one place.”
Martins stresses that everyone can make a difference. “Look at your next plate of food and ask where it came from, how it got to you. Every time you eat you can choose to support farming that’s shown to be good, rather than abusive, to nature and people. You vote with your wallet, your feet, and your mouth.”
Follow @NatGeoExplorers on Twitter
My name is Dino J. Martins, I am a Kenyan entomologist and I love insects. The Kiswahili word for insect is dudu and if you didn't know already, insects rule the world!
In Their Words
“Every single person on our planet has a diet that includes food made possible by pollinating insects. When this connection is threatened, all of humanity is threatened.”
Martins discusses the age old relationship between honeybees and humans—and its importance in the future.
Traditionally, it's the birds and the bees that get all the attention-unless you're an entomologist. Then it's the bees and the bees, not to mention the flies and the wasps and the moths.
Our Explorers in Action
Meet female explorers who have pushed the limits in adventure, science, and more. | <urn:uuid:05948a26-6a20-4242-9ad6-ead65affaddb> | 3.375 | 1,299 | Nonfiction Writing | Science & Tech. | 49.168064 | 297 |
Fri Mar 21 18:02:28 GMT 2008 by Gordon
Why is it that gamma rays cannot penerate the earth's atmosphere when they will happily travel though thick lead.
Fri Mar 21 18:59:29 GMT 2008 by Radek
Air in atmosphere corresponds to ... One meter of lead!
Fri Mar 21 19:24:17 GMT 2008 by Tony Byron
"The atmosphere shields us from cosmic rays about as effectively as a 13-foot layer of concrete,..."
"The Earth's atmosphere would soak up most of the gamma rays, Melott says, but their energy would rip apart nitrogen and oxygen molecules, creating a witch's brew of nitrogen oxides, especially the toxic brown gas nitrogen dioxide that colours photochemical smog (see graphic)."
(long URL - click here)
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Falling Objects and Bouncing
Location: Outside U.S.
Date: April 2008
I am looking to compare different masses, objects, shapes
and compare these to dents made in a specific plate (e.g.
polystyrene). For this experiment I would need not only to be able
to work out the velocity of the object but also how much air
resistance is effecting the object plus the amount of air is jammed
between the object and the plate.
If possible, I would also be
looking for a way to measure how much, for instance, an object would
bounce back, or how much weight and height will get me the best
results, but I also need to find a formula to see wether any of my
results make any sense. I was thinking of letting an object
dimensions around 5 x 5 (base) by 5-10 (height) depending on object
otherwise for sphere a 3 cm radius object drop from around 3 meters
object mass around 250g to 1kg. I do not know if pressure, humidity
or temperature matters.
It sounds like you're asking for someone to 1. validate your methodology,
and 2. suggest any other factors you need to consider. Is that right? (if
not, reply and let me know what else).
First, the methodology. It sounds like you have an ambitious approach, but I
think some organization up front will really help you get good value from
your efforts. There is a method known as 'design of experiments' that might
help. I am going to walk you through some basic steps, and hopefully it will
Step one is to have a hypothesis. What are you trying to prove? It sounds
like you are testing something about elastic collisions (such as the
relationship between objects and the mark they leave on a plate), but I am
not clear what.
Step two is to organize and categorize your variables. You have two kinds of
variables: independent and dependent. An independent variable is something
you can set yourself (such as how high to drop the object, which object with
which properties, etc.). A dependent variable, often called a response
variable, is one that is determined by independent variables. The mark left
on the plate or the height the object bounces might be response variables. A
third type of "variable" is a factor that you do not intentionally change (I
put "variable" in quotes because sometimes they change and sometimes they
do not). There are lots of these factors, some of which you can control and
some you cannot. You might always choose to use the same target plate --
that is a factor that you hold constant. You might work outside, and have to
deal with wind or temperature changes -- these affect your results, but you
cannot control them. It is a good idea to record variables and factors that
affect your results -- they may be helpful later in interpreting your
Step three is to revisit your hypothesis -- restate your idea in terms of
the variables that you can measure. Saying "I want to see what happens....".
is not as powerful as saying something like "A change of independent
variable A will lead to a change in dependent variable B in this way C."
Step four is to set up your equipment to actually test your hypothesis. Keep
it simple -- pick materials and equipment that fit what you are trying to
test. Remove things that will introduce uncontrollable variables. The more
variables you try to change, the harder the experiment will be to run and
the harder the results will be to analyze. Sometimes you have to have a lot
of variables, but it is often a good idea to start simple first, and then
work your way up to more complicated experiments.
I strongly recommend you read about 'design of experiments' to help you
understand the approach I am suggesting here. The Internet has a ton of information,
as would a library too.
Now for your specific situation.
It sounds like you are trying to do experiments involving colliding objects.
Have you studied 'kinetic energy' in physics yet? I would start there. You
can get all the equations you need. I would specifically study elastic and
inelastic collisions. Usually collisions are not purely one or the other.
With a rubber ball, the ball deforms as it strikes a hard object. Some
energy is dissipated in the deformation, and some is returned elastically.
If you are hitting an expanded Polystyrene ('Styrofoam') target, the energy of the
falling object will be partially/mostly absorbed by the Styrofoam. For your
objects and distances (~1kg, ~10m), I think you can safely neglect air/wind
effects. If you consider objects of different shapes, now you have a very
difficult-to-control factor as now the orientation of the object affects how
it bounces (I would avoid this variable, to be honest -- stick with
spheres). As for weights and masses, it probably does not matter that much
unless you use very light, low-density objects (they will be affected by
air). Ball bearings, rocks, and other similar 'heavy' objects should all
Hope this helps,
That is a massively difficult and computationally intensive endeavor
you want to undertake! I am afraid that the best answer I can give, is
to say that with without a supercomputer running extremely complex
Finite Element Analysis software, and a lot of very expensive computer
time, there is no way to do what you are suggesting. It is amazing how
complex it is to accurately describe something as seemingly simple as
dropping a block though air! Further, before you can even think of
attempting to see how far an object would bounce off your polystyrene
plate, you would need to mathematically characterize the detailed
physical characteristics of both the plate and the falling object.
So, I am sorry, but to do what you want to do is simply impossible with
the resources available to someone like you or even me.
You have a pretty complicated project. For a "dropping" distance of ~ 3
meters, air pressure, humidity and temperature will probably be negligible.
For a sphere, Stokes' Law says that the shear viscosity is F=6 x pi x a x nu
x v (for Reynolds numbers 1 (true for air)). For heavy objects of radius
'a' the velocity 'v' falling through air with a viscosity 'nu' will not be
significant I don't think. How bodies of different shape fall is a complicated
problem because they tend to tumble, so you should probably stick to spheres.
Relating the indentation of the base to the mechanical parameters may be very
tricky too. Not all polystyrene, for example, has the same elasticity, which
determines how much of the energy of the falling object is absorbed compared
to how much is retained by the falling object.
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