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ORS 4 (Octahedral
Research Satellite 4), also known as Environmental Research
Satellite-18 (ERS-18), was launched
on 28 April 1967. The elliptical orbit had an apogee of 111,553 km, a
perigee of 8631 km, and an inclination of 32.9 degrees. The orbital period
was 2840 minutes. The spacecraft was a spin stabilized octahedron that
weighed 7.8 kg and measured 29.3 cm along each triangular edge. Each of the
8 triangular faces contained solar cells, allowing for an average power
output of 4 Watts. The spin rate was initially 6 rpm. There was a
large coning during the early lifetime and owing to improper dynamic
balancing, the final stable spin axis was ~ 90 degrees from the intended
one. This change of orientation caused only minor effects in the data
interpretation. The satellite carried a solar aspect sensor that determined
the angle between the satellite-Sun line and the satellite spin axis to
within 7.5 degrees. The spacecraft operated well from launch until 3 June
1968, when a preset timer turned off the transmitter.
The primary objectives of this satellite were to measure the cosmic gamma-
ray spectrum between 0.25-6 MeV, monitor the solar X-ray flux, obtain a
background measurement for a prototype space nuclear detonation detector,
and measure charged particles within the magnetosphere.
The gamma-ray experiment consisted of 2 separate detector systems. The main
system was used to measure the cosmic gamma-ray spectrum in the range 0.25-
6 MeV. It consisted of a 7.62 cm diameter by 6.35 cm long NaI crystal
surrounded on all sides but one by a 1 cm thick plastic scintillation
counter. The 2 crystals were optically separate and viewed by separate
photomultiplier tubes. The plastic counter served as a charged particle
rejector. A five channel differential pulse height analyzer and 2 integral
discriminators were used to measure the energy loss in the central
detector. Each segment was sampled for 4.7 s every 75.2 s. A second gamma-ray
detector system was used to determine the feasibility of a simple heavily
shielded NaI crystal to measure delayed gamma-rays from a nuclear
detonation in space. The sole purpose was to obtain the background counting
rate as a function of position in the magnetosphere.
The spectrum determined by the ORS 4 detector above 1 MeV was considerably
above the extension of the diffuse cosmic background X-ray spectrum
previously detected by Ranger III and other experiments. This led to the
belief that there was an additional cosmic or galactic gamma-ray component
above the one accounted for by the intergalactic electrons scattering on
the 3 degree Kelvin background radiation.
- Vette et al. 1970, Ap J Lett, 160, pp.L161-170.
- Vette et al. 1970, IAU Symp. 37, p. 335. | <urn:uuid:dd3b131b-676d-4277-b3b2-175cf92c8b94> | 3.1875 | 635 | Knowledge Article | Science & Tech. | 55.552974 |
1. What is .NET Framework?
.NET Framework is a complete environment that allows developers to develop, run, and deploy the following applications:
.NET Framework also enables a developer to create sharable components to be used in distributed computing architecture. NET Framework supports the object-oriented programming model for multiple languages, such as Visual Basic, Visual C#, and Visual C++. .NET Framework supports multiple programming languages in a manner that allows language interoperability. This implies that each language can use the code written in some other language.
2. What are the main components of .NET Framework?
.NET Framework provides enormous advantages to software developers in comparison to the advantages provided by other platforms. Microsoft has united various modern as well as existing technologies of software development in .NET Framework. These technologies are used by developers to develop highly efficient applications for modern as well as future business needs. The following are the key components of .NET Framework:
3. List the new features added in .NET Framework 4.0.
The following are the new features of .NET Framework 4.0:
4. What is an IL?
Intermediate Language is also known as MSIL (Microsoft Intermediate Language) or CIL (Common Intermediate Language). All .NET source code is compiled to IL. IL is then converted to machine code at the point where the software is installed, or at run-time by a Just-In-Time (JIT) compiler.
5. What is Manifest?
Assembly metadata is stored in Manifest. Manifest contains all the metadata needed to do the following things
The assembly manifest can be stored in a PE file either (an .exe or) .dll with Microsoft
intermediate language (MSIL code with Microsoft intermediate language (MSIL) code or in a
stand-alone PE file, that contains only assembly manifest information.
6. What are code contracts?
Code contracts help you to express the code assumptions and statements stating the behavior of your code in a language-neutral way. The contracts are included in the form of pre-conditions, post-conditions and object-invariants. The contracts help you to improve-testing by enabling run-time checking, static contract verification, and documentation generation. | <urn:uuid:842102be-7ab9-4b1d-8f18-c361fa8e4034> | 3.015625 | 459 | Q&A Forum | Software Dev. | 38.690569 |
They Might Be Giants
We don't even have a jar big enough to catch it in." Those were the first words out of my mother's mouth when she saw the giant moth. About 5 or 6 inches wide in wingspan, it was fluttering against a tiled wall-in our bathroom, of all places. It appeared to be covered with something resembling green fur, and it was huge. It finally stopped moving and clung to the shower curtain. My sister and I caught it in a shoe box and let it go outside.
I later learned the moth we saw that night was a luna moth, one of about 13 species of giant silk moths found in Missouri. Members of the Saturniidae family, they have silky, carpet plush wings, delicate legs and inviting furry bodies. "Velvety" may be the best word to describe them. The Saturniids are the largest members of the Order Lepidoptera, or butterflies and moths, and are among the most spectacular animals found in North America's forests and neighborhoods.
The majority of the world's 1,500 species of Saturniids live in the tropics. About a dozen species are found in Europe, including the cold reaches of the North Cape of Norway and part of Siberia. About 50 species reside in North America. No Saturniids have been known to become extinct, but many are endangered, especially the tropical inhabitants.
In Missouri, we are most likely to see giant silk moths after midnight in late May or June. Many people wait years to see one, in part because the adult stage of these colorful and largest of all moths lasts for only about one week.
The giant silk moths begin life like most Lepidoptera. Usually at night, females emit pheromones to attract mates. Males "smell" the pheromone up to miles away with the help of sensitive receptors located at the tips of their featherlike antennae. Males often fly great distances to reach females and, once united, couples remain together about a day while they mate.
Female moths usually lay eggs the next day. They search for trees or shrubs that provide nutritious leaves for the new larvae. The largest Saturniid found in North America, the Cecropia moth, may lay more than 100 eggs, usually on the undersides of leaves on oak, hickory and other hardwoods. Cecropias may have a wing span of up to 7 inches. Females fly from leaf to leaf, sometimes tree to tree, dispersing their eggs. Female Saturniids die | <urn:uuid:06495a4f-8ec8-4311-85f6-07af5597489c> | 3.453125 | 528 | Personal Blog | Science & Tech. | 56.537708 |
What is EXAMPLES OF ECOLOGICAL BACKLASH?
Some examples of ecological backlash: Pest control resistance- bugs become immune to treatments and chemicals Effects of an oil spill on the enviroment- loss of fish, dirty ...
What is ECOLOGICAL BACKLASH EXAMPLES? Mr What will tell you the definition or meaning of What is ECOLOGICAL BACKLASH EXAMPLES
Ecology is the study of organisms and their environments. The types of ecology are population ecology and community ecology. There is also the study of behavioral
What is EXAMPLES OF ECOLOGICAL BACKLASH? Mr What will tell you the definition or meaning of What is EXAMPLES OF ECOLOGICAL BACKLASH
Definition of ecological backlash – Our online dictionary has ecological backlash information from A Dictionary of Plant Sciences dictionary. Encyclopedia.com: English, psychology and medical dictionaries
What are example of ecological backlashes? ChaCha Answer: Ecological backlash involves the counter-responses of pest populations or o...
Ecological backlash reduce the effectiveness of pesticides, create pests immune to eradication, change habitat patterns and threaten otherwise safe ...
Best Answer: From several sites: ecological backlash The unexpected and detrimental consequences of an environmental modification (e.g. dam construction) which may outweigh ...
Best Answer: Grizzly man killed by grizzlies. http://en.wikipedia.org/wiki/Grizzly_Man ... YOU'RE FROM DASMARINAS NATIONAL HIGH SCHOOL, RIGHT? Correct me if I'm wrong. I ...
examples: larch sawfly resistant to introduced ichnenmonid; house flies resistant to pteromalid (in lab) ... Other Forms of Ecological Backlash; Enhanced Microbial Degradation; insecticides and herbicides rapidly degraded by soil microbes; ...
Free Essays on Example Of Ecological Backlashes for students. Use our papers to help you with yours 1 - 30.
Science & Environmental Health Network - Precautionary Principle ... Jan 16, 2003 . On-the-ground examples of ecological backlash from technologies we .
Ecological backlash and its management ... For example. Render the resistance gene "functionally" recessive with extremely high doses of the insecticide 2. and is commonly added to insecticides to enhance suppression at low to moderate levels of resistance. C. 1.
There are many causes of ecological backlash and all of these are attributed to the "acts of man" like: 1. Dam construction which alter the natural ...
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Ecological Backlash - download or readfalse online. ... Ecological backlasb involves the countei-iesponses of pest populations oi othei biotic
ECOLOGICAL BACKLASHES Ppt Presentation ... Deforestation The removal of a forest or stand of trees where the land is thereafter converted to a non-forest use Examples of deforestation include conversion of forestland to farms, ... backlash of the new deal. By: ...
Essays on Example Of Ecological Backlash for students to reference for free. Use our essays to help you with your writing 1 - 60.
To view this website you will need any broadband connection and the Flash plug-in ... Counting Since 1st August 2005 :
Ecological backlash meaning? ChaCha Answer: Ecological backlash involves the counter-responses of pest populations or other biotic fa...
Best Answer: There are many causes of ecological backlash and all of these are attributed to the "acts of man" like: 1. Dam construction which alter the natural ecosystem of ...
Ecological backlash example are 1. throwing garbage in the river - water pplution 2. eligal logging -Ewan Ko 3.pag kakaingin - Hnd Ko ALm 4. improper wastedisposal -pollution and f ...
The climate change backlash and the case for ecological sustainability. By Willy De Backer on 22 January, 2010. ... No, what we need is to produce the blueprint and the real life examples for a new resource-constrained, global and equitable prosperity.
The ecological backlash - nature versus man,. [St. Lucia, Q.] : University of Queensland Press. MLA Citation. Thomson, J. M. The ecological backlash - nature versus man, by J. M. Thomson University of Queensland Press [St. Lucia, Q.] 1970.
What is ecological backlash? Instantly find the definition, meaning and translation of ecological backlash at TermWiki.com
What Is Ecological Backlash. What Is An Ecological Footprint. Weblink Page Faq What Is The Individual Income Tax Return. Frequently Asked Questions What Is The Reliacard Visa Debit Card. What IS An. Ecological Footprint. Grade Level: Elementary and Middle School. Subject Correlation: Science.
Give me a example of out look in life? It maybe positive: "I will study very well, graduate from a good college, have a great job, and be able to support my family."
ecological backlash, ecological backlashes, ecological backlash examples, ecological backlash definition, ecological backlash in the philippines, ecological backlashes picture, ecological backlash pictures, ecological backlashes examples, ...
Example sentences . The rich are certainly not the only targets in the current populist backlash. ... Ecological backlash. Conservative backlas... Backlash movie. Coupling backlash. Nearby Words. backing. backing away. backing dog. backing down. backing for.
Ecological backlash? ecological backlash The unexpected and detrimental consequences of an environmental modification (e.g. dam construction) which may outweigh the gains anticipated from the modification scheme.
Ecological backlash mainlymanifests in the form of resistance, resurgence, and replacement- the three "R" s ofpest management awareness.Example Ecological BacklashesGuimaras Oil SpillIt was said that the captain has no capacity to manage the ship for it was overloadedwith oil tankers.
What is example of ecological backlash? Ecology is the study of organisms and their environments. The types of ecology are population ecology and community ecology.
On-the-ground examples of ecological backlash from technologies we have already released into the environment provide ample rationale for adopting Mr. Hurd's precautionary approach to introducing novelties into the universe. Ecological Failures
Sample Picture On Ecological Backlash. Report On Ecological Footprint In China. Sample Report On Findings Recommendations. The Clear Picture On Clear Channel Communications, Inc. A. Report on Ecological Footprint In China 35 CCICED - WWF Report on Ecological Footprint in China. Free Download ...
Environmental Backlash in the Evangelical Sub-Culture. Richard T. Wright Gordon College 255 Grapevine Road Wenham, MA 01984. ... Criticism of environmentalism is consistent with World's general stance on environmental issues. For example, ...
The ecological backlash - nature versus man by James Miln Thomson; 1 edition; First published in 1970; Subjects: Ecology
Prominent examples of ecological backlash that have occurred through the years include, the Chernobyl disaster that happened in Ukraine in 1986.
You can probably think of more examples. What up with this? Where did all this come from? ... > Why does there seem to be an "environmental backlash" strain in some modern > SF? That certainly sounds to me like you're claiming that there is a trend.
If the response of the public to the politicians' actions was to stage huge protests, then that would be an example of a backlash.
The ecological backlash - nature versus man / by J. M. Thomson. Author. Thomson, J. M. (James Miln), 1921- Published [St. Lucia, Q.] : University of Queensland Press, Physical Description. 15 p. ; 22 cm. Series. University of Queensland inaugural lectures;
For example, in a pair of gears backlash is the amount of clearance between mated gear teeth. Theoretically, the backlash should be zero, but in actual practice some backlash must be allowed to prevent jamming.
For example, molecular ecology revealed promiscuous sexual behaviour and multiple male partners in tree swallows previously thought to be socially monogamous In a biogeographical context, the marriage between genetics, ecology and evolution resulted in a new sub-discipline called phylogeography
Expanding Trade With China Creates Ecological Backlash. Dennis Normile; Summary. Scientists in the United States and China are scrambling to cope with an unintended consequence of increasing economic ties--a two-way flow of unwelcome plants and animals. ...
Environmental backlash email@example.com Mon, 10 Jun 1996 11:46:13 EST. Messages sorted by: Next message: Peter Vibert: "postmortem" Previous message: Paul Arveson: "postmortem"
One of the most famous examples of political backlash occurred in the British colonies during the 18th century. When English rulers decided unilaterally to raise taxes on such common goods as stamps and tea, ...
What-Are-Some-Examples-of-Ecology - What are the examples of ecological backlash? : Some examples of ecological backlash: Pest control resistance- bugs become i...
Lecture #23: Environmental Backlash Suggested Readings: Norman J. Vig & Michael E. Kraft, Environmental Policy: New Directions for the Twenty-First Century, 2002. William Shutkin, The Land That Could Be: Environmentalism and Democracy in the 21st Century, 2000.
I personally doubt that disastrous ecologic backlash can be avoided simply by applying to our problems more science and more technology. ... Wilber, Ken, Sex, Ecology, Spirituality: The Spirit of Evolution, (Shambhala, 1995), p. 4: ...
ecological backlash pictures ecological backlash involves the counter-responses of pest populations or other biotic factors in the environment that diminish the effectiveness of pest management
Ecological Backlash Sample Questions With Multiple Choices . Latest for Ecological Backlash Sample Questions With Multiple Choices. Dls Score Size Time Name; 73 6 804 KB 22 hours ago Ecological Backlash Sample Questions With Multiple Choices - Full Version;
If you didn't find what you were looking for you can always try Google Search
Add this page to your blog, web, or forum. This will help people know what is What is EXAMPLES OF ECOLOGICAL BACKLASH | <urn:uuid:973efa01-f7ce-4c32-9a11-40723cabf9a3> | 3 | 2,189 | Content Listing | Science & Tech. | 35.019365 |
In the previous article we introduced Schrödinger's equation and its solution, the wave function, which contains all the information there is to know about a quantum system. Now it's time to see the equation in action, using a very simple physical system as an example. We'll also look at another weird phenomenon called quantum tunneling.
In the first article of this series we introduced Schrödinger's
equation and in the second we saw it in action using a simple example. But how should
we interpret its solution, the wave function? What does it tell us
about the physical world?
London 2012 vowed to be the cleanest Olympics ever, with more than 6,000 tests on athletes for performance enhancing drugs. But when an athlete does fail a drug test can we really conclude that they are cheating? John Haigh does the maths.
In the 1920s the Austrian physicist Erwin Schrödinger came up with what has become the central equation of quantum mechanics. It tells you all there is to know about a quantum physical system and it also predicts famous quantum weirdnesses such as superposition and quantum entanglement. In this, the first article of a three-part series, we introduce Schrödinger's equation and put it in its historical context.
In our article Mapping the medals we came up with our very own prediction of the 2012 Olympic medal counts for the top 20 countries! This interactive map tells you how our predictions stack up: click on a country to see its actual medal count, our prediction and the results from 2008.
Predicting the final Olympic medal count is a black art. Sport, with all its intricacies and vagaries, is always susceptible to variations in form, weather conditions and simple random events. But we like a challenge! So without further ado, here is our predicted 2012 London Olympic medal count. | <urn:uuid:459c21bc-5230-4714-ad0b-1e902c93b222> | 3.03125 | 381 | Content Listing | Science & Tech. | 55.392946 |
Peering though layers of the Sun
Using two STEREO instruments that view the Sun in extreme UV light, we can combine frames taken at about the same time and see features from both. The focus of interest here iss an active region coming around the edge of the Sun on February 23, 2008. We are comparing the emission which is most hot in 286 A and (mostly) relatively cool in 304 A so you can see their relative locations (one wavelength is represented by yellow in the movie, the other is represented by orange). Understanding why the sun is hot or cool in different locations is a big challenge in solar physics. This technique is a way to visualize how different solar features are revealed two of the four wavelengths of light taken by the EUVI instrument on STEREO.
Last Revised: May 17, 2013 17:35:01 UTC
Responsible NASA Official:
Webmaster: Kevin Addison | <urn:uuid:4acd8a29-fe60-4e6a-8aa4-a277b3f59442> | 3.796875 | 185 | Knowledge Article | Science & Tech. | 40.43274 |
Science Fair Project Encyclopedia
- This article is about the components of sound, harmonics. See also: Harmony. In mathematics, see harmonic (mathematics). These two concepts are related, as the mathematical theory describes the vibrations of strings and air.
In acoustics and telecommunication, the harmonic of a wave is a component frequency of the signal that is an integral multiple of the fundamental frequency. For a sine wave, it is an integral multiple of the frequency of the wave. For example, if the frequency is f, the harmonics have frequency 2f, 3f, 4f, etc.
In musical terms, harmonics are component pitches of a harmonic tone which sound at whole number multiples above, or "within", the named note being played on a musical instrument. Non-whole number multiples are called partials or inharmonic overtones. It is the amplitude and placement of harmonics and partials which give different instruments different timbre (despite not usually being detected separately by the untrained human ear), and the separate trajectories of the overtones of two instruments playing in unison is what allows one to perceive them as separate. Bells have more clearly perceptible partials than most instruments.
Sample for a harmonic series:
|1f||440 Hz||fundamental tone||first harmonic|
|2f||880 Hz||first overtone||second harmonic|
|3f||1320 Hz||second overtone||third harmonic|
Amplitudes are varying.
In many musical instruments, it is possible to play the upper harmonics without the fundamental note being present. In a simple case (e.g. recorder) this has the effect of making the note go up in pitch by an octave; but in more complex cases many other pitch variations are obtained. In some cases it also changes the timbre of the note. This is part of the normal method of obtaining higher notes in wind instruments, where it is called overblowing. The extended technique of playing multiphonics also produces harmonics. On string instruments it is possible to produce very pure sounding notes, called harmonics by string players, which have an eerie quality, as well as being high in pitch which are located on the nodes of the strings. Harmonics may be used to check at a unison the tuning of strings which are not tuned to the unison. For example, lightly fingering the node found half way down the highest string of a cello produces the same pitch as lightly fingering the node 1/3 of the way down the second highest string. For the human voice see throat singing, which uses harmonics.
Harmonics may be used as the basis of just intonation systems or considered as the basis of all just intonation systems. Composer Arnold Dreyblatt is able to bring out different harmonics on the single string of his modified double bass by slightly altering his unique bowing technique halfway between hitting and bowing the strings.
- artificial harmonic
- harmonic series (music)
- Harmonics Theory
- pure tone
- flageolet tone
- just intonation
- stretched octave
This article incorporates material from Federal Standard 1037C
The contents of this article is licensed from www.wikipedia.org under the GNU Free Documentation License. Click here to see the transparent copy and copyright details | <urn:uuid:02128074-9da8-4b81-95b8-1215d0815270> | 4.5 | 691 | Knowledge Article | Science & Tech. | 37.528968 |
- Navigational mechanisms of migrating monarch butterflies
Trends in Neurosciences, Volume 33, Issue 9, 1 September 2010, Pages 399-406
Steven M. Reppert, Robert J. Gegear and Christine Merlin
AbstractRecent studies of the iconic fall migration of monarch butterflies have illuminated the mechanisms behind their southward navigation while using a time-compensated sun compass. Skylight cues, such as the sun itself and polarized light, are processed through both eyes and are probably integrated in the brain's central complex, the presumed site of the sun compass. Time compensation is provided by circadian clocks that have a distinctive molecular mechanism and that reside in the antennae. Monarchs might also use a magnetic compass because they possess two cryptochromes that have the molecular capability for light-dependent magnetoreception. Multiple genomic approaches are now being used with the aim of identifying navigation genes. Monarch butterflies are thus emerging as an excellent model organism in which to study the molecular and neural basis of long-distance migration.
Abstract | Full Text | PDF (484 kb)
- The Monarch Butterfly Genome Yields Insights into Long-Distance Migration
Cell, Volume 147, Issue 5, 23 November 2011, Pages 1171-1185
Shuai Zhan, Christine Merlin, Jeffrey L. Boore and Steven M. Reppert
SummaryWe present the draft 273 Mb genome of the migratory monarch butterfly (Danaus plexippus) and a set of 16,866 protein-coding genes. Orthology properties suggest that the Lepidoptera are the fastest evolving insect order yet examined. Compared to the silkmoth Bombyx mori, the monarch genome shares prominent similarity in orthology content, microsynteny, and protein family sizes. The monarch genome reveals a vertebrate-like opsin whose existence in insects is widespread; a full repertoire of molecular components for the monarch circadian clockwork; all members of the juvenile hormone biosynthetic pathway whose regulation shows unexpected sexual dimorphism; additional molecular signatures of oriented flight behavior; microRNAs that are differentially expressed between summer and migratory butterflies; monarch-specific expansions of chemoreceptors potentially important for long-distance migration; and a variant of the sodium/potassium pump that underlies a valuable chemical defense mechanism. The monarch genome enhances our ability to better understand the genetic and molecular basis of long-distance migration.
Summary | Full Text | PDF (1753 kb)
- Connecting the Navigational Clock to Sun Compass Input in Monarch Butterfly Brain
Neuron, Volume 46, Issue 3, 5 May 2005, Pages 457-467
Ivo Sauman, Adriana D. Briscoe, Haisun Zhu, Dingding Shi, Oren Froy, Julia Stalleicken, Quan Yuan, Amy Casselman and Steven M. Reppert
SummaryMigratory monarch butterflies (Danaus plexippus) use a time-compensated sun compass to navigate to their overwintering grounds in Mexico. Although polarized light is one of the celestial cues used for orientation, the spectral content (color) of that light has not been fully explored. We cloned the cDNAs of three visual pigment-encoding opsins (ultraviolet [UV], blue, and long wavelength) and found that all three are expressed uniformly in main retina. The photoreceptors of the polarization-specialized dorsal rim area, on the other hand, are monochromatic for the UV opsin. Behavioral studies support the importance of polarized UV light for flight orientation. Next, we used clock protein expression patterns to identify the location of a circadian clock in the dorsolateral protocerebrum of butterfly brain. To provide a link between the clock and the sun compass, we identified a CRYPTOCHROME-staining neural pathway that likely connects the circadian clock to polarized light input entering brain.
Summary | Full Text | PDF (587 kb)
Copyright © 2011 Elsevier Inc. All rights reserved.
Cell, Volume 147, Issue 5, 970-972, 23 November 2011
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A Genome Befitting a MonarchCorresponding author
- The monarch butterfly is famous for its annual fall migration from eastern North America to central Mexico, but it has also been an important model for studies in long-distance migration. Now, Zhan et al. present the genome of the monarch, opening up the detailed characterization of the butterfly's navigational system and unique social life. | <urn:uuid:27b93b9e-439a-4911-b9d8-3edc774055a1> | 3 | 934 | Academic Writing | Science & Tech. | 23.52339 |
Under the top-level Window object, comes the Document object. This object represents the head and body of the HTML page loaded in the browser, including all its images, forms and links. Like the Window object, this one too comes with its own methods and properties.
One of the Document object's commonly-used properties is the write() method, which can be used to write text to the Web page at run-time. Take a look at the following example, which demonstrates how this works:
// open document and write to it document.open(); document.write("<html><head><body>This is what you said: <br /><i>" + text + "</i></body></head></html>");
// close and display document.close(); } </script> </head> <body>
Here, when the user enters some data into the form input box and clicks the "Write!" button, the writeToDoc() function is invoked. This function first reads the data entered by the user into a variable, then begins writing to the document. This writing process consists of first opening a stream to the document with document.open(), then writing to it with document.write() and then closing the stream with document.close(). The data written to the document is displayed only after document.close() is called.
All the other elements of the page - forms, links, images - are organized under the Document object as arrays. Using the Document object as base, therefore, it's easy to access any of these elements and manipulate them (I've done this in some of the previous examples, to access form values). Take a look at this next example, which uses these object arrays to return some statistics about the number of links, images and forms within the document:
<html> <head> </head> <body>
<!-- add some elements to the page --> <form> <input type="text" size="20"> <input type="button" value="Click me"> </form>
Since the images, forms and links within a document are structured as arrays under the Document object, it's easy to calculate the total number of items of each type - simply obtain the size of the corresponding array.
Of course, there's a lot more you can do with the Document object. Sadly, however, most of it involves manipulating the contents of the HTML document, not of the browser displaying it, and therefore doesn't fall under the ambit of this tutorial. If you're interested, though, you will find the following links most instructive:
And that's about all I have time for at the moment. See you soon!
Note: Examples are illustrative only, and are not meant for a production environment. Examples have been tested on Microsoft Internet Explorer 5.x only. Melonfire provides no warranties or support for the source code described in this article. | <urn:uuid:3353192d-ecc9-4598-946d-ca757be05a8a> | 3.71875 | 595 | Documentation | Software Dev. | 52.132743 |
Browsing 100 - 110 results of 235 programs for subject - Geology/Earth Science
Climate researcher Billy D'Andrea and colleagues explore the remote "back lakes" of Greenland. To understand how Earth’s climate system has changed over time, scientists need to find, develop and use natural recorders of temperature and precipitation. One natural thermometer comes in the form of alkenones: trans-fats produced by certain algae. Meet Dr. Ethan Brodsky from the U. of Wisconsin, who advised a group of undergraduate students in the design and build of an electric snowmobile. Video produced by Ice Stories correspondent Zoe Courville. The Mars Phoenix Lander will have been collecting data and sending it back to earth for a month! Exploratorium Senior Scientist Paul Doherty will examine the data and tell us what new information we've gained about Mars. We'll also get an update on our old friends, the Mars rovers Spirit and Opportunity!
Alaska's coastal range is covered in literally thousands of thaw lakes. Ken Hinkel, Yongwei Sheng and John Lenters are embarking on a project to reveal the subtle energy dynamics that take place within these lake systems. Join us as we celebrate the beginning of summer in the Arctic and the long, cold winter in Antarctica. We'll connect live to two polar field sites: Summit Camp atop Greenland's vast ice sheet, where the sun will be shining 24 hours a day, and the South Pole Research Station, now in the middle of 6 months of darkness.
Dr. Jewel Bennett, an endangered species biologist with the US Fish and Wildlife Service's Fairbanks field office, is in Barrow leading a survey team tracking the endangered Steller's and Spectacled Eiders' populations. Inupiaq elders, local experts and scientific researchers partner on the North Slope to study and understand the changing environment. Wendy Eisner and Chris Cuomo join us to talk about their project: Indigenous Knowledge and Landscape in Northern Alaska. In today's program Dr. Bart Kempenaers, a behavioral ecologist from the Max Planck Institiute of Ornithology in Seewiesen, Germany, talks about the research he and his team are doing on arctic breeding shorebirds in Barrow, Alaska. Amanda Grannas' research group at Villanova University studies a wide range of topics under the umbrella of "analytical environmental chemistry", including the impacts of pollutants in the snow and ice. We'll chat with Amanda about her current research in the Arctic. | <urn:uuid:aedd628c-69b7-431c-8f4f-39b16a68009b> | 2.90625 | 514 | Content Listing | Science & Tech. | 42.552273 |
Look up monthly U.S., Statewide, Divisional, and Regional Temperature, Precipitation, Degree Days, and Palmer (Drought) rankings for 1-12, 18, 24, 36, 48, 60-month, and Year-to-Date time periods. Data and statistics are as of January 1895.
Please note, Degree Days are not available for Agricultural Belts
Contiguous U.S. Temperature Rankings, May 1907
More information on Climatological Rankings
(out of 119 years)
|2nd Coldest||1917||Coldest to Date|
|117th Warmest||1934||Warmest since: 1906| | <urn:uuid:1bec9f1f-5b8c-4ead-9739-6d6e5eec1311> | 2.75 | 138 | Structured Data | Science & Tech. | 59.147692 |
That would be something, but as the UN Environment Programme pointed out this month, those current commitments are nowhere near enough to cap warming at 2 °C above pre-industrial levels, which many regard as the maximum "safe" warming. Fearing the worst, leading climate scientists at a conference in Oxford, UK, last year warned that we could see 4 °C of warming as early as 2055, with likely effects including massive changes to rainfall patterns, the wholesale collapse of African farming and forced migration of hundreds of millions of people.
In the case of a diplomatic stalemate, our last resort may be geoengineering solutions like parasols in space or large-scale chemical carbon capture from the atmosphere. Researchers distressed by the failure of diplomacy are increasingly keen to explore such options as a planetary insurance policy, though a meeting of the UN Convention on Biodiversity in Japan recently sought to ban such efforts if they threatened species.
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Why Do It?
Mon Nov 29 15:24:32 GMT 2010 by Mike Davidson
If there is a vanishingly small chance of reaching agreement, why are all these ecologically aware people jetting to a luxury resort to talk?
Surely this could have been a tele conference?
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Can information out speed light?
Date: Around 1993
According the theory of relativity, nothing can surpass the speed
of light, even the flow of information. But what of events that necessarily
take place instantaneously? Ex: An object moves, and the gravitational force
instantly changes proportionately a light-year away. I believe that Einstein
resolved this difficulty in terms of gravity's warping space - time, but I
still do not understand his explanation. And on a more basic level, if I were
to shake a move a one light- year long pole, would not the tip move
instantaneously, beating light by roughly 12 months? Or would some sort of
spring action occur just to thwart my attempt of disproving relativity?
Actually, it turns out that all forces, including gravity, the
electromagnetic and other forces, are what is called "retarded". That means
that although they look like they act at a distance, they do not act
instantaneously at a distance. In your example, the gravitational field one
light-year away would not start changing until exactly one year later. Time-
dependent forces are tricky. Concerning a pole that was extremely long - how
do you suppose forces move from one end to the other? They actually cannot
move any (or at least not much) faster than the speed of sound in the pole.
Very rigid poles have very high speeds of sound but far less than the speed of
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Update: June 2012 | <urn:uuid:cacb4608-0815-42b9-a774-61eb189aff88> | 3.625 | 320 | Knowledge Article | Science & Tech. | 46.77834 |
.TH CMPDYLIB 1 "November 3, 1997" "Apple Computer, Inc." .SH NAME cmpdylib \- compare two dynamic shared libraries for compatibility .SH SYNOPSIS .B cmpdylib .I oldLibrary .I newLibrary .SH DESCRIPTION .B cmpdylib compares two versions of a dynamic shared library to see if they are compatible with each other. If the two versions are incompatible, the reason is printed to stdout, and the exit status is nonzero. If they are compatible, nothing is printed, and the exit status is zero. .PP To see if the two versions are compatible, .B cmpdylib first verifies that .I newLibrary was built for all of the architectures that .I oldLibrary was built for. If so, for each architecture, it checks to see if the global symbols defined in .I oldLibrary are still defined in .I newLibrary. It then looks for new symbols, symbols defined in .I newLibrary that are not defined in .I oldLibrary. If it finds new symbols, it compares the compatibility version numbers of the two libraries. If the compatibility version number of .I newLibrary is greater than .IR oldLibrary , the libraries are still compatible. If the compatibility version number is the same or less, the libraries are incompatible. .SH OPTIONS .TP .I oldLibrary The older version of the library. .TP .I newLibrary The newer version of the library. .SH EXAMPLES This example shows the result of performing .B cmpdylib on two incompatible versions of the Foundation library. As stated, the versions are incompatible because the newer version was not built for the ppc architecture. .PP cmpdylib /System/Library/Frameworks/Foundation.framework/Foundation Foundation_proj/Foundation .br cmpdylib: file: Foundation_proj/Foundation does not contain architecture: ppc .br cmpdylib: new dynamic shared library: Foundation_proj/Foundation does not contain architecture ppc .SH DIAGNOSTICS The exit status is zero if the library versions are compatible and nonzero if they are incompatible. .SH BUGS There are lots of other things that could be checked for that are not (such as the Objective C API). | <urn:uuid:e3434c6e-7849-4d56-8697-4cb9230dcd0d> | 2.6875 | 472 | Documentation | Software Dev. | 48.760431 |
Intercellular Air Space
The ubiquity of interconnected air-filed intercellular spaces in thick plant tissues were demonstrated over 90 years ago, wherein such spaces are present in almost every plant tissue – both thick and thin —but received remarkably little attention in research and textbooks. The intercellular air space is vital in the process of photosynthesis and to other roles in the function of the plants. Higher plants have interconnected air spaces due to the fact that they undergo respiration in all massive plant tissue, such as large fruits, and potato tubers, at least during growth and development.
Other Intercellular air space Functions
Aside from its common function, the Intercellular air space serves as pathways for diffusion of carbon dioxide (CO2) for photosynthesis. This space (with adjacent cells) in the leaf also provides refractive index discontinuities that cause the leaf to scatter much of the incoming radiation. Aquatic plants or plant part floats in water because of the air-filed intercellular spaces. Respiration of crop plant roots submerged in flooded soils to a distance of several centimeters from an air source is possible because of diffusion of air in longitudinally interconnected air-filled intercellular spaces.
With the use of a small maize example of roots, the thickness at which a plant tissue needs air spaces to facilitate respiration can be approximately calculated. Due to the fact that the intercellular spaces of small roots are not radially interconnected, it does not function as a major path in the radial movement of oxygen (O2) but when such roots are in aerated soil, they can obtain oxygen through the root tissue’s radial movement. | <urn:uuid:fbd22d4d-f597-4b8e-ab8c-c93b8ae31c6d> | 3.640625 | 339 | Knowledge Article | Science & Tech. | 22.225 |
Now that looks like fun. Of course we intuitively know it's completely fake, and involves the usual videographic sleight of hand, but let's apply some basic physics to the situation to check our intuition.
First of all, the "diver," after being launched off the ramp, travels a horizontal distance of at least 50 meters before landing in the pool. Assuming a 45-degree launch angle, which gives us the maximum trajectory if we neglect air resistance (air resistance will only make matters worse), let's calculate the absolute minimum speed we need to leave the ramp to stick the landing. What we have here is a good old-fashioned projectile!
Our projectile (again neglecting air friction) will have a constant velocity in the horizontal direction. Thus we get a horizontal motion equation as follows:
Δx = v0 cos (45) t
where Δx is the horizontal distance of 50 meters, v0 is the launch velocity, and t is the time of flight.
In the vertical acceleration we have a constant downward acceleration due to gravity of g = 9.8 m/s2. Assuming we are launched from approximately the same height where we land, we get
Δy = 0 = v0 sin (45) t + ½ at2
Combining the two equations, doing a little algebra, and solving for v0 we find that
v0 = 22 m/s or about 50 miles per hour!
Now, are we to believe that the diver is able to get up to such a speed by sliding down that slip-and-slide? Not likely. Being extremely generous by neglecting the very non-negligible force of friction (yes, even on a slip-and-slide), estimating that the diver is at most maybe 10 meters higher than his launch point, then using conservation of energy, we can calculate the maximum possible speed he would have on takeoff. This is going to be a severe overestimate, due to our neglecting friction, but let's see what we get.
According to conservation of energy, we know that the potential energy (mgΔh) that he loses due to the height difference between the start and the launch point will be converted to kinetic energy (½ mv2).
mgΔh = ½ mv2
where v is his launch velocity. We get v = 14 m/s (around 30 miles per hour).
The physics don't lie. It canna' be done, Cap'n!
Adam Weiner is the author of Don't Try This at Home! The Physics of Hollywood Movies.
Five amazing, clean technologies that will set us free, in this month's energy-focused issue. Also: how to build a better bomb detector, the robotic toys that are raising your children, a human catapult, the world's smallest arcade, and much more. | <urn:uuid:c12f3224-75ec-4be5-ae87-fcb99bd6b72b> | 2.6875 | 588 | Personal Blog | Science & Tech. | 61.063881 |
There are about 150 species of army ants in the New World (i.e. North, South and central America). They are all classified in the ant sub family Ecitonini. Although army ant species are found from Kansas to Argentina, few people in North America realize that there are plenty of army ants living in the US because most army ants only come out at night and many live underground.
Eciton burchelli and Eciton hamatum are the most visible and best studied of the New World army ants because they forage above ground and during the day. Their range stretches from southern Mexico to the northern part of South America.
In Africa, thrushes of the genus Alethes follow army-ant swarms, as do some bulbuls in both Africa and Asia.
New World army ants belong to the subfamily Ecitoninae. This subfamily is further broken into two groups, Cheliomyrmex and the Ecitonini. The most predominant species of Eciton is Eciton burchelli, whose common name is army ant and which is considered to be the archetypal species.
Army ant taxonomy remains ever-changing, and genetic analysis will continue to provide more information about the relatedness of the various species.
Eciton army ants have a bi-phasic lifestyle where they alternate between a nomadic phase and a stationary stage. In the stationary or statary phase ('statary' is an old English word meaning "to stand in place"), which lasts about three weeks, the ants remain in the same location every night. They make a nest out of their own bodies, protecting the queen and her eggs in the middle. This temporary home is known as a bivouac. In the nomadic phase the ants move their entire colony to a new location nearly every night for two weeks.
When the ants first enter the statary phase, the queen's body swells massively and she lays as many as 250,000 eggs in less than a week. While the eggs mature, the ants swarm with less frequency and intensity. When the eggs hatch, the excitement caused by the increased activity of the larvae causes the colony to enter the nomadic phase. The colony swarms much more intensely and nearly every day, and the ants move to a new location every night. After two weeks, around the time when the larvae begin to pupate, the colony again enters the statary phase, and the cycle begins anew.
Because of the regularity and intensity of E. burchelli and E. hamatum swarms, many insect, bird and butterfly species have evolved complex relationships with these ants. There are butterflies that lay their eggs on insects disabled by the ants. There are ant-mimicking staphylinid beetles, shaped like the ants they follow, that run with the swarm preying on stragglers or other insects injured or flushed by army ant activity; and there are some insects that spend their entire lives hidden in Eciton colonies mimicking ant-larvae. There are also more than 10 species 'ant-birds' that rely on the ants partially or completely for their food. Some of these birds actively check army-ant bivouacs each morning, follow the foraging trail to the swarm front, and prey on insects fleeing the ants.
Watching an E. burchelli swarm move through the forest is an amazing experience. The swarm pours forward amoebically, scouring the leaf-litter, bushes, and climbing high into trees. Despite being almost blind, E. burchelli are highly effective foragers, catching and killing nearly every small creature they find in their path.
The first sign of the approaching swarm is quiet a jumping and scurrying in the leaf-litter as insects begin fleeing for their lives. The first army ants arrive as a small trickle. Individual workers run forward, extending the pheromone trail very slightly before turning quickly back the way they came. As each ant turns, another passes it extending the trail a little further. Small insects begin to appear, flushed by the arriving invaders. A burst of red leaf-litter ants, larvae clutched in their mandibles, run for their lives up the nearest plant stem.
The steady trickle of army-ant scouts grows and thickens to a flood and suddenly the leaf-litter boils with terrifying ferocity as tens of thousands of ants cover the ground. A spider, flushed from its home, flees frantically, finding no escape. Jaws clamp down on every limb and soon the only sign of life is a tight, dark pile of stinging ants. An earthworm spasms and jumps, flinging ants in all directions, but its movements only attract more attackers until it is quickly stung to death and cut into pieces. A cockroach staggers from a hole, ants clinging to all sides and then collapses, swiftly becoming another thick pile of busily working ants.
As the front slowly passes, a maze-like network of trails develops behind it. Ants carrying small pieces of prey enter into the steady stream of workers running down the long trail home.
All text is available under the terms
of the GNU Free Documentation License | <urn:uuid:762f2911-8341-444e-82a3-1918978e22e6> | 3.109375 | 1,062 | Knowledge Article | Science & Tech. | 48.883272 |
Data reported by the weather station: 916910 (NFNK)
Latitude: -18.23 | Longitude: -178.8 | Altitude: 2
|Main||Year 1980 climate||Select a month|
To calculate annual averages, we analyzed data of 364 days (99.45% of year).
If in the average or annual total of some data is missing information of 10 or more days, this is not displayed.
The total rainfall value 0 (zero) may indicate that there has been no such measurement and / or the weather station does not broadcast.
|Annual average temperature:||25.3°C||364|
|Annual average maximum temperature:||29.7°C||364|
|Annual average minimum temperature:||23.1°C||364|
|Annual average humidity:||79.3%||364|
|Annual total precipitation:||1972.36 mm||364|
|Annual average visibility:||28.8 Km||364|
|Annual average wind speed:||9.7 km/h||364|
Number of days with extraordinary phenomena.
|Total days with rain:||182|
|Total days with snow:||0|
|Total days with thunderstorm:||16|
|Total days with fog:||1|
|Total days with tornado or funnel cloud:||0|
|Total days with hail:||1|
Days of extreme historical values in 1980
The highest temperature recorded was 40°C on April 19.
The lowest temperature recorded was 9°C on June 8.
The maximum wind speed recorded was 64.8 km/h on March 24. | <urn:uuid:ced18ee6-8d19-4a11-b3a7-816ac2948903> | 2.953125 | 357 | Structured Data | Science & Tech. | 72.888955 |
The neutrino mass measurement should cause a revised estimate of
"omega," the mass density of the universe. But so far, I haven't seen
anything to suggest that this measurement will either make, or break,
inflation theory. (There are other, independent measurements which set
limits on the mass density and the "cosmological constant.") Neutrino
mass measurements give additional data in helping to construct a "Grand
Unified Theory" of physics -- which may in turn help resolve the
question of inflation -- but that could still take many years or decades
to work out.
To what extent do physicists believe inflation theory, and what are the
implications for apologetics?
Inflation theory solves a few problems in non-inflationary cosmology.
Three "problems" in particular are: (1) The scarcity of magnetic
monopoles in the observable universe. (2) The "flatness" of the
observable universe. Inflation predicts that the mass density of the
universe ("omega") plus the cosmological constant ("lambda") should be
very close to 1. (Non-inflationary big-bang cosmology does not set such
tight limits.) Current observations set omega + lambda between roughly
0.3 and 2. (Recent supernova observations may have measured omega
and lambda even more precisely.) (3) The cosmic microwave background is
very nearly in thermal equilibrium everywhere we observe --- including
parts of the sky which should be "causally disconnected" from each
other. In non-inflationary big-bang cosmology, we know of no particular
reason why different parts of the universe which never had a chance to
interact with each other should be a the same temperature; the observed
thermal equilibrium is expected in inflation theory.
Because of how inflation solves these problems, I think most physicists
give inflation theory -- although it is still speculative -- a fair bit
A prediction of inflation theory is the "many different universes." As
I understand it, it happens like this: Right after the big bang, the
"four basic forces" (gravity, electromagnetism, strong and weak nuclear
forces) operate as a single, unified force described by what is often
called the "theory of everything" (TOE). As the universe cools, gravity
uncouples from the other three forces, which are now described by the
"Grand Unified Theory." (Particle theorists are, of course, working
very hard on figuring out the GUT.) As the universe cools further, the
mathematical symmetries which GUTs have at higher energies break down.
The strong nuclear force uncouples from the weak nuclear force and
electromagnetism. The exact details of this "symmetry breaking" are not
understood because we don't yet know the details of the GUT, but it is
known that those symmetry-breaking details set the values of many
"fundamental constants" in physics: particle masses, coupling strengths
of the forces, etc.
The "inflationary epoch" is thought to happen after the TOE separates
into gravity + GUT, but before the spontaneous symmetry breaking of GUT
into strong force + electro-weak force. If inflation theory is true,
space expands (and matter cools) exponentially fast during the
inflationary epoch. The "spontaneously symmetry breaking" happens at
slightly different times in different regions of space. Each region
becomes its own "island universe," each much larger than our observable
universe. Since the symmetry-breaking happened differently in each
"universe," each could have somewhat different strong-force, weak-force,
and electromagnetic coupling constants, particle masses, etc.
What does this have to do with apologetics? If inflation theory is
true, it may have some impact on the "fine tuning" argument. It is
known that many of the "fundamental constants" of physics fall into very
narrow ranges which make life possible. If inflation theory is true,
then there could be a very great many different universes, each with its
own set of fundamental constants.
But how different could they be? That is unknown. All "universes"
which came out of inflation would have the same TOE (theory of
everything) and the same GUTs. Since we don't yet know what the correct
GUT is, we don't know how much variability there could be in the
"fundamental constants" set by symmetry breaking. Even supposing that
inflation *would* produce a huge number of universes with a great
variety of fundamental constants -- some of them "naturally" falling
into ranges suitable for life -- it still begs two important questions:
(1) How "finely-tuned" is the GUT and the TOE? and (2) Why should they
exist at all? I wouldn't dare predict an answer to the first question.
Whether inflation theory is true or not, we can praise the Creator for
an amazing creation. As for using "fine tuning" for apologetics, it
would seem that wise use is cautious use.
(Many thanks to my wife, Deborah Haarsma, for explaining inflationary
cosmology to me. Again.)
> Book on inflation:
> Alan H. Guth
> "The Inflationary Universe: The Quest for a New Theory of Cosmic
> I read a good review of it. Should be up to date, and straight from
> the source.
> This is Addison-Wesley's page for it: | <urn:uuid:dc25a615-d469-4046-82d4-5743cba0996b> | 2.828125 | 1,191 | Comment Section | Science & Tech. | 38.767314 |
Modern languages, like Fantom and Scala are ditching the Java like Threading model for an Actor based model. So is there something wrong with Threads? Why do we need actors? Turns out that it’s really simple.
There is nothing wrong with threads in java. Its just that variables are shared between threads. Each thread can see and modify the same variables. To prevent accidental corruption you need to “synchronize” blocks of your code so only one thread can access it at a time.
With actors, its sort of like each thread gets its own variables.(its own state). Each actor can only see and modify these.
Remember Object Oriented encapsulation? – Where each function in a class can only see and modify variables(if its private) in its class? Think of Actors as applying the same principles to Threads. Its a new Level of encapsulation for Threads.
Imagine you and your friend decide to write this post down on a piece of paper, each willing to write half of it. The problem is, you have a shared paper to write down to. Now if both of you keep writing in the paper at the same time, you corrupt the paper. So you need to take turns(A.K.A synchronize). You do it this way because that’s the simplest way. While one of you holds the paper and writes to it, the other waits. But this way you aren’t really working in parallel, are you? This how threads work. Lets see actors.
Now imagine there’s a rule that no body shares papers. So, each one of you is forced to get a piece of paper to write to. You are not allowed to write on (or even see) others paper. Now, since you have your own papers to write to, you can work independently, even on separate rooms.
There’s Another rule, you are not allowed to talk to each other synchronously. No tapping on your friends back or giving him a phone call, thus disturbing him while he is writing. But you are allowed to send him email. The difference is, he decides when to check the email. If he wants to complete something, and then check the email, his choice. And how does he give an answer to your question? By sending back a reply through email. You get the point.
You don’t have any control on when, if at all your partner will see your message. So you can’t guarantee the systems behaviour if you were allowed to change the message after you sent it. Luckily, email doesn’t allow you to do that. So Email’s Perfect.
That’s all. You got it, din’t you? :) | <urn:uuid:a9714695-cf8a-4624-bee1-2c2ed1d74e1b> | 2.984375 | 573 | Personal Blog | Software Dev. | 72.692823 |
Metamaterials and the possibility of negative refraction are interesting, but before industries based on classical and quantum electrodynamics can take them seriously, questions of faster-than-light propagation must be addressed.
A negative value of n is required so that the velocity reverses Snell's Law of refraction, but this cannot be valid with modulus of n < 1 and dispersion curves which indicate that all the velocities are faster than the speed of light (c). How can metamaterials be viable for modulus of refractive index |n| < 1 when the propagation curves indicate Vgroup = Vphase = -3c?
This can be seen where dn/d? = 0 for :-
We now have much literature1,2 with curves that correspond to the profoundly researched anomalous dispersion of Sommerfeld Brillouin- Stratton, (modulus of n < 1 for both positive and negative refractive index n.
How is it possible to have negative refractive index without negative wave impedance (and the implied source of energy)? There are also problems with energy density in classical and quantum electrodynamics.
There are increasing numbers of papers in which scientists claim to have proven extraordinary phenomena by applying the concept of group velocity to the anomalous dispersion of waves. Two of the greatest wave theorists, Arnold Sommerfeld and Lon Brillouin, have dealt with the subject.
In separate papers, Sommerfeld and Brillouin wrote that, in anomalous dispersion, the group velocity cannot be the signal velocity.1 Indeed, in anomalous dispersion, the group velocity goes through both negative and positive infinite values. It also goes through values greater than the speed of light (as does the phase velocity).2
In the anomalous dispersion of Sommerfeld Brillouin- Stratton, the incident wave and resonances interfere to cause apparent speed > c, and/or waves apparently travelling backwards. The published values of +0.9 > n > -0.6 cannot occur, especially where Vgroup = Vphase > c, thus invalidating signal and energy velocity.
1. A. Sommerfeld, Annalen der Physik 44, 177 (1914); L. Brillouin, Annalen der Physik 44, 203 (1914). For a lucid English-language digest of the two papers, see ref.
2, p. 334. 2. J. A. Stratton, Electromagnetic Theory, McCheers Publishers.
Dr. Max J. Lazarus
Department of Physics
University of Lancaster, | <urn:uuid:b2110378-9489-4004-9bb5-bf5b0112a45b> | 2.84375 | 537 | Comment Section | Science & Tech. | 42.425 |
Dust Stream From Comet Tempel 1
Photograph courtesy NASA, ESA, P. Feldman (Johns Hopkins University) and H. Weaver (Johns Hopkins University Applied Physics Laboratory)
A new jet of dust streams from the icy nucleus of the Tempel 1 comet, caught in this Hubble Space Telescope image. The jet extends about 1,400 miles (2,200 kilometers)—roughly half the distance across the U.S.—in the direction of the sun. Comets frequently show outbursts of activity, but astronomers still don't know exactly why they occur. | <urn:uuid:8679b55b-2764-4326-9c6b-13188a74ba95> | 3.34375 | 116 | Truncated | Science & Tech. | 58.611512 |
The electric potential, which I will denote by $\Phi$, is originally defined by the following relation to the electric field (if the math is unfamiliar, don't worry I'm just including it for completeness)
\mathbf E = -\nabla \Phi
One consequence of this is that
The electric potential is only defined up to an additive constant
This means, in particular, that one has the freedom to pick any point in space, usually called a reference point, at which the potential is zero. Once you pick this point, then the value of the potential $\Phi$ at any other point is completely determined by the definition above.
However, if you don't choose such a point, then additive ambiguity in the definition of potential makes it so only calculating differences in potential makes sense. In this case, it wouldn't make sense to say that "so and so point in the circuit has such and such value."
Punchline. The electric potential is defined in such a way that only differences in potential make sense unless one picks a reference point at which the value of the potential is specified.
Additionally, voltage is usually used as a term for differences in electric potential between two points, so it does not suffer from the same ambiguity as the term electric potential. So in standard parlance, it would be appropriate to say "potential at a point A" (provided a reference point has been chosen) but it would not be appropriate to say "voltage at point A." | <urn:uuid:3e5ae856-04af-40c9-ad60-92664a76e6a5> | 3.34375 | 308 | Q&A Forum | Science & Tech. | 31.742363 |
I know that there's a difference between relativistic rest mass. Relativistic mass is "acquired" when an object is moving at speeds comparable to the speed of light.Rest mass is the inherent mass that ...
If photons are spin-1 bosons, then doesn't quantum mechanics imply that the allowed values for the z-component of spin (in units of $\hbar$) are -1, 0, and 1? Why then in practice do we only use the ...
I studied that when an object moves with a velocity comparable to the velocity of light the (relativistic) mass changes...but I am really eager to know how does this alteration take place....If anyone ...
With relativistic physics, we can apply force to see resistance against acceleration. It'd give us relativistic mass and we have well established formula to get to the Rest Mass as long as we know the ... | <urn:uuid:d2bce4c8-4de9-43e7-a908-21510af7d803> | 2.984375 | 189 | Q&A Forum | Science & Tech. | 67.117984 |
For resonance to occur, is it true that the force lags behind the motion by $\pi/2$? I saw some notes written that the motion lags behind the force by $\pi/2$ which makes no sense to me. As I watched ...
I believe the purpose of a tuning fork is to produce a single pure frequency of vibration. How do two coupled vibrating prongs isolate a single frequency? Is it possible to produce the same effect ...
What is actually a resonating vibration and resonance? I have searched many books and made Google search too but couldn't understand it clearly.
In my Physics textbook, it says that if two pendulums of the same natural frequency are placed next to each other and if one is set into vibration, the other starts resonating and when the first one ... | <urn:uuid:bbf51701-7701-4772-b47c-0bb71c103be4> | 3.1875 | 166 | Q&A Forum | Science & Tech. | 63.563207 |
Oct. 3 , 2006: In June 1912, Novarupta—one of a chain of volcanoes on the Alaska Peninsula—erupted in what turned out to be the largest blast of the twentieth century. It was so powerful that it drained magma from under another volcano, Mount Katmai, six miles east, causing the summit of Katmai to collapse to form a caldera half a mile deep. Novarupta also expelled three cubic miles of magma and ash into the air, which fell to cover an area of 3,000 square miles more than a foot deep.
Despite the fact that the eruption was comparable to that of the far more famous eruption of Krakatau in Indonesia in 1883 and so near the continental United States, it was hardly known at the time because the area was so remote from English-speaking people.
Right: An aerial view of the Novarupta Dome in Alaska. USGS photo by Gene Iwatsubo, July 29, 1987. [More]
Almost a hundred years later, researchers are paying attention. Novarupta is near the Arctic Circle and its impact on climate appears to be quite different from that of "ordinary" tropical volcanoes, according to recent research by climatologists using a NASA computer model.
When a volcano anywhere erupts, it does more than spew clouds of ash, which can shadow a region from sunlight and cool it for a few days. It also spews sulfur dioxide. If the eruption is strongly vertical, it shoots that sulfur dioxide high into the stratosphere more than 10 miles above Earth.
This can create a kind of nuclear winter (a.k.a. "volcanic winter") for a year or more after an eruption. In April 1815, for instance, the Tambora volcano in Indonesia erupted. The following year, 1816, was called "the year without a summer," with snow falling across the United States in July. Even the smaller June 1991 eruption of Pinatubo in the Philippines cooled the average temperature of the northern hemisphere summer of 1992 to well below average.
But both those volcanoes as well as Krakatau were in the tropics.
Novarupta is just south of the Arctic Circle.
Using a NASA computer model at the the Goddard Institute for Space Studies (GISS), Prof. Alan Robock of Rutgers University and colleagues found that Novarupta's effects on the world's climate would have been different. (Their research was funded by the National Science Foundation.)
Robock explains: "The stratosphere's average circulation is from the equator to the poles, so aerosols from tropical volcanoes tend to spread across all latitudes both north and south of the Equator." Aerosols would quickly circulate to all parts of the globe.
But the NASA GISS climate model showed that aerosols from an arctic eruption such as Novarupta tend to stay north of 30ºN—that is, no further south than the continental United States or Europe. Indeed, they would mix with the rest of Earth's atmosphere only very slowly.
This bottling up of Novarupta's aerosols in the north would make itself felt, strangely enough, in India. According to the computer model, the Novarupta blast would have weakened India's summer monsoon, producing "an abnormally warm and dry summer over northern India," says Robock.
Why India? Cooling of the northern hemisphere by Novarupta would set in motion a chain of events involving land and sea surface temperatures, the flow of air over the Himalayan mountains and, finally, clouds and rain over India. It's devilishly complex, which is why supercomputers are needed to do the calculations.
To check the results, Robock and colleagues are examining weather and river flow data from Asia, India, and Africa in 1913, the year after Novarupta. They are also investigating the consequences of other high-latitude eruptions in the last few centuries.
Do Indians need to keep an eye on Arctic volcanoes? The GISS computer says so. Stay tuned to Science@NASA for updates.
|More to the story...|
The article "Climatic response to high-latitude volcanic eruptions," by Robock, Schmidt, and three other authors and published in the Journal of Geophysical Research in 2005, can be downloaded here.
Volcanic Eruptions and Climate -- an earlier primer to the entire subject by Alan Robock and published in Review of Geophysics in May 2000
A detailed bibliography about Novarupta from the Alaska Volcano Observatory at .
More about NASA's Goddard Institute for Space Studies—a laboratory of the Earth-Sun Exploration Division of NASA's Goddard Space Flight Center and a unit of Columbia University’s Earth Institute | <urn:uuid:63a4c6b1-2850-41cf-b23f-67aa4da643e8> | 4.375 | 985 | Knowledge Article | Science & Tech. | 44.521373 |
Poly Area Architecture and Organization
The architecture focuses on separating the UI code from the algorithmic code to accomodate testing and also potential replacement of the low-level graphic library (PyGame). In addition, there is a little module called config.py that lets users configure the look-and-feel.
There are three modules in the algorithmic core:
- The polygon module is responsible for the main algorithm. It has a custom Polygon class that provides some important methods used by the calc_polygon_area() function and its support functions: find_Second_top_point() and remove_top_triangle(). It uses functions from the triangle and helpers modules.
- The triangle module contains two functions: herons_formula() and calc_triangle_area(). It also has two test functions: test_herons_formula() and test_calc_triangle_area(). This is a good example of bottom up programming. It is a very small bit of functionality (calculating the area of a triangle) encapsulated in its own module with its own tests. It is very easy to implement, test and if necessary modify it (e.g. implement the calculation using a different formula).
- The helpers module is a support module that contains many simple and general-purpose functions that are not tied specifically to the polygon triangulation algorithm. This module can potentially be reused in other computational geometry programs. It follows the same pattern as the triangle module and has a test function for each function. Some functions are: find_line_coeeficients(), calc_distance(), and intersect().
Then there is one big UI module and a config module.
- The ui module is responsible for all the visual aspects of poly area and the interaction with the user. It lets you draw a polygon and make sure you draw a valid polygon. Once the polygon is closed it is divided into triangles and its area is calculated and you can visualize the algorithm operation step by step by pressing the spacebar. There is a fair amount of functionality involved and the code to verify that the polygon is valid is actually more complicated then the core algorithm. The ui module uses the mainloop and pygame_objects modules.
- The config module resembles a Windows .ini file. It just contains some variables such as grid resolution, line thickness, and colors. The ui module reads this file and uses the values when rendering the UI.
There are two PyGame-related infrastructure modules:
- The mainloop module encapsulates the typical event loop of a GUI program and provides a PyGame-based implementation. In addition to some PyGame incantations it manages a list of object it renders to the screen in each iteration. These objects must support a simple interface and objects can be added/removed dynamically from the list during the program's run.
- The pygame_objects module contains several objects that support the mainloop interface.
Finally there is a BaseObject base class.
Testing is not as rigorous as I would implement in a professional project (100% coverage), but it is pretty good. I didn't implement negative tests (tests that provide bad input on purpose to make sure the code fails as expected with the proper exception and helpful error message) because writing these tests take a lot of time (usually there are many more bad inputs than good inputs) and I control the using code, so I can make sure no bad inputs are provided.
The triangle.py and helpers.py have self tests. Normally, they should be imported and used by other modules, but if you run them directly then they execute a test() function. This is done via the module's __name__ attribute.
if __name__=='__main__': test()
The __name__ attribute is set by the interpreter when the module is being run directly as in:
There are internal tests for the following modules:
- The tests for the triangle module are very simple. The test_herons_formula() functions makes sure that the when passing 3, 4 and 5 as the triangle sides the herons_formula() function correctly returns the area as 6:
def test_herons_formula(): a = 3 b = 4 c = 5 assert herons_formula(a, b, c) == 6
- The test for the compute_triangle_area() module is almost the same except that it passes the vertices of an equivalent triangle:
def test_calc_triangle_area(): p1 = (0, 0) p2 = (0, 3) p3 = (4, 0) assert calc_triangle_area(p1, p2, p3) == 6
- The helpers module contains simple tests for all its functions. For example, here is the test_find_line_coefficients() function:
def test_find_line_coefficients(): line = ((1,0), (1,3)) assert find_line_coefficients(*line) == None line = ((0,0), (5,5)) assert find_line_coefficients(*line) == (1, 0) line = ((4,5), (5,5)) assert find_line_coefficients(*line) == (0, 5)
There is a standalone test (in its own module) for the polygon module: polygon_test. The reason this test is separate is that the polygon module has relatively a lot of code and cluttering it with test code would make it harder to navigate and less readable. The polygon_test module has multiple test functions for different aspects of the polygon module and a central test() function that runs all the specific test functions:
def test(): test_is_triangle() test_split() test_find_second_top_point() test_remove_top_triangle() test_calc_polygon_area() if __name__=='__main__': test() print 'Done.'
To test the polygon module properly different types of polygons are used as test subjects. The same group of polygons is used for multiple tests. The test polygons are defined globally at the beginning of the module as a set of vertices:
triangle = ((0,0), (0,3), (4,0)) rectangle = ((0,0), (0,3), (4,3), (4,0)) parallelogram = ((0,0), (3,1), (4,5), (1,4)) concave = ((0,0), (3,6), (6,0), (3,3)) concave2 = ((0,0), (4,6), (4,1), (5,3), (5,0)) ... concave12 = (0,1), (1,0), (1,1), (2,0), (2, 2)
When the test polygons became more complicated I added a little sketch comment to some of them. That helped a lot visualizing what happens during the algorithm execution. For example, here is the concave11 test polygon:
""" o / \ / \ o o o \ | \ | \ | \ | o o """ concave11 = ((0,1), (1, 2), (2, 1), (2, 0), (1, 1), (1, 0))
Inside each test function Polygon objects are instantiated using the test polygon vertices. Here is the test_is_triangle() function:
def test_is_triangle(): """ """ p = Polygon(triangle) assert p.is_triangle() p = Polygon(rectangle) assert not p.is_triangle() p = Polygon(parallelogram) assert not p.is_triangle() p = Polygon(concave) assert not p.is_triangle() p = Polygon(concave2) assert not p.is_triangle() | <urn:uuid:90343b6f-8d61-46ff-96d7-86729c0742f3> | 3.328125 | 1,683 | Documentation | Software Dev. | 43.92998 |
Sea level rise of more than 3 feet plausible by 2100
Melting glaciers in Antarctica and Greenland may push up global sea levels more than 3 feet by the end of this century, according to a scientific poll of experts that brings a degree of clarity to a murky and controversial slice of climate science.
Such a rise in the seas would displace millions of people from low-lying countries such as Bangladesh, swamp atolls in the Pacific Ocean, cause dikes in Holland to fail, and cost coastal mega-cities from New York to Tokyo billions of dollars for construction of sea walls and other infrastructure to combat the tides.
Estimating how much sea levels will rise from ice sheet melting is one of the more challenging aspects of climate science. Some evidence suggests recent accelerated melting is related to changes in ocean and atmospheric temperature, though natural variability may play an important role.
In addition, glaciers respond to external forces such as warmer temperatures in different ways, even when they are located right next to each other. As a result, there is tremendous uncertainty in the scientific community over how the melting will affect sea levels over the next century.
Venice Aqua Alta via Shutterstock.
Read more at Science on NBC News. | <urn:uuid:18c43c42-21a1-434c-a71a-10bcdb2d89c8> | 3.40625 | 245 | Truncated | Science & Tech. | 35.63316 |
brewer's yeast: see yeast.
The Columbia Electronic Encyclopedia, 6th ed. Copyright © 2012, Columbia University Press. All rights reserved.
More on brewer's yeast from Fact Monster:
- yeast - yeast yeast, name applied specifically to a certain group of microscopic fungi and to commercial ...
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- glycolysis - glycolysis glycolysis , term given to the metabolic pathway utilized by most microorganisms (yeast ...
- Encyclopedia: Moneran and Protistan - Encyclopeadia articles concerning Moneran and Protistan. | <urn:uuid:6f8bf80c-717b-4ac0-9bb3-c90a679f0f00> | 3.09375 | 137 | Structured Data | Science & Tech. | 27.540392 |
There are currently three, maybe four, methods of power generation that meet the criteria for base load power production. These are fossil fuels, typically coal, hydropower, geothermal, and nuclear.
Fossil fuels have a host of problems and concerns, from the production of CO2 and other greenhouse gases, acid rain, toxic ash, and a significant release of radioactivity. Of these, the most worrying is the production of greenhouse gases. The ongoing consensus regarding fossil fuels is that their use has been responsible for raising the average global temperature, and will continue to do so.
To solve the problem of greenhouse gases, we have to stop emitting them. Hydropower and geothermal, while useful as part of the base load, are too dependent on geography to be viable worldwide. Solar and wind are too intermittent, and so they can add to power production, but cannot carry the base load. Conservation is very useful, but it can only go so far. We need an alternative to replace fossil fuels, and in the short term the most viable contender is nuclear power. No less a personage than James Lovelock, originator of the Gaia hypothesis, agrees.
Nuclear power comes laden with its own baggage, however, and it is heavy indeed. Beyond the threat of possible radioactive contamination from the power plant itself, there is the matter of the nuclear waste material generated. Of course, the biggest issue looming over nuclear power is the matter of nuclear weapons proliferation.
There have been accidents at nuclear power plants, and accidents in the mining, processing, and transportation of nuclear materials. Some of these have resulted in the release of small amounts of radioactive material in to the environment. However, in terms of environmental damage and loss of life, these accidents pale in comparison to those in the mining, processing, and burning of coal. Outside of the former Soviet Union and former Warsaw Pact nations, the number of deaths attributable to nuclear power mining, processing, and power production are extremely low, especially in comparison to coal. Less than a handful, compared to hundreds from coal mining alone, let alone the effects of pollution and climate change.
Former Eastern bloc nations have seen some very serious accidents, most notably Chernobyl, but there been others. These can be attributed, in large part, to the poorer training of the operators, and the poorer design and construction of the reactors. Western-made reactors, on the other hand, are designed to be much safer.
On a long-term basis, the matter of the disposal of nuclear waste is a big problem. Fuel reprocessing can greatly reduce the amount of waste created, and is common for most European nations and Japan. Reprocessing can reduce waste from 27 tons per year to 5 tons per reactor per year. Compare this to a coal-fired plant of similar capacity that produces upwards of 400,000 tons of ash per year. Then again, coal ash won’t be radioactive for thousands of years, which is the issue that must be addressed in regards to nuclear power.
Spent reactor fuel is sealed as well as possible, and currently the waste is stored at reactor sites, awaiting a final resting place. While that waste does produce heat and radiation, this will fall off drastically over 40 years, making the material much easier to handle as it gets older. The long-lasting radiation, the type that lasts for thousands, or even millions, of years, is comparatively low-level, and is easily blocked. Underground storage in geologically stable regions is the long-term method chosen by all nations that make use of nuclear power.
It is this long-term storage that is problematic. We are essentially making decisions for people (or their successors) millions of years in the future, which is presumptuous, to say the least. It is either that, though, or poison ourselves with CO2. These are difficult decisions.
Then there is the nuclear weapons threat. While the fuel used in a reactor is not the same as the material used in warheads, if you’ve got the first, you can make the second. This is a difficult issue to address. Commercial nuclear power simply makes weapon creation easier. If a nations decides that it wants, or need, nuclear weapons, the presence, or absence, of civilian power will not be a factor. Advances in reactor technology, such as thorium reactors, are capable of producing power without creating material for use in atomic weapons.
Nuclear power is dangerous. However, the risk from using nuclear power, at this point in time, are less than the risks of continued use of fossil fuels. It is possible that future technological advances, like orbiting solar power or even nuclear fusion power, will solve the problem of clean energy for us. Until then, however, we have to use what we have. Conservation can only take us so far, and after that, the best choice looks increasingly like nuclear power, for better or worse. | <urn:uuid:fe3fa0ec-0394-4398-9137-dc5575c2e18c> | 3.75 | 1,006 | Nonfiction Writing | Science & Tech. | 43.939559 |
Rivers and Biodiversity
River systems are the zone of Earth’s highest biological diversity – and also of our most intense human activity. Freshwater biodiversity is in a state of crisis, a consequence of decades of humans exploiting rivers with large dams, water diversions and pollution. Freshwater species are even more endangered than those on land.
Large dams harm biological diversity by flooding land, fragmenting habitat, isolating species, interrupting the exchange of nutrients between ecosystems, and cutting off migration routes. They reduce water and sediment flows to downstream habitat, and change the nature of a river’s estuary, where many of the world’s fish species spawn. The impacts from dams increase the vulnerability of entire ecosystems to other threats, such as climate change.
The irretrievable loss of the Yangtze River baiji dolphin to the Three Gorges Dam or the extinction of a third of all wild salmon runs on dammed rivers throughout the US West are just the most charismatic examples of how humans are shredding the safety net that supports our own existence and viability.
We’re losing life forms that have the ability to nourish us, keep our water clean, produce breathable air and fertile soil, and ultimately make our planet the amazing place it is. If we don’t protect our biological richness and diversity, we undercut the re-generative capacity of the Earth, we undermine the prospect of life creating the conditions conducive to life.
The huge impact of large dams on biodiversity can be slowed and even reversed. First, dams proposed for environmental hotspots of biodiversity should stopped, and these rivers permanently protected by law . Rivers rich with migratory species are especially inappropriate for dams and should be deemed off limits. The planet’s most lethal dams should be decommissioned. And dam planning processes and standards must be improved: most of the time, we may be aware of only a fraction of the species a watershed holds before damming proceeds. It’s time for a revolution in how environmental assessments are conducted.
World Rivers Review: Special focus on Biodiversity (December 2011) | <urn:uuid:55960a03-463c-4ea5-8568-44fcb15f314b> | 3.84375 | 436 | Knowledge Article | Science & Tech. | 27.914819 |
Discussion about math, puzzles, games and fun. Useful symbols: ÷ × ½ √ ∞ ≠ ≤ ≥ ≈ ⇒ ± ∈ Δ θ ∴ ∑ ∫ • π ƒ -¹ ² ³ °
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Is there a way to make inequality of imaginery numbers?if there is please show a example.
Then, -1>-9 => i<3i,so square root of nagetive number changes inequality sign?
So,is there a way to make complex number inequallity?
In mathematics, you don't understand things. You just get used to them.
Probability is the most important concept in modern science, especially as nobody has the slightest notion what it means.
90% of mathematicians do not understand 90% of currently published mathematics.
Writing "pretty" math (two dimensional) is easier to read and grasp than LaTex (one dimensional).
LaTex is like painting on many strips of paper and then stacking them to see what picture they make. | <urn:uuid:310e01b0-22c3-4a47-90df-c10c3a788fea> | 2.796875 | 227 | Comment Section | Science & Tech. | 59.029048 |
Illustration courtesy NASA/CXC/M. Weiss
An artist's rendering, made using data collected by the orbiting Chandra X-ray Observatory, shows a quasar galaxy with a jet of high-energy particles extending more than 100,000 light-years from the supermassive black hole at its center. The object, located 12 billion light-years from Earth, is the most distant such jet ever detected. These quasar jets are formed when electrons emitted from a black hole impact with cosmic background radiation left by the big bang, giving astronomers clues about the conditions in the early universe. | <urn:uuid:c11ec7fe-afbd-4077-9c6f-f842e4ef9972> | 3.609375 | 119 | Truncated | Science & Tech. | 42.35625 |
A VERY special conversation began last month and is expected to continue throughout this year. Researchers in Tokyo and California are using lasers to "talk" to an orbiting satellite and get a reply. This is the first time lasers have been used to provide two-way communications with space.
The aim is to develop laser-based communications between geostationary satellites and between geostationary and low Earth orbit satellites. These laser "bridges" should enable ground stations around the world to collect data from Earth observation satellites that are not directly in view. They could also provide continuous links with crewed space stations and space planes.
The experiments are being carried out by a team drawn from the Communications Research Laboratory of the Ministry of Post and Telecommunications in Tokyo and NASA's Jet Propulsion Laboratory in Pasadena, California.
CRL will use the results of the tests to upgrade the optical equipment on board the ...
To continue reading this article, subscribe to receive access to all of newscientist.com, including 20 years of archive content. | <urn:uuid:d36fcbcd-cea2-47aa-8f15-c8c26e9ef738> | 3.796875 | 208 | Truncated | Science & Tech. | 35.227517 |
Want to stay on top of all the space news? Follow @universetoday on Twitter
As you probably know, the Earth is rotating on its axis. This gives us day and night. Of course it’s impossible, but what would happen if the Earth stopped spinning? Remember, this isn’t possible, it can’t happen, so don’t worry.
Everything would be launched in a ballistic trajectory sideways
The first thing to think about is the momentum of everything on the surface of the Earth. You’re held down by gravity and you’re whizzing through space at a rotational velocity of 1,674.4 km/h (at the equator). You can’t feel it because of momentum. Just like how you can’t feel that you’re moving in a car going down the highway. But you feel the effects when you stop, or get into an accident. And so, if the Earth suddenly stopped spinning, everything on the surface of the Earth at the equator would suddenly be be moving at more than 1,600 km/hour sideways. The escape velocity of Earth is about 40,000 km/hour, so that isn’t enough to fly off into space; but it would cause some horrible damage as everything flew in a ballistic trajectory sideways. Imagine the oceans sloshing sideways at 1,600 km/hour.
The rotational velocity of the Earth decreases as you head away from the equator, towards the poles. So as you got further away from the equator, your speed would decrease. If you were standing right on the north or south pole, you’d barely even feel it.
A day would last 365 days
The next problem is that day and night wouldn’t work the same any more. Right now the Earth is rotating on its axis, returning the Sun to the same position every 24 hours. But if the Earth stopped spinning, it would then take 365 days for the Sun to move through the sky and return to the same position. Half of the Earth would be baked for half a year, while the other hemisphere was in darkness. It would get very hot on the sunny side, and very cold in the shadowed side.
The Earth would become a perfect sphere
This might seem minor compared to the other catastrophes, but the Earth would become an almost perfect sphere. The Earth is currently rotating on its axis, completing one turn approximately every 24 hours. This rotational velocity causes the Earth to bulge out around its equator, turning our planet into an oblate spheroid (a flattened ball). Without this spin, gravity would be able to pull the Earth into a nice perfect sphere.
The Earth would no longer be tilted
The Earth’s tilt is defined by how the planet is rotating compared to the Sun. This axis of rotation defines the Earth’s seasons. But without any rotation, the concept doesn’t make sense any more. There’s still a north pole of the planet, where the radiation from the Sun is at its lowest angle, and an equator, where the light hits most directly. But there would no longer be seasons.
We’ve also recorded an episode of Astronomy Cast all about planet Earth. Listen here, Episode 51: Earth. | <urn:uuid:7c3e54f9-7ea1-4139-b3e8-42793494a073> | 4.03125 | 688 | Truncated | Science & Tech. | 65.086783 |
This area of Lakeport, California was flooded due to extreme weather during the 1998 El Niño event. El Niño causes changes in rainfall patterns around the world.
Click on image for full size
Courtesy of FEMA
El Niño and Other Climate Events
Sometimes there is a change in the way air moves through parts of the atmosphere. And there are sometimes changes in the way water moves through the ocean too. This disturbs typical weather patterns, or climate, for a few weeks or a few months or a year or more. Weather conditions return to their normal patterns when the atmosphere and ocean return to normal.
These events in the atmosphere and ocean can cause changes in the weather near the disruption and far from it. Changes in the atmosphere in one place that affect weather far away are called teleconnection patterns. Scientists are trying to sort out how this works so that they can better understand and predict weather patterns worldwide.
There are several different events that happen in the atmosphere and oceans. The largest are described below. These events are natural parts of the Earth’s climate. However they might be changing because of global warming.
The El Niño-Southern Oscillation (ENSO) is the strongest natural variation in climate. It is a disruption of the ocean-atmosphere system in the tropical Pacific that causes changes to weather and climate in places around the globe. Both phases of ENSO – El Niño and La Niña – can cause changes in weather including intense rainstorms, drought, and a change in the amount of storms.
Changes in the North Atlantic Oscillation (NAO) cause variability in Northern Hemisphere winter conditions like the amount of snow and cold temperatures. The NAO is closely related to the Arctic Oscillation and is also affected by ENSO.
Shop Windows to the Universe Science Store!
The Fall 2009 issue of The Earth Scientist
, which includes articles on student research into building design for earthquakes and a classroom lab on the composition of the Earth’s ancient atmosphere, is available in our online store
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RadixSort Algorithm in Java
Radix sort is a non comparing sort. It's performance is O(kn), where k is the maximum number of digits in inputs's decimal representation. It uses a queue to store number for each decimal digit. At each pass, it simply classifies inputs depending on the current decimal digit, starting from the least significant one. | <urn:uuid:8733d337-78e8-4476-b031-5147a6c021bb> | 3.5 | 74 | Knowledge Article | Software Dev. | 50.61 |
Reversing evolution: conspicuous mimicry vs. camoflage
Two papers this week on the type of mimicry named for Henry Bates, whose book on exploring the Amazon was published shortly after The Origin of Species. Batesian mimic species resemble foul-tasting or dangerous species, thereby avoiding being eaten, even though they are not actually dangerous themselves. Bates worked on butterflies whose wing patterns resembled those of other species. Butterflies are still the best-known examples of mimicry, but there are also examples of mimicry (involving behavior) in snakes and octopi.
The two papers are:
Once a Batesian mimic, not always a Batesian mimic: mimic reverts back to ancestral phenotype when the model is absent
by Kathleen Prudic and Jeffrey Oliver, of the University of Arizona, and
Colour pattern specification in the Mocker swallowtail Papilio dardanus: the transcription factor invected is a candidate for the mimicry locus H
by Rebecca Clark and colleagues in the UK, Australia, Kenya, and Germany. Both were published in Proceedings of the Royal Society.
The first paper asks how mimicry evolves when the distasteful “model� species is absent. Model species are usually brightly and distinctively colored, so the mimics are, too. But what happens if the model becomes too rare to “train� predators to avoid that pattern, or if the mimic moves into an area where the model isn’t found? The mimic could, perhaps, die out under these conditions.
Prudic and Oliver used molecular methods to develop a family tree for admiral butterfly species. Based on this tree, they concluded that the common ancestor of the admirals was inconspicuous, black with a white band that apparently makes it hard to see. Some admiral species have evolved to mimic different model species. But some of these evolved further, reversing this evolutionary path and becoming inconspicuous again. These species are found, as you might expect, in areas where the model is absent. So, in this case, reverse evolution was fast enough to avoid extinction. The reversal itself could have been rapid, if only a small genetic change was needed. Or the conditions that increased predation on the conspicuous mimics could have developed slowly.
Evolutionary reversals are not necessarily rare. Peter and Rosemary Grant found that the populations of Galapagos finches (made famous by Darwin) can evolve rapidly in response to dry years, but the effects are reversed in wet years, so there may be little long-term trend.
When natural selection favors a phenotype (such as wing pattern) that it previously eliminated, restoration of the old phenotype may not involve an exact return to the original genotype. The second paper identifies an actual gene responsible for the appearance of another butterfly mimic, the Mocker swallowtail. The gene identified was previously found to be involved in wing patterns (“eyespots�) in another butterfly species.
Both papers make heavy use of molecular tools that would have astounded Bates or Darwin, but they would perhaps be pleased that questions they raised are still of interest. | <urn:uuid:26f0ec0d-d0ab-4409-8324-da769c1d7e9d> | 3.09375 | 657 | Personal Blog | Science & Tech. | 31.313068 |
Above: Whichever came first, they're equally delicious. Egg photo by , licensed. Chicken photo by
Today I read possibly one of the dumbest science news articles of all time, or at least the most condescending. Somewhere in here is news of an interesting study. English scientists have isolated the protein responsible for the formation of hard-shelled eggs in chickens, a step forward in developmental science that could potentially yield applications for materials science. So, how to make sure this mildly interesting study grabs the attention of Joe Six-pack? Put out a press release to every major media outlet claiming to have solved the "age old problem" (really?) of which came first, the chicken or the egg?
The Chicken and the egg: Ancient mystery solved?
Not only is this silly eyeball-grabbing headline a blatant attempt to pander to the lowest common denominator and point out what a complete joke science reporting has become, it assumes the absolute worst about the reader's level of science comprehension and interest. And it's obviously completely wrong!
The articles in question "argue" that because a protein for forming eggshells is found inside chickens, this proves that the chicken came before the egg.
Not only is this severely flawed logic, you don't need a discovery to prove the answer one way or the other: If you really want an answer to this rhetorical philosophical conundrum, it's obvious using simple logic and knowledge of how evolution works.
Let's define some terms first. I think implicit in this old riddle is the fact that we're talking about chickens Gallus gallus and chicken eggs here, specifically.
Nothing in the report suggests that proteins for hard shells originated with modern chickens. In fact, we know from observation that all other bird species, including those more primitive than chickens, lay hard-shelled eggs (though as PZ Myers points out in the link below, they often use a different protein). We know based on fossil evidence that hard-shelled eggs were laid by not only non-avian theropods but also sauropods and ornithischians. In contrast, softer shelled eggs are found in crocodilians and pterosaurs. So we know that the hard-shelled egg this protein (or the genes coding for it or similar proteins) allows evolved among ornithodirans sometime after pterosaurs diverged but before ornithischian and saurischian dinosaurs split. So, let's ballpark it to the early-mid Triassic period for the appearance of hard-shelled eggs. Even allowing for the broadest possible definition of "chicken" (Galliformes), the earliest you can say chicken-like creatures walked he earth is the late Cretaceous, when the stem-anseriform Vegavis lived (so we know that the chicken line must have split from the duck line by that time).
That covers the hard shelled egg in general, which clearly came long before the chicken. What about modern chickens specifically and their eggs? This gets down to the biological species concept, of which there are many and they all overlap. Is a chicken anything that can successfully breed with any random clucker down at the farm? If so, we're getting into some sticky concepts of ring species and sub-species here, which just muddy the waters, especially when ancestral species are taken into account. Let's just say for our purposes, a "chicken" means the type specimen of Gallus gallus domesticus, and its specific genome. The species this bird belongs to, however you define it, diverged from an ancestral population that we can say was non-chicken. The relevant mutations or changes in allele frequency that define the line between chicken and non-chicken almost certainly did not occur inside the living adult non-chicken and were then passed on to its offspring in some kind of Lamarckian evolutionary event. Rather, they would have taken place in the cell divisions leading to the formation of the first true chicken egg.
Put more simply, a non-chicken did not spontaneously transform into a chicken via some kind of Fantastic Four style cosmic wave, and it did not spring spontaneously with all its essential chickenness in place from the head of Zeus. Rather, a non-chicken had to have laid an egg containing a chicken embryo. Can this be said to be a chicken egg, if it was laid by a non-chicken? I'd day yes, as it contains a chicken. Though ultimately, maybe this classic paradox is better left to philosophers after all.
PZ Myers of Pharyngula has done his own write-up on this travesty of science reporting and goes into more detail on the protein angle, well worth a read here. PZ says that "you simply can't make the conclusion the reporter was making here" but, given the prevalence of this exact conclusion in other articles from other news sources, everybody is simply copying one idiot science writer or, more likely, this conclusion was actively promoted by a press release. I can't decide which would be worse.
EDIT: This is getting hilarious. No, not the plethora of tragically inevitable comments from creationists, but watching the American media slowly realize that every single one of their science writers who allowed this nonsense to be repeated on their pages are being laughed at by people who took middle school biology, even in their own comments. Case in point: A single editor's note has been made on the CNN Article headline: "Maybe." Not, "Sorry, our so-called journalists are too stupid to recognize an obvious load of crap when they see it, or at the very least point out the crap being served to them in press release form. The people responsible have been fired and we're hiring a literate this time."
Just, "Maybe. Maybe not. Reality: you decide!" | <urn:uuid:5ccd9ab1-89c1-4daf-ac8d-0227eea7e42a> | 2.90625 | 1,197 | Personal Blog | Science & Tech. | 45.213999 |
World storm surge records
There's still not much to talk about the tropical Atlantic today. The Intertropical Convergence Zone (ITCZ), the band of intense thunderstorms that spans the tropical Atlantic between Africa and the Lesser Antilles Islands, has grown more active in the past few days, though. The two tropical waves in the ITCZ closest to the coast of Africa bear some scrutiny this week as they cross the Atlantic. However, none of the models are currently forecasting development of these waves, and there is plenty of wind shear and dry air that will interfere with potential development.
World storm surge records
In preparation for the release of a major new storm surge section of the web site, I've been researching storm surge records. The Bathurst Bay Cyclone, also known as Tropical Cyclone Mahina, which struck Bathurst Bay, Australia on March 5, 1899, is generally credited with the world record for storm surge. The cyclone's storm surge is variously listed at 13 - 14.6 meters (43 - 48 feet). The Category 5 cyclone was a monster--with sustained winds in excess of 175 mph and a central pressure between 880 and 914 mb. Mahina killed at least 307 people, mostly on pearling ships, and was the deadliest cyclone in Australian history. The eyewitness account of Mahina's record storm surge was provided by Constable J. M. Kenny, who journeyed to Barrow Point on Bathurst Bay to investigate a crime on the day of the storm. While camped on a ridge 40 feet above sea level and 1/2 mile inland, Kenny's camp was inundated by a storm wave, reaching waist-deep. On nearby Flinders Island, fish and dolphins were found on top of 15 meter (49 foot) cliffs. However, an analysis by Nott and Hayne (2000) found no evidence of storm-deposited debris higher than 3 - 5 meters above mean sea level in the region. They also cited two computer storm surge simulations of the cyclone that were unable to generate a surge higher than three meters. Indeed, Bathurst Bay is not ideally situated to receive high storm surges. The Great Barrier Reef lies just 20 - 40 km offshore, and the ocean bottom near the bay is not shallow, but steeply sloped. Both of these factors should conspire to keep storm surges well below the record 13 - 14.6 meters reported. The authors concluded that the actual surge from the Bathurst Bay Cyclone may have been 3 - 5 meters. The observed inundation at 13 meters elevation, plus the observation of dolphins deposited at 15 meters above sea level, could have been caused by high waves on top of the surge, they argue. Waves on top of the surge (called "wave run-up") can reach five times the wave height at the shore for steeply fronted coasts like at Bathurst Bay. Since waves in the Bathurst Bay Cyclone could easily have been 3 meters, 15 meters of wave run-up on top of the surge is quite feasible. Since wave run-up doesn't count as surge, the status of the 1899 Bathurst Bay Hurricane as the world-record holder for storm surge is questionable. However, the event is certainly the record holder for the high water mark set by a tropical cyclone's storm surge, an important category in its own right.
Figure 1. Satellite image of Bathurst Bay, Queensland Province, Australia. The record 43 - 48 foot storm surge wave occurred on Barrow Point, marked by an "x" on the map above. Image credit: NASA.
Figure 2. Track of the 1899 Bathurst Bay cyclone. Bathurst Bay is located at the point where the 914 mb pressure is listed. Image credit: Whittingham, 1958.
Australian storm surge records
The largest storm surges in Australia occur in Gulf of Carpentaria, due to the large expanse of shallow water there (the Gulf of Carpentaria is the large bay to the left of the zoomed-in map of Bathurst Bay shown above). According to an email I received from Australian hurricane scientist Jeffrey Callaghan, "From all reports the storm surge from the disastrous 5 March 1887 cyclone flooded almost all of Burketown (some 30km inland from the Gulf). A copy of a 1918 report to the Queensland Parliament from the Department of Harbours and Rivers Engineer refers to the sea rising to 5.5 metres above the highest spring tide level at the Albert River Heads. This level is about 8 metres (26.2 feet) above Australian Height Datum (AHD). The biggest measured surge in the Gulf of Carpenteria occurred on 30 March 1923, when a surge of 21.4 feet was recorded at a Groote Eylandt Mission".
So what is the world storm surge record if the Bathurst Bay cyclone does not qualify? Well, I haven't researched storms in the Indian Ocean or Pacific Typhoons yet, but it might be difficult to find any storm that beats Hurricane Katrina's 27.8 foot storm surge.
Nott, J, N. Hayne, 2000: How high was the storm surge from Tropical Cyclone Mahina?", Australian Journal of Emergency Management, Autumn 2000.
Anonymous, 1899, The Outridge Report--The Pearling Disaster 1899: A Memorial", The Outridge Company, 1899
Whittingham, 1958, "The Bathurst Bay hurricane and associated storm surge", Australian Meteorological Magazine, No. 27, pp. 40-41. Scanned and put on-line courtesy of John McBride.
I'll have an update on Tuesday, when the latest CSU seasonal hurricane forecast comes out at 11am EDT. | <urn:uuid:62097da5-2b7b-43d3-b67e-16b2efe4e4c0> | 2.984375 | 1,166 | Personal Blog | Science & Tech. | 59.513778 |
Science in the News, November 2003 -- The Sun continues its dramatic spate of activity, unleashing three more powerful solar flares. Over the last ten days, the sun has blasted tons of superhot gases into space, some of it directly aimed at Earth. These solar flares have been the most powerful ever recorded since regular monitoring began. Powerful flares are given an "X" designation to indicate their intensity. Last week, there were two flares that were at the level of X7 and X10. On Tuesday, November 4th, there was a flare that was an X20 or above. These massive ejections of gases from the solar surface have sent geomagnetic storms that have pummeled the Earth. The flares last week disrupted satellite-based communications systems and and some airplane communications. As Harvard solar astrophysicist John L. Kohl said, "To have two huge [eruptions] coming out of an active region within a day -- both aimed right at Earth -- there's no precedent for that. It goes beyond anything we've seen." Researchers believe that although these latest blasts were not aimed directly towards the Earth, the atmosphere could still be effected by clouds of particles that could cause some geomagnetic storms.
What is a solar flare? Solar flares originate near the edge of sunspots. A sunspot is an area of especially intense electromagnetic activity on the Sun's surface. Sunspots appear as dark spots because they are much cooler than the surrounding area. Much of the surface of the sun is around 5400°C (9700°F), but the surface temperature within sunspots can be as "cool" as 4,000°C (7200°F). In areas of such intense electromagnetic activity, tension builds. The energy from this tension is sometimes released in tremendous surface explosions called solar flares. According to NASA, the energy released during a solar flare is equivalent to "millions of 100-megaton hydrogen bombs exploding at the same time."
Typically, solar flare activity coincides with the solar cycle. The solar cycle, also known as the sunspot cycle, is an 11-year cycle of rising and falling electromagnetic activity on the sun's surface. The remarkable thing about solar events of late 2003 is that they are extremely powerful but do not coincide with the solar cycle. For such a dramatic eruption of solar activity to occur during a lull period of the solar cycle is unusual. | <urn:uuid:a7fadaa7-5975-45c6-ae56-75f6d20827e5> | 3.625 | 487 | Knowledge Article | Science & Tech. | 43.517769 |
Earth Moon Comparison
May 09, 2001
The above image shows the Earth and the moon as viewed from the Odyssey spacecraft on its journey to Mars. Even though the Earth and its satellite look pretty small (the moon is a mere speck), at the time this photograph was taken (late April), Odyssey was more than 15 times closer to the Earth than to Mars - it was 4,639,830 km (2,883,050 miles) from Earth. The spacecraft won't arrive at Mars until October 24 - it was launched on April 7. Odyssey carries three scientific instruments designed to tell us what the Martian surface is made of and its radiation environment.
This image shows the true distance relationship between the Earth and the moon as well as the size difference comparison. Earth and its satellite are approximately 385,000 km apart - about 30 Earth diameters. Odyssey is traveling at a speed of 3.3 kilometers per second (7,474 miles per hour) relative to the Earth. Even though the Earth has a diameter of 12,756 km compared to a diameter of 3,476 for that of the moon, since this image was taken in infrared light, the moon looks smaller than it's actual size. It's much cooler (less emissive), and thus it's not as bright as is the Earth. The darker area on the lower portion of the Earth's disk is Antarctica. | <urn:uuid:a97a71b0-209e-468f-aafd-01ecaa8a25d4> | 3.875 | 281 | Knowledge Article | Science & Tech. | 66.505183 |
2007 Lecture Series
Dr. Jerry Nelson
Making it Big in Astronomy
(December 19, 2007) In 1977 Jerry Nelson was physicist at UC’s Lawrence Berkeley Laboratory, and he was asked to join a group to vision the future of US astronomy. For Nelson it was a once-in-a-lifetime chance to design a major apparatus with “cosmic implications.” His work translated into the revolutionary twin 10-meter Keck telescopes. Decades later, Nelson’s gift for devising solutions to large technical challenges continues to make its mark in astronomical innovation.
Science Standards: How Information is Collected and Analyzed; How a Telescope Works
Dr. Edward C. Stone
Voyager Mission: The Journey Continues
(June 22, 2007) From the “Evenings with Astronomers” series. Dr. Edward C. Stone, the David Morrisroe Professor of Physics at Caltech and one of the leading scientists of our time, has been the project scientist for the Voyager mission since 1972. As the two Voyager spacecraft flew by Jupiter, Saturn, Uranus and Neptune, they revealed a Solar System with worlds of unimagined diversity. The Voyagers are now exploring the Solar System’s final frontier, its outermost region called the heliosphere, which, like a bubble, envelops our Sun and all the planets.
Science Standards: Describe the nature of our solar system; discuss current scientific views about our solar system; describe how technology is being used to conduct scientific investigations.
Dr. Charles Beichman
Are There Other Worlds? Modern Answers to a 2500-Year-Old Question
(May 22, 2007) From the “Evenings with Astronomers” Series. Dr. Charles Beichman of the Michelson Science Center at Caltech talks about the 21st century tools being used to answer one of the most ancient questions: “Are there other worlds like our own?” How are astronomers probing the birthplace of stars and planets? How will scientists know if a planet supports life? Dr. Beichman explains the modern search for answers.
Science Standards: Design and conduct investigations to answer questions; Use the problem-solving process to address current issues; Describe what constitutes the universe.
Dr. Michael Brown
Pluto and Other Dwarf Planets: Discoveries in our Solar System
(March 27, 2007) From the “Evenings with Astronomers” series. In 2005, Dr. Michael Brown and his colleagues discovered 2003 UB313, now officially known as “Eris.” The discovery marked the first time in 75 years that an object larger than Pluto had been found in our Solar System. The discovery turned the astronomical world on its head. Scientists had to consider if size was the only metric by which to define a planet. The debate unleashed an avalanche of questions concerning planetary science and the role scientists play in defining the word “planet” for local and global communities.
Science Standards: Earth in the Solar System; Forces that Shape the Earth; Scientific Views of the Universe.
Dr. Taft Armandroff
The Astronomical Frontier: New Opportunities for Discovery
(February 27, 2007) Dr. Taft Armandroff of the W. M. Keck Observatory kicks off the second annual “Evenings with Astronomers” lecture series. In this talk, Dr. Armandroff charts the significant technological milestones in astronomical research and describes how new technology is being applied to answer profound questions about the cosmos.
Science Standards: Scientific Inquiry; Technological Impacts; Relating the Nature of Technology to Science.
Limitation of Liability:
The W. M. Keck Observatory is not liable for any direct, indirect, incidental, special, consequential or other damages arising out of the use or download of any files on this page by any person or organization. These limitations apply to all causes of action and is intended to be as broad as possible. | <urn:uuid:8f069bd1-aded-4d9a-995f-04f2b718b86c> | 3.296875 | 821 | Content Listing | Science & Tech. | 45.432111 |
I'm trying to understand the proof for eccentricity; I can get about halfway through it. The problem I'm having is summarized below
If e<1, you get the equation of an ellipse of the form
The foci of an ellipse are at a distance c from the center, where
This shows that
It follows from equations 4 and 5 that the eccentricity is given by
If someone could help explain how is derived, or really what it means I'd be so grateful. I'm using Calculus Early Transcendentals 6th Ed. by Stewart (Ch. 10, Sect. 6). | <urn:uuid:b402727b-5cb3-4a81-8e7b-836cd8342db1> | 3.078125 | 129 | Q&A Forum | Science & Tech. | 73.014773 |
what is the domain and range?
describe the level curves, the boundary of the domain and determine if the domain is an open or closed or neither region.
Also what points (x,y) in the plane is this function continuous.
i dont really understand these questions at all. I dont really understand the range of 2 variable functions as well as the level curves all that well. For the second question im not real sure where to start. | <urn:uuid:fb9b004a-3dd8-4eb1-a0ed-c904900e1427> | 2.8125 | 92 | Q&A Forum | Science & Tech. | 67.824615 |
Can you order the digits from 1-6 to make a number which is
divisible by 6 so when the last digit is removed it becomes a
5-figure number divisible by 5, and so on?
Use the clues to work out which cities Mohamed, Sheng, Tanya and
Bharat live in.
How many different shaped boxes can you design for 36 sweets in one
layer? Can you arrange the sweets so that no sweets of the same
colour are next to each other in any direction?
Follow the clues to find the mystery number.
Find the smallest whole number which, when mutiplied by 7, gives a
product consisting entirely of ones.
In a square in which the houses are evenly spaced, numbers 3 and 10
are opposite each other. What is the smallest and what is the
largest possible number of houses in the square?
The planet of Vuvv has seven moons. Can you work out how long it is
between each super-eclipse?
If these elves wear a different outfit every day for as many days
as possible, how many days can their fun last?
Can you work out the arrangement of the digits in the square so
that the given products are correct? The numbers 1 - 9 may be used
once and once only.
There is a clock-face where the numbers have become all mixed up. Can you find out where all the numbers have got to from these ten statements?
This multiplication uses each of the digits 0 - 9 once and once only. Using the information given, can you replace the stars in the calculation with figures?
Can you fill in this table square? The numbers 2 -12 were used to
generate it with just one number used twice.
In the multiplication sum, some of the digits have been replaced by letters and others by asterisks. Can you reconstruct the original multiplication?
Make a pair of cubes that can be moved to show all the days of the
month from the 1st to the 31st.
What do the digits in the number fifteen add up to? How many other
numbers have digits with the same total but no zeros?
Suppose we allow ourselves to use three numbers less than 10 and
multiply them together. How many different products can you find?
How do you know you've got them all?
Seven friends went to a fun fair with lots of scary rides. They
decided to pair up for rides until each friend had ridden once with
each of the others. What was the total number rides?
Can you replace the letters with numbers? Is there only one
solution in each case?
Put 10 counters in a row. Find a way to arrange the counters into
five pairs, evenly spaced in a row, in just 5 moves, using the
How many shapes can you build from three red and two green cubes? Can you use what you've found out to predict the number for four red and two green?
Place eight dots on this diagram, so that there are only two dots
on each straight line and only two dots on each circle.
Can you substitute numbers for the letters in these sums?
In a bowl there are 4 Chocolates, 3 Jellies and 5 Mints. Find a way
to share the sweets between the three children so they each get the
kind they like. Is there more than one way to do it?
The Zargoes use almost the same alphabet as English. What does this
birthday message say?
There were chews for 2p, mini eggs for 3p, Chocko bars for 5p and
lollypops for 7p in the sweet shop. What could each of the children
buy with their money?
If we had 16 light bars which digital numbers could we make? How
will you know you've found them all?
Lolla bought a balloon at the circus. She gave the clown six coins
to pay for it. What could Lolla have paid for the balloon?
Sitting around a table are three girls and three boys. Use the
clues to work out were each person is sitting.
On a digital 24 hour clock, at certain times, all the digits are
consecutive. How many times like this are there between midnight
and 7 a.m.?
Can you put plus signs in so this is true? 1 2 3 4 5 6 7 8 9 = 99
How many ways can you do it?
Find the product of the numbers on the routes from A to B. Which
route has the smallest product? Which the largest?
Find all the different shapes that can be made by joining five
equilateral triangles edge to edge.
There are seven pots of plants in a greenhouse. They have lost
their labels. Perhaps you can help re-label them.
Mr McGregor has a magic potting shed. Overnight, the number of
plants in it doubles. He'd like to put the same number of plants in
each of three gardens, planting one garden each day. Can he do it?
Katie had a pack of 20 cards numbered from 1 to 20. She arranged
the cards into 6 unequal piles where each pile added to the same
total. What was the total and how could this be done?
I was in my car when I noticed a line of four cars on the lane next
to me with number plates starting and ending with J, K, L and M.
What order were they in?
When intergalactic Wag Worms are born they look just like a cube.
Each year they grow another cube in any direction. Find all the
shapes that five-year-old Wag Worms can be.
There are 78 prisoners in a square cell block of twelve cells. The
clever prison warder arranged them so there were 25 along each wall
of the prison block. How did he do it?
You have two egg timers. One takes 4 minutes exactly to empty and
the other takes 7 minutes. What times in whole minutes can you
measure and how?
Given the products of diagonally opposite cells - can you complete
Can you rearrange the biscuits on the plates so that the three
biscuits on each plate are all different and there is no plate with
two biscuits the same as two biscuits on another plate?
A mathematician goes into a supermarket and buys four items. Using
a calculator she multiplies the cost instead of adding them. How
can her answer be the same as the total at the till?
Stuart's watch loses two minutes every hour. Adam's watch gains one
minute every hour. Use the information to work out what time (the
real time) they arrived at the airport.
Can you help the children find the two triangles which have the
lengths of two sides numerically equal to their areas?
Look carefully at the numbers. What do you notice? Can you make
another square using the numbers 1 to 16, that displays the same
A merchant brings four bars of gold to a jeweller. How can the
jeweller use the scales just twice to identify the lighter, fake
Zumf makes spectacles for the residents of the planet Zargon, who
have either 3 eyes or 4 eyes. How many lenses will Zumf need to
make all the different orders for 9 families?
There are 4 jugs which hold 9 litres, 7 litres, 4 litres and 2
litres. Find a way to pour 9 litres of drink from one jug to
another until you are left with exactly 3 litres in three of the
On a digital clock showing 24 hour time, over a whole day, how many
times does a 5 appear? Is it the same number for a 12 hour clock
over a whole day?
George and Jim want to buy a chocolate bar. George needs 2p more
and Jim need 50p more to buy it. How much is the chocolate bar? | <urn:uuid:9fd345a8-76c7-4aee-8f2f-d3980b5ba76e> | 2.96875 | 1,662 | Content Listing | Science & Tech. | 75.094877 |
At the Sanaga-Yong Chimpanzee Rescue Center, chimpanzees form a gallery of grief, looking on as Dorothy–a beloved female felled in her late 40s by heart failure–is borne to her burial.
Image: National Geographic / Monica Szczupider
The Prancing Papio has brought attention to this powerful photograph presented by National Geographic showing chimpanzees focused on the body of a recently deceased member of their community. I still remember the powerful effect it had on me when I saw Jane Goodall’s The People of the Forest which showed how one young male, who was fully capable of taking care of himself, was so distraught by his mother’s death that he refused to leave his nest for days and eventually died. It was a clear example of the power that mourning had over our evolutionary cousins.
As The Daily Mail reported about the photograph:
Until recently, describing scenes such as this in terms of human emotions such as “grief” would have been dismissed by scientists as naive anthropomorphising. But a growing body of evidence has suggested that “higher” emotions – such as grieving for a loved one and even a deep understanding of what death is – may not just be the preserve of our species.
Chimpanzees – as revealed in November’s National Geographic magazine – and closely related bonobos maintain hugely complex social networks, largely held together by sex and grooming. They have often been observed apparently grieving for lost family and tribe members by entering a period of quiet mourning, showing subdued emotions and behaviour. | <urn:uuid:99b6c674-a456-4ab6-93eb-7e2129fd76a1> | 2.90625 | 318 | Personal Blog | Science & Tech. | 26.514816 |
Over twenty scientists, after six years of collaboration, have completed the most comprehensive picture of mammalian ancestry to date, just after the extinction of dinosaurs, 65 million years ago. The last common ancestor from which all placental mammals emerged. Image © Carl Buell
The researchers using a combination of physical and genetic data, reconstructed the family tree of placental mammals, comprising today over 5,100 species.
read more wired | <urn:uuid:bc694d98-8c5b-4fb6-980d-4a0c8e3d64b0> | 3.109375 | 85 | Truncated | Science & Tech. | 22.093039 |
osmium (Os)Article Free Pass
osmium (Os), chemical element, one of the platinum metals of Groups 8–10 (VIIIb), Periods 5 and 6, of the periodic table and the densest naturally occurring element. A gray-white metal, osmium is very hard, brittle, and difficult to work, even at high temperatures. Of the platinum metals it has the highest melting point, so fusing and casting are difficult. Osmium wires were used for filaments of early incandescent lamps before the introduction of tungsten. It has been used chiefly as a hardener in alloys of the platinum metals, though ruthenium has generally replaced it. A hard alloy of osmium and iridium has been used for tips of fountain pens and phonograph needles, and osmium tetroxide is used in certain organic syntheses.
Pure osmium metal does not occur in nature. Osmium has a low crustal abundance of about 0.001 part per million. Though rare, osmium is found in native alloys with other platinum metals: in siserskite (up to 80 percent), in iridosmine, in aurosmiridium (25 percent), and in slight amounts in native platinum. Processes for isolating it are an integral part of the metallurgical art that applies to all platinum metals.
The English chemist Smithson Tennant discovered the element together with iridium in the residues of platinum ores not soluble in aqua regia. He announced its isolation (1804) and named it for the unpleasant odour of some of its compounds (Greek osme, odour).
Of the platinum metals, osmium is the most rapidly attacked by air. The powdered metal, even at room temperature, exudes the characteristic odour of the poisonous, volatile tetroxide, OsO4. Because solutions of OsO4 are reduced to the black dioxide, OsO2, by some biological materials, it is sometimes used to stain tissues for microscopic examinations.
Osmium is, with ruthenium, the most noble of the platinum metals, and cold and hot acids are without effect on them. It can be dissolved by fused alkalies, especially if an oxidizing agent such as sodium chlorate is present. Osmium will react at 200° C with air or oxygen to form OsO4.
Osmium exhibits oxidation states from 0 to +8 in its compounds, with the exception of +1; well-characterized and stable compounds contain the element in +2, +3, +4, +6, and +8 states. There are also carbonyl and organometallic compounds in the low oxidation states −2, 0, and +1. Ruthenium is the only other element known to have an oxidation state of 8. (The chemistries of ruthenium and osmium are generally similar.) All compounds of osmium are easily reduced or decomposed by heating to form the free element as a powder or sponge. There is an extensive chemistry of the tetroxides, oxohalides, and oxo anions. There is little, if any, evidence that simple aquo ions exist, and virtually all their aqueous solutions, whatever the anions present, may be considered to contain complexes.
Natural osmium consists of a mixture of seven stable isotopes: osmium-184 (0.02 percent), osmium-186 (1.58 percent), osmium-187 (1.6 percent), osmium-188 (13.3 percent), osmium-189 (16.1 percent), osmium-190 (26.4 percent), osmium-192 (41.0 percent).
|melting point||3,000° C (5,432° F)|
|boiling point||about 5,000° C (9,032° F)|
|specific gravity||22.48 (20° C)|
|oxidation states||+2, +3, +4, +6, +8|
|electron config.||[Xe]4f 145d66s2|
What made you want to look up "osmium (Os)"? Please share what surprised you most... | <urn:uuid:eeb69422-9f5c-4330-bd38-4c9095f2bbe4> | 3.578125 | 899 | Knowledge Article | Science & Tech. | 53.292528 |
Coral Reef Overview
- What is a coral reef?
- What is coral?
- What is a coral polyp?
- Where do corals live?
- How old are coral reefs?
- How is coral constructed?
- How long does it take coral to grow?
- How do corals get their shape?
- How do coral polyps eat?
- How do corals get their color?
- How do corals reproduce?
- What do corals need to survive?
- What are the different types of reefs?
Coral reefs are massive structures made of limestone deposited by living things. Although thousands of species inhabit coral reefs, only a fraction produce the limestone that builds the reef. The most important reef-building organisms are the corals.
Coral reefs support approximately 25 percent of all known marine species. As one of the most complex ecosystems on the planet, coral reefs are home to more than 4,000 species of fish, 700 species of coral, and thousands of other plants and animals.
Imagine a coral reef like a bustling city: the buildings are made of coral and thousands of inhabitants live in, on, or near the buildings. In this sense, a coral reef is like a metropolis under the sea.
Although coral is often mistaken for a rock or a plant, it is actually composed of tiny, fragile animals called coral polyps. When people say coral, they are referring to these little animals and the skeletons they leave behind after they die.
Although there are hundreds of different species of corals, they are generally classified as either hard coral or soft coral.
Hard corals grow in colonies and are the architects of coral reefs. Including such species as brain coral and elkhorn coral, hard coral create skeletons out of calcium carbonate (also known as limestone), a hard substance that eventually becomes rock. Hard corals are hermatypes, or reef-building corals, and need tiny algae called zooxanthellae (pronounced zo-zan-THEL-ee) to survive. Generally, when we talk about coral, we are referring to hard corals.
Soft corals, such as sea fingers and sea whips, are soft and bendable and often resemble plants or trees. These corals do not have stony skeletons, but instead grow wood-like cores for support and fleshy rinds for protection. They are referred to as ahermatypes, or non–reef building corals, and they do not always have zooxanthellae. Soft corals are found in both tropical seas and in cool, dark regions.
A coral polyp is an invertebrate (spineless animal; they are cousins to anemones and jellyfish) that ranges in size from tiny (no bigger than a pinhead) up to a foot in diameter. One coral branch or mound is covered by thousands of coral polyps, which when grouped together, is called a coral colony. Thus, each coral branch or mound is one colony of coral polyps. A polyp has a saclike body and an opening, or mouth, encircled by stinging tentacles called cnidae. The polyp uses calcium carbonate (limestone) from seawater to build itself a hard, cup-shaped skeleton. This limestone skeleton protects the soft, delicate body of the polyp. Coral polyps are usually nocturnal, meaning that they stay inside their skeletons during the day. At night, polyps extend their tentacles to feed.
Coral reefs are found in more than 100 countries around the world. Most reefs are located between the Tropics of Cancer and Capricorn, in the Pacific Ocean, the Indian Ocean, the Caribbean Sea, the Red Sea, and the Arabian Gulf. Corals are also found farther from the equator in places where warm currents flow out of the tropics, such as in Florida and southern Japan. Worldwide, coral reefs cover an estimated 110,000 square miles (284,300 square kilometers).
Coral reefs grow best in warm water (70–85° F or 21–29° C). It is possible for soft corals to grow in places with warmer or colder water, but growth rates in these types of conditions are very slow. Corals prefer clear and shallow water, where lots of sunlight filters through to their symbiotic algae. It is possible to find corals at depths of up to 300 feet (91 meters), but reef-building corals grow poorly below 60–90 feet (18–27 meters). Corals need salt water to survive, so they also grow poorly near river openings or coastal areas with excessive run-off.
The geological record indicates that ancestors of modern coral reef ecosystems were formed at least 240 million years ago. Most established coral reefs are between 5,000 and 10,000 years old. Although size sometimes indicates the age of a coral reef, this is not always true. Different species of coral grow at different rates depending on water temperature, oxygen level, amount of turbulence, and availability of food.
Coral reefs are complex, multistory structures with holes and crevices shared by various creatures. If a coral reef is likened to a bustling city, then a coral colony is like a single apartment building with many rooms and hallways that house different marine species. Not all coral species build reefs. The actual architects of coral reefs are hard or stony corals, which are referred to as hermatypic, or reef-building corals. As the polyps of stony corals grow, they produce limestone skeletons. When they die, their skeletons are left behind and used as foundations for new polyps, which build new skeletons over the old ones. An actual coral branch, or mound, is composed of layer upon layer of skeletons covered by a thin layer of living polyps.
Other types of animals and plants also contribute to the structure of coral reefs. Many types of algae, seaweed, sponge, sediment, and even mollusks like giant clams and oysters add to the architecture of coral reefs. When these organisms die, they also serve as foundations for new corals.
Corals grow at different rates depending on water temperature, salinity, turbulence, and the availability of food. The massive corals are the slowest growing species, adding between 5 and 25 millimeters (0.2–1 inch) per year to their length. Branching and Staghorn corals can grow much faster, adding as much as 20 centimeters (8 inches) to their branches each year.
The variety of coral shapes and sizes largely depends on the species. Some corals form hard and pointed shapes, while others form soft and rounded shapes. The shape of coral colonies also depends on the location of the coral. For example, in areas with strong waves corals tend to grow into robust mounds or flattened shapes. In more sheltered areas, the same species may grow into more intricate shapes with delicate branching patterns.
Coral polyps eat in two different ways according to the species. Many coral polyps are nourished by a tiny algae called zooxanthellae (pronounced zo-zan-THEL-ee). The algae live within the coral polyps, using sunlight to make sugar for energy just like plants. Zooxanthellae process the waste of the polyp to retain important nutrients and in turn provide the polyp with oxygen. Meanwhile, the coral polyps provide the algae with carbon dioxide and a safe, protected home. Zooxanthellae living within the tissue of hard corals can supply them with up to 98 percent of their nutritional needs.
Another way that corals eat is by catching tiny floating animals known as zooplankton. At night , coral polyps come out of their skeletons to feed, making the reef look like a wall of hungry mouths. The polyps stretch out their long, stinging tentacles to capture the zooplankton that are floating by. The captured plankton are then put into the polyps' mouths and digested in their stomachs.
Most coral polyps have clear bodies and their skeletons are white, like human bones. Generally, their brilliant color comes from the zooxanthellae living inside their tissues. Several million zooxanthellae live and produce pigments in just one square inch of coral. These pigments are visible through the clear body of the polyp and are what gives coral its beautiful color.
Coral reproductive methods vary according to the species. Some species, such as Brain and Star corals, are hermaphrodites, meaning they produce both sperm and eggs at the same time. Other corals, such as Elkhorn and Boulder corals, are gonochoric, meaning that they produce single-sex colonies. In these species, all of the polyps in one colony produce only sperm, and all of the polyps in another colony produce only eggs.
Coral larvae are formed in two different ways. The larvae are either (1) fertilized within the body of a polyp or (2) fertilized outside of the polyp's body in the water. Fertilization of an egg within the body of a coral polyp is achieved from sperm that is released through the mouth of another polyp. The sperm and egg merge and form a planula larva, which matures inside the body of its mother. When the larva is ready, it gets spit out into the water through the mouth of its mother. O
Other species of coral reproduce by ejecting large quantities of eggs and sperm into the surrounding water. When this happens, the eggs and sperm fertilize in the water. This process is called coral spawning. In some areas, mass coral spawning events occur on one particular night per year and scientists can predict exactly when this will happen. Trillions of eggs and sperm are simultaneously released into the water in one of the most astounding acts of synchronicity in the natural world!
Once in the sea, larvae are naturally attracted to the light. They swim to the surface of the ocean, where they remain for days or even weeks. If predators do not eat the larvae during this time, they fall back to the ocean floor and attach themselves to a hard surface. An attached planula metamorphasizes into a coral polyp and begins to grow—dividing itself in half and making exact genetic copies of itself. As more and more polyps are added, a coral colony develops. Eventually the coral colony becomes mature, begins reproducing, and the cycle of life continues.
Sunlight: Corals need to grow in shallow water where sunlight can reach them. Corals depend on the zooxanthellae (algae) that grow inside of them for oxygen and other things, and since this algae needs sunlight to survive, corals also need sunlight to survive. Corals rarely develop in water deeper than 165 feet (50 meters).
Clear water: Corals need clear water that lets sunlight through to survive; they don't thrive well when the water is opaque. Sediment and plankton can cloud water, which decreases the amount of sunlight that reaches the zooxanthellae.
Warm water temperature: Reef-building corals require warm water conditions to survive. Different corals living in different regions can withstand various temperature fluctuations. However, corals generally live in water temperatures of 68–90° F or 20–32° C.
Clean water: Corals are sensitive to pollution and sediments. Sediments can settle on coral, blocking out sunlight and smothering coral polyps. Pollution from sewage and fertilizers increase nutrient levels in the water, harming corals. When there are too many nutrients in the water, the ecological balance of the coral community is altered.
Saltwater: Corals need saltwater to survive and require a certain balance in the ratio of salt to water. This is why corals don't live in areas where rivers drain fresh water into the ocean.
Scientists generally divide coral reefs into four classes: fringing reefs, barrier reefs, atolls, and patch reefs.
Fringing reefs grow near the coastline around islands and continents. They are separated from the shore by narrow, shallow lagoons. Fringing reefs are the most common type of reef that we see.
Barrier reefs also parallel the coastline but are separated by deeper, wider lagoons. At their shallowest point they can reach the water's surface forming a "barrier" to navigation. The Great Barrier Reef in Australia is the largest and most famous barrier reef in the world.
Atolls are rings of coral that create protected lagoons and are usually located in the middle of the sea. Atolls usually form when islands surrounded by fringing reefs sink into the sea or the sea level rises around them (these islands are often the tops of underwater volcanoes). The fringing reefs continue to grow and eventually form circles with lagoons inside.
Patch reefs are small, isolated reefs that grow up from the open bottom of the island platform or continental shelf. They usually occur between fringing reefs and barrier reefs. They vary greatly in size, and they rarely reach the surface of the water. | <urn:uuid:627a2ce7-163a-4b04-96ad-06c17f870e52> | 3.875 | 2,713 | Knowledge Article | Science & Tech. | 49.244155 |
DNA sequencing is the determination of the precise sequence of nucleotides in a sample of DNA.
The most popular method for doing this is called the dideoxy method.DNA is synthesized from four deoxynucleotide triphosphates. The top formula shows one of them: deoxythymidine triphosphate (dTTP). Each new nucleotide is added to the 3' OH group of the last nucleotide added.
|Link to discussion of DNA synthesis.|
|The bottom formula shows the structure of azidothymidine (AZT), a drug used to treat AIDS. AZT (which is also called zidovudine) is taken up by cells where it is converted into the triphosphate. The reverse transcriptase of the human immunodeficiency virus (HIV) prefers AZT triphosphate to the normal nucleotide (dTTP). Because AZT has no 3' -OH group, DNA synthesis by reverse transcriptase halts when AZT triphosphate is incorporated in the growing DNA strand. Fortunately, the DNA polymerases of the host cell prefer dTTP, so side effects from the drug are not so severe as might have been predicted.|
Because all four normal nucleotides are present, chain elongation proceeds normally until, by chance, DNA polymerase inserts a dideoxy nucleotide (shown as colored letters) instead of the normal deoxynucleotide (shown as vertical lines). If the ratio of normal nucleotide to the dideoxy versions is high enough, some DNA strands will succeed in adding several hundred nucleotides before insertion of the dideoxy version halts the process.At the end of the incubation period, the fragments are separated by length from longest to shortest. The resolution is so good that a difference of one nucleotide is enough to separate that strand from the next shorter and next longer strand. Each of the four dideoxynucleotides fluoresces a different color when illuminated by a laser beam and an automatic scanner provides a printout of the sequence.
|If you wish to see a representative example of a DNA sequence (455 nucleotides of the lysU gene of E. coli) which was generated by an automated sequencing device, LINK HERE. (The file size is 172K.) (The image is courtesy of Pharmacia Biotech Inc., Piscataway, NJ.)| | <urn:uuid:328f3f9d-47de-4845-b830-f0819ee0488c> | 4.09375 | 501 | Knowledge Article | Science & Tech. | 35.699737 |
Phase Specimens and Amplitude Specimens
Specimens that do not possess much color but a different refractive index that the surrounding mounting medium can be referred to as phase specimens as they cause a phase-shift in of the light. The unaided human eye is not capable of detecting this phase shift. This phase shift is then converted into a brightness difference by the optics of the phase-contrast microscope. Bacteria are a good example here. They are nearly completely transparent but nevertheless appear darker or brighter (depending on the optics) than the background.
Amplitude specimens possess a color and are able to decrease the brightness of the passing light all on their own. These specimens are best observed using bright-field microscopy. Pigmented structures (such as chloroplasts) and specimens that are selectively stained are examples.
Many specimens are a combination of these two. Here the choice of the right kind of microscope is important in order to see that what one wants to see. Phase contrast microscopes will optically darken certain structures to the extent that it is not possible to see the natural color of the structure. In this case it is probably better to use bright field microscopy. Stained bacteria, for example, should be observed in bright field.
Advantages and disadvantages of bright field and phase contrast microscopy
Advantages of bright-field microscopy:
- The optics do not change the color of the observed structures. Sometimes stains are used to make certain structures visible. The optics of a bright field microscope do not change these colors.
- Bright-field optics is generally cheaper than phase contrast optics
- Bright-field microscopy requires fewer adjustments before one is able to observe the specimens.
Advantages of phase contrast microscopy:
- It is possible to visualize certain structures that are otherwise invisible. This includes certain cell organelles which can not be seen well in bright field.
- Sometimes the phase contrast image subjectively looks better than a bright field image due to the details visible.
To see pictures of phase contrast specimens, read this post: Bacteria in phase contrast | <urn:uuid:41e09510-473f-4e0a-bca2-6ac39ffc20a6> | 3.6875 | 430 | Knowledge Article | Science & Tech. | 33.5467 |
| The St. Lawrence Island Shrew is named for the only geographic location in which it has been found, St. Lawrence Island in the Bering Sea, between Alaska and Siberia. It is the only shrew on the island, and it is common there. It has a brown back and paler sides, and is closely related to the Cinereus Shrew and the Pribilof Island Shrew. Details of the biology of the St. Lawrence Island shrew are not known. It and the Pribilof Island Shrew probably evolved from a common ancestor after the last Ice Age. During the Ice Age all the islands in the Bering Sea were probably connected. As the ice melted and the sea level rose, some became separate islands, and over millions of years, the shrews living on them evolved into separate species.
Also known as:
St. Lawrence Shrew
Hall, E. R., and R. M. Gilmore, 1932. New mammals from St. Lawrence Island, Bering Sea, Alaska, p.392. University of California Publications in Zoology, 38:391-404.
Mammal Species of the World | <urn:uuid:00154d1a-867b-4d73-8c7d-bb891482f702> | 3.265625 | 236 | Knowledge Article | Science & Tech. | 66.509585 |
Impact on Animals
Would a dramatic change in the Earth's magnetic field affect creatures that rely on it during migration?
As this time line shows, our planet's magnetic shield has reversed its direction hundreds of times.
Gallery of Auroras
Auroras like those displayed here would be visible every night of the year during a magnetic field reversal.
See a Reversal
Watch a simulated flip of the Earth's magnetic field, from the first signs of instability to the final reversal.
TV Program Description
NOVA News Minute
Watch a news clip related to NOVA's "Magnetic Storm" program.
Links & Books
Buy the Video |
Watch a Preview
Don't miss upcoming NOVA broadcasts and companion Web sites—subscribe to our | <urn:uuid:194a3f7e-b0a6-4574-95d4-d2b8fc35f706> | 3.046875 | 156 | Truncated | Science & Tech. | 44.295 |
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Introduction to magnetism, covering the magnetosphere, magnetic field lines and electromagnetic waves.
A good revision guide to magnetism and electromagnetism aimed at UK GCSE level. Simply explained and well presented with animated diagrams.
Almost every aspect of magnetism dealt with comprehensively with illustrations, many links and a great number of straightforward magnetism experiments.
An explanation of magnetism from howstuffworks.com: How you make magnets, why they stick and some common myths about magnetism.
A site linking to many other sites, each dealing with an aspect of Electricity and Magnetism
Animated tutorial on basic electricity and magnetism including static charge, moving charge, voltage, resistance, and current. Requires flash.
A catalogue of electricity and magnetism animations.
Introduction to magnetic fields and forces.
Instructions on how to make high magnetic fields without the need for large currents
A series of ideas and magnetic models for teachers to make, including a levitating magnet.
Showing 1 - 10 of 35 | <urn:uuid:3019bcb7-d2a2-49ab-9775-13d4b75109ad> | 3.265625 | 303 | Content Listing | Science & Tech. | 38.62397 |
Hylarana fonensis (Rödel and Bangoura, 2004)
White-lipped Frog (English)
This species is known so far from two localities in the Simandou Range of south-eastern Guinea: the northeastern flank of the Pic de Fon Forest and the Parc National de Haute Niger (Rödel and Bangoura, 2004).
This species is named for the Pic de Fon forest reserve.
H. fonensis is a large, slender frog with pointed a snout, and it has a very distinct, concave loreal region. H. fonensis’ skin is very rough due to numerous tubercles on almost all dorsal surfaces with a uniform beige-brown back. This species most distinct feature is it’s comparatively broad dorsolateral ridges that stretch from posterior corner of the eye to the groin. Males have huge protruding glands on the upper arms, extensive webbing on the feet andtoe tips that are long, slender, and pointed (Rodel and Bangoura, 2004).
The holotype measures 59.3 mm in snout-vent length, while the paratypes range from 59.8-63.8 mm.
The holotype, an adult male in breeding condition, has a head width of 18.4 mm, approximately one third of SVL, and head length of 21.7 mm. The eye diameter is 6.8 mm, slightly smaller than the diameter of the tympanum (7.3 mm). The interorbital distance (6.5 mm) nearly equals the eye diameter; the eye-snout distance is 10.1 mm. The nostril is closer to the snout (3.9 mm) than to eye (5.6 mm). The canthus rostralis distinct and sharply protruding, and the loreal region is concave. A distinct yellowish lip extends posterior to the angle of mouth. The back and head are a uniform beige-brown, densely covered with round tubercles. The surface of the skin is shagreened with larger tubercles present on the back and upper part of flanks and smaller tubercles on the head, eyelids and dorsal part of the yellowish lip, border of the tympanum and loreal region, the dorsolateral ridges, the upper parts of hind legs and upper arm. Lower parts of flanks and extremities are regularly and densely covered with much smaller spinules. The dorsolateral ridges are distinct and protruding, stretching to the groin. The flanks are dark brown to black on the dorsal half, and the ventral half are marbled in dark grey and yellowish-olive. The arms are nearly a uniform dark olive. There are black glands on anterior part of upper arms (6.5 mm long). The long and thin fingers have very small discs and are without webbing. The finger formula is as follows: 1>2<3>4. Large nuptial pads are present on the external sides of thumbs, almost same colour as rest of the finger. The hind legs are slightly darker than back with indistinct black bars on thighs (5-6) and tibia (2). The femur (29.7 mm) is half of the SVL; the tibia (32.1 mm) is slightly longer than half SVL. The foot, including the longest toe measures 49.1 mm. There is a distinct inner and outer metatarsal tubercle; the outer is much larger and elongated, and the inner one is round. The toes are long and slender with slightly pointed tips that are not enlarged to discs. The webbing formula is as follows: 1 (0), 2 i/e (1-0), 3 i/e (1-0), 4 i/e (1.75), 5 (0). The outer part of toe 5 has a skin fringe covered with spinules. Webbing is dark grey. The ventral surface appears smooth but bears minute spinules; the belly and lower parts of thighs are granular. The throat is dirty dark brown, and there are no traces of vocal sacs. The breast is yellowish brown and belly is beige. Lower parts of the hind legs are yellowish-brown, and the sides have small brown spots.
H. fonensis has a similar appearance to A. albolabris and A. asperrima; however, A. albolabris and A. asperrima males have much darker backs than H. fonensis. In A. albolabris the backs are nearly always coloured with irregular black spots, while in A. asperrima these spots are often present but occasionally might be absent (Rodel and Bangoura, 2004).
Habitat and Ecology
H. fonensis occurs in symparty with A. albolabris. H. fonensis has been found in northeastern flank of the Pic de Fon and the Parc National de Haute Niger forest habitat. These parks consist mainly of Guinea savannah, but also include some forest remnants that harbour tropical forest species. It has been suggested that this species might be widespread in the Guinean transition zone between rainforest and humid Guinea savannah (Rodel and Bangoura, 2004).
- Amnirana fonensis Rödel and Bangoura, 2004 (synonym)
- Hydrophylax fonensis — Frost, 2006 (synonym)
- Hylarana fonensis — Che, Pang, Zhao, Wu, Zhao, and Zhang, 2007 (synonym) | <urn:uuid:48a88f19-d80e-427e-a393-9a588f9741ee> | 2.796875 | 1,172 | Knowledge Article | Science & Tech. | 69.205613 |
- Use “Pascal” notation for SQL server Objects Like Tables, Views, Stored Procedures. Also tables and views should have ending “s”.
- If you have big subset of table group than it makes sense to give prefix for this table group. Prefix should be separated by _.
- Use following naming convention for Stored Procedure. sp<Application Name>_[<group name >_]<action type><table name or logical instance> Where action is: Get, Delete, Update, Write, Archive, Insert… i.e. verb
- Use following Naming pattern for triggers: TR_<TableName>_<action><description>
- Indexes : IX_<tablename>_<columns separated by_>
- Primary Key : PK_<tablename>
- Foreign Key : FK_<tablename_1>_<tablename_2>
- Default: DF_<table name>_<column name>
DF_ UserDetails _UserName
- Normalize Database structure based on 3rd Normalization Form. Normalization is the process of designing a data model to efficiently store data in a database. (Read More Here)
- Avoid use of SELECT * in SQL queries. Instead practice writing required column names after SELECT statement.
SELECT Username, Password
- Use SET NOCOUNT ON at the beginning of SQL Batches, Stored Procedures and Triggers. This improves the performance of Stored Procedure. (Read More Here)
- Properly format SQL queries using indents.
Example: Wrong Format
SELECT Username, Password FROM UserDetails ud INNER JOIN Employee e ON e.EmpID = ud.UserID
Example: Correct Format
SELECT Username, Password
FROM UserDetails ud
INNER JOIN Employee e ON e.EmpID = ud.UserID
- Practice writing Upper Case for all SQL keywords.
SELECT, UPDATE, INSERT, WHERE, INNER JOIN, AND, OR, LIKE.
- It is common practice to use Primary Key as IDENTITY column but it is not necessary. PK of your table should be selected very carefully.
- If “One Table” references “Another Table” than the column name used in reference should use the following rule :
Column of Another Table : <OneTableName> ID
If User table references Employee table than the column name used in reference should be UserID where User is table name and ID primary column of User table and UserID is reference column of Employee table.
- Columns with Default value constraint should not allow NULLs.
- Practice using PRIMARY key in WHERE condition of UPDATE or DELETE statements as this will avoid error possibilities.
- Always create stored procedure in same database where its relevant table exists otherwise it will reduce network performance.
- Avoid server-side Cursors as much as possible, instead use SELECT statement. If you need to use cursor then replace it next suggestion.
- Instead of using LOOP to insert data from Table B to Table A, try to use SELECT statement with INSERT statement. (Read More Here)
INSERT INTO TABLE A (column1, column2)
SELECT column1, column2
FROM TABLE B
- Avoid using spaces within the name of database objects; this may create issues with front-end data access tools and applications. If you need spaces in your database object name then will accessing it surround the database object name with square brackets.
- Do not use reserved words for naming database objects, as that can lead to some unpredictable situations. (Read More Here)
- Practice writing comments in stored procedures, triggers and SQL batches, whenever something is not very obvious, as it won’t impact the performance.
- Do not use wild card characters at the beginning of word while search using LIKE keyword as it results in Index scan.
- Indent code for better readability. (Example)
- While using JOINs in your SQL query always prefix column name with the table name. (Example). If additionally require then prefix Table name with ServerName, DatabaseName, DatabaseOwner. (Example)
- Default constraint must be defined at the column level. All other constraints must be defined at the table level. (Read More Here)
- Avoid using rules of database objects instead use constraints.
- Do not use the RECOMPILE option for Stored Procedure unless there is specific requirements.
- Practice to put the DECLARE statements at the starting of the code in the stored procedure for better readability (Example)
- Put the SET statements in beginning (after DECLARE) before executing code in the stored procedure. (Example)
Reference : Pinal Dave (http://blog.SQLAuthority.com) | <urn:uuid:da051586-5540-4d88-a432-7f529011f4f2> | 2.953125 | 1,008 | Documentation | Software Dev. | 33.016413 |
First, don't be worried about learning another language or syntax because DocBook is fairly straight forward and most contributors simply cut-n-paste existing files, modify the content, then commit. It's just plain text.
What is DocBook? The following is a quote from » DocBook: The Definitive Guide:
DocBook is a very popular set of tags for describing books, articles, and other prose documents, particularly technical documentation. DocBook is defined using the native DTD syntax of SGML and XML. Like HTML, DocBook is an example of a markup language defined in SGML/XML.
Simply this means that writing a DocBook file is no more than writing a text file and using a few simple "tags" when needed. Like HTML, an opening tag is a < bracket followed by the tag's name, optionally some arguments, and then the > bracket (e.g. <para> for paragraphs). A closing tag is a < bracket followed by a / sign, the tag name, then the closing > bracket (e.g. </para> for paragraphs). For example uses, have a look at an existing file within the PHP manual sources, or use the documentation skeletons.
As described above, DocBook uses a similar structure to HTML with the main difference being DocBook uses tags to define the meaning whereas HTML often times defines the look and layout. So the idea behind DocBook is to define as much as possible about the information so that build and rendering software will intelligently output the text into many formats.
We use DocBook because it makes it easy to generate several formats of our documents (HTML, PDF, Microsoft HTML Help (CHM), RTF, etc.), and DocBook is the standard way for storing structured technical information.
Note: DocBook version upgrade history
On January 2, 2007 we upgraded from DocBook 4.1.2 to 4.5 and then to DocBook 5 at around June 20, 2007. These upgrades included changes to most files in the phpdoc CVS repository. | <urn:uuid:99a766fa-841b-4a71-8780-0d84ad4391c5> | 2.84375 | 420 | Knowledge Article | Software Dev. | 57.20371 |
In meteorology, lee waves are atmospheric standing waves. The most common form is mountain waves, which are atmospheric internal gravity waves. These were discovered in 1933 by two German glider pilots, Hans Deutschmann and Wolf Hirth, above the Krkonoše. They are periodic changes of atmospheric pressure, temperature and orthometric height in a current of air caused by vertical displacement, for example orographic lift when the wind blows over a mountain or mountain range. They can also be caused by the surface wind blowing over an escarpment or plateau, or even by upper winds deflected over a thermal updraft or cloud street.
The vertical motion forces periodic changes in speed and direction of the air within this air current. They always occur in groups on the lee side of the terrain that triggers them. Usually a turbulent vortex, with its axis of rotation parallel to the mountain range, is generated around the first trough; this is called a rotor. The strongest lee waves are produced when the lapse rate shows a stable layer above the obstruction, with an unstable layer above and below.
Both lee waves and the rotor may be indicated by specific wave cloud formations if there is sufficient moisture in the atmosphere, and sufficient vertical displacement to cool the air to the dew point. Waves may also form in dry air without cloud markers. Wave clouds do not move downwind as clouds usually do, but remain fixed in position relative to the obstruction that forms them.
- Around the crest of the wave, adiabatic expansion cooling can form a cloud in shape of a lens (lenticularis). Multiple lenticular clouds can be stacked on top of each other if there are alternating layers of relatively dry and moist air aloft.
- The rotor may generate cumulus or cumulus fractus in its upwelling portion, also known as a "roll cloud". The rotor cloud looks like a line of cumulus. It forms on the lee side and parallel to the ridge line. Its base is near the height of the mountain peak, though the top can extend well above the peak and can merge with the lenticular clouds above. Rotor clouds have ragged leeward edges and are dangerously turbulent.
- A foehn wall cloud may exist at the lee side of the mountains, however this is not a reliable indication of the presence of lee waves.
- A pileus or cap cloud, similar to a lenticular cloud, may form above the mountain or cumulus cloud generating the wave.
- Adiabatic compression heating in the trough of each wave oscillation may also evaporate cumulus or stratus clouds in the airmass, creating a "wave window" or "Foehn gap".
Lee waves provide a possibility for gliders to gain altitude or fly long distances when soaring. World record wave flight performances for speed, distance or altitude have been made in the lee of the Sierra Nevada, Alps, Patagonic Andes, and Southern Alps mountain ranges. The Perlan Project is working to demonstrate the viability of climbing above the tropopause in an unpowered glider using lee waves, making the transition into stratospheric standing waves. They did this for the first time on August 30, 2006 in Argentina, climbing to an altitude of 50,671 ft (15,447 m). The Mountain Wave Project of the Organisation Scientifique et Technique du Vol à Voile focusses on analysis and classification of lee waves and associated rotors.
The conditions favoring strong lee waves suitable for soaring are:
- A gradual increase in windspeed with altitude
- Wind direction within 30° of perpendicular to the mountain ridgeline
- Strong low-altitude winds in a stable atmosphere
- Ridgetop winds of at least 20 knots
The rotor turbulence may be harmful for other small aircraft such as balloons, hang gliders and para gliders. It can even be a hazard for large aircraft; the phenomenon is believed responsible for many aviation accidents and incidents including the in-flight break up of BOAC Flight 911, a Boeing 707, near Mt. Fuji, Japan in 1966, and the in-flight separation of an engine on an Evergreen International Airlines Boeing 747 cargo jet near Anchorage, Alaska in 1993.
The rising air of the wave, which allows gliders to climb to great heights, can also result in high altitude upset in jet aircraft trying to maintain level cruising flight in lee waves. Rising, descending or turbulent air in or above the lee waves can cause overspeed or stall, resulting in mach tuck and loss of control, especially when the aircraft is operated near the "coffin corner".
Other varieties of atmospheric waves
There are a variety of distinctive types of waves which form under different atmospheric conditions.
- Wind shear can also create waves. This occurs when an atmospheric inversion separates two layers with a marked difference in wind direction. If the wind encounters distortions in the inversion layer caused by thermals coming up from below, it will create significant shear waves in the lee of the distortions that can be used for soaring.
- Hydraulic jump induced waves are a type of wave that forms when there exists a lower layer of air which is dense, yet thin relative to the size of the mountain. After flowing over the mountain, a type of shock wave forms at the trough of the flow, and a sharp vertical discontinuity called the hydraulic jump forms which can be several times higher than the mountain. The hydraulic jump is similar to a rotor in that it is very turbulent, yet it is not as spatially localized as a rotor. The hydraulic jump itself acts as an obstruction for the stable layer of air moving above it, thereby triggering wave. Hydraulic jumps can distinguished by their towering roll clouds, and have been observed on the Sierra Nevada range as well as mountain ranges in southern California.
- Kelvin–Helmholtz instability can occur when velocity shear is present within a continuous fluid or when there is sufficient velocity difference across the interface between two fluids.
- Rossby waves (or planetary waves) are large-scale motions in the atmosphere whose restoring force is the variation in Coriolis effect with latitude.
See also
- Tokgozlu, A; Rasulov, M.; Aslan, Z. (January 2005). "Modeling and Classification of Mountain Waves". Technical Soaring 29 (1): p. 22. ISSN 0744-8996.
- "Article about wave lift". Retrieved 2006-09-28.
- Pagen, Dennis (1992). Understanding the Sky. City: Sport Aviation Pubns. pp. 169–175. ISBN 0-936310-10-3. "This is the ideal case, for an unstable layer below and above the stable layer create what can be described as a springboard for the stable layer to bounce on once the mountain begins the oscillation."
- FAI gliding records
- Perlan Project
- OSTIV-Mountain Wave Project
- - accessed 2009-11-03
- Lindemann, C; Heise,R.; Herold,W-D. (July 2008). "Leewaves in the Andes Region, Mountain Wave Project (MWP) of OSTIV". Technical Soaring 32 (3): p. 93. ISSN 0744-8996.
- NTSB Accident brief 20001211X11963
- Eckey, Bernard (2007). Advanced Soaring Made Easy. Eqip Verbung & Verlag GmbH. ISBN 3-9808838-2-5.
- Observations of Mountain-Induced Rotors and Related Hypotheses: a Review by Joachim Kuettner and Rolf F. Hertenstein
Further reading
- Grimshaw, R., (2002). Environmental Stratified Flows. Boston: Kluwer Academic Publishers.
- Jacobson, M., (1999). Fundamentals of Atmospheric Modeling. Cambridge: Cambridge University Press.
- Nappo, C., (2002). An Introduction to Atmospheric Gravity Waves. Boston: Academic Press.
- Pielke, R., (2002). Mesoscale Meteorological Modeling. Boston: Academic Press.
- Turner, B., (1979). Buoyancy Effects in Fluids. Cambridge: Cambridge University Press.
- Whiteman, C., (2000). Mountain Meteorology. Oxford Oxfordshire: Oxford University Press.
- http://www.inglaner.com/meteorologia_onda.htm chronological collection of meteorological data, satpics and cloud images of mountain waves in Bariloche, Argentina. In Spanish
- http://www.mountain-wave-project.com official website
|Wikimedia Commons has media related to: Lee waves| | <urn:uuid:f621344b-0119-4b91-be87-70ece0d1dbb5> | 4.625 | 1,815 | Knowledge Article | Science & Tech. | 50.157931 |
Although Drupal itself provides a central CVS repository for the Drupal core code and contributed projects management, it is well known that people use other tools for their own purposes. There were several ocassions, when private Subversion repositories were used to develop new core functionality (such as Forms API or the multilanguage changes coming up in Drupal 6). Some people also like using BZR to manage their own changes easily.
A very detailed introduction hit my web browser today though, explaining how can you manage and even upgrade your Drupal installation (including contributed modules) using Git, even keeping local modifications.
It is well-known that Git is a distributed version control system that was created by Linus Torvalds to help with the development of Linux kernel. Distributed version control systems, such as Git, are contrasted with centralized version control systems, such as Subversion. Linux kernel development is characterized by hundreds of contributors and several dozens of development sub-projects, all spread out across the Internet. The repositories contain thousands of files and many thousands of revisions.
We show that Git is actually capable of handling much more lightweight problems, without any unnecessary overhead, with only half a dozen of commands to remember.
It is good to see people experimenting with stuff, not because I see Git would be a good fit for the community at large, due to the lack of good and easy tools around it, but because the community gets knowledge on how different tools compare, to use them more effectively. Especially now, when this year's Google Summer of Code sponsors Jakob Petsovits working on making the version control infrastructure system agnostic. | <urn:uuid:8f23aaf6-84f8-4d49-9de8-8a84601c2886> | 2.6875 | 329 | Personal Blog | Software Dev. | 25.180727 |
The Naming of Life: Marine Taxonomy
Taxonomy and Scientific Classification
Today's classification system was developed by Carl Linnaeus as an important tool for use in the study of biology and for use in the protection of biodiversity. Without very specific classification information and a naming system to identify species' relationships, scientists would be limited in attempts to accurately describe the relationships among species. Understanding these relationships helps predict how ecosystems can be altered by human or natural factors.
Preserving biodiversity is facilitated by taxonomy. Species data can be better analyzed to determine the number of different species in a community and to determine how they might be affected by environmental stresses. Family, or phylogenetic, trees for species help predict environmental impacts on individual species and their relatives.
Linnaean Taxonomic System
Carl Linnaeus was born in 1707 and died in 1778. He created the entire category of systematic zoology and botany as well as a classification scheme—still used by biologists today. His masterpiece was the Systema Naturae. Linnaeus invented the classification system to establish consensus on plant and animal names and to understand complex evolutionary relationships between organisms. The Linnaean taxonomic system begins with the most general category of Domain or Kingdom and becomes increasingly specific until it ends with a specific genus and species name derived from Greek and/or Latin roots.
Based on concepts introduced by his scientist predecessors, Linnaeus developed his system so that each species had a Latin double name. The first name is the genus and the second is the species name. This two-word naming system is called binomial nomenclature. The name is always italicized with the genus capitalized and the species in lowercase letters.
There are 8 general taxonomic groupings, starting with the most general and ending at the most specific. The groupings are: Domain, Kingdom, Phylum (or Division for plants), Class, Order, Family, Genus and Species. In some cases, subgroups are included for accuracy such as subclass, superorder, suborder, and infraorder to name a few. The naming of life can become incredibly complex. When the species grouping is not specific enough, subspecies categories are added. Domains are also sometimes added above the kingdom level, if a high level of generality is needed. On the other hand, if more detail is needed, tribes can be added between family and genus categories and sections or series can be added between genus and species categories.
The five Kingdoms are Monera, Protista, Fungi, Plantae, and Animalia. Under each Kingdom, Phylums are listed and under each Phylum there are many Classes (and so on). With over 10,000 species, Kingdom Monera consists of unicellular bacteria and cyanobacteria. Kingdom Monera is also the only kingdom made up of prokaryotic cells or cells without nuclei and organelles not surrounded by a membrane. The other four kingdoms consist of eukaryotes or cells with nuclei and organelles bound by a membrane. Kingdom Protista consists of 250,000 species of single celled protozoans and macroscopic algae. There are 100,000 species in Kingdom Fungi and they are usually either heterotrophic haploid or dikaryotic cells. There are 250,000 species in Kingdom Plantae and they all are autotrophic forms of plants that keep the embryo on the female part of the plant. With over 1,000,000 species, Kingdom Animalia consists of multicellular animals that lack a cell wall (plant cells have a rigid cell wall) and form a blastula early in life.
To demonstrate how an organism is classified, let us use the classification of the commonly named “the blue whale”. The information provided by this common name is not enough to put the whale into any evolutionary relationship with other organisms. Scientists however, call the blue whale by its scientific name—Balaenoptera musculus. An example of how scientists would classify and name a blue whale is as follows:
- All whales are animals because they have more than one cell, eat food and originate from a fertilized egg—so they first are categorized into the most general category—Kingdom Animalia.
- Whales are placed into the Phylum Chordata (the category below Kingdom) because they have a spinal cord and gill pouches. In fact, humans are also in Phylum Chordata.
- Because they are warm-blooded, produce milk for their young and have a heart with four chambers, whales are in the Class Mammalia.
- At the “Order” category, whales begin to be distinguished from humans and other land mammals. Whales are classified as cetaceans because they live in the water all year round. The suborder is Mysticeti due to the baleen plates in the mouths of whales, helping them to filter in food.
- Blue whales have folds around their throat that expand to take in large volumes of water when feeding. Because not all whales have this characteristic, blue whales are placed into the Family “Balaenidae”.
- Within the Family is another group of species more immediately related to each other. The “Genus” for blue whales is Balaenoptera.
- The definition of a species includes many factors, especially the requirement that individuals must be able to successfully breed with each other. The species name for blue whales is musculus, meaning that in addition to other common traits, whales of the species musculus are able to breed with each other and provide viable (living) offspring. The final scientific name is Balaenoptera musculus with the genus capitalized and the species name in lower case letters and both italicized.
A phylogenetic tree is similar to a family tree except that it shows evolutionary relationships between species rather than relationships between individuals. Phylogenetic trees contain a lot of information and can reveal how far back in time a species began, along with the most recent common ancestors between species. DNA analysis is used to provide information to support the construction of phylogenetic trees. Every “node” on a phylogenetic tree is referred to as a taxonomic unit and represents a common ancestor. Scientists can zoom in on a particular part of a phylogenetic tree, omitting the “root” of the tree in order to focus on a particular segment. A rooted tree is simply the bigger, zoomed-out picture.
The Science of Classification
Taxonomists are responsible for the discovery of new species, analysis and compilation of collected data, and the release of new information to the public, including other scientists. The research requires valuable identification skills, the ability to categorize and recognize species relationships, an understanding of ecosystems and ecology, knowledge of species distribution, and the ability to determine keystone species. They must also be able to submit data and explain the synthesis clearly for people in communities.
Scientists have relied on Linnaeus's system of classification for the last two hundred years. After Darwin's time, it became clear that another dimension could be added to the phylogenetic tree so taxonomic groups would represent the principle of common descent. Related taxa (or categories) were moved to occupy what can be visualized as a bunch of leaves on a particular branch. These relatively new and helpful groupings are referred to as monophyletic groups.
A new development in taxonomy is the revelation that using a cladogram can make it easier to view evolutionary relationships. A cladogram is basically an isolated branch of the phylogenetic tree turned sideways with each line indicating the amount of time between the ancestor and the species. Each “clade” represents a monophyletic group. Because it is only a short branch of the entire tree it is not usually necessary to refer to the more general Linnaean form of classification.
Taxonomy is becoming more important as scientists struggle to identify species in order to understand the subtle relationships and complex reactions of ecosystems threatened by human pursuits. The study of taxonomy provides a solid foundation for the research needed for the conservation of marine life.
As of March 22, 2012:
212,906 accepted species; of which 192,888 are checked (91%)
361,601 species names including synonyms
447,277 taxa (infraspecies to kingdoms)
"The aim of a World Register of Marine Species (WoRMS) is to provide an authoritative and comprehensive list of names of marine organisms, including information on synonymy. While highest priority goes to valid names, other names in use are included so that this register can serve as a guide to interpret taxonomic literature.
The content of WoRMS is controlled by taxonomic experts, not by database managers. WoRMS has an editorial management system where each taxonomic group is represented by an expert who has the authority over the content, and is responsible to control the quality of the information. Each of these main taxonomic editors can invite several specialists of smaller groups within their area of responsibility.
This register of marine species grew from the European Register of Marine Species (ERMS), and its combination with several other species registers maintained at the Flanders Marine Institute (VLIZ). Rather than building separate registers for all projects, and to make sure taxonomy used in these different projects is consistent, we developed a consolidated database called ‘Aphia'. A list of marine species registers included in Aphia is available below. MarineSpecies.org is the web interface to this database. The WoRMS is an idea that is being developed, and will combine information from Aphia with other authoritative marine species lists which are maintained by others (e.g. AlgaeBase, FishBase, Hexacorallia, NeMys)."
Feedback & Citation
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Help us continue to share the wonders of the ocean with the world, raise awareness of marine conservation issues and their solutions, and support marine conservation scientists and students involved in the marine life sciences. Join the MarineBio Conservation Society or make a donation today. We would like to sincerely thank all of our members, donors, and sponsors, we simply could not have achieved what we have without you and we look forward to doing even more. | <urn:uuid:37472eb6-c180-408f-b4cc-f411083b3938> | 3.546875 | 2,128 | Knowledge Article | Science & Tech. | 27.317939 |
Chapter 8. Microscale Gas Chemistry:
Hydrogen sulfide is a colorless gas with an offensive stench and is said to smell like rotten eggs. The gas can be detected at a level of 2 parts per billion. To put this into perspective, 1 mL of the gas distributed evenly in a 100-seat lecture hall is about 20 ppb.
B. Physical Properties
Hydrogen sulfide has a structure similar to that of water.
This is where the similarity ends, however. Sulfur is not nearly as electronegative as oxygen so that hydrogen sulfide is not nearly as polar as water. Because of this, comparatively weak intermolecular forces exist for H2S and the melting and boiling points are much lower than they are in water. Hydrogen sulfide and water boil at -60.7 oC and +100.0 oC , respectively.
Hydrogen Sulfide, H2S Atomic mass: 34.08 g/mol melting point -85.5 oC boiling point -60.7 oC
Hydrogen sulfide has been known since early times. The chemistry of H2S has been studied since the 1600s. In the 19th century, Petrus Johannes Kipp, a Dutch pharmacist invented a convenient device for the generation of a variety of gases in which a liquid and solid were the reagents. The ‘Kipp generator’ was especially useful for the generation of hydrogen sulfide and hydrogen. The device shown at right was one of the earliest and would not be familiar to chemists who remember using the Kipp generator in chemistry lab. More information on the use of this device is given in the history portion of our gas chemistry web site.
D. Natural Abundance
Natural gas contains up to several percent H2S(g) and as such are called sour gas wells from their offensive stench. Volcanoes also discharge hydrogen sulfide. Anaerobic decay aided by bacteria produces hydrogen sulfide, which in turn, produces sulfur. This process accounts for much of the native sulfur found in nature.
E. Industrial Production
Commercially hydrogen sulfide is obtained from "sour gas" natural gas wells.
F. Industrial Uses
Hydrogen sulfide has few important commercial uses. However, it is used to produce sulfur which is one of the most commercially important elements. About 25% of all sulfur is obtained from natural gas and crude oil by conversion of 1/3 of the H2S to SO2 and then followed by the reaction between H2S and SO2:
2 H2S(g) + 3 O2(g) ---> 2 SO2(g) + 2 H2O(g)
16 H2S(g) + 8 SO2(g) ---> 3 S8(g) + 16 H2O(g)
Hydrogen sulfide has
been used for well over a century as a method of qualitative analysis of
metal ions. In fact, the Chemistry Building at the University of
Illinois in 1915 had a built-in supply of hydrogen sulfide to the various
labs, i.e., H2S 'on tap'! The gas was stored
in a 500-gallon tank! (Chemical Discovery and Invention in
the Twentieth Century, Sir William Tildon, 1917)
G. Gas Density of H2S
The density of hydrogen sulfide is 1.393 g/L at 25 oC and 1 atm. This is 18% greater than that of air.
H. Gas Solubility of H2S
Hydrogen sulfide dissolves in water to make a solution that is weakly acidic. At 0 oC 437 mL H2S(g) will dissolve in 100 mL H2O, producing a solution that is about 0.2 M. However, the solution process is fairly slow. The solution equilibrium is
Return to Experiments | <urn:uuid:50f01827-0641-471c-9693-f3a1f799f88f> | 3.703125 | 819 | Knowledge Article | Science & Tech. | 63.730746 |
Array Conformability Rules
Operands may be arrays, in which case the operation is performed on each element of the array(s) to produce an array result. Binary operands need not have identical dimensions, but their dimensions must be conformable. Two arrays are conformable if their first dimensions match, their second dimensions match, their third dimensions match, and so on up to the number of dimensions in the array with the fewer dimensions. Two array dimensions match if either of the following conditions is met:
Unit length or missing dimensions are broadcast (by copying the single value) to the length of the corresponding dimension of the other operand. The result of the operation has the number of dimensions of the higher rank operand, and the length of each dimension is the longer of the lengths in the two operands. | <urn:uuid:3befad22-800d-453b-9d16-fd01cd376c83> | 3.015625 | 165 | Documentation | Software Dev. | 35.368826 |
MP-FORTH is a language created to be a quick, useful language that will be fun and pain-free to develop both on small-screen devices (read: iPhone) as well desktops. MP-FORTH stands for Multi-Precision FORTH, because it is essentially a re-creation of FORTH with a heterogeneous stack, designed for interactive use. It is linguistically similar to the way that most HP RPN calculators do programming, with a few tricks up its sleeves.
MP-FORTH, like python, and many other modern languages, uses GMP and MPFR to do unlimited arithmetic. This means that you're limited by available RAM, not 32 or 64 bits. Want to take 2^65 and work on it as an integer? Do it! (This would be “2 65 pow” in MP-FORTH). MP-FORTH is designed for use on small devices, so you can set keys for commonly used functions and words, and program without having to type, type, type. Really, MP-FORTH is also a different way of thinking about programming, as you'll find out. Oh, and if you bought TouchRPN (thanks!), you're stuck with it! Haha!
Getting Started To get started knowing MP-FORTH it's probably best to start with KeyRPN, a desktop front-end for MP-FORTH. It's a lot easier to peek, poke, and mess around with it than it is to try to do it with the keyboard mode in TouchRPN. Download KeyRPN (sorry, MacOSX only so far, port it!).
Okay, now that you have a terminal in front of you, let's add some numbers:
1 1 +
Giving you the result
Surprised? In MP-FORTH the operands usually precede the operator (numbers are operands, addition is an operator). This holds for most of the operators and functions. Let's take the sin of a pi/2:
pi 2 / sin
There is no real syntax to MP-FORTH, everything is simply whitespace delimited. Everything is separated by whitespace. This is logical to a fault. For example, the string creation operator is a double-quote, terminated with a double quote. This means that
” hello ” represents the string “hello”, and
” hello world ” represents “hello world”, but
” hello world” is an unterminated string (the second quote is considered part of the world token) that will eat all of your code, and most likely throw a warning.
FORTH comments are enclosed by parenthesis. ( and ) on their own.
In RPN lingo, and FORTH lingo, the top of the stack (conveniently at the bottom of most displays of the stack…), is X, the second is Y, and the third is Z. So the + operator takes X and Y, adds them, and pushes them in to X.
Words are the FORTH name for functions, they are groupings of code that execute on the stack. There is no notion of arguments, just the stack. So, words take any number of operands, remove them from the stack, and spit out any number of results, back on to the stack. For example, ”+” takes two operands, and returns one (the sum of the two operands). Some functions are more complex, taking 3 or 4 operands. More than that is generally frowned upon, but is not impossible.
To make a word, use ”: <wordname>”. Word names can have any non-whitespace characters in them. Yes, ANY characters, including quotes, brackets, numbers, underscores, etc. They probably shouldn't start with a number. After the word name, just stick MP-FORTH code until the function is done, then terminate with a ”;” on its own (remember, everything is whitespace delimited). Here we make a word that adds 1 to the X register of the stack. The code to do this is simply:
: 1+ ( add 1 to X ) 1 ( push 1 onto the stack ) + ( add X to Y );
or, without comments,
: 1+ 1 + ;
The first comment after the word name is the “documentation” part of the word, which you can access using the “doc” keyword (syntax
doc <wordname>, it is a lookahead operand). All other comments just explain what's going on.
Once you have defined this function, you can call it anytime by simply using its name, 1+. For a more real example, let's take a look at how MP-FORTH does the trigonometric functions:
: sinh dup exp swap neg exp - 2 / ;
: sin i * sinh i / ;
Basically, MPF defines sin in terms of the complex side of the hyperbolic sin, which in turn is defined in terms of exponentials.
MP-FORTH allows you to define both constants and variables. The differences between these two concepts are subtle. Let's start with the simpler idea, constants.
Constants are created with the “constant” word. It is a lookahead word that works like this:
<value> constant <name>
It takes the value in the X register, and stores it in a word, <name>. It works exactly the same (exactly the same), as defining a word with <name> and <value> as the code:
: <name> <value> ;
Variables work slightly differently than constants. They are more useful, but also slightly harder to grasp and use. You create a variable with the word:
This created a variable of name name. If you now use the word name, you'll see something odd on the stack, VAR: (null). This is because there is nothing stored in the variable yet. To store something in it, use the ! word, like so:
<value> <name> !
The ! operator takes the value in Y and stores it to the variable reference in X.
To recall, use the @ operator:
Comparison works using the <, > and = operators. They work as expected:
2 1 < ( results False )
2 1 > ( results True )
2 1 = ( results False )
Conditionals are done using the
then keywords. The
if block takes the X register of the stack, and if it evaluates to True, executes everything up until an
else or a
then clause. If an
else keyword is present, it will skip everything between
then. If X evaluated to False, then it will execute the code between
<truth> if ( executed if <truth> is True ) else ( executed if <truth> is false ) then
<truth> if ( executed if <truth> is True ) then
You can use the
not operator to flip conditionals.
In MP-FORTH, the
repeat keywords control looping. The options are as follows:
begin <block> again ( Executes <block> forever )
begin <block> ( flag ) until ( Executes until the flag is true )
begin <block1> ( flag ) while <block2> repeat ( more later )
The first example,
begin <code> again, loops <code> forever. The second expects a flag at the end of <code>, which it check to see if it should keep looping. So, if the code doesn't leave an extra flag at the end, that will eat up the stack until an error occurs, or until it sees a False value.
begin until will eat up all true values on the stack. The last example basically executes <block1> (which it expects a flag out of), each time it's true, also executing <block2>. Once the flag executes to false, it doesn't execute <block2> and exits out.
As of 1.1.3, MP-FORTH supports multi-base entry and display of integers. Integers can be entered in binary, octal, decimal, or hexadecimal:
0b101011 - bin entry
0o172645 - octal entry
1389750 - dec entry
0x1248AFC - hex entry
The display base can be any base, and is set using the
setibase - sets the display base to the X register. Ex:
2 setibase : sets base to binary
8 setibase : sets base to octal
10 setibase : sets base to decimal
16 setibase : sets base to hex
setibase works with any integer between 2 and 62. | <urn:uuid:1471ab34-d73c-4517-931e-47b340941009> | 2.71875 | 1,852 | Tutorial | Software Dev. | 64.76703 |
Two class days
System.out.println—what's the difference?
printlnbegins a new line after what it prints
printlncan have 0 or 1 parameters
- p. 66: Syntax of variable declaration - What does the syntax diagram mean? - Examples? - Reserved words:
final - Listing 2.5: PianoKeys.java - Assignment (
=): - p. 69: syntax - Listing 2.6: Geometry.java - Java is a strongly typed language: each variable must be declared with a type, and can only store values of compatible types. - Declaring constants with
byte= 8 bits signed
short= 16 bits signed
int= 32 bits signed
long= 64 bits signed
float= 32 bits
double= 64 bits
char= character (Unicode?), 16 bits
boolean= logical, 1 bit (at least conceptually)
Page 72: Syntax of a decimal integer literal
Besides primitive types, Java also has reference types (objects).
-(unary, as signs)
%left to right
-(binary, meaning add and subtract) left to right
9.0 / 5.0instead of
9 / 5?
(long) 21 (double) 21 (float) 2.1
Narrowing conversions (to a smaller data type, may lose information) and widening conversions (to a larger data type, usually do not lose information—when might they ever?)
In the second half of this chapter, the content changes from core Java language features to some of the important Java libraries. In addition, we will begin using classes that somebody has already defined. We will look in greater depth at using classes and objects in Chapter 3, and at writing our own classes in Chapter 4. For the time being, we will write only simple classes with a
main method and nothing else.
abc 123 45.67
Scanner in0 = new Scanner(System.in); // stdin Scanner in1 = new Scanner("1 2 3 4"); // "reads" from the string Scanner in2 = new Scanner("friends.data"); // ditto Scanner in3 = new Scanner(new File("friends.data")); // file input
Some colors have names:
paintmethod is run automatically whenever the applet needs to be displayed.
runmethod; but at this stage, we are just using the method inherited from
paintmethod uses methods of the class
java.awt.Graphics(also called a graphics context). We may think of a Graphics object as something that can be drawn or painted on; a "page" for drawing; a graphical output device.
java.awt.Graphics(see Figure 2.12 on p. 99): | <urn:uuid:ddf393f6-da7b-4556-a299-1be531b79e9d> | 4 | 575 | Documentation | Software Dev. | 67.670083 |
Criteria for Magnetosphere
Why does Earth have a magnetosphere and Venus does not?
As you know magnetospheres are believed to be caused by the currents
produced by the motion of charged particles within the planet.
Electrical currents have an allied magnetic field. While we cannot
be sure why, Venus apparently has very little magnetic field. This
could mean that the chemical substances that are needed to produce
the electrical current, or the physical requirements -such as motion
of a molten core- are not present in Venus. I do not think it is
established why Venus lacks these chemical or physical requirements,
but the data certainly indicates that it must because our probes show
that Venus has orders of magnitudes weaker magnetic fields than that
Greg (Roberto Gregorius)
Click here to return to the Astronomy Archives
Update: June 2012 | <urn:uuid:a249c2df-9e2b-476a-8b53-385683882acd> | 3.90625 | 175 | Audio Transcript | Science & Tech. | 24.947087 |
“Daddy, do you know where this cheese came from?”
I absolutely love this video demonstrating that learning science can be – and should be – fun. Enjoy!
This series is a result of a collaboration between broadcast media (NBC) and scientists (National Science Foundation.)
From Eureka Alert:
National Science Foundation and NBC Learn launch ‘Chemistry Now’ video series
Videos celebrate International Year of Chemistry; available cost-free to students, teachers and fans of chemistry.
In celebration of the International Year of Chemistry, the National Science Foundation (NSF) and NBC Learn, the educational arm of NBC News, have teamed up to launch “Chemistry Now,” a weekly online video series that uncovers and explains the science of common physical objects in our world and the changes they undergo every day. The series also looks at the lives and work of scientists on the frontiers of 21st century chemistry.
“Chemistry Now” consists of 32 learning packages that aim to break down the chemistry behind things such as cheeseburgers and chocolate or soap and plastics. A new topic will be explored each week starting in January and running through May. The series will then resume in the fall of 2011 to keep pace with the academic school year.
Made especially for students and teachers to explore chemistry in and beyond the classroom, the online videos are matched with lesson plans from the National Science Teachers Association (NSTA) and are available cost-free on NBC Learn and NSF’s Science360 websites and on the NSTA blog.
Weekly content includes original video stories that illustrate real-world applications of chemistry; current events and archival news stories related to chemistry; original source documents and images from the Chemical Heritage Foundation; articles from the archives and current publications of Scientific American; and content-coordinated lesson plans for middle and high school students, produced by national curriculum specialists at NSTA.
In addition, the “Chemistry Now” series will profile NSF-sponsored scientists who are hard at work on the next generation of chemistry breakthroughs.
“The International Year of Chemistry is an excellent opportunity to reach out to the public and convey to them the ways in which chemistry is involved in their lives each and every day,” said Matthew Platz, director of NSF’s Division of Chemistry. “We are especially excited about the opportunity that this collaboration gives us to reach out to large numbers of intelligent, energetic young people who might not have imagined that they could be contributing members of this thrilling, dynamic field.”
“Chemistry Now” builds on a number of other collaborations between NBC Learn and NSF in their partnership to advance the understanding of and interest in science, technology, engineering and math. As part of the partnership, NBC Learn oversees all production of the learning packages and contributes original video, as well as historic news coverage, documentary materials and current news broadcasts from NBC News.
“Today’s students thrive on the opportunity to learn from real life examples of what they are studying in school,” said Soraya Gage, executive producer of NBC Learn. “Using unique and engaging storytelling, NBC News can help break down barriers to understanding complicated scientific concepts.”
“‘Chemistry Now’ provides a fantastic opportunity for teachers to supplement classroom learning by using video and lesson plans that are supported with rich, accessible pedagogy,” said Francis Eberle, executive director of NSTA. “We are delighted to contribute to the project, and we know chemistry educators will find the packages useful.”
Previous NSF/NBC Learn partner projects include: “The Science of the Winter Olympics” and “The Science of NFL Football.” | <urn:uuid:1b9c8acf-36f9-43ad-bf80-2834f412b1d1> | 3.21875 | 783 | Comment Section | Science & Tech. | 30.265871 |
Angel’s Madagascar frog (Boehmantis microtympanum)
|Size||Male length: 5.3 cm (2)|
Female length: 7.6 cm (2)
Angel’s Madagascar frog is classified as Endangered (EN) on the IUCN Red List (1).
With marbled greyish or greenish-brown upperparts, the large-bodied Angel’s Madagascar frog (Boehmantis microtympanum) is perfectly camouflaged amongst the mossy, granite rocks of its preferred habitat (2) (3). In contrast to the upperparts, the belly is white, with scattered dark spots becoming denser around the throat. The eyes are large and prominent with a golden or brownish-copper iris speckled with black, while the area around eye and upper lip is marked with whitish spots. The hind feet of Angel’s Madagascar frog are fully webbed, and each digit has a swollen, white tip, enabling this species to cling to moist rocks amongst fast-flowing water. Interestingly, the external ear drum of Angel’s Madagascar frog is much smaller than in most frog species and, in addition, it is not known to produce any vocalisations. This may reflect the fact that hearing is not a particularly important sense for this species, as it lives amidst the continuous, loud noise of rushing water (2).
Angel’s Madagascar frog is endemic to Madagascar, where it is restricted to just five locations within an area of less than 500 square kilometres in the extreme south-east of the island (1).
Angel’s Madagascar frog is found in and around fast-flowing rocky streams within undisturbed, as well as degraded, areas of humid, mature forest (1), between elevations of 50 and 1,120 metres (2).
A relatively sedentary species, Angel’s Madagascar frog spends the majority of the time perched on a rock or boulder nearby or within a turbulent stream. Nevertheless, when disturbed this species demonstrates impressive energy, leaping from its rocky refuge into the water and skittering along the surface before clambering out onto another emergent object (2). Angel’s Madagascar frog generally commences activity at dusk, or occasionally in the late afternoon, continuing throughout the night (2) (3). During this time it hunts for insects, small freshwater crustaceans and smaller frogs, devouring its prey whole. Although Angel’s Madagascar frog is active throughout the year, its growth slows during the dry season (March to September), when temperatures are lower and food is less abundant (4).
Like most other frogs, the life-cycle of Angel’s Madagascar frog consists of an aquatic, gilled tadpole phase, and an air-breathing adult phase (2) (5). The female lays over 300 eggs, usually within a shallow pool on the surface of a rock, which are fertilised by the male and swell into a gelatinous mass. Once hatched, the tadpoles are believed to remain in the pool or enter the stream, where they eventually metamorphose into juvenile frogs (2). The male Angel’s Madagascar frog reaches sexual maturity at about two years old, around a year earlier than the female. This is a useful reproductive strategy as it allows the females to reach a larger size, where they are capable of producing a greater amount of eggs (4). This species has a relatively long lifespan reaching up to seven years (2).
Owing to its restricted range, Angel’s Madagascar frog is highly vulnerable to the ongoing, large-scale degradation and destruction of forest that is occurring in south-east Madagascar. Although this species remains relatively abundant at some localities, a multitude of threats including expanding human settlements, agriculture, logging, livestock grazing, charcoal manufacture and the spread of invasive eucalyptus, are causing its population to decline. The pressures have already proven severe enough to cause local extinctions around Fort Dauphin, near the southern limit of the Angel’s Madagascar frog’s range (1).
While there are no known conservation measures specifically targeting Angel’s Madagascar frog, it is found in two protected areas, the Andohahela and Midongy-du-Sud National Parks (1). Nevertheless, increased protection of this species’ habitat, along with educational programs to inform local people of how best to manage the forests sustainably, are vital measures that must be implemented if Angel’s Madagascar frog is to be conserved (6).
Angel’s Madagascar frog is one of nearly 2,000 species of amphibian worldwide threatened with extinction. Having produced the comprehensive Global Amphibian Assessment, which assesses the conservation status of all known amphibian species, the IUCN is now working towards mitigating threats to these species through the creation of the Amphibian Action Conservation Plan (7) (8).
To learn more about the Global Amphibian Assessment, visit:
Amphibians on the IUCN Red List:
To learn more about conservation in Madagascar visit:
Madagascar Wildlife Conservation:
This information is awaiting authentication by a species expert, and will be updated as soon as possible. If you are able to help please contact:
- Endemic: a species or taxonomic group that is only found in one particular country or geographic area.
IUCN Red List (December, 2008)
- Andreone, F. and Nussbaum, R.A. (2006) A revision of Mantidactylus microtis and M. microtympanum, and a comparison with other large Madagascan stream frogs (Anura: Mantellidae: Mantellinae). Zootaxa, 1105: 49–68.
AmphibiaWeb - Angel’s Madagascar frog (March, 2009)
- Guarino, F.M., Andreone, F. and Angelini, F. (1998) Growth and longevity by skeletochronological analysis in Mantidactylus microtympanum, a rain-forest anuran from southern Madagascar. Copeia, 1998: 194–198.
- Halliday, T. and Adler, K. (2002) The New Encyclopedia of Reptiles and Amphibians. Oxford University Press, Oxford.
EDGE of Existence - Angel’s Madagascar frog (March, 2009)
AmphibiaWeb (March, 2009)
Global Amphibian Assessment (March, 2009) | <urn:uuid:6c59c252-2ad8-4e9b-87be-a867d9071c44> | 3.484375 | 1,352 | Knowledge Article | Science & Tech. | 38.229358 |
|Page 1 | Page 2 | Page 3 | Page 4||
Return to Experiments Table of Contents
Youíll have to imagine that in an actual plant, high pressure steam blasts against a series of such turbine wheels on the same shaft. The shaft, in turn, drives an electric generator, which produces the electricity. Itís amazing how powerful steam is. | <urn:uuid:7aca1218-6df4-4a5e-9ee7-c8f414bd35f9> | 2.8125 | 74 | Truncated | Science & Tech. | 51.924048 |
Even though it doesn’t quite qualify as a 'proper' planet, the second most massive asteroid in the Solar System, Vesta – which has a diameter of approximately 530 kilometres – exhibits numerous planetary characteristics. This is just one of the many significant results of NASA's Dawn mission, published in the journal Science on 11 May 2012. The Dawn spacecraft has been orbiting Vesta since 16 July 2011. The German Aerospace Center (DLR) is involved in the mission.
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DLR respects the confidentiality of your details and will not pass them on to third parties. | <urn:uuid:523764e1-1898-4fea-9b89-54c4fea87ae1> | 3.078125 | 128 | Truncated | Science & Tech. | 48.58 |
http://www.sciencenews.org/view/generic ... or_methane
Certainly coming much sooner that expected............from the article:
"While it’s no ice-nine, a frozen form of methane trapped in ocean sediments could be cause for concern. Warm Gulf Stream waters off the east coast of North America are converting large amounts of the substance into methane gas, which could lead to underwater landslides and influence global climate.
A good portion of the biological carbon on Earth is stored in the seafloor as methane hydrate, a frozen mixture of methane and water formed at high pressure and low temperature. Changes in the temperature or direction of the Gulf Stream, which carries warm water north from the Gulf of Mexico, have heated sediments in a strip along the North Atlantic seafloor by 8 degrees Celsius, unlocking 2.5 billion metric tons of methane from deep-sea caches, scientists report in the Oct. 25 Nature."
It must also be noted that these methane hydrate deposits at lower levels and colder are still subject to rapid releases from landslides above. It takes only a few pounds of mechanical pressure to cause it to fizz out. All it takes in temperature is an increase of 1*C to fizz out.
Also, doing the math on the warming effect of these releases, at 25 times the warming effects of CO2 that is like 25 times 2.5 gigatons or 62.5 GT equivalent of CO2. Last year humans released 26.4 GT of CO2. In 15 years the methane breaks down into water vapor and CO2. | <urn:uuid:f42094d0-dff1-4d0d-a7a0-eee73bec090f> | 3.296875 | 329 | Comment Section | Science & Tech. | 66.156587 |
Scientists Now Using Earthworms to Make Quantum Dots
Incredibly small, subatomic things operate by a different set of rules than the rest of us. Those rules are known as quantum physics. Nanoscale-sized bits of semiconductor are known as quantum dots, and they are used to make sure the electrons they contain are influenced by quantum effects. They're very useful for things like making smaller electronic components and better medical imaging, but they're also difficult to produce. That's why scientists are researching how to use earthworms to produce quantum dots.Read on... | <urn:uuid:9e25ea60-4790-477a-95ce-30abdbd3fc1a> | 3.265625 | 114 | Truncated | Science & Tech. | 45.173454 |
Phillip E. Parker
Wichita State University
In the beginning there was geometry, and it was codified by Euclid about 300 BC. Some 1500 years later, the contemporary thought was that there could be only this one, true geometry. This culminated in Kant's argument in his Critique of Pure Reason in 1781 that Euclidean geometry was an a priori synthetic truth. Others appealed to experience or relied on innate truths, but almost all philosophers and mathematicians were agreed.
Unfortunately for their certitude, however, Lambert had already proved the existence of a noneuclidean geometry in 1766, but this was not generally known until somewhat later and was not recognized until much later. In 1799, Gauss was already doubting the privileged rôle of Euclidean geometry, and by 1817 his doubt had become assured . Meanwhile, Schweikart had found a noneuclidean geometry by 1816 , but did not take the final step of observing that it could not be determined if the universe were Euclidean or not. This remained for Bolyai , beginning about 1820, and independently Lobachevsky , about 1826.
Thus by 1840 it had become clear to the experts that there were at least two geometries. In 1854, Riemann gave his inaugural lecture at Göttingen on the topic of Gauss's choice: the foundations of geometry . He presented the audience with an infinity of new geometries, those now called metric geometries.
In this lecture, Riemann also gave what turned out to be the notion of space most suitable for geometry. This was an ``n-fold extended quantity," now called a manifold of dimension n. In dimension 3, a manifold can be envisaged as various blobs of ordinary space glued together in a precisely specified way. Clearly, there are a lot of these spaces. On each such space, one then specifies a geometry by means of an auxiliary object called a metric.
Some harbored doubts about the ``truth'' of noneuclidean geometries for several years, but by 1872 when Klein gave his inaugural lecture at Erlangen they were mostly assuaged. He enlarged the world of geometries yet again in another major way, declaring that a geometry is the study of those properties which are preserved by a group of transformations, in any space, whether metric or not.
As one might guess, Riemann's and Klein's notions of a geometry do not coincide. Both are very extensive theories, each including vast arrays of examples of more or less practical applicability. The part in common has turned out to be the best place to test our further understanding of geometrical concepts and notions. The particular subset of the common part where they most closely mesh consists of those groups which are simultaneously manifolds and in which the group somehow describes its own geometry via a metric. Thus we combine Riemann's and Klein's geometries on the same space.
Now each group has an operation by which one may compose two elements and obtain a third. If the order in which two elements are composed does not affect the outcome, the group is called commutative. Thus in a commutative group, which element is to the right and which is to the left in a composition does not matter. But the operations of these geometric groups are not commutative in general, so one must make a choice of whether one will write down the left- or right-handed version of the theory. It has become traditional to write down the left-handed version and leave it to the reader as an exercise to work out the right-handed version, if desired. Because the geometry is preserved by or remains invariant under the group operation, one then speaks of left-invariant geometries on groups which are simultaneously manifolds. The Norwegian mathematician S. Lie was the first to study such groups extensively, so they are called Lie groups. Thus we arrive at left-invariant metrics on Lie groups as the tightest combination of the geometries of Riemann and Klein.
Traditionally, only some of these metric geometries were studied: the so-called definite ones. These are the most natural generalizations of Euclidean geometry. A summary of the state of knowledge in 1976 may be found in . As early as 1905, however, some applications in physics required the use of the much larger class of indefinite metric geometries. Unfortunately, very little is yet known about indefinite left-invariant metrics on Lie groups, and only one particular type has been studied in any generality [1, 14]. In dimension 3, we have determined all possible left-invariant metric geometries on Lie groups . In this dimension there are only two types; but in each higher dimension, there are many types of indefinite metrics while there is essentially only one type of definite metric.
One class of Lie groups that is most tractable consists of the nilpotent Lie groups. In a certain technical sense, they are the ones that are the closest to being commutative. The left-invariant metric geometries on commutative Lie groups are Euclidean geometry and its nearest indefinite relatives. Thus the left-invariant metric geometries on nilpotent Lie groups are those that are closest to being familiar while still exhibiting distinctive new features. This makes them an ideal place to enhance our limited understanding of indefinite metric geometric concepts and notions.
Among the nilpotent Lie groups, the very nearest to the commutative groups are those called 2-step. In recent years, some of the most exciting new results in definite metric geometries have been obtained with 2-step nilpotent Lie groups; e.g., . The definite left-invariant metric geometry of these was recently studied in some detail , and this is a focus of continuing research; e.g., .
We are now studying indefinite left-invariant metric geometries on 2-step nilpotent Lie groups. This is another step in a long-term program to increase significantly our knowledge of the general features of indefinite metric geometries. Other recent parts of this program include [2, 4, 6]. Indefinite left-invariant metric geometries on 2-step nilpotent Lie groups exhibit several new phenomena that do not occur in the definite case. Some of these provide links to other areas of current mathematical research, such as splitting of foliations or decoupling of systems of differential equations, thereby enriching much more than just geometric study.
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The Partial Derivative of B
The Partial Derivative of the Magnetic Flux Density
On this page we define the symbol:
Briefly, this is simply the negative of the rate of change of the B field with respect to time. The Magnetic Flux Density (B) is defined here.
To define this fully, let's say we have a magnetic flux density B, which is a vector field and a function of (x,y,z,t) (3-spatial variables and time). We write the B field in terms of its x-, y- and z-components:
From the partial derivative page, we know that the partial derivative of B with respect to time is the rate of change of the B field in time (that is, we ignore any spatial variation in the B field and are only concerned with how it changes versus time). And the negative sign in Equation simply negates each of the components. Hence, we can rewrite Equation as:
Finally, since the B field is measured in Webers/meter^2 [Wb/m^2] and the derivative means "per second" [1/s], then the units of Equation are Webers/meter-squared-seconds [Wb/m^2-s]. But we also know from the Faraday's Law Equality Page that this is equivalent to Volts/meter^2 [V/m^2].
This page on the partial derivative of the magnetic flux density has been copyrighted. The copyright belongs to Maxwells-Equations.com, 2012. | <urn:uuid:b5444610-4454-4222-ae30-5a4265d0f03e> | 2.921875 | 333 | Documentation | Science & Tech. | 58.0425 |
A BLAZING row has broken out between fisheries scientists over whether fishing fleets are depleting the world's oceans of their large species.
Fishing boats are thought to target smaller species only once the big, predatory ones are fished out. In the 1990s, Daniel Pauly of the University of British Columbia in Vancouver, Canada, calculated how high up the food chain the boats' catches were on average, and found that this mean trophic level (MTL) was falling. The MTL has since been adopted by the UN Convention on Biological Diversity as its main measure of ocean biodiversity.
Now Trevor Branch of the University of Washington in Seattle is contesting Pauly's conclusions. When he compiled the MTL for catches between 1950 and 2005, he found that it fell until the late 1980s then rose again (Nature, vol 468, p 431). "I'm saying we're depleting everything equally," he says.
Pauly says the interpretation is flawed, as fishing fleets moved into new areas during the 80s and 90s. "Expansion resets the clock, because you're exploiting a new ecosystem."
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Our solar system consists of the Sun, 8 planets, satellites, comets and asteroids, but as far as we know, there is only life on Earth. Will we ever discover otherwise? How much do we really know about our universe? Discover the Museum’s role in space exploration and research.
We know that the solar system formed around 4.5 billion years ago but what is the evidence for this and how did it happen?
With a circumference of over 40,000 kilometres, the Earth feels very large. In relation to our solar system, our galaxy and beyond it is in fact tiny.
Humans have been fascinated by the Moon for centuries and in 1969 we visited for the first time. But how did it get there? What is it made from? And why does it go through different phases?
Are we alone? Explore the places in our solar system where life might be found in a search for life in our galaxy and beyond.
Take a virtual tour of Mars, looking out for the north pole and the ancient highlands as you rotate the Red Planet’s globe. | <urn:uuid:59629bc5-7e12-4567-87b1-3804cd295b0b> | 4 | 224 | Content Listing | Science & Tech. | 69.013667 |
If the weather is just right you can see across Lake Erie to Canada as if it’s only a few miles away!
Lake Erie is 50 miles wide. That means the U.S. shore is 50 miles away from Canada. Locals have long attested to being able to see trees and buildings on the Canadians side of Lake Erie when the weather is clear.
Eyewitnesses say that Canada only appears to be about three miles away when the weather is perfectly clear. Then when the weather turns slightly, Canada slowly fades away and can’t be seen.
Experts say it is simply a mirage. During an atmospheric inversion, a layer of cold air blankets the lake and is followed by increasingly warm layers of air. When an atmospheric inversion occurs, it causes light to filter through the layers and bend from across the lake. It forms a type of lens and makes it can create the illusion of distant objects. | <urn:uuid:9f7f4f62-f8b9-43ed-a750-f081f8f567d1> | 3.640625 | 190 | Knowledge Article | Science & Tech. | 67.105282 |
Example below demonstrates working of bigdecimal class ulp method. Method returns bigdecimal values. Method returns the size of an ulp. which is the size of a unit at the last place of the bigdecimal object value.
Method returns +1 for a positive bigdecimal value. Actually this ulp size is the difference between the bigdecimal value and just the next number after the bigdecimal value. For example, if the bigdecimal value is 4 then its next value is 5, and there difference that is one, is the value that the ulp method generates.
The scale of the result will be same as that of the this.object value.
Method represents the bigdecimal object value in scientific notations if required. For example if method generates 5E-5, then it means 5 * ten to the power minus 5.
Method generates NumberFormatException, if it finds the bigdecimal value other than integers and double types values.
Syntax for using the method: public
Suppose we have bigdecimal objects x & y;
then y = x.ulp();
If you are facing any programming issue, such as compilation errors or not able to find the code you are looking for.
Ask your questions, our development team will try to give answers to your questions. | <urn:uuid:4ef01b2d-7cc7-431a-94f9-e15923a550cd> | 3.28125 | 273 | Documentation | Software Dev. | 49.542765 |
Powerful Ideas on
IMAGINE A NEW breed of all-electric
cars that can travel 300 miles or more
before needing a quick rechargealmost three times farther than current
hybrid models that rely on gasoline
as a backup.
Innovative science in the university's
recently launched Energy Frontier
Research Center may lead to such a
vehicle within a decade, says Gary
Rubloff, the Minta Martin Professor of
Engineering and director of the center.
Working with Sang Bok Lee, associate
professor of chemistry and biochemistry,
Rubloff is developing "super
batteries" that can store more energy,
deliver more power and recharge much
faster than existing devices can. The
key, says Rubloff, is exploiting the honeycomb
patterns of nanoscale pores in
aluminum oxide, using arrays of these
nanowires to build compact yet
extremely efficient batteries.
Linking faculty from engineering,
chemical and life sciences and computer
science, the energy research center
was funded with $14 million from the
U.S. Department of Energy as part of a
new program that brings together
groups of leading scientists to address
fundamental energy issues. -TV
Where Have All the Frogs Gone?
Lips's research on exotic frogs was featured in a Nature documentary.
FROGS AND OTHER amphibians are mysteriously disappearing from the
planet, and biologist Karen Lips is racing against time to save them. One-third
of the 6,300 species of amphibians are in decline and 168 have gone
extinct in the last 20 years, with more disappearing each day. The
crisis has required Lips and her colleagues to act as detectives at a
crime scene, investigating sites where they find the bodies of thousands
of dead frogs to unravel what went wrong.
The golden frog used to be common in Panama. Photocredit: Andrew Young
Copyright ©1995 - 2008 Public Broadcasting Service (PBS).
All Rights Reserved
While pollution and other environmental factors are taking their toll
on frogs, Lips and others discovered that it's an unusual fungus, called
, or Bd, that's causing massive frog die-offs
in locations as disparate as Panama, Australia and the National Zoo in
Washington, D.C. Unfortunately, these experts don't know where this fungus
originated and don't know how to stop it. They do know that it likes cool, wet
climates, where frogs also thrive, and that it spreads rapidly.
After Lips documented the disease's rapid and devastating impact on
frogs in Costa Rica and Panama, her colleagues rushed to evacuate frogs
from the forests of Central Panama to save them from the advancing fungus.
Today, their facility shelters 58 species of frogsincluding some of
the rarest on earth.
Lips is also investigating the fungus's impact in the U.S. and whether it has
caused the decline of several species of salamanders in Appalachia, which has
the highest biodiversity of salamanders in the world. In addition, she is documenting
the impact that these extinctions are having on ecosystems.
"Once amphibians are eliminated from an ecosystem, everything else
changes," she explains. "Snakes disappear, algae grows, sediments accumulate
and affect water quality. We don't know yet how many of these
changes are irrevocable." -KB | <urn:uuid:1565b16e-75f7-4097-a669-939f779f701d> | 3.265625 | 717 | Content Listing | Science & Tech. | 38.403501 |
Technology - Science
Follow the Curiosity rover on Twitter (@MarsCuriosity) and Facebook
Get answers to some of the most common questions about Curiosity: http://bit.ly/h56pie
INFORMATION ABOUT THE MISSION
Mission name: Mars Science Laboratory
Rover name: Curiosity rover
Size: About the size of a car -- 10 feet long (not including the arm), 9 feet wide and 7 feet tall!
Weight: 900 kilograms (2,000 pounds)
Features: Geology lab, rocker-bogie suspension, rock-vaporizing laser and lots of cameras
Mission: To search areas of Mars for past or present conditions favorable for life, and conditions capable of preserving a record of life
Launch: Nov. 26, 2011, from Cape Canaveral, Fla.
Arrival: August 5, 2012 PDT
Length of mission on Mars: The prime mission will last one Mars year or about 23 Earth months.
Mission Fact sheet: Download the PDF
For information about Curiosity’s power source and to obtain high-resolution images, visit:
Free registration with Ustream is required to participate in the chat box. The chat is open to all guests from around the planet.
• Be courteous.
• Use respectful language.
• Stay on topic.
• Protect your private information.
You're online, and Curiosity is, too. "Like," follow and get news here:
• Facebook: http://www.facebook.com/MarsCuriosity
• Twitter: http://twitter.com/marscuriosity
• Mission pages: http://mars.jpl.nasa.gov/msl/
Two other rovers, Spirit and Opportunity, have been on Mars since 2004. You can read about those rovers here, or follow @MarsRovers on Twitter.
For news on other missions at NASA's Jet Propulsion Laboratory, visit:
• Facebook: http://www.facebook.com/NASAJPL
• Twitter: http://twitter.com/NASAJPL
• Homepage: http://www.jpl.nasa.gov/ | <urn:uuid:64380924-f8b7-4946-a5e2-928e665f4cec> | 3 | 440 | Knowledge Article | Science & Tech. | 58.276401 |
Lifting the Fog: A Brief History of RadarJuly 6th, 2012 | Krissy Klinger
One of the worst airplane disasters in history occurred as a consequence of a series of unfortunate events. The location of the disaster was the island of Tenerife, the largest and most populated island of the Canary Islands, on March 27th, 1977. Two Boeing 747 planes prepared for departure on a crowded runway where they were instructed to follow a procedure called “backtaxi” where a portion of the runway is used as a taxiway for aircraft to taxi in the opposite direction from which they will take off. Through a series of misinterpreted communications between air traffic controllers and the pilots, one of the planes began their take off before the other, backtaxiing plane had cleared the same runway. Dense fog shrouded the planes from sight and they did not realize that they were barreling towards disaster until they were 2,000 feet from each other. A detailed account of the events of this fateful day can be found here.
Of all the events that led up to the disaster, the straw that broke the camel’s back was a dense layer of fog that clouded the two planes from each others', and the air traffic controller’s, vision. Unfortunately, the small airport on Tenerife was not equipped with ground-based radar, a tool that would have allowed the controllers to see the location of the planes even with the heavy cover of fog. Although this disaster happened 35 years ago, ground-based radar technology was already available, in fact, this technology was developed long before 1977.
The interest in radar systems exploded during World War 2 as several countries realized the value of radar which could detect incoming enemy warplanes, control antiaircraft gunfire, navigate ships, and guide airplanes. In fact, one of the first radars developed by the United States (SCR-270) actually spotted the Japanese warplanes headed towards Pearl Harbor, but the sightings were shrugged off as U.S. planes.
Although radar is often associated with weather these days, precipitation detection via radar was actually an unintentional discovery. Radar engineers during WW2 realized that storms appeared as large, moving clusters on their screens, which would obscure the intended ship or aircraft targets. Following this discovery, dozens of meteorologists were trained in radar technology and surface-based and airborne weather radar observations were established by 1943.
After the war, technological advances on radar slowed, but governments across the world continued weather radar research. Left over military radars from WW2 were used by the weather service of the U.S. The WSR-57 (Weather Survelliance Radar – 1957) was the first generation of radars specifically designed for a national warning network. The WSR-57 was an improvement on earlier radar technology as it provided more detailed information about storm strength, however, the reflectivity data was still very coarse and the inclusion of velocity data did not occur until the full development of the Doppler radar. In 1974, the network of radars was expanded with the WSR-74 (Weather Surveillance Radar – 1974) which were an updated version of the WSR-57. The WSR-74’s filled in gaps across the country that were not covered by the WSR-57 network, improving forecasts and severe weather warnings.
The utility of the Doppler frequency shift for radar was discovered before WW2, but it took several years to develop the technology to the point where it could be used for meteorological purposes. After years of study and development, the WSR-88D (Weather Surveillance Radar – 1988 Doppler) finally replaced the network of WSR-57 and WSR-74 radars in the early 1990’s. A network of 150 of these WSR-88D or NEXRAD (Next Generation Radar) were spread out across the country providing forecasters with detailed information from storms including hail, tornadic signatures, downbursts, gust fronts, and precipitation measurements. Today, Doppler radar is the primary radar used by meteorologists in the U.S.
Various software upgrades have been applied to the WSR-88D, in fact, by the end of 2012 the entire fleet of radars is scheduled to have the biggest radar system upgrade since the WSR-88D was fielded. According to the National Weather Service, “This upgrade, known as dual-polarization technology, will greatly enhance these radars by providing the ability to collect data on the horizontal and vertical properties of weather (e.g., rain, hail) and non-weather (e.g., insect, ground clutter) targets.”
Radar has a wide range of applications, developed initially as a tool of war and ending up as a staple of the meteorologist's weather segment on the evening news. Radar technology has helped not only in war and weather, but has far-reaching implications for fishermen, police, bird watchers, astronomers, and air traffic controllers, to name a few. The perfect storm of events that led up to the horrific airplane collision of 1977 in Tenerife could have been avoided had the airport been equipped with ground-based radar. Radar would have been able to "see" through the dense fog to alert the air traffic controllers that the two airplanes were on a collision course of historic proportions.
blog comments powered by Disqus | <urn:uuid:5b565573-f286-4d66-bc8f-cd18e5152cc5> | 3.734375 | 1,101 | Truncated | Science & Tech. | 40.154903 |
Some of the excited engineers and staff on landing day.
Click on image for full size
Jet Propulsion Laboratory, Pasadena, CA
Headlines declare: Mars Pathfinder Lands on July 4th
The Mars Pathfinder was launched on a rocket last December. The spacecraft landed on Mars on July 4th, 1997.
If you had the chance to visit Mars, you might take pictures of your trip. This is exactly what the Mars Pathfinder does. It has a camera that will take pictures of Mars.
If you were on the surface of Mars, you might collect rocks there. The Pathfinder spacecraft has a rover that does this. The rover searches the surface of Mars and collects rocks that can be tested.
Mars Pathfinder will finish its surface mission in August 1997.
Shop Windows to the Universe Science Store!
Learn about Earth and space science, and have fun while doing it! The games
section of our online store
includes a climate change card game
and the Traveling Nitrogen game
You might also be interested in:
People were really excited when Pathfinder landed on Mars on July 4, 1997. The Mars Pathfinder mission (MPF for short!) was sent to Mars to look at the rocks and soil of Mars. The MPF was actually 2 parts,...more
The Mars Odyssey was launched April 7, 2001. After a six-month journey, the Odyssey arrived at Mars on October 24, 2001. The instruments onboard the Mars Odyssey will study the minerals on the surface...more
The Mars 2005 mission is still in the planning stages. It is set to launch in the year 2005. ...more
Aerobraking slowed the Mars Global Surveyor down when it reached Mars. Aerobraking also helped MGS to get into the right orbit for mapping the surface of Mars. Aerobraking means that the MGS flew through...more
Mars Global Surveyor carries an instrument which measures the heights of things. This instrument is called an altimeter, or "altitude-meter". The graph to the left shows the results returned from Mars...more
Mars Global Surveyor carries an instrument which measures the heights of things. The picture to the left shows Mars Global Surveyor's measurement of the size of the giant cliff which separates the southern...more
Mars Global Surveyor carries an instrument which measures the heights of things. The picture to the left shows the results returned from Mars Global Surveyor's measurement of the size of some of the Martian...more | <urn:uuid:03a185ba-14a6-46ae-a7b5-ac1452cf32b7> | 3.25 | 502 | Content Listing | Science & Tech. | 69.640809 |
Discover the cosmos! Each day a different image or photograph of our fascinating universe is featured, along with a brief explanation written by a professional astronomer.
2004 December 16
Explanation: The grand, winding arms are almost mesmerizing in this face-on view of NGC 7424, a spiral galaxy with a prominent central bar. About 40 million light-years distant in the headlong constellation Grus, this island universe is also about 100,000 light-years across making it remarkably similar to our own Milky Way. Following along the winding arms, many bright bluish clusters of massive young stars can be found. The star clusters themselves are several hundred light-years in diameter. And while massive stars are born in the arms of NGC 7424, they also die there. Notably, this galaxy was home to a powerful stellar explosion, supernova SN 2001ig, which faded before this deep European Southern Observatory image was recorded.
Authors & editors:
NASA Web Site Statements, Warnings, and Disclaimers
NASA Official: Jay Norris. Specific rights apply.
A service of: LHEA at NASA / GSFC
& Michigan Tech. U. | <urn:uuid:43d71459-1b12-4906-8a61-91d47c786d59> | 3.390625 | 238 | Knowledge Article | Science & Tech. | 46.084089 |
Physics Teacher's Inventions Fair
Learning Science by Doing Science
Paul Doherty, The Exploratorium
Scientists look at what everyone has looked at and see what no one has seen
Teachers help others to see what they have never seen before.
Students ask questions that help their teachers to see what they have never seen before.
The Exploratorium Website: www.exploratorium.edu
Paul Doherty's website: www.exo.net/~pauld
The virtual Exploratorium is named The Splo in the
virtual world of Second Life,
Image Real and Virtual Look through a long focal length lens at a distant object and see both a real and a virtual image of the object simply by moving your head.
Finding rays Look at a small bright light source in a dimly look room, notice rays of light. Do experiments to find out where these rays are located.
Ringing Aluminum Rod Strike a rod and find its pattern of vibration with your fingers.
Floating in Copper Float a magnet between thick sheets of aluminum or copper.
Whirly Explore the sounds made by a corrugated plastic tube.
While I am attending the Physics Teachers Invention Fair I will be sharing many small experiments. Here are a few of them.
Laser Speckle, A white surface like that of a sheet of paper or a lightbulb appears to have light and dark spots on it when it is illuminated by laser light. These spots move in interesting ways.
Silent collisions: Magnets collide on a pencil without touching creating an elastic collision.
Audible magnetic domains, A coil of wire wrapped around an iron core can be attached to an audio amplifier which will make the changing magnetic domains audible....the Barkhausen effect.
Scientific Explorations with Paul Doherty
20 August 2007 | <urn:uuid:11dab56a-0fb6-4783-a0aa-da26658105bb> | 3.203125 | 377 | Content Listing | Science & Tech. | 55.607256 |
Nanotechweb reports on nanoparticles pinpointing brain activity.
Scientists could be a step closer to unraveling the mysteries of human memory thanks to a nanoparticle-based imaging technique developed at Bordeaux University. The team is observing how biomolecules change position within a cultured rat synapse, the junction between nerve cells, by labeling the biomolecules with tiny gold particles.
This is essentially another step in reverse engineering our brains, which is important because...
Wait a minute... I dedicated a whole FAQ to why it's important to reverse engineer the brain.
Read that instead. | <urn:uuid:4855296f-9159-4171-88e8-65360a66bce4> | 2.921875 | 121 | Truncated | Science & Tech. | 29.145909 |
What impact might mitigation of diffuse nitrate pollution have on river water quality in a rural catchment?
Hutchins, Michael G.. 2012 What impact might mitigation of diffuse nitrate pollution have on river water quality in a rural catchment? Journal of Environmental Management, 109. 19-26. 10.1016/j.jenvman.2012.04.045Full text not available from this repository.
Observations of river flow, river quality and solar radiation were collated to assess the degree to which light and nutrients may be limiting phytoplankton growth at seven sites in the River Ouse catchment in NE England under average conditions. Hydraulic information derived from river network model applications was then used to determine where river water has sufficient residence time above the tidal limit to facilitate bloom development. A nitrate model (NALTRACES) was developed to estimate the impact of land management change on mean river nitrate concentrations. Applications of this model showed that although agricultural activity contributes substantially to nitrate loads in the Ouse it is likely to have little impact on phytoplankton growth, which could still occur extensively in its absence given favourable sunny and dry conditions. As an example of a means of controlling light availability, establishing full riparian tree cover would appear to be a considerably more effective management scenario than suppressing inputs to the river of nitrate or phosphorus. Any actions should be prioritised in headwater areas such as the upper reaches of the Swale and Ure tributaries. These conclusions are in broad agreement with those arising from more detailed simulations at daily resolution using the QUESTOR river quality model. The combination of simple modelling approaches applied here allows an initial identification of suitable spatially-targeted options for mitigating against phytoplankton blooms which can be applied more widely at a regional or national level.
|Programmes:||CEH Topics & Objectives 2009 onwards > Water > WA Topic 1 - Variability and Change in Water Systems > WA - 1.3 - Model, attribute and predict impacts of climate and land cover change on hydrological and freshwater systems
CEH Topics & Objectives 2009 onwards > Water > WA Topic 3 - Science for Water Management > WA - 3.4 - Develop novel and improved methods to enable the sustainable management of freshwaters and wetlands
|Additional Keywords:||nitrate, phytoplankton, river water quality, catchment modelling, pollution mitigation, policy|
|NORA Subject Terms:||Ecology and Environment
|Date made live:||13 Jun 2012 10:38|
Actions (login required) | <urn:uuid:3451515e-8255-47db-80c9-10953f03f590> | 2.984375 | 535 | Academic Writing | Science & Tech. | 20.775358 |
Java applet for simulating spin systems
This is a simple Ising-type model written in Java. It simulates a system of spins located on the grid points of a lattice.
The spins are coupled to a heat bath with a temperature T = 1 / beta.
This applet then updates the spins on the lattice in order
to simulate the behavior of the spins for a given temperature.
You can adjust the size of the lattice by changing the values in the upper left
corner of the window. The default values define a two-dimensional lattice.
However, by changing
the number of points for the 3rd or 4th dimension from 1 to some other value you
can simulate a 3 or 4 dimensional system. The display of the spins on the right
always shows one plane within your lattice.
- The spins have a fixed length set to 1. You
can choose the number of spin directions between 2 (the standard Ising model)
Beneath the number of spin orientations the value of the spin is shown, averaged over the lattice
and over the updates of the lattice. Also, its variation (errorbar) is shown.
When all spins are aligned the average spin is 1, whereas if all spin orientations
are completely random the spin average will approach 0 (one spin pointing upward
and one downward add up to zero).
- There are several options for the spin-spin interaction. The option
nearest neighbor means that a given spin interacts with its neighboring spins alone.
In the case of a 2-dimensional system this means a spin interacts with its left,
right, upper, and lower, i.e. 4, neighboring spins. In case of the choice
plus diagonal there are 4 more neighbors (upper-left, upper-right, ...).
The interaction strength is constant for these two cases. For the other two options
exp(-r)/r and exp(-r/2)/r
each spin interacts with every other spin on the lattice.
The strength of the interaction is given by the mathematical expressions just stated
(so-called Yukawa potentials),
where r is the distance between each pair of interacting spins.
Those options need a lot more computing, so the applet will slow down.
- You can change the temperature of the system by changing the value of beta which is
the inverse of the temperature as mentioned before. A large value of beta means that
the temperature is small and all spins tend to align with each other. Beta equal to
0 translates to infinite temperature which has the effect that all spins behave
completely randomly. You can also change the character of the spin system from
so-called ferromagnetic to anti-ferromagnetic by changing the sign of beta.
For positive beta the spins tend to align along the same direction, whereas in the case
of beta negative adjacent spins try to orient themselves in an anti-parallel way.
The specific structure
of the spins system will depend on your choice of interaction, however.
Playing around with
the various options will give you some idea of the different phases of your spin system.
- In addition you can switch on an external field which is always oriented along
the vertical axis. A positive value of the external field yields a tendency of the spins
to orient themselves pointing upward on the screen, whereas for a negative value the spins
tend to point downward. The strength of this
effect depends, of course, on the value you choose for the field.
- Before getting to the controls in the lower left part of the applet window,
let us discuss the display on the right side. As mentioned before in the upper right
the spins of the lattice are shown (or a single plane of the system in case of a
3 or 4 dimensional system). The arrows symbolize the direction of the spins. Each direction
is also connected to a specific color of the background. So you might
either look at the arrows or the colors to get an idea of what is happening with the
- There are four segments in the lower right corner. The upper left panel shows a plot of
the value of the spin averaged over the lattice (blue)
and the same value averaged over all updates of the lattice (red) as they change with
successive updates of the spins on the lattice.
Here, first the average spin for a given lattice is determined, and then the absolute
value of this quantity is averaged over the updates - in contrast to the procedure
for the average value of the spin shown in the upper left part of the window.
The reason is that - without any additional external field - it is, e.g., equally probable to
have all spins pointing upward or downward. Thus, the average of this value tends to zero
over time even if all the spins are always aligned. This is not the case if one averages
over the absolute value as done here.
- The lower right panel shows the current spin averaged over the lattice. The orientation of
the arrow and its color represents the average spin direction whereas the absolute value
of the spin determines the size of the arrow.
- The upper right panel shows the correlation of the spin with another spin at some distance.
The horizontal axis represents the distance between the two spins, the vertical axis
is the value of the correlation (which is always one at distance 0, which is the leftmost
point in the plot). The red dots show the current values of the correlation averaged
over the lattice, the blue points (including black error bars)
are the corresponding values averaged over all updates of the lattice
(axis labels are still missing everywhere, I hope I'll get to fixing this, soon).
You can change either the value of the temperature or the external field continuously.
To do that you specify an amount of change in the lower left segment of the window,
and in addition the number of updates of the lattice after which the value of the
temperature or the field is altered. The applet will start with the continuous change
after you have entered the value for the amount of change. The value of
the average spin of the system with changing temperature/field is then plotted
in the lower left panel on the right part of the window. In case the increment is positive
green points mark the value and the evolution is plotted from left to right,
for a decrement the color is orange and the plotting is done from right to left.
The reason for this procedure is that sometimes when the spin orientations change drastically
with a change of parameters (phase transition) this change occurs differently if you
go from lower to higher values of the parameters or the other way round. Here, for instance,
you can choose a positive increment of the external field which will generate a green curve
and then you can change the sign of the increment and the average is spin is plotted from
right to left in orange. You can directly see whether both curves turn out to be on top of each
other or not (a so-called hysteresis or memory effect).
You can also go back and forth with the increments changing the
dimension of the system in-between and so on.
The curves don't get erased during the plotting. In order to clear the panel click
on the erase plot button. You can also interrupt the change of the parameters by
clicking on the stop button with the mouse. You can continue by clicking on it for a
- In case you need a break, click on the pause
button, which will freeze the applet until you
click on it again. There is also a help button which is, unfortunately, not yet
This applet still needs improvement. I'll try to fix the deficiencies with time.
Now have fun playing around with the parameters! | <urn:uuid:ad933aa9-aa4b-4421-8b1f-6fbf04b963eb> | 3.546875 | 1,634 | Tutorial | Science & Tech. | 51.744077 |
Forests, through growth of trees and an increase in soil carbon, contain a large part of the carbon stored
on land. Forests present a significant global carbon stock. Global forest vegetation stores 283 Gt of
carbon in its biomass, 38 Gt in dead wood and 317 Gt in soils (top 30 cm) and litter. The total carbon
content of forest ecosystems has been estimated at 638 Gt for 2005, which is more than the amount of carbon
in the entire atmosphere. This standing carbon is combined with a gross terrestrial uptake of carbon, which
was estimated at 2.4 Gt a year, a good deal of which is sequestration by forests. Approximately half of the
total carbon in forest ecosystems is found in forest biomass and dead wood.
Other terrestrial systems also play an important role. Most of the carbon stocks of croplands and
grasslands are found in the below-ground plant organic matter and soil.
Human activities, through land use, land-use change and forestry (LULUCF) activities, affect changes in
carbon stocks between the carbon pools of the terrestrial ecosystem and between the terrestrial ecosystem
and the atmosphere.
Management and/or conversion of land uses (e.g. forests, croplands and grazing lands) affects sources and
sinks of CO2, CH4 and N2O. According to the IPCC WGIII (2007), during the decade of the 1990s,
deforestation in the tropics and forest re-growth in temperate and boreal zones remained the major factors
contributing to emissions and removals of greenhouse gases (GHG) respectively. The IPCC WG1 (2007) reported
that estimated CO2 emissions associated with land-use change, averaged over the 1990s, were 0.5 to 2.7 GtC
yr–1, with a central estimate of 1.6 GtCyr-1.
The role of LULUCF activities in the mitigation of climate change has long been recognized. Mitigation
achieved through activities in the LULUCF sector, either by increasing the removals of GHGs from the
atmosphere or by reducing emissions by sources, can be relatively cost-effective.
Estimated sectoral economic potential (Gt CO2-eq /yr) for global mitigation for forestry and
agriculture as a function of carbon price (USD) in 2030 from bottom-up studies (Source: SPM IPCC 4AR,
General mitigation options could include forest-related activities such as reducing emissions from
deforestation and degradation, enhancing the sequestration rate in new or existing forests, and using wood
fuels and wood products as substitutes for fossil fuels and more energy-intensive materials. A variety of
options for mitigation of GHG emissions also exists in other land systems. The most prominent example is
agriculture, where options include improved crop and grazing land management (e.g., improved agronomic
practices, nutrient use, tillage and residue management), restoration of organic soils that are drained for
crop production, and restoration of degraded lands.
However, the main drawback of LULUCF activities is their potential reversibility and non-permanence of
carbon stocks as a result of human activities, (with the release of GHG into the atmosphere), disturbances
(e.g. forest fires or disease), or environmental change, including climate change. | <urn:uuid:e1b5d97a-afb8-4d7a-9034-e228687327e3> | 3.953125 | 711 | Knowledge Article | Science & Tech. | 41.944592 |
In the very long line of Greek mathematicians from Thales of Miletus and Pythagoras of Samos in the 6th century BC to Pappus of Alexandria in the 4th century AD, Archimedes of Syracuse (287 - 212 BC) is the undisputed leading figure. His pre-eminence is the more remarkable when we consider that this dazzling millenium of mathematics contains so many illustrious names, including Anaxagoras, Zeno, Hippocrates, Theodorus, Eudoxus, Euclid, Eratosthenes, Apollonius, Hipparchus, Heron, Menelaus, Ptolemy and Diophantus. (See the St Andrews archive History of Mathematics for information about these mathematicians.)
Although his main claim to fame is as a mathematician, Archimedes is also known for his many discoveries and inventions in physics and engineering, which include the following.
Before discussing the work covered in his book Measurement of the Circle , we mention briefly a few of the other significant contributions which Archimedes made to mathematics.
1. C H Edwards. The Historical Development of the Calculus , Springer-Verlag, New York, 1979.
2. T L Heath. A History of Greek Mathematics (2 vols.) , Dover, New York, 1981.
The following three propositions are contained in Archimedes' book Measurement of the Circle .
(i) The area of a circle is equal to that of a right-angled triangle where the sides including the right angle are respectively equal to the radius and circumference of the circle.
(ii) The ratio of the area of a circle to that of a square with side equal to the circle's diameter is close to 11:14. (This is of course equivalent to saying that is close to the fraction 22 over 7.)
(iii) The circumference of a circle is less than three and one-seventh times its diameter but more than three and ten-over-seventy-one times the diameter. He obtained these inequalities by considering the circle with radius unity and estimating the perimeters of inscribed and circumscribed regular polygons of ninety-six sides.
Here we summarize the main points in the paper by Phillips with the above title.
1. Let p(n) and P(n) respectively denote half the perimeter of the inscribed and circumscribed regular n-gons of the unit circle. It can be shown that p(2n) and P(2n) are simply related to p(n) and P(n). The most obvious way is to express p(2n) as a function of p(n) only, and to express P(2n) solely in terms of P(n). However, there is a more elegant way of proceeding, in which both P(n) and p(n) are used to compute each of P(2n) and p(2n) : it happens that P(2n) is the harmonic mean of P(n) and p(n), and p(2n) is the geometric mean of P(n+1) and p(n). (Click on means for definitions of the harmonic and geometric mean.)
2. It is easily verified that P(3) is 3 times the square root of 3, and p(3) one half of this. We can compute P(6) and p(6) from the "double mean" process defined above, then P(12) and p(12), and so on. After five applications of the double mean process, we find that P(96) = 3.1427 and p(96) = 3.1410 to 4 decimal places. This is consistent with Archimedes' proposition (iii) above.
3. Some analysis shows that the quantity u(n)=(2p(n) + P(n))/3 is a closer approximation to than either of P(n) or p(n).
4. It can be shown similarly that the quantity v(n) = (4p(2n) - p(n))/3 is a closer approximation to than either of p(n) or p(2n). The approximation p(n) differs from by a quantity which tends to zero like one-over-n-squared; however, v(n) differs from by a quantity which tends to zero like one-over-n-to-the-power-4. The same remarks hold if we replace "p" by "P" in the relation for v(n). The process used in computing v(n) is called extrapolation to the limit, also known as Richardson extrapolation.
5. In fact, the error between p(n) or P(n) and is a power series in the variable x = one-over-n-squared, beginning with the term in x. The computation of v(n) is defined so that the error between v(n) and has a series in x beginning with the term in x-squared.
6. To produce still faster convergence to , we "remove" the term in x-squared, by computing w(n) = (16v(2n) - v(n))/15. We can extend this process further, using w(2n) and w(n) to remove the term in x-cubed from the error, and so on. This is called repeated extrapolation. For more information on extrapolation to the limit, see any text on numerical analysis. (Phillips and Taylor, Theory and Applications of Numerical Analysis , is one that comes to mind.)
7. Beginning with p(3), p(6), p(12), p(24), p(48) and p(96), the "raw material" computed by Archimedes, we can extrapolate five times. The final number in this calculation differs from by less than one unit in the eighteenth decimal place. (We obtain a similar result if we use the "P" sequence in place of the "p" sequence.)
8. It is geometrically obvious that the two sequences P(n) and p(n) converge to the common limit . What if we assign arbitrary positive values to P(3) and p(3)? It can be shown that the two sequences converge to a common limit which can be expressed as a multiple of an inverse cosine or an inverse hyperbolic cosine (cosh), depending on whether p(3) is less than or greater than P(3).
9. In particular, let us choose any value of t > 1 and write a = t-squared. Then let us choose P(3) = (a-1)/(a+1) and p(3) = (a-1)/(2t), and compute the "P" and "p" sequences using the "double mean" process defined in paragraph 1 above. Note that P(3) < p(3). In this case the two sequences converge to the common limit log t.The above method of the logarithm should not be regarded as a serious practical algorithm, since there are faster methods available. See, for example, Borwein and Borwein, Pi and the Arithmetic-Geometric Mean .
In the first paragraph of the previous section, we combined the harmonic and geometric means in a "double mean" process. In order to generalize this, Foster and Phillips used of a class of abstract means. For a definition of this class and associated material, click on means.
Foster and Phillips define an "Archimedean" process where, given positive real numbers x(0) and y(0), the sequences (x(n)) and (y(n)) are computed recursively from
This generalizes the process defined in paragraph 1 of the previous section. It can be shown that the two sequences defined by this "Archimedean" process converge monotonically to a common limit. Moreover, assuming that the functions M and N possess continuity of their derivatives up to second order, the two sequences converge to zero in a first order manner, meaning that the errors tend to zero asymptotically like a geometric sequence. Somewhat surprisingly, no matter what means M and N we choose, with the properties specified above, the common ratio of this geometric sequence is always one-quarter. Thus about three further decimal digits of accuracy are gained for every five iterations carried out in an "Archimedean" process, since 4 to the power 5 (1024) is approximately 1000.
Foster and Phillips consider also the superficially similar "Gaussian" process where, again given positive real numbers x(0) and y(0), the sequences (x(n)) and (y(n)) are computed recursively from
This generalizes the famous "arithmetic-geometric mean" process which Gauss used to compute an elliptic integral. In this classical case, M and N are (obviously from its name) the arithmetic and geometric means, and it is well known that the "arithmetic-geometric mean" process converges quadratically . This means that the error in x(n+1) behaves asymptotically as a multiple of the square of the error in x(n), with the errors in y(n+1) and y(n) being related similarly.
Foster and Phillips show that this quadratic convergence carries over to the general "Gaussian" process defined above provided that the means M and N possess continuity of their derivatives up to second order. | <urn:uuid:c1d978ff-01ae-4fc1-9a32-71490b78e10d> | 3.765625 | 2,005 | Academic Writing | Science & Tech. | 60.753431 |
Science Fair Project Encyclopedia
In words: you start with 0 and 1, and then produce the next Fibonacci number by adding the two previous Fibonacci numbers. The first Fibonacci numbers (sequence A000045 in OEIS) for n = 0, 1,... are
As documented by Donald Knuth in The Art of Computer Programming, this sequence was first described by the Indian mathematicians Gopala and Hemachandra in 1150, who were investigating the possible ways of exactly bin packing items of length 1 and 2. In the West, it was first studied by Leonardo of Pisa, who was also known as Fibonacci (c. 1200), to describe the growth of an idealized rabbit population. The numbers describe the number of pairs in the rabbit population after n months if it is assumed that
- in the first month there is just one new-born pair,
- new-born pairs become fertile from their second month on
- each month every fertile pair begets a new pair, and
- the rabbits never die
Suppose that in month n we have a pairs of fertile and newly born rabbits and in month n + 1 we have b pairs. In month n + 2 we will necessarily have a + b pairs, because all a pairs of rabbits from month n will be fertile and produce a pairs of offspring, while the newly born rabbits in b will not be fertile and will not produce offspring.
The term Fibonacci sequence is also applied more generally to any function g where g(n + 2) = g(n) + g(n + 1). These functions are precisely those of the form g(n) = aF(n) + bF(n + 1) for some numbers a and b, so the Fibonacci sequences form a vector space with the functions F(n) and F(n + 1) as a basis.
In particular, the Fibonacci sequence L with L(1) = 1 and L(2) = 3 is referred to as the Lucas numbers. This sequence was described by Leonhard Euler in 1748, in the Introductio in Analysin Infinitorum. The significance in the Lucas numbers L(n) lies in the fact that raising the Golden ratio to the nth power yields:
Lucas numbers are related to Fibonacci numbers by the relation:
- L(n) = F(n - 1) + F(n + 1)
As was pointed out by Johannes Kepler, the ratio of adjacent Fibonacci numbers, i.e.
- F(n + 1) / F(n),
converges to the golden mean φ. In modern form:
- x2 = x + 1,
a quadratic equation with
- φ,1 - φ
as solutions. If we multiply both sides by xn, we get
- xn + 2 = xn + 1 + xn.
Thus the two functions
— as well as all linear combinations
— satisfy the Fibonacci recurrence.
By adjusting the coefficients to get the proper initial values F(0) = 0 and F(1) = 1, we obtain
This generates the closed form formula for the Fibonacci numbers as
- a formula that has become known as Binet 's formula. Or simply,
where φ is the golden ratio number.
As n goes to infinity, the second term converges to zero, so the Fibonacci numbers approach the exponential φn/√5, hence their convergent ratios. In fact the second term starts out small enough that the Fibonacci numbers can be obtained from the first term alone, by rounding to the nearest integer.
Computing Fibonacci numbers
Computing Fibonacci numbers by computing powers of the golden mean is not very practical except for small values of n, since rounding errors will accrue and floating point numbers usually don't have enough precision.
The straightforward recursive implementation of the Fibonacci sequence definition is also not advisable, since it would compute many values repeatedly (unless the programming language has a feature which allows the storing of previously computed function values, such as memoization). Therefore, one usually computes the Fibonacci numbers "from the bottom up", starting with the two values 0 and 1, and then repeatedly replacing the first number by the second, and the second number by the sum of the two.
and employs exponentiating by squaring.
Note that this matrix has a determinant of +1 or -1, and thus it is a 2x2 unimodular matrix. This property can be understood in terms of the continued fraction representation for the golden mean: φ=[1;1,1,1,1,...]. The Fibonacci numbers occur as the ratio of successive convergents of the continued fraction for φ, and the matrix formed from successive convergents of any continued fraction has a determinant of +1 or -1.
See also: Fibonacci number program
The Fibonacci numbers occur in a formula about the diagonals of Pascal's triangle (see binomial coefficient).
In music Fibonacci numbers are sometimes used to determine tunings, and, as in visual art, to determine the length or size of content or formal elements. Examples include Béla Bartók's Music for Strings, Percussion, and Celesta.
Every positive integer can be written in a unique way as the sum of distinct Fibonacci numbers in such a way that the sum does not include any two consecutive Fibonacci numbers. This is known as Zeckendorf's theorem, and a sum of Fibonacci numbers that satisfies these conditions is called a Zeckendorf representation.
Since the conversion factor 1.609 for miles to kilometers is close to the golden mean φ, the decomposition of distance in miles into a sum of Fibonacci numbers becomes nearly the kilometer sum when the Fibonacci numbers are replaced by their successors. This method amounts to a radix 2 number register in base φ being shifted. To go from kilometers to miles shift the register down the Fibonacci sequence instead.
Fibonacci numbers in nature
Fibonacci sequences have been noted to appear in biological settings, such as the branching patterns of leaves in grasses and flowers, branching in bushes and trees, the arrangement of tines on a pine cone, seeds on a raspberry and the like. Przemyslaw Prusinkiewicz has advanced the idea that these can be in part understood as the expression of certain algebraic constraints on free groups, specifically as certain Lindenmeyer grammers . Generally one sees Fibonacci numbers arise in the study of the fractal Fuchsian groups and Kleinian groups, and systems that possess such symmetries. For example, the solutions to reaction-diffusion differential equations (such as that seen in the Belousov-Zhabotinsky reaction) can show such a patterning; in biology, genes often express themselves through gene regulatory networks, that is, in terms of several enzymes controlling a reaction, which can be modelled with reaction-diffusion equations. Such systems rarely give the Fibonacci sequence exactly or directly; rather, the relationship occurs deeper in the theory. Similar patterns also occur in non-biological systems, such as in sphere packing models.
A generalization of the Fibonacci sequence are the Lucas sequences. One kind can be defined thus:
- U(0) = 0
- U(1) = 1
- U(n+2) = PU(n+1) − QU(n)
where the normal Fibonacci sequence is the special case of P = 1 and Q = -1. Another kind of Lucas Sequence begins with V(0) = 2, V(1) = P. Such sequences have applications in number theory and primality proving.
The Fibonacci polynomials are another generalization of Fibonacci numbers.
- F(n + 1) = F(n) + F(n − 1)
- F(0) + F(1) + F(2) + ... + F(n) = F(n + 2) − 1
- F(1) + 2 F(2) + 3 F(3) + ... + n F(n) = n F(n + 2) − F(n + 3) + 2
These identities can be proven using many different methods. But, among all, we wish to present an elegant proof for each of them using combinatorial arguments here. In particular, F(n) can be interpreted as the number of ways summing 1's and 2's to n − 1, with the convention that F(0) = 0, meaning no sum will add up to -1, and that F(1) = 1, meaning the empty sum will "add up" to 0. Here the order of the summands matters. For example, 1 + 2 and 2 + 1 are considered two different sums and are counted twice.
Proof of the first identity. Without loss of generality, we may assume n ≥ 1. Then F(n + 1) counts the number of ways summing 1's and 2's to n.
When the first summand is 1, there are F(n) ways to complete the counting for n − 1; and the first summand is 2, there are F(n − 1) ways to complete the counting for n − 2. Thus, in total, there are F(n) + F(n − 1) ways to complete the counting for n.
Proof of the second identity. We count the number of ways summing 1's and 2's to n + 1 such that at least one of the summands is 2.
As before, there are F(n + 2) ways summing 1's and 2's to n + 1 when n ≥ 0. Since there is only one sum of n + 1 that does not use any 2, namely 1 + … + 1 (n + 1 terms), we subtract 1 from F(n + 2).
Equivalently, we can consider the first occurrence of 2 as a summand. If, in a sum, the first summand is 2, then there are F(n) ways to the complete the counting for n − 1. If the second summand is 2 but the first is 1, then there are F(n − 1) ways to complete the counting for n − 2. Proceed in this fashion. Eventually we consider the (n + 1)-th summand. If it is 2 but all of the previous n summands are 1's, then there are F(0) ways to complete the counting for 0. If a sum contains 2 as a summand, the first occurrence of such summand must take place in between the first and (n + 1)-th position. Thus F(n) + F(n − 1) + … + F(0) gives the desired counting.
Proof of the third identity. This identity can be established in two stages. First, we count the number of ways summing 1's and 2's to -1, 0, …, or n + 1 such that at least one of the summands is 2.
By our second identity, there are F(n + 2) − 1 ways summing to n + 1; F(n + 1) − 1 ways summing to n; …; and, eventually, F(2) − 1 way summing to 1. As F(1) − 1 = F(0) = 0, we can add up all n + 1 sums and apply the second identity again to obtain
- [F(n + 2) − 1] + [F(n + 1) − 1] + … + [F(2) − 1]
- = [F(n + 2) − 1] + [F(n + 1) − 1] + … + [F(2) − 1] + [F(1) − 1] + F(0)
- = F(n + 2) + [F(n + 1) + … + F(1) + F(0)] − (n + 2)
- = F(n + 2) + F(n + 3) − (n + 2).
On the other hand, we observe from the second identity that there are
- F(0) + F(1) + … + F(n − 1) + F(n) ways summing to n + 1;
- F(0) + F(1) + … + F(n − 1) ways summing to n;
- F(0) way summing to -1.
Adding up all n + 1 sums, we see that there are
- (n + 1) F(0) + n F(1) + … + F(n) ways summing to -1, 0, …, or n + 1.
Since the two methods of counting refer to the same number, we have
- (n + 1) F(0) + n F(1) + … + F(n) = F(n + 2) + F(n + 3) − (n + 2)
Finally, we complete the proof by subtracting the above identity from n + 1 times the second identity.
The power series
has a simple and interesting closed-form solution for x < 1/φ:
In particular, math puzzle-books note the curious value s(1/10)/10=1/89. The sum is easily proved by noting that
and then explictly evaluating the sum.
Reciprocal sum constant
The sum of the reciprocals of all the Fibonacci numbers converges: (OEIS number: A079586 )
See also the Mathworld article on the subject.
A tribonacci number is like a Fibonacci number, but instead of starting with two predetermined terms, the sequence starts with three predetermined terms and each term afterwards is the sum of the preceding three terms. The first few tribonacci numbers are:
OEIS number: A000073
A tetranacci number is like a tribonacci number, only that starting with four predetermined terms and each term afterwards being the sum of the preceding four terms. The first few tetranacci numbers are
OEIS number: A000078
Pentanacci, hexanacci and heptanacci numbers have been computed, but they have not interested researchers much.
A repfigit or Keith number is an integer, that when its digits start a Fibonacci sequence with that number of digits, the original number is eventually reached. An example is 47, because the Fibonacci sequence starting with 4 and 7 (4,7,11,18,29,47) reaches 47. A repfigit can be a tribonacci sequence if there are 3 digits in the number, a tetranacci number if the number has four digits, etc. The first few repfigits are
14, 19, 28, 47, 61, 75, 197, 742, 1104, 1537, 2208, 2580, 3684, 4788, 7385, 7647, 7909
OEIS number: A007629
- The Golden Mean and the Physics of Aesthetics
- The Golden Section: Phi
- Computing Fibonacci numbers on a Turing Machine
- The Fibonacci Quarterly — an academic journal devoted to the study of Fibonacci numbers
- The Fibonacci Series
- Hemachandra's application to Sanskrit poetry
- Representations of Integers using Fibonacci numbers
- Fibonacci Flim-Flam
- Museum of Harmony and Golden Section
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In this chapter, we develop a very basic CORBA application, designed to demonstrate some of the key concepts for using Common Lisp for distributed objects.
The chapter aims to show you the sort of coding involved in using CORBA with Common Lisp, and to get a client/server application up and running quickly. It is not concerned so much with explaining how things work. Subsequent chapters go into more detail, using a deeper example, and explaining the approach we have taken to implementing the CORBA architecture for Common Lisp.
In this example application, a client program asks a server program for a string and prints it to standard output. This chapter is going to take you through the basic steps needed to create the application. | <urn:uuid:23cff116-4855-459a-b2f0-356d6fe06880> | 2.765625 | 144 | Documentation | Software Dev. | 46.268367 |
Bubbles and Temperature
Does the temperature of water affect how long bubbles will
is my science project i would like to know the answer and why. i
would also like to know if heat and expansion or cold and contraction
have anything to do with the results. thanks.
Here's how science projects work: you pose a question (you've posed a
very good one), and you devise a method of discovering the answer (your
method is flawed, in part because it only works if somebody already
knows the answer). There are other flaws in your method of discovering
1) it's no fun
2) at best, all it gets you is the answer. I'm a science-fair judge,
and I'll tell you a secret about science fair judges: we don't care all
that much if a kid gets the right answer; we REALLY care if the method
of discovering the answer is well considered by the kid, and well
executed by the kid -- even if it's completely wrong for some technical
reason a kid would be unlikely to consider or understand.
Here's the approach I would take: Why do bubbles ever pop? Why should
they not last forever? Do different ones last for different lengths of
time? Are bubbles uniform in structure and constant from birth to
violent death, or does their structure evolve in time? Where does the
water that makes up the skin of a bubble go? What would you do if you
were a water molecule at the surface of a bubble? Does your answer
depend on whether you're on the inside surface or the outside surface?
What do water molecules at other water surfaces (e.g., lakes, bathtubs,
raindrops) do? If you can identify any pop causes, do any of them seem
likely to be temperature dependent? Can you think of a test that would
Other things equal, the higher the temperature, the shorter is the life of
the bubble. The reason for this is that the rate of evaporation of water [in
the bubble's skin] increases dramatically with increasing temperature. This
makes the thickness of the film smaller and also changes the relative
concentration of the components of the bubble solution.
Search the Web for "bubbles". There is a wealth of info there. There are
also several elementary books you can order from Barnes & Noble or Amazon.
I would suggest doing the experiment to find your answer. put bubbles in
hot water and some in cold water and record your results. Make sure you use
the same amount of water, and the same amount of liquid soap (or bubbles) in
your experiment. Good luck.
Click here to return to the General Topics Archives
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Foraging ecology of the black flying fox (Pteropus alecto) in the seasonal tropics of the Northern Territory, Australia
Carol Palmer, Owen Price and Christine Bach
27(2) 169 - 178
Pteropus alecto uses landscape patchiness at two scales: firstly, between broad vegetation types (i.e. eucalypt open forest/savanna woodland versus rainforest vegetation); secondly, within vegetation types. Radio-collared Pteropus alecto selected foraging sites that were richer in flower or fruit resources than floristically similar sites and moved through the landscape in response to the flowering and fruiting of a number of plant species occurring in different vegetation types. Abundance of P. alecto within four monitored rainforest patches and the outside vegetation fluctuated substantially during the study. Overall, P. alecto was more abundant in the rainforests than in the surrounding vegetation. P. alecto foraged on the flowers and fruit from 23 species in 11 families.
Full text doi:10.1071/WR97126
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It is important to realize that with new information about subdivision or correlation of relative time, or new measurements of absolute time, the dates applied to the time scale can and do change. Revisions to the relative time scale have occurred since the late 1700s. The numerically calibrated geologic time scale has been continuously refined since approximately the 1930s (e.g., Holmes, 1937), although the amount of change with each revision has become smaller over the decades (see fig. 1.5 and 1.6 of Harland et al.) and a few numerical estimates were available previously (but often for the duration of the entire scale rather than its individual subdivisions).
In addition, like any good scientific measurement, every dated boundary has an uncertainty associated with it, expressed as "+- X millions of years". These can not be included in the diagram for practical reasons, but can be found in Harland et al., 1990, along with a detailed description of the history of earlier-proposed time scales and the terminology, methodology and data involved in constructing this geological time scale.
Because of continual refinement, none of the values depicted in this diagram should be considered definitive, eventhough some have not changed significantly in a long time and are very well constrained (e.g., the Cretaceous/Tertiary boundary has been at 65+-1 Ma for decades, and has been tested innumerable times, with almost all dates somewhere between 64 and 66 million years). The overall duration and relative length of these large geologic intervals is unlikely to change much, but the precise numbers may "wiggle" a bit as a result of new data.
This gelogical time scale is based upon Harland et al., 1990, but with the Precambrian/Cambrian boundary modified according to the most recently-published radiometric dates on that interval, revising the boundary from 570+-15 million years to 543+-1 million years ago (Grotzinger et al., 1995). Other changes have been proposed since 1990 (e.g., revision of the Cretaceous by Obradovich, 1993), but are not incorporated because they are relatively small.
The time scale is depicted in its traditional form with oldest at the bottom and youngest at the top -- the present day is at the zero mark. Geologic time is finely subdivided through most of the Phanerozoic (see Harland et al., 1990 for details), but most of the finer subdivisions (e.g., epochs) are commonly referred to by non-specialists only in the Tertiary. Because of the vast difference in scale, the younger intervals have been successively expanded to the right to show some of these finer subdivisions.
geological time scale
Grotzinger, J.P.; Bowring, S.A.; Saylor, B.Z.; and Kaufman, A.J., 1995 (Oct.27). Biostratigraphic and geochronologic constraints on early animal evolution. Science, v.270, p.598-604. [The most recent revision of the age of the Precambrian/Cambrian boundary.]
Harland, W.B.; Armstrong, R.L.; Cox, A.V.; Craig, L.E.; Smith, A.G.; and Smith, D.G., 1990. A geologic time scale, 1989 edition. Cambridge University Press: Cambridge, p.1-263. ISBN 0-521-38765-5 [One of the more recent compilations of the entire geologic time scale.]
Holmes, A., 1937. The Age of the Earth (new edition, revised). Nelson:London, p.1-263. [One of the earlier attempts at an integrated geochronologic time scale.]
Obradovich, J.D., 1993. A Cretaceous time scale. IN: Caldwell, W.G.E. and Kauffman, E.G. (eds.), Evolution of the Western Interior Basin. Geological Association of Canada, Special Paper 39, p.379-396. [Proposes revisions to the Cretaceous time scale at the resolution of stages (finer divisions than shown on diagram above) and sub-stages.]
This file may be freely used for non-commercial purposes provided its original source is indicated. Please contact the author for other arrangements.
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Dropping Objects from the Database
The DROP statement is used to drop the following objects from the database:
The CASCADE or RESTRICT keywords may be used to specify the action to be taken if other objects exist that are dependent on the object being dropped.
- If RESTRICT (the default) is specified, an error is returned if other objects are affected and the drop operation is aborted.
- If CASCADE is specified, dependent objects are dropped as well.
System database objects can only be dropped by their creator. Private database objects can only be dropped by the creator of the schema to which they belong.
Therefore use caution when using the DROP statement with CASCADE, as the operation may have a recursive effect on all objects relating to it. For example, when a table is dropped, all views, synonyms, routines and triggers created on or referencing that table are also dropped.
The DROP statement removes whole objects from the database. It cannot be used to remove columns from tables, this is done by the ALTER TABLE statement, see Altering Tables.
Dropping Databanks and Tables
Drop the CURRENCIES table:DROP TABLE currencies RESTRICT;
If the keyword CASCADE is specified, all views, synonyms and indexes based on CURRENCIES are also dropped as well as any functions, procedures and triggers referencing the table.
Drop the MIMER_STORE databank:DROP DATABANK mimer_store RESTRICT;
If the keyword CASCADE is specified, all tables in the MIMER_STORE databank are also dropped and any views, synonyms, triggers and indexes based on those tables are also dropped as well as any functions, procedures and triggers referencing any of the dropped objects.
An attempt is automatically made to delete the physical databank file when a databank is dropped.
There may be occasions, because of access rights issues in the file system, when the database server's attempt to delete the physical databank file might fail. If recommended procedures for databank file management are followed, see the Mimer SQL System Management Handbook, the databank file should be deleted correctly.
When a sequence is dropped, all the objects (i.e. constraints, domains, functions, procedures, tables, triggers and views) referencing the sequence are also dropped.
Drop the CUSTOMER_ID_SEQ sequence:DROP SEQUENCE customer_id_seq CASCADE;
The specification of CASCADE ensures that the sequence is dropped even if it is being referenced by other objects in the database.
When a domain is dropped, existing columns assigned the domain retain all the properties of the domain. No new columns may however be assigned the domain.
Drop the EUROS domain:DROP DOMAIN euros RESTRICT;
Note: If you re-create a domain that has been dropped, the domain will be seen as a completely new domain and it will not be associated with any columns that belonged to the old domain.
To change the restrictions on the columns that were defined with a domain that has been dropped, use the ALTER TABLE statement.
When an ident is dropped, everything that the ident has created (including other idents and everything created by those idents) as well as all privileges granted by the ident are dropped. For this reason, physical users should never own objects, except for synonyms and personal views.
Drop the MIMER_ADM ident:DROP IDENT mimer_adm RESTRICT;
Dropping Functions, Modules, Procedures and Triggers
The effect of using the keyword CASCADE can be rather dramatic when modules, routines and triggers are dropped. For this reason it is recommended that all modules, routines and triggers be created by running a command file so they can be easily reconstructed in case of being dropped in error.
Drop the function called MIMER_STORE_BOOK.FORMAT_ISBN:DROP FUNCTION mimer_store_book.format_isbn CASCADE;
Drop the procedure called COMING_SOON:DROP PROCEDURE coming_soon CASCADE;
Drop the module called MIMER_STORE_MUSIC.ROUTINES:DROP MODULE mimer_store_music.routines CASCADE;
Drop the trigger called PRODUCTS_AFTER_INSERT:DROP TRIGGER products_after_insert CASCADE;
About Dropping Modules and Routines
The following points should be noted when dropping modules and routines:
- When a module is dropped, all the routines contained in it will be dropped (this is not a cascade effect, but it may provoke cascade effects).
- If a routine is dropped and it is referenced from another object, the referencing object will also be dropped.
- If a routine belonging to a module is to be dropped as a consequence of a cascade, only that routine is dropped (the other routines in the module and the module itself will remain unaffected).
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Permeability of Fault-Related Rocks, and Implications for Hydraulic Structure of Fault Zones
Journal of Structural Geology
The permeability structure of a fault zone in granitic rocks has been investigated by laboratory testing of intact core samples from the unfaulted protolith and the two principal fault zone components; the fault core and the damaged zone. The results of two test series performed on rocks obtained from outcrop are reported. First, tests performed at low confining pressure on 2.54-cm-diameter cores indicate how permeability might vary within different components of a fault zone. Second, tests conducted on 5.1-cm-diameter cores at a range of confining pressures (from 2 to 50 MPa) indicate how variations in overburden or pore fluid pressures might influence the permeability structure of faults. Tests performed at low confining pressure indicate that the highest permeabilities are found in the damaged zone (10−16–10−14m2), lowest permeabilities are in the fault core (<10−20–10−17m2), with intermediate permeabilities found in the protolith (10−17–10−16m2). A similar relationship between permeability and fault zone structure is obtained at progressively greater confining pressure. Although the permeability of each sample decays with increasing confining pressure, the protolith sustains a much greater decline in permeability for a given change in confining pressure than the damaged zone or fault core. This result supports the inference that protolith samples have short, poorly connected fractures that close more easily than the greater number of more throughgoing fractures found in the damaged zone and fault core. The results of these experiments show that, at the coreplug scale, the damaged zone is a region of higher permeability between the fault core and protolith. These results are consistent with previous field-based and in-situ investigations of fluid flow in faults formed in crystalline rocks. We suggest that, where present, the two-part damaged zone-fault core structure can lead to a bulk anisotropy in fault zone permeability. Thus, fault zones with well-developed damaged zones can lead to enhanced fluid flow through a relatively thin tabular region parallel to the fault plane, whereas the fault core restricts fluid flow across the fault. Although this study examined rocks collected from outcrop, correlation with in-situ flow tests indicates that our results provide inexact, but useful, insights into the hydromechanical character of faults found in the shallow crust.
Evans, J. P., Forster, C. B., and Goddard, J. V., 1997, Permeabilities of fault-related rocks and implications for fault-zone hydraulic structure, J. Structural Geology, v. 19, pp. 1393-1404. | <urn:uuid:8ed2c9fb-1a06-4b82-b25b-ac59ebe06843> | 2.765625 | 576 | Academic Writing | Science & Tech. | 38.609823 |
You are at: | Home | Introduction | The Men and Climate Change
The men have always emitted CO2 to the atmosphere, in fact, every time we exhale. But something happen that made men to triplicate (or more) the emission of CO2 and GHG (Greenhouse gases) to the environment: Energy sources like carbon and oil, used in the industries, since the 2 nd period of Industrial Revolution. First, with carbon for energy the water steam motor, and then the oil, and then full oil combustion, and. well, today. Every time you start your car you're producing a lot more CO2 that you should normally emit. And other gases too, like methane, produced by all the trash and chemical waste, or CFC (Chlorofluorocarbons), produced by the refrigerators or aerosols.
Greenhouse Effect top
Joseph Fourier in 1824 raised the theory of the Greenhouse Effect. but, what the hack is the Greenhouse effect?
The theory consist that some gases, like oxygen and nitrogen do not "absorb" the Sun's heat, but gases like carbon dioxide (CO2) do. These gases are the so called GHG (Greenhouse gases). The problem is that all that GHG accumulated in the atmosphere absorb a lot of the heat that arrive Earth, and the rest to surface. Well, all that energy in the GHG is moved inside and outside of the Earth, and when a lot of that heat is moved to the inside, is called "Greenhouse Effect".
If the emissions don't stop soon, the planet is going to absorb all the heat, and "shoot" it into the surface, causing Global Warming, or the GHG is going to cover the entire atmosphere, causing Global Dimming. The climate is a chain, if a factor is changed, it will be change for completely.
Skeptic people top
There is a lot of people that thinks this change is just a "causality" ("cause and effect") or a coincidence that all that CO2 and GHG is accumulated in the atmosphere, that men is just half-guilty for what's happening right now, because climate or weather is a too big system for be affected by the human. Finally is the person that thinks the climate is so fragile that just a little change in one of the gases in the atmosphere can be catastrophic. But this doesn't really matters, because is a fact that people must decrease the CO2 and GHG emissions. Look: since the beginning of the Industrial Revolution, the CO2 emissions have increased 100 ppm (Parts-per million) in just 100 years. Aren't you convinced? Well, other thing: Almost 70% of GHG is just water steam, and almost all people are convinced that water steam is inoffensive. We are just informing people of the real problem that Climate Change is causing now. Please, help, is easy, and you even save a lot of money.
Scientifics and Climate Change top
Maybe you have read that the scientists are not absolutely sure about the Climate Change, but the truth is that every institute that actually study about the climate is in agreement that climate is changing. Is almost impossible now that a scientist say that is 100% sure about the Climate Change is going to destroy the world, but all are in agreement that is actually dangerous. The facts that are not totally verified are: the temperature that the Earth is actually going to have and the zones are going to flood, because is pretty hard to determine.
The human is actually affecting the climate, but we still don't know if the world is getting warm or cold. We have to stop the gas emissions and energy consuming before the Clime Change effects increase more. If you want some good tips to know how to help stop Climate Change, go to 'Solutions' page, there you will know how to: Decrease your CO2 emissions, save energy, use new types of energy and products (like hybrid cars) that will decrease emissions and energy-waste, and more information about how to help. If you follow some of our advices, you will be helping to save the world (and saving lots and lots of money too). | <urn:uuid:d3cfab53-f2ac-4913-a7af-b373e37019de> | 2.984375 | 867 | Knowledge Article | Science & Tech. | 49.409348 |
1. Enter the left side of the
inequality into Y1.
2. Enter the right side of the inequality into
3. Enter the inequality into
Y3 using the inequality symbols found
under 2nd MATH (TEST).
Remember the Y1
and Y2 are found
Just as we saw in
Linear Inequalities, a small
bar appears representing the graph of the value
1, showing where the
inequality is true. In this case, the inequality
is true for 2 < x < 5. To determine
the "exact" values for the endpoints, use the
INTERSECT option (2nd
TRACE (CALC) #5 intersect) with
Looking at the table shows that the
alternate between being a 0
(false) and a 1 (true).
(Arrow to the right to "see" the column for
Remember that < will not "include" the | <urn:uuid:1e22ebe5-e21c-4afb-b8b7-5ce2ebd1bcf1> | 3.53125 | 200 | Tutorial | Science & Tech. | 62.605893 |
Nanotechnology as a whole is fairly simple to understand, but developing this universal technology into a nanorobot has been slightly more complicated.
To date, scientists have made significant progress but have not officially released a finished product in terms of a nanorobot that functions on an entirely mechanical basis.
Many of the nanobot prototypes function quite well in certain respects but are mostly or partly biological in nature, whereas the ultimate goal and quintessential definition of a nanorobot is to have the microscopic entity made entirely out of electromechanical components.
In fact, researchers anticipate that due to the complicated nature of their construction, nanobots will only fully emerge after several generations of partly-biological nanobot forerunners have been constructed in order to make them.
Nanorobots are essentially an adapted machine version of bacteria. They are designed to function on the same scale as both bacteria and common viruses in order to interact with and repel them from the human system.
Since they are so small that you can’t see them with your naked eye, they will also possibly be used to perform “miracle” functions such as cleaning your kitchen (“the kitchen that cleans itself!”) invisibly weaving fabric, cooking food slowly but steadily, and essentially performing other functions that humans could do, but—let’s face it—will probably be too lazy to do ourselves by the time these nanobots become functional.
Since the best way to create a nanobot is to use another nanobot, the problem lies in getting started. Humans are able to perform one nano-function at a time, but the thousands of varied applications required to construct an autonomous robot would be exceedingly tedious for us to execute by hand, no matter how high-tech the laboratory. So it becomes necessary to create a whole set of specialized machine-tools in order to speed the process of nanobot building.
Researchers have been chipping away at this problem for decades. In 1989 they discovered how to manually operate the system; a group of IBM engineers lined individual atoms up one by one until they had spelled out their company’s name.
In doing so they not only created the smallest business logo in history, but also discovered for themselves just how long and grueling the process of hand-building even a single nanobot would be. True, nanobots measure more like six atoms across, but they are far more complicated in design and need to be engineered in such a way that they are autonomous.
The ideal nanobot consists of a transporting mechanism, an internal processor and a fuel unit of some kind that enables it to function. The main difficulty arises around this fuel unit, since most conventional forms of robotic propulsion can’t be shrunk to nanoscale with current technology. Scientists have succeeded in reducing a robot to five or six millimeters, but this size still technically qualifies it as a macro-robot.
One possible solution is to adhere a fine film of radioactive particles to the nanobot’s body. As the particles decay and release energy the nanobot would be able to harness this power source; radioactive film can be enlarged or reduced to any scale without a drop in efficiency occurring.
Another nice side effect of this system is its ability to renew automatically. With the constant circulating nuclear energy it would supply, this fuel cell would never need to be replaced. This puts it several notches above solar cells or conventional battery packs of any size, which were previously the other two options being considered for equipping the nanorobot.
The other problem with constructing a successful nanorobot lies in breaking its materials down small enough. Metal that might be used for the robot’s construction behaves one way in relatively large quantities and a completely different way on the nanoscale—in fact, this is the entire basis for nanotechnology as a discipline.
Experts believe that silicon might make the ideal material, especially since it has been traditionally used for delicate electronics, particularly small computer parts. Microscopic silicon components called transducers have so far been successfully built into nanorobot legs.
Scientists are hard at work on designing a body built out of transducers; they are encountering slight problems in agreeing on what the final shape of the standard nanobot should be.
Very few researchers support the biped-humanoid design, since this has given test robots a strange, clumsy shuffle. The nanobot needs to be fast, aerodynamic and smooth-moving in order to complete its functions. Some people think that a spider-like body would work best, but many nanorobot researchers also think that a smaller version of the centipede might be best.
They hope that by equipping the nanobot with several sets of fast-moving legs and keeping its body low to the ground, they can create a quick, efficient machine that would also be suitably shaped for introduction into human blood vessels to perform functions such as clearing away built-up cholesterol or repairing tissue damage.
These tasks are key to the concept of a nanorobot, since it is anticipated that many of their most useful applications will be in the medical field. Doctors and researchers expect nanobots to be useful for a wide variety of things, since a robot this small can actually interact with materials on their molecular and atomic level. Because of this special capability, the nanobots can build or destroy particle by particle.
They could rebuild tissue molecules in order to close a wound, or rebuild the walls of veins and arteries to stop bleeding and save lives. They could make their way through the bloodstream to the heart and perform heart surgery molecule by molecule without many of the risks and discomfort associated with traditional open-heart operations. Likewise, researchers hope that nanorobots will have many miraculous effects on brain research, cancer research, and finding cures for difficult diseases like leukemia and AIDS.
Although standardized nanorobot production has not yet been fully realized, scientists are hard at work developing a system for constructing these tiny helpers. Chances are good that sometime in the next 25 years they will make their public debut. | <urn:uuid:8ba8712b-c098-450e-88a4-035bb0fc7dca> | 3.90625 | 1,261 | Knowledge Article | Science & Tech. | 26.274242 |
|A typical crank. |
Image: Hoangquan hientrang via wikimedia
The cranks of a bicycle are what connect the pedals to the front gears. They're lever arms that cyclists exert a force onto the end of, through the pedals, in order to turn the front gears. The front gears pull the chain which then spins the rear wheel, sending the bike speeding along.
|Z-Torque cranks. Image from z-torque.com|
The inventor, Glenn Coment, claims that his zig-zag design gives peddlers more leverage resulting in more power, but keeps the pedals at the same distance away from the center of rotation. However even a basic understanding of how levers work would show that this is impossible.
Glenn's nephew Jason is licensing the design to make them out of carbon fiber. In the fundraising video, he gives a brief physics lesson about how his cranks supposedly work.
“Pedaling your bike is similar to using a wrench to tighten or loosen a bolt. Any mechanic will tell you if you need more torque to loosen a stubborn bolt, just go get a bigger wrench. That’s because by moving your applied force further away from the pivot point, you gain more leverage," Jason Coment said.
So far he's right. Torque is the twisting force a rotating lever or wheel exerts on its axis. Increasing the length of a lever arm, like a wrench, exerts more torque on its bolt. The longer the lever arm, the more torque is produced by the same amount of force pushing on the end of the lever.
|A "second class lever" is the same kind|
of lever as a crank.
"That’s why with the patented Z-Torque bicycle crank we have solved that problem for you," Jason Coment claims. "You see we extended the crank arms past the length of a standard crank, giving you more leverage, but we then brought pedal back towards the axle to keep your rotation at the same diameter.”
He incorrectly claims that a cyclist can get more torque by having a crank arm that's "longer" but bends back towards the center, keeping the pedals the same distance away from the axis as a traditional straight crank. Levers don't work like that. It doesn't matter what shape the lever arm is, it only matters how far away the pedal is from the center of rotation.
“Having a wiggly line between one and the other doesn’t do anything about the torque," said David Gordon Wilson, an emeritus professor of engineering at MIT and author of Bicycling Science. “The tortuous form of the crank is just crazy.”
He said one could imagine welding a piece of aluminum straight between the pedal and the axis of rotation on the angled cranks. The leverage of the cranks would be the same whether the crank arm is straight, angled curved, or any other shape. The only thing that matters for leverage is how far the pedals, the source of the exerted force, is from the axis of rotation.
“This Z-crank has no redeeming features whatsoever,” Wilson said.
Coment's design isn't new, designs for curved or angled cranks have been around since the 1930s. He's had prototypes for his Z-Torque cranks since 1995, a patent on them since 1999, and a website selling aluminum versions since at least 2009. Recently he's been trying to expand and make carbon fiber versions. In September of last year, Coment launched a Kick-starter project to raise $50,000 to buy tools and equipment, but missed his goal by more than $47,000. He's now trying again, on a different crowd-funding website, "Rock the Post" with a more modest $7,500 goal.
The website also claims that the cranks give riders "Less perceived effort to pedal." In the medical world, I think they would call that a "placebo." | <urn:uuid:6ee6f53e-372b-429e-8a3d-39e76e769382> | 3.453125 | 830 | Nonfiction Writing | Science & Tech. | 64.406823 |