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Im doing this study and i have this question which I'm not 100% sure on, got me pretty stumped. anyone think they can help me?!
When a bowstring is pulled back in preparation in preparation for shooting an arrow, the string behaves like a spring. Suppose the string is drawn 0.700 m and held with a force of 450 N.
(a) What is the elastic constant of the bow?
(b) How much energy is stored in the string?
(c) Where does the energy stored in the string come from? | <urn:uuid:be100361-b747-432b-aa82-bae6a31a0f9c> | 3.0625 | 114 | Q&A Forum | Science & Tech. | 87.800794 |
Many curiosity values in atmospheric physics take on new life in the blogosphere. One of them is the value in Kiehl & Trenberth 1997 for the “atmospheric window” flux:
Here is the update in 2009 by Trenberth, Fasullo & Kiehl:
The “atmospheric window” value is probably the value in KT97 which has the least attention paid to it in the paper, and the least by climate science. That’s because it isn’t actually used in any calculations of note.
What is the Atmospheric Window?
The “atmospheric window” itself is a term in common use in climate science. The atmosphere is quite opaque to longwave radiation (terrestrial radiation) but the region from 8-12 μm has relatively few absorption lines by “greenhouse” gases. This means that much of the surface radiation emitted in this wavelength region makes it to the top of atmosphere (TOA).
The story is a little more complex for two reasons:
- The 8-12μm region has significant absorption by water vapor due to the water vapor continuum. See Visualizing Atmospheric Radiation – Part Ten – “Back Radiation” for more on both the window and the continuum
- Outside of the 8-12 region there is some transparency in the atmosphere at particular wavelengths
The term in KT97 was not clearly defined, but what we are really interested in is what value of surface emitted radiation is transmitted through to TOA – from any wavelength, regardless of whether it happens to be in the 8-12 μm region.
Calculating the Value
One blog that I visited recently had many commenters whose expectation was that upward emitted radiation by the surface would be exactly equal to the downward emitted radiation by the atmosphere + the “atmospheric window” value.
To illustrate this expectation let’s use the values from figure 2 (the 2009 paper) – note that all of these figures are globally annually averaged:
- Upward radiation from the surface = 396 W/m²
- Downward radiation from the atmosphere (DLR or “back radiation”) = 333 W/m²
- These commenters appear to think the atmospheric window value is probably really 63 W/m² – and thus the surface and lower atmosphere are in a “radiative balance”
This can’t be the case for fairly elementary reasons – but let’s look at that later.
In Visualizing Atmospheric Radiation – Part Two I describe the basics of a MATLAB line by line calculation of radiative transfer in the atmosphere. And Part Five – The Code gives the specifics, including the code.
Running v0.10.4 I used some “standard atmospheres” (examples in Part Twelve – Heating Rates) and calculated the flux from the surface to TOA:
- Tropical – 28 W/m² (52 W/m²)
- Midlatitude summer – 40 W/m² (58 W/m²)
- Midlatitude winter – 59 W/m² (62 W/m²)
- Subarctic summer – 50 W/m² (61 W/m²)
- Subartic winter – 55 W/m² (56 W/m²)
- US Standard 1976 – 65 W/m² (72 W/m²)
These are all clear sky values, and the values in brackets are the values calculated without the continuum absorption to show its effect. Clear skies are, globally annually averaged, about 38% of the sky.
These values are quite a bit lower than the values found in the new paper we discuss in this article, and at this stage I’m not sure why.
This paper is: Outgoing Longwave Radiation due to Directly Transmitted Surface Emission, Costa & Shine (2012):
This short article is intended to be a pedagogical discussion of one component of the KT97 figure [which was not updated in Trenberth et al. (2009)], which is the amount of longwave radiation labeled ‘‘atmospheric window.’’ KT97 estimate this component to be 40 W/m² compared to the total outgoing longwave radiation (OLR) of 235 W/m²; however, KT97 make clear that their estimate is ‘‘somewhat ad hoc’’ rather than the product of detailed calculations. The estimate was based on their calculation of the clear-sky OLR in the 8–12 μm wavelength region of 99 W/m² and an assumption that no such radiation can directly exit the atmosphere from the surface when clouds are present. Taking the observed global-mean cloudiness to be 62%, their value of 40 W/m² follows from rounding 99 x (1 – 0.62).
Presumably the reason why KT97, and others, have not explicitly calculated this term is that the methods of vertical integration of the radiative transfer equation in most radiation codes compute the net effect of surface emission and absorption and emission by the atmosphere, rather than each component separately. In the calculations presented here we explicitly calculate the upward irradiance at the top of the atmosphere due to surface emission: we will call this the surface transmitted irradiance (STI).
In other words, the value in the KT97 paper is not needed for any radiative transfer calculations, but let’s try and work out a more accurate value anyway.
First, how the clear sky values vary with latitude:
Figure 3 – Clear sky values
Note that the dashed line is “imaginary physics”. The water vapor continuum exists but it is very interesting to see what effect it contributes. This is seen by calculating the effect as if it didn’t exist.
We see that in the tropics STI is very low. This is because the effect of the continuum is dependent on the square of the water vapor concentration, which itself is strongly dependent on the temperature of the atmosphere.
The continuum absorption is so strong in the tropics that STIclr in polar regions (which is only modestly influenced by the continuum) is typically 40% higher than the tropical values.Figure 3 shows the zonal and annual mean of the STIclr to emphasize the role of the continuum. The STIclr neglecting the continuum (dash-dotted line) is generally more than 80 W/m² at all latitudes, with maxima in the northern subtropics (mostly associated with the Sahara desert), but with little latitudinal gradient throughout the tropics and subtropics; the tropical values are reduced by more than 50% when the continuum is included (dashed lines). The effect of the continuum clearly diminishes outside of the tropics and is responsible for only around a 10% reduction in STIclr at high latitudes.
Interestingly, these more detailed calculations yield global-mean values of STIclr of 66 and 100 W/m², with and without the continuum, very close to the values (65 and 99 W/m²) computed using the single global-mean profile, in spite of the potential nonlinearities due to the vapor pressure–squared dependence of the self-continuum.
For people unfamiliar with the issue of non-linearity – if we take an “average climate” and do some calculations on it, the result will usually be different from taking lots of location data, doing the calculations on each, and averaging the results of the calculations. Climate is non-linear. However, in this case, the calculated value of STIclr on an “average climate” does turn out to be similar to the average of STIclr when calculated from climate values in each part of the globe.
We can appreciate a little more about the impact of the continuum on this atmospheric window if we look at the details of the calculation vs wavelength:
Figure 4 – Highlighted orange text added
Here is the regional breakdown:
Figure 5 – Clear and All-sky values – Orange highlighted text added
Note that conventionally in climate science clear sky results are the climate without clouds (i.e., a subset), whereas ‘cloudy sky’ results are the results with both clear and cloudy (i.e., all values).
The authors comment:
When including clouds, the STI is reduced further (Fig. 2c) because clouds absorb strongly throughout the infrared window. In regions of high cloud amount, such as the midlatitude storm tracks, the STI is reduced from a clear-sky value of 70 W/m² to less than 10 W/m². As expected, values are less affected in desert regions. The subtropics are now the main source of the global mean STI. The effect of clouds is to reduce the STI from its clear-sky value of 66 W/m² by two-thirds to a value of about 22 W/m²
Clear-sky STI (STIclr) is calculated by using the line by line model Reference Forward Model (RFM) version 4.22 (Dudhia 1997) in the wavenumber domain 10–3000 cm-1 (wavelengths 3.33–1000 mm) at a spectral resolution of 0.005 cm-1. The version of RFM used here incorporates the Clough–Kneizys–Davies (CKD) water vapor continuum model (version 2.4); although this has been superseded by the MT-CKD model, the changes in the midinfrared window (see, e.g., Firsov and Chesnokova 2010) are rather small and unlikely to change our estimate by more than 1 W/m²..
..Irradiances are calculated at a spatial resolution of 10° latitude and longitude using a climatology of annual mean profiles of pressure, water vapor, temperature, and cloudiness described in Christidis et al. (1997). Although slightly dated, the global-mean column water amount is within about 1% of more recent climatologies.
Carbon dioxide, methane, and nitrous oxide are assumed to be well mixed with mixing ratios of 365, 1.72, and 0.312 ppmv, respectively. Other greenhouse gases are not considered since their radiative forcing is less than 0.4 W/m² (e.g., Solomon et al. 2007; Schmidt et al. 2010); we have performed an approximate estimate of the effect of 1 ppbv of chlorofluorocarbon 12 (CFC12) (to approximate the sum of all halocarbons in the atmosphere) on the STIclr and the effect is less than 1%.
Likewise, aerosols are not considered. It is the larger mineral dust particles that are more likely to have an impact in this spectral region; estimates of the impact of aerosol on the OLR are typically around 0.5 W/m² (e.g., Schmidt et al. 2010). The impact on the STI will depend on, for example, the height of aerosol layers and the aerosol radiative properties and is likely a larger effect than the CFCs if they are mostly at lower altitudes; this is discussed further in section 4. The surface is assumed to have an emittance of unity.
And later in assumptions:
Our assumption that the surface emits as a blackbody could also be examined, using emerging datasets on the spectral variation of the surface emittance (which can deviate significantly from unity and be as low as 0.75 in the 1000–1200 cm-1 spectral region, in desert regions; e.g., Zhou et al. 2011; Vogel et al. 2011). Some decision would need to made, then, as to whether or not infrared radiation reflected by surfaces with emittances less than zero should be included in the STI term as this reflection partially compensates for the reduced emission. Although locally important, the effect of nonunity emittances on the global-mean STI is likely to be only a few percent.
The point here is that if we consider the places with emissivity less than 1.0 should we calculate the value of flux reaching TOA without absorption from both surface emission AND surface reflection? Or just surface emission? If we include the reflected atmospheric radiation then the result is not so different. This is something I might try to demonstrate in the Visualizing Atmospheric Radiation series.
As is standard in radiative transfer calculations, spherical geometry is taken into consideration via the diffusivity approximation, as outlined in this comment.
Why The Atmosphere and The Surface cannot be Exchanging Equal Amounts of Radiation
This is quite easy to understand. I’ll invent some numbers which are nice round numbers to make it easier.
Let’s say the surface radiates 400 and has an emissivity of 1.0 (implying Ts=289.8 K). The atmosphere has an overall transmissivity of 0.1 (10%). That means 360 is absorbed by the atmosphere and 40 is transmitted to TOA unimpeded. For the radiative balance required/desired by the earlier mentioned commenters the atmosphere must be emitting 360.
Thus, under these fictional conditions, the surface is absorbing 360 from the atmosphere. The atmosphere is absorbing 360 from the surface. Some bloggers are happy.
Now, how does the atmosphere, with a transmissivity of 10%, emit 360? We need to know the atmosphere’s emissivity. For an atmosphere – a gas – energy must be transmitted, absorbed or reflected. Longwave radiation experiences almost no reflection from the atmosphere. So we end up with a nice simple formula:
Transmissivity, t = 100% – absorptivity
Absorptivity, a = 90%.
What is emissivity? It turns out, explained in Planck, Stefan-Boltzmann, Kirchhoff and LTE, that emissivity = absorptivity (for the same wavelength).
Therefore, emissivity of the atmosphere, e = 90%.
So what temperature of the atmosphere, Ta, at an emissivity of 90% will radiate 360? The answer is simple (from the Stefan Boltzmann equation, E=eσTa4, where σ=5.67×10-8):
Ta = 289.8 K
So, if the atmosphere is exactly the same temperature as the surface then they will exchange equal amounts of radiation. And if not, they won’t. Now the atmosphere is not at one temperature so it makes it a bit harder to work out what the right temperature is. And the full calculation comes from the radiative transfer equations, but the same conclusion is reached with lots of maths – unless the atmosphere is at the same temperature as the surface then they will not exchange equal amounts of radiation.
The authors say:
This study presents what we believe to be the most detailed estimate of the surface contribution to the clear and cloudy-sky OLR. This contribution is called the surface transmitted irradiance (STI). The global- and annual- mean STI is found to be 22 W/m². The purpose of producing the value is mostly pedagogical and is stimulated by the value of 40 W/m² shown on the often-used summary figures produced by KT97 and Trenberth et al. (2009).
Earth’s Annual Global Mean Energy Budget, Kiehl & Trenberth, Bulletin of the American Meteorological Society (1997) – free paper
Earth’s Global Energy Budget, Trenberth, Fasullo & Kiehl, Bulletin of the American Meteorological Society (2009) – free paper
Outgoing Longwave Radiation due to Directly Transmitted Surface Emission, Costa & Shine, Journal of the Atmospheric Sciences (2012) – paywall paper | <urn:uuid:6a0ee484-7b19-408e-ac78-725428b86bbb> | 3.484375 | 3,308 | Personal Blog | Science & Tech. | 49.507164 |
University Consortium for Atmospheric Research (UCAR)
The Extreme Weather Sourcebook is a database maintained by the Societal Impacts Program (SIP) at NCAR of statistics on extreme weather events. The Sourcebook is intended as a resource for researchers, policy makers, the media, and the general public, among other users. This page from the Sourcebook showcases data on tornado damages as total losses for the years 1950-2009 in the United States.
This description of a site outside SERC has not been vetted by SERC staff and may be incomplete or incorrect. If you
have information we can use to flesh out or correct this record let us know. | <urn:uuid:3221447c-95be-4fb8-9a41-4d1ab3a40267> | 2.78125 | 134 | Knowledge Article | Science & Tech. | 37.261664 |
DO YOU DO WITH A BEAR IN THE NEIGHBORHOOD?
Last week I heard about a dramatic environmental observation. The caller, Teresa, was a former colleague who had heard all kinds of environmental tales from people calling or emailing over the years when we worked together. So when she said, "I just saw something in our yard that I thought you should know about," I was attentive.
bears live around here?" she asked. "Because I just saw one
walking through our yard!" I responded that black bears had been
reported in South Carolina on rare occasions, but very seldom in residential
areas, and then asked, "Did you get a photograph?"
The American black bear is one of eight species of bears that inhabit the earth today, and is among the least threatened environmentally. The cave bear, which went extinct less than 10,000 years ago, would have made nine. According to "Walker's Mammals of the World" by R. M. Nowak (1999, Johns Hopkins University Press, Baltimore), bears are divided into subgroups based on the closeness of their evolutionary relationships. One taxonomic scheme places the American black bear in a group with brown (including the grizzlies), Asiatic black, polar, sun, and sloth bears. The spectacled bear of South America and the panda of China are alone in separate subfamilies.
seem to be doing well, but some species of bears are probably not far
from becoming extinct in the wild. The Malayan sun bear is the smallest
bear in the world, seldom reaching 150 pounds. Because of overhunting,
logging of forests, and poorly regulated laws, sun bears are declining
throughout their Asian range. Another Asian species, the sloth bear, is
a shaggy black beast with a light-colored V or Y on its chest. These bears
eat termites from large mounds by sucking them up like a vacuum cleaner.
Estimates are that fewer than 10,000 remain in the wild, yet up to 1,000
are killed each year for the absurd tradition of eating their gall bladders.
Polar bear habitat is disappearing at an alarming rate. If the current environmental trajectory continues, it will mean the end of the species. Unless public attitudes about habitat protection, global warming, and the importance of letting other species share the planet with us change--and soon--most of today's bears may shortly join the extinct cave bear in that black hole called extinction.
you do if you see a black bear walking through your yard? Let it wander
wherever it chooses or report it to animal control? To me, either option
sounds fine. Just don't feed it or try to treat it like a pet. Getting
to see a free-ranging bear up close, especially outside of Great Smoky
Mountains National Park or other areas where they are protected, makes
for a memorable experience. The thrill of seeing a black bear anywhere
would surpass most other wildlife sightings, and to know that enough of
them are still around for one to amble through a suburban neighborhood
is kind of exciting. | <urn:uuid:15397127-b47f-4f8f-9edd-7cda43ce7aaf> | 2.765625 | 651 | Personal Blog | Science & Tech. | 55.919714 |
Remember in Jurassic Park when they got dinosaur DNA from an ancient mosquito’s stomach? Well, if they had been interested in dinosaur proteins, they only had to look at a dinosaur bone.
Dinosaur bones are at least 65 million years old. And all of the meat has turned to stone. Over this amount of time and with this much abuse, scientists thought no DNA or proteins could survive. They were wrong.
Recently, scientists were able to pull proteins out of a T. rex bone. Now they have done some additional work that suggests dinosaurs are closely related to birds. It is amazing that our technology has become so sensitive that we can examine dinosaur proteins. | <urn:uuid:3857fd43-a238-4918-89ae-7edb86e12353> | 3.390625 | 136 | Personal Blog | Science & Tech. | 58.679966 |
Old Faithful Geyser in Yellowstone National Park, Wyoming, derives its name and its considerable fame from the regularity (and beauty) of its eruptions. As they do with most geysers in the park, rangers post the predicted tiems of eruptions on signs nearby and people gather beforehand to witness the show. R.A. Hutchinson, a park geologist, collected measurements of the eruption durations (X, in minutes) and the subsequent intervals before the next eruption (Y, in minutes) over an 8--day period.
Weisberg, S. (1985). Applied Linear Regression, John Wiley \& Sons, New York, p. 231.
Documentation reproduced from package Sleuth2, version 1.0-7. License: GPL (>= 2) | <urn:uuid:7eae8e4b-b66b-4f54-8b4e-edebb11ec099> | 2.6875 | 164 | Knowledge Article | Science & Tech. | 57.38428 |
Computers powerful enough to model the electrical activity of the whole human brain, or to predict climatic disasters in time to prepare for them, will be available within four years. This claim was made independently by two supercomputer makers this month as they announced plans to build forerunners of such computers.
Such computing problems are known as the Grand Challenges. They also include modelling the flow of turbulent fluids, and the Human Genome Project, an international programme to discover the entire genetic blueprint of human beings.
Grand Challenges require such huge quantities of data to be processed that even today's fastest computers would need decades to finish the calculations. But machines which can perform a million million calculations a second, a rate known as a teraflop, should be able to cut this time to a few days.
Parystec, a small German company based at Aachen, last week revealed its plans ...
To continue reading this article, subscribe to receive access to all of newscientist.com, including 20 years of archive content. | <urn:uuid:4ef86ca5-9b65-4a25-a3a6-9eb9f0f3f558> | 3.84375 | 209 | Truncated | Science & Tech. | 40.656364 |
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Writes a string to a file
STRFILE(<cCharacterstring>, <cFile>, [<lOverwrite>],
[<nOffset>], [<lCutOff>]) --> nRecordedByte
<cCharacterstring> Designates the character string to write to a
<cFile> Designates a file name. Drive and path designations are
permitted, but no wildcards.
<lOverwrite> If not designated or designated as .F., determines
whether or not a new file is created. When .T., it writes to an
existing file. The default is create new file (.F.).
<nOffset> Designates an offset within the file from which the
<cCharacterstring> string is to be written. The default is End of file.
<lCutOff> When this optional parameter is designated as .T., the
function truncates the file if data written ends before the last file
byte. The default is no cut off (.F.).
STRFILE() returns the actual number of bytes written.
This function provides another capability besides writing the contents
of a string to a file. In contrast to the CA-Clipper Fxxxx() functions,
only one function call is necessary to write data to a file. However,
it can result in some speed disadvantages, since files acted on by
STRFILE() cannot be held open.
If the target file is unavailable, the STRFILE() function always creates
. The attribute to create a new file, can be designated with the
. As recommended with the share mode, reads and writes from
other network programs should be locked out with SETSHARE() for this
period of time.
. This function acknowledges the setting for CSETSAFETY().
. Add to the end of a file:
? STRFILE("ABCDEFGH", "TEST.TXT", .T.) // Result: 8
. A file with drive and path designations, result: 10:
? STRFILE("0123456789", "C:\TEXT\TEST.TXT", .T.)
. Data in an existing file is overwritten from position 20 with
a designated string:
? STRFILE("NANTUCKET", "TEST.TXT", .T., 20) // Result: 9
. A 5-character string is written starting at position 10 in an
existing file 20-characters long. Since the final parameter is
specified as .T. once, and specified as .F. once, you see different
? STRFILE(REPLICATE("X", 20), "TEST.TXT")
? STRFILE("AAAAA", "TEST.TXT", .T., 10, .F // "XXXXXXXXXXAAAAAXXXXX"
? STRFILE("AAAAA", "TEST.TXT", .T., 10, .T // "XXXXXXXXXXAAAAA"
See Also: FILESTR() SETSHARE() SETFCREATE() CSETSAFETY()
Online resources provided by: http://www.ousob.com --- NG 2 HTML conversion by Dave Pearson | <urn:uuid:ee4d4ff7-9d34-4056-b04e-5c10dab9475a> | 3.140625 | 687 | Documentation | Software Dev. | 65.647003 |
Differential & Selective Bacterial Growth Media
MacConkey's, Mannitol Salt & Blood Agar
LAB NOTES from Science Prof Online
Bacterial growth media are used in labs to provide nutrients, moisture and a surface for bacteria to grow on. Some media will grow just about any type of bacteria, whereas other types are specialized to only grow certain microbes and to often provide additional information that can help identify microbes.
Selective Bacterial Growth Media
Specialized media can be selective; formulated to grow only certain microbes while inhibiting
Article Summary: Agar media are used to grow bacteria in the laboratory. There are also specialized media that provide information on the identity of the microbes growing.
Differential & Selective Bacterial Growth Agar
You have free access to a large collection of materials used in a college-level introductory microbiology course. The Virtual Microbiology Classroom provides a wide range of free educational resources including PowerPoint Lectures, Study Guides, Review Questions and Practice Test Questions.
1. Sterile Blood Agar plate, 2. BAP alpha hemolysis; 3 & 4. beta hemolysis; 5. gamma would show growth on top of the media, but when viewed from the bottom, shows no change in the red color of the medium.
Media Both Selective & Differential
Some specialized media are both selective and differential, others are either or. The MacConkey’s and Mannitol Salt described above are both selective and differential bacterial growth media.
In addition to MacConkey’s agar only growing Gram-negative bacteria (the selective aspect of the medium), MAC has special additives that cause lactose fermenting bacteria (microbes that can metabolize the sugar lactose) to grow in pink colonies, whereas Gram-negative non-lactose fermenting bacteria will grow in colorless colonies. Mannitol Salt is also both selective and differential. This medium only grows salt-loving bacteria (so it is selective). In addition, bacteria that grow on MSA that can ferment mannitol, a sugar alcohol, will turn the medium from its original pink color to a bright, neon yellow. This color change is clinically significant in that Staphylococcus aureus, a disease-causing bacterium, is a mannitol fermenter, while S. epidermidis, a beneficial bacteria that normally grows on the surface of the skin and mucous membranes, is not a mannitol fermenter.
Sources and Helpful Links
- Bauman, R. (2005) Microbiology. Pearson Benjamin Cummings.
- Schauer, Cynthia (2009) Applied Microbiology HCR120 Laboratory Manual, Kalamazoo Valley Community College.
1. Sterile plate of MacConkey's Agar (MAC); 2, LAC- Salmonella on left, LAC+ E. coli on right, both plates are MAC; 3. Happy LAC+ microbe on MAC; 4. Lac+, Gram- microbe growing on MAC, 5. Colony directly under word "MacConkey's" os a colorless non-lactose fermenter. Click here for more MacConkey's Agar Images.
1. Sterile plate of Mannitol Salt Agar (MSA), 2. Staphylococcus epidermidis growing on MSA, 3 Mannitol + bacteria on left plate, Mannitol - bacteria on right plate, both plates are MSA; 4. Mannitol + bacteria on left, Mannitol - bacteria on right, both plated together on one MSA plate; 5. Same plate from bottom.
Page last updated: 4/2013
Portions of this article originally appeared on Suite101 online magazine.
VIDEO: How to Interpret MacConkey's Agar (MAC)
Bacterial Growth Medium
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VIDEO: How to Interpret Mannitol Salt Agar (MSA) Specialized Bacterial Growth Medium
VIDEO: How to Interpret
Blood Agar (BAP) Specialized
Bacterial Growth Medium
the growth of others. For example MacConkey’s (MAC) selective bacterial growth medium will only grow Gram-negative bacteria. Mannitol Salt medium (MSA) will only grow halophilic (salt-loving) bacteria, such as Staphylococcus & Micrococcus. While selective media do not typically identify bacteria down to the species level, they do help narrow down the search.
Differential Bacterial Growth Media
Differential media typically display some type color change in the presence of certain bacteria. Blood Agar (BAP) is another type of differential medium. BAP is rich in nutrients and contains sheep blood. It is not selective, and will grow many different types of microbes. Blood agar medium is, however, differential. It will display a color change in the presence of bacteria that can lyse (break down) the red blood cells in the medium. Bacteria that grow on this medium will produce one of three hemolytic patterns:
- alpha-hemolysis = partial lysis of the red blood cells, which gives the medium a bruised appearance
- beta-hemolysis = complete lysing of the red blood cells, which turns the agar from red to clear
- gamma-hemolysis = no lysis of the red blood cells and no change to the appearance of the mediums color
The beta-hemolytic bacteria Streptococcus pyogenes, is a pathogen that will completely break down the red blood cells in this agar, causing clear areas to form around its colonies growing on BAP.
Sterile MacConkey's, Mannitol Salt & Blood Agar (clockwise from top left) | <urn:uuid:3e6a32b6-7156-4846-9659-07fed261850c> | 2.984375 | 1,214 | Knowledge Article | Science & Tech. | 32.750738 |
[Carl Sagan speaking:] “There are in fact 100 billion galaxies, each of which contains something like a 100 billion stars.” Well, Carl Sagan would have loved to get the latest estimate of our galaxy’s planet count.
Caltech astronomers set their sites on a star called Kepler 32. It’s an M dwarf star, a class that’s smaller and cooler than our sun, and accounts for about three quarters of the stars in the Milky Way. But what’s really cool about this particular star, from the astronomers’ point of view, is that its five planets orbit in a plane that the Kepler telescope sees edge on. So the star’s light dims each time a planet passes between it and the scope, which makes the planets easier to detect.
Now, taking into account the percentage of M dwarf systems that lie in a similar edge on orientation, and the number of planetary systems the Kepler telescope has already detected, the researchers figure our galaxy is host to at least 100 billion planets. Their calculations are served up in The Astrophysical Journal. [Link to come.]
Many of those planets may be the size of Earth. But we’re the only planet that produced Carl Sagan.
[The above text is a transcript of this podcast.] | <urn:uuid:8931d6cb-11d6-43f6-a5b2-7320883c317d> | 3.59375 | 267 | Truncated | Science & Tech. | 61.552839 |
|Previous||UML Classes||Table of Contents||UML Packages||Next|
A type constrains the values represented by a typed element.
PackageableElement (from Kernel ) on page 111
A type serves as a constraint on the range of values represented by a typed element. Type is an abstract metaclass.
No additional attributes
No additional associations
No additional constraints
The query conformsTo() gives true for a type that conforms to another. By default, two types do not conform to each other.
This query is intended to be redefined for specific conformance situations.
conformsTo(other: Type): Boolean;conformsTo = false
A type represents a set of values. A typed element that has this type is constrained to represent values within this set.
No general notation | <urn:uuid:e61aeabf-ab2e-4fc9-bd41-2ea3cceb92d7> | 2.6875 | 171 | Documentation | Software Dev. | 33.911665 |
This photo, taken from space, shows the Southeast Pacific Ocean on the left, with patches of stratocumulus clouds along the coast of South American. Moving to the right (east) one can see the low lying coastal Atacama Desert and the Andes Mountain Range.
Click on image for full size
Image Courtesy of NASA
What are VOCALS' scientific questions?
The VOCALS scientists are very curious people. They want to find answers to three main questions:
How do small particles in the air affects the formation of stratus clouds and the drizzle they produce?
How do the oceans, atmosphere, and land affect each other in the Southeast Pacific region?
How well do measurements taken by instruments on satellites
far above the Earth compare to those made on ships, airplanes, and on the land?
All of these questions must be answered! They are very important to scientists. VOCALS' results will help us to know how the whole Earth's climate is influenced by the Southeast Pacific region.
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Scientists must work very hard! It will take time for them to understand the information they collected during VOCALS. They must study the measurements and use them to improve their models of clouds,...more
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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.
2009 April 10
Explanation: These two frames, taken with a video camera and a telescope, reveal remarkable details of the International Space Station (ISS) orbiting some 350 kilometers above planet Earth. Recorded during last month's visit by the crew of shuttle orbiter Discovery on mission STS-119, the pictures show extended solar arrays glinting in bright sunlight against a dark sky. They also likely capture the blurred image of a spacewalking astronaut during the mission's EVA-2 (Extravehicular Activity-2)! The astronaut is installing equipment along one of the station's truss assemblies. Astronomer Ralf Vandebergh, who often images the ISS during its favorable passes through Dutch skies, comments that no other bright ISS structures occupy the position indicated in the inset, and that a reflective, white-suited astronaut would be visible against the truss and correspond to the bright blur. Vandebergh notes that the timing and location further suggest the spacewalker is STS-119 astronaut Joseph Acaba.
Authors & editors:
Jerry Bonnell (UMCP)
NASA Official: Phillip Newman Specific rights apply.
A service of: ASD at NASA / GSFC
& Michigan Tech. U. | <urn:uuid:529567a3-03e9-42fa-96a3-38462c91af79> | 2.984375 | 283 | Knowledge Article | Science & Tech. | 32.271119 |
Structured Query Language (SQL)
The SQL Reference Guide is a multipart document designed to introduce the reader to the basics of SQL. In most Relational Database Management Systems [RDBMS] that use Structured Query Language [SQL] the following is the standard syntax. There are differences between SQL Server, MySQL, Oracle, PostgreSQL, and any other that might be in use. To keep the document consistent everything is written for SQL Server and examples from other database engines will be provided.
SQL has a few major clauses that are necessary in order to retrieve information from the database. Some of them are required others are optional. Every SQL query must contain a SELECT and a FROM clause. Everything else is optional however the WHERE clause is necessary to control what data will be returned from the query. | <urn:uuid:12ec4ee6-1e3e-46b2-98c8-9b180e62173f> | 3.71875 | 161 | Documentation | Software Dev. | 35.785989 |
There are five classes in an inheritance diagram, four of which represent synchronous servers of four types:
+------------+ | BaseServer | +------------+ | v +-----------+ +------------------+ | TCPServer |------->| UnixStreamServer | +-----------+ +------------------+ | v +-----------+ +--------------------+ | UDPServer |------->| UnixDatagramServer | +-----------+ +--------------------+
Note that UnixDatagramServer derives from UDPServer, not from UnixStreamServer -- the only difference between an IP and a Unix stream server is the address family, which is simply repeated in both Unix server classes.
Forking and threading versions of each type of server can be created using the ForkingMixIn and ThreadingMixIn mix-in classes. For instance, a threading UDP server class is created as follows:
class ThreadingUDPServer(ThreadingMixIn, UDPServer): pass
The mix-in class must come first, since it overrides a method defined in UDPServer. Setting the various member variables also changes the behavior of the underlying server mechanism.
To implement a service, you must derive a class from BaseRequestHandler and redefine its handle() method. You can then run various versions of the service by combining one of the server classes with your request handler class. The request handler class must be different for datagram or stream services. This can be hidden by using the handler subclasses StreamRequestHandler or DatagramRequestHandler.
Of course, you still have to use your head! For instance, it makes no sense to use a forking server if the service contains state in memory that can be modified by different requests, since the modifications in the child process would never reach the initial state kept in the parent process and passed to each child. In this case, you can use a threading server, but you will probably have to use locks to protect the integrity of the shared data.
On the other hand, if you are building an HTTP server where all data is stored externally (for instance, in the file system), a synchronous class will essentially render the service "deaf" while one request is being handled - which may be for a very long time if a client is slow to receive all the data it has requested. Here a threading or forking server is appropriate.
In some cases, it may be appropriate to process part of a request synchronously, but to finish processing in a forked child depending on the request data. This can be implemented by using a synchronous server and doing an explicit fork in the request handler class handle() method.
Another approach to handling multiple simultaneous requests in an environment that supports neither threads nor fork() (or where these are too expensive or inappropriate for the service) is to maintain an explicit table of partially finished requests and to use select() to decide which request to work on next (or whether to handle a new incoming request). This is particularly important for stream services where each client can potentially be connected for a long time (if threads or subprocesses cannot be used).
See About this document... for information on suggesting changes. | <urn:uuid:08f765ad-0a8a-46cf-83df-f5e3eaac2257> | 3.234375 | 644 | Documentation | Software Dev. | 35.526051 |
Conic Sections/Types of Conic Sections
A conic section is defined as the locus of all points where the distance from the point to the focus and the point to a straight line known as the directrix is a constant ratio. This ratio is known as the eccentricity of the section.
- If the ratio is 1, the section is known as a parabola.
- If the ratio is less than one, the section is an ellipse. A circle is a special case of an ellipse.
- If the ratio is greater than one, the section is hyperbola.
All conic sections can be formed by taking the intersection of a cone and a plane, hence the name.Last modified on 24 February 2011, at 13:24 | <urn:uuid:51d6b34f-aad4-4d1a-8853-bcd0b54dd827> | 3.78125 | 160 | Knowledge Article | Science & Tech. | 65.195122 |
The sched module defines a class which implements a general purpose event scheduler:
class class sched.scheduler(timefunc, delayfunc)
The scheduler class defines a generic interface to scheduling events. It needs two functions to actually deal with the “outside world” — timefunc should be callable without arguments, and return a number (the “time”, in any units whatsoever). The delayfunc function should be callable with one argument, compatible with the output of timefunc, and should delay that many time units. delayfunc will also be called with the argument 0 after each event is run to allow other threads an opportunity to run in multi-threaded applications.
>>> import sched, time >>> s = sched.scheduler(time.time, time.sleep) >>> def print_time(): print "From print_time", time.time() ... >>> def print_some_times(): ... print time.time() ... s.enter(5, 1, print_time, ()) ... s.enter(10, 1, print_time, ()) ... s.run() ... print time.time() ... >>> print_some_times() 930343690.257 From print_time 930343695.274 From print_time 930343700.273 930343700.276
In multi-threaded environments, the scheduler class has limitations with respect to thread-safety, inability to insert a new task before the one currently pending in a running scheduler, and holding up the main thread until the event queue is empty. Instead, the preferred approach is to use the threading.Timer class instead.
>>> import time >>> from threading import Timer >>> def print_time(): ... print "From print_time", time.time() ... >>> def print_some_times(): ... print time.time() ... Timer(5, print_time, ()).start() ... Timer(10, print_time, ()).start() ... time.sleep(11) # sleep while time-delay events execute ... print time.time() ... >>> print_some_times() 930343690.257 From print_time 930343695.274 From print_time 930343700.273 930343701.301
scheduler instances have the following methods and attributes:
scheduler.enterabs(time, priority, action, argument)
Schedule a new event. The time argument should be a numeric type compatible with the return value of the timefunc function passed to the constructor. Events scheduled for the same time will be executed in the order of their priority.
Executing the event means executing action(*argument). argument must be a sequence holding the parameters for action.
Return value is an event which may be used for later cancellation of the event (see cancel()).
scheduler.enter(delay, priority, action, argument)
Schedule an event for delay more time units. Other then the relative time, the other arguments, the effect and the return value are the same as those for enterabs().
Remove the event from the queue. If event is not an event currently in the queue, this method will raise a ValueError.
Return true if the event queue is empty.
Run all scheduled events. This function will wait (using the delayfunc() function passed to the constructor) for the next event, then execute it and so on until there are no more scheduled events.
Either action or delayfunc can raise an exception. In either case, the scheduler will maintain a consistent state and propagate the exception. If an exception is raised by action, the event will not be attempted in future calls to run().
If a sequence of events takes longer to run than the time available before the next event, the scheduler will simply fall behind. No events will be dropped; the calling code is responsible for canceling events which are no longer pertinent.
Read-only attribute returning a list of upcoming events in the order they will be run. Each event is shown as a named tuple with the following fields: time, priority, action, argument.
New in version 2.6. | <urn:uuid:43c8210c-fcca-4c42-b8cb-3a4d537ac4ff> | 3.1875 | 875 | Documentation | Software Dev. | 56.016109 |
Pulsars are objects in space that send out frequent burst of electromagnetic radiation, mainly in the form of radio waves or gamma rays. Pulsars receive their name from these pulses. Pulsars are rapidly spinning neutron stars (see Neutron star) which are surrounded by an extremely powerful magnetic field which surrounds the star and rotates with it. This magnetic field creates a strong electric field that tears electrons and protons from the star's surface. As these particles flow from the star, they emit energy in the form of radio waves or gamma waves. With a giant radio telescope, an astronomer can detect a pulse of radio waves each time the pulsar rotates and the beam sweeps past the earth.
Pulsars rotate at the rate of twice a second. They eventually lose energy and slow down. They do this in such a gradual and predictable manner that their pulses can be used to tell time.
Anthony Hewish and Jocelyn Bell, British astronomers, at Cambridge University discovered the space phenomena in 1967. Today, scientist study pulsars to learn more about the motions at the center of globular clusters, the matter between stars in the Milky Way, and other topics as well. Also, they still continue to investigate on how pulsars turn their enormous rotational energy into radio beams.
Check out the diagram of a pulsar | <urn:uuid:a30530d6-bb47-4bd1-b593-ca2d81d84c9d> | 4.28125 | 271 | Knowledge Article | Science & Tech. | 45.708343 |
Source of Energy
Artificial tides, a Moon-based Source of Energy?
A method of having the Moon create artificial tides, for energy harvesting.
This presentation was conceptualized around 1998, but only
first placed on the Internet in March 2010.
Conceptualized around 1998, on the Internet March 2010|
- This is presented here as a LESSON regarding alternative energy production
and usage, but it happens to be a perfectly valid new method of creating
energy for the production of electricity and other purposes.
- The concept is extremely simple and even obvious, and so I have been
amazed that hundreds of people have not told me they thought of it! But
unfortunately, even though it certainly WORKS, the matter of being practical
is a different matter!
- You know that the Moon causes tides in the world's oceans. Actually, in
the land as well, but to a smaller effect. The REASON that the
Moon causes tides is actually very simple. Imagine that you are an
adult man who weighs exactly 200.0 pounds (where there is no Moon,
exclusively due to the mass of the Earth attracting you downward (Newton,
gravitation, all that stuff). [You might look at our Tides presentation
for the math.] Now say that the Moon was directly over your head.
Separate from the attraction of the Earth, the Moon also gravitationally
attracts you to it, now exactly straight upward! The Moon is much less
massive than the Earth and much farther away. The Tides presentation gives
the math to show that it causes a LIFTING EFFECT on you by about one part in
8,700,000! (That is accurate only when the Moon is at its average distance
from us [it varies due to an elliptical orbit] and we are also ignoring
the [smaller] contribution of tides due to the gravitation of the Sun).
- So you actually weight LESS when the Moon is overhead than six hours
earlier or later when it is on the horizon! But not much! Your scale
would show you lighter by about 1/2500 ounce (or 0.01 gram), way too small
an amount for your bathroom scale to show!
- So now say that you have a decent sized swimming pool (30,000 gallons
of water) BUT you support it on top of a "sturdy one-inch-thick
flattened balloon" of air underneath it.
- Whenever the pool is heavier (as when human bodies have jumped into it)
it becomes a little heavier than before, which slightly COMPRESSES the air
in that balloon underneath it. Similarly, when the Moon passes overhead and
makes the pool LIGHTER, the air in the balloon expands in volume because
of the lower pressure and therefore it has greater volume (Ideal Gas Law)
and therefore the balloon gets a tiny bit taller.
- The entire swimming pool gets LIFTED UP on that air cushion, due to the
Moon going overhead, essentially identical to the way that ocean tides exist.
- So you let the weight of the pool drop back down, and capture that
Potential Energy and convert it into electricity or whatever!
- What is wrong with this picture?
Actually, NOTHING is wrong with it! It WILL WORK as described in the
simple process above! Solution to all future power shortages? We should
Just thinking up an idea like this only the first step. NOW it is
necessary to do some math to see if it is actually practical or not.
It turns out that the vast majority of "good ideas" are not
actually practical! And we will see in the math that there are very
big difficulties in this one!
Using the info given above, we have 30,000 gallons of water in the
pool. This is about 250,000 pounds of water. (density of water, weight).
Our pool has a footprint of 40 feet by 20 feet, or 800 square feet
or 1,152,000 square inches. (area)
The air that was first put in the balloon had a natural air pressure of
about 14.7 pounds per square inch. Our weight of water just increased that
by about 0.2 PSI (weight divided by area, or 250,000 / 1,152,00 or about
0.2 PSI differential), so we now have the air
pressure in the balloon at around 14.9 PSI. The one-inch thick balloon
has now squeezed to about 14.7/14.9 or 0.988 inch, barely any
change in thickness (because we have SUCH a large area of the pool
This is with NO Moon or the Moon on the horizon.
When the Moon is overhead, the entire pool weighs a little less, actually
reduced by 250,000 pounds times 1/8,700,000 or 0.029 pound. In other
words, the entire pool now weighs LESS, at 249,999.971 pounds!
Since the entire pool is now lighter, the increase in the air pressure
in the balloon is less. We can calculate that the pressure decrease
in the balloon is around one two-millionth of a PSI. When we divide
this by the overall air pressure inside the balloon, we can see that the
balloon's pressure changed by about one part in 40 million.
That means that the height of the balloon changes by that same fraction,
or about one forty-millionth of an inch!
Unfortunately, this tiny dimension is comparable to things inside an
But continuing with our math, we now see that the Moon passing overhead
has LIFTED around 250,000 pounds of water by about one forty-millionth of
an inch! Multiplying, we then see that we now have some NEW POTENTIAL
ENERGY, in an amount of about 1/160 inch-pound or 1/2200 foot-pound.
This is actually NEW Potential Energy, which did not exist six
hours earlier! (It actually came from a really tiny change in the
orbit of the Moon, where Energy is still Conserved!)
We created this new potential energy over a six hour period. Therefore
we created this new energy at the rate of 1/2200 ft-lb / 21600 seconds,
or about one fifty-millionth of a ft-lb/sec. In the Metric system,
we have around 120,000 kg of water being raised 0.0000000006 meter in
those 21600 seconds, which is about 1/30 of a microWatt!
A REALLY small amount of power or electricity!
The point of this lesson is that things that seem to be extremely
promising, and are even certainly true, might not be PRACTICAL!
With the device as described above, you would need to build thirty
million such swimming pools, just to create a total of ONE WATT of
electrical power (from these artificial tides).
There ARE ways to improve this performance. If the air is in a very thick
balloon and given a different starting pressure, the performance can be
significantly better. If the pool is a thousand feet deep, ditto. But
such devices have other problems that our technology cannot yet solve
This presentation was first placed on the Internet in March 2010.
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C Johnson, Theoretical Physicist, Physics Degree from Univ of Chicago | <urn:uuid:79aa6930-31b0-4ab6-bf34-50eb03176f84> | 3.65625 | 2,495 | Nonfiction Writing | Science & Tech. | 50.388643 |
According to the Cherubim particle model, the elementary particles that comprise every electron carry 1/4 of the electron's charge and can only move in an absolute 2-D plane. This limitation is at odds with experimental observations. In this post, I will describe the strange and fascinating properties of electrons, as predicted by the model.
La Mano de Dios
During the 1986 World Cup quarter finals, the famous Argentinian striker, Diego Maradona, scored a winning goal against the English team with a handball.
Source: Bob Thomas Sports Photography, Getty Images, taken 22 June 1986
Unbelievably, the goal was allowed by the referee even though it was illegal. Argentina went on to win the World Cup with a final win against West Germany. This incident quickly became known as the Hand of God goal (la Mano de Dios) in fútbol circles. So, what does this have to do with Ezekiel, electrons and cherubim? Let me first say that I'm having a little fun here because I happen to like soccer as a sport. Second, recall that a hand in Ezekiel's vision is a symbol that stands for a special property that allows one cherub to grab or hold on to another. I realize that I am mixing my metaphors but the point I want to make is that sometimes, with a helping hand, awesome things can be achieved that would be impossible otherwise.
Human Hands Under their Wings
One of the problems with having a composite electron is that its constituents have the same charge polarity and, as a result, they repel each other. It is for this reason that cherubim, the charged elementary constituents of the electron, must have a special property that holds them together and prevents them from flying apart. This property is symbolized in Ezekiel's text by the hands.
Ezekiel 1:8.Under their wings on their four sides they had the hands of a man. All four of them had faces and wings.It makes sense to conclude from this verse that, since every cherub has four wings, it must also have four hands. However, why does the verse mention only four sides? Given that a cherub has four faces, shouldn't we expect it to have eight sides in total, one for each direction? Yes, of course. However, I don't think that Ezekiel was referring to facial orientations. I think he was referring to a different kind of sides. I think he was talking about the four possible directions of motion of a cherub. The four sides are really associated with the four wings of the cherub, that is to say, its four possible directions of travel.
That being said, why must every cherub have four hands? After all, each cherub only needs to hold on to three other cherubim. Having four hands means that every cherub has one extra free hand. I call this free hand, la mano de Dios not just because it reminds me of Diego Maradona's famous handball but because this is what explains the observed motion of electrons.
The Four Free Hands of the Electron
Since an electron is composed of four cherubim, it follows that every electron has four free hands. The question is, what are those hands for? In my opinion, they are used for grabbing another electron. At this point, I think you can probably guess where I am going with this. According to the Cherubim model, which I derived from the ancient Biblical metaphors, electrons do not move alone. They travel in pairs.
The Road Ahead
The main purpose of a particle model is to explain why particles come in certain configurations and properties. The second purpose is to predict the existence of heretofore undiscovered configurations and properties. If I am right, we will eventually be able to use the Cherubim model to explain the mass and composition of not just protons and neutrons but the mass number of the various nuclei as well. And we should be able to do this starting from the mass of the electron. This is the road ahead and I will follow it wherever it leads.
I truly believe in the old Christian adage, search and you will find. Who knows what delightful surprises await us around every corner? In Part VI, I will describe electron pairing in more detail and explain why pairing is an essential aspect of electron movement and overall behavior. I will also explain why there are three types of electrons. I know, I had promised to do this in this post but I think it's best that I leave it for the next one. | <urn:uuid:9b210c9c-d5a4-4b03-8efa-77c7eafea391> | 2.71875 | 936 | Personal Blog | Science & Tech. | 56.366476 |
by Monaca NobleRemember Snowmageddon 2010, the east coast storms that dumped up to three feet of snow over the mid-Atlantic? The February snowstorm was the largest in the region in nearly 90 years, resulting in the heaviest snowfall on record for Delaware (26.5 inches) and the third heaviest snowfall in Baltimore (24.8 inches). The storm made a big impression on Dr. João Canning-Clode and other scientists at the Smithsonian Environmental Research Center, who began to wonder if the storm, and the December/January cold snap that preceded it, would lead to the deaths and potential disappearance of marine invaders from southern climates.
Spurred on by the relatively recent increase in ocean surface temperatures, new marine invaders are beginning to spread northward along the southern and mid-Atlantic coasts from the Caribbean. This particular northern migration has been termed the “Caribbean Creep”, although the phenomenon of northward migration is not limited to that region. Many of the non-native species creeping northward are doing so because they are able to tolerate a wide range of temperatures. But what happens to these fair-weather travelers during a cold snap?
In January 2010 a cold snap in the southeast meant higher death rates for manatees, sea turtles, crocodiles and other high-profile species. But there was also evidence that Caribbean Creep invaders, like the Green Porcelain Crab (Petrolisthes armatus), had declined dramatically as a result of the January chill. Green Porcelain Crabs have a very large presumed native range that includes the tropical eastern Pacific from Mexico to Peru, the western Atlantic from the Gulf Coast of Florida to southern Brazil, and the eastern Atlantic from Senegal to Angola. But recently the crabs have moved north into Georgia and South Carolina.
To investigate further Dr. Canning-Clode and his colleagues experimentally tested the cold-water tolerances of green crabs in a study published in PLoS ONE. Introduced crabs collected in Georgia were brought to the lab, where they were subjected to one of three temperature treatments. The first was a control treatment, held at a constant, moderate winter temperature. The second was a cold treatment in which the temperature fluctuated to mimic the cold snap of January 2010. The third treatment tested extreme conditions, ones which would be expected in a more severe winter.
Most of the crabs in the control treatment survived (83%), but many of the crabs in the cold treatment (61%) and all of the crabs in the extreme cold treatment died. Those crabs that did survive the frigid waters were sluggish, making them more vulnerable to predators and possibly impacting their ability to feed. Prolonged exposure to cold temperatures may further jeopardize the crab’s ability to withstand future cold events, as two other record cold snaps occurred in February and March 2010. The loss of over 60% of the population each time could explain the disappearance of this species in Georgia, suggesting that extreme cold temperature events may limit or prevent the northward spread of the invasive Green Porcelain Crab.
Several climate models have predicted that climate change will lead to a continued decline of global biodiversity over the next 100 years and the increased spread of invasive species. Many of these models have focused on temperature increases, but few have evaluated the impact of severe weather like cold snaps. For example, several studies have reported mass die-offs of shallow-water marine invertebrates in the winter but have not linked these to climate change models. Dr. Canning-Clode and his collaborators suggest that these episodic cold weather snaps should be accounted for in future climate studies in aquatic environments.
“The core message of this paper is that yes, climate change is happening, but the cold is also part of this change,” says Dr. Canning-Clode. “We believe these periodic cold events will limit the range expansion of Petrolisthes armatus as well as other Caribbean creep species.” | <urn:uuid:85c4153b-c253-46ae-90e9-2c456039d0e8> | 3.671875 | 803 | Academic Writing | Science & Tech. | 36.874264 |
Next: Representing the subsets I,
Previous: Linear Search : the Move-To-Front
Here the heuristic is slightly different from the Move-To-Front method : once
found, the transition is swapped with the immediately preceding one,
performing an incremental bubble sort at each access.
Of course, these two techniques provide a sensitive speed-up only if the
probabilities for each transition to be accessed are not uniform.
These are the seven representations that caught our attention at first but that
set of containers will be broadened when a special need is to be satisfied.
What is obvious here is that each of these structures has advantages and
drawbacks, whether on space complexity or on time complexity. All these
constraints have to be taken in account in order to construct code adapted to | <urn:uuid:0b01cd4d-1c02-46d1-a198-f16d4a249bbf> | 3.0625 | 169 | Documentation | Software Dev. | 25.7052 |
[Full Text Link]
Chelonia mydas Species ID:
A hard-shelled sea turtle with a brown, green, or black oval shell (1) possessing two large curved flippers at the front of the body and two short rounded flippers at the rear (2). The head is small with a blunt snout (3) and two elongated rectangular scales (4) just above each eye distinguish this from other sea turtles. Males have a tail that extends past the two rear flippers, while females have a shorter tail (5) Maximum size:
1.4m (the largest hard-shelled marine turtle) Longevity:
Up to 75 years Status:
Endangered according to the IUCN endangered species list Green Turtles & People:
Green turtles have long been sought after by fishermen for their eggs, meat, and shell, while coastal development has disrupted nesting activity. These and other human activities have caused a population decline of roughly 50% in the green sea turtle in the last decade, a trend that will be difficult to reverse in this slow-growing species.
This turtle is found throughout the world’s tropical seas, and is widespread throughout the Caribbean Coral Reef Zone:
Shore zone, back reef, fore reef and drop-off zones Favourite Habitats:
These large vegetarians frequent seagrass beds but can also be found in algae-covered reef areas where they tend to sleep at night Depth Range:
0–35 m (0–115 ft)
A Day in The Life:
Dawn: Turtles begin roaming the reef looking for food
Day: Turtles usually feed and in season may also migrate or mate
Dusk: Feeding declines and turtles seek shelter for the night
Night: Turtles settle under reef ledges to sleep. In season, nesting occurs on beaches
Who Eats Who
The adult green turtle is herbivorous, feeding on seagrass and algae. Young green turtles are omnivorous, and become strictly herbivorous when they reach adulthood. The large size and hard shell of adult green turtles make them vulnerable to only the largest predators, such as the tiger shark, while virtually all reef predators can eat the small juveniles.
Scuba Diver & Snorkeler Best Practices
Carefully select entry and exit points. Carefully select points of entry and exit from the water to avoid damaging the coral reef. | <urn:uuid:f0084a0b-6de4-4b42-8630-132779d3a1f4> | 3.234375 | 495 | Knowledge Article | Science & Tech. | 40.423225 |
Signal(Sig_Val val, ckt_time time): The Signal constructor accepts a signal value (which is simply an enumerated type) and the time at which the signal occurred. The corresponding private members of the Signal object are then initialized with these values.
\ friend ostream &operator <<(ostream &os, const Signal &sig): This is an overloaded operator function which lets the implementation use the standard insertion operator (<<) to display the value and time of a Signal object on standard output.
Sig_Val get_value(): This is a simple accessor function which returns the value of the signal.
ckt_time get_time(). This is a simple accessor function which returns the time at which the signal occurred.
void set_value(Sig_Val newval): This method changes the value of the signal to the specified value. It is used only by the replace() method of the Wire class and is intended for future support of zero-delay component simulation. | <urn:uuid:ff2a24b4-ec9f-4dbb-ac38-52e15a505cb7> | 2.75 | 209 | Documentation | Software Dev. | 36.249681 |
SQL Set Functions
Part of the SQL For Dummies Cheat Sheet
The SQL set functions give you a quick answer to questions you may have about the characteristics of your data as a whole. How many rows does a table have? What is the highest value in the table? What is the lowest? These are the kinds of questions that the SQL set functions can answer for you.
|COUNT||Returns the number of rows in the specified table|
|MAX||Returns the maximum value that occurs in the specified table|
|MIN||Returns the minimum value that occurs in the specified table|
|SUM||Adds up the values in a specified column|
|AVG||Returns the average of all the values in the specified column| | <urn:uuid:6fc09772-7032-4181-8f20-0544a7c6cd55> | 2.734375 | 153 | Documentation | Software Dev. | 59.217455 |
The information presented in this chapter provides the reader with an understanding of ground water’s origin, environment, movement, and interaction with surface water. For all practical purposes, ground water is all water beneath the surface of the earth. Because ground water is hidden from view, many people think of its occurrence in the form of underground lakes, streams, and veins. While such features exist in the limited settings of cavernous limestone and the lavas of some volcanic flows, most ground water occurs as water filling pore spaces between rock grains in sedimentary rocks or in crevices such as fractures and faults in crystalline rocks (Figure 2.1).
Figure 2.1 Porosity and permeability of common geologic units that form aquifers. Water-filled voids are represented in blue.
The ultimate source of ground water is precipitation (in the form of rain, snow, or hail). The precipitation that does not evaporate or immediately flow to rivers, streams, or lakes percolates into the ground, where some of it eventually reaches the water table. The concept of the hydrologic cycle is central to understanding the occurrence of ground water. The hydrologic cycle, as the name implies, is an endless dynamic process of the circulation of water between the atmosphere, the oceans, and the land. The basic components of the hydrologic cycle are shown schematically in Figure 2.2. Seventy-one percent of all U.S. precipitation originates from land surface evaporation, whereas the remaining 29 percent is produced by evaporation from the oceans. The integrated nature of the hydrologic cycle makes ground water vulnerable to pollution sources in the atmosphere, on or within land surfaces, or in surface waters.
Figure 2.2 The hydrologic cycle describes the circulation of water between
the atmosphere, land, and open water bodies.
The degree and rate of infiltration (recharge) will vary widely depending upon the land use, soil physical properties and moisture content, and the intensity and duration of precipitation. When rainfall is intense, exceeding the rate of infiltration, water accumulates on the surface and runs off downhill as overland flow. Water that infiltrates the ground surface becomes soil moisture, which may evaporate or be taken up by vegetation as nourishment. Excess soil moisture is pulled down by gravity and percolates through the ground to some depth where all the openings within the soil or rock are saturated with water. The top of that zone of saturation is called the water table. | <urn:uuid:cff29f22-cf67-4f85-a183-de890bc959f0> | 4.15625 | 512 | Knowledge Article | Science & Tech. | 34.143111 |
Revised: May 2012
Were it not for a handful of hobbyists, space flight would never have gotten off the ground. The nuclei of the teams that launched the first satellites, cosmonauts, and astronauts were science fiction fans who took their interests in astronomy and space flight so seriously that, in spite of the worldwide depression of the Thirties, they formed clubs in Germany, America, and the former Soviet Union to design and build rockets with their own resources. During the Space Race, the superpowers recognized that encouraging amateur astronomy and model rocketry would grow their technical workforces. Today, websites like the Zooniverse bring the challenge and pleasure of amateur astronomy to a linked-in nation. The NASA HQ library, as the only NASA library which the public can visit, offers this webpage as a list of resources that should be useful to anyone who would like to join the ranks of rocketeers and astronomers. You may also find useful resources in our webpages on Children's Space Resources and Science Fair Projects. Please exercise proper caution when embarking on a course of research, especially with one involving rockets or the Sun.
All items are available at the Headquarters Library, except as noted. NASA Headquarters employees and contractors: Call x0168 or email Library@hq.nasa.gov for information on borrowing or in-library use of any of these items. Members of the public: Contact your local library for the availability of these items. NASA Headquarters employees can request additional materials or research on this topic. The Library welcomes your comments or suggestions about this webpage.
- Bakich, Michael E. The Cambridge Guide to the Constellations. Cambridge, UK; New York, NY: Cambridge University Press, 1995. ISBN: 0521465206
- QB802 .B35 1995 READY-REF
- Clark, Roger N. Visual Astronomy of the Deep Sky. Cambridge, UK; New York, NY: Cambridge University Press & Sky Publishing Corporation, 1990. ISBN: 0521361559
- QB64 .C58 1988 BOOKSTACKS
- Discovery Channel. Night Sky: An Explore Your World Handbook. New York, NY: Discovery Books, 1999. ISBN: 1563318016
- QB64 .N495 1999 BOOKSTACKS
- Ferris, Timothy. Seeing in the Dark: How Backyard Stargazers are Probing Deep Space and Guarding Earth from Interplanetary Peril. New York, NY: Simon and Schuster, 2002. ISBN: 0684865793
- QB43 .F47 2002 BOOKSTACKS
- Heywood, John. Radio Astronomy and How to Build Your Own Telescope. New York, NY: Arc Books, 1964.
- QB475 .H47 1963 BOOKSTACKS
- Johnson, Gaylord and Irving Adler. Discover the Stars. New York, NY: Sentinel Books, 1957.
- QB801.6 .J65 1957 BOOKSTACKS
- Kaler, James B. The Ever-changing Sky: A Guide to the Celestial Sphere. New York, NY: Cambridge University Press, 1996. ISBN: 0521380537
- QB145 .K33 1996 BOOKSTACKS
- King-Hele, Desmond. Observing Earth Satellites.New York, NY: Van Nostrand Reinhold, 1983. ISBN: 0442248776
- TL796.8 .K47 BOOKSTACKS
- Levy, David H. The Sky: A User's Guide. New York, NY: Cambridge University Press, 1991. ISBN: 0521391121
- QB63 .L42 1991 BOOKSTACKS
- Muirden, James. Astronomy with Binoculars. Princeton, NJ: Van Nostrand, 1963.
- QB44.M95 A8 1963 BOOKSTACKS
- Binoculars are among the easiest tools for the newcomer to amateur astronomy.
- Newton, Jack. The Cambridge Deep-sky Album. Cambridge, UK; New York, NY: Cambridge University Press, 1983. ISBN: 0521256682
- QB63 .N478 BOOKSTACKS
- Norton, Arthur Philip, and J. Gall Inglis. A Star Atlas and Reference Handbook (Epoch 1950) for Students and Amateurs. Edinburgh, UK: Gall and Inglis, 1959.
- QB65 .N882 1959 READY-REF
- Parkes, Mike. Starry Night Backyard. Toronto, Ont.: SPACE.com Canada, Inc., 2000.
- QB63 .S83 2000B CDROM
- Pasachoff, Jay M. Peterson First Guide to the Solar System. Boston, MA: Houghton Mifflin Co., 1990. ISBN: 0395524512
- QB46 .P277 1990 BOOKSTACKS
- Sidgwick, J.B. Amateur Astronomer's Handbook. London, UK: Faber and Faber, 1955.
- QB44 .S56 BOOKSTACKS
- __________. Observational Astronomy for Amateurs. Hillside, NJ: Enslow Publishers, 1982. ISBN: 0894900676
- QB64 .S56 1982 BOOKSTACKS
- Stine, G. Harry. Handbook of Model Rocketry. New York, NY: Arco Pub., 1983. ISBN: 0668053585
- TL844 .S75 1983 BOOKSTACKS
- Taylor, Peter O. Observing the Sun. New York, NY: Cambridge University Press, 1991. ISBN: 0521401100
- QB521.4 .T39 1991 BOOKSTACKS
- Texereau, Jean. How to Make a Telescope. Richmond, VA: Willmann-Bell, 1984. ISBN: 0943396042
- QB88 .T413 1984 BOOKSTACKS
- Vehrenberg, Hans. Atlas of Deep-sky Splendors. Cambridge, UK; New York, NY: Cambridge University Press; Cambridge, MA: Sky Pub. Corp., 1983. ISBN: 0521258340.
- QB65 .V413 1983 BOOKSTACKS
- Webb, Thomas William. Celestial Objects for Common Telescopes. New York, NY: Dover Publications, 1962.
- QB64 .W36 BOOKSTACKS
- The Observer's Handbook
- This is an annual.
- Sky and Telescope
- NASA HQ library doesn't have an active subscription.
- Sport Rocketry
- NASA HQ library doesn't have an active subscription.
Benson, Tom. Beginner's Guide to Aeronautics. Sept. 23, 2010. [May 4, 2012].
Night Sky Network. 2012 [May 4, 2012].
Watanabe, Susan. Amateur Astronomy. Nov. 30, 2007 [May 4, 2012].
Astronomical League. 2012 [May 4, 2012].
Harvard-Smithsonian Astrophysical Observatory. Current Night Sky. May 2012 [May 4, 2012].
International Planetarium Society. March 11, 2012 [May 4, 2012].
Kronk, Gary. Meteor Showers Online. 2012 [May 4, 2012].
The site lists the major meteor showers for the year. Meteors can be observed without any special equipment.
National Association of Rocketry. April 28, 2012 [May 4, 2012].
United States Naval Observatory. The Sky This Week. 2012 [May 4, 2012]. | <urn:uuid:314aeda9-316d-4cc9-954a-9d50d669c1d6> | 2.96875 | 1,549 | Structured Data | Science & Tech. | 73.270234 |
22/08/12 | LONDON
Outdoor learning sites such as botanic gardens, zoos and wetlands offer unique locations for children to gain first hand experiences of inquiry based science education (IBSE.) This course at WAKEHURST PLACE introduces the concept of IBSE and places its delivery in a botanical garden, to visiting school groups,delivered to support the UK national curriculum. A 'must attend' course for any educator wanting to inspire the next generation of plant scientists and environmentalists.
20/07/12 | Bremen, Germany
A study by German researchers shows that the continuously rising atmospheric carbon dioxide level may lead to the growth of many trees in African savannahs by 2010. These would then no longer be savannahs, but forests. According to the study, dense woods could develop in Africa if a certain carbon dioxide level is exceeded.
20/07/12 | Southern Ocean
In the search for methods to limit global warming, it seems that stimulating the growth of algae in the oceans might be an efficient way of removing excess carbon dioxide from the atmosphere after all. | <urn:uuid:527c5472-da6c-412e-b353-666ff8af472f> | 2.734375 | 228 | Content Listing | Science & Tech. | 35.668409 |
12 December 2010
Posted in Science Live!
Think about a shallow tide pool that is subject to enormous changes in salinity, temperature, and water level. Now try to imagine the deepest, coldest, darkest part of the ocean, which is over 36,000 feet underwater. The open ocean covers nearly 70% of our entire planet, with an incredible abundance of all kinds of life.
In doing some research for an upcoming floor program on the different ocean animals and the zones of the ocean they live in, I read about an amazing program called the Census of Marine Life, which is a ten year project to try and document life in the ocean from all different locations and depths. The ultimate goal of the project was to develop a better understanding of the ocean and its inhabitants by researching the number of species, where they live, and how many live there. It is hard enough to try and keep track of a few fish in a fish tank, let alone to try and document all the species in the ocean!
If you are interested in learning more visit: www.coml.org. | <urn:uuid:58aa0096-ec34-4941-b4b3-376464be3290> | 3.765625 | 221 | Personal Blog | Science & Tech. | 54.861579 |
PHP Database Related Using PostgreSQL With PHP Tutorial
Top Tutorials related to:PHP Database Related Using PostgreSQL With PHP Tutorial What is PHP ?
What is PHP, a tutorial which gives you a small introduction to PHP language.
PHP Database: In this tutorial you will get to know about databases, tables, query and other related things like how to access databases using PHP etc. This is the first index page of this tutorial
PHP Create Database
PHP Create Database: In this tutorial you will get to know about how to create database in PHP, using WAMP server, and MySQL console.
Displaying Database using PHP
Till now, we have done the creation part of database and table. In this tutorial, I will show you how to insert the information by using form on a website with the help of PHP Script.
PHP stands for Hypertext Preprocessor; PHP is server-side scripting language for development of web applications.
PHP Ajax and Database
PHP Tutorials from RoseIndia
PHP is scripting language used for development of dynamic web applications. Best combination to use PHP is Linux, Apache, MySQL and PHP (LAMP stack). Its very easy to learn PHP and develop dynamic web applications for your website and Intranet. | <urn:uuid:e521ce9a-59ac-4eac-b70a-e6a02881abba> | 2.734375 | 261 | Tutorial | Software Dev. | 48.286658 |
The landscape and weather change greatly during the year in regions that have four distinct seasons.
Click on image for full size
Images Courtesy of Corel
The Four Seasons
The Earth travels around the sun one full time per year. During this year, the seasons change depending on the amount of sunlight reaching the surface and the Earth's tilt as it revolves around the sun.
Since the Earth's axis points to the same direction all year long, the northern hemisphere is tilted away from the sun in winter, and towards the sun in summer. When it is summer in the northern hemisphere, it is winter in the southern hemisphere.
At the equator, there are no seasons because the sun is always striking and the temperatures remain high there. In general, the summer and winter temperatures get lower the further away from the equator. At the poles, it is either daylight or nig
httime for six months at a time depending on the Earth's tilt.
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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Rainbows appear in the sky when there is bright sunlight and rain. Sunlight is known as visible or white light and is actually a mixture of colors. Rainbows result from the refraction and reflection of...more | <urn:uuid:497f12c1-7498-41f2-bba1-c99982682b27> | 3.65625 | 570 | Content Listing | Science & Tech. | 61.29529 |
2.2 Non-essential Built-in Functions
There are several built-in functions that are no longer essential to learn,
know or use in modern Python programming. They have been kept here to
maintain backwards compatibility with programs written for older versions
Python programmers, trainers, students and bookwriters should feel free to
bypass these functions without concerns about missing something important.
||function, args[, keywords])|
The function argument must be a callable object (a
user-defined or built-in function or method, or a class object) and
the args argument must be a sequence. The function is
called with args as the argument list; the number of arguments
is the length of the tuple.
If the optional keywords argument is present, it must be a
dictionary whose keys are strings. It specifies keyword arguments
to be added to the end of the argument list.
Calling apply() is different from just calling
function(args), since in that case there is always
exactly one argument. The use of apply() is exactly
Deprecated since release 2.3.
Use the extended call syntax with
||object[, offset[, size]])|
The object argument must be an object that supports the buffer
call interface (such as strings, arrays, and buffers). A new buffer
object will be created which references the object argument.
The buffer object will be a slice from the beginning of object
(or from the specified offset). The slice will extend to the
end of object (or will have a length given by the size
Return a tuple consisting of the two numeric arguments converted to
a common type, using the same rules as used by arithmetic
operations. If coercion is not possible, raise TypeError.
See About this document... for information on suggesting changes.
Enter string in the table of ``interned'' strings and return
the interned string - which is string itself or a copy.
Interning strings is useful to gain a little performance on
dictionary lookup - if the keys in a dictionary are interned, and
the lookup key is interned, the key comparisons (after hashing) can
be done by a pointer compare instead of a string compare. Normally,
the names used in Python programs are automatically interned, and
the dictionaries used to hold module, class or instance attributes
have interned keys.
Changed in version 2.3:
Interned strings are not
immortal (like they used to be in Python 2.2 and before);
you must keep a reference to the return value of intern()
around to benefit from it. | <urn:uuid:a785827c-07c9-4e62-82ec-a66d46ad1876> | 3.109375 | 550 | Documentation | Software Dev. | 47.913364 |
To begin with let us recall what entropy is. It's a measure for the number of micro-states compatible with a given macro-state. The macro-state could for example be given by one billion particles with a total energy E in a bag of size V. You then have plenty of possibilities to place the particles in the bag and to assign a velocity to them. Each of these possibilities is a micro-state. The entropy then is the logarithm of that number. Don't worry if you don't know what a logarithm is, it's not so relevant for the following. The one thing you should know about the total entropy of a system is that it can't decrease in time. That's the second law of thermodynamics.
It is generally believed that black holes carry entropy. The need for that isn't hard to understand: if you throw something into a black hole, its entropy shouldn't just vanish since this would violate the second law. So an entropy must be assigned to the black hole. More precisely, the entropy is proportional to the surface area of the black holes, since this can be shown to be a quantity which only increases if black holes join, and this is also in agreement with the entropy one derives for a black hole from Hawking radiation. So, black holes have an entropy. But what does that mean? What are the microstates of the black hole? Or where are they? And why doesn't the entropy depend on what was thrown into the black hole?
While virtually nobody in his right mind doubts black hole have an entropy, the interpretation of that entropy is less clear. There are two camps: On the one side those who believe the black hole entropy counts indeed the number of micro-states inside the black hole. I guess you will find most string theorists on this side, since this point of view is supported by their approach. On the other side are those who believe the black hole entropy counts the number of states that can interact with the surrounding. And since the defining feature of black holes is that the interior is causally disconnected from the exterior, these are thus the states that are assigned to the horizon itself. These both interpretations of the black hole entropy are known as the volume- and surface-interpretations respectively. You find a discussion of these both points of view in Ted Jacobson's paper "On the nature of black hole entropy" [gr-qc/9908031] and in the trialogue "Black hole entropy: inside or out?" [hep-th/0501103].
A recent contribution to this issue comes from Steve Hsu and David Reeb in their paper
Steve is a neighbor here on blogspot over at Information Processing. In their paper Steve and David examine the question how much matter one can stuff into a volume bounded by a given surface, and how much entropy this matter can carry. In flat space-time the relation between the volume of an area and its surface is trivial, it's just Euclidean geometry. But not so if space-time is strongly curved!
To see this, consider the often made analogy of a curved space to a rubber sheet. Draw a circle on it. That's your surface. But it's a rubber sheet, meaning you can deform the sheet inside the circle arbitrarily. You could for example form it to a bag and stuff a lot of gold into it.
This pictorial terminology is sadly not my invention: these kind of solutions have been known to be possible in General Relativity for a long time, and have been dubbed “bags of gold” by Wheeler already in the early 70s. Their defining property is that they have a potentially arbitrarily large interior volume, but a small surface area.
Steve and David in their paper now construct a weird kind of solution they dub “monsters,” which exemplifies what one can do with these bags. To understand what a monster is, consider some stuff (eg coins of gold) dispersed in space-time, such that the background is to good approximation flat. Now pick up these coins and put them closely together - so close that they almost, but not entirely, form a black hole. What you achieve in this way is that you get a strong gravitational field and a deviation of the volume-surface relation from flat space. That process of picking up and redistributing the coins should not be thought of as a process that is actually dynamically happening, but just as a way to create the initial conditions*. If you create these initial conditions carefully you can achieve most importantly two things:
- You can get the asymptotic mass a far away observer would measure (ADM mass) to be arbitrarily small, no matter how many coins you have had. The reason for this is that the strong gravitational field contributes with a negative binding energy.
- You can similarly get an arbitrarily large entropy inside a sphere with fixed surface area, think of the coins as the particles forming a particular micro-state. The reason is that the volume can get arbitrarily large, and you can stuff all the coins in, even though the surface area and the asymptotic mass might remain small.
The authors also show in their paper that if you create the monster state and let it evolve in time, it inevitably forms a black hole. Since it can have been arbitrarily close to being a black hole, it is plausible to expect that almost all of this entropy goes into the black hole. If the volume interpretation of the black hole entropy was correct, this would be in conflict with it. Weirder than that, the monster solution must have come out of a white hole in the past. This solution is thus very similar to an expanding and re-collapsing closed FRW universe embedded in empty space.
Despite these monster solutions existing in GR, there remains the question however whether they do exist in reality, since they are somewhat pathological and constructed. Though it might be possible to argue these states will never be formed from any sensible initial condition, in a quantum theory the situation is more tricky since everything that can happen does happen - even though it might be very improbable. That means the monsters could be spontaneously formed through tunneling processes. That might however in practice not happen even once during the lifetime of the universe.
Steve was visiting PI in November and gave a very clear talk about the monsters, that is recommendable if you want to know more details. You can find it at PIRSA 08110026 and the slides are here.
* You shouldn't take the picture too literally though, much like in the often used example with the marble on the rubber-sheet it is slightly misleading as there isn't actually something "on" the spacetime (the sheet) that extends into an additional dimension. | <urn:uuid:475a185d-d262-4635-9610-dbf4859c74fc> | 3.21875 | 1,375 | Comment Section | Science & Tech. | 49.319198 |
Have you ever played the game Telephone? In this game, several people sit in a circle, and the first person whispers an arbitrary message to his or her neighbor, as quietly as possible. The message is passed by successive whispers around the circle, and the last person attempts to repeat the message out loud. Typically, the message has become completely garbled by the time it reaches the last player. Why is this? The problem (or the game) is that whispering is a rather inaccurate mode of information transfer, so mistakes accumulate around the circle until the message is lost. In fact, errors can plague transfer of information in any form, including biological genomes.
The information for making a living organism is encoded in the genome as a series of chemical letters (adenine, guanine, cytosine, and thymine). Longer genomes have the potential to encode more information and thus more complex organisms. In 1971, Nobel laureate Manfred Eigen realized that the probability of making a mistake limits the length of the genome. If errors are relatively rare, most daughter genomes are faithful copies of the original. However, if errors are too common, daughter genomes usually contain mistakes, and their daughters would contain even more mistakes, and so on. In that case, the information of the genome would degrade over time.
Eigen proved that the maximum length of the genome is inversely proportional to the rate of mistakes per letter, simply because longer genomes contain more opportunities to make mistakes (Eigen, M., Naturwissenschaften 58, 465). If the genome is longer than this critical threshold, then an "error catastrophe" ensues: Error-ridden replication essentially randomizes the genome after several generations. This principle also suggests that mechanisms to reduce mistakes can set the stage for the evolution of more complex organisms. Indeed, modern organisms generally have multiple proofreading mechanisms, such that mistakes are usually very rare. (Some viruses, like HIV, are notable exceptions and appear to exist near the edge of the error catastrophe.)
Although the concept of the error threshold was originally developed to understand the limits of biological information, we can see surprising illustrations of this idea in everyday life. Take a look at the name of this lake in central Massachusetts:
Photo: Irene Chen
According to locals, it means "You fish on your side, I fish on my side, and nobody fishes in the middle" (see the Wikipedia article for more information). Now, check out this sign from the Massachusetts Turnpike Authority:
Photo: Bree Bailey
Looks the same, right? But look again:
There are two errors in this sign! Notice that the short, four-letter word "Lake" was copied correctly, but that the long, 45-letter word "Chargoggagoggmanchauggagoggchaubunagungamaugg" was copied with two errors, for an error rate of approximately 4%. If the MTA were to use its sign as a template for more signs, you can imagine how the information in the lake name would quickly disappear. Fortunately for humans, whose genome is more than 3 billion letters long, our DNA replication is substantially more accurate! | <urn:uuid:1db4f84c-5262-4766-b90e-73a1398d94ff> | 3.71875 | 642 | Knowledge Article | Science & Tech. | 27.69533 |
Mathematical Methods of Theoretical Physics →
Abstract: Course material for mathemathical methods of theoretical physics intended for an undergraduate audience. Table of Contents 1 Unreasonable effectiveness of mathematics in the natural sciences 23 2 Methodology and proof methods 27 3 Numbers and sets of numbers 31 Part II: Linear vector spaces 33 4 Finite-dimensional vector spaces 35 4.1 Basic definitions 35 —4.1.1 Fields of real...
if you miss/missed the 80’s
I’m sorry but I cannot take you seriously if you use Comic Sans as your email font
My Top 5 Artists (Week Ending 2012-6-10) →
Elizabeth & the Catapult (24) Monty Python (14) Edward Sharpe & The Magnetic Zeros (13) God Is An Astronaut (4) The American Dollar (3) Imported from Last.fm Tumblr by JoeLaz
The greatest enemy of knowledge is not ignorance, it is the illusion of...– Stephen Hawking (via scienceisbeauty)
It has often been said that a person does not really understand something until...– Legendary computer scientist and professor Donald Knuth. (via lifeandcode) | <urn:uuid:8652cdaa-97ed-4377-b897-4b74c622d98a> | 2.71875 | 246 | Content Listing | Science & Tech. | 58.221895 |
Humans have been exploring this planet for almost 70,000 years. We have all been born out of, what is now Northern Ethiopia, and migrated all over the planet.
This picture shows the genetic heritage and migration of my own mother's DNA over the past 70 -100,000 years. She was a member of Haplogroup K.
This picture shows my father's migration. He and I am a member of DNA Haplogroup Q:
This is ironic because, a) I was born in England, and b) I just became a US citizen -- which cost me a lot of time and money. Yet my ancestors must have traversed the US some 50,000 years ago
I received these results as part of a series of DNA tests that are relatively inexpensive to obtain.
I've always wondered why I was "pulled" to come from my birthplace in England to the US, but also have this innate affection for Greece.
Now I can see that my ancestors were in both places.
All human beings have DNA that reveals the history and wanderings / migrations of their ancestors. Some went south to India and some went to Polynesia and Australia, others went to Northern Europe and Russia.
This is how our planet was initially populated.
We have continued of course to explore: (the "New World", Australia, the Silk Route, often conquering and destroying to bring home riches and worse. Hopefully we are beginning to grow up.
Now we are beginning to explore Space.
This will not happen immediately. Just as my own ancestors must have adapted (mutated) over centuries, to seek shelter, warmth and nutrition amidst changing climates and different types of foods, our own bodies will need to adapt to life in Space.
So we have several problems to overcome in Human Space exploration.
1. Getting anywhere -- building transport vehicles to take us places, and
2. Adapting to survive in extreme climates. In space, we are subject not just to extreme temperatures, but also to solar radiation -- something we are largely protected from on Earth, and
3. Our bodies are not yet acclimated -- as a specie -- for long term space flight. In a weightless environment, we must exercise strenuously to avoid losing bone density.
We are at the beginning.
We can get into Low Earth Orbit (LEO), but it's dangerous, and wildly expensive.
We have been to the moon, but we didn't stay there.
Other peoples are planning outposts and maybe in a few years from now, we will have figured out how to sustain ourselves safely in space.
This section deals with human exploration of Space. | <urn:uuid:ab830eac-9995-461a-b87c-e51bf63ab79c> | 2.9375 | 548 | Personal Blog | Science & Tech. | 55.749312 |
Flooded Fields in Oakville, Iowa
Photograph by John Stanmeyer/VII
Flooded fields surround an Oakville, Iowa, farmstead in the wake of heavy rains that saturated the Midwest in the summer of 2008. Rivers topped their banks and broke through levees, flooding farms and cities alike—some 100 blocks of Cedar Rapids were submerged and millions of acres of wheat and corn crops were ruined.
Some climate scientists believe that more extreme rain and flooding events are likely as Earth’s climate changes.
Drought-Stricken Australian Outback
Photograph by Jason Edwards
A forlorn tree stands sentinel in the parched fields of a devastated, drought-stricken farm in the Australian outback.
A decade-long drought in the region dried up waterways, decimated crops, and left livestock with nowhere to feed—prompting many graziers to destock their ranches. The arrival of rains in the wake of Tropical Cyclone Olga finally began to bring relief to New South Wales in February 2010.
Chile’s San Rafael Glacier
Photograph by Maria Stenzel
Huge columns of ice calve off Chile’s San Rafael glacier and crash into the sea.
Thousands of tourists visit the 30,000-year-old glacier each year, to see its impressive sprawl from the slopes of the Andes to the sea. Visitors are treated to a spectacular show, but also sobering evidence of San Rafael’s mortality. The 286-square-mile (741-square-kilometer) glacier is receding by some 328 linear feet (100 meters) each year.
Flooded Street in Bangladesh
Photograph by Pavel Rahman/AP
Commuters struggled to reach their offices by boat as floodwaters filled the streets of Dhaka, Bangladesh, in August 2002.
But other Asians faced far worse. Torrential monsoon rains in Bangladesh, India, and Nepal killed hundreds and displaced tens of millions from their homes.
Bangladesh is especially susceptible to flooding. The low-lying nation fills with the floodwaters of four major rivers fueled by Himalayan snowmelt and monsoon rains.
Photograph by Bradley E. Clift
This Honduran “desert” was pasture and farmland before Hurricane Mitch arrived in November 1998. Torrential rains unleashed the full fury of a flooded Choluteca River, which washed away entire villages, threw trees like matchsticks, and transported enough sand from the mountains to create an artificial desert.
The deadly storm killed thousands of people and destroyed so much of Honduras’s agricultural and transportation infrastructure that President Carlos Flores Facusse said the disaster had destroyed 50 years of progress in his country.
Photograph by Lisa Hoffner/Wildeyephoto
Digging deep to deliver water to his cattle, a Samburu tribesman toils during Kenya’s crippling drought in August 2009, working a newly dug well in the dry bed of the Ewaso Nyiro River.
Lack of rain in the always arid region reached critical levels last year, killing hundreds of thousands of livestock and costing herdsmen dearly.
Elephants and other iconic animals were also desperate, and dying, from lack of water, and sometimes jostled with humans for space at the new wells.
Photograph courtesy NASA
Seen from the International Space Station, Grey Glacier, part of Chile and Argentina’s massive Southern Patagonian Ice Field, looks immovable even as it spills down from the Andes and splashes into Grey Lake in three distinct lobes.
The Southern Patagonian Ice Field is the biggest collection of glacial ice anywhere except Antarctica and Greenland. In 1996 the Grey Glacier alone measured 104 square miles (270 square kilometers) in area and stretched for 17 miles (28 kilometers). But like many glaciers worldwide scientists say it has been shrinking markedly in recent decades.
Bangladesh Girl Swimming Through Flood
Photograph by Pavel Rahman/AP
In search of drinking water, a Bangladeshi girl swims though a flooded Dhaka suburb with empty containers in tow.
The nation’s long history of catastrophic flooding reared its ugly head in the summer of 2003, when more than 2.5 million people were marooned by raging rivers. Low-lying, coastal Bangladesh is geographically vulnerable to flooding. Like other poor nations it’s also economically ill equipped to deal with such disasters in a changing world.
Lake Boga, Australia
Photograph by Amy Toensing
Soon after this image was taken, Australia’s Lake Boga went dry for the first time in a century because of a crippling drought in New South Wales.
When the water disappeared in 2008, fish died by the thousands and swamped the resort community with a strong stench. Tourists were replaced by swarms of midges breeding in the lakebed mud.
The lake’s future now seems brighter, however. It’s slated to be refilled when rains return, and retained as a reservoir in a large local irrigation network.
Photograph by John Stanmeyer / VII
Camels are hardy beasts, but even they have their limits. This unfortunate animal died of starvation in a remote Ethiopian encampment called Mabaalea village, another victim of starvation spurred by drought.
Rains have been scarce in the country’s Afar region and have failed to nourish the pasture land on which both animals and people depend. In 2009 the nonprofit aid organization Oxfam estimated that some 23 million East Africans were critically short of food and water, as a cycle of drought continues.
Lake Powell, Arizona
Photograph by Vincent Laforet
A cliff wall “bathtub ring” shows the shifting water levels of Lake Powell, in Arizona and Utah. This 2007 image evidences a lake surface 94 feet (28.6 meters) below “full pool” conditions, which were last seen in 1985.
Reduced rainfall, and increased water demands by thirsty western U.S. states, have led some to wonder whether the reservoir is sustainable.
China’s Hunan Province Rice Paddy
Photograph by Wang Wei/ChinaFotoPress/Getty Images
China’s Hunan Province is a major rice-producing region, but recent hot, dry weather has left villagers with little to do but ponder their parched paddies and struggle to sustain themselves in continuing drought.
In the summer of 2009, Chinese authorities warned that as many as one million people were running short of critical drinking water as drought expanded in the region.
Dry Delta in Colorado River
Photograph by Jonathan Waterman/NG Missions
For eons the Colorado River’s journey from the Rocky Mountains ended in Mexico’s Sea of Cortez. Now the river routinely peters out well short of the shore, leaving its delta dry.
Shifting precipitation patterns are partly responsible, as are dams and the staggering water requirements of the Americans along its banks. The average U.S. resident directly uses 100 gallons (378.5 liters) of water per day, compared to just 5 gallons (18.9 liters) daily for an average African. It takes some 1,800 gallons (6,800 liters) of water a day to support an average American’s lifestyle.
Sandra is a leading authority on international freshwater issues and is spearheading our global freshwater efforts.
He's paddled the Colorado River from its headwaters to the delta, in an effort to bring awareness to this mighty river at risk.
For more than 15 years, Osvel Hinojosa Huerta has been resurrecting Mexico's Colorado River Delta wetlands.
Water Currents, by Sandra Postel and Others
A year in the making, this video highlights nature's splendor.
A wetland flourishes in Mexico thanks to a treatment plant.
Scientists investigate the impacts of "micro plastics" on lake ecosystems.
Special Ad Section
The World's Water
NG's new Change the Course campaign launches. When individuals pledge to use less water in their own lives, our partners carry out restoration work in the Colorado River Basin.
A special series on how grabbing water from poor people and future generations threatens global food security, environmental sustainability, and local cultures. | <urn:uuid:517c6a40-4794-4dd9-82ca-7b7ffdfd214a> | 3.375 | 1,713 | Content Listing | Science & Tech. | 44.052652 |
Been at this for hours..
the temperature ,P, of a conductor at time, t, is given by
Where P^0 is the initial temperature and T is a constant.
Express T in terms of P,P^0 and t and determine its value when p^0 = 190, P= 20 and t = 40
Any help would be much appreciated...Thanks | <urn:uuid:687bf1a2-35c7-4e86-88a9-60ed4a1c7460> | 2.75 | 79 | Comment Section | Science & Tech. | 100.78298 |
Video: Leo on Bioluminescence
Beyond the reach of sunlight, thousands of feet below the surface of the ocean, some creatures create their own light known as "bioluminescence." Take a trip through the mind of Leo Smith, who asks questions about deep sea fish evolution. Patterns in diversity can offer clues to why fish have evolved so many ways of brightening up the deep sea. Some seem to use light to blend into their surroundings, others to lure prey out of the surroundings, or even to attract mates.
Visit the Field's new exhibition "Creatures of Light" to see how fish and other organisms make their own light.
See more of the Field Revealed! | <urn:uuid:9a304e1c-4993-4c6b-8b09-5331265c3adf> | 3.21875 | 141 | Truncated | Science & Tech. | 56.701468 |
What’s in an animal’s scientific name? Tributes to dead presidents, professions of love, and sometimes even adolescent humor.
I got to thinking about taxonomy—or how scientists name new species—after reading that a species of rugged darkling beetle, Stenomorpha roosevelti, had been named after President Theodore Roosevelt. (Not that “rugged darkling” isn’t cool enough in itself.)
The taxonomic system, developed by 18th-century Swedish biologist Carolus Linnaeus, breaks down organisms into seven major divisions called taxa, from kingdom to species. Every identified species on Earth also has a scientific name with two parts, which is called “binomial nomenclature.” (Read more about Linnaeus, the “name giver,” in National Geographic magazine.)
The new beetle’s name honors both Roosevelt’s dedication to conservation and the hundredth anniversary of a speech he gave in Tempe, Arizona, according to Arizona State University, whose scientists participated in the discovery.
Speaking of beetle honorifics, a new leaf beetle was recently named Arsipoda geographica, in recognition for the sponsorship of the National Geographic Society, society grantee Jesús Gómez-Zurita wrote this month on NewsWatch.
A new species of beaked toad nicknamed the Mr. Burns toad. Photograph courtesy Robin Moore, ILCP
Other scientists dub new species out of gratitude. Fedex, for instance, is lucky enough to be forever linked to a 300-million-year-old amphibian with bone-ripping tusks. Scientists named Fedexia strieglei as a gesture of thanks to the FedEx shipping company, which owns the land where the fossils were found, study co-author Dave Berman of the Carnegie Museum of Natural History in Pittsburgh told me in March 2010.
Likewise, the chocolate company Cadbury got a sweet nod in Kryoryctes cadburyi, a cat-size, quill-covered, dinosaur-era mammal named by paleontologists who subsisted mostly on their chocolate during a dig.
Pop culture can also provide nomenclative inspiration. Take Calumma tarzan, found recently in a tiny patch of forest—also called the Tarzan Forest—on the vast Indian Ocean island of Madagascar. Study leader Philip-Sebastian Gehring, an evolutionary biologist at the Technical University of Braunschweig, thought the name might promote conservation of the reptile—after all, “Tarzan stands for a jungle hero and fighting for protecting the forest,” he said in 2010.
In western Colombia in 2010, scientists happened upon a new beaked toad that was nicknamed the Mr. Burns toad. The new species has a “long, pointy, snoutlike nose [that] reminds me of the nefarious villain Mr. Burns from The Simpsons television series,” Conservation International expedition leader Robin Moore said in a statement in November.
Dinosaurs in particular are often bestowed with fierce monikers, like Bistahieversor sealeyi, the 29-foot-long (9-meter-long) dinosaur that once reigned over the Wild West. Eversor means “destroyer” in Latin.
Brontomerus mcintoshi—”thunder thighs” in Greek—was a powerful plant-eater that used its superstrong thighs to kick and flail predators, I reported in February.
Also, everyone knows love can make you do crazy things—like name a strange, fleshy-lipped fish after your significant other.
Marine biologist Nicola King of the University of Aberdeen, Scotland, named the Antarctic critter Pachycara cousinsi after her fiance, geophysicist Michael Cousins.
“Beauty is in the eye of the beholder,” King said in 2008.
But hands-down my favorite scientific name, at least for now, is Phallus drewesii—a suggestively shaped mushroom named, with permission, for a distinguished herpetologist with an sense of humor—Robert Drewes of the California Academy of Sciences.
Phallus drewesii, a new species of stinkhorn fungus (read more). Photograph courtesy Brian A. Perry, University of Hawaii
Brendan Borrell, in his 2009 Scientific American blog post about P. drewesii‘s discovery, said it best: “Herpetologist Robert Drewes will forever be remembered for his two-inch Phallus.” | <urn:uuid:a58cc8df-9e09-4f81-9e21-5e847f6d2efd> | 3.1875 | 954 | Nonfiction Writing | Science & Tech. | 31.237717 |
Phil Gentry has provided us with the June global lower temperature anomaly analysis from the MSU data.
Global temperatures continue to rise
Global Temperature Report: June 2011 Global climate trend since Nov. 16, 1978: +0.14 C per decade
June temperatures (preliminary)
Global composite temp.: +0.31 C (about 0.56 degrees Fahrenheit) above 30-year average for June.
Northern Hemisphere: +0.38 C (about 0.68 degrees Fahrenheit) above 30-year average for June.
Southern Hemisphere: +0.25 C (about 0.45 degrees Fahrenheit) above 30-year average for June.
Tropics: +0.24 C (about 0.43 degrees Fahrenheit) above 30-year average for June.
May temperatures (revised):
Global Composite: +0.13 C above 30-year average
Northern Hemisphere: +0.15 C above 30-year average
Southern Hemisphere: +0.12 C above 30-year average
Tropics: -0.04 C below 30-year average
(All temperature anomalies are based on a 30-year average (1981-2010) for the month reported.)
Notes on data released July 7, 2011:
Color maps of local temperature anomalies may soon be available on-line at:
The processed temperature data is available on-line at: vortex.nsstc.uah.edu/data/msu/t2lt/uahncdc.lt
As part of an ongoing joint project between UAHuntsville, NOAA and NASA, Dr. John Christy, a professor of atmospheric science and director of the Earth System Science Center (ESSC) at The University of Alabama in Huntsville, and Dr. Roy Spencer, a principal research scientist in the ESSC, use data gathered by advanced microwave sounding units on NOAA and NASA satellites to get accurate temperature readings for almost all regions of the Earth. This includes remote desert, ocean and rain forest areas where reliable climate data are not otherwise available.
The satellite-based instruments measure the temperature of the atmosphere from the surface up to an altitude of about eight kilometers above sea level. Once the monthly temperature data is collected and processed, it is placed in a “public” computer file for immediate access by atmospheric scientists in the U.S. and abroad.
Neither Christy nor Spencer receives any research support or funding from oil, coal or industrial companies or organizations, or from any private or special interest groups. All of their climate research funding comes fromfederal and state grants or contracts. | <urn:uuid:107df935-0088-4ca4-b916-e342afdc1279> | 2.734375 | 531 | Academic Writing | Science & Tech. | 46.287272 |
NEW HAVEN, Conn.--In an ambitious attempt to replicate nature, various researchers are seeking to create fuels from water and sunlight, much the way plants do.
California Institute of Technology professor Nate Lewis on Saturday gave a snapshot of the "swing for the fences" research his lab is pursuing to make fuels directly from water and sunlight. Caltech last year was picked as the lead for a newly created Joint Center for Artificial Photosynthesis (JCAP) to run the Department of Energy's Fuels from Sunlight Energy Innovation Hub.
The center is one of many so-called solar fuels efforts that seek to bypass the traditional biofuel method of growing plants and then convert biomass to a transportable, liquid fuel. Other researchers and companies are seeking to genetically engineer microbes that secrete fuels or develop cheaper methods for splitting water to make hydrogen fuel.
During a talk at the Yale Climate & Energy Institute's annual conference, Lewis described the concepts driving his research and what form a solar fuel generator could take.
The sun is the largest source of energy, but storing solar energy with conventional means, such as batteries, is very expensive, he said. The notion behind his research is to store solar energy in the chemical bonds of fuels. Light-duty transportation will move toward electric vehicles because they are more efficient than internal combustion engines, but there is still a need for liquid fuels in other forms of transportation or to generate power when there is no sun.
"It's inevitable that we will find a way to efficiently take the biggest energy source we have in the sun and store it in chemical fuels, thereby obviating the storage problem, thereby having a drop-in replacement fuel, and thereby solving the (fuel) infrastructure problem," he said. "We are going to do this. The question is how fast and how soon." … Read more | <urn:uuid:c7cf1954-dad2-4a12-a28b-e7e5f3a3cf4e> | 3.421875 | 371 | Truncated | Science & Tech. | 36.02012 |
WA) or a designated USGS station name, if the site has a gaging station. The station identification number is the designated USGS station number. The full names of all sampling crew members should be entered as the investigators, with the crew leader's name in parentheses. Information on reach conditions is also noted and includes relevant observations concerning recent flooding or local weather conditions. The reference location is a permanent structure that is easily identifiable, such as a USGS gage or bridge pier. This location is recorded as a description of the structure (for example, USGS gage) and by latitude and longitude coordinates. In addition, the exact reach length sampled is noted and information on water quality (conductivity, temperature, and dissolved oxygen) is recorded. Conductivity is recorded at ambient water temperature and thus is ambient conductivity, not specific conductance.
The equipment use section provides the opportunity to record the methods used (for example, electrofishing and seining), the gear used (backpack, towed, or boat electrofishing gear), and aspects of how the gear was used (the length of time that sampling was conducted). When using electrofishing gear, a field strength meter is used to determine the strength of the electrical field, and this information is recorded on the data sheet. Relevant information concerning the use of a particular gear is noted under "Comments" (for example, "Electrofishing gear developed mechanical problems during sampling and may not be operating at peak efficiency").
The fish species data sheet is also divided into two sections--site information and species information. The study unit designation, sampling date, station name and identification number, and investigators are completed as with the fish equipment data sheet. The name of the fish taxonomic specialist is recorded. The code for the sampling gear as provided on the fish equipment data sheet, such as "11A" for backpack electrofishing, first pass, is also entered. The fish species data sheet has an entry for a page number and a cumulative page number. The page number is used by the sampling crew to consecutively number field data sheets; therefore, the page number is unique only for a particular field sampling team during a specific field effort. At least one fish species data sheet is completed for each of the two electrofishing passes and for each additional method. For example, when recording species data for a sampling reach that is sampled using backpack electrofishing and kick seining, at least three fish species data sheets are completed--one for each electrofishing pass and one for kick seining.
The species information section provides the opportunity to record the data collected from each fish. Fish are identified to the species level, and the scientific name is recorded following the taxonomic nomenclature of fish as established by the American Fisheries Society's Committee on Names of Fishes (Robins and others, 1991). Total length, standard length, and weight are entered as previously described. The presence of external anomalies is noted using a two-letter code (table 2) similar to that used by the Ohio Environmental Protection Agency (Ohio Environmental Protection Agency, 1987). | <urn:uuid:066328c6-dd2e-433b-a420-8e490d1b42c3> | 2.75 | 631 | Documentation | Science & Tech. | 23.920243 |
The Linux kernel is the core of the operating system and offers an interface for programs to access the hardware. The kernel contains most of the device drivers.
To create a kernel, it is necessary to install the kernel source code first. The recommended kernel sources for a desktop system are sys-kernel/gentoo-sources. These are maintained by the Gentoo developers, and patched to fix security vulnerabilities, functional problems, as well as to improve compatibility with rare system architectures.
Before installing, check the active USE flags:
|build||No||No||!!internal use only!! DO NOT SET THIS FLAG YOURSELF!, used for creating build images and the first half of bootstrapping [make stage1]|
|deblob||No||Remove binary blobs from kernel sources to provide libre license compliance.|
|symlink||No||Force kernel ebuilds to automatically update the /usr/src/linux symlink|
Now install gentoo-sources:
There are various alternative kernel sources in the Portage tree:
- sys-kernel/vanilla-sources - The official, non-patched Linux kernel sources. Note that because they are left as is, and do not contain any additional patches, they are not supported by Gentoo developers.
- A full list with short descriptions can be found by searching with emerge:
- Manual configuration
- Manual configuration enables you, with some effort, to create a custom-fit kernel configuration.
- Automatic configuration
- genkernel is a tool to automatically configure and setup a kernel. The needed drivers for your system are detected and loaded at boot time.
- Steps to upgrade to a new kernel using an existing configuration.
- Steps to completely remove old kernels.
See the kernel category. | <urn:uuid:87eca8e0-5304-4fde-9562-e8c79b253145> | 3.40625 | 371 | Documentation | Software Dev. | 32.767967 |
A planet moves around the Sun in an elliptical orbit (see Fig. 8.39). (a) Show that the external torque acting on the planet about an axis through the Sun is zero, (b) Since the torque is zero, the planet’s angular momentum is constant. Write an expression for the planet’s angular momentum in terms of its mass m, its distance rfrom the Sun. and its angular velocity ω. (c) Given r and ω. how much area is swept out during a short time ∆r? [Hint: Think of the area as a fraction of the area of a circle, like a slice of pie; if ∆t is short enough, the radius of the orbit during that time is nearly constant.] (d) Show that the area swept out per unit time is constant. You have just proved Kepler’s second law! | <urn:uuid:fd9fd017-e012-4a52-aa26-be6e12d69235> | 3.71875 | 184 | Tutorial | Science & Tech. | 79.224545 |
Thanks to Gristmill for pointing to this amazing advertisment from a 1962 issue of Life Magazine. Humble Oil later merged with Standard to become Exxon.
And it's all true!
Reporting in the journal Nature in September, researchers from British Antarctic Survey and the University of Bristol describe how analysis of millions of NASA satellite measurements from both vast, polar ice sheets shows that the most profound ice loss is a result of glaciers speeding up where they flow into the sea.
The authors conclude that this ‘dynamic thinning’ of glaciers now reaches all latitudes in Greenland, has intensified on key Antarctic coastlines, is penetrating far into the ice sheets’ interior and is spreading as ice shelves thin by ocean-driven melt. Ice shelf collapse has triggered particularly strong thinning that has endured for decades.For an overview of the Arctic, check out the Arctic Report Card, released earlier this month. | <urn:uuid:79d45b39-b74f-417b-a89c-fd2b07fbe7e8> | 2.984375 | 183 | Personal Blog | Science & Tech. | 38.710861 |
A motorist suddenly notices a stalled car and slams on the brakes, decelerating at the rate of 6.3 . Unfortunately this isn't good enough, and a collision ensues. From the damage sustained, police estimate that the car was moving at 18 at the time of the collision. They also measure skid...
A source of emitting sound of 616hz is bloked on block 'A' which is attached to the free end of string. The detector fixed on block 'B' attached to free end of spring Sb detects the sound .The blocks A and B are simultaneously displaced towards each other through distance of...
a horizontal circular wire loop of radius lies in a plane perpendicular to a uniform magnetic field pointing from above into the plane of the loop, has a magnitudr of. if in the wire is reshaped from a circle into a square, but remains in the same plane, the current in the loop during the...
Two air carts of mass = 0.80 and = 0.44 are placed on a frictionless track. Cart 1 is at rest initially, and has a spring bumper with a force constant of 690 . Cart 2 has a flat metal surface for a bumper, and moves toward the bumper of the stationary cart with an initial speed = 0.62 ....
A wire carries a current of 9.8 A in a direction that make an angle of 32.4 with the direction of the magnetic field of strength 0.262 T. Find the magnetic force on a 5.4 m length of the wire. Answer in units of N.
Make an estimate of the bound current flowing round either magnet if the equilibrium height between the magnet is 4 cm, the mass of each magnet is 2g, and their radius is 2cm. Calculate also the magnetic moment for either magnet which equal to I* R^2.
A more realistic model of such a magnet can be derived by assuming a constant magnetization throughout M=kz. where k is constant and z is the main axis. This will produce bound currents on the two surface of equal size but opposite direction to one another. there will be no bound volume...
2. One electron collides elastically with a second electron initially at rest. After the collision, the radii of their trajectories are 1.00 cm and 2.40 cm. the trajectories are perpendicular to a uniform magnetic field of magnitude 0.044 T. Determine the energy (in keV) of the incident electron
A particle leaves the origin with an initial velocity = (5.06) m/s and a constant acceleration = ( - 4.91 - 1.94) m/s2. When the particle reaches its maximum x coordinate, what are (a) its velocity, (b) its position vector?
Suppose the traffic light is hung so that the tensions T1 and T2 are both equal to 72 N. Find the new angles they make with respect to the x-axis. (By symmetry, these angles will be the same.)
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1. Can you show me step by step how to solve this problem?:
- The Earth’s rate of rotation is constantly decreasing, causing the day to increase in duration. In the year 2000 the Earth takes about 0.548 s longer to complete 365 revolutions than it did in the year 1900.
- (a) What is the average angular acceleration of the Earth?
- (b) If this average acceleration remains constant, in what year will the Earths rotation come to rest?
2. I do not understand this Ideal Gas Law and Kinetic Theory question. Can you help me set it up?
- A spherical balloon is made from a material whose mass is 3.00-kg. The thickness of the material is negligible compared to the 1.5-m radius of the balloon. The balloon is filled with helium (He) at a temperature of 305-degrees K and just floats in the air, neither rising nor falling. The density of the surrounding air is 1.19-kg/m^3. Find the absolute pressure of the helium gas | <urn:uuid:56f638c2-5f38-46fc-a211-c03653343b48> | 2.9375 | 917 | Q&A Forum | Science & Tech. | 71.919302 |
Echoes of Greenland
by Eve Lamborn
Editor's Note: The world's oceans are rising every year, and scientists are watching polar ice sheets carefully. Perhaps melting caused by global warming is contributing to the increase in water level. Come along with University of Kansas student Eve Lamborn now, as she recounts her Fantastic Journey to Greenland last summer with KU scientists who used radar to measure the ice.
It was early June and I was shivering.
Though I was wearing my winter coat, the brisk wind set my teeth chattering. The cold was forgotten as a sharp crack echoed across the boulder field where I was perched — and was followed by a deep boom.
The wind I felt was blowing off the Greenland ice sheet. I was 56 kilometers (35 miles) north of the Arctic Circle, watching chunks of ice fall off a glacier. I could see a crack that had been slowly widening for the last half an hour across the face of the glacier, a tantalizing hint that a giant piece of ice was going to give way. I just knew that it was going to fall any second. Of course, I had been thinking that for 30 minutes now.
As I sat there listening to the wind and counting the minutes, small pieces of ice dropped into the water. Then, without warning, a huge piece split off and thundered down. The chunk broke apart as it fell, and the impact sent a wave of water and projectiles hurtling into the air. The reverberations echoed across the rocks.
That piece, which could have smashed a large house, was a tiny fraction of the ice sheet, which is 3 kilometers (1.9 miles) thick in some places and covers 80 percent of Greenland.
Last summer, I was in Greenland (the world's largest island) on the ultimate field trip. Scientists at the University of Kansas, where I go to school, have developed two types of airborne radar to measure Greenland's polar ice sheet. Every summer, they travel into the field to operate their radar and gather data, and I got to tag along as the science reporter.
They are studying polar ice because they think that global warming is making the ice melt more than usual, causing the ocean level to rise. Their research is funded by NASA and the National Science Foundation.
KU scientists led by Prasad Gogineni have developed a radar that measures the thickness of the ice. KU scientist Pannirselvam Kanagaratnam has developed one that maps layers formed by snowfall, which helps determine if snow is accumulating on the ice. Using these two tools, we hope to make useful discoveries.
The plane we flew in, a P-3 Orion, is a former submarine hunter used by the United States Navy and later purchased by NASA. Instead of torpedoes, the bomb bay underneath the plane carries scientific equipment. Instead of flying over oceans searching for enemy subs, the plane flies over ice gathering scientific data.
The inside of the plane was filled with lasers, global positioning systems, radar equipment, and computers. This was no regular airplane!
I received a safety briefing before my first flight. Pilot Chris Pali showed me how to operate the emergency escape hatch, breathing systems, escape rope, and life rafts. He explained how to use the rescue flares and signal mirror. Should we be stranded on the ice, everyone on board had a winter survival kit, complete with parka and boots.
I got to sit in the cockpit for a premium view of the spectacular scenery. Sometimes the ice looked soft and hazy, like waves on the water, and other times it was jagged and sharp. Sometimes we were so far out on the ice that it stretched to the horizon like a huge, frozen ocean. Other times we skimmed over glaciers that were dropping icebergs into the sea. The ice was so white, it hurt my eyes.
During the first flight, I wasn't prepared for the bumpiness. I felt like I was on an amusement park ride as I tried to take pictures while the plane pitched and rocked.
The town we stayed in, Kangerlussuaq, is the home of Greenland's major international airport, and that's about it. There aren't many people in Greenland, but there are caribou, musk ox, and lots of mosquitoes. Instead of grass, tundra covers the ground, and we were so far north that it didn't even get dark at night.
The natives of Greenland are the Inuit people, and they speak Greenlandic. I learned that I already knew two words in their language: kayak and igloo.
The scientists took their data home to begin analyzing it, trying to understand how the ice is changing so that they can predict what it might do in the future. I was sad to leave the pristine wilderness and rugged hills behind when I returned home, but it was nice to watch a sunset again.
- What kind of a biome is Greenland?
[anno: Greenland is a tundra.]
- Compared to a tropical rain forest, are there many living things in Greenland's kind of biome?
[anno: Because Greenland is a tundra, it does not have as many plants and animals as a tropical rain forest.]
- Even though Greenland and a tropical rain forest are very different, why are they both important places for scientists to study? Write a few sentences to explain your answer.
[anno: Answers may vary. Possible answers could include that the tropical rain forest is important because it has many different species of plants and animals, and we might find new medicines amongst these plants and animals. It also produces a lot of oxygen for the planet. The tundra in Greenland is important because it contains a lot of fresh water that has been frozen for a long time in the ice sheets. If the climate is changing quickly on the planet because of human activities, we might see these effects on melting glaciers in Greenland.] | <urn:uuid:818a85c2-0247-419a-a3ee-29adff58358b> | 3.515625 | 1,218 | Truncated | Science & Tech. | 55.805723 |
isolating cells from Cockroach - (Mar/05/2012 )
I have been given the following task: you have cockroaches and in these cockroaches you will find unicellular eukaryotic cells that are visable with the naked eye, how would you isolate these cells and grow then?
This is what I came up with:
since they are visable with the naked eye, I would dissect some of the cockroaches, look for the unicellular cells and simple collect them in fresh media for eukaryotic cells and check if they grow.
But where I am stuck is: how do I make sure I only have the correct cells and not for example bacteria?
I would think, I could add some antibotics to the fresh media to have a pure culture?
And then if I have them isolated, I would need to check if they are doing allright, maybe I can do some viability test?
Sounds ok. Maybe, wash the extracted cells a few times in media with antibiotics. | <urn:uuid:5faf110d-e49e-4ae7-9adb-e2c7165b66c7> | 2.875 | 213 | Q&A Forum | Science & Tech. | 54.356111 |
Forest fertilization has increased 800% in the southeastern United States from 1990 to 1999, according to a story in today’s ScienceDaily. The move to more intensive forest practices is designed to increase productivity, but at what cost?
I was fully expecting the report to indicate damning impacts on water quality in the research area’s streams, but apparently that’s not the case. In this study, the fertilization and herbicide application has small and short-lived impacts on water quality. Much of this minimal effect is due to streamside buffers that help stabilize channels, and prevent direct application in streams.
I’m encouraged by these findings, but wonder about the long-term balance of this approach. Certainly the biodiversity of these for-profit forests is completely lacking (herbicide application!?). I don’t have issue with these commercial forests as a whole, and understand the highly managed environments for timber and pulp paper production. I just wonder about the proliferation of such highly-managed forest plots, particularly if they’re spurred by carbon markets to offset greenhouse gases.
I can envision a scenario where scientists determine the optimum species for carbon offset. Then corporations move in to clearcut natural forests to create one-species tracts, reaping the financial benefits of carbon credits.
Reduced Emissions from Forest Degradation (REDD) initiatives have the potential to spur such scenarios in the developing world where land costs are cheap, and climate conditions are ripe for quick vegetative growth.
Others have commented on the potential for REDD to unleash a land rush by industrial agriculture giants and forestry firms. I’m pleased to learn that there are organizations like Sekala that are are working with spatial tools in remote and threatened forests in the developing world to ensure a balanced and long-term approach. | <urn:uuid:419d3211-9f44-44e2-9d6e-2619cbde0c17> | 3.015625 | 369 | Personal Blog | Science & Tech. | 32.531402 |
Strombus, common name the true conches, is a genus of medium to large sea snails with an operculum, marine gastropod mollusks in the family Strombidae, the true conchs and their immediate relatives.
The genus Strombus was named by Carl Linnaeus in 1758. There were around 50 living species recognized, which vary in size from fairly small to very large. Six species live in the greater Caribbean region, including the Queen Conch, and the West Indian Fighting Conch, Strombus pugilis. However, since 2006, many species have now been assigned to discrete genera.2] These new genera are however not yet found in most textbooks, collector's guides, etc.
Worldwide, several of the larger species are economically important as food sources; these include the endangered queen conch or pink conch Strombus gigas (now usually known as Eustrombus gigas or Lobatus gigas) which very rarely also produces a pink, gem quality pearl.
In the geological past, a much larger number of species of Strombus existed. Of the living species, most are in the Indian and Pacific Oceans.
Many species of true conchs live on sandy bottoms among beds of sea grass in tropical waters. They eat algae and have a claw-shaped operculum.
Like almost all shelled gastropods, conches have spirally constructed shells. Again, as is normally the case in many gastropods, this spiral shell growth is usually right-handed, but on very rare occasions it can be left-handed.
True conches have long eye stalks, with colorful ring-marked eyes at the tips. The shell has a long and narrow aperture, and a short siphonal canal, with another indentation near the anterior end called a stromboid notch. This notch is where one of the two eye stalks protrudes from the shell. The true conch has a foot ending in a pointed, sickle-shaped, operculum which can be dug into the substrate as part of an unusual "leaping" locomotion.
True conches grow a flared lip on their shells only upon reaching sexual maturity. This is called an alated outer lip or alation.
Strombus shells have a flaring outer lip with a notch near the anterior end called the stromboid notch through which the animal may protrude one of its stalked eyes.
A cladogram based on sequences of nuclear histone H3 gene and mitochondrial cytochrome-c oxidase I (COI) gene showing showing phylog enic relations of (32 analyzed) species that used to belong to the genus Strombus and Lambis:
- Strombus alatus Gmelin, 1791
- Strombus gracilior G.B. Sowerby I, 1825
- Strombus pugilis Linnaeus, 1758
- Strombus accipiter Dillwyn, 1817 : synonym of Lobatus costatus (Gmelin, 1791)
- Strombus aurisdianae Linnaeus, 1759 : synonym of Euprotomus aurisdianae (Linnaeus, 1758)
- Strombus bituberculatus Lamarck, 1822 : synonym of Lobatus raninus (Gmelin, 1791)
- Strombus bulla R?ding, 1798 : synonym of Euprotomus bulla (R?ding, 1798)
- Strombus canarium Linnaeus, 1758 : synonym of Laevistrombus canarium (Linnaeus, 1758)
- Strombus costatus aguayoi Jaume & del Valle, 1947 : synonym of Lobatus costatus (Gmelin, 1791)
- Strombus decorus (R?ding, 1798) : synonym of Conomurex decorus (R?ding, 1798)
- Strombus dehelensis : synonym of Conomurex fasciatus (Born, 1778)
- Strombus dentatus Linnaeus, 1758 : synonym of Tridentarius dentatus (Linnaeus, 1758)
- Strombus epidromis Linnaeus, 1758 : synonym of Labiostrombus epidromis (Linnaeus, 1758)
- Strombus erythrinus is a synonym for Canarium erythrinum Dillwyn, 1817
- Strombus fasciatus Born, 1778 : synonym of Persististrombus latus (Gmelin, 1791)
- Strombus fusiformis is a synonym for Canarium fusiforme Sowerby, 1842
- Strombus gallus Linnaeus, 1758 : synonym of Lobatus gallus (Linnaeus, 1758)
- Strombus gibberulus Linnaeus, 1758 : synonym of Gibberulus gibberulus (Linnaeus, 1758)
- Strombus gigas is a synonym for Eustrombus gigas L., 1758
- Strombus guidoi Man in t'Veld & De Turck, 1998 : synonym of Laevistrombus canarium guidoi (Man in 't Veld & De Turck, 1998)
- Strombus goliath Schr?ter, 1805 : synonym of Lobatus goliath (Schr?ter, 1805)
- Strombus haemastoma Sowerby, 1842 : synonym of Canarium haemastoma (Sowerby II, 1842)
- Strombus hickeyi Willan, 2000 : synonym of Dolomena hickeyi (Willan, 2000)
- Strombus inermis Swainson, 1822 : synonym of Lobatus costatus (Gmelin, 1791)
- Strombus integer Swainson, 1823 : synonym of Lobatus costatus (Gmelin, 1791)
- Strombus jeffersonia Van Hyning, 1945 : synonym of Lobatus costatus (Gmelin, 1791)
- Strombus labiatus is a synonym for Canarium labiatum R?ding, 1798
- Strombus labiosus Gray in Wood, 1828 : synonym of Dolomena labiosa (Wood, 1828)
- Strombus latus Gmelin, 1791 : synonym of Persististrombus latus (Gmelin, 1791)
- Strombus lentiginosus Linnaeus, 1758 : synonym of Lentigo lentiginosus (Linnaeus, 1758)
- Strombus listeri Gray, 1852 : synonym of Mirabilistrombus listeri (Gray, 1852)
- Strombus luhuanus Linnaeus, 1758 : synonym of Conomurex luhuanus (Linnaeus, 1758)
- Strombus magolecciai Macsotay & Villarroel, 2001 : synonym of Lobatus magolecciai (Macsotay & Campos, 2001)
- Strombus marginatus C. Linnaeus, 1758 : synonym of Margistrombus marginatus (Linnaeus, 1758)
- Strombus mutabilis Swainson, 1821 : synonym of Canarium mutabile (Swainson, 1821)
- Strombus oldi Emerson, 1965 : synonym of Tricornis oldi (Emerson, 1965)
- Strombus persicus (Swainson, 1821) : synonym of Conomurex persicus (Swainson, 1821)
- Strombus plicatus R?ding, 1798 : synonym of Dolomena plicata (R?ding, 1798)
- Strombus sinuatus Humphrey, 1786: synonym of Sinustrombus sinuatus ([Lightfoot], 1786)
- Strombus terebellatus Sowerby, 1842 : synonym of Terestrombus terebellatus (G.B. Sowerby II, 1842)
- Strombus tricornis (Humphrey, 1786) : synonym of Tricornis tricornis (Lightfoot, 1786)
- Strombus urceus Linnaeus, 1758 : synonym of Canarium urceus (Linnaeus, 1758)
- Strombus ustulatus (Schumacher, 1817) : synonym of Canarium urceus urseus (Linnaeus, 1758)
- Strombus variabilis Swainson, 1820 : synonym of Dolomena variabilis (Swainson, 1820)
- Strombus wilsoni Abbott, 1967 : synonym of Canarium wilsonorum (Abbott, 1967) | <urn:uuid:2cfd196d-4377-4f8d-a50f-ce600b21b558> | 4.09375 | 1,942 | Knowledge Article | Science & Tech. | 30.780486 |
Spreading like the ``Harlem Shake’’ meme, it seems every math classroom across the land now observes an in-school holiday called Pi Day. For the uninitiated, Pi Day is cleverly celebrated on March 14, or 3/14. A quick trip over to Pinterest regales you with endless examples of the hackneyed puns, cartoons, song lyrics, decimal expansions, and other non-activities that grace school walls to mark this annular (HA!) event.
Never mind that in Europe and many other parts of the world, Pi Day would be celebrated on 31/4 or the 31st of April, or perhaps on 3/14, the 3rd day of Dodecember, 14th month of the year—if such dates actually occurred—ergo maybe π only exists within US borders. Let's not start World War π over such differences.
The notion of Pi Day offends our math sensibilities on many levels, so if it were up to us, this half-baked practice would be shelved, and replaced with more intellectually challenging activities. (Also here and here.) We don’t want to be party poopers or sticks-in-the-mud, though, so we’ll file away our petition, but proceed with our reasoning anyway.
Unbeknownst to slightly more than three people, π is a ratio that exists in nature; if you traveled to another planet inhabited by 5-armed 3-eyed beings, their mathematicians would know π, too. The dissonance arises in decimal approximations for π, whether it be 3.14, 3.14159 (Yay, Purdue!), or π calculated to lots and lots of digits. These approximations manifest one characteristic that is definitely not universal, and that is they are represented in base 10, which is just one base among infinitely many, but happens to be the number system most earthlings use.
If you write π in base 9, the first 3 digits are 3.12, in base 11, 3.16. In base 2, π begins 11.001001000011...; in hexadecimal, it begins 3.243F6A8885A300... (yes, those are letters in there). Are there bases in which Pi Day could be celebrated on the same day in the US and France? Coincidentally, π in base e (the e of natural logarithms, or the ``other’’ commonly studied math number which exists in nature) begins 10.10..., so that would make Pi-e Day October 10 anywhere. (π in base π = 10.) But even π in base e wouldn’t resolve the unspoken contradiction of Pi Day: π is a universal constant, but any rendering of π as a decimal approximation is arbitrary. If students should learn one important dichotomy in mathematics, it’s to understand the difference between the immutable and the intractable (a notion that can certainly be extended beyond the mathematical sphere).
Mathematics is rife with arbitrary choices. After learning base 10 place value and arithmetic, one of the next really arbitrary numbers students encounter is 360, the number of degrees in a circle—but how many teachers stop to explain its history? Martians might have divided a circle into 680 degrees. Such choices may have odd consequences: a triangle’s angles add to 180, a right angle has 90 degrees, your shadow is as long as your height only when the sun is at a 45 degree angle—the arbitrary choice, um, casts its shadow far and wide. Not every student makes it to trigonometry, often where radian measure is introduced, which finally resolves this particular discordance, thanks to π.
Readers, we hope you realize much of our critique of Pi Day has been somewhat tongue-in-cheek, but our sense is that many Pi Day observances emphasize form over substance. However, you shouldn’t think we are dissing π or want students to be kept out of the inner circle of knowledge; in fact, it’s quite the opposite. We want π to be afforded the proper respect and honor it so roundly deserves. The challenge lies in the delivery: if students don't gain a level of discernment early on, they may never fully understand not only the hows and whys of π, but of 60 minutes in an hour, 12 inches in a foot, why there was a leap year in 2000 and generally every four years but there won’t be a February 29 in 2100, and won't acquire many of the myriad elements of number sense that are the hallmark of a socially cognizant and mathematically proficient student.
That's why we are particularly incensed, first by Common Core’s general neglect, and then by its shabby treatment of such an essential topic: the concept of π.
First, our approach: how would we at ccssimath.blogspot.com like π to first enter students' consciousness? Instead of Pi Day posters and platitudes, one of the simplest but most effective activities would be to let students calculate π's first few digits themselves—without our spoiling the story's ending (suggested lesson plan to follow).
At what age is it appropriate for π to be introduced, in terms of both conceptual understanding and performing calculations? We’re not here today to talk about Common Core’s treatment of decimal arithmetic, but discovering π is a classroom activity that can follow soon after the learning of decimal division, which Common Core covers in 5.NBT.7. We agree that Grade 5 is the right year to learn how to divide decimals, but rather than covering this obtuse procedure solely as a rote exercise, calculating π is a worthwhile and memorable application of decimal division.
After a class discussion of circle nomenclature, our suggested classroom activity for Grade 5 introduces π surreptitiously:
With centimeter tape measures in hand, groups of students carefully measure the circumferences and diameters of various round objects. The class makes a table of measured values and calculates the quotients. When they see time and time again the same answer result from division, whether it be from big circular objects or small ones—eureka!—they will have unwittingly discovered π for themselves.We think students won't likely forget where π comes from when they've taken a central role in the discovery process, as opposed to aimless Pi Day references to the symbol, to pictures of circles, or to π's digits, perhaps before they understand the meaning of a decimal point.
Purists may counter: what about a real derivation of π or π's irrationality? Nothing says those deeper investigations can't be revisited, but we're talking fifth grade here, folks.
Calculating π in class is an age-appropriate activity, but to reach a useful mathematical understanding, several skills need to coalesce and be applied: decimal division and ratios. Measurement is a skill we've assumed students can already do with some accuracy, and we hope they can make tables of values. Actually, we have it a bit backward: ratios are a concept that don’t need to be previously known; but calculating π is the perfect activity to introduce ratios.
An added bonus of introducing ratios while learning about π is that it skips past the simplistic notion that ratios should have integral values. When students see whole number ratios first, they may be lulled into the false notion that ratios are always in whole denominations. That, in fact, is the path on which CCSSI would have students walk: 6.RP.1 introduces the concept of ratios and the first example Common Core offers is “The ratio of wings to beaks in the bird house at the zoo was 2:1, because for every 2 wings there was 1 beak.” Another dumbing down of the standards.
Common Core, in contrast to our plan for Grade 5, doesn’t introduce ratios until Grade 6, which is too late and too simplistic. Worse still, Common Core doesn’t introduce π until—not fifth, not sixth—but Grade 7. It’s far too late.
Decimal division, ratios and π—they belong together.
In contrast to our preference, π is rarely introduced as a ratio in American math education. How might we substantiate this allegation? Teachers, we’d like you to help us with a survey. At the beginning of a class, without warning, tell your students to take out a piece of paper and in 20 seconds write their answers to this orally posed question: ``What is π?’’ No hints, no rules, no suggestions; they’re not being scored. How many will write the Greek letter or the transliteration ``pi’’? How many will write a decimal approximation? How many will write 22/7 or some other fractional approximation? Tabulate the results, and write them and the grade level in the comments section at the end of this post.
The real distinction we want to draw is: How many students wrote any of the answers above versus how many wrote an answer like ``π is the ratio of a circle’s circumference to its diameter’’. We’d expect that not many wrote this last type of answer, because it’s not the first thing to come to mind. We can't prove it, though, so that’s the question we’d like answered.
The point we make is that it will lead to deeper understanding for students to first learn the meaning of π, not its representation.
Incidentally, students in China (and some other countries) may have an unintentional advantage. The mathematical term that elementary students first learn when calculating and discovering the concept of π is a three character word that literally means ``circle circumference ratio’’. They use the Chinese term long before using the Greek letter π, so in effect, they’re imprinting ``circle circumference ratio’’ as π's definition.
If not as a ratio, how does π formally enter many American math classes? Primarily in terms of two formulas that are written, memorized and practiced together, then provided on exam cheat sheets anyway and tested. In spite of all the preparation, questions with π in them are too often bungled.
In the following open-ended question asking for the circumference of a circle (the diameter was 5 cm), the NAEP analysis provided four representative student answers, and three of those answers cited the circle area formula. None of the four cited the correct circumference formula, and overall, only 28% of American 12th graders got the right answer, considered to be in the range from 15.0 to 16.4 cm (allowing for measurement error).
Lesson unlearned, this faulty approach to ``teaching'' π is exactly what Common Core advocates. π (implicitly) premieres in standard 7.G.4, which states, ``Know the formulas for the area and circumference of a circle and use them to solve problems; give an informal derivation of the relationship between the circumference and area of a circle.’’ Common Core wants students to ``know’’ (read: memorize) the circumference and area formulas and be able to plug numbers into them, without ever needing to understand what π really means.
(Under Common Core, Grade 7 students may not have studied circles for three years: no mention of circles has been made since the fourth grade’s 4.MD.5a.)
As for the second part of 7.G.4, the wording is somewhat misleading: students shouldn’t think of the relationship between circumference and area because circumference is a length, and one does not use the circumference to determine the area; but both the circumference and area of a circle are related to π. Perhaps the standard implies the area formula may be derived from the circumference formula (which itself could have been determined in class after the Grade 5 activity previously described), but that’s a teacher-led exercise to be done in class (also preferably in Grade 5, see below), and not on a test.
One derivation of the circle area formula comes from cutting a circle into successively thinner equal wedges, rearranging them into the approximate shape of a parallelogram-cum-rectangle, and applying the area formula b x h:
Completing the proof is left to the reader. Another bonus: Grade 5 students aren’t formally learning limits or calculus yet, but in terms of concept, this derivation is awfully close.
Go ahead, celebrate Pi Day, as even the US Department of Education suggests (we'll pass). But let’s show students what π really means and how it's really used, instead of following Common Core’s plan to continue throwing π’s at them and making us eat humble pie when they don't get it. | <urn:uuid:665ad377-a72a-4e46-881d-d1cc7e0ff4a1> | 2.859375 | 2,733 | Personal Blog | Science & Tech. | 53.337072 |
New in version 2.0.
Source code: Lib/xml/dom/minidom.py
xml.dom.minidom is a minimal implementation of the Document Object Model interface, with an API similar to that in other languages. It is intended to be simpler than the full DOM and also significantly smaller. Users who are not already proficient with the DOM should consider using the xml.etree.ElementTree module for their XML processing instead
DOM applications typically start by parsing some XML into a DOM. With xml.dom.minidom, this is done through the parse functions:
from xml.dom.minidom import parse, parseString dom1 = parse('c:\\temp\\mydata.xml') # parse an XML file by name datasource = open('c:\\temp\\mydata.xml') dom2 = parse(datasource) # parse an open file dom3 = parseString('<myxml>Some data<empty/> some more data</myxml>')
The parse() function can take either a filename or an open file object.
Return a Document from the given input. filename_or_file may be either a file name, or a file-like object. parser, if given, must be a SAX2 parser object. This function will change the document handler of the parser and activate namespace support; other parser configuration (like setting an entity resolver) must have been done in advance.
If you have XML in a string, you can use the parseString() function instead:
Both functions return a Document object representing the content of the document.
What the parse() and parseString() functions do is connect an XML parser with a “DOM builder” that can accept parse events from any SAX parser and convert them into a DOM tree. The name of the functions are perhaps misleading, but are easy to grasp when learning the interfaces. The parsing of the document will be completed before these functions return; it’s simply that these functions do not provide a parser implementation themselves.
You can also create a Document by calling a method on a “DOM Implementation” object. You can get this object either by calling the getDOMImplementation() function in the xml.dom package or the xml.dom.minidom module. Using the implementation from the xml.dom.minidom module will always return a Document instance from the minidom implementation, while the version from xml.dom may provide an alternate implementation (this is likely if you have the PyXML package installed). Once you have a Document, you can add child nodes to it to populate the DOM:
from xml.dom.minidom import getDOMImplementation impl = getDOMImplementation() newdoc = impl.createDocument(None, "some_tag", None) top_element = newdoc.documentElement text = newdoc.createTextNode('Some textual content.') top_element.appendChild(text)
Once you have a DOM document object, you can access the parts of your XML document through its properties and methods. These properties are defined in the DOM specification. The main property of the document object is the documentElement property. It gives you the main element in the XML document: the one that holds all others. Here is an example program:
dom3 = parseString("<myxml>Some data</myxml>") assert dom3.documentElement.tagName == "myxml"
When you are finished with a DOM tree, you may optionally call the unlink() method to encourage early cleanup of the now-unneeded objects. unlink() is a xml.dom.minidom-specific extension to the DOM API that renders the node and its descendants are essentially useless. Otherwise, Python’s garbage collector will eventually take care of the objects in the tree.
Break internal references within the DOM so that it will be garbage collected on versions of Python without cyclic GC. Even when cyclic GC is available, using this can make large amounts of memory available sooner, so calling this on DOM objects as soon as they are no longer needed is good practice. This only needs to be called on the Document object, but may be called on child nodes to discard children of that node.
Write XML to the writer object. The writer should have a write() method which matches that of the file object interface. The indent parameter is the indentation of the current node. The addindent parameter is the incremental indentation to use for subnodes of the current one. The newl parameter specifies the string to use to terminate newlines.
For the Document node, an additional keyword argument encoding can be used to specify the encoding field of the XML header.
Changed in version 2.1: The optional keyword parameters indent, addindent, and newl were added to support pretty output.
Changed in version 2.3: For the Document node, an additional keyword argument encoding can be used to specify the encoding field of the XML header.
Return the XML that the DOM represents as a string.
With no argument, the XML header does not specify an encoding, and the result is Unicode string if the default encoding cannot represent all characters in the document. Encoding this string in an encoding other than UTF-8 is likely incorrect, since UTF-8 is the default encoding of XML.
With an explicit encoding argument, the result is a byte string in the specified encoding. It is recommended that this argument is always specified. To avoid UnicodeError exceptions in case of unrepresentable text data, the encoding argument should be specified as “utf-8”.
Changed in version 2.3: the encoding argument was introduced; see writexml().
Return a pretty-printed version of the document. indent specifies the indentation string and defaults to a tabulator; newl specifies the string emitted at the end of each line and defaults to \n.
New in version 2.1.
Changed in version 2.3: the encoding argument was introduced; see writexml().
The following standard DOM methods have special considerations with xml.dom.minidom:
This example program is a fairly realistic example of a simple program. In this particular case, we do not take much advantage of the flexibility of the DOM.
import xml.dom.minidom document = """\ <slideshow> <title>Demo slideshow</title> <slide><title>Slide title</title> <point>This is a demo</point> <point>Of a program for processing slides</point> </slide> <slide><title>Another demo slide</title> <point>It is important</point> <point>To have more than</point> <point>one slide</point> </slide> </slideshow> """ dom = xml.dom.minidom.parseString(document) def getText(nodelist): rc = for node in nodelist: if node.nodeType == node.TEXT_NODE: rc.append(node.data) return ''.join(rc) def handleSlideshow(slideshow): print "<html>" handleSlideshowTitle(slideshow.getElementsByTagName("title")) slides = slideshow.getElementsByTagName("slide") handleToc(slides) handleSlides(slides) print "</html>" def handleSlides(slides): for slide in slides: handleSlide(slide) def handleSlide(slide): handleSlideTitle(slide.getElementsByTagName("title")) handlePoints(slide.getElementsByTagName("point")) def handleSlideshowTitle(title): print "<title>%s</title>" % getText(title.childNodes) def handleSlideTitle(title): print "<h2>%s</h2>" % getText(title.childNodes) def handlePoints(points): print "<ul>" for point in points: handlePoint(point) print "</ul>" def handlePoint(point): print "<li>%s</li>" % getText(point.childNodes) def handleToc(slides): for slide in slides: title = slide.getElementsByTagName("title") print "<p>%s</p>" % getText(title.childNodes) handleSlideshow(dom)
The xml.dom.minidom module is essentially a DOM 1.0-compatible DOM with some DOM 2 features (primarily namespace features).
Usage of the DOM interface in Python is straight-forward. The following mapping rules apply:
The following interfaces have no implementation in xml.dom.minidom:
Most of these reflect information in the XML document that is not of general utility to most DOM users.
|||The encoding string included in XML output should conform to the appropriate standards. For example, “UTF-8” is valid, but “UTF8” is not. See http://www.w3.org/TR/2006/REC-xml11-20060816/#NT-EncodingDecl and http://www.iana.org/assignments/character-sets .| | <urn:uuid:994ac003-74cb-4d9d-81d9-af7117a337e5> | 3.015625 | 1,928 | Documentation | Software Dev. | 47.551603 |
Siamese Fighting Fish, commonly and incorrectly referred to as Betta fish (this is just a sub-species), inhabit Thai rice paddies in the wild and have become popular pets. They have aggressive behavior (thus the name) and are often hostile towards one another, especially between two males. Males are bigger than females and they have longer fins that almost look like feathers. One unique characteristic of Siamese Fighting Fish are the bubble nests that the male fish make when they breed. They gulp in air with their mouths from the surface, wrap it in a bubble of saliva, and spit the bubbles out continuously until a nest forms. When the female is ready, she emits the eggs and they float up to the bubble nest where they will eventually hatch.
Molecular Biology and Genetics
Statistics of barcoding coverage
|Specimen Records:||34||Public Records:||27|
|Specimens with Sequences:||31||Public Species:||22|
|Specimens with Barcodes:||31||Public BINs:||20|
|Species With Barcodes:||23|
Macropodinae is a subfamily of marsupials in the family Macropodidae, which includes the kangaroos, wallabies, and related species. The subfamily includes about ten genera and at least 51 species. It includes all living members of the Macropodidae except for the Banded Hare-wallaby (Lagostrophus fasciatus), the only surviving member of the subfamily Sthenurinae.
- Dendrolagus (tree-kangaroos)(12 species)
- Dorcopsis (greater dorcopsises)(4 species)
- Dorcopsulus (lesser dorcopsises)(2 species)
- Lagorchestes (hare-wallabies)(4 species, 2 extant)
- Macropus (kangaroos, wallaroos, and wallabies))(16 species, 13 extant)
- Onychogalea (nail-tail wallabies))(3 species, 2 extant)
- Petrogale (rock-wallabies)(16 species)
- Setonix (quokka)
- Thylogale (pademelons)(7 species)
- Wallabia (swamp wallaby)
Different common names are used for macropodines, including "wallaby" and "kangaroo", with the distinction sometimes based exclusively on size. In addition to the well-known kangaroos, the subfamily also includes other specialized groups, such as the arboreal tree-kangaroos (Dendrolagus), which have body masses between 4 and 13 kg, and a relatively long prehensile tail.
EOL content is automatically assembled from many different content providers. As a result, from time to time you may find pages on EOL that are confusing.
To request an improvement, please leave a comment on the page. Thank you! | <urn:uuid:85f2bec3-8c18-40e4-8b22-ef5e1bf034ad> | 2.9375 | 631 | Knowledge Article | Science & Tech. | 25.058451 |
Sorgenfrey line (idea)
Return to Sorgenfrey line (idea)
|The Sorgenfrey line, named after Robert Sorgenfrey (1915-1996), is the lower limit topology on the real numbers, R.
This topology has as its basis the collection of all half-open intervals [a, b) where a < b. The collection of open sets in R that comprises this topological space is therefore the collection of unions of half-open intervals in R, sometimes written R L
(Actually it's written with a fancy lowercase l that is not reproducible in my html, and which I guess stands for 'lower limit'.)
To show this is a topological space, we need to show that the unions and finite intersections of all open sets are themselves open sets, which we can do as follows:
R and the empty set are open by stipulation.
None of which is what is interesting about the Sorgenfrey line itself, which apparently has something to do with the fact that while it is itself a normal space (yeah, right), though non-metrizable, its self-product, R L x R L, sometimes known as the Sorgenfrey plane, is not normal. | <urn:uuid:84f5dbed-1738-40cb-8059-b77b32f54bf2> | 3.125 | 264 | Personal Blog | Science & Tech. | 37.721 |
Summer is a critical time for polar bears and climate change is lengthening Arctic summers, which could have a substantial effect on bear populations. However, much of what is known about polar bears comes from studying them out on Arctic sea ice during late winter and spring. During summer, most sea ice retreats far to the north, leaving some bears on shore for several months. Scientists suspect that these bears face difficult conditions on land; temperatures are warm and there’s little to eat. In contrast, some bears follow the retreating ice north, where temperatures are cooler and there may be opportunities to hunt seals.
To find out how polar bears fare in the summer, PhD candidate John Whiteman and his advisors Drs. Henry Harlow and Merav Ben-David are collaborating with scientists from the US Geological Survey and the US Fish and Wildlife Service. They are capturing and examining bears in early summer and attaching GPS-tracking collars, then re-capturing the same bears in late summer and examining them again. Comparing early- and late-summer indicators of body fat, muscle, and diet tells the scientists how well polar bears are faring in summer months. Additionally, they can use this information to forecast how longer Arctic summers may affect polar bear populations. | <urn:uuid:9155e62a-aae5-4e5f-afd1-fac090d491e9> | 4.03125 | 254 | Knowledge Article | Science & Tech. | 41.038035 |
In a previous post, the hunt for the roots, I showed how to develop the formula for the second degree polynomial. In this post I want to develop the formulas for the third and forth degree. Unfortunately this means that this whole post will be algebra and nothing else. This formulas were originally developed in the 16 century - you can read more about this in the post linked above.
A little warning - in this post I don't solve numerical examples, so I use letters to denote numbers that would be known in a numerical example, but I freely move them around. This means that if in one line I wrote bx, in the next line I will also write bx even if I should write (b+4)x instead, and the same with the sign of b. To use the formulas you will need to follow the simplification process, and then to aplly the final formula to the result.
Lets start. The idea is to get the general formula for the equation of the form:
Lets suppose that x=u-v (this step is called uglification):
Now to the forth degree. We need to solve an equation of the form:
The first step is to use the same method I used in solving the third degree polynomial, to reduce the problem to:
Now, if only the left side was a square.... Well, it is again time for uglification. Lets look on:
Now, when this will be a perfect square? The answer is simple. We need the discriminant to be equal zero. This means that:
We can now take the root and get the simple equation: | <urn:uuid:ef9707dc-70d4-4e86-9cb6-63ce51d357fa> | 3.171875 | 339 | Tutorial | Science & Tech. | 65.90835 |
- number and height of the barriers as well as the wells between barriers can easily be modified
- A single quantum well formed by two finite barriers result in resonance transmissions.
- A double quantum well slits the resonance peaks into two components.
- For N barriers, one gets N-1 quantum wells, resulting in resonance transmissions with N-1 peaks.
- The resonances peaks overlap and form a band.
- The positions of the peaks for a dispersion that is similar to the periodic potential dispersion computed in the standard Kroenig-Penney model
Researchers should cite this work as follows:
Gerhard Klimeck; Benjamin P Haley (2009), "Piece-Wise Constant Potential Barriers Tool Demonstration: Bandstructure Formation with Finite Superlattices," https://nanohub.org/resources/6836. | <urn:uuid:39f340c7-f57e-487f-85a2-035b5b32f17e> | 3.25 | 177 | Knowledge Article | Science & Tech. | 41.675595 |
By Jason Palmer
Science and technology reporter, BBC News
Even the bonds to the hydrogen atoms at the pentacene's periphery can be seen
The detailed chemical structure of a single molecule has been imaged for the first time, say researchers.
The physical shape of single carbon nanotubes has been outlined before, using similar techniques - but the new method even shows up chemical bonds.
Understanding structure on this scale could help in the design of many things on the molecular scale, particularly electronics or even drugs.
The IBM researchers report their findings in the journal Science.
It is the same group that in July reported the feat of measuring the charge on a single atom.
In both cases, a team from IBM Research Zurich used what is known as an atomic force microscope or AFM.
Their version of the device acts like a tiny tuning fork, with one of the prongs of the fork passing incredibly close to the sample and the other farther away.
When the fork is set vibrating, the prong nearest the sample will experience a minuscule shift in the frequency of its vibration, simply because it is getting close to the molecule.
Comparing the frequencies of the two prongs gives a measure of just how close the nearer prong is, effectively mapping out the molecule's structure.
The microscope must be kept under high vacuum and exceptionally cold
The measurement requires extremes of precision. In order to avoid the effects of stray gas molecules bounding around, or the general atomic-scale jiggling that room-temperature objects experience, the whole setup has to be kept under high vacuum and at blisteringly cold temperatures.
However, the tip of the AFM's prong is not well-defined and isn't necessarily sharp on the scale of single atoms. The effect of this bluntness is to blur the instrument's images.
The researchers have now hit on the idea of deliberately picking up just one small molecule - made of one atom of carbon and one of oxygen - with the AFM tip, forming the sharpest, most well-defined tip possible.
Their measurement of a pentacene molecule using this carbon monoxide tip shows the bonds between the carbon atoms in five linked rings, and even suggests the bonds to the hydrogen atoms at the molecule's periphery.
Tip of the iceberg
Lead author of the research Leo Gross told BBC News that the group is aiming to combine their ability to measure individual charges with the new technique, characterising molecules at a truly unprecedented level of detail.
That will help in particular in the field of "molecular electronics", a potential future for electronics in which individual molecules serve as switches and transistors.
Although the approach can trace out the ethereal bonds that connect atoms, it cannot distinguish between atoms of different types.
The team aims to use the new technique in tandem with a similar one known as scanning tunnelling microscopy - in which a tiny voltage is applied across the sample - to determine if the two methods in combination can deduce the nature of each atom in the AFM images.
That would help the entire field of chemistry, in particular the synthetic chemistry used for drug design.
The results are of wide interest to others who study the nano-world with similar instruments. For them, implementing the same approach is as simple as picking up one of these carbon monoxide molecules with their AFM before taking a measurement. | <urn:uuid:a8c29b3e-d0ef-45ec-98b3-0898ece3d0bf> | 3.265625 | 691 | Truncated | Science & Tech. | 33.091705 |
Let's assume the following for conceptual simplicity:
The plate is an insulator with uniform surface charge density $\sigma$.
The electric field $\mathbf E(\mathbf x)$ is uniform, so there exists some vector $\mathbf E_0$ for which $\mathbf E(\mathbf x) = \mathbf E_0$ for all $\mathbf x$.
In both cases, the force on the plate $P$ is given by
\mathbf F = \int_P dA \sigma \, \mathbf E(\mathbf x)
where $dA$ is a surface area element on the plate. Since the electric field was assumed constant, it comes out of the integral, and the remaining integral just gives the total charge $Q$ on the plate, so we get
\mathbf F = Q\mathbf E_0
The result is the same in both cases! However, if the electric field were not uniform, or if the charge density on the plate were not uniform, then in general the results would have been different.
Hope that helps! | <urn:uuid:2eb8ae3c-7aaf-4745-827d-3cf031f665c6> | 2.78125 | 231 | Q&A Forum | Science & Tech. | 56.35176 |
There are generally 4 uses for the parentheses
() in Python.
- It acts the same way as most of the other mainstream languages - it's a construct to force an evaluation precedence, like in a math formula. Which also means it's only used when it is necessary, like when you need to make sure additions and subtractions happen first before multiplications and divisions.
It is a construct to group immutable values together in the same spirit as a similar set notation in math. We call this a tuple in Python. Tuple is also a basic type. It is a construct to make an empty tuple and force operator precedence elevation.
- It is used to group imported names together in import statements so you don't have to use the multi-line delimiter
\. This is mostly stylistic.
- In long statements like
decision = (is_female and under_30 and single
is_male and above_35 and single)
the parenthesis is an alternative syntax to avoid hitting the 80 column limit and having to use
\ for statement continuation.
In any other cases, such as inside the
for predicates and the
return statement I'd strongly recommend not using
() unless necessary or aid readability (defined by the 4 points above). One way to get this point across is that in math,
(1) and just
1 means exactly the same thing. The same holds true in Python.
People coming from the C-family of languages will take a little bit getting used to this because the
() are required in control-flow predicates in those languages for historical reasons.
Last word for
return statements, if you are only returning 1 value, omit the
(). But if you are returning multiple values, it's OK to use
() because now you are returning a grouping, and the
() enforces that visually. This last point is however stylistic and subject to preference. Remember that the
return keywords returns the result of a statement. So if you only use
, in your multiple assignment statements and tuple constructions, omit the
(), but if you use
() for value unpacking and tuple constructions, use
() when you are returning multiple values in
return. Keep it consistent. | <urn:uuid:2167e400-cc5d-48f2-bff9-759cd0ed8988> | 4.0625 | 460 | Q&A Forum | Software Dev. | 43.926356 |
Kaggle recently ran another great competition, which I was very fortunate to win. The goal of this competition: detect clouds of dark matter floating around the universe through their effect on the light emitted by background galaxies.
From the competition website:
There is more to the Universe than meets the eye. Out in the cosmos exists a form of matter that outnumbers the stuff we can see by almost 7 to 1, and we don’t know what it is. What we do know is that it does not emit or absorb light, so we call it Dark Matter. Such a vast amount of aggregated matter does not go unnoticed. In fact we observe that this stuff aggregates and forms massive structures called Dark Matter Halos. Although dark, it warps and bends spacetime such that any light from a background galaxy which passes close to the Dark Matter will have its path altered and changed. This bending causes the galaxy to appear as an ellipse in the sky.
The task is then to use this “bending of light” to estimate where in the sky this dark matter is located.
Although the description makes this sound like a physics problem, it is really one of statistics: given the noisy data (the elliptical galaxies) recover the model and parameters (position and mass of the dark matter) that generated them. After recovering these dark matter halos, their positions could then be uploaded to the Kaggle website where a complicated loss function was used to calculate the accuracy of our estimates.
Bayesian analysis provided the winning recipe for solving this problem:
- Construct a prior distribution for the halo positions , i.e. formulate our expectations about the halo positions before looking at the data.
- Construct a probabilistic model for the data (observed ellipticities of the galaxies) given the positions of the dark matter halos: .
- Use Bayes’ rule to get the posterior distribution of the halo positions: , i.e. use to the data to guess where the dark matter halos might be.
- Minimize the expected loss with respect to the posterior distribution over the predictions for the halo positions: , i.e. tune our predictions to be as good as possible for the given error metric.
For step 1. I simply assumed that the dark matter halos were distributed uniformly at random across the sky. Step 2 is more complicated. Fortunately the competition organizers provided us with a set of training skies for which the positions of the dark matter halos was known, as well as a summary of the physics behind it all. After reading through the tutorials and forum posts it became clear that the following model should be reasonable:
where denotes the normal distribution, is the tangential direction, i.e. the direction in which halo bends the light of galaxy , is the mass of halo , and is a decreasing function in the euclidean distance between galaxy and halo .
After looking at the data I fixed the variance of the Gaussian distribution at 0.05. Like most competitors I also noticed that all skies seemed to have a single large halo, and that the other halos were much smaller. For the large halo I assigned the halo mass a log-uniform distribution between 40 and 180, and I set . For the small halos I fixed the mass at 20, and I used . The resulting model is likely to be overly simplistic but it seems to capture most of the signal that is present in the data. In addition, keeping the model simple protected me against overfitting the data. Note that I assumed that the galaxy positions were independent of the halo positions, although it turns out this may not have been completely accurate.
After completing step 1 and 2, step 3 and 4 are simply a matter of implementation: I choose to use a simple random-walk Metropolis Hastings sampler to approximate the posterior distribution in step 3. The optimization in step 4 was done using standard gradient-based optimization, with random restarts to avoid local minima.
Like I remarked in the competition forums, the outcome of this competition was more noisy than is usual: final prediction accuracy was judged on a set of only 90 cases, with an evaluation metric that is very sensitive to small (angular) perturbations of the predictions. The public leaderboard standings were even more random, being based on only 30 cases. In fact, the 1.05 public score of my winning submission was only about average on the public leaderboard. All of this means I was very lucky indeed to win this competition. Nevertheless, runner-up Iain Murray seems to have taken a very similar approach, suggesting there is at least something to be said for looking at this kind of problem from a Bayesian perspective.
Finally, I would like to thank the organizers Dave and Tom, and sponsor Winton Capital for organizing a great competition. Looking at a problem different from the standard regression/classification problems was very refreshing.
I will post the Matlab code for my solution sometime later this week | <urn:uuid:4564838e-b6e7-4ba4-a4b7-dc159ac71597> | 3.15625 | 1,030 | Personal Blog | Science & Tech. | 46.224805 |
For the first time, scientists at Exeter University have captured on film the process by which plants alert each other to possible dangers. When a plant is under attack it releases a gas which warns neighbouring plants to protect themselves.The ability of plants to communicate with one another isn't new; the novelty is that this has now been "captured on film." It's doesn't seem likely that the flashes shown on the video are "real" - perhaps they are CGI representations of more subtle changes. The flashes (beginning at 1:30) are said to be evidence of "biological activity." One suggestion at the Reddit thread: "my guess is that these are transgenic plants containing a foreign gene known as a "reporter" that produces a visual signal of some kind in response to the gas they are interested in. This signal could be light, but it is probably very, very dim."
And I wonder what gas the plants are releasing that serves as the messenger?
(I can't embed the video; those interested will need to view it at the link.)
And a hat tip to 127001y in the Reddit thread for suggesting the phrase I used for the title. | <urn:uuid:c319e6b6-416b-49f8-817c-1305f897ed7f> | 2.96875 | 240 | Personal Blog | Science & Tech. | 55.534993 |
A) A ring with a 15cm radius and with a uniform charge of 20
microcoulombs is in the yz-plane with the origin at its center.
What isthe force on a -3 micro coulombs charge on the x-axis at
I tried to plug in the numbers for the above equations and
can'tseem to get the right answer. I first solved for E and
thenmultiplied it to Q which is -3*10^(-6) C...correct?
The answer should be -6.83 N, but I can't seem to figure
B) How many electrons must be removed from a conducting sphere
witha 3cm radius to make the electric field its surface
C) Two electrons separated by 2*10^(-10) m are released from
rest.What is the speed of each electron when they are a large
distanceapart. (Both electrons should have the same speed.)
Thanks for the help. Will rate lifesaver!!! | <urn:uuid:ffc98d53-eb57-4b1d-b251-be2d36b900b7> | 2.796875 | 208 | Q&A Forum | Science & Tech. | 83.83452 |
Major Section: HISTORY
Examples: :pc 3 ; print the third command executed :pc :max ; print the most recent command :pc :x ; print the most recent command :pc fn ; print the command that introduced fnSee command-descriptor.
Pc takes one argument, a command descriptor, and prints the command
identified by that descriptor. See command-descriptor. For
ACL2 !>:pc foo LVd 52 (DEFUN FOO (X) X)
Pcalways prints a space first, followed by three (possibly blank) characters (``LVd'' above) explained below. Then
pcprints the command number, a number uniquely identifying the command's position in the sequence of commands since the beginning of the user's session. Finally, the command itself is printed.
pc always prints a space first, some history commands, for
pe, use the first column of output to delimit a
region of commands or to point to a particular event within a
:pcs 52 54 will print something like
/LVd 52 (DEFUN FOO (X) X) LV 53 (DEFUN BAR (X) (CONS X X)) \ 54 (DEFTHM FOO-BAR (EQUAL (CAR (BAR X)) (FOO X))) : ... 127 (DEFUN LATEST (X) X)Here, the two slash characters in the first column are intended to suggest a bracket delimiting commands 52 through 54. The last command printed by
pcsis always the most recent command, i.e., the command at
:here, and is separated from the rest of the display by an elipsis if some commands are omitted.
pe command will print a particular event within a
command block and will indicate that event by printing a ``
the first column. The symbol is intended to be an arrow pointing at
the event in question.
true-listp-app might print:
1 (INCLUDE-BOOK "list-book") \ > (DEFTHM TRUE-LISTP-APP (EQUAL (TRUE-LISTP (APP A B)) (TRUE-LISTP B)))using the arrow to indicate the event itself. The slash printed to connect the command,
include-book, with the event,
defthm, is intended to suggest a tree branch indicating that the event is inferior to (and part of) the command.
The mysterious three characters sometimes preceding a command have the following interpretations. The first two have to do with the function symbols introduced by the command and are blank if no symbols were introduced.
At any time we can classify our function symbols into three disjoint
sets, which we will here name with characters. The ``
functions are those in
program mode. The ``
L'' functions are
logic mode whose guards have not been verified. The
V'' functions are those in
logic mode whose guards have
been verified. Note that
cause function symbols to be reclassified. If a command introduces
function symbols then the first mysterious character indicates the
class of the symbols at the time of introduction and the second
character indicates the current class of the symbols (if the current
class is different from the introductory class).
Thus, the display
PLd 52 (DEFUN FOO (X) X)tells us that command 52 introduced a
programfunction but that some command after 52 changed its mode to
logicand that the guards of
foohave not been verified. That is,
foo's termination has been verified even though it was not verified as part of the command that introduced
foo. Had a subsequent command verified the guards of
foo, the display would contain a
P d 52 (DEFUN FOO (X) X)indicates that
foowas introduced in
programmode and still is in that mode.
The third character indicates the enabled/disabled status of the
runes introduced by the command. If the status character is blank
then all the runes (if any) introduced are enabled. If the status
character is ``
D'' then some runes were introduced and they are
all disabled. If the status character is ``
d'' then at least
one, but not all, of the runes introduced is disabled. Thus, in the
L d 52 (DEFUN FOO (X) X)we see that some rune introduced by command 52 is disabled. As noted in the documentation for rune, a
defuncommand introduces many runes, e.g., the axiomatic definition rule,
(:definition fn), the executable counterpart rule,
(:executable-counterpart fn), and type-prescriptions,
(:type-prescription fn). The display above does not say which of the runes based on
foois disabled, but it does tell us one of them is; see disabledp for how to obtain the disabled runes for a given function symbol. | <urn:uuid:db71ebea-2115-4eea-9c50-8f7c7df590fc> | 3.40625 | 1,042 | Documentation | Software Dev. | 57.583128 |
Pacific Rocky Intertidal Monitoring: Trends and Synthesis
Click here for Long-Term trends
Click here for Biodiversity Survey findings
East Point is located in the Northern Channel Islands, within the Channel Islands National Marine Sanctuary, on Santa Rosa Island, California. This site is located in an Area of Special Biological Significance (San Miguel, Santa Rosa, and Santa Cruz Islands ASBS) in Channel Islands National Park. This site receives roughly 200-300 visitors per year. Hard, coarse, volcanic rock forms the reef at the eastern tip of the island. A low, sloping, rocky bluff backs the reef. At the point, the reef flat extends about 60 m from the bluff, stepping down with abrupt changes in biota from barnacles to rockweed, to mussels, to surfgrass. Because of the low slope though, the zones tend to be wide. The lower reef has many channels and small pools.
East Point is dominated by consolidated volcanic bedrock, and the area surrounding the site is comprised of a mixture of consolidated bedrock and sandy beach. The primary coastal orientation of this site is southeast.
Long-Term Monitoring Surveys at East Point were established in 1986, and are done by Channel Islands National Park. Long-Term MARINe surveys currently target the following species: Chthamalus/Balanus (Acorn Barnacles), Mytilus (California Mussel), Hesperophycus (Olive Rockweed), Silvetia (Golden Rockweed), Endocladia (Turfweed), and Phyllospadix (Surfgrass). In addition, motile invertebrates and mussel size structure are monitored at this site. Click here to view Long-Term trends at this site.
Biodiversity Surveys were done by University of California Santa Cruz in 2001 and 2004. The Biodiversity Survey grid encompasses one section that is approximately 35 meters (along shore) x 20 meters (seaward). Click here to view Biodiversity Survey findings at this site.
For more information about East Point, please contact Dan Richards | <urn:uuid:d2f0fbf1-2928-4342-8acb-7a7658d96d9e> | 2.859375 | 424 | Knowledge Article | Science & Tech. | 36.925235 |
MARSES Project Information
MARSES is an integrated research experiment devoted to searching for water, water-ice or permafrost layers believed to exist at some depth under the visible surface of Mars. There is much evidence that water once was abundant on Mars. There are stream lined islands formed by flowing water, flow patterns reminiscent of wadis in Earth deserts, and outflow channels thought to have been formed by sudden out-rush of subterranean water. Secondary tasks are the measurement of the soil properties of the subsurface of Mars which include porosity, electrical resistance of the liquid phase, thermal conductivity, temperature dependence.
Estimates of Martian water ranges from a 50 to a 500 m deep planet-wide ocean. No obvious mechanism for the escape of water from the planet has been devised. Jean?s escape of water via the atmosphere is very slow (of the order of 3 m over 5 Gy). Assuming that Mars was formed with approximately the same relative amount of water as the Earth, it must be assumed that a substantial fraction of this water remains on Mars in one form or another. It is commonly believed to be bound as ice in the polar caps and, in the ground, as ice, icy permafrost or even as water. There is also indirect evidence for widespread presence of ice, bearing permafrost and liquid fase of water through the existence of rampart craters, terrain softening, chaotic terrain and thermokarst.
In order to ensure the greatest possible penetration of the electromagnetic waves into the ground the wavelength must be chosen as long as possible.
A main task of the MARSES system is to examine changes in subsurface properties of local areas regolith on Mars surface, and to relate them to optical Images and other remote sensing data in order to understand the nature of different terrain forms.
The responsibility for the development of the MARSES system and for the coordination of the modifications of the MARSES system and its operation will rest with MPICh, with key partners in JPL/NASA , IRE/RAS and IKI/RAS (Russia), CNRS CEPHAG and SA (France) and ESA/SSD (the Netherlands). A brief summary of the questions addressed by MARSES and the measurements which must be made in order to answer them is given in the following table. | <urn:uuid:98da7851-bedf-4961-a726-d4f33cb4a508> | 3.796875 | 481 | Knowledge Article | Science & Tech. | 33.365664 |
Hello, I am fairly new at Java and just have a couple of questions to help me understand exactly what kind of program, class I am supposed to write.
Create an Interval class that represents an interval of numeric values. For example, it could represent the interval [1,2].
This class will be used to perform computations on uncertain quantities. For example, if you have a number in the range [1, 2] and another number in the range [0.1, 0.3], then their sum must be in the range [1.1, 2.3]. This can be used to answer questions like "If you have between 1000 and 2000 people, and between 10% and 15% of them have a pet goat, what are the most and least people that could have a pet goat?"
From what I understand so far is I have to ask the user to input two intervals one the range of people next the range of percentages.
Ensure that instances of your class are immutable (you can't change the interval that an object represents after you create it), and support the following operations:
add: add two intervals, returning the interval in which the sum must lie.
I do not understand what I need to add. The only operations I see necessary is multiplying the percentages by the range of people. This part of the assignment confuses me the most.
multiply: multiply two intervals, returning the interval in which the product must lie.
equals: test if two Interval objects represent the same numeric interval.
This is the second part of the assignment that confuses me as well. Why do I need to test two intervals to have the same numeric interval? I don't see the point in this.
Implement a toString method that provides a nice representation of the interval.
Include a main method that tests your class's functionality. It should test the operations using a variety of intervals, including the following cases:
0-width intervals (like [1, 1])
Intervals that lie in (0, +∞)
Intervals that lie in (-∞, 0)
Intervals containing 0.
Optional: support unbounded intervals, like (-∞, 3], [-3, ∞), or (-∞, ∞).
And finally, I am having trouble finding out how to get the user to enter the value for infinity.
Thank you, for any helpful hints. | <urn:uuid:76724f32-1d6c-4d95-9818-da534f13679a> | 2.828125 | 506 | Q&A Forum | Software Dev. | 63.840086 |
Hal Weaver Eyes
Astronomers have been treated to an amazing display of two
spectacular comets over the past year, and the grand finale is
coming in early April.
That's when comet Hale-Bopp, the largest and one of the most unusual comets ever observed by astronomers, will peak in brightness as it makes its closest approach to the sun.
Taken alone, the two cometary visitations are exciting. But when you throw in 1994's extraordinary observations of a comet actually colliding with the planet Jupiter, it just doesn't get any better, said astrophysicist Hal Weaver.
"This is really a golden age of cometary astronomy," said Weaver, who specializes in research on comets and their connection to the origin of the solar system.
Hale-Bopp was discovered in July 1995 by amateur astronomers Alan Hale of Cloudcroft, N.M., and Thomas Bopp, of Glendale, Ariz. Only a few months later, an amateur Japanese astronomer peering through a pair of binoculars spotted comet Hyakutake, which peaked last spring.
Since then Weaver has been hopping from one project to another, juggling scientific papers about both comets and stealing away to various meetings to talk about his work.
"When baseball season starts this spring, I don't know what I'm going to do," said the astronomer, who has two sons, Alex, 8, and Eric, 5.
Not that he's complaining.
Quite the opposite. Hopkins astronomers are celebrating Hale-Bopp's arrival with ambitious science projects; Weaver trekked to Hawaii last week, observing the comet with an infrared telescope on the windy summit of Mauna Kea, a 796-foot dormant volcano. Next month other Hopkins scientists, led by astrophysicist Paul Feldman, will travel to White Sands, N.M., launching a rocket that will rise above the Earth's atmosphere to observe ultraviolet light from Hale-Bopp.
"We will enhance our knowledge because it's a particularly bright comet, and we are looking at it with new technology, so it's a big leap of understanding," said Feldman, who is chairman of the Department of Physics and Astronomy.
Comets bombarding the Earth billions of years ago may have provided vital water and organic compounds necessary for the genesis of life.
"But I don't promise definitive answers to the very large questions, like, Where did life come from?" Feldman said. However, considering that cometary bombardments probably have played an important role in Earth's evolution, Hale-Bopp's appearance is profound.
"It's obviously of great interest to have a comet that's this large coming in," Feldman said, noting that one compelling question has to be, "What's the probability that such a comet could hit the Earth?"
According to one estimate, a comet might hit Earth once every three million years. But there is no fear of that happening with Hale-Bopp; it will reach its closest distance to Earth, 122 million miles, on March 22.
Hale-Bopp returns to Earth only about once every 3,000 years, so astronomers are taking advantage of its rare visit.
Their goal: to learn and confirm important details about the composition and origin of comets; by doing so, they will help to uncover secrets surrounding the formation of the solar system, 4.6 billion years ago. They may even gather information about the original material that existed in space before the solar system was born.
"This is a unique opportunity," Weaver said. "We have never had the chance to examine a comet in this much detail over this large a range of distance from the sun."
Hale-Bopp was unusually bright when it was still a great distance from the sun, well outside the orbit of Jupiter. For that reason, it has given scientists their best view ever of the changes in a comet's solid nucleus as it gets closer to, and is progressively heated by, the sun. Those changes, in turn, provide information about the composition and structure of comets.
Scientists are interested in comets because of their place in cosmic history.
"We think that when you look at a comet today you are looking back into the past," said Weaver, a research scientist in the Department of Physics and Astronomy.
The solar system was born from a huge cloud of gas and dust, which coalesced into larger and larger bodies, eventually forming the planets. But many smaller, left-over bodies were driven to the outskirts of the solar system by the gravitational forces of the giant gas planets, Jupiter, Saturn, Neptune and Uranus.
There, far from the sun's warming influence, these comets, frozen "dirty snowballs" of ice and dust, preserved the original material from the solar system's birth. Studying comet Hale-Bopp might enable astronomers to "take a scoop out of" the original material from the interstellar cloud that condensed to form the solar system, Weaver said.
He led a team of astronomers who used the Hubble Space Telescope to observe the comet for a one-year period, ending in mid-October 1996, when Hale-Bopp came too close to the sun from Earth's perspective to be viewed safely with the space telescope. Looking too close to the sun could subject the telescope to dangerous heating.
For that reason, astronomers will have to use telescopes on the ground and on sounding rockets to observe the comet as it approaches its rendezvous with the sun.
During their yearlong study, astronomers learned surprising details about Hale-Bopp. Some of their findings contradict conventional thinking about how comets are put together. The astronomers observed ultraviolet light from the comet with Hubble and the International Ultraviolet Explorer satellite.
By examining Hubble images, researchers estimated that the comet's nucleus may be 30-40 kilometers (about 22 miles) in diameter. In comparison, the potato-shaped nucleus of Halley's Comet, considered to be a large one, had an equivalent diameter of about 10 kilometers.
"Hale-Bopp looks like it's a monster in that respect," Weaver said. The average comet is thought to have a nu-cleus of about 5 kilometers in diameter.
Another surprise is the way in which the comet would suddenly grow brighter and then return to its usual brightness within an hour or so.
"The surface of Hale-Bopp's nucleus must be an incredibly dynamic place, with new 'vents' being turned on, possibly triggered by the rotation of an icy region into sunlight, and then turned off again," Weaver said.
Also surprising is the way in which various types of ices are being vaporized. A well-accepted cometary model suggests that dust particles and various chemical compounds, such as carbon dioxide and carbon disulfide, are all contained inside frozen water. As the comet nears the sun, it heats up, vaporizing the water and releasing other material and dust particles that were contained in the ice. The dust is spewed off in a huge tail extending millions of miles, reflecting sunlight and brightening the comet.
But their observations have astronomers wondering about that model. They found that various chemicals have been vaporizing independently of water. While the vaporization rate of water increased more than 10-fold between April and October 1996, there was only a twofold increase in the rate of dust being released.
If the model were correct, water, dust and the other components should be released at relative rates.
"The poor correlation between the water and dust production suggests that much of the dust and water might be coming from physically different regions of the nucleus," Weaver said. "Similarly, carbon disulfide may be coming from yet another patch. Some of these effects have been observed in other comets. But Hale-Bopp will probably provide the most revealing portrait of the workings of a cometary nucleus since the spacecraft missions to comet Halley in 1986."
Comets and asteroids are similar in that they are both
believed to be left over from the formation of the solar system,
about 4.6 billion years ago.
A swirling cloud of gas and dust initially produced a rocky material, which coagulated into larger and larger bodies that merged to form the planets.
But not all the material went into building the planets. Some bodies, called asteroids, inhabit a vast belt located between the orbits of Mars and Jupiter. Because of their relative closeness to the sun, they formed hot, vaporizing lighter substances, such as water, leaving behind dried-out rocky hulks.
But other leftover bodies, called comets, were formed from material located much farther from the sun, outside the orbits of Uranus and Neptune. Because they coalesced so far away, comets were born cold, at temperatures as low as minus 260 degrees Celsius, or about minus 435 degrees Fahrenheit.
Therefore, they have been preserved over billions of years, perhaps harboring some of the original material from which the solar system formed, whereas the planets have undergone major changes over time from geological, thermal and atmospheric processes.
Comets have been called "dirty snowballs" because they contain dust mixed with frozen compounds, including water, carbon dioxide and carbon disulfide. But asteroids are like the dirt in the snowball, without the icy components.
Comets come from two regions in the outer solar system. One region is a disk of bodies called the Kuiper belt, located outside the orbit of Neptune. The other region, called the Oort cloud, is much larger and may extend to 9 trillion miles from the sun, nearly halfway to the nearest star, Alpha Centauri. Comets in the Oort cloud sometimes end up in orbits that take them into the inner solar system when they are jostled out of place by the gravitational field of a star, or a giant molecular cloud, from which new stars form. Scientists believe that is what happened to comet Hale-Bopp at least 30,000 years ago. It takes roughly 3,000 years to complete one orbit, which extends from outside the orbit of Pluto to about 85 million miles from the sun.
Another class of comets, called "short-period" comets, take less than 200 years to complete an orbit around the sun and are thought to have originated in the Kuiper belt.
Comets and asteroids do occasionally hit the Earth, but asteroids are considered more dangerous than comets. That's because the asteroid belt is so full that they collide with one another, throwing off debris that can end up in unstable orbits, hitting the innermost planets, including Earth.
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Data and reporting
In this section:
Information about our local wildlife is essential for us, if we are to identify those species which most urgently require conservation action. This information is gathered by professional ecologists, local naturalist groups and members of the public, and is collected by local biological record centres across the UK. In Nottinghamshire, biodiversity data is held by the Nottinghamshire Biological and Geological Record Centre (NBGRC), which is based at Wollaton Park in Nottingham.
The primary function of the NBGRC is to map the areas within the county that are particularly valuable for wildlife - locally these are known as Site of Importance for Nature Conservation (SINCs), also known as Local Wildlife Sites. To find out more about these sites and how they are selected, please follow the link below.
If you have made any sightings of mammals, birds, amphibians, reptiles, fish, plants or fungi then please send these records to the NBGRC at NBGRCG@nottinghamcity.gov.uk providing details of the species you have seen, along with a date of the sighting, the location (with a six figure grid reference if possible), and any other information such as the numbers of animals seen.
To find out more about Visit the NBGRC website.
BARS is an information system that supports the planning, monitoring and reporting requirements of national, local and company Biodiversity Action Plans (BAPs). It also allows users to learn about the progress being made with local and national BAPs.
Partners of Notts Biodiversity Action Group report on their activity towards Local Biodiversity Action Plan targets each year during annual monitoring rounds, which will now use BARS. This process allows the partnership to measure success, identify and address any gaps in work and highlight areas in which partners can work together. This monitoring process allows Notts BAG to report to the UK Biodiversity Action Plan on progress made towards the national BAP targets in the local area.
If you do not have a BARS username, you can still search the BARS database to learn about the status of BAP species and habitats, and the conservation action that is underway. | <urn:uuid:604e10de-b22e-4c47-a0c9-41f84e8bf454> | 3.203125 | 449 | Knowledge Article | Science & Tech. | 32.322583 |
Q 'n A
Answers To Your Questions
SPACE TODAY ONLINE ~~ COVERING SPACE FROM EARTH TO THE EDGE OF THE UNIVERSE
Q. How old is the Universe? — Ashley B.
A. Many astronomers say the Universe is 13.7 billion years old, plus or minus 10 percent.
How do they know? There are four approaches to calculating the age.
1. One method of judging the age of the Universe involves its expansion. Astronomers see the Universe expanding. Galaxies around our Milky Way galaxy are moving away at a significant speed. That is one of the reasons cosmologists believe the Universe began in a Big Bang and has been expanding ever since. Using powerful instruments like the Hubble Space Telescope, astronomers have been able to look at objects dating back most of the way to the Big Bang. This has allowed them to estimate the rate that the Universe has been expanding in the past. Projecting the data backwards, they calculated the Universe shrank to a single point somewhere between 13.5 billion and 14 billion years ago.
2. A second method of measuring the age of the Universe involves the age of white dwarf stars. A white dwarf is a small dense star, about the size of Earth, that has undergone gravitational collapse and is at the final stage of its evolution. Initially all stars are powered by hydrogen fusion but, after they run out of fuel, white dwarfs keep shining because they are hot. However, hot things cool off. White dwarfs gradually cool at a rate astronomers have calculated. The oldest white dwarfs have ages that range from 13.0-13.5 billion years.
3. A third method of assessing the age of the Universe is the study of star clusters. As with white dwarfs, astronomers have found that the oldest star clusters are 13.0-13.5 billion years old.
4. A fourth method of finding the age of the Universe looks at cosmic microwave background radiation. CMB radiation is a faint microwave electromagnetic signal that comes from all points in the sky. Scientists explain it as fossil radiation left over from an early stage in the development of the Universe. They consider CMB to be strong evidence of the Big Bang. They say that during the first 300,000 years of the Universe, it was filled with a foggy plasma. As the Universe expanded and cooled, hydrogen atoms began to form into protons and electrons. As a result, space became increasingly transparent. CMB seen today is light that was released when most of the hydrogen atoms formed and that has been traveling through space for billions of years. By analyzing variations in the intensity of the CMB radiation, astronomers calculate the age of the Universe at 13.72 billion years.
Looking back in time. The deepest image of the Universe recorded by the Hubble Space Telescope shows the faintest objects. Because they are the most distant objects, the image is the equivalent of using a time machine to view the formation of the oldest galaxies. They may have formed fewer than one billion years after the Universe's birth in what cosmologists call the Big Bang.
Source: How Old Is the Universe? by Vanderbilt University astronomy professor David A. Weintraub, published 2010 by Princeton University Press, ISBN: 9780691147314
Ask Space Today Online another question
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What is Phenology?
What is Phenology?
Literally, phenology refers to “the science of appearance.” In the simplest terms, phenology is the study that measures the timing of life cycle events in all living things. The life cycle of an organism is the period of time involving a single generation through reproduction. So, when we think of a life cycle in an organism, we are not necessarily referring to the life span, but rather, the period of time it takes to reproduce a generation. Life cycle events are also known as phenophases. In plants, this includes first leaf, budburst, first flower, last flower, first ripe fruit, seed dispersal, and leaf color change, among others. In animals, the phenophases include mating, offspring production, molting, hibernation, and migration, among others.
Scientists who study phenology – phenologists – are interested in the timing of specific biological events with relation to seasonal and climatic change. Seasonal and climatic changes are some of the non living or abiotic components of the environment that impact the living or biotic components. Seasonal changes can include variations in day length, temperature, and rain or snowfall. Phenologists attempt to learn more about the abiotic factors that plants and animals respond to. In other words, how do plants and animals know it is time to migrate, hibernate, set flower, disperse seeds, or enter dormancy? What ‘calendar' or ‘clock' do they use to begin flowering, leafing, or mating?
When teaching lessons on phenology, I sometimes have folks wonder if phenologists are really just studying 'seasonality.' The term seasonality is used to describe changes in the abiotic environment such as the dates of first and last frost whereas the term phenology is used for studying the timing of biological events as influenced by seasonality.
Phenophases occur throughout the life cycle of an organism, however, spring is generally the time that we see a marked increase in the phenological activity that can even appear to be dramatic in contrast to winter. Depending on where you live, think of the changes in your local environment that tell you spring is almost here. In the Washington, DC area, cherry blossoms are a sure sign that spring is on its way. In many parts of the country, hearing the songs of the first robins of the season are what you look forward to. California poppies are an indicator of spring to many along the Pacific shores. In the Midwest, the greening up of fields and pastures is a signal that winter is almost over.
The timing of phenological events such as leaf budburst and first flower can be quite sensitive to environmental conditions. For example, in a particularly warm and dry spring these phenophases might occur weeks earlier than usual, whereas in an exceptionally cool and wet spring they may be delayed by an equal amount of time. As a result, the timing of phenophases tends to vary among years based on patterns of weather, climate, and resource availability. Phenological records based on human observations are a valuable asset in the environmental sciences because they provide something that human-made instruments do not: integrative measures of the physical, chemical, and biological environments. This sensitively to environmental change means that phenological studies are simple and cost-effective way to measure changes in the climate over the long-term.
Cloned Lilac (Syringa chinensis, 'Red Rothomagensis') phenological events from buds bursting to full bloom.
Photographs by Prof. Mark D. Schwartz, Dept. of Geography, UW-Milwaukee, Milwaukee, WI
Phenological observations have been used for centuries to maximize crop production, prepare for seasonal allergies, and anticipate optimal wildflower viewing conditions. Today, this well established science is used to track the effect of global warming and climate change on organisms and to make predictions about the future health of the environment.
History of Phenology
Phenology is one of the oldest branches of environmental science dating back thousands of years. Observations of phenological events have provided indications of the progress of the natural calendar since pre-agricultural times.
Many cultures have traditional phenological proverbs and sayings which attempt to forecast future weather and climate: "If oak's before ash, you're in for a splash. If ash before oak, you're in for a soak". But the indications can be pretty unreliable, as an alternative version of the rhyme shows: "If the oak is out before the ash, 'Twill be a summer of wet and splash; If the ash is out before the oak,'Twill be a summer of fire and smoke."
The Chinese are credited with the first written phenological records dating back to around 974 B.C. For the past 1200 years, observations of the timing of peak cherry blossoms in Japan have been recorded. In Europe, the Swedish botanist Carolus Linnaeus systematically recorded flowering times for 18 locations in Sweden over many years. His meticulous notes also recorded the exact climatic conditions when flowering occurred.
Linnaeus, and a British landowner, Robert Marsham, share the honor of being considered the ‘fathers' of modern plant phenology. Marsham's work, Indication of Spring, was the result of keeping systematic records of phenophases on his estate. His observations in the form of dates recorded the first occurrence of events such as flowering, bud burst, and the emergence or flight of an insect. For generations, Marsham's family maintained records of phenological events over unprecedentedly long periods of time, eventually ending with the death of Mary Marsham in 1958. The records of the Marsham family showed trends that were observed and related to long-term climate records.
Interest in phenology continues today. In the United States, the National Phenology Network (NPN) engages both professional scientists and citizen scientists in recording phonological events. In Europe, the European Phenology Network has monitoring, research and educational remits. Nature's Calendar in both the Netherlands and the United Kingdom have active Web sites and events. Canada has PlantWatch and many other countries, including China and Australia have phenological programs.
Why is Phenology Important?
From the historical records and observations, we know that phenological events can vary from year to year. Ecosystems can recover from variation between years, but when these changes happen consistently over many years, the timing of events such as flowering, leafing, migration, and insect emergence can impact how plants and animals are able to thrive in their environments.
The success of an ecosystem or food chain depends on the timing of phenological events. Many animals rely on leaves, buds, flowers and fruit for their food. If the timing of the emergence of leaves, buds, and flowers is greatly changed, it can result in fewer seeds and insects which would impact the animals that depend on insects for their food.
Phenology is also concerned with the relationships among the phenophases of individuals of the same or different species. For example, when do California Poppies bloom relative to the activity and the abundances of their bumblebee pollinators? Are there always pollinators available to transfer pollen between flowering California Poppy plants, or does pollinator activity change throughout the flowering season or from year to year? Do individual Elderberry plants produce their berries at the same time as their seed dispersers need (and eat) them most, or are many of their berries unsuccessfully dispersed because they ripen and remain uneaten on the plants that bear them?
California poppy is a native plant in California . This plant provides color and beauty as well as wildlife habitat.
For many plants, the growing season is triggered by rising air temperatures. Fruit trees flower in response to rising temperatures. Let's take a closer look at cherry trees. They flower in response to warming temperatures, so if it is warmer earlier in the year, the flowers will bloom earlier as well. There is evidence that this is actually happening in some places in the country. For example, Washington DC has traditionally had a Cherry Blossom Festival during the first two weeks in April, culminating in mid April with a parade. Over the past few decades, the cherry trees have been blooming earlier and earlier, so that peak bloom is now at the beginning, rather than during the celebration at the end of the festival.
Cherry trees, as well as many other fruit trees like apples, peaches and pears, are pollinated by insects, which have a seasonal life cycle – they take time to develop from egg to larva to adult. If the trees flower earlier in the season, they may be out of synch with their pollinators. For example if an insect is still in the egg or larval stage, they will not be able to fly from tree to tree and transport pollen from one plant to another. Without pollination, the flowers are not fertilized, and will not produce fruit.
Cherry Trees in full flower in New York
Photo courtesy of Paul Alaback, University of Montana
In addition to affecting our food supply, phenological events can also affect human health. Pollen allergies can be exacerbated by some changes in growing conditions. People are allergic to pollen from all kinds of plants, and when the flowering time changes, those reactions will change as well.
Changes in the timing of phenological events have important implications for scientific research. Scientists use phenological data in computer models that project future climate scenarios and the projected impacts of such changes on the environment. Scientists are also interested in how phenology can inform the monitoring of drought conditions and the assessment of risk related to wildfires.
Changes in phenological events can have a significant impact on how we live our lives and interact with our environment on a daily basis. When you start to considerof all the potential impacts due to changes in the timing of leafing, flowering, or migration, it becomes clear that phenology is a very important environmental science.
Phenology Today (from The Phenology Handbook )
Some of the most rigorous phenological studies performed today are carried out by environmental scientists representing a wide range of approaches, including population biologists, community ecologists, climatologists, hydrologists, and specialists in satellite-driven remote-sensing. The integration of scientific disciplines makes for particularly powerful studies because the site intensive nature of one tool (e.g., botanical inventories and detailed phenological studies) can complement the geographically extensive information provided by another (e.g., satellites). Let's consider this in more detail in the following example.
At the continental scale, sensors in NASA's MODIS satellites in space measure the amount of sunlight reflected from the earth's surface. Leaves reflect light that is particularly rich in wavelengths in the near-infrared portion of the light spectrum, which the human eye cannot see but that satellite sensors can measure. The reflectance of light from leaves is greatest in mid-summer when leaves are most abundant, and lowest in winter when grasslands, shrublands, and forest trees are mostly bare. Thus, satellites detect the onset of spring by detecting a rapid increase in the reflectance of infrared wavelengths – this phenomenon is called green-up. Alternatively, the senescence of leaves in the autumn leads to a decrease in reflectance, and this is called brown-down. By collecting these remotely-sensed data on a regular basis and on a large geographic scale, scientists can accurately measure the onset of spring growth across the entire Northern or Southern Hemisphere.
At the same time as green-up is detected around the world by satellites, plant-watchers on Earth can observe the fine details of this process. Families, students, nature enthusiasts, and professional botanists who regularly visit a natural landscape can track green-up on a daily or weekly basis. By identifying which habitats and plant species are leafing out, we can identify the phenological events and species that contribute most to the infrared reflectance values observed from space (this process is called "ground-truthing").
At an even finer spatial scale (e.g., from square miles to square meters), biogeochemical sensors can measure daily and seasonal fluctuations in temperature, precipitation, atmospheric gasses, sunlight, soil nutrients, stream flow, and other components of the abiotic environment upon which plants and animals require for growth. With these data on hand, scientists can determine the influence of environmental factors on phenological patterns.
Project BudBurst Web site
The Phenology Handbook: a guide to phenological monitoring or students, families, teachers, and nature enthusiasts. | <urn:uuid:0da06caf-c818-4a21-9952-430647ad7bb3> | 3.609375 | 2,584 | Knowledge Article | Science & Tech. | 30.966608 |
Chapter 1 - Windows Controls
IN THIS CHAPTER
One of the early premises of the Windows operating system was to define a common set of user interface elements to be shared by all applications. The idea was that a user could learn one application and apply that knowledge to other applications. Each application shared common
The development of the Windows UI (User Interface) controls has not been limited to just advances in the Microsoft Windows environment; rather, many third-party companies have built their entire livelihood off of creating custom controls for Windows developers. Often, these custom controls
The reason for the thriving market is customer driven. Customers expect that applications have the latest UI elements found in typical Microsoft products. Somehow a slick up-to-date UI
I have often been asked, "Why doesn't Microsoft release its UI
Developing custom controls is a
The remainder of this chapter discusses basic control concepts such as runtime verses design-time support. In addition, the basic anatomy of controls is covered.
Regardless of the type of control being developed, its use should be immediately obvious to the user of the control. After all, if the
Consider a menu, a toolbar, and a command button. Although each control looks different, users expect that when they left-click the control, some action will take place within the application. The action is, of course, application specific; however, the control's behavior is common among all applications. This common functionality is the cornerstone of Windows development because it allows users to learn one application and apply that knowledge to other Windows-based applications.
All Windows-based controls, both common and custom, share several common traits. These traits include the various properties and events used to define the control's appearance and behavior. Common properties include
The subject of properties and events as defined within .NET development should be already familiar to you; therefore, only a brief discussion of their use is covered here. | <urn:uuid:0e78782d-fe4c-428a-b8cb-5a4457be25dd> | 3.3125 | 386 | Truncated | Software Dev. | 29.826717 |
Abstract written by OBIS-USA using Excerpts from CRED Homepage
The need for conservation of coral ecosystems throughout the world requires knowledge concerning the ecological requirements of species that make up the system, causes for the loss of any of the component organisms, and the requirements for the survival of remaining species. The collection of systematic information concerning what ... taxa are present, or biodiversity assessment, is a prerequisite for determining the factors previously mentioned. The task of conservation is further supported by an ongoing monitoring program, which uses the biodiversity assessment as its baseline for detecting changes through time.
Historically, the biodiversity assessments and monitoring programs for coral reefs have focused strictly on the charismatic fauna such as cnidarians and fish. Coral reefs are compared to rainforest habitat when referring to their biodiversity. Rainforest ecosystems are viewed from the perspective of the canopy components but are made up of a wealth of less charismatic fauna that contribute greatly to the biodiversity. In the case of coral reefs this is also true; the cryptic sponge, mollusk, echinoderm, crustacea, annelid, bryozoan, and tunicate fauna are an integral component to the overall biodiversity.
The Coral Reef Ecosystem Investigation (CRED) program of the National Oceanic and Atmospheric Administration-National Marine Fisheries Service, Honolulu Laboratory includes a marine invertebrate component as part of its rapid ecological assessment (REA) activities in the tropical Pacific. The marine invertebrate component is done in conjunction with surveys of fish, corals, and macroalgae to create a complete benthic survey of coral reef areas that are included in the scope of the program.
Data was published on the OBIS-USA web site March 31, 2010 and is available at http://www.usgs.gov/obis-usa.
Record Count 64,435, Taxa Count 444
Please see the CRED homepage for additional information at http://www.pifsc.noaa.gov/cred/index.php | <urn:uuid:3b5cdbaf-bf42-4e45-a4f3-58e6aa5c149f> | 3.578125 | 412 | Knowledge Article | Science & Tech. | 23.653394 |
Chemical reaction in which at least one of the reactants is a high-molar-mass substance.
PAC, 2004, 76, 889
(Definitions of terms relating to reactions of polymers and to functional polymeric materials (IUPAC Recommendations 2003))
on page 894
IUPAC. Compendium of Chemical Terminology, 2nd ed. (the "Gold Book"). Compiled by A. D. McNaught and A. Wilkinson. Blackwell Scientific Publications, Oxford (1997). XML on-line corrected version: http://goldbook.iupac.org (2006-) created by M. Nic, J. Jirat, B. Kosata; updates compiled by A. Jenkins. ISBN 0-9678550-9-8. doi:10.1351/goldbook | <urn:uuid:25c10637-63e6-4ea5-8d59-1ef373e72a19> | 2.859375 | 171 | Knowledge Article | Science & Tech. | 76.434444 |
“Examples of animals exhibiting maladaptive responses to evolutionary novel objects and becoming trapped. (A) A Cuban tree frog (Osteopilus septentrionalis) ingesting a decorative light that mimics the bioluminescent qualities of its insect prey. (B) A black-footed albatross (Phoebastria nigripes) killed by the ingestion of small, often colorful, floating garbage that mimics food items. (C) A giant jewel beetle (Julodimorpha bakewelli) attempting to mate with a beer bottle that produces supernormal strengths of coloration and reflection cues associated with female conspecifics . (D) Mayflies blanketing, mating, and ovipositing on a storefront window that strongly reflects horizontally polarized light, their primary habitat selection cue in locating natural water bodies.”
Credit: (Source) Images by James Snyder (A), Chris Jordan (B), Darryl Gwynne (C), and Will Milne (D) (Copyrighted, reproduced here as fair use).
Carl Zimmer has an article summarizing the research presented by Robertson, Rehage, and Sih concerning evolutionary traps, when “rapid environmental change triggers organisms to make maladaptive behavioral decisions.” In other words, we change the environment in ways that cause animals to exhibit behaviors harmful to themselves.
Zimmer gives the example of the albatross, which “will peck at brightly colored pieces of plastic floating in the water, for example. It’s a response that used to give them energy but now can fill their guts with trash.” Witherington gives the example of sea turtles, which “have evolved the tendency to migrate toward the light of the moon upon emerging from their sand nests. However, in the modern world, this has resulted in them tending to orient towards bright beach-front lighting, which is a more intense light source than the moon. As a result the hatchlings migrate up the beach and away from the ocean where they exhaust themselves, desiccate and die either as a result of exhaustion, dehydration or predation.” Sea turtles also mistake plastic bags for jellyfish and consume them. In 2011 Darryl Gwynne and David Rentz won an IgNobel for their research on the giant jewel beetle, which attempts to mate with a certain brand of beer bottle because they exhibit “supernormal strengths of coloration and reflection cues associated with female conspecifics.” | <urn:uuid:c346205e-c681-4a94-982e-0412ed2d749a> | 3.359375 | 518 | Knowledge Article | Science & Tech. | 25.391169 |
The importance of the Laplacian is a reflection of the importance of Riemannian geometry, both for its own sake and in these other fields. (Obviously, absent a generalization, you can't have a Laplacian without a Riemannian metric.) In Riemannian geometry, the Laplacian is the first scalar linear differential operator available which is "covariant", i.e., that depends only on the Riemannian structure and not on extra choices such as coordinates.
It's natural for the first non-trivial possible structure of a given type to be fundamental. One reason is that it can be an approximation to something else with higher-order terms. For example, in the wave equation, if it is meant as a realistic model of sound waves, actually there are all kinds of higher order, non-linear effects; but one begins with the Laplace operator as the correct approximation for small waves. It has to be correct because it's the only one available. The same thing happens with heat and the heat equation.
Actually, something interesting happens if you relax the use of the word "scalar". If you have a spin manifold, then there is a Dirac operator, which is a Laplacian-like operator that is just as important. But even apart from that construction, there are various other operators, such as the Hodge Laplacian, that act on vector and tensor fields rather than on scalar functions. These are not exactly the same as the original Laplacian, but they tend to get the same name. | <urn:uuid:cb7bdc9a-fceb-4f16-b1ed-f2f1c445c099> | 3.203125 | 334 | Q&A Forum | Science & Tech. | 42.5212 |
Assembly: System.Windows.Forms (in system.windows.forms.dll)
/** @property */ public Color get_ForeColor () /** @property */ public void set_ForeColor (Color value)
public override function get ForeColor () : Color public override function set ForeColor (value : Color)
Property ValueA Color that represents the foreground color of the DataGridView. The default is the value of the DefaultForeColor property.
The ForeColor property is an ambient property. An ambient property is a control property that, if not set, is retrieved from the parent control. For example, a Button will have the same BackColor as its parent Form by default. For more information about ambient properties, see the AmbientProperties class or the Control class overview.
The DataGridView control uses the value of the ForeColor property as the default value of the ForeColor property of DataGridViewCellStyle returned by the DefaultCellStyle property. Changing the ForeColor value automatically updates the DefaultCellStyle property, changing the foreground text color for any cell that inherits the value. Header cells override the value by default, and you can override the value for specific rows, columns, and cells. For more information about cell style inheritance, see Cell Styles in the Windows Forms DataGridView Control.
Windows 98, Windows 2000 SP4, Windows Millennium Edition, Windows Server 2003, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP SP2, Windows XP Starter Edition
The .NET Framework does not support all versions of every platform. For a list of the supported versions, see System Requirements. | <urn:uuid:dba4e938-b7f7-408a-96f9-1aefc455d671> | 2.890625 | 333 | Documentation | Software Dev. | 30.062815 |
Chapter 15 - Numerical Models
- Numerical models are used to simulate oceanic flows with realistic
and useful results. The most recent models include heat fluxes through
the surface, wind forcing, mesoscale eddies, realistic coasts and sea-floor
features, and more than 20 levels in the vertical.
- Recent models are now so good, with resolution near 0.1°, that
they show previously
unknown aspects of the ocean circulation,
- Numerical models are not perfect. They solve discrete equations, which
are not the same as the equations of motion described in earlier chapters.
- Numerical models cannot reproduce all turbulence of the ocean because
the grid points are tens to hundreds of kilometers apart. The influence
of turbulent motion over smaller distances must be calculated from theory,
and this introduces errors.
- Numerical models can be forced by real-time oceanographic data from
ships and satellites to produce forecasts of oceanic conditions, including
El Niño in the Pacific, and the position of the Gulf Stream in
- Coupled ocean-atmosphere models have much coarser spatial resolution
so that that they can be integrated for hundreds of years to simulate
the natural variability of the climate system and its response to increased
CO2 in the atmosphere. | <urn:uuid:d0171134-779a-4c01-be68-f7561cfdab17> | 3.453125 | 270 | Knowledge Article | Science & Tech. | 23.622841 |
cutting and burning trees
Why are scientists in Panama acting like Tarzan? Why are they climbing trees in the jungles of South America and Asia? It is well known that tropical rain forests all over the world are disappearing. People are cutting and burning them so they can use the land for farms. Unfortunately, they are also destroying wildlife that no one has ever seen, thousands of species that live at the tops of the trees. This is why groups of scientists are looking for ways to get to the top of these forests and study these species that live so high off the ground. But there is little time. The great trees are burning. Rain forests have already given us many things: coffee, cocoa, medicines like quinine, and no one knows what we will lose as the forests disappear.
It seems that man always needs more land. People want land so they can build houses and roads so they can have bigger farms. IN recent years there have been many projects to drain the marshes near rivers and lakes. Wet land is drained to make dry land. But marshes are needed, too. They are the natural habitat of many birds, animals, fish, plants. They are places where birds can find food as they fly from the cold north to warmer places in the wintertime. Then in the spring when the snow melts, much of the water stays in the marshes, and the rivers do not flood. Marshes also act like filters. This is nature’s way of keeping water pure.
When something like an oil spill happens and wildlife is in danger, we hear about it on television and read about it in the newspapers. But man is interfering with nature in many other ways that we hear little about. | <urn:uuid:a1e530c4-1594-4747-a939-9283029974b0> | 3.046875 | 349 | Nonfiction Writing | Science & Tech. | 66.651451 |
A massive iceberg that had been blocking traditional shipping routes to McMurdo Station, the National Science Foundation’s research station in Antarctica, snapped in two seemingly overnight. The B-15A iceberg seemed to be intact in the Terra MODIS image recorded on October 7, 2003. But Moderate Resolution Imaging Spectroradiometer (MODIS) images starting on October 9 show the iceberg in two pieces. The largest section, top, is about 75 miles long, and the shorter section, called B-15J, is 20-25 miles long. On December 15, 2003, B-15A fractured again. The new iceberg, B-15K, is visible on the left edge of B-15A beginning on December 16, 2003. It is about 37 miles long and 4 miles wide.
The B-15A iceberg broke off the Ross Ice Shelf in 2000 and drifted to its present location. It was one of the largest icebergs scientists had ever observed breaking from the shelf. It and a second large iceberg, C-19, trapped sea ice in the passage that supply ships typically used to get to the research station on Ross Island. C-19 swung out to sea in 2002, freeing some of the trapped ice. Scientists at the University of Wisconsin-Madison who first noticed the recent break say that it is unclear how B-15A’s break-up will affect previously trapped ice.
The Ross Ice Shelf is a vast field of snow and ice extending from the continent into the Ross Sea on the western Pacific coast of Antarctica. As glaciers slide off the continent and push the shelf out, the outer edges crumble into a myriad of icebergs such as B-15A.
In this series of images, starting on October 7, 2003, the B-15A iceberg points out into the Ross Sea. After the break, it began to drift away from the B-15J iceberg, which is slowly rotating and moving next to the smooth white Ross Ice Shelf. The B-15K iceberg began to move away from the B-15A iceberg after breaking off on December 15. The C-16 iceberg, which broke off the Ross Ice Shelf in the same event as the B-15 iceberg, sits to the left of B-15J. | <urn:uuid:1315f1b0-c1fe-49e3-8228-a963f3344e4f> | 3.859375 | 465 | Knowledge Article | Science & Tech. | 64.931171 |
The Tunguska Comet
Space shuttle science shows how 1908 Tunguska explosion was caused by a comet
The research, accepted for publication June 24, 2009 by the journal Geophysical Research Letters, connects the two events by what followed each about a day later: brilliant, night-visible clouds, or noctilucent clouds, that are made up of ice particles and only form at very high altitudes and in extremely cold temperatures.
"It's almost like putting together a 100-year-old murder mystery," said Michael Kelley, the James A. Friend Family Distinguished Professor of Engineering at Cornell who led the research team. "The evidence is pretty strong that the Earth was hit by a comet in 1908." Previous speculation had ranged from comets to meteors.
The researchers contend that the massive amount of water vapor spewed into the atmosphere by the comet's icy nucleus was caught up in swirling eddies with tremendous energy by a process called two-dimensional turbulence, which explains why the noctilucent clouds formed a day later many thousands of miles away.
The space shuttle exhaust plume, the researchers say, resembled the comet's action.
A single space shuttle flight injects 300 metric tons of water vapor into the Earth's thermosphere, and the water particles have been found to travel to the Arctic and Antarctic regions, where they form the clouds after settling into the mesosphere.
Kelley and collaborators saw the noctilucent cloud phenomenon days after the space shuttle Endeavour (STS-118) launched on Aug. 8, 2007. Similar cloud formations had been observed following launches in 1997 and 2003.
Following the 1908 explosion, known as the Tunguska Event, the night skies shone brightly for several days across Europe, particularly Great Britain -- more than 3,000 miles away.
Kelley said he became intrigued by the historical eyewitness accounts of the aftermath, and concluded that the bright skies must have been the result of noctilucent clouds. The comet would have started to break up at about the same altitude as the release of the exhaust plume from the space shuttle following launch. In both cases, water vapor was injected into the atmosphere.
The scientists have attempted to answer how this water vapor traveled so far without scattering and diffusing, as conventional physics would predict.
"There is a mean transport of this material for tens of thousands of kilometers in a very short time, and there is no model that predicts that," Kelley said. "It's totally new and unexpected physics."
Scientists have long tried to study the wind structure in these upper regions of the atmosphere, which is difficult to do by such traditional means as sounding rockets, balloon launches and satellites, explained Charlie Seyler, Cornell professor of electrical engineering and paper co-author.
"Our observations show that current understanding of the mesosphere-lower thermosphere region is quite poor," Seyler said. The thermosphere is the layer of the atmosphere above the mesosphere.
Understanding the events surrounding the Tunguska impact can help astrobiologists determine if similar impacts are likely to occur in the future. Impact events can cause profound effects on the Earth's environment and, ultimately, the biosphere. Impacts may have been responsible for mass extinctions in the Earth's past - and many scientists believe that impacts could pose a threat to life in the future. | <urn:uuid:86f6820c-b936-4a2a-8e44-54de4254438c> | 3.4375 | 696 | Knowledge Article | Science & Tech. | 37.630563 |
Methods can accept properties and values that tell the method more specifically what to do, these go in the parenthesis. For instance, you might tell a child to sit down or you might want to tell them to sit down right now in the blue chair. The "right now" and "blue chair" part would be properties and values. Just like a child unfamiliar with the word might just look at you confused if you told them to sit down on the chaise, you can only tell an object or method about activities and things they are familiar with (unless you teach them about them first.) In our case, we are passing the value "Hello world!".
document.write( argument_one[, argument_two, ...])
The W3C Document Object Model (DOM) | <urn:uuid:4ca8b9fe-fb39-4434-b974-9f9a5eeb40d3> | 3.125 | 159 | Documentation | Software Dev. | 70.9699 |
Log in or register to follow or vote for this project.
Global Warming, I’m certain by now most of the public worldwide know what this concept is about, and most probably tired of hearing what a huge problem it is but no long term solutions are being proposed. Unfortunately that is still a working progress, but in the mean time we can try to reduce the after effects of Global warming such as climate change by tackling each greenhouse gas in the atmosphere such as Methane.
Methane (CH4) is the primary component of natural gas and an important energy source. Methane is also a green house gas, meaning that its presence in the atmosphere affects the Earth’s temperature and climate system. Due to its relatively short life time in the atmosphere (9-15 years) and its global warming potency – 20 times more effective than carbon dioxide (CO2) in trapping heat in the atmosphere – reducing methane emissions should be an effective means to reduce climate warming on a relatively short timescale.
Human influenced sources of methane include landfills, natural gas and petroleum production and distribution systems, agricultural activities, coal mining, stationary and mobile combustion, wastewater treatment, and certain industrial processes. About 60% of global methane emissions come from these sources and the rest are from natural sources (IPCC, 2001). Natural sources include wetlands, termites, oceans, and hydrates (which consists of methane molecules each surrounded by a cage of water molecules and are present in seafloor deposits around the world.
The historical record, based on analysis of air bubbles trapped in ice sheets, indicates that methane is more abundant in the earth’s atmosphere now than at any time during the past 400,000 years (IPCC, 2001). Over the last two centuries, methane concentrations in the atmosphere have more than doubled.
Based on the above information it is quite evident that methane emissions are a huge problem if not trapped in time and used effectively. There are methods being introduced to reduce methane in the atmosphere involving various technology and utilization of many organisms, but I believe all the methods work but the most effective method would be trapping methane in the atmosphere. This method is possible, but currently it only applies to CO2; but that might just change.
One of the most effective methods of methane reduction is methane fermentation by microbes. Methane fermentation is the consequence of a series of metabolic interactions among various groups of microorganisms. My interest is the ability of methane-oxidizing archaea and sulfur-reducing bacteria to work in consortia to oxidize methane anaerobically in anoxic marine sediments. Scientists believe that archaea uses the reversed methanogenesis pathway to produce carbon dioxide and another, unknown substance. This unknown substance is then used by the sulfur-reducing bacteria to gain energy from the reduction of sulfate to hydrogen sulfide. With this knowledge many scientist are still try to figure out how to bring methane in atmosphere to these microbes in order to reduce it by oxidation process. In addition to the problem I came up with a solution that tackles the problem in a different direction…
My aim is to reduce methane in the atmosphere by using the methane-oxidizing archaea and sulfur-reducing bacteria still working in consortia but in a controlled manner and preferably working in the atmosphere not on the ground level.
Based on the knowledge I obtained, theoretically if we can create a controlled environment for the methane-oxidizing archaea and sulfur-reducing bacteria and contain the environment then transport them to the atmosphere, trap methane for them and allow them to oxidize the trapped methane, methane will be reduced greatly in the atmosphere.
I believe I have found a way to do this. I introduce the MOM-Bot 1.0 (Methane Oxidizing Microbot)
The main function of the MOM-Bot 1.0 is to act as a carrier of the methane-oxidizing archaea and sulfur-reducing bacteria to the atmosphere, but also aid in trapping air from the atmosphere filtering methane gas from the mixture of gases in atmospheric air by condensing the gas, then evaporating the organic compound once separated from the rest of the gases and then transported to the microbes for oxidation reaction.
Below is a link which will direct you to the schematic diagram indicating all the equipment used to create the machine and how it operates.
The MOM-Bot will be controlled by an operator by using a computer, therefore it will be equip with wireless technology and it will consist of a motherboard with CPU attached to it. It will get its source of energy from a micro hydro-electric generator. The operator only controls the units 1-3 based on time intervals which will be determined by experiments on how long it takes to reach a specific amount of liquid methane in a specific volume of test tube, and how long it takes for the test tube to be emptied.
Air enters unit 1 by centrifugal compressor which is then carried through the pipette tubes down to the Dewar flask, the flask is filled with liquid nitrogen and a test tube which will contain liquid methane is submerged into the liquid nitrogen. The air from the Atmosphere will then be transported into the test tube where methane gas in the air will be condensed into liquid phase due to the decreased temperature by the liquid nitrogen. The rest of the gases will not be condensed; as the liquid methane increase the pressure increases pushing the rest of the air through the second pipette tube and also the second centrifugal compressor will help by pulling the air toward it into unit 2 and released back into the atmosphere. After a certain time when the liquid methane has reached a certain volume in the test tube, it will be drained into the third compartment by opening the gate which is the pathway for it to travel downwards into the third compartment. The gate is opened by Unit 3 after a certain time, the large turn wheel is activated rotating anti-clockwise at a certain degree based on the width of the pipette tube on the test tube to the third compartment causing the small turn wheel attached to the gate handle to rotate clock-wise moving the gate handle backwards. Once the liquid methane is drained the large turn wheel will rotated at the same degree as before clockwise, causing the small turn wheel to rotate anti-clockwise pushing the gate handle forward and closing the gate. The liquid methane while entering the third compartment, some of it will be evaporated some will then be poured into a spherical container, and then later the liquid will also evaporate into the gaseous methane. The liquid methane only evaporates at temperatures equal or greater than room temperature, therefore there will be a micro heater in the spherical container ensuring that the third compartment’s temperature is at room temperature or slightly above. The side wall of the spherical cylinder have micro pores or holes allowing the methane gas to diffuse to the rest of compartment area then later also diffusing into the controlled microbe environment where the gas will be oxidized.
The machines operation and functions are theoretical; experiments still need to be done for example to see if methane gas will be able to be separated from air by condensation.
I believe the invention will reduce methane gas already in the atmosphere by a great percentage, hence reducing climate change. The best part is the machine does not release any harmful gases and operates by an eco-friendly generator, and this means the machine does not contribute to global warming. Methods of how the machine will be transported to the atmosphere are still being studied.
Hawthorne,W.R. 1964. Aerodynamics OF Turbines and Compressors. Princeton New Jersey: Princeton University press.
Holmes, A.J; Roslev, P. 1999. Characterization of methanotrophic bacterial populations in soils showing atmospheric methane uptake. Applied and Environmental Microbiology 65 (8): 33122-8
Houghton, J.T., Ding, Y., Griggs, D.J., Noguer, M., van der Linden, P.J., Dai, K., Maskell, and Johnson, C.A. 2001. IPCC 2001: Climate Change 2001: The Scientific basis.Contribution woring group to the Third Assessment Report of the Intergovernmental Panel on climate change. Cambridge University Press, Cambridge, United Kingdom and New York, 881pp.
Dlugokencky, E.J., Houweling, S., Bruhwiler, L., Masarie, K.A., Lang, P.M., Miller, J.B., Tans. P.P. 1992. Atmospheric methane levels off: Temporary pause or new steady state? Geophysical Research Letters. 30(19).
Kellermann, M. 2009. Strange Diet For Methane Consuming Microorganisms. http://www.mpg.de/6613279/methane-cell-metabolism Max-Planck-Gesellschaft. Accessed 1/1/2013
Stodola, A.1945. Steam and gas Turbines. New York: P.smith | <urn:uuid:7be16f0d-3f96-45d5-88f2-b99146054ca4> | 3.640625 | 1,846 | Personal Blog | Science & Tech. | 41.301095 |
Study Estimates Land Available for Biofuel Crops
ScienceDaily (Jan. 10, 2011) — Using detailed land analysis, Illinois researchers have found that biofuel crops cultivated on available land could produce up to half of the world's current fuel consumption -- without affecting food crops or pastureland.
Published in the journal Environmental Science and Technology, the study led by civil and environmental engineering professor Ximing Cai identified land around the globe available to produce grass crops for biofuels, with minimal impact on agriculture or the environment.
Many studies on biofuel crop viability focus on biomass yield, or how productive a crop can be regionally. There has been relatively little research on land availability, one of the key constraints of biofuel development. Of special concern is whether the world could even produce enough biofuel to meet demand without compromising food production.
"The questions we're trying to address are, what kind of land could be used for biofuel crops? If we have land, where is it, and what is the current land cover?" Cai said.
Article continues: http://www.sciencedaily.com/releases/2011/01/110110130936.htm | <urn:uuid:4d021a48-c1af-4a97-b0d8-fa3a40c5dbd6> | 2.96875 | 242 | Truncated | Science & Tech. | 41.76391 |
DNA Walk is a vectorial representation of DNA sequences transformed into a planer trajectory. Two pairs of complementary nucleotides (A-T, G-C) is suitable for two dimensional vectorization, so the DNA sequence is moved upwards for A, downwards for T, to right for G, and to left for C, visualizing the trajectory.
DNA Walk makes patterns in the genomes sequences apparent. Clustering of repeats, palindromes, horizontally transferred genes, telomeres, and GC skew can be easily spotted using this visualization approach. Following is the DNA Walk of Escherichia coli, which is highly skewed in GC vector, and leading/lagging strands can be quickly identified from this diagram.
Origin of DNA Walk is marked by the cross-section of gray axes, and nucleotides change color from red to green as the position of the given nucleotide progresses within the sequence. Several areas in genome may have unusual structures, for example, the one below in Escherichia coli genome forming a hairpin-like structure having reversed nucleotide composition.
GC skew is the excess of C over G in certain regions, formulated as (C-G)/(C+G). In bacterial genomes, replicational selection prefers Guanine over Cytosine in leading strands, therefore positive GC skew value is typically observed in leading strands, and negative in lagging strands. In fact, GC skew is often utilized to define the positions of replication origin and terminus in bacterial genomes. In many bacterial genome projects, the position 1 in genome flatfiles correspond to the putative replication origin.
DNA Walk is therefore the integrated representation of GC skew and AT skew. Conversely, GC skew can be considered as the projection of DNA Walk in GC vector.
- Lobry, J.R., 1996. Asymmetric substitution patterns in the two DNA strands of bacteria. Mol. Biol. Evol. 13, 660-665
In this way, genomes with high GC skew becomes extremely linear V-shaped graph as in the following example of Clostridium perfringens,
or highly random when GC skew is not observable, as in the genome of Gloeobacter violaceus.
Upon searching, search results are shown as pins on the map, or as text shown in collapsible window on the right-most side. Clicking on each of the pins or text result entries will bring up a dialogue baloon, which shows the following information:
- gene name
- product description
- Gene Ontology terms if available
- 3D structure if PDB entry was found
- Links to UniProt, KEGG, NCBI RefSeq, and PDB (if link was found) | <urn:uuid:7d43515d-cdf4-4038-96d3-cd546356dde4> | 3.28125 | 559 | Knowledge Article | Science & Tech. | 42.554217 |
A draft solution to the so-called "P versus NP" problem generated excitement in 2010 – will 2011 bring a correct proof?
Vinay Deolalikar made waves in August when his draft solution to a mathematical problem that haunts computer science hit the internet.
It's known as "P versus NP", and a correct solution is worth $1 million. Sadly for Deolalikar, of Hewlett-Packard Labs in Palo Alto, California, his work didn't check out. But the flurry of online activity surrounding the paper demonstrated a new way of doing mathematics - via blogs and wikis - and generated fresh excitement around the problem.
Formulated in 1971, P versus NP deals with the relationship between two classes of problems that are encountered by computers. P problems are relatively easy for computers to solve. But it can take an impracticably long time to solve NP problems, such as finding the shortest route between several cities - though it is easy to show whether a possible solution is correct.
If P = NP, computers may eventually be able to solve a host of complex problems, from protein folding to factorising very large numbers. The ability to solve the latter would spell trouble for algorithms that we rely on for internet security. Most people assume the opposite is true, that P ≠ NP; had Deolalikar's paper been correct, it would have proved this.
The Clay Mathematics Institute in Cambridge, Massachusetts, has promised $1 million to the first person who can prove it one way or the other. To find out how likely this is to happen in 2011, see "Prediction: Its time has not come".
Prediction: Its time has not come
Unlike many problems in science, highly theoretical enigmas like P versus NP are rarely solved piecemeal. Instead, they tend to remain unsolved for years and then, apparently out of nowhere, a proof that works pops up.
Predicting these breakthroughs might seem impossible, but we devised a way to estimate the likelihood of P versus NP being solved next year. We compared its "age", or the time since the problem was formulated, to other long-standing mathematical problems.
First we compared P versus NP with 18 mathematical problems, from Fermat's last theorem to the Poincaré conjecture, that were not solved until more than a decade after their "births" (see graph). This made arriving at a solution to P versus NP in 2011, when it will turn a sprightly 40, look premature: just 22 per cent of these other problems were solved before they turned 40. By the same logic, in 2024, we should be on the lookout for a solution to P versus NP. That's when it turns 53, the age by which 50 per cent of the problems we examined were solved.
Here's hoping that solving P versus NP turns out to be faster than proving the Honeycomb conjecture, which states that if you need to divide a surface into tiled shapes of equal size, a hexagon is the shape that requires the smallest length of dividing lines. Proving that took more than 1500 years.
We also compared P versus NP to 26 other problems that still haven't been solved. In 2011, it will be younger than 81 per cent of those. Samuel Arbesman and Rachel Courtland
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Thu Dec 23 10:29:50 GMT 2010 by Eric Kvaalen
Your method is flawed because it assumes that the P versus NP problem will be solved. Your graph (second illustration) only contains solved problems. There are many conjectures that remain unsolved, and I think many will never be solved. P versus NP may be in that category.
Mon Dec 27 18:40:19 GMT 2010 by Chris Curtis, Auckland, New Zealand
The method is certainly not flawed, as you don't have the contextual basis with which to make assignment of truth or falsity in this case. And if you did, you wouldn't need to add a circular, self-contradictory farce in this way.
When you can deduce an answer by pointing out an assumption and showing the basis for which that assumption to be flawed, then that's cool to do, but only if you have the capability to logically show that basis, instead of what you have done so royally.
"There are many conjectures that remain unsolved and I think many will never be solved."
This is about the only case where ad hominen attacks are allowed and for comedy value. What you "think" without more context has a null value here and is an assumption that your ability to think could change any law of logic and so is also not needed.
Furthermore, you state that there are many unsolved conjectures without separating them into ones that are true and ones that are false (better to worry first about enumerating things that exist than include the ones that will turn out to be false and don't exist). If there is a case of a conjecture being false, then a solution does not exist for that conjecture. Peel the onion a bit and you end up realising that any graph like this would only contain solved problems. These are the set of things we have found to exist and can prove (in maths). The wrong things we found along the way turned out not to exist and we binned them (quite rightly).
"Absence of evidence is not evidence of absence".
I'm fairly sure God would have this on his headstone in Eric's extra Universe, since it is the Universe included for no good reason... the "Universe of things that Do Not Exist". God probably holds on to his immortality and can safely store that headstone there...
Though I love New Zealand, most people here have banished their left/right indicator stick to the same extra Universe of Non Existence and with quite a few other driving behaviours whose existence I previously quite enjoyed. After a while, this whiny property related to driving-uptightness goes away,often when a new train station opens near by.
By the way, PvNP is a pun and a triple one at that...
Think P is Possible. Think NP is Not Possible. Think the "v" is the AND operator and you have the two sets. Those things that are true and those things that are false (including which exist and which do not). Whenever you can't ask your question in a way that is described logically by what you know in a way that is true or false by the time you ask it, Eric or an agent of the same nature is involved and you need to check that what you think exists, actually does...
You don't need to define what doesn't exist... its the empty set i.e. the point in time when you finish defining what does exist first, since at the end of that definition, you've implied by finishing it all of what can be left in other set.
PvNP is not a question of equivalence, just an example that we don't understand what we're asking half the time at least...
Mon Dec 27 19:25:51 GMT 2010 by Chris Curtis - Riemann Hypthesis Example: PvNP
The Riemann Hypothesis can be solved with the solution to PvNP and since some people don't care about prize money....
1. Take the functional equation for the Riemann Zeta function, expand out the Riemann Zeta function on the right hand side (usually the fifth factor on the right) using the same functional equation and you have the Riemann Zeta function as a product on the left and you now have the SAME Riemann Zeta function as a factor with some others on the right.
2. Factor commutivity alone tells you that this function only equals zero on the critical line when the imaginary part is the same size and opposite in sign to the Real value for 1/2 + 0 i since orthogonal lines to the Real axis, like the critical line, have constant Real contribution from their factors. Since the imaginary contribution is constant orthogonal to the imaginary axis, its the only thing that changes on the critical line, performing the occasional flip in sign to create a non-trivial zero.
3. So, take that equation expansion, realise that the real components form the factors are pairs of reciprocals on that line. Use Euler's reflection symmetry to get rid of the Gamma Function to just leave the final three imaginary terms, which are an equivalence between a sine function with the input (Pi X yi) and the square of two sine functions with an input product of (Pi/2 X yi) and Bob's your uncle... as long as you don't leave anything equal to zero instead of minus one or one, you'll realise this whole hypothesis is about the silver and golden ratios and constructibility versus common sense.
Anyone with a grasp of equations will quickly spot Knuff's Series, do a bit of substitution, sticking other sequential primes in with that series instead of 2 and 3... hey, presto you have a simple equation for the enumeration of non-trivial zeros. One step and boom, you have your prime number sequence and any kind of factor patterns.
4. Then by showing that the Riemann Zeta Function is not reciprocal between any two points equidistant from the critical line and orthogonal to it, which from your "balanced" expansion of the functional equation, using itself, kinda already shows. Two points equidistant from the critical line and opposite in sign from a zero, would have to be reciprocal for the hypothesis to be false, none of the points are and only one pair needs to be show, since zero would be the value all the way across the strip orthogonal to the critical line, if it was reciprocal in a single place (since this would require it to be reciprocal in all places on that line for these pairs of points).
Basically they are non-trivial because the first one is "the other end" of the square root of two or Pi (depending on which non-existent irrational number you need the most) as a construction and the next non-trivial zero is the effect of the 1.9 dimensional recursive properties of this particular fractal function created by a terrible attempt at a number system with which the ancient Egyptians would not have taken your offer for any camels seriously. Nor the Babylonian Astronomers who used numbers in their words for brevity. Clever ones, them. Still, squaring a sine function and relating it to a non-squared one and with Pi as the units and part of the modulus (since we're talking about y i, not x) within the units of those sine functions is pretty much the only simple way such patterns as non-trivial zero or prime number distribution would make sense, no?
I'm suprised Knuff didn't realise the hypothesis was trivial from his series: that the connection is the value of the zeta function at 1/2 + 0 i, though the other crazier stuff from PvNP explains why it sent John Nash a bit crackers, if he already had a propensity for the wackier things and came anywhere near solving PvNP.
Mon Dec 27 15:13:54 GMT 2010 by Jeb
- Was "century" perhaps intended here?
"- from Fermat's last theorem to the Poincaré conjecture, that were not solved until more than a *decade* after their "births"
Tue Dec 28 19:32:10 GMT 2010 by Joao
In the third paragraph of the sidebar "Prediction: Its time has not come", you meant to say "century", not "decade".
"First we compared P versus NP with 18 mathematical problems, from Fermat's last theorem to the Poincaré conjecture, that were not solved until more than a decade after their "births""
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Whiteflies have a strange life cycle that involves spending almost their entire lives in a sessile (immobile) state.
First-stage nymphs - termed "crawlers"
- hatch from eggs
- can walk short distances
- or are carried by air currents
Once the crawler has selected a feeding site under a suitable leaf it undergoes its first moult.
Second, third and fourth immature stages
- do not have functioning legs and simply
- feed on the plant host’s phloem sap - if the plant dies, so do they.
- secrete white, waxy, material as pretty filaments and curls - the final nymphal stage resembling some sort of exotic confectionary.
- emerge from their unlikely-looking “puparia”
- just a couple of millimetres from wing-tip to wing-tip
- disperse by flying
- can mate | <urn:uuid:d7e2a935-b75b-430a-b698-b2761d6579d5> | 3.40625 | 194 | Knowledge Article | Science & Tech. | 34.415205 |
The cold dry air of winter is perfect for some hair-raising experiments. Have you ever noticed how your hair sometimes stands straight up when you pop out from under your snuggly blankets in the morning? When you try to comb your hair, it might even get worse! Did you ever wonder why this happens?
In the photo, the boy's hair is standing up for the same reason your hair is so hard to control in the cold, dry winter days. Some folks call their hair "staticy" when it stands up. The reason for the hair standing up is static electricity.
To understand about static electricity, let's first look at the material world around you. Everything you can feel, touch, see, smell, hear and taste is made up of matter. Matter is made of very tiny atoms and groups of atoms called molecules. These are too small to see, but they are really there. Atoms are made of even smaller parts. Without going into too much detail, we can simplify our view of atoms as having a positively charged central core called a nucleus.
Surrounding the positively charged nucleus are negatively charged particles called electrons. Atoms normally have the same number of positively charged particles in the nucleus as there are negatively charged electrons surrounding the nucleus. When the atom has exactly the same number of positive and negative particles, the overall charge of the atom is zero or electrically neutral.
Some objects' atoms have outer electrons that can be easily removed by just rubbing one object on another. When this happens, a charge unbalance in normally neutrally charged atoms occurs. Many people have noticed this when you scuff your shoes on a rug or carpet on a dry winter day. Electrons are rubbed off of the carpet and onto your shoes and onto you! Shoes are usually made of plastic or rubber that holds on to the negative electric charge. If you touch an object that conducts electric charge like a metal doorknob or your friend you will see, hear and feel an electrical spark. The small spark you see is the result of the excess negative charge jumping to a less electrically negative object.
The lightning that you see during a thunderstorm is the result of very large-scale electrical sparking events between the ground and the sky. The thunder you hear is the very large scale "snap" or "pop" sound you hear from static electric sparks you create.
The static electricity generator in the photo has a rubber belt inside it that rubs as it goes around in a loop powered by a motor. As the belt moves around, it "charges up" with electrons and carries this excess of electrons to the spherical metal ball where they are stored. If a person's hand is also on the ball, the person can also "charge up" with a negative overall charge.
Did you ever hear the phrase "opposites attract"? When your hand is on the static generator your body, including your hair all takes on the same charge. If opposite charges attract, then if the charge is the same, the opposite happens and they repel, or push away, from each other - and ta-da! Your hair stands up!
Not everyone has a static generator, but you may have some of the materials at home to try your own static experiments.
Activity: Static Hair and Balloon
1) You will need a normal or party balloon.
2) Blow up (inflate) the balloon not quite to maximum size. You may need to get an adult to help you.
3) Tie a knot in the balloon to hold in the air. Do not be afraid to ask for help.
4) Make sure you do the next step after you wash your hair and before you apply any additional hair products to your hair.
5) While standing in front of a mirror, gently rub the balloon back and forth four to five times on your hair and slowly lift the balloon.
6) Notice that your hair is attracted to the balloon.
Electrons (negatively charged particles) from your hair have been rubbed onto the surface of the balloon making the surface of the balloon (that rubbed your hair) negatively charged with excess electrons. Your hair has fewer electrons and now has an excess of positive charges. Why does the balloon attract your hair? Remember - opposites attract.
Now that you know a little bit about static electricity, pay attention to all of the ways static electricity is around you every day. From the socks that stick together in the dryer to your unruly "morning hair," static electricity is all around us.
- Libby and Robert Strong and Richard Pollack work with the SMART Center, a hands-on science outreach and education organization in the northern Ohio Valley, the headquarters of which is located at the SMART-Centre Market, 30 22nd St., Wheeling. Visit them at www.smartcenter.org. | <urn:uuid:7d93b9e7-b145-4c9d-9a7f-f31d83b2ff00> | 3.625 | 991 | Tutorial | Science & Tech. | 56.97227 |
[ edit ] Haskell :: Functional Programming with Types Haskell is a functional programming language. If you have programmed before and would like to see a little bit of how Haskell works and is different from other programming languages, you can get an overview . Haskell is unique for two reasons. The first is that it is purely functional. If you have a function and you call it twice in two different places with the same arguments then it will return exactly the same value both times.
HackageDB (or just Hackage) is a collection of releases of Haskell packages. Each package is in the Cabal format, a standard way of packaging Haskell source code that makes it easy to build and install. These pages are a basic web interface to the Hackage package database. Finding packages
From HaskellWiki The number of Haskell packages is growing rapidly. The section 'Haskell library collections' gives an ordering of all these packages by relative importance. | <urn:uuid:602bdff8-c087-4243-9b32-fb9578e288c0> | 2.75 | 185 | Knowledge Article | Software Dev. | 40.020519 |
Scientists at the Bureau of Reclamation have increased the spatial resolution of the newest climate models to make them more useful for water managers.
Heat from cities can have far-reaching effects, disrupting circulation patterns and changing surface air temperatures thousands of miles away, according to a new study published in Nature Climate Change.
As the climate continues to warm, North American Monsoon precipitation will likely decrease in the early season (June-July) and increase in the late season (September-October), according to a new publication accepted to the Journal of Geophysical Research.
In the period 2021-2040, several regions in the Southwest will experience reduced soil moisture and runoff, according to a recent study published in Nature Climate Change.
Winter precipitation in the Southwest is likely to decrease by about 7.5 percent in the future, according to a new study led by University of Arizona researchers.
Previously rare extreme summer temperatures are occurring more frequently in some regions of the U.S.—especially in the Southwest, the upper tier of the Midwest, and the Atlantic coast—due to climate change, according to a new study in Climatic Change.
New studies both confirm global warming and warn there is little time left to keep warming below 2˚C from pre-industrial levels, the target needed to avert dangerous climate change. Berkeley Earth has submitted four papers for peer review that confirm the amount of warming determined by earlier studies. | <urn:uuid:0fa683a7-f61a-46aa-a000-564b7d616098> | 3.578125 | 284 | Knowledge Article | Science & Tech. | 27.827045 |
The ASSEMBLY sample program demonstrates how to construct an assembly between two products. An assembly relationship is constructed to relate the configuration management instances as well as the geometry. The program is broken down into functions which handle portions of the complete relationship. The input file for the program must contain at least two products with geometry.
- "assembly_in.stp" contains sample input for this program.
- "assembly_out_cdsr.stp" contains the sample output from this program with an assembly that uses context_dependent_shape_representation.
- "assembly_out_cdsr.stp" contains the sample output from this program with an assembly that uses mapped_item.
The program reads the "assembly_in.stp" data set and saves two different versions of it called "output_with_mapped_item.stp" and "output_with_cdsr.stp". STEP files are text, so you can look at them with a text editor or right-click "Browse" them with the STEP Part 21 file browser to see the contents.
In the list above, select your Visual Studio version or platform, then right click on the link to save the zipped project files to your local disk. Unpack the zipfile.
On Windows, open the enclosed project file with Visual Studio and compile the program by selecting "Build All". The project creates a Console application that you can run from the command line. When using the 64bit version of ST-Developer, change the platform from "win32" to "X64" in the Visual Studio Configuration Manager before building.
On MacOS, Linux, and other Unix systems, the project directory contains a makefile that builds the sample program. The makefile uses the ROSE, ROSE_INCLUDE, and ROSE_LIB environment variables described in the ST-Developer installation notes. Compile the program by typing "make".
The Windows projects also include a makefile that you can use by typing "nmake", but you must run vcvars32.bat (found in the Visual Studio C++ bin directory) to make sure that the C++ compiler is in the command line search path. | <urn:uuid:463e196b-3838-494e-be91-775e100d339f> | 3.046875 | 461 | Tutorial | Software Dev. | 48.326727 |
Conservationists warned the rare Chinese white dolphins, also known as pink dolphins for their unique colour, face extinction unless urgent action against pollution and other threats is taken.
Nicky Phillips For more than 3 billion years since single-celled organisms first appeared on the planet, life has evolved in one direction only. When a plant or animal becomes extinct, there is no coming back.
Michael Bachelard SOME of the richest and most biodiverse forests in Indonesia will soon be opened up for commercial exploitation under a plan drafted by the new government of Aceh.
Andrew Darby A ONCE-PRIZED table fish is being considered for the threatened species list, in a further challenge to fisheries managers.
Tom Arup and Bridie Smith A team of scientists and conservationists is pushing to escalate Victoria's faunal emblem, Leadbeater's possum, up the national threatened species list to critically endangered - one step below...
Richard Gray, London Freshwater fish are the most endangered group of animals on the planet, with more than a third facing extinction, according to a report British scientists are preparing.
Rosslyn Beeby Australia will witness the ''managed extinction'' of one of its rarest mammals, Leadbeater's possum, unless the federal government intervenes to save its old growth mountain ash habitat, a leading...
Ben Cubby, ENVIRONMENT AUSTRALIA must create a new, expanded network of protected wetlands around its coastline or see many bird, animal and plant species become extinct as sea levels rise, the House of Representatives...
Adam Morton The orange-bellied parrot faces extinction inside five years, with as few as 50 birds left in the wild, scientists warn.
Overfishing and pollution putting fish, sharks and whales in extreme danger - with extinction 'inevitable', study finds.
More than a fifth of the world's plant species faces the threat of extinction, according to research released on Wednesday.
Adam Morton It is not every day you get a chance to make an animal extinct twice. According to scientists, Victoria is steadily working on it.
Peter Hannam The final report of a cross-party inquiry into Australia's biodiversity and climate change produced only 'weak and ineffective' recommendations, the Australian Conservation Foundation said.
Tom Arup The state government has been dragging its feet in attempts to save Victoria's faunal emblem. Any disappearance this time could be permanent.
Many species of birds, amphibians and corals not currently under threat will be at risk from climate change and have been wrongly omitted from conservation planning, an international study finds.
Nardine Groch Sponsors of a new website, platypusSPOT, hope to amass a community-driven database on platypus distribution, which they say is essential for the effective management and conservation of the iconic...
A decline in the diversity of farmed plants and livestock breeds is gathering pace, threatening future food supplies for the world's growing population, the head of a new United Nations panel on...
A controversial plan to allow Queensland farmers to clear their own land as they see fit is a rubber stamp from reality.
Anthony Ham The battle to save the African rhinoceros has all the ingredients for a Hollywood thriller. There are armed baddies with good guys in hot pursuit. There is a hint of glamour.
Tom Arup Victoria's state-owned timber company will reduce logging by 25 per cent in the bushfire-ravaged mountain ash forests of the central highlands -- but will wait until mid-2017 to make the shift. | <urn:uuid:0e584f43-a7a7-4f50-915c-0fbb701c443f> | 2.859375 | 731 | Content Listing | Science & Tech. | 40.040623 |
have incorporated an aerosol module into the NASA GMAO GEOS-4 general
circulation model and data assimilation system. Aerosols are
particles and droplets suspended in the atmosphere and transported by
the winds. Including the aerosols in the GEOS-4 model allows us
to simulate their global distributions. Aerosols play important
roles in Earth’s climate system, by reflecting and absorbing
solar and thermal radiation, by modifying the properties of clouds, and
by interacting chemically with other constituents in the atmosphere.
a part of this research we are forecasting the global distributions of
tropospheric aerosol species such as dust, smoke, sulfate, and seasalt
particles. The purpose of these chemical weather forecasts is to
support decision making in NASA field missions. Potential
applications of this work are to climate and air quality studies. | <urn:uuid:24f642f8-0909-4222-88b8-bcfc1040c3b2> | 3.421875 | 184 | Academic Writing | Science & Tech. | 23.160611 |
To find out what tree rings are telling us about droughts in the Colorado Basin, and to get some current perspective on the current eleven-year drought in the region, listen to my radio story for The California Report and view the slide show of my journey to the region. — Gretchen Weber
Abbie Tingstad is a paleoclimatologist whose doctoral work at UCLA involved reconstructing climate in the Upper Colorado River Basin, using tree rings and lake sediments.
By Abbie Tingstad
Unlike biology, chemistry, or most mainstream sciences, it’s hard to envision what someone who studies paleoclimatology actually does. I run into a lot of blank stares at dinner parties. So I’ve started describing the field as “climate forensics.”
Paleoclimatology and forensics of the Law & Order or Bones variety share the basic goal of reconstructing something that has happened in the past. In the latter, of course, the sequence of events that led to a crime is put together. In the former, researchers identify past variations in climate. These sciences also have quite a lot in common when it comes to the basic methodology:
1. Collection of evidence
I’ll use the example of tree rings, something I have direct experience working with from my research in northeastern Utah. Based on river gauge data, this area of the Colorado River Basin originates 10-15% of Upper Basin water, which is why my colleagues and I were interested in understanding the incidence of past droughts here.
In this case, my climate “fingerprints” were moisture-sensitive Piñon pines. We searched for sites that appeared to have very old living trees — identifiable by trunk size, the open appearance of the branches, and the presence of dead limbs — and lots of dead trees. We used a manual coring device to take pencil-sized samples from both living and dead trees.
2. Lab work
Back at UCLA, I mounted the delicate samples onto wooden holders with an adhesive. Then my assistants and I sanded each sample using progressively finer sandpaper, until individual cells within annual rings were visible under a light microscope.
I counted the annual rings on each of the live samples back in time, starting with the ring closest to the bark. I noted recurring patterns of narrow rings, which are generally associated with climate events unfavorable for tree growth (for example, during the Dust Bowl drought). These patterns allowed me to identify when the dead trees lived. As I had hoped, some of the dead trees were older than any of the living trees, allowing a longer reconstruction.
After dating the samples, I measured the widths of the annual rings using a microscope attached to a computer. I then used statistical software to check the accuracy of my dating and to generate one time sequence per site, based on the ring widths of all the individual trees.
3. Reconstruction of events
In a crime lab, analysts will compare fingerprints, residue samples, or other forms of evidence with a database to place the evidence into context. Paleoclimatologists do the same, except we use instrumental climate information. In the Uinta Mountains research, I found that the tree rings correlated well with measures of moisture such as streamflow and snowpack over the 20th century time period for which instrumental data are available. Using a statistical technique called linear regression, I developed a mathematical expression to estimate these climate variables based on tree ring widths. Applying these models to the entire data sets, I developed reconstructions for Uinta Mountains streamflow and snowpack going back several centuries.
My colleagues and I used these estimates of past hydrology to analyze drought frequency, length, and severity. This information extends knowledge of baseline conditions for water management beyond the 20th century.
4. Comparison with other lines of evidence
Even if a paleoclimate record may appear to be a “smoking gun,” researchers validate their work by developing climate reconstructions for a particular area based on different types of data and/or by comparing their work with that of others. As in criminal investigations, the strongest case is made when independent forms of evidence all point to the same conclusion.
At the end of a paleoclimate investigation, researchers are able to present strong evidence for things like long droughts in the Western U.S. during Medieval times, or shifts in the way El Niño behaves, or that late-20th century temperatures are high in the context of relatively recent Earth history. However, paleoclimatology is an imperfect science. Tree rings, lake and ocean sediments, corals, glaciers, and other archives imprinted by past climates cannot compete with modern instruments. But like many good crime scene reconstructions, a few distorted or missing bits don’t make the big picture wrong. | <urn:uuid:30222697-321c-4da8-a3f6-ed24b36dc378> | 3.4375 | 993 | Nonfiction Writing | Science & Tech. | 33.620021 |
Cosmic X-rays May Reveal New Form of Matter
Chandra observations of RX J1856.5-3754 and the pulsar in 3C58 suggest that the matter in these collapsed stars is even denser than nuclear matter, the most dense matter found on Earth. This raises the possibility that these stars are composed of free quarks or crystals of sub-nuclear particles, rather than neutrons.
By combining Chandra and Hubble Space Telescope data, astronomers found that RX J1856 radiates like a solid body with a temperature of 700,000 degrees Celsius and has a diameter of about 7 miles.
This size is too small to reconcile with the standard models of neutron stars. One exciting possibility, predicted by some theories, is that the neutrons in the star have dissolved at very high density into a soup of "up," "down" and "strange" quarks to form a "strange quark star," which would explain the smaller radius.
Observations of 3C58, the remnant of a supernova noted on Earth in AD 1181, reveal that the pulsar in the core has a temperature much lower than expected. This suggests that an exotic, denser state of matter might exist inside this star as well.
These observations demonstrate that the universe can be used as a laboratory to explore physics under conditions that are not accessible on Earth. | <urn:uuid:7635515f-82ab-41cc-8187-b5e1139c8a3d> | 3.3125 | 281 | Knowledge Article | Science & Tech. | 46.931187 |
The hybridization for both of the oxygen atoms will be sp2 and the hybridization of the carbon atom will be sp. Remember when there is a multiple bond you only count the attached atom as one atom, because the pi-bond will require unhybridized p orbitals. Thus each oxygen atom has a carbon atom and two non-bonded pairs for a total of three groups. The carbon atom has two atoms attached for a total of two groups.
The oxygen-carbon-oxygen bond angle is 180o.
The pi-bonds lie at right angles to each other because the two unhybridized p orbitals of the carbon atom are at right angles. In the following drawing, the non-bonded electron pairs for the oxygen atoms are shown as red hybrid orbitals with these in the plane of the paper for the oxygen atom on the left and coming out and going back of the plane of the paper for the oxygen atom on the right. The pi-bond shown in blue is in the plane of the paper and the pi-bond shown in green is perpendicular to the plane of the paper.
The electron-pair geometry is linear for the carbon atom and trigonal planar for both oxygen atoms.
The molecular geometry is linear. | <urn:uuid:6d466cff-ca35-48a7-8561-1e5d863bc5f4> | 3.75 | 262 | Knowledge Article | Science & Tech. | 54.939444 |
Groovy Science is a symbolic manipulation library for Groovy that is intended to be easy to "glue" to existing scientific Java (and Groovy) libraries.
There are no archive releases of Groovy Science yet, but the current source can be found at http://svn.codehaus.org/groovy-contrib/science/. To use it, you can do any of the following things:
- Build it in its own project, and have your project reference that project.
- Copy the source into your own project.
- Make a .jar file yourself, and use that.
Groovy Science has been successfully built and used under Java 1.6.0 Update 7 and Groovy 1.5.1.
(to be written)
The centerpiece of the library is the SymbolicExpression class. A SymbolicExpression is a representation of the "application" of an operator object to a list of other SymbolicExpressions. This makes for a simple tree structure, and it is not unlike the way Lisp code is represented in s-expressions.
import org.codehaus.groovy.science.SymbolicExpression import static org.codehaus.groovy.science.SymbolicExpression.expr Object plusOp = new Object(); Object leafOp = new Object(); SymbolicExpression leaf = expr( leafOp ); SymbolicExpression myExpression = expr( plusOp, leaf, leaf ); assert myExpression.operator == plusOp; assert myExpression.argumentList == [ leaf, leaf ]; assert myExpression.argumentList[ 0 ].operator == leafOp; assert myExpression.argumentList[ 0 ].argumentList == ;
The SymbolicExpression class overloads almost all of the operators that can be overloaded in Groovy. So, instead of building all expressions using expr, you can sometimes take advantage of Groovy's own syntax:
import org.codehaus.groovy.science.SymbolicExpression import static org.codehaus.groovy.science.SymbolicExpression.expr import org.codehaus.groovy.science.OverloadableOperators Object leafOp = new Object(); SymbolicExpression leaf = expr( leafOp ); assert leaf + leaf == expr( OverloadableOperators.Plus, leaf, leaf ); assert leaf[ leaf ] == expr( OverloadableOperators.GetAt, leaf, leaf );
If you wanted to represent an expression like "1 + 1", you could do so as follows:
import org.codehaus.groovy.science.SymbolicExpression import static org.codehaus.groovy.science.SymbolicExpression.expr SymbolicExpression one = expr( 1 ); SymbolicExpression onePlusOne = one + one;
If you do that, though, you might run the risk of confusing your constants with your other operators. To help keep your constants clearly identified, you can use the ConstantOperator class:
import org.codehaus.groovy.science.SymbolicExpression import static org.codehaus.groovy.science.SymbolicExpression.expr import org.codehaus.groovy.science.ConstantOperator import static org.codehaus.groovy.science.ConstantOperator.* // for con, unCon, and isCon SymbolicExpression one = con( 1 ); SymbolicExpression onePlusOne = one + one; assert one == expr( new ConstantOperator( 1 ) ); assert one.operator.value == 1; assert unCon( one ) == 1; assert isCon( one ); assert !isCon( onePlusOne );
- Ross Angle [rokitna at hotmail]
Please contact the team members by e-mail. | <urn:uuid:866fffb9-843d-41be-998c-36d426ffa4aa> | 2.859375 | 795 | Documentation | Software Dev. | 36.241944 |
|CONTENTS | PREV | NEXT||Java Remote Method Invocation|
The Java SE platform's distributed object model is similar to the Java SE platform's object model in the following ways:
- A reference to a remote object can be passed as an argument or returned as a result in any method invocation (local or remote).
- A remote object can be cast to any of the set of remote interfaces supported by the implementation using the syntax for casting built into the Java programming language.
- The built-in
instanceofoperator can be used to test the remote interfaces supported by a remote object.
The Java SE platform's distributed object model differs from the Java SE platform's object model in these ways:
- Clients of remote objects interact with remote interfaces, never with the implementation classes of those interfaces.
- Non-remote arguments to, and results from, a remote method invocation are passed by copy rather than by reference. This is because references to objects are only useful within a single virtual machine.
- A remote object is passed by reference, not by copying the actual remote implementation.
- The semantics of some of the methods defined by class
java.lang.Objectare specialized for remote objects.
- Since the failure modes of invoking remote objects are inherently more complicated than the failure modes of invoking local objects, clients must deal with additional exceptions that can occur during a remote method invocation. | <urn:uuid:f664af41-5876-4f9f-995f-4dbcf3af7c83> | 2.90625 | 286 | Documentation | Software Dev. | 23.034167 |
North American Ecology (US and Canada)
Resident in western North America, north to Alaska, with isolated populations in New Brunswick and Quebeck (Scott 1986). Habitats are mostly transition to lower Hudsonian Zone woodland openings, sometimes chaparral. Host plants are usually herbaceous and include many species, but mostly in one family, Leguminosae. Eggs are laid on the host plant singly. Individuals overwinter as larvae. There is a either one or two flights based on latitude, with the approximate flight time late May -July 15 in the northern part of the range, Mar1-Apr30 in California, and late April ? Aug15 in most of the rest of the range (Scott 1986).
- Scott, J. A. 1986. The butterflies of North America. Stanford University Press.
No one has provided updates yet. | <urn:uuid:999db8cc-9f9f-45ff-925e-201ed5cc5100> | 2.90625 | 173 | Knowledge Article | Science & Tech. | 45.254451 |