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There are four numeric types: plain integers, long integers,
floating point numbers, and complex numbers.
Plain integers (also just called integers)
are implemented using long in C, which gives them at least 32
bits of precision. Long integers have unlimited precision. Floating
point numbers are implemented using double in C. All bets on
their precision are off unless you happen to know the machine you are
Complex numbers have a real and imaginary part, which are both
implemented using double in C. To extract these parts from
a complex number z, use
Numbers are created by numeric literals or as the result of built-in
functions and operators. Unadorned integer literals (including hex
and octal numbers) yield plain integers. Integer literals with an
"L" or "l" suffix yield long integers
("L" is preferred because "1l" looks too much like
eleven!). Numeric literals containing a decimal point or an exponent
sign yield floating point numbers. Appending "j" or
"J" to a numeric literal yields a complex number.
Python fully supports mixed arithmetic: when a binary arithmetic
operator has operands of different numeric types, the operand with the
``smaller'' type is converted to that of the other, where plain
integer is smaller than long integer is smaller than floating point is
smaller than complex.
Comparisons between numbers of mixed type use the same rule.2.3 The functions int(), long(), float(),
and complex() can be used
to coerce numbers to a specific type.
All numeric types support the following operations, sorted by ascending priority (operations in the same box have the same priority; all numeric operations have a higher priority than comparison operations):
||sum of x and y|
||difference of x and y|
||product of x and y|
||quotient of x and y||(1)|
||absolute value or magnitude of x|
||x converted to integer||(2)|
||x converted to long integer||(2)|
||x converted to floating point|
||a complex number with real part re, imaginary part im. im defaults to zero.|
||conjugate of the complex number c|
||x to the power y|
||x to the power y|
[1, 2]is considered equal to
[1.0, 2.0], and similar for tuples. | <urn:uuid:0e6451e1-d390-4b41-98e1-099626c80867> | 4.53125 | 521 | Documentation | Software Dev. | 48.769293 |
Kirchhoff's law of thermal radiation
||This article includes a list of references, but its sources remain unclear because it has insufficient inline citations. (December 2008)|
- See also Kirchhoff's laws for other laws named after Kirchhoff.
In thermodynamics, Kirchhoff's law of thermal radiation refers to wavelength-specific radiative emission and absorption by a material body in thermodynamic equilibrium, including radiative exchange equilibrium.
A body at temperature T radiates electromagnetic energy. A perfect black body in thermodynamic equilibrium absorbs all light that strikes it, and radiates energy according to a unique law of radiative emissive power for temperature T, universal for all perfect black bodies. Kirchhoff's law states that:
- For a body of any arbitrary material, emitting and absorbing thermal electromagnetic radiation at every wavelength in thermodynamic equilibrium, the ratio of its emissive power to its dimensionless coefficient of absorption is equal to a universal function only of radiative wavelength and temperature, the perfect black-body emissive power.
Here, the dimensionless coefficient of absorption (or the absorptivity) is the fraction of incident light (power) that is absorbed by the body when it is radiating and absorbing in thermodynamic equilibrium. In slightly different terms, the emissive power of an arbitrary opaque body of fixed size and shape at a definite temperature can be described by a dimensionless ratio, sometimes called the emissivity, the ratio of the emissive power of the body to the emissive power of a black body of the same size and shape at the same fixed temperature. With this definition, a corollary of Kirchhoff's law is that for an arbitrary body emitting and absorbing thermal radiation in thermodynamic equilibrium, the emissivity is equal to the absorptivity. In some cases, emissive power and absorptivity may be defined to depend on angle, as described below.
Kirchhoff's Law has another corollary: the emissivity cannot exceed one (because the absorptivity cannot, by conservation of energy), so it is not possible to thermally radiate more energy than a black body, at equilibrium. In negative luminescence the angle and wavelength integrated absorption exceeds the material's emission, however, such systems are powered by an external source and are therefore not in thermodynamic equilibrium.
Before Kirchhoff's law was recognized, it had been experimentally established that a good absorber is a good emitter, and a poor absorber is a poor emitter. Naturally, a good reflector must be a poor absorber. This is why, for example, lightweight emergency thermal blankets are based on reflective metallic coatings: they lose little heat by radiation.
One may suppose a second system, a cavity with walls that are opaque, rigid, and not perfectly reflective to any wavelength, to be brought into connection, through an optical filter, with the blackbody enclosure, both at the same temperature. Radiation can pass from one system to the other. For example, suppose in the second system, the density of photons at narrow frequency band around wavelength were higher than that of the first system. If the optical filter passed only that frequency band, then there would be a net transfer of photons, and their energy, from the second system to the first. This is in violation of the second law of thermodynamics, which requires that there can be no net transfer of heat between two bodies at the same temperature.
In the second system, therefore, at each frequency, the walls must absorb and emit energy in such a way as to maintain the black body distribution. The absorptivity is the ratio of the energy absorbed by the wall to the energy incident on the wall, for a particular wavelength. This will be proportional to where is the intensity of black body radiation at wavelength and temperature . The emissivity of the wall is defined as the ratio of emitted energy to the amount that would be radiated if the wall were a perfect black body. That will be where is the emissivity at wavelength . These two quantities must be equal, or else the distribution of photon energies in the cavity will deviate from that of a black body. This yields Kirchhoff's law:
By a similar, but more complicated argument, it can be shown that, since black body radiation is equal in every direction (isotropic), the emissivity and the absorptivity, if they happen to be dependent on direction, must again be equal for any given direction.
Average and overall absorptivity and emissivity data are often given for materials with values which differ from each other. For example, white paint is quoted as having an absorptivity of 0.16, while having an emissivity of 0.93. This is because the absorptivity is averaged with weighting for the solar spectrum, while the emissivity is weighted for the emission of the paint itself at normal ambient temperatures. The absorptivity quoted in such cases is being calculated by:
while the average emissivity is given by:
Where is the emission spectrum of the sun, and is the emission spectrum of the paint. Although, by Kirchhoff's law, in the above equations, the above averages and are not generally equal to each other. The white paint will serve as a very good insulator against solar radiation, because it is very reflective of the solar radiation, and although it therefore emits poorly in the solar band, its temperature will be around room temperature, and it will emit whatever radiation it has absorbed in the infrared, where its emission coefficient is high.
Black bodies
Near-black materials
It has long been known that a lamp-black coating will make a body nearly black. Some other materials are nearly black in particular wavelength bands. Such materials do not survive all the very high temperatures that are of interest.
An improvement on lamp-black is found in manufactured carbon nanotubes. Nano-porous materials can achieve refractive indices nearly that of vacuum, in one case obtaining average reflectance of 0.045%.
Opaque bodies
Bodies that are opaque to thermal radiation that falls on them are valuable in the study of heat radiation. Planck analyzed such bodies with the approximation that they be considered topologically to have an interior and to share an interface. They share the interface with their contiguous medium, which may be rarefied material such as air, or transparent material, through which observations can be made. The interface is not a material body and can neither emit nor absorb. It is a mathematical surface belonging jointly to the two media that touch it. It is the site of refraction of radiation that penetrates it and of reflection of radiation that does not. As such it obeys the Helmholtz reciprocity principle. The opaque body is considered to have a material interior that absorbs all and scatters or transmits none of the radiation that reaches it through refraction at the interface. In this sense the material of the opaque body is black to radiation that reaches it, while the whole phenomenon, including the interior and the interface, does not show perfect blackness. In Planck's model, perfectly black bodies, which he noted do not exist in nature, besides their opaque interior, have interfaces that are perfectly transmitting and non-reflective.
Cavity radiation
The walls of a cavity can be made of opaque materials that absorb significant amounts of radiation at all wavelengths. It is not necessary that every part of the interior walls be a good absorber at every wavelength. The effective range of absorbing wavelengths can be extended by the use of patches of several differently absorbing materials in parts of the interior walls of the cavity. In thermodynamic equilibrium the cavity radiation will precisely obey Planck's law. In this sense, thermodynamic equilibrium cavity radiation may be regarded as thermodynamic equilibrium black-body radiation to which Kirchhoff's law applies exactly, though no perfectly black body in Kirchhoff's sense is present.
A theoretical model considered by Planck consists of a cavity with perfectly reflecting walls, initially with no material contents, into which is then put a small piece of carbon. Without the small piece of carbon, there is no way for non-equilibrium radiation initially in the cavity to drift towards thermodynamic equilibrium. When the small piece of carbon is put in, it transduces amongst radiation frequencies so that the cavity radiation comes to thermodynamic equilibrium.
A hole in the wall of a cavity
For experimental purposes, a hole in a cavity can be devised to provide a good approximation to a black surface, but will not be perfectly Lambertian, and must be viewed from nearly right angles to get the best properties. The construction of such devices was an important step in the empirical measurements that led to the precise mathematical identification of Kirchhoff's universal function, now known as Planck's law.
Kirchhoff's perfect black bodies
Planck also noted that the perfect black bodies of Kirchhoff do not occur in physical reality. They are theoretical fictions. Kirchhoff's perfect black bodies absorb all the radiation that falls on them, right in an infinitely thin surface layer, with no reflection and no scattering. They emit radiation in perfect accord with Lambert's cosine law.
Original statements
Prior to Kirchhoff's studies, it was known that for total heat radiation, the ratio of emissive power to absorptive ratio was the same for all bodies emitting and absorbing thermal radiation in thermodynamic equilibrium. This means that a good absorber is a good emitter. Naturally, a good reflector is a poor absorber. For wavelength specificity, prior to Kirchhoff, the ratio was shown experimentally by Balfour Stewart to be the same for all bodies, but the universal value of the ratio had not been explicitly considered in its own right as a function of wavelength and temperature.
Kirchhoff's original contribution to the physics of thermal radiation was his postulate of a perfect black body radiating and absorbing thermal radiation in an enclosure opaque to thermal radiation and with walls that absorb at all wavelengths. Kirchhoff's perfect black body absorbs all the radiation that falls upon it.
- Kirchhoff's postulated spectral radiance I was a universal function, one and the same for all black bodies, only of wavelength and temperature.
The precise mathematical expression for that universal function I was very much unknown to Kirchhoff, and it was just postulated to exist, until its precise mathematical expression was found in 1900 by Max Planck. It is nowadays referred to as Planck's law.
Then, at each wavelength, for thermodynamic equilibrium in an enclosure, opaque to heat rays, with walls that absorb some radiation at every wavelength:
- For an arbitrary body radiating and emitting thermal radiation, the ratio E / A between the emissive spectral radiance, E, and the dimensionless absorptive ratio, A, is one and the same for all bodies at a given temperature. That ratio E / A is equal to the emissive spectral radiance I of a perfect black body, a universal function only of wavelength and temperature.
See also
Cited references
- Kirchhoff 1860
- Planck 1914
- Milne 1930, p. 80
- Chandrasekhar 1950, p. 8
- Mihalas & Weibel-Mihalas 1984, p. 328
- Goody & Yung 1989, pp. 27–28
- Rybicki & Lightman, pp. 15–20.
- Rybicki, George B. and Lightman, Alan P., "Radiative Processes in Astrophysics" (John Wiley and Sons, New York, 1979)
- Ai Lin Chun, "Carbon nanotubes: Blacker than black," Nature Nanotechnology (25 Jan 2008), doi:10.1038/nnano.2008.29.
- Z.-P. Yang et al., "Experimental Observation of an Extremely Dark Material Made By a Low-Density Nanotube Array," Nano Letters vol. 8, pp. 446-451 (2008).
- Kirchhoff, G. (1862). Appendix, Über das Verhältniß zwischen dem Emissionsvermögen und dem Absorptionsvermögen der Körper für Wärme und Licht, to Untersuchungen über das Sonnenspectrum und die Spectren der chemischen Elemente, Ferd. Dümmler's Verlagsbuchhandlung, Berlin, pages 22-39. Reprinted with the same title in Kangro, H. (1972), Otto Zeller Verlag, Osnabrück, ISBN 3–535–00820–4, pages 45–64.
- Chandrasekhar, S. (1960) . Radiative Transfer (Revised reprint ed.). Dover Publications. ISBN 978-0-486-60590-6.
- Goody, R. M.; Yung, Y. L. (1989). Atmospheric Radiation: Theoretical Basis (2nd ed.). Oxford University Press. ISBN 978-0-19-510291-8.
- Kirchhoff, G. (1860). "Ueber das Verhältniss zwischen dem Emissionsvermögen und dem Absorptionsvermögen der Körper für Wärme and Licht". Annalen der Physik und Chemie (Leipzig) 109: 275–301. Translated by Guthrie, F. as Kirchhoff, G. (1860). "On the relation between the radiating and absorbing powers of different bodies for light and heat". Philosophical Magazine. Series 4, volume 20: 1–21.
- Mihalas, D.; Weibel-Mihalas, B. (1984). Foundations of Radiation Hydrodynamics. Oxford University Press. ISBN 0-19-503437-6.
- Milne, E.A. (1930). "Thermodynamics of the Stars". Handbuch der Astrophysik. 3, part 1: 63–255.
- Planck, M. (1914). The Theory of Heat Radiation. Masius, M. (transl.) (2nd ed.). P. Blakiston's Son & Co. OL 7154661M.
General references
- Evgeny Lifshitz and L. P. Pitaevskii, Statistical Physics: Part 2, 3rd edition (Elsevier, 1980).
- F. Reif, Fundamentals of Statistical and Thermal Physics (McGraw-Hill: Boston, 1965). | <urn:uuid:e56b16f2-7689-4060-aeac-68418ed2cead> | 3.703125 | 3,063 | Knowledge Article | Science & Tech. | 41.584254 |
E5 -- Problematis traiectoriarum reciprocarum solutio
(Solution to the problem of reciprocal trajectories)
This article contains Euler's first published use of complex numbers and a many-axis geometric construction.
Euler also calls functions f(x) for which f(x) = f(-x) even functions, perhaps the first use of this term.
Originally published in Commentarii academiae scientiarum Petropolitanae 2, 1729, pp. 90-111
Opera Omnia: Series 2, Volume 6, pp.
Reprinted in Comment. acad. sc. Petrop. 2, ed. nova, Bononiae 1741, pp. 79-97 + 1 diagram
Return to the Euler Archive | <urn:uuid:ddb60098-33e5-4b43-9e3a-6406a7731842> | 2.75 | 166 | Knowledge Article | Science & Tech. | 57.64 |
The no cloning theorem states that it is impossible to make an exact copy of something at the quantum level while retaining the original. More precisely, it says we can't make an exact copy of an arbitrary, unknown quantum state. This was first revealed by Wootters and Zurek in 1982. It may be possible to make copies if we relax some of the requirements (exactness, what kinds of states we can copy, or how much we know about the state), though to what degree is still an open question at the current time. The issue of quantum cloning is of interest to physicists for one reason because making copies is a basic part of doing error correction in a classical computer. Physicists want to build a quantum computer, which will also need error correction, and the extent to which copying of states is possible could be rather important. It is also interesting on a more basic level that nature seems to forbid making an exact copy of something. In quantum teleportation we are able to send an exact copy of something to a remote location but only by destroying the original.
So, why can't we make a copy of a quantum state? Well, I'll try to sketch the basics in plain English, then we can delve into the mathematical details for the experts. In quantum mechanics there are two ways you can change a quantum state,measuring the system and introducing potentials to the system that cause it to evolve according to Schrodinger's Equation. It turns out that neither of these methods allows one to make an exact copy of a system. You can't use a potential to do it, because if you examine the process closely, you find that it would violate the principle of superposition. It's not possible to do it by measurement because a measurement can generally have several different results, unless the system starts out in the desired state, which wouldn't be arbitrary. So, generally, the measurement could result in any number of other states. In essence, the measurements generally destroy quantum information about the state being measured.
We consider a system that consists of 3 subsystems. The first is the state to be copied, the second is the system to be copied to (the "blank" system"), and the third represents the copying apparatus, and anything else for that matter. Generally, the exact copying of an arbitrary unknown state can be represented schematically as
|ψ>A*|i>B*|η>C → |ψ>A*|ψ>B*|η(ψ)>C
where |ψ> is the state to be copied, |i> is the initial ("blank") state of the system to be copied to, and |η> is everything else. |η(ψ)> is the final state of all other parts of the system, which may depend on the state being copied. First we discuss why measurement is not useful in making a copy and discuss unitary evolution.
If a measurement is performed on the system and it is not already in an eigenstate of that measurement operator, then the system will collapse into one of several possible states in a stochastic fashion. This destroys information about the original state and leads to a result that cannot be exactly controlled or predicted. If system starts in an eigenstate of the measurement operator, then the measurement does nothing. Either way, a measurement cannot be a useful part of a process that will lead to an exact copy of the original state.
A copying mechanism that works via unitary evolution would copy an arbitrary state |ψ> by the process
U |ψ>A*|i>B*|η>C = |ψ>A*|ψ>B*|η(ψ)>C
Now suppose that |φn> is a complete orthonormal set on subsystem A, so
|ψ> = Σn an |φn>
U |ψ>A*|i>B*|η>C = Σn an U |φn>A*|i>B*|η>C = Σn an |φn>A*|φn>B*|η(φn)>C
|ψ>A*|ψ>B*|η(ψ)>C = Σn,m an am |φn>A*|φm>B*|η(ψ)>C
These two expressions are supposed to be the same, but they aren't, showing that our hypothesized copying process is not possible and not, in fact, linear, since that's the only property of the evolution we used. Put another way, the ideal copying mechanism would violate the superposition principle if it worked for more than one specific state. Of course, if it worked only for one predefined state then it wouldn't be much use, since if we know the state initially we should be able to generate it (in principle) even without copying.
We can conclude that it is not possible to clone an arbitrary unknown state exactly; however, we have not ruled out the possibility that one could perform cloning by relaxing one of the constraints. If we restricted the set of states to be copied or had some knowledge of them, we might be able to make a copy. Also, we might be able to make some degree of approximate copy, but it is unclear how close we could get to an exact copy (or, indeed, how to measure "closeness"). We could also explore mechanisms by which an exact copy is produced with some probability (less than %100). These issues are still currently being researched.
Here * is used to denote the tensor product of two states.
Note: The derivation here is mine, so it may contain mistakes, but the result is widely known.
- No cloning theorem Wikipedia.org
- Quantum Copying: Beyond the No-cloning Theorem Buzek, V. and Hillery, M., Phys. Rev. A 54, 1844 (1996) | <urn:uuid:63a21c46-ba3a-4b0e-b5b9-a8a4704e7386> | 3.5625 | 1,257 | Knowledge Article | Science & Tech. | 51.071795 |
The surface albedo determines the amount of reflected solar radiation at the earth surface, its vegetation and clouds. The albedo is thus a key parameter for the shortwave radiation budget of the earth surface and the Earth as a whole. The surface albedo depends on land cover and radiative properties of the soil, snow and vegetation. Different types of surface albedo data products exist which allow to take into account the dependency of surface albedo on the illumination conditions (clear sky, diffuse conditions). The albedo is derived from spectral observations of the reflected sunlight in the visible frequency range by sensors like the MeteoSAT Satellites, the Medium Resolution Imaging Spectrometer (MERIS) and the Moderate Resolution Imaging Spectroradiometer (MODIS). Values of the albedo are typically given without units. Since it is the ratio between reflected and incident solar radiation it takes values between 0 and 1. An albedo of 1 means that all incident solar radiation is reflected. Clouds, snow and ice have a high albedo, land surfaces and vegetation have a comparably low albedo (see the Figure).
Data sources / products of the surface albedo are:
Surface Solar Irradiance
The surface solar irradiance is a key parameter for the shortwave radiation budget of the earth surface and the Earth as a whole. The surface solar irradiance depends on the path length of the solar radiation through the atmosphere, on aerosol concentration, on cloud cover and on the surface albedo (see above). The surface solar irradiance is derived from spectral observations of the reflected sunlight in the visible frequency range by sensors like the MeteoSAT Satellites, the Medium Resolution Imaging Spectrometer (MERIS) and the Moderate Resolution Imaging Spectroradiometer (MODIS). Unit is Watts / m².
Land surface temperature
The land surface temperature is a key parameter for the quantification of the sensible heat flux and the long-wave radiation budget of the earth surface. Clear-sky (cloud free) conditions are required to determine the land surface temperature from satellite data. The satellite sensor measures the thermal (infrared) emission of the surface. The energy received by the sensor is translated into an infrared surface temperature which in turn is converted into the surface temperature with the aid of the infrared surface emissivity. This procedure, however, requires depending on the satellite sensor a number of corrections like for atmospheric scattering. Satellite sensors used are the Advanced Very High Resolution Radiometer (AVHRR), MeteoSAT, the Moderate Resolution Imaging Spectroradiometer (MODIS) and the (Advanced) Along Track Scanning Radiometer ((A)ATSR). Land surface temperatures are given in degree Celsius (°C) or Kelvin (K).
The shown Figure displays an application of land surface temperatures (LST) that have been derived from MODIS data: Anomalies of the LST for the month of Juli of the record summer 2003.
Vegetation / Land use
Land use and vegetation play an important role for a number of applications and processes, e.g. the determination of sensible and latent heat fluxes, evaporation and soil moisture, retrieval of snow cover and depth, and quantification of the short- and long-wave radiation budget over bare, vegetated and other parts of the land surface, e.g. urban areas. In order to derive land use categories and vegetation coverage from space again data from a number of different satellite sensors can be used, operating in the visible (see Albedo) and/or the infrared (see Land surface temperature) part of the electromagnetic spectrum (AVHRR, MODIS, MeteoSAT, MERIS, MIPAS, SPOT). In order to end up with geophysical products of interest (see below) often data from several frequencies have to be combined and a number of corrections has to be carried out (for atmospheric attenuation, cloud cover, solar angle, satellite viewing angle, et cet.)
These three parameters are amongst those most widely used:
a) photosynthetically active radiation (fAPAR)
b) leaf area index (LAI)
c) Normalized Differenced Vegetation Index (NDVI) (see Figure
In addition one can (partly based on the above-mentioned parameters) derive the land cover type (i.e. needleleaf forest, broadleaf forest, savanna, et cet.) according to, e.g., definitions of the International Geosphere Biosphere Programme (IGBP).
The moisture content of the soil is a key variable which has a strong influence on the partitioning of the available energy at the land surface. In case of sufficient water supply the evapotranspiration rate of the land surface is higher, while it is lower in case of low moisture content. As a consequence, soil moisture affects the energy exchange between the land surface and the atmosphere, which also affects the development of the atmospheric boundary layer.
Different satellite based methods have been developed to retrieve soil moisture information of the upper few centimeters of the soil from satellite data using active or passive microwave remote sensing methods. Satellite sensors used for this are the Advanced SCATterometer (ASCAT) aboard METOP and the Advanced Microwave Scanning Radiometer (AMSR-E) aboard the EOS-Satellites TERRA and AQUA. In 2009 the European Space Agency has launched a dedicated soil moisture satellite mission: Soil Moisture and Ocean Salinity (SMOS).
The topography of the Earth (on land and below the water line, i.e. the bathymetry) surface influences air flow and ocean currents, land hydrology (e.g. run-off) and glacier flow. In order to understand and correctly interpret climate-relevant processes, and in order to predict the impact potential future climate change may have, a global topography data set is important.
Here, we offer the topography data set: ETOPO1, with a spatial resolution of 1' (one arc minute = 1 nautical mile = 1.852 km); this is the successor of similar data sets with coarser spatial resolution: ETOPO2v2 and ETOPO5. The offered ETOPO1 data set is grid registered and over land shows the ice sheet surface (not the bedrock) (see NOAA-NGDC).
The ETOPO1 data set is a composite comprising a number of different data sources; information about these and the methods used to combine these is given in the ETOPO1 Development Report.
Access: (Attention: File size is 250 Mb - 400 Mb!) via
in the formats: geotiff, netCDF-GMT4, and netCDF-GDAL. The latter alternative is offered because of problems with GDAL reading the other, GMT4-based version (see readme-file).
ETOPO1 data have to be cited like this:
Amante C., and B. W. Eakins, 2009, ETOPO1 1 arc-minute global relief model: procedures, data sources and analysis, NOAA Technical Memorandum NESDIS NGDC 24, 19 pp., National Geophysical Data Center, Marine Geology and Geophysics Division, Boulder, Colorado.
More information is given under NOAA-NGDC.
For those of you who work with the Antarctic and require information about its topography, the location of observation stations, rock outcrops, etc., we recommend the latest issue of the Antarctic Digital Database (ADD) Version 6.0 hosted by BAS and SCAR.
Thanks to the work of the IBCAO a new bathymetric chart of the Arctic Ocean has been released recently. This Version 3.0 now comes with a grid resolution of 500 m x 500 m. More details you can find in Jakobsson et al. (2012).
Occurrence and distribution of permafrost or frozen soil plays a fundamental role for the hydrological cycle and biochemical fluxes (like of CO2 or Methane) between soil and atmosphere. Spatial-temporal changes of permafrost distribution and layer thickness can be seen as indicator of climate change. Its amplification in Arctic and sub-Arctic regions seems to have initiated a reduction in permafrost distribution and vertical extent in some areas already.
We link here to a unique data set of permafrost distribution, vertical extent and other related parameters that has been compiled at the ETH-Zurich:
On the above-mentioned web site you can find versions of this data set as kml-file for Google Earth, in ArcGIS format and as raw binary file (3 GB!). The spatial resolution of this data set is 30 arcseconds (that is less than 1 km). It covers the area 60°S to 90°N and comprises 43200 x 18000 grid cells.
For further reading and citation of the data set the following reference is mandatory: Gruber, S. 2012: Derivation and analysis of a high-resolution estimate of global permafrost zonation, The Cryosphere, 6, 221-233. doi:10.5194/tc-6-221-2012.
Couple of users are interested in information about countries in a gridded format, e.g. to calculate a country mean temperature.
For those users we offer a netCDF-File with gridded country area information with the area each country occupies coded with a specific number on a 0.5° x 0.5° grid. The country associated with the respective number given in the netCDF file can be read in the corresponding table.
For users who need to know the land-water-distribution at fine spatial resolution we offer here the MOD44W data set. It is based on data of the SRTM shuttle mission and MODIS and provides the land-water-distribution at 250 m spatial resolution. More details are given here. | <urn:uuid:28867159-231b-47f0-93c9-6b4997e52375> | 4.34375 | 2,062 | Knowledge Article | Science & Tech. | 34.40321 |
INDONESIAN ASTEROID: Earlier this month, with no warning, a ~10-meter wide asteroid hit Earth's atmosphere above Indonesia and exploded. The break-up was so powerful, it triggered nuclear test ban sensors thousands of kilometers away. A just-released analysis of infrasound data shows that the asteroid detonated with an energy equivalent of about 50 kton of TNT, similar to a small atomic bomb. This significant impact has received relatively little attention in Western press.
Details are available today on http://spaceweather.com
From the Telegraph (UK):
*Asteroid explosion over Indonesia raises fears about Earth's defences*
*An asteroid that exploded in the Earth's atmosphere with the energy
of three Hiroshima bombs this month has reignited fears about our
planet's defences against space impacts.*
By Tom Chivers
Published: 10:23AM GMT 27 Oct 2009
On 8 October, the rock crashed into the atmosphere above South Sulawesi,
The blast was heard by monitoring stations 10,000 miles away, according
to a report by scientists at the University of Western Ontario
Scientists are concerned that it was not spotted by any telescopes, and
that had it been larger it could have caused a disaster.
The asteroid <http://www.telegraph.co.uk/science/space
have been around 10 metres (30ft) across, hit the atmosphere at an
estimated 45,000mph. The sudden deceleration caused it to heat up
rapidly and explode with the force of 50,000 tons of TNT.
Luckily, due to the height of the explosion -- estimated at between 15
and 20 km (nine to 12 miles) above sea level -- no damage was caused on
However, if the object had been slightly larger -- 20 to 30 metres (60
to 90ft) across -- it could easily have caused extensive damage and loss
of life, say researchers.
Very few objects smaller than 100 meters (300ft) across have been
spotted and catalogued by astronomers.
Tim Spahr, director of the Minor Planet Center
warned that it was inevitable that minor asteroids would go unnoticed.
He said: "If you want to find the smallest objects you have to build
more, larger telescopes.
"A survey that finds all of the 20-metre objects will cost probably
multiple billions of dollars."
The fireball was spotted by locals in Indonesia, and a YouTube video
taken that day <http://www.youtube.com/watch?v=yeQBzTkJNhs
show a large dust cloud consistent with a bright, daylight fireball",
according to the Ontario researchers.
An asteroid or comet fragment around 60 meters across is believed to
have been behind the Tunguska Event
took place over Russia in 1908. The blast has been estimated at
equivalent to 10-15 million tons of TNT -- enough to destroy a large city.
The White House
is to develop a policy on the space object impact threat by October next
Asteroid Impactor Reported over Indonesia
Don Yeomans, Paul Chodas, Steve Chesley
NASA/JPL Near-Earth Object Program Office
October 23, 2008
On October 8, 2009 about 03:00 Greenwich time, an atmospheric fireball
blast was observed and recorded over an island region of Indonesia. The
blast is thought to be due to the atmospheric entry of a small asteroid
about 10 meters in diameter that, due to atmospheric pressure, detonated
in the atmosphere with an energy of about 50 kilotons (the equivalent of
50,000 pounds of TNT explosives).
The blast was recorded visually and reported upon by local media
representatives. See the YouTube video at:
A report from Elizabeth Silber and Peter Brown at the University of
Western Ontario indicates that several international very-long
wavelength infrasound detectors recorded the blast and fixed the
position near the coastal city of Bone in South Sulawesi, island of
Sulewesi. They note that the blast was in the 10 to 50 kT range with the
higher end of this range being more likely.
Assuming an estimated size of about 5-10 meters in diameter, we would
expect a fireball event of this magnitude about once every 2 to 12 years
on average. As a rule, the most common types of stony asteroids would
not be expected to cause ground damage unless their diameters were about
25 meters in diameter or larger.
A more extensive report by Elizabeth Silber and Peter Brown of the
University of Western Ontario is here.
Summary of Preliminary Infrasonic Analysis of the Oct 8, 2009
Elizabeth Silber and Peter Brown
Meteor Infrasound group
Dept. of Physics and Astronomy,
Univ. of Western Ontario
Released: October 19, 2009
On Oct 8, 2009, media reports appeared in the local press in Indonesia
concerning a loud air blast occurring near 11am local time (0300 UT).
Subsequent to these first media reports, additional English language
reports appeared suggesting the event was meteoritic.
Indonesian language reports more clearly identify a bright fireball,
accompanied by an explosion and lingering dust cloud as the origin of
the air blast. Finally, a YouTube video posted on the same day appears
to show a large dust cloud consistent with a bright, daylight fireball.
Based on these initial reports, a detailed examination was made of all
International Monitoring System (IMS) infrasound stations of the
Comprehensive Nuclear-Test-Ban Treaty Organization (CTBTO). From this
initial examination, a total of 11 stations showed probable signals from
a large explosion centered near 4.5S, 120E, with an origin time near
0300 UT on Oct 8, 2009, consistent with the media reports. This signal
was notable for having been (a) detected at many IMS stations, including
five at ranges over 10,000 km (and one at a nearly 18,000 km range) and
(b) being confined to very low frequencies. Both of these observations
suggest the explosion source was of very high total energy. All signal
motions were between 0.27 - 0.32 km/s, consistent with stratospheric
We have used the Air Force Technical Application Centre (AFTAC)
period-yield relation as described by ReVelle (1997) as the most robust
basic indicator of source energy. To generate measured periods, the
average periods of all phase-aligned stacked waveforms at each station
were measured, according to the technique described in Edwards et al
(2006). These periods were then averaged to produce a single, global
average period of 13.4 sec and the AFTAC yield relation applied; this
produced an average source yield of 31 kT of TNT. Averaging the
individual yields from all stations produces a mean source energy near
50 kT of TNT while using only the eight stations having the highest
signal-to-noise-ratio (SNR) and using the local observed periods of the
waveform at maximum amplitude produces a yield estimate of 40 kT of TNT,
all of which are basically consistent. It is important to note, however,
that the standard deviation of this measurement is nearly 30 kT. That
is, the best source energy estimate would be 40 +/- 30 kT TNT. Note that
much of this variation may be due to the signal emanating from different
portions of the fireball trail as observed at different stations; each
period measurement is a "sample" of the size of the cylindrical blast
cavity at that particular segment of the trail detected by any one
station. As such, the out of atmosphere yield for this event is likely
higher than these measurements suggest - very probably in the ~50 kT range.
The yield estimates based on infrasonic amplitude are very uncertain in
this instance as the propagation distances are much larger than is
typical and outside the range limits where such relations have been
developed (e.g. Edwards et al, 2006) and hence the period relationship
(which was generated using a dataset of nuclear explosions having yields
in this range) is more applicable.
Some examples of the detected and processed waveforms are shown in the
Based on these infrasound records, it appears that a large (40-50 kT
TNT) bolide detonation occurred near 0300 UT on Oct 8, 2009 near the
coastal city of Bone in South Sulawesi, Indonesia. The infrasonic
geolocation is not precise enough to determine if the bolide was over
water or land, but it was relatively near the coast.
Follow-on observations from other instruments or ground recovery efforts
would be very valuable in further refining this unique event.
Using an average impact velocity for NEAs of 20.3 km/s, the energy
limits (10 - 70 kT) suggested by this analysis correspond to an object
5-10 m in diameter. Based on the flux rate from Brown et al (2002), such
objects are expected to impact the Earth on average every 2 - 12 years
Brown P., Spalding R.E., ReVelle D.O., Tagliaferri E. and Worden S.P.
2002. The flux of small near-Earth objects colliding with the Earth,
Nature, 420, 314-316.
Edwards W.N., Brown P.G., ReVelle D.O., 2006. Estimates of Meteoroid
Kinetic Energies from Observations of Infrasonic Airwaves, Journal of
Atmospheric and Solar-Terrestrial Physics, 68: 1136-1160.
ReVelle D.O. 1997. Historical Detection of Atmospheric Impacts by Large
Bolides using Acoustic-Gravity Waves, Annals of the New York Academy of
Sciences, Near-Earth Objects - The United Nations International
Conference, editor J.L. Remo, New York Academy of Sciences, 822, 284-302.
*Appendix : Example waveform detections.*
In each of the following the infrasound signals across each station have
been array processed in windows (typically of 30-60 second length) to
search for coherent signals with consistent back-azimuth measurements.
The top panel in each display is the F-statistic, a measure of the
relative coherency of the signal across the array elements in any
particular window (essentially a SNR measure). The second window shows
the apparent trace velocity of the acoustic signal across the array in
the direction of the peak F-stat. Similarly, the third plot shows the
best estimate for the signal back-azimuth in the direction of maximum
F-stat for each window. The fourth plot shows the raw pressure signal
for one array element bandpassed according to the chosen Low - High
frequency combination, shown in the boxes of the lower plot.
Signal as detected at IS05AU (Australia) as a range of 5000 km - the
green area highlights the airwave signal
Signal as detected at IS07AU (Australia) from a range of 2300 km.
Signal as detected at IS13CL (Easter Island) at 13500 km range showing a
distinct signal with a dominant period near 16.5 seconds. | <urn:uuid:16745a7d-6dfd-4f40-ae81-e0f3a76a9e94> | 3.046875 | 2,390 | Knowledge Article | Science & Tech. | 47.475717 |
Posted at 6:59 AM on November 8, 2007
by Paul Huttner
Here's a new twist on climate change. Something is sparkling in Greenland these days, and it's not ice.
It seems the rush is on in Greenland for diamonds. Newly exposed rock that was under a sheet of ice several years ago has revealed some impressive diamond finds, including a 2.4 carat rock in a western Greenland trial dig.
This highlights a new era of oil mineral, and other natural resource exploration in the new Arctic frontier. As new islands emerge, new land areas jut out from under dissapearing ice.
Posted at 2:18 PM on November 8, 2007
by Mark Seeley
Over the years, meteorologists have come up with ingredients methods to
forecast specific weather events, especially winter snowfalls. Such methods
are used along with the numerical guidance models produced by the
These methods apply a cookbook-style ingredients list that
forecasters can use to estimate the precipitation process and apply to the
size and intensity of storms. Fundamentally, this gets to the formation of water
droplets or ice crystals, their structure, abundance, and longevity in the
Such methods are often built on case studies (historically documented)
using the pre- and post-storm data sets. In addition to measured precipitation
amounts these data sets may contain winds, mixing ratios, temperatures, stability
indices and other attributes. This approach truly lets history be our teacher.
A description of ingredients methods can be found here.
I am aware that the National Weather Service in Chanhassen, Minnesota has used the Garcia
Method (Crispin Garcia, 1994) and the Wetzel Ingredients Method (Suzanne Wetzel,
2001) for forecasting precipitation from winter storms. I suspect there are a
number of other methods in use as well. | <urn:uuid:7f308471-a957-4206-887c-604be30d5647> | 2.921875 | 385 | Comment Section | Science & Tech. | 40.618906 |
Markovnikov was a Russian chemist who lived from 1838 to 1904. He studied at Kazan University and later went back to teach there. During his lifetime he was able to study chemistry and work in a laboratory know as "the cradle of Russian organic chemistry." His major accomplishment was made in 1869 in discovering the Markovnikov rule. This is very useful in predicting products in addition reactions. Markovnikov contributed to the structure of cyclic molecules. He also discovered that isobutyric and butyric acids are isomers. He is also discovered the four carbon ring and the seven carbon ring. Before this it was believed that there was only a six carbon ring. He did most of research with organic chemistry. As you can see he made a lot of discoveries in his chemistry research.
Vladimir Vasilevich Markovnikov was born on December 22, 1838, in Nizhny Novgorod, Russia. He studied under Butlerov in Kazan and St. Petersburg. He had contributed to the field of organic chemistry by his discovery of the four-carbon ring in 1879, and the seven-carbon ring in 1889. He was best unknown for "predicting the regiochemistry of addition reactions of hydrogen halides, sulfuric acid, water, ammonia, etc. to unsymmetrical alkenes. This is known as the Markovnikov Rule, which he developed in 1869." Another important finding was that butyric and isobutyric acids are isomers of each other because they differ only in their structure, while sharing the exact same chemical formula. He passed away in February 1904, Moscow, Russia.
Vladimir Markovnikov, he lived from 1838 to 1904. He was a famous Russian scientist who developed the Markovnikov Rule in 1869. The rule is useful in addition reactions. He later discovered the four-carbon ring and the seven-carbon ring. Another finding he made was that butyric and isobutyric acids are isomers of each other. He became a chemistry professor at Moscow University from 1873 to 1893.
Vladimir Vasilevich MARKOVNIK - http://www.pmf.ukim.edu.mk/PMF/Chemistry/chemists/markovnikov.htm
Vladimir Vasilevich Markovnikov was born in Nizhny, Novgorod Russia on
December 22, 1838. He contributed to the field of organic chemistry by his
discovery of the four-carbon ring in 1879, and the seven-carbon ring in 1889.
It was the belief, prior to these discoveries, that carbon rings only existed
with six carbons. Marknikov is also responsible for a rule that predicts the
molecular structure of the products of addition reactions. This rule was named
the Markovnikov Rule and is used quite often by those in the chemistry field.
Another important finding was that butyric and isobutyric acids are isomers of
each other because they differ only in their structure, while sharing the
exact same chemical formula.
Reference: Zdravkovski, Z,
Vladimir Vasilevich MARKOVNIKOV, February 18, 1997, http://www.pmf.ukim.edu.mk/PMF/Chemistry/chemists/markovnikov.htm
Vladimir Vasilyevich Markovnikov is a Russian organic chemist born on 22 Dec 1838 and died in Feb 1904. In 1869 while studying addition reactions, he noticed a trend in the structure of the favored product. This trend is called the Markovnikov Rule, and it states that in the addition of HX to an alkene, hydrogen adds to the carbon with the most hydrogen atoms, and X adds to the carbon with the most alkyl groups. It is also popularly stated as “Them that has – gits”. The Markovnikov Rule is known as an empirical rule, which is a useful aid for predicting experimental results.
Chemical Reactivity, URL http://www.cem.msu.edu/~reusch/VirtualText/ addene1.htm (9-24-03).
Today in Science History,
Vasilevich Markovnikov (Markowinkoff) was born in December 22, 1838 in Nizhny,
Russia and died February 1904 in Moscow, Russia.
During his lifetime he was able to study chemistry and work in a
laboratory know as “the cradle of Russian organic chemistry.”
The location with such a name is Kazan University, where he studied
under Butlerov and also returned to teach later.
His other places of study include St. Petersburg and Germany, where he
studied under Erlenmeyer and Kolbe.[i]
When he became a professor he was colleagues with such great minds as
Alexander Zaitsev and taught students such as A. Arbuzov and S. Reformatsky.
Markovnikov is best know for noticing a pattern in the addition
reactions of hydrogen halides to unsymmetrical
alkenes. Developed in
1869, this is know as the Markovnikov Rule which is useful in predicting the
molecular structures of products in addition reactions.
He also proved that not only six-atomed rings can exist, which was the
thought at the time, by preparing structures with four and seven carbon atoms.
Markovnikov is also acclaimed for showing that butyric and isobutyric acids
have the same chemical formula but different structures and are therefore
Markovnikov worked with reactions of
alkenes, and came up with a rule that states "When an unsymmetrically
substituted alkene reacts with a hydrogen halide, the hydrogen adds to the
carbon that has the greater number of hydrogens, and the halogen adds to the
carbon having fewer hydrogens." This rule is very important when studying
the mechanisms of reactions of alkenes.
In 1945 Alexander Erminingeldovich Arbuzov founded and headed the chemical institute of Kazan Branch of the USSR Academy of Sciences. The institute received universal acknowledgement owing to the works of a group of chemistry researchers in which Vladimir Markovnikov was a part of. Markovnikov’s rule states that “ when an unsymmetrical alkene reacts with a hydrogen halide to give an alkyl halide, the hydrogen adds to the carbon that has the greater number of hydrogen substituents, and the halogen to the carbon have the fewer number of hydrogen substituents. Markovnikov’s rule also included regiochemistry, which are the specific carbons of the alkene to which the H and the X attach.
Gooch, E. Eugene.J.chem.Educ.2001
Vladimir Markovnikov attended Russia’s Kazan University and had Alexander Butlerov as his chemistry teacher. Markovnikov became Butlerov’s teacher assistant in 1860. In 1869, while working on his doctoral thesis, he developed the theory of chemical structure experimentally and theoretically. A year later, he developed Markovnikov’s Rule, which states that when an unsymmetrically substituted alkene reacts with a hydrogen-halide, the hydrogen goes to the carbon with the most hydrogens and the halogen goes to the carbon with the least hydrogens. Markovnikov also studied the composition of petroleum hydrocarbons to see if it has any practical use. He became a chemistry professor at Moscow University from 1873 to 1893.
Vladimir Markovnikov was born on December 22, 1838 in Nizhny Novgorod, Russia. He graduated in 1860 after studying with Butlerov in Kazan and in St. Petersburg. Following two years in Germany, he returned to Russia where he replaced Butlerov at the Kazan University. Markovnikov died in February of 1904 in Moscow, Russia.
Markovnikov’s major contribution to the field of chemistry was in predicting the regiochemistry of the addition of a hydrogen halide to alkenes. He theorized that when an alkene reacts with a hydrogen halide, the hydrogen from the hydrogen halide will add on to the carbon of the alkene that has the greatest number of hydrogens. Furthermore, the halogen from the hydrogen halide will add on to the carbon of the alkene with the lower number of hydrogens.
In addition, Markovnikov discovered that in cyclic molecules, four and
seven carbon atom rings are possible structures along with six atom rings.
He also found butyric and isobutyric acids to be isomers because they
possess the same chemical formula but have different structures.
No Author. Vladimir Vasilevich Markovnikov, February 18, 1997, | <urn:uuid:39b42760-973d-4c37-aa21-7f1704ba6b28> | 2.96875 | 1,849 | Knowledge Article | Science & Tech. | 41.542648 |
A Kemp's Ridley sea turtle on the Cayman Turtle Farm, Grand Cayman.
© CI/Photo by Russ Mittermeier
Conservationists are trying to save the few remaining Kemp's Ridleys, the world's smallest and most
endangered sea turtles. Fishing nets and coastal development continue to threaten the species.
The Kemp's and Olive Ridley turtes are the only sea turtles that exhibit synchronous mass nesting, termed arribadas (Spanish for ‘arrivals’) where tens of thousands of females nest during the same 3-7 day period once a month.
Kemp’s ridley’s nearly went extinct without notice, and are now on the rise due to an incredible binational collaboration that included transplanting eggs from Mexico to Texas' South Padre beaches. The turtles were "head-started", meaning hatchling turtles were grown in captivity to larger sizes before being released in an attempt to mimize the number of turtles lost to predators.
Only nesting areas are in Rancho Nuevo, Tamaulipas, Mexico, and in Texas; non-nesting range Northwest Atlantic Ocean, Gulf of Mexico, and Caribbean. Kemp's Ridley turtles have the most restricted geographic range of all sea turtle species.
Body size (adults)
Length 60-70 cm; mass up to 60 kg
For all life stages, mostly benthic invertebrates (e.g. crabs of all types, other crustaceans; mollusks) and sometimes jellies
Every 1-3 yr; ~1-3 clutches of eggs per season; 90-130 eggs per clutch; ~30 g grams each (ping-pong ball size); hatchlings emerge after ~60 days of incubation; ~25mm in length and weigh ~15-20 grams) | <urn:uuid:d516167a-fb84-42e4-82c1-a98ceef7972c> | 3.59375 | 378 | Knowledge Article | Science & Tech. | 48.417982 |
The CPU understands machine language. The machine language instructions are encoded as strings of bits. The instruction set is dependent on the type of CPU. The instructions are primitive like load, add, store, jump.
The machine instruction that adds 3 to register D1 might be encoded as the bit string:
0101 011 000000 001
Writing and understanding machine language code is error prone. The first step was to have short mnemonics for the primitive operations instead of binary strings. The above instruction could be written as:
ADD 3, D1
This is assembly language programming. An assembler translates the mnemonics to machine code. But even the assembly language code is unwieldy. The time to write, debug, understand, and maintain a piece of code is proportional to the number of lines of instruction.
A high level language allows common operations such as expression evaluation, repetition, assignment, and conditional action to be invoked in a single high-level statement. Examples of high level languages - Fortran, Pascal, C, C++, Lisp, SmallTalk, Basic, Java, Perl, PHP, Python, Ruby.
A computer does not understand a program that is written in a high level language. A compiler translates a high level program into machine code for that particular CPU and saves it to a file known as object code or executable code. To run the program the executable has to be loaded and then run. The advantage of compiled code is that the compiler can optimize the code for you. The disadvantage of compiled code is that this code is specific only for a particular type of processor and will not run on any processor.
There is another way to run the code. A special program called the interpreter can take the source code and translate each line of code to machine language and run it for you. The disadvantage is that you have to have the source code available each time the code is run and it is slow. The advantage, however, is that since you are working from the source code each time, the source code can be ported from one machine to another since it is just text file. Python is an interpreted language. | <urn:uuid:e1ee73cc-d581-4560-befa-ea311a50ca7e> | 4.21875 | 435 | Academic Writing | Software Dev. | 44.290909 |
Although we have already considered sombre ( Eso) and tobacco darkening ( Etob), alleles of the extension locus which cause darkening of the coat, there are a number of other unrelated determinants which also produce similar effects. Thus, as mentioned previously, yellow ( Ay/;B/) mice are often characterized, especially in outbred populations, by variable degrees of sootiness. In some animals the sootiness is confined to a mid-dorsal streak, in others this streak is wider, covering the entire back and sometimes the flanks, so that only the belly is phenotypically "yellow." This situation is due to the admixture of hairs possessing significant amounts of eumelanin to the yellow fur. If these hairs are relatively few, the animal appears to be dingy yellow; with increasing numbers, however, the dorsum becomes darker until, at the extreme, an animal with a dark sable back and yellow belly is produced. 39 As in the case of Eso and Etob, these modifications are not limited to animals of yellow genotype as the amount of phaeomelanin may also be drastically reduced in black agouti ( A/;B/) and even in nonagouti animals. This dark form of agouti has been termed "umbrous" 40 ( Barrows, 1934; Mather and North, 1940).
The initial studies on the inheritance of factors which darken the coat color of mice were conducted more than 60 years ago. In 1916 Little attempted to alter the agouti pattern by crossing the darkest heterozygous agouti animals selected from a "sooty yellow" stock to nonagouti mice from the same stock. Both the agouti and nonagouti animals became darker as the selected crossing progressed ( Little, 1916). These findings indicated that the darkly pigmented phenotypes resulted from the cumulative action of a number of genes and that high concentrations of these genes could even make nonagouti mice look darker. This was subsequently substantiated by Dunn ( 1920a) who demonstrated that the responsible factors were inherited independently of the agouti series. Dunn ( 1920a) also firmly established that both the sable and umbrous phenotypes had an essentially similar hereditary basis. If the genes responsible for producing the sable phenotype in Ay/ mice were incorporated into A/ animals, their backs were almost black, and agouti hairs with yellow tips were confined to the flanks and belly. Dunn's investigations also revealed that the expression of both umbrous and sable varied between wide limits and that the darker grades produced the more variable offspring. This indicated that the factors responsible for the darkening were either largely dominant in their effects or very strongly cumulative ( Robinson, 1959). 41
Barrows ( 1934) too studied the umbrous phenotype. Unlike Dunn, he concluded that it depended upon the presence of a in the heterozygous condition along with one or more dominant or semidominant modifying "umbrous genes" whose effect was to make nonagouti partially dominant to agouti.
|For the U allele:|
|U Allele (MGI)||Gene (MGI)||All Alleles (MGI)|
Although, as the work above testifies, sable and umbrous phenotypes often result from the cumulative effect of an unknown number of genes, as already noted ( Section II) they can also be produced by single Mendelian factors. The first of these was described by Mather and North( 1940) and was appropriately designated "umbrous" ( U). Umbrous (linkage not known) is a semidominant which appears to interact with a.
Contrary to usual belief,
A is not invariably fully dominant to
a, even in the absence of
A/a;u/u phenotype displays a slight darkening along the medial line as compared with
A/A;u/u. The difference is difficult to perceive in living mice, but becomes more obvious from comparisons of skins, although some overlapping occurs (
Mather and North, 1940). This slight darkening effect which
a has when heterozygous with A is further augmented by the presence of
U. Thus as a consequence of the interaction of
U and a the following six agoutis may be ranked for increasing umbrous:
A/A;u/u < A/a;u/u = A/A;U/u < A/A;U/U = A/a;U/u < A/a;U/U.
While the basis for this interaction is not known, Mather and North ( 1940), like Barrows ( 1934), stress that U may modify the dominance of agouti over nonagouti. In fact a significant part of their paper is devoted to discussing this possibility with regard to various theories of dominance. Although they may be correct, the alternative and simpler explanation, that a is itself an "umbrous gene" acting in concert with U, should not be overlooked. This possibility is attractive especially since, as noted above, even in the absence of U, A/a mice may be slightly darker than A/A animals.
Mather and North ( 1940; Grüneberg, 1952) noted that a sable color of low intensity occurred in Ay/a;U/U mice, but reported that umbrous had no effect upon nonagouti individuals. This, however, is not the case as a/a;U/U animals are significantly darker than a/a;u/u mice with a phenotype bearing a close resemblance to extreme nonagouti ( ae/ae) and sombre ( Eso/) ( Poole and Silvers, unpublished). Indeed, the difference between a/a;U/U and a/a;u/u animals is so striking that it is difficult to understand how it was overlooked.
More recently Robinson ( 1959) described a similar "umbrous" gene segregating in a stock of fancy origin but no tests were made to determine whether this mutation was the same as, or allelic with, Mather and North's. This is unfortunate since it is not known whether Robinson's failure to detect any obvious differences between umbrous animals of Ay/at versus Ay/Aw or Aw/at versus Aw/Aw genotypes was due to the fact that his mutant was different from the one previously described, or to the fact that umbrous may not interact with at the way it does with a, or to the fact that prepared skins were not critically matched.
|For the mg allele:|
|mg Allele (MGI)||Gene (MGI)||All Alleles (MGI)|
In 1960 Lane and M.C. Green described a recessive umbrous gene which they named mahogany ( mg). The mutation appeared in agouti mice of unknown origin and the animals fit the descriptions of umbrous as given by Barrows and by Mather and North. "the central dorsal hairs were considerably darker than those of normal agouti mice, the yellow ticking characteristic of agouti being considerably reduced. The darkening was present but less intense in the lateral hairs. The ventral hairs were almost solid grey with no yellow ticking. In addition the ears and tail appeared more deeply pigmented than those of normal wild-type mice" ( Lane and M.C. Green, 1960). Mahogany proved to be detectable also in nonagouti mice; a/a;mg/mg mice are coal black with no lightly pigmented hairs evident behind the ears or around the perineum. The tail, feet, and ears are also darker than in normal nonagouti animals ( Lane and M.C. Green, 1960). In fact, in general appearance nonagouti mahogany mice fit the description of the nonagouti mice selected for dark modifiers by Little ( 1916), mice homozygous for extreme nonagouti, and nonagouti mice homozygous for U. Mahogany proved to be on chromosome 2, about 12 cM from agouti. 42
|For the md, nc and da alleles:|
|md Allele (MGI)||Gene (MGI)||All Alleles (MGI)|
|nc Allele (MGI)||Gene (MGI)||All Alleles (MGI)|
|da Allele (MGI)||Gene (MGI)||All Alleles (MGI)|
Three other umbrous mutations have been reported and briefly described. Mahoganoid ( md), another recessive (chromosome 16), 43 occurred in the C3H/HeJ strain and is identical to mahogany ( mg) on both agouti and nonagouti backgrounds ( Lane, 1960a). Nonagouti curly ( nc), which is probably an allele of md. 44 is likewise recessive and was recognized in an F2 animal from a mutagenesis experiment using caffeine. The deviant was nonagouti with black pinna hairs and curly whiskers. nc, like Eso, is epistatic to Aw so that nc/nc;Aw/Aw mice look like ae/ae animals but have curly whiskers and a slightly plush coat (R.J.S. Phillips, personal communication). 45 nc homozygotes also have a reduced viability (R.J.S. Phillips, 1963, 1971).
Finally, dark (da) arose in the CBA/Fa strain. Animals homozygous for this recessive mutation are smaller than normal with reduced fertility. When combined with A or Ay, dark produces a phenotype in which the yellow pigment on the back is replaced by black so that both look nonagouti except on the flanks. The darkening of the back of A/da/da decreases as the animal becomes older. This umbrous gene, which was reported by Falconer ( 1956a), has been assigned to chromosome 7. Unfortunately, it may be extinct.
Before concluding this section it should be mentioned that there are certain yellows of the fancy which are known under the name of "reds" ( Grüneberg, 1952). Such animals are genetically brown ( Ay/;b/b) and the intensity of their "red" coat is probably dependent on intensifiers, analogous to, but distinct from, the "umbrous" genes ( Dunn, 1916). A detailed analysis of this phenotype has not yet been made. | <urn:uuid:80b41a66-79f8-48b6-9cd7-f3fba2aca12a> | 3.296875 | 2,188 | Academic Writing | Science & Tech. | 38.566455 |
GNU/Linux has taken the world of computers by storm. At one time, personal computer users were forced to choose among proprietary operating environments and applications. Users had no way of fixing or improving these programs, could not look "under the hood," and were often forced to accept restrictive licenses. GNU/Linux and other open source systems have changed that—now PC users, administrators, and developers can choose a free operating environment complete with tools, applications, and full source code.
A great deal of the success of GNU/Linux is owed to its open source nature. Because the source code for programs is publicly available, everyone can take part in development, whether by fixing a small bug or by developing and distributing a complete major application. This opportunity has enticed thousands of capable developers worldwide to contribute new components and improvements to GNU/Linux, to the point that modern GNU/Linux systems rival the features of any proprietary system, and distributions include thousands of programs and applications spanning many CD-ROMs or DVDs.
The success of GNU/Linux has also validated much of the UNIX philosophy. Many of the application programming interfaces (APIs) introduced in AT&T and BSD UNIX variants survive in Linux and form the foundation on which programs are built. The UNIX philosophy of many small command line-oriented programs working together is the organizational principle that makes GNU/Linux so powerful. Even when these programs are wrapped in easy-to-use graphical user interfaces, the underlying commands are still available for power users and automated scripts.
A powerful GNU/Linux application harnesses the power of these APIs and commands in its inner workings. GNU/Linux's APIs provide access to sophisticated features such as interprocess communication, multithreading, and high-performance networking. And many problems can be solved simply by assembling existing commands and programs using simple scripts. | <urn:uuid:bafdbba9-408d-4ef3-b803-03ec6d72e513> | 3.03125 | 373 | Knowledge Article | Software Dev. | 22.70422 |
IN CLOSE-UP, they look like something out of a 1950s B-movie. Colonies of fossilised creatures, dubbed "hairy blobs", have been discovered in one of the harshest environments on Earth. The find may turn out to be crucial for spotting signs of extraterrestrial life in rocks on other planets.
Kathleen Benison, a geologist at Central Michigan University, Mount Pleasant, led a team that studied the sediments formed by acidic and very salty lakes in modern day Western Australia, and those deposited around 250 million years ago in North Dakota. It is very difficult to survive in such a tough environment and few signs of life have ever been found in these sorts of lakes.
Inside the halite and gypsum "evaporite" minerals, which form as the lake waters dry up, Benison and colleagues found previously unknown fossilised blobs at both the modern and ancient sites, ranging in size from 0.05 to 1.5 ...
To continue reading this article, subscribe to receive access to all of newscientist.com, including 20 years of archive content. | <urn:uuid:5a9e3c32-cdc8-48d2-abec-5a5467467a74> | 3.921875 | 227 | Truncated | Science & Tech. | 50.631293 |
Bats Upside Down
Name: Drew H
When bats sleep upside down does all their blood rush to
their heads like when people are hanging upside down?
Bats are so small that, unlike humans, the problem of blood distribution is
not a huge problem. They are able to wrap themselves into a small package and
like most mammals, they can regulate blood flow by contracting their blood
vessels to direct and achieve blood flow.
Up-dated July 2008
I concur with the other answer here. I had noticed several sources on the internet
that describe "special valves" that keep blood from pooling in the head (I was
studying to co-lead a presentation on bats), however none of my bat books describe
this. In fact, the book "Flying Foxes" by Leslie Hall (2001) states: "It was once
thought that bats had a series of valves in their blood vessels which prevented
blood rushing to their heads when they were upside down. No such valves have been
found and it is considered that bat's small size and the small amount of blood allow
them to sleep upside-down." I would consider the valves a myth until shown otherwise.
The internet claims usually mention that similar valves in human veins prevent blood
from pooling up in our legs, however this mechanism relies on fairly regular movement
to "squish" the blood past the valves (which explains the discomfort of standing
motionless for a few minutes), and they are not important during the relative
motionlessness of sleep, since we sleep laying down. So in summary, the relatively
small size of bats (and many similar sized animals in the insect world that can rest
upside down) is probably the prime reason.
Click here to return to the Zoology Archives
Update: June 2012 | <urn:uuid:f884201d-89b4-45e8-b3a8-0881b8013a6b> | 3.390625 | 374 | Q&A Forum | Science & Tech. | 46.228894 |
We've been impressed in the past by aerogel, a lattice-like solid that's almost entirely made of air but can support weight and also has tremendous insulating properties. Then last year an ultralight metal caught our eye, weighing in at 99.99 percent air, which leaves 0.01 percent solid.
Now we are excited to meet aerographite, a sponge grown of carbon nanotubes that's the least dense solid ever: a cubic centimeter of it weighs just two ten-thousandths of a gram.
Five amazing, clean technologies that will set us free, in this month's energy-focused issue. Also: how to build a better bomb detector, the robotic toys that are raising your children, a human catapult, the world's smallest arcade, and much more. | <urn:uuid:f78d05ea-7ca4-4d4a-86b1-96c2fdb41b5f> | 2.875 | 165 | Content Listing | Science & Tech. | 58.070313 |
What's your secret message?: With just a few household items--and a little bit of science--you can make an invisible ink message that will reveal itself under just the right conditions. Image: iStockphoto/JoKMedia
Have you ever wondered how spies and secret agents could leave secret messages? Invisible ink might sound high tech, but you can create—and read!—a top secret message with one simple kitchen ingredient: lemons. George Washington's army used this same concept to send secret messages during the American Revolutionary War. What message will you write?
Lemon juice—and the juice of most fruits, for that matter—contains carbon compounds. These compounds are pretty much colorless at room temperature. But heat can break down these compounds, releasing the carbon. If the carbon comes in contact with the air, a process called oxidation occurs, and the substance turns light or dark brown.
• One half of a lemon (use caution when cutting)
• One half teaspoon of water
• Small bowl
• White paper
• A lamp with a lightbulb that puts off a lot of heat, such as a 100-watt incandescent bulb or another heat source, such as a radiator
• Optional: Pencil (to write a decoy message on your paper)
• Squeeze the juice of your lemon half into the bowl.
• Add the water and mix with a spoon.
• Think of a secret message you would like to write—and to whom you're going to deliver it!
• Extra: If you want to be super secret, you can write a boring old message or draw a picture on the paper with a pencil before you write your secret message to disguise it even further.
• Soak the Q-tip in the lemon juice-and-water solution.
• Use the damp Q-tip to write your top-secret message on the piece of paper.
• Wait a few minutes for the paper to dry. While you're waiting, you can switch on your lamp to give the lightbulb time to heat up (being careful not to touch the hot bulb itself).
• When the paper is dry, hold it up to the hot lamp for a few minutes (but don't let the paper get so hot that it burns). What happened to your invisible ink? How long did it take for the change to occur?
• Extra: Try this activity with other acidic liquids, such as apple juice or vinegar. Which ones work best? | <urn:uuid:945e98a7-9363-4f54-8152-8119b183c62f> | 2.8125 | 513 | Tutorial | Science & Tech. | 61.815693 |
It’s pretty common to view outer space as a beautiful entity that we wish we could visit, but there are some things in outer space that we as humans never get to fully appreciate.
A team of scientist at the National Center for Atmospheric Research (NCAR) have created a computer-generated (super computer to be exact) image of a sunspot.
The images take on a beauty that one might not associate with the often forgotten sunspot (you know, forgotten among stars and planets and even supernovas). Check out the gallery for the different scientific renditions of the sunspots.
Super Computer Sunspotography
1,510 clicks in 199 w
More Stats +/- | <urn:uuid:934aa04b-e3c2-46f2-bbf1-5487b1bb813a> | 3.203125 | 141 | Truncated | Science & Tech. | 37.409773 |
by Gary Leo Welz, M.A./M.S.
Waves are familiar to us from the ocean, the study of sound, earthquakes, and other natural phenomenon. But as any surfer can tell you, ocean waves come in very different sizes, as can all waves. To fully understand waves, we need to understand measurements associated with these waves, such as how often they repeat (their frequency), and how long they are (their wavelength), and their vertical size (amplitude).
While these measurements help describe waves, they do not help us make predictions about wave behavior. In order to do that, we need to look at waves more abstractly, which we can do using a mathematical formula. It is possible to look at waves mathematically because a wave's shape repeats itself over a consistent interval of time and distance. This behavior mirrors the repetition of the circle. Imagine drawing a circle on a piece of paper. Now imagine drawing that same shape while your friend slowly pulled the piece of paper out from under your pencil – the line you would have drawn traces out the shape of a wave. To better appreciate this idea, take a look at the "Circle to a Wave" link in the Experiment! section on the right menu. One rotation around the circle completes one cycle of rising and falling in the wave, as seen in the picture below.
Figure 1: Circle on a cartesian plane.
Mathematicians use the sine function (Sin) to express the shape of a wave. The mathematical equation representing the simplest wave looks like this:
This equation describes how a wave would be plotted on a graph, stating that y (the value of the vertical coordinate on the graph) is a function of the sine of the number x (the horizontal coordinate).
The sine function is one of the trigonometric ratios originally calculated by the astronomer Hipparchus of Nicaea in the second century B.C. when he was trying to make sense of the movement of the stars and moon in the night sky. More than 2000 years ago, when Hipparchus began to study astronomy, the movement of objects in the sky was a mystery. Hipparchus knew that the stars and moon tended to move through the night sky in a semi-circular fashion. Thus he felt that understanding the shape of a circle was important to understanding astronomy. Hipparchus began to observe that there was a relationship between the radius of a circle, the center angle made by a pie slice of that circle, and the length of the arc of that pie piece. If one knew any two of these values, the third value could be calculated. It was later realized that this relationship also applies to right triangles. Knowing one angle measure of a right triangle, you can calculate the ratio of the sides of the triangle. The exact size of the triangle can vary, but the ratio of the lengths of the sides is defined by the angle size. The specific relationships between the angle measure and the sides of the triangle are what we call the trigonometric functions, the three main functions consisting of:
Figure 2: Triangle.
The word trigonometry means "measurement of triangles" and sine along with the cosine and tangent are called the trigonometric ratios because they originated with the ancient study of triangles.
But how do triangles relate to waves? In the early 17th century, two Frenchmen named Rene Descartes and Pierre Fermat co-developed what would become known as the Cartesian coordinate plane, more commonly known as the (x,y)-graphing plane. This invention was an extraordinary advance in the history of mathematics because it brought together, for the first time, the integration of the two great, but distinct branches of mathematics: geometry, the science of space and form, and algebra, the science of numbers. The invention of the Cartesian coordinate system soon led to the graphing of many mathematical relations including the sine and cosine ratios.
As it turns out, the trigonometric functions can also be defined in relation to the "unit circle," i.e. a circle with a radius equal to 1. When we put the unit circle on the Cartesian plane, we can begin to see how this works if we draw a triangle within the circle, as seen in the diagram below. According to our earlier discussion, the sine of angle A in the diagram equals the ratio of the opposite side over the hypotenuse. However, remember that we are working with a unit circle and the length of the hypotenuse is equal to the radius of the circle, or 1. Therefore,
Figure 3: Shows the unit circle on the Cartesian Plane with an inscribed triangle. The point on the circle touched by the radius has coordinates (x,y).
If we redraw this triangle as we move counterclockwise on the circle, we can begin to see that the trigonometric functions, in this case sine and cosine, take on a periodic quality. This means that sine, for example, increases to a maximum at the top of the circle, decreases to zero as we sweep left, and begins to take on negative values as we continue around the circle. At the bottom of the circle the sine function reaches a minimum value and the process begins again as we reach the right side of the circle. To better appreciate this idea, review the animation Sine, Cosine, and the Unit Circle linked below.
As you saw in the animation above, as angle A increases, the values of the trigonometric functions of A undergo a periodic cycle from 0, to a maximum of 1, down to a minimum of -1, and back to 0. There are several ways to express the measure of the angle A. One way is in degrees, where 360 degrees defines a complete circle. Another way to measure angles is in a unit called the radian, where 2π radians defines a complete circle. Angles smaller than 360 can de defined as fractions of this unit, for example 90° can be written as π/2 or 1.57 radians, 180° equals π or 3.14 radians.
If we now plot the sine of the angle measured in radians along the Cartesian coordinate system, we see that we again get the characteristic rise and fall. However, since the angle measure is plotted along the x-axis (instead of the cosine of the angle), the graph that results is a continuous curve on the coordinate plane that resembles a physical wave, as seen below.
Figure 4: Sine graph.
If you look closely at this graph you will see that the wave crosses the x-axis at multiples of 3.1416… – the value of pi. One full wave is completed at the value 6.2832…, or 2π, exactly the circumference of the unit circle.
Understanding the origin of the sine function makes it easier to understand how it operates in relation to waves. As we saw earlier, the basic formula representing the sine function is:
In this formula, y is the value on the y-axis obtained when one carries out the function Sin(x) for points on the x-axis. This results in the graph of the basic sine wave. But how can we represent other forms of waves, especially ones that are larger or longer? To graph waves of different sizes we need to add other terms to our formula. The first we will look at is amplitude.
In this modification of the formula, A gives us the value of the amplitude of the wave – the distance it moves above and below the x-axis, or the height of the wave. In essence, what the modifier A does is increase (or amplify) the result of the function Sin(x), thus leading to larger resulting y values.
To modify the wavelength of a wave, or the distance from one point on a wave to an equal point on the following wave, the modifier k is used, as seen in the formula below.
The multiplier k extends the length of the wave. Remember from our earlier discussion that the wavelength of our most simple wave is 2π, therefore wavelength in the final formula is determined simply be dividing 2π by the multiplier k, so wavelength (λ) = 2π/k.
If you would like to study this relationship further, the "Shape of a Wave" link in the Experiment! section at right shows you how the shape of a wave changes when amplitude or wavelength are varied. Further research on how values for A and k changes can be conducted by using the "Wave Calculator" link in the Research section.
Since waves always are moving, one more important term to describe a wave is the time it takes for one wavelength to pass a specific point in space. This term, referred to as the period, T, is equivalent to the wavelength, T = Period = 2π/k, however it is given in units of time (sec) rather than distance.
Understanding the mathematics behind wave functions allows us to better understand the natural world around us. For example, the differences between the colors you see on this page have to do with different wavelengths of light perceived by your eyes. Similarly, the difference between a bird’s song and the roar of a locomotive is due to the size of the sound waves emitted. Waves, and thus the mathematics of waves, constantly surround us.
Gary Leo Welz, M.A./M.S. "Wave Mathematics: Trigonometric Functions," Visionlearning Vol. MAT-1 (1), 2006. | <urn:uuid:5ed177b8-1f38-4205-9e25-4b1ad958f8fb> | 4.1875 | 1,961 | Knowledge Article | Science & Tech. | 51.8376 |
White Hake (Urophycis tenuis) - Wiki
From Wikipedia, the free encyclopedia
[Photo] White hake, Urophycis tenuis. From plate 89 of Oceanic Ichthyology by G. Brown Goode and Tarleton H. Bean, published 1896.
The white hake or mud hake, Urophycis tenuis, is a phycid hake of the genus Urophycis, found in the northwest Atlantic Ocean from North Carolina to Newfoundland, at depths of about 1,000 metres. It grows to about 4 ft (1.2 m).
The coloration is purplish brown on the back, fading to a dirty white beneath. Habits, range and commercial value are the same as for the red hake.
|The text in this page is based on the copyrighted Wikipedia article shown in above URL. It is used under the GNU Free Documentation License. You may redistribute it, verbatim or modified, providing that you comply with the terms of the GFDL.| | <urn:uuid:c1ddd8f6-4820-4121-83d1-e351226731fa> | 3.0625 | 224 | Knowledge Article | Science & Tech. | 55.711611 |
Liverworts on the Green Tree of Life
Bryophytes as a natural group
Liverworts, along with mosses and hornworts, are often referred to as “Bryophytes.” There is strong evidence, however, that bryophytes, broadly defined in this way, are an artifical (i.e., non-monophyletic) group. Instead, the three bryophytes groups appear to form an evolutionary grade leading to the tracheophytes or true vascular plants. The three bryophyte groups (mosses, liverworts, hornworts) share a haploid-dominant life and unbranched sporophytes, traits that appear to be plesiotypic within the land plants (embryophytes). As early diverging lineages of green plants, the bryophyte groups comprise the oldest extant lineages of land plants. However, which group of bryophytes was the first to diverge, taking hold of terrestrial habitats for the first time? And which group is most closely related to that most successful group of plants, the vascular plants?
Phylogenetic relationships among bryophyte groups
Identifying the earliest branch in the land plant tree of life has been an elusive goal over the past two decades. Nearly every possible hypothesis of the relationships among bryophytes (hornworts, liverworts, and mosses) and tracheophytes (vascular plants) has been advanced. Early phylogenetic studies of this problem converged on liverworts as the sister group to the rest of the embryophytes (Mishler and Churchill, 1984 [morphology], Mishler et al., 1994 [nuclear DNA and morphology], Lewis et al., 1997 [chloroplast DNA]). Fossil evidence (Edwards et al., 1995), analyses of the entire chloroplast genome (Kugita et al., 2003), analyses of group II mitochondrial introns (Qiu et al., 1998; Pruchner et al., 2001; Groth-Malonek et al., 2005), and mitochondrial DNA editing (Steinhauser et al. 1999) also support this hypothesis. Nevertheless, some studies support the hornworts as the earliest-diverging taxon, with mosses and liverworts forming a clade that is sister to the tracheophytes (Hedderson et al. 1996, 1998 (nrDNA); Garbary and Renzaglia, 1998 (morphology); Nishiyama and Kato (cpDNA) 1999; Renzaglia et al. 2000 (morphology); Nickrent et al. 2000 (nrDNA, mtDNA, cpDNA). A few recent studies have suggested that bryophytes are monophyletic and sister to the tracheophytes (Nishiyama et al., 2004; Goremykin and Hellwig, 2005).
Currently, the National Science Foundation funds an ATOL project focused upon resolving the earliest evolutionary splits in the land plant tree: The Green Tree of Life. Preliminary results from this project suggest that the liverworts are the earliest lineage – that is, are sister to all other groups of land plants -- followed by the mosses, and finally, the hornworts as sister to the tracheophytes. This conclusion is supported by mitochondrial data (Groth-Malonek and Knoop, 2005; Groth-Malonek et al., 2005) as well as combined data from the chloroplast and nuclear genomes (Davis, 2005).
The importance of determining phylogenetic relationships
among early land plants
The placement of bryophytes in the embryophyte phylogeny is important for interpreting the evolution of many important and fundamental plant characteristics including stomata, IAA (auxin) conjugation, chloroplast morphology, and sperm morphology. For example, stomata are absent on liverwort sporophytes, but they are present in mosses and hornworts. In addition, liverworts do not conjugate IAA, while the rest of embryophytes do (Sztein et al., 1995). If liverworts are the earliest lineage, it is most parsimonious to infer the origin of stomata and IAA conjugation after the liverworts split from the rest of the embryophytes. A similar scenario is presented with the consideration of chloroplast pyrenoids and sperm cells. Pyrenoids are present in the chloroplasts of green algae and hornworts, but are absent from other embryophytes (Renzaglia and Vaughn, 2000). If liverworts diverged first, then there have been multiple losses of pyrenoids, or else pyrenoids independently evolved in the hornwort lineage. Likewise, green algae and hornworts have sperm cells with asymmetrically attached flagella, but swimming sperm in all other embryophytes have symmetrically attached flagella (Renzaglia et al., 2000). In the context of current ideas about early land plant phylogeny, asymmetrical attachment of sperm flagellae is best interpreted as an independent gain in the hornworts, or multiple independent gains of symmetrically attached flagella in the other embryophyte groups. | <urn:uuid:c784476a-883c-4f66-8408-cc58a05efc09> | 3.328125 | 1,095 | Academic Writing | Science & Tech. | 35.214184 |
The spade-toothed beaked whale may be the world's rarest whale. It was initially described in 1872 from a skull collected in the Chatham Islands, New Zealand. Other skull fragments were found on White Island, New Zealand in the 1950's and on Robinson Crusoe Island, Chile in 1986. No live animals had been observed. In December 2010, two whales presumed to be a mother and calf stranded and then died on Opape Beach, near to the White Island locality. Officials originally identified them as Gray's beaked whales, the most common beaked whale to strand in this area. Scientists took samples and photographs, then buried the bodies on the beach. To everyone's surprise, DNA testing from those samples indicated that these were instead the elusive spade-toothed beaked whale. Scientists have used the photographs to describe this whale's appearance for the first time. They have also recovered most of the skeletal remains for further analysis. (Thompson et al. 2012).
- Thompson, Kirsten, C. Scott Baker, Anton van Helden, Selina Patel, Craig Millar, and Rochelle Constantine. 2012. “The World’s Rarest Whale.” Current Biology 22 (21) (November): R905–R906. doi:10.1016/j.cub.2012.08.055. http://dx.doi.org/10.1016/j.cub.2012.08.055.
No one has provided updates yet. | <urn:uuid:08308acf-8f59-4abe-b703-9bd05e429db5> | 3.921875 | 310 | Knowledge Article | Science & Tech. | 73.08375 |
The water flowing through Venice's famous canals laps at buildings a little higher every year and not only because of a rising sea level. Although previous studies had found that Venice has stabilized, new measurements indicate that the historic city continues to slowly sink, and even to tilt slightly to the east.
- Venice to suffer fewer storm surgesFri, 10 Jun 2011, 10:33:59 EDT
- New fog warning system in Venice region pays for itself 10 times overMon, 25 Oct 2010, 11:24:02 EDT
- UI study measures levels of PCBs flowing from Indiana canal to air and waterWed, 24 Feb 2010, 17:19:29 EST
- Carbon sinks losing the battle with rising emissionsTue, 17 Mar 2009, 9:44:00 EDT
- Sink or source? A new model to measure organic carbon in surface watersFri, 4 Mar 2011, 8:36:03 EST | <urn:uuid:9621b922-1abf-4b9e-af4d-9c919b85bbd2> | 3.0625 | 185 | Content Listing | Science & Tech. | 42.61561 |
One can choose to generate solar power through Photovoltaics (PV) or Concentrated Solar Power (CSP) technologies.
PV: Based on the ‘photovoltaic effect’ of semiconductors, PV cells generate power by converting solar irradiation to electrical direct current. Photons from sunlight impart energy to the semiconductor’s free electrons, bumping them up to the next energy level. The electrons now behave as charge carriers and their movement results in electric current. PV panels or modules are formed by connecting a number of cells to one another, which are then connected in multiples or arrays for large scale production.
The two PV modules in competition with each other are crystalline silicon (c-Si) and thin film. So far in India, thin film has been more popular due to the Domestic Content Requirement (DCR) lobbied on c-Si modules in phase one of the National Solar Mission (NSM). [Refer to the post ‘The Domestic Content Requirement (DCR) in India‘ to know more.]
India currently has a total grid installed PV capacity of 1,050MW, most of which has been installed in Gujarat and then Rajasthan. [Read BRIDGE TO INDIA’s November 2012 edition of the INDIA SOLAR HANDBOOK for more.]
CSP: CSP systems are used to convert solar irradiation to heat energy, which is then converted to electrical energy. The sun’s rays are concentrated onto a small area through reflection and refraction using mirrors and lenses, and the heat produced is used to power turbines (generally steam) which generate electricity.
Globally, PV technology is becoming more and more preferable to CSP due to the declining costs of PV modules and simpler technology, construction and maintenance. India, however, holds significant promise for CSP as it is believed that costs can be driven down to a notable extent. [Refer to a post ‘The CSP opportunity in India’ at the BRIDGE TO INDIA blog.] | <urn:uuid:60a7e9a4-026a-4e33-8c5d-bedf13e420fd> | 4 | 425 | Knowledge Article | Science & Tech. | 40.141069 |
why 360 degrees?
See also the
Dr. Math FAQ:
segments of circles
Browse High School Conic Sections, Circles
Stars indicate particularly interesting answers or
good places to begin browsing.
Selected answers to common questions:
Find the center of a circle.
Is a circle a polygon?
Volume of a tank.
Why is a circle 360 degrees?
- Differentiating and Integrating the Formula for Area of Circle [05/11/1998]
The formula for a circle's circumference is the derivative of the formula
for its area. What is the significance of this?
- Distance from Point to Ellipse [05/19/1997]
How do you find the minimum distance from a point to an ellipse when the
point can be either inside or outside the ellipse?
- Distance of Chord from Circumference [12/31/1997]
Is it possible to calculate the vertical distance, at a right angle, from
a chord to the circumference of a circle?
- Distance to Mars [07/25/1997]
What is the distance from Earth to Mars?
- Dividing a Circle using Six Lines [08/29/2001]
What is the largest number of regions into which you can divide a circle
using six lines?
- Do Circles Have Corners? [08/06/1999]
Can you have angles or corners without edges?
- Donkey Grazing Half a Field [08/08/1997]
A donkey is attached by a rope to a point on the perimeter of a circular
field. How long should the rope be so that the donkey can graze exactly
half the field?
- Drawing a Circle Tangent to an Angle [05/13/2000]
Given an angle and any point inside it not on its bisector, how can you
draw a circle that goes through the point and is tangent to both sides of
the angle with just a compass and protractor?
- Drawing An Ellipse [11/24/1997]
How do you draw an ellipse with only a straight edge and a compass?
- Drawing or Constructing an Ellipse or Oval [02/22/2006]
I know you can draw an ellipse using a string and two tacks. How do I
determine the length of the string and the location of the tacks to
draw an ellipse of a particular size?
- Earth's Curvature [07/07/2003]
How far would you have to 'walk' in no gravity to get 1 foot off the
- Earth's Rotational Speed [07/25/1999]
If you were standing at the equator at sea level, how fast would you be
travelling in relation to the center of the earth?
- Ellipse Area and Circumference [04/19/2001]
How can I draw an ellipse and find the area and circumference?
- Ellipse Bounding A Rectangle [7/15/1996]
How do I calculate the ellipse bounding any given rectangle?
- Ellipse Equation [03/11/1999]
How do I get the equation of an ellipse, given four points and the
inclination of the major axis?
- Ellipse Geometry [08/09/1998]
I wish to draw a line departing at a given angle from the long axis of an
ellipse and bisecting the perimeter of the ellipse at right angles to the
tangent at that point...
- An Ellipse Or A Circle? - Parametric Equations [12/05/1998]
Is this parametric equation elliptical or a circle?... And how do I
compute the slopes at points 0, pi/4, pi/2, 3pi/2,and 2pi?
- Ellipses: Pythagorean Relationship [2/12/1996]
In an ellipse with major axis of 2a, minor axis of 2b, and foci c (on the
major axis), the relationship c squared = a squared - b squared holds
true... how do the three numbers fit into a Pythagorean relationship?
- Elliptical Orbits in the Solar System [05/22/2005]
I want to have my students draw a scale model of the solar system that
shows the orbits of the planets. Assuming I have the apogee and
perigee of each planet's orbit about the sun, they need to construct 9
ellipses with some degree of accuracy. What's the best way to go about
- Endpoint of an Arc [06/25/2001]
Given the center of the circle, the angle of the arc, the radius of the
circle, and the starting point of the arc, determine the end point of the
arc using cartesian coordinates.
- Equation for an Arch [09/09/1997]
I am trying to draw an arch that will go in the ceiling of a building.
The arch will be at a maximum height of 28 inches...
- Equation of a Circle [05/13/2003]
Find the equation of a circle with the center at point (3, -4) and
- Equation of a Parabola [12/20/2001]
Given several points that appear to be a parabola, how do you approximate
the equation that would give a similar graph?
- Equilateral Shapes Inscribed in a Circle [04/07/2003]
Is there a general formula for the length of a side of an equilateral
shape that is inscribed in a circle?
- Escaping the Tiger [07/10/2003]
A man stands in the center of a circle. On the circumference is a
tiger that can only move around the circle. The tiger can run four
times as fast as the man. How can the man escape the circle without
being eaten by the tiger?
- Euclidean Formula for Orthogonal Circles [04/11/2001]
When considering the case when circle C has center at the origin and
radius 1, we need to show that the equation of the circle orthogonal to
circle C and with center (h,k) is given by: x^2-2hx+y^2-2ky+1=0.
- An Euler Circle Proof [03/26/1999]
I'm having trouble with the incenter and the inradius.
- Find Circle Center and Radius [09/21/2001]
Given three sets of (x,y) coordinates that lie on the circumference of a
circle, how do you find the center and radius of the circle?
- Finding a Parabola [2/5/1996]
Find the equation of the parabola that is one unit away from X^2 at all
- Finding a Point on a Circle [5/28/1996]
How do I find the y1 value?
- Finding Miles Per Hour [03/06/2002]
If a wheel is making 64.2 revolutions per minute, how many miles per hour
is it going?
- Finding Quadratic Roots Geometrically or Graphically [12/07/2004]
How do you find the roots of a quadratic function geometrically? For
example, what is the algorithm to find roots for f(x) = x^2 + 1 by
looking at the graph?
- Finding Radius Given Arc Length and Chord to Arc Height [08/28/2005]
I'm purchasing a curved piece of glass for some furniture. The curve
(arc) is 60 inches long. The height (the midpoint of the chord to the
center of the arc) is 11 inches. I need to know the radius of this
curve so the glass company can make my glass. Any thoughts?
- Finding Radius Given the Length of a Chord [04/09/2006]
Two points on a circle are 78 units apart and the distance from the
circle to the center of the chord connecting them is 12 units. How do
I calculate the radius?
- Finding the Area of an Arc [1/23/1996]
When you draw a circle and make a chord from one point to another, how
would you find the area of that arc (formula)?
- Finding the Axes of an Ellipse from a Known Cone [01/26/2001]
I'm trying to solve a specific situation regarding lighting when viewed
as an oblique circular cone...
- Finding the Center of a Circle [06/06/1999]
How can I find the center and radius of a circle that is in the form:
Ax^2 + Cy^2 + Dx + Ey + F = 0?
- Finding the Center of a Circle [5/29/1996]
How can you find the center of a circle using a ruler and compass?
- Finding the Center of a Circle from 2 Points and Radius [01/24/1997]
Given two points on a circle and the circle's radius, find the center
coordinates of the circle.
- Finding the Center of a Circle from 2 Points [06/01/1999]
How do you find the centre of a circle if you are given 2 points on the
circle and the radius? | <urn:uuid:37aca3f3-6751-41a3-97d6-648c03076e2f> | 4.03125 | 2,000 | Q&A Forum | Science & Tech. | 73.924879 |
Let G = . How many elements are there in the group G? Also show that G is not cyclic.
I know that no. of elements in = 6 and no. of elements in = 10. So can i conclude that the total number of elements is then 60?
As for the cyclic part, i dont have any idea where to start from. I know that a group is cyclic if for every element , , where r is the generator of the cyclic group. But how do i show that such a generator does not exist? | <urn:uuid:aa9d0769-6a4e-4f61-bd36-e1736de289f6> | 2.84375 | 113 | Q&A Forum | Science & Tech. | 86.03806 |
Scorpions belong to the arachnid group (invertebrates with four pairs of legs and two body parts) along with such animals as spiders, ticks and mites. They are distinguished from other arachnids because they possess a large pair of pincers and a tail with a venomous sting on the tip. They are a very primitive group that has existed with the same basic body plan for some 450 million years.
Scorpion, Urodacus sp.Photographer: Alan Henderson. Source: Museum Victoria
Some of the interesting biological features of scorpions include:
This latter factor is one of the reasons why scorpions have survived for such a long time – they spend most of their lives resting under rocks, pieces of wood, or in burrows and expend very little energy. This results is the need for only occasional meals.
World-wide there are 1500 known species of scorpions. Australia has about 80 species (although many have yet to be named scientifically), and Victoria has nine known species. They are widely distributed. Many people are under the impression that scorpions are desert creatures, but although there are many more species in the drier parts of Australia, scorpions are found in quite cool and wet regions of Australia.
Scorpions are often feared because of the sting on their tail and the potential lethal nature of the venom. Several thousand people die each year from scorpion stings, but these deaths are from the stings of about 25 species that inhabit northern Africa, the Middle East, India, Mexico and parts of South America. None of these potentially lethal species occur in Australia. The Australian species can inflict a painful sting that results in swelling and pain for several hours, but there have not been any confirmed deaths of people from stings from Australian scorpions. Medical advice should be sought if you are stung by a scorpion.
A Scorpion sting (SEM)Photographer: Dr Ken Walker / Source: Museum Victoria
Walker, K. L., Yen, A. L. and Milledge, G. A. 2003. Spiders and Scorpions commonly found in Victoria. Royal Society of Victoria: Melbourne.
Hi Isobel, scorpions excrete through the anus, generally in the form of nitrogenous waste. A simple internet search should provide you with many online resources.
It is possibly a baby scorpion, or a species that is quite small even as adults. The other likely animal it could be is pseudo scorpion. Pseudo scorpions are small and do not have the ‘tail’ of normal scorpions but they do have the two obvious pincers at the front of their bodies.
Hi Josie, the information written above may be able to help you, as well as the links in the top right hand corner. In addition here are a few interesting sites on scorpions that you may be able to use for your school project, click here, here and here. We have forwarded your enquiry regarding venom and pincer size to our Live Exhibits Department, and will post an answer as soon as we hear from them.
Hi Josie, the size of the scorpion is not the only indicator of the amount of venom it contains. A great little trick to know is to look at its pincers (claws) and compare them to the size of the tail (sting). If it has really big claws and a small sting it is indicating that it uses power rather than venom to subdue its prey and tends to be less potent a venom. If you look up a Rainforest Scorpion and a Spider Hunting Scorpion on the internet and look at photos you will be able to work out which one relies on venom and which normally just uses power.
The museum does not provide eradication advice perhaps you can contact your environmental officer at your local council for further advice.
Scorpions will take moving prey of any size up to and including their own size, but generally cope best with prey about one third of their body size or less. They naturally feed on ground-dwelling invertebrates such as crickets and beetle larvae (mealworms), so moths may be difficult for them to catch but other than that there is no reason not to feed moths to scorpions.
We love receiving comments, but can’t always respond.
Hi Joey, Baw Baw Frog numbers have collapsed in recent years, this link to the Melbourne Zoo website will provide you with some information on possible reasons ...
To read the latest tweets from @museumvictoria
Follow Museum Victoria on
When did Cambodian people first start coming to Australia | <urn:uuid:c9efb281-d36f-4f61-9158-86dc9dfc8065> | 3.609375 | 951 | Knowledge Article | Science & Tech. | 54.468013 |
Early Aerobic Bacteria
Location: Outside U.S.
Date: Summer 2009
I know that cellular respiration in mitochondria needs both
the membranes of the mitochondria so as to maintain a proton motive gradient.
If the theory of endosymbiosis is true, then how did the primitive aerobic
bacteria with only a single membrane carry out respiration?
There can be a proton gradient across a cell membrane, not just across a
membrane within a cell. For example, certain bacteria and archaea have a
proton gradient across their membranes (inside vs. outside), and can still
respire without internal membranes.
Hope this helps,
Click here to return to the Molecular Biology Archives
Update: June 2012 | <urn:uuid:0576977b-1875-4fcc-b58a-4be4738ecae7> | 3.34375 | 157 | Q&A Forum | Science & Tech. | 36.297727 |
There are to be 6 homes built on a new development site. They could
be semi-detached, detached or terraced houses. How many different
combinations of these can you find?
This challenge is to design different step arrangements, which must
go along a distance of 6 on the steps and must end up at 6 high.
Vincent and Tara are making triangles with the class construction set. They have a pile of strips of different lengths. How many different triangles can they make? | <urn:uuid:a85ad334-31cb-45dc-8962-5ac67a96690a> | 2.765625 | 102 | Q&A Forum | Science & Tech. | 63.313253 |
qsort - sort a table of data
void qsort(void *base, size_t nel, size_t width,
int (*compar)(const void *, const void *));
[CX] The functionality described on this reference page is aligned with the ISO C standard. Any conflict between the requirements described here and the ISO C standard is unintentional. This volume of IEEE Std 1003.1-2001 defers to the ISO C standard.
The qsort() function shall sort an array of nel objects, the initial element of which is pointed to by base. The size of each object, in bytes, is specified by the width argument. If the nel argument has the value zero, the comparison function pointed to by compar shall not be called and no rearrangement shall take place.
The application shall ensure that the comparison function pointed to by compar does not alter the contents of the array. The implementation may reorder elements of the array between calls to the comparison function, but shall not alter the contents of any individual element.
When the same objects (consisting of width bytes, irrespective of their current positions in the array) are passed more than once to the comparison function, the results shall be consistent with one another. That is, they shall define a total ordering on the array.
The contents of the array shall be sorted in ascending order according to a comparison function. The compar argument is a pointer to the comparison function, which is called with two arguments that point to the elements being compared. The application shall ensure that the function returns an integer less than, equal to, or greater than 0, if the first argument is considered respectively less than, equal to, or greater than the second. If two members compare as equal, their order in the sorted array is unspecified.
The qsort() function shall not return a value.
No errors are defined.
The comparison function need not compare every byte, so arbitrary data may be contained in the elements in addition to the values being compared.
The requirement that each argument (hereafter referred to as p) to the comparison function is a pointer to elements of the array implies that for every call, for each argument separately, all of the following expressions are nonzero:((char *)p - (char *)base) % width == 0 (char *)p >= (char *)base (char *)p < (char *)base + nel * width
The Base Definitions volume of IEEE Std 1003.1-2001, <stdlib.h>
First released in Issue 1. Derived from Issue 1 of the SVID.
The DESCRIPTION is updated to avoid use of the term "must" for application requirements.
IEEE Std 1003.1-2001/Cor 1-2002, item XSH/TC1/D6/49 is applied, adding the last sentence to the first non-shaded paragraph in the DESCRIPTION, and the following two paragraphs. The RATIONALE is also updated. These changes are for alignment with the ISO C standard. | <urn:uuid:2de144cb-6142-4715-85b5-f3bcea33c106> | 2.796875 | 629 | Documentation | Software Dev. | 53.587906 |
Mission Type: Lander, Orbiter
Launch Vehicle: Titan IIIE-Centaur (TC-3 / Titan no. E-3 / Centaur no. D-1T)
Launch Site: Cape Canaveral, Fla., USA
NASA Center: Jet Propulsion Laboratory, Langley Research Center
Spacecraft Mass: 3,527 kg
1) imaging system
2) atmospheric water detector
3) infrared thermal mapper
1) imaging system
2) gas chromatograph mass spectrometer
4) x-ray fluorescence
5) biological laboratory
6) weather instrument package (temperature, pressure, wind velocity)
7) remote sampler arm
1) retarding potential analyzer
2) upper-atmosphere mass spectrometer
Deep Space Chronicle: A Chronology of Deep Space and Planetary Probes 1958-2000, by Asif A. Siddiqi, NASA Monographs in Aerospace History No. 24
NSSDC Master Catalog, http://nssdc.gsfc.nasa.gov/nmc/
Viking-A was scheduled to launch before Viking-B, but had to launch second due to a problem with its batteries that had to be repaired.
After a successful launch and a midcourse correction on 19 September 1975, Viking 2 entered orbit around Mars on 7 August 1976, nearly a year after launch.
As with Viking 1, photographs of the original landing site indicated rough terrain, prompting mission planners to select a different site at Utopia Planitia near the edge of the polar ice cap where water was located, that is, where there was a better chance of finding signs of life.
The lander separated from the orbiter without incident on 3 September 1976 and, after atmospheric entry, landed safely at 22:37:50 UT about 6,460 kilometers from the Viking 1 landing site. Touchdown coordinates were 47.968° north latitude and 225.71° west longitude
Photographs of the area showed a rockier, flatter site than that of Viking 1. The lander was in fact tilted 8.5° to the west. The biology experiments with scooped-up soil produced similar results to that of its twin -- inconclusive on the question of whether life exists or ever has existed on the surface of Mars. Scientists believed that Martian soil contained reactants created by ultraviolet bombardment of the soil that could produce characteristics of organisms living in Earth soil.
The orbiter continued its successful imaging mission, approaching as close as 28 km to the Martian moon Deimos in May 1977. A series of leaks prompted the termination of orbiter 2 operations on 24 July 1978, while lander 2 continued to transmit data until 12 April 1980. In total, the two orbiters returned 51,539 images of Mars at 300 meters resolution, that is, about 97 percent of the surface. The landers returned 4,500 photos of the two landing sites. | <urn:uuid:af926bfe-4753-4935-8f14-453a77af9e23> | 3.203125 | 602 | Knowledge Article | Science & Tech. | 50.689665 |
Goals: International Sun-Earth Explorer-3 (ISEE-3) was to investigate the solar wind and its interaction with Earth's magnetic field, among other phenomena in interplanetary space. It was later renamed International Cometary Explorer (ICE) and used to study two comets during an extended mission.
Accomplishments: ISEE-3 conducted the first deep survey of Earth's magnetic tail. Then, after a series of complex flybys of the Moon, the spacecraft was renamed the International Cometary Explorer (ICE) and became the first spacecraft to fly past a comet (Giacobini-Zinner). Its observations supported the theory that comets are "dirty snowballs." The following year, it joined international exploration of Comet Halley by providing data on the solar wind approaching the comet. | <urn:uuid:7fc49103-9c19-4b54-9998-e8a6cc52b11a> | 3.59375 | 165 | Knowledge Article | Science & Tech. | 25.795 |
You are looking at historical revision 20452 of this page. It may differ significantly from its current revision.
This page contains a list of tutorials we have written (or would like someone to write) about Chicken Scheme.
- JRM's Syntax-rules Primer for the Merely Eccentric
- A famous and very friendly introduction to the R5RS high-level macro system known as syntax-rules.
- Introduction to "explicit renaming" macros, the low-level macro system used in Chicken.
- Macro systems and chicken (long)
- An excellent post by Alex Shinn, explaining different macro systems.
- How to use assertions in your code as a way to detect programming errors.
- Autoconf - Automake
- A tutorial explaining how to use Autoconf and Automake in software packages containing Scheme files meant to be compiled by Chicken.
- Eggs Tutorial
- A tutorial about creating Chicken eggs.
- Chicken on handhelds
- A guide to using Chicken on embedded devices.
- Compiling Chicken on Windows XP with MinGW
- For the Windows using C/C++ newbies like me. | <urn:uuid:c86543f1-7204-480a-b69f-97bdac3c07da> | 2.6875 | 240 | Content Listing | Software Dev. | 43.355282 |
The compiler.ast module defines an abstract syntax for Python. In the abstract syntax tree, each node represents a syntactic construct. The root of the tree is Module object.
The abstract syntax offers a higher level interface to parsed Python source code. The parser module and the compiler written in C for the Python interpreter use a concrete syntax tree. The concrete syntax is tied closely to the grammar description used for the Python parser. Instead of a single node for a construct, there are often several levels of nested nodes that are introduced by Python's precedence rules.
The abstract syntax tree is created by the compiler.transformer module. The transformer relies on the builtin Python parser to generate a concrete syntax tree. It generates an abstract syntax tree from the concrete tree.
The transformer module was created by Greg Stein and Bill Tutt for an experimental Python-to-C compiler. The current version contains a number of modifications and improvements, but the basic form of the abstract syntax and of the transformer are due to Stein and Tutt. | <urn:uuid:1ad58729-29c1-433c-b39f-b829951683ce> | 3.234375 | 207 | Documentation | Software Dev. | 47.145 |
Tuesday 18 June
Cromwell chafer (Prodontria lewisi)
Cromwell chafer fact file
- Find out more
- Print factsheet
Cromwell chafer description
The Cromwell chafer is a Critically Endangered beetle found at just one site in Cromwell, New Zealand. It is a flightless beetle that belongs to the same family as dung beetles. This large beetle has pale reddish-brown wing cases (elytra) which are strongly convex and feature deep lines passing along their length. Females are longer and wider than males, but males have longer lower legs (tibiae) and larger hind feet (2).Top
Cromwell chafer biology
The Cromwell chafer is a nocturnal species, active during the spring and summer from August to March. It emerges at night to feed on speedwell (Veronica arvensis), cushion plant (Raoulia australis), sheep's sorrel (Rumex acetosella) and a number of lichens (2). Activity is highest on warm nights when humidity is low, and they tend not to emerge if the temperature is below six degrees Celsius. (2). In the day, adults burrow up to half a metre deep in the soil, typically at the base of silver tussock (Poa cita); they tend to return to the same burrow that they used the previous day (2). Studies have shown that females do not disperse, but it is the males that wander in search of females to mate with. Males also tend to emerge earlier in the year than females (3)
Very little is known of the larval stage of this beetle. It is thought that they may be associated with the roots of silver tussock, and that they may take more than one year to develop. Pupae of this species have never been found (3).Top
Cromwell chafer range
This beetle is endemic to New Zealand, where it is found at just one site near Cromwell in Central Otago, on the South Island (3). This 81 hectare area became the Cromwell Chafer Beetle Nature Reserve in 1983 (3). Within this site, just four discrete populations are known (2).Top
Cromwell chafer habitat
This beetle is found in an area of windblown sand dunes, beneath which there is a bed of gravel. Six vegetation types have been found in the area (3). The beetle is associated with scabweeds (Raoulia species) and silver tussock (Poa laevis) (4). The vegetation cover is dynamic, as there is heavy grazing by rabbits (3).Top
Cromwell chafer status
Classified as Critically Endangered (CR) by the IUCN Red List 2007 (1).Top
Cromwell chafer threats
The original range of the Cromwell chafer was around 500 hectares, but this was reduced to just 100 hectares following the construction of the Clyde Dam and the expansion of the township of Cromwell (4). Threats facing this species are not fully understood, but are thought to include predation by introduced hedgehogs (Erinaceus europaeus). The little owl (Athene noctua) is also known to predate upon this species (3). Habitat alteration is also likely to be a problem (2). At the present time, large areas of apparently suitable habitat are not occupied by this beetle. It is imperative that the reasons for its present distribution and the factors limiting the population are understood (3).Top
Cromwell chafer conservation
The site supporting this species has been fully protected since it became a nature reserve in 1983. Research and monitoring of the Cromwell chafer populations are on-going, and current work is focusing on the predation risk posed by hedgehogs and other predators, potential competitors, and understanding the life history of the species (3). Hopes are that the knowledge gained from these studies will help to develop and guide the effective conservation of this unique and very rare beetle.Top
Find out more
For more information on the Cromwell chafer see:
- Ferreira, S. M. and McKinlay, B. (1999) Conservation monitoring of the Cromwell chafer beetle (Prodontria lewisii) between 1986 and 1997. Science for Conservation 123. Department of Conservation, Wellington, N.Z.
AuthenticationThis information is awaiting authentication by a species expert, and will be updated as soon as possible. If you are able to help please contact: firstname.lastname@example.orgTop
- A species or taxonomic group that is only found in one particular country or geographic area.
- Larval stage
- Stage in an animal’s lifecycle after it hatches from the egg. Larvae are typically very different in appearance to adults; they are able to feed and move around but usually are unable to reproduce.
- Active at night.
- Stage in an insect’s development when huge changes occur, which reorganise the larval form into the adult form. In butterflies the pupa is also called a chrysalis.
- IUCN Red List (February, 2008)
- New Zealand Department of Conservation: Beetles- scarabs and staphylinids. Scarab beetles: dung beetles, chafer beetles (February, 2008)
- Ferreira, S.M. and McKinlay, B. (1999) Conservation monitoring of the Cromwell chafer beetle (Prodontria lewisii) between 1986 and 1997. Science for Conservation 123. Department of Conservation, Wellington, N.Z. Available at:
- The State of Our Invertebrate Animals. New Zealand Ministry of the Environment (March, 2004)
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Asian Longhorned Beetle (ALB)
Asian Longhorned Beetle - Anoplophora glabripennis
Asian Longhorned Beetle
Photograph credit: Kenneth R. Law,
USDA APHIS PPQ,
On September 13, 1996, the Systematic Entomology Laboratory of the Agricultural Research Service confirmed a specimen sent to them for identification as A. glabripennis. This pest was collected on maple and horse chestnut trees by the New York City Parks and Recreation Department at Green Point in northern Brooklyn County. It was initially identified by E. Richard Hoebeke of Cornell University. The Longhorned beetle is a pest found in China, Japan and Korea. This was the first detection of this pest in the United States.
The early stages of larvae of this beetle feed between the xylem and the phloem, and the later stages feed only on the xylem, inhibiting the tree's vascular system. It is most destructive when larvae cross perpendicular to the flow, thereby cutting off many vascular paths. Larvae can cut off the flow from vasular tissue and essentially girdle the tree. Adults emerge through three-quarter-inch holes in the bark. Recorded in the literature are the following hardwood hosts in Asia: Ulmus parvifolia (elm), Salix babylonica (willow), and Populus species (poplar). Hosts found in Brooklyn include Aesculus (horsechesnut) and Acer species (Norway, sugar and silver maples).
Watch a clip about Asian Longhorned Beetle on DEC TV.
Outreach and Educator Materials
- DEC Asian Longhorned Beetle Poster (PDF) (8 1/2 x 11) (245 KB)
- DEC Asian Longhorned Beetle Poster (PDF) (28 x 36) (4.9 MB)
- View EAB materials for educators
More about Asian Longhorned Beetle (ALB):
- Asian Longhorned Beetle Photograph - Asian Longhorned Beetle - Photograph | <urn:uuid:d8910b17-9247-4361-bbad-8e1104a7696f> | 2.953125 | 410 | Knowledge Article | Science & Tech. | 42.440208 |
Technologies on the road to Mars
The hatch to the airlock opens, revealing a human figure encased in a white pressure suit. After a brief glance at the strange surroundings through his bowl-shaped visor, the ambassador from Earth gingerly steps outside and begins to descend the ladder.
Within minutes, the visitor from another world reaches the bottom rung and prepares for a 'giant leap' - humanity's first imprint in the pristine, orange sands that stretch as far as the eye can see. The human exploration of Mars has begun.
Science fiction? At present, the answer is yes, but this fictional scenario may become a reality by the year 2030. In order to achieve such an ambitious target, ESA has introduced its new Aurora programme. This will eventually enable European astronauts to venture beyond Earth's orbit to the Moon, Mars and beyond.
One of the first requirements of Aurora has been to identify the key technologies that will be needed to send robots, and then people, to explore the solar system. This important task was undertaken by a team of ESA experts, known as the Technical Support Team; the 11 'technology streams' identified for development over the next few decades are shown in the following table.
|1||automated guidance, navigation and control and mission analysis|
|3||data processing and communication technologies|
|4||entry, descent and landing|
|5||crew aspects of exploration|
|6||in situ resources utilisation|
|9||robotics and mechanisms|
|10||structures, materials and thermal control|
This was followed on 12 February 2002 by a Call for Exploration Technology Proposals, was sent to small and medium-sized companies and research and development institutes across Europe and Canada. The major European prime contractors - Astrium, Alcatel and Alenia Spazio - were already pursuing exploration studies for Aurora.
"We were 'fishing' for really new ideas and processes," said Dietrich Vennemann, human missions manager for the Aurora programme. "We were also aiming to involve new companies that would not normally take part in space activities. We wanted them to tell us about their new ideas, to explain their potential and then suggest what steps would be required to take their proposals further."
The response was astounding with a total of 119 proposals submitted. Of these, 36 were awarded a contract, 45 were put 'on hold' and six were transferred as candidates for other ESA programmes.
The final presentations by most of the 36 successful applicants were made during a meeting at the European Space Research and Technology Centre (ESTEC) in the Netherlands from 9 to 11 December.
Since each of the 11 technology streams was represented at the meeting, the presentations covered a wide range of topics including:
- the design of an ultrasonic drill to obtain rock cores
- helium-filled balloons to explore the atmosphere and surface of Mars
- inflatable landing systems
- automated spacecraft rendezvous
- options for a Martian ascent vehicle
- regenerative solid oxide fuel cells
- an onboard intelligent payload planner
- space food preparation
- plasma thrusters
- biomedical technologies for human Mars missions
- dust analysers for Mars
In the coming weeks, ESA technical officers will make their recommendations as to which proposals offer the most promise for further study and development.
Meanwhile, further study contracts are currently being issued in the context of generic technologies to tackle major problems affecting every space mission under the Aurora programme, e.g. guidance, navigation and control, and radiation exposure. | <urn:uuid:23c3eb28-5a21-4bbe-81bc-fb4d9f45e8a7> | 3.25 | 725 | Knowledge Article | Science & Tech. | 28.189933 |
Our recent studies on isotope anomalies in planetary atmospheres, especially in Titan's atmosphere show an indication that our early Sun underwent during the first 600 million years after its origin a very active period which is called Post-T-Tauri phase.
We investigate the particle and radiation environment during such an early solar period, where the solar wind particle density and soft x-ray flux is up to 1000 times higher than at present. We cooperate in our study with colleagues from the Sun in time project, and use a of nine solar like G-type stars with an age between 70 million and 9 billion years.
The physical parameters from these stars were obtained by observations with the ROSAT and ASCA x-ray satellites.
Our study investigates:
- How much such a strong solar wind outflow will affect non-or weakly magnetized planets and solar system bodies. An increased x-ray luminosity of the young Sun and an enhanced solar EUV radiation will also affect the photoionization rates of the paleoatmospheres of terrestrial planets.
- Our investigation is also very important for exobiology since the early radiation environment in the planetary nebular and planetary forming time period was very important for the formation of complex organic molecules and the interaction with comets and asteroids. | <urn:uuid:b7a88dd5-f9a7-4c2f-abfb-0da2047670bf> | 3.078125 | 258 | Knowledge Article | Science & Tech. | 22.022757 |
Following the distinction made by Gene Rasmusson (Rasmusson et al., 1991) in the wind data, we also looked at the low-frequency mode (LFM) associated with ENSO (Figure 2, again in the color well). In that case, the amplitudes are even more tightly connected to the tropical Pacific and the west coast of the Americas. While a QBO-type oscillation does seem to be more global, this LFM is really concentrated in the tropical Pacific.
As for the spatial patterns, we took a group of eight stations just a little bit north of the equator in the western tropical Pacific and did a Hovmöller diagram (Figure 3). We wanted to look at the eastward-propagating signal in the quasi-biennial component of the zonal winds Dr. Rasmusson mentioned. We actually combined the two components, QBO and LFM. In this plot, which goes from 145°E to 155°W and includes data from 1950 to 1976, you can see that there is not so much a propagating as a standing signal, and actually there seems to be something of a nodal line about 175°W.
So I think that we are getting on with this business of trying to define the spatial modes of interannual and interdecadal variability, which obviously is more interesting than just looking at spectral peaks. And perhaps what we should be noticing is that the peaks are in the same places, not in different places, for various records. | <urn:uuid:39e8c24f-44b1-4826-b1bd-5357e0df1366> | 2.75 | 311 | Academic Writing | Science & Tech. | 53.309306 |
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In 1960 the Nobel Prize was awarded to Donald Glaser for designing the Bubble Chamber as a detector for use in nuclear physics. This is the presentation speech which gives an overview of the ...
A Marvin and Milo activity about bubbles. All you need is two glasses, skimmed milk, whole milk and two straws
Researchers are looking at how sound bounces of bubbles in beer. This can tell them how the fluid is moving around the bubbles and has consequences for studying volcanic eruptions or monitoring food ...
A personal homepage of a mathematician in Ireland talking about physics of stout beer, including why bubbles affect the flavour, why bubbles sink and how bubbles start.
In this series of experiments, you will control the action of a piston in a pressure chamber which is filled with an ideal gas.
Overview of the development of the spark chamber and a description of both function and uses in particle detectors.
A great video showing what happens when a bubble gets hit by a shock wave travelling at Mach 3
Description of the background to a cloud chamber particle detector.
Optical illusion or physics-defying bubbles? The answer is here.
Experiments with less familiar bubbles - bubbles of water.
Showing 11 - 20 of 46 | <urn:uuid:d535f71f-71ea-49c7-a7a5-e93fb879b1f1> | 2.9375 | 342 | Content Listing | Science & Tech. | 61.144249 |
Gypaetus barbatus , Photo: Michael Lahanas
Gypaetus barbatus (Linnaeus, 1758)
* Carolus Linnaeus: Systema Naturae ed.10 p.87
The Lammergeier, Lammergeyer, or Bearded Vulture, Gypaetus barbatus ("Bearded Vulture-Eagle"), is the only member of the genus Gypaetus. Traditionally considered an Old World vulture, it actually forms a minor lineage of Accipitridae together with the Egyptian Vulture (Neophron percnopterus), its closest living relative. They are not much more closely related to the Old World vultures proper than to, for example, hawks, and differ from the former by their feathered neck. Although quite dissimilar, Egyptian and Bearded Vulture both have a lozenge-shaped tail that is unusual among birds of prey.
It eats mainly carrion and lives and breeds on crags in high mountains in southern Europe, Africa, India, and Tibet, laying one or two eggs in mid-winter which hatch at the beginning of spring. Populations are resident.
Unlike most vultures, the Lammergeier does not have a bald head. This huge bird is 95–125 cm (37–49 in) long with a wingspan of 275–308 cm (108–121 in) (10 feet), and is quite unlike most other vultures in flight due to its large, narrow wings and long, wedge-shaped tail feathers. It weighs 4.5–7.5 kg (9.9–17 lb).
The adult has a buff-yellow body and head, the latter with the black moustaches which give this species its alternative name. It may rub mud over its chin, breast and leg feathers, giving these areas a rust-coloured appearance. The tail feathers and wings are grey. The juvenile bird is dark all over, and takes five years to reach full maturity. The Lammergeier is silent, apart from shrill whistles at the breeding crags, and can live up to 40 years in captivity.
Like other vultures it is a scavenger, feeding mostly from carcasses of dead animals. It usually disdains the rotting meat, however, and lives on a diet that is 90% bone marrow. The Lammergeier can swallow whole bones up to the size of a lamb's femur and its powerful digestive system quickly dissolves even large pieces. The Lammergeier has learned to crack bones too large to be swallowed by carrying them up to a height and then dropping them onto rocks below, smashing them into smaller pieces and exposing the nutritious marrow. This learned skill requires extensive practice by immature birds and takes up to seven years to master. Its old name of Ossifrage ("bone breaker") relates to this habit. Live tortoises are also dropped in similar fashion to crack them open. Although dropping bones is a regular habit, the Lammergeier also obtains food by other means and has been known to seize and carry off live prey such as a two foot monitor lizard.
The habitat is exclusively mountainous terrain (500–4,000 m/1,600–13,000 ft). An individual has been seen at 24,000 feet (7,300 m). The bird breeds from mid-December to mid-February, laying 1 to 2 eggs which hatch between 53 and 58 days. After hatching the young spend 106 to 130 days in the nest before fledging. Typically, the Lammergeier nests in caves and on ledges and rock outcrops.
Although the Lammergeier is threatened within its range in Europe, the species has a large range across Asia and Africa and is relatively common across much of that range. As such the species is listed as least concern by the IUCN and BirdLife International, although there is some evidence of decline. It was formerly killed in significant numbers because people feared (without justification) that it carried off children and domestic animals; the bird was also hunted as a trophy.
This species was first described by Linnaeus in his Systema naturae in 1758 as Vultur barbatus. The name of the Lammergeier originates from German Lämmergeier, which means "lamb-vulture" or "lamb-hawk". The name stems from the belief that it attacked lambs.
The Greek playwright Aeschylus was said to have been killed in 456 or 455 BC by a tortoise dropped by an eagle who mistook his bald head for a stone – if this incident did occur, the Lammergeier is a likely candidate for the "eagle".
More recently, in 1945, it is said that Shimon Peres (called Shimon Persky at the time) and David Ben-Gurion found a nest of Bearded Vultures in the Negev desert. The bird is called peres in Hebrew, and Shimon Persky liked it so much he adopted it as his surname.
Bearded Vulture is considered a threatened species in Iran. Iranian mythology considers the rare Lammergeier the symbol of luck and happiness. It was believed that if the shadow of a Huma fell on one, he would rise to sovereignty.
1. ^ BirdLife International (2008). Gypaetus barbatus. In: IUCN 2008. IUCN Red List of Threatened Species. Downloaded on 1 November 2008. Database entry includes justification for why this species is of least concern
Source: Wikipedia, Wikispecies: All text is available under the terms of the GNU Free Documentation License | <urn:uuid:4e615058-8e3e-4600-9f34-cffd37d71109> | 3.171875 | 1,181 | Knowledge Article | Science & Tech. | 55.678076 |
The world's newest flower is a species less than 140 years old hailing from southern Scotland, but its parents are from the Andes and North America's west coast. The yellow monkey flower, or Mimulus peregrinus—Latin for "wanderer," is described in the journal Phytokeys. (Click on the image for higher resolution.)
Mario Vallejo-Marin, a plant evolutionary biologist at the University of Stirling in Scotland, discovered M. peregrinus on a stream bank. Leaf and flower characteristics indicate its ancestors are M. guttatus and M. luteus, two species of monkey flowers transported from the Americas and cultivated by Victorian gardeners in the 1800s.
M. peregrinus's genus turns up around the world but most species grow in North America and Australia. Different monkey flower species can hybridize, although their offspring carry an odd number of chromosomes, rendering them sterile. "The classic example is if you cross a horse and a donkey, you get a sterile individual—a mule," Vallejo-Marin says. A rare mutation duplicated the entire genome of M. peregrinus. This polyploidic event evened out the number of chromosomes and the flower avoided a genetic dead-end.
"Theory predicted this plant would exist somewhere, and every time we came across a patch of hybrids, I would look," Vallejo-Marin says. On a trip with his family, he discovered a patch of hybrid flowers producing plenty of seeds. After analyzing the DNA, he confirmed the new species.
Several other species have cropped up this way over the past 200 years, but the recent discovery gives scientists a chance to watch the origin of a species as it happens. New genetic characteristics may arise as M. peregrinus spreads in the wild. The polyploidy is a "genomic revolution," says Vallejo-Marin, because the plant has twice the amount of genetic material it can use to adapt to changing environmental conditions. Adaptability gives invasive species their edge, he says, and could help life cope with climate change.
Deadline: Jul 25 2013
This challenge provides an opportunity for Solvers to build a web-based or mobile “app” to explore data relationships in scholarly conte
Deadline: Jul 14 2013
Reward: $1,000,000 USD
This is a Reduction-to-Practice Challenge that requires written documentation and&
Get Both Print & Tablet Editions for one low price!X | <urn:uuid:74cf6414-c997-40d9-832a-f2fd821b4c15> | 3.609375 | 524 | Truncated | Science & Tech. | 42.297384 |
What do we know about the life and habits of the colossal squid?
We know very little about the colossal squid’s life history, diet, or behaviour, because they live at extreme depths in freezing water. They are also very rarely captured. The first report of a colossal squid was in 1925, when the head and arms were discovered in a sperm whale stomach. Since then, a total of only eight adult colossal squid have been reported, and six of those were remains recovered from the stomachs of caught whales.
Colossal squid live in Antarctic waters, but may come as far north as the southern waters of New Zealand. They live at depths of 1000 metres or more.
Colossal squid have a very narrow oesophagus between their mouth and their stomach, and have to bite their food into small pieces before they swallow it. No intact stomach has ever been recovered, but behaviour suggests a fondness for toothfish. Many squid are cannibalistic, so colossal squid may even eat each other from time to time.
Colossal squid beak, reproduced courtesy of Kathrin Bolstad.
Scientists don’t know much about the reproductive cycle of the colossal squid, mainly because only females have been found. The male probably has a fairly large penis to implant sperm directly into the female.
All squid lay eggs. Some lay single eggs, others lay clusters of eggs in a large jelly-like floating mass. Giant squid lay eggs in this way, so colossal squid probably do the same. The eggs hatch out into tiny versions of the adult which become mature adults in one–three years.
How common are colossal squid?
Reports of colossal squid have been very few. But these creatures must be more common than the reports suggest.
Whales eat colossal squid, and the squid beaks stay in the whale’s stomach for a long time because they are not easily digested. Scientists have estimated the number of colossal squid from the beaks found in the stomachs of sperm whales in the Southern Ocean. They believe that colossal squid might form as much as 77% of a sperm whale’s diet.
More information from the blog
> The largest invertebrate on the planet
> Chromatophores and skin
> Dissection of the smaller specimen of colossal squid
> Smaller colossal squid, continued
> What's all that beak business
> Hooks and suckers
> The eye | <urn:uuid:8b43b8f3-f91e-472b-8420-a8a5a6eae414> | 3.75 | 495 | Knowledge Article | Science & Tech. | 54.303953 |
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mass extinctions and technology
An old question I would like to reintroduce:
"If human beings were to become extinct in the next 500 years due to
global warming, pestilence or other catastrophe, what if anything would
remain of our civilization to reveal us to the next super species, 65
million years from now?" .
I sent a standard email to 100's of paleontologists and archaeologists
(PHd's in the USA and worldwide), asking this question to try and get some
consensus. I received approximately 60 replies. The results are as
follows. About 20 thought there would be direct evidence to reveal
us. About 30 were uncertain. About 10 thought there would be no evidence
to reveal us.
There seems to be no consensus in paleontology and archaeology.
This raises an even more interesting question. What if a civilization such
as ours existed tens of millions of years ago and we are not aware of
it? I am not suggesting human beings were present 10's of millions of
years ago, but perhaps an earlier super species.
This is an interesting hypothesis, but it would be even more interesting if
we had a method of testing it.
How to test this hypothesis:
Make the following assumptions:
1. Locatable and identifiable remains of a Pre-Human Civilization (PHC)
are mostly microscopic
Widespread microscopic remains of PHC's may exist in the sedimentary
record. The remains may be in the form of particles, persistent organic
pollutants, trace elements, isotopes or other types.
2. Given two isolated civilizations, be they isolated by time OR space,
technology will evolve along similar lines.
Common themes will prevail, with regard to the technological progression in
isolated civilizations. This is given that many natural laws, that
constrain or direct technological advancement, would be consistent between
the two systems. This assumption is more relevant to civilizations
separated by time, as the physical environment is more likely similar.
For example, if we consider two such earth civilizations, we might expect
to see non-sustainable utilization of the earths resources in both. Such
activity might include fossil fuel energy or mass extinction. We might also
expect to see the development of synthetic compounds such as persistent
It seems intuitive, that the more fundamental the technology, the more
likely it will be common to both civilizations. Whereas the more elaborate,
or obscure a technological advance, the less likely we would see it
represented in both civilizations.
3. Let us assume that mass extinction and heavily industrialized
civilization are closely related.
Let us assume the PHC would cause a gradual mass extinction, as does our
1. What to look for - Industrial tracers
A suitable industrial tracer must meet three criteria:
1. Entirely of industrial/anthropogenic/xenobiotic origin.
2. Is widespread in the atmosphere, causing it to be a detectable
contaminant of most of the earths recently laid sediments.
3. Very stable in the environment over time.
For example, we might look for organic pollutants. PCB's, DDE (metabolite
of DDT) and phthalates (plasticizers) are all found in remote marine
atmosphere (Report in Science, p163, Vol. 211, 1981). These compounds are
all exclusively industrial in origin. DDE and certain congeners of PCB are
also very stable in the environment.
2. Where to look
Let us assume the PHC would cause a mass extinction, as does our existing
civilization. The target sediment will surround and incorporate extinction
event sediment. For example, KT Boundary clay. A good place to look might
be cores from the ocean drilling program (ODP) as they are less likey
contaminated (see ODP leg 171B -
3. The experiment
Examine extinction event sediment for presence of an industrial tracer
(IT). ie. most environmental labs can detect a wide range of anthropogenic
pollutants down to parts per trillion. If IT is present in extinction
event sediment, this will indicate a PHC.
Industrial tracer levels should be checked in sediment from random sites in
Any suggestions from the list greatly appreciated.
Southern Cross University
50% of the worlds flora and fauna could be on the path to extinction within
the next 100 years - National Geographic | <urn:uuid:7acf0103-33ac-4ad2-9e8c-82a81561589e> | 3.25 | 954 | Comment Section | Science & Tech. | 41.815271 |
This data set contains monthly averaged wind stress over the global ocean for the years 1870 through 1976. The data are given on a 2 deg latitude x 2 deg longitude grid. Monthly data for each month of the averaged years of the period include zonal and meridional Wind_U Stress and Wind_V Stress. The unit of measurement for the wind stress variables is dynes/cm**2. Over 35 million surface observations covering the world ocean from 1870-1976 have been processed for the purpose of calculating monthly normals and standard errors of the eastward and northward components of the wind stress and work done by the winds in the lower 10 m of the atmosphere. The fields are intended to serve as boundary conditions for models of ocean circulation. | <urn:uuid:aaab1da5-cc4e-48fd-8401-5f45f773262a> | 2.796875 | 150 | Content Listing | Science & Tech. | 54.505523 |
Tag: Ice Shelves
3 time-lapsed photos show the incredible disintegration of the Filchner ice shelf in Antarctica. Within a 24-hour space, an area of sea ice larger than the state of Rhode Island broke away from the Ronne-Filchner Ice Shelf and shattered into many smaller pieces. The Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA’s Aqua and Terra satellites [...]
Scientists who study the melting of Greenland’s glaciers are discovering that water flowing beneath the ice plays a much more complex role than they previously imagined. Researchers previously thought that meltwater simply lubricated ice against the bedrock, speeding the flow of glaciers out to sea. Now, new studies have revealed that the effect of meltwater [...]
SYDNEY (Nov. 12) – A large iceberg was spotted off an island about halfway between Antarctica and Australia, a rare sight in waters so far north, Australian scientists said Thursday. Australian Antarctic Division researchers working on Macquarie Island, about 930 miles southeast of Tasmania, first saw the iceberg last Thursday about 5 miles off the [...]
Posted: November 13th, 2009 under Climate Change, Nature, Tipping Points.
Tags: Antarctica, Ice Shelves, icesheet loss, Ross Ice Shelf, sea level rise, Southern Ocean, Tipping Points, West Antarctic
Starting this month, a giant NASA DC-8 aircraft loaded with geophysical instruments and scientists will buzz at low level over the coasts of West Antarctica, where ice sheets are collapsing at a pace far beyond what scientists expected a few years ago. The flights, dubbed Operation Ice Bridge, are an effort by NASA in cooperation [...]
Posted: October 11th, 2009 under Climate Change, General, Nature, Negotiations, Tipping Points.
Tags: Antarctica, catastrophic climate change, Climate Change, global warming, Ice Shelves, icesheet loss, Larsen Ice Shelf, science, sea level rise, West Antarctic
British Antartic Survey have released the most comprehensive picture of the rapidly thinning glaciers along the coastline of both the Antarctic and Greenland ice sheets has been created using satellite lasers. The findings are an important step forward in the quest to make more accurate predictions for future sea level rise. Reporting this week in [...]
Posted: October 9th, 2009 under Climate Change, General, Nature, Negotiations, Tipping Points.
Tags: arctic, catastrophic climate change, Climate Change, global warming, greenland, Ice Shelves, icesheet loss, science, sea level rise, West Antarctic
By Bob Williamson – Chair & Founder of the Greenhouse Neutral Foundation Should we claim eureka in Greek εὕρηκα!,” meaning “I have found it! the once ancient agreed principle of physics to be a conspiracy and a sham? Not that I am one to question the wider scientific community – well not often – well [...]
Posted: October 4th, 2009 under Climate Change, Foundation News, General, Nature, Tipping Points.
Tags: arctic, Climate Change, global warming, Ice Shelves, icesheet loss, Ross Ice Shelf, sea level rise, stop climate change, West Antarctic | <urn:uuid:344d84df-03ed-4736-9bae-c2f16cb9421e> | 2.875 | 658 | Content Listing | Science & Tech. | 40.323461 |
Kolkata: There was a huge solar flare in 1859. It was so large that it could be seen with the naked eye. In 1989, a solar storm wiped out Canada's northern electric grid. Canada was out of power for almost three days.
Violent magnetic emissions from the sun could one day destroy all electronic equipment on earth.
An Indian scientist from Indian Institute of Science Education and Research has helped NASA predict when such explosions are likely to happen.
"The activity of the sun affects satellites, air traffic on polar routes, telecommunications. So there is a huge industry in trying to develop forecasting capabilities," said Dibyendu Nandi of Indian Institute of Science Education and Research....more
01:41 PM, Mar 08, 2011 | <urn:uuid:43548af3-a206-47ff-a246-ab6bad2855c5> | 2.984375 | 153 | Truncated | Science & Tech. | 52.42204 |
As I understand the basic idea of particle filter is to predict the state of the particle by generating N different possible state. After that, each possible state is evaluated by a predict model (give the weight to each particle).
So...let say, if my particle is (x, y, z). Then, because there are M different possible values for x, N possible values for y and L different possible values for z. The number of particles that I need to generate is M*N*L? | <urn:uuid:45c520ad-8de4-4327-911f-f45ca97e0bc6> | 2.8125 | 102 | Q&A Forum | Science & Tech. | 66.66239 |
For many reasons, a server can never allow access to its entire directory hierarchy. Although there is really no indication of this given to the web browser, every path given in a requested URI is therefore a virtual path; early in the processing of a request, the virtual path given in the request must be translated to a path relative to the filesystem root, so that Apache can determine what resource is really being requested. This path can be considered to be a physical path, although it may not physically exist.
For instance, in mod_perl systems, you may intend that the translated path does not physically exist, because your module responds when it sees a request for this non-existent path by sending a virtual document. It creates the document on the fly, specifically for that request, and the document then vanishes. Many of the documents you see on the Web (for example, most documents that change their appearance depending on what the browser asks for) do not physically exist. This is one of the most important features of the Web, and one of the great powers of mod_perl is that it allows you complete flexibility to create virtual documents.
Alias /foo /home/httpd/foo
will map all requests starting with /foo to the files starting with /home/httpd/foo/. So when Apache receives a request to http://www.example.com/foo/test.pl, the server will map it to the file test.pl in the directory /home/httpd/foo/.
Additionally, ScriptAlias assigns all the requests that match the specified URI (i.e., /cgi-bin) to be executed by mod_cgi.
ScriptAlias /cgi-bin /home/httpd/cgi-bin
is actually the same as:
Alias /cgi-bin /home/httpd/cgi-bin <Location /cgi-bin> SetHandler cgi-script Options +ExecCGI </Location>
where the SetHandler directive invokes mod_cgi. You shouldn't use the ScriptAlias directive unless you want the request to be processed under mod_cgi. Therefore, when configuring mod_perl sections, use Alias instead.
Under mod_perl, the Alias directive will be followed by a section with at least two directives. The first is the SetHandler/perl-script directive, which tells Apache to invoke mod_perl to run the script. The second directive (for example, PerlHandler) tells mod_perl which handler (Perl module) the script should be run under, and hence for which phase of the request. Later in this chapter, we discuss the available Perl*Handlers for the various request phases. A typical mod_perl configuration that will execute the Perl scripts under the Apache::Registry handler looks like this:
When we say Perl*Handler, we mean the collection of all Perl handler directives (PerlHandler, PerlAccessHandler, etc.).
Alias /perl/ /home/httpd/perl/ <Location /perl> SetHandler perl-script PerlHandler Apache::Registry Options +ExecCGI </Location>
The last directive tells Apache to execute the file as a program, rather than return it as plain text.
When you have decided which methods to use to run your scripts and where you will keep them, you can add the configuration directive(s) to httpd.conf. They will look like those below, but they will of course reflect the locations of your scripts in your filesystem and the decisions you have made about how to run the scripts:
ScriptAlias /cgi-bin/ /home/httpd/cgi-bin/ Alias /perl/ /home/httpd/perl/ <Location /perl> SetHandler perl-script PerlHandler Apache::Registry Options +ExecCGI </Location>
In the examples above, all requests issued for URIs starting with /cgi-bin will be served from the directory /home/httpd/cgi-bin/, and those starting with /perl will be served from the directory /home/httpd/perl/.
mod_perl, modperl, Apache, perl, cgi, html, mod_perl, e-commerce, scalability, free, open source, OSS, apache, squid, high availability, modperl, linux, unix, Web, www, mod_perl, webserver, admin, apache, book, webmaster, tools, modperl, guide, docs, documentation, help, mod_perl, perl, information, apache, script, errata, eric cholet, perl, apache, mod-perl, stas bekman, mod_perl, cool, perl, Apache, performance, speed, choice
Other projects to check out: meta-religion.com is for those interested in Religious, Spiritual and Esoteric Phenomena. i-want-a-better.com is a community of people discussing what they would like to be improved in their lives and things they use and interact with. You may also want to find a healer in your area or read articles on variety of topics. | <urn:uuid:0c085e76-250e-4b85-808a-a13a637e424b> | 2.953125 | 1,077 | Documentation | Software Dev. | 44.52 |
A team of physicists have curbed the hope that quantum physics might be squared with common sense. At least if we want to hang on to Einstein's highly respected theory of relativity. Their result concerns what Einstein called "spooky action at a distance" and it may soon be possible to test their prediction in the lab.
The 2012 Nobel Prize for Physics has been awarded to Serge Haroche and David J. Wineland for ground-breaking work in quantum optics. By probing the world at the smallest scales they've shed light on some of the biggest mysteries of physics and paved the way for quantum computers and super accurate clocks.
If you're bored with your holiday snaps, then why not turn them into fractals? A new result by US mathematicians shows that you can turn any reasonable 2D shape into a fractal, and the fractals involved are very special too. They are intimately related to the famous Mandelbrot set.
The laws of symmetry are unforgiving, but a team of researchers from the US have come up with a pattern-producing technique that seems to cheat them. The new technique is called moiré nanolithography and the researchers hope that it will find useful applications in the production of solar panels and many other optical devices.
In the 1920s the Austrian physicist Erwin Schrödinger came up with what has become the central equation of quantum mechanics. It tells you all there is to know about a quantum physical system and it also predicts famous quantum weirdnesses such as superposition and quantum entanglement. In this, the first article of a three-part series, we introduce Schrödinger's equation and put it in its historical context.
In the previous article we introduced Schrödinger's equation and its solution, the wave function, which contains all the information there is to know about a quantum system. Now it's time to see the equation in action, using a very simple physical system as an example. We'll also look at another weird phenomenon called quantum tunneling.
In the first article of this series we introduced Schrödinger's
equation and in the second we saw it in action using a simple example. But how should
we interpret its solution, the wave function? What does it tell us
about the physical world? | <urn:uuid:5286d8e8-6e0a-4907-8d0f-bcb68046e676> | 3.203125 | 466 | Content Listing | Science & Tech. | 50.263635 |
The Radio Aurora Explorer (or RAX) is the first CubeSat mission sponsored by the National Science Foundation to study space weather.
RAX is a joint venture between the University of Michigan and SRI International. Its primary mission objective is to study large plasma formations in the ionosphere, the highest region of our atmosphere. These plasma instabilities are known to spawn magnetic field-aligned irregularities (FAI), or dense plasma clouds known to disrupt communication between Earth and orbiting spacecraft.
To study FAI, the RAX mission will utilize a large incoherent scatter radar in Poker Flats, Alaska (known as PFISR). PFISR will transmit powerful radio signals into the plasma instabilities that will be scattered into space. During that time, the RAX spacecraft will be orbiting overhead and recording the scatter signals with an onboard receiver.
These signal recordings will be processed by an onboard computer and transmitted back to our ground stations where scientists will analyze them. The goal of this one-year science mission is to enhance our understanding of FAI formation so that short-term forecast models can be generated. This will aid spacecraft operators with planning their mission operations around periods of expected communication disruption.
Click here for more information on the RAX mission science.
Click here for a short video explaining what RAX CubeSats do in orbit.
|(Images © RAX Team unless otherwise noted)
(*RAX-1 image courtesy of T. Beck) | <urn:uuid:cfffed81-484c-4176-897e-88c9253d05a2> | 3.484375 | 295 | Knowledge Article | Science & Tech. | 31.91943 |
From the ocean weather will eat this idea alive department comes a ridiculous bit of wishful thinking from the world’s lead scientist on “the coral reefs are going to die and its all your fault” discipline.
Yes, it is our hot headed buddy from Brisbane, Ove Hoegh-Guldberg, with what just might be the wackiest climate change technology proposal ever – it is his blue tarp moment:
Scientists have proposed stringing up shade cloth over coral reefs and sending electric currents through the sea to help marine ecosystems weather the effects of climate change.”
“The paper also discusses the genetic engineering of species to help them adapt better to climate change, and mitigating ocean acidification by adding base minerals to the water.”
Professor Hoegh-Guldberg has pointed out conventional approaches to climate change have so far failed to prevent damage to the reef.”
Here’s the paper: Rau, G., McLeod, E.L. & Hoegh-Guldberg, O. (2012) The need for new ocean conservation strategies in a high-carbon dioxide world Nature Climate Change doi:10.1038/nclimate1555
And here’s the money quote:
In particular, various methods for reducing or mitigating thermal stress in corals have been proposed or demonstrated. For example, efforts to artificially shade sections of a reef during periods of thermal stress using buoyant shade cloth have been applied on the Great Barrier Reef. Light exacerbates the effect of heat stress and causes reef-building corals to bleach. Consequently, shading corals can reduce the extent of coral bleaching.
The Great Barrier Reef has an area of 348,000 square kilometers. It’s bigger than the UK, Holland and Switzerland combined. So perhaps we could just cover 1%, that’s only three and a half thousand square kilometers and then ask the water to stay in one spot?
Not to mention the the first storm that rolls through will pretty much blow any tarps, cloths, covers, etc to bits and beyond. Ah, I love the sound of shredded grant money in the morning.
I should apologize for this comparison to inventor Rube Goldberg, who made wacky looking inventions that actually worked. Ove Hoegh-Guldberg’s invention is not only wacky, but unworkable.
Loved this bit from Jo Nova:
Alistair Hobday Research Scientist – Marine and Atmospheric Research at CSIRO said novel solutions are required. “We need to be mature enough to listen to all sorts of arguments.”
To which Jo Nova, unfunded non government critic said: We need scientists who are mature enough to spot a plan that is bonkers.
h/t to WUWT reader Martin Clark | <urn:uuid:8a888444-ed61-49dc-847b-ae3887928565> | 3.109375 | 584 | Personal Blog | Science & Tech. | 51.680297 |
is the chemical compound with the formula [Co(NH3
. This coordination compound is considered an archetypal "Werner complex", named after the pioneer of coordination chemistry, Alfred Werner
Alfred Werner was a Swiss chemist who was a student at ETH Zurich and a professor at the University of Zurich. He won the Nobel Prize in Chemistry in 1913 for proposing the octahedral configuration of transition metal complexes. Werner developed the basis for modern coordination chemistry...
. This salt consists of [Co(NH3
trications with three Cl−
anions. The term "ammine" refers to ammonia in its metal complexes, and the prefix hex (Greek: six) indicates that there are six ammonias per cation.
Originally this compound was described as a "luteo" (Latin: yellow) complex, but this name has been discarded as modern chemistry considers color less important than molecular structure. Other similar complexes also had color names, such as purpureo (Latin: purple) for a pentammine complex, and praseo (Greek: green) and violeo (Latin: violet) for two isomeric tetrammine complexes.
Properties and structure
is diamagnetic, with a low-spin octahedral
In chemistry, octahedral molecular geometry describes the shape of compounds where in six atoms or groups of atoms or ligands are symmetrically arranged around a central atom, defining the vertices of an octahedron...
Co(III) center. The cation obeys the 18-electron rule
The 18-electron rule is a rule of thumb used primarily for predicting formulas for stable metal complexes. The rule rests on the fact that valence shells of a transition metal consists of nine valence orbitals, which collectively can accommodate 18 electrons either as nonbinding electron pairs or...
and is considered to be a classic example of an exchange inert metal complex. As a manifestation of its inertness, [Co(NH3
can be recrystallized unchanged from concentrated hydrochloric acid
Hydrochloric acid is a solution of hydrogen chloride in water, that is a highly corrosive, strong mineral acid with many industrial uses. It is found naturally in gastric acid....
: the NH3
is so tightly bound to the Co(III) centers that it does not dissociate to allow its protonation. In contrast, labile metal ammine complexes, such as [Ni(NH3
, react rapidly with acids reflecting the lability of the Ni(II)-NH3
bonds. Upon heating, hexamminecobalt(III) begins to lose some of its ammine ligands, eventually producing a stronger oxidant.
The chlorides in [Co(NH3
can be exchanged with a variety of other anions such as nitrate
The nitrate ion is a polyatomic ion with the molecular formula NO and a molecular mass of 62.0049 g/mol. It is the conjugate base of nitric acid, consisting of one central nitrogen atom surrounded by three identically-bonded oxygen atoms in a trigonal planar arrangement. The nitrate ion carries a...
A bromide is a chemical compound containing bromide ion, that is bromine atom with effective charge of −1. The class name can include ionic compounds such as caesium bromide or covalent compounds such as sulfur dibromide.-Natural occurrence:...
, and iodide
An iodide ion is the ion I−. Compounds with iodine in formal oxidation state −1 are called iodides. This page is for the iodide ion and its salts. For information on organoiodides, see organohalides. In everyday life, iodide is most commonly encountered as a component of iodized salt,...
to afford the corresponding [Co(NH3
derivative. Such salts are bright yellow and display varying degrees of water solubility.
is not available, [Co(NH3
is prepared from cobalt(II) chloride
Cobalt chloride is an inorganic compound of cobalt and chloride, with the formula CoCl2. It is usually supplied as the hexahydrate CoCl2·6H2O, which is one of the most commonly used cobalt compounds in the laboratory. The hexahydrate is deep purple in color, whereas the anhydrous form is sky blue...
. The latter is treated with ammonia
Ammonia is a compound of nitrogen and hydrogen with the formula . It is a colourless gas with a characteristic pungent odour. Ammonia contributes significantly to the nutritional needs of terrestrial organisms by serving as a precursor to food and fertilizers. Ammonia, either directly or...
and ammonium chloride
Ammonium chloride NH4Cl is an inorganic compound with the formula NH4Cl. It is a white crystalline salt that is highly soluble in water. Solutions of ammonium chloride are mildly acidic. Sal ammoniac is a name of natural, mineralogical form of ammonium chloride...
followed by oxidation. Oxidants include hydrogen peroxide
Hydrogen peroxide is the simplest peroxide and an oxidizer. Hydrogen peroxide is a clear liquid, slightly more viscous than water. In dilute solution, it appears colorless. With its oxidizing properties, hydrogen peroxide is often used as a bleach or cleaning agent...
Oxygen is the element with atomic number 8 and represented by the symbol O. Its name derives from the Greek roots ὀξύς and -γενής , because at the time of naming, it was mistakenly thought that all acids required oxygen in their composition...
in the presence of charcoal catalyst. This salt appears to have been first reported by Fremy.
The acetate salt can be prepared by aerobic oxidation of cobalt(II) acetate
Cobalt acetate is the cobalt salt of acetic acid. It may also be found as the tetrahydrate.It may be formed by the reaction between cobalt oxide or hydroxide and acetic acid:...
, ammonium acetate
Ammonium acetate is a chemical compound with the formula CH3COONH4 . It is a white solid, which can be derived from the reaction of ammonia and acetic acid...
, and ammonia in methanol. The acetate salt is highly water-soluble to the level of 1.9M (20 °C), vs. 0.26M for the trichloride.
is a component of some protein crystallization methods to help solve their structures by X-ray crystallography
X-ray crystallography is a method of determining the arrangement of atoms within a crystal, in which a beam of X-rays strikes a crystal and causes the beam of light to spread into many specific directions. From the angles and intensities of these diffracted beams, a crystallographer can produce a... | <urn:uuid:2e6d7f9b-7651-4c62-84bc-56a6d341c529> | 3.5625 | 1,455 | Knowledge Article | Science & Tech. | 41.033903 |
Ask a question about 'Lobochilotes'
Start a new discussion about 'Lobochilotes'
Answer questions from other users
is a genus of fish
Fish are a paraphyletic group of organisms that consist of all gill-bearing aquatic vertebrate animals that lack limbs with digits. Included in this definition are the living hagfish, lampreys, and cartilaginous and bony fish, as well as various extinct related groups...
in the Cichlidae family.
It contains the following species:
- Lobochilotes labiatus
Lobochilotes labiatus is a species of fish in the Cichlidae family. It is found in Burundi, the Democratic Republic of the Congo, Tanzania, and Zambia. Its natural habitats are freshwater lakes and inland deltas.-References:... | <urn:uuid:77940f0c-2154-45ef-804a-e5142fa51677> | 3.140625 | 178 | Q&A Forum | Science & Tech. | 33.0103 |
Ask a question about '
Start a new discussion about '
Answer questions from other users
Full Discussion Forum
In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...
of grass in the
The Poaceae is a large and nearly ubiquitous family of flowering plants. Members of this family are commonly called grasses, although the term "grass" is also applied to plants that are not in the Poaceae lineage, including the rushes and sedges...
Grassbase - The World Online Grass Flora | <urn:uuid:1d72a132-3ae7-427f-a079-f20214728d80> | 2.96875 | 127 | Q&A Forum | Science & Tech. | 44.143367 |
Wednesday 15 May
Caterpillar hunting wasp (Delta dimidiatipenne)
Caterpillar hunting wasp fact file
- Find out more
- Print factsheet
Caterpillar hunting wasp description
Named for its habit of hunting caterpillars to feed its young, the caterpillar hunting wasp (Delta dimidiatipenne) belongs to one of the largest orders of insects, the Hymenoptera, which includes the wasps, bees and ants (3) (4). All of the insects in this group have compound eyes, two ocelli, biting mouthparts, and two pairs of membranous wings which are linked together during flight by tiny hooks (3).
The caterpillar hunting wasp has a dull red head, with black markings from behind the eyes to the top of the head, which extend to the back of the neck. The thorax is black, except for two red patches on the second segment and on the upper parts of the third and last segments (2). The thorax and the first segment of the abdomen are fused together, creating a narrow ‘waist’ which is red with some black at the base (2) (3). The abdomen is mainly black, apart from a red band just below the waist. The wings are rust-coloured with grey-brown tips, and may sometimes have a purplish tinge. The tips of the antennae are usually black (2).
The male caterpillar hunting wasp is similar in appearance to the female, although it is slightly smaller and more slender, with a yellow face (2).
- Also known as
- potter wasp, red potter wasp. Top
Walker, D.H. and Pittaway, A.R. (1987) Insects of Eastern Arabia. Macmillan Publishers Ltd., London. Available at:
Abu Dhabi Environment Agency:
- In arthropods (crustaceans, insects and arachnids) the abdomen is the hind region of the body, which is usually segmented to a degree (but not visibly in most spiders). In crustacea (e.g. crabs) some of the limbs attach to the abdomen; in insects the limbs are attached to the thorax (the part of the body nearest to the head) and not the abdomen. In vertebrates the abdomen is the part of the body that contains the internal organs (except the heart and lungs).
- Pair of sensory structures on the head of invertebrates
- Stage in an animal’s lifecycle after it hatches from the egg. Larvae are typically very different in appearance to adults; they are able to feed and move around but usually are unable to reproduce.
- A simple eye which has a single, thickened, cuticular lens.
- Part of the body located near the head in animals. In insects, the three segments between the head and the abdomen, each of which has a pair of legs. In vertebrates the thorax contains the heart and the lungs.
ITIS (January, 2011)
- Srinivasan, G. and Girish Kumar, P. (2010) New records of potter wasps (Hymenoptera: Vespidae: Eumeninae) from Arunachal Pradesh, India: five genera and ten species. Journal of Threatened Taxa, 2(12): 1313-1322.
- Walker, D.H. and Pittaway, A.R. (1987) Insects of Eastern Arabia. Macmillian Publishers Ltd, London.
- O'Toole, C. (2002) The New Encyclopedia of Insects and their Allies. Oxford University Press, Oxford.
- Dvorak, L. and Castro, L. (2007) New and noteworthy records of vespid wasps (Hymenoptera: Vespidae) from the Palaearctic region. Acta Entomologica Musei Nationalis Pragae, 47: 229-136.
- Preston-Mafham, R. and Preston-Mafham, K. (1993) The Encyclopedia of Land Invertebrate Behaviour. MIT Press, Cambridge, Massachusetts.
Emirates Natural History Group (January, 2011)
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- teachers, lecturers and students may incorporate the Material in their educational material (including, but not limited to, their lesson plans, presentations, worksheets and projects) in hard copy and digital format for use within a registered educational establishment, provided that the integrity of the Material is maintained and that copyright ownership and authorship is appropriately acknowledged by the End User.
Caterpillar hunting wasp biology
Nest building is a characteristic behaviour of the caterpillar hunting wasp. The female constructs a nest from sand or mud (3), using its jaws to feed the dry material into the scooped front legs and mixing it with saliva from the mouth to form a kind of plaster (4) (6). The wasp then lays down pellets of mud by dribbling the wet clay onto the nest, moulding the material into a small mud pot (3) (4) (6). The caterpillar hunting wasp uses its antennae to gauge the shape and size of the nest, finishing it off by adding a slight lip to the entrance (3) (7). The nest is hung from walls or rocks and hardens as it dries (3) (7).
Once the nest is complete, the female caterpillar hunting wasp lays a single egg inside the chamber, suspending it from the roof by a thread of silk (3) (6) (7). The female provisions the nest with several caterpillars, which are eaten by the larva during its development inside the nest (4) (7). The adult caterpillar hunting wasp feeds on nectar (2).Top
Caterpillar hunting wasp range
A wide-ranging species, the caterpillar hunting wasp is found from northwest Africa, Egypt and Somalia, throughout the Middle East, and east to India and Nepal (2) (5). The caterpillar hunting wasp is also found in the Canary Islands, where it has recently become established and is now widespread (5).Top
Caterpillar hunting wasp habitat
The caterpillar hunting wasp is known from a variety of desert habitats (6).Top
Caterpillar hunting wasp status
The caterpillar hunting wasp has yet to be assessed by the IUCN.Top
Caterpillar hunting wasp threats
There are no known threats to the caterpillar hunting wasp.Top
Caterpillar hunting wasp conservation
There are no known conservation measures in place for the caterpillar hunting wasp.Top
Find out more
Find out more about insects of the Middle East:
Find out more about conservation in the United Arab Emirates:
This information is awaiting authentication by a species expert, and will be updated as soon as possible. If you are able to help please contact:
More »Related species
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Last month, during routine functional performance testing of the mutibeam mapping echosounders on the Schmidt Ocean Institute
s flagship R/V Falkor, the team aboardincluding researchers from the University of New Hampshire, Ifremer, and Woods Hole Oceanographic Institutiondiscovered the S.S. Terra Nova, a whaler, sealer and polar exploration ship that sunk off the southern coast of Greenland in September, 1943, after being damaged by ice.
The performance verification of R/V Falkors scientific echo sounders precedes oceanographic research cruises set to begin in 2013. The tests included a shallow water survey off the southern coast of Greenland to assess the Kongsberg EM710 multibeam mapping echo sounders performance in complex topography. The testing took place on July 11, 2012, as part of the planned R/V Falkor field trials during the transit of the vessel from Newcastle, UK to Nuuk, Greenland.
Researchers selected the test survey site for several reasons: It allowed testing of ship's mapping capabilities at seafloor depths between 10 and 1800 meters, and the glacial activity in the area created distinct and prominent seafloor features. Because of the glaciers, the Schmidt Ocean Institute survey team expected to see mixtures of deposits from soft sediment to gravel and boulders deposited by icebergs and glaciers. Different seabed compositions enable testing of the reception quality of the high/low back scatter signals by the multibeam system. Icebergs common to the area leave significant gouging marks on the seabed, which would effectively test bathymetric mapping data.
In addition to meeting all of these criteria for the test site, the region was also familiar to Schmidt Ocean Institute Marine Technician Leighton Rolley, who had read that the polar exploration vessel S.S. Terra Nova was reported lost off Southern Greenland in 1943. With all the topographical considerations and with the secondary possibility of using a wreck as a calibration reference for the sonar equipment, the Schmidt Ocean Institute had prioritized this location as the optimal spot for this round of tests.
Approximate estimated position of the wreck was used as the central point for the test survey. An area roughly five nautical miles around this position was selected for the survey to encompass various features, shallows and slopes necessary to evaluate the sonar performance.
As a result of the survey, the chosen area yielded excellent topographical data that enabled comprehensive verification of the EM710 performance. The bathymetric data produced by EM710 during these sonar trials was of very high quality, substantially exceeding expectations. All members of a collaborative group of sonar experts from Schmidt Ocean Institute, University of New Hampshire, and Ifremer who were present on-board to evaluate the systems operational capabilities were satisfied with the outcomes of the sonar trials.
As anticipated, numerous iceberg strikes and gouges were observed on the seabed along with striking features not listed on the existing nautical charts. The contrast between hard and soft sediment signatures exceeded expectations. Gullies and gouges had collected soft sediment, while the surrounding flat seabed consisted largely of gravel and coarse material deposited by icebergs and glaciers with clearly contrasting backscatter.
On the first line of the calibration survey, on-board survey expert Jonathan Beaudoin from the University of New Hampshire had noted a feature on the seabed which remained initially unidentified. Upon completion of the main calibration exercise, SOI technician Leighton Rolley and Jonathan reviewed each of the many potential targets identified during the 12 hours of surveying, and the target was noted as a strong candidate for further investigation. Multibeam data expert Jean Marie from Ifremer analyzed the feature in more detail, finding its length (57m) to match the reported length of the Terra Nova.
Encouraged by the similarity in length, the acoustic survey team post-processed the collected multi-beam data to verify the observed feature. A shorter survey from several angles reaffirmed the possibility that the team had found a wreck.
During the earlier stages of the transatlantic cruise, the Schmidt Ocean Institute marine technicians had an opportunity to develop a weighted camera package to film the plankton net trawls conducted by scientists aboard R/V Falkor from Woods Hole Oceanographic Institution. This footage was designed for community outreach work to show how these nets capture plankton which our scientists then study.
This camera package (Simple High Resolution IMaging Package, or SHRIMP), a solid metal frame with two attached cameras and three to four dive flashlights for light to document the planned plankton net tows. As the observed feature lay within the depth range of the SHRIMP, the Schmidt Ocean Institute team decided to use the camera to take a closer look.
The package dropped to a position just above the target to help identify the nature of this 57 m long feature observed in the EM710 output mapping data. Camera tows across the top of the target showed the remains of a wooden wreck laying on the seabed. The camera footage also identified the funnel of the vessel, next to the wreck. The forecastle of the vessel appeared to be peeled upwards to the port side and at an angle from the rest of the ship. The team compared the funnel image with historical photographs of the S.S. Terra Nova. All observations jointly identified this wreck as the sunken S.S. Terra Nova.
The discovery of the lost S.S. Terra Nova, one of the most famous polar exploration vessels, was an exciting achievementin addition to serving to successfully verify the performance and operational condition of the Schmidt Ocean Institute's R/V Falkor multibeam echo sounders. The discovery was made possible thanks to the collaborative and exhaustive efforts of all those onboard. Schmidt Ocean Institute offers its profound thanks to the sonar experts and scientific representatives from the University of New Hampshire, Ifremer, and Woods Hole Oceanographic Institution for their excellent support throughout this cruise.
S.S. Terra Nova was discovered during the testing of R/V Falkor scientific multibeam echo sounders. The permit for the instrument testing off the southern coast of Greenland was issued to the Schmidt Ocean Institute by the United States Department of State. When the permit was issued, the U.S. Department of State requested that the Schmidt Ocean Institute does not release information about any possible wreck discoveries that may occur as a result of the sonar testing unless authorized to do so by the U.S. government.
In compliance with this requirement, upon the discovery of the wreck, Schmidt Ocean Institute first informed the U.S. Department of State. Following consultations with the appropriate authorities in the United Kingdom and Denmark governments, the U.S. Department of State authorized the Schmidt Ocean Institute to release the information about this discovery, as long as the exact location or depth of the wreck are not disclosed to protect the site of obvious historical significance from unwanted attention.
Written for the Schmidt Ocean Institute by Leighton Rolley, Marine Technician aboard R/V Falkor and edited by Genny Biggs | <urn:uuid:87915c08-b164-4029-bc5b-df6528b42165> | 2.765625 | 1,442 | Knowledge Article | Science & Tech. | 33.138361 |
© Wikimedia Commons, Creative Commons Attribution-Share Alike 3.0 license. Author: Sponk, 23 March 2010.
These two molecules, RNA on the left and DNA on the right, form the basis of life as we know it. They have a remarkably simple structure, each being made of a set of four base molecules called nitrogenous bases. The bases of DNA form pairs, which attach to one another and twist into a double helix, while RNA forms a single helix. Biologists can study how DNA replicates and how the instructions contained within its molecular structure are carried out through chemical reactions in a living organism. Predicting the emergent phenomenon of life and how each organism with its own unique features arises from the structure of these molecules is far more difficult. (Unit: 9) | <urn:uuid:231af621-93cf-4506-a218-413a92dd4075> | 3.9375 | 163 | Knowledge Article | Science & Tech. | 44.26323 |
Software Design (CSC-223 97F)
Outline of Class 12: Tools
- A reminder that majors should see Mr. Imig to have your pictures taken
for the majors' board.
- The reading on greedy algorithms
is almost ready.
- For the first part of
you only have to recreate your fellow student's
routine (although you will do so in a separate class).
- Tony and Omar will be presenting on Monday instead of Friday.
- Anyone who hasn't made their directory readable (Kevin N., ...)
better do so asap.
- We'll spend some time today discussing a few Java issues that you
seem to be having probems with.
- I've made some fairly significant modifications to the
syllabus. We'll be doing algorithms
next week, instead of this week; and doing
make this week
instead of next week.
- In helping some of you folks (and hearing from Andrew about some of
the more common problems), it seems that there are a few more things
that we need to cover in a little more depth.
- Don't initialize non-static fields when you declare them.
Initialization (particularly initialization that involves allocation)
should be done in your constructor.
- Remember that
static (also known as "class")
variables and methods are associated
with the class as a whole (although they can also be used in conjunction
with individual objects).
- You need not create objects (instantiate the class) to use
static variables and methods.
- All the objects in a class share the static variables, so
a change in one will affect all objects.
- Non-static methods and fields can only be used in conjunction with
- You must create objects to use these methods and fields
(even if you're working within the same "class").
- Within a non-static method, you can refer to other non-static
methods and fields.
- Within a static method, you need to create an object in order
to use that object's non-static methods and fields.
main method is a static method. You can,
however, create objects in the current class for use iwthin that
- In creating constructors for subclasses, you will often want to call the
constructor of the superclass. The constructor for a superclass is called
- An odd coding tip. Rather than doing comparision with
var == value
value == var
(so that it won't compile if you mistakenly use one equal sign
instead of two).
- There's a link to the standard Java API in my home directory.
- Since RCS keeps track of a number of things, such as the author of
the latest version of your code (and even the "number" of the latest
version of your code), there's no reason for you to have to hand-code
- RCS permits you to insert a number of keywords of the
$keyword$ in your code, and replaces them
- Particularly useful ones are
- I'd caution against using
$Author$ as that only gives
you the author of the latest revision.
- Other keywords are documented in the man page for
- Even with the most modular design, there will be times that more
than one programmer will need to work on the same file (but hopefully
on different parts of the same file).
- There are also times that you might want to try different extensions to
the same piece of code.
- RCS supports version trees to accomodate these and similar
- The tree is given by the numbering hierarchy.
- The main branch of the tree has versions of the form
- Primary branches have versions of the form
- To start a new version tree, use the
-r option when you
check in a file. If you give three parts (e.g., a.b.c) to the version
number, it should start a new branch of the form a.b.c.1
- You can use
rcsmerge to merge in changes to a document
rcsdiff to compare two versions.
rcsmerge doesn't seem to work with the
fields mentioned above (at least in my tests). That is, if you use
the fields in comments,
- The form of
rcsmerge is a little odd.
rcsmerge -rrev1 -rrev2 file
finds the changes between rev1 and rev2 and
then makes those changes to the current version of the file (which
should be checked out).
- You can learn more about the rcs version tree by looking at the man
- Some of the following instructions are left purposefully vague so that you
think about how to express them in RCS.
- I also want you to get used to reading manual pages.
- Create a simple Java class with no body.
- Add it to an RCS archive (with
rcs -i and
- Add a field within that class. Check in the modified version as part
of a new branch.
- Return to the main branch.
- Add a
- Check that in as part of the main branch.
rcsdiff to compare your changes.
- Merge your two versions together.
- Try the same, but using overlapping changes. | <urn:uuid:4af8a46a-544c-4020-ac62-bfe48ca74a35> | 3.28125 | 1,129 | Documentation | Software Dev. | 66.082257 |
Many of the questions asked in #postgresql revolve around using sequences in PostgreSQL. To avoid answering the same questions again and again, I thought it would be worthwhile to summarize the basic steps involving in using sequences in PostgreSQL.
A sequence is a special kind of database object designed for generating unique numeric identifiers. It is typically used to generate artificial primary keys. Sequences are similar, but not identical, to the AUTO_INCREMENT concept in MySQL.
Sequences are most commonly used via the
serial pseudotype. A
serial is a special data type that encodes the following
For example, this command creates both a new table and a new sequence
generator, and associates the sequence with the
id column of the table:
test=# CREATE TABLE users ( test(# id SERIAL, -- assign each user a numeric ID test(# name TEXT, test(# age INT4 test(# ); NOTICE: CREATE TABLE will create implicit sequence "users_id_seq" for serial column "users.id" CREATE TABLE
In this case, the sequence is automatically assigned the name users_id_seq. To avoid hard-coding the name of the sequence in SQL queries, we can use the pg_get_serial_sequence() function, as described below.
Note that using
serial does not implicitly create an
index on the column, or mark the column as a primary key. That can
be easily done, however:
CREATE TABLE users ( -- make the "id" column a primary key; this also creates -- a UNIQUE constraint and a b+-tree index on the column id SERIAL PRIMARY KEY, name TEXT, age INT4 );
If you're using
serial, the default value for the serial column will
be the next value produced by the sequence. To specify that an
INSERT should take the default value for a given column, either
omit that column from the INSERT's column list, or specify
the DEFAULT keyword as the column's value.
INSERT INTO users (name, age) VALUES ('Mozart', 20);
INSERT INTO users (name, age, id) VALUES ('Mozart', 20, DEFAULT);
You can use the currval() function, which returns the most recent value generated by a sequence for the current session. currval() takes a single parameter: the name of the sequence. We can use the function pg_get_serial_sequence() to find the name of the sequence associated with a given serial column:
SELECT currval(pg_get_serial_sequence('users', 'id'));
Note that if no values have been generated by the sequence yet in the current session, currval() will yield an error.
That is, if one database client inserts a row into a table that includes a sequence-generated value, wouldn't it be possible for another insertion into the table to modify the sequence, causing a subsequent currval() by the first client to return the wrong results?
No: sequences were designed to elegantly avoid this problem. currval() returns the last value generated by the sequence for the current session: if concurrent database clients generate sequence values, the currval() seen by a given session does not change (until the session generates a new sequence value, for example).
To use the currval() method shown above, we'd need two queries: one to insert into the table, and another to fetch the sequence value assigned to the new row. Since client-server roundtrips can be expensive, this is not ideal. One way around this is to send the INSERT and the SELECT as a single query string. For example, in PHP:
pg_exec("INSERT INTO users (name, age) VALUES ('Bach', 15); SELECT currval(pg_get_serial_sequence('users', 'id'));")
This executes two queries, but does only a single roundtrip between the client and server, so the additional performance overhead of the second query should be negligible.
Alternatively, users of PostgreSQL 8.2 and later can take advantage of the INSERT ... RETURNING clause:
INSERT INTO users (name, age) VALUES ('Liszt', 10) RETURNING id;
which returns the value of the
id column for the newly-inserted row.
Sequences generate 64-bit signed integers. The
that we used above is a 32-bit signed integer: if you want to use the
full 64-bit range of the underlying sequence, use the
Yes, there can. Sequences are intended for generating unique identifiers — not necessarily identifiers that are strictly sequential. If two concurrent database clients both attempt to get a value from a sequence (using nextval()), each client will get a different sequence value. If one of those clients subsequently aborts their transaction, the sequence value that was generated for that client will be unused, creating a gap in the sequence.
This can't easily be fixed without incurring a significant performance penalty. For more information, see Elein Mustein's "Gapless Sequences for Primary Keys" in the General Bits Newsletter.
Sequence operations are essentially non-transactional. nextval() increments the value of the sequence and is not rolled back if its transaction is later aborted; currval() returns the last value generated by the sequence for the current session, regardless of transaction boundaries.
The easiest way to do this is to create the sequence by hand, and
then set the default clauses for the sequence-generated columns by
hand, rather than using the
CREATE SEQUENCE common_fruit_id_seq; CREATE TABLE apples ( id INT4 DEFAULT nextval('common_fruit_id_seq') NOT NULL, price NUMERIC ); CREATE TABLE oranges ( id INT4 DEFAULT nextval('common_fruit_id_seq') NOT NULL, weight NUMERIC );
nextval() is a function that produces a new sequence value.
Note that when using sequences in this manner, the sequence won't be automatically dropped when the table is dropped, and you won't be able to use pg_get_serial_sequence().
Consult the PostgreSQL documentation: | <urn:uuid:51f6042f-3356-478d-8012-b8f369d54415> | 3.421875 | 1,316 | Documentation | Software Dev. | 33.238336 |
A CONTRACEPTIVE spray for plants is being developed that could eradicate certain weeds from farmers' fields and cut herbicide use.
Ed Newbigin of Melbourne University and colleagues at CSIRO, Australia's national research organisation, are planning to exploit the mechanism that prevents certain plants self-fertilising. They want to target the "self-incompatibility" (SI) receptor present on the stigma of some plant species, which blocks self-pollination by binding to a pollen protein specific to that individual plant.
The team is developing a molecule that will bind to the SI receptor in wild radish, a weed that infests barley, wheat and rape (canola). This will prevent seeds from forming, so the weed will die out. Because the wild radish's SI mechanism is unique to its family of plants, the spray would have no effect on grain crops such as barley and wheat, which have no SI mechanism at all.
"We aim to use this ...
To continue reading this article, subscribe to receive access to all of newscientist.com, including 20 years of archive content. | <urn:uuid:d04af281-58bc-4c6f-8cb2-b82d72defbc5> | 3.0625 | 228 | Truncated | Science & Tech. | 49.52613 |
Diamonds are the hardest solid materials we know, and the ghostly space-age materials known as aerogels are the least dense. Looking for a challenge, scientists at Lawrence Livermore National Laboratory decided to combine these substances and turn out a spongy, translucent version of a girl’s best friend.
Future humans won't have to wait to travel to Pandora for the chance to mine unobtanium, because Neptune and Uranus may have diamond icebergs floating atop liquid diamond seas closer to home. The surprise finding comes from the first detailed measurements of the melting point of diamond, Discovery News reports.
Five amazing, clean technologies that will set us free, in this month's energy-focused issue. Also: how to build a better bomb detector, the robotic toys that are raising your children, a human catapult, the world's smallest arcade, and much more. | <urn:uuid:4855b894-2bed-4c01-90aa-4216952a39a2> | 3.0625 | 178 | Content Listing | Science & Tech. | 34.742069 |
Changes of Land Cover and Land Use and Greenhouse Gas Emissions in Northern Eurasia: Impacts on Human Adaptation and Quality of Life at Regional and Global Scales
Funded by the National Science Foundation
Northern Eurasia accounts for about 20% of the Earth’s land surface and 60% of the terrestrial land cover north of 40°N. It contains 70% of the Earth's boreal forests and more than two-thirds of the Earth's land that is underlain by permafrost. The region is covered by vast areas of peatland, complex tundra in the north and semi-deserts and deserts in the south, including the Mongolia plateau. The surface air temperature has increased in the last half century and this increase will continue during this century. To date, studies have generally focused on analyzing climate change effects on biogeochemical processes and mechanisms governing the carbon and water dynamics in the region or potential changes in the distribution of natural vegetation. While the team will also examine such issues, they will focus on how patterns of land use in Northern Eurasia may change in the future due to the following:
- Economic pressures for providing food, fiber and fuel to a growing global population.
- Opportunities for expanding managed ecosystems into areas that experience a more favorable climate in the future.
- Abandonment of managed ecosystems in other areas that experience a less favorable climate.
The research team will examine how these future changes in land use and land cover could influence the exchange of CO2 and CH4 between terrestrial ecosystems and the atmosphere, terrestrial carbon storage and primary productivity, water supply, and radiative forcing of the atmosphere through changes in surface albedo. They will also assess how human adaptation and quality of life may be impacted by these changes. To conduct this analysis, a system of linked models that include the MIT Emissions Prediction and Policy Analysis (EPPA) model of the world economy, the SiBCliM bioclimatic vegetation model, and the Terrestrial Ecosystem Model (TEM) will be used.
The multi-disciplinary U.S. scientific team includes ecosystem scientists, biogeochemical modelers, and economists, which will be complemented by international collaborators from the Russian Academy of Sciences, the International Institute of Applied Systems Analysis (IIASA) in Austria, the National Institute for Environmental Studies in Japan, and the Chinese Academy of Sciences.
- Qianlai Zhuang, Departments of Earth & Atmospheric Sciences and Agronomy
203 S. Martin Jischke Drive
West Lafayette, IN 47907
- Phone: 765-494-5146
- Fax: 765-496-9322 | <urn:uuid:900bd8a6-5910-4743-ad12-608e4f72fb16> | 3.21875 | 547 | Knowledge Article | Science & Tech. | 21.034106 |
Wild Things: Life as We Know It
Cobras, sharks, lemurs, hermit crabs and more...
- By T. A. Frail, Megan Gambino, Laura Helmuth, Erica R. Hendry and Abigail Tucker
- Smithsonian magazine, July-August 2010,
(Franco Banfi / Photolibrary)
Scientists suspected that the common thresher shark used its long tail to capture food—and now they have video to prove it. Researchers working off the coast of Southern California with an underwater camera recorded 29 shark strikes. In the 19 successful strikes, a shark swung the upper part of its caudal fin to hit and stun a fish, immobilizing its prey before digging in to eat.
“Birch (Betula spp.) leaves adsorb and re-release volatiles specific to neighbouring plants – a mechanism for associational herbivore resistance?” Sari J. Himanen et al., New Phytologist, March 10, 2010
“A seasnake’s colour affects its susceptibility to algal fouling,” R. Shine et al., Proceedings of the Royal Society B, April 7, 2010
“Mate choice and mate competition by a tropical hummingbird at a floral resource,” Ethan J. Temeles and W. John Kress, Proceedings of the Royal Society B, February 3, 2010
“Socially induced brain development in a facultatively eusocial sweat bee Megalopta genalis (Halictidae),” Adam R. Smith et al., Proceedings of the Royal Society B, March 24, 2010
“Conditioned taste aversion enhances the survival of an endangered predator imperiled by a toxic invader,” Stephanie O’Donnell et al., Journal of Applied Ecology, April 13, 2010 | <urn:uuid:a3a1ba0b-f035-4052-b67a-95e30dc5d19a> | 3.109375 | 384 | Content Listing | Science & Tech. | 50.083391 |
As it happens, we are building a lot of flat-screen TV sets and computer monitors these days. Gallium is thought to make up 0.0015 percent of the Earth’s crust and there are no concentrated supplies of it. We get it by extracting it from zinc or aluminum ore or by smelting the dust of furnace flues. Dr. Reller says that by 2017 or so there’ll be none left to use. Indium, another endangered element—number 49 in the periodic table—is similar to gallium in many ways, has many of the same uses (plus some others—it’s a gasoline additive, for example, and a component of the control rods used in nuclear reactors) and is being consumed much faster than we are finding it. Dr. Reller gives it about another decade.
Read more. Very interesting. Via. | <urn:uuid:61882820-cbfa-46af-b6fd-554281502917> | 3.1875 | 180 | Truncated | Science & Tech. | 67.10875 |
Data reported by the weather station: 916500 (NFNR)
Latitude: -12.5 | Longitude: 177.05 | Altitude: 26
|Main||Year 1986 climate||Select a month|
To calculate annual averages, we analyzed data of 362 days (99.18% of year).
If in the average or annual total of some data is missing information of 10 or more days, this is not displayed.
The total rainfall value 0 (zero) may indicate that there has been no such measurement and / or the weather station does not broadcast.
|Annual average temperature:||27.0°C||362|
|Annual average maximum temperature:||29.1°C||362|
|Annual average minimum temperature:||25.4°C||362|
|Annual average humidity:||-||-|
|Annual total precipitation:||3394.72 mm||361|
|Annual average visibility:||42.6 Km||362|
|Annual average wind speed:||8.3 km/h||362|
Number of days with extraordinary phenomena.
|Total days with rain:||188|
|Total days with snow:||0|
|Total days with thunderstorm:||19|
|Total days with fog:||1|
|Total days with tornado or funnel cloud:||0|
|Total days with hail:||0|
Days of extreme historical values in 1986
The highest temperature recorded was 31.5°C on March 21.
The lowest temperature recorded was 20.4°C on July 20.
The maximum wind speed recorded was 64.8 km/h on December 24. | <urn:uuid:1d2dd612-0156-46fc-bffe-0eb281b51340> | 2.859375 | 358 | Structured Data | Science & Tech. | 72.600303 |
New Scientist said:
The standard model of particle physics assumes the Higgs boson is an elementary particle. But what if, rather like the proton, it is itself made up of particles?
We know the standard model is incomplete because it cannot explain all the phenomena we observe (see "Beyond Higgs: Deviant decays hint at exotic physics"). Tweaking the model to make the Higgs a composite of quark-like particles, bound together by a new force, could solve this problem. It turns out that there is more than one way to arrange these new particles and forces to produce something akin to dark matter.
To see if the boson reported last week at CERN near Geneva, Switzerland, could be such a composite, Alex Pomarol from the Autonomous University of Barcelona in Spain has started to compare decay data for the new particle with predictions of how a composite Higgs would decay inside the Large Hadron Collider. He told the International Conference on High Energy Physics in Melbourne, Australia, that the observed decays are not outside the range predicted by composite models - and that a composite Higgs is a possibility. | <urn:uuid:5efb2282-4e56-49c0-9b50-825db8ffb64b> | 3.140625 | 231 | Comment Section | Science & Tech. | 29.275 |
Upper Level Low - Meteorological Physical Background
by ZAMG and FMI
Upper Level Lows are closed cyclonically circulating eddies in the middle and upper troposphere. They are sometimes also called "cold drops", because the air within an Upper Level Low is colder than in its surroundings.
The development of a typical Upper Level Low goes through four stages, during which a bottom of an upper trough is detached from the main stream, until it finally fills up or merges with another trough:
- Upper level trough
- Final stage
1. Upper Level Trough stage
The prerequisite of the forming of the Upper Level Low are unstable waves within the main stream, where the temperature wave is behind the geopotential wave.
- There is cold advection within the trough and warm advection on the ridge of the geopotential wave.
- The vertical axis of the trough has a backward-oriented inclination with height.
- The amplitudes of the waves increase; the wavelenght can decrease.
Cyan: 500 hPa geopotential height, green: 500 hPa temperature
2. Tear-off stage
- The amplitudes of the waves increases further.
- The isohypses form an inverse omega-shape and the cold air flows into the middle of this omega.
- Often at the same time the ridge behind the main upper trough continues to move eastward quicklier than the trough, appearing to "fall
- In the end of this stage the cold bottom of the trough is detached from the main stream.
3. Cut-off stage
- The bottom of the upper trough is completely detached from the main stream forming a closed circulation.
- If there is a strong forward-falling ridge behind, it may also separate from the main stream and form an upper level high (a counterpart for the
upper level low). This happens in most of the ULL cases.
- The cold core of the Upper level Low warms up slowly because of the diabatic warming of the sinking clod air.
- If a cold Upper Level Low is situated over a warm surface, convection arises within the core. This occurs especially over the Atlantic Ocean
(Canarian Isles) and over the Mediterranean in summertime.
- Another location for convection is ahead of the low within the area of a thickness ridge.
4. Final stage
Within an Upper Level Low there is convection, unless the surface is very cold. The air near the surface is warm and the circulation is slowed down by the friction. The convection brings warm air and friction upwards. Consequently, the Upper Level Low weakens slowly.
- In most cases the Upper Level Low merges with the main stream before it has completely dissolved by the convection. Usually a large trough in
the main stream approaches from the rear and catches the upper level low.
- The Upper Level Low can also merge with another Upper Level Low.
For an example see Key Parameters.
If the Upper Level Low is far from the main stream, it can dissolve solely by convection. This kind of development occurs mostly in southern areas; in Europe they can be found over the Mediterranean.
Upper Level Lows can be divided into two classes according to their size and lifetime:
- small lows with a lifetime of 2-4 days
- big lows with a lifetime of 5-14 days
Big lows are slightly more common than small ones.
Note that over land an Upper Level Low can also form when a surface low of an extratropical cyclone disappears due to friction. This is just a late stage of a cyclone development and the upper low fills up relatively quickly. | <urn:uuid:c339e705-48c2-47be-ae5a-bf00d6e80176> | 4.0625 | 765 | Knowledge Article | Science & Tech. | 50.072835 |
Wildlife Spectacle: The Butterfly Effect
Monarch butterflies, each smaller than the palm of your hand, migrate thousands of miles every year, thus ensuring the survival of the species.
From November to March, black-and-orange flecks fill the sky in central Mexico’s mountains and along the California coast. These airborne dots are monarch butterflies (Danaus plexippus) flitting about in their winter habitat. They flutter and float by day; before the sun disappears, they glide to the trees and gather in clusters, creating a forest of tangerine-tinted trunks as they huddle together for warmth. Anyone lucky enough to witness this display is privy to a mysterious phenomenon. Though these animals, part of the Lepidoptera insect order, weigh only as much as a paper clip, they migrate up to 3,000 miles annually, using the sun’s position in the sky to stay on course. Their Mexican wintering sites were unknown until 1975, when Kenneth Brugger, working with monarch researchers Fred and Norah Urquhart, discovered a colony on Sierra Pelon, an 11,483-foot mountain.
Click on the thumbnail images below to download PDFs of the pullout.
The Flight Cycle
The monarch migration is unlike that of any other Lepidoptera. As August days grow shorter and cooler, the butterflies emerge across the northern United States and southern Canada. They gorge on nectar in preparation for their long journey. Scientists don’t fully understand which cues trigger monarchs to move to warmer climes, but some surmise it’s based on the sun’s angle in the sky. Monarchs west of the Colorado Rockies—a tiny percentage of the world’s population—head toward the Pacific Ocean, taking up residence in Monterey pines and eucalyptus trees along California’s coast. The millions-strong eastern population migrates to oyamel fir forests high atop 12 mountains in central Mexico. The trees, which grow only at altitudes of roughly 7,900 to 11,800 feet, offer a cool, protected, moisture-filled environment where the butterflies live out the winter. All migrating swarms reach their destinations by mid-November. In March, as the days lengthen, the overwintering butterflies start to produce the hormones their bodies need to create the next generation. The insects fly north, each female laying hundreds of eggs on milkweed plants in the southern United States. Finally, after fulfilling their reproductive responsibilities, these nine-month-old monarchs die. Their offspring, which live just three to five weeks, take over, like a relay team with a twofold mission: to move north and to procreate as they go. One generation after the next—up to four—pushes toward Canada, mating and laying eggs before dying. Likely spurred by late summer’s shorter days, the last generation, which will live for up to nine months, turns around and heads south, starting the process again.
An Endangered Habitat
North America’s monarchs may number in the hundreds of millions, but both their breeding and wintering grounds are at risk. Between the thousands of acres lost daily to development and the widespread, indiscriminate use of herbicides, good monarch habitat—particularly that containing milkweed, which is absolutely key to these butterflies—is disappearing fast. Meanwhile, development along California’s valuable coast, and demand for Mexico’s oyamel fir trees, used to build furniture and houses, mean potentially fewer places for the insects to settle during cold months. What’s more, as the firs are cut down—both legally and illegally—the loss of trees and the resulting drop in temperature make the Mexican forests inadequate habitat for the butterflies.
Females lay hundreds of eggs but don’t play favorites, usually depositing each egg on a different milkweed plant.
In the two-week larval stage, the caterpillar feeds on milkweed and molts five times before entering chrysalis.
The cocoon-like pod looks green but is actually clear. It turns brown, yellow, and orange before the monarch emerges.
It’s easy to tell males and females apart. Females, like this one, lack a black spot on the back of each wing.
As evening approaches, monarch butterflies huddle together to keep warm, swathing tree trunks with their clusters. These colorful insects are among the millions that migrate thousands of miles from the northeastern United States and southern Canada to their winter sanctuary near Angangueo, Mexico.
- Each Mexican colony hosts individuals from various parts of the eastern population. That means that even if one winter colony suffers a catastrophe, there will still be monarchs from others to head north and reproduce throughout the species’ summer range.
- Monarchs fly 25 to 30 miles a day (farther in favorable conditions) for several weeks to reach their winter homes.
- Small populations of these majestic butterflies also live outside of North America, in Australia, Indonesia, the Canary Islands, and Spain.
- It’s romantic to believe the popular myth that monarchs return to the exact trees to which their great-grandparents migrated, but it’s simply not true. They do, however, travel to the same regions as their ancestors.
WHAT YOU CAN DO
The easiest way to help monarchs is to plant milkweed, which is essential to their larval and pupal stages, and other nectar sources. You can create supporting habitat in home gardens, parks, almost anywhere. Perennials such as black-eyed Susans and annuals such as zinnias are good nectar sources, but dozens of other flower species will do the trick as well. You can also track monarch arrivals and departures in your area, and report your findings to Monarch Watch, Journey North, or other similar organizations.
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Expressions are used in a variety of contexts within SQL statements, particularly in search condition predicates and the
An expression always evaluates to a single value.
The syntax of an expression is as follows:
Note: A user-defined-function is created by using the CREATE FUNCTION statement.
A unary operator operates on only one operand.
The prefix operator
+(unary plus) does not change its operand.
The prefix operator
-(unary minus) reverses the sign of its operand.
A binary operator operates on two operands.
The binary operators specify addition (
+), subtraction (
-), multiplication (
*) and division (
/) for numerical operands, and concatenation (
||) for string operands.
Note: The operand of a binary operator may not be a set function that includes the keyword DISTINCT.
When a column name is used as an operand, it represents the single value contained in the column for the row currently addressed when the expression is evaluated.
The column name may be qualified by the name of the table or view, see Identifiers.
Evaluating Arithmetical Expressions
Expressions within parentheses are evaluated first. When the order of evaluation is not specified by parentheses, the customary arithmetical rules apply, i.e. multiplication and division are performed before addition and subtraction and operators with the same precedence are applied from left to right.
If any operand in an expression is
NULL, the whole expression evaluates to
NULL. No other expressions evaluate to
NULL. Division by zero results in a run-time error.
Arithmetical expressions with mixed numerical and character data are illegal.
Note: Where host variables are used in expressions, type conversion may result in apparently incompatible data types being accepted, see Data Types in SQL Statements.
The type and precision of the result of an arithmetical expression is determined in accordance with the rules described below. If there are more than two operands in an expression, the type and precision of the result is derived in accordance with the sequence in which the component binary operations are performed.
Formal Evaluation Rules
Formally, the arithmetical rules are summarized as follows:
INTEGER(p)2 DECIMAL(p, s)3
1p = max(15, p', p")
2operators +, -: p = min(45, max(p', p")+1)
operator *: p = min(45, p'+p")
operator /: p = p'
3operator +, -: p = min(45, max(p'-s', p"-s")+max(s', s")+1), s = max(s', s")
operator *: p = min(45, p'+p"), s = min(45, s'+s")
operator /: p = min(45, max(15, p'+p")), s = p-(p'-s')-s"
Descriptive Evaluation Rules
In descriptive terms, the rules are as follows:
- If any of the operands is floating point, the result is floating point.
- If all the operands are integer, the result is integer.
- If all the operands are decimal, or decimal and integer operands are mixed, the result is decimal.
For addition and subtraction, the number of positions to the left of the decimal point (i.e. the difference between precision and scale) in the result is the greatest number of positions in any operand plus 1. The scale of the result is the greatest scale of any of the operands. The precision may not exceed 45. For example:
The scale of the result is the sum of the scales of the operands. Neither the precision nor the scale may exceed 45. If the value of the result does not fit into the precision and scale, overflow occurs. For example:
The scale of the result is calculated as the precision of the result, less the number of positions to the left of the decimal point in the dividend, less the scale of the divisor. An error occurs if this calculation gives a negative value for the scale. For example:
Evaluating String Expressions
The result of a string concatenation expression is a string containing the first operand string directly followed by the second.
The following rules apply:
- If string literals or fixed-length host variables are concatenated, any trailing blanks in the operands are retained.
- If a fixed-length character column value is directly concatenated with another string, any trailing blanks in the column value up to the defined fixed length of the column are retained.
- If a variable-length character column value is directly concatenated with another string, any trailing blanks in the column value up to the actual length of the column value are retained.
- If a fixed-length character value and a variable-length character value are concatenated, the result will be a variable-length character value.
- If a character value and a national character value are concatenated, the result will be a national character value.
- If either of the operands in a concatenation expression is
NULL, the result of the expression is
- When concatenating string expressions, the resulting string's collation depends on whether and where a collation has been specified:
- If no collation(s) have been specified for the column-definition, in a domain or explicitly in the concatenation statement, then the resulting string has the Mimer SQL default collation. See Character Sets.
- If one string has a specific collation and the other(s) do not then they are coerced into having the specific collation.
- If the strings have specific but differing collations, the resulting string has the Mimer SQL default collation.
For more information, see the Mimer SQL User's Manual, Collations.
A select specification can be used as an expression. This is commonly known as scalar subqueries. A scalar subquery may not return more than one value. The result of an empty subquery is null.
ExamplesSET total = (SELECT COUNT(*) FROM categories) SELECT c.surname, c.forename, (SELECT COUNT(*) FROM orders WHERE customer_id = c.customer_id) AS orders FROM customers AS c
The last example shows a correlated subquery i.e. a subquery with a reference to a column in a table not present in the subquery itself.
Mimer Information Technology AB
Voice: +46 18 780 92 00
Fax: +46 18 780 92 40 | <urn:uuid:b247f49f-66a4-48fc-a830-66a8ce925ec1> | 3.4375 | 1,417 | Documentation | Software Dev. | 41.681203 |
An ampere-hour or amp-hour (symbol Ah, AHr, A·h, A h) is a unit of electric charge, with sub-units milliampere-hour (mAh) and milliampere second (mAs). One ampere-hour is equal to 3600 coulombs. The ampere-hour is frequently used in measurements of electrochemical systems such as electroplating and electrical batteries. The commonly seen milliampere-hour (mAh or mA·h) is one-thousandth of an ampere-hour (3.6 coulombs).
A milliampere second (mAs or mA·s) is a unit of measure used in X-ray imaging diagnostic imaging and radiation therapy. This quantity is proportional to the total X-ray energy produced by a given X-ray tube operated at a particular voltage. The same total dose can be delivered in different time periods depending on the X-ray tube current.
An ampere-hour is not a unit of energy. In a battery system, for example, accurate calculation of the energy delivered requires integration of the power delivered (product of instantaneous voltage and instantaneous current) over the discharge interval. Generally, the battery voltage varies during discharge; an average value or nominal value may be used to approximate the integration of power.
- "Full Conversion Table (sorted by Category)" Allmeasures.com, 2004, webpage: AM-Conversion-table.
- X-ray Safety Handbook, 9.0 Terms and Definitions, VirginiaTech Environmental, Health and Safety Services
- National Research Council (U.S.) (2004). Meeting the energy needs of future warriors. National Academies Press. p. 27. ISBN 0-309-09261-2.
|This standards- or measurement-related article is a stub. You can help Wikipedia by expanding it.| | <urn:uuid:2246519a-999d-4601-b9e4-0ad3b9d1e587> | 3.4375 | 397 | Knowledge Article | Science & Tech. | 42.05382 |
Comments: Population decline in the Pribilof Islands in the 1980s apparently was due to harvests of females during the 1960s, increased mortality at sea (e.g., due to entanglement in debris such as discarded fishing nets), and perhaps reduced prey availability caused by increased commercial fishing in the North Pacific and Bering Sea. Substantial numbers are killed in the high-seas squid driftnet fishery between 40 and 50 degrees N latitude (Reeves et al. 1992). Until a new international fur seal treaty is established, this species remains vulnerable to renewed killing at sea.
No one has provided updates yet. | <urn:uuid:2a2ce880-4086-4399-b798-22007df27888> | 3.03125 | 130 | Structured Data | Science & Tech. | 44.643636 |
It’s been raining for about two weeks straight in Minnesota and my kids are climbing the walls. Yesterday, they built an amazing fort and played in it for an hour before they came to me asking what they could do next.
This easy experiment kept them busy for a little while.
Take a plastic comb and comb your hair a number of times, or rub it on some tissue paper. Tiny charged particles called electrons will collect on the comb and give it a negative charge.
Now, run a very thin stream of water from a faucet and hold the comb next to it without actually touching the water. What happens?
The stream of water is positively charged and is attracted to the opposite (negative) charge of the comb, pulling and bending the stream of water toward the comb.
Many more experiments to follow in the next few months! We’re planning a summer of science between our many sporting activities, so get those science notebooks ready and follow along with us!
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6th August 2006 - 02:57 PM
QUOTE (sdogv+Aug 5 2006, 09:08 PM)
So are you suggesting edges are space/energy, time/energy, and mass/energy are interactions of the six "edges" which in a regular tetrahedron have unique "directions", .....sideways?
I'm suggesting there are no actual edges. There is no actual volume or surface area to space, matter, energy, or time. There is the appearance of such (finite/beginning & end), but this is just the apparent "event horizon" of an otherwise, actual continuum (infinite).
To arrive at an actual surface requires "is". This does not mean, however, the universe "is not". There is of world of "is not actual" between the two. The "very persistent illusion" Einstein referred to.
6th August 2006 - 05:34 PM
Hey EE. I posted an "edge" analysis in Math thread, summarized here. f =r/R where a prolate spheroid approximated as a round pencil of radius r and length R, while for an oblate spheroid is assumed to be a flat plate of thickness r and radius R.
I find it significant that the "f" value to equal value for a tetrahedron is ~15 for BOTH prolate and oblate, while the "f" value to equal that of a sphere is ~4.5 for prolate and 0.014 for oblate.
Seems as if geometric "structure" is involved some way...??? Tetrhedrons have discrete "edges" while spherical "edges" are continuous, i.e. blurry. SO WHAT?
6th August 2006 - 07:02 PM
Do the places where a non-sperical shape's edges meet, come to a point? How sharp is that point? It is non-spherical? I think I've described it right.
18th November 2006 - 04:31 PM
Hey, EE and anyone else interested in crazy ideas. (a recurrent dream of some 30 years)
From a thermodynamic point of view, there is a system and an environment. How does one define either (or both) at THE beginning?
Can one exist without the other? Can existence be defined without time? Consider an existence of mass as a "system" and the existence of energy as an "environment". A tiny particle of mass generally has a short time of existence. Let's ignore the arrogance of humans and assume that it has a desire for a longer time of existence. Then, by exploiting its environment it strives to get more massive, i.e. "time" is the result of mass growth such that it has a longer existence.
Certainly living things tend to congregate, i.e. flocks of birds, schools of fishes, and herds of animals, and biologists have ascertianed time for existence of living things is roughly related to their mass,... over 2l orders of magnitude from bacteria to whales!.
Is their any reason not to consider that there is no such thing as totally inaminate matter? That is, "bigger" things generally enslave and exploit "smaller" things.And the "smaller" things give up and rely on their memory to act as their environment dictates. e.g., water "memory" dictates it to respond to temperature by boiling and freezing, absorb/transmit/refract frequencies of light, etc,
Do we really know that any atom/molecule/particle of mass that we look at is the same one that we looked at in a previous instant?
In the macro world above the Planck mass, matter organizes such that it can be said to "live", longer if they are "bigger", while in the micro world below the Planck mass, their time of existence is straining our measurements of time resolution.
In short, at any position that mass exists, there can be motion as it is exploited by its environment OR their can be growth as it exploits the enivornment (gravity?). Certainly motion and growth are two processes which we try to understand, i.e. mass occupies a position while energy occupies the space which surrounds. (Their interconvertability8 is suggested by E-mc^2 = hf.) So may there be an "equilibrium" between mass (position) and time (change)?
Security of existence is gained by a longer time to exist. Freedom of existence is gained by a shorter time to exist.
Kind of silly as I look at it, but what the hell. (Can't "grow" much any more so my time is becoming limited.) Maybe someone can pick it up in another generation. (I'll keep trying. )
11th December 2006 - 05:10 AM
I'll bite on your dream and go out on a limb. You got "silly", I got "sillier".
I could have sworn I responded to this. I know I was preparing a response, because it interested me quite a bit. Guess the war over at the math thread distracted me.
Matter, energy, space, and time are equal yet different. They are all expressions of distance from center (0) that make up yes, a FULLY ANIMATED universe. Back to that in a bit.
There is NO WAY to define a difference between COMPONENT and ENVIRONMENT.
Matter is no more inside energy, than energy is inside matter. And they are no more inside space and time, than space and time are inside them. At any size, small or large, it is impossible to determine a pecking order. We will NEVER arrive at an infinitesmial size or infinite size. It's "oxymoronic" to think we will.
You'll notice I didn't include SYSTEM in that explanation. The "system" is NOT WITHIN the universe. The universe is a PASSIVE DEPENDENT ILLUSION. It is ANIMATED by a PROCESS that takes place because of and within, a GREATER REALITY (explanation not included).
The animation occurs between a FOCUS and REFLECTION. The question is, how much of the animation is able to REFLECT and FOCUS, upon itself or anything else? This is where the question of CONSCIOUSNESS comes in. Consciousness is where the question of WILL comes in.
The universe "HAPPENING" is because of a conscious will. That which is in it, however, which appears to have a "conscious will", can NOT ever say "I became conscious because of my will or I have a will because I am conscious". That's just the DELUSION of the illusion.
All components of the universe are a CHARACTER in the animation. No matter what they are or their relative size. Matter, energy, space, and time are all characters. Sometimes they're positive and sometimes they're negative. Even space and time have have a charge. They can all be attractive or repulsive.
The more space and time between me and an "attractive positive mass" standing across the room, the more repulsive and negative the space and time seem. When I get close enough to her to realize she may be pretty but her energy is negative and repulsive, suddenly the more space and time between me and her, becomes positive and attractive. Unless you apply the uncertainty principle, and factor in how desperate I may or may not be. Then the big brain and small brain get in a tug of war, and by the time they've worked it out, she's long gone out the front door, on the arm of her next victim.
So, in many ways, the longer the time the more secure the existence and the shorter time the more freedom, but less assurance of the existence. The other guy's big brain didn't take the time to think, so he probably perished that night. But then again, I can't be certain. Maybe I was projecting something and she was a nice (and a little naughty) girl afterall.
Yes, the greater the mass the more time it contains.
Oh yeah, GRAVITY. It's NOT within the universe. It's part of the greater reality.
11th December 2006 - 05:13 AM
Oops, accidently posted my sillyness twice. This is just to modify the second posting. Is there a "delete post" button I'm missing?
2nd November 2007 - 12:43 AM
So are you talking panpsychism? a core of awareness in the mass of everything, all creatures, great and small? | <urn:uuid:514d8629-5bd4-45b4-9b4c-fad1b34a171b> | 2.703125 | 1,811 | Comment Section | Science & Tech. | 60.278348 |
At one stage of a water treatment process the number of particles of foreign matter per litre present in the water has a poisson distribution with mean 10. The water then enters a filtration bed which should extract 75% of foreign matter. The manager of the treatment works orders a study into the effectiveness of this filtration bed. 20 samples, each of 1 litre, are taken from the water and 64 particles of foreign matter are found. Using a suitable approximation test, at the 5% level of significance, weather or not there is evidence that the filter bed is failing to work properly. | <urn:uuid:855d78bc-de9a-4dfa-b459-612f2579430f> | 2.96875 | 121 | Tutorial | Science & Tech. | 51.223087 |
Lionfish and zebra mussels are problematic aquatic invaders along U.S. coasts. How lionfish will affect native fish populations and commercial fishing industries along the Atlantic coast has yet to be determined. Zebra mussels are known to cost the United States billions of dollars each year through economic losses and control costs.
Did you know that it's National Invasive Species Awareness Week? Invasive species are a big problem in the U.S. and around the world. Non-native animals and plants can harm both the natural resources in an ecosystem as well as threaten human use of these resources.
Invasive species reduce biodiversity, compete with native organisms for limited resources, and alter habitats—they can even cause extinctions of native plants and animals! This equates to huge economic impacts and major disruptions of coastal and Great Lakes ecosystems. Take a few minutes out of your day to learn more about aquatic invasive species. | <urn:uuid:035db8d9-76c1-44ca-9093-463769659984> | 3.234375 | 185 | Knowledge Article | Science & Tech. | 38.795569 |
I often hear people claim "global warming will cause the ice-caps to melt, and that will cause the water levels in the ocean to rise, and that will cause major world-wide flooding."
Now, ignoring the question "are ice cap melting", I am still wondering how it is possible for melting ice-caps to cause water levels to rise.
Here is why I am skeptical:
According to the law of displacement, the volume of an immersed object will be exactly equal to the volume of the displaced fluid. Therefor, if an icecap is floating in water, the displacement of the water would be based on the volume of the icecap, not it's shape, and the levels should be the same regardless of whether or not it is melted.
In fluid mechanics, displacement occurs when an object is immersed in a fluid, pushing it out of the way and taking its place. The volume of the fluid displaced can then be measured, as in the illustration, and from this the volume of the immersed object can be deduced (the volume of the immersed object will be exactly equal to the volume of the displaced fluid).
In the case of an object that floats, the amount of fluid displaced will be equal in weight to the displacing object.
The icecap will have the same weight, regardless of whether it is in ice form, or liquid form.
So how is it that people claim that melting ice caps can cause floods? Shouldn't water level stay exactly the same? | <urn:uuid:96f0440c-db0b-425f-abed-780537e3d3e1> | 3.328125 | 305 | Q&A Forum | Science & Tech. | 50.796837 |
A sequence of groups is just a list of groups with homomorphisms going down the list: . We’ll use to refer to the homomorphism from to . We say that a sequence is “exact” if the image of is the kernel of for each .
What does this mean? First off, if we start with an element of and hit it with we get something in . Since this is the same as , if we now apply we go to the identity element of . That is, the composition is always the trivial homomorphism sending all of to the identity in .
On the other hand, if we have an element in the kernel of it’s also in the image of . This means that if an element gets sent to the identity in the next group, it must have come from an element in the previous group.
So why should we care? Well, a number of different things can be very nicely said with exact sequences. If we write for the group containing only one element, we can set up a sequence: . What does it mean for this sequence to be exact? Well there’s only one homomorphism from to any group, and its image is just the identity element in . So the kernel of is trivial — is a monomorphism.
Now let’s flip the diagram over to . There’s only one homomorphism possible from any group to , and its kernel is the whole domain. This means that the image of has to be all of — is an epimorphism.
Let’s put these two together to get a sequence . Exactness at means that is a monomorphism, which we can think of as describing a copy of sitting inside . Exactness at means that is an epimorphism. What does exactness at mean? The image of is that copy of , which has to also be the kernel of . That is, is (isomorphic to) . We call any sequence of this form a “short exact sequence”.
Remember that the First Isomorphism Theorem tells us that we can factor any homomorphism into an epimorphism from the domain onto a quotient, followed by a monomorphism putting that quotient into the codomain. We can use that here to weave any exact sequence out of short exact sequences. Here is the (really cool) diagram:
Each of the diagonal lines is a short exact sequence, and as it says each (nontrivial) group off the main line is the image of one of the homomorphisms on the line and the kernel of the next.
We can also write an exact sequence . This just says that the homomorphism between and is an isomorphism. It’s really nice when this shows up in the middle of a longer exact sequence. If we can show that and are both trivial the sequence looks like , so and are immediately isomorphic.
Another way exact sequences show up is in describing the structure of a group. We know that every group is a quotient of a free group. That is, there is some free group so that is exact. Then the kernel of this projection is another group, so it’s the quotient of another free group . Now the sequence is exact. This is the presentation of by generators and relations. But the homomorphism from to might have a nontrivial kernel — there might be relations between the relations. In that case we can describe those relations as the quotent of another free group : is exact. We can keep going like this to construct an exact sequence called a “free resolution of “. It’s particularly nice if the process terminates at some point, giving a sequence . A free resolution of a group that has only finitely many terms gives a lot of information about the structure of . | <urn:uuid:07f38389-e10b-4ae5-8d2d-8d6bbce245b9> | 3.9375 | 798 | Personal Blog | Science & Tech. | 62.813293 |
Robin Ince examines Schrodinger's Cat, the paradox at the heart of quantum physics, and discovers its influence on science and popular culture. Fifty years after the death of Nobel laureate Erwin Schrodinger, the quantum mysteries of his cat-in-a-box paradox still continue to drive physicists in research today. Can a living thing be both alive and dead at the same time?
Schrodinger's experiment was an almost playful creation, but one that stabbed at the heart of the 1930s physics establishment. By the 1950s, US physicist Hugh Everett concluded that, indeed, both a dead cat and an alive cat can exist, but in separate universes. His 'Many Worlds' theory inspired authors, from Philip K Dick to Philip Pullman.
Robin follows in the Austrian physicist's footsteps to Oxford University, where Schrodinger was once a fellow, and unearths some original archive at Magdalen College. Physicist Sir Roger Penrose speaks about its impact on quantum theory to this day. Why has Schrodinger's Cat gained such currency not just in science but popular culture? Writer Alan Moore tells how it created a new wave of 1960s sci-fi literature.
So why has Schrodinger's Cat caught the imagination of non-scientists? How is it misinterpreted and used to explain mankind's many unknowns? What is its place at the cutting edge of quantum physics? Robin meets today's physicists and thinkers who still tangle with the idea. And we find, no doubt, that Schrodinger's Cat (in all probability) is very much alive today.
Producer: Dominic Byrne
A Loftus production for BBC Radio 4.
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A number of generator configurations have been devised to accommodate the Hall effect. In a Faraday generator, as shown in part A of the figure, the electrode walls are segmented and insulated from each other to support the axial electric field and the electric power is taken out in a series of loads. In the alternate configuration known as a Hall generator, the Faraday...
What made you want to look up "Faraday generator"? Please share what surprised you most... | <urn:uuid:3863bd35-72d8-4bec-a220-375efd4b9bbc> | 3 | 130 | Truncated | Science & Tech. | 45.943182 |
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...and some resembling spiderwebs (the arachno-boranes). Which type of structure is obtained correlates with the number of valence electrons in the molecule, and the correlation is expressed by Wade’s rules. These rules are empirical, but they can be justified by a consideration of the numbers of 3c,2e and ordinary 2c,2e bonds that are needed in each type of structure. They constitute an...
...electrons (from the metal atoms and the ligands). This set of correlations for clusters is similar to the 18-electron rule for mononuclear organometallics, and these guidelines are often called Wade’s rules after the British chemist Kenneth Wade, who first recognized that a triangular cluster such as Ru 3(CO) 12 usually has 48 valence electrons, a tetrahedron such as...
What made you want to look up "Wade's rules"? Please share what surprised you most... | <urn:uuid:c9f71d8a-7ee5-4694-8c4d-1b22383cc2b8> | 3.4375 | 232 | Truncated | Science & Tech. | 52.458997 |
Forbes, B.C., Fauria, M.M. and Zetterberg, P. 2010. Russian Arctic warming and 'greening' are closely tracked by tundra shrub willows. Global Change Biology 16: 1542-1554.
Remote sensing data suggest that tundra vegetation in North America may be responding to recent warming via enhanced photosynthetic activity (Goetz et al., 2005; Verbyla , 2008), and the authors write that "at a circumpolar scale, the highest photosynthetic activity and strongest growth trends are reported in locations characterized by erect shrub tundra (Reynolds et al., 2006)," noting that "live leaf phytomass from deciduous shrubs, shown to have increased in northern Alaska during the second half of the last century (Sturm et al., 2001; Tape et al., 2006), is believed to be a key driver of the observed trends (Jia et al., 2003; Goetz et al., 2005; Verbyla, 2008)."
What was done
Working with Salix lanata L. (sensu latu) -- an abundant deciduous dioecious willow with nearly circumpolar geographic distribution from the northern boreal forest to the northern limits of the Low Arctic -- Forbes et al. analyzed annual ring growth for 168 stem slices of 2- to 3-cm thickness that they collected from 40 discrete individuals spread across 15 sample sites within an area of approximately 3 x 2.3 km, which was located at about 68°40'N, 58°30'E.
What was learned
The three researchers say they found "a clear relationship with photosynthetic activity for upland vegetation at a regional scale for the period 1981-2005, confirming a parallel 'greening' trend reported for similarly warming North American portions of the tundra biome," and they state that "the standardized growth curve suggests a significant increase in shrub willow growth over the last six decades."
What it means
Noting that "the quality of the chronology as a climate proxy is exceptional," Forbes et al. state that their findings "are in line with field and remote sensing studies that have assigned a strong shrub component to the reported greening signal since the early 1980s," adding that the growth trend agrees with the qualitative observations of nomadic reindeer herders, which suggest there have been "recent increases in willow size in the region." In fact, they say that their analysis "provides the best proxy assessment to date that deciduous shrub phytomass has increased significantly in response to an ongoing summer warming trend," as the warming- and CO2-induced Greening of the Earth continues almost everywhere.
Goetz, S.J., Bunn, A.G., Fiske, G.J. and Houghton, R.A. 2005. Satellite-observed photosynthetic trends across boreal North America associated with climate and fire disturbance. Proceedings of the National Academy of Sciences USA 102: 13,521-13,525.
Jia, G.J., Epstein, H.E. and Walker, D.A. 2003. Greening of arctic Alaska, 1981-2001. Geophysical Research Letters 30: 31-33.
Reynolds, M.K., Walker, D.A. and Maier, H.A. 2006. NDVI patterns and phytomass distribution in the circumpolar Arctic. Remote Sensing of Environment 102: 271-281.
Sturm, M., Racine, C. and Tape, K. 2001. Increasing shrub abundance in the Arctic. Nature 411: 546-547.
Tape, K., Sturm, M. and Racine, C.H. 2006. The evidence for shrub expansion in northern Alaska and the Pan-Arctic. Global Change Biology 32: 686-702.
Verbyla, D. 2008. The greening and browning of Alaska based on 1982-2003 satellite data. Global Ecology and Biogeography 17: 547-555.Reviewed 22 September 2010 | <urn:uuid:c7ddc1da-f99f-4b89-8383-e33095056af4> | 3.0625 | 859 | Knowledge Article | Science & Tech. | 66.700283 |
Common Lisp the Language, 2nd Edition
These functions perform various transformations on characters, including case conversions.
The function character coerces its argument to be a character if possible; see coerce.
(character x) == (coerce x 'character)
The argument char must be a character object. char-upcase attempts to convert its argument to an uppercase equivalent; char-downcase attempts to convert its argument to a lowercase equivalent.
char-upcase returns a character object with the same font and bits attributes as char, but with possibly a different code attribute. If the code is different from char's, then the predicate lower-case-p is true of char, and upper-case-p is true of the result character. Moreover, if (char= (char-upcase x) x) is not true, then it is true that
(char= (char-downcase (char-upcase x)) x)
Similarly, char-downcase returns a character object with the same font and bits attributes as char, but with possibly a different code attribute. If the code is different from char's, then the predicate upper-case-p is true of char, and lower-case-p is true of the result character. Moreover, if (char= (char-downcase x) x) is not true, then it is true that
(char= (char-upcase (char-downcase x)) x)
Note that the action of char-upcase and char-downcase may depend on the bits and font attributes of the character. In particular, they have no effect on a character with a non-zero bits attribute, because such characters are by definition not alphabetic. See alpha-char-p.
X3J13 voted in March 1989 (CHARACTER-PROPOSAL) to replace the notion of bits and font attributes with that of implementation-defined attributes. The effect of char-upcase and char-downcase is to preserve implementation-defined attributes.
digit-char weight &optional (radix 10) (font 0)
All arguments must be integers. digit-char determines whether or not it is possible to construct a character object whose font attribute is font, and whose code is such that the result character has the weight weight when considered as a digit of the radix radix (see the predicate digit-char-p). It returns such a character if that is possible, and otherwise returns nil.
digit-char cannot return nil if font is zero, radix is between 2 and 36 inclusive, and weight is non-negative and less than radix.
If more than one character object can encode such a weight in the given radix, one will be chosen consistently by any given implementation; moreover, among the standard characters, uppercase letters are preferred to lowercase letters. For example:
(digit-char 7) => #\7 (digit-char 12) => nil (digit-char 12 16) => #\C ;not #\c (digit-char 6 2) => nil (digit-char 1 2) => #\1
Note that no argument is provided for specifying the bits component of the returned character, because a digit cannot have a non-zero bits component. The reasoning is that every digit is graphic (see digit-char-p) and no graphic character has a non-zero bits component (see graphic-char-p).
X3J13 voted in March 1989 (CHARACTER-PROPOSAL) to eliminate the font argument from the specification of digit-char.
The argument char must be a character object. char-int returns a non-negative integer encoding the character object.
If the font and bits attributes of char are zero, then char-int returns the same integer char-code would. Also,
(char= c1 c2) == (= (char-int c1) (char-int c2))
for characters c1 and c2.
This function is provided primarily for the purpose of hashing characters.
The argument must be a non-negative integer.
int-char returns a character object c such that
(char-int c) is equal to integer, if possible; otherwise
int-char returns false.
X3J13 voted in March 1989 (CHARACTER-PROPOSAL) to eliminate int-char.
The argument char must be a character object. If the character has a name, then that name (a string) is returned; otherwise nil is returned. All characters that have zero font and bits attributes and that are non-graphic (do not satisfy the predicate graphic-char-p) have names. Graphic characters may or may not have names.
The standard newline and space characters have the respective names Newline and Space. The semi-standard characters have the names Tab, Page, Rubout, Linefeed, Return, and Backspace.
Characters that have names can be notated as #\ followed by the name. (See section 22.1.4.) Although the name may be written in any case, it is stylish to capitalize it thus: #\Space.
char-name will only locate ``simple'' character names; it will not construct names such as Control-Space on the basis of the character's bits attribute.
The easiest way to get a name that includes the bits attribute of a character c is (format nil "~:C" c).
The argument name must be an object coerceable to a string as if by the function string. If the name is the same as the name of a character object (as determined by string-equal), that object is returned; otherwise nil is returned. | <urn:uuid:a7d121a5-2d88-49e9-a64e-ce81e547e459> | 3.90625 | 1,192 | Documentation | Software Dev. | 50.346111 |
Milton Banana wrote:
I have some questions about this Global Energy Budget. Every measurement is in Watts per square meter. 341 of shortwave radiation comes in. 102 of the shortwave is reflected back out. 239 IR going out. All outgoing adds up to 341. What comes in goes out. That makes sense. Here’s where things get a little muddy in my mind. 161 Wm^2 absorbed by the surface. But the surface releases almost twice the (356) watts per square meter of IR.
And has 333 in total back radiation to the surface from the atmosphere.
How is that possible? 356 Wm^2 is above the measured amount of shortwave radiation coming in from the Sun hence my last question in the post proceeding. "Is there another source of heat other than the Sun?"
It is part of a heat cycle. The ground radiates, the atmosphere radiates back, the ground radiates, the atmospere radiates back, and so on. The depiction is an average day and thus does not show just the total in and out, but the cycle of energy within the day.
Another question. Almost 100 percent of that release is back radiated 333 Wm^2.
How is it possible that according to this study the atmosphere (CO2?) is back radiating almost 100 percent of IR?
All of the GHGs and clouds are included. It is ~84% of the IR and that is how the planet remains warmer than it would without the Greenhouse Effect. It still leaves 40+ W m^2 which can be added to the retained energy, which is no small amount. | <urn:uuid:983583c5-809b-42bf-a8c1-816b3e3ea8ea> | 3.296875 | 338 | Comment Section | Science & Tech. | 74.639744 |
IT WAS recently reported in The Scotsman that up to 2500 tonnes of nuclear waste had been deposited on top of a million-tonne dump of Second World War munitions in a stretch of sea no more than ten kilometres off the southwest coast of Scotland called Beauforts Dyke (see "Danger from the deep", New Scientist, 18 November).
Feedback gathers that this is not quite true - and that the truth is stranger still. The UK Atomic Energy Authority did divert a cargo to Beauforts Dyke in 1981, but it was just nine tonnes of innocuous concrete in steel drums. The idea was to test a technique that would allow waste drums to be jettisoned overboard at any point on either side of the ship.
Why? To foil Greenpeace. Activists had perfected the art of positioning inflatables directly beneath the existing dumping apparatus, which was capable of dropping drums only from ...
To continue reading this article, subscribe to receive access to all of newscientist.com, including 20 years of archive content. | <urn:uuid:72144f92-f06d-4bf0-8d38-00ba821bd503> | 3.375 | 208 | Truncated | Science & Tech. | 56.286283 |
Department of Physics, University of California, Berkeley
Materials Sciences Division, Lawrence Berkeley National Lab
ARPES (Angle-Resolved Photoemission Spectroscopy) is an experimental technique based on several refinements of the photoelectric effect initially observed by Heinrich Hertz in 1887.
When photons of a well-defined energy hν are incident upon a sample, measurement of the electron's kinetic energy and exit angle gives information about the momentum and energy of
the electron state in the material. In particular, ARPES data directly gives the binding energy of the emitted electrons and the components of momentum parallel to the surface.
However, since the electrons interact with the surface upon emission, less information is given relating to momentum in the direction normal to the sample surface.
More explicitly, if a photoemitted electron leaves the sample with kinetic energy Ekin at an angle θ to the normal, its binding energy
and momentum parallel to the surface are given by
To obtain high-quality data, ARPES experiments are conducted in an ultra-high vacuum chamber which minimizes surface contamination and interactions between the photoemitted electrons and any potential interference between the emission and detection processes. Additionally, ARPES experiments are often performed at cryogenic temperatures to minimize thermal broadening of the data. This capability also allows for the study of high-temperature superconductors below their critical temperatures, where the electrons take on a fundamentally different structure.
The technique has opened many doors in the study of crystalline solids such as high-temperature superconductors, graphene, and topological insulators each of which is particularly suited to ARPES due to their two-dimensional nature. In particular, ARPES has been used to map out Fermi surfaces in these materials, like those for the cuprate (left) and iron pnictides (right) shown above. ARPES has also been used to explore the superconducting gap and pseudogap of cuprate superconductors as a function of temperature and momentum.
Synchrotron ARPES offers flexibility in terms of being able to easily vary photon energy, which makes it easy to optimize matrix element effects (which describe the interaction between the electromagnetic field and the electrons in the sample) to the parameters of different samples which otherwise limit the usefulness of ARPES spectra. With high photon energies (15-150 eV), electrons from a large area of momentum space are photoemitted and thus available for study. For many samples, electrons from the first several Brillouin zones can be photoemitted and thus mapped out using synchrotron ARPES. Our group uses synchrotron radiation from the Advanced Light Source (ALS) at Lawrence Berkeley National Lab, utilizing several different beamlines: HERS at BL 10.0.1, Angle and Spin-resolved Photoemission at BL 12.0.1, and MERLIN at BL 4.0.3.
In order for a photoemission experiment to work, the photon energy hν must be greater than the work function φ of the material being probed. Developments in nonlinear optics have led to systems of nonlinear crystals which can take 1.5 eV photons from a titanium sapphire laser and create a fourth harmonic at 5.9 eV. This photon energy is sufficient to induce photoemission in many samples, and is used in our lab. This lower energy results in a higher momentum resolution for a given angular resolution when compared to experiments performed with synchrotron radiation. As a tradeoff, less of momentum space is available for study. | <urn:uuid:a82fef1c-6809-4339-9c6d-c692e33cca9a> | 3.21875 | 743 | Knowledge Article | Science & Tech. | 20.277057 |
Free Body Diagrams
Practice your skill at constructing free-body diagrams for a given physical situation. Twelve different descriptions of a physical situation are presented; your goal is to determine the type and relative magnitude of the forces acting upon the described object.
- Use the pull-down menus on the right side of the screen to identify the types of forces acting in the rightward, leftward, upward and downward directions.
- Use the pull-down menus to identify the relative magnitude of each individual force. The important factor is not whether you indicate Large, Medium or Small, but rather that you indicate whether the rightward force is larger, smaller or of the same magnitude as the rightward force.
- When you have identified the type and relative magnitude of all applicable forces, click on the Check Answer button at the bottom of the screen.
- Repeat steps 1-3 until you have successfully answered all twelve problems.
- If necessary, use the Try New Problem button to skip the given problem; you will have to do the problem later.
- If necessary, use the Web Help button to obtain help from The Physics Classroom Tutorial. If you do use the Web Help button, do not close this window containing this page with the Shockwave file. If you do, you will have to reopen the Shockwave file and start over.
Tutorial information on forces, Newton's Laws, and free-body diagrams is available at The Physics Classroom Tutorial.
You will need the Shockwave plug-in to view the files.
Download the plug-in here. | <urn:uuid:a4036e34-0257-4482-a66f-41b7b2a19e9e> | 4.21875 | 322 | Tutorial | Science & Tech. | 45.162558 |
Bind a name to a socket
#include <sys/types.h> #include <sys/socket.h> int bind( int s, const struct sockaddr * name, socklen_t namelen );
- The file descriptor to be bound.
- A pointer to the sockaddr structure that holds the address to be bound to the socket. The socket length and format depend upon its address family.
- The length of the sockaddr structure pointed to by name.
Use the -l socket option to qcc to link against this library.
When a socket is created with socket(), it exists in a namespace (address family) but has no name assigned to it. The bind() function assigns a name to that unnamed socket.
|The bind() function assigns a local address. Use connect() to assign a remote address.|
The rules used for binding names vary between communication domains.
- An error occurred (errno is set).
- The requested address is protected, and the current user has inadequate permission to access it.
- The specified address is already in use.
- The specified address isn't available from the local machine.
- Invalid descriptor s.
- The name parameter isn't in a valid part of the user address space.
- The socket is already bound to an address.
- The given file descriptor isn't for a socket. | <urn:uuid:f02a3aaf-a3de-47ef-8879-fa0ab5914b99> | 3.40625 | 286 | Documentation | Software Dev. | 60.245884 |
This is my first blog ever. I am not going to make any advanced apologies about my writing. I am not going to attempt to impress you by chirping that I am writing this blog on such-and-such flight, or explain that I am reporting from a particularly nice part of the world only because I was forced to go there for work. I am going to try to enlighten you, the intelligent reader, about physics and stimulate interest in the LHC: what we do and how we do it and why. And then I am going to go fishing.
Here is my short take on why we have built the LHC, its true raison d’être. We are searching for the mechanism of electroweak symmetry breaking (ESB). A particle physicist puts this in the context of the so-called gauge bosons that mediate the forces: W, Z, and γ. Why are the W and Z massive (100 times that of the proton) while the photon (γ), the ordinary particle of light, is massless? To make it more intuitive, let’s look at the two fundamental forces involved, the “weak” nuclear force (bad name, but we are stuck with it) and electromagnetism. The weak force allows the sun to shine and you can’t get any more fundamental than that! Those weak interactions, that burn protons by allowing one of them to transform into a neutron which gets fused to another proton to form a deuteron, occur only at extremely short distances, even orders of magnitude smaller than the proton size. On the other hand, electricity has an infinite range, as easily demonstrated by looking at a distant star at night. The electron in the star emits a photon that travels many light years before it is captured by an electron in your eye. Add a sophisticated telescope and one may observe photons that have traveled billions of light years to reach us. So one fundamental force has an extremely TINY range and its close sibling has an INFINITE range!
How does an electron know that it should interact with another electron? Here is the conceptual picture of the interaction. (I was lucky enough to have Richard Feynman explain this to me in his own scruffy manner. Maybe I will write a Feynman blog in the future to relate my own stories.) An electron or any other charge is perpetually surrounded by a cloud of photons that it is continually emitting and absorbing photons. By doing this, the electron is checking if there is another charge around to push or pull. A free electron can’t really emit a photon and conserve energy and momentum. BUT the photon can “borrow” some energy from the electron for a short time as long as the product of borrowed energy times the time interval is smaller than Planck’s constant. This rule is called the uncertainty principle and lies at the heart of quantum mechanics. Although it retains a mysterious je ne sais quoi to this day, it is well tested experimentally. So our electron sends out its messenger photons on a mission to check if there are any other charges to push or pull. Since the photon is traveling on borrowed energy, it can only go large distances because it is massless. It is this masslessness of the photon that gives the electric force an infinite range.
Now how about the weak force? Enter W and Z. In the 1980s I was fortunate to work on the experiment that discovered these massive particles which had been searched for for decades. This discovery experimentally established the quantum nature of the weak force, that quarks and leptons really interact by exchanging W and Z particles. That there are 2 particles has to do with the detailed properties of the weak force: the W changes a quark or lepton into a different type (flavor) while the Z cannot. A quark in the proton sends out a W messenger to see if there is another quark around that wants to play (analogous to the electron sending out its photon messenger). This W can only live for a time allowed by the uncertainty principle. Now comes the big difference between electricity and weak. The W not only has to borrow kinetic energy to move but it also has to borrow some energy for its mass meaning that our W messenger cannot travel very far. The quark in one proton can only interact with the quark in the other proton (via weak force) if the quarks are VERY close together. The large mass of the W gives the weak force its short range. There is our broken symmetry: the W and Z have large mass and the photon is massless. Approximate symmetry can be restored if we can study interactions at an energy scale so large, or equivalently a distance scale so small, that the W and Z mass energies and the short range of the weak force are irrelevant. The forces become unified resulting in one happy electroweak force.
Another way to look at the consequence of the W having mass is that probability for a the weak interaction grows with energy. One can see this on dimensional grounds. This interaction probability cannot grow forever. There is a mathematical bound referred to as the unitarity limit of about 1.7 TeV. This means when Ws and Zs with this energy scale interact, we do not understand much of anything about what will happen. How’s that for exciting (!)? The reader will notice that 1.7 TeV is a VERY large energy for W and Z particles. The LHC will not reach this scale for Ws and Zs for a very, very long time. This is why once upon a time we wanted to build a 40 TeV machine (but don’t get me started on that…). However, all is not so gloomy as the following lesson tells.
There is an elegant historical analogy to ESB. Before the age of modern physics, the classical radius of the electron- the distance beyond which where the electrostatic potential energy exceeds the mass energy of the electron- posed a formidable barrier beyond which classical physics made no sense. This distance is 10^-15 m which corresponds to an electron approaching the GeV/c scale. It turns out, however, that we did not have to get anywhere this limit to discover revolutionary new physics: quantum mechanics was waiting to be discovered at the Bohr radius (10^-10 m) and relativistic quantum field theory at the Compton wavelength (10^-12 m). Okun called the classical electron radius the “paper tiger” and QM and QFT the “real tigers”. Here is a slide that Okun showed on my first trip to Moscow on Oct. 9, 1989:
The LHC was not yet a project and we were designing a detector for the 40 TeV machine. Of the zillion talks I have heard since then on supercollider physics, not one has been as clear and as informative and void of nonsense as the 5 slide talk by Okun. I gave a colloquium at ITEP in on Dec. 3, 2003 at the invitation of Okun and Michael Danilov, the lab director and I showed the 5 slides to the amusement of Okun. So the lesson is: when we collide Ws and Zs at a TeV or so, we WILL learn something exciting BUT if we are lucky we may learn something exciting well before reaching the unitarity limit. Let us hope so or its going to be a very long ride!
For the up and coming experts, a superb technical explanation of the electroweak physics has been given in a series of lectures by Tini Veltman (Nobel Prize, 1999) that have been published in a CERN Yellow Report 1997.
Picture (courtesy Claudia-Elizabeth Wulz) of me with Tini and Carlo Rubbia on the occasion of the later’s 75th birthday.
Having suffered through my explanation of why we have built the LHC, I now owe you something fun. Dark energy- which we shall NOT observe at the LHC- has become increasingly fashionable with the announcement of this year’s Nobel Prize. Dark energy is explained in a brilliant 1 m 39 s video by Sean Carroll: 2011
Time for me to go fishing. More on that later… | <urn:uuid:8caeef94-e09d-44f0-bd9f-35527b0ade0a> | 2.84375 | 1,700 | Personal Blog | Science & Tech. | 55.739223 |
This deficit supports the hypothesis that between 100 and 200 million years after its formation, Earth was made up of an ocean of molten magma, which gradually cooled. The work, which was carried out in collaboration with the Laboratoire de Géologie de Lyon (CNRS / Université Lyon 1 / ENS de Lyon) and the University of Copenhagen, was published on 1 November 2012, in the journal Nature.
Earth is believed to have formed 4.58 billion years ago, by accretion of material in the Solar System. The heat produced by the accretion process, as well as by the decay of radioactive elements, caused this material to melt. As a result, 100 to 200 million years after its formation, Earth must have been made up of an ocean of molten magma, in the center of which a metallic core formed. The ocean gradually cooled. Earth's crust then appeared, and the process of continental drift began. The crystallization of the molten magma is likely to have been accompanied by the chemical layering of Earth: concentric layers with distinct chemical compositions became differentiated. It is the signature of these primordial inhomogeneities that the researchers found in the Isua rocks. | <urn:uuid:8a11c21b-19fe-4c47-9bfd-5e15767e52dd> | 4.28125 | 244 | Knowledge Article | Science & Tech. | 46.0425 |
In this section, we will explore the concept of method
in the reference of object oriented programming techniques.
As we earlier described in the topic class, a class have two major parts state and behavior. States are represented by variables and behaviors are defined by methods.
If you are facing any programming issue, such as compilation errors or not able to find the code you are looking for.
Ask your questions, our development team will try to give answers to your questions. | <urn:uuid:9dc8373a-4d66-47bb-835e-4a8ad3f7cb5c> | 3.25 | 95 | Documentation | Software Dev. | 45.749976 |
Boletín de la Sociedad Botánica de México
versión impresa ISSN 0366-2128
MARTINEZ-OREA, Yuriana; CASTILLO-ARGUERO, Silvia; GUADARRAMA-CHAVEZ, M. Patricia y SANCHEZ, Irene. Post-fire seed bank in a xerophytic shrubland. Bol. Soc. Bot. Méx [online]. 2010, n.86, pp. 11-21. ISSN 0366-2128.
Through the seedling emergence method we studied the effects of fire on the soil seed bank of a xerophytic shrubland in two consecutive years. We compared its composition and abundance in two sites, one burned and one unburned. An important proportion of seeds died due to the high temperatures reached by fire. In addition, species richness and, diversity were also negatively affected. These variables showed statistical differences between sites and years. After one year, seed bank abundance and diversity reached higher values. Dominant species were perennial herbs in terms of species number, and in terms of seedling abundance the dominant life form was a tree. However, fire was not a determinant factor in terms of species composition. These results are important to explain the changes in vegetation after a fire, specially if we consider that this site is a natural preserve immersed in an urban area.
Palabras llave : fire; seed bank; xerophytic shrubland. | <urn:uuid:4e39ec7d-31c8-4496-b04f-25f4721463cf> | 2.6875 | 315 | Academic Writing | Science & Tech. | 44.888333 |
How long can you hold your breath? Crucian carp (Carassius carassius), a close relative to the goldfish, is capable of living for months without oxygen. Scientists at the University of Oslo have recently unpacked the mechanisms allowing Crucian carp to exhibit superior breath holding skills.
First, lets gain some background knowledge about this extraordinary carp. Crucian carp inhabit lakes, ponds and slow-moving rivers throughout Europe and Asia. They are considered a medium-sized cyprinid (weighing less than 3.3 pounds) and commonly exhibit a dark green back, golden sides and reddish fins. Crucian carp are commonly caught for sport and occasionally are found in freshwater aquariums.
What allows the Crucian carp to survive months without oxygen? Lets take a look. Professor Goran Nilsson, University of Oslo, discovered the Crucian carp is able to change its gill structure to avoid becoming oxygen deprived (known as anoxia). The carp also has a high affinity for oxygen when compared to other vertebrate therefore resorts to producing alcohol and tranquilizers when oxygen supplies are limited. With these mechanisms, the Crucian carp is able to spend days, even months without a fresh breath of air.
So what does this mean? Researchers are hoping to understand how different animals cope with the lack of oxygen giving way to clues about how humans can go longer without direct oxygen supplies. As stated by Nilsson, "Anoxia related diseases are the major causes of death in the industrilized world." What professions or situations do you see benefiting most from prolonged breath holding? | <urn:uuid:ce4c75a1-8ee3-46b0-b988-ce52eba5df61> | 3.484375 | 330 | Knowledge Article | Science & Tech. | 40.455533 |
Beckett has been fascinated by batteries for as long as I can remember, so his latest suggestion for a science topic should not have been a surprise. Beckett wanted to know how toys work. We talked about the mountain of toys he has and about the energy makes them work -- whether the energy comes from him pushing a car or throwing an airplane, or from batteries or rubber bands. This led naturally enough to a discussion about potential energy and kinetic energy.
Potential energy is stored energy, energy that is waiting to be used, and it comes in many forms. The most basic form of potential energy is provided by gravity -- an object that is not at rest on the surface of the earth probably has some potential gravitational energy in it. We pulled out one of Rowan's toys and asked him to demonstrate. When the ball is poised at the top of the ramp, it has potential energy. Gravity is pulling it down, but until it is free to move, the energy is being stored in it. As soon as Rowan lets go, gravity begins pulling the ball down, and it rolls down the ramp until it hits the bottom. The energy it has while it is rolling is called kinetic energy. You can repeat this experiment with our without Rowan's 'gravity dance.'
Next we talked about wind-up toys. This type of toy stores energy in a coil of metal in a form called spring tension. Winding the toy places a spring under tension. The metal of the spring is flexible, but it has a manufactured coil shape that it returns to when the tension is released. You can see examples of this everywhere -- bend a stick or plastic spoon without breaking it and it will snap back to its original shape, or yank a rubber band from normal size to three times its size and let it snap. Even when you gently fold (without creasing) one end of a sheet of paper to the other end and let go, the paper will slowly unfold back to flat. (There is not a lot of energy there, but it is there.)
Wind-up toys generally have a tiny coil spring that can hold enough energy to move a small toy. Beckett has a lot of toys that use this type of potential energy -- bath toys that swim, little robots that walk, and lots of cars. We found a little plane with wind up wheels to demonstrate.
Finally, we dug through the pile of toys and found a car with a flywheel, also called an inertia wheel. This toy uses a large rotating mass and a set of gears to translate the movement of the large rotating mass into forward motion for the car. Without getting too Einstein-y about it, the large mass of the flywheel is stepped down with a set of gears to propel the car. The flywheel 'stores' energy using the law of conservation of energy, which says that energy cannot be created or destroyed, but can only change its form. In this case, when the flywheel is set in motion, it has a certain amount of energy that can be harnessed using the gears and transferred to the wheels.
Other Energy Sources
The boys and I also talked about the many toys they both have that are powered by batteries. The batteries store potential energy chemically and release the energy over time as the electrical circuit is completed. The chemistry is far too complicated to explain here, so we looked at other ways of creating electricity. We started with Beckett's solar powered car, which uses photovoltaic cells to turn solar energy into electricity to move the car. This is fairly straightforward: the photons of light hit the photo-cell, where they are converted into electrons.
Next, we looked at other ways to make electricity -- lemon and potato batteries, for example -- that use a simple chemical reaction to generate electricity. The lemon stores potential energy in the acid that can be released by inserting two different metals and starting a reaction. The lemon also stores another kind of potential energy -- in the form of calories that can be eaten, changed by a different chemical reaction, and consumed in our bodies as fuel.
There are other forms of energy used by toys -- Beckett and Rowan both have toys that use magnetic energy in one form or another, and most balls use elastic potential energy to bounce along with gravity. Some toys use light energy to play. The best toys require a large dose of kid energy to play. What kinds of toys do you have, and what kind of energy do they need?
A Quick Update on Groundhog Day
We've had a week of unusually warm weather, so I wanted to share an update on Puxsutawney Phil because Beckett asked about him this morning on the way to school. "Dad," he said, "does a groundhog really decide when spring is?"
I tried to think of a 'science' question I could ask him to help him figure it out, but the best I could come up with was this: "Well, do you think a groundhog can control or predict the weather for the whole planet? "
This turned out to be exactly the right question, because he immediately brightened and smiled. "Obviously not," he said.
"And why not?" I asked.
"Because half the planet is in the dark during their nighttime, so no shadows!"
I thought this was a great answer with a certain kind of logic and even science to it. No light means no shadow, and no shadow means no prediction.
Be sure to ask a kid in your life if groundhogs really determine the weather. If you need help, you can check out our very first blog post here, and find out what really determines the seasons.
Science Dad, AKA Vince Harriman, is a freelance writer living in Annapolis. His two sons, Beckett - 6 and Rowan - 2 1/2 ask him ‘why’ approximately 6,549 times a day. | <urn:uuid:7536c57a-b7d4-495f-8693-7e602613e89f> | 3.65625 | 1,207 | Personal Blog | Science & Tech. | 57.063665 |
Four years ago Columbia University psychologist Betsy Sparrow turned to her husband after looking up some movie trivia online and asked, “What did we do before the Internet?” Thus, Sparrow set out to investigate how Google, and all the information it proffers, has changed how people think. Four psychology experiments later Sparrow has her answer, which was published in Science this past August. “[The Web] is an external memory storage space, and we make it responsible for remembering things,” she says.
In one of Sparrow’s experiments she presented two groups of undergraduates with trivia statements. Individuals in one group, who were told they could retrieve the information later on their computer, had worse recall than subjects in the other group, who knew in advance they could not do so. Together with the rest of her results, this finding suggests that Internet users have learned to remember how to find a fact rather than the fact itself.
Does this mean the Web is dumbing us down? Certainly not, she says: “Memory is much greater than memorizing.” Our brain may simply be adapting to present circumstances, Sparrow points out. “We’re in an Internet world.” | <urn:uuid:865436e3-cb04-433d-83da-137cd9e08a4a> | 3.265625 | 248 | Knowledge Article | Science & Tech. | 47.643369 |
California birds are getting slightly bigger, according to a study published in Global Change Biology in which researchers measured and weighed 33,000 birds over the past 40 years. The increases were small, but significant: in the last 25 years robins have grown 0.2 ounces in mass and 1/8th of an inch in wing length, for example. But the finding runs counter to the only other long-term study measuring avian size in North America, which found that birds in Pennsylvania have shrunk slightly over recent decades. And it seems to disagree with other recent suggestions that animals may shrink in a warming world: Bergmann’s rule holds that animals generally get bigger as they get farther away from the equator, because larger animals are better able to retain heat.
So what’s going on? The researchers have a number of hypotheses, all related to climate change. More severe weather on the West Coast, for example, could perhaps favor bulked-up birds that can store more energy to survive storms. Or maybe warmer temperatures cause changes in rainfall patterns that ultimately lead to more food for birds (a pattern that may be different elsewhere, like on the East Coast).
But it doesn’t seem clear as yet that the change is related to climate at all; couldn’t it stem from some other, unidentified factors, like changes in the birds’ habitats due to human settlement? Or greater food availability due to other reasons? The study raises a number of thorny questions scientists will need to examine.
Reference: Rae E. Goodman, Gretchen Lebuhn, Nathaniel E. Seavy, Thomas Gardali, Jill D. Bluso-Demers. Avian body size changes and climate change: warming or increasing variability? Global Change Biology, 2011; DOI: 10.1111/j.1365-2486.2011.02538.x
Image: Joi / Flickr | <urn:uuid:9c0ded85-4759-479e-8538-63e13bcecb12> | 3.40625 | 390 | Personal Blog | Science & Tech. | 57.352091 |
June 19, 2009
As I have written about many times here on Dinosaur Tracking, paleontologists presently have an overwhelming amount of evidence that birds are living dinosaurs. That doesn’t mean that everything about the dinosaur-to-bird transition is well-understood, though. For years scientists have been faced with a puzzle involving the hands of living birds and bird-like dinosaurs. The dinosaurs most closely related to birds appeared to have a thumb and two fingers (digits I-II-III) while studies of the embryonic development of birds showed that they have fingers II-III-IV. This difference would have to be accounted for, and a bizarre new theropod dinosaur described by an international team of scientists in yesterday’s edition of Nature provides a crucial clue to this fossil puzzle.
The new dinosaur, named Limusaurus inextricabilis, is so strange that I almost don’t know where to start describing it. It lived about 156 million to 161 million years ago in what is now western China, and it was one of the dinosaurs that became mired in the famous “Dinosaur Death Trap” featured by National Geographic. Yet while scientists were able to identify it as a ceratosaur, one of the early groups of theropod dinosaurs, it was like no other ceratosaur they had ever seen. Instead of packing a mouthful of sharp teeth, like Ceratosaurus, Limusaurus did not have a tooth in its entire mouth! A pile of stones was found in its stomach region that probably ground up food inside its gut, and it is likely that this theropod dinosaur was actually a herbivore.
What is making headlines, though, is that Limusaurus had at least one feature that is very important to understanding how avian dinosaurs (i.e. birds) evolved. Since we know that theropod dinosaurs evolved from five-fingered ancestors, it has long been assumed that, to end up with digits I, II and III, they lost two fingers: their pinky and ring fingers (or digits IV-V). In this way the fingers were reduced and lost, probably due to changes during embryological development, from the outermost finger moving in. What Limusaurus shows, though, is that after some dinosaurs lost their pinky they began to lose their thumb.
This is not what would have been expected, but it is clear that Limusaurus has a greatly reduced thumb and an enlarged second digit. In this way the second finger functionally became like a thumb, but what if Limusaurus was just an oddball? We can’t know if it was directly ancestral to any other dinosaurs, but the paleontologists then looked at the hands and fingers of other dinosaurs more closely related to birds (the coelurosaurus) and found their answer not in the finger bones, but in the wrist bones. The finger bones of these later dinosaurs alone might make it hard to tell if they were really I-II-III or II-III-IV, but the wrist bones provided a clearer picture. The wrist bones of dinosaurs more closely related to birds did not change as much as the fingers. They retained signs that the modified finger bones they were attached to were really II-III-IV, and this finally makes sense of both the fossil and embryological evidence.
Now keep in mind that Limusaurus is probably not directly ancestral to the dinosaurs that gave rise to birds. It is not a “missing link” (and the phrase “missing link” itself is more confusing than helpful when thinking about evolution). What the skeleton of Limusaurus suggests, though, is that there was a significant shift in hand shape going on among ceratosaurs during the Jurassic, and Limusaurus provides a window into how this change occurred. If the hypothesis of the authors is correct, and there is much reason to think it is, then we should expect to find other theropod dinosaurs with similar hand anatomy that link some ceratosaurs to tetanuran dinosaurs, the group to which coelurosaurs (and hence birds) belong.
There is much more to discuss about Limusaurus than any one blogger can cover, though, so have a look at what some other science bloggers have to say about this new find:
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Comparator and Comparable in Java Examples
Difference between Comparator and Comparable in Java is very popular Java interview question mostly asked in telephonic round and writing code to sort object using Comparable or Comparator is popular on written test round of interview.The question was this “How you will sort Employee object based on his EmployeeID and his name” and this involves the use of both Comparable as well as Comparator interface in Java. This post is my revision on Java fundamentals similar to I did about equals method in Java and some tips to override hashCode in Java. All of these methods are fundamentals in Java programming language and correct understanding is must for any Java developer. Comparators and comparable in Java are two interfaces which is used to implement sorting in Java. It’s often required to sort objects stored in any collection classes like ArrayList, HashSet or in Array and that time we need to use either compare() or compareTo() method defined in java.util.Comparator and java.lang.Comparable. In this Java tutorial we will see example of Comparator and Comparable to sort object in Java and discuss some best practices around when to use Comparator interface etc. Any way before moving ahead Let’s see some important differences between Comparable and Comparator in Java.
Comparator vs Comparable in Java
Here are some of the common differences, which is worth remembering to answer this question if asked during a telephonic or face to face interview:
1) Comparator in Java is defined in java.util package while Comparable interface in Java is defined in java.lang package, which very much says that Comparator should be used as an utility to sort objects which Comparable should be provided by default.
2) Comparator interface in Java has method public int compare (Object o1, Object o2) which returns a negative integer, zero, or a positive integer as the first argument is less than, equal to, or greater than the second. While Comparable interface has method public int compareTo(Object o) which returns a negative integer, zero, or a positive integer as this object is less than, equal to, or greater than the specified object.
3) If you see then logical difference between these two is Comparator in Java compare two objects provided to him, while Comparable interface compares "this" reference with the object specified. I have shared lot of tips on how to override compareTo() method and avoid some common mistakes programmer makes while implementing Comparable interface.
4) Comparable in Java is used to implement natural ordering of object. In Java API String, Date and wrapper classes implements Comparable interface.Its always good practice to override compareTo() for value objects.
5) If any class implement Comparable interface in Java then collection of that object either List or Array can be sorted automatically by using Collections.sort() or Arrays.sort() method and object will be sorted based on there natural order defined by CompareTo method.
6)Objects which implement Comparable in Java can be used as keys in a SortedMap like TreeMap or elements in a SortedSet for example TreeSet, without specifying any Comparator.
These were combination of some theoretical and practical differences between Comparator and Comparator interface in Java. It does help you to decide when to use Comparator vs Comparable but things will be more clear when we some best practices around using both of these interfaces. Now let’s see an example of Comparator in Java:
Example of using Comparator and Comparable in Java
So in Summary if you want to sort objects based on natural order then use Comparable in Java and if you want to sort on some other attribute of object then use Comparator in Java. Now to understand these concepts lets see an example or real life coding:
1) There is class called Person, sort the Person based on person_id, which is primary key in database
2) Sort the Person based on there name.
For a Person class, sorting based on person_id can be treated as natural order sorting and sorting based on name field can be implemented using Comparator interface. To sort based on person_id we need to implement compareTo() method.
Generally you should not use difference of integers to decide output of compareTo method as result of integer subtraction can overflow but if you are sure that both operands are positive then its one of the quickest way to compare two objects. See my post things to remember while overriding compareTo in Java for more tips on compareTo.
And for sorting based on person name we can implement compare(Object o1, Object o2) method of Java Comparator class.
Similar guidelines applies while implementing compare() method as well and instead of using subtraction operator, its better to use logical operator to compare whether two integers are equal to, less than or greater than. You can write several types of Java Comparator based upon your need for example reverseComparator , ANDComparator , ORComparator etc which will return negative or positive number based upon logical results. String in Java even provides an special comparator called CASE_INSENSITIVE_ORDER, to perform case insensitive comparison of String objects.
How to Compare String in Java
String is immutable in Java and one of the most used value class. For comparing String in Java we should not be worrying because String implements Comparable interface and provides a lexicographic implementation for CompareTo method which compare two strings based on contents of characters or you can say in lexical order. You just need to call String.compareTo(AnotherString) and Java will determine whether specified String is greater than , equal to or less than current object. See my post 4 example to compare String in Java for alternatives ways of comparing String.
How to Compare Dates in Java
Dates are represented by java.util.Date class in Java and like String, Date also implements Comparable in Java so they will be automatically sorted based on there natural ordering if they got stored in any sorted collection like TreeSet or TreeMap. If you explicitly wants to compare two dates in Java you can call Date.compareTo(AnotherDate) method in Java and it will tell whether specified date is greater than , equal to or less than current String. See my post 3 ways to compare Dates in Java for more alternatives of comparing two dates.
When to use Comparator and Comparable in Java
At last let’s see some best practices and recommendation on when to use Comparator or Comparable in Java:
1) If there is a natural or default way of sorting Object already exist during development of Class than use Comparable. This is intuitive and you given the class name people should be able to guess it correctly like Strings are sorted chronically, Employee can be sorted by there Id etc. On the other hand if an Object can be sorted on multiple ways and client is specifying on which parameter sorting should take place than use Comparator interface. for example Employee can again be sorted on name, salary or department and clients needs an API to do that. Comparator implementation can sort out this problem.
2) Some time you write code to sort object of a class for which you are not the original author, or you don't have access to code. In these cases you can not implement Comparable and Comparator is only way to sort those objects.
3) Beware with the fact that How those object will behave if stored in SorteSet or SortedMap like TreeSet and TreeMap. If an object doesn't implement Comparable than while putting them into SortedMap, always provided corresponding Comparator which can provide sorting logic.
4) Order of comparison is very important while implementing Comparable or Comparator interface. for example if you are sorting object based upon name than you can compare first name or last name on any order, so decide it judiciously. I have shared more detailed tips on compareTo on my post how to implement CompareTo in Java.
5) Comparator has a distinct advantage of being self descriptive for example if you are writing Comparator to compare two Employees based upon there salary than name that comparator as SalaryComparator, on the other hand compareTo()
Related Java Tutorial from Javarevisited Blog | <urn:uuid:437ede86-c77d-44e1-8b0b-68bce45db4fe> | 3.859375 | 1,698 | Personal Blog | Software Dev. | 26.605396 |
The Earth's Atmosphere
- The region extending above about 60 km to beyond 1000 km altitude, where the
concentration of ions is large enough to influence radio propagation. It is divided into several
regions: D (60 to 100 km), E (100 to 150 km), F (150 to 1000 km). The F region is further
divided into F1 and F2 regions, with F2 blending into the magnetosphere.
- Broadly defined, this is the region the motion of charged particles is controlled by the
geomagnetic field. However, this definition includes most of the ionosphere, and common
usage places the magnetosphere's lower boundary around the F2 ionosphere region.
Back to Propagation | <urn:uuid:f13874cf-bdcb-4e5b-abcc-05abf328b44f> | 3.4375 | 152 | Knowledge Article | Science & Tech. | 51.744333 |
A dusty plasma is a plasma containing nanometer or micrometer-sized particles suspended in it. Dust particles may be charged and the plasma and particles behave as a plasma, following electromagnetic laws for particles up to about 10 nm (or 100 nm if large charges are present). Dust particles may form larger particles resulting in "grain plasmas".
Dusty plasmas are interesting because the presence of particles significantly alters the charged particle equilibrium leading to different phenomena. It is a field of current research. Electrostatic coupling between the grains can vary over a wide range so that the states of the dusty plasma can change from weakly coupled (gaseous) to crystalline. Such plasmas are of interest as a non-Hamiltonian system of interacting particles and as a means to study generic fundamental physics of self-organization, pattern formation, phase transitions, and scaling.
The temperature of dust in a plasma may be quite different from its environment. For example: | <urn:uuid:73322af5-65c4-4456-8861-2ef8281ecb73> | 3.421875 | 196 | Knowledge Article | Science & Tech. | 27.953842 |
American bees Botanys Breeches Bumblebee Coevolution conservation Dutchman’s earthworms ethnobotany Ian jayhawks Kestrel McLeod native Pollination Queen species wildflowers Wildflowers
See Wild Ideas...the Podcast 10 for discussion of mobbing behavior how game theory strategies apply to the risk-benefit of smaller birds mobbing a predator.
From Gordon: digitalis is purple foxglove (Digitalis purpurea) Definition: phytopharmacology is pharmaceutical research in which the active ingredient has been derived from a plant.
Joann wanted to let listeners know that butterflies don’t hibernate they over-winter. Definition: coevolution is a change in the genetic composition of one species (or group of species) in response to a genetic change in another. | <urn:uuid:bec74774-c298-4e6b-b1f5-d65cfb7c82df> | 2.796875 | 169 | Audio Transcript | Science & Tech. | 20.277706 |