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Researchers at the European Molecular Biology Laboratory (EMBL) and the University of Rome "La Sapienza" have found a way to restore some of the "regenerative" ability of tissues, which happens naturally in animals at the embryonic stage of development, but is lost shortly after birth. The scientists work, published this week in PNAS, gives new insight into how stem cells can be mobilized across the body, and how they take on specialized functions in tissue.
"Many labs have reported the integration of stem cells into various types of tissues, but on a small scale," says Prof. Nadia Rosenthal, Coordinator of EMBLs Mouse Programme in Monterotondo, Italy. "This is the first study to show that stem cells can be mobilized to achieve a major regeneration of damaged tissue."
In a collaboration with the group of Antonio Musarò at the University of Rome, the scientists investigated muscle tissue in mice, discovering that stem cells can travel large distances to reach an injury. They also found a special form of a protein called mIGF-1 induces the muscle to send the distress signal that summons them.
Trista Dawson | EMBL
World’s Largest Study on Allergic Rhinitis Reveals new Risk Genes
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Plant mothers talk to their embryos via the hormone auxin
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For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.
To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...
For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.
Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...
Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.
A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...
Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.
"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....
Ultra-short, high-intensity X-ray flashes open the door to the foundations of chemical reactions. Free-electron lasers generate these kinds of pulses, but there is a catch: the pulses vary in duration and energy. An international research team has now presented a solution: Using a ring of 16 detectors and a circularly polarized laser beam, they can determine both factors with attosecond accuracy.
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AD Geothermal energy. By : Alegría Rosales and Dorothy Puga. Geothermal energy. E nergy that comes from the beneath the Earth’s surface down where the temperatures are extremely high. It is the heat from the Earth that can be hot water or hot rock.
By: Alegría Rosales and Dorothy Puga
Only suitable in places that have hot rocks in the Earth that produce steam for long periods.
Hard to transport.
Not many locations available to use the energy.
Not many locations adapt its use. | <urn:uuid:d51a3500-9f22-4328-ae73-39dd938464fb> | 2.5625 | 115 | Knowledge Article | Science & Tech. | 53.340238 | 95,638,263 |
Moment magnitude scale
|Part of a series on|
The scale was developed in the 1970s to succeed the 1930s-era Richter magnitude scale (ML). Even though the formulas are different, the new scale retains a continuum of magnitude values similar to that defined by the older one. Under suitable assumptions, as with the Richter magnitude scale, an increase of one step on this logarithmic scale corresponds to a 101.5 (about 32) times increase in the amount of energy released, and an increase of two steps corresponds to a 103 (1,000) times increase in energy. Thus, an earthquake of Mw of 7.0 releases about 32 times as much energy as one of 6.0 and nearly 1,000 times that of 5.0.
The moment magnitude is based on the seismic moment of the earthquake, which is equal to the shear modulus of the rock near the fault multiplied by the average amount of slip on the fault and the size of the area that slipped.
Popular press reports of earthquake magnitude usually fail to distinguish between magnitude scales, and are often reported as "Richter magnitudes" when the reported magnitude is a moment magnitude (or a surface-wave or body-wave magnitude). Because the scales are intended to report the same results within their applicable conditions, the confusion is minor.
- 1 History
- 2 Definition
- 3 Relations between seismic moment, potential energy released and radiated energy
- 4 Comparative energy released by two earthquakes
- 5 Comparison with Richter scale
- 6 Subtypes of Mw
- 7 See also
- 8 Notes
- 9 Sources
- 10 External links
Richter scale: the original measure of earthquake magnitude
In 1935, Charles Richter and Beno Gutenberg developed the local magnitude (ML) scale (popularly known as the Richter scale) with the goal of quantifying medium-sized earthquakes (between magnitude 3.0 and 7.0) in Southern California. This scale was based on the ground motion measured by a particular type of seismometer (a Wood-Anderson seismograph) at a distance of 100 kilometres (62 mi) from the earthquake's epicenter. Because of this, there is an upper limit on the highest measurable magnitude, and all large earthquakes will tend to have a local magnitude of around 7. Further, the magnitude becomes unreliable for measurements taken at a distance of more than about 600 kilometres (370 mi) from the epicenter. Since this ML scale was simple to use and corresponded well with the damage which was observed, it was extremely useful for engineering earthquake-resistant structures, and gained common acceptance.
Modified Richter scale
The Richter scale was not effective for characterizing some classes of quakes. As a result, Beno Gutenberg expanded Richter's work to consider earthquakes detected at distant locations. For such large distances the higher frequency vibrations are attenuated and seismic surface waves (Rayleigh and Love waves) are dominated by waves with a period of 20 seconds (which corresponds to a wavelength of about 60 km). Their magnitude was assigned a surface wave magnitude scale (Ms). Gutenberg also combined compressional P-waves and the transverse S-waves (which he termed "body waves") to create a body-wave magnitude scale (mb), measured for periods between 1 and 10 seconds. Ultimately Gutenberg and Richter collaborated to produce a combined scale which was able to estimate the energy released by an earthquake in terms of Gutenberg's surface wave magnitude scale (Ms).
Correcting weaknesses of the modified Richter scale
The Richter scale, as modified, was successfully applied to characterize localities. This enabled local building codes to establish standards for buildings which were earthquake resistant. However a series of quakes were poorly handled by the modified Richter scale. This series of "great earthquakes", included faults that broke along a line of up to 1000 km. Examples include the 1957 Andreanof Islands earthquake and the 1960 Chilean quake, both of which broke faults approaching 1000 km. The Ms scale was unable to characterize these "great earthquakes" accurately.
The difficulties with use of Ms in characterizing the quake resulted from the size of these earthquakes. Great quakes produced 20 s waves such that Ms was comparable to normal quakes, but also produced very long period waves (more than 200 s) which carried large amounts of energy. As a result, use of the modified Richter scale methodology to estimate earthquake energy was deficient at high energies.
The concept of seismic moment was introduced in 1966, by Keiiti Aki, a professor of geophysics at the Massachusetts Institute of Technology. He employed elastic dislocation theory to improve understanding of the earthquake mechanism. This theory proposed that the seismologic readings of a quake from long-period seismographs are proportional to the fault area that slips, the average distance that the fault is displaced, and the rigidity of the material adjacent to the fault. However, it took 13 years before the Mw scale was designed. The reason for the delay was that the necessary spectra of seismic signals had to be derived by hand at first, which required personal attention to every event. Faster computers than those available in the 1960s were necessary and seismologists had to develop methods to process earthquake signals automatically. In the mid-1970s Dziewonski started the Harvard Global Centroid Moment Tensor Catalog. After this advance, it was possible to introduce Mw and estimate it for large numbers of earthquakes. Hence the moment magnitude scale represented a major step forward in characterizing earthquakes.
Introduction of an energy-motivated magnitude Mw
Most earthquake magnitude scales suffered from the fact that they only provided a comparison of the amplitude of waves produced at a standard distance and frequency band; it was difficult to relate these magnitudes to a physical property of the earthquake. Gutenberg and Richter suggested that radiated energy Es could be estimated as
(in Joules). Unfortunately, the duration of many very large earthquakes was longer than 20 seconds, the period of the surface waves used in the measurement of Ms. This meant that giant earthquakes such as the 1960 Chilean earthquake (M 9.5) were only assigned an Ms 8.2. Caltech seismologist Hiroo Kanamori recognized this deficiency and he took the simple, but important, step of defining a magnitude based on estimates of radiated energy, Mw, where the "w" stood for work (energy):
Kanamori recognized that measurement of radiated energy is technically difficult since it involves integration of wave energy over the entire frequency band. To simplify this calculation, he noted that the lowest frequency parts of the spectrum can often be used to estimate the rest of the spectrum. The lowest frequency asymptote of a seismic spectrum is characterized by the seismic moment, M0. Using an approximate relation between radiated energy and seismic moment (which assumes stress drop is complete and ignores fracture energy),
(where E is in Joules and M0 is in N-m), Kanamori approximated Mw by
Moment magnitude scale
The formula above made it much easier to estimate the energy-based magnitude Mw, but it changed the fundamental nature of the scale into a moment magnitude scale. Caltech seismologist Thomas C. Hanks noted that Kanamori’s Mw scale was very similar to a relationship between ML and M0 that was reported by Thatcher & Hanks (1973)
Hanks & Kanamori (1979) combined their work to define a new magnitude scale based on estimates of seismic moment
Although the formal definition of moment magnitude is given by this paper and is designated by M, it has been common for many authors to refer to Mw as moment magnitude. In most of these cases, they are actually referring to moment magnitude M as defined above.
Moment magnitude is now the most common measure of earthquake size for medium to large earthquake magnitudes, but in practice seismic moment, the seismological parameter it is based on, is not measured routinely for smaller quakes. For example, the United States Geological Survey does not use this scale for earthquakes with a magnitude of less than 3.5, which is the great majority of quakes.
Current practice in official earthquake reports is to adopt moment magnitude as the preferred magnitude, i.e. Mw is the official magnitude reported whenever it can be computed. Because seismic moment (M0, the quantity needed to compute Mw) is not measured if the earthquake is too small, the reported magnitude for earthquakes smaller than M 4 is often Richter's ML.
Popular press reports most often deal with significant earthquakes larger than M ~ 4. For these events, the official magnitude is the moment magnitude Mw, not Richter's local magnitude ML.
where M0 is the seismic moment in dyne⋅cm (10−7 N⋅m). The constant values in the equation are chosen to achieve consistency with the magnitude values produced by earlier scales, such as the Local Magnitude and the Surface Wave magnitude.
Relations between seismic moment, potential energy released and radiated energy
Seismic moment is not a direct measure of energy changes during an earthquake. The relations between seismic moment and the energies involved in an earthquake depend on parameters that have large uncertainties and that may vary between earthquakes. Potential energy is stored in the crust in the form of elastic energy due to built-up stress and gravitational energy. During an earthquake, a portion of this stored energy is transformed into
- energy dissipated in frictional weakening and inelastic deformation in rocks by processes such as the creation of cracks
- radiated seismic energy .
The potential energy drop caused by an earthquake is approximately related to its seismic moment by
where is the average of the absolute shear stresses on the fault before and after the earthquake (e.g. equation 3 of Venkataraman & Kanamori 2004). Currently, there is no technology to measure absolute stresses at all depths of interest, or method to estimate it accurately, thus is poorly known. It could be highly variable from one earthquake to another. Two earthquakes with identical but different would have released different .
The radiated energy caused by an earthquake is approximately related to seismic moment by
where is radiated efficiency and is the static stress drop, i.e. the difference between shear stresses on the fault before and after the earthquake (e.g. from equation 1 of Venkataraman & Kanamori 2004). These two quantities are far from being constants. For instance, depends on rupture speed; it is close to 1 for regular earthquakes but much smaller for slower earthquakes such as tsunami earthquakes and slow earthquakes. Two earthquakes with identical but different or would have radiated different .
Because and are fundamentally independent properties of an earthquake source, and since can now be computed more directly and robustly than in the 1970s, introducing a separate magnitude associated to radiated energy was warranted. Choy and Boatwright defined in 1995 the energy magnitude
where is in J (N.m).
Comparative energy released by two earthquakes
Assuming the values of are the same for all earthquakes, one can consider Mw as a measure of the potential energy change ΔW caused by earthquakes. Similarly, if one assumes is the same for all earthquakes, one can consider Mw as a measure of the energy Es radiated by earthquakes.
Under these assumptions, the following formula, obtained by solving for M0 the equation defining Mw, allows one to assess the ratio of energy release (potential or radiated) between two earthquakes of different moment magnitudes, and :
As with the Richter scale, an increase of one step on the logarithmic scale of moment magnitude corresponds to a 101.5 ≈ 32 times increase in the amount of energy released, and an increase of two steps corresponds to a 103 = 1000 times increase in energy. Thus, an earthquake of Mw of 7.0 contains 1000 times as much energy as one of 5.0 and about 32 times that of 6.0.
Comparison with Richter scale
The moment magnitude (Mw>) scale was introduced to address the shortcomings of the Richter scale (detailed above) while maintaining consistency. Thus, for medium-sized earthquakes, the moment magnitude values should be similar to Richter values. That is, a magnitude 5.0 earthquake will be about a 5.0 on both scales. Unlike other scales, the moment magnitude scale does not saturate at the upper end; there is no upper limit to the possible measurable magnitudes. However, this has the side-effect that the scales diverge for smaller earthquakes.
Subtypes of Mw
Various ways of determining moment magnitude have been developed, and several subtypes of the Mw scale can be used to indicate the basis used.
- Mwb – Based on moment tensor inversion of long-period (~10 - 100 s) body-waves.
- Mwr – From a moment tensor inversion of complete waveforms at regional distances (~ 1,000 miles). Sometimes called RMT.
- Mwc – Derived from a centroid moment tensor inversion of intermediate- and long-period body- and surface-waves.
- Mww – Derived from a centroid moment tensor inversion of the W-phase.
- Mwp (Mi) – Developed by Seiji Tsuboi for quick estimation of the tsunami potential of large near-coastal earthquakes from measurements of the P-waves, and later extended to teleseismic earthquakes in general.
- Mwpd – A duration-amplitude procedure which takes into account the duration of the rupture, providing a fuller picture of the energy released by longer lasting ("slow") ruptures than seen with Mw.
- Hanks & Kanamori 1979.
- "Glossary of Terms on Earthquake Maps". USGS. Archived from the original on 2009-02-27. Retrieved 2009-03-21.
- "USGS Earthquake Magnitude Policy (implemented on January 18, 2002)". Archived from the original on May 4, 2016.
- "On Earthquake Magnitudes".
- Kanamori 1978.
- Aki 1966b.
- Dziewonski & Gilbert 1976.
- "Global Centroid Moment Tensor Catalog". Globalcmt.org. Retrieved 2011-11-30.
- Aki 1972.
- Kanamori 1977.
- Boyle 2008.
- Kanamori 1977.
- Kostrov 1974; Dahlen 1977.
- Choy & Boatwright 1995
- USGS Technical Terms used on Event Pages.
- Tsuboi et al. 1995.
- Bormann, Wendt & Di Giacomo 2013, §126.96.36.199, p. 135.
- Bormann, Wendt & Di Giacomo 2013, §188.8.131.52, pp. 137–128.
- Aki, Keiiti (1966b), "4. Generation and propagation of G waves from the Niigata earthquake of June 14, 1964. Part 2. Estimation of earthquake moment, released energy and stress-strain drop from G wave spectrum" (PDF), Bulletin of the Earthquake Research Institute, 44: 73–88.
- Aki, Keiiti (April 1972), "Earthquake Mechanism", Tectonophysics, 13 (1–4): 423–446, Bibcode:1972Tectp..13..423A, doi:10.1016/0040-1951(72)90032-7.
- Bormann, P.; Wendt, S.; Di Giacomo, D. (2013), "Chapter 3: Seismic Sources and Source Parameters" (PDF), in Bormann, New Manual of Seismological Observatory Practice 2 (NMSOP-2), doi:10.2312/GFZ.NMSOP-2_ch3.
- Boyle, Alan (May 12, 2008), Quakes by the numbers, MSNBC, retrieved 2008-05-12,
That original scale has been tweaked through the decades, and nowadays calling it the "Richter scale" is an anachronism. The most common measure is known simply as the moment magnitude scale..
- Choy, George L.; Boatwright, John L. (10 September 1995), "Global patterns of radiated seismic energy and apparent stress", Journal of Geophysical Research, 100 (B9): 18205–28, Bibcode:1995JGR...10018205C, doi:10.1029/95JB01969.
- Dahlen, F. A. (February 1977), "The balance of energy in earthquake faulting", Geophysical Journal International, 48 (2): 239–261, Bibcode:1977GeoJ...48..239D, doi:10.1111/j.1365-246X.1977.tb01298.x.
- Dziewonski, Adam M.; Gilbert, Freeman (1976), "The effect of small aspherical perturbations on travel times and a re-examination of the corrections for ellipticity" (PDF), Geophysical Journal of the Royal Astronomical Society, 44 (1): 7–17, Bibcode:1976GeoJ...44....7D, doi:10.1111/j.1365-246X.1976.tb00271.x.
- Hanks, Thomas C.; Kanamori, Hiroo (May 10, 1979), "A Moment magnitude scale" (PDF), Journal of Geophysical Research, 84 (B5): 2348–50, Bibcode:1979JGR....84.2348H, doi:10.1029/JB084iB05p02348, Archived from the original on August 21, 2010.
- Kanamori, Hiroo (July 10, 1977), "The energy release in great earthquakes" (PDF), Journal of Geophysical Research, 82 (20): 2981–2987, Bibcode:1977JGR....82.2981K, doi:10.1029/jb082i020p02981.
- Kanamori, Hiroo (February 2, 1978), "Quantification of Earthquakes" (PDF), Nature, 271: 411–414, Bibcode:1978Natur.271..411K, doi:10.1038/271411a0.
- Kostrov, B. V. (1974), "Seismic moment and energy of earthquakes, and seismic flow of rock [in Russian]", Izvestiya, Akademi Nauk, USSR, Physics of the solid earth [Earth Physics], 1: 23–44 (English Trans. 12–21).
- Thatcher, Wayne; Hanks, Thomas C. (December 10, 1973), "Source parameters of southern California earthquakes", Journal of Geophysical Research, 78 (35): 8547–8576, Bibcode:1973JGR....78.8547T, doi:10.1029/JB078i035p08547.
- Tsuboi, S.; Abe, K.; Takano, K.; Yamanaka, Y. (April 1995), "Rapid Determination of Mw from Broadband P Waveforms", Bulletin of the Seismological Society of America, 85 (2): 606–613
- Utsu, T. (2002), Lee, W.H.K.; Kanamori, H.; Jennings, P.C.; Kisslinger, C., eds., "Relationships between magnitude scales", International Handbook of Earthquake and Engineering Seismology, International Geophysics, Academic Press, A (81), pp. 733–46.
- Venkataraman, Anupama; Kanamori, H. (11 May 2004), "Observational constraints on the fracture energy of subduction zone earthquakes" (PDF), Journal of Geophysical Research, 109 (B05302), Bibcode:2004JGRB..109.5302V, doi:10.1029/2003JB002549. | <urn:uuid:2e133996-8497-4d0a-a47d-0277a7798c23> | 4.21875 | 4,157 | Knowledge Article | Science & Tech. | 51.078874 | 95,638,269 |
What is byssal thread?
byssal thread meaning one of many thin, hairlike filaments secreted by certain mollusks for attachment to a substrate
The byssal gland is located within the foot of the mussel. It produces secretions which are used to form byssal threads for attachment to substrates. (Photo: Great Lakes Sea Grant Network Exotic Species Library, Ontario Ministry of Natural Resources)
reference: Coral Reef Information System – GlossaryWhat is | <urn:uuid:18e5a609-a416-4138-8c99-40b448c3654d> | 2.734375 | 101 | Knowledge Article | Science & Tech. | 24.581275 | 95,638,293 |
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Math Lessons and Worksheets
Pi is Irrational
Pi is an irrational number. This means that pi cannot be written as a fraction of two whole numbers and that the decimal digits of pi continue infinitely without any repeating pattern. Pi is roughly 3.14159265358979323846.... Using computers, pi has been calculated to many million of digits past the decimal point. For many purposes, using the approximation 3.1416 is sufficient. Good approximations for pi are 22/7 and 355/113.
Pi is used in many calculations, including finding the circumference and area of a circle, and the volume and surface area of a sphere, cone, and cylinder. Pi is also used in geometry, probability and statistics, and many other fields.
(radius = r)
|2π r||π r2|
(radius = r)
|4π r2||(4/3) π r3|
(radius = r, height = h)
|2π r h (without the ends)||π r2 h|
The Name Pi
Mathematicians began using word pi (the Greek letter π) for this ratio in the early 1700s; the name pi was given to this number because p is short for perimeter.
Pi Day is a mathematical holiday celebrated by math classes on March 14th (3/14), with the peak celebration occuring at at 1:59 p.m (3/14 1:59). Pie, pizza, and other round foods are often served at Pi Day celebrations.
Write Eight Round Things
Think of and write eight round things. Then, for each word, write a sentence containing the word. Sample answers: pie, disk, pie plate, necklace, plate, circle, wheel, pupil of the eye.
Write Eight Round Things in Categories
Think of and write eight round things in categories, including: food, sports item, school item, household item, animal, article of clothing, part of a vehicle, astronomical object. Then, for each word, write a sentence containing the word. Sample answers: pizza, basketball hoop, globe, plate, sand dollar, bracelet, steering wheel, moon.
Draw Four Round Things
Draw four round things. Below each item, write its name.
Draw Four Spherical Things
Draw four spherical things. Below each item, write its name.
A Printable Worksheet
In this worksheet, the student measures the circumference and diameter of three circles, and then calculates the ratios of the circumferences to the diameters (approximating pi). The student will need a ruler and a short length of string or yarn (a bit less than a foot long); the yarn is used to measure the circumferences. Or go to the pdf version.
What is Pi?
A Printable Worksheet
A printout about what pi is. Measure the circumference and diameter of four printed circles, then determine what relationship between the circumference and the diameter gives a constant value (pi). This printable worksheet demonstrates to the student that pi is the ratio of a circle's circumference to diameter, for any circle The student will need a ruler and a short length of string or yarn (a bit less than a foot long); the yarn is used to measure the circumferences. Or go to the pdf version.
|All-Purpose Check-Off Card
Print a card that is good for many occasions, including Happy Birthday, Valentine's Day, Mother's Day, Father's Day, Congratulations, Graduation, Get Well Soon, Pi Day, Easter, Christmas, Hanukkah, Ramadan, Anniversary, New Year or Many Thanks. Just print the card, then check off the appropriate occasion.
Label Lower-case Greek Letters
Label the lower-case Greek letters.
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Restrictions on night flights could ease the aviation industry's fast-growing contribution to global warming, say UK scientists.
Dr Nicola Stuber and fellow meteorologists at the University of Reading report
their findings in today's issue of the journal Nature.
certain altitudes, aircraft produce contrails - condensation trails caused
when the plane's hot exhaust hits the chilly atmosphere.
contrails have a surprisingly big but also complex effect on the climate.
Because they are clouds, they trap heat that is emitted by the Earth's
surface, creating a "greenhouse effect" that adds to warming.
during daytime, these clouds have a cooling effect because they are white and
thus reflect some of the Sun's energy back into space. In certain conditions,
contrails can exist for several hours.
Stuber and team estimate the
radiation caused by contrails at a busy flight corridor in southeast
Using high-resolution aircraft flight data and routine weather
balloon data, they looked at "persistent" contrails: wakes that remained for
an hour or more after the aircraft had flown over.
account for only 22% of Britain's annual air traffic but contribute between 60
to 80% of the greenhouse effect from contrails, the scientists
Winter flights warm more
Stuber and team also
found that flights during the winter months could contribute more to global
"We also found that flights between December and February
contribute half of the annual mean climate warming, even though they account
for less than a quarter of annual air traffic," says Stuber.
there are fewer flights during the winter months, the conditions needed to
form contrails - the right temperature, amount of moisture in the air and
aircraft altitude - are found more often then.
Global emissions of man-made CO2 are between 6.2 billion
and 6.9 billion tonnes per year. Added to this are around 1.5 billion tonnes
from land use.
Commercial aircraft account for only a small
contribution compared with power stations, industry and road traffic.
However, passenger travel is growing at the rate of around 5% a year,
which means that this share will grow fast.
A 1999 estimate by the UN's
Intergovernmental Panel on Climate Change (IPCC) found that the airline
industry accounted for 2% of man-made CO2 emissions in 1992. But it would rise
to as much as 15% by 2050.
Environmentalists are angry, complaining
that airlines get a free ride when it comes to environmental taxes.
Changing altitude could also help
In addition to
rescheduling night flights for the daytime, planes could diminish their
contribution to global warming by changing their altitude.
published last year in the journal Transportation Research suggests
that the regions of "ice-supersaturated" air where contrails form is only
about 500 metres thick.
The goal would be to fit sensors on aircraft
that could inform pilots where this layer lies, thus enabling them to shift | <urn:uuid:47c24078-261b-417f-b59e-68e1b505584b> | 3.6875 | 623 | News Article | Science & Tech. | 45.998122 | 95,638,317 |
is a right angled triangle.
It is measured that
Now, calculate value of the cosine at angle by considering the length of the adjacent side and length of the hypotenuse.
The value of cosine at the angle is for the triangle .
is another right angled triangle and it is measured that,
Repeat same procedure to calculate the value of cosine at an angle for the right angled triangle .
List of most recently solved mathematics problems.
Learn how to solve easy to difficult mathematics problems of all topics in various methods with step by step process and also maths questions for practising. | <urn:uuid:2633c57b-ce9a-4ee7-8135-50fb44c2884e> | 3.703125 | 122 | Content Listing | Science & Tech. | 47.353127 | 95,638,323 |
The atom consists of a nucleus, where most of the mass of the atom is concentrated, with electrons in orbits around the nucleus. The electrons are negatively charged. In a material that is an electrical conductor, such as copper, aluminum, and a number of other metals, it is possible for certain of the electrons to move from atom to atom along the conductor. The force that can cause these electrons to move along the conductor is called a voltage, or electromotive force (emf).
KeywordsFossil Fuel Electric Power Electric Power Generation Hydroelectric Power Nuclear Fission
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Members of Working Group 4 attempted to account for human needs and impacts in the understanding of the role of forests in the global carbon (C) cycle. A major factor in the postindustrial era is the rapidly expanding human population, and the attendant acceleration of landuse change which directly influences C storage in global forests, particularly in the tropics. The important roles of forest ecosystems and their management are increasingly being recognised in global strategies proposed to mitigate the effects of anticipated climate change. Many of these strategies however, focus entirely on the biophysical aspects of the problem while ignoring human needs, and in the opinions of some, ignoring the socio-economic realities facing developing and developed countries alike. If human needs are not fully considered in international policy and management decisions relating to the world’s forests, it is likely there will be increased suffering and this will cause greater problems, both within and between countries, hence delaying or even destroying the opportunity for progress.
KeywordsForest Management Sustainable Forest Management Mitigation Option Tropical Deforestation Global Forest
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This chapter outlines the Basic programming concepts in MATLAB such as loop generation and program flux control. Programming style and debugging techniques are also presented.
KeywordsEvent Table Output Argument Input Argument Catch Statement Programming Style
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.
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Floods, Food Chains, and Ecosystem Processes in Rivers
Disturbance regimens link species and ecosystems. For example, floods that scour channels in river drainage networks can also alter trophic networks that link river biota. The impacts of flood disturbance regimens on trophic structure vary among communities, depending on the attributes of constituent species. In the midwestern United States, where algivorous fish are the principal herbivores, floods may spatially rearrange predators and prey among pool habitats, but larger (reach) scale food chain patterns are not affected, or if altered, are rapidly restored. In California rivers, where fish faunas are relatively depauperate, invertebrates are the chief primary consumers. Here, hydrologic disturbance or its absence does affect food chain length at the reach scale. Scouring floods allow weedy invertebrate species to dominate early successional primary consumer guilds. These species are resilient following physical disturbance but subsequently vulnerable to predation. After prolonged low flow during drought, or in regulated channels with artificially stabilized hydrographs, lower trophic levels become dominated by armored or sessile taxa that are relatively invulnerable to predators. In these late successional communities, the biomass of primary producers is chronically suppressed, and energy flow to higher trophic levels appears to attenuate. In addition, other ecosystem functions may be changed, including nitrogen fixation and river–watershed exchange mediated by floating algal mats
KeywordsTrophic Level Food Chain Aquatic Insect Lower Trophic Level Food Chain Length
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In offshore waters with relatively low primary production, drifting seaweeds composed of Sargassum species form an identical ecosystem such as an oasis in desert. Commercially important pelagic fishes such as jack mackerel (Trachurus japonicus) and yellow tail (Seriola quinqueradiata) spawn in East China Sea pass their juvenile period accompanying drifting seaweeds. Therefore drifting seaweeds are very important not only in offshore ecosystem but also fishery resources. However the distribution of drifting seaweeds in East China Sea has scarcely known. Then we conducted two research cruises of R/V Hakuho-Maru in May 2002 and in March 2004. During the cruises, drifting seaweeds were visually observed from the bridge and sampled with a towing net. The observation revealed that the drifting seaweeds were distributed along the front between the Kuroshio Current and coastal waters and mainly composed of one seaweed species, Sargassum horneri (Turner) C. Agardh from spring to early summer. There are no reports on geographical distribution of this species in the coasts south of southern Kyushu Island in Japan. Kuroshio Current flows northeastward there. Buoys with GPS attached to drifting seaweeds released off Zhejiang Province, China, in March 2005 to track their transport. Their positions monitored by ORBCOM satellite showed that they were transported to the area in East China Sea, where the drifting seaweeds were observed during the cruises, in 2 months. These facts suggest that S. horneri detached from Chinese coast in March or months earlier than March could be transported to fringe area of continental shelf and waters influenced by Kuroshio Current from March to May. Therefore the Sargassum forests, especially S. horneri, along the Chinese coast play a very important role in the ecosystem of the East China Sea as a source of drifting seaweeds. © 2006 Elsevier B.V. All rights reserved.
Mendeley saves you time finding and organizing research
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A nitrogenous base, or nitrogen-containing base, is an organic molecule with a nitrogen atom that has the chemical properties of a base. The main biological function of a nitrogenous base is to bond nucleic acids together. A nitrogenous base owes its basic properties to the lone pair of electrons of a nitrogen atom.
Nitrogenous bases are typically classified as the derivatives of two parent compounds, pyrimidine and purine. They are non-polar and due to their aromaticity, planar. Both pyrimidines and purines resemble pyridine and are thus weak bases and relatively unreactive towards electrophilic aromatic substitution.
Role in nucleic acids
In the biological sciences, nitrogenous bases are increasingly termed nucleobases because of their role in nucleic acids - their flat shape is particularly important when considering their roles as the building blocks of DNA and RNA. A set of five nitrogenous bases is used in the construction of nucleotides, which in turn build up the nucleic acids like DNA and RNA. These nitrogenous bases are adenine (A), uracil (U), guanine (G), thymine (T), and cytosine (C). The nitrogenous bases form hydrogen bonds between opposing DNA strands to form the rungs of the "twisted ladder" or double helix of DNA or a biological catalyst that is found in the nucleotides. Adenine is always paired with thymine, and guanine is always paired with cytosine. These are known as base pairs. Uracil is only present in RNA, replacing thymine. Pyrimidines include thymine, cytosine, and uracil. They have a single ring structure. Purines include adenine and guanine. They have a double ring structure.
- Nelson, David L. and Michael M Cox (2008). Lehninger Principles of Biochemistry, ed. 5, W.H. Freeman and Company. p. 272. ISBN 071677108X.
- Carey, Francis A. (2008). Organic Chemistry, ed. 6, Mc Graw Hill. p. 1206. ISBN 0072828374.
- Angstadt, Carol N (1997) Purine and Pyrimidine Metabolism. library.med.utah.edu
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When a copy constructor may be called?
(A) When an object of the class is returned by value.
(B) When an object of the class is passed (to a function) by value as an argument.
(C) When an object is constructed based on another object of the same class
(D) When compiler generates a temporary object.
(E) All of the above
Explanation: See When is copy constructor called?
Quiz of this Question
- C++ | Constructors | Question 3
- C++ | Constructors | Question 4
- C++ | References | Question 1
- C++ | Class and Object | Question 3
- C++ | Constructors | Question 6
- C++ | Misc C++ | Question 8
- C++ | Misc C++ | Question 7
- C++ | Inheritance | Question 14
- C++ | Misc C++ | Question 6
- C++ | const keyword | Question 5 | <urn:uuid:530624e8-5e9d-4be9-b7e8-3f257251e3f6> | 2.796875 | 203 | Q&A Forum | Software Dev. | 69.603034 | 95,638,347 |
A progressive increase in the brightness of the planet Neptune suggests that, like Earth, the distant planet has seasons.
A time series of images of the planet Neptune taken by the Hubble Space Telescope illustrate increasing cloudiness that is a hallmark of seasonal change. The growing bands of clouds in the southern hemisphere of the planet suggest seasonal change. Because the planet takes about 165 years to orbit the sun, the seasons on Neptune last more than 40 years.
Image credit: L. Sromovsky, P.Fry (University of Wisconsin), and NASA
Observations of Neptune made during a six-year period with NASAs Hubble Space Telescope by a group of scientists from the University of Wisconsin-Madison and NASAs Jet Propulsion Laboratory (JPL) show that the planet is exhibiting a significant increase in brightness. The changes, observed mostly in the planets southern hemisphere, show a distinct increase in the amount and brightness of the banded cloud features that are a distinctive feature of the planet.
"Neptunes cloud bands have been getting wider and brighter," says Lawrence A. Sromovsky, a senior scientist at UW-Madisons Space Science and Engineering Center and a leading authority on Neptunes atmosphere. "This change seems to be a response to seasonal variations in sunlight, like the seasonal changes we see on Earth."
Lawrence Sromovsky | EurekAlert!
Subaru Telescope helps pinpoint origin of ultra-high energy neutrino
16.07.2018 | National Institutes of Natural Sciences
Nano-kirigami: 'Paper-cut' provides model for 3D intelligent nanofabrication
16.07.2018 | Chinese Academy of Sciences Headquarters
For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.
To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...
For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.
Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...
Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.
A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...
Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.
"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....
Ultra-short, high-intensity X-ray flashes open the door to the foundations of chemical reactions. Free-electron lasers generate these kinds of pulses, but there is a catch: the pulses vary in duration and energy. An international research team has now presented a solution: Using a ring of 16 detectors and a circularly polarized laser beam, they can determine both factors with attosecond accuracy.
Free-electron lasers (FELs) generate extremely short and intense X-ray flashes. Researchers can use these flashes to resolve structures with diameters on the...
13.07.2018 | Event News
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03.07.2018 | Event News
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16.07.2018 | Earth Sciences | <urn:uuid:e0987f45-3ce6-412b-90ca-194107caa555> | 3.46875 | 919 | Content Listing | Science & Tech. | 38.026937 | 95,638,348 |
Altogether, the six tables of Chapters 2–7 list a grand total of 465 enzymes, each of which during its catalytic cycle forms a covalent bond with its substrate or some fragment of it. These long lists of enzymes point the contrast between the abundance of positive evidence for covalent catalysis and the total dearth of positive evidence for single-displacement catalysis (1). How these enzymes are apportioned among the six major classes of enzymes recognized by the Enzyme Commission (hereinafter referred to as the EC enzymes) is shown in Table 8.1 at the end of this chapter. It is clear that at least 21% of all the EC enzymes effect their catalysis through covalent enzyme-substrate intermediates. This figure assumes an even greater significance when it is realized that the vast majority of the 2200 EC enzymes have never been investigated from the standpoint of chemical mechanism. Prior to the survey embodied in the tables of Chapters 2–7, the prevalence of so much covalent catalysis by enzymes was hardly suspected.
KeywordsHydro Lases Enzyme Commission Code Number Pure Logic Scientific Inference
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Energy Band Theory
In this chapter the one-electron energy band theories for the crystalline solids are presented. The importance of energy band theories for a crystalline solid is due to the fact that many important physical and optical properties of a solid can be readily explained by using its energy band structure. In general, the energy band structure of a solid can be constructed by solving the one-electron Schrödinger equation for electrons in a crystalline solid which contains a large number of interacting electrons and atoms. To simplify the difficult task of solving the Schrödinger equation for the many-body problem in a crystal, the effects that arise from the motion of atomic nuclei must be neglected (i.e., it is assumed that the nuclei are at rest in equilibrium positions at each lattice site). Under this condition, the nuclear coordinates enter the problem only as a constant parameter. However, even though the problem has been confined as a purely electronic one, there are still the many-electron problems in the system which cannot be solved explicitly. Therefore, it is necessary to apply additional approximations to solving the Schrödinger equation for electrons in a crystalline solid.
KeywordsEnergy Band Electron Wave Function Valence Band Maximum Conduction Band Minimum Energy Band Structure
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By Rick Moriarty | firstname.lastname@example.org
By now, you're probably aware of the impending 2017 solar eclipse. On Aug. 21, the moon will block the sun's light along a 70-mile-wide path from the West Coast to the East Coast of the United States.
Those inside the path will see a total eclipse, in which the day will turn to night as the moon completely blocks the sun's light. Those outside the "path of totality" will see a partial eclipse.
It will be the first total eclipse visible coast to coast since 1918. So here are some cool facts about our celestial neighbor, earth's only permanent natural satellite, that you can impress your friends with as you await the Great American Eclipse.
1. When and how was the moon formed?
The moon was formed about 4.5 billion years ago, not long after the earth was formed. After studying moon rocks brought back by the Apollo astronauts, most scientists concluded that the moon is actually a big chunk of the earth that got ejected into space when a Mars-sized object struck the young (and still hot and molten) earth.
2. Is the dark side of the moon really dark?
The far side of the moon always faces away from the earth and is often called the "dark side of the moon." But it's not really dark. Just like with the earth, the moon rotates on its axis, so the far side gets its daily dose of sunlight just like the near side does.
The term "dark side of the moon" probably came about because the far side could not be seen by humans until the space age. So it was dark to us in the sense that it was unknown and mysterious.
Earth "rises" over the lunar horizon as seen from Apollo 11 in July 1969. (NASA)
3. How far is the moon from earth?
When it formed, the moon was only 14,000 miles from the earth, so it would have looked many times bigger in the sky than it does today. It's moving away from us at the rate of 1.6 inches a year - about as fast as fingernails grow - and is now an average of 238,855 miles from us. (We say average because the moon's orbit is not a perfect circle.)
4. Does the moon really create our ocean tides?
The moon's gravitational tug is the primary cause of our ocean tides. The much larger sun also helps create our tides, but to a much lesser extent because of its greater distance from earth. By the way, tides were much bigger when the moon was significantly closer to the earth, and high tides were more frequent and went hundreds of miles inland. | <urn:uuid:3d37de3e-e2bb-46be-b561-d0998473a65d> | 3.671875 | 555 | Listicle | Science & Tech. | 75.121224 | 95,638,386 |
Mystery of 'proton spin' solved? Particle collider reveals that quarks AND gluons may hold answer to great subatomic puzzle
- Researchers using a collider in New York say they have solved 'spin' mystery
- Since an experiment in 1987 the origins of proton spin have been unknown
- It had once been thought to be cause exclusively by quarks
- But this was proved to be wrong in the failed experiment 27 years ago
- Now a new study says gluons play an important role in proton spin
- Could bring to a close one of the greatest mysteries of subatomic physics
In 1987 scientists at the European Muon Collaboration (EMC) at Cern were left baffled when their experiment to work out why and how protons 'spin' was unsuccessful.
The conundrum became known as the ‘proton spin crisis’ and has continued to prove puzzling for 27 years, but now researchers think they have the answer.
A study has shown that a subatomic particle known as a gluon may be responsible for giving the proton the majority of its spin, bringing to an end a decades-long puzzle.
Researchers using a collider in New York say they have solved the 'spin' mystery of protons. Since an experiment in 1987 the origins of proton spin have been unknown. It had once been thought to be cause exclusively by three quarks (illustrated), but now scientists think gluons play an important role
SUBATOMIC PHYSICS IN BRIEF
Atoms are usually made of protons, neutrons and electrons
These are made of even smaller elementary particles.
Elementary particles, also known as fundamental particles, are the smallest particles we know to exist.
They are subdivided into two groups, the first being fermions, which are said to be the particles that make up matter.
The second are bosons, the force particles that hold the others together.
Within the group of fermions are subatomic particles known as quarks.
When quarks combine in threes, they form compound particles known as baryons.
Protons are probably the best-known baryons.
quarks interact with corresponding anti-particles (such as
anti-quarks), which have the same mass but opposite charges.
When this happens, they form mesons.
often turn up in the decay of heavy man-made particles, such as those
in particle accelerators, nuclear reactors and cosmic rays.
Mesons, baryons, and other kinds of particles that take part in interactions like these are called hadrons.
The latest research was conducted by Dr Daniel de Florian from the University of Buenos Aires and colleagues using a collider at Brookhaven National Laboratory in Upton, New York.
Previously it had been thought that the proton’s spin was caused exclusively by subatomic particles known as quarks.
But the experiment in 1987 had showed that quarks failed to account for the entirety of the proton’s spin.
Quarks are the subatomic particles that make up larger particles such as protons, while gluons are the ‘glue’ that holds them together.
The term spin here is somewhat of a misnomer here, however.
It does not describe the process of actual spinning, like a ball rotating, but it refers to what is basically ‘quantum spinning’, also called ‘nuclear spin’.
Spin at a quantum level - the smallest you can possibly get - is defined as a physical constant that explains how particles have a magnetic field, interact and so on.
How protons get this physical constant, however, was a mystery.
Subatomic particles are said to have different values of spin - for example quarks have a spin of ½ in either a positive or negative direction.
Protons have a spin of ½, which had led scientists to believe their spin could be accounted by two quarks of one orientation spin, and one the other.
This, however, was not the case, with only a quarter of the proton’s spin coming from the quarks.
‘That was the naïve idea 25 years ago,’ Dr Daniel de Florian tells Scientific American.
‘By the end of the ‘80s it was possible to measure the contribution of the spin of the quarks to the spin of the proton, and the first measurement showed it was 0 percent. That was a very big surprise.’
Later measurements would show this contribution to be up to 25 per cent of the proton’s spin, leaving at least 75 per cent still accounted for.
WHAT IS A QUARK?
Quarks are elementary particles, the smallest particles we know to exist.
When they combine they form compound particles known as hadrons.
Quarks are said to have six ‘flavours’: Up, Down, Charm, Strange, Top and Bottom.
Combinations of quarks within these flavours gives rise to the ‘larger’ particles.
Groups of three quarks are known as baryons.
An example of a baryon is a proton, which is made of two 'Up' quarks and a 'Down' quark.
The latest research was conducted by Dr Daniel de Florian from the University of Buenos Aires and colleagues using a collider at Brookhaven National Laboratory in Upton, New York. The Relativistic Heavy Ion Collider (top, center) is 2.4 miles (3.9 kilometres) in circumference, and dominates Brookhaven's 5,265-acre campus
The new research shows that gluons, which have a spin of 1, contribute as much as half of the proton’s spin.
This was based on proton-proton collisions at the Relativistic Heavy Ion Collider (RHIC).
When protons are smashed together their interaction is controlled by the strong force.
This is determined by gluons, meaning they are intricately involved in the collisions of protons.
The orientation of the protons’ spins was then used to determine that gluons must indeed have an effect on spin.
More data is needed from collisions at lower momentum to confirm the result, but for now it looks like one of the great mysteries in subatomic physics might finally be solved.
And doing so will enable scientists to better understand how particles get their mass.
One of the other unsolved mysteries of subatomic physics is that of confinement - why quarks, gluons and so forth are only ever found within other subatomic particles like protons, and not by themselves.
Solving this would help explain how quarks and gluons in turn get their own spin.
This result could be an important factor in determining where proton mass comes from.
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The evidence for this potentially record-breaking speed comes, in part, from the features highlighted in this composite image. X-ray observations from Chandra (green) and XMM-Newton (purple) have been combined with infrared data from the 2MASS project and optical data from the Digitized Sky Survey (colored red, green and blue, but appearing in the image as white).
Using Chandra, XMM-Newton, and the Parkes radio telescope, researchers have found evidence for what may be the fastest moving pulsar ever seen. The large field of view contains XMM-Newton data (purple) that contains supernova remnant, which as been combined infrared and optical data (colored red, green and blue that appears as white). The Chandra image in bright green shown in the inset ("X-ray close-up") reveals a comet-shaped X-ray source well outside the boundary of the supernova remnant. Astronomers think object is a pulsar that may be moving at about 6 million miles per hour, which would make it one of the fastest ever detected if confirmed. Credit: X-ray: NASA/CXC/UC Berkeley/J. Tomsick et al and ESA/XMM-Newton; Optical: DSS, 2MASS/UMass/IPAC-Caltech/NASA/NSF
The large area of diffuse X-rays seen by XMM-Newton was produced when a massive star exploded as a supernova, leaving behind a debris field, or supernova remnant known as SNR MSH 11-16A. Shocks waves from the supernova have heated surrounding gas to several million degrees Kelvin, causing the remnant to glow brightly in X-rays.
The Chandra image shown in the inset ("X-ray close-up") reveals a comet-shaped X-ray source well outside the boundary of the supernova remnant. This source consists of a point-like object with a long tail trailing behind it for about 3 light years. The bright star nearby and also the one in SNR MSH11-16A are both likely to be foreground stars unrelated to the supernova remnant.
The point-like X-ray source was discovered by the International Gamma-Ray Astrophysics Laboratory, or INTEGRAL, and is called IGR J11014-6103 (or IGR J11014 for short). It may be a rapidly spinning, super-dense star (known as a "pulsar", a type of neutron star) that was ejected during the explosion. If so, it is racing away from the center of the supernova remnant at millions of miles per hour.
The favored interpretation for the tail of X-ray emission is that a pulsar wind nebula, that is, a "wind" of high-energy particles produced by the pulsar, has been swept behind a bow shock created by the pulsar's high speed. (A similar case was seen in another object known as PSR B1957+20 [http://chandra.harvard.edu/photo/2003/b1957/closer_look.html]).
The elongated emission is pointing towards the center of MSH 11-61A where the pulsar would have been formed, supporting the idea that the Chandra image is of a pulsar wind nebula and its bow shock. Another interesting feature of the Chandra image, also seen with XMM-Newton, is the faint X-ray tail extending to the top-right. The cause of this feature is unknown, but similar tails have been seen from other pulsars that also do not line up with the pulsar's direction of motion.
Based on earlier observations, astronomers estimate that the age of MSH 11-61A is approximately 15,000 years, and it lies at a distance of about 30,000 light years away from Earth. Combining these values with the distance that the pulsar has appeared to have traveled from the center of the MSH 11-61A, astronomers estimate that IGR J11014 is moving at a speed between 5.4 million and 6.5 million miles per hour.
The only other neutron star associated with a supernova remnant that may rival this in speed is the candidate found in the supernova remnant known as G350.1-0.3. The speed of the neutron star candidate in this system is estimated to lie between 3 and 6 million miles per hour (http://chandra.harvard.edu/photo/2012/g350/).
The high speeds estimated for both IGR J11014 and the neutron star candidate in G350.1-0.3 are preliminary and need to be confirmed. If they are confirmed, explaining the high speeds of the neutron star presents a severe challenge to existing models for supernova explosions.
One important caveat in the conclusion that IGR J11014 may be the fastest moving pulsar is that pulsations have not been detected in it during a search with the Commonwealth Scientific and Industrial Research Organization (CSIRO) Parkes radio telescope. This non-detection is not surprising for a pulsar located about 30,000 light years away.
However, there are other pieces of evidence that support the pulsar interpretation. First, the lack of detection of a counterpart to the X-ray source in optical or infrared images supports the idea that it is a pulsar, since such objects are very faint at these wavelengths. Also, there are no apparent differences in the brightness of the source between XMM-Newton observations in 2003 and the Chandra observations in 2011, behavior that is expected if IGR J11014 is a pulsar. Finally, the X-ray spectrum of the source, that is, its signature in energy, is similar to what astronomers expect to see for a pulsar.
These results were published in the May 10, 2012 issue of The Astrophysical Journal Letters. The authors were John Tomsick and Arash Bodaghee (University of California, Berkeley), Jerome Rodriguez and Sylvain Chaty (University of Paris, CEA Saclay), Fernando Camilo (Columbia University), Francesca Fornasini (UC Berkeley), and Farhid Rahoui (Harvard-Smithsonian Center for Astrophysics).
NASA's Marshall Space Flight Center in Huntsville, Ala., manages the Chandra program for NASA's Science Mission Directorate in Washington. The Smithsonian Astrophysical Observatory controls Chandra's science and flight operations from Cambridge, Mass.
Megan Watzke | EurekAlert!
Computer model predicts how fracturing metallic glass releases energy at the atomic level
20.07.2018 | American Institute of Physics
What happens when we heat the atomic lattice of a magnet all of a sudden?
18.07.2018 | Forschungsverbund Berlin
A new manufacturing technique uses a process similar to newspaper printing to form smoother and more flexible metals for making ultrafast electronic devices.
The low-cost process, developed by Purdue University researchers, combines tools already used in industry for manufacturing metals on a large scale, but uses...
For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.
To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...
For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.
Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...
Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.
A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...
Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.
"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....
13.07.2018 | Event News
12.07.2018 | Event News
03.07.2018 | Event News
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The ends of the chromosomes, the telomeres, are repetitive DNA sequences that shorten every time a cell divides during the process of duplicating its genome. Once the telomeres become very short the cell stops dividing. Thus, telomeres work like a cellular clock that keeps an eye on the number of cell divisions.
And once the cell's time is over it can no longer divide. Circumventing this control mechanism is crucial for tumor cells in order to proliferate without limits. In the majority of tumors this is accomplished by reactivating telomerase, an enzyme that normally extends the telomeres only in embryonic cells, and thus resets the cellular clock during development. However, a 10-15% fraction of tumors keeps on dividing without telomerase by making use of what is called the ALT-mechanism for "Alternative Lengthening of Telomeres". The hallmark of ALT cancer cells is a special type of complexes of promyelocytic leukemia (PML) protein at the telomeres that are termed ALT-associated PML nuclear bodies or APBs.
ALT-tumors can be identified by the presence of APBs on fluorescence microscopy images since normal cells do not have these structures. However, the function of APBs has remained mysterious. In a recent study, Inn Chung and Karsten Rippe from the German Cancer Research Center together with Heinrich Leonhard from the LMU in Munich applied a novel approach to study APBs. They succeeded in artificially making APBs in living cells by tethering PML and other APB proteins to the telomeres. In this manner they could not only trace the assembly of APBs but were able to investigate what happens after APB formation. They could show that the de novo formed APBs induced the extension of the telomere repeat sequence by a DNA repair synthesis mechanism. This demonstrates for the first time that APBs have an important function for the alternative telomere lengthening mechanism, and suggests that disrupting APBs would stop proliferation of ALT-positive tumor cells once their telomeres become too short. This makes APBs a promising new target of cancer cells, in which the ALT mechanism is active.
Publication: Chung, I., Leonhardt, H. & Rippe, K. (2011). De novo assembly of a PML nuclear subcompartment occurs through multiple pathways and induces telomere elongation. J. Cell Sci., doi: 10.1242/jcs.084681.
The German Cancer Research Center (Deutsches Krebsforschungszentrum, DKFZ), employing over 2,500 staff members, is the largest biomedical research institute in Germany. More than 1,000 scientists are working to investigate the mechanisms of cancer development, identify cancer risk factors and develop new strategies for better cancer prevention, more precise diagnosis and effective treatment of cancer patients. In addition, the staff of the Cancer Information Service (KID) provides information about this widespread disease for patients, their families, and the general public. DKFZ is funded by the German Federal Ministry of Education and Research (90%) and the State of Baden-Wuerttemberg (10%) and is a member of the Helmholtz Association of National Research Centers.
Dr. Sibylle Kohlstaedt | EurekAlert!
Barium ruthenate: A high-yield, easy-to-handle perovskite catalyst for the oxidation of sulfides
16.07.2018 | Tokyo Institute of Technology
The secret sulfate code that lets the bad Tau in
16.07.2018 | American Society for Biochemistry and Molecular Biology
For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.
To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...
For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.
Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...
Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.
A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...
Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.
"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....
Ultra-short, high-intensity X-ray flashes open the door to the foundations of chemical reactions. Free-electron lasers generate these kinds of pulses, but there is a catch: the pulses vary in duration and energy. An international research team has now presented a solution: Using a ring of 16 detectors and a circularly polarized laser beam, they can determine both factors with attosecond accuracy.
Free-electron lasers (FELs) generate extremely short and intense X-ray flashes. Researchers can use these flashes to resolve structures with diameters on the...
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12.07.2018 | Event News
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UConn study finds that catch-and-release practices in recreational fishing may not be as benign as intended.
The most aggressive largemouth bass in the lake are also the ones most prized by anglers. These are the fish that literally 'take the bait' and put the fun into both competitive and casual sport fishing.
Then, according to the rules of catch-and-release, the captive is unhooked and tossed back to swim away without any lasting consequences. But a new UConn study says there is an impact; the evolutionary path of a species may be on the line.
In a recent paper published in the journal PLOS ONE, a team of researchers led by Jan-Michael Hessenauer and Jason Vokoun of the Department of Natural Resources and the Environment, found the practice of catch-and-release appears to influence which fish are the species' fittest.
"This scenario genetically favors the fish with lower metabolisms, the fish that are less likely to be caught by anglers," Vokoun says. "It suggests that we may be permanently changing exploited fish populations over the long term."
The potential for recreational fishing to act as an evolutionary force is well established in theory. But this is the first study to identify outcomes of selection from recreational fishing of wild populations using unfished populations as a reference.
Researchers compared populations of largemouth bass in two lakes that are open to recreational fishing and two that have been undisturbed for hundreds of years. Connecticut has significant wild populations of largemouth bass living in protected bodies of water due to stringent management practices enforced by local water companies.
The researchers collected baby fish from the fished and unfished lakes and transferred them to a protected location with no anglers and no predation from larger fish. Prior to being released into the pens, each fish was tagged so it could later be identified by its place of origin.
Despite their different origins, the two populations grew up in the same environment and experienced the same rearing conditions. After one year, the researchers measured the fishes' resting metabolism.
They found that a significantly higher number of fish taken from the lakes where fishing was allowed had lower metabolic rates compared with the fish taken from protected bodies of water.
"The results point to a reduction in the type of behavior that is so prized by anglers," says Hessenauer, a doctoral student.
Several factors may be influencing this, according to Vokoun, associate professor of natural resources and the environment and director of UConn's Wildlife & Fisheries Conservation Center. Male Largemouth Bass are aggressive nest guarders, and if they are removed permanently, the nest will likely fail.
More aggressive females that are caught and released may suffer physiological stress that results in egg resorption and the production of fewer offspring, he says. If the same fish are caught more than once, their energy levels may be depleted, and typical behavior altered.
Vokoun adds that catch-and-release practices put physiological stress on the fish that can result in the disruption of reproductive behavior, as well as some unintended post-release mortality.
While a catch-and-release strategy may have some unintended drawbacks, Hessenauer and Vokoun don't dispute that it is well intended, or that it does make a contribution to the conservation of freshwater fish populations.
The next step in the research will be to breed fish that come from protected areas with those that come from unprotected areas, with the hope that the offspring will inherit some of the vigor and persistence of their wild kin.
The current findings may have implications for the catch-and-release strategy, says one of the study's co-authors, Robert Jacobs, Eastern District supervisor for the Inland Fisheries Division of the Connecticut Department of Energy and Environmental Protection (DEEP), which funded the study.
"People affect the genetics of plant and animal populations just by the way we interact with them, and this study contributes to a body of knowledge that will help us truly understand how traditional management strategies may become less relevant over time," he says. "The findings in this study may be a strong signal that we need to be much more creative in the ways we manage our inland fisheries."
Jan-Michael Hessenauer | EurekAlert!
Barium ruthenate: A high-yield, easy-to-handle perovskite catalyst for the oxidation of sulfides
16.07.2018 | Tokyo Institute of Technology
The secret sulfate code that lets the bad Tau in
16.07.2018 | American Society for Biochemistry and Molecular Biology
For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.
To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...
For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.
Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...
Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.
A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...
Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.
"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....
Ultra-short, high-intensity X-ray flashes open the door to the foundations of chemical reactions. Free-electron lasers generate these kinds of pulses, but there is a catch: the pulses vary in duration and energy. An international research team has now presented a solution: Using a ring of 16 detectors and a circularly polarized laser beam, they can determine both factors with attosecond accuracy.
Free-electron lasers (FELs) generate extremely short and intense X-ray flashes. Researchers can use these flashes to resolve structures with diameters on the...
13.07.2018 | Event News
12.07.2018 | Event News
03.07.2018 | Event News
16.07.2018 | Life Sciences
16.07.2018 | Earth Sciences
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Small forces make a big difference in beach erosion, according to new article in Physics of Fluids, which may lead to better solutions for sustainable beaches
People standing on a beach often feel the water tugging the sand away from under their feet. This is the undertow, the current that pulls water back into the ocean after a wave breaks on the beach.
Large storms produce strong undertows that can strip beaches of sand. By predicting how undertows interact with shorelines, researchers can build sand dunes and engineer other soft solutions to create more robust and sustainable beaches.
"Formulation of the Undertow Using Linear Wave Theory," a new paper in the journal Physics of Fluids, clears up some of the controversy in undertow modeling, so planners can assess erosion threats faster and more accurately.
The paper's authors are coastal engineer Greg Guannel of the Natural Capital Project, which seeks smarter ways to integrate natural resources into development, and Tuba Ozkan-Haller, an associate professor of coastal engineering at Oregon State University.
Researchers have studied undertow for more than 40 years, and have developed very accurate models of its behavior. The most sophisticated ones are based on Navier-Stokes equations, which describe fluid flow in exquisite detail.
Unfortunately, such precision comes at a price. The mathematics are complex and it takes powerful supercomputers to run them quickly.
"You can't use them to solve day-to-day erosion problems," Guannel said.
For real-world use, researchers need mathematical shortcuts, the engineering equivalent of rounding numbers so they are easier to work with. Researchers turn to linear wave theory, which simplifies things by using idealized forms. Beaches, for example, are wall. Waves are given perfect "S" shapes based on average properties. Instead of modeling everything, researchers make assumptions about some of the weaker forces acting on waves.
"We try to come up with a set of equations that describes flow properties in one step, rather than hundreds of steps, so we can solve problems faster," Guannel said.
Several research teams, each with its own approach, built simplified models based on linear theory. And each came up with a different solution.
This bothered Guannel, who said, "If you start with a single theory, no matter how you approach the problem, you should come up with only one solution, not many."
So Guannel and Ozkan-Haller retraced the work of each team. They found their differences were not due to approach, but to the way they handled weak forces generated by waves. They then developed more consistent ways to describe those forces. The strongest of them was the force exerted by water moving from the top of the wave to the bottom.
"A major advance in our paper was to describe that force correctly," Guannel said.
Another weak force is advection, which occurs as the undertow is sucked into the larger current created by the waves. "In the larger scheme of things, advection of the undertow is weak. But here, it can play an important role," Guannel explained.
"We found that all the differences between researchers were due to the erroneous formulation or the neglect of these weak terms. When we add them back in, everyone who did the math correctly comes up with the same solution," he said.
Instead of debating methodology, researchers can now focus on improving the accuracy of their models. If they can do this, Guannel said, they can build better models to help preserve the shoreline and enable beaches to recover faster after storms.
The article "Formulation of the Undertow Using Linear Wave Theory" is authored by G. Guannel and H.T. Özkan-Haller. It appears in the journal Physics of Fluids on May 13, 2014 (DOI: 10.1063/1.4872160). After that date, it can be accessed at: http://scitation.aip.org/content/aip/journal/pof2/26/5/10.1063/1.4872160
ABOUT THE JOURNAL
Physics of Fluids is devoted to the publication of original theoretical, computational, and experimental contributions to the dynamics of gases, liquids, and complex or multiphase fluids. See: http://pof.aip.org
Jason Socrates Bardi | Eurek Alert!
What happens when we heat the atomic lattice of a magnet all of a sudden?
17.07.2018 | Forschungsverbund Berlin
Subaru Telescope helps pinpoint origin of ultra-high energy neutrino
16.07.2018 | National Institutes of Natural Sciences
For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.
To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...
For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.
Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...
Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.
A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...
Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.
"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....
Ultra-short, high-intensity X-ray flashes open the door to the foundations of chemical reactions. Free-electron lasers generate these kinds of pulses, but there is a catch: the pulses vary in duration and energy. An international research team has now presented a solution: Using a ring of 16 detectors and a circularly polarized laser beam, they can determine both factors with attosecond accuracy.
Free-electron lasers (FELs) generate extremely short and intense X-ray flashes. Researchers can use these flashes to resolve structures with diameters on the...
13.07.2018 | Event News
12.07.2018 | Event News
03.07.2018 | Event News
17.07.2018 | Information Technology
17.07.2018 | Materials Sciences
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Paper Published Based on RNA Game
News Feb 18, 2016
A scientific paper written by video-gamers has been accepted for publication in a peer-reviewed journal, perhaps the first time since the days of Benjamin Franklin that work led by non-credentialed “citizen scientists” will appear in such a format.
The paper describes a new set of rules, derived intuitively by players of a video game called Eterna, for determining the difficulty of designing desired structures composed of RNA molecules. Unlike previous crowdsourcing efforts for which scientific experts have reached out to online gamers, the gamers themselves took the lead in this paper. Three experienced Eterna gamers distilled their community’s ideas into online Google documents and then contacted expert researchers at the Stanford University School of Medicine and elsewhere to independently test their ideas using high-performance supercomputers. The final paper is a condensed version of the gamers’ own documents.
Once dismissed as a relatively boring component of living cells, RNA is now understood to underlie virtually every critical process in biology and is increasingly appreciated as a potential medical and industrial tool. While each RNA molecule begins its existence as a linear chain of subunits, it quickly folds into a thermodynamically stable shape that depends on the molecule’s particular sequence of component subunits. That shape, in turn, dictates which cell components the RNA molecule will interact with and how. Scientists’ improving ability to computationally model and design RNA raises the promise of a new generation of RNA-based therapies customized to specific cancers, viruses, neurological abnormalities and inherited disorders.
Crowdsourcing scientific discovery
The paper, which will also appear in March in a special print issue of the journal devoted to RNA design, signifies an evolution of how crowdsourcing can impact scientific discovery, said its senior author, Rhiju Das, PhD, associate professor of biochemistry at Stanford. The paper’s research was not guided or collated by expert scientists, as has been the case in prior work from Eterna and other scientific discovery projects, but by the non-experts in the gaming community. “It’s important to capture these insights and make them both public and credible via publication in peer-reviewed journals,” he said.
One striking finding of the Eterna consortium (known as the Eterna Massive Open Laboratory): RNA molecules that are symmetrical, pleasing to the eye and that fold stably are also hard to design; the more symmetrical the desired shape, the more difficult to achieve it.
It’s important to capture these insights and make them both public and credible via publication in peer-reviewed journals.
Launched in 2011 by Das and Adrien Treuille, PhD, an assistant professor of computer science at Carnegie-Mellon University, Eterna now boasts more than 100,000 registered players, said Das. The interactive online video game challenges players to design chemical sequences of RNA that fold stably into desired shapes. Sequences that look promising in terms of their thermodynamic stability — as predicted by algorithms whose job it is to assess this feature — are synthesized in Das’ laboratory and tested to see what structure the RNA sequences actually assume.
Anyone age 13 or older can register to play by going to the game’s official website, Eternagame.org. No special skills or biochemistry training of any sort are required.
“It’s not even necessary to know what RNA is or does,” Das said.
Rating RNA-design difficulty
Until now, there has been no established rating scale for RNA-design difficulty, Das said. A biomedical researcher is not able to easily assess the difficulty of designing an RNA structure for a diagnostic or therapy, and therefore may waste significant time and money trying to create difficult or near-impossible shapes for an RNA molecule to assume. Even though attaining a rating scale for RNA design was not the mission of Eterna, experienced Eterna gamers noted how useful such a difficulty rating would be in guiding new players from easier to harder “puzzles.” These experienced gamers took it upon themselves to compile a list of particular features that render RNA shapes difficult to design sequences for. They carried out tests using their own personal computers. They then contacted scientists in Das’ lab with a set of predictions to test their ideas — a set of 100 hypothetical RNA shapes that experienced Eterna players rated from relatively “designable” to nearly “intractable.” The scientists used Stanford supercomputers to test these predictions against a half-dozen standard algorithms developed for the purpose of supplying RNA sequences that fold into specified shapes, and they found that the players’ rankings correlated strongly with the algorithms’ ability to solve these puzzles. Indeed, the hardest puzzles, which could be solved by experienced Eterna players, were not solvable by any of the algorithms even when given numerous days of computer time.
In some cases, these now-confirmed intuitions overthrow conventional thinking in the RNA-design community about which designs are likely to be attainable and which intractable, Das said. For instance, “the players discovered on their own, and the algorithms independently confirmed, that the more symmetrical a requested structure is, the harder it will be to design,” he said.
Hay Fever Risk Genes Overlap with Autoimmune DiseaseNews
In a large international study involving almost 900,000 participants, researchers from the University of Copenhagen and COPSAC have found new risk genes for hay fever. It is the largest genetic study so far on this type of allergy, which affects millions of people around the world.READ MORE
Hidden Signals in RNAs Regulate Protein SynthesisNews
Scientists have long known that RNA encodes instructions to make proteins. In a new study published in Nature, scientists describe how the protein-making machinery identifies alternative initiation sites from which to start protein synthesis.READ MORE
ExPecto Patronum! Magical Machine Learning Tool Summons DNA Dark Matter DataNews
A new machine learning framework, dubbed ExPecto, can predict the effects of mutations in the so-called “dark matter” regions of the human genome. ExPecto pinpoints how mutations can disrupt the way genes turn on and off throughout your body. | <urn:uuid:1746e348-c3ef-42e9-849c-1ef3d95148d0> | 2.984375 | 1,298 | News Article | Science & Tech. | 22.422434 | 95,638,457 |
Functions (Section 1.4, Chapter 3) are convenient tools to abstract behaviour and computation. E.g. once the function sqrt (double) has been properly defined, one does not need to remember how it computes its result in order to use it. Moreover, if one prefers an alternative algorithm for the computation of sqrt (double), it is easy to change just the function body of the definition, without disturbing the rest of the program’s code. One can say that the computation of sqrt (double) is encapsulated inside its definition which can be changed at will, as long as the specification of the function, i.e. its interface, remains the same.
KeywordsClass Object Class Definition Rational Class Conversion Function Assignment Operator
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Observations of Shock and Undular Bore Formation in Internal at a Shelf Break
Large amplitude internal waves at semi-diurnal tidal frequency (internal tides) are observed to be generated over the slope region of the Australian North West Shelf and propagate shoreward over shoaling bathymetry. In deep water the waves are nearly linear in shape and are seen to steepen and become strongly non-linear as they propagate. The waves steepen at the leading edge to the point where an internal hydraulic jump or shock forms. The shocks are generally downwards and are weak shocks seen as undular bores. At times a second, and weaker, backward shock forms on the trailing edge of the wave. The undular bores are followed by a train of oscillations that can be reasonably described as solitons. An analytical model using a perturbed extended Korteweg-de Vries equation is used to describe the evolution of an initially sinusoidal wave as it progagates over an exponential depth profile, in the presence of a background current of constant shear, and breaks to form a shock. The model predictions, of the distance the wave propagates before forming a shock, and of the height of the shock as it propagates, compare well with observations.
KeywordsInternal Wave Internal Tide Shelf Break Shock Strength Buoyancy Frequency
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- 5.Holloway, P.E. (1991) On the dissipation of internal tides. In, Tidal Hydrodynamics, ed B. Parker, John Wiley, New York.(In Press)Google Scholar | <urn:uuid:13522655-6dfa-4ec2-863a-16c9fd988148> | 2.796875 | 332 | Academic Writing | Science & Tech. | 40.803994 | 95,638,466 |
A Basic Mathematics Approach to Concepts of Chemistry
This book should be of interest to chemistry students.
- Paperback | 320 pages
- 213.36 x 281.94 x 12.7mm | 793.78g
- 08 Feb 1990
- Cengage Learning, Inc
- CA, United States
- 4th Revised edition
Table of contents
Whole numbers. Signed numbers. Powers of ten. Logarithms. Measurement concepts and dimensional analysis. The metric system, density, specific gravity and specific heat. The division and properties of matter. Atomic structure. Chemical bonding and formula writing. Naming compounds. Balancing chemical equations. Weight relations in chemistry. Chemical equations and stoichiometry. The concentration of solutions. The gas laws. Test answers. Glossary. Appendix. Index. | <urn:uuid:9b7a021e-f5f3-4d3a-9bb9-271469652e74> | 3.6875 | 167 | Product Page | Science & Tech. | 48.502946 | 95,638,481 |
Geothermal and Seismic Activity
At least four volcanoes have had seismic activity since 1985, including Mount Garibaldi (three events), Mount Cayley (four events), Mount Meager (seventeen events) and the Silverthrone Caldera (two events). Seismic data suggest that these volcanoes still contain active magma chambers, indicating that some Garibaldi Belt volcanoes are likely active, with significant potential hazards. The seismic activity corresponds with some of Canada's recently formed volcanoes and with persistent volcanoes that have had major explosive activity throughout their history, such as Mount Garibaldi, Mount Cayley and Mount Meager.
A series of hot springs adjacent to the Lillooet River valley, such as the Harrison, Sloquet, Clear Creek and Skookumchuck springs, are not known to occur near areas with recent volcanic activity. Instead, many are located close to 16-26 million year old intrusions that are interpreted to be the roots of heavily eroded volcanoes. These volcanoes formed part of the Cascade Volcanic Arc during the Miocene period and their intrusive roots extend from the Fraser Valley in the south to Salal Creek in the north. The relationship of these hot springs to the Garibaldi Belt is not clear. However, a few hot springs are known to exist in areas that have experienced relatively recent volcanic activity. About five hot springs exist in valleys near Mount Cayley and two small groups of hot springs are present at Mount Meager. The springs at Meager might be evidence of a shallow magma chamber beneath the surface. No hot springs are known to exist at Mount Garibaldi like those found at Mount Meager and Mount Cayley, although there is evidence of abnormal high heat flow at the adjacent Table Meadows and other locations. Abnormal warm water adjacent to Britannia Beach could be geothermal activity linked to the Watts Point volcanic zone. | <urn:uuid:3a07c9cd-a834-4724-8a0b-bf77e83ac115> | 3.703125 | 388 | Knowledge Article | Science & Tech. | 30.735888 | 95,638,526 |
In physics, a quantum mirage is a peculiar result in quantum chaos. Every system of quantum dynamical billiards will exhibit an effect called scarring, where the quantum probability density shows traces of the paths a classical billiard ball would take. For an elliptical arena, the scarring is particularly pronounced at the foci, as this is the region where many classical trajectories converge. The scars at the foci are colloquially referred to as the "quantum mirage".
The quantum mirage was first experimentally observed by Hari Manoharan, Christopher Lutz and Donald Eigler at the IBM Almaden Research Center in San Jose, California in 2000. The effect is quite remarkable but in general agreement with prior work on the quantum mechanics of dynamical billiards in elliptical arenas.
The mirage occurs at the foci of a quantum corral, a ring of atoms arranged in an arbitrary shape on a substrate. The quantum corral was demonstrated in 1993 by Lutz, Eigler, and Crommie using an ellipitical ring of iron atoms on a copper surface using the tip of a low-temperature scanning tunneling microscope to manipulate individual atoms. The ferromagnetic iron atoms reflected the surface electrons of the copper inside the ring into a wave pattern, as predicted by the theory of quantum mechanics.
The size and shape of the corral determine its quantum states, including the energy and distribution of the electrons. To make conditions suitable for the mirage the team at Almaden chose a configuration of the corral which concentrated the electrons at the foci of the ellipse.
When scientists placed a magnetic cobalt atom at one focus of the corral, a mirage of the atom appeared at the other focus. Specifically the same electronic properties were present in the electrons surrounding both foci, even though the cobalt atom was only present at one focus. In scanning tunneling microscopy, an atomically sharp metal tip is advanced towards the atomically flat sample surface until electron tunneling out of the atom and into the advancing tip becomes effective. Using the sharp tip we can also arrange atoms adsorbed on the surface into unique shapes; for example, 48 adsorbed iron atoms on Cu(111) arranged into a 14.26 nm diameter circle. The electrons on the copper surface are trapped inside the circle formed by the iron atoms. A standing wave pattern emerges with a large peak at the center due to the constructive interference of electrons on the copper surface as they scatter off the adsorbed iron atoms.
IBM scientists are hoping to use quantum mirages to construct atomic scale processors in the future.
- Ball, Philip (26 November 2009). "Quantum objects on show" (PDF). Nature. 462 (7272): 416. Bibcode:2009Natur.462..416B. doi:10.1038/462416a. Retrieved 2009-01-12.
- Crommie MF, Lutz CP, Eigler DM (8 October 1993). "Confinement of electrons to quantum corrals on a metal surface" (PDF). Science. 262 (5131): 218–20. Bibcode:1991Sci...254.1319S. doi:10.1126/science.262.5131.218. Retrieved 2011-11-08.
- Rogers, Ben (2011). Nanotechnology: Understanding Small Systems. Boca Raton, Florida: CRC Press. p. 9. | <urn:uuid:d8e8fa3b-b49f-4716-9932-d6877e033ccd> | 2.6875 | 717 | Knowledge Article | Science & Tech. | 48.24454 | 95,638,537 |
Mechanisms of cross-shore distribution pattern of the intertidal mud crabMacrophthalmus japonicus
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In the intertidal mud crabMacrophthalmus japonicus, most large crabs occurred in the upper sandy areas. Mechanisms of the size-dependent distribution were interpreted experimentally. In the lower muddy area, food was more abundant and crab density was much higher than in the upper area. Under the high density conditions, interaction among large crabs became severe and more large crabs abandoned their burrows. In the experiment on burrowing-site selection, large crabs burrowed only in the muddy side under the low density, but also in the sandy side under high density conditions. The burrowing in the upper sandy area may be advantageous for large crabs, though food availability is lower, because of less competition and higher survivorship under the low crab density.
Key wordsactivity interaction mud crab size-dependent cross-shore distribution stationary tendency
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whats the square root of 72
Jul 27, 2015
Scientific Notation Beginner Help (aka the Scientific Notation Batle against Challenger Base VIII)
Why does -2000 * 10^-6= -2.0-*10^-3
If i sell 64 of something and for each something i get 75$ from how much money would i get?
How to simplify equation with exponent?
Write the explicit formula that represents the geometric sequence -2, 8, -32, 128
The square root of 144 is?
If a one dollar bill is 0.0001 meters thick, how many meters tall would a stack of 4 trillion one dollar bills be? Write your answer in scie
Suppose that 6% of the eighth graders and 3% of the seventh graders at Washington Junior High participate in MATHCOUNTS. There are 1.5 times
A vendor has six jugs of punch with capacities of 13, 15, 16, 21, 21, and 22 gallons. One jug, which he keeps for himself, is full of blue p
Agents J and K work in a long hallway with 4000 equally-spaced, consecutive offices. The agents decide to walk toward each other so they can
12 Online Users | <urn:uuid:de9dbe24-daa3-4615-8590-fac4b1e7e8d4> | 3.109375 | 259 | Q&A Forum | Science & Tech. | 77.537214 | 95,638,543 |
New camera will help scientists further understand neutrinos
Down at the South Pole, where temperatures drop below negative 100 degrees Fahrenheit and darkness blankets the land for six months at a time, the South Pole Telescope (SPT) searches the skies for answers to the mysteries of our universe.
Photo: Bradford Benson, Fermilab and University of Chicago
A wafer of detectors for the SPT-3G camera undergoes inspection at Fermilab.
This mighty scavenger is about to get a major upgrade — a new camera that will help scientists further understand neutrinos, the ghost-like particles without electric charge that rarely interact with matter.
The 10-meter SPT is the largest telescope ever to make its way to the South Pole. It stands atop a two-mile thick plateau of ice, mapping the cosmic microwave background (CMB), the light left over from the big bang. Astrophysicists use these observations to understand the composition and evolution of the universe, all the way back to the first fraction of a second after the big bang, when scientists believe the universe quickly expanded during a period called inflation.
One of the goals of the SPT is to determine the masses of the neutrinos, which were produced in great abundance soon after the big bang. Though nearly massless, because neutrinos exist in huge numbers, they contribute to the total mass of the universe and affect its expansion. By mapping out the mass density of the universe through measurements of CMB lensing, the bending of light caused by immense objects such as large galaxies, astrophysicists are trying to determine the masses of these elusive particles.
To conduct these extremely precise measurements, scientists are installing a bigger, more sensitive camera on the telescope. This new camera, SPT-3G, will be four times heavier and have a factor of about 10 more detectors than the current camera. Its higher level of sensitivity will allow researchers to make extremely precise measurements of the CMB that will hopefully make it possible to cosmologically detect neutrino mass.
"In the next several years, we should be able to get to the sensitivity level where we can measure the number of neutrinos and derive their mass, which will tell us how they contribute to the overall density of the universe," explained Bradford Benson, the head of the CMB Group at the Department of Energy's Fermilab. "This measurement will also enable even more sensitive constraints on inflation and has the potential to measure the energy scale of the associated physics that caused it."
SPT-3G is being completed by a collaboration of scientists spanning the DOE national laboratories, including Fermilab and Argonne, and universities including the University of Chicago and University of California, Berkeley. The national laboratories provide the resources needed for the bigger camera and larger detector array while the universities bring years of expertise in CMB research.
"The national labs are getting involved because we need to scale up our infrastructure to support the big experiments the field needs for the next generation of science goals," Benson said. Fermilab's main role is the initial construction and assembly of the camera, as well as its integration with the detectors. This upgrade is being supported mainly by the Department of Energy and the National Science Foundation, which also supports the operations of the experiment at the South Pole.
Once the camera is complete, scientists will bring it to the South Pole, where conditions are optimal for these experiments. The extreme cold prevents the air from holding much water vapor, which can absorb microwave signals, and the sun, another source of microwaves, does not rise between March and September.
The South Pole is accessible only for about three months during the year, starting in November. This fall, about 20 to 30 scientists will head down to the South Pole to assemble the camera on the telescope and make sure everything works before leaving in mid-February. Once installed, scientists will use it to observe the sky over four years.
"For every project I've worked on, it's that beginning — when everyone is so excited not knowing what we're going to find, then seeing things you've been dreaming about start to show up on the computer screen in front of you — that I find really exciting," said University of Chicago's John Carlstrom, the principal investigator for the SPT-3G project.
Andre Salles | newswise
Subaru Telescope helps pinpoint origin of ultra-high energy neutrino
16.07.2018 | National Institutes of Natural Sciences
Nano-kirigami: 'Paper-cut' provides model for 3D intelligent nanofabrication
16.07.2018 | Chinese Academy of Sciences Headquarters
For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.
To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...
For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.
Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...
Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.
A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...
Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.
"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....
Ultra-short, high-intensity X-ray flashes open the door to the foundations of chemical reactions. Free-electron lasers generate these kinds of pulses, but there is a catch: the pulses vary in duration and energy. An international research team has now presented a solution: Using a ring of 16 detectors and a circularly polarized laser beam, they can determine both factors with attosecond accuracy.
Free-electron lasers (FELs) generate extremely short and intense X-ray flashes. Researchers can use these flashes to resolve structures with diameters on the...
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16.07.2018 | Earth Sciences | <urn:uuid:14f23246-6a31-4815-8809-a82c2327f2c7> | 3.6875 | 1,535 | Content Listing | Science & Tech. | 37.474732 | 95,638,545 |
1.1 – The Nature of Environmental Threats
Most of our economic and social activities are supported by services provided by the natural environment. We extract from it natural resources, such as fresh water, minerals and energy and discharge waste residuals into it. The natural environment is important to our well being as we enjoy amenities like fresh air and water and view beautiful natural sceneries.
However facing problems of global warming, ozone depletion and exhaustion of natural resources and their impacts, such as the loss of biodiversity and the weakening of resilience capacity, it becomes increasingly important to argue “whether the global economic system can continue to grow without undermining the natural systems which are its ultimate foundation” (Perman et al., 2003). More then ever, our society need to put the environment high on the agenda, whether our concern of the environment originates from a belief that the environment has a certain intrinsic value or purely is intended to serve as an economic resource base or waste sink. The limits to the resource capacity of our natural environment as well as to the assimilative capacity to absorb waste are obvious. Exceeding these limits will cause global, regional and local environmental changes that are sometimes irreversible and as a consequence will have long-term effects on the global economy and the quality of life around the globe.
The sustainability problem
The question on how to sustain global economic development over generations within natural and social limits is called the sustainability problem. The sustainability problem has been recognized by the international community and since the publication of the famous Brundlandt report “Our Comming Future’, many studies have been undertaken to address its issues in more detail. Roughly speaking sustainability is the achievement of current economic and social targets without compromising future generations to do so, or to speak with the Brundlandt report: “Sustainable development is development that meets the needs of the present without compromising the ability of future generations to meet their own needs …. “ (WCED, 1987) As figure 1.1 shows, sustainability implies the implication of three sectors: planet (environment sustainability), people (social sustainability) and profit or prosperity (economic sustainability).
The challenge of achieving sustainable development is to make decisions while considering these three interests simultaneously. Finding this balance for a specific case is a complex assignment and is determined by a lot of (local) variables. According to the Brundlandt report, it would also involve a transformation in our economy and society including the alleviation of poverty. To further illustrate the interdependence of planet and profit, the next paragraph describes a model to quantify the environmental impacts from economic activities.
Environmental impact of economic activities
The environmental impact of economic activities can be qualified by extractions from and insertions into the environment, expressed by the IPAT identity. In terms of mass or volume, environmental impact is determined by multiplying numbers of population (P), affluence (A) and technology (T). Technology is defined as the use of materials, resource consumption and waste generation per unit production (expressed in mass of volume), while affluence is economic growth in developed and developing countries per capita (expressed in monetary terms). An increase in population or of one of the other variables will then lead to an increase in environmental impact. The IPAT identity is a materials based reference for environmental impact in terms of mass or volume and is useful to get a glance about what drives the sizes of the economy’s impacts on the environment. The following paragraph explains how materials do impact the environment. More information on the IPAT identity and calculations are available in Perman et al. (2003), pp. 28-33
The nature of environmental threats
The origin of environmental problems could be traced back to materials that in one way or the other have an adverse effect on the environment. As mentioned earlier, technology is one of its main drivers. Technology refers to both resource consumption and waste generation and is crucial to the understanding of environmental impact in physical terms. Resource consumption are material extractions from the environment and resource problems arise when the current use of natural capital threatens future availability. Waste generation and disposal can be looked at in terms of insertions into the environment. The flow of waste residuals is defined as pollution.
Pollution problems and their impacts are characterized by (Graedel and Howard-Grenville, 2005):
• Environmental impact potential of materials
• Spatial scale of impact
• Damage potential (severity of hazards)
• Degree of exposure
• Remediation and reversibility time
• Quantity of materials used (throughput)
It is obvious that pollution also has adverse effects on the future availability of natural resources. For example, when heavy metals at high concentration are leaching from landfills to groundwater resources, the surrounding watersystem may get disturbed in such a way that it becomes unsuitable for drinking water purposes any more. This illustrates the understanding that pollution occurs when waste disposal exceeds the assimilative capacity of the environment and also that when this occurs, it reduces the assimilative capacity of the system itself.
In addition to material insertions and extractions, the nature of pollution problems is determined by the spatial scale of the impact. Environmental threats occur at different scales. Some pollutants can have global impact, while other pollutants cause damages in the vicinity of their source. Current global environmental threats are caused by pollutants that are locally emitted but have global effects on ecosystems and economies. These effects include sea level rise, desertification, a loss of biodiversity. From the perspective of resources, the exhaustion of natural resources, such as tropical rain forests, minerals and fresh water sources have global scarcity effects and impact regional and local ecosystems and economies as well. A current global environmental threat that is of special importance in this course, is the problem of climate change, but also ozone depletion and exhaustion of natural resources are important. Sections 1.7 and 1.8 discuss regional and local environmental threats | <urn:uuid:af465a96-4a26-4f0a-a672-0c414ed15e34> | 3.65625 | 1,194 | Academic Writing | Science & Tech. | 12.168799 | 95,638,551 |
|M4 in Scorpius. Click for larger view.|
Messier 4 is a very rich globular cluster, and was the first globular cluster in which individual stars were resolved. It also happens to one of the closest globular clusters to Earth, at a mere 7,200 light years. Because it's so close, it appears fairly large on the sky: depending on where you want to draw the cutoff point, it appears nearly the same size as the full moon does, 36.0 arcminutes across (the moon varies between 29.3 to 34.1 arcminutes depending on its position in orbit). For ease of comparison, I've decided not to crop the images from the size they come out of the camera so you can easily see the difference in apparent sizes between objects. (This might come back to bite me when I'm looking at really small clusters, especially since M4 is one of the larger ones on the sky, but we'll see how it goes.) Keep in mind that apparent size differences are not absolute size differences, which is why I will post the actual size when possible; M4 is about
Finally, M4 has the distinction of being the first globular cluster in which a millisecond pulsar was discovered. | <urn:uuid:71013eef-5360-4ea0-bc6e-bad0ddb1dea5> | 3.40625 | 256 | Personal Blog | Science & Tech. | 61.363442 | 95,638,575 |
Accepted name: Falco vespertinus
Common name: Red-footed Falcon
Georgian name: წითელფეხა შავარდენი
Taxonomic rank: Species
Taxonomy according to: http://www.birdlife.org/datazone/info/taxonomy
Registration reference not available, personal observation by author.
Remark: BB, M
Species seasonal life history at a given site:
YR-R = Year-round resident; breeder, present throughout the year.
YR-V = Year-round visitor; non-breeder, present throughout the year.
BB = Breeding bird; breeder, absent during non-breeding period.
SV = Summer visitor; non-breeder, present in spring and summer.
WV = Winter visitor; non-breeder, present in late fall, winter and early spring
M = Migrant; bird of passage; present primarily in fall and spring.
ND = Not defined; found but its status not known yet.
FB = Former breeder.
Cas = Casual; recorded irregularly; less expected because normal range is far away.
IUCN Status: NT
National Red list status: EN
Editor/Contact Person: Zura Javakhishvili
Contact address: firstname.lastname@example.org
Contributors: Lexo Gavashelishvili
Citation: Zura Javakhishvili, Lexo Gavashelishvili, 2016-12-04. [http://www.biodiversity-georgia.net/index.php?taxon=Falco vespertinus]. .Falco vespertinus. in: Tarkhnishvili D, Chaladze G (Editors). 2013. Georgian biodiversity database. http://www.biodiversity-georgia.net/. Downloaded on: 20 July 2018 | <urn:uuid:2c0508c5-c3d5-41b4-89a1-e62481d74f54> | 2.671875 | 446 | Structured Data | Science & Tech. | 44.079097 | 95,638,592 |
Tin: the essentials
Tin atoms have 50 electrons and the shell structure is 126.96.36.199.4. The ground state electronic configuration of neutral tin is [Kr].4d10.5s2.5p2 and the term symbol of tin is 3P0.
Ordinary tin is a silvery-white metal, is malleable, somewhat ductile, and has a highly crystalline structure. Due to the breaking of these crystals, a "tin cry" is heard when a bar is bent. The element has two allotropic forms. On warming, grey, or α-tin, with a cubic structure, changes at 13.2°C into white, or β-tin, the ordinary form of the metal. White tin has a tetragonal structure. When tin is cooled below 13.2°C, it changes slowly from white to grey. This change is affected by impurities such as aluminium and zinc, and can be prevented by small additions of antimony or bismuth. The conversion was first noted as growths on organ pipes in European cathedrals, where it was thought to be the devils work. This conversion was also speculated to be caused microorganisms and was called "tin plague" or "tin disease".
Tin resists distilled, sea, and soft tap water, but is attacked by strong acids, alkalis, and acid salts. Oxygen in solution accelerates the attack. When heated in air, tin forms SnO2. It is, or was, used to plate steel, making "tin cans". Tin is used as one component in bell metals.
Tin: physical properties
- Density of solid: 7310 kg m-3
- Molar volume: 16.29 cm3
- Thermal conductivity: 66.6 (polycrystalline; 515 parallel to c axis, 745 perpendicular to c axis) W m‑1 K‑1
Tin: heat properties
- Melting point: 505.08 [231.93 °C (449.47 °F)] K
- Boiling point: 505.08 [231.93 °C (449.47 °F)] K
- Enthalpy of fusion: 20.5 kJ mol-1
Tin: atom sizes
- Atomic radius (empirical): 145 pm
- Molecular single bond covalent radius: 140 (coordination number 4) ppm
- van der Waals radius: 242 ppm
- Pauling electronegativity: 1.96 (Pauling units)
- Allred Rochow electronegativity: 1.72 (Pauling units)
- Mulliken-Jaffe electronegativity: 2.21 (sp3 orbital)
Tin: orbital properties
- First ionisation energy: 708.58 kJ mol‑1
- Second ionisation energy: 1411.88 kJ mol‑1
- Third ionisation energy: 2943.4 kJ mol‑1
Tin: crystal structure
Tin: biological data
- Human abundance by weight: 200 ppb by weight
Tin might be a necessary element in very, very, small quantities in rats. Organotin compounds are used as bactericides and fungicides in marine environments but cause environmental concern as they cause severe problems to local wildlife.
Reactions of tin as the element with air, water, halogens, acids, and bases where known.
Tin: binary compounds
Binary compounds with halogens (known as halides), oxygen (known as oxides), hydrogen (known as hydrides), and other compounds of tin where known.
Tin: compound properties
Bond strengths; lattice energies of tin halides, hydrides, oxides (where known); and reduction potentials where known.
Tin: historyTin was discovered by Known since ancient times in unknown at not known. Origin of name: from the Anglo-Saxon word "tin" (the origin of the symbol Sn comes from the Latin word "stannum" meaning "tin").
Tin has the most stable isotopes (10) of all elements. Tin isotopes are used in a variety of applications. Sn-112 is used as precursor in the production of the radioisotope Sn-113 while Sn124 is used for producing Sb-124. Sn-116 and Sn-117 can both be used for the production of the medical radioisotope Sn-117m which is used in treating bone cancer. Both Sn-118 and Sn-119 have been evaluated for the production of Sn-119m.
Isolation: tHere is normally little need to isolate tin metal in the laboratory as it is readily available commercially. Tin is commonly available as the mineral cassiterite, SnO2. Reduction of this dioxide with burning coal results in tin metal and was probably how tin was made by the ancients.
SnO2 + 2C → Sn + 2CO | <urn:uuid:f16aae7f-4baf-4b1b-a4f7-4be49ea91d05> | 3.828125 | 1,035 | Knowledge Article | Science & Tech. | 65.04187 | 95,638,606 |
I am moving on to writing more applets. These are simple programs to get my bearings. The most important methods in JApplet are init() and paint(). You add items or objects to the screen in the init() function. And you draw things such as labels and buttons in the paint() function.
If you handle some GUI events like button clicks, the pattern is to call repaint() to get the screen updated based on the user input. It is funny how quickly I forget my Java basics when I do not code for a long time. These rules have not been committed to heart.
For example, I had to rediscover how to convert a String to an int. You create an Integer object, passing the String into the constructor. Then you can assign the resulting Integer to a variable of type int. Also you need to qualify Math package functions with "Math." to get your Java to compile.
Some topics are universal. Break down complex routines into multiple subroutines (functions). Make use of constants instead of magic numbers. In Java this is done with public static final variables. I will say I am starting to get some bearings on how to do drawing on the Canvas. The upper left hand corner of the screen has coordinates (0,0). Increasing x goes to the right. Increasing y goes down.
Mysterious Double Instance Hampering Performance - I study the existing code base. Confer with a colleague. Then I determine the optimal plan to change the functionality to load only a slice of all the dat...
4 days ago | <urn:uuid:ad953b9c-3f18-4435-955a-3066af64f6f9> | 2.75 | 320 | Personal Blog | Software Dev. | 64.822028 | 95,638,623 |
Concept: Materials science
- Proceedings of the National Academy of Sciences of the United States of America
- Published 3 months ago
Poly(ethylene terephthalate) (PET) is one of the most abundantly produced synthetic polymers and is accumulating in the environment at a staggering rate as discarded packaging and textiles. The properties that make PET so useful also endow it with an alarming resistance to biodegradation, likely lasting centuries in the environment. Our collective reliance on PET and other plastics means that this buildup will continue unless solutions are found. Recently, a newly discovered bacterium, Ideonella sakaiensis 201-F6, was shown to exhibit the rare ability to grow on PET as a major carbon and energy source. Central to its PET biodegradation capability is a secreted PETase (PET-digesting enzyme). Here, we present a 0.92 Å resolution X-ray crystal structure of PETase, which reveals features common to both cutinases and lipases. PETase retains the ancestral α/β-hydrolase fold but exhibits a more open active-site cleft than homologous cutinases. By narrowing the binding cleft via mutation of two active-site residues to conserved amino acids in cutinases, we surprisingly observe improved PET degradation, suggesting that PETase is not fully optimized for crystalline PET degradation, despite presumably evolving in a PET-rich environment. Additionally, we show that PETase degrades another semiaromatic polyester, polyethylene-2,5-furandicarboxylate (PEF), which is an emerging, bioderived PET replacement with improved barrier properties. In contrast, PETase does not degrade aliphatic polyesters, suggesting that it is generally an aromatic polyesterase. These findings suggest that additional protein engineering to increase PETase performance is realistic and highlight the need for further developments of structure/activity relationships for biodegradation of synthetic polyesters.
Inducing thermal gradients in fluid systems with initial, well-defined density gradients results in the formation of distinct layered patterns, such as those observed in the ocean due to double-diffusive convection. In contrast, layered composite fluids are sometimes observed in confined systems of rather chaotic initial states, for example, lattes formed by pouring espresso into a glass of warm milk. Here, we report controlled experiments injecting a fluid into a miscible phase and show that, above a critical injection velocity, layering emerges over a time scale of minutes. We identify critical conditions to produce the layering, and relate the results quantitatively to double-diffusive convection. Based on this understanding, we show how to employ this single-step process to produce layered structures in soft materials, where the local elastic properties vary step-wise along the length of the material.
The response of amorphous steels to shock wave compression has been explored for the first time. Further, the effect of partial devitrification on the shock response of bulk metallic glasses is examined by conducting experiments on two iron-based in situ metallic glass matrix composites, containing varying amounts of crystalline precipitates, both with initial composition Fe49.7Cr17.7Mn1.9Mo7.4W1.6B15.2C3.8Si2.4. The samples, designated SAM2X5-600 and SAM2X5-630, are X-ray amorphous and partially crystalline, respectively, due to differences in sintering parameters during sample preparation. Shock response is determined by making velocity measurements using interferometry techniques at the rear free surface of the samples, which have been subjected to impact from a high-velocity projectile launched from a powder gun. Experiments have yielded results indicating a Hugoniot Elastic Limit (HEL) to be 8.58 ± 0.53 GPa for SAM2X5-600 and 11.76 ± 1.26 GPa for SAM2X5-630. The latter HEL result is higher than elastic limits for any BMG reported in the literature thus far. SAM2X5-600 catastrophically loses post-yield strength whereas SAM2X5-630, while showing some strain-softening, retains strength beyond the HEL. The presence of crystallinity within the amorphous matrix is thus seen to significantly aid in strengthening the material as well as preserving material strength beyond yielding.
Globally ordered colloidal crystal lattices have broad utility in a wide range of optical and catalytic devices, for example, as photonic bandgap materials. However, the self-assembly of stereospecific structures is often confounded by polymorphism. Small free energy differences often characterize ensembles of different structures, making it difficult to produce a single morphology at will. Current techniques to handle this problem adopt one of two approaches: that of the “top-down,” or “bottom-up” methodology, whereby structures are engineered starting from the largest or smallest relevant length scales, respectively. However, recently a third approach for directing high fidelity assembly of colloidal crystals has been suggested which relies on the introduction of polymer co-solutes into the crystal phase [N. A. Mahynski, A. Z. Panagiotopoulos, D. Meng, S. K. Kumar, Nat. Commun., 2014, 5, 4472]. By tuning the polymer’s morphology to interact uniquely with the void symmetry of a single desired crystal, the entropy loss associated with polymer confinement has been shown to strongly bias the formation of that phase. However, previously this approach has only been demonstrated in the limiting case of close-packed crystals. Here we show how this approach may be generalized and extended to complex open crystals, illustrating the utility of this “structure-directing agent” paradigm in engineering the nanoscale structure of ordered colloidal materials. The high degree of transferability of this paradigm’s basic principles between relatively simple crystals and more complex ones suggests this represents a valuable addition to presently known self-assembly techniques.
Under high-strain-rate compression (strain rate approximately 10(3) s(-1)), nacre (mother-of-pearl) exhibits surprisingly high fracture strength vis-à-vis under quasi-static loading (strain rate 10(-3) s(-1)). Nevertheless, the underlying mechanism responsible for such sharply different behaviors in these two loading modes remains completely unknown. Here we report a new deformation mechanism, adopted by nacre, the best-ever natural armor material, to protect itself against predatory penetrating impacts. It involves the emission of partial dislocations and the onset of deformation twinning that operate in a well-concerted manner to contribute to the increased high-strain-rate fracture strength of nacre. Our findings unveil that Mother Nature delicately uses an ingenious strain-rate-dependent stiffening mechanism with a purpose to fight against foreign attacks. These findings should serve as critical design guidelines for developing engineered body armor materials.
The potential of thermoelectric materials to generate electricity from the waste heat can play a key role in achieving a global sustainable energy future. In order to proceed in this direction, it is essential to have thermoelectric materials that are environmentally friendly and exhibit high figure of merit, ZT. Oxide thermoelectric materials are considered ideal for such applications. High thermoelectric performance has been reported in single crystals of Ca3Co4O9. However, for large scale applications single crystals are not suitable and it is essential to develop high-performance polycrystalline thermoelectric materials. In polycrystalline form, Ca3Co4O9 is known to exhibit much weaker thermoelectric response than in single crystal form. Here, we report the observation of enhanced thermoelectric response in polycrystalline Ca3Co4O9 on doping Tb ions in the material. Polycrystalline Ca3-xTbxCo4O9 (x = 0.0-0.7) samples were prepared by a solid-state reaction technique. Samples were thoroughly characterized using several state of the art techniques including XRD, TEM, SEM and XPS. Temperature dependent Seebeck coefficient, electrical resistivity and thermal conductivity measurements were performed. A record ZT of 0.74 at 800 K was observed for Tb doped Ca3Co4O9 which is the highest value observed till date in any polycrystalline sample of this system.
Electronic carriers in graphene show a high carrier mobility at room temperature. Thus, this system is widely viewed as a potential future charge-based high-speed electronic material to complement-or replace-silicon. At the same time, the spin properties of graphene have suggested improved capability for spin-based electronics or spintronics and spin-based quantum computing. As a result, the detection, characterization and transport of spin have become topics of interest in graphene. Here we report a microwave photo-excited transport study of monolayer and trilayer graphene that reveals an unexpectedly strong microwave-induced electrical response and dual microwave-induced resonances in the dc resistance. The results suggest the resistive detection of spin resonance, and provide a measurement of the g-factor, the spin relaxation time and the sub-lattice degeneracy splitting at zero magnetic field.
Understanding radiation responses of Fe-based metals is essential to develop radiation tolerant steels for longer and safer life cycles in harsh reactor environments. Nanograined metals have been explored as self-healing materials due to point-defect recombination at grain boundaries. The fundamental defect-boundary interactions, however, are not yet well understood. We discover that the interactions are always mediated by formation and annealing of chain-like defects, which consist of alternately positioned interstitials and vacancies. These chain-like defects are closely correlated to the patterns of defect formation energy minima on the grain boundary, which depend on specific boundary configurations. Through chain-like defects, a point defect effectively translates large distances, to annihilate with its opposite, thus grain boundaries act as highly efficient defect sinks that cannot saturate under extreme radiation conditions.
Mechanics is an important component in the regulation of cell shape, proliferation, migration and differentiation during normal homeostasis and disease states. Biomaterials that match the elastic modulus of soft tissues have been effective for studying this cell mechanobiology, but improvements are needed in order to investigate a wider range of physicochemical properties in a controlled manner. We hypothesized that polydimethylsiloxane (PDMS) blends could be used as the basis of a tunable system where the elastic modulus could be adjusted to match most types of soft tissue. To test this we formulated blends of two commercially available PDMS types, Sylgard 527 and Sylgard 184, which enabled us to fabricate substrates with an elastic modulus anywhere from 5 kPa up to 1.72 MPa. This is a three order-of-magnitude range of tunability, exceeding what is possible with other hydrogel and PDMS systems. Uniquely, the elastic modulus can be controlled independently of other materials properties including surface roughness, surface energy and the ability to functionalize the surface by protein adsorption and microcontact printing. For biological validation, PC12 (neuronal inducible-pheochromocytoma cell line) and C2C12 (muscle cell line) were used to demonstrate that these PDMS formulations support cell attachment and growth and that these substrates can be used to probe the mechanosensitivity of various cellular processes including neurite extension and muscle differentiation.
Because of its optical and electrical properties, large surfaces, and compatibility with standard silicon processes, porous silicon is a very interesting material in photovoltaic and microelectromechanical systems technology. In some applications, porous silicon is annealed at high temperature and, consequently, the cylindrical pores that are generated by anodization or stain etching reorganize into randomly distributed closed sphere-like pores. Although the design of devices which involve this material needs an accurate evaluation of its mechanical properties, only few researchers have studied the mechanical properties of porous silicon, and no data are nowadays available on the mechanical properties of sintered porous silicon. In this work we propose a finite element model to estimate the mechanical properties of sintered meso-porous silicon. The model has been employed to study the dependence of the Young’s modulus and the shear modulus (upper and lower bounds) on the porosity for porosities between 0% to 40%. Interpolation functions for the Young’s modulus and shear modulus have been obtained, and the results show good agreement with the data reported for other porous media. A Monte Carlo simulation has also been employed to study the effect of the actual microstructure on the mechanical properties. | <urn:uuid:2af2eb23-f31f-4f2b-b108-67d19ab3797a> | 2.640625 | 2,653 | Content Listing | Science & Tech. | 18.005634 | 95,638,627 |
Laser-cooled positron source
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We examine, theoretically, the feasibility of producing a sample of cold (⩽4 K), high-density (≈1010/cm3) positrons in a Penning trap. We assume9Be+ ions are first loaded into the trap and laser-cooled to approximately 10 mK where they form a uniform density column centered on the trap axis. Positrons from a moderator are then injected into the trap along the direction of the magnetic field through an aperture in one endcap of the trap so that they intersect the9Be+ column. Positron/9Be+ Coulomb collisions extract axial energy from the positrons and prevent them from escaping back out the entrance aperture. Cooling provided by cyclotron radiation and sympathetic cooling with the laser-cooled9Be+ ions causes the positrons to eventually coalesce into a cold column along the trap axis. We present estimates of the efficiency for capture of the positrons and estimates of densities and temperatures of the resulting positron column. Positrons trapped in this way may be interesting as a source for antihydrogen production, as an example of a quantum plasma, and as a possible means to produce a bright beam of positrons by leaking them out along the axis of the trap.
KeywordsRadiation Magnetic Field Thin Film Density Column Uniform Density
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A fundamental challenge to understanding patterns in ecological systems lies in employing methods that can analyse, test and draw inference from measured associations between variables across scales. Hierarchical linear models (HLM) use advanced estimation algorithms to measure regression relationships and variance-covariance parameters in hierarchically structured data. Although hierarchical models have occasionally been used in the analysis of ecological data, their full potential to describe scales of association, diagnose variance explained, and to partition uncertainty has not been employed. In this paper we argue that the use of the HLM framework can enable significantly improved inference about ecological processes across levels of organization. After briefly describing the principals behind HLM, we give two examples that demonstrate a protocol for building hierarchical models and answering questions about the relationships between variables at multiple scales. The first example employs maximum likelihood methods to construct a two-level linear model predicting herbivore damage to a perennial plant at the individual- and patch-scale; the second example uses Bayesian estimation techniques to develop a three-level logistic model of plant flowering probability across individual plants, microsites and populations. HLM model development and diagnostics illustrate the importance of incorporating scale when modelling associations in ecological systems and offer a sophisticated yet accessible method for studies of populations, communities and ecosystems. We suggest that a greater coupling of hierarchical study designs and hierarchical analysis will yield significant insights on how ecological processes operate across scales.
Mendeley saves you time finding and organizing research
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Nucleation is the first step in the formation of either a new thermodynamic phase or a new structure via self-assembly or self-organization. Nucleation is typically defined to be the process that determines how long an observer has to wait before the new phase or self-organized structure appears. For example, if a volume of water is cooled (at atmospheric pressure) below 0° C, it will tend to freeze into ice. Volumes of water cooled only a few degrees below 0° C often stay completely ice free for long periods. At these conditions, nucleation of ice is either slow or does not occur at all. However, at lower temperatures ice crystals appear after little or no delay. At these conditions ice nucleation is fast. Nucleation is commonly how first-order phase transitions start, and then it is the start of the process of forming a new thermodynamic phase. By contrast new phases at continuous phase transitions start to form immediately.
Nucleation is often found to be very sensitive to impurities in the system. These impurities may be too small to be seen by the naked eye, but still can control the rate of nucleation. Because of this, it is often important to distinguish between heterogeneous nucleation and homogeneous nucleation. Heterogeneous nucleation occurs at nucleation sites on surfaces in the system. Homogeneous nucleation occurs away from a surface.
- 1 Characteristics
- 2 The nucleation of crystals
- 3 Examples
- 4 References
Nucleation is usually a stochastic (random) process, so even in two identical systems nucleation will occur at different times. This behaviour is similar to radioactive decay. A common mechanism is illustrated in the animation to the right. This shows nucleation of a new phase (shown in red) in an existing phase (white). In the existing phase microscopic fluctuations of the red phase appear and decay continuously, until an unusually large fluctuation of the new red phase is so large it is more favourable for it to grow than to shrink back to nothing. This nucleus of the red phase then grows and converts the system to this phase. The standard theory that describes this behaviour for the nucleation of a new thermodynamic phase is called classical nucleation theory.
For nucleation of a new thermodynamic phase, such as the formation of ice in water below 0° C, if the system is not evolving with time and nucleation occurs in one step, then the probability that nucleation has not occurred should undergo exponential decay as seen in radioactive decay. This is seen for example in the nucleation of ice in supercooled small water droplets. The decay rate of the exponential gives the nucleation rate. Classical nucleation theory is a widely used approximate theory for estimating these rates, and how they vary with variables such as temperature. It correctly predicts that the time you have to wait for nucleation decreases extremely rapidly when supersaturated.
It is not just new phases such as liquids and crystals that form via nucleation followed by growth. The self-assembly process that forms objects like the amyloid aggregates associated with Alzheimer's disease also starts with nucleation. Energy consuming self-organising systems such as the microtubules in cells also show nucleation and growth.
Heterogeneous nucleation, nucleation with the nucleus at a surface, is much more common than homogeneous nucleation. Heterogeneous nucleation is typically understood to be much faster than homogeneous nucleation using classical nucleation theory. This predicts that the nucleation slows exponentially with the height of a free energy barrier ΔG*. This barrier comes from the free energy penalty of forming the surface of the growing nucleus. For homogeneous nucleation the nucleus is approximated by a sphere, but as we can see in the schematic of macroscopic droplets to the right, droplets on surfaces are not complete spheres and so the area of the interface between the droplet and the surrounding fluid is less than a sphere's . This reduction in surface area of the nucleus reduces the height of the barrier to nucleation and so speeds nucleation up exponentially.
Computer simulation studies of simple models
Classical nucleation theory makes a number of assumptions, for example it treats a microscopic nucleus as if it is a macroscopic droplet with a well-defined surface whose free energy is estimated using an equilibrium property: the interfacial tension σ. For a nucleus that may be only of order ten molecules across it is not always clear that we can treat something so small as a volume plus a surface. Also nucleation is an inherently out of thermodynamic equilibrium phenomenon so it is not always obvious that its rate can be estimated using equilibrium properties.
However, modern computers are powerful enough to calculate essentially exact nucleation rates for simple models. These have been compared with the classical theory, for example for the case of nucleation of the crystal phase in the model of hard spheres. This is a model of perfectly hard spheres in thermal motion, and is a simple model of some colloids. For the crystallization of hard spheres the classical theory is a very reasonable approximate theory. So for the simple models we can study, classical nucleation theory works quite well, but we do not know if it works equally well for (say) complex molecules crystallising out of solution.
The spinodal region
Phase-transition processes can also be explained in terms of spinodal decomposition, where phase separation is delayed until the system enters the unstable region where a small perturbation in composition leads to a decrease in energy and, thus, spontaneous growth of the perturbation. This region of a phase diagram is known as the spinodal region and the phase separation process is known as spinodal decomposition and may be governed by the Cahn–Hilliard equation.
The nucleation of crystals
In many cases, liquids and solutions can be cooled down or concentrated up to conditions where the liquid or solution is significantly less thermodynamically stable than the crystal, but where no crystals will form for minutes, hours, weeks or longer. Nucleation of the crystal is then being prevented by a substantial barrier. This has consequences, for example cold high altitude clouds may contain large numbers of small liquid water droplets that are far below 0° C.
In small volumes, such as in small droplets, only one nucleation event may be needed for crystallisation. In these small volumes, the time until the first crystal appears is usually defined to be the nucleation time. In larger volumes many nucleation events will occur. A simple model for crystallisation in that case, that combines nucleation and growth is the KJMA or Avrami model.
Primary and secondary nucleation
The time until the appearance of the first crystal is also called primary nucleation time, to distinguish it from secondary nucleation times. Primary here refers to the first nucleus to form, while secondary nuclei are crystal nuclei produced from a preexisting crystal. Primary nucleation describes the transition to a new phase that does not rely on the new phase already being present, either because it is the very first nucleus of that phase to form, or because the nucleus forms far from any pre-existing piece of the new phase. Particularly in the study of crystallisation, secondary nucleation can be important. This is the formation of nuclei of a new crystal directly caused by pre-existing crystals.
For example, if the crystals are in a solution and the system is subject to shearing forces, small crystal nuclei could be sheared off a growing crystal, thus increasing the number of crystals in the system. So both primary and secondary nucleation increase the number of crystals in the system but their mechanisms are very different, and secondary nucleation relies on crystals already being present.
Experimental observations on the nucleation times for the crystallisation of small volumes
It is typically difficult to experimentally study the nucleation of crystals. The nucleus is microscopic, and thus too small to be directly observed. In large liquid volumes there are typically multiple nucleation events, and it is difficult to disentangle the effects of nucleation from those of growth of the nucleated phase. These problems can be overcome by working with small droplets. As nucleation is stochastic, many droplets are needed so that statistics for the nucleation events can be obtained.
To the right is shown an example set of nucleation data. It is for the nucleation at constant temperature and hence supersaturation of the crystal phase in small droplets of supercooled liquid tin; this is the work of Pound and La Mer.
Nucleation occurs in different droplets at different times, hence the fraction is not a simple step function that drops sharply from one to zero at one particular time. The red curve is a fit of a Gompertz function to the data. This is a simplified version of the model Pound and La Mer used to model their data. The model assumes that nucleation occurs due to impurity particles in the liquid tin droplets, and it makes the simplifying assumption that all impurity particles produce nucleation at the same rate. It also assumes that these particles are Poisson distributed among the liquid tin droplets. The fit values are that the nucleation rate due to a single impurity particle is 0.02/s, and the average number of impurity particles per droplet is 1.2. Note that about 30% of the tin droplets never freeze; the data plateaus at a fraction of about 0.3. Within the model this is assumed to be because, by chance, these droplets do not have even one impurity particle and so there is no heterogeneous nucleation. Homogeneous nucleation is assumed to be negligible on the timescale of this experiment. The remaining droplets freeze in a stochastic way, at rates 0.02/s if they have one impurity particle, 0.04/s if they have two, and so on.
This data is just one example but it does illustrate common features of the nucleation of crystals in that there is clear evidence for heterogeneous nucleation, and that nucleation is clearly stochastic.
The freezing of small water droplets to ice is an important process, particularly in the formation and dynamics of clouds. Water (at atmospheric pressure) does not freeze at 0° C, but rather at temperatures that tend to decrease as the volume of the water decreases and as the water impurity increases.
Thus small droplets of water, as found in clouds, may remain liquid far below 0° C.
An example of experimental data on the freezing of small water droplets is shown at the right. The plot shows the fraction of a large set of water droplets, that are still liquid water, i.e., have not yet frozen, as a function of temperature. Note that the highest temperature at which any of the droplets freezes is close to -19° C, while the last droplet to freeze does so at almost -35° C. The data is from work by Dorsch and Hacker.
Examples of the nucleation of fluids (gases and liquids)
- Clouds form when wet air cools (often because the air rises) and many small water droplets nucleate from the supersaturated air. The amount of water vapor that air can carry decreases with lower temperatures. The excess vapor begins to nucleate and to form small water droplets which form a cloud. Nucleation of the droplets of liquid water is heterogeneous, occurring on particles referred to as cloud condensation nuclei. Cloud seeding is the process of adding artificial condensation nuclei to quicken the formation of clouds.
- Bubbles of carbon dioxide nucleate shortly after the pressure is released from a container of carbonated liquid.
- Nucleation in boiling can occur in the bulk liquid if the pressure is reduced so that the liquid becomes superheated with respect to the pressure-dependent boiling point. More often, nucleation occurs on the heating surface, at nucleation sites. Typically, nucleation sites are tiny crevices where free gas-liquid surface is maintained or spots on the heating surface with lower wetting properties. Substantial superheating of a liquid can be achieved after the liquid is de-gassed and if the heating surfaces are clean, smooth and made of materials well wetted by the liquid.
- Some champagne stirrers operate by providing many nucleation sites via high surface-area and sharp corners, speeding the release of bubbles and removing carbonation from the wine.
- The Diet Coke and Mentos eruption offers another example. The surface of Mentos candy provides nucleation sites for the formation of carbon-dioxide bubbles from carbonated soda.
- Both the bubble chamber and the cloud chamber rely on nucleation, of bubbles and droplets, respectively.
Examples of the nucleation of crystals
- The most common crystallisation process on Earth is the formation of ice. Liquid water does not freeze at 0° C unless there is ice already present, cooling significantly below 0° C is required to nucleate ice and so for the water to freeze. For example, small droplets of very pure water can remain liquid down to below -30° C although ice is the stable state below 0° C.
- Many of the materials we make and use are crystalline, but are made from liquids, eg crystalline iron made from liquid iron cast into a mold. So the nucleation of crystalline materials is widely studied in industry. It is used heavily in the chemical industry for cases such as in the preparation of metallic ultradispersed powders that can serve as catalysts. For example, platinum deposited onto TiO2 nanoparticles catalyses the liberation of hydrogen from water. It is an important factor in the semiconductor industry, as the band gap energy in semiconductors is influenced by the size of nanoclusters.
- H. R. Pruppacher and J. D. Klett, Microphysics of Clouds and Precipitation, Kluwer (1997).
- Sear, R.P. (2007). "Nucleation: theory and applications to protein solutions and colloidal suspensions" (PDF). J. Phys. Condens. Matter. 19 (3): 033101. Bibcode:2007JPCM...19c3101S. doi:10.1088/0953-8984/19/3/033101.
- Sear, Richard P. (2014). "Quantitative Studies of Crystal Nucleation at Constant Supersaturation: Experimental Data and Models". CrystEngComm. 16 (29): 6506. doi:10.1039/C4CE00344F.
- Duft, D.; Leisner (2004). "Laboratory evidence for volume-dominated nucleation of ice in supercooled water microdroplets". Atmospheric Chemistry and Physics. 4 (7): 1997. doi:10.5194/acp-4-1997-2004.
- Gillam, J.E.; MacPhee, C.E. (2013). "Modelling amyloid fibril formation kinetics: mechanisms of nucleation and growth". J. Phys. Condens. Matter. 25 (37): 373101. Bibcode:2013JPCM...25K3101G. doi:10.1088/0953-8984/25/37/373101.
- Mendez-Villuendas, Eduardo; Bowles, Richard (2007). "Surface Nucleation in the Freezing of Gold Nanoparticles". Physical Review Letters. 98 (18): 185503. arXiv: . Bibcode:2007PhRvL..98r5503M. doi:10.1103/PhysRevLett.98.185503. PMID 17501584.
- Auer, S.; D. Frenkel (2004). "Numerical prediction of absolute crystallization rates in hard-sphere colloids". J. Chem. Phys. 120 (6): 3015. Bibcode:2004JChPh.120.3015A. doi:10.1063/1.1638740.
- Mendez-Villuendas, Eduardo; Saika-Voivod, Ivan; Bowles, Richard K. (2007). "A limit of stability in supercooled liquid clusters". The Journal of Chemical Physics. 127 (15): 154703. arXiv: . Bibcode:2007JChPh.127o4703M. doi:10.1063/1.2779875. PMID 17949187.
- Botsaris, GD (1976). Mullin, J, ed. Secondary Nucleation — A Review in Industrial Crystallisation. Springer. pp. 3–22.
- Pound, Guy M.; V. K. La Mer (1952). "Kinetics of Crystalline Nucleus Formation in Supercooled Liquid Tin". Journal of the American Chemical Society. 74 (9): 2323. doi:10.1021/ja01129a044.
- Dorsch, Robert G; Hacker, Paul T (1950). "Photomicrographic Investigation of Spontaneous Freezing Temperatures of Supercooled Water Droplets". NACA Technical Note. 2142.
- K. F. Kelton of Washington University in St. Louis, USA and A. L. Greer of University of Cambridge, UK (2010) Nucleation in Condensed Matter: Applications in Materials and Biology (Elsevier Science & Technology, Amsterdam) link.
- Palmans, Roger; Frank, Arthur J. (1991). "A molecular water-reduction catalyst: Surface derivatization of titania colloids and suspensions with a platinum complex". The Journal of Physical Chemistry. 95 (23): 9438. doi:10.1021/j100176a075.
- Rajh, Tijana; Micic, Olga I.; Nozik, Arthur J. (1993). "Synthesis and characterization of surface-modified colloidal cadmium telluride quantum dots". The Journal of Physical Chemistry. 97 (46): 11999. doi:10.1021/j100148a026. | <urn:uuid:ff6ec8bf-4fa3-4b49-bc1f-fea22079b7d7> | 3.953125 | 3,764 | Knowledge Article | Science & Tech. | 49.277041 | 95,638,669 |
Electron Configurations Animation
With the assistance of an undergraduate student, Mr. Tim Perk, the electron configuration animation has been converted from a Shockwave to a Flash version. The new link to the animaton is
Dr. Michael Abraham (The University of Oklahoma) and I are working on an activity that will use this animation. When this activity is ready I will post information on this page. If you are interested in other useful animations and simulations that include guided and open-inquiry activities please check out the MoLE Web site. This site contains simulations that represent particulate level models of gases, chemical equilibrium, chemical kinetics, stoichiometry, acids and bases, molecular models (VSEPR, bond and molecular dipoles, polarity, bond order, isomerism, solid state structures and periodicity). The site also includes guided and open-inquiry activities with simulations on gases, electrochemistry, stoichiometry, thermochemistry, chemical kinetics, acids and bases, stocihiometry. The activities are available to printout and duplicate for use in your classroom. Each activity includes a link to a simulation.
To access these animation click on the link below. We require teachers to give us your name, school and an e-mail address to access the materials. The Mole web site link is,
The link to the original animation on electron configurations is below. This animation
was created using MacroMedia Director and requires the Shockwave plugin from
If, when you go to this page you receive a 'blank' screen, or you receive
a message that you need a particular plug-in to view the file go to http://www.macromedia.com/shockwave/download/instructions/streaming.html
and dowload the plug-in for Shockwave for your particular platform. Enjoy.
The electron configuration animation was done by Nancy Gettys, Judd Wheeler
and myself for an AP Chemistry By Satellite course that I taught in the early
NOTE: If you are using an intel-based Macintosh please checkout the following link for important information to run this animation in Shockwave.
John I. Gelder
Department of Chemistry
Oklahoma State University
Stillwater, OK 74078 | <urn:uuid:121bbee9-c6da-4251-98f5-d052782cd6d8> | 2.5625 | 458 | Tutorial | Science & Tech. | 24.611571 | 95,638,698 |
Ground StationsThe Space Flight Laboratory operates a Mission Control Center (MCC) that is connected to S-band and UHF ground stations located at UTIAS.
Propulsion for Micro and Small SatellitesPropulsion systems that leverage existing cold gas systems that have been previously developed by the University of Toronto Institute for Aerospace Studies (UTIAS) Space Flight Laboratory (SFL) and have flown or will shortly fly in low Earth orbit are under development.
Radiation Test ProgramHigh performance, low power consumption, low cost, and availability are the principal attractive features of "Commercial Off The Shelf" (COTS) electronics.
XPOD Separation SystemThe XPOD Separation System was developed through the SFL CanX Nanosatellite Program. The XPOD is an enclosed "jack-in-the-box" container for separating nanosatellites from virtually any launch vehicle.
SFL-Led Nanosatellite Team Receives Canadian Alouette Award for Precise Autonomous Formation Flight
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Space Flight Laboratory (SFL) Nanosatellite Validates Aircraft Tracking, Prepares for Deorbit Demo
Mar 30 2017
Deep Space Industries and SFL selected to provide satellites for HawkEye 360’s Pathfinder mission
May 26 2016
Deep Space Industries Teams with UTIAS Space Flight Laboratory to Demonstrate Autonomous Spacecraft Maneuvering
Jan 26 2016
SFL’s Josh Newman Wins 1st Place in Small Satellite Student Competition for CanX-4 and CanX-5 Formation Flying Mission Contribution
Aug 12 2015
UniBRITE Achieves Arcminute-Level Fine Pointing for First of its Kind Space Astronomy Mission
Jun 09 2013
Next Generation Automatic Identification System Satellites to be Developed under Communitech Program
Apr 19 2013
AISSat-1 celebrates six months of success on-orbit, first nanosatellite with high performance pointing
Jan 12 2011
New Microsatellite Science and Technology Center (MSTC) planned for completion in late 2011
Dec 15 2010 | <urn:uuid:972d2412-73b7-478b-8db4-8795a74b210a> | 2.734375 | 420 | Content Listing | Science & Tech. | -10.311 | 95,638,717 |
This tutorial explains and gives examples on how to make a web page dynamic by using Ajax technology. It is not intended to be an Ajax reference, but rather contains practical code samples showing how to make web pages dynamic and pleasant to use. The examples shown here can be used as building blocks for your own web pages.
PHP is the language used in the server script examples. In the PHP code samples there is also an example of connecting to and querying a MySQL database using PHP functions.
This tutorial also contains a brief MySQL reference sections showing examples of table creation, select, insert, update and delete commands.
In addition to showing how to use the Ajax technology I also show examples of dynamically updating a dropdown selection list, dynamically updating a HTML table, and dynamically updating text and headers. All without performing a page reload. All of the data is contained within the application, no internet connection is required.
The application contains the following categories:
About Ajax Tutorial
What is Ajax
XMLHttpRequest Object Details
Create XMLHttpRequest Obj
Basic PHP Server Script
Parse Server Response Basic
Parse Server Response Advanced
Dynamic Dropdown List | <urn:uuid:cf09adb8-a387-4b89-b75a-34abae1638a4> | 2.734375 | 235 | Tutorial | Software Dev. | 29.960256 | 95,638,723 |
Study suggests honeybees have zero knowledge
In the new study, researchers from Australia and France trained bees to determine the value of zero
Honeybees have now mastered a concept that even a preschool-aged child can't—the value of zero. In other words, they can recognize that zero means nothing.
There's been quite a lot of research to show that honeybees can count, but never if they can determine the value of zero. In the new study published today in Science, researchers from Australia and France trained bees to do just that.
This concept isn't as evident as it might seem. Preschool age kids require training to learn the idea. Researchers have demonstrated the concept of zero in dolphins, parrots and all kinds of primates, but this is a first for an invertebrate insect.
Using little sugar rewards, the researchers trained the bees to come to the counting apparatus and showed them sets of numbers. If the bees chose the lowest number, they would get the reward. The training took five or six hours, but the bees learned to correctly identify the lowest number each time, including when presented with a blank sheet.
"They chose to land predominantly on the blank sheet," said Dr. Adrian Dyer, the senior author of the study and research fellow in the Department of Physiology at Monash University in Australia. "[This] showed that they understood that this representation was less than one and, thus, they understood the concept of zero."
The bees scored about 70 to 80 per cent on their greater than or less than math tests, which is better than the average pre-schooler at the same task.
Counting plays a big part of the bees' survival as a hive
Bees are social creatures that communicate to the rest of the colony about all kinds of things with sophisticated signals using dance-like manoeuvers. These signals convey the direction and distance of possible sources of food and zero may play a role in that.
"Being able to quantify things or understanding how to count is probably high value for navigation, food management, actually a number of things, which we think humans find counting very useful for," said Dyer.
For example, the bees might tell the hive about not having any food or not seeing any flowers on the foraging run. Therefore, counting plays a big part of their survival as a hive, the same way the concept of no food, no money, or zero anything is vital to humans as a species.
Understanding zero is not an innate concept
There is evidence that in Roman times the idea of zero as a numerical value either wasn't realized or wasn't considered significant—for instance, there is no Roman numeral for zero. And previous research into ancient civilizations suggests that the idea of nothing as a number wasn't that obvious.
The lack of zero as a concept could be because these civilizations had other ways of showing zero that didn't require a number, or that they didn't need zero as a value, or just that it wasn't realized yet.
Today, humans need zero. It's an important concept to realize from an evolutionary perspective. So bees must need the idea of zero too, or else it would never have evolved with the level of accuracy on display in these tests.
It's not the size of the brain, but what you do with it
For a long time, the human brain—full of billions of neurons—was considered the only one capable of a more abstract value of zero, or any form of intelligence for that matter.
Then researchers proved that birds could do it (specifically, the African grey parrot), most primates and now bees, with only a million or so neurons in the brain. This growing evidence around the intelligence of other species suggests that brain size has nothing to do with it.
"It's possible that brain size is not an indication of intelligence," said Dyer. "That said and done, we have to think humans are pretty amazing at what we do. So our brain can do many, many complex things. And perhaps the size of our brain gives us the flexibility to do many multiple tasks." | <urn:uuid:9be3da9d-6edd-4c2d-a45a-bba8fd9d4f8a> | 3.296875 | 840 | News Article | Science & Tech. | 50.971565 | 95,638,724 |
How the discovery of water and carbon monoxide vapour surrounding alien planet could hold the key to how Earth was formed
- The planet, known as HR 8799c, has seven times the mass of Jupiter
- Observations suggest the solar system was created in a similar way to Earth
- Discovery means there could be as-yet undetected Earth-like planets
Astronomers have detected clouds of carbon monoxide and water vapour around a huge gassy planet orbiting a star 130 light years away.
The study is the most detailed yet of the atmosphere of an 'exoplanet'.
In future, scientists hope to use similar techniques to uncover signatures of life in the atmospheres of Earth-like worlds.
Discovery: An artist's impression of the HR 8799 star system at an early stage in its evolution, showing the planet HR 8799c, as well as a disk of gas and dust, and interior planets
The planet, known as HR 8799c, has seven times the mass of Jupiter and is one of four similar planets distantly orbiting the star.
Observations suggest the solar system was created in a similar way to our own, with gas giants forming far away from their parent star and smaller, rocky planets closer in.
If this model is correct, there could be as-yet undetected Earth-like planets waiting to be found.
'The results suggest the HR 8799 system is like a scaled-up Solar System,' said Dr Quinn Kanopacky, one of the astronomers from the University of Toronto in Canada.
Light wavelength 'colours' act like fingerprints for different elements. By studying the light from a distant planet, scientists can make assumptions about what elements are contained in its atmosphere.
New model: The study could help scientists discover how our own solar system and Earth was formed
The presence of oxygen’s cousin ozone or carbon dioxide, for instance, could indicate that a world harbours life.
Because HR 8799c is so big and far out - about the same distance from its star as Pluto is from the Sun - astronomers were able to image it directly rather than infer its presence.
The observations were made using the Keck II 10-metre telescope in Hawaii, one of the two largest optical telescopes in the world.
Dr Bruce Macintosh, from the Lawrence Livermore National Laboratory in California, US, one of the co-authors of the research published in the journal Science, said: 'This is the sharpest spectrum ever obtained of an extrasolar planet. This shows the power of directly imaging a planetary system.
'It is the exquisite resolution afforded by these new observations that has allowed us to really begin to probe planet formation.'
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Directions and possibilities of mathematical geology
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This paper considers the present state of mathematical geology. Three directions are recognized: applied, theoretical, and mathematical. Applied mathematical geology includes formal use of mathematics to solve problems and computer processing of data. Success is achieved by a correspondence of mathematical methods used to the nature of geological data. This correspondence can be demonstrated by purely mathematical means. Theoretical mathematical geology uses mathematics as a “language” of geology; however, a number of methodological problems must be solved: formalization of initial geological concepts and creation of a strict conceptual basis, substantiation of initial principles of mathematical simulation, creation of theoretical geological models, problems of elementary and coincidence in geology, and methodological substantiations of possibilities of any mathematical model to approximate geological models. The essense and significance of these problems are considered. The main task of mathematical geology is to prove its correspondence to the nature of the geological objects studied, geological data obtained, and geological problems solvable. Finally, the main problems of mathematical geology are not so much mathematical as geological and methodological.
Key wordsmathematics geology problems direction principle methodology theoretical geological model
Unable to display preview. Download preview PDF. | <urn:uuid:f37f2dd9-1f2f-49ad-97ef-f4c65b8c6329> | 3.359375 | 251 | Truncated | Science & Tech. | -16.186382 | 95,638,730 |
Now, a University of Florida researcher has concluded that crocodiles really do bawl while banqueting – but for physiological reasons rather than rascally reptilian remorse.
UF zoologist Kent Vliet observed and videotaped four captive caimans and three alligators, both close relatives of the crocodile, while eating on a spit of dry land at Florida’s St. Augustine Alligator Farm Zoological Park.
He found that five of the seven animals teared up as they tore into their food, with some of their eyes even frothing and bubbling.
“There are a lot of references in general literature to crocodiles feeding and crying, but it’s almost entirely anecdotal,” Vliet said. “And from the biological perspective there is quite a bit of confusion on the subject in the scientific literature, so we decided to take a closer look.”
A paper about the research appears in the latest edition of the journal BioScience.
Vliet said he began the project after a call from D. Malcolm Shaner, a consultant in neurology at Kaiser Permanente, West Los Angeles, and an associate clinical professor of neurology at the University of California, Los Angeles.
Shaner, who co-authored the paper, was investigating a relatively rare syndrome associated with human facial palsy that causes sufferers to cry while eating. For a presentation he planned to give at a conference of clinical neurologists, he wanted to know if physicians’ general term for the syndrome, crocodile tears, had any basis in biological fact.
Shaner and Vliet uncovered numerous references to crocodile tears in books published from hundreds of years ago to the present.
The term may have gained wide popularity as a result of a passage in one book, “The Voyage and Travel of Sir John Mandeville,” first published in 1400 and read widely, they write.
Says the passage, “In that country be a general plenty of crocodiles …These serpents slay men and they eat them weeping.”
Shaner and Vliet also found reference to crocodiles crying in scientific literature, but it was contradictory or confusing, to say the least.
One scientist, working early last century, decided to try to determine if the myth was true by rubbing onion and salt into crocodiles’ eyes. Shaner said. When they didn’t tear up, he wrongly concluded it was false. As Shaner said, “The problem with those experiments was that he did not examine them when they were eating. He just put onion and salt on their eyes.”
As a result, Vliet decided to do his own observations.
In the myth, crocodiles often cry while eating humans. However, deadpanned Shaner, “we were not able to feed a person to the crocodiles.”
Instead, Vliet had to settle for the dog biscuit-like alligator food that is the staple at the St. Augustine alligator farm. He decided to observe alligators and caimans, rather than crocodiles, because they are trained at the farm to feed on dry land. That’s critical to seeing the tearing because in water the animals’ eyes would be wet anyway.
The farm’s keepers don’t train the crocodiles to feed on land because they are so agile and aggressive, Vliet said. But he said he feels sure they would have the same reaction as alligators and caimans, because all are closely related crocodilians.
What causes the tears remains a bit of a mystery.
Vliet said he believes they may occur as a result of the animals hissing and huffing, a behavior that often accompanies feeding. Air forced through the sinuses may mix with tears in the crocodiles’ lacrimal, or tear, glands emptying into the eye.
But one thing is sure: faux grief is not a factor. “In my experience,” Vliet said, “when crocodiles take something into their mouth, they mean it.”
Kent Vliet | EurekAlert!
Scientists uncover the role of a protein in production & survival of myelin-forming cells
19.07.2018 | Advanced Science Research Center, GC/CUNY
NYSCF researchers develop novel bioengineering technique for personalized bone grafts
18.07.2018 | New York Stem Cell Foundation
For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.
To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...
For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.
Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...
Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.
A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...
Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.
"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....
Ultra-short, high-intensity X-ray flashes open the door to the foundations of chemical reactions. Free-electron lasers generate these kinds of pulses, but there is a catch: the pulses vary in duration and energy. An international research team has now presented a solution: Using a ring of 16 detectors and a circularly polarized laser beam, they can determine both factors with attosecond accuracy.
Free-electron lasers (FELs) generate extremely short and intense X-ray flashes. Researchers can use these flashes to resolve structures with diameters on the...
13.07.2018 | Event News
12.07.2018 | Event News
03.07.2018 | Event News
19.07.2018 | Earth Sciences
19.07.2018 | Power and Electrical Engineering
19.07.2018 | Materials Sciences | <urn:uuid:a319e313-b073-494e-a77e-3556232d4842> | 2.765625 | 1,517 | Content Listing | Science & Tech. | 43.066415 | 95,638,733 |
A leading astrophysicist from Queen's University Belfast has warned that an asteroid strike is just a matter of time.
Professor Alan Fitzsimmons from the University's Astrophysics Research Centre has said it is a case of when an asteroid collision will happen, rather than if it will happen.
This is an Asteroid impact near the Russian city of Chelyabinsk in February 2013.
Credit: Alan Fitzsimmons
Joined by scientist Brian Cox and astronauts such as Apollo 9 astronaut Rusty Schweickart and International Space Station astronaut Nicole Stott, Professor Fitzsimmons is highlighting the threat for Asteroid Day, a global event next Friday (30 June).
On that day in 1908, a small asteroid exploded over Tunguska in Siberia and devastated 800 square miles. Professor Fitzsimmons is warning that a similar unexpected strike in today's world could easily destroy a major city and a larger asteroid could be more dangerous.
Professor Fitzsimmons commented: "It is important to know that scientists and engineers have made great strides in detecting Near-Earth Asteroids and understanding the threat posed by them. Over 1,800 potentially hazardous objects have been discovered so far, but there are many more waiting to be found.
"Astronomers find Near-Earth Asteroids every day and most are harmless. But it is still possible the next Tunguska would take us by surprise, and although we are much better at finding larger asteroids, that does us no good if we are not prepared to do something about them."
The discussions and presentations will be streamed live from Luxembourg on 30 June at https:/
Professor Fitzsimmons is a member of the NEOshield-2 project, funded by the European Research Council to study how to deflect dangerous asteroids.
Queen's University is also a partner in the Pan-STARRS project in Hawai'i - the most successful asteroid hunter currently in operation, as well as the Large Synoptic Survey Telescope project, which will provide a quantum leap in asteroid discoveries.
Emma Gallagher | EurekAlert!
What happens when we heat the atomic lattice of a magnet all of a sudden?
18.07.2018 | Forschungsverbund Berlin
Subaru Telescope helps pinpoint origin of ultra-high energy neutrino
16.07.2018 | National Institutes of Natural Sciences
For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.
To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...
For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.
Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...
Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.
A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...
Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.
"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....
Ultra-short, high-intensity X-ray flashes open the door to the foundations of chemical reactions. Free-electron lasers generate these kinds of pulses, but there is a catch: the pulses vary in duration and energy. An international research team has now presented a solution: Using a ring of 16 detectors and a circularly polarized laser beam, they can determine both factors with attosecond accuracy.
Free-electron lasers (FELs) generate extremely short and intense X-ray flashes. Researchers can use these flashes to resolve structures with diameters on the...
13.07.2018 | Event News
12.07.2018 | Event News
03.07.2018 | Event News
19.07.2018 | Earth Sciences
19.07.2018 | Power and Electrical Engineering
19.07.2018 | Materials Sciences | <urn:uuid:80b6039e-ddc3-41b1-a009-b909dacb0974> | 2.828125 | 1,060 | Content Listing | Science & Tech. | 40.897284 | 95,638,734 |
Extended Discrete Green's Theorem
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This discrete Green's theorem (A Discrete Green's Theorem) connects a given function's double integral over a given domain and the linear combination of the values of the function's cumulative distribution function at the corners of the domain. This suggests a natural extension; by partitioning the domain into rectangles and a curvilinear part, we divide the calculation of the function's double integral over the domain into two parts: the integral over the rectangular domain is calculated using the discrete Green's theorem, and the curvilinear part is calculated via the usual double integral. The "sewing" between these two parts is performed using the parameter of tendency, as suggested in the slanted integration method (Slanted Line Integral). The formula stated by this theorem is simply: , where is the slanted line integral of over the edge of the domain .[more]
In this Demonstration you can control the location of the points , the curvature of each edge connecting two adjacent vertices, the curve's orientation, and which of the subcurves is calculated. A green, red, or black vertex or edge indicates a positive, negative, or zero tendency. A blue vertex or edge means that the tendency is not calculated.[less]
Snapshot 1: The only vertices that do not occur in the final linear combination are (since the tendency is zero at these vertices). Let us detail the calculations that led to the theorem's statement:
⨠⨠⨠â¨â¨ ⨠⨠⨠.
Here the first step is due to the additivity of the slanted integral, the second step is due to the definition of the slanted integral and the curve's tendencies at the specific points, and the last step is due to the discrete Green's theorem.
Snapshot 3: Note that here the vertices and meet. Thus, these vertices' coefficient is ( and cancel). A more delicate deduction occurs in the upper-left corner of the domain. To simplify the discussion, let us denote the intersection point of the edges and by . The double integral over the whole rectangle should be deducted: part of it does not intersect the given domain, and the double integral over the other part is calculated twice (once for each of the edges and —the dark yellow part in the graph). Indeed, we note that the integral is automatically deducted, since (according to the discrete Green's theorem): , and thus the deduction is bidirectional: the integral over the rectangle is deducted, the unwanted vertices are deducted, and in return we get with a coefficient, as we would expect in the discrete Green's theorem for the polygon .
Snapshot 4: This snapshot depicts the following property of the slanted line integral: if is closed, then where is the curve taken with reversed orientation. It is easy to see from this snapshot that:
A rigorous formulation of the theorem is as follows. Let be a simply connected domain in , whose boundary is a tendable curve (its tendency is defined everywhere). Let be an integrable function and let , , be a cumulative distribution function of . Then , where is the slanted line integral of over the boundary of the domain , regardless of the choice of points used to calculate the slanted line integral. This theorem can be improved by selecting the points on the curve such that the computational efficiency is maximized, rather than by selecting the points arbitrarily.
The theory of semidiscrete calculus is given in .
A. Finkelstein. "The Theory behind the 'Summed Area Tables' Algorithm: A Simple Approach to Calculus," (May 25, 2010). http://arxiv.org/abs/1005.1418. | <urn:uuid:c42ed350-110f-49c8-9976-b6f7030bf927> | 2.53125 | 853 | Documentation | Science & Tech. | 43.742051 | 95,638,739 |
Scientists are exploring an irregularity in Earth’s cautious magnetic field that has been named the ‘South Atlantic Anomaly’.
College of Rochester analysts have accumulated new information from locales in southern Africa to broaden their record of Earth’s magnetic field back a large number of years to the principal thousand years.
This information has empowered them to get a setting to clarify later, continuous changes in the magnetic field, most unmistakably in a territory in the Southern Hemisphere.
As indicated by specialists the new information likewise gives more confirmation that a locale in southern Africa may assume an interesting part in magnetic shaft inversions.
The magnetic field that encompasses Earth not just manages whether a compass needle focuses north or south, yet in addition shields the planet from unsafe radiation from space. Almost 800,000 years prior, the shafts were exchanged: north pointed south and the other way around.
The posts have never totally turned around since, yet for as long as 160 years, the quality of the magnetic field has been diminishing at a disturbing rate. The locale where it is weakest, and proceeding to debilitate, is an expansive zone extending from Chile to Zimbabwe called the South Atlantic Anomaly.
Keeping in mind the end goal to put these generally late changes into authentic point of view, Rochester analysts—drove by John Tarduno, an educator and seat of EES—accumulated information from locales in southern Africa, which is inside the South Atlantic Anomaly, to aggregate a record of Earth’s magnetic field quality over numerous hundreds of years.
Information beforehand gathered by Tarduno and Rory Cottrell, an EES explore researcher, together with hypothetical models created by Eric Blackman, an educator of material science and space science at Rochester, recommend the center district underneath southern Africa might be the origin of later and future post inversions.
The specialists found that the magnetic field in the locale changed from 400-450 AD, from 700-750 AD, and again from 1225-1550 AD.
This South Atlantic Anomaly, along these lines, is the latest show of a repeating marvel in Earth’s center underneath Africa that at that point influences the whole globe.
Seismological information has uncovered a denser locale far below southern Africa called the African Large Low Shear Velocity Province.
The district is found ideal over the limit between the hot fluid external center and the stiffer, cooler mantle. Sitting over the fluid external center, it might sink marginally, aggravating the stream of iron and eventually influencing Earth’s magnetic field.
A noteworthy change in the magnetic field would have wide-achieving consequences; the magnetic field empowers streams in anything with long wires, including the electrical lattice.
Changes in the magnetic field could hence cause electrical lattice disappointments, route framework glitches, and satellite breakdowns. A debilitating of the magnetic field may likewise mean more unsafe radiation achieves Earth—and trigger an expansion in the frequency of skin malignancy.
Rabbit and Tarduno caution, in any case, that their information does not really predict an entire post inversion.
“We now know this abnormal conduct has happened no less than two or three times previously the previous 160 years, and is a piece of a greater long haul design,” Hare says. “Notwithstanding, it’s essentially too soon to state for certain whether this conduct will prompt a full shaft inversion.”
Regardless of whether an entire shaft inversion isn’t sooner rather than later, be that as it may, the debilitating of the magnetic field quality is fascinating to scientists, Tarduno says. “The likelihood of a proceeded with rot in the quality of the magnetic field is a societal worry that benefits proceeded with study and checking.”
This examination was financed by the US National Science Foundation. | <urn:uuid:952d189f-212a-47f1-86d0-3be9ab4e0ef3> | 3.140625 | 789 | News Article | Science & Tech. | 27.039459 | 95,638,747 |
Is the story of Exploding Dots truly relevant to both primary AND secondary students? You said it starts at the very beginning of mathematics.
Have you ever seen an abacus? It just a set of rods with beads on it. On a basic abacus each rod has ten beads which you slide to the top. But the idea is that when you do slide all ten beads to the top, you push them back down again and slide just one bead up on the next rod over. People have been using abaci for millennia for counting and doing arithmetic.
But the amazing thing is, if you take this familiar idea and tweak it just a little, a whole new universe of amazing mathematics opens up to you. Instead of using beads and rods, draw dots and boxes. Instead of sliding beads, make them explode. Now you have … you got it … Exploding Dots!
Primary School: See the arithmetic algorithms as a beautiful story and see the role they play in advanced high-school mathematics.
High School: Start at the beginning and within 20-30 minutes you’ll be doing polynomial algebra and infinite sums with astounding clarity. You will see the WHOLE story of arithmetic and algebra united.
What exactly is Global Math Week? How do I and my students participate?
Global Math Week starts October 10 and ends October 17. (It is actually eight days long!)
The idea is that we’re asking teachers and math club leaders and math circle leaders, or anyone, to have a first conversation on the topic of Exploding Dots with students some time during that week – one class period, half a class period, even just 15 minutes is possible and will count!
Then know that millions of people across the planet have already had this experience and millions more will be doing so with you during Global Math Week 2018. Wow!
Here’s what to do:
What are Exploding Dots?
Exploding Dots is the name of an astounding mathematical story that starts at the very beginning of mathematics – it assumes nothing – and swiftly takes you a wondrous journey through grade school arithmetic, high-school polynomials algebra, infinite sums, and advanced mathematics and unsolved research problems baffling mathematicians still to this day.
It starts with the mathematics you already know and transforms it in astounding new light. You and your students will immediately see the power YOU EACH have to play with and understand advanced mathematics with absolute ease.
Learn about the magic of Exploding Dots RIGHT NOW here!
See a one-hour lecture (the full story!) here.
For what grade levels are Exploding Dots best suited?
The story of Exploding Dots is best for students aged around 10 or so, for high school students, for college students, and for all adults interested in exploring cool and exciting mathematics!
Youngsters just starting out to learn about numbers, place value, and basic arithmetic can enjoy the pre-Exploding Dots (język angielski) activities provided by our partner organization Matific. That work too counts towards Global Math Week!
Is there material to engage younger students too? Can my whole K-12 school participate?
Exploding Dots is the story of the surprising power of thinking deeply about place value. As such, K-3 educators play a vital role in setting the scene for this story. Our partner organization, Matific, is providing a suite of pre-Exploding Dots activities so that the whole community of K-12 teachers and students can participate in Global Math Week.
How long will it take me to go through an Exploding Dots experience with students?
Not long! In 15 minutes you can have your first “wow” moment. In 30 minutes you can have a mind-blown moment. In a little bit more time you can have multiple mind-blown moments. And soon after that you can see a whole universe of mathematics to explore and play with before your very eyes.
After course, it is up to you how fast or slow you want to experience and play with this story. Do it all in one hit. (A complete, fast, action-packed version takes 75 minutes.) Do little bits, all slowly. Just do one bit or two, or all of the bits over a period of time. It’s your math to enjoy, so enjoy it and do it any way you like best!
Really? Only 15 minutes of class time?
Yes! In 15 minutes it is possible to have a first “wow” moment with students in the story of Exploding Dots. That wow moment counts! See the 15-minute guide here to see how.
Of course, longer experiences and conversations are welcome too.
How will I know that people all across the planet are having the same experience as me and my students? How will they know that we are part of the global phenomenon?
There are two things to do here: Make sure you register on our Global Math Week site so that your students are counted as part of the global conversation – and that will make sure your city registers too on the map, and your country!
And then when you do have your first Exploding Dots conversation with students -- whenever in the week you choose to do it -- do let the world know you’re doing it. Make a comment about the experience, share a photo, share a video on social media. Our official hashtag on twitter is #gmw2018 but you can do #explodingdots too. You can post on our Facebook page too.
I'll be leading an Exploding Dots session this year, but will have a mixed audience of students: some who saw it last year and some who have never seen it. Is there an Exploding Dots activity I can do that will work for everyone at once?
Yes! Check our James' EXPERIENCE 11: Grape Codes & Napier's Checkerboard of his personal site for two activities which can be done independently or together (depending on how much time you have) and give a new Exploding Dots experience with no prerequisite knowledge.
For those looking for some advanced mathematics, EXPERIENCE 10 is new too!
Do you really expect tens of thousands, hundreds of thousands, if not millions of people to be discovering the magic of Exploding Dots all during that week?
Yes! And we can say that with confidence. During our inaugural Global Math Week in 2017 over 1.7 million students took part in the global event, and folk have been continuing to play with Exploding Dots ever since. We’re going for a total count of 10 million students for Global Math Week 2018!
So don’t miss out! Register! Plan to do something –big or little – with students. And have their participation count by registering.
This is a wonderful and amazing global phenomenon. Make sure you and your students count!
Where do I go to get started?
Does the topic of Exploding Dots follow a particular curriculum?
Exploding Dots covers arithmetic and algebra of school mathematics – and more! – but is not tied to a particular curriculum. It is directly relevant to classroom work and remains universal.
Do I need technology in my classroom?
We have full technology, low technology, and no technology options available for conducting Exploding Dots with students. The teaching guides here explain how.
Are the materials provided free? Do they go away after Global Math Week?
All the materials will remain freely available in perpetuity. There is plenty of time to explore the whole Exploding Dots experience at your and your students’ leisure.
Are materials available in multiple languages? Are they captioned?
We are a grass-roots organization and our volunteers are helping us translate materials into multiple languages. Each chapter of James’s personal site here (see lesson 1.1, lesson 2.1, lesson 3.1, and so on) shows the materials we currently have translated.
James' videos have high-quality English captions, thanks to our partner organization dotsub.com, and our volunteers are translating those subtitles into other languages too.
If you would like to help with this translation work, please write to us: firstname.lastname@example.org.
Can we post comments, photos, and videos somewhere? | <urn:uuid:f6ccbe92-2efb-40dc-978c-de037148e988> | 3.546875 | 1,721 | FAQ | Science & Tech. | 58.651868 | 95,638,750 |
Virtual Python Environment builder
You can install virtualenv with pip install virtualenv, or the latest development version with pip install virtualenv==dev.
You can also use easy_install, or if you have no Python package manager available at all, you can just grab the single file virtualenv.py and run it with python virtualenv.py.
What It Does
virtualenv is a tool to create isolated Python environments.
The basic problem being addressed is one of dependencies and versions, and indirectly permissions. Imagine you have an application that needs version 1 of LibFoo, but another application requires version 2. How can you use both these applications? If you install everything into /usr/lib/python2.7/site-packages (or whatever your platform’s standard location is), it’s easy to end up in a situation where you unintentionally upgrade an application that shouldn’t be upgraded.
Or more generally, what if you want to install an application and leave it be? If an application works, any change in its libraries or the versions of those libraries can break the application.
Also, what if you can’t install packages into the global site-packages directory? For instance, on a shared host.
In all these cases, virtualenv can help you. It creates an environment that has its own installation directories, that doesn’t share libraries with other virtualenv environments (and optionally doesn’t access the globally installed libraries either).
The basic usage is:
$ python virtualenv.py ENV
If you install it you can also just do virtualenv ENV.
This creates ENV/lib/pythonX.X/site-packages, where any libraries you install will go. It also creates ENV/bin/python, which is a Python interpreter that uses this environment. Anytime you use that interpreter (including when a script has #!/path/to/ENV/bin/python in it) the libraries in that environment will be used.
$ python virtualenv.py --distribute ENV
You can also set the environment variable VIRTUALENV_USE_DISTRIBUTE.
A new virtualenv also includes the pip installer, so you can use ENV/bin/pip to install additional packages into the environment.
Environment variables and configuration files
virtualenv can not only be configured by passing command line options such as --distribute but also by two other means:
Each command line option is automatically used to look for environment variables with the name format VIRTUALENV_<UPPER_NAME>. That means the name of the command line options are capitalized and have dashes ('-') replaced with underscores ('_').
For example, to automatically install Distribute instead of setuptools you can also set an environment variable:
$ export VIRTUALENV_USE_DISTRIBUTE=true $ python virtualenv.py ENV
It’s the same as passing the option to virtualenv directly:
$ python virtualenv.py --distribute ENV
This also works for appending command line options, like --find-links. Just leave an empty space between the passsed values, e.g.:
$ export VIRTUALENV_EXTRA_SEARCH_DIR="/path/to/dists /path/to/other/dists" $ virtualenv ENV
is the same as calling:
$ python virtualenv.py --extra-search-dir=/path/to/dists --extra-search-dir=/path/to/other/dists ENV
virtualenv also looks for a standard ini config file. On Unix and Mac OS X that’s $HOME/.virtualenv/virtualenv.ini and on Windows, it’s %HOME%\\virtualenv\\virtualenv.ini.
The names of the settings are derived from the long command line option, e.g. the option --distribute would look like this:
[virtualenv] distribute = true
Appending options like --extra-search-dir can be written on multiple lines:
[virtualenv] extra-search-dir = /path/to/dists /path/to/other/dists
Please have a look at the output of virtualenv --help for a full list of supported options.
Some paths within the virtualenv are slightly different on Windows: scripts and executables on Windows go in ENV\Scripts\ instead of ENV/bin/ and libraries go in ENV\Lib\ rather than ENV/lib/.
To create a virtualenv under a path with spaces in it on Windows, you’ll need the win32api library installed.
Beginning with virtualenv version 1.5 PyPy is supported. To use PyPy 1.4 or 1.4.1, you need a version of virtualenv >= 1.5. To use PyPy 1.5, you need a version of virtualenv >= 1.6.1.
Creating Your Own Bootstrap Scripts
While this creates an environment, it doesn’t put anything into the environment. Developers may find it useful to distribute a script that sets up a particular environment, for example a script that installs a particular web application.
To create a script like this, call virtualenv.create_bootstrap_script(extra_text), and write the result to your new bootstrapping script. Here’s the documentation from the docstring:
Creates a bootstrap script, which is like this script but with extend_parser, adjust_options, and after_install hooks.
This returns a string that (written to disk of course) can be used as a bootstrap script with your own customizations. The script will be the standard virtualenv.py script, with your extra text added (your extra text should be Python code).
If you include these functions, they will be called:
- You can add or remove options from the parser here.
- adjust_options(options, args):
- You can change options here, or change the args (if you accept different kinds of arguments, be sure you modify args so it is only [DEST_DIR]).
After everything is installed, this function is called. This is probably the function you are most likely to use. An example would be:def after_install(options, home_dir): if sys.platform == 'win32': bin = 'Scripts' else: bin = 'bin' subprocess.call([join(home_dir, bin, 'easy_install'), 'MyPackage']) subprocess.call([join(home_dir, bin, 'my-package-script'), 'setup', home_dir])
This example immediately installs a package, and runs a setup script from that package.
Here’s a more concrete example of how you could use this:
import virtualenv, textwrap output = virtualenv.create_bootstrap_script(textwrap.dedent(""" import os, subprocess def after_install(options, home_dir): etc = join(home_dir, 'etc') if not os.path.exists(etc): os.makedirs(etc) subprocess.call([join(home_dir, 'bin', 'easy_install'), 'BlogApplication']) subprocess.call([join(home_dir, 'bin', 'paster'), 'make-config', 'BlogApplication', join(etc, 'blog.ini')]) subprocess.call([join(home_dir, 'bin', 'paster'), 'setup-app', join(etc, 'blog.ini')]) """)) f = open('blog-bootstrap.py', 'w').write(output)
Another example is available here.
In a newly created virtualenv there will be a bin/activate shell script. For Windows systems, activation scripts are provided for CMD.exe and Powershell.
On Posix systems you can do:
$ source bin/activate
This will change your $PATH to point to the virtualenv’s bin/ directory. (You have to use source because it changes your shell environment in-place.) This is all it does; it’s purely a convenience. If you directly run a script or the python interpreter from the virtualenv’s bin/ directory (e.g. path/to/env/bin/pip or /path/to/env/bin/python script.py) there’s no need for activation.
After activating an environment you can use the function deactivate to undo the changes to your $PATH.
The activate script will also modify your shell prompt to indicate which environment is currently active. You can disable this behavior, which can be useful if you have your own custom prompt that already displays the active environment name. To do so, set the VIRTUAL_ENV_DISABLE_PROMPT environment variable to any non-empty value before running the activate script.
On Windows you just do:
And type deactivate to undo the changes.
Based on your active shell (CMD.exe or Powershell.exe), Windows will use either activate.bat or activate.ps1 (as appropriate) to activate the virtual environment. If using Powershell, see the notes about code signing below.
If using Powershell, the activate script is subject to the execution policies on the system. By default on Windows 7, the system’s excution policy is set to Restricted, meaning no scripts like the activate script are allowed to be executed. But that can’t stop us from changing that slightly to allow it to be executed.
In order to use the script, you have to relax your system’s execution policy to AllSigned, meaning all scripts on the system must be digitally signed to be executed. Since the virtualenv activation script is signed by one of the authors (Jannis Leidel) this level of the execution policy suffices. As an adminstrator run:
PS C:\> Set-ExecutionPolicy AllSigned
Then you’ll be asked to trust the signer, when executing the script. You will be prompted with the following:
PS C:\> virtualenv .\foo New python executable in C:\foo\Scripts\python.exe Installing setuptools................done. Installing pip...................done. PS C:\> .\foo\scripts\activate Do you want to run software from this untrusted publisher? File C:\foo\scripts\activate.ps1 is published by Eemail@example.com, CN=Jannis Leidel, L=Berlin, S=Berlin, C=DE, Description=581796-Gh7xfJxkxQSIO4E0 and is not trusted on your system. Only run scripts from trusted publishers. [V] Never run [D] Do not run [R] Run once [A] Always run [?] Help (default is "D"):A (foo) PS C:\>
If you select [A] Always Run, the certificate will be added to the Trusted Publishers of your user account, and will be trusted in this user’s context henceforth. If you select [R] Run Once, the script will be run, but you will be prometed on a subsequent invocation. Advanced users can add the signer’s certificate to the Trusted Publishers of the Computer account to apply to all users (though this technique is out of scope of this document).
Alternatively, you may relax the system execution policy to allow running of local scripts without verifying the code signature using the following:
PS C:\> Set-ExecutionPolicy RemoteSigned
Since the activate.ps1 script is generated locally for each virtualenv, it is not considered a remote script and can then be executed.
The --system-site-packages Option
If you build with virtualenv --system-site-packages ENV, your virtual environment will inherit packages from /usr/lib/python2.7/site-packages (or wherever your global site-packages directory is).
This can be used if you have control over the global site-packages directory, and you want to depend on the packages there. If you want isolation from the global system, do not use this flag.
Using Virtualenv without bin/python
Luckily, it’s easy. You must use the custom Python interpreter to install libraries. But to use libraries, you just have to be sure the path is correct. A script is available to correct the path. You can setup the environment like:
activate_this = '/path/to/env/bin/activate_this.py' execfile(activate_this, dict(__file__=activate_this))
This will change sys.path and even change sys.prefix, but also allow you to use an existing interpreter. Items in your environment will show up first on sys.path, before global items. However, global items will always be accessible (as if the --system-site-packages flag had been used in creating the environment, whether it was or not). Also, this cannot undo the activation of other environments, or modules that have been imported. You shouldn’t try to, for instance, activate an environment before a web request; you should activate one environment as early as possible, and not do it again in that process.
Making Environments Relocatable
Note: this option is somewhat experimental, and there are probably caveats that have not yet been identified. Also this does not currently work on Windows.
Normally environments are tied to a specific path. That means that you cannot move an environment around or copy it to another computer. You can fix up an environment to make it relocatable with the command:
$ virtualenv --relocatable ENV
This will make some of the files created by setuptools or distribute use relative paths, and will change all the scripts to use activate_this.py instead of using the location of the Python interpreter to select the environment.
Note: you must run this after you’ve installed any packages into the environment. If you make an environment relocatable, then install a new package, you must run virtualenv --relocatable again.
Also, this does not make your packages cross-platform. You can move the directory around, but it can only be used on other similar computers. Some known environmental differences that can cause incompatibilities: a different version of Python, when one platform uses UCS2 for its internal unicode representation and another uses UCS4 (a compile-time option), obvious platform changes like Windows vs. Linux, or Intel vs. ARM, and if you have libraries that bind to C libraries on the system, if those C libraries are located somewhere different (either different versions, or a different filesystem layout).
If you use this flag to create an environment, currently, the --system-site-packages option will be implied.
The --extra-search-dir Option
When it creates a new environment, virtualenv installs either setuptools or distribute, and pip. In normal operation, the latest releases of these packages are fetched from the Python Package Index (PyPI). In some circumstances, this behavior may not be wanted, for example if you are using virtualenv during a deployment and do not want to depend on Internet access and PyPI availability.
As an alternative, you can provide your own versions of setuptools, distribute and/or pip on the filesystem, and tell virtualenv to use those distributions instead of downloading them from the Internet. To use this feature, pass one or more --extra-search-dir options to virtualenv like this:
$ virtualenv --extra-search-dir=/path/to/distributions ENV
The /path/to/distributions path should point to a directory that contains setuptools, distribute and/or pip distributions. Setuptools distributions must be .egg files; distribute and pip distributions should be .tar.gz source distributions.
Virtualenv will still download these packages if no satisfactory local distributions are found.
If you are really concerned about virtualenv fetching these packages from the Internet and want to ensure that it never will, you can also provide an option --never-download like so:
$ virtualenv --extra-search-dir=/path/to/distributions --never-download ENV
If this option is provided, virtualenv will never try to download setuptools/distribute or pip. Instead, it will exit with status code 1 if it fails to find local distributions for any of these required packages. The local distribution lookup is done in this order and the following locations:
- The current directory.
- The directory where virtualenv.py is located.
- A virtualenv_support directory relative to the directory where virtualenv.py is located.
- If the file being executed is not named virtualenv.py (i.e. is a boot script), a virtualenv_support directory relative to wherever virtualenv.py is actually installed.
Compare & Contrast with Alternatives
There are several alternatives that create isolated environments:
workingenv (which I do not suggest you use anymore) is the predecessor to this library. It used the main Python interpreter, but relied on setting $PYTHONPATH to activate the environment. This causes problems when running Python scripts that aren’t part of the environment (e.g., a globally installed hg or bzr). It also conflicted a lot with Setuptools.
virtual-python is also a predecessor to this library. It uses only symlinks, so it couldn’t work on Windows. It also symlinks over the entire standard library and global site-packages. As a result, it won’t see new additions to the global site-packages.
This script only symlinks a small portion of the standard library into the environment, and so on Windows it is feasible to simply copy these files over. Also, it creates a new/empty site-packages and also adds the global site-packages to the path, so updates are tracked separately. This script also installs Setuptools automatically, saving a step and avoiding the need for network access.
zc.buildout doesn’t create an isolated Python environment in the same style, but achieves similar results through a declarative config file that sets up scripts with very particular packages. As a declarative system, it is somewhat easier to repeat and manage, but more difficult to experiment with. zc.buildout includes the ability to setup non-Python systems (e.g., a database server or an Apache instance).
I strongly recommend anyone doing application development or deployment use one of these tools.
Refer to the contributing to pip documentation - it applies equally to virtualenv.
Virtualenv’s release schedule is tied to pip’s – each time there’s a new pip release, there will be a new virtualenv release that bundles the new version of pip.
Running the tests
Virtualenv’s test suite is small and not yet at all comprehensive, but we aim to grow it.
The easy way to run tests (handles test dependencies automatically):
$ python setup.py test
If you want to run only a selection of the tests, you’ll need to run them directly with nose instead. Create a virtualenv, and install required packages:
$ pip install nose mock
Or select just a single test file to run:
$ nosetests tests.test_virtualenv
Status and License
Changes & News
- Fixed minor issue in –relocatable. Thanks, Cap Petschulat.
- Bumped the version string in virtualenv.py up, too.
- Fixed rST rendering bug of long description.
- Update embedded pip to version 1.1.
- Fix –relocatable under Python 3. Thanks Doug Hellmann.
- Added environ PATH modification to activate_this.py. Thanks Doug Napoleone. Fixes #14.
- Support creating virtualenvs directly from a Python build directory on Windows. Thanks CBWhiz. Fixes #139.
- Use non-recursive symlinks to fix things up for posix_local install scheme. Thanks michr.
- Made activate script available for use with msys and cygwin on Windows. Thanks Greg Haskins, Cliff Xuan, Jonathan Griffin and Doug Napoleone. Fixes #176.
- Fixed creation of virtualenvs on Windows when Python is not installed for all users. Thanks Anatoly Techtonik for report and patch and Doug Napoleone for testing and confirmation. Fixes #87.
- Fixed creation of virtualenvs using -p in installs where some modules that ought to be in the standard library (e.g. readline) are actually installed in site-packages next to virtualenv.py. Thanks Greg Haskins for report and fix. Fixes #167.
- Added activation script for Powershell (signed by Jannis Leidel). Many thanks to Jason R. Coombs.
- Gave user-provided --extra-search-dir priority over default dirs for finding setuptools/distribute (it already had priority for finding pip). Thanks Ethan Jucovy.
- Updated embedded Distribute release to 0.6.24. Thanks Alex Gronholm.
- Made --no-site-packages behavior the default behavior. The --no-site-packages flag is still permitted, but displays a warning when used. Thanks Chris McDonough.
- New flag: --system-site-packages; this flag should be passed to get the previous default global-site-package-including behavior back.
- Added ability to set command options as environment variables and options in a virtualenv.ini file.
- Fixed various encoding related issues with paths. Thanks Gunnlaugur Thor Briem.
- Made virtualenv.py script executable.
- Restored ability to run on Python 2.4, too.
- Restored ability to run on Python < 2.7.
- Updated embedded distribute release to 0.6.19.
- Updated embedded pip release to 1.0.2.
- Fixed #141 - Be smarter about finding pkg_resources when using the non-default Python intepreter (by using the -p option).
- Fixed #112 - Fixed path in docs.
- Fixed #109 - Corrected doctests of a Logger method.
- Fixed #118 - Fixed creating virtualenvs on platforms that use the “posix_local” install scheme, such as Ubuntu with Python 2.7.
- Add missing library to Python 3 virtualenvs (_dummy_thread).
- Start to use git-flow.
- Added support for PyPy 1.5
- Fixed #121 – added sanity-checking of the -p argument. Thanks Paul Nasrat.
- Added progress meter for pip installation as well as setuptools. Thanks Ethan Jucovy.
- Added –never-download and –search-dir options. Thanks Ethan Jucovy.
- Added Python 3 support! Huge thanks to Vinay Sajip and Vitaly Babiy.
- Fixed creation of virtualenvs on Mac OS X when standard library modules (readline) are installed outside the standard library.
- Updated bundled pip to 1.0.
- Moved main repository to Github: https://github.com/pypa/virtualenv
- Transferred primary maintenance from Ian to Jannis Leidel, Carl Meyer and Brian Rosner
- Fixed a few more pypy related bugs.
- Updated bundled pip to 0.8.2.
- Handed project over to new team of maintainers.
- Moved virtualenv to Github at https://github.com/pypa/virtualenv
- Added _weakrefset requirement for Python 2.7.1.
- Fixed Windows regression in 1.5
- Include pip 0.8.1.
- Add support for PyPy.
- Uses a proper temporary dir when installing environment requirements.
- Add --prompt option to be able to override the default prompt prefix.
- Fix an issue with --relocatable on Windows.
- Fix issue with installing the wrong version of distribute.
- Add fish and csh activate scripts.
- Include pip 0.7.2
- Fix for Mac OS X Framework builds that use --universal-archs=intel
- Fix activate_this.py on Windows.
- Allow $PYTHONHOME to be set, so long as you use source bin/activate it will get unset; if you leave it set and do not activate the environment it will still break the environment.
- Include pip 0.7.1
- Include pip 0.7
- Allow activate.sh to skip updating the prompt (by setting $VIRTUAL_ENV_DISABLE_PROMPT).
- Include pip 0.6.3
- Fix activate.bat and deactivate.bat under Windows when PATH contained a parenthesis
- Include pip 0.6.2 and Distribute 0.6.10
- Create the virtualenv script even when Setuptools isn’t installed
- Fix problem with virtualenv --relocate when bin/ has subdirectories (e.g., bin/.svn/); from Alan Franzoni.
- If you set $VIRTUALENV_USE_DISTRIBUTE then virtualenv will use Distribute by default (so you don’t have to remember to use --distribute).
- Include pip 0.6.1
- Fix pip installation on Windows
- Fix use of stand-alone virtualenv.py (and boot scripts)
- Exclude ~/.local (user site-packages) from environments when using --no-site-packages
- Include pip 0.6
- Updated setuptools to 0.6c11
- Added the –distribute option
- Fixed packaging problem of support-files
- Virtualenv now copies the actual embedded Python binary on Mac OS X to fix a hang on Snow Leopard (10.6).
- Fail more gracefully on Windows when win32api is not installed.
- Fix site-packages taking precedent over Jython’s __classpath__ and also specially handle the new __pyclasspath__ entry in sys.path.
- Now copies Jython’s registry file to the virtualenv if it exists.
- Better find libraries when compiling extensions on Windows.
- Create Scripts\pythonw.exe on Windows.
- Added support for the Debian/Ubuntu /usr/lib/pythonX.Y/dist-packages directory.
- Set distutils.sysconfig.get_config_vars()['LIBDIR'] (based on sys.real_prefix) which is reported to help building on Windows.
- Make deactivate work on ksh
- Fixes for --python: make it work with --relocatable and the symlink created to the exact Python version.
- Use Windows newlines in activate.bat, which has been reported to help when using non-ASCII directory names.
- Fixed compatibility with Jython 2.5b1.
- Added a function virtualenv.install_python for more fine-grained access to what virtualenv.create_environment does.
- Fix a problem with Windows and paths that contain spaces.
- If /path/to/env/.pydistutils.cfg exists (or /path/to/env/pydistutils.cfg on Windows systems) then ignore ~/.pydistutils.cfg and use that other file instead.
- Fix ` a problem <https://bugs.launchpad.net/virtualenv/+bug/340050>`_ picking up some .so libraries in /usr/local.
- Remove the [install] prefix = ... setting from the virtualenv distutils.cfg – this has been causing problems for a lot of people, in rather obscure ways.
- If you use a boot script it will attempt to import virtualenv and find a pre-downloaded Setuptools egg using that.
- Added platform-specific paths, like /usr/lib/pythonX.Y/plat-linux2
- Real Python 2.6 compatibility. Backported the Python 2.6 updates to site.py, including user directories (this means older versions of Python will support user directories, whether intended or not).
- Always set [install] prefix in distutils.cfg – previously on some platforms where a system-wide distutils.cfg was present with a prefix setting, packages would be installed globally (usually in /usr/local/lib/pythonX.Y/site-packages).
- Sometimes Cygwin seems to leave .exe off sys.executable; a workaround is added.
- Fix --python option.
- Fixed handling of Jython environments that use a jython-complete.jar.
- Update to Setuptools 0.6c9
- Added an option virtualenv --relocatable EXISTING_ENV, which will make an existing environment “relocatable” – the paths will not be absolute in scripts, .egg-info and .pth files. This may assist in building environments that can be moved and copied. You have to run this after any new packages installed.
- Added bin/activate_this.py, a file you can use like execfile("path_to/activate_this.py", dict(__file__="path_to/activate_this.py")) – this will activate the environment in place, similar to what the mod_wsgi example does.
- For Mac framework builds of Python, the site-packages directory /Library/Python/X.Y/site-packages is added to sys.path, from Andrea Rech.
- Some platform-specific modules in Macs are added to the path now (plat-darwin/, plat-mac/, plat-mac/lib-scriptpackages), from Andrea Rech.
- Fixed a small Bashism in the bin/activate shell script.
- Added __future__ to the list of required modules, for Python 2.3. You’ll still need to backport your own subprocess module.
- Fixed the __classpath__ entry in Jython’s sys.path taking precedent over virtualenv’s libs.
- Added a --python option to select the Python interpreter.
- Add warnings to the modules copied over, for Python 2.6 support.
- Add sets to the module copied over for Python 2.3 (though Python 2.3 still probably doesn’t work).
- Added support for Jython 2.5.
- Added support for Python 2.6.
- Fix a problem with missing DLLs/zlib.pyd on Windows. Create
- bin/python (or bin/python.exe) even when you run virtualenv with an interpreter named, e.g., python2.4
- Fix MacPorts Python
- Added –unzip-setuptools option
- Update to Setuptools 0.6c8
- If the current directory is not writable, run ez_setup.py in /tmp
- Copy or symlink over the include directory so that packages will more consistently compile.
- Fix build on systems that use /usr/lib64, distinct from /usr/lib (specifically CentOS x64).
- Fixed bug in --clear.
- Fixed typos in deactivate.bat.
- Preserve $PYTHONPATH when calling subprocesses.
- Fix include dir copying on Windows (makes compiling possible).
- Include the main lib-tk in the path.
- Patch distutils.sysconfig: get_python_inc and get_python_lib to point to the global locations.
- Install distutils.cfg before Setuptools, so that system customizations of distutils.cfg won’t effect the installation.
- Add bin/pythonX.Y to the virtualenv (in addition to bin/python).
- Fixed an issue with Mac Framework Python builds, and absolute paths (from Ronald Oussoren).
- Improve ability to create a virtualenv from inside a virtualenv.
- Fix a little bug in bin/activate.
- Actually get distutils.cfg to work reliably.
- Added lib-dynload and config to things that need to be copied over in an environment.
- Copy over or symlink the include directory, so that you can build packages that need the C headers.
- Include a distutils package, so you can locally update distutils.cfg (in lib/pythonX.Y/distutils/distutils.cfg).
- Better avoid downloading Setuptools, and hitting PyPI on environment creation.
- Fix a problem creating a lib64/ directory.
- Should work on MacOSX Framework builds (the default Python installations on Mac). Thanks to Ronald Oussoren.
- Windows installs would sometimes give errors about sys.prefix that were inaccurate.
- Slightly prettier output.
- Added support for Windows.
- Give a better warning if you are on an unsupported platform (Mac Framework Pythons, and Windows).
- Give error about running while inside a workingenv.
- Give better error message about Python 2.3.
Fixed packaging of the library.
Initial release. Everything is changed and new! | <urn:uuid:dd965768-dfc6-48ff-9c57-691043499731> | 2.6875 | 7,069 | Documentation | Software Dev. | 51.97416 | 95,638,779 |
Wildlife face many threats with spreading urbanization, including habitat loss and inbreeding when populations become fragmented and isolated. It doesn't help that there is a billion-dollar international industry dedicated to the illegal trafficking of wild animals or wild animal parts.
The Conservation Genetics Lab at the University of Arizona is working to conserve and protect wild animals around the world.
"Our work here deals with using genetics for wildlife conservation," said Ashwin Naidu, a doctoral candidate in the School of Natural Resources and the Environment.
One of the largest threats to wildlife is loss of genetic diversity through inbreeding, which can lead to lower levels of reproductive fitness or disease susceptibility and can endanger a population's survival.
As urbanization increases, more and more wildlife habitats are destroyed, leaving populations of wild species cut off from each other, marooned on isolated "islands" of natural land in a sea of human development. Small populations that become trapped in these fragmented habitats are unable to breed outside of their local gene pool – and the Conservation Genetics Lab steps in to help.
The researchers use genetic techniques to identify whether small populations of wild animals that have become isolated because of habitat fragmentation are inbred or in danger of becoming inbred.
"We want to know how individuals are related to each other across a landscape," said Naidu. "We have populations of species, and we want to see if there is genetic differentiation, indicating a barrier between the populations, or if there is gene flow across the populations."
The researchers extract DNA from animal samples such as hair, bones or carcasses, or blood samples and cheek swabs if the animal is captured.
"We amplify DNA to look for certain areas in the genome," said Naidu. "Every species has a unique DNA sequence known as a DNA barcode and every individual has a unique genetic fingerprint."
There are several specific locations on a genome where the order of genes or base-pair sequences varies between individuals, populations or species, said Naidu. "One is the nuclear DNA, DNA contained inside the cell's nucleus. Another is mitochondrial DNA, or DNA located inside the mitochondria of the cell."
"Once we amplify and generate multiple copies of these locations, all of this data is analyzed through DNA sequence analysis software," said Naidu. "If we want to look at variation within individuals we look at unique genome types, what we call DNA fingerprints. If we want to look at variation within species we look at the mitochondrial DNA sequences called barcodes."
DNA fingerprints and barcodes from individual samples then are compared with a genetic database of species and populations that previously have been studied.
If a population is found to have inbred, the Conservation Genetics Lab goes to the rescue.
"We take a few individuals from populations that show good genetic diversity and we introduce them, or trans-locate them, into the population that is suffering from inbreeding," said Naidu. "When we introduce new genetic variation into a small population that is undergoing inbreeding, we have the potential to bring them back to a higher genetic diversity."
"We observe and monitor these populations to see if they're doing well. Then we genetically test them again to find out the level of genetic diversity after the translocation. Has it balanced, is it good enough for their survival? If it's not, then we need more translocations."
The same technique is applied to endangered or critically endangered animals that require captive breeding. Animals that are bred in captivity for good genetic diversity can be reintroduced to the wild to genetically rescue the wild population.
Genetics also can be used to identify species in areas where they previously haven't been known to exist. "Sometimes we find samples of an animal, such as feces, carcasses, bones or hair, and this is evidence for presence of the animal. But how do you confirm what species of animal it is? Genetics is a very useful tool for identifying the species," said Naidu. "DNA evidence can be obtained from ancient sources as well, such as fossils or bones which are being excavated."
And wildlife forensic genetics has yet another application: catching criminals.
Forensic genetics can be used to identify the victims and criminals in wildlife crime cases in the same way that genetics is used to solve human crime cases. The Conservation Genetics Lab along with state and federal wildlife management agencies works to fight against cases of wildlife crime.
"Wildlife forensics particularly deals with investigating crime cases where you have a shipment of animals or animal parts that have been transported internationally and are seized by officials at the border, or later are identified as not being native to the country they are found in," said Naidu. "How would you know which country or which region these animal parts or animals came from? Wildlife forensic genetics is really kicking in because of all this new technology that's available for species identification and source population identification."
Forensic genetics can answer questions such as the species, origin and source population of the animal or animal part, as well as identify whether it was bred in captivity or caught in the wild. "All of these are general questions when you look at samples such as meat, hides, burnt skin or other morphologically unidentifiable samples where you need to extract DNA and identify them genetically," said Naidu.
The lab also deals with specific cases of wildlife crime.
"Let's say a hunter has a license to shoot one species, but he has shot another species and claims that this is what he had a hunting license for," said Naidu. "But a wildlife manager sees a little bit of blood or some hair or remains from the animal in the bed of the hunter's vehicle and wants to know exactly what species it is and which population it belonged to. So he collects some samples from the back of the truck and sends them to the lab and we identify species or individuals to determine whether it is really the species the hunter had a license for."
Once evidence is obtained showing that a hunter illegally has taken a species, the evidence may be presented in court. "These results are so scientifically robust that they are just like human DNA court cases," said Naidu. "There are a lot of cases in illegal or in wildlife crime that need good scientists to go and testify in courts and I think that's a very important move that needs to be made by scientists for the benefit of wildlife conservation in this world."
"My dream is to establish a lab and a forensic unit that will focus particularly on wildlife forensic genetics dealing with collection of field evidence, chain of custody and presentation of evidence to testify in court. This lab would operate on global standards and allow for communication between other such labs," said Naidu.Naidu's research is funded by the U.S. Fish and Wildlife Service and the Arizona Game and Fish Department. He is also associated with the International Union for Conservation of Nature's Cat Specialist Group.
Daniel Stolte | The University of Arizona
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Series: The Butterflies of Costa Rica and their Natural History Volume: 2
By: Philip J DeVries
288 pages, Col plates, bw plates, illus, figs, tabs
The first detailed treatment of over 250 species, the book provides a thorough natural history for each. The guide illustrates nearly all of the Costa Rican species in colour and provides a large sample of detailed line drawings and scanning electron micrographs of rionid early stages for the first time ever. The coverage also makes the book very useful for identifying rionids throughout Mexico, Central America, and substantial portions of South America.
Invaluable to anyone studying the butterflies of the Neotropics. New Scientist
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Greater Resolution for Cryo-Electron Microscopy
News Mar 24, 2017 | Original Story from Lawrence Berkeley National Laboratory
Credit: C. Hryc and the Chiu Lab, Baylor College of Medicine
Cryo-electron microscopy (cryo-EM), which enables the visualization of viruses, proteins, and other biological structures at the molecular level, is a critical tool used to advance biochemical knowledge. Now Lawrence Berkeley National Laboratory (Berkeley Lab) researchers have extended cryo-EM’s impact further by developing a new computational algorithm that was instrumental in constructing a 3-D atomic-scale model of bacteriophage P22 for the first time.
Over 20,000 two-dimensional cryo-EM images of bacteriophage P22 (also known as the P22 virus that infects the common bacterium Salmonella) from Baylor College of Medicine were used to make the model. The results were published by researchers from Baylor College of Medicine, Massachusetts Institute of Technology, Purdue University and Berkeley Lab in the Proceedings of the National Academies of Sciences earlier in March.
“This is a great example of how to exploit electron microscopy technology and combine it with new computational methods to determine a bacteriophage’s structure,” said Paul Adams, Berkeley Lab’s Molecular Biophysics & Integrated Bioimaging division director and a co-author of the paper. “We developed the algorithms, the computational code, to optimize the atomic model so that it best fit the experimental data.” Pavel Afonine, a Berkeley Lab computational research scientist and paper co-author, took the lead in developing the algorithm using Phenix, a software suite used traditionally in X-ray crystallography for determining macromolecular structures.
The successful rendering of bacteriophage P22’s 3-D atomic-scale model allows researchers to peek inside the virus’ protein coats at resolution. It is the culmination of several years of work that previously had enabled Baylor College researchers to trace out most of the protein’s backbone, but not the fine details, according to Corey Hryc, co-first author and a graduate student of Baylor biochemistry professor Wah Chiu.
“Thanks to this exquisite structural detail, we have determined the protein chemistry of the P22 virus,” Chiu said. “I think it is important that we provide detailed annotations with the structure so other researchers can use it for their future experiments,” he added. Chiu’s lab has been using cryo-EM and computer reconstruction techniques to build 3-D molecular structures for almost 30 years.
The findings could have valuable biological implications as well. Thanks to the 3-D atomic-scale model, it’s now “possible to see the interactions between the pieces making up the P22 virus, which are critical to making it stable,” Adams said. This helps researchers figure out how to make chemicals that can bind to certain proteins. Adams underscores that the ability to understand the configuration of atoms in molecular space can be used to generate new insights into drug design and development.
Hryc, C. F., Chen, D., Afonine, P. V., Jakana, J., Wang, Z., Haase-Pettingell, C., . . . Chiu, W. (2017). Accurate model annotation of a near-atomic resolution cryo-EM map. Proceedings of the National Academy of Sciences, 114(12), 3103-3108. doi:10.1073/pnas.1621152114
This article has been republished from materials provided by Lawrence Berkeley National Laboratory. Note: material may have been edited for length and content. For further information, please contact the cited source.
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Chief Meteorologist Eric Elwell explains about what we can expect to see during the eclipse.
Whether or not you’re inside the path of totality will determine what you see in the sky. If you’re outside the path, you’ll likely see a partial (not total) eclipse.
To determine the most accurate eclipse path, according to Wright, you have to figure out where the moon’s shadow will fall on the Earth’s surface, which requires taking into account the elevation differences on both the moon and Earth’s surfaces, he told Space.com.
Using elevation data from NASA’s Shuttle Radar Topography Mission, the locations of the Earth, moon and sun at each line of latitude or longitude and how long it takes sunlight to travel to the moon and down to Earth, Wright was able to compute where exactly the eclipse will cross and for how long. | <urn:uuid:07fe4547-555f-4e2d-adad-ee58549020ae> | 2.9375 | 187 | News Article | Science & Tech. | 47.792 | 95,638,825 |
Earth's internal heat budget
Earth's internal heat budget is fundamental to the thermal history of the Earth. The flow of heat from Earth's interior to the surface is estimated at 47 terawatts (TW) and comes from two main sources in roughly equal amounts: the radiogenic heat produced by the radioactive decay of isotopes in the mantle and crust, and the primordial heat left over from the formation of the Earth.
Earth's internal heat powers most geological processes and drives plate tectonics. Despite its geological significance, this heat energy coming from Earth's interior is actually only 0.03% of Earth's total energy budget at the surface, which is dominated by 173,000 TW of incoming solar radiation. The insolation that eventually, after reflection, reaches the surface penetrates only several tens of centimeters on the daily cycle and only several tens of meters on the annual cycle. This renders solar radiation minimally relevant for internal processes.
Heat and early estimate of Earth's age
Based on calculations of Earth's cooling rate, which assumed constant conductivity in the Earth's interior, in 1862 William Thomson (later made Lord Kelvin) estimated the age of the Earth at 98 million years, which contrasts with the age of 4.5 billion years obtained in the 20th century by radiometric dating. As pointed out by John Perry in 1895 a variable conductivity in the Earth's interior could expand the computed age of the Earth to billions of years, as later confirmed by radiometric dating. Contrary to the usual representation of Kelvin's argument, the observed thermal gradient of the Earth's crust would not be explained by the addition of radioactivity as a heat source. More significantly, mantle convection alters how heat is transported within the Earth, invalidating Kelvin's assumption of purely conductive cooling.
Global internal heat flow
Estimates of the total heat flow from Earth’s interior to surface span a range of 43 to 49 terawatts (TW) (a terawatt is 1012 watts). One recent estimate is 47 TW, equivalent to an average heat flux of 91.6 mW/m2, and is based on more than 38,000 measurements. The respective mean heat flows of continental and oceanic crust are 70.9 and 105.4 mW/m2.
While the total internal Earth heat flow to the surface is well constrained, the relative contribution of the two main sources of Earth's heat, radiogenic and primordial heat, are highly uncertain because their direct measurement is difficult. Chemical and physical models give estimated ranges of 15–41 TW and 12–30 TW for radiogenic heat and primordial heat, respectively, and recent results indicate their contributions may be roughly equal.[when?]
The structure of the Earth is a rigid outer crust that is composed of thicker continental crust and thinner oceanic crust, solid but plastically flowing mantle, a liquid outer core, and a solid inner core. The fluidity of a material is proportional to temperature; thus, the solid mantle can still flow on long time scales, as a function of its temperature and therefore as a function of the flow of Earth's internal heat. The mantle convects in response to heat escaping from Earth's interior, with hotter and more buoyant mantle rising and cooler, and therefore denser, mantle sinking. This convective flow of the mantle drives the movement of Earth's lithospheric plates; thus, an additional reservoir of heat in the lower mantle is critical for the operation of plate tectonics and one possible source is an enrichment of radioactive elements in the lower mantle.
Earth heat transport occurs by conduction, mantle convection, hydrothermal convection, and volcanic advection. Earth's internal heat flow to the surface is thought to be 80% due to mantle convection, with the remaining heat mostly originating in the Earth's crust, with about 1% due to volcanic activity, earthquakes, and mountain building. Thus, about 99% of Earth's internal heat loss at the surface is by conduction through the crust, and mantle convection is the dominant control on heat transport from deep within the Earth. Most of the heat flow from the thicker continental crust is attributed to internal radiogenic sources, in contrast the thinner oceanic crust has only 2% internal radiogenic heat. The remaining heat flow at the surface would be due to basal heating of the crust from mantle convection. Heat fluxes are negatively correlated with rock age, with the highest heat fluxes from the youngest rock at mid-ocean ridge spreading centers (zones of mantle upwelling), as observed in the global map of Earth heat flow.
The radioactive decay of elements in the Earth's mantle and crust results in production of daughter isotopes and release of particles and heat energy, or radiogenic heat. Four radioactive isotopes are responsible for the majority of radiogenic heat, uranium-238 (238U), uranium-235 (235U), thorium-232 (232Th), and potassium-40 (40K). Due to a lack of rock samples from below 200 km depth, it is difficult to determine precisely the radiogenic heat throughout the whole mantle, although some estimates are available. For the Earth's core, geochemical studies indicate that it is unlikely to be a significant source of radiogenic heat due to an expected low concentration of radioactive elements. Radiogenic heat production in the mantle is linked to the structure of mantle convection, a topic of much debate, and it is thought that the mantle may either have a layered structure with a higher concentration of radioactive heat-producing elements in the lower mantle, or small reservoirs enriched in radioactive elements dispersed throughout the whole mantle.
|Mean mantle concentration
Geoneutrino detectors can detect the decay of 238U and 232Th and thus allow estimation of their contribution to the present radiogenic heat budget, while 235U is unobserved, and 40K is not detectable but is known to contribute 4 TW of heating. However, the decay of 235U and 40K contributed a large fraction of radiogenic heat flux to the early Earth, which was also much hotter than at present. Initial results from measuring the geoneutrino products of radioactive decay from within the Earth, a proxy for radiogenic heat, yielded a new estimate of half of the total Earth internal heat source being radiogenic, and this is consistent with previous estimates.
Primordial heat is the heat lost by the Earth as it continues to cool from its original formation, and this is in contrast to its still actively-produced radiogenic heat. The Earth core's heat flow—heat leaving the core and flowing into the overlying mantle—is thought to be due to primordial heat, and is estimated at 5–15 TW. Estimates of mantle primordial heat loss range between 7 and 15 TW.
The early formation of the Earth's dense core could have caused superheating and rapid heat loss, and the heat loss rate would slow once the mantle solidified. Heat flow from the core is necessary for maintaining the convecting outer core and the geodynamo and Earth's magnetic field, therefore primordial heat from the core enabled Earth's atmosphere and thus helped retain Earth's liquid water.
Heat flow and plate tectonics
Controversy over the exact nature of mantle convection makes the linked evolution of Earth's heat budget and the dynamics and structure of the mantle difficult to unravel. There is evidence that the processes of plate tectonics were not active in the Earth before 3.2 billion years ago, and that early Earth's internal heat loss could have been dominated by advection via heat-pipe volcanism. Terrestrial bodies with lower heat flows, such as the Moon and Mars, conduct their internal heat through a single lithospheric plate, and higher heat flows, such as on Jupiter's moon Io, result in advective heat transport via enhanced volcanism, while the active plate tectonics of Earth occur with an intermediate heat flow and a convecting mantle.
|Wikimedia Commons has media related to Earth's internal heat budget.|
- Davies, J. H., & Davies, D. R. (2010). Earth's surface heat flux. Solid Earth, 1(1), 5–24.
- Donald L. Turcotte; Gerald Schubert (25 March 2002). Geodynamics. Cambridge University Press. ISBN 978-0-521-66624-4.
- Buffett, B. A. (2007). Taking earth's temperature. Science, 315(5820), 1801–1802.
- Archer, D. (2012). Global Warming: Understanding the Forecast. ISBN 978-0-470-94341-0.
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- Thomson, William. (1864). On the secular cooling of the earth, read 28 April 1862. Transactions of the Royal Society of Edinburgh, 23, 157–170.
- Ross Taylor, Stuart (26 October 2007). "Chapter 2: The Formation Of The Earth And Moon". In Martin J. van Kranendonk; Vickie Bennett; Hugh R.H. Smithies. Earth's Oldest Rocks (Developments in Precambrian Geology Vol 15, 2007). Elsevier. pp. 21–30. ISBN 978-0-08-055247-7.
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- Dye, S. T. (2012). Geoneutrinos and the radioactive power of the Earth. Reviews of Geophysics, 50(3).
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- Arevalo Jr, R., McDonough, W. F., & Luong, M. (2009). The K/U ratio of the silicate Earth: Insights into mantle composition, structure and thermal evolution. Earth and Planetary Science Letters, 278(3), 361–369.
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- Moore, W. B., & Webb, A. A. G. (2013). Heat-pipe Earth. Nature, 501(7468), 501–505.
- Pease, V., Percival, J., Smithies, H., Stevens, G., & Van Kranendonk, M. (2008). When did plate tectonics begin? Evidence from the orogenic record. When did plate tectonics begin on planet Earth, 199–208.
- Stern, R. J. (2008). Modern-style plate tectonics began in Neoproterozoic time: An alternative interpretation of Earth’s tectonic history. When did plate tectonics begin on planet Earth, 265–280. | <urn:uuid:28df1263-129a-4dd9-9e44-2be64898d4b8> | 4.21875 | 2,498 | Knowledge Article | Science & Tech. | 62.568049 | 95,638,851 |
Aristotle, writing in 350 BCE in his History of Animals, pondered the origin of life. He favored spontaneous generation, where “some come from putrefying earth or vegetable matter, as is the case with a number of insects, while others are spontaneously generated in the inside of animals out of the secretions of their several organs.”
Obviously, Aristotle did not consider the possibility that the ingredients for life—amino acids, the building blocks of proteins—could form when icy comets crash into planets. This “shock synthesis” may explain how simple organic molecules formed in our Solar System 4.5 to 3.8 billion years ago, just before life arose on Earth. Now, an international team has recreated these conditions by firing a steel projectile at high velocity at ice mixtures similar to those found on comets. The shock, they report in a paper published on September 15, 2013, triggered the formation of several amino acids and their precursors.
As space scientist Mark Price of the University of Kent at Canterbury in the U.K. explains in an email exchange, impact craters can be found everywhere in the Solar System, along with the ingredients for life: water and carbon dioxide locked up, in the form of ice, on the surface of icy moons and comets. The antecedents of amino acids, including ammonia and methanol, have also been discovered on comets including Halley and Hale-Bopp. “Therefore, to synthesize amino acids, all that has to happen is for an icy comet to impact a surface, or a rocky asteroid to impact an icy surface,” he wrote to me.
Price and colleague Zita Martins of Imperial College London used the University of Kent’s light gas gun—a hefty contraption used “for investigations of hypervelocity impact phenomena”—to fire the two-millimeter-diameter projectile at ice mixtures analogous to those found on a comet. (The mixtures consisted of ammonia gas dissolved in water, carbon dioxide, and methanol ice.) Analysis of the resulting mix showed the presence of two simple amino acids encoded by genes: alanine and glycine. What this tells us, according to Price, is that “amino acids and other complex organic molecules considered to be necessary for the development of life are widespread throughout the Solar System. This therefore implies that if the conditions are right, then life could have evolved elsewhere in the Solar System.”
I had only one other question: Does firing a light gas gun produce a satisfying bang? Not really. “It actually is quite unexciting,” Price wrote. “If it works correctly, all you hear is a dull clunk, as the whole gun is under vacuum. After each shot, the launch tube and barrel have to be cleaned, so we spend more time cleaning than firing.” | <urn:uuid:a5ff6274-60e9-4719-9ff1-aabd9d77faed> | 3.84375 | 597 | Nonfiction Writing | Science & Tech. | 34.394416 | 95,638,887 |
These simulations are examples of how global land-use changed from 1700 to 1990. The human-disturbed landscape includes intensive cropland (red), and marginal cropland used for grazing (pink). Other landscape includes, for example, tropical evergreen and deciduous forest (dark green), savanna (light green), grassland and steppe (yellow), open shrubland (maroon), temperate deciduous forest (blue), temperate needleleaf evergreen forest (light yellow), and hot desert (orange). Of particular importance in this paper is the expansion of the cropland and grazed land between 1700 and 1900. Credit: from Klein Goldewijk, K., 2001: Estimating global land use change over the past 300 years: The HYDE Database. Global Biogeochemical Cycles, 15, 417-433
Global Land Use in 1990
Credit: from Klein Goldewijk, K., 2001: Estimating global land use change over the past 300 years: The HYDE Database. Global Biogeochemical Cycles, 15, 417-433
While many scientists and policy makers have focused only on how heat-trapping gases like carbon dioxide are altering our global climate, a new NASA-funded study points to the importance of also including human-caused land-use changes as a major factor contributing to climate change.
Land surface changes, like urban sprawl, deforestation and reforestation, and agricultural and irrigation practices strongly affect regional surface temperatures, precipitation and larger-scale atmospheric circulation. The study argues that human-caused land surface changes in places like North America, Europe, and southeast Asia, redistribute heat regionally and globally within the atmosphere and may actually have a greater impact on climate than that due to anthropogenic greenhouse gases combined.
The study also proposes a new method for comparing different human-influenced agents of climate change in terms of the redistribution of heat over land and in the atmosphere. Using a single unit of measurement may open the door to future work that more accurately represents human-caused climate change.
Krishna Ramanujan | EurekAlert!
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The low-cost process, developed by Purdue University researchers, combines tools already used in industry for manufacturing metals on a large scale, but uses...
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To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...
For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.
Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...
Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.
A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...
Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.
"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....
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Understanding Oxygen as an Exoplanet BiosignatureJune 18, 2018 / Written by: Julie Fletcher
Potential false positive mechanisms for O2. This cartoon summarizes the atmospheric mechanisms by which O2 could form abiotically at high abundance in a planetary atmosphere (Meadows, 2017).
Researchers are studying how environmental context can help determine whether oxygen (O2) detected in extrasolar planetary observations is more likely to have a biological source. The team provide an in-depth, interdisciplinary example of O2 biosignature identification and observation, which serves as the prototype for the development of a general framework for biosignature assessment.
The article, Exoplanet Biosignatures: Understanding Oxygen as a Biosignature in the Context of Its Environment, is an open access article in the journal Astrobiology. The work was supported by the NASA Astrobiology Program and in part by the NASA Astrobiology Institute’s Virtual Planetary Laboratory and Alternative Earths Teams.
- Electron Acceptors and Carbon Sources for a Thermoacidophilic Archaea
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- Supporting SHERLOC in the Detection of Kerogen as a Biosignature
- New Estimates of Earth's Ancient Climate and Ocean pH
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This is an image of Newton’s Cannon. Given a high enough elevation, shooting a canon-ball at increasing velocity will cause it to travel further and further until it just goes into orbit, falling around the earth. That is what’s happening inside the ISS. It’s called free-fall - the same as Newton’s canon-ball. The ISS is falling toward... Continue Reading →
This is a no frill video (no audio) produced by scientists, to depict just how much junk "litter" we have floating around up in space, some of it going 35,000 miles per hour. Just something to think about.
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Python's filesystem abstraction layer
Python's Filesystem abstraction layer.
Think of PyFilesystem's
FS objects as the next logical step to
file objects. In the same way that file objects abstract a
single file, FS objects abstract an entire filesystem.
Let's look at a simple piece of code as an example. The following
function uses the PyFilesystem API to count the number of non-blank
lines of Python code in a directory. It works recursively, so it will
.py files in all sub-directories.
def count_python_loc(fs): """Count non-blank lines of Python code.""" count = 0 for path in fs.walk.files(filter=['*.py']): with fs.open(path) as python_file: count += sum(1 for line in python_file if line.strip()) return count
We can call
count_python_loc as follows:
from fs import open_fs projects_fs = open_fs('~/projects') print(count_python_loc(projects_fs))
project_fs = open_fs('~/projects') opens an FS object that
maps to the
projects directory in your home folder. That object is
count_python_loc when counting lines of code.
To count the lines of Python code in a zip file, we can make the following change:
projects_fs = open_fs('zip://projects.zip')
Or to count the Python lines on an FTP server:
projects_fs = open_fs('ftp://ftp.example.org/projects')
No changes to
count_python_loc are necessary, because PyFileystem
provides a simple consistent interface to anything that resembles a
collection of files and directories. Essentially, it allows you to write
code that is independent of where and how the files are physically
Contrast that with a version that purely uses the standard library:
def count_py_loc(path): count = 0 for root, dirs, files in os.walk(path): for name in files: if name.endswith('.py'): with open(os.path.join(root, name), 'rt') as python_file: count += sum(1 for line in python_file if line.strip())
This version is similar to the PyFilesystem code above, but would only
work with the OS filesystem. Any other filesystem would require an
entirely different API, and you would likely have to re-implement the
directory walking functionality of
PyFilesystem2 owes a massive debt of gratitude to the following developers who contributed code and ideas to the original version.
- Ryan Kelly
- Andrew Scheller
- Ben Timby
Apologies if I missed anyone, feel free to prompt me if your name is missing here.
Release history Release notifications
Download the file for your platform. If you're not sure which to choose, learn more about installing packages.
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|fs-2.0.24-py2.py3-none-any.whl (117.4 kB) Copy SHA256 hash SHA256||Wheel||py2.py3||Jun 28, 2018|
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Stick some cubes together to make a cuboid. Find two of the angles by as many different methods as you can devise.
A right-angled isosceles triangle is rotated about the centre point of a square. What can you say about the area of the part of the square covered by the triangle as it rotates?
A ladder 3m long rests against a wall with one end a short distance from its base. Between the wall and the base of a ladder is a garden storage box 1m tall and 1m high. What is the maximum distance. . . .
Shows that Pythagoras for Spherical Triangles reduces to Pythagoras's Theorem in the plane when the triangles are small relative to the radius of the sphere.
Re-arrange the pieces of the puzzle to form a rectangle and then to form an equilateral triangle. Calculate the angles and lengths.
A dot starts at the point (1,0) and turns anticlockwise. Can you estimate the height of the dot after it has turned through 45 degrees? Can you calculate its height?
If you continue the pattern, can you predict what each of the following areas will be? Try to explain your prediction.
What is the volume of the solid formed by rotating this right angled triangle about the hypotenuse?
Prove Pythagoras' Theorem using enlargements and scale factors.
If a ball is rolled into the corner of a room how far is its centre from the corner?
In a right-angled tetrahedron prove that the sum of the squares of the areas of the 3 faces in mutually perpendicular planes equals the square of the area of the sloping face. A generalisation. . . .
Three squares are drawn on the sides of a triangle ABC. Their areas are respectively 18 000, 20 000 and 26 000 square centimetres. If the outer vertices of the squares are joined, three more. . . .
What are the shortest distances between the centres of opposite faces of a regular solid dodecahedron on the surface and through the middle of the dodecahedron?
Can you work out the dimensions of the three cubes?
A belt of thin wire, length L, binds together two cylindrical welding rods, whose radii are R and r, by passing all the way around them both. Find L in terms of R and r.
A white cross is placed symmetrically in a red disc with the central square of side length sqrt 2 and the arms of the cross of length 1 unit. What is the area of the disc still showing?
Four circles all touch each other and a circumscribing circle. Find the ratios of the radii and prove that joining 3 centres gives a 3-4-5 triangle.
Triangle ABC is an equilateral triangle with three parallel lines going through the vertices. Calculate the length of the sides of the triangle if the perpendicular distances between the parallel. . . .
A fire-fighter needs to fill a bucket of water from the river and take it to a fire. What is the best point on the river bank for the fire-fighter to fill the bucket ?.
Find the sides of an equilateral triangle ABC where a trapezium BCPQ is drawn with BP=CQ=2 , PQ=1 and AP+AQ=sqrt7 . Note: there are 2 possible interpretations.
An observer is on top of a lighthouse. How far from the foot of the lighthouse is the horizon that the observer can see?
A tetrahedron has two identical equilateral triangles faces, of side length 1 unit. The other two faces are right angled isosceles triangles. Find the exact volume of the tetrahedron.
Chris is enjoying a swim but needs to get back for lunch. If she can swim at 3 m/s and run at 7m/sec, how far along the bank should she land in order to get back as quickly as possible?
The largest square which fits into a circle is ABCD and EFGH is a square with G and H on the line CD and E and F on the circumference of the circle. Show that AB = 5EF. Similarly the largest. . . .
ABCD is a rectangle and P, Q, R and S are moveable points on the edges dividing the edges in certain ratios. Strangely PQRS is always a cyclic quadrilateral and you can find the angles.
The area of a square inscribed in a circle with a unit radius is, satisfyingly, 2. What is the area of a regular hexagon inscribed in a circle with a unit radius?
It is obvious that we can fit four circles of diameter 1 unit in a square of side 2 without overlapping. What is the smallest square into which we can fit 3 circles of diameter 1 unit?
What is the same and what is different about these circle questions? What connections can you make?
Six circular discs are packed in different-shaped boxes so that the discs touch their neighbours and the sides of the box. Can you put the boxes in order according to the areas of their bases?
A 1 metre cube has one face on the ground and one face against a wall. A 4 metre ladder leans against the wall and just touches the cube. How high is the top of the ladder above the ground?
Can you make sense of the three methods to work out the area of the kite in the square?
Sets of integers like 3, 4, 5 are called Pythagorean Triples, because they could be the lengths of the sides of a right-angled triangle. Can you find any more?
Can you make sense of these three proofs of Pythagoras' Theorem?
Describe how to construct three circles which have areas in the ratio 1:2:3.
Draw a square and an arc of a circle and construct the Golden rectangle. Find the value of the Golden Ratio.
If the altitude of an isosceles triangle is 8 units and the perimeter of the triangle is 32 units.... What is the area of the triangle?
A ribbon runs around a box so that it makes a complete loop with two parallel pieces of ribbon on the top. How long will the ribbon be?
Take any rectangle ABCD such that AB > BC. The point P is on AB and Q is on CD. Show that there is exactly one position of P and Q such that APCQ is a rhombus.
What remainders do you get when square numbers are divided by 4?
Find the ratio of the outer shaded area to the inner area for a six pointed star and an eight pointed star.
Draw two circles, each of radius 1 unit, so that each circle goes through the centre of the other one. What is the area of the overlap?
Equal circles can be arranged so that each circle touches four or six others. What percentage of the plane is covered by circles in each packing pattern? ...
A spider is sitting in the middle of one of the smallest walls in a room and a fly is resting beside the window. What is the shortest distance the spider would have to crawl to catch the fly?
The net of a cube is to be cut from a sheet of card 100 cm square. What is the maximum volume cube that can be made from a single piece of card?
The ten arcs forming the edges of the "holly leaf" are all arcs of circles of radius 1 cm. Find the length of the perimeter of the holly leaf and the area of its surface.
What is the relationship between the arithmetic, geometric and harmonic means of two numbers, the sides of a right angled triangle and the Golden Ratio?
Three circular medallions fit in a rectangular box. Can you find the radius of the largest one?
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Given any three non intersecting circles in the plane find another circle or straight line which cuts all three circles orthogonally. | <urn:uuid:c1452559-0b48-43f5-b9e2-7562275d81e6> | 3.953125 | 1,715 | Content Listing | Science & Tech. | 73.836804 | 95,638,974 |
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The author also uses research materials of other environmental scientists which complements his own study of the environmental problems.
The research made by UNEP is a deep study into environmental problems affected by adverse actions of the tourists and their activity. The article provides latest information about the state of affairs of the resources, nature and environment in the recreational areas and stresses negative effects locally.
The article is very beneficial for the research paper because it provides complete and relevant information about all the issues it concerns. The structure of the work provides a logical information presentation which contributes to its better perception and understanding. The benefit of this work is also that it deals with the aesthetic aspect of environment deterioration and pollution because this is the thing that is ignored the most when human beings perform any
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Justice Breyer delivered the opinion of the Court This court grants certiorari to the plaintiffs, who ask the question of whether there can be a discharge or outfall under the Clean Water Act if there is water that flows from one part of the river through a concrete channel or engineer river improvement, as part of the municipal separate storm sewer system, into the lower part of the same river.
Such gases include but are not limited to carbon dioxide (CO2), methane (CH4) and nitrous oxide (NO). These greenhouse gases entrap the light from sun and its heat in the atmosphere of the Earth. This results into an increase in temperature. The rise in temperature is very harmful for the life on Earth, of both animals and plants.
This man made mayhem since pre-industrial period has caused the increase of greenhouse gases like carbon dioxide, methane, and nitrous oxide. These gases trap the infrared radiation from the sun in the earth’s atmosphere and emit it, warming the planet.
Principally, the term can be best described by considering the meaning of each of the words used. The term environmental is used to describe the nature of the surrounding. It can be natural surroundings, social surrounding, built environment, learning environments, political surrounding, economical, technological surrounding and informational environment.
gh measures to defend and conserve the natural resources. It has been already confirmed by numerous researches that international business activities facilitates in achieving economic development which also proves to be advantageous for other contributing countries as well.
Hence, consumer products and their use or consumption leaves a very large environmental footprint on our planet Earth (Keane, 2010, p.25). Evaluation of the history of humankind demonstrates that development of humankind has been linked with increased consumption of products.
Name: Instructor: Course: Date: The Negative Impacts of Hydro-Fracking Hydro-fracking, also referred to as hydraulic fracturing, is the process of using many gallons of water mixed with sand and many chemicals to fracture shale rock, which is found many feet below the surface of the earth.
ade in the field of science and technology was focused towards the improvement of the human condition and people believed that wars and diseases would only be temporary occurrences and that the spirit of humanity will prevail. However with the beginning of the World Wars and
The specific characters once expressed are magnified using mutation breeding which means crossing the natural strains and the mutated strains. The introduction of genetically modified organisms and food in the food industry has brought up new arguments
Australia is currently facing numerous challenges regarding the preservation and conservation of the environment. Environmental pollution in the areas of water, air, and land continues to cause problems in the country. The pollution has led to land degradation, an imbalance in the natural ecosystem and contributed to climate change.
10 Pages(2500 words)Research Paper
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Let us find you another Research Paper on topic Environmental Problem for FREE! | <urn:uuid:3c69c11c-6205-4cbf-8d14-1acff12d4741> | 2.859375 | 779 | Truncated | Science & Tech. | 29.903182 | 95,638,975 |
This tutorial explains, Introduction to java bean and How to create first java Bean program step by step. The prerequisite required is understanding of core-java and servlet and jsp technologies. you can find step by step development of first servlet program and jsp program.
Java bean is a reusable software component. It encapsulates many objects into one object, so we can access this object from multiple places. A JavaBean class propertes can be read, write, read only, or write only. so these properties are accessed through getPropertyName() & serPropertyName() methods in the JavaBean’s implementation class.
How to access java bean properties in jsp ?
useBean action declares a JavaBean for use in a JSP. Once declared, the bean becomes a scripting variable that can be accessed by both scripting elements and other custom tags used in the JSP.
The syntax for the useBean tag is:
<jsp:useBean id= "instanceName"
scope= "page | request | session | application"
beanName="packageName.className | <%= expression >">
Basically, Java Bean is a java class that should follow these conventions, these are the unique characteristics that distinguish a JavaBean from other Java classes:
It should have a no-arguments constructor.
It should be Serializable ( is the process of converting a java object into byte array so that it can be preserved.Normally,when execution of java program is over,objects get destroyed. But due to serialization,those objects will be preserved in memory buffer/file.).
It should provide methods to set and get the values of the properties, known as getter and setter methods.
It is a reusable software component. A Java bean encapsulates many objects into one object, so we can access this object from multiple places. Moreover, it provides the easy maintenance.
A JavaBean property may be read, write, read only, or write only. JavaBean properties are accessed through two methods in the JavaBean’s implementation class.
Here, you can download source code project developed using netbeans editor. Test-Java-bean-first-program-digitalpadm.zip (881 downloads)
Install Java Development Kit (JDK) first, then Install Netbeans version above 8 , Please choose setup according to your operating system. during installation select glass fish server or apache tomcat server as shown below.
Following video shows step by step instruction to develop first java bean program using netbeans.
Download Source code : Test-Java-bean-first-program-digitalpadm.zip (881 downloads)
Related Tutorials : | <urn:uuid:a302b898-02e5-4bb2-b7d1-b012320274e9> | 3.4375 | 562 | Tutorial | Software Dev. | 38.390662 | 95,638,984 |
phaeophyta defined in 1951 yearphaeophyta - phaeophyta;
phaeophyta - Brown algae (seaweeds). Division of algae. Brown to olive-green in colour. Possess chlorophylls a and c, α-, β-carotene and xanthophylls, including brown pigment fucoxanthin which masks other pigments. Main food reserve is polysaccharide laminarin. Cell wall of two layers, inner of cellulose, outer of mucilaginous pectic material. Very diverse in form, ranging from minute (less than 1 mm long), filamentous, to very long and complex, differentiated into a disc or root-like basal attachment part, and a stem-like part of varying lengths, bearing a branched or unbranched, ribbon or leaf-like part, often provided with air bladders, e.g. bladder wrack; up to 60-70 metres in length in largest forms with relatively complex internal structure. Asexual reproduction by fragmentation of thallus or by mostly laterally biflagellate zoospores. Sexual reproduction isogamous, gametes motile or anisogamous, by fusion of small, motile, male gamete with arge, non-motile egg. Marine (with rare exceptions), usually abundant in cold water. Benthic, common inhabitants of inter-tidai zone. A species of Sargassum is exceptional in being pelagic, accumulating in large quantities in the Sargasso sea near the West Indies.
near phaeophyta in Knolik
definition of word "phaeophyta" was readed 761 times | <urn:uuid:59dd5e31-b682-4072-bccf-9abcc51ac82a> | 3.25 | 353 | Knowledge Article | Science & Tech. | 33.37767 | 95,638,994 |
Jicamarca Radio Observatory
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Jicamarca Radio Observatory - Lima, Peru
Geophysics Institute of Peru|
National Science Foundation
|Wavelength||6 m (50 MHz)|
|Telescope style||Radio telescope|
|Collecting area||288 m2 (3,100 sq ft)|
The Jicamarca Radio Observatory (JRO) is the equatorial anchor of the Western Hemisphere chain of Incoherent Scatter Radar (ISR) observatories extending from Lima, Peru to Søndre Strømfjord, Greenland. JRO is the premier scientific facility in the world for studying the equatorial ionosphere. The Observatory is about half an hour drive inland (east) from Lima and 10 km from the Central Highway ( , 520 meters ASL). The magnetic dip angle is about 1°, and varies slightly with altitude and year. The radar can accurately determine the direction of the Earth's magnetic field (B) and can be pointed perpendicular to B at altitudes throughout the ionosphere. The study of the equatorial ionosphere is rapidly becoming a mature field due, in large part, to the contributions made by JRO in radio science.
JRO’s main antenna is the largest of all the incoherent scatter radars in the world. The main antenna consists of a 300m x 300m square array composed of 18,432 cross-polarized dipoles. The main research areas of the observatories are: the stable equatorial ionosphere, ionospheric field aligned irregularities, the dynamics of the equatorial neutral atmosphere and meteor physics.
- 1 History
- 2 Facilities
- 3 Main Research Areas
- 4 Coherent scatter echoes
- 5 Non-conventional Studies
- 6 Summary of Scientific Contributions and Milestones (since 1961)
- 7 JRO Directors and Principal Investigators
- 8 See also
- 9 References
- 10 External links
The Jicamarca Radio Observatory was built in 1960–61 by the Central Radio Propagation Laboratory (CRPL) of the National Bureau of Standards (NBS). This lab later became part of the Environmental Science Service Administration (ESSA) and then the National Oceanic and Atmospheric Administration (NOAA). The project was led by Dr. Kenneth L. Bowles, who is known as the “father of JRO”.
Although the last dipole was installed on April 27, 1962, the first incoherent scatter measurements at Jicamarca were made in early August 1961, using part of the total area projected and without the transmitter's final stage. In 1969 ESSA turned the Observatory over to the Instituto Geofísico del Perú (IGP), which had been cooperating with CRPL during the International Geophysical Year (IGY) in 1957–58 and had been intimately involved with all aspects of the construction and operation of Jicamarca. ESSA and then NOAA continued to provide some support to the operations for several years after 1969, in major part due to the efforts of the informal group called “Jicamarca Amigos” led by Prof. William E. Gordon. Prof. Gordon invented the incoherent scatter radar technique in 1958.
A few years later the National Science Foundation began partially supporting the operation of Jicamarca, first through NOAA, and since 1979 through Cornell University via Cooperative Agreements. In 1991, a nonprofit Peruvian organization—called Ciencia Internacional (CI)—was created to hire most observatory staff members and to provide services and goods to the IGP to run the Observatory.
Since 1969, the great majority of the radar components have been replaced and modernized with “home made” hardware and software, designed and built by Peruvian engineers and technicians. More than 60 Ph.D. students, many from US institutions and 15 from Peru, have done their research in association with Jicamarca.
JRO’s main instrument is the VHF radar that operates on 50 MHz (actually on 49.9 MHz ) and is used to study the physics of the equatorial ionosphere and neutral atmosphere. Like any other radar, its main components are: antenna, transmitters, receivers, radar controller, acquisition and processing system. The main distinctive characteristics of JRO’s radar are: (1) the antenna (the largest of all the ISRs in the world) and (2) the powerful transmitters.
- Antenna. The main antenna consists of 18432 cross-polarized half-wavelength dipoles occupying an area of 288m x 288m. The array is subdivided in quarters, each quarter consisting of 4x4 modules. The main beam of the array can be manually steer +/- 3 degrees from its on-axis position, by changing cables at the module level. Being modular, the array can be configured in both transmission and reception on a variety of configurations, allowing for example: simultaneous multi-beam observations, applications of multi-baseline radar interferometry as well as radar imaging, etc.
- Transmitters. Currently,[when?] JRO has three transmitters, capable of delivering 1.5 MW peak power each. Soon a fourth transmitter will be finished to allow the transmission of 6 MW as in the early days. Each transmitter can be fed independently and can be connected to any quarter section of the main array. This flexibility allows the possibility of transmitting any polarization: linear, circular or elliptical.
- Other. The remaining components of the radar are constantly being changed and modernized according to the technology available. Modern electronic devices are used for assembling the receivers, radar controller and acquisition system. The first computer in Peru came to JRO in the early 1960s. Since then, different computer generations and systems have been used.
Radar Modes of Operation
The main radar operates in mainly two modes: (1) incoherent scatter radar (ISR) mode, and (2) coherent scatter (CSR) mode. In the ISR mode using the high power transmitter, Jicamarca measures the electron density, electron and ion temperature, ion composition and vertical and zonal electric fields in the equatorial ionosphere. Given its location and frequency of operation, Jicamarca has the unique capability of measuring the absolute electron density via Faraday rotation, and the most precise ionospheric electric fields by pointing the beam perpendicular to the Earth's magnetic field. In the CSR mode the radar measures the echoes that are more than 30 dB stronger than the ISR echoes. These echoes come from equatorial irregularities generated in troposphere, stratosphere, mesosphere, equatorial electrojet, E and F region. Given the strength of the echoes, usually low power transmitters and/or smaller antenna sections are used.
JULIA stands for Jicamarca Unattended Long-term Investigations of the Ionosphere and Atmosphere, a descriptive name for a system designed to observe equatorial plasma irregularities and neutral atmospheric waves for extended periods of time. JULIA is an independent PC-based data acquisition system that makes use of some of the exciter stages of the Jicamarca main radar along with the main antenna array. In many ways, this system duplicates the function of the Jicamarca radar except that it does not use the main high-power transmitters, which are expensive and labor-intensive to operate and maintain. It can therefore run unsupervised for long intervals. With its pair of 30 kW peak power pulsed transmitters driving a (300 m)^2 modular antenna array, JULIA is a formidable coherent scatter radar. It is uniquely suited for studying the day-to-day and long-term variability of equatorial irregularities, which until now have only been investigated episodically or in campaign mode.
A large quantity of ionospheric irregularity data have been collected during CEDAR MISETA campaigns beginning in August, 1996, and continuing through the present. Data include daytime observations of the equatorial electrojet, 150 km echoes and nighttime observations of equatorial spread F.
Besides the main radar and JULIA, JRO hosts, and/or helps in the operations of, a variety of radars as well as radio and optical instruments to complement their main observations. These instruments are: various ground-based magnetometers distributed through Peru, a digital ionosonde, many GPS receivers in South America, an all-sky specular meteor radar, a bistatic Jicamarca-Paracas CSR for measuring E region electron density profile, scintillation receivers in Ancon, a Fabry–Perot Interferometer in Arequipa, a small prototype of AMISR UHF radar, …
Main Research Areas
The main research areas of JRO are the studies of: the equatorial stable ionosphere, the equatorial field aligned irregularities, equatorial neutral atmosphere dynamics, and meteor physics. Here are some examples of the JRO topics
- Stable ionosphere
- Topside: What controls the light ion distribution? Why are the equatorial profiles so different from those at Arecibo? What is the storm time response of the topside?
- F region: Do current theories fully explain electron and ion thermal balance? Do we understand the electron collision effects on ISR theory now? What is the effect of F-region dynamics near sunset on the generation of ESF plumes? What are the effects of N-S winds on inter-hemispheric transport?
- E region: What are the basic background parameters in the equatorial E region? What is the morphology of the density profiles in this difficult to probe region? How does this morphology affect the E-region dynamo?
- D region: What effects do meteor ablation and mesospheric mixing have on the composition in this region?
- Unstable Ionosphere
- F region: plasma processes, including nonlinear processes, that govern the generation of plasma plumes? What are the precursor phenomena in the late afternoon F region that control whether or not an F-region plume will be generated after sunset?
- Daytime Valley echoes (or so-called 150 km echoes). What are the physical mechanisms causing them? (still a puzzle after more than 40 years!).
- E region: What are the nonlinear plasma physics processes that control the final state of the equatorial electrojet instabilities? To what extent do these instabilities affect the conductivity of the E region, and by extension, the conductivity of the auroral zone E region, where similar, but stronger and more complicated, instabilities exist?
- Neutral atmosphere dynamics. What are the tidal components at low latitudes for the different seasons and altitudes? How strong are the wind shears in the mesosphere? What are the characteristics of gravity waves? Can we see evidence of lower atmosphere gravity wave coupling with the ionosphere?
- Meteor physics. Where are the meteoroids coming from? What are the mass and size of the meteoroids? What is the equivalent visual magnitude of meteors detected at JRO? Can we use meteor echoes to diagnose the atmosphere/ionosphere at altitudes where they occur?
Coherent scatter echoes
|Most common ionospheric/atmospheric coherent echoes|
|Strength above |
|150 km echoes||150 km||130-170||Daytime||10-30|
|Neutral atmosphere||MST||0.2-85||All day||30-50|
|Non-specular meteor||Non-specular||95-115||All day||20-50|
|Specular meteor||Specular||80-120||All day||30-60|
Besides the ISR and CSR observations, the main JRO system has been used as radio telescope, a VHF heater, and planetary radar. As radio telescope the main array has been used to study the Sun, radio stars (like Hydra), magnetosphere synchrotron radiation, Jupiter radiation. In the 1960s JRO was used as to study Venus and the surface of the Moon and more recently the Sun. Recently, the equatorial electrojet has been weakly modulated using JRO as a VHF heater to generate VLF waves.
Summary of Scientific Contributions and Milestones (since 1961)
- 1961. First observations of incoherent scatter echoes. First ISR in operation.
- 1961–63. Explanation of the physical processes behind the Equatorial electrojet plasma irregularities (Farley-Buneman instability.)
- 1962. First temperatures and composition measurements of the equatorial ionosphere.
- 1963 First electron density measurements of the equatorial Magnetosphere (the highest from ground based measurements even now).
- First VHF radar echoes from Venus.
- 1964. Discovery of the so-called 150 km echoes. The physical mechanisms behind these echoes are still (as of August 2008) a mystery.
- 1965. VHF radar measurements of the Moon’s surface roughness. Test run and used by NASA in 1969 for the Apollo 11 with Neil Armstrong knew he was going to tread.
- 1965–69. Development of Faraday rotation and double pulse techniques. Jicamarca is the only ISR that uses this technique in order to obtain absolute electron density measurements in the ionosphere.
- 1967. Application of a complete theory about the incoherent spread that includes the effects of collisions between ions and the presence of the magnetic field. Gyro Resonance experiment that verified the complete theory of incoherent scatter.
- 1969. Development of the pulse-to-pulse technique to measure ionosphere Doppler shifts with very good precision. Later, the same technique was applied to Meteorological radars.
- 1969–72. First measurements of the zonal and vertical equatorial ionospheric drifts.
- 1971. Development of the radar interferometry technique to measure size and location of the echoing region.
- 1972–74. Development of the MST (Mesosphere, Stratosphere, Troposphere) radar to measure winds and clear air turbulence. Smaller versions of this type of radars are called wind profilers.
- Since 1974. Promotion and participation in international rocket campaigns to study atmospheric and ionospheric irregularities. JRO measurements complement the in-situ measurements perform with rockets launched from Punta Lobos, Peru.
- 1976. Explanation of the physics behind spread F irregularities
- 1981–82 Improvement of the radar interferometry technique to measure the zonal drifts of ionospheric irregularities (EEJ and ESF).
- Development of the Frequency Domain Interferometry (FDI) technique that allows measurements of fine altitude structure of echoes.
- 1987. Dr. Tor Hagfors, former JRO Director, received the URSI Balthasar van del Pol Gold Medal, for Contributions to radar engineering and the theory and experimental development of the incoherent scatter techniques”
- Since 1991. Development of the radar Imaging technique by Peruvian scientists and US colleagues. This technique permits the observation of fine angular structure inside the beam, and therefore discriminate between time and space ambiguities.
- 1993. Installation of the first MST radar in the Antarctica.
- 1994. First observations of Polar Mesosphere Summer Echoes (PMSE) in the Antarctica and discovery of a significant asymmetry with respect to Arctic echoes.
- 1996. Prof. Donald T. Farley, former JRO Director and Principal Investigator, received the URSI Appleton Prize for “Contributions to the development of the incoherent scatter radar technique and to radar studies of ionospheric instabilities”.
- 1997. First VHF radar on board of a scientific ship (BIC Humboldt), which has allowed the study of the PMSE in different Antarctic latitudes.
- 1999. Dr. Ronald F. Woodman, former JRO Director, received the URSI Appleton Prize for “Major contributions and leadership in radar studies of the ionosphere and neutral atmosphere”.
- 2000. Radar technique to “compress” antennas, using binary phase modulation of the antenna modules
- 2001. First electron density measurements of electrons between 90 and 120 km of altitude using a small bistatic radar system.
- First observation of pure two stream E region irregularities during counter electric field conditions.
- Jicamarca 40th Anniversary Workshop.
- Since 2003. Improved perpendicular to the magnetic field observations, accompanied by refinements in theory and computations, to measure simultaneously drifts and electron densities.
- Unambiguous measurements of the ESF spectra in the topside using aperiodic pulsing.
- Discovery of 150 km echoes using beams pointing away from perpendicular to the magnetic field.
- 2005. First E region zonal wind profiles from Equatorial electrojet echoes.
- 2006. Multi-radar observations of EEJ irregularities: VHF and UHF, vertical and oblique beams, and radar imaging.
- 2007. Identification of sporadic meteor populations using 90 hours of JRO’s meteor head echoes.
- First ISR full profile measurements of the equatorial ionosphere.
- First observation of meteor shower from meteor-head echoes.
- 2009. Installation of a Fabry–Perot Interferometer at JRO (MeriHill Observatory).
JRO Directors and Principal Investigators
- JRO Directors
- 1960–1963, Dr. Kenneth Bowles (Ph.D., Cornell University)
- 1964–1967, Dr. Donald T. Farley (Ph.D., Cornell University)
- 1967–1969, Dr. Tor Hagfors (Ph.D., Stanford University)
- 1969–1974, Dr. Ronald Woodman (Ph.D., Harvard University)
- 1974–1977, Dr. Carlos Calderón (Ph.D., Dartmouth College)
- 1977–1980, Dr. Pablo Lagos (Ph.D., Massachusetts Institute of Technology)
- 1980–2000, Dr. Ronald Woodman (Ph.D., Harvard University)
- 2001–2012, Dr. Jorge L. Chau (Ph.D., University of Colorado)
- 2013–present, Dr. Marco Milla (Ph.D., University of Illinois at Urbana-Champaign)
- JRO Principal Investigators
- Arecibo Observatory
- Millstone Hill Observatory
- Sondrestrom Upper Atmospheric Research Facility
|Wikimedia Commons has media related to Jicamarca Radio Observatory.|
- Jicamarca Radio Observatory official site
- Instituto Geofísico del Perú
- JRO's news
- JRO databases
- Upper Atmosphere research at Cornell University
- List of Publications Related to JRO
- Satellite Image
- Jicamarca Movies
- Incoherent Scatter Radars around the world
- The Advanced Modular Incoherent Scatter Radar, Alaska-USA, Resolute Bay-Canada
- Arecibo Observatory, Puerto Rico
- The European Incoherent Scatter Radat Network (EISCAT), Norway-Sweden-Finland
- The Irkutsk ISR, Russia
- The Jicamarca Radio Observatory, Peru
- Millstone Hill Observatory, USA
- The Middle-Upper Atmosphere Radar, Japan
- The Sondrestrom Research Facility, Greenland | <urn:uuid:787e13e4-c8b3-4e86-8852-aa6b0add2a82> | 2.796875 | 4,043 | Knowledge Article | Science & Tech. | 34.524503 | 95,639,007 |
It seems the Earth is trying to balance out global warming itself. There could be a natural balance level that the planet is attempting to reach. In Australia an unusual phenomenon has taken place.
We have had a lot of rain in coastal regions, while inland it remains dry. The arid regions have soaked up the excess water only gradually releasing it to the ocean, so sea levels have not increased. Indeed, sea level has fallen 7 millimeters.
Damaging floods cost Queenslanders millions of dollars. It was so bad that insurance companies refused to reinsured low-lying towns. Even the dry Northern Territory had floods. One of two very close La Ninas was the strongest ever recorded. The year 2012 was rain, rain and more rain.
This is not something that global warming critics should put forward as a natural solution. Only in Australia does the unusual geographic structure of the continent exist. Humid air moved slowly east but moved as far south as Melbourne, pushing up rainfall 20 per cent. Tropical air has never reached Melbourne before.
The fall in sea level is only a blip on the rising graph. The average rise is 3.2 millimeters a year. By the end of the century ocean levels are expected to increase by 820 millimeters, up from previous estimates of 590.
Rising use of carbon fuel may make sea levels rise even more. The oil "boom" in the US threatens all the good work being done by environmentalists to change behavior. Higher production has pushed "peak oil" well into the future. Enthusiasm for non-carbon power sources is waning. | <urn:uuid:582c5004-fd97-49f5-96bb-f79be43ad77c> | 3.09375 | 324 | Personal Blog | Science & Tech. | 57.528225 | 95,639,026 |
Part of the Graduate Texts in Physics book series (GTP)
The essential points of this first chapter are The definition of a complex system The notion of emergence The definition of a model The notion of dynamical system
KeywordsPhase Space Wood Chip Emergent Property Logistic Equation Emergent Behavior
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.
Unable to display preview. Download preview PDF.
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A new article by researchers from the University of Montana, the U.S. Geological Survey and Montana Fish, Wildlife & Parks asserts that climate warming is increasing the hybridization of trout – interbreeding between native and non-native species – in the interior western United States.
Clint Muhlfeld, a research assistant professor in the UM Division of Biological Sciences’ Flathead Lake Biological Station and research ecologist with the USGS Northern Rocky Mountain Science Center in Glacier National Park, is the lead author of the article, titled “Invasive hybridization in a threatened species is accelerated by climate change,” which was published in the latest issue of Nature Climate Change. Co-authors are Ryan Kovach, a postdoctoral scholar at UM’s Flathead Lake Biological Station, and Leslie Jones, a UM doctoral student who works with Muhlfeld and USGS.
Specifically, rapid increases in stream temperature and decreases in spring flow over the past several decades contributed to the spread of hybridization between native westslope cutthroat trout and the introduced rainbow trout – the world’s most widely introduced invasive fish – across the Flathead River system in Montana and British Columbia, Canada.
Experts have hypothesized that climate change could decrease worldwide biodiversity through cross-breeding between invasive and native species, but this study is the first to directly and scientifically support this prediction. The study was based on 30 years of research by scientists with UM, USGS and Montana FWP.
Hybridization has contributed to the decline and extinction of many native fishes worldwide, including all subspecies of cutthroat trout in western North America, which have enormous ecological and socioeconomic value. The researchers used long-term genetic monitoring data coupled with high-resolution climate and stream temperature predictions to measure whether climate warming enhances interactions between native and non-native species through hybridization.
“Climatic changes are threatening highly prized native trout as introduced rainbow trout continue to expand their range and hybridize with native populations through climate-induced ‘windows of opportunity,’ putting many populations and species at greater risk than previously thought,” Muhlfeld said.
“The study illustrates that protecting genetic integrity and diversity of native species will be incredibly challenging when species are threatened with climate-induced invasive hybridization,” he said.
Westslope cutthroat trout and rainbow trout both spawn in the spring and can produce fertile offspring when they interbreed. Over time, a mating population of native and non-native fish will result in only hybrid individuals with substantially reduced fitness because their genomes have been altered by non-native genes that are maladapted to the local environment. Protecting and maintaining the genetic integrity of native species is important for a species’ ability to be resilient and better adapt to a rapidly changing climate.
Historical genetic samples revealed that hybridization between the two species was largely confined to one downstream Flathead River population. However, the study noted, during the past 30 years, hybridization rapidly spread upstream, irreversibly reducing the genetic integrity of native westslope cutthroat trout populations. Genetically pure populations of westslope cutthroat trout are known to occupy less than 10 percent of their historical range.
The rapid increase in hybridization was associated with climatic changes in the region. From 1978 to 2008, the rate of warming nearly tripled in the Flathead basin, resulting in earlier spring runoff, lower spring flooding and flows, and warming summer stream temperatures. Those locations with the greatest changes in stream flow and temperature experienced the greatest increases in hybridization.
Relative to cutthroat trout, rainbow trout prefer these climate-induced changes and tolerate greater environmental disturbance. These conditions likely have enhanced rainbow trout spawning and population numbers, leading to massive expansion of hybridization with westslope cutthroat trout.
“The evolutionary consequences of climate change are one of our greatest areas of uncertainty because empirical data addressing this issue are extraordinarily rare,” Kovach said. “This study is a tremendous step forward in our understanding of how climate change can influence evolutionary process and ultimately species biodiversity.”
Overall, aquatic ecosystems in western North America are predicted to experience earlier snowmelt in the spring, reduced late spring and summer flows, warmer and drier summers, and increased water temperatures – all of which indicate increased hybridization between these species.
Additional UM-affiliated authors are UM Wildlife Biology Program Director Winsor Lowe, UM Associate Professor of Conservation Ecology Gordon Luikart and Regents Professor Emeritus Fred Allendorf. Authors not affiliated with UM are Robert Al-Chokhachy with the USGS Northern Rocky Mountain Science Center, Matthew Boyer with Montana FWP in Kalispell and Robb Leary with Montana FWP in Missoula.
The study was supported by the Great Northern Landscape Conservation Cooperative, the U.S. Department of the Interior’s Northwest Climate Science Center, the National Climate Change and Wildlife Science Center, the National Science Foundation and Bonneville Power Administration.
Clint Muhlfeld, research assistant professor, UM Division of Biological Sciences, 406-600-9686, firstname.lastname@example.org .
Clint Muhlfeld | Eurek Alert!
Upcycling of PET Bottles: New Ideas for Resource Cycles in Germany
25.06.2018 | Fraunhofer-Institut für Betriebsfestigkeit und Systemzuverlässigkeit LBF
Dry landscapes can increase disease transmission
20.06.2018 | Forschungsverbund Berlin e.V.
For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.
To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...
For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.
Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...
Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.
A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...
Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.
"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....
Ultra-short, high-intensity X-ray flashes open the door to the foundations of chemical reactions. Free-electron lasers generate these kinds of pulses, but there is a catch: the pulses vary in duration and energy. An international research team has now presented a solution: Using a ring of 16 detectors and a circularly polarized laser beam, they can determine both factors with attosecond accuracy.
Free-electron lasers (FELs) generate extremely short and intense X-ray flashes. Researchers can use these flashes to resolve structures with diameters on the...
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Working with accessibility in mind should be a default consideration for every website you build. Unfortunately, that is not always the case, especially for new developers. Many of us are not initially aware of the extremely helpful and important Web Content Accessibility Guidelines (WCAG) that define how to make web content accessible for people with disabilities. In fact, these guidelines were just updated as of January 2018.
Following these guidelines not only benefit all of your users but can also have a positive effect on your Search Engine Optimization (SEO). Here are five best practices, all of which and more are included in our Bootcamp curriculum, that you should be implementing in your workflow to build a better, more inclusive web experience.
1. Provide a descriptive alternative text for all of your image elements
This is the first thing you should do when working to make your website accessible. Yes, it’s great to pair a stunning image with the paragraph of text you just wrote, it’s also important to understand that not all of your users will be able to view your image. Providing alternative text allows your image to be changed into other forms your user may need.
For example, a person using a screen reader will have the alt text read out loud to them to provide a description of the image. For this reason, it is also important that we provide a meaningful descriptive alt text. Your alt text will also show up on the page if your image fails to load, and has great SEO value. Therefore, striving to provide all necessary alt texts will help all users, not just those who rely on a screen reader.
2. Use Semantic HTML
Knowing how to write proper semantic code is probably the first important skill you can pick up as a web developer. A semantic element clearly describes its meaning to you, the browser, and anyone using assistive tech to navigate your website. You should avoid using < div > and < span > when you could be using a more descriptive tag.
3. Check Your Colour Contrast
Aside from simply not looking bad, the low colour contrast between text colours and background colours will greatly reduce readability. To meet level AA of the Web Content Accessibility Guidelines (WCAG), you need to have a contrast ratio of 4:5:1 for normal text and 3:1 for large text. Below, you can see that the sentence on the left is much easier to read than the sentence on the right.
A great tool to make sure you’re hitting the guidelines is Jonathan Snook’s Colour Contrast Check.
4. Provide a Skip to Main Content Option
Providing users with a skip-to-main content option will improve the user experience for those who use their keyboard to navigate your site. This is especially beneficial when you have a large navigation bar or a header with a ton of information.
Standard skip to main content buttons are typically not visible on the page and are created specifically for users ‘tabbing’ through your website. In this animation, you can see the user has their cursor in the address bar. Upon first click of the tab key, the “Skip to main content” button appears and they are able to get to the page’s main content.
5. Be Cautious with Elements in the Focus State
Browsers come with default stylings for elements in focus, often resembling a blue outline. If you take another look at the animation above, you will see that effect when our user tabs down to the main content.
Although this default styling may not align with your web design, many users rely on this outline to help them identify which element is in focus. If you remove this outline, be sure to replace it with something else that helps a user identify elements in focus! An easy way to do this is to make sure you are adding a focus state to any element you add a hover state too.
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Oversized landforms discovered beneath the Antarctic ice sheet
Former ice sheets occupying Scandinavia and North America left numerous landforms on today's surface that witness of their hydrological system underneath them. However, most landforms have, so far, never been observed under contemporary ice sheets - not least because they are relatively small and buried under kilometer thick ice.
A team of scientists led by the Université libre de Bruxelles (ULB, Belgium) and the Bavarian Academy of Sciences (Germany) have now discovered an active hydrological system of water conduits and sediment ridges below the Antarctic ice sheet. Their study reveals that the scale of these subglacial features is five times bigger than those seen in today's deglaciated landscapes. The newly discovered, oversized sediment ridges actively shape the ice hundreds kilometers downstream, by carving deep incisions at the bottom of the ice. This is of interest for the stability of the floating ice shelves, as numerous studies show that ice shelf thinning has major consequences for ice sheet stability.
Subglacial conduits form under large ice sheets as part of their basal hydrological system. These tunnels have a typical diameter of several meters to tens of meters, and they funnel the subglacial melt water towards the ocean. However, new geophysical observations by the Laboratoire de Glaciologie of the ULB show that these conduits widen considerably the closer they come to the ocean. A new mathematical model explains this widening with the vanishing overburden pressure at the location where the ice becomes afloat on the ocean.
As the conduits widen, the outflow velocity of the subglacial water decreases, which leads to increased sediment deposition at the conduit's portal. Over thousands of years, this process builds up giant sediment ridges - comparable in height with the Eiffel tower - below the ice. Active sedimentation in subglacial water conduits seems to drive the formations of Eskers - elongated ridges of gravel which are commonly observed today in areas where former ice sheets have retreated. However, the remainders of today's Eskers are considerably smaller in size than those now discovered in Antarctica.
Giant conduits that can sap the ice from below
The evolving sediment ridges leave scars at the bottom of the ice as the ice flows over them. These scars are transmitted to the floating ice shelves farther downstream forming ice-shelf channels. Ice in these channels is up to half as thin as their surroundings, making them a weak spot when exposed to melting from the warmer ocean. It was originally thought that ice-shelf channels are carved by melting due to the ocean only, but this seems only part of the story: "Our study shows that ice-shelf channels can already be initiated on land, and that
the size of the channels significantly depends on sedimentation processes occurring over hundreds to thousands of years" indicates Reinhard Drews, lead author of the study.
The novel link between the subglacial hydrological system, sedimentation, and ice-shelf stability, offers new opportunities to unravel key processes beneath the Antarctic ice sheet, and also improves our ability to reconstruct the ice-sheet extent in the Northern Hemisphere during the last ice ages.
More information: R. Drews et al, Actively evolving subglacial conduits and eskers initiate ice shelf channels at an Antarctic grounding line, Nature Communications (2017). DOI: 10.1038/NCOMMS15228
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"Adapting to Change"Image by Linda Feltner (visit gallery »)
Copyright © 2007 Pinellas County, FL. This image is not available for reuse and is protected by copyright.
TitleAdapting to Change Contact
»Linda Feltner DescriptionBrooker Creek Preserve Environmental Education Center, Pinellas County, FL. Organisms living here year round must adapt to changing water levels. Outdoor interactive exhibits interpret the freshwater wetlands and varied habitats of the watershed. Exhibit shown: lindafeltner.com/interpretation.html > Parks and Visitor Centers KeywordsAdaptations, water levels, swamp ecosystem Media Color Categories Child/Youth, Nature, Science Subject(s) Animal, Botanical, Amphibians, Birds, Entomology, Invertebrates, Mammals, Reptiles, Vertebrates, Ecosystem, Editorial, Landscape | <urn:uuid:056d8c39-7cc0-4640-bc60-1bf9f55b7f95> | 2.671875 | 197 | Truncated | Science & Tech. | 2.457727 | 95,639,066 |
From Microservices Patterns by Chris Richardson
In this article, I describe the API gateway pattern. I discuss its benefits and drawbacks. I also describe various design issues that you must address when developing an API gateway.
As you may know, there are numerous drawbacks with services accessing services directly. It’s often impractical for a client to perform API composition over the Internet. The lack of encapsulation makes it difficult for developers to change service decomposition and APIs. Services sometimes use communication protocols that aren’t suitable outside of the firewall. Consequently, a much better approach is to use what’s known as an API gateway.
Pattern: API gateway
Implement a service which is the entry point into the microservices-based application from external API clients. See: http://microservices.io/patterns/apigateway.html.
An API gateway is a service which is the entry point into the application from the outside world. It’s responsible for request routing, API composition, and other functions, such as authentication. Let’s take a look at the API gateway pattern.
Overview of the API gateway pattern
The drawbacks of clients making multiple requests in order to display information to the user are well known (I describe them in my book!). A much better approach is for a client to make a single request to what’s known as an API gateway. An API gateway is a service which is the single entry-point for API requests into an application from outside the firewall. It’s similar to the Facade pattern from object-oriented design. Like a facade, an API gateway encapsulates the application’s internal architecture and provides an API to its clients. It might also have other responsibilities, such authentication, monitoring, and rate limiting. Figure 1 shows the relationship between the clients, the API gateway, and the services.
Figure 1. The API gateway is the single entry-point into the application for API calls from outside the firewall
The API gateway is responsible for request routing, API composition, and protocol translation. All API requests from external clients first go to the API gateway. The API gateway routes some requests to the appropriate service. The gateway handles other requests using the API Composition pattern and invoking multiple services and aggregating the results. It might also translate between client-friendly protocols such as HTTP and WebSockets and client-unfriendly protocols which are used by the services.
One of the key functions of an API gateway is request routing. An API gateway implements some API operations by routing requests to the corresponding service. When it receives a request, the API gateway consults a routing map that specifies which service to route the request to. A routing map might, for example, map an HTTP method and path to the HTTP URL of a service. This function is identical to the reverse proxying features provided by web servers such as NGINX.
An API gateway typically does more than reverse proxying. It might also implement some API operations using API composition. In my book, I use an example application called FTGO to teach how to move from monolithic architecture to microservices. The FTGO API gateway, for example, implements the
Get Order Details API operation using API composition. As figure 2 shows, the mobile application makes one request to the API gateway, which fetches the order details from multiple services.
Figure 2. An API gateway often does API Composition, which enables a client such as mobile device to efficiently retrieve data using a single API request.
The FTGO API gateway provides a coarse-grained API that enables mobile clients to retrieve the data they need with a single request. For example, the mobile client makes a single
getOrderDetails() request to the API gateway.
An API gateway might also perform protocol translation. The API gateway might provide a RESTful API to external clients even though the application services use a mixture of protocols internally include REST and gRPC. When needed, the implementation of some API operations translate between the RESTful external API and the internal gRPC-based APIs.
The API gateway provides each client with client-specific API
An API gateway could provide a single one-size-fits-all (OSFA) API. The problem with a single API is that different clients often have different requirements. For instance, a third-party application might require the
Get Order Details API operation to return the complete
Order details, while a mobile client only needs a subset of the data. One way to solve this problem is to give clients the option of specifying in a request which fields and related objects the server should return. This approach is adequate for a public API that must serve a broad range of third-party application, but it often doesn’t give clients the control they need.
A better approach is for the API gateway to provide each client with its own API. For example, the FTGO API gateway can implement provide the FTGO mobile client with an API which is specifically designed to meet its requirements. It might even have different APIs for the Android and iPhone mobile applications. The API gateway also implements a public API for third-party developers to use.
Implementing edge functions
Although an API gateway’s primary responsibilities are API routing and composition, it may also implement what are known as edge functions. An edge function is, as the name suggests, a request processing function which is implemented at the edge of an application.
Examples of edge functions that an application might implement include:
- authentication – verifying the identity of the client making the request
- authorization – verifying that the client is authorized to perform that particular operation
- rate limiting – limiting how many requests per second are allowed from either a specific client and/or from all clients
- caching – cache responses to reduce the number of requests made to the services
- metrics collection – collect metrics on API usage for billing analytics purposes
- request logging – log requests
Three different places in your application allow you to implement these edge functions.
The first option is to implement these edge functions in the backend services. This might make sense for some functions such as caching, metrics collection, and possibly authorization, but it’s generally more secure if the application authenticates requests on the edge before they reach the services.
The second option is to implement these edge functions in an edge service which is upstream from the API gateway. The edge service is the first point of contact for an external client. It authenticates the request and performs other edge processing before passing it to the API gateway.
An important benefit of using a dedicated edge service is that it separates concerns. The API gateway focusses on API routing and composition. Another benefit is that it centralizes responsibility for critical edge functions such as authentication. This particularly valuable when, as I describe below, an application has multiple API gateways that are possibly written using a variety of languages and frameworks. The drawback of this approach is that increases network latency because of the extra hop. It also adds to the complexity of the application.
As a result, it’s often convenient to use the third option and implement these edge functions, like authorization, in the API gateway itself. One less network hop exists, improving latency. Fewer moving parts reduces complexity.
API gateway architecture
An API gateway has a layered, modular architecture. Its architecture, which is shown in figure 3, consists of two layers, the API layer and a common layer. The API layer consists of one or more independent API modules. Each API module implements an API for a particular client. The common layer implements shared functionality including edge functions such as authentication.
Figure 3. An API gateway has a layered modular architecture. The API for each client is implemented by a separate module. The common layer implements functionality which is common to all APIs such as authentication
In this example, the API gateway has three API modules:
- Mobile API, which implements the API for the FTGO mobile client
- Public API, which implements the API for third-party developers.
An API module implements each API operation in one of two ways. Some API operations map directly to single service API operation. An API module implements these operation by routing requests to the corresponding service API operation. It might implement these API operations using a generic routing module that reads a configuration file describing the routing rules.
An API module implements other, more complex API operations using API composition. The implementation of this API operation consist of custom code. Each API operation implementation handles requests by invoking multiple services and combining the results.
API gateway ownership model
An important question that you must answer is who is responsible for the development of the API gateway and its operation? One option is for a separate team to be responsible for the API gateway. The drawback of this option is that it’s similar to SOA, where an Enterprise Service Bus (ESB) team was responsible for all ESB development. If a developer working on the mobile application needs access to a particular service, they must submit a request to the API gateway team and wait for them to expose the API. This kind of centralized bottleneck in the organization is counter to the philosophy of the microservice architecture, which promotes loosely-coupled autonomous teams.
A better approach, which has been promoted by Netflix, is for the client teams—the mobile, web, and public API teams—to own the API module that exposes their API. An API gateway team is responsible for developing the
Common module and for the operational aspects of the gateway. This ownership model, which is shown in figure 4, gives the teams control over their APIs.
Figure 4. A client team owns their API module. As they change the client, they can change the API module and not ask the API Gateway team to make the changes.
When a team needs to change their API, they check in the changes to the source repository for the API gateway. In order to work well, the API gateway’s deployment pipeline must be fully automated. Otherwise, the client teams are often blocked waiting for the API gateway team to deploy the new version.
Using the Backends for front ends pattern
One concern with an API gateway is that responsibility for it is blurred. Multiple teams contribute to the same code base. An API gateway team is responsible for its operation. Although not as bad as an SOA ESB, this blurring of responsibilities is counter to the microservice architecture philosophy of “if you build, it you own it.”
The solution is to have an API gateway for each client, the Backends for front ends (BFF) pattern, which was pioneered by Phil Calçado (http://philcalcado.com/) and his colleagues at SoundCloud. As figure 5 shows, each API module becomes its own standalone API gateway which is developed and operated by a single client team.
Figure 5. The Backend for front end pattern defines a separate API gateway for each client. Each client team owns their API gateway. An API gateway team owns the common layer.
Pattern: Backends for front ends
Implement a separate API gateway for each type of client. See:http://microservices.io/patterns/apigateway.html.
The Public API team owns and operates their API gateway, the mobile team owns and operates theirs, and so on. In theory, different API gateways could be developed using different technology stacks, but this risks duplicating code for common functionality such as the code that implements edge functions. Ideally, all API gateways use the same technology stack. The common functionality is a shared library implemented by the API gateway team.
As well as clearly defining responsibilities, the BFF pattern has other benefits. The API modules are isolated from one another, which improves reliability. One misbehaving API can’t readily impact other APIs. The BFF pattern also improves observability because different API modules are different processes. Another benefit of the BFF pattern is that each API is independently scalable. And the BFF pattern reduces startup time, because each API gateway is a smaller, simpler application.
Benefits and drawbacks of an API gateway
As you might expect, the API gateway pattern has both benefits and drawbacks.
Benefits of an API gateway
A major benefit of using an API gateway is that it encapsulates the internal structure of the application. Rather than having to invoke specific services, clients talk to the gateway. The API gateway provides each client with a client-specific API. This reduces the number of round trips between the client and application. It also simplifies the client code.
Drawbacks of an API gateway
The API gateway pattern also has some drawbacks. It’s yet another highly available component that must be developed, deployed, and managed. This creates the risk that the API gateway becomes a development bottleneck. Developers must update the API gateway in order to expose their services’ API. It’s important that the process for updating the API gateway is as lightweight as possible. Otherwise, developers are forced to wait in line in order to update the gateway.
Despite these drawbacks, for most real-world applications it makes sense to use an API gateway. If necessary, you can use the Backends for front ends patterns to enable the teams to develop and deploy their APIs independently.
Netflix as an example of an API gateway
A great example of an API gateway is the Netflix API. The Netflix streaming service is available on hundreds of different kinds of devices, including televisions, Blu-ray players, smart phones, and so on. Initially, Netflix attempted to have a one-size-fits-all style API for their streaming service (http://www.programmableweb.com/news/why-rest-keeps-me-night/2012/05/15). Unfortunately, they soon discovered that it didn’t work well because of the diverse range of devices and their different needs. Today, they use an API gateway that implements a separate API for each device. The client device team develops and owns the API implementation.
In the first version of the Netflix API gateway, each client team implemented their API using Groovy scripts that perform routing and API composition. Each script invoked one or more service APIs using Java client libraries provided by the service teams. On the one hand, this works well and client developers have written over thousands of scripts. The Netflix API gateway handles billions of requests per day; on average, each API calls fans out to six to seven backend services. Netflix has found this monolithic architecture to be somewhat cumbersome.
As a result, Netflix is now moving to an API gateway architecture which is similar to the Backends for front-end patterns. In this new architecture, client teams write API modules using NodeJS. Each API module runs its own Docker container. The scripts don’t invoke the services directly. Instead, they invoke a second “API gateway,” which exposes the service APIs using Netflix Falcor. Netflix Falcor is an API technology which does declarative, dynamic API composition, and enables a client to invoke multiple services using a single request. This new architecture has a number of benefits. The API modules are isolated from one another, which improves reliability and observability. Also, the client API module is independently scalable.
Now you know all about the API gateway pattern. If you want to learn more about the book, read the free first chapter of Microservice Patterns on liveBook here. | <urn:uuid:919321e8-2c02-440a-ace8-bbbcbc275826> | 2.859375 | 3,152 | Truncated | Software Dev. | 34.453168 | 95,639,068 |
Authors: George Rajna
EPFL physicists have found a way to reverse electron spins using electric fields for the first time, paving the way for programmable spintronics technologies. Manipulating light in a variety of ways—shrinking its wavelength and allowing it to travel freely in one direction while stopping it cold in another—hyperbolic metamaterials have wide application in optical communications and as nanoparticle sensors. A new way of enhancing the interactions between light and matter, developed by researchers at MIT and Israel's Technion, could someday lead to more efficient solar cells that collect a wider range of light wavelengths, and new kinds of lasers and light-emitting diodes (LEDs) that could have fully tunable color emissions. A team of researchers at the Center for Relativistic Laser Science, within the Institute for Basic Science (IBS) have developed a method to measure the shape of laser pulses in ambient air. Studying the fleeting actions of electrons in organic materials will now be much easier, thanks to a new method for generating fast X-rays. In a laboratory at the University of Rochester, researchers are using lasers to change the surface of metals in incredible ways, such as making them super water-repellent without the use of special coatings, paints, or solvents. The interaction of high-power laser light sources with matter has given rise to numerous applications including; fast ion acceleration; intense X-ray, gamma-ray, positron and neutron generation; and fast-ignition-based laser fusion. Conventional electron accelerators have become an indispensable tool in modern research. An outstanding conundrum on what happens to the laser energy after beams are fired into plasma has been solved in newly-published research at the University of Strathclyde. Researchers at Lund University and Louisiana State University have developed a tool that makes it possible to control extreme UV light-light with much shorter wavelengths than visible light.
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| Bothroponera crassa|
The few collections of B. crassa indicate that it is neither common nor widespread in Africa. Ten males were collected from Kenya, Laikipia District, Mpala Research Centre at night (8:30 to 9:30 pm) where they were flying at lights. (Joma and Mackay 2017)
Joma and Mackay (2017) - A member of the Bothroponera sulcata species complex. Worker The Bothroponera crassa workers are characterized by being relatively small (total length 6.0 - 8.8 mm), having the anterior medial margin of the clypeus convex with a smooth and shiny medial raised area, but without a clypeal carina (this raised area varies among B. crassa individuals and they may have a small depressed area anteriorly or even a short trough).
The head, pronotum, petiole and postpetiole are roughly sculptured with a few scattered punctures, but not on the 4th to 7th abdominal segments. The mandibles are smooth to striate with scattered punctures. The pronotal humerus is rounded anteriorly. The lateropropodeum is compressed laterally to form a slender lateropropodeum with concave sides as seen from above. The posteropropodeum usually declines gradually. The apex of the petiole is nearly flat with a straight anterior face while it is slightly concave posteriorly (side view). The apex of the petiole is slightly higher than the postpetiole and the dorsopropodeum.
It is difficult to separate B. crassa from Bothroponera ilgii, Bothroponera notaula, Bothroponera silvestrii and Bothroponera kruegeri because these species have similar dorsopropodea and posteropropodea. The total length of the worker of B. crassa ranges from 6.00 - 8.80 mm, which overlaps that of B. ilgii (8.35 - 9.40 mm), B. notaula (7.60 mm), and B. silvestrii (5.25 - 7.05 mm). The obvious characters that can separate those species are the structure of the clypeus and the form of the propodeum. The clypeus of B. crassa always has a smooth and shiny medial raised area, but without a groove in the two type specimens or with no more than a partial clypeal groove in other three specimens from Kenya. On the other hand, the type specimens of B. ilgii have a complete longitudinal shiny raised strip on the anterior medial area of the clypeus that forms a narrowed groove, and this area has a partial groove in the specimens from Kenya, Tanzania and Ethiopia. The anterior medial area of the clypeus of B. notaula forms a shiny smooth longitudinal strip with a clear wide groove. The other character is the structure of the lateropropodeum. This area is laterally compressed in B. crassa, including the three specimens from Kenya, apparently for the positioning of the metafemora (best seen from above). This character separates B. crassa from all of the others in the complex including B. ilgii, B. kruegeri and the B. notaula. Conversely, B. ilgii has a convex lateropropodeum. Finally, the propodeum is subquadrate and angulate between the faces of B. crassa, while it is mostly rounded (broadly curved) in B. ilgii.
Male The head of the B. crassa male is suborbiculate, excluding the mandibles and the mouthparts. The ocelli are relatively large. The notauli are absent on the dorsum of the scutum. The metanepisternum is well developed and distinguished from the propodeum and mesopleuron with a suture, while the metakatepisternum is narrowed and poorly defined. The dorsopropodeum is gradually sloped posteriorly to reach the insertion of the petiole at the lowest medial point of the propodeum. The petiole is small; its width is less than that of the dorsopropodeum (seen from above) and the height is less than the postpetiolar height and with a bluntly rounded apex. The pronotum, scutum, scutellum, propodeum, petiole and postpetiole are roughly sculptured. The postpetiole is rounded anteriorly.
The male of Bothroponera crassa is similar to other known males of the Bothroponera sulcata complex, including B. ilgii, B. kruegeri, B. notaula, Bothroponera ryderae, B. silvestrii, and Bothroponera soror. The notauli are absent in B. crassa and B. ilgii while they are present in B. soror, B. notaula, B. ryderae and B. silvestrii. The notauli in B. kruegeri are not well defined. The pronotum, scutum, scutellum and propodeum are roughly sculptured with a few scattered punctures on surface of B. soror. The petiole and postpetiole with the rest of the gastral segments of B. soror are less sculptured (rough) than they are in B. crassa. The pronotum, scutum, scutellum and propodeum of B. ilgii and B. crassa are rough (not punctuated). The head, pronotum, scutum, scutellum, metanotum, propodeum and petiole of males of B. silvestrii, B. notaula, B. ryderae and B. kruegeri are rough, but shiny while the postpetiole and 4th to 7th abdominal segments are mostly smooth and shiny. The petiole and postpetiole with the rest of gastral segments of B. crassa are similar to that of B. soror (rough); unfortunately, the gaster is missing in the only male specimen of B. ilgii; therefore, the measurement is missing in B. ilgii. The dorsopropodeum gradually slopes posteriorly in B. ilgii and B. crassa similarly to that in B. kruegeri whereas the dorsopropodeum is strongly curved nearly angulate posteriorly in B. soror. The dorsopropodeum in the males of B. notaula and B. ryderae is moderately broadly curved posteriorly to gradually reach the connection of the posteropropodeum with the petiole. The medial ocelli are large in B. crassa (0.20 - 0.25 mm), B. notaula (0.20 - 0.25 mm) and B. kruegeri (0.35 mm), which distinguish them from species with small medial ocelli including B. soror (0.10 - 0.15 mm), B. ryderae (0.16 mm), B. silvestrii (0.12 - 0.13 mm) and B. ilgii (0.17 mm).
Keys including this Species
Eastern Africa (Eritrea, Kenya and Somalia).
Distribution based on Regional Taxon Lists
Check distribution from AntMaps.
Distribution based on specimens
The following information is derived from Barry Bolton's New General Catalogue, a catalogue of the world's ants.
- crassa. Ponera crassa Emery, 1877b: 366, fig. (w.) ERITREA.
- Combination in Bothroponera: Emery, 1892a: 111.
- Combination in Pachycondyla (Bothroponera): Emery, 1895a: 177; Emery, 1901a: 46.
- Combination in Bothroponera: Wheeler, W.M. 1922a: 73; Santschi, 1930a: 53.
- Combination in Pachycondyla: Brown, in Bolton, 1995b: 304.
- Combination in Bothroponera: Schmidt & Shattuck, 2014: 77.
- See also Joma & McKay 2017: 14.
Unless otherwise noted the text for the remainder of this section is reported from the publication that includes the original description.
Joma and Mackay (2017) - (n=4), HL 1.45 - 1.75, HW 1.25 - 1.45, ML 0.75 - 0.95, EW 0.20 - 0.30, EL 0.30 - 0.40, SL 1.20 - 1.45, FL 2.00 - 2.40, WL 2.30 - 2.70, WPL 3.25 - 3.40, PL 0.60 - 0.75, PW 0.85 - 0.90, PH 1.05 - 1.15, CI 82.85 - 86.20, OI 24.00 - 27.58, Mandl 51.72 - 54.28, SI 96.00 - 100.00, Peti 120.00 - 141.66. Head quadrate, mandibles narrow with about 7-8 teeth, compound eyes relatively large; clypeus complex, dorsum shiny, smooth to striate with scattered punctures; scape extends slightly past posterior lateral corner of head; malar space length 0.25 length from upper edge of eye to edge of posterior lateral corner 0.85 mm; pronotal humerus rounded; dorsopropodeum slightly slopes posteriorly to form posteropropodeum; petiole slightly rounded from top, anterior face straight, slightly concave posteriorly, apex of petiole slightly higher than heights of postpetiole and dorsopropodeum; entire body covered with fine hairs; head covered with short erect hairs (less than 0.10 mm); hairs on ventral surface moderately long (0.15 - 0.35 Dorsum of pronotum, propodeum covered with short erect scattered hairs (0.15 mm); petiole postpetiole covered with moderately long erect (0.20 mm); long erect hairs (0.25 mm) arranged edges of posteropropodeum; color of entire body dark reddish-black or dark brownish; legs light brown or reddish brown; mandibles reddish brown.
Joma and Mackay (2017) - (n=14), HL 1.05 - 1.20, HW 0.70 - 0.95, ML 0.25 - 0.35, EW 0.45 - 0.60, EL 0.60 - 0.80, SL 0.25 - 0.35, FL 5.05 - 5.55, WL 2.25 - 2.80, WPL 2.85 - 3.45, PL 0.60 - 0.65, PW 0.55 - 0.65, PH 0.75 - 0.85, CI 66.66 - 79.16, OI 84.21 - 85.71, Mandl 23.80 29.16, SI 35.71 - 36.84, Peti 91.66 - 100.00. length ranges from 5.90 - 7.50 mm; eyes large, cover most of sides of head, distance between 0.65 - 0.70 mm, medial ocellus width 0.20 - mm; scape shorter (0.30 mm) and thicker than second funicular segment, three times longer mm) than first funicular segment; pronotum laterally and rounded anteriorly; dorsum of rounded (side view); scutellum subtriangular elevated in lateral view; metanotum raised between scutellum and propodeum; mesopleuron divided anapleural sulcus to form infra katepisternum supra anepisternum; fine short (less than 0.05 dense hairs cover entire body; moderately long (0.15 - 0.25 mm) scattered on dorsum of scutellum, metanotum, propodeum, petiole, postpetiole, suture between pronotum and scutum; hairs dorsum of scutellum, petiole and ventral surface of postpetiole slightly denser than on other parts; ventral surface of head with moderately long mm) erect hairs; color mostly brown, light brown to yellowish.
Eritrea: Bogos, Sciotel, 15°30’0’’ N; 38°14’0’’ E, O. Becaari 1870, type, Ponera crassa: Emery; syntype, Ponera crassa Emery 1877. Museo Civico di Genova (2w, lectotype and paralectotype, here designated, Museo Civico di Storia Naturale, Genoa).
The type specimens of B. crassa were collected from Sciotel in Eritrea, 15°30'0" N; 38°14'0" E, by Beccari; however, in several publications, the type specimens of B. crassa were reported from Ethiopia.
Joma and Mackay (2017) - The majority of the specimens that were identified as B. crassa in many Museums and in previous studies are similar but are actually Bothroponera crassior (=Bothroponera ilgii) and Bothroponera soror.
- Brown, W. L., Jr. 1995a. [Untitled. Taxonomic changes in Pachycondyla attributed to Brown.] Pp. 302-311 in: Bolton, B. A new general catalogue of the ants of the world. Cambridge, Mass.: Harvard University Press, 504 pp. (page 304, Combination in Pachycondyla; revived combination)
- Emery, C. 1877a. Catalogo delle formiche esistenti nelle collezioni del Museo Civico di Genova. Parte prima. Formiche provenienti dal Viaggio dei signori Antinori, Beccari e Issel nel Mar Rosso e nel paese dei Bogos. [part]. Ann. Mus. Civ. Stor. Nat. 9: 363-368 (page 366, fig. worker described)
- Emery, C. 1892a. Sopra alcune formiche raccolte dall'Ingegnere L. Bricchetti Robecchi nel paese dei Somali. [part]. Ann. Mus. Civ. Stor. Nat. 32[=(2(12): 110-112 (page 111, Combination in Bothroponera)
- Emery, C. 1895b. Esplorazione del Giuba e dei suoi affluenti compiuta dal Cap. V. Bottego durante gli anni 1892-93 sotto gli auspicii della Società Geografica Italiana. Risultati zoologici. X. Formiche. Ann. Mus. Civ. Stor. Nat. 35[=(2(15): 175-184 (page 177, Combination in Pachycondyla (Bothroponera))
- Emery, C. 1901b. Notes sur les sous-familles des Dorylines et Ponérines (Famille des Formicides). Ann. Soc. Entomol. Belg. 45: 32-54 (page 46, Combination in Pachycondyla (Bothroponera))
- Joma, A.M.A. & Mackay, W.P. 2017. Revision of the African ants of the Bothroponera sulcata species complex (Hymenoptera: Formicidae: Ponerinae). Transactions of the American Entomological Society. 143:7-71.
- Santschi, F. 1930a. Description de Formicides éthiopiens nouveaux ou peu connus. V. Bull. Ann. Soc. Entomol. Belg. 70: 49-77 (page 53, Combination in Bothroponera)
- Schmidt, C.A. & Shattuck, S.O. 2014. The higher classification of the ant subfamily Ponerinae (Hymenoptera: Formicidae), with a review of ponerine ecology and behavior. Zootaxa. 3817, 1–242 (doi:10.11646/zootaxa.3817.1.1)
- Wheeler, W. M. 1922b. Ants of the American Museum Congo expedition. A contribution to the myrmecology of Africa. II. The ants collected by the American Museum Congo Expedition. Bull. Am. Mus. Nat. Hist. 45: 39-269 (page 73, Combination in Bothroponera) | <urn:uuid:8c84e32b-1708-4bff-bbe7-4d4e63d0eaf3> | 2.703125 | 3,664 | Knowledge Article | Science & Tech. | 67.280881 | 95,639,102 |
Q1. à¿-D-Galactopyranose has [à¿]D = +150.7o, and à¿-D-galactopyranose has [à¿]D = +52.8o. When either of them is dissolved in water and allowed to reach equilibrium, the specific rotation of the solution will be +80.2o. What are the percentages of each anomer at equilibrium?© BrainMass Inc. brainmass.com July 22, 2018, 1:08 am ad1c9bdddf
OK...your basic idea is in the neighborhood...but your approach is wrong.
Let us use A & B (for the alpha, beta values of 150.7 and 52.8 respectively) to set the problem up
and X & Y for ...
An algebraic manipulation to ascertain the percent components of a mixture. | <urn:uuid:a6a27afe-1789-4f74-b05d-b8b744945d00> | 3.03125 | 187 | Q&A Forum | Science & Tech. | 83.578729 | 95,639,105 |
This ring system is the most distinctive of the entire solar system and consists mostly of dust, gas, rock and ice particles. Saturn is not the only planet in our solar system with rings: Jupiter, Uranus and Neptune also have ring systems – these are however much smaller and darker.
An international team of scientists of which Prof. Joachim Saur from the Institute of Geophysics and Meteorology of the University of Cologne is also a member, have made an amazing discovery: from observations made from the spacecraft Cassini, the scientists have come to the conclusion that the Saturn moon Rhea is encircled by a disk consisting of material which may comprise a ring system.
This would mean that Rhea is the only known moon with a ring system! The material of the disk comprises debris and ice particles, some as large as a meter in size.
This discovery means that Saturn, the so-called lord of the rings, has gained a small companion with rings or a disk. These results have been published in a current edition of the magazine Science.
Patrick Honecker | alfa
Nano-kirigami: 'Paper-cut' provides model for 3D intelligent nanofabrication
16.07.2018 | Chinese Academy of Sciences Headquarters
Theorists publish highest-precision prediction of muon magnetic anomaly
16.07.2018 | DOE/Brookhaven National Laboratory
For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.
To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...
For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.
Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...
Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.
A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...
Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.
"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....
Ultra-short, high-intensity X-ray flashes open the door to the foundations of chemical reactions. Free-electron lasers generate these kinds of pulses, but there is a catch: the pulses vary in duration and energy. An international research team has now presented a solution: Using a ring of 16 detectors and a circularly polarized laser beam, they can determine both factors with attosecond accuracy.
Free-electron lasers (FELs) generate extremely short and intense X-ray flashes. Researchers can use these flashes to resolve structures with diameters on the...
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+44 1803 865913
By: Tim R New(Editor)
435 pages, 41 colour & 19 b/w photos and illustrations, tables
The history of interest and practice in insect conservation is summarised and traced through contributions from many of the leaders in the discipline, to provide the first broad global account of how insects have become incorporated into considerations of conservation. The essays collectively cover the genesis and development of insect conservation, emphasising its strong foundation within the northern temperate regions and the contrasts with much of the rest of the world. Major present-day scenarios are discussed, together with possible developments and priorities in insect conservation for the future.
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Suborbital spacecraft are launched into space, but do not have enough speed to achieve orbit. They experience several minutes of microgravity ("free fall") and exposure to the environment of space before falling back to Earth.
Dr Duncan Law-Green and Mr David Boyce of the Department of Physics & Astronomy at the University of Leicester have each been awarded $5,000 by the Universities Space Research Association (USRA) to design microgravity experiments for submission to NASA. They are currently working with the Space Research Centre (SRC) at Leicester on the development of their proposals.
The NASA programme was originally conceived by Dr. Alan Stern, former head of NASA's Science Mission Directorate. A successful submission may lead to a pilot programme of suborbital research flights sometime around 2011-2012.
The proposed Leicester experiments deal with the physical and chemical properties of regolith, or the powdery material found on the surface of the Moon and other rocky bodies in the solar system. Improved knowledge of the properties and potential uses of this material will be very important for when humans return to the Moon in around 2020.
Dr. Law-Green commented "Leicester has a long history of research with suborbital rockets. A Leicester experiment will shortly be flying on a Black Brant rocket from White Sands, New Mexico. The advantage of the new commercial suborbital spaceplanes like SpaceShipTwo, is that they will provide scientists with cheaper and more frequent access to space, as well as the ability to have a researcher in place to monitor an experiment in real-time. If we want to fly an experiment again the following day, we will be able to do that more easily with a spaceplane than with a conventional sounding rocket. The research potential of this new generation of commercial manned spacecraft is very exciting."
Ather Mirza | alfa
What happens when we heat the atomic lattice of a magnet all of a sudden?
17.07.2018 | Forschungsverbund Berlin
Subaru Telescope helps pinpoint origin of ultra-high energy neutrino
16.07.2018 | National Institutes of Natural Sciences
For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.
To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...
For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.
Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...
Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.
A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...
Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.
"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....
Ultra-short, high-intensity X-ray flashes open the door to the foundations of chemical reactions. Free-electron lasers generate these kinds of pulses, but there is a catch: the pulses vary in duration and energy. An international research team has now presented a solution: Using a ring of 16 detectors and a circularly polarized laser beam, they can determine both factors with attosecond accuracy.
Free-electron lasers (FELs) generate extremely short and intense X-ray flashes. Researchers can use these flashes to resolve structures with diameters on the...
13.07.2018 | Event News
12.07.2018 | Event News
03.07.2018 | Event News
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On the measurement of proper time in general relativity by means of atomic clocks
The quantity τ, which is called the proper time of a particle in the general theory of relativity, has the following meaning: it is the time measured by clocks moving with the particle. The question arises of how proper time is measured by real clocks. At present, atomic clocks are the most accurate, being stabilized by the frequency of intraatomic transitions. In the present paper, the stability of the reference frequency of such clocks is considered, i.e., the possible discrepancies between the proper time and the time measured by atomic clocks.
KeywordsGeneral Relativity General Theory Proper Time Reference Frequency Atomic Clock
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In July Matthias joined an international research campaign at a drying lake in Spain (Laguna de Gallocanta)
Microbiology of lakes and reservoirs
As a consequence of temporary or permanent stratification and external inputs of nutrients and organic matter, lakes develop redox gradients which are associated with a variety of aerobic and anaerobic microbial metabolic reactions. These gradient-bound reactions are not only of general interest to microbiologists, but provide starting points for management of various water quality problems.
Our current study objects are lakes and reservoirs which are affected by an increasing load of dissolved organic carbon and pit lakes, some of which are meromictic (permanently stratified). Our group studies the microbial reactions of the iron, sulphur, carbon and nitrogen cycles and the organisms involved therein. We also investigate the formation and emission of greenhouse gases (carbon dioxide, methane) from lakes and their temporarily drying shorelines. A recent field of work is microplastics in inland waters, which has received increasing public attention during the last years.
We are especially interested in redox boundaries in standing waters, where a transition from oxic to anoxic conditions takes place. These are found in the sediments and at the sediment-water interface, but also within the water column of stratified lakes (chemocline/redoxcline). The water surface as the interface to the atmosphere is of crucial importance for the exchange of gases and is being studied in the field using floating chambers. Plastic particles in lakes also represent surfaces which we study with respect to the influence of different polymers and typical geochemical situations in lakes on microbial colonization and activity. Regarding sediments, the activity of different physiological groups of microbes and their dependence on biotic and abiotic parameters is studied. We adopt high-resolution methods which allow measurements of microbial activity and associated biogeochemical processes in the sub-millimeter range. To supplement the in situ studies, we also study microbial activities with the aid of controlled microcosm experiments in the laboratory. | <urn:uuid:aace1e65-4722-4cdb-a31b-8090fee2b04d> | 2.734375 | 408 | Knowledge Article | Science & Tech. | 8.223112 | 95,639,212 |
Broadening the Global Security Debate: Regional and Global Dialogues on Environmental Issues
Evidence is mounting in many countries that traditional, economically-important activities are posing increasing threats to the environment. The stresses are being felt simultaneously at the regional, national and global level. These impacts of human activity take many forms. Damage from the loss of forests and the acidification of lakes and streams are proving a major cost to economies in Europe, the United States and Canada. Dangerous levels of water pollution from agricultural and industrial chemicals can be measured from China to California, from Poland to the Philippines. Soil erosion threatens agricultural productivity from Iowa to India. Tropical deforestation in Asia, Latin America and Africa increases the risk of soil erosion at the same time that it reduces forest productivity and biological diversity.
KeywordsSoil Erosion Security Council Ozone Depletion United Nations Environment Programme Tropical Deforestation
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A joint University of Hawaii / Carnegie Institution study published in the advance online edition of Nature Geoscience links the pre-human stability to connections between carbon dioxide in the atmosphere and the breakdown of minerals in the Earth’s crust. While the process occurs far too slowly to have halted the historical buildup of carbon dioxide from human sources, the finding gives scientists new insights into the complexities of the carbon cycle.
Ken Caldeira of the Carnegie Institution’s Department of Global Ecology and Richard Zeebe of the University of Hawaii studied levels of carbon dioxide in the atmosphere over the past 610,000 years using data from gas bubbles trapped in Antarctic ice cores. They used these records, plus geochemical data from ocean sediments, to model how carbon dioxide released into the atmosphere by volcanoes and other natural sources is ultimately recycled via carbon-bearing minerals back into the crust.
When carbon dioxide levels in the atmosphere rise, the chemical reactions that break down silicate minerals in soils are accelerated. Among the products of these reactions are calcium ions, which dissolve in water and are washed to the ocean by rivers. Marine organisms such as mollusks combine the calcium ions with dissolved carbon dioxide to make their shells (calcium carbonate), which removes both calcium and carbon dioxide from the ocean, restoring the balance.
The researchers found that over hundreds of thousands of years the equilibrium between carbon dioxide input and removal was never more than one to two percent out of balance, a strong indication of a natural feedback system. This natural feedback acts as a thermostat which is critical for the long-term stability of climate. During Earth's history it has probably helped to prevent runaway greenhouse and icehouse conditions over time scales of millions to billions of years — a prerequisite for sustaining liquid water on Earth's surface.
“The system is finely in tune,” says Caldeira. “That one or two percent imbalance works out to an average imbalance in natural carbon dioxide emissions that is thousands of times smaller than our current emissions from industry and the destruction of forests.”
Previous researchers had suggested that such a system existed, but Caldeira and Zeebe’s study provides the first observational evidence supporting the theory, and confirms its role in stabilizing the carbon cycle. But because it operates over such a long time scale—the time scale over which landscapes are eroded and washed to the sea—this geological feedback system offers little comfort with respect to the current climate crisis.
Carbon dioxide is added naturally to the atmosphere and oceans from volcanoes and hydrothermal vents at a rate of about 0.1 billion tons of carbon each year. Human industrial activity and destruction of forests is adding carbon about 100 times faster, approximately 10 billion tons of carbon each year.
“The imbalance in the carbon cycle that we are creating with our emissions is huge compared to the kinds of imbalances seen over the time of the glacial ice core records,” says Caldeira. “We are emitting CO2 far too fast to expect mother nature to mop up our mess anytime soon. Continued burning of coal, oil and gas will result in long-term changes to our climate and to ocean chemistry, lasting many thousands of years.”
Global study of world's beaches shows threat to protected areas
19.07.2018 | NASA/Goddard Space Flight Center
NSF-supported researchers to present new results on hurricanes and other extreme events
19.07.2018 | National Science Foundation
A new manufacturing technique uses a process similar to newspaper printing to form smoother and more flexible metals for making ultrafast electronic devices.
The low-cost process, developed by Purdue University researchers, combines tools already used in industry for manufacturing metals on a large scale, but uses...
For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.
To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...
For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.
Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...
Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.
A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...
Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.
"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....
13.07.2018 | Event News
12.07.2018 | Event News
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20.07.2018 | Materials Sciences | <urn:uuid:a8007944-8b37-479c-ac9b-40147da2511b> | 4.3125 | 1,229 | Content Listing | Science & Tech. | 35.771129 | 95,639,233 |
UGA Researchers Work on Creating Stress- and Disease-resistant Trees
News Feb 21, 2015
Researchers at the University of Georgia think they've come up with a system to identify the genes in trees responsible for stress tolerance, which includes everything from extreme temperatures to disease. Now they're using a new $490,000 grant to identify those genes and figure out how they work.
Identifying those stress-control genes and understanding their function could help create trees that can resist the very things that can kill them, said C.J. Tsai, the lead researcher on the project.
Tsai, a Georgia Research Alliance Eminent Scholar and professor with joint appointments in UGA's Warnell School of Forestry and Natural Resources and the department of genetics in the Franklin College of Arts and Sciences, has been working for years on ways to create better-growing threes. Key to that is making them more resistant to stressful scenarios like extreme temperatures, disease and drought-but first they need to zero in on the genes that help with that.
"Successfully manipulating one or more of the genes under stressful scenarios could lead to better-growing trees, and the results could also be translated to food crops," said Tsai, who is also director of the Plant Center at UGA. "The implications of this project could be far-reaching."
Tsai and her team already have one candidate gene family from a previous study. The nucleoredoxin genes produce small redox proteins involved in cellular redox regulation. These genes were turned on when they increased salicylic acid in poplars.
While they gear up to identify additional candidates, the team will manipulate the nucleoredoxin genes to see the effects on plant stress response.
This project, funded by the U.S. Department of Agriculture, follows a previous study in which Tsai's team reported that the levels of salicylic acid-a naturally occurring chemical that protects plants from harmful environmental changes-could be greatly increased in poplar trees without stunting growth, which had been a common problem in other plants. Those findings are valuable to this new project, she said.
Salicylic acid is very important to plants because it regulates processes like photosynthesis and defenses against abiotic and biotic stresses-temperature, drought and disease.
"All those stresses promote the generation of damaging oxidants, and salicylic acid is thought to mitigate some of the damaging effects," Tsai said.
In the previous study, they identified many metabolites and genes that responded to increased salicylic acid.
"It turned out that many of those genes and metabolites were also increased when control trees were grown under heat stress," Tsai explained. "That's when we realized that trees overproducing salicylic acid created an opportunity for identifying novel stress-mitigating genes. It's like these trees have been ‘stress-primed' by salicylic acid."
In the new project, Tsai and fellow UGA researchers Scott Harding and Liangjiao Xue, also dually housed in Warnell and the genetics department, and Magdy Alabady in the plant biology department will compare tree responses to heat, drought and elevated levels of salicylic acid to identify genes that act downstream of salicylic acid to trigger defense. They also will study the involvement of small RNAs in this regulation.
RNAs are molecules that convey genetic information from DNA into proteins. Unlike typical genes that code for proteins, small RNA genes produce only small RNAs, but no proteins. The small RNAs are known to play important roles in plant defense as well as in animals by regulating the function of other genes.
By integrating the information they can obtain about gene expression, metabolite profiling and small RNA regulation from these trees, the researchers hope to identify novel cascades of cellular events that regulate plant stress tolerance.
Tsai said poplars were chosen for the studies because of their naturally high levels of salicylic acid compared to other plants, and also because they are a common biofuel feedstock.
Tsai's team is involved in two other new USDA grants that could have far-reaching implications:
• Her lab is collaborating with scientists at Penn State University, who are looking at how poplar trees respond to the Asian longhorned beetle, one of the most threatening invasive pests in the U.S. Tsai and Harding will receive about $100,000 from a $450,000 grant for the project, led by Penn State's Kelli Hoover. They'll be analyzing tissue samples for differences in a class of phenolic glycosides between American and Asian poplars to identify clues that would explain why the exotic tree is resistant to the beetle but native trees are not.
• With a $100,000 exploratory grant, Tsai and collaborators Alabady and Xue are investigating why some trees like poplar, oak and cherry flower early in the spring without leaves, while others like eucalyptus, chestnut and crepe myrtles don't flower until much later and require the presence of leaves. The new grant will allow them to compare pollen gene expression profiles of the early- and late-flowering tree species. They are particularly interested in carbohydrate metabolism genes-genes involved in synthesis, transport and use of sugars-because early- and late-flowering trees need to obtain sugars through different pathways to sustain the pollen development.
The findings could have a significant impact on multiple research fields, Tsai said.
"Flowering is key to breeding and crop productivity and is highly sensitive to climate change and plays many ecological roles through its interaction with bees and insects," she said. "Flower development is also an important focus of basic research, and most of our knowledge about flower development comes from studies with annual plants, such as petunias and snapdragons. However, trees grow and reproduce for decades in harsh and changing environments, and how they manage their resources to ensure their reproductive success needs to be better understood."
Analytical Tool Predicts Disease-Causing GenesNews
Predicting genes that can cause disease due to the production of truncated or altered proteins that take on a new or different function, rather than those that lose their function, is now possible thanks to an international team of researchers that has developed a new analytical tool to effectively and efficiently predict such candidate genes.
Single Gene Change in Gut Bacteria Alters Host MetabolismNews
Scientists have found that deleting a single gene in a particular strain of gut bacteria causes changes in metabolism and reduced weight gain in mice. The research provides an important step towards understanding how the microbiome – the bacteria that live in our body – affects metabolism.READ MORE
Gotta Sample 'Em All! Underwater Pokéball Captures Ocean LifeNews
A new device developed by Wyss Institute reseachers safely traps delicate sea creatures inside a folding polyhedral enclosure and lets them go without harm using a novel, origami-inspired design. The ultimate aim is to allow the sea creatures to be (gently) analyzed in high detail.READ MORE | <urn:uuid:f5b149f3-4730-4d95-b7c6-679cc3410dfc> | 2.640625 | 1,439 | News Article | Science & Tech. | 29.270383 | 95,639,239 |
|Emperor gum moth, Opodiphthera eucalypti|
Moths comprise a group of insects related to butterflies, belonging to the order Lepidoptera. Most lepidopterans are moths, and there are thought to be approximately 160,000 species of moth, many of which are yet to be described. Most species of moth are nocturnal, but there are also crepuscular and diurnal species.
Differences between butterflies and moths
While the butterflies form a monophyletic group, the moths, comprising the rest of the Lepidoptera, do not. Many attempts have been made to group the superfamilies of the Lepidoptera into natural groups, most of which fail because one of the two groups is not monophyletic: Microlepidoptera and Macrolepidoptera, Heterocera and Rhopalocera, Jugatae and Frenatae, Monotrysia and Ditrysia.
Although the rules for distinguishing moths from butterflies are not well established, one very good guiding principle is that butterflies have thin antennae and (with the exception of the family Hedylidae) have small balls or clubs at the end of their antennae. Moth antennae are usually feathery with no ball on the end. The divisions are named by this principle: "club-antennae" (Rhopalocera) or "varied-antennae" (Heterocera).
The modern English word "moth" comes from Old English "moððe" (cf. Northumbrian "mohðe") from Common Germanic (compare Old Norse "motti", Dutch "mot", and German "motte" all meaning "moth"). Its origins are possibly related to the Old English "maða" meaning "maggot" or from the root of "midge" which until the sixteenth century was used mostly to indicate the larva, usually in reference to devouring clothes.
Moth larvae, or caterpillars, make cocoons from which they emerge as fully grown moths with wings. Some moth caterpillars dig holes in the ground, where they live until they are ready to turn into adult moths.
Moths evolved long before butterflies, with fossils having been found that may be 190 million years old. Both types of lepidoptera are thought to have evolved along with flowering plants, mainly because most modern species feed on flowering plants, both as adults and larvae. One of the earliest species thought to be a moth-ancestor is Archaeolepis mane, whose fossil fragments show scaled wings similar to caddisflies in their veining.
Significance to humans
Some moths, particularly their caterpillars, can be major agricultural pests in many parts of the world. Examples include corn borers and bollworms. The caterpillar of the gypsy moth (Lymantria dispar) causes severe damage to forests in the northeastern United States, where it is an invasive species. In temperate climates, the codling moth causes extensive damage, especially to fruit farms. In tropical and subtropical climates, the diamondback moth (Plutella xylostella) is perhaps the most serious pest of brassicaceous crops. Also in sub-Saharan Africa, the African sugarcane borer is a major pest of sugarcane, maize, and sorghum.
Several moths in the family Tineidae are commonly regarded as pests because their larvae eat fabric such as clothes and blankets made from natural proteinaceous fibers such as wool or silk. They are less likely to eat mixed materials containing some artificial fibers. There are some reports that they may be repelled by the scent of wood from juniper and cedar, by lavender, or by other natural oils; however, many consider this unlikely to prevent infestation. Naphthalene (the chemical used in mothballs) is considered more effective, but there are concerns over its effects on human health.
Moth larvae may be killed by freezing the items which they infest for several days at a temperature below −8 °C (18 °F).
Despite being notorious for eating clothing, most moth adults do not eat at all. Many, like the Luna, Polyphemus, Atlas, Promethea, cecropia, and other large moths do not have mouth parts. While there are many species of adult moths that do eat, there are many that will drink nectar.
Some moths are farmed for their economic value. The most notable of these is the silkworm, the larva of the domesticated moth Bombyx mori. It is farmed for the silk with which it builds its cocoon. As of 2002[update], the silk industry produces more than 130 million kilograms of raw silk, worth about 250 million U.S. dollars, each year.
Not all silk is produced by Bombyx mori. There are several species of Saturniidae that also are farmed for their silk, such as the Ailanthus moth (Samia cynthia group of species), the Chinese oak silkmoth (Antheraea pernyi), the Assam silkmoth (Antheraea assamensis), and the Japanese silk moth (Antheraea yamamai).
The larvae of many species are used as food, particularly in Africa, where they are an important source of nutrition. The mopane worm, the caterpillar of Gonimbrasia belina, from the family Saturniidae, is a significant food resource in southern Africa. Another saturniid used as food is the cavorting emperor (Usta terpsichore). In one country alone, Congo, more than 30 species of moth larvae are harvested. Some are sold not only in the local village markets, but are shipped by the ton from one country to another.
Predators and parasites
Nocturnal insectivores often feed on moths; these include some bats, some species of owls and other species of birds. Moths also are eaten by some species of lizards, cats, dogs, rodents, and some bears. Moth larvae are vulnerable to being parasitized by Ichneumonidae.
Baculoviruses are parasite double-stranded DNA insect viruses that are used mostly as biological control agents. They are members of the Baculoviridae, a family that is restricted to insects. Most baculovirus isolates have been obtained from insects, in particular from Lepidoptera.
There is evidence that ultrasound in the range emitted by bats causes flying moths to make evasive maneuvers because bats eat moths. Ultrasonic frequencies trigger a reflex action in the noctuid moth that causes it to drop a few inches in its flight to evade attack. Tiger moths also emit clicks which can foil bats' echolocation.
Attraction to light
Moths frequently appear to circle artificial lights, although the reason for this behavior remains unknown. One hypothesis is called celestial or transverse orientation. By maintaining a constant angular relationship to a bright celestial light, such as the moon, they can fly in a straight line. Celestial objects are so far away that, even after travelling great distances, the change in angle between the moth and the light source is negligible; further, the moon will always be in the upper part of the visual field, or on the horizon. When a moth encounters a much closer artificial light and uses it for navigation, the angle changes noticeably after only a short distance, in addition to being often below the horizon. The moth instinctively attempts to correct by turning toward the light, thereby causing airborne moths to come plummeting downward, and resulting in a spiral flight path that gets closer and closer to the light source.
- Atlas moth (Attacus atlas), the largest moth in the world
- White witch moth (Thysania agrippina), the Lepidopteran with the longest wingspan
- Madagascan sunset moth (Chrysiridia rhipheus), considered to be one of the most impressive and beautiful Lepidoptera
- Death's-head hawkmoth (Acherontia spp.), is associated with the supernatural and evil and has been featured in art and movies
- Peppered moth (Biston betularia), the subject of a well-known study in natural selection
- Luna moth (Actias luna)
- Grease moth (Aglossa cuprina), known to have fed on the rendered fat of humans
- Emperor gum moth (Opodiphthera eucalypti)
- Polyphemus moth (Antheraea polyphemus)
- Bogong moth (Agrotis infusa), known to have been a food source for southeastern indigenous Australians
- Ornate moth (Utetheisa ornatrix), the subject of numerous behavioral studies regarding sexual selection
- Moths of economic significance
- Gypsy moth (Lymantria dispar), an invasive species pest of hardwood trees in North America
- Winter moth (Operophtera brumata), an invasive species pest of hardwood trees, cranberry and blueberry in northeastern North America
- Corn earworm or cotton bollworm (Helicoverpa zea), a major agricultural pest
- Indianmeal moth (Plodia interpunctella), a major pest of grain and flour
- Codling moth (Cydia pomonella), a pest mostly of apple, pear and walnut trees
- Light brown apple moth (Epiphyas postvittana), a highly polyphagous pest
- Silkworm (Bombyx mori), for its silk
- Wax moths (Galleria mellonella, Achroia grisella), pests of bee hives
- Duponchelia fovealis, a new invasive pest of vegetables and ornamental plants in the United States
Leaf-shaped moth (Pergesa acteus)
Giant grey moth (Agrius convolvuli)
Moth in India (Daphnis nerii)
Six-spot burnet moths mating (Zygaena filipendulae)
A caterpillar of death's-head hawkmoth
Mating pair of Laothoe populi, or poplar hawkmoths, showing two different color variants.
White-Lined Sphinx moth in Colorado, United States
Closeup of a common clothes moth
Giant silk moth (Adelowalkeria tristygma)
Adult emperor moth (Gonimbrasia belina)
- Clothing moth
- Comparison of butterflies and moths
- List of moths
- "Moths". Smithsonian Institution. Retrieved 2012-01-12.
- Scoble, MJ 1995. The Lepidoptera: Form, function and diversity. Oxford, UK: Oxford University Press; 404 p.
- Darby, Gene (1958). What is a Butterfly. Chicago: Benefic Press. p. 41.
- Chihuahuan Desert Nature Center
Evolution of Moths and Butterflies Archived 2014-01-06 at the Wayback Machine.
Studying the evolution of butterflies and moths is challenging, since fossils are so rare. But the few Lepidopteran fossils that exist, captured in amber or compressed in fine-grained rocks, show great detail. The earliest Lepidopteran fossils appear in rocks that are about 190 million years old. These tiny fragments of scaled wings and bodies clearly indicate that moths evolved before butterflies.
- The First Decade of Genetically Engineered Crops in the United States Archived 2010-06-22 at WebCite. USDA.
- Conlong, D. E. (1994-02-01). "A review and perspectives for the biological control of the African sugarcane stalkborer Eldana saccharina Walker (Lepidoptera: Pyralidae)". Agriculture, Ecosystems & Environment. 48 (1): 9–17. doi:10.1016/0167-8809(94)90070-1.
- Scott, Thomas (1995). Concise Encyclopedia Biology. Walter de Gruyter. ISBN 3-11-010661-2.
- Choe, D.-H. "Clothes Moths" in How to Manage Pests: Pests of Homes, Structures, People, and Pets. University of California
- "Table 74. Raw silk: production (including waste)". Food and Agriculture Organization of the United Nations. Retrieved 2008-10-02.
Table lists worldwide raw silk production 132,400 metric tonnes in 2002
- "Silk Exchanges of Tamil Nadu and Andhra Pradesh". Central Silk Board of India. Archived from the original on March 7, 2007. gives silk prices in rupees. Exchange rate is about 50 RS to dollar.
- "Silk Worm Farming". Vegan Society. Archived from the original on June 19, 2008. Retrieved 2008-10-02.
World Raw Silk Production in 1996 is listed as 83,670 metric tonnes
- "Some Edible Species". Food-Insects.com. Archived from the original on 2014-11-07.
- Jones, G; D A Waters (2000). "Moth hearing in response to bat echolocation calls manipulated independently in time and frequency". Proceedings of the Royal Society B: Biological Sciences. 267 (1453): 1627–32. doi:10.1098/rspb.2000.1188. PMC . PMID 11467425.
- Kaplan, Matt (July 17, 2009) Moths Jam Bat Sonar, Throw the Predators Off Course. National Geographic News
- Some Moths Escape Bats By Jamming Sonar (video). npr.org. July 17, 2009.
- "Why Are Moths Attracted to Flame?". npr.org. August 18, 2007.
- Tait, Malcolm (2006). Animal Tragic: Popular Misconceptions of Wildlife Through the Centuries. Think Books. p. 38. ISBN 1-84525-015-X.
- Brundage, Adrienne (March 23, 2009), Other Arthropods of Forensic Importance, Texas A&M University, Texas A&M University Forensic Entomology Lecture
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Outstanding places with cryptozoological phenomena around the world
This is unique list of some 50 cryptids which are linked to certain place and observed repeatedly over a longer time period.
- Ennedi Tiger – Chad, Ennedi. People in Ennedi mountains have interesting stories about very strong, elusive tigerlike cat, similar to extinct (?) Machairodus cats. According to stories this purported sabertooth cat is living in caves. Locals even consider that there are two species – one in mountains (Hadjel, Gassingram) and one in water (Mourour N’gou).
- Lake Kashiba – Zambia, Copperbelt Province. Lake in a sinkhole. The lake is 220 by 160 m large, it is approximately 100 m deep. Water level is some 10 m below the rims of sinkhole, water is lucid and deep blue. Numerous legends are linked to this lake, including a legend about lake monster. There are other similar sinkholes in this region.
- Lake Ngozi – Tanzania, Mbeya. Enormous and picturesque crater lake. Locals consider this place to be magical, with many mysteries. According to local legends here lives a lake monster which comes out from the water in sunny days.
- Lake Tele – Republic of the Congo, Likuala. Round freshwater lake deep in swampland and rainforest, possible impact crater. According to local stories in this lake and surrounding area lives mokèlé-mbèmbé – purported giant reptile. This remote area is very rich with rare species of plants and animals including a population of more than 120 thousand gorillas. Many other cryptids reported, such as mahamba – giant crocodile.
- Ayia Napa Sea Monster – Cyprus, Famagusta. Legendary sea monster which, reportedly, is occasionally seen near the coast, most frequently at Cape Greco.
- Bardia Elephants – Nepal, Bheri. In this virgin Terai forest lives a population of weird elephants. These animals are larger than any known Asian elephants and have unusual appearance, making them more similar to mammooths.
- Bukit Timah Monkey Man – Singapore. Although the Bukit Timah rainforest is very small and surrounded by modern city, there are reports about hominid living in this forest.
- Cheonji – abode of Lake Tianchi Monster – North Korea, Ryanggang and China, Jilin. According to legends and modern stories in this beautiful crater lake lives a monster.
- Cat-fox in Kayan Mentarang National Park – Indonesia, North Kalimantan. It is possible that in this pristine tropical forest lives carnivore – an animal which looks like a cross between fox and cat. This animal was photographed on cameras of BBC researchers in 2005.
- Endau-Rompin National Park and Mawas – Malaysia, Johor and Pahang. One of the oldest tropical rainforest complexes in the world which contains many rare plants and animals. Forest is 870 km² large. Indigenous people in this forest tell stories about encounters with Mawas – mythical, human like creatures who are 3 – 4 m tall. There are also recent sightings of this creature.
- Kanas Lake Monsters – China, Xinjiang. According to legends in this lake live giant fish or similar creatures, which are some 10 – 15 m long. These animals have been caught on video, including an aerial which shows a group of some 15 creatures crossing the lake (2012).
- Khumjung Monastery – Nepal, Sagarmatha. In this monastery is located a purported scalp of yeti. Research shows that it is a fake made of Himalayan serow skin.
- Kok-Kol Lake and Aidahar – Kazakhstan, Jambyl. Unusual montane lake which, reportedly, emits sounds – long whistles or sighs. This could be explained with emissions of gas from the bottom of lake. According to stories of many locals sometimes here is seen a monster – Aidakhar – which comes out from the lake and hunts sheep. This monster was been observed also by some scientists but there is no evidence whether it exists in reality.
- Lake Labynkyr Monster – Russia, Sakha Republic. Local Yakuts tell legends about fierce, giant animal who lives in this lake. Geologists have noticed this animal in 1953 and later there have appeared unusual legends about the charms of this lake.
- Mae Charim Yeties – Thailand, North. Local people frequently have met enormous, hairy and black creatures in this remote, mountainous area of Thailand. According to some stories local people never leave their villages after the dark due to these aggressive animals.
- Mande Burung near Balpakram, Garo Hills – India, Meghalaya. Many local people are convinced that in the extensive subtropical forests in Garo Hills live large (some 3 m tall), man-like creatures which are covered with hair. Especially frequently these animals are seen in a forested canyon near Balpakram.
- Pangboche Monastery and Pangboche Hand – Nepal, Sagarmatha. In this monastery was located a hand of dead, unknown creature, a hominid which was not human. Parts of hand were stolen in 1959, the remaining parts disappeared in 1999.
- Peppara Forest and Kallanas – India, Kerala. A population of suspected dwarf elephants reportedly lives in this forest. Here lives the common Asian elephant (Elephas maximus) but local people are convinced that considerably smaller elephants – Kallanas – hide from the common elephants further up in the mountains. Maximum height of Kallanas is 1.5 m.
- Sakteng Wildlife Sanctuary – Bhutan, Trashigang. Gorgeous primeval forest in Himalaya, mostly – temperate forests and subalpine ecosystems. One of the reasons for the creation of this sanctuary is protection of migoi – man-like cryptid, whose existence has not been proved but local people are convinced that it exists.
- Shennongjia white animals – China, Hubei. Virgin montane forest with very high diversity of plants and animals. This is ancient forest with little climatic change since the Jurassic period. As a result here live many ancient species. Peculiar are the many reported sightings of diverse white animals – bears (Bai-Xiong), snakes, monkeys, deer, crows, weasels. Many local people have reported sightings of big human-like animals.
- Shishi-Kuh Valley – Pakistan, Khyber Pakhtunkhwa. Area where many researchers and local people have spotted footprints and sounds made by unknown animals. Many local people often have seen an ape-like creature which is similar to Neanderthal man. This animal is called Barmanu and it has been spotted in other areas too.
- Vũ Quang – Vietnam, North Central Coast. Remote, forested region, where numerous new species of animals and plants have been found over the last decades and several more are reported but their existence has not been proved yet. One of the most intriguing ones is batutut (Nguoi Rung) – a human like creature, which is approximately 1.8 m tall and covered with hair.
Australia and Oceania
- Ropen of Umboi Island – Papua New Guinea, Umboi Island, Morobe Province. According to tales and legends sometimes here is seen a featherless, enormous flying creature. In the night, while flying, it is glowing for several seconds. It is seen in other parts of Papua New Guinea as well but most frequent it is in Umboi. Some believe that this might be a flying reptile similar to pterosaur.
- Kakamora caves (Kakangora caves) – Solomon Islands, Makira-Ulawa. Legendary, inaccessible caves, where, according to locals, live Kakamora people – ancient dwarf people, just one meter tall, walking naked and endowed with incredible strength. Many believe that these people still exist.
- Lake Murray Monster – Papua New Guinea, Western Province. Over the last 10 years in Lake Murray repeatedly has been spotted enormous carnivore, a reptile which is named Au Angi-Angi. It is similar to Theropoda dynosaurs.
- Am Fear Liath Mòr (Greyman) – United Kingdom, Scotland, between Aberdeenshire and Moray. Mythical creature which, reportedly, haunts the highlands around Ben Macdui mountain. According to the eyewitnesses this is very tall, human like creature which is covered with short hair. Many travellers report uneasy, fearsome feelings in this area.
- Brosno Lake Monster – Russia, Tver Oblast. Some 4 – 5 m long, serpent-like creature, which has been observed in this lake since the 19th century or even the 13th century. Photographed in 1996. Later investigations though have shown that stories could have been created by large bubbles of gas coming from the lake bed.
- Lagarfljót – Iceland, Austurland. This large lake, according to legends, has a monster – Lagarfljotsormurinn (Lagarfljot Worm) – living in it.
- Loch Morar Monster – Morag – United Kingdom, Scotland, Highland. In this lake more than 30 times has been observed a serpent-like creature, which, reportedly, is some 6 m long.
- Loch Ness Monster – Nessie – United Kingdom, Scotland, Highland. Best known cryptid in the world albeit not too credible. Nessie is a supposed creature living in Loch Ness – large lake in Scottish Highlands. By many considered to be a surviving reptile similar to plesiosaurs. Attained world wide fame in 1933 although supposedly mentioned already in the 6th century AD. Numerous search expeditions with state of the art technologies have found some unexplained phenomena but there have been no convincing proofs for existance of Nessie.
- Seljordsvatnet Monster – Selma – Norway, Telemark. A lake monster which is similar to Nessie. This monster has been sighted since the 18th century. It was filmed in 2012.
- Storsjöodjuret – Sweden, Jämtland. A lake monster is reported in Storsjön lake since 1635. This animal is reportedly some 6 m long and looks like aquatic reptile with fins across its back.
- Cayuga Lake Monster – Old Greeny – United States, New York. Sightings of serpent-like monster have been reported here since the early 19th century. Already by the end of the 19th century it was sighted 69 times at least, but there have been multiple reports in the 20th century as well.
- Chickcharney – mysterious bird in Andros Island – Bahamas, forests of Andros Island. According to tales of locals in the forests of this island lives approximately 1 m tall creature which resembles an owl. There is a possibility that here survives the flightless owl Tyto pollens, which was 1 m tall and was last reported in the 16th century.
- Crescent Lake Monster – Cressie – Canada, Newfoundland and Labrador. According to the tales of ancient Native Canadians and contemporary people in this lake lives enormous, eel-like creature. Numerous giant eels attacked a group of divers in the 1980s.
- Flathead Lake Monster – United States, Montana. Lake monster which, reportedly, is similar to Loch Ness monster. First reported sighting took place in 1889 and since then it has been seen numerous times. In 1993 the monster was seen 13 times, including two times with two monsters at once.
- Headless Man Valley in Nahanni National Park – Canada, British Columbia. Site of legends where several gold seekers died in mysterious conditions in the early 20th century – reportedly, their heads were ripped off. Some link these attacks to the mysterious people called Naha – but this is little likely. Here are reported other cryptids as well, e.g. nuk-luk – man-like hominid and waheela – giant wolves which are somewhat similar to bears.
- Islesboro Up-island spider – United States, Maine. In small area of Islesboro island are observed wolf spiders of unusual size, with a leg span reaching 20 cm. According to local legends these spiders arrived here in a coffin.
- Lake Champlain monster – Champ – United States, Vermont and New York as well as Canada, Quebec. Well known lake monster which has been seen more than 300 times since 1609. It’s existence though has not been proved. Animal is similar to snake.
- Lake Simcoe Monster – Igopogo – Canada, Ontario. Impressive lake monster which is similar both to sea serpent and canine. It is seen rarely but consistently throughout several centuries at least. Animal made sudden appearance during the boat race in 1991.
- Lake Tahoe Monster – Tessie – United States, California and Nevada. Many times in this lake has been sighted 3 – 25 m long serpent-like monster.
- Lake Utopia Monster – Old Ned – Canada, New Brunswick. In this lake every few years is observed a monster, which, according to different reports, is 3 – 15 m long. It looks like a cetacean and it is possible that it comes here from the sea.
- Lizard Man of Scape Ore Swamp – United States, South Carolina. In abandoned areas of Lee country over the last decades is reported fearsome, approximately 2 – 2.1 m tall monster with lizard-like skin. This monster repeatedly attacked cars in events which resemble scenes from horror movies.
- Lusca – giant octopus of Andros blue holes – Bahamas, in blue holes around Andros Island. There are numerous stories about giant squids which reportedly live in the sinkholes near the coast of Andros. According to these stories this monster is up to 23 m or even 60 m long.
- Memphremagog Lake monster – Memphre – Canada, Quebec. A lake monster, which reportedly looks like a whale or plesiosaur. First sightings have been reported in 1816 but there are also recent ones, e.g. in 2005.
- Okanagan Lake monster – Ogopogo – Canada, British Columbia. A serpent-like monster which is reported since the 19th century. This serpent reportedly is 12 – 15 m long.
- Reindeer Lake Monster – Canada, Saskatchewan and Manitoba. Reportedly there is a monster in the Deep Bay, which eats reindeer who fall through the ice. In 2006 it killed several dogs.
- Wallowa Lake Monster (Big Wally) – United States, Oregon. Many reports, including legends of native people about enormous, manatee-like animal, which is up to 15 m long.
- Nahual Huapi Lake Monster – Nahuelito – Argentina, Río Negro. A purported lake monster living in the enormous Nahual Huapi Lake. Stories tell that this animal is similar to a plesiosaur, 4.5 – 6 m long. The first stories about the animal have been recorded in the late 19th century.
Described places with cryptozoological phenomena
Cryptozoology is very exciting pseudoscience – a discipline which stands between true science and folklore.
It deals with legendary animals which seem to exist but their existence has not been proved.
Stories which are never ending
The most interesting aspect of this discipline is the following: often it seems that just one more step – a final proof or one more expedition is needed and the elusive cryptid (undiscovered animal) will be discovered, it will receive its Latin name and will be added to the long list of known species. Nope… just like in a good TV drama the story goes on and on and becomes more and more interesting with every next turn because cryptid just can not be "discovered".
There is no need to belittle cryptozoology – it is a pastime of many outstanding personalities including many of the best biologists. Numerous expeditions have been organized to remote parts of Earth and have brought home many interesting scientific discoveries. Members of expeditions sometime manage to get some proof of the existence of cryptids, but, alas, this is not a common science but cryptozoology: proof is lost on the way home. Such are the rules of this "genre".
This category includes places where on a regular basis can be observed cryptozoological phenomena.
Wondermondo does not include all legends and stories related to cryptozoology. Here are included only these cases which are:
- Linked to a certain place. Here are not included these cryptids which are reported in different places of larger regions – e.g. giant anaconds of South America or the fearsome j’ba fofi (1.5 m large spider) of Central Africa. In fact Wondermondo tries to keep the 500 km² rule and avoids to include landmarks which take larger area than this.
- Repeating over a longer time. Cryptozoology has many cases when some weird beasts are seen only once or few times over a short time period. Such cases are not included here – Wondermondo describes more or less permanent phenomena. There are rather many cryptids which are well known for many centuries.
- Recent. It seems, cryptids sometimes die too. There are cases when weird animals were seen on a regular basis in the past but are not reported for many decades. Such cases are not included here.
Most popular cryptids
There are two kinds of cryptids which are reported all over the world and are a lot more popular than any others. These are: a) lake monsters and b) hominids.
Unofficial queen of cryptozoology is Nessie – Loch Ness Monster. If foreigners would be asked to list top five things associated with Scotland, Nessie most likely would be on this list. But there are hundreds of lakes (as well as rivers, sinkholes and sea bays) around the world with similar stories about dragon-like or serpent-like monsters. Lake monsters are known for centuries in such diverse countries as China, Japan, Tanzania, Congo, Canada and other countries.
Lake monsters for most part are enormous, much larger than any known freshwater fish and reptiles. It is tempting to assume that these cryptids have descended from dinosaurs but almost everyone understands that this is nonsense – such enormous animals can not survive more than 60 million years and finally live in comparatively small waterbodies without being discovered. It is also tempting to explain all encounters with casual, boring explanations – floating logs, groups of common fish, fraud, wishful thinking etc. But this does not help as well – there are many cases when reputable people or even large groups of people have clearly observed large, unusual animals in these lakes.
It is known that in parallel to modern humans there were living several more species or subspecies of humans which went extinct not that long ago. The dwarf Homo floresiensis lived on Flores island (Indonesia) some 17,000 years ago – in time when modern humans created magnificent rock art in Australia and elsewhere in the world.
This leaves a minor possibility that somewhere still is living a group of these "alternate" humans. Who knows – may be the popular legends about small forest spirits and gnomes tell about another human species (see the story about dwarf people of Kakamora Caves)?
Many stories tell about another kind of elusive human-like beings – enormous, hairy primates who live in mountains, large forests and sometimes – even near cities in every continent of the world (of course, except Antarctica). For example, thousands of countryside people in Meghalaya or Chitral have no doubts that these beings exist. Cryptozoologists speculate that these could be surviving giant apes, such as Gigantopithecus, which, according to more common science is extinct for some 100 thousand years. This 3 m tall giant lived in China and India.
Other kinds of cryptids are less popular but not less exciting. What about flying reptiles which are reported in Umboi Island (Papua New Guinea)? Or possible subspecies of mammoth in Nepal? May be there exist giant squids which hide in the mysterious blue holes near Andros (Bahamas)?
World (and human mind…) is exciting!
In this book, Denver Michaels examines reports of lake monsters in the United States and Canada. Simply put, Michaels’ title says it all—people are seeing something—sincere, honest people report seeing strange creatures in the water on a regular basis. The reports are real; moreover, there is much more to the plethora of sightings than just the misidentification of known animals and hoaxes. Michaels also takes the time to examine the bodies of water where cryptids are said to dwell.
Bigfoot hunters and their brethren are often depicted as outcasts, misfits, or passionate amateurs toiling in solitude. But has this always been the case? This fresh and entertaining study looks at the surprisingly complex relationship between professional scientists and cryptozoologists. | <urn:uuid:a6a6032f-fdd7-4ac2-b486-6307a7ba236a> | 2.546875 | 4,376 | Listicle | Science & Tech. | 42.997909 | 95,639,265 |
Environmental scientists have new tools for monitoring the health of northern forests — and they’re orbiting many miles above Earth.
Using sensor data collected by satellites, scientists have developed an index to track photosynthesis in evergreens, revealing subtle natural rhythms and seasonal cycles that signal how these trees adapt to climate change.
“Past satellite studies have focused primarily on using ‘greenness’ indices … as indicators of seasonally photosynthetic activity,” project lead Dr. John Gamon told Digital Trends. “While these approaches work well for some types of vegetation, they work poorly in evergreens that lack large seasonal changes in green leaf display — after all, they are ‘evergreen!’”
To see these hidden rhythms on a large scale, Gamon and his team used new combinations of satellite frequency bands, including one that NASA uses to study oceans and one that tracks what Gamon calls the “invisible glow” of chlorophyll. They then developed an index to analyze the changes.
“Satellites are now starting to have the right tools for the job,” Gamon said. “This understanding of how these things are connected in a coherent way depends not only on new satellite data but on a network of collaborating scientists and field sites … and involves a lot of on-the-ground validation.”
Virtually all life on Earth depends on photosynthesis in some way so it is a vital sign of the planet’s overall health.
“Besides releasing oxygen,” Gamon said, “photosynthesis helps regulate our atmosphere by absorbing carbon dioxide … which helps regulate our climate and slow down climate change.” The process also helps humidify Earth by releasing water vapor. “In a warming world, active photosynthesis means a productive world and a more stable climate, which are all indicators of planetary health,” he added.
Slowing photosynthesis, meanwhile, indicates something in the system is failing, Gamon said. It is important then to keep track of even the subtle pigment changes in evergreens, which are particularly telling because they occupy 14 percent of all land on Earth and significantly impact environmental productivity.
“As an example of ‘ill health’ conveyed by evergreen photosynthesis, the recent declines of evergreen forests in much of the western U.S. and Canada due to warming, drought, insects, and wildfire are all indicators of severe stress and can be seen as a decline in planetary health in the face of changing climate,” Gamon said. “In this way, forest activity is a key indicator of planetary health.”
Gamon is now focused on analyzing these changes in photosynthesis detected with the new tools and index in an effort to determine how these vital systems will respond to a changing climate. His study appeared in the journal Proceedings of the National Academy of Sciences this week.
- Astronomers make huge exoplanet discovery haul in record time
- CRISPR could one day help conservationists save our ocean’s coral
- Get your Sagan on with 60 awe-inspiring photos of the final frontier
- Awesome Tech You Can’t Buy Yet: Laptop screen extenders and self-healing tents
- CRISPR gene-editing could help feed future generations | <urn:uuid:e3fc26bc-d465-4133-82d1-da8c8b3c7c25> | 3.875 | 687 | News Article | Science & Tech. | 27.955938 | 95,639,274 |
Polymer plastic solar cells remain an industry priority because of their light weight, flexibility and cost-effectiveness. Now scientists from Stony Brook University and the U.S. Department of Energy’s (DOE) Brookhaven National Laboratory (BNL) have demonstrated that these types of solar cells can be more efficient and have more stability based on new research findings.
Led by Miriam Rafailovich, Ph.D., a Distinguished Professor at Stony Brook University, and Chang-Yong Nam, Ph.D., a scientist at BNL and Adjunct Professor at Stony Brook, the research team discovered that by adding a common inert polymer, called polystyrene, these solar cells undergo an optimized internal morphology, resulting in a higher device performance.
The discovery solves a problem with polymer plastic solar cells. Most of these cells require an additive included for high device performance – a non-active small chain molecule to control internal morphology. But the additive is known to cause stability problems under light and heat, thus compromising performance and efficiency.
The new study, published in Advanced Materials Interfaces, demonstrates that replacing the additive with the inert polymer potentially solves this problem. In a previously published paper in Nanoscale, the researchers used a similar approach, but, with a different polymer.
This earlier work illustrated that a newly engineered polymer plastic solar cell increases optimal thickness – a quality that is better suited for industrial production by low-cost coating methods. The significance of this result was featured on the U.S. Department of Energy (DOE) website.
Zhenhua Yang et al. Roles of Interfacial Tension in Regulating Internal Organization of Low Bandgap Polymer Bulk Heterojunction Solar Cells by Polymer Additives, Advanced Materials Interfaces (2018). DOI: 10.1002/admi.201800435
Hongfei Li et al. A new strategy to engineer polymer bulk heterojunction solar cells with thick active layers via self-assembly of the tertiary columnar phase, Nanoscale (2017). DOI: 10.1039/C7NR03789A | <urn:uuid:4f7e25a6-57e1-4bdd-937f-0c78516b7b3d> | 2.953125 | 435 | News Article | Science & Tech. | 31.537017 | 95,639,279 |
Temporal sequences of images called Satellite Image Time Series (SITS). a multitemporal classification approach for Very High Resolution (VHR) SITS to use .
A Satellite Image Time Series (SITS) is a set of satellite images taken from the same scene at different times. A SITS makes use of different satellite sources to obtain a larger data series with short time interval between two images. In this case, it is fundamental to observe the spatial resolution and registration constraints.. Sensors with high spatial and temporal resolutions make the observation of .
Download citation A method for generat. There is an increasing demand for satellite remote sensing data with both high spatial and temporal resolution in .
Object-based classification of grassland from high resolution satellite image time series with Gaussian mean map kernels. Presented by Stéphane Girard1.
. information about the temporal classification derived from satellite image time series (SITS) provided by high–resolution satellites such as Venus, SENTINEL-2, .
satellite Earth observation data, due to its high temporal resolution and large. from Landsat time series (LTS) and high spatial resolution imagery for land cover
This paper deals with the classification of grassland management practices using high resolution satellite image time series. Grasslands considered in this work .
This talk deals with the classification of grassland management practices using high resolution satellite image time series. In this work, grasslands are .
. of grassland use intensities by means of satellite image time series. The high spatial and temporal resolution of the Sentinel satellites (one image taken .
Tidal inundation ("Rob") investigation using time series of high resolution satellite image data and from institu measurements along northern coast of Java .
the utility of temporal map algebra for time series satellite image analysis, we. on the 1982-1993 monthly time series Advanced Very High Resolution . | <urn:uuid:3dffa4d6-72cc-4dae-b128-c120451ea7b1> | 2.8125 | 384 | Content Listing | Science & Tech. | 19.996924 | 95,639,280 |
Carbon atoms can attach to each other and form straight or branched chains and ringed structures of organic compounds.
Today millions of different organic compounds are known.
- 4 classes of macromolecules and their functions
- Isomers of biomolecules
- Functional groups
- Monomers and polymers
Structures of organic compounds form biological polymers and act as the backbones of different types of biological molecules. All 4 classes of macromolecules (biomolecules of life) are carbon based.
Some examples of important biological molecules include vitamins, enzymes, polyphenols, and plenty of others.
While the most of carbon containing molecules are organic compounds, there are a few exceptions.
Such compounds as carbides, carbonates, simple oxides of carbon (CO2), allotropes of carbon and cyanides are considered to be inorganic.
Each of 4 major types of biomolecules is an important cell component and performs a wide variety of functions.
4 major classes of biological molecules include:
- Carbohydrates (monosaccharides, oligosaccharides, polysaccharides)
- Lipids (triglycerides, phospholipids, steroids)
- Nucleic Acids (DNA, RNA)
Besides their specific roles, carbohydrates, lipids, and proteins can serve as a source of energy, while nucleic acids are the most important macromolecules for the continuity of life.
Plants and algae produce millions of tons of carbohydrates each year through photosynthesis.
The major function of carbohydrates is to provide energy, particularly through glucose.
During cellular respiration, glucose is broken down and oxidized within cells. This process is used to synthesize ATP – the source of energy for cellular reactions. When the quantity of ATP are sufficient, simple carbohydrates are converted to carbohydrate polymers (glycogen or starch) or fat and stored.
Carbohydrates also have other important functions in all living organisms.
For example, they serve as building materials within the plant cells and perform cell-to-cell identification when attached to the external surfaces of the cytoplasmic membrane.
Lipids include a diverse group of biomolecules. They are insoluble in water and include mostly nonpolar carbon–carbon or carbon–hydrogen bonds.
This type of biomolecules is the most common energy-storing molecule for long-term use. Excess carbohydrates are converted into fat for later usage. 1 g of fat is equal to 38 kJ (versus 17 kJ for carbohydrates and proteins).
Lipids perform many different functions in a cell.
For example, plants and animals use fat as insulation from the environment. Lipids are an important part of all cellular membranes and many hormones.
Proteins are the most diverse group of 4 major types of biomolecules. Their macromolecular structures and functions vary greatly.
Each living cell contains thousands of proteins each performing a unique function. They can act as structural building blocks and functional molecules, involved in almost every task of the cell. All enzymes are proteins.
This class of macromolecules is all polymers of 20 amino acids.
Nucleic acids store and carry the hereditary information for the functioning of the cell.
The nucleic acids include two major classes of biological molecules, deoxyribonucleic acid (DNA) and ribonucleic acid (RNA), and consist of nucleotides.
Protein and nucleic acid enzymes catalyze biochemical reactions in both catabolism and anabolism of macromolecules.
Catabolism - the breakdown of biomolecules in living organisms.
Anabolism - the synthesis of complex biological macromolecules.
One of the basic qualities of organic compounds - to possess a variety of properties, depends, in particular, on their ability to form isomers.
Isomers are macromolecules with the same molecular formula but different structures.
There are two main types of isomers:
- Structural isomers
Structural isomers of macromolecules differ in the placement of their covalent bonds.
Examples of structural isomers is biological molecules of carbohydrates - glucose and fructose. Because of their different structures, they have different properties and are metabolized differently.
Stereoisomers have similar placements of their covalent bonds but differ in how these bonds are made to the surrounding atoms. Stereoisomers can be geometrical or optical.
Geometrical isomers can have different physical, but similar chemical properties.
Examples of geometrical isomers are glucose and galactose.
Optical isomers (enantiomers) usually have similar chemical and physical properties, but enzymes can distinguish one biomolecule from another.
Typically, one optical isomer is biologically active, and the other is inactive.
When one biological molecules react with other biomolecules, generally just the functional groups are involved. Therefore, each functional group of biomolecule has a specific role in cell metabolism.
Functional groups of different types of biomolecules are specific groups (moieties) of atoms within molecules that are responsible for the characteristic chemical reactions of those molecules.
These functional groups include such groups as hydroxyl, carbonyl, carboxyl, amino, sulfhydryl, and phosphate groups.
Many biomolecules have more than one functional group.
Each functional group is able to modify the chemical properties of the macromolecules to which it bonds.
Hydroxyl group is the functional group of alcohols. It adds polarity to biological molecules.
Carbonyl groups of aldehydes and ketones generally also increase polarity and reactivity of biological molecules.
Biomolecules containing carbonyls tend to be volatile and stimulate senses with both pleasant and unpleasant odors.
A carboxyl group of carboxylic acids contains both a carbonyl group and a hydroxyl group, bonded to the same carbon atom.
Biological macromolecules containing carboxyl groups are often highly polar and reactive. Common biomolecules, containing the carboxyl functional groups, are fatty acids and amino acids.
Amino groups also increase polarity and reactivity of a biological macromolecule. They readily form hydrogen bonds with other polar molecules and water. Amines are weakly basic.
Amino and carboxyl groups of amino acids react to each other to form peptide bonds of proteins.
Phosphate groups are highly acidic and reactive. Phosphates are essential to the metabolic processes of photosynthesis and cellular respiration.
A transfer of a phosphate group from one molecule to another delivers energy to chemical reactions.
The sulfhydryl (–SH) group is essential to protein stabilization.
Amino acids with –SH groups form bonds called disulfide bridges (S–S bonds) that help protein molecules to take on and maintain a specific shape.
Most biological macromolecules are made from single subunits, or building blocks, called monomers.
The monomers combine with each other using covalent bonds to form larger macromolecules known as polymers.
Polymers can be divided into two groups:
- natural polymers (different types of biomolecules),
- synthetic polymers.
Two main type of reactions involved in synthesis and degradation of biological molecules are hydrolysis and dehydration.
Polymers are broken down into monomers in a process known as hydrolysis, which means “to split water,” a reaction in which a water molecule is used during the breakdown.
In a dehydration reaction, the hydrogen of one monomer combines with the hydroxyl group of another monomer, releasing a molecule of water and forming a polymer.
In a process of hydrolysis, a water molecule is used to brake down a macromolecule into monomers.
Dehydration and hydrolysis reactions are catalyzed by specific enzymes made up of proteins.
4 types of biomolecules (natural polymers) are formed from smaller building blocks called monomers.
4 biological molecules and their monomers
|Carbohydrates||Monosaccharides||energy storage, component of plant cell walls, outer skeleton of insects and related groups|
|Proteins||Amino acids||catalysis, support and structure|
|Nucleic acids (DNA, RNA)||Nucleotides||encoding of hereditary information|
|energy storage, component of cell membranes, message transmission (hormones), pigments in photosynthesis|
References & further readings:
Cooper GM. The Cell: A Molecular Approach. 2nd edition. Sunderland (MA): Sinauer Associates; 2000. The Molecular Composition of Cells. | <urn:uuid:47605eb1-115b-4a4b-94c4-00145f47a14c> | 3.78125 | 1,831 | Knowledge Article | Science & Tech. | 12.986046 | 95,639,308 |
New Haven scientists learn more about ancient sea monster (video)
NEW HAVEN -- Luckily, they're not around anymore, but sea creatures of less than 500 million years ago had to contend with a predator much larger than previously known.
It's the largest example ever found of this type of animal, looking like a 3-foot lobster tail with giant eyes and two gnarly appendages coming off the front of its head that brought unfortunate fish into its circular mouth.
It's "the first big nasty predator we get in the rock record," said Derek Briggs, director of the Yale Peabody Museum of Natural History. The other finding is that it was still living as recently as 472 million years ago in the Ordovician period, 30 million years later than scientists had thought.
"These things disappear from the Cambrian rock record at about 510 million years, and we had no idea whether they just went extinct or whether we weren't finding the right kind of rocks to preserve them in younger sediments," said Briggs.
A former Yale researcher, Peter Van Roy, now at Ghent University in his native Belgium, working with collectors in Morocco, realized the fossils they had found were parts of this sea monster, known as an anomalocaridid. They were invertebrates on an early branch of the tree that includes shrimps, horseshoe crabs and scorpions, Briggs said. But the branch led to a dead end; there are no anomalocaridids around today except those preserved in rock.
"In Morocco south of the Atlas Mountains, we have a very substantial thickness of mudstones over a very wide area, which yield these things," Briggs said. "And that shows that they were actually still around; it's just that we weren't finding them because we weren't looking in the right places."
The find is particularly exciting for Briggs because unusually preserved fossils are his specialty. Holding a fossil that reveals one of the front appendages, he says, "These things were actually interpreted as shrimp bodies ... and when I worked on this as a graduate student back in the '70s I realized that this was not a body but actually some kind of leg, some kind of appendage or limb, but we didn't have the rest of the body at all."
A fossil of the mouth "was originally interpreted as some kind of jellyfish because of its radial symmetry." The only complete specimens were only about 8 inches long, he said.
It wasn't until the 1980s that he and others realized the various parts preserved in rock fit together as a larger animal, about 2 feet long.
Another unusual feature of the creature is the flaps that may have functioned as gills and the filaments that assisted breathing arranged across its back.
"Modern shrimps and horseshoe crabs and other kinds of water-dwelling arthropods have little filaments on their limbs," Briggs said. "In this case you have the filaments right across the back of the animal.
"And it may in some ways have been perhaps something to do with the size of it ... it needed a lot of oxygen exchange with the water because it was such a big animal."
Learning how this predator looked and functioned tells scientists a lot about their fellow sea-dwellers. "The interval of time that we now see them in Morocco was the time when life was beginning to diversify dramatically in the oceans," Briggs said. "And what it means is that these large predators were around at the time and probably other kinds of animals were evolving adaptations to deal with the sorts of pressures that having big predators around would have imposed."
Van Roy's and Briggs' paper about the discovery appears in the May 26 issue of the journal Nature. A National Geographic Society Research and Exploration grant supported the work.
The scientists have yet to name the animal. "The main pitch of the article is that it's huge and it lived another 30 million years" after it was thought to be extinct, Briggs said.
"This was a pretty substantial predator," he said, joking, "If you got in a seafood restaurant it would keep the whole place going for a week or two."
Call Ed Stannard at 203-789-5743. Follow him on Twitter @EdStannardNHR. To receive breaking news first, text the word nhnews to 22700. Standard msg+data rates may apply. | <urn:uuid:711d8053-423a-4d97-babc-360bb413801d> | 3.203125 | 907 | Truncated | Science & Tech. | 55.996052 | 95,639,344 |
The system will have limited access between June 29th and July 20th as the system is transferred to a new server.
Modeling colony collapse disorder in honeybees as a contagion
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Honeybee pollination accounts annually for over $14 billion in United States agriculture alone. Within the past decade there has been a mysterious mass die-off of honeybees, an estimated 10 million beehives and sometimes as much as 90% of an apiary. There is still no consensus on what causes this phenomenon, called Colony Collapse Disorder, or CCD. Several mathematical models have studied CCD by only focusing on infection dynamics. We created a model to account for both healthy hive dynamics and hive extinction due to CCD, modeling CCD via a transmissible infection brought to the hive by foragers. The system of three ordinary differential equations accounts for multiple hive population behaviors including Allee effects and colony collapse. Numerical analysis leads to critical hive sizes for multiple scenarios and highlights the role of accelerated forager recruitment in emptying hives during colony collapse. | <urn:uuid:e89eee45-d4d7-4949-8fc2-d2dbae8e930d> | 2.859375 | 220 | Academic Writing | Science & Tech. | 19.782732 | 95,639,376 |
Ruby can override existing classes and methods.
For example, consider Ruby's String class.
If you create a string, you end up with an object of class String; for example:
x = "This is a test" puts x.class
You can call a number of different methods upon the String object stored in x:
x = "This is a test" puts x.length puts x.upcase
You can override the length method of the String class:
class String def length # w w w .j a va2 s . c o m 20 end end puts "This is a test".length puts "a".length puts "A really long line of text".length | <urn:uuid:61f42cc1-b39f-431c-8032-688ea9a643b3> | 3.703125 | 143 | Documentation | Software Dev. | 97.956333 | 95,639,386 |
This Is Why The Event Horizon Telescope Still Doesn’t Have An Image Of A Black Hole
“Of all the black holes visible from Earth, the largest is at the galactic center: 37 μas.
With a theoretical resolution of 15 μas, the EHT should resolve it.
Despite the incredible news that they’ve detected the black hole’s structure at the galactic center, however, there’s still no direct image.”
Last year, data from the South Pole Telescope, a 10-meter radio telescope located at the South Pole, was added to the Event Horizon Telescope team’s overall set of information. Here we are, though, half a year later, and we still don’t have a direct image of the event horizon for the galactic center’s black hole. There aren’t any problems; the issue is that we have to successfully calibrate and error-correct the data, and that takes time and care to get it right. Science isn’t about getting the answer in the time you have to get it; it’s about getting the right answer in the time it takes to get things right. From that point of view, there’s every reason this is worth waiting for.
The Event Horizon Telescope team is on the right track; here’s where we are right now in our quest to create the first image of a black hole’s event horizon!
The Milky Way Is Hiding Tens Of Thousands Of Black Holes
“This study is of tremendous importance, since it provides us with the first real evidence of what LISA will be looking for, further motivating us to look for these events that, as we now know, must exist. Unlike LIGO’s black holes, these inspiraling events will give us weeks, months, or even years of lead-up time, allowing us to pinpoint exactly where and when we’ll need to look to see these mergers coming. This is the first confirmation of the theory that tens of thousands of black holes ought to exist around supermassive ones at the centers of galaxies, and allows us to better predict how many gravitational wave events we’re likely to see coming from them.“
At the center of our Milky Way, our galaxy houses a supermassive black hole: Sagittarius A*. At four million solar masses, it’s the most massive object in our entire galaxy, while orbiting around it are stars, gas, dust, and many other astrophysical objects. This is a region where new star formation is rampant, and so, in theory, there ought to be many thousands of black holes within just a few light years of Sagittarius A*, some of which ought to be detectable through their emission of X-rays from binary companions. For nearly 20 years, such a detection was elusive, since the flares that occur when black holes absorb large amounts of matter are too rare. But now, using the full suite of archival data from the Chandra X-ray observatory, scientists have found the steady, low-level X-ray emission these systems give off, revealing a population of approximately 10,000 black holes within 3 light years of Sagittarius A*.
The Milky Way is hiding tens of thousands of black holes near the galactic center, and for the first time, we’ve just revealed the surefire signs that they exist.
The Milky Way Is Still Growing, Surprising Scientists
“It’s no big secret that galaxies grow over time. The force of gravity is powerful enough to pull smaller galaxies, gas clouds, and star clusters into larger ones, even over distances of millions of light years. Our own Milky Way has likely devoured hundreds of smaller galaxies over its lifetime, and continues to absorb the dwarf satellites which surround us. But there’s a steadier, more subtle way that galaxies grow: by continuing to form stars from the gas already inside. While most of the stars that form will do so in the plane or central bulge of a spiral galaxy like our own, a new study has shown that galaxies also grow outward over time, meaning that their physical extent increases in space. The implication is that our own galaxy is increasing in size by 500 meters per second: growing by a light year every 600,000 years.”
Imagine a galaxy all by its lonesome out there in the Universe. It’s full of stars, with gas, dust, plasma, and dark matter permeating all throughout it. What’s going to happen to the galaxy over time? You might think that it will continue to form new stars in its spiral arms, while older stars burn out and eventually die. All of that is true, but there’s a subtle but important effect that really adds up over cosmic time: the physical extent of where stars can be found grows as even isolated galaxies age. The Milky Way itself is growing at a rate of 500 m/s, typical of spiral galaxies around this size. It means that by time the Universe is three times as old as it presently is, Milky Way-like galaxies will have grown to be twice as large as they presently are.
While our galaxy itself won’t ever make it to that stage, due to our upcoming merger with Andromeda, many will. Come get the full story here.
This Is How The Milky Way Is Eating Our Galactic Neighbors
“New star formation is triggered by mutual gravitational interactions combined with the Milky Way’s tug.
The gas within these galaxies gets shunted into new clusters, including the local group’s largest star-forming region: 30 Doradus.
But these gravitational interactions also strip the gas away from these dwarfs, where the Milky Way will devour it.
The largest gas stream seems to connect both galaxies, but which cloud it originated from was a mystery.
Until, that is, scientists led by Andrew Fox looked at the absorption effects of this gas from background quasar light.”
While the visible Universe extends for tens of billions of light years, our local group of galaxies extends for only a few million. Around our own Milky Way are a handful of dwarf galaxies, including two bright ones: the Large and Small Magellanic Clouds. These two galaxies contain large numbers of young stars, show evidence of hot, glowing gas, and are destined to be devoured by our Milky Way in cosmically short order. But until that happens, they’re engaged in a cosmic tug-of-war with one another, battling to expel the gas from each other and capture it for themselves. Because the Milky Way is nearby, the expelled gas is getting stretched and drawn into our own galaxy, but which cloud, the Large or the Small, did it arise from?
Owing to new work by a Hubble team led by Andrew Fox, we finally know it’s the Small Magellanic Cloud. Here’s how, and here’s what it means for science.
Einstein’s Ultimate Test: Star S0-2 To Encounter Milky Way’s Supermassive Black Hole
“The largest, closest single mass to Earth is Sagittarius A*, our Milky Way’s supermassive black hole, weighing in at 4,000,000 solar masses.
The star S0-2 makes the closest known approach to this black hole, reaching a minimum distance of just 18 billion kilometers.
That’s only three times the Sun-Pluto distance, or a meager 17 light-hours.”
After a 16 year wait, the closest star to the Milky Way’s supermassive black hole, S0-2, will make its closest approach later this year. At its closest, it should be moving at a whopping 2.5% the speed of light, enabling us to test out Einstein’s relativity in an entirely new regime. We should, for the first time, be able to measure the gravitational redshift from our galactic center, and to track the relativistic “kick” that Einstein’s theory predicts when an orbit gets modified by traveling close to an extremely large mass. New studies have recently shown that S0-2 doesn’t appear to have a binary companion, which makes it even more interesting for such an observation, which won’t come again until the year 2034. As a bonus, scientists hope to shed light on how stars form in the harsh environment of the galactic center at all.
Come find out how the newest test of Einstein could push us past the limits of relativity, or confirm it in an entirely new way!
Milky Way Houses Up To 100 Million Black Holes, With Big Implications For LIGO
“How many black holes are there in the Milky Way? This straightforward question has proven extremely difficult to answer, since black holes are so difficult to directly detect. However, scientists not only have developed indirect methods for locating and even weighing them, we also understand how the Universe forms them: from stars and stellar remnants. If we can understand the different stars that existed at all different times in our galaxy’s history, we should be able to infer exactly how many black holes — and of what mass — exist in our galaxy today. Thanks to a comprehensive study by a trio of researchers from UC Irvine, the first accurate estimates of the number of black holes found in Milky Way-like galaxy have now been made. Not only is our galaxy filled with hundreds of billions of stars, but we also are home to up to 100 million black holes.”
When LIGO announced their first discovery of a black hole-black hole merger, it came as a surprise to almost everyone. The shocking part wasn’t that LIGO had seen merging black holes, but that they were discovered to be so massive. At right around ~30 solar masses each, these were black holes that were much larger than expected, forcing astronomers to confront the fact that they didn’t have a good, comprehensive model for how many black holes – and what mass they should be – were in the Universe. To help this, a trio of researchers from UC Irvine just used the best information we have to simulate galaxy growth and formation, along with stellar evolution, to figure this out. The results they found were that a Milky Way-sized galaxy should have up to 100 million black holes in it, mostly around 10 solar masses each, with a few percent of them being significantly higher in mass. Meanwhile, smaller, lower-mass (and lower-metallicity) galaxies would have fewer black holes that were more massive on average.
This remarkable result gives us our first-ever precise estimate of how many black holes should be in our galaxy, and paves the way for understanding what LIGO (and other gravitational wave observatories) should see in the future!
Are Mass Extinctions Periodic, And Are We Due For One?
“If we start looking at the craters we find on Earth and the geological composition of the sedimentary rock, however, the idea falls apart completely. Of all the impacts that occur on Earth, less than one quarter of them come from objects originating from the Oort cloud. Even worse, of the boundaries between geological timescales (Triassic/Jurassic, Jurassic/Cretaceous, or the Cretaceous/Paleogene boundary), and the geological records that correspond to extinction events, only the event from 65 million years ago shows the characteristic ash-and-dust layer that we associate with a major impact.”
65 million years ago, a catastrophic impact from outer space caused the last great mass extinction on Earth, destroying 30% of the species that lived on our world at the time. These mass extinction events happened many times in Earth’s past, and the Solar System also passes through denser stellar regions of space periodically, as determined by the orbit of the Sun and stars in the Milky Way. It’s a combination of facts that might make you wonder whether the extinction events are also periodic, and if so, whether periodic impacts are predictable. If so, then shouldn’t we be aware of whether we’re living in a time of increased risk, and prepare ourselves for that possibility accordingly? After all, the dinosaurs didn’t have a space program or the capability of deflecting a dangerous object like the one that wiped them out.
But before we go that route, we should take a good look at what the data shows. Are mass extinctions periodic? Are we due? Let’s find out!
How Does Earth Move Through Space? Now We Know, On Every Scale
“Ask a scientist for our cosmic address, and you’ll get quite a mouthful. Here we are, on planet Earth, which spins on its axis and revolves around the Sun, which orbits in an ellipse around the center of the Milky Way, which is being pulled towards Andromeda within our local group, which is being pushed around inside our cosmic supercluster, Laniakea, by galactic groups, clusters, and cosmic voids, which itself lies in the KBC void amidst the large-scale structure of the Universe. After decades of research, science has finally put together the complete picture, and can quantify exactly how fast we’re moving through space, on every scale.”
It’s hard to believe, but despite being at rest here on the surface of Earth, we’re actually hurtling through the Universe in a variety of impressive ways. The Earth spins on its axis, giving someone at the equator a speed of some 1700 km/hr. Yet at even faster speeds, the Earth orbits the Sun, the Sun moves through the Milky Way, and there’s a great cosmic motion that applied to the Milky Way galaxy beyond even that. For a long time, we’ve been able to measure the total effect of all these motions, summed up, by measuring our motion relative to the cosmic microwave background: the leftover glow from the Big Bang. But it’s only very, very recently that we’ve identified the source of all the gravitational causes of this motion. While we’ve known of stars, galaxies, and the large-scale structure of where matter is, it’s new that we’ve quantified the effects of these great cosmic voids.
By combining everything together, we can finally explain the grand total of all of our cosmic motion through the Universe. Come get the full, complete story at last!
We’re Way Below Average! Astronomers Say Milky Way Resides In A Great Cosmic Void
“If there weren’t a large cosmic void that our Milky Way resided in, this tension between different ways of measuring the Hubble expansion rate would pose a big problem. Either there would be a systematic error affecting one of the methods of measuring it, or the Universe’s dark energy properties could be changing with time. But right now, all signs are pointing to a simple cosmic explanation that would resolve it all: we’re simply a bit below average when it comes to density.”
When you think of the Universe on the largest scales, you likely think of galaxies grouped and clustered together in huge, massive collections, separated by enormous cosmic voids. But there’s another kind of cluster-and-void out there: a very large volume of space that has its own galaxies, clusters and voids, but is simply higher or lower in density than average. If our galaxy resided near the center of one such region, we’d measure the expansion rate of the Universe to be higher-or-lower than average when we used nearby techniques. But if we measured the global expansion rate, such as via baryon acoustic oscillations or the fluctuations in the cosmic microwave background, we’d actually arrive at the true, average rate.
We’ve been seeing an important discrepancy for years, and yet the cause might simply be that the Milky Way lives in a large cosmic void. The data supports it, too! Get the story today.
What Will The Death Of The Milky Way Look Like?
“On Earth, we’ve got another billion years or two before the oceans boil and the planet becomes uninhabitable. The Sun will heat up, swell into a red giant, fuse helium in its core, then blow off its outer layers and contract into a white dwarf. But new stars will pop up, too, and shine, and keep the galaxy alive and rife with stars far into the future. But even our own Milky Way will cease to exist: first as we know it, and later on, entirely. When enough time passes, there will be no stars, stellar remnants, or even black holes left at all. This is the cosmic story of the ultimate end of our home in space.”
In the far future, all the galaxies within our Local Group will merge together, with enough gas and stellar material to form trillions upon trillions of new stars. But the amount of fuel is finite, and gravitational interactions are chaotic. At some point, the star forming material contained in our galaxy will come to an end, while more and more stars and stellar remnants are ejected from the galaxy. What will be left, at that point? Just a few stellar corpses orbiting in a halo of dark matter around a central, supermassive black hole. That mass will grow larger and larger, up until a certain point. Once it’s grown all it can, Hawking radiation will result in the decay of that central black hole, unbinding the last structures of normal matter. In the end, there will be nothing left but a large, massive clump of dark matter in the abyss of empty space.
Need something to look forward to? How about the death of the Milky Way, and the return of the Universe to a cold, empty, unstructured state! | <urn:uuid:dd44feab-9417-4e91-b945-7ba830761e11> | 3.109375 | 3,705 | Content Listing | Science & Tech. | 49.061935 | 95,639,389 |
A student in a maths class was trying to get some information from her teacher. She was given some clues and then the teacher ended by saying, "Well, how old are they?"
Can you explain the strategy for winning this game with any target?
Given the products of adjacent cells, can you complete this Sudoku?
Play the divisibility game to create numbers in which the first two digits make a number divisible by 2, the first three digits make a number divisible by 3...
A game for two people, or play online. Given a target number, say 23, and a range of numbers to choose from, say 1-4, players take it in turns to add to the running total to hit their target.
Got It game for an adult and child. How can you play so that you know you will always win?
The clues for this Sudoku are the product of the numbers in adjacent squares.
Arrange the four number cards on the grid, according to the rules, to make a diagonal, vertical or horizontal line.
A game that tests your understanding of remainders.
In this problem we are looking at sets of parallel sticks that cross each other. What is the least number of crossings you can make? And the greatest?
Find a cuboid (with edges of integer values) that has a surface area of exactly 100 square units. Is there more than one? Can you find them all?
If you have only four weights, where could you place them in order to balance this equaliser?
Ben passed a third of his counters to Jack, Jack passed a quarter of his counters to Emma and Emma passed a fifth of her counters to Ben. After this they all had the same number of counters.
What do the numbers shaded in blue on this hundred square have in common? What do you notice about the pink numbers? How about the shaded numbers in the other squares?
Imagine a wheel with different markings painted on it at regular intervals. Can you predict the colour of the 18th mark? The 100th mark?
Starting with the number 180, take away 9 again and again, joining up the dots as you go. Watch out - don't join all the dots!
Investigate the smallest number of moves it takes to turn these mats upside-down if you can only turn exactly three at a time.
Can you find a relationship between the number of dots on the circle and the number of steps that will ensure that all points are hit?
Given the products of diagonally opposite cells - can you complete this Sudoku?
Andrew decorated 20 biscuits to take to a party. He lined them up and put icing on every second biscuit and different decorations on other biscuits. How many biscuits weren't decorated?
Can you fill in this table square? The numbers 2 -12 were used to generate it with just one number used twice.
This article for teachers describes how number arrays can be a useful reprentation for many number concepts.
The planet of Vuvv has seven moons. Can you work out how long it is between each super-eclipse?
A game for 2 or more people. Starting with 100, subratct a number from 1 to 9 from the total. You score for making an odd number, a number ending in 0 or a multiple of 6.
Can you complete this jigsaw of the multiplication square?
Choose any 3 digits and make a 6 digit number by repeating the 3 digits in the same order (e.g. 594594). Explain why whatever digits you choose the number will always be divisible by 7, 11 and 13.
Ben’s class were cutting up number tracks. First they cut them into twos and added up the numbers on each piece. What patterns could they see?
A game for 2 people using a pack of cards Turn over 2 cards and try to make an odd number or a multiple of 3.
Follow the clues to find the mystery number.
Use the interactivity to create some steady rhythms. How could you create a rhythm which sounds the same forwards as it does backwards?
Can you complete this calculation by filling in the missing numbers? In how many different ways can you do it?
Look at three 'next door neighbours' amongst the counting numbers. Add them together. What do you notice?
Can you order the digits from 1-3 to make a number which is divisible by 3 so when the last digit is removed it becomes a 2-figure number divisible by 2, and so on?
Can you work out some different ways to balance this equation?
Have a go at balancing this equation. Can you find different ways of doing it?
Four of these clues are needed to find the chosen number on this grid and four are true but do nothing to help in finding the number. Can you sort out the clues and find the number?
Factors and Multiples game for an adult and child. How can you make sure you win this game?
Suppose we allow ourselves to use three numbers less than 10 and multiply them together. How many different products can you find? How do you know you've got them all?
Investigate the sum of the numbers on the top and bottom faces of a line of three dice. What do you notice?
Here is a machine with four coloured lights. Can you develop a strategy to work out the rules controlling each light?
In a square in which the houses are evenly spaced, numbers 3 and 10 are opposite each other. What is the smallest and what is the largest possible number of houses in the square?
An investigation that gives you the opportunity to make and justify predictions.
What happens if you join every second point on this circle? How about every third point? Try with different steps and see if you can predict what will happen.
In this activity, the computer chooses a times table and shifts it. Can you work out the table and the shift each time?
Nearly all of us have made table patterns on hundred squares, that is 10 by 10 grids. This problem looks at the patterns on differently sized square grids.
I am thinking of three sets of numbers less than 101. Can you find all the numbers in each set from these clues?
I am thinking of three sets of numbers less than 101. They are the red set, the green set and the blue set. Can you find all the numbers in the sets from these clues?
Can you predict when you'll be clapping and when you'll be clicking if you start this rhythm? How about when a friend begins a new rhythm at the same time?
A three digit number abc is always divisible by 7 when 2a+3b+c is divisible by 7. Why?
This big box multiplies anything that goes inside it by the same number. If you know the numbers that come out, what multiplication might be going on in the box? | <urn:uuid:845d4128-705a-4296-b187-341119096891> | 3.328125 | 1,426 | Content Listing | Science & Tech. | 73.622004 | 95,639,411 |
Learn Servlet Life Cycle
If we talk about Servlet Life Cycle, we would need to cover the entire process starting from its initialization till the destruction which is basically wrapped in four stages that are:
This is the initial stage of Servlet Life Cycle in which servlet container loads the servlet from web.xml, which is done either during initiation or when the first request is made. If the attribute <load-on-startup> of web.xml file has a positive value then the Servlet will be loaded else it will load when the first request comes for service. After loading of the servlet, the container creates the instances of the Servlet by using Class.forName(ServletName).newInstance().
Once the instances are created the second stage called Initialization begins in which the servlet container calls the init() method and passes the servlet initialization parameters to the init() method. One thing that is to be known is, the init() must be called by the servlet container prior to the Servlet can serve any request. The initialization parameter continues until the Servlet is destroyed. The init() method is called only once during the entire life cycle of the servlet. The servlet will only be available for service if it is servlet code is loaded successfully without any error otherwise it will be not available for service.
Once the initialization process has been completed successfully, the Servlet becomes available for service. Moreover, servlet creates a separate thread for each of the request made and the the servlet container calls the service() method for servicing any request. The service() method evaluates the kind of request and calls the suitable method (doGet() or doPost()) to execute the request and send response to the client using the methods of the response object.
If the Servlet is no longer needed to serve any request further, the servlet container calls for the destroy() method. Like the init() method this destroy() method is also called only once in the entire life cycle of the servlet. Once the destroy() method is called, it indicates to the servlet container not to send any request for service and the Servlet releases all the resources related to it. Java Virtual Machine is responsible for the memory associated with the resources for garbage collection.
For complete Servlet Life Cycle Example: Click here | <urn:uuid:34329306-49ad-453b-a735-bb91212f947f> | 2.796875 | 473 | Documentation | Software Dev. | 36.198262 | 95,639,417 |
Species Detail - Collybia distorta - Species information displayed is based on all datasets.
Terrestrial Map - 10kmDistribution of the number of records recorded within each 10km grid square (ITM).
Marine Map - 50kmDistribution of the number of records recorded within each 50km grid square (WGS84).
Agaricus distortus, Collybia prolixa var. distorta, Rhodocollybia prolixa var. distorta
5 September (recorded in 1992)
21 October (recorded in 2004)
National Biodiversity Data Centre, Ireland, Collybia distorta, accessed 19 July 2018, <https://maps.biodiversityireland.ie/Species/158506> | <urn:uuid:9a26f2f5-f797-4445-84d1-7787523526ed> | 2.78125 | 155 | Structured Data | Science & Tech. | 29.392658 | 95,639,431 |
In the above code snippet, notice that we have used a .js file called ModernizrBuild.js that has been downloaded from http://www.modernizr.com/download/ website.
It basically helps us to check if a particular feature of HTML5 is supported in the browser or not. To know more about the Modernizr, please visit its website as mentioned above.
Coming to the above code snippet, in this case we are using Modernizr to check if audio is supported into the browser from which our page is browsed. If not, on the page loads user gets “Audio is NOT supported” as an alert.
As soon as the page loads, it checks for the Modernizr.audio property, if this is true it means that audio is supported in the browser that is being used to browse this page.
Next we have found out the audio, volume and seekbar elements on the page and stored them in the variable.
On load of the window we have set the
durationchange event of the audio element that helps us to update the time elapsed for audio play in the label element and setting the min and max range for the seekbar range element. We are also setting the volume element value to the default audio element volume that will be the system default volume.
On change of the volume range element, we have set audio volume to the value selected by the user. If the value selected by the user is 0, we simply mute the audio otherwise unmute it.
In this function, we are setting the minimum and maximum range of the seekbar range element.
In this function, we are setting the current time of the audio element to the seekbar selected value by the user.
In this function, we are simply getting the current position of the audio play and getting the hour, minute and seconds lapsed and writing in the label element. We are also setting the seekbar min, max and value to the audio startTime, duration and currentTime values respectively so that the seekbar value is in sync with the audio running position.
This function simply checks if audio is paused, it plays (by calling the play() method on audio element) the audio else if it is ended already then change its position to 0 (ie beginning) and plays it.
This function checks if the audio is already playing, if yes then call pause() function that pauses the audio.
In this function, we check if the audio is muted already, then set muted property of the audio element to false so that it will be unmuted and set the volume range element to the audio volume. If the audio is not muted then it mutes and set the volume range element to 0.Views: 3670 | Post Order: 103 | <urn:uuid:313cea2e-54b5-4ebd-91e8-0a0f5f9fe3f5> | 2.6875 | 567 | Documentation | Software Dev. | 53.029117 | 95,639,444 |