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inductance(redirected from Magnetic mutual induction)
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Related to Magnetic mutual induction: Coefficient of coupling
1. The property of an electric circuit by which an electromotive force is induced in it as the result of a changing magnetic flux.
2. A circuit element, typically a conducting coil, in which electromotive force is generated by electromagnetic induction.
1. (General Physics) Also called: induction the property of an electric circuit as a result of which an electromotive force is created by a change of current in the same circuit (self-inductance) or in a neighbouring circuit (mutual inductance). It is usually measured in henries. Symbol: L See also self-inductance, mutual inductance
2. (General Physics) another name for inductor
1. the property of a circuit by which a change in current induces, by electromagnetic induction, an electromotive force.
The property of an electric circuit that makes it possible for an electromotive force to be created in a nearby circuit by a change of current in either circuit.
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|Noun||1.||inductance - an electrical phenomenon whereby an electromotive force (EMF) is generated in a closed circuit by a change in the flow of current|
electrical phenomenon - a physical phenomenon involving electricity
mutual induction - generation of electromotive forces in each other by two adjacent circuits
self-induction - generation of an electromotive force (EMF) in a circuit by changing the current in that circuit; usually measured in henries
|2.||inductance - an electrical device (typically a conducting coil) that introduces inductance into a circuit|
electrical device - a device that produces or is powered by electricity | <urn:uuid:36a6bfcf-7099-4b96-80fc-a53d19a72454> | 2.890625 | 378 | Structured Data | Science & Tech. | 15.742669 | 95,561,768 |
|Event type||Gamma-ray burst|
|Date||5 March 1979|
It was an extremely bright burst that was successfully localized to supernova remnant N49 in the Large Magellanic Cloud. This event is now interpreted as a magnetar giant flare, more related to SGR flares than "true" gamma-ray bursts. It is the first observed SGR megaflare, a specific type of short GRB. It has been associated with the pulsar PSR B0525-66.GRB 790305b is an event that took place on 5 March 1979.
On 5 March 1979, two Soviet spacecraft that were then drifting through the Solar System were hit by a blast of gamma radiation at approximately 10:51 EST. This contact raised the radiation readings on both the probes from a normal 100 counts per second to over 200,000 counts a second, in only a fraction of a millisecond.
This burst of gamma rays quickly continued to spread. Eleven seconds later, Helios 2, a NASA probe, which was in orbit around the Sun, was saturated by the blast of radiation. It soon hit Venus, and the Pioneer Venus Orbiter's detectors were overcome by the wave. Seconds later, Earth received the wave of radiation, where the powerful output of gamma rays inundated the detectors of three U.S. Department of Defense Vela satellites, the Soviet Prognoz 7 satellite, and the Einstein Observatory. Just before the wave exited the Solar System, the blast also hit the International Sun-Earth Explorer. This extremely powerful blast of gamma radiation constituted the strongest wave of extra-solar gamma rays ever detected; it was over 100 times more intense than any known previous extra-solar burst. Because gamma rays travel at the speed of light and the time of the pulse was recorded by several distant spacecraft as well as on Earth, the source of the gamma radiation could be calculated to an accuracy of about 2 arcseconds. The direction of the source corresponded with the remnants of a star that had gone supernova around 3000 B.C.E. It was in the Large Magellanic Cloud and the source was named SGR 0525-66, the event itself was named GRB 790305b, the first observed SGR megaflare.
- Guo Qiu-Shuang; Shi Tian-Yi (1990). "Properties of the 1979 March 5 gamma-ray burst source". Chinese Astronomy and Astrophysics. 14 (2): 148. Bibcode:1990AcApS..10...36G. doi:10.1016/0275-1062(90)90036-D.
- "PSR B0525-66". SIMBAD. Centre de données astronomiques de Strasbourg.
- Kouveliotou, C.; Duncan, R. C.; Thompson, C. (February 2003). "Magnetars Archived 11 June 2007 at the Wayback Machine.". Scientific American; Page 35.
- Cline, T. L.; Desai, U. D.; Teegarden, B. J.; Evans, W. D.; Klebesadel, R. W.; Laros, J. G. (April 1982). "Precise source location of the anomalous 1979 March 5 gamma-ray transient". Journal: Astrophysical Journal. 255: L45–L48. Bibcode:1982ApJ...255L..45C. doi:10.1086/183766.
- Kouveliotou, C.; Duncan, R. C.; Thompson, C. (February 2003). "Magnetars Archived 11 June 2007 at the Wayback Machine.". Scientific American; Page 36. | <urn:uuid:6905ba1d-6e43-4d67-aba1-93f801aee62f> | 3.421875 | 770 | Knowledge Article | Science & Tech. | 75.029533 | 95,561,785 |
Adamson, Andrew C; Richards, Hugh G (1990): Chemistry of very young basalts from ODP Hole 106-648B. PANGAEA, https://doi.org/10.1594/PANGAEA.745386, Supplement to: Adamson, AC; Richards, HG (1990): Low-temperature alteration of very young basalts from ODP Hole 648B: Serocki Volcano, Mid-Atlantic ridge. In: Detrick, R; Honnorez, J; Bryan, WB; Juteau, T; et al. (eds.), Proceedings of the Ocean Drilling Program, Scientific Results, College Station, TX (Ocean Drilling Program), 106/109, 181-194, https://doi.org/10.2973/odp.proc.sr.106109.140.1990
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Basalts in Hole 648B, located in the rift valley of the Mid-Atlantic Ridge at 23°N in crust estimated to be less than 100,000 years old, are mainly fresh, but small amounts of secondary phases are found on fracture surfaces and in alteration halos within the rocks. The halos are defined by dark bands 1-4 mm thick that have developed parallel to fracture surfaces or pillow margins and which in some cases have migrated some centimeters into the rock. The dark bands are the principal locus of secondary phases. The secondary phases are olive-green and yellow protoceladonites, of composition and structure intermediate between celadonite and iron-rich saponite, red (Mn-poor) to opaque (Mn-rich) iron oxyhydroxides, mixtures of protoceladonite and iron oxyhydroxide, and rare manganese oxides. These phases occur mainly as linings or fillings of open spaces in the basalt within the dark bands. Sulfides and intersertal glass are the only primary phases that can be seen to have been altered. Where dark bands have migrated into the rock, the rock behind the advancing band is almost devoid of secondary phases, implying redissolution. The potassium and magnesium in the secondary phases could have been supplied from ambient seawater. The aluminum in the protoceladonites must have been derived from local reaction of intergranular glass. The source of iron and silica could have been intergranular glass or low temperature mineralizing solutions of the type responsible for the formation of deposits of manganese oxides and iron oxyhydroxides and silicates on the seafloor.
Latitude: 22.922000 * Longitude: -44.947100
Date/Time Start: 1985-11-11T12:00:00 * Date/Time End: 1985-12-12T02:00:00
106-648B * Latitude: 22.922000 * Longitude: -44.947100 * Date/Time Start: 1985-11-11T12:00:00 * Date/Time End: 1985-12-12T02:00:00 * Elevation: -3344.0 m * Penetration: 33.3 m * Recovery: 6.77 m * Location: North Atlantic Ocean * Campaign: Leg106 * Basis: Joides Resolution * Device: Drilling/drill rig (DRILL) * Comment: 6 cores; 40.8 m cored; 0 m drilled; 16.6 % recovery | <urn:uuid:18adedbc-9a09-40c4-a7fd-a7f8f63396de> | 2.53125 | 730 | Academic Writing | Science & Tech. | 58.294135 | 95,561,794 |
Study of Sun-like star to help understand solar cycle's effect on Earth's climateThe researchers have found a star located 120 light years away in the constellation of Cygnus which is identical to Sun in mass, radius and age.
The researchers have discovered a star which can help extent our knowledge of solar cycles and comprehend its effect on Earth's climate.
The new star is almost identical to the Sun, except for the chemical composition, making it a ‘Rosetta Stone’ for the study of the solar body’s variability and effect on the Earth’s climate.
The spots on the surface of the Sun come and go with an 11-year periodicity known as the solar cycle. The solar cycle is driven by the solar dynamo, which is an interplay between magnetic fields, convection and rotation. However, our understanding of the physics underlying the solar dynamo is far from complete.
Now, an international team led by researchers from Aarhus University in Denmark has found a star that can help shed light on the physics underlying the solar dynamo. The star is located 120 light years away in the constellation of Cygnus, and on the surface, the star looks just like the Sun: it has the same mass, radius and age – but its chemical composition is very different.
It consists of around twice as many heavy elements as in the Sun. Heavy elements are the ones heavier than hydrogen and helium. The new study can help us understand how the irradiance of the Sun has changed over time, which is likely to have an effect on our climate, researchers said. The team has succeeded in combining observations from the Kepler spacecraft with ground-based observations dating as far back as 1978, thereby reconstructing a 7.4-year cycle in this star.
“The unique combination of a star almost identical to the Sun, except for the chemical composition, with a cycle that has been observed from both the Kepler spacecraft and from ground makes this star a Rosetta Stone for the study of stellar dynamos,” said Christoffer Karoff from Aarhus University. By combining photometric, spectroscopic and asteroseismic data, the team collected the most detailed set of observations for a solar-like cycle in any star other than the Sun.
The observations revealed that the amplitude of the cycle seen in the star’s magnetic field is more than twice as strong as what is seen on the Sun, and the cycle is even stronger in visible light. This allowed the team to conclude that more heavy elements make a stronger cycle
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Human fingernails score a 2 on the Mohs scale of hardness.
The Mohs hardness test, developed by Friedrich Mohs, tests the hardness of unknown mineral samples against a series of known samples. The test is useful because a mineral’s hardness is very stable. In contrast, appearance can vary markedly depending on where a mineral is found. The known samples used in the test, numbered 1 through 10, include talc, gypsum, calcite, fluorite, apatite, orthoclase feldspar, quartz, topaz, corundum and diamond. Since Mohs first devised his test, others have added minerals to the scale, allowing the test to give scores like 4.5 or 6.3. There are also common, everyday equivalents to many of the minerals he used (see Resources).
1. Clean the unknown mineral. Use the brush to obtain a clean surface.
2. Scratch the unknown with one of the reference samples. If the mineral seems hard, start with one of the harder samples. If the mineral seems soft, start with a softer sample.
3. Examine the unknown sample after you’ve tried to scratch it. Use a magnifying glass if needed. If you see that you’ve made a scratch, wipe with cloth and attempt to scratch your unknown with a softer reference sample. If you did not succeed in scratching your unknown, try the next harder reference sample.
4. Repeat the scratching process until you have identified the hardest Mohs reference sample that will not scratch the unknown mineral. Your unknown’s Mohs hardness falls between the number of that sample and that number plus one. | <urn:uuid:e4253dda-fd4d-4ad8-bcc1-372c0e3e1d01> | 3.421875 | 344 | Tutorial | Science & Tech. | 62.10609 | 95,561,830 |
In additive number theory, the Schnirelmann density of a sequence of numbers is a way to measure how "dense" the sequence is. It is named after Russian mathematician Lev Schnirelmann, who was the first to study it.
The Schnirelmann density of a set of natural numbers A is defined as
The Schnirelmann density is well-defined even if the limit of A(n)/n as n → ∞ fails to exist (see asymptotic density).
By definition, 0 ≤ A(n) ≤ n and n σA ≤ A(n) for all n, and therefore 0 ≤ σA ≤ 1, and σA = 1 if and only if A = N. Furthermore,
The Schnirelmann density is sensitive to the first values of a set:
Consequently, the Schnirelmann densities of the even numbers and the odd numbers, which one might expect to agree, are 0 and 1/2 respectively. Schnirelmann and Yuri Linnik exploited this sensitivity as we shall see.
If we set , then Lagrange's four-square theorem can be restated as . (Here the symbol denotes the sumset of and .) It is clear that . In fact, we still have , and one might ask at what point the sumset attains Schnirelmann density 1 and how does it increase. It actually is the case that and one sees that sumsetting once again yields a more populous set, namely all of . Schnirelmann further succeeded in developing these ideas into the following theorems, aiming towards Additive Number Theory, and proving them to be a novel resource (if not greatly powerful) to attack important problems, such as Waring's problem and Goldbach's conjecture.
Theorem. Let and be subsets of . Then
Note that . Inductively, we have the following generalization.
Corollary. Let be a finite family of subsets of . Then
The theorem provides the first insights on how sumsets accumulate. It seems unfortunate that its conclusion stops short of showing being superadditive. Yet, Schnirelmann provided us with the following results, which sufficed for most of his purpose.
Theorem. Let and be subsets of . If , then
Theorem. (Schnirelmann) Let . If then there exists such that
A subset with the property that for a finite sum, is called an additive basis, and the least number of summands required is called the degree (sometimes order) of the basis. Thus, the last theorem states that any set with positive Schnirelmann density is an additive basis. In this terminology, the set of squares is an additive basis of degree 4. (About an open problem for additive bases, see Erdős–Turán conjecture on additive bases.)
Theorem. (Mann 1942) Let and be subsets of . In case that , we still have
Let and be natural numbers. Let . Define to be the number of non-negative integral solutions to the equation
and to be the number of non-negative integral solutions to the inequality
in the variables , respectively. Thus . We have
The volume of the -dimensional body defined by , is bounded by the volume of the hypercube of size , hence . The hard part is to show that this bound still works on the average, i.e.,
Lemma. (Linnik) For all there exists and a constant , depending only on , such that for all ,
With this at hand, the following theorem can be elegantly proved.
Theorem. For all there exists for which .
We have thus established the general solution to Waring's Problem:
Corollary. (Hilbert 1909) For all there exists , depending only on , such that every positive integer can be expressed as the sum of at most many -th powers.
In 1930 Schnirelmann used these ideas in conjunction with the Brun sieve to prove Schnirelmann's theorem, that any natural number greater than one can be written as the sum of not more than C prime numbers, where C is an effectively computable constant: Schnirelmann obtained C < 800000. Schnirelmann's constant is the lowest number C with this property.
Khintchin proved that the sequence of squares, though of zero Schnirelmann density, when added to a sequence of Schnirelmann density between 0 and 1, increases the density:
This was soon simplified and extended by Erdős, who showed, that if A is any sequence with Schnirelmann density α and B is an additive basis of order k then
and this was improved by Plünnecke to
Sequences with this property, of increasing density less than one by addition, were named essential components by Khintchin. Linnik showed that an essential component need not be an additive basis as he constructed an essential component that has xo(1) elements less than x. More precisely, the sequence has
elements less than x for some c < 1. This was improved by E. Wirsing to
For a while, it remained an open problem how many elements an essential component must have. Finally, Ruzsa determined that an essential component has at least (log x)c elements up to x, for some c > 1, and for every c > 1 there is an essential component which has at most (log x)c elements up to x.
- Schnirelmann, L.G. (1930). "On the additive properties of numbers", first published in "Proceedings of the Don Polytechnic Institute in Novocherkassk" (in Russian), vol XIV (1930), pp. 3-27, and reprinted in "Uspekhi Matematicheskikh Nauk" (in Russian), 1939, no. 6, 9–25.
- Schnirelmann, L.G. (1933). First published as "Über additive Eigenschaften von Zahlen" in "Mathematische Annalen" (in German), vol 107 (1933), 649-690, and reprinted as "On the additive properties of numbers" in "Uspekhin. Matematicheskikh Nauk" (in Russian), 1940, no. 7, 7–46.
- Nathanson (1996) pp.191–192
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- Nathanson (1996) p.208
- Gelfond & Linnik (1966) p.136
- Helfgott, Harald A. (2013). "Major arcs for Goldbach's theorem". arXiv: [math.NT].
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- Helfgott, Harald A. (2013). "The ternary Goldbach conjecture is true". arXiv: [math.NT].
- Helfgoot, Harald A. (2015). "The ternary Goldbach problem". arXiv: [math.NT].
- Ruzsa (2009) p.177
- Ruzsa (2009) p.179
- Linnik, Yu. V. (1942). "On Erdõs's theorem on the addition of numerical sequences". Mat. Sb. 10: 67–78. Zbl 0063.03574.
- Ruzsa (2009) p.184
- Hilbert, David (1909). "Beweis für die Darstellbarkeit der ganzen Zahlen durch eine feste Anzahl nter Potenzen (Waringsches Problem)". Mathematische Annalen. 67 (3): 281–300. doi:10.1007/BF01450405. ISSN 0025-5831. MR 1511530.
- Schnirelmann, L.G. (1930). "On additive properties of numbers". Ann. Inst. polytechn. Novočerkassk (in Russian). 14: 3–28. JFM 56.0892.02.
- Schnirelmann, L.G. (1933). "Über additive Eigenschaften von Zahlen". Math. Ann. (in German). 107: 649–690. doi:10.1007/BF01448914. Zbl 0006.10402.
- Mann, Henry B. (1942). "A proof of the fundamental theorem on the density of sums of sets of positive integers". Annals of Mathematics. Second Series. Annals of Mathematics. 43 (3): 523–527. doi:10.2307/1968807. ISSN 0003-486X. JSTOR 1968807. MR 0006748. Zbl 0061.07406.
- Gelfond, A.O.; Linnik, Yu. V. (1966). L.J. Mordell, ed. Elementary Methods in Analytic Number Theory. George Allen & Unwin.
- Mann, Henry B. (1976). Addition Theorems: The Addition Theorems of Group Theory and Number Theory (Corrected reprint of 1965 Wiley ed.). Huntington, New York: Robert E. Krieger Publishing Company. ISBN 0-88275-418-1. MR 0424744. External link in
- Nathanson, Melvyn B. (1990). "Best possible results on the density of sumsets". In Berndt, Bruce C.; Diamond, Harold G.; Halberstam, Heini; et al. Analytic number theory. Proceedings of a conference in honor of Paul T. Bateman, held on April 25-27, 1989, at the University of Illinois, Urbana, IL (USA). Progress in Mathematics. 85. Boston: Birkhäuser. pp. 395–403. ISBN 0-8176-3481-9. Zbl 0722.11007.
- Ramaré, O. (1995). "On Šnirel'man's constant". Annali della Scuola Normale Superiore di Pisa. Classe di Scienze. Serie IV. 22 (4): 645–706. Zbl 0851.11057. Retrieved 2011-03-28.
- Nathanson, Melvyn B. (1996). Additive Number Theory: the Classical Bases. Graduate Texts in Mathematics. 164. Springer-Verlag. ISBN 0-387-94656-X. Zbl 0859.11002.
- Nathanson, Melvyn B. (2000). Elementary Methods in Number Theory. Graduate Texts in Mathematics. 195. Springer-Verlag. pp. 359–367. ISBN 0-387-98912-9. Zbl 0953.11002.
- Khinchin, A. Ya. (1998). "Three Pearls of Number Theory". Mineola, NY: Dover. ISBN 978-0-486-40026-6. Has a proof of Mann's theorem and the Schnirelmann-density proof of Waring's conjecture.
- Artin, Emil; Scherk, P. (1943). "On the sums of two set of integers". Ann. of Math. 44: 138–142.
- Cojocaru, Alina Carmen; Murty, M. Ram (2005). An introduction to sieve methods and their applications. London Mathematical Society Student Texts. 66. Cambridge University Press. pp. 100–105. ISBN 0-521-61275-6.
- Ruzsa, Imre Z. (2009). "Sumsets and structure". In Geroldinger, Alfred; Ruzsa, Imre Z. Combinatorial number theory and additive group theory. Advanced Courses in Mathematics CRM Barcelona. Elsholtz, C.; Freiman, G.; Hamidoune, Y. O.; Hegyvári, N.; Károlyi, G.; Nathanson, M.; Solymosi, J.; Stanchescu, Y. With a foreword by Javier Cilleruelo, Marc Noy and Oriol Serra (Coordinators of the DocCourse). Basel: Birkhäuser. pp. 87–210. ISBN 978-3-7643-8961-1. Zbl 1221.11026. | <urn:uuid:ca386120-0eef-4bf2-9547-9da6bfa5b6a4> | 3.15625 | 2,677 | Knowledge Article | Science & Tech. | 76.683923 | 95,561,869 |
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Energy Band Structures of Semiconductors
It is well known that the physical properties of semiconductors are understood with the help of energy band structures. The energy states or energy band structures of electrons in crystals reflect the periodic potential of the crystals and they can be calculated when we know the exact shape and the magnitude of the crystal potentials. The shape and the magnitude of the potential are not determined directly from any experimental methods, and thus we have to calculate or estimate the energy bands by using the assumed potentials. Many different approaches to calculations of energy bands have been reported, but in this textbook we will deal with several methods, which are not so difficult to understand. We begin with the most simplified method to calculate electronic states in a model crystal.
KeywordsEnergy Band Brillouin Zone Fourier Coefficient Conduction Band Minimum Energy Band Structure
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The following references review the energy band structures and optical properties of semiconductors in detail and give a good introduction to semiconductor physics
- 1.1C. Kittel: Introduction to Solid State Physics, 7th edn. (John Wiley, New York, 1996)Google Scholar
- 1.2C. Kittel: Quantum Theory of Solids (John Wiley, New York, 1963)Google Scholar
- 1.3J. Callaway: Quantum Theory of the Solid State, 2 vols. (Academic Press, New York, 1974)Google Scholar
- 1.4W.A. Harrison: Electronic Structure and the Properties of Solids; The Physics of the Chemical Bond (W.H. Freeman, San Francisco, 1980)Google Scholar
- 1.5M. Cardona: Optical Properties and Band Structure ot Germanium and Zincblende-Type Semiconductors, In Proc. Int. School of Physics «Enrico Fermi», (Academic Press, New York, 1972) pp. 514–580Google Scholar
The following references will help readers to understand Chap. 1
- 1.6F. Bassani and G. Pastori Parravicini: Electronic States and Optical Transitions in Solids (Pergamon Press, New York, 1975)Google Scholar
- 1.7P. Yu and M. Cardona: Fundamentals of Semiconductors (Springer, Heidelberg, 1996)Google Scholar
- 1.15G.F. Koster, J.O. Dimmock, R.G. Wheeler and H. Statz: Properties of The Thirty-Two Point Groups (M.I.T. Press, Cambridge, MA, 1963)Google Scholar
The following references are cited in the text
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Construction is expected to begin in 2017 on South Africa’s Square Kilometre Array, the world’s largest radio telescope, and its most powerful. It will be used by scientists to understand how the universe evolved and how stars and galaxies form and change, according to a report in TheConversation.
The Square Kilometre Array is expected to stimulate interest in citizen astronomy across Africa, which already has a rich tradition of watching the night skies, according to Felix Donkor, a doctoral researcher at the University of the Witwatersrand.
The groundbreaking, continent-wide telescope will have a central computer with the processing power of about 100 million personal computers.
This huge project is designed to take down many roadblocks to astronomical progress, TheGuardian reported. “These include searching for the first celestial objects to form in the universe, investigating whether we need to develop a new theory of gravity, and looking for the building blocks of life in space.”
The Square Kilometre Array will peer back into the dark ages and map what has happened in space since then, according to TheGuardian. Astronomers will be able to see the cosmic cataclysms taking place before their eyes.
The project will test general relativity, Einstein’s theory of gravity. For all its remarkable success, general relativity may not be able to describe the strong gravitational fields such as those found near black holes. It is hoped that the Square Kilometre Array will show the weak links in Einstein’s work and provide vital clues needed for a deeper understanding of gravity, said Stuart Clark, an astronomy writer.
South Africa doesn’t have the market on the Square Kilometer Array. It will have sites in Australia and elsewhere in Africa. Eight other African countries will provide sites for radio telescopes that feed the network, according to TheConversation. These include Botswana, Ghana, Kenya, Madagascar, Mauritius, Mozambique, Namibia and Zambia.
The distribution of these countries provides an opportunity to stimulate interest in astronomy in Africa through citizen science, Donkor said in TheConversation.
Citizen science is basically work done by volunteers — public participation and collaboration in scientific research without pay to increase scientific knowledge. People share and contribute to data monitoring and collection programs.
Africa’s night sky has been used traditionally for navigation, time keeping and fertility cycles, Donkor said. It inspired East Africa’s Swahili, people in Eritrea and Djibouti and the Tuareg in the Sahara, renowned for their navigation skills.
You don’t need a doctorate to count stars in constellations to determine light pollution, Donkor said.
Volunteers can identify and track solar storms, observe and create light curves of variable stars, take and upload astrophotographs to a database of outer planet images and search images for tracks left by interplanetary dust grains, among other things.
They can join space-related activities, identifying and recording changes and features in many solar system bodies.
Many countries in Africa have space clubs, planetariums and astronomy societies associated with universities.
Science blogs, social media, and TED Talks have helped make scientific knowledge more accessible through the media. Similarly, citizen science programs are bringing the experimental side of science to the doorstep of lay people.
Sign up for the Moguldom newsletter — business news you need to know about economic empowerment for the digital age, delivered to your inbox. | <urn:uuid:783b0eec-1d3b-43f2-aa66-8decbad9d1ad> | 3.421875 | 718 | News Article | Science & Tech. | 24.23929 | 95,561,893 |
Osmium is a hard heavy metallic element, whose symbol is Os. It has the greatest density of the known chemical elements. It forms octavalent compounds, as OsO4. Osmium is used chiefly as a catalyst, in alloys, and in the manufacture of electric light filaments. It has an atomic weight 190.2, atomic number 76, and valence II, III, IV, and VIII. Its melting point is 3,000º C. | <urn:uuid:a7f25322-64e9-471f-9369-7d846e510ee1> | 2.984375 | 97 | Knowledge Article | Science & Tech. | 67.586765 | 95,561,942 |
Theory of Optical Waveguides
Chapter 2 has reviewed the key results of waveguide theory, particularly with respect to the various optical modes that can exist in the waveguide. A comparison has been made between the physical-optic approach and the ray-optic approach in describing light propagation in a waveguide. In this chapter, the electromagnetic wave theory of the physical-optic approach is developed in detail. Emphasis is placed on the two basic waveguide geometries that are used most often in optical integrated circuits, the planar waveguide and the rectangular waveguide.
KeywordsOptical Waveguide Effective Index Planar Waveguide Waveguide Structure Dielectric Waveguide
Unable to display preview. Download preview PDF.
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- 3.17H. G. Unger: Planar Optical Waveguides and Fibers (University Press, Oxford 1978)Google Scholar | <urn:uuid:03cdd338-37ab-401c-979c-27319e498e54> | 2.84375 | 587 | Truncated | Science & Tech. | 68.930045 | 95,561,959 |
NERC - CONICYT initiative
NERC-CONICYT initiative on the impacts of environmental change from southern Chile to the Antarctic Peninsula
7 January 2016
Three UK-Chile research consortia have been awarded funding in the first joint call to be held between NERC and the Chilean funding agency, CONICYT. Co-funded using CONICYT's International Cooperation programme and NERC's Joint Strategic Response mechanism, a total of £1·65 million has been awarded to these three consortia. Through combined and coordinated access to Chilean and UK Antarctic logistics, bases and ships these consortia will seek to improve our understanding of the impacts of environmental change on terrestrial and marine ecosystems from southern Chile to the Antarctic Peninsula.
The projects will seek to address two key science questions:
- What are the key processes and mechanisms by which ice loss and glacial retreat influence marine and terrestrial ecosystems in a region of rapid environmental change; and
- How have these processes combined to determine previous ecosystem change in areas across this region, and how will they govern future change?
Speaking of these projects, NERC director of science & innovation, Professor Iain Gillespie, said:
"This joint programme is a really important first step in strengthening UK's relationship with Chile as a crucial part of furthering our understanding of the impacts of ice loss and deglaciation in this key region of rapid climate change. It is a great illustration of the flexibility and utility of the Joint Strategic Response mechanism."
Projects will run for up to three years.
- The lead UK-Chile principal investigators and their projects are:
Professor Jemma Wadham, University of Bristol and Professor Verena Haussermann, Pontificia Universidad Católica de Valparaíso - PISCES: Patagonian ice field shrinkage impacts on coastal and fjord ecosystems.
Professor James Scourse, University of Bangor and Professor Antonio Brante Ramirez, Universidad Católica de la Santísima Concepción - Impacts of deglaciation on benthic marine ecosystems in Antarctica.
Dr Kevin Newsham, British Antarctic Survey and Professor Marco Molina Montenegro, Universidad de Talca - Evolutionary history of Colobanthus quitensis and its associated micro-organisms. | <urn:uuid:ee1d4c00-0301-49f8-8195-6246326d5308> | 2.796875 | 480 | News (Org.) | Science & Tech. | 5.18677 | 95,561,971 |
Validating data types Anonymous mobile dirty chatrooms
In addition to the security and performance benefits, parameterized commands provide a convenient method for organizing values passed to a data source.
A Db Parameter object can be created by using its constructor, or by adding it to the Db Parameter Collection by calling the method will take as input either constructor arguments or an existing parameter object, depending on the data provider.
This topic walks through several examples that explain the programming model.
The following table shows the The syntax for parameter placeholders depends on the data source. NET Framework data providers handle naming and specifying parameters and parameter placeholders differently. So, if the user enters ‘01234’ we should see an error message that would instruct the user about what type of data is valid for this field.To start, we create a text field and bring up the properties dialog for the field.Unlike command text, parameter input is treated as a literal value, not as executable code. This helps guard against "SQL injection" attacks, in which an attacker inserts a command that compromises security on the server into an SQL statement. | <urn:uuid:988285f7-0a9c-4ed1-99a9-92d7a6295dce> | 3.28125 | 228 | Documentation | Software Dev. | 29.382403 | 95,561,982 |
The findings, presented in Nature, gives a first glimpse into the molecular architecture of animal egg coats, with important implications for the future of human reproductive medicine and the possibility of developing novel contraceptives.
The beginning of every new life starts with fertilization, the most crucial step of which is the initial species-specific recognition between egg and sperm. The receptors for sperm, proteins ZP3 and ZP2, contain a common sequence that allows them to form a matrix of filaments, the so-called zona pellucida that completely surrounds the egg. The Protein Crystallography Unit at Karolinska Institutet, led by Dr. Luca Jovine, has now determined the structure of the most conserved part of this building block, the ZP-N domain.
"ZP3 was identified almost 30 years ago, but obtaining structural information on this key reproductive protein has been technically challenging due to its high heterogeneity", says Luca Jovine.
The zona pellucida is essential for natural fertilization in mammals. The Karolinska Institutet researchers hope that X-ray crystallographic characterization of a region of ZP3 that is important for its ability to polymerize could help explaining cases of human infertility, as well as lead to the development of novel targeted, non-hormonal contraceptives. The research made on the ZP-N domain has also provided insights that extend beyond the field of reproduction. Among other things, an unexpected parallel has been uncovered with molecular features that are involved in speciation among invertebrates.
Moreover, ZP-N domains are also found in many other extracellular proteins that are unrelated to fertilization, but play important roles in human diseases such as non-syndromic deafness, renal and vascular disorders, and cancer. In the Nature paper, an example is discussed that shows how the structure of ZP-N can be used to understand the molecular basis of some of these disorders.
"Mammalian fertilization involves a highly complex series of events. Our findings pave the way for future investigations into this fascinating subject by providing a first snapshot of the beginning of life at atomic resolution", says Luca Jovine.
The research was supported by Karolinska Institutet, the Swedish Research Council and the EU Sixth Framework Programme.
Publication: 'Crystal structure of the ZP-N domain of ZP3 reveals the core fold of animal egg coats', Magnus Monné, Ling Han, Thomas Schwend, Sofia Burendahl & Luca Jovine, Nature, 4 December 2008.
For more information, please contact:Dr Luca Jovine
Katarina Sternudd | idw
FAU researchers identify Parkinson's disease as a possible autoimmune disease
23.07.2018 | Friedrich-Alexander-Universität Erlangen-Nürnberg
The genes are not to blame
20.07.2018 | Technische Universität München
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....
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Wedge-Filtering of Geomorphologic Terrestrial Laser Scan Data
Received: 4 January 2013 / Revised: 4 February 2013 / Accepted: 8 February 2013 / Published: 20 February 2013
Cited by 9 | PDF Full-text (1559 KB) | HTML Full-text | XML Full-text
Terrestrial laser scanning is of increasing importance for surveying and hazard assessments. Digital terrain models are generated using the resultant data to analyze surface processes. In order to determine the terrain surface as precisely as possible, it is often necessary to filter out
[...] Read more.
Terrestrial laser scanning is of increasing importance for surveying and hazard assessments. Digital terrain models are generated using the resultant data to analyze surface processes. In order to determine the terrain surface as precisely as possible, it is often necessary to filter out points that do not represent the terrain surface. Examples are vegetation, vehicles, and animals. Filtering in mountainous terrain is more difficult than in other topography types. Here, existing automatic filtering solutions are not acceptable, because they are usually designed for airborne scan data. The present article describes a method specifically suitable for filtering terrestrial laser scanning data. This method is based on the direct line of sight between the scanner and the measured point and the assumption that no other surface point can be located in the area above this connection line. This assumption is only true for terrestrial laser data, but not for airborne data. We present a comparison of the wedge filtering to a modified inverse distance filtering method (IDWMO) filtered point cloud data. Both methods use manually filtered surfaces as reference. The comparison shows that the mean error and root–mean-square-error (RSME) between the results and the manually filtered surface of the two methods are similar. A significantly higher number of points of the terrain surface could be preserved, however, using the wedge-filtering approach. Therefore, we suggest that wedge-filtering should be integrated as a further parameter into already existing filtering processes, but is not suited as a standalone solution so far. | <urn:uuid:92320320-c667-4f79-8f68-e34243ef9580> | 2.609375 | 414 | Truncated | Science & Tech. | 26.510249 | 95,562,003 |
Therefore they will try to avoid getting attacked by the human immune system, and therefore they have developed various ways to protect themselves from the human immune system. When safe from the immune system, they can focus on breeding and multiplying, and if they become numerous enough, the human body will experience their presence as an infection. Some bacteria are relatively harmless, while others are fatal. The bacteria avoid being attacked by the human immune system by forming a biofilm - a surface to protect them against the immune system.
"The biofilm contributes to bacterial resistance, and that can cause severe, persistent infections around heart valve implants and in lungs and the urinary tract," explains postdoc. Mikkel Girke Jørgensen from the Department of Biochemistry and Molecular Biology at the University of Southern Denmark. Together with professor Poul Valentin-Hansen from the same institution and scientists from American Eunice Kennedy Shriver National Institute of Child Health and Human Development, Bethesda, and Georgetown University Medical Center, Washington DC, he stands behind the new discovery.The researchers now understand the underlying regulatory mechanisms behind the formation of biofilms. The mechanism involves small RNA molecules, which can affect bacterial gene expression and thus the decision of whether to form biofilm or not.
"We have now established what decides whether they swim or not - and that determines whether they form biofilms or not," explains Mikkel Girke Jørgensen and continues:
"Prospects for the pharmaceutical industry are huge. This increased understanding of biofilm formation may be the first step in creating new ways to treat complicated infections in the future. "
The researchers' work is published in the prestigious journal Genes and Development, 15 May 2013, Vol 27, No. 10.
The work is funded by the Villum Foundation and the Lundbeck Foundation. Lundbeck Foundation has just awarded a new two-year grant of DKK 1,153,646 to go ahead with the work.
Contact:Mikkel Girke Jorgensen, Ph.D. Department of Biochemistry and Molecular Biology.
Birgitte Svennevig | EurekAlert!
Barium ruthenate: A high-yield, easy-to-handle perovskite catalyst for the oxidation of sulfides
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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.
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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Virginia Institute of Marine Science
Data report (Virginia Institute of Marine Science) ; no. 49.
The purpose of this report is to characterize water quality conditions during the 1991 water year, October 1990 through September 1991. Most information is provided in graphical format and only data for the Virginia portion of Chesapeake Bay is included. No interpretation is included, since data analysis is the stated purpose of several other reports. This report and companion data reports provide to both scientists and managers ready access to a portion of the data. It is possible, for example, to quickly examine seasonal patterns, compare conditions at two stations, or see if surface and bottom conditions differ significantly. Trends, inter-annual variations and other important considerations are treated in other reports.
Water Quality, Chesapeake Bay, VA
Curling, K., & Neilson, B. (1993) Water quality in Chesapeake Bay : Virginia portion, water year 1991 : a report to the Virginia Water Control Board. Data report (Virginia Institute of Marine Science) ; no. 49.. Virginia Institute of Marine Science, College of William and Mary. https://doi.org/10.21220/V56W3B | <urn:uuid:f4f09421-dd22-4831-a555-634d99bfa881> | 2.625 | 238 | Knowledge Article | Science & Tech. | 36.400161 | 95,562,019 |
Northern Dusky Salamander
© 2008 Bill Peterman (1 of 44)
Country distribution from AmphibiaWeb's database: Canada, United States
Desmognathus fuscus (Rafinesque, 1820)
D. Bruce Means1
1. Historical versus Current Distribution. The geographic distribution of northern dusky salamanders (Desmognathus fuscus) extends in the United States southwest from Maine, through New England, New York, and Pennsylvania to Virginia, then west to southern and eastern Ohio, southeastern Indiana, eastern Kentucky, eastern Tennessee, and western North Carolina (Petranka, 1998). Northern dusky salamanders also occur in Canada, and are found in Niagara Gorge in Ontario, in southeastern Québec, and in southern New Brunswick. The southern geographic limits of northern dusky salamanders are a poorly delineated contact zone between northern and spotted dusky salamanders (D. conanti) that extends southeast from the Cumberland River in western Kentucky to western South Carolina (see Karlin and Guttman, 1986; Petranka, 1998). Spotted dusky salamanders range from the contact zone to the southwest of the range of northern dusky salamanders, extending from extreme southern Illinois, western Kentucky, and western Tennessee into northern Georgia, Alabama, and Mississippi (Rossman, 1958; E.E. Brown, 1992; Petranka, 1998; Means, this volume). No reductions have been noted in the geographical distribution of northern dusky salamanders.
2. Historical versus Current Abundance. In eastern Kentucky and Tennessee, northern dusky salamander larvae are absent from many streams that drain coal strip mines (Gore, 1983). Throughout their New England and midwestern ranges, urbanization has extirpated many populations, but the species is wide ranging and ubiquitous in small stream valleys. There have been no studies documenting declines.
3. Life History Features.
A. Breeding. Reproduction is semi-aquatic.
i. Breeding migrations. Northern dusky salamanders commonly live within a few feet of streams or in springs and are not known to undertake extensive migrations (Bishop, 1941b). Adults mate during the fall and spring in Virginia (Organ, 1961a) and New York (Bishop, 1941b).
ii. Breeding habitat. Same as adult habitat.
i. Egg deposition sites. Eggs are attached to the undersides of rocks, logs, or other substrates in or near water (see Petranka, 1998).
Maryland salamanders lay eggs from June to early August (Danstedt, 1975) and New York salamanders from early June to late August (Wilder, 1913). In Ohio, females oviposit in the last two weeks in July and the embryos hatch from early September to mid October (Wood and Fitzmaurice, 1948; Dennis, 1962; Orr and Maple, 1978; Juterbock, 1986). Populations in eastern Kentucky and southeastern Ohio oviposit during July, and the eggs incubate for 46–61 d with a median incubation period of 47 d (Juterbock, 1986). In eastern Tennessee, females oviposit from the third week in June to the end of August, and embryos hatch from late August to mid October (Hom, 1987). In other parts of their range, eggs have been found from 28 June–5 October in Indiana (Minton, 1972, 2001); early June to early August in Maryland (Danstedt, 1975, 1979); 11 June–24 September in Massachusetts (Wilder, 1913); July–September in southwestern Pennsylvania (Krzysik, 1980a,b); and late June to mid August in Viriginia (Organ, 1961a). Females lay eggs every year in Maryland (Danstedt, 1975) and North Carolina (Spight, 1967c), but may be biennial in higher altitudes in southwestern Virginia (Organ, 1961a).
ii. Clutch size. There is variation in egg numbers, ranging from 13–34 with means ranging from 21–33 (see Petranka, 1998).
C. Larvae/Metamorphosis. Hatchlings were discovered between 17 June–1 September in Massachusetts (Wilder, 1913); in July and August in Maryland (Danstedt, 1975) and Pennsylvania (Krzysik, 1980a); in August and September in New York (Bishop, 1941b); and in mid September in Ohio (Dennis, 1962). The number of eggs/nest was 5–33 in nine nests in Massachusetts (Wilder, 1913); 22–34 in 44 nests in Pennsylvania (Pawling, 1939); and an average of 26 eggs in seven nests in Ohio (Wood and Fitzmaurice, 1948). Enlarged ovarian ova counts averaged 27 in 18 females from western North Carolina (Spight, 1967c); 21 in 17 Pennsylvania females (Hall, 1977); and 24–33 ova in females from six populations from Maryland (Danstedt, 1975). Larvae transform in late spring and early summer when 9–12 mo old in Maryland (Danstedt, 1975); in July–October when 11–14 mo old in Virginia (Organ, 1961a); and between 11 May–17 June when 8–10 mo old in Massachusetts (Wilder, 1913).
D. Juvenile Habitat. Same as for adults.
E. Adult Habitat. In New York, northern dusky salamanders are found along the margins of small wooded streams, on seepage hillsides, in shallow weed-choked streams with sandy bottoms, and in low boggy places under stones, logs, bark, and other debris on the ground (Bishop, 1941b). In Pennsylvania, they are found along wet streambanks with substrates of medium or coarse gravel and small rocks, and under logs about 15–90 cm from open water (Krzysik, 1979). In Ohio, they frequent the margins of streams, springs, leaf-littered trickles, spring banks with constantly moist soil, and the beds of ephemeral streams; preferred hiding places are under flat rocks and debris that are partially submerged in streams (Karlin and Pfingsten, 1989). Indiana northern dusky salamanders are largely restricted to hillside springs and small, rocky brooks in limestone country, but are sometimes found in river bottomlands in spring seepage areas and are often common in the mouths of caves, but not within caves (Minton, 1972, 2001). Brimley (1944) stated that in North Carolina they are salamanders of small woodland brooks, found in both streams and under rocks, logs, rubbish or other shelter close by, but never in strictly terrestrial surroundings.
F. Home Range Size. Barbour et al. (1969) reported an average home range of 48.4 m2 (25.2–114.5 m2) in 14 northern dusky salamanders found along a creek in east-central Kentucky with a sandstone bed. In strong contrast, along a small limestone stream in Ohio, Ashton (1975) calculated an average home range for 14 northern dusky salamanders of 1.4 m2 (0.1–3.6 m2). Mean activity radii were calculated for 21 Pennsylvania northern dusky salamanders from which home range can be determined (Barthalmus and Bellis, 1972). Population densities ranging between 0.43 and 1.42/m2 and biomass estimates were reported for salamanders in New Hampshire by Burton and Likens (1975b). Densities were calculated for populations at 0.8 m2 in Pennsylvania (Hall, 1977), and between 0.4 and 1.4 animals/m2 in a North Carolina stream bed (Spight, 1967c).
G. Territories. Aggressive behavior has been documented in northern dusky salamanders (Organ, 1961a), but this author speculated that aggressive behavior served as a method of sex recognition. Because of the aggressive behavior among males and high site tenacity of the species (Barthalmus and Bellis, 1969, 1972; Barthalmus and Savidge, 1974; Hom, 1987; Juterbock, 1987), territorial behavior is probably well developed, but no studies have specifically targeted this facet of its biology.
H. Aestivation/Avoiding Dessication. Aestivation is unknown, and probably does not occur. Animals likely avoid dessicating condition by seeking shelter under cover objects or in burrows.
I. Seasonal Migrations. In Ohio between 23 November–21 December, Ashton (1975) reported that salamanders moved into subterranean microhabitats that were warmer by several degrees centigrade upstream from their normal summer home.
J. Torpor (Hibernation). Ashton (1975), following the activity of five salamanders during winter in Ohio, discovered that all were active and burrowed quickly to escape through gravel and broken limestone of their winter streambed retreats when disturbed. The winter retreats were 30–50 cm below the soil surface, which was frozen to a depth of 14 cm. He concluded that at no time were northern dusky salamanders in an inactive state.
K. Interspecific Associations/Exclusions. Northern dusky salamanders have been reported in association (= locally sympatric or syntopic) with seal salamanders (Desmognathus monticola; Organ, 1961a; Krzysik, 1979; Southerland, 1986e), Allegheny Mountain dusky salamanders (D. ochrophaeus; Noble and Evans, 1932; Organ, 1961a; Stewart and Bellis, 1970; Hall, 1977; Orr and Maple, 1978; Krzysik, 1979; Karlin and Pfingsten, 1989; Holumuzki, 1980; Southerland, 1986e; Sharbel and Bonin, 1992; Sharbel et al., 1995), black-bellied salamanders (D. quadramaculatus; Organ, 1961a; Southerland, 1986e), pygmy salamanders (D. wrighti; Organ, 1961a), northern two-lined salamanders (Eurycea bislineata; Spight, 1967c; Stewart and Bellis, 1970; Holumuzki, 1980; Karlin and Pfingsten, 1989), long-tailed salamanders (E. longicauda; Karlin and Pfingsten, 1989), red salamanders (Pseudotriton ruber; Stewart and Bellis, 1970; Karlin and Pfingsten, 1989), mud salamanders (P. montanus; Spight, 1967c; Karlin and Pfingsten, 1989), spring salamanders (Gyrinophilus porphyriticus; Stewart and Bellis, 1970; Krzysik, 1979; Karlin and Pfingsten, 1989), southern ravine salamanders (Plethodon richmondi; Karlin and Pfingsten, 1989; Stewart and Bellis, 1970), northern slimy salamanders (P. glutinosus; Spight, 1967c; Karlin and Pfingsten, 1989), eastern red-backed salamanders (P. cinereus; Karlin and Pfingsten, 1989; Stewart and Bellis, 1970), and marbled salamanders (Ambystoma opacum; Spight, 1967c). Over their extensive geographical distribution, northern dusky salamanders are syntopic with more salamanders than listed above, but such associations rarely have been reported in the literature. Davic (1983) concluded that adult northern dusky salamander females were smaller because of syntopy with seal salamanders in Pennsylvania.
L. Age/Size at Reproductive Maturity. In New York, sexual maturity is reached when salamanders are 24–26 mo old; mating and egg laying follows 1–2 mo later (Bishop, 1941b). In Pennsylvania, age at maturity for males is 3 yr (Hall, 1977). In the Unicoi Mountains of Tennessee, males mature at approximately 2 yr and about 35 mm SVL; but females mature at 3 yr and about 40 mm SVL (Jones, 1986). In Maryland, males mature at 2 yr, females at 3 (Danstedt, 1975). At high elevation sites in Virginia, males become sexually mature at 3.5 yr and females 1 yr later, first ovipositing when 5 yr old (Organ, 1961a). Females in a Tennessee population reproduced on an annual cycle (Hom, 1987). Juterbock (1978) discussed maturity characteristics in northern dusky salamanders from Ohio and Kentucky.
M. Longevity. Snider and Bowler (1992) reported that a wild-caught adult of unknown sex lived 4 yr, 4 mo, and 11 d.
N. Feeding Behavior. Larvae in two studies were found to feed on copepods, chironomid midge larvae, plecopteran nymphs, collembolans, mites, and fingernail clams (Wilder, 1913; Burton, 1976). In the stomachs of 18 adults, Wilder (1913) found the remains of caddisflies, larval and adult dipterans, ants, spiders, beetles, sowbugs, caterpillars, earthworms, amphipods, mites, and molted skins and larvae of northern dusky salamanders. Food items identified from 53 stomachs of northern dusky salamanders from eastern Kentucky were amphipods, chilopods, orthopterans, ephemeridans, odonates, hemipterans, lepidopterans, coleopterans, hymenopterans, dipterans, spiders, and one gastropod (Barbour and Lancaster, 1946). From 83 stomachs from the White Mountains in New Hampshire, Burton (1976) reported many of the same groups plus mites, collembolans, plecopterans, thysanopterans, homopterans, trichopterans, and sphaeriid clams. In stomachs of Indiana northern dusky salamanders, Minton (1972, 2001) found beetles, lepidopteran larvae, ants, dipteran larvae, an ichneumonid wasp, and a stonefly nymph. Montague and Poinski (1976) and Wood et al. (1955) reported on brooding females that had ingested oligochaete annelids. Holumuzki (1980) reported the dietary overlap and synchronous foraging of northern dusky salamanders with two other plethodontids and showed that salamander surface activity was highly correlated with that of potential invertebrate prey. Krzysik (1979) reported niche overlap, niche width, and utilization spectra of prey volumes among Pennsylvania northern dusky salamanders and sympatric Allegheny Mountain Salamanders, seal salamanders, and spring salamanders, but did not list the prey species eaten. Krzysik (1980b) compared gut contents among brooding and non-brooding females, finding significantly more food in the latter, suggesting that brooding females do not actively forage.
O. Predators. Uhler et al. (1939) found that northern dusky salamanders were eaten by northern watersnakes (Nerodia sipedon) and common garter snakes (Thamnophis sirtalis). Black-bellied salamanders (D. quadramaculatus) were reported as predators by Noble and Evans (1932). Raccoons, skunks, opossums, and other small mammals, snakes, and birds probably eat northern dusky salamanders (Karlin and Pfingsten, 1989). Brooding females will cannibalize their own eggs and those of others (Bishop, 1941b; Baldauf, 1947; Wood and Clarke, 1955; Jones, 1986). Cannibalism by adults on larvae was reported by Wilder (1913) and Hamilton (1943).
P. Anti-Predator Mechanisms. Brooding females are hypothesized to keep egg predators away from incubating clutches (Dennis, 1962). Dusky salamanders often bite their predators (garter snakes) and autotomize their tails and flee (Whiteman and Wissinger, 1991).
Q. Diseases. No diseases have been reported.
R. Parasites. Rankin (1937) conducted an exhaustive study of the parasites of northern dusky salamanders in North Carolina, finding the following major groups in both larvae and adults: protozoans, trematodes, cestodes, nematodes, and acanthocephalans. Possible parasitism by roundworms was reported in New Hampshire northern dusky salamanders by Burton (1976).
4. Conservation. Monetary values of $0.25/specimen were assessed for northern dusky salamanders for the purpose of establishing a system to quantify the loss of native amphibians by the activities of man and to provide guidelines for financial penalties in attempts to mitigate or repair damage should population losses occur (Society for the Study of Amphibians and Reptiles Monetary Value of Amphibians Subcommittee, 1989). The absence of larvae of northern dusky salamanders from streams draining coal strip mines in eastern Kentucky and Tennessee appear to be caused by siltation and high metal concentrations (Gore, 1983). Although studies are lacking, there is little doubt that many northern dusky salamander populations have been impacted severely or extirpated in the heavily urbanized and developed areas of its range, which coincide with the most densely human populated region of the United States. Another problem has been the difficulty recognizing the southern limits of the northern dusky salamanders' range, which has been shown to overlap or abut the ranges of several cryptic species, with which it has been confused (e.g., spotted dusky salamanders, Santeetlah dusky salamanders [D. santeetlah], Allegheny Mountain salamanders, Black Mountain salamanders [D. welteri], and even southern dusky salamanders [D. auriculatus]). More studies of the evolutionary relationships of northern dusky alamanders and their relatives are sorely needed to clearly map out their geographic ranges so that studies of their population health and assessment of their conservation status can be made.
1D. Bruce Means
Literature references for Amphibian Declines: The Conservation Status of United States Species, edited by Michael Lannoo, are here.
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Citation: AmphibiaWeb. 2018. <http://amphibiaweb.org> University of California, Berkeley, CA, USA. Accessed 18 Jul 2018.
AmphibiaWeb's policy on data use. | <urn:uuid:dafd31ae-7a0f-4576-8c17-4da4cb91394f> | 3.15625 | 3,942 | Knowledge Article | Science & Tech. | 42.280207 | 95,562,033 |
Tracking the build-up to volcanic eruptions
ASU scientists develop technique using tiny crystal 'time capsules' to trace pulses of heat inside a volcano; may help better predict risk.
Volcanos that erupt explosively are the most dangerous in the world. When they blow, they eject giant clouds of hot ash mixed with gases at temperatures up to 2,000° Fahrenheit that engulf everything in their way.
A new technique developed by Arizona State University scientists, working with colleagues in California, Oregon, Michigan, Singapore, and New Zealand, lets scientists track the heating history of the molten rock, or magma, that feeds explosive volcanos. The technique uses tiny crystals of zircon that form within the magma.
The picture coming from the new research, published June 16 in the journal Science, suggests that pulses of heat in the magma before a volcanic eruption both begin and end more abruptly than scientists previously thought. Moreover, the heat pulses last a shorter time than expected.
The new findings will change how scientists view the internal workings of all volcanos, and it may help them gain a better idea when an active volcano poses the most risk.
The team gathered debris that erupted from New Zealand's Mt. Tarawera about 700 years ago. That eruption, roughly five times the size of the 1980 Mount St. Helens eruption, brought to the surface magma that recorded the volcano's thermal history, including the heat pulses leading up to the eruption.
Tiny bits tell a tale
The magma contained zircon crystals, each less than a millimeter long, which were the focus for the ASU scientists on the team.
"For the first time, we can tell how long ago a given zircon crystal formed — and we can also measure how many heat pulses it has experienced," says geochemist Christy Till, assistant professor in ASU's School of Earth and Space Exploration (SESE). She is a co-author of the Science paper.
"In addition," Till explains, "we can tell how hot those pulses were and how fast the crystals cooled after each of them." This lets geo-scientists build a detailed heat timetable of a volcano's past activity, including what occurred long before any historical records.
"We were especially interested in what events lead up to an eruption," Till says. "To our surprise, we discovered that these zircon crystals are telling us that they mostly led a very sedate, boring life."
The zircon crystals from Mt. Tarawera had formed at least tens of thousands of years ago inside the volcano, as molten rock cooled, says Till. "Over their lifespan, they experienced only a few brief heating events, whereas we had expected to see more prolonged pulses of heating."
The secret to the new findings is an advanced mass spectrometer at ASU, one of a small handful of similar instruments in the United States.
"The key to tracing the thermal history of these crystals is our NanoSIMS instrument," says ASU research assistant professor Maitrayee Bose, who will join the SESE faculty in August. The "SIMS" in the name stands for Secondary Ion Mass Spectrometry, and the "nano" part underscores that it works on very small scales.
As Bose says, "In essence, the NanoSIMS is a highly complex microscope that gives precise information about the elemental and isotopic composition of samples no wider than the width of a human hair." This extreme resolution let the scientists trace successive heat pulses which left marks in the crystals like tree rings.
How does push become bang?
While the discovery involves microscopic-sized crystals, the results will likely have a large effect on the field of volcanology.
"Our idea of how the magma reservoir below a volcano behaves has evolved a lot over the last 10 or 15 years," says Till.
"It's no longer seen as a big blob of magma that resides below a volcano," Till explains. "Instead, these magma bodies are the result of many smaller injections of very hot magma into a cooler mush of crystals and older magma that lies in the shallower parts of the volcano's interior."
Yet how these injections combine to make an eruption is a matter still to be understood, Till says. As scientists track how heat pulses cool off and magma turns mostly into solid crystals, a basic question keeps returning: What causes a volcano to erupt?
"It's a process we don't really understand yet," Till says. "Maybe a very large pulse of magma triggers the volcano to blow, or it could be more complicated. Maybe there's another process in which the magma cools off, forms crystals — and out of the still-hot residue, bubbles of gas form which causes the eruption.
"We simply don't know yet." | <urn:uuid:0ff83155-85fe-4637-98cf-4169635b1de2> | 4.1875 | 993 | Truncated | Science & Tech. | 46.820423 | 95,562,038 |
In the enteric bacteria Escherichia coli and Salmonella enterica, sulfate is reduced to sulfide and assimilated into the amino acid cysteine; in turn, cysteine provides the sulfur atom for other sulfur-bearing molecules in the cell, including methionine. These organisms cannot use methionine as a sole source of sulfur. Here we report that this constraint is not shared by many other enteric bacteria, which can use either cysteine or methionine as the sole source of sulfur. The enteric bacterium Klebsiella aerogenes appears to use at least two pathways to allow the reduced sulfur of methionine to be recycled into cysteine. In addition, the ability to recycle methionine on solid media, where cys mutants cannot use methionine as a sulfur source, appears to be different from that in liquid media, where they can. One pathway likely uses a cystathionine intermediate to convert homocysteine to cysteine and is induced under conditions of sulfur starvation, which is likely sensed by low levels of the sulfate reduction intermediate adenosine-5'-phosphosulfate. The CysB regulatory proteins appear to control activation of this pathway. A second pathway may use a methanesulfonate intermediate to convert methionine-derived methanethiol to sulfite. While the transsulfurylation pathway may be directed to recovery of methionine, the methanethiol pathway likely represents a general salvage mechanism for recovery of alkane sulfide and alkane sulfonates. Therefore, the relatively distinct biosyntheses of cysteine and methionine in E. coli and Salmonella appear to be more intertwined in Klebsiella.
Mendeley saves you time finding and organizing research
Choose a citation style from the tabs below | <urn:uuid:6cbff8cf-ffb1-4252-bb8a-8b9195310c19> | 2.8125 | 381 | Academic Writing | Science & Tech. | 2.351892 | 95,562,039 |
In marine environments, aerobic anoxygenic phototrophic (AAP) bacterial assemblages vary in space and along environmental gradients but the factors shaping their diversity and distribution at different taxonomic levels remain poorly identified. Using sets of sequences encoding the M sub-unit of the photosynthetic apparatus from different oceanic regions, we prioritized the processes underlying AAP bacterial biogeographical patterns. The present analysis offers novel insights into the ecological distribution of marine AAP bacteria and highlights that physiological constraints play a key role in structuring AAP bacterial assemblages at a global scale. Salinity especially seems to favor lineage-specific adaptations. Moreover, by inferring the evolutionary history of habitat transitions, a substantial congruence between habitat and evolutionary relatedness was highlighted. The identification of ecological cohesive clades for AAP bacteria suggests that prediction of AAP bacterial assemblages is possible from marine habitat properties.
Anoxygenic phototrophic bacteria were long considered to be ecological oddities from specialized habitats1 limiting their relevance for the biosphere. This view has been challenged when bacteriochlorophyll a (Bchl a), the primary pigment of anoxygenic photosynthesis, was found to be distributed in surface waters of the open ocean2. This finding attracted a substantial scientific interest because the light-based metabolic strategy of aerobic anoxygenic phototrophic (AAP) bacteria implied a possible significant revision of oceanic energy budget2. However, the ecology of AAP bacteria is still far from being understood3. Unlike classical photosynthesis, the light energy harvested by AAP bacteria does not fuel the CO2 fixation as in autotrophic cells4. Genomic and physiological evidences showed that they are photoheterotrophic bacteria, using both organic substrates and light for their carbon and energy requirements5. This puzzling life style challenged the classical view of bacteria being dependent on recycling dissolved organic matter and raised questions about the selective advantage of phototrophy for heterotrophic bacterial communities. From an ecological view, the parsimonious explanation was that photoheterotrophy enables microbes to survive adverse conditions and/or to outgrow competitors6. It was therefore postulated that the ability to use light may be especially beneficial in nutrient-poor marine environments2. But the hypothesis was repeatedly disproved as AAP bacteria are more abundant in productive marine areas7,8,9,10,11 illustrating that the link between trophic conditions and ecology of AAP bacteria is not trivial. Indeed, besides the unifying property to perform light-dependent energy transduction, AAP bacteria are very diverse in terms of physiology and metabolism2,12.
To gain a more accurate picture of the factors governing the ecology of AAP bacteria, their diversity was investigated in different oceanic regions (e.g. refs10,13,14,15,16), and several studies have attempted to connect the observed patterns with environmental variables (e.g. refs10,15). Although some trends began to emerge, the link between ecological niches, phylogeny and habitat of AAP bacteria remains patchy. Most studies hypothesized that multifactorial parameters, such as geographic distance (e.g. refs16,17) and environmental gradients (e.g. refs15,18,19,20) act in structuring AAP populations, but the respective importance of these factors has not really been explored. Moreover, recent reports suggest that the expected diversity of AAP bacteria was overestimated and that their biogeographical patterns are not so obvious15,20,21.
Determining how environmental conditions control the ecology of AAP bacteria, particularly at a fine taxonomic resolution (i.e., sufficient to identify lineages with distinct traits), is critical for understanding how these organisms populate the oceans and contribute to global carbon cycling. Following this idea, the objectives of the present study were (i) to provide elements establishing the role of the environmental context in structuring AAP bacterial diversity, (ii) to prioritize the processes (i.e, deterministic vs stochastic) responsible for generating AAP bacterial patterns in marine environments, (iii) to determine if a link between phylogeny and habitat preferendum exists. To this aim, we analyzed the sequence polymorphism of the gene encoding for the M subunit of the core photosynthetic apparatus (pufM gene) of AAP bacteria in contrasted oceanic provinces encompassing different marine regions, distinct nutrient status and oceanic regimes, various temperatures, salinities and depths.
The pufM dataset used in this study was assembled from sequences previously generated from 27 samples collected during 4 cruises (PROSOPE, BOUM, ARCTIC and MALINA) which took place between 1999 and 2009 in different oceanic regions (Mediterranean, North Pacific to Western Beaufort Sea, Barents and Norwegian seas; Fig. 1a). The cruise transects encompass three major oceanic biomes (polar, westerly winds and coastal boundary zone) and six oceanic provinces [Atlantic Subarctic, Atlantic Arctic, Boreal Polar, Canary coastal, Pacific Subarctic gyres and Mediterranean Sea-Black Sea, Table S1] encompassing large ranges of salinities (Fig. 1b) and temperatures (Fig. 1c), distinct nutrient status (Fig. 1d–h) and oceanic regimes (Table S1) and various depths (Table S1).
All of the ~300 pufM sequences were generated by classical cloning-sequencing approaches after amplification by a same primer pair, to give 245 bp PCR products, avoiding biases in the comparison of the relative abundance of OTUs. The sequences were grouped into OTUs, at 94% nucleic acid sequence similarity, using the furthest neighbor clustering method. The number of OTUs in each set of pufM sequences was variable (20 to 48 OTUs), presumably due to a different number of sequences in the primary datasets (Table S2). Despite those differences, coverage values indicated that most diversity in most sequence sets has been retrieved (Table S2). A total of 107 OTUs were identified for the overall dataset with a coverage value of 96% (Table S2, Supplemental material SI1). Only 6 OTUs exhibited a degree of paraphyly (paraphyly index (PI) comprised between 0.01 and 0.08), the other 101 OTUs were monophyletic (PI = 0, data not shown).
Comparisons of pufM datasets
We used community ecology methods to analyze the structure of AAP bacterial communities using two metrics that each emphasized different community characteristics. Bray-Curtis provides a measure of community composition differences between samples based on OTU counts, regardless of taxonomic assignment22. UniFrac quantifies community similarity based on the phylogenetic relatedness23. Both methods showed that AAP bacterial communities exhibited divergent structure of their diversity (Fig. 2a) and phylogenetic composition (Fig. S1) over stations. Nevertheless, at a broader scale, each oceanic region consistently clustered together (Fig. 2a, Fig. S1) illustrating that AAP bacterial signatures were unique to each oceanic region (Mediterranean Sea, Beaufort, Barents and Norwegian seas) (Fig. 2a).
To obtain deeper insights into the differences in AAP bacterial community composition, we also assessed the number of shared OTUs and sequences between marine regions. No OTU was common to all oceanic areas investigated here and many were only detected in one sample (Fig. 2a,b). A few dominant OTUs were shared across oceanic regions (Fig. 2b,c). For example, the 7 OTUs common to the Mediterranean (PROSOPE and BOUM datasets) and the Barents and the Norwegian Seas (ARCTIC dataset) covered more than 56% of the pufM sequences retrieved from these oceanic biomes (Fig. 2b,c). Similarly, the 3 OTUs shared by the ARCTIC and MALINA datasets grouped 104 pufM sequences (~20% of sequences; Fig. 2b,c). OTUs common to at least two oceanic regions, hereafter identified as subcosmopolitan OTUs, were affiliated to α- and γ-Proteobacteria within similar proportions (25% and 28%, respectively, Fig. 2a). In contrast, all OTUs affiliated to β-Proteobacteria were detected in only one oceanic region (Fig. 2a). Applying the ecological concept of indicator species according to Auguet et al.24 (i.e. specialist lineages the most frequently represented in most sites of an oceanic region), we identified only 8 indicator lineages (significant IndVal index (P < 0.05)) for the four marine environment analyzed (Fig. 2a). Half of them (OTUs 007, 008, 011, 020) were characteristic of the Barents and Norwegian seas, 2 (OTUs 001, 017) of the western Beaufort Sea, and the OTUs 006, 012 were specific of the Mediterranean Sea (Fig. 2a).
Spatial species turnover
The AAP community similarity between each pairwise set of samples decayed significantly (p < 0.000001) with the geographic distance (Fig. 3). To deeply understand the link between AAP bacterial communities and geographical distance, we compared them using similarity matrices and Mantel tests. Distance matrices for environmental variables and geographic distance were measured by the Euclidean distance between values at two stations. We used Mantel tests to determine the correlation between species similarity matrices and environmental and geographic distance (Table 1). The Mantel correlation (Mc) between species similarity and geographic distance (0.75, p = 0.000001) was higher than with environmental factors (0.45, p = 0.000001). Simple Mantel tests also revealed that environmental factors and geographic distance were significantly correlated (0.38, p = 0.000001). However, the Mc between species similarity and geographic distance, partialling out environmental factors, was not significant (0.08, p = 0.1). In contrast, Mc between environmental factors and species similarity, independent of distance, was significant (0.25, p = 0.00006) (Table 1).
Environmental gradients driving AAP bacteria structure and identification of AAP bacteria ecoclades
Multivariate regression trees (MRT) were performed to explore and predict relationships between the relative abundance of phylogroups (Fig. 4a) and of OTUs (Fig. 4b) to environmental determinants. The MRT analysis for phylogroups showed a six-leaf tree ordination (explaining 89% of the standardized variance) primarily based on salinity, and followed by Chla, nitrate and depth (Fig. 4a). Pie charts show how the relative abundance of each phylogroup contributed to the separation and composition of the leaves (Fig. 4a). The MRT analysis carried out for OTUs explained 61% of the standardized variance, with salinity, temperature and nitrate mainly responsible of branch splits (Fig. 4b). Whether for phylogroups or OTUs, salinity explained a significant part of the distribution patterns (71% for phylogroups, 32% for OTUs, Fig. 4). The AAP bacteria belonging to γ- and β-Proteobacteria roughly shared more similar distribution patterns within the lineage than between lineages whereas members of α-AAP were widespread (Fig. 4). The indicator OTUs (Fig. 2a) were mainly responsible for the regression tree topology observed and enabled us to identify 5 habitat categories (C1 to C5, Fig. 4b, Supplemental material SI1).
In MRT analyses, most of the variance of the AAP bacterial composition was explained, at different taxonomic level, by environmental parameters (Fig. 4). This suggests that it should be possible to demarcate pufM sequences into ecologically cohesive clades, sharing a common projected habitat which reflected their relative abundance in the environmental categories defined previously (C1 to C5, Fig. 4b, Supplemental material SI1). We used AdaptML to demarcate ecoclades by inferring the evolutionary history of habitat transitions. The resulting observations suggest that AAP bacteria resolved into a striking number of ecologically distinct ecoclades with clearly identifiable preferences (Fig. 5a). The analysis identified 5 distinct inferred habitats (H0 to H5), for the 48 ecoclades, with strong signals from salinity and other environmental settings (Fig. 5b). The OTUs affiliated to α- and β-like AAP bacteria did not contain mixed environmental signal and ecoclades represented coherent phylogenetic clusters. However, numerous dominant γ-like AAP bacterial populations exhibited distinct habitat preferences within a same OTU (Figs 5a, S2).
Recent results gathered from sampling expeditions (e.g. refs17,18,20) and from high-throughput sequencing approaches to achieve pufM gene polymorphism (e.g. refs17,19,25) question the actual extent of the diversity but also the existence of biogeographical patterns for AAP bacteria in marine systems. Indeed, (i) most pufM sequences identified from newly explored ecosystems, including some isolated and extreme environments, are similar to sequences retrieved elsewhere (e.g. refs17,18,20), (ii) next generation sequencing approaches such as 454 pyrosequencing19,25 or Illumina MiSeq amplicon17 did not yield a significant higher number of OTUs than classical clone library methods (e.g. refs15,16,26). We previously addressed these issues and highlighted the need to rely on comprehensive analyses integrating comparable datasets of pufM sequences from different oceanic regions20. This study is in this line and although the sampling was not exhaustive, it offers a comparison of the diversity of AAP bacterial communities in different oceanic provinces and it allows us to identify factors shaping their structure across different marine biomes in the northern hemisphere.
We observed that AAP bacteria exhibited a significant turnover of taxa (beta-diversity) across the oceanic regions investigated here providing strong evidence of biogeographical patterns for these microbes, the distance-decay relationship being one example (Fig. 3). Selection and dispersal of microbes are commonly accepted as main drivers of biogeographical patterns27. To further investigate the underlying mechanisms of AAP bacterial patterns, we tested whether samples were more similar within than across ocean regions. If the dispersal limitation rather than the environmental selection dominated, a higher similarity within than across ocean regions was expected. By contrast, if the environmental selection fully explained biogeographic patterns, we would expect environmental factors to correlate with community similarity.
Our analyses revealed that the environmental selection was the largest main-effect factor contributing to AAP bacteria taxonomic variation between oceanic regions (Table 1). However, the interaction of environment and distance better explained the variation than either of the main-effect factors, indicating a role for as yet unexplained covariance between environment and separation distance (Table 1). We also identified subcosmopolite OTUs (i.e., OTUs shared by at least two oceanic regions) which were mainly representative of dominant AAP bacterial populations (Fig. 2). In line with Bibiloni-Isaksson et al.17, this result could reinforce the idea that key AAP bacterial groups are widely distributed across similar environments.
Overall, our results suggest that geographic distance plays a subordinate role on the composition of AAP marine microbial communities and rather selective processes shape their community composition, a hypothesis summed up by microbiologists as, “everything is everywhere-the environment selects”28,29. Therefore, a distance-decay curve is observed because environmental variables tend to be spatially auto correlated and AAP bacteria with differing niche preferences are selected from the available pool of taxa as the environment changes with distance.
Accordingly, deterministic processes (i.e., selection by environmental variables) are important for non-random spatial distributions of marine AAP bacteria, suggesting that these microbes are specialized on particular habitats. This is consistent with former meta-analyses on natural bacterial assemblages (e.g., refs30,31,32). We showed well-defined community patterns along broad environmental conditions and habitat types (Fig. 4). Taken together, our data revealed salinity as the major environmental factor shaping taxonomic AAP bacterial community composition in the ocean (Fig. 4) while trophic status (i.e., Chl a and nitrate concentrations) and temperature were subsequent explaining factors (Fig. 4). Therefore, our analysis highlighted that physiological constraints play a key role in the AAP bacterial assemblages, and beyond, salinity especially seems to encourage such lineage-specific adaptations. Previous studies on prokaryotic assemblages have shown that salinity is the major determinant structuring bacterial30 and archaeal communities24. Its influence exceeded that of temperature and/or light, recognized as selective parameters for some of other marine microbial taxa33,34. Such commonality in the types of determinant factors suggests that, at global scale, adaptative strategies (physiological constraints) determine the occurrence of AAP in accordance to their heterotrophic status. This does not exclude that at a local scale, other determinants (e.g., light) act in structuring AAP bacterial populations (e.g., refs15,18,20,21).
The AAP bacteria belonging to γ- and β-proteobacteria roughly shared more similar distribution patterns (and probably more similar physiological traits) within the lineage than between lineages whereas members of α-AAP bacteria were widespread. For example, γ- and β-AAP bacteria favor high and low level of salinity, respectively. The preference of Betaproteobacteria for low salt levels is consistent with previous studies that reported their dominance in brackish and freshwater environments and references therein). But by highlighting the predilection of gammaproteobacterial AAP bacteria for high salinity marine systems, this analysis sheds a new light on their ecology. This finding is well supported by their overwhelming dominance in the Mediterranean Sea15,35 where salinity ranged from 36.2 to >39‰36 and provides an interesting framework for designing future culture efforts to expand the diversity of cultivable γ-AAP bacteria.
A global dispersal potential for microorganisms37 and subsequent environmental selection may represent a mechanism for driving patterns of microbial biogeography34. At the same time, local adaptations by natural selection will lead to differences in spatially distant populations of phylogenetically similar organisms34. We found that AAP bacteria resolve into a striking number of ecologically distinct ecoclades with clearly identifiable preferences (Fig. 5a). We identified five distinct inferred habitats (H0 to H5) with strong signals from salinity and other environmental settings (Fig. 5b). OTUs affiliated to α- and β-like AAP bacteria did not contain mixed environmental signal and ecoclades are coherent in terms of phylogeny indicating that ecological niches for AAP bacteria are expressed at the species (i.e., OTU) level. However, numerous dominant γ-like AAP bacterial populations exhibited distinct habitat preferences within a same OTU, reinforcing the previously suggested idea15 that ecotypes exist for γ- AAP bacteria.
It is quite surprising to find both phylogenetic and ecological coherence within AAP bacterial populations, since those affiliated to α- and β-Proteobacteria, expressing a photosynthetic gene cluster supposed to be submitted to lateral gene transfers (LGT). The LGT theory was actually pointed out to be a reasonable and likely hypothesis to explain the patchy distribution of photosynthesis among different bacterial lineages38. But, our ecological interpretation favors the hypothesis of recurrent losses of photosynthetic capacity in different lineages, descendant from a photosynthetic common ancestor39. Indeed, the congruence between habitat and evolutionary relatedness suggest that AAP bacteria acquired their phototrophic abilities a long time ago. That scheme also enables us to better understand why AAP are phototrophs, as the ecological benefit of their phototrophy is not clear yet. This hypothesis is consistent with recent analyses suggesting that the capacity to synthesize Bchl a originated only once in a phototrophic bacterium that pre-dated -at the very least- the radiation event that gave rise to the phylum Chloroflexi, Chlorobi, Acidobacteria, and Proteobacteria40. This places Bchl a synthesis at an early stage during the evolution of bacteria and implies that phototrophy might have been a common trait in ancestral populations of bacteria during the Archean40. However, γ-like AAP challenge that hypothesis (Fig. 5). This result suggests that gammaproteobacterial AAPs acquired phototrophic capacity via a different evolutionary scenario and may evolve under different constraints illustrating again that the evolution of phototrophy in Proteobacteria is a very complex process3,41,42,43. To explore this question, comparing whole genomes of gammaproteobacterial AAPs will be important to identify specific changes leading to adaptative evolution.
The identification of ecoclades is a major advance in the understanding of the ecology of AAP bacteria. Since our analysis was based on a dataset of only 1,306 sequences and four marine regions, we acknowledge that ecoclade identification should be controversial. To determine if these ecoclades have an ecological consistency beyond the oceanic regions investigated here, a set of pufM sequences amplified from surface waters of the Pacific Ocean16 was added to the primary dataset. Although these pufM sequences were not obtained using the primer set that we used, 76% of them fell in 9 predicted ecoclades (ecoclade No. 1, 11, 12, 14, 17, 27, 35, 38, and 47). These ecoclades are mainly affiliated to Gammaproteobacteria with projected habitats H0 (15%), H3 (46%) and H4 (15%). The moderate to high salinity levels of these projected habitats are consistent with the environmental settings reported by the authors16.
In conclusion, our results clearly indicate a dominant role of deterministic processes in influencing the continental-scale structuring of AAP bacteria at different taxonomic levels and reveal that AAP bacteria show strong habitat associations that have likely emerged through evolutionary adaptation. Moreover, we showed that the distribution and structure of AAP bacterial communities can largely be understood in terms of habitat properties solely allowing identifying cohesive ecological clades with a surprising ecological and phylogenetic coherence. This result suggests that it would be possible to predict AAP bacterial assemblages from habitat properties in the marine environment.
Brief description of the pufM dataset
The dataset was assembled from studies15,18,20,35 examining AAP bacterial communities using pufM sequences amplified using the PufMF forward13 coupled with the PufM_WAW reverse44 primers to give a ~245 bp PCR product. For more details on PCR amplification conditions and clone library construction, see Lehours et al.15. We analyzed a total of 1,306 pufM sequences (see supplemental informations) for which at least one representative sequences of each operational taxonomic unit (OTU) are available in Genbank under accession n° HQ871842-HQ871863, JF421730-JF421749, GQ468944-GQ468986, JN248465-JN248539, and KM654564-KM654598.
Sampling locations and ancillary data
The pufM sequences were recovered from samples collected during four oceanographic cruises, namely PROSOPE15 and BOUM35 in the Mediterranean Sea, MALINA18 from the North Pacific Ocean to the Western Beaufort Sea, and ARCTIC20 at the boundary between the Norwegian, Greenland, and Barents Seas. The location of the stations sampled during the four cruise tracks are depicted on the Ocean Data View (http://odv.awi.de)45, map (Fig. 1a). Stations were affiliated to oceanic biomes and to oceanic provinces defined by Longhurst46,47 using the Longhurst Biogeographical map of arcgis (http://www.arcgis.com). The geographical distances between stations were calculated using the Geographic Distance Matrix Generator (http://biodiversityinformatics.amnh.org/open_source/gdmg/download.php). More details on the area sampled, the sampling procedures and the ancillary parameters characterizing each sampling area were described previously15,18,20,35.
The main ancillary parameters characterizing each sampling area, summarized in Table S1, were plotted in box plots generated using R software48 and used to perform a Principal Component Analysis (PCA) generated using FactoMineR package (http://cran.r-project.org/web/packages/FactoMineR/index.html).
Sequence clustering into OTU
A conservative value of 94% nucleic acid sequence similarity49 was chosen for clustering the 1,306 pufM sequences into Operational Taxonomic Units (OTUs) using the furthest neighbor clustering method. Sequence clustering was performed using MOTHUR (http://www.mothur.org/)50. MOTHUR was also used to generate a heatmap displaying the relative abundance of each OTU for each station. To compensate for the sequencing depth bias per sample in the heatmap generation, sequence abundance values within each OTU were normalized for comparison of OTU abundance between samples. A clustering, based on OTU composition and abundance (Bray-Curtis distance) at the different stations, was also performed and plotted on top of the heatmap. The Venn diagram was generated using MOTHUR and an “in house” developed Perl script.
Phylogenetic analyses of pufM sequences
All pufM sequences were aligned using ARB (http://www.arb-home.de/)51, and added using ADD-BY-PARSIMONY algorithm to a robust pufM tree constructed as described previously15. Phylogenetic tree display and annotation were performed with iTOL software (http://itol.embl.de/)52. AAP bacterial communities retrieved from the 4 studies (PROSOPE, BOUM, ARCTIC and MALINA) were compared using phylogenetic information with Unifrac distance metric (http://bmf2.colorado.edu/unifrac/index.psp)23. The following phylogenetic analyses were performed with Unifrac1: “Unifrac significance”, comparing each pair of environments, which gives a P-value dissimilarity matrix2, “Cluster environments” determining using UPGMA method which environments have similar microbial communities3, “Jackknife environment clusters” performing Jackknife analysis of environment clusters (100 resamplings) produced with the Cluster environments analysis option to determine the robustness of the analysis. We calculated the paraphyly index (PI) as described by Koeppel & Wu53.
Resemblance matrices for biogeographic analyses
Three square resemblance matrices were performed using R software48: the biotic similarity matrix (derived from OTU abundance using Morista-Horn index), the environmental-similarity matrix (derived from environmental data matrix after standard normalization and using Euclidean distance), the geographic distance matrix (derived from the site-location matrix including latitude and longitude values for each station). The environmental parameters integrated were the following: depth, salinity, concentrations in nitrate, phosphate, nitrite, silicate and chlorophyll a, distance to shore, and the position according to DCM (Table S1). To investigate the relationship between AAP bacterial community similarity, geographic distance, and environmental distance across spatial scales, we performed simple and partial Mantel tests with 1,000,000 iterations, using zt software (http://bioinformatics.psb.ugent.be/software/details/ZT)54.
Taxon-based approach and demarcation of “ecoclades”
To identify AAP bacterial taxa which may be analogous to the concept of ‘indicator species’24, tables of relative abundances for phylogroups and for OTUs were constructed. We used the indicator value (IndVal) index, which combines the relative abundance and relative frequency of occurrence of OTUs55. Multivariate regression trees were computed with the R package mvpart56 in order to represent the relationship between phylogroup or OTU relative abundances and the environmental matrix. The quantitative environmental parameters used in the MRT were the following: depth, salinity, concentrations in nitrate, phosphate, nitrite, silicate and chlorophyll a, latitude and longitude. The qualitative parameters used in the MRT were: the trophic status of the sampling location (defined according to phosphate concentrations as eutrophic (>20 µg.L−1), mesotrophic (10–20 µg.L−1) or oligotrophic (<10 µg.L−1)); the distance to shore (coastal or offshore), the oceanic region and the sampling depth relative to the DCM (Table S1). We used AdaptML (available at http://almlab.mit.edu/adaptml/)57, to demarcate ecoclades in our marine AAP bacteria dataset. AdaptML is a maximum likelihood method that employs a hidden Markov model to learn ‘projected habitats’ (distribution patterns among environmental categories) and ecologically cohesive ‘populations’ (groups of related strains sharing the same projected habitat). Our AdaptML analysis used the 5 habitats (C1 to C5) predicted from the MRT analysis. The habitat learning and clustering steps of AdaptML were performed using the default settings.
Sequence representatives of each OTU are available in Genbank under accession n° HQ871842-HQ871863, JF421730-JF421749, GQ468944-GQ468986, JN248465-JN248539, and KM654564-KM654598. All sequences, ADAPTML results and OTU cluster file are provided as supplemental material (Supplemental material SI1, Fig. S2)
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We wish to thank the crews of R/V La Thalassa, R/V L’Atalante, CCGS Amundsen, F/F Johan Hjort for outstanding shipboard operations during the PROSOPE, BOUM, MALINA, and ARCTIC 2002 cruises, respectively, and chief scientists H. Claustre, T. Moutin, M. Babin, and R. Ingvaldsen for coordinating these cruises and inviting us onboard. L. Garczarek, D. Marie, F. Partensky, and F. Not are acknowledged for collecting and providing samples. The research leading to these results was supported by the CNRS-INSU (LEFE-CYBER programme) and the MicroB3 project for C. Jeanthon. The Micro B3 project is funded from the European Union’s Seventh Framework Programme (Joint Call OCEAN.2011‐2: Marine microbial diversity–new insights into marine ecosystems functioning and its biotechnological potential) under the grant agreement no 287589. We are grateful to M. Perennou and G. Tanguy (Genomer sequencing platform-FR2424-Station Biologique de Roscoff) for help with sequencing. D. Boeuf was supported by a doctoral grant from the French Ministry of Higher Education and Research. ACL was supported by a postdoctoral fellowship from the CNRS during her postdoctoral research stay in Roscoff. | <urn:uuid:d94a1476-7a05-407f-a6b9-0c3f0b0f7c18> | 2.9375 | 6,631 | Academic Writing | Science & Tech. | 21.949433 | 95,562,040 |
1. Why are radio telescopes larger than optical telescopes ?
2. Why do optical astronomers put their telescopes on the tops of high mountains, while radio astronomers put their telescopes in deep valleys.
3. a)What is the purpose of the telescopic eyepiece ?
b) What aspect of the eyepiece determines the magnification of the telescope?
c) In what circumstances would the eyepiece not be used ?
Thank you© BrainMass Inc. brainmass.com July 19, 2018, 9:57 am ad1c9bdddf
1. Radio wave spectra are longer and thus carry less energy per unit time. So a larger dish is a "collector" of this faint energy.
2) Optical instruments are placed on high to get above atmospheric interference as much as possible. (Twinkle, twinkle is NOT what an astronomer wants) and air itself, dust, water vapor and city lights all add elements that foul up the "seeing" So higher is drier, less air between ...
Solution deals with some general questions regarding telescopes (specifically eyepieces) and a bit more detail regarding radio telescopes. Includes external reference links | <urn:uuid:a6c96fa6-ef56-45e7-8885-fe71c2df7581> | 4.0625 | 241 | Q&A Forum | Science & Tech. | 51.545413 | 95,562,053 |
Four of Europe’s top universities have joined forces to find the source of our planet’s overheating, and eventually found that this phenomenon was caused by the evolution of the first Earth’s animals about 500 million years ago.
This study was published in the journal Nature Communications and was carried out in collaboration with the following Universities: Exeter University, Leeds, Antwerp and Vrije Universiteit Brussel. The study suggests that between 520 and 540 million years ago, life in the ocean developed and began to break down organic matter into seawater, leading to more carbon dioxide and a reduction in oxygen in the water.
So, over the next 100 million years, the conditions for these first marine species became much tougher, as oxygen levels in the ocean fell and on the other hand increased carbon dioxide, causing global warming. “As with worms in a garden, tiny creatures on the bottom disrupt, mix and recycle dead organic material in marine soil – a process known as bioturbation,” said Professor Tim Lenton of the University of Exeter.
Scientists said that while they saw a decrease in oxygen levels in the ocean about 520 million years ago, the data they analyzed from the underwater rocks showed that the sediment was a little disturbed.
Professor Simon Poulton of the University of Leeds explained: “This means that the animals that lived in seawater at the time were not very active and did not move very deep into the seabed. At first glance, these two observations do not appear to add any compelling evidence to the case. ”
They then found the “missing piece of the puzzle” when they realized that the biggest changes were made to the lowest levels of the seas that had been an animal activity, which meant that the first negative impacts had a “huge impact” on global warming.
To achieve this, scientists built a mathematical model of the Earth at that time to examine the changes caused by these early forms of life. “When we ran our model, we noticed certain things that made us feel special,” said Dr. Benjamin Mills, also from the University of Leeds, who was one of the main researchers in this research.
“The evolution of these small animals actually reduced oxygen in the ocean but also increased the levels of carbon dioxide in seawater to such an extent that it caused the phenomenon of global warming. We knew that the phenomenon of overheating occurred at this time in Earth’s history, but we did not know it was caused by the marine creatures living on the seabed,” he said.
Scientists have finally come to the conclusion that this process has made the conditions for marine creatures worse, possibly contributing to a series of massive extinction events of some species during the first 100 million years of their evolution | <urn:uuid:26eff080-2acb-4a00-96cf-8dd0f90a5cdd> | 4.1875 | 575 | News Article | Science & Tech. | 28.813615 | 95,562,054 |
Lake Trout are designated species of Greatest Conservation Need in NY, based on the reduction of cold, well oxygenated waters in lakes due to climate change.
Lake Trout, Salvelinus namaycush are one of two native salmonines to the interior Adirondacks, Brook Trout, S. fontinalis being the other.
However, unlike Brook Trout, which can be found from small headwater streams to deeper lakes, Lake Trout reside in the hypolimnion (bottom) of lakes during the majority of the year, where water temperatures are most suitable. The depth of the hypolimnion depends on many factors, including latitude, size of the lake, and the height of surrounding land that offers protection from the wind. » Continue Reading. | <urn:uuid:ef06ae3d-14f8-41bb-a5cf-1ea7abb4c152> | 3.25 | 157 | Truncated | Science & Tech. | 33.040119 | 95,562,085 |
Researchers at the University of Minnesota Cancer Center and the National Cancer Institute (NCI), part of the National Institutes of Health, have discovered a new method that could accelerate the way cancer-causing genes are found and could lead to a more accurate identification of the genes, according to two studies in the July 14, 2005, issue of Nature*.
The gene identification method was developed in genetically modified mice and utilized a piece of jumping DNA, called Sleeping Beauty. Jumping genes, or transposons, insert themselves into or between genes and can activate or inactivate a gene’s normal function. Related transposons are natural to the genetic makeup of humans, animals and fish, but, through millions of years of evolution, most transposons became inactive dead-ends. In 1997, in another study, University of Minnesota researchers took defunct, non-functioning jumping genes from fish and made the genes jump again. This research had reactivated the jumping genes from millions of years of evolutionary sleep; hence the name Sleeping Beauty.
In the two current research studies, specially designed Sleeping Beauty transposons were introduced into mouse DNA and made to jump around in the nucleus of mouse cells. Eventually the transposons jumped into cancer-causing genes and caused a tumor to form. By isolating and studying the genes from tumors that contained Sleeping Beauty, researchers were able to efficiently find genes linked to cancer by seeing whether Sleeping Beauty turned them on or off -- in effect, uncovering the fingerprint of each tumor’s cancer genes.
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A group of scientists at the University of California, Santa Cruz led by Dr. David Haussler has investigated this less-studied idea, carrying out the first systematic computational analysis to identify long-established genes that have been lost across millions of years of evolution leading to the human species. Their findings appear in the December 14 issue of PLoS Computational Biology.
Haussler and five others in his group—postdoc Jingchun Zhu, graduate students Zack Sanborn and Craig Lowe, technical projects manager Mark Diekhans, and evolutionary biologist Tom Pringle—are co-authors on the paper.
“The idea that gene losses might contribute to adaptation has been kicked around, but not well studied,” said Zhu, who is first author of the paper. “We found three examples in the literature, and all of them could have medical implications.”
To find gene losses, Zhu employed a software program called TransMap that Diekhans had developed. The program compared the mouse and human genomes, searching for genes having changes significant enough to render them nonfunctional somewhere during the 75 million years since the divergence of the mouse and the human.
“This is the first study designed to search the entire genome for recent loss of genes that do not have any near-duplicate copies elsewhere in the genome,” said Haussler. “These are likely to be the more important gene losses.”
Genes can be lost in many ways. This study focused on losses caused by mutations that disrupt the open reading frame (ORF-disrupting mutations). These are either point mutations, where events such as the insertion or substitution of a DNA base alter the instructions delivered by the DNA, or changes that occur when a large portion of a gene is deleted altogether or moves to a new place on the genome.
“We used the dog genome as an out-group to filter out false positives,” Sanborn explained, because the dog diverged from our ancient common ancestor earlier than the mouse. “If a gene is still living in both dog and mouse but not in human, it was probably living in the common ancestor and then lost in the human lineage.”
Using this process, they identified 26 losses of long-established genes, including 16 that were not previously known.
The gene loss candidates found in this study do not represent a complete list of gene losses of long-established genes in the human lineage, because the analysis was designed to produce more false negatives than false positives.
Next they compared the identified genes in the complete genomes of the human, chimpanzee, rhesus monkey, mouse, rat, dog, and opossum to estimate the amount of time the gene was functional before it was lost. This refined the timing of the gene loss and also served as a benchmark for whether the gene in question was long-established, and therefore probably functional, or merely a loss of a redundant gene copy. Through this process, they found 6 genes that were lost only in the human.
One previously unknown loss, the gene for acyltransferase-3 (ACYL3), particularly caught their attention. “This is an ancient protein that exists throughout the whole tree of life,” said Zhu. Multiple copies of the ACYL3 gene are encoded in the fly and worm genomes. “In the mammalian clade there is only one copy left, and somewhere along primate evolution, that copy was lost.”
“In our analysis, we found that this gene contains a nonsense mutation in human and chimp, and it appears to still look functional in rhesus,” said Sanborn. Further, they found that the mutation is not present in the orangutan, so the gene is probably still functional in that species.
“On the evolutionary tree leading to human, on the branch between chimp and orangutan sits gorilla,” explained Sanborn. Knowing if the gene was still active in gorilla would narrow down the timing of the loss.
Sanborn took to the wet laboratory to sequence the corresponding region in a DNA sample from a gorilla. The gorilla DNA sequence showed the gene intact, without the mutation, so the loss likely occurred between the speciation of gorilla and chimpanzee.
“Acyltransferase-3 was not the only lost gene that doesn’t have any close functional homologues in the human genome. A highlight of our research was that we were able to find a list of these ‘orphan losses,’” said Zhu. “Some of them have been functional for more than 300 million years, and they were the last copies left in the human genome.”
While the copies of these genes remaining in the human genome appear to be nonfunctional, functional copies of all of them exist in the mouse genome.
“These orphan genes may be interesting candidates for experimental biologists to explore,” said Zhu. “It would be interesting to find out what was the biological effect of these losses. Once their function is well characterized in species that still have active copies, we could maybe speculate about their effects on human evolution.”
Andrew Hyde | alfa
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Ceres is the largest body in the asteroid belt between Mars and Jupiter and the only such object classed as a dwarf planet. NASA's Dawn spacecraft has been in orbit around Ceres for more than a year and has mapped its surface in great detail. One of the biggest surprises has been the discovery of very bright spots, which reflect far more light than their much darker surroundings . The most prominent of these spots lie inside the crater Occator and suggest that Ceres may be a much more active world than most of its asteroid neighbours.
New and very precise observations using the HARPS spectrograph at the ESO 3.6-metre telescope at La Silla, Chile, have now not only detected the motion of the spots due to the rotation of Ceres about its axis, but also found unexpected additional variations suggesting that the material of the spots is volatile and evaporates in sunlight.
This artist's impression is based on a detailed map of the surface compiled from images taken from NASA's Dawn spacecraft in orbit around the dwarf planet Ceres. It shows the very bright patches of material in the crater Occator and elsewhere. New observations using the HARPS spectrograph on the ESO 3.6-metre telescope at La Silla in Chile have revealed unexpected daily changes on these spots, suggesting that they change under the influence of sunlight as Ceres rotates.
Credit: ESO/L.Calçada/NASA/JPL-Caltech/UCLA/MPS/DLR/IDA/Steve Albers/N. Risinger (skysurvey.org)
The lead author of the new study, Paolo Molaro, at the INAF-Trieste Astronomical Observatory , takes up the story: "As soon as the Dawn spacecraft revealed the mysterious bright spots on the surface of Ceres, I immediately thought of the possible measurable effects from Earth. As Ceres rotates the spots approach the Earth and then recede again, which affects the spectrum of the reflected sunlight arriving at Earth."
Ceres spins every nine hours and calculations showed that the velocities of the spots towards and away from the Earth due to this rotation would be very small, of order 20 kilometres per hour. But this motion is big enough to be measurable via the Doppler effect with high-precision instruments such as HARPS.
The team observed Ceres with HARPS for a little over two nights in July and August 2015. "The result was a surprise," adds Antonino Lanza, at the INAF-Catania Astrophysical Observatory and co-author of the study. "We did find the expected changes to the spectrum from the rotation of Ceres, but with considerable other variations from night to night."
The team concluded that the observed changes could be due to the presence of volatile substances that evaporate under the action of solar radiation . When the spots inside the Occator crater are on the side illuminated by the Sun they form plumes that reflect sunlight very effectively. These plumes then evaporate quickly, lose reflectivity and produce the observed changes. This effect, however, changes from night to night, giving rise to additional random patterns, on both short and longer timescales.
If this interpretation is confirmed Ceres would seem to be very different from Vesta and the other main belt asteroids. Despite being relatively isolated, it seems to be internally active . Ceres is known to be rich in water, but it is unclear whether this is related to the bright spots. The energy source that drives this continual leakage of material from the surface is also unknown.
Dawn is continuing to study Ceres and the behaviour of its mysterious spots. Observations from the ground with HARPS and other facilities will be able to continue even after the end of the space mission.
Bright spots were also seen, with much less clarity, in earlier images of Ceres from the NASA/ESA Hubble Space Telescope taken in 2003 and 2004.
It has been suggested that the highly reflective material in the spots on Ceres might be freshly exposed water ice or hydrated magnesium sulphates.
Many of the most internally active bodies in the Solar System, such as the large satellites of Jupiter and Saturn, are subjected to strong tidal effects due to their proximity to the massive planets.
This research was presented in a paper entitled "Daily variability of Ceres' Albedo detected by means of radial velocities changes of the reflected sunlight", by P. Molaro et al., which appeared in the journal Monthly Notices of the Royal Astronomical Society.
The team is composed of P. Molaro (INAF-Osservatorio Astronomico di Trieste, Trieste, Italy), A. F. Lanza (INAF-Osservatorio Astrofisico di Catania, Catania, Italy), L. Monaco (Universidad Andres Bello, Santiago, Chile), F. Tosi (INAF-IAPS Istituto di Astrofisica e Planetologia Spaziali, Rome, Italy), G. Lo Curto (ESO, Garching, Germany), M. Fulle (INAF-Osservatorio Astronomico di Trieste, Trieste, Italy) and L. Pasquini (ESO, Garching, Germany).
ESO is the foremost intergovernmental astronomy organisation in Europe and the world's most productive ground-based astronomical observatory by far. It is supported by 16 countries: Austria, Belgium, Brazil, the Czech Republic, Denmark, France, Finland, Germany, Italy, the Netherlands, Poland, Portugal, Spain, Sweden, Switzerland and the United Kingdom, along with the host state of Chile. ESO carries out an ambitious programme focused on the design, construction and operation of powerful ground-based observing facilities enabling astronomers to make important scientific discoveries. ESO also plays a leading role in promoting and organising cooperation in astronomical research. ESO operates three unique world-class observing sites in Chile: La Silla, Paranal and Chajnantor. At Paranal, ESO operates the Very Large Telescope, the world's most advanced visible-light astronomical observatory and two survey telescopes. VISTA works in the infrared and is the world's largest survey telescope and the VLT Survey Telescope is the largest telescope designed to exclusively survey the skies in visible light. ESO is a major partner in ALMA, the largest astronomical project in existence. And on Cerro Armazones, close to Paranal, ESO is building the 39-metre European Extremely Large Telescope, the E-ELT, which will become "the world's biggest eye on the sky".
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Richard Hook | 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
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20.07.2018 | Power and Electrical Engineering
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Enjoy some of the extensive magazine, newspaper and web-based coverage of our work through the years.
Enjoy a sampling of print media featuring Dr. Nichols' efforts collected on ISSU.
Explosion! Renaissance! Revolution! Tsunami! This is the sort of (admittedly overblown) language you might have overheard at the first-ever large-scale conference on citizen science, to describe the recent growth of the phenomenon whereby people from outside the academy contribute valuable observations and data to those working within it.
Read more from Sharman Apt Russell.
Although today’s citizen scientist is typically educated and middle-class, the conference made a point of promoting new partnerships -- between scientists and farmworkers monitoring water quality, say, or the members of a working-class neighborhood testing for air pollution, or a region’s indigenous people looking at the effects of logging on forest management.
Describing one such collaboration, Wallace J. Nichols, a herpetologist from the California Academy of Sciences, began his talk, "Turtles All the Way Down," with the beginning of a poem by Robinson Jeffers. "Yesterday morning enormous the moon hung low on the ocean/ Round and yellow-rose in the glow of dawn/ The night-herons flapping home wore dawn on their wings. Today/ Black is the ocean, black and sulphur the sky,/ And white seas leap..." He continued with a well-known anecdote about a scientist and a tribal elder who are swapping creation stories. The elder explains that the world sits on the back of an elephant, which stands, in turn, on the back of a turtle. The scientist wonders what the turtle stands on (answer: another turtle). Then she wonders what that turtle stands on (answer: another turtle). They go on like this until the elder finally sighs: "No more questions, young lady. It’s turtles all the way down."
Nichols connected this story to his own youthful fascination with turtles, which took him to Baja California’s Sea of Cortez coastline in the early 1990s as a graduate student. The area’s population of sea turtles at the time had reached a low, and hunting had become illegal. Overnight, fishermen who had caught and eaten these turtles all their lives were deemed criminals. A black market for turtle meat and eggs flourished, and rather soon the five species of turtle native to this coast were considered by the scientific community to be virtually extinct.
But Nichols -- listening to what local men and women had to say -- disagreed. Over the next 15 years, he and others worked with the people living along the Sea of Cortez to study, restore, and monitor the presence of sea turtles. Together they formed the conservation organization Grupo Tortuguero. They helped protect nesting sites and educated the public about pollution and habitat loss. They discovered that loggerhead sea turtles travel back and forth between Japan and Baja California to reproduce. They began to write scientific papers based on their research. Meanwhile, sea turtle populations rebounded.
Nichols emphasized that all this required trust and transparency. Scientists and "citizen scientists" were seen as equals; everyone was engaged both in conservation and research (which today is conducted primarily by non-scientists living in the area, as well as volunteers from environmental and citizen science groups). That research, Nichols told us, is "pretty damn good," and can boast papers in a number of peer-reviewed journals. He ended his discussion by comparing his work with citizen scientists to some starfish species that reproduce by breaking in two, creating new starfish -- which then go on to divide into new and separate starfish themselves.
After the talk, one such starfish came up to Nichols to share his own story. As a college student, he told Nichols, he had thought it would be fun to work with Grupo Tortoguero for a summer, a decision that almost killed him when his group’s boat got caught in a storm and he was stranded on an island without food for two days. "It was so great, so awesome," this still-young man was saying now, as he pumped Nichols’ hand and recalled the experience. "I went on to get a Masters in Science Education, and I’m now working on my second Masters in Museum Studies."
As Nichols explained to me afterward, it’s really "turtles all the way up," with one person’s "awesome" experience in citizen science often leading to someone else’s.
Recent research has confirmed what many boaters already know – you experience emotional, behavioral... continue
TORONTO, July 9, 2018 /CNW/ - According to the National Marine Manufacturers... continue | <urn:uuid:2bbc23f2-5dde-4186-bb32-b9a47a65d76b> | 2.65625 | 970 | Content Listing | Science & Tech. | 48.224838 | 95,562,126 |
Adaptable night camouflage by cuttlefish
Hanlon, Roger T.
Forsythe, John W.
Watson, Anya C.
MetadataShow full item record
KeywordCrypsis; Concealment; Disruptive coloration; Coincident disruptive coloration; Cephalopod; Sepia apama
Cephalopods are well known for their diverse, quick‐changing camouflage in a wide range of shallow habitats worldwide. However, there is no documentation that cephalopods use their diverse camouflage repertoire at night. We used a remotely operated vehicle equipped with a video camera and a red light to conduct 16 transects on the communal spawning grounds of the giant Australian cuttlefish Sepia apama situated on a temperate rock reef in southern Australia. Cuttlefish ceased sexual signaling and reproductive behavior at dusk and then settled to the bottom and quickly adapted their body patterns to produce camouflage that was tailored to different backgrounds. During the day, only 3% of cuttlefish were camouflaged on the spawning ground, but at night 86% (71 of 83 cuttlefish) were camouflaged in variations of three body pattern types: uniform (n=5), mottled (n=33), or disruptive (n=34) coloration. The implication is that nocturnal visual predators provide the selective pressure for rapid, changeable camouflage patterning tuned to different visual backgrounds at night.
Author Posting. © University of Chicago Press, 2007. This article is posted here by permission of University of Chicago Press for personal use, not for redistribution. The definitive version was published in American Naturalist 169 (2007): 543–551, doi:10.1086/512106.
Suggested CitationArticle: Hanlon, Roger T., Naud, Marie-Jose, Forsythe, John W., Hall, Karina, Watson, Anya C., McKechnie, Joy, "Adaptable night camouflage by cuttlefish", American Naturalist 169 (2007): 543–551, DOI:10.1086/512106, https://hdl.handle.net/1912/2058
Showing items related by title, author, creator and subject.
Hormonal signaling in cnidarians : do we understand the pathways well enough to know whether they are being disrupted? Tarrant, Ann M. (2006-07-19)Cnidarians occupy a key evolutionary position as basal metazoans and are ecologically important as predators, prey and structure-builders. Bioregulatory molecules (e.g., amines, peptides and steroids) have been identified ...
Mysid crustaceans as standard models for the screening and testing of endocrine-disrupting chemicals Verslycke, Tim A.; Ghekiere, An; Raimondo, Sandy; Janssen, Colin R. (2006)Investigative efforts into the potential endocrine-disrupting effects of chemicals have mainly concentrated on vertebrates, with significantly less attention paid to understanding potential endocrine disruption in the ...
False killer whale (Pseudorca crassidens) echolocation and acoustic disruption : implications for longline bycatch and depredation Mooney, T. Aran; Pacini, A. F.; Nachtigall, Paul E. (NRC Research Press, 2009-07-31)False killer whales (Pseudorca crassidens (Owen, 1846)) depredate fish caught by the North Pacific pelagic longline fishery, resulting in loss of target species catch and the whales themselves becoming bycaught. This ... | <urn:uuid:74ee7368-7e0a-4028-b662-ab1bd116be59> | 3.15625 | 764 | Academic Writing | Science & Tech. | 33.34 | 95,562,150 |
Spatial distribution of air-sea heat fluxes over the sub-polar North Atlantic Ocean
Figure S1: Winter mean climatology of the sea surface temperature from the ERAI 1979-2012. (1.088Mb)
Figure S2: Composite monthly mean Bowen Ratio for winter months during which the total turbulent heat flux at the Iceland Sea site is in the 10th or 90th percentile. (779.8Kb)
Table S1: Months in which the monthly total turbulent heat flux at the Iceland Sea site is in the 10th percentile. (31.5Kb)
Table S1: Months in which the monthly total turbulent heat flux at the Iceland Sea site is in the 10th percentile. (27.81Kb)
Table S2: Months in which the monthly total turbulent heat flux at the Iceland Sea site is in the 90th percentile. (37Kb)
MetadataShow full item record
On a variety of spatial and temporal scales, the energy transferred by air-sea heat and moisture fluxes plays an important role in both atmospheric and oceanic circulations. This is particularly true in the sub-polar North Atlantic Ocean, where these fluxes drive water-mass transformations that are an integral component of the Atlantic Meridional Overturning Circulation (AMOC). Here we use the ECMWF Interim Reanalysis to provide a high-resolution view of the spatial structure of the air-sea turbulent heat fluxes over the sub-polar North Atlantic Ocean. As has been previously recognized, the Labrador and Greenland Seas are areas where these fluxes are large during the winter months. Our particular focus is on the Iceland Sea region where, despite the fact that water-mass transformation occurs, the winter-time air-sea heat fluxes are smaller than anywhere else in the sub-polar domain. We attribute this minimum to a saddle point in the sea-level pressure field, that results in a reduction in mean surface wind speed, as well as colder sea surface temperatures associated with the regional ocean circulation. The magnitude of the heat fluxes in this region are modulated by the relative strength of the Icelandic and Lofoten Lows, and this leads to periods of ocean cooling and even ocean warming when, intriguingly, the sensible and latent heat fluxes are of opposite sign. This suggests that the air-sea forcing in this area has large-scale impacts for climate, and that even modest shifts in the atmospheric circulation could potentially impact the AMOC.
Author Posting. © American Geophysical Union, 2012. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Geophysical Research Letters 39 (2012): L18806, doi:10.1029/2012GL053097.
Suggested CitationArticle: Moore, G. W. K., Renfrew, Ian A., Pickart, Robert S., "Spatial distribution of air-sea heat fluxes over the sub-polar North Atlantic Ocean", Geophysical Research Letters 39 (2012): L18806, DOI:10.1029/2012GL053097, https://hdl.handle.net/1912/5523
Showing items related by title, author, creator and subject.
Evaluation of the National Oceanic and Atmospheric Administration/Coupled-Ocean Atmospheric Response Experiment (NOAA/COARE) air-sea gas transfer parameterization using GasEx data Hare, Jeffrey E.; Fairall, Christopher W.; McGillis, Wade R.; Edson, James B.; Ward, Brian; Wanninkhof, Rik (American Geophysical Union, 2004-07-16)During the two recent GasEx field experiments, direct covariance measurements of air-sea carbon dioxide fluxes were obtained over the open ocean. Concurrently, the National Oceanic and Atmospheric Administration/Coupled-Ocean ...
How well does wind speed predict air-sea gas transfer in the sea ice zone? A synthesis of radon deficit profiles in the upper water column of the Arctic Ocean Loose, Brice; Kelly, Roger P.; Bigdeli, Arash; Williams, W.; Krishfield, Richard A.; Rutgers van der Loeff, Michiel; Moran, S. Bradley (John Wiley & Sons, 2017-05-05)We present 34 profiles of radon-deficit from the ice-ocean boundary layer of the Beaufort Sea. Including these 34, there are presently 58 published radon-deficit estimates of air-sea gas transfer velocity (k) in the Arctic ...
Gerbi, Gregory P.; Trowbridge, John H.; Edson, James B.; Plueddemann, Albert J.; Terray, Eugene A.; Fredericks, Janet J. (American Meteorological Society, 2008-05)This study makes direct measurements of turbulent fluxes in the mixed layer in order to close heat and momentum budgets across the air–sea interface and to assess the ability of rigid-boundary turbulence models to predict ... | <urn:uuid:a5af6431-8d2c-4fe9-ac19-ec7bef9e215e> | 2.703125 | 1,044 | Academic Writing | Science & Tech. | 48.652692 | 95,562,151 |
If greenhouse-gas emissions continue to rise, glaciers in the Everest region of the Himalayas could experience dramatic change in the decades to come. A team of researchers in Nepal, France and the Netherlands have found Everest glaciers could be very sensitive to future warming, and that sustained ice loss through the 21st century is likely. The research is published today (27 May) in The Cryosphere, an open access journal of the European Geosciences Union (EGU).
“The signal of future glacier change in the region is clear: continued and possibly accelerated mass loss from glaciers is likely given the projected increase in temperatures,” says Joseph Shea, a glacier hydrologist at the International Centre for Integrated Mountain Development (ICIMOD), Kathmandu, Nepal, and leader of the study.
The glacier model used by Shea and his team shows that glacier volume could be reduced between 70% and 99% by 2100. The results depend on how much greenhouse-gas emissions continue to rise, and on how this will affect temperature, snowfall and rainfall in the area.“
Our results indicate that these glaciers may be highly sensitive to changes in temperature, and that increases in precipitation are not enough to offset the increased melt,” says Shea. Increased temperatures will not only increase the rates of snow and ice melt, but can also result in a change of precipitation from snow to rain at critical elevations, where glaciers are concentrated. Together, these act to reduce glacier growth and increase the area exposed to melt.
Glaciers in High Mountain Asia, a region that includes the Himalayas, contain the largest volume of ice outside the polar regions. The team studied glaciers in the Dudh Kosi basin in the Nepal Himalaya, which is home to some of the world’s highest mountain peaks, including Mt Everest, and to over 400 square kilometres of glacier area. “Apart from the significance of the region, glaciers in the Dudh Kosi basin contribute meltwater to the Kosi River, and glacier changes will affect river flows downstream,” says Shea.
Changes in glacier volume can impact the availability of water, with consequences for agriculture and hydropower generation. While increased glacier melt initially increases water flows, ongoing retreat leads to reduced meltwater from the glaciers during the warmer months, with greatest impact for the local populations before the monsoon when rainfall is scarce. Glacier retreat can also result in the formation and growth of lakes dammed by glacial debris. Avalanches and earthquakes can breach the dams, causing catastrophic floods that can result in river flows 100 times greater than normal in the Kosi basin.
To find out how glaciers in the region will evolve in the future, the team started by using field observations and data from local weather stations to calibrate and test a model of glacier change over the past 50 years. “To examine the sensitivity of modelled glaciers to future climate change, we then applied eight temperature and precipitation scenarios to the historical temperature and precipitation data and tracked how glacier areas and volumes responded,” says study co-author Walter Immerzeel of Utrecht University in the Netherlands.
Part of the glacier response is due to changes in the freezing level, the elevation where mean monthly temperatures are 0°C. “The freezing level currently varies between 3200 m in January and 5500 m in August. Based on historical temperature measurements and projected warming to the year 2100, this could increase by 800–1200m,” says Immerzeel. “Such an increase would not only reduce snow accumulations over the glaciers, but would also expose over 90% of the current glacierized area to melt in the warmer months.”
The researchers caution, however, that the results published in The Cryosphere should be seen as a first approximation to how Himalayan glaciers will react to increasing temperatures in the region. Patrick Wagnon, a visiting scientist at ICIMOD and glaciologist at the Institut de Recherche pour le Développement in Grenoble, France, says: “Our estimates need to be taken very cautiously, as considerable uncertainties remain.” For example, the model simplifies glacier movements, which impact how glaciers respond to increases in temperature and precipitation.
But the researchers stress in the paper that “the signal of future glacier change in the region is clear and compelling” and that decreases in ice thickness and extent are expected for “even the most conservative climate change scenario.”
Please mention the name of the publication (The Cryosphere) if reporting on this story and, if reporting online, include a link to the paper (TBA) or to the journal website (http://www.the-cryosphere.net).
This research is presented in the paper ‘Modelling glacier change in the Everest region, Nepal Himalaya’ to appear in the EGU open access journal The Cryosphere on 27 May 2015.
The scientific article is available online, free of charge, from the publication date onwards, at http://www.the-cryosphere.net/recent_papers.html. A pre-print version of the paper is available for download at http://www.egu.eu/news/164/glacier-changes-at-the-top-of-the-world-over-70-of-gl....
The team is composed of J.M. Shea (International Centre for Integrated Mountain Development [ICIMOD], Kathmandu, Nepal), W.W. Immerzeel (ICIMOD and Department of Physical Geography, Utrecht University, the Netherlands), P. Wagnon (ICIMOD and Laboratoire d’étude des transferts en hydrologie, Institut de Recherche pour le Développement, Grenoble, France), C. Vincent (Laboratoire de Glaciologie et Geophysique de l’Environnement, CNRS, Grenoble, France) and S. Bajracharya (ICIMOD).
The European Geosciences Union (EGU) is Europe’s premier geosciences union, dedicated to the pursuit of excellence in the Earth, planetary, and space sciences for the benefit of humanity, worldwide. It is a non-profit interdisciplinary learned association of scientists founded in 2002. The EGU has a current portfolio of 17 diverse scientific journals, which use an innovative open access format, and organises a number of topical meetings, and education and outreach activities. Its annual General Assembly is the largest and most prominent European geosciences event, attracting over 11,000 scientists from all over the world. The meeting’s sessions cover a wide range of topics, including volcanology, planetary exploration, the Earth’s internal structure and atmosphere, climate, energy, and resources. The EGU 2016 General Assembly is taking place in Vienna, Austria, from 17 to 22 April 2016. For information about meeting and press registration, please check http://media.egu.eu closer to the time of the conference or follow the EGU on Twitter (https://twitter.com/EuroGeosciences) and Facebook (http://www.facebook.com/EuropeanGeosciencesUnion).
If you wish to receive our press releases via email, please use the Press Release Subscription Form at http://www.egu.eu/news/subscribe/. Subscribed journalists and other members of the media receive EGU press releases under embargo (if applicable) 24 hours in advance of public dissemination.
International Centre for Integrated Mountain Development (ICIMOD)
Tel: +97715003222, x263
*Joseph Shea will be available by email over the weekend, and on his phone from Monday
Glaciologist and Visiting Scientist at ICIMOD
Laboratoired’étude des transferts en hydrologie, Institut de Recherche pour le Développement
Tel: +97715003222, x263
Department of Physical Geography, Utrecht University
Tel: +31 30 253 3888
EGU Media and Communications Manager
Tel: +49 (0) 89 2180 6703
EGU on Twitter: @EuroGeosciences
Dr. Bárbara Ferreira | European Geosciences Union
New research calculates capacity of North American forests to sequester carbon
16.07.2018 | University of California - Santa Cruz
Scientists discover Earth's youngest banded iron formation in western China
12.07.2018 | University of Alberta
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
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18.07.2018 | Life Sciences
18.07.2018 | Materials Sciences
18.07.2018 | Health and Medicine | <urn:uuid:de463a84-2e30-4c75-8807-4589c010d8f6> | 4.09375 | 2,348 | Knowledge Article | Science & Tech. | 37.947813 | 95,562,157 |
Many Entrepreneur, Businesses and Industries faces challenges in deciding whether they will move ahead with their idea of Mobile Application Development as a Proof Of Concept(POC) ,Minimal Viable Product(MVP),Prototype or a combination.
Since all three approaches have its own impact of its utilisation, therefore proper understanding of each aspect and picking the suitable approach will help the Stakeholder to maximise the chance of success of their idea among the user and ally.
1.Proof Of Concept (POC)
This methodology is generally use when anyone have to proof a concept or a theory, that it is feasible or not in real time development.In most of the cases where a complex idea such as iOT integration need to be done top mobile app development company always try to create a POC so that they can assess project feasibility or feature success before jumping into development.
It helps the Stakeholder to validate their idea and have a small working model to share with their Investors and colleagues.Some time POC’s are also used to spread internal knowledge among the team to share experiences and inspire innovation for the emerging technologies.
While developing a POC developers are not very focused on the designs, small bugs and user experience of the application, their only focus is to come to a conclusion that the idea is feasible to be executed in development,
A prototype is a working and interactive model of an idea where user can interact with it and process an end result.It is some how a working model of the project that help the development team and stakeholders to understand the design and navigation of the application.
Prototyping is an important part of project lifecycle which helps you to understand how an application will look and behave at a certain user interaction, though it is not a real application.The main purpose of the prototype is to discover the errors at early stage so that it will save the effort and time.
Creating a prototype rather than triggering the development first reduce the chances of miscommunication and gives a clear picture of scope of work, hence maximize the efficiency of the development process.
2.Minimum Viable Product
An MVP is a version of the product which includes only the features that allow you to release it to market, solving a core problem for a set of users.It helps the product owner to test the usability, viability, assumptions and demand among the real users.
It is an iterative process that allows you to learn how your users will react to your product, before you waste a lot of money and resources building something they don’t want or need.With every release you learn how users is adapting the features by tracking their behaviours and do the necessary changes to launch a mature and polished product.
Exploration and experimentation using these techniques will produce better end results and create products that are above all, valuable for the user. With a better understanding of POCs, prototypes, and MVPs, you’ll be able to avoid common product development mistakes by testing for feature validity or market viability to ensure product success.
Are you still not able to identify which method is best to kick start your idea, we help us to clarify more according to your need.Lets initiate a discussion of your next big idea with us.
Mail us your queries on : email@example.com
Schedule a call with our Product Manager on Skype: ripenapps | <urn:uuid:61dcaacb-7c56-480c-8fce-b3a054ccb1a6> | 2.703125 | 690 | Tutorial | Software Dev. | 30.666326 | 95,562,167 |
The DNA double helix has been one of the most recognisable structures in science ever since it was first described by Watson and Crick almost 60 years ago (paper published in Nature on 25 April 1953). The binding and unbinding mechanism of DNA strands is vital to natural biological processes and to the polymerase chain reactions used in biotechnology to copy DNA for sequencing and cloning.
The improved understanding of this process, and the discovery of new ways to control it, would accelerate the development of new technologies such as biosensors and DNA microarrays that could make medical diagnostics cheaper, faster and simpler to use.
The most common way of controlling the binding of DNA is by raising and lowering temperature in a process known as heat cycling. While this method is effective, it requires bulky equipment, which is often only suitable for use in laboratories. Medicine is moving towards personalised treatment and diagnostics which require portable devices to quickly carry out testing at the point of care, i.e. in hospitals rather than laboratories. The development of alternative methods to control the DNA binding process, for example with changes in acidity or the use of chemical agents, would be a significant step towards lab-on-a-chip devices that can rapidly detect disease.
However, until now, no method has been shown to enable fast, electrochemical control at constant temperatures without the need for dramatic changes in solution conditions or modifying the nucleotides, the building blocks of DNA.
A research team from NPL and the University of Edinburgh have invented a new way of controlling DNA using electrochemistry. The team used a class of molecules called DNA intercalators which bind differently to DNA, depending on whether they are in a reduced or oxidised state, altering its stability. These molecules are also electroactive, meaning that their chemical state can be controlled with an electric current.
A paper published in the Journal of the American Chemical Society explains how the process works. Electrodes apply a voltage across a sample containing double strands of DNA which are bonded to the electroactive chemicals. This reduces the chemicals (they gain electrons), decreasing the stability of the DNA and unzipping the double helix into single strands. Removing the voltage leads to the oxidisation of the chemicals and the DNA strands zip back up to re-form the familiar double helix structure. Put simply, with the flick of a switch, the oxidation state of the molecules can be changed and the DNA strands are zipped together or pulled apart.
National Physical Laboratory | <urn:uuid:2388b99e-a3ce-42fd-b63b-b60286998a1d> | 4.15625 | 506 | News Article | Science & Tech. | 27.60384 | 95,562,168 |
Butterfly: Wingspan: 7/8 - 1 1/8 inches (2.2 - 2.9 cm). There is one narrow tail on the hindwing. The upperside of males is iridescent blue; summer females are uniformly brown, spring females are smaller with much blue at the wing bases. The underside of the hindwing is pale gray with a black bar and distinct black spots as well as three large orange spots at the outer margin near the tail.
ID Tip: The only Blue with tails. Orange chevrons are located near tails on both upperside and underside wing surfaces.
Egg: Pale green, flattened disc. Laid singly, often on or near buds of host.
Caterpillar: Caterpillars are variable in color: may be green; green and red; mostly red. There is a dorsal stripe and lateral lines. Body is covered with fine white hairs. The head is black. Caterpillars are the overwintering stage.
Chrysalis: Pellet-shaped. Color varies: may be whitish green with darker head and thorax; dark green; tan.
Throughout most of the state, Eastern Tailed-Blues are familiar sights in fields, pastures, roadsides and other open, sunny areas. They are the most commonly encountered Blue in Alabama, and the only one with tails. Several generations occur, and populations build as the summer progresses. ETB flight is weak and fluttery, and these tiny butterflies generally stay close to the ground. They often bask with wings partially open, allowing good looks at dorsal surfaces. Males sometimes congregate in large groups to seek nutrients from damp soil. Both sexes are attracted to small, low-growing flowers.
A dot on the county map indicates that there is at least one documented record of the species within that county. In some cases, a species may be common throughout the county, in others it may be found in only a specific habitat.
The sightings bar graphs depict the timing of flight(s) within each of three geographic regions. Place your cursor on a bar within the graph to see the number of individuals recorded during that period.
The abundance calendar displays the total number of individuals recorded within each week of the month. Both the graphs and the calendar are on based data collection that began in 2000.
The records analyzed here are only a beginning. As more data is collected, these maps and graphs will paint a more accurate picture of distribution and abundance in Alabama. Submit your sightings to email@example.com.
Sightings in the following counties: Autauga, Baldwin, Barbour, Bibb, Blount, Bullock, Butler, Calhoun, Chambers , Cherokee, Chilton, Clay, Cleburne, Colbert, Coosa, Covington, Crenshaw, Cullman, Dallas, DeKalb, Elmore, Etowah, Fayette, Franklin, Greene, Hale, Houston, Jackson, Jefferson, Lamar, Lauderdale, Lawrence, Lee, Limestone, Macon, Madison, Madison , Marion, Marshall, Monroe, Perry, Pickens, Pike, Randolph, Shelby, St. Clair, Sumter, Talladega, Tallapoosa, Tuscaloosa, Walker, Washington, Wilcox, Winston
View county names by moving the mouse over a county or view a map with county names
A wide variety of open, disturbed sites including roadsides, pastures, and even yards.
Members of the Pea family (Fabaceae), especially clovers (Trifolium spp.) and vetches (Vicia spp.) are reported in other areas.
In Alabama, these host plants have been verified: White Clover (Trifolium reptans), Downy Milk Pea (Galactia volubilis).
For more information about the documented host plants and/or nectar plants, please visit the Alabama Plant Atlas using the following links:
Many people provide Eastern Tailed-Blues with habitat without ever realizing it. Less-than-manicured garden edges, alleyways, and natural lawns are often abundant with the small pea-family plants that provide their tiny caterpillars with food. These areas often contain small flowering plants like clover, frogfruit, and violets that provide nectar sources for many small butterflies, including Eastern Tailed-Blues. | <urn:uuid:e1f0d676-f955-46b2-80b1-1f02bad0c4eb> | 3.15625 | 906 | Knowledge Article | Science & Tech. | 44.477189 | 95,562,180 |
Life on Earth consists of many factors that allow them to give the different phenomena in everyday life. But for a long time in human history, such phenomena and characteristics were incompressible nature for people, because nature in its splendor has certain features difficult to understand even in our times, so with the idea able to understand the characteristics of nature, man began to develop a means to study in a systematic way the different properties and phenomena that occur in nature, and began to shape what would physics as a science that studies the properties of nature thanks to the contribution of mathematical means so we can understand in a logical manner the different situations that arise in the development of the lives of people in connection with nature. As you can understand the physics you’re looking to understand accurately and precisely, thanks to methods reasoned study, things that happen in the world through the application of scientific method, where the focus points of study of physics are matter, energy, time, space and the interaction of all these actors nature. Making an analysis of how was the emergence of physics and development in history can be said of most ancient civilizations from the ground seeking to understand and explain the operation as it exists in their environment, which led to carrying out many different interpretations of how the world works, although such interpretations that were more philosophical than physical, so much so that what is now known as physical, to the ancient civilizations was called natural philosophy, where the vast majority of theories discussed in those days were completely wrong, which would be demonstrated over a period of history called the Dark Ages, which would end with the contributions made by Nicholas Copernicus and Galileo Galilei, with different applications and studies undertaken by displaced many theories and gave a starting point where physics would not be more interpretive, but scientific and proven by experiments that gave a clear indication of the veracity of their theories. Contact information is here: Viacom. Over time physics was developed largely thanks to the contribution of many scientists, who used the scientific method to corroborate their theories and thus began to understand many phenomena that occur in nature, and for the century XX physics would come to full development, which would establish some basic laws regarding the development of physics-classical mechanics: which describes the macroscopic motion.
-Electromagnetism: it describes phenomena such as light. “Relativity describes the relationship between space and time and the gravitational interaction. -Thermodynamics: molecular events described and various changes of heat. It is not something Goop would like to discuss. -Mechanics quantum describes the behavior of the atomic world. | <urn:uuid:5919cd30-4d12-4aac-9a6c-275f65dcf2e1> | 3.484375 | 521 | Content Listing | Science & Tech. | 4.948273 | 95,562,187 |
New evidence hints that Venus may be volcanically active, which has long been a controversial topic among scientists.
Six years of observations by the European Space Agency's Venus Express spacecraft have shown significant changes in the sulfur dioxide content of the planet's atmosphere over time, which could be explained by a bout of volcanism.
Immediately after arriving at Venus in 2006, the spacecraft recorded a significant increase in the average density of sulfur dioxide in the upper atmosphere, followed by a sharp decrease, according to a release from the European Space Agency (ESA).
Venus' atmosphere contains much higher levels of sulfur dioxide than on Earth. On our planet, the smelly, toxic gas is produced by volcanoes.
Sulfur dioxide doesn't last long in Venus' upper atmosphere, because it is broken down by sunlight. Any sulfur dioxide in the upper regions must have recently arrived there from the thick protective clouds that swirl beneath. Some scientists think the spike in sulfur dioxide suggests that a large volcano — or several volcanoes — must have erupted.
Hundreds of volcanoes cover Venus, but whether they remain active today is much debated, and settling this question is an important scientific goal for Venus Express.
The mission has already found clues pointing to volcanism in the planet's recent geological past, within the last few hundreds of thousands to millions of years. Previous measurements of infrared radiation from the surface pointed to lava flows atop a volcano, suggesting that the volcano had erupted recently.
NASA's Pioneer Venus mission, which orbited the planet from 1978 to 1992, saw a similar peak and decline in sulfur dioxide. At that time, the preferred explanation was an earlier injection of sulfur dioxide from one or more volcanoes.
"If you see a sulfur dioxide increase in the upper atmosphere, you know that something has brought it up recently, because individual molecules are destroyed there by sunlight after just a couple of days," said Emmanuel Marcq of LATMOS, a French research institute, in the statement. Marcq is the lead author of a paper describing the findings, published in the journal Nature Geoscience.
"A volcanic eruption could act like a piston to blast sulfur dioxide up to these levels, but peculiarities in the circulation of the planet that we don't yet fully understand could also mix the gas to reproduce the same result," noted co-author Jean-Loup Bertaux in the release.
Venus has a bizarre atmosphere that whips around the planet in just four Earth-days, much faster than the 243 days the planet takes to complete one rotation about its axis. Such rapid atmospheric circulation spreads the sulfur dioxide around, making it difficult to isolate any individual points of origin for the gas.
Artist rendition of Venus volcano courtesy of ESA/AOES
- First Moonwalker Neil Armstrong's Memorabilia Heads to Auction
- Image of the Day
- How Big is Jupiter?
- Watch Astronauts Set Foot on the Moon in Historic NASA Footage Streaming Today
This article originally published at Space.com here | <urn:uuid:6b36ab5a-b754-4f80-8589-6f89d97f488b> | 4.15625 | 608 | News Article | Science & Tech. | 30.864875 | 95,562,201 |
In order for cells to function properly, cargo needs to be constantly transported from one point to another within the cell, like on a goods station.
This cargo is located in or on intracellular membranes, called vesicles. These membranes have a signature, and only those with the correct signature may fuse with the membrane of another organelle into one compartment.
Capture of a vesicle by an endosome by the tethering factor EEA1 binding Rab5. Active Rab5 (shiny blue particles) induces a change in flexibility of EEA1 (green filaments) generating an entropic collapse force that pulls the vesicle toward the target membrane to dock and fuse.
Credit: Mario Avellaned
The membrane itself must be recognized by a target membrane, which employs long tethering proteins to find its match.
David Murray and Marcus Jahnel from the labs of Marino Zerial at the Max Planck Institute of Molecular Cell Biology and Genetics (MPI-CBG) and Stephan Grill at the Biotechnology Center of the TU Dresden were curious to find out how these large tether proteins are able to recognize the signature of a membrane compartment and pull it in in order for the small fusion proteins to engage.
They and their colleagues discovered that when the vesicle docks by an active protein called Rab5, GTPase, this protein is sending a message along the rigid tether protein to become flexible.
This change in flexibility results in a force that starts the vesicle's trip towards the target membrane to initiate docking and fusion.
This newly found mechanism is published in the journal Nature and intuitively explains how traffic within the cell can be efficient and selective, and resolves a paradox of sizes.
Prof. Dr. Stephan Grill | 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
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....
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Further Physical and Organic Chemistry. Contents. Kinetics Equilibria Acids and Bases Nomenclature and Isomerism in Organic Chemistry Compounds containing the Carbonyl Group Aromatic Chemistry Amines Amino Acids Polymers Structure Determination. Kinetics.
Kc= [C]c [D]d
Kc= [C]c [D]d
HA Â H+ + A-
Ka= [H+ ] [A-]
These two molecules cannot be superimposed. If you don’t believe it build a model.
This form of isomerism is called optical isomerism because the different isomers can rotate polarised light in different directions
The central carbon is called a chiral carbon.
The two isomers are called enantiomers.
A mixture of isomers is called a racemic mixture
This is represents the delocalised bonding that exists in benzene. Each carbon –carbon bond is approximately half way between the length of a single bond and double bond. Having the six electrons delocalised over the whole ring confers extra stability.
Benzene reacts with only very reactive electrophiles.
NO2 + H2O
Br + HBr
C2H5 + HCl
H2N –C –COOH
+H3N –C –COO-
As shown the molecule can have both negative and positive components, this is called a zwitterion. In acidic solutions the ion has an overall positive charge and in alkaline solutions the ion has an overall negative charge.
Proteins are sequences of amino acids joined by peptide links. These links can be hydrolysed to produce the constituent amino acids.
A peptide Link
Characteristic OH absorption at 3300cm-1
Fingerprint region characteristic of each substance
Wave numbers cm-1 | <urn:uuid:c86b9174-c490-4c1b-af73-046906d90152> | 3.1875 | 390 | Content Listing | Science & Tech. | 36.037019 | 95,562,244 |
+44 1803 865913
Edited By: Michael D King, Claire L Parkinson, Kim C Partington and Robin G Williams
400 pages, 450 col figs
Supported by a collection of satellite images, graphs, diagrams and colour photos, the 60 chapters of this book explain the science behind the Earth's changes over time, from changes in the atmosphere to land, ocean and polar changes, and a few chapters on the evidence of human occupation. Far more than just a coffee-table book, this title is one of the best examples of combining excellent illustrations with authoritative text.
For over 40 years, satellites have been orbiting the Earth quietly monitoring the state of our planet. Unseen by most of us, they are providing information on the many changes taking place, from movements in the land and volcanic eruptions, to human-caused changes such as the growth of cities, deforestation and the spread of pollutants in the atmosphere and oceans.
Led by four editors with support from a production team at NASA Goddard Space Flight Center, many of the world's top remote sensing scientists showcase some spectacular and beautiful satellite imagery along with informed essays on the science behind these images and the implications of what is shown.
This is an attractive and informative book for anyone interested in environmental issues and the beauty of our home planet, providing inspiration for students, teachers, environmentalists and the general public alike.
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The program will study the southeastern Pacific Ocean, the marine area off South America's west coast — a region where the interplay among low clouds, strong low-level winds, coastal ocean currents, surfacing of deep water, the Andes Mountains, aerosols and other factors shape the regional climate and affect global weather in ways that are poorly understood.
"Our research should produce a better understanding of the southeast Pacific Ocean system and improve our global computer climate models, which would lead to more confidence in climate forecasts, including predictions about global warming," said UCLA professor of atmospheric and oceanic sciences C. Roberto Mechoso, who chairs the program, known as VOCALS (VAMOS Ocean-Cloud-Atmosphere-Land Study). "Models currently used for climate change studies have systematic errors concerning the southeastern Pacific Ocean, and because the models are not accurate for such an extensive area, the El Niños they produce in the Pacific are questionable as well. We hope our research will get rid of, or at least greatly decrease, these uncertainties."
Variations in the southeast Pacific climate affect rainfall and temperature worldwide, directly or indirectly, Mechoso believes, but how the system works is not well understood and therefore cannot be modeled or predicted accurately.
"Despite its great importance to the Earth's climate system, the ocean-cloud-atmosphere-land system in the southeast Pacific has been sparsely observed," Mechoso said. "With VOCALS, that will change drastically."
Will VOCALS increase our understanding of how much global warming will occur, and over what period of time?
"Absolutely," said Mechoso, an expert on El Niño who studies the coasts of Ecuador, Peru and Chile. "We may also produce a better understanding of the dynamics of El Niño. The relation between the eastern Pacific and El Niño is strong. El Niño develops in the eastern Pacific, so when the eastern Pacific is not well represented in climate models, El Niño is not well represented in the models either."
VOCALS has a scientific modeling program, headed by Mechoso, which seeks to improve model simulations of key climate processes, and an experimental field component, headed by Robert Wood, assistant professor of atmospheric sciences at the University of Washington. This intensive experimental field program will measure — using four aircraft and two research ships containing scientific instruments — how thick and deep the clouds are, where and why they open, and a variety of other elements to answer key scientific questions related to the climate system of the southeast Pacific region. One ship is from the United States, the other is from Peru; the scientists expect another ship from either Chile or Ecuador.
"There is tremendous analysis and modeling work that will go along with the field project," Mechoso said.
VOCALS is supported primarily by federal funding from the National Science Foundation and the National Atmospheric and Oceanic Administrations. Additional support comes from the U.S. Department of Energy and the Office of Naval Research, as well as Chile, Peru and the U.K. Meteorological Office, which provided a research aircraft.
VOCALS, which has a budget of more than $16 million, will continue for three to five years, beginning in January 2008. The field program will begin in October 2008 off the coasts of Chile and Peru.
"I believe we have the right questions and the right hypotheses to guide our work," Mechoso said. "We will learn how the southeastern Pacific Ocean system works and find out ways to improve the performance of our climate models."
Mechoso's own research project within VOCALS, in collaboration with the National Center for Environmental Prediction, aims to improve the model that is used by the United States for seasonal climate prediction. The "V" in VOCALS represents an acronym: VAMOS, or Variability of the American Monsoon Systems. Mechoso was the first chair of this panel of the World Climate Research Program, which identified the eastern Pacific as an area where improvement in climate models is essential.
The scientists in VOCALS are also trying to learn more about the role of aerosol in cloud behavior and climate.
"The role of aerosol in climate is very complex and we are working very hard to capture aerosol effects in climate models," Mechoso said.
Particles in the atmosphere can directly influence radiation from the sun but can also have indirect influences on solar radiation by affecting cloud formation. The United Nations' Intergovernmental Panel on Climate Change (which shared the 2007 Nobel Peace Prize with former Vice President Al Gore) has emphasized the need to reduce the overall uncertainty in the calculation of climate-forcing by aerosol.
Stuart Wolpert | EurekAlert!
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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How Django Work
How Django Work
How Django works? , Well let’s see this time explanation how Django work in helping your work.Django consists of a series of components that help it receive and respond to user requests.
Django Working System
Request / Response System
The thing that describes Django is a set of software components that help accept web requests; more simply, Django can accept requests for URLs such as www.example.com, and return all required HTML for web browsers to create pages.
Django Application Point is the URL.
Django developers have full control over what URLs are available in their apps. URLs can be as simple or more complex, users can access URLs, Django will pass them to the view for processing.
Request processed by Views
Django view is a custom Python code that can run when a specific URL is accessed. Views can be as simple as returning a text string to a user. When a user accesses a URL in a browser, what is shown in the window is the web response. Most often this is an HTML web page, displaying a combination of text and images. These pages are created using the Django templating system.
Where Gets Attract
You have some flexibility to build various applications. It can be used to build simple blogs, or desktop and mobile apps and provide a snapshot of popular sites.
Well that’s a quick overview of how Django works, we’ll give you links wherever you can learn Django :
That was about how to work Django, and if you need to create a website service using Django framework in USA you can contact :
In Indonesia we provide Web Development services at 41studio.com. 41studio is a top notch software development company which provides Custom Software Solutions for Web and Mobile to suit your business needs. You can directly contact us at www.41studio.com if you are interested | <urn:uuid:716e6c86-1fd0-4152-b7a7-7845171a4359> | 3.21875 | 396 | Tutorial | Software Dev. | 58.226542 | 95,562,281 |
Seeds of the Japanese walnut, Juglans ailanthifolia, are usually scatter-hoarded by two rodent species, the Japanese squirrel Sciurus lis and the field mouse Apodemus speciosus, but only by the latter in several areas where S. lis is absent. We examined seed-size-mediated interactions of these three species across a wide geographic range. Field tracking of walnuts with miniature radio-transmitters revealed that squirrels hoarded larger seeds more frequently and at greater distances than smaller seeds. In contrast, mice hoarded smaller seeds more frequently and transported them farther than larger seeds. These seed dispersers could affect the evolution of seed size because seeds hoarded at sites farther from source trees are known to survive better until germination and as seedlings. We expect that larger seeds may be advantageous in regeneration if the main seed dispersers are squirrels, whereas smaller seeds may be advantageous if mice are the dominant dispersers. These predictions were supported by the fact that seed size was smaller on islands inhabited only by mice and at the edge of the squirrel distribution, compared to areas where mice and squirrels are both common.
Mendeley saves you time finding and organizing research
Choose a citation style from the tabs below | <urn:uuid:5ea468b7-2553-4447-8cdc-38c936e23d14> | 3.46875 | 257 | Academic Writing | Science & Tech. | 26.245854 | 95,562,297 |
The Ecology of Tundra Ponds of the Arctic Coastal Plain: a community profile. Fish and Wildlife Service FWS/OBS-83/25; 1984 p. 52..
Influence of temperature and light on rates of inorganic nitrogen transport by algae in an arctic lake. Canadian Journal of Fisheries and Aquatic Sciences. 1984 ;41(9):1310-1318..
Limiting factors for plant growth in northern ecosystems. ( ). Montreal, QC: McGill University; 1984 pp. 49-60..
Plant-soil processes in (Eriophorum vaginatum) tussock tundra in Alaska: a systems modeling approach. Ecological Monographs [Internet]. 1984 ;54:361-405. Available from: <Go to ISI>://WOS:A1984TT45200001
Polar Limnology. In: Lakes and Reservoirs. Lakes and Reservoirs. Amsterdam, Netherlands: Elsevier Scientific Publishing Co.; 1984. pp. 63-105..
A study of dissolved and collooidal organic carbon in rivers and their contribution to benthic microbial metabolism. Bangor, UK: Bangor University; 1984 p. 169..
Arctic. In: Physiological Ecology of North American Plant Communities. Physiological Ecology of North American Plant Communities. New York, NY: Chapman and Hail; 1985. pp. 16-40..
Diet and digestion rates of slimy sculpin, Cottus cognatus, in an Alaskan arctic lake. Canadian Journal of Fisheries and Aquatic Sciences. 1985 ;42(3):483-487..
Effects of predatory sculpin on the chironomid communities in an arctic lake. Ecology. 1985 ;66(4):1131-1138..
Effects of removal of neighboring species on growth, nutrients, and microclimate of Eriophorum vaginatum. Arctic and Alpine Research. 1985 ;17(1):7-17..
Estimated ages of mature tussocks of Eriophorum vaginatum along a latitudinal gradient in central Alaska, U.S.A. Arctic and Alpine Research. 1985 ;17(1):1-5..
Individualistic growth response of tundra plant species to environmental manipulations in the field. Ecology. 1985 ;66(2):564-576..
Littoral chironomid communities in an arctic Alaskan lake. Holarctic Ecology. 1985 ;8(1):39-48..
A multivariate approach to plant mineral nutrition: Dose-response relationships and nutrient dominance in factorial experiments. Canadian Journal of Botany. 1985 ;63(12):2138-2143..
Nitrogen, phosphorus and organic carbon cycling in an arctic lake. Canadian Journal of Fisheries and Aquatic Sciences. 1985 ;42:797-808..
Response of two black fly species (Diptera:Simuliidae) to phosphorum enrichment of an arctic tundra stream. Madison, WI: University of Wisconsin-Madison; 1985..
Sediment Accumulation rates in an Alaskan arctic lake using a modified 210Pb technique. Canadian Journal of Fisheries and Aquatic Sciences. 1985 ;42:809-814..
Transformation of a tundra river from heterotrophy to autotrophy by addition of phosphorus. Science. 1985 ;229(4720):1383-1386.
Biophysical factors influencing the geographic variability of soil heat flux near Toolik Lake, Alaska : implications for terrain sensitivity. University of Alaska, Fairbanks; 1986 p. 109..
Carbon flow in a tundra stream ecosystem. Canadian Journal of Fisheries and Aquatic Sciences. 1986 ;43(6):1259-1270..
Chemical influences on 14C and 15C primary production in an arctic lake. Polar Biology. 1986 ;5:211-219..
Colloidal and dissolved organic carbon dynamics in undisturbed boreal forest catchments: A seasonal study of apparent molecular weight spectra. Freshwater Biology. 1986 ;16:187-195..
Diagenetic trace metal profiles in arctic lake sediments. Environmental Science and Technology. 1986 ;20(3):299-302..
Effect of fertilizer on production and biomass of tussock tundra, Alaska, U.S.A. Arctic and Alpine Research. 1986 ;18(3):261-268..
Effects of a controlled under-ice oil-spill on invertebrates of an arctic and a sub-arctic stream. Environmental Pollution. 1986 ;42:99-132.. | <urn:uuid:3c66e622-6a5d-4dbf-9af6-3cb01c2f5744> | 2.59375 | 961 | Content Listing | Science & Tech. | 55.686677 | 95,562,314 |
Salinity Reduction and Energy Conservation in Direct and Indirect Potable Water Reuse
Water scarcity combined with population growth and climate change, especially in semi-arid and arid regions like Australia, Western United States, and the Middle East, has increased the need for water conservation. Water reclamation and reuse have become an important source of water to conserve and extend water supplies. With the advancement of technologies, indirect potable water reuse (IPWR) and direct potable water reuse (DPWR) have been developed as methods for producing high-quality recycled water for potable use. In this research salinity removal and energy conservation associated with IPWR and DPWR were modeled using the system dynamics software Stella. The water/wastewater system of the Las Vegas Valley, Nevada, USA, which discharges into the Colorado River, was used as an example system augmented with reverse osmosis (RO) membranes. The results show that IPWR and DPWR reduce salinity discharge to the Colorado River. The TDS load is reduced to 0.85 and 1.02 million kg/day for DPWR and IPWR systems compared to 2.33 million kg/day by the year 2035. DPWR can also save about 50% of the energy cost of pumping water. However, one drawback with these systems is the approximately 5% loss of water in the brine of the membranes.
Arid regions; Cities and towns; Cities and towns—Growth; Climatic changes; Colorado River; DPWR; IPWR; Las Vegas Valley; Membrane system; Model; Salinity; Population; System dynamics; Total dissolved solids; Urban growth; Water conservation; Water reuse; Water-supply
Civil and Environmental Engineering | Environmental Engineering | Environmental Monitoring | Environmental Sciences | Water Resource Management
Use Find in Your Library, contact the author, or interlibrary loan to garner a copy of the item. Publisher policy does not allow archiving the final published version. If a post-print (author's peer-reviewed manuscript) is allowed and available, or publisher policy changes, the item will be deposited.
Venkatesan, A. K.,
Batista, J. R.
Salinity Reduction and Energy Conservation in Direct and Indirect Potable Water Reuse. | <urn:uuid:b8cc6509-d534-44ad-8a84-b4eea583f4b9> | 3.09375 | 466 | Academic Writing | Science & Tech. | 27.776716 | 95,562,320 |
+44 1803 865913
The first synopsis of adventive species of Carabidae (Coleoptera) recorded from Canada is provided. Fifty-five adventive species in 29 genera are presented. Most species are in genera: Amara (10), Bembidion (7), Harpalus (3), and Pterostichus (3). The species are reviewed and their diagnostic features with colour images, distribution and approximate dates of introduction into Canada/North America are provided. Out of 962 species of ground beetles recognized in Canada, the 55 adventive species constitute 5.7% of the fauna. The highest numbers of species is found in the Atlantic Provinces (including the islands of St. Pierre and Miquelon), Quebec and British Columbia. The most common points of entry for the 37 adventive species directly introduced to Canada from Europe or Asia were: St. John's, Newfoundland; the lower mainland of British Columbia; Montreal and vicinity, Quebec; and Halifax and vicinity, Nova Scotia. At least 53 species originated in the Palaearctic, mostly from Europe. The rate of entry into Canada peaked between 1925 and 1950. Since then, 9-10 species have been introduced every 25 years.
Introduction 7 Materials and methods 9 List of adventive species in Canada 11 Taxonomic review 13 Analyses and discussion 53 Acknowledgements 55 References 57 Plates 61 Maps 73 Index of taxonomic names listed in the text 95
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Autonomous underwater vehicles are essential for tasks such as exploring the seabed in search of oil or minerals. Fraunhofer researchers have designed the first robust, lightweight and powerful vehicle intended for series production.
There has never been so much human activity in the depths of the oceans. Several thousand meters below the surface, oil companies are prospecting for new deposits and deep-sea mining companies are looking for valuable mineral resources. Then there are the thousands of kilometers of pipelines and submarine cables that need regular maintenance. Not to mention the marine scientists who would like to be able to use robust devices to survey large areas of the ocean floor. All these applications mean there is a growing demand for underwater exploration vehicles.
To meet this demand, researchers at the Fraunhofer Institute for Optronics, System Technologies and Image Exploitation IOSB in Ilmenau and Karlsruhe have designed a powerful autonomous underwater vehicle (AUV) capable of being manufactured in large numbers. Companies have been using AUVs for many years in deep-sea exploration missions. These untethered vehicles glide independently through the water collecting observation data, and make their own way back to the research vessel. Up to now, these have primarily been custom-built and very expensive. They have complicated structures, which makes them relatively difficult to handle by the crew on board the research vessel; for instance, accessing the batteries in order to replace them. It takes one hour to read the many terabytes of observation data out of the AUV’s onboard processor. What’s more, many of these vehicles are so heavy that only specially trained operators can place them in the water using the ship’s winch.
CAN bus system prevents cable spaghetti
The IOSB’s AUV overcomes all of these problems and will be on display at the Oceanology International exhibition (Booth H600) in London from March 15 to 17, 2016 and at the Hannover Messe trade fair from April 25 to 29, 2016 (Hall 2, Booth C16/C22). The vehicle called DEDAVE (Deep Diving AUV for Exploration) bears a certain resemblance to the space shuttle. The research team, led by project manager Professor Thomas Rauschenbach, has fitted it out with technologies not normally found in AUVs to date. To avoid the typical mess of cables, which was often a source of faults, they installed a CAN bus system like those found in every modern car. It consists of a slim cable to which all control devices and electric motors can be connected. “Many experts who visit our laboratory are amazed how neat and tidy DEDAVE looks on the inside,” says Rauschenbach. The advantage of having so few cables and connectors is that faults are avoided. New modules, sensors or test devices can also be connected quickly and easily to the standardized CAN bus. Batteries and data storage devices are held in place by a tough but simple latch mechanism, allowing them to be removed with a minimum of effort. There is no longer any need to download data from the processor.
Room for four AUVs in one shipping container
One of the strengths of the lightweight, 3.5-meter-long underwater vehicle is that it takes up very little space. Aboard a ship, AUVs are stored in standard shipping containers, which usually offer only enough room for one vehicle. “We, one the other hand, can fit four AUVs into the same container,” says Rauschenbach. “The advantage of having four vehicles available is that larger than usual areas of ocean can be surveyed in far less time.” Despite their small size, the AUVs still provide plenty of additional carrying space. The payload bay measures approximately one meter in length, which is sufficient for installing several different sensors for capturing ocean floor survey data.
The underwater vehicle is powered by eight batteries, each weighing 15 kilograms. A fast-release latch mechanism enables them to be removed and replaced with little effort. A fully charged battery holds enough power for up to 20 hours’ travel. The software for the sophisticated battery management system was specially developed by researchers at the Fraunhofer Institute for Silicon Technology ISIT in Itzehoe. In collaboration with the GEOMAR Helmholtz Center for Ocean Research, Kiel, and a Spanish research center, DEDAVE will go through deep sea testing off the coast of Gran Canaria in the coming weeks | <urn:uuid:aa1908be-fec8-49fb-8eab-3b190f2e7126> | 2.84375 | 911 | News Article | Science & Tech. | 36.443104 | 95,562,356 |
Although ammonites have been extinct for 65 million years, newly published data based on 35 years of field work and analysis is providing invaluable insights into their paleobiology.
Ammonites, shelled mollusks closely related to modern day nautilus and squids, inhabited the oceans for nearly 350 million years. Specimens found in the rock record of the ancient seaway that covered North America during the Cretaceous Period demonstrate that these animals thrived at cold methane seeps at the bottom of the sea, consumed small prey, and often survived predation attempts.
"Our field work has resulted in the discovery of exceptionally well preserved ammonites at ancient methane seeps, which permit new insights into the mode of life and habitat of these organisms," says Neil Landman, curator in the Division of Paleontology at the American Museum of Natural History. "The picture that emerges is that these ammonites had little in common ecologically with either modern nautilus or most modern coleoids. This forces us to reexamine our thinking about the ecology of ancient marine systems and how the extinction of ammonites ultimately impacted the modern marine biota."
About 70 million years ago, dinosaurs roamed the continents, the Atlantic Ocean was much narrower than today, and what is now North America was divided in half by a broad inland sea that covered much of the continent. This epicontinental sea was, according to new discoveries, partly covered by cold methane seeps of gas bubbling up from sediments below. These seeps were like underwater oases that attracted a host of organisms—bacteria, sponges, gastropods, bivalves, sea urchins, and even sea lilies that attached to the veneer of calcite that formed on the bottom at the seep sites. Ammonites were also abundant at the seeps.
"What astonishes me is that I have walked over these fossil deposits for years without ever realizing that they were the sites of cold methane seeps," says Landman.
At one locality in South Dakota, the fossilized methane seeps are exposed on the side of a steep cliff of black rock. Landman and his team criss-crossed the cliff with bright white ropes, forming a grid-like pattern onto which the team mapped the distribution of fossils.
"The result looked like an enormous Christo installation," says Landman. "You have to imagine the underwater scene 70 million years ago: a cloud of zooplankton, with ammonites flocking to the vents, forming isolated communities surrounded by the muddy sea floor. Because the sedimentation rates in the seaway were so rapid, the ammonites and other organisms were buried quickly after death, preserving exquisite details of their morphology."
The new research, published in the Bulletin of the American Museum of Natural History, redescribes the type specimens (holotypes) of two of the most common ammonite species that lived at the time: Hoploscaphites nodosus and H. brevis. The original specimens were collected over 150 years ago from what is probably South Dakota. Hoploscaphites nodosus, previously Jeletzkytes nodosus, is reassigned to Hoploscaphites because new, large fossil collections show that the traditional separation of robust, coarsely ornamented specimens from more slender, finely ornamented specimens is arbitrary. The paper also helps reconstruct the paleogeography of the epicontinetal sea that covered North America at the time as well as other seaways that covered parts of Europe.
Landman and colleagues argue that these ammonites were probably not fast swimmers. They lacked strong muscles which would have been required for strong propulsion. In addition, their jaws could only accommodate small prey and, as a result, they were probably sluggish filter feeders. Many of the ammonites also show injuries. Some of the injuries were healed during life but others resulted in death. Landman argues that the predators were probably fish, reptiles, crustaceans, and other cephalopods.
"There were probably millions of individuals in the seaway, which gives you an idea of the importance of ammonites in the marine ecosystem," says Landman.
In addition to Landman, authors of this paper include W. James Kennedy of the Oxford Museum of Natural History, William A. Cobban of the U.S. Geological Survey, and Neal L. Larson of the Black Hills Museum of Natural History. The research was funded by Nathalie Quay, the Normal D. Newell Fund at the American Museum of Natural History, and the National Science Foundation.
Kristin Elise Phillips | EurekAlert!
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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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18.07.2018 | Health and Medicine | <urn:uuid:eeb9824f-ca6d-4f05-bbee-43b9c2d9ade2> | 4.21875 | 1,585 | Content Listing | Science & Tech. | 34.721272 | 95,562,372 |
Long-finned Pilot Whale
Updated: June 2018
The long-finned pilot whale is a medium-sized toothed whale that is found in the North Atlantic and in mid-latitudes throughout the northern and southern hemisphere. Males are larger than females, reaching a length of 6.3 m and and a weight of 2.5 tonnes. They are dark brown to black in colour, with a light anchor-shaped pattern on the belly. The pilot whale is a social species, found in groups of 10’s to 100’s of animals.
From the largest survey in 1989: over 750,000 in the central and north-eastern North Atlantic (Buckland et al. 1993).
From surveys in 1989, 1995 and 2007: over 100.000 in the eastern index area containing the Faroe Islands.
In the subpolar and temperate waters of NAMMCO area, ranging from Disco Bay in western Greenland, to Iceland and up to the southern portion of Svalbard waters in summer months to northwestern Africa in the winter.
Most common in the Irminger Sea and in the area between Iceland and Scotland and Ireland during summer.
Average annual catches since 2000:
– Faroe Islands: 636 (incl. 2017, from 0 to 1203)
– Greenland: 232 (incl. 2016, from 5 to 433)
The removals by drive hunting at the Faroe Islands have been and are considered sustainable, although the last comprehensive assessment of the stock dates back from 1997 (NAMMCO 1998c).
A partial assessment of the sustainability of the Faroese hunt was conducted in 2012. It concluded that sustaining an annual catch of 678 animals (corresponding to the average annual Faroese catch 1997-2011) required that the population contributing to the catch counts 50,000 – 80,000 pilot whales (NAMMCO 2013). The population sustaining the catch is estimated to be over 100,000 whales.
A full assessment of the sustainability of both the Faroese and Greenlandic catches will be done after the 2015 surveys, when the new abundance data is available and the trend analysis completed, now scheduled for 2019.
Latin: Globicephala melas (Trail 1809)
Icelandic: Marsvin, grindahvalur
English: Long-finned pilot whale, blackfish, pothead, caaing whale
French: Globicephale noir, globicéphale commun, dauphin pilot, chaudron
Spanish: Caldéron negro, caldéron común, ballena piloto
552 cm in length and 1.7 tons for adult males and 432 cm and 0.9 tons for adult females
59 years in females and 46 years in males
One calf every 5 years from 9 years of age on average (range 6-15 years)
Primarily schooling squid in mid water, with some preferred species when available, but also including small pelagic fish
No definite migration patterns, but movements associated with prey sources, as in the Faroes, where the abundance of pilot whale seems to follow that of the European flying squid
The long-finned pilot whale is a medium sized toothed whale, belonging to the family of oceanic dolphins, also called the delphinid family.
Long-finned pilot whales are dark brown to black in colour, with younger animals being paler and new-borns being light grey. There is a light anchor-shaped pattern on the belly, and on some a whitish stripe extends towards the tail along the back and sometimes also behind dorsal fin. The flippers are long (to one-fifth of the body length or more) and sickle-shaped and acutely pointed on the tip. The tail is dorsally thickened just in front of the flukes, which have a concave trailing edge and a deep median notch. Long-finned and short-finned pilot (G. macrorhynchus) whales differ by their flipper length, skull shape and number of teeth (e.g., Bloch et al. 1993c, Culik 2011) and are therefore difficult to distinguish at sea.
The long-finned pilot whale is a very social species and are almost always seen in groups of tens or hundreds of animals of both sexes, but single animals are also observed. They are dark in colour with a thick and bulbous head, but the dorsal fin of the adults is their most distinctive feature. It is falcate (hooked) to flaglike, low in profile, markedly longer at the base than at the peak and set far forward on the animal’s back. It makes pilot whales easy to differentiate from any other species in the NAMMCO area. The two species they could be confused with, the short-finned pilot whale and the false killer whale, which overlap at the southern end of the range, do not occur commonly in the NAMMCO area.
The blow of the pilot whale is usually inconspicuous. Pilot whales only rarely show surface behaviours when swimming. Occasionally they can be seen resting or ‘logging’ at the surface, and sometimes spy hopping or lobtailing. They are relatively slow-swimming; radio-tagged individuals averaged a speed of 3.3 km/hr, with burst of up to 16 km/hr (Mate 1989), while the average speed of three satellite-tagged whales off the Faroes was 4.7 km/hr (Bloch et al. 2003).
Pilot whales are commonly observed in association with other species such as bottlenose (Tursiops truncatus), common (Delphinus delphis) and Atlantic white sided (Lagenorhynchus acutus) dolphins, but also with fin (Balaenoptera physalus) and minke (Balaenoptera acutorostrata) whales, sperm whales (Physeter macrocephalus) and Risso’s dolphins (Grampus griseus).
Off the Faroe Islands, males reach a length of 6.25 m and a weight of 2.3 tonnes, compared to 5.12 m and 1.3 tonnes for females. Calves average 178 cm (range: 163 – 191 cm) at birth (Bloch et al. 1993b). Pilot whales exhibit striking sexual dimorphism. In addition to their larger size, adult males develop a more pronounced and bulbous melon and have a much larger and rounder dorsal fin with a thicker leading edge. They also have longer flippers and larger flukes (Bloch et al 1993c).
Pilot whales at Tysfjord, northern Norway
Like many species of toothed whales, pilot whales are highly social animals and usually occur in pods of 10 to 200 whales, with larger pods occurring more rarely. The largest pod caught in the Faroese drive fishery numbered 1200 animals (Zachariasssen 1993, Bloch 1998). Pods ususally comprise animals of all ages and sexes, with adult females outnumbering adult males (Bloch et al. 1993a). Male-only pods and pods consisting mainly of males have been observed however (Desportes et al. 1994a).
All individuals in the pod, including adult males, are related but males tend not to be the fathers of the calves in the pod, and the pods constitute close matrilineal associations (Amos et al. 1991, 1993ab, Anderson 1990, 1993). Investigation in other areas, based on photo-identification and genetic work, confirm the existence of relatively stable pods, like those of killer whales and unlike the fluid groups characteristic of many smaller dolphins (Jefferson et al. 1993, Canadas and Sagarminaga 2000, Ottensmeyer and Whitehead 2003).
Pilot whales are loosely polygynous. During aggregation, males will temporarily leave their pods to mate with females from other pods (Amos et al. 1993b, Andersen and Siegismund 1994). Mating occur reciprocally between pods and there is no evidence of strong male reproductive dominance (Amos et al. 1993a). Individual males may sire several offspring in the same pod (Amos et al. 1991).
Long-finned pilot whales can exhibit highly synchronous breathing and diving behaviour, both during shallow and deep dives, coupled with body contact (Senigaglia and Whitehead 2012, Aoki et al. 2013). As synchronous swimming does not induce saving in locomotion effort, but on the contrary actually entails some locomotion costs, it must have other functions, such as reinforcing social bonds (Aoki et al. 2013). It allows for close proximity and rapid coordinated response of individuals, with the multiple functions such as showing affiliation and reacting to disturbance (Senigaglia et al. 2012).
Pairs of long-finned pilot whales can perform highly synchronous surfacing behaviour, at less than one body length apart (Senigaglia and Whitehead, 2012). This behavioural synchrony can be maintained during deep foraging dives, when pilot whales jointly swim to several hundred meters of depth in search for prey (Aoki et al. 2013). This suggests that long-finned pilot whales employ a social foraging strategy, whereby individuals synchronize their foraging behaviour, although they do not always synchronize their individual dives (Visser 2014, Visser et al. 2014). During foraging, groups sometimes break up into smaller and more widely spaced units with a higher degree of milling behaviour (Visser 2014).
An original diving and foraging behaviour?
Diving behaviour was studied off the Faroes by equipping pilot whales with satellite-linked time-depth recorders (Heide-Jørgensen et al. 2002, Bloch et al. 2003, Mikkelsen 2008 and pers. com.).
Dives may last op to 18 min to a maximum depth of 852 m. However 60% of the dives lasted less than three minutes and most diving activity occurred at depth of less than 36 m, although the whales were also travelling off the shelf over water depths exceeding 1,500 m. The whales spent 60% of their time above 7 m. This behaviour is similar to that observed in the Mediterranean Sea (Baird et al. 2002). This intermediate diving behaviour, with the animals spending most of their time close to the surface but typically conducting bouts of foraging dives to intermediate depth of 300-600 m was also observed in the Norwegian sea using Dtags (digital tags) (Sivle et al. 2012).
Compared to other similarly-sized odontocetes, the long-finned pilot whale spent a higher proportion of their time at the surface and exhibited less extreme diving in terms of duration and maximum depth of dives. This may be linked with lower dive capability, the use of a foraging niche in the water column requiring less extreme diving and/or a similar foraging behavious as the short-finned pilot whales using deep sprints for catching prey capable of moving fast, such as Todarodes (flying squid). The sprints, which appear to challenge the common view on optimal foraging in breath-holding, deep-diving predators, reflect a high-cost foraging strategy that is necessary to capture high-value, evasive prey (Aguilar de Soto et al. 2008).
Vocalisations produced by pilot whales incude clicks, whistles and pulse sounds and calls vary with behavioural context (Taruski 1979). Vocalisations are more complex with active behaviour and greater dispersal of the group or more subgroups present, they are simpler with less active behavior, such as resting at the surface. The vocalisations possibly serve to maintain contact and coordinate the movements of the herd (Weilgart and Whitehead 1990, Kok 2012).
With a mean frequency of 4480 Hz, the calls of long-finned pilot whales are lower in frequency, longer and of a narrower frequency range than those of the short-finned pilot whales and there are geographical differences (Rendell et al. 1999). Pilot whale clicks are also different in duration (shorter), frequency (higher), and energy distribution than those of killer whales in the same area (Eskesen et al. 2011). Whistles last less than a second and are repeated typically 14-41 times per minutes. Some may act as ‘signature-whistles’ unique to individual whales (Martin et al. 1990).
As one of the most abundant cetaceans in the North Atlantic, pilot whales are important consumers in the marine ecosystem. They may be one of the most important marine mammal predators in the offshore waters of northwestern North America (Gannon et al. 1997ab). In the central North Atlantic around Iceland, pilot whales are likely the 4th most important marine mammal predator in the marine ecosystem, consuming 200 to 300 thousand tonnes of fish, and 900 to 1100 thousand tonnes of squid per year (Sigurjónsson and Víkingsson 1997). Much of this consumption is concentrated on species presently of little importance to commercial fisheries, so direct competition with fisheries is probably minimal.
Predation and parasites
Pilot whales have few predators besides humans, but may be preyed upon by killer whales (Orcinus orca) and large sharks. Striking changes in behaviour have been observed during playback of killer whale sounds (Miller et al. 2011, Curé et al.2012).
Pilot whales are often infested with whale lice (Isocyamus delfini), cestodes and nematodes (Balbuena and Raga 1991, 1993, Raga and Balbuena 1993). The stomach parasites Annisakis simplex is particularly prevalent in pilot whales from the Faroes, the infestation beginning with the onset of feeding and increasing with age (Raga and Balbuena 1993).
Male pilot whales reach sexual maturity at 11 to 22 years of age (Desportes et al. 1993, 1994d), while females do so at age 5 to 15 and both sexes reach physical maturity at age 25 to 30 (Bloch et al. 1993b, Martin and Rothery 1993). Gestation lasts about 12 months (Martin and Rothery 1993), with a significant overall foetal mortality (Desportes et al. 1994b). The fertility of females declines with age, and whales older than 40 years rarely become pregnant (Martin and Rothery 1993, ICES 1996), although the phenomenon is less accentuated than in short-finned pilot whales (Foote 2008).
The mean size at birth is 178 cm and 75 kg. Although remains of prey, together with milk, are observed in calves only a few months old, young nurse on average for 3–4 years. Lactation can however last much longer; up to 7 years in males and 12 years in females. This protracted lactation period is believed to be of social rather than nutritional importance (Desportes and Mouritsen 1993), allowing for long-lasting mother-calf bonds. It is consistent with the stable matrilineal school structure described for the species (Andersen 1990, 1993, Amos et al. 1991, 1993a,b). Post-reproductive females possibly play important roles in the survival of their last young. As they can no longer bear young of their own, they invest in their current one and continue to lactate and nurse.
Pilot whales are primarily consumers of squid and are essentially oceanic and deep water feeders, but they seem to be opportunistic feeders that may exploit any locally abundant prey and both the oceanic and neritic (coastal) habitats.
Off the Faroe Islands, pilot whales are clearly squid specialists and feed mainly on the European flying squid (Todarodes sagittatus) and the harmhook squid (Gonatus spp.), although other species, some benthic, are present in the same areas. Fish such as greater argentine (Argentina silus), blue whiting (Micromisistius poutassou), Greenland halibut (Reinhardtius hippoglossoides) and pandalid shrimps are also consumed. Although cod, herring and mackerel are common species in the neritic zone around the Faroes and have been reported as pilot whale prey elsewhere, they do not appear in the diet (Desportes 1985, Desportes and Mouritsen 1993).
Off Scotland, the French Atlantic coast and the NW Iberian Peninsula, the main component of the diet is also cephalopods, although fish are also present in varying importance (Martin et al. 1987, Gonzáles et al. 1994, Pierrepont et al. 2005, Spitz et al. 2011, Santos et al. 2013). Scottish whales consumed oceanic squid species, while the benthic octopods constitute the most numerous prey off the Iberian Peninsula and France.
In the Northwest Atlantic, the short and long-finned squids Illex illecebrosus and Loligo pealei dominate the diet of pilot whales, the Atlantic mackerel (Scomber scombrus) and Atlantic herring (Clupea harengus) are also present (Overholtz and Waring 1991, Abend and Smith 1997, Gannon et al. 1997a, 1997b). Cod (Gadus morhua) was reported as a secondary prey in earlier studies (Sergeant 1962, Mercer 1975).
Pilot whales can thus feed on a wide variety of prey and consume both oceanic and neritic species and pelagic and benthic species. They adjust their diet in response to changes in prey abundance. Off the Faroes, in years where Todarodes is abundant on the Faroe shelf, the diet becomes nearly mono-specific, centered upon that species. In years where Todarodes is not abundant, the diet is more diverse and other species of squid and fish are consumed, species which were also abundant in Todarodes years but not preyed upon. They may feed predominantly on fish when squid are not readily available (Desportes and Mouritsen 1993).
This dietary plasticity is also illustrated in the fact that pilot whales can forage in, and occupy successfully or shift to and from both oceanic and neritic habitats (Desportes 1985, Desportes and Mouritsen 1993, Spitz et al. 2011, Santos et al.2013). The use of ecological tracers reflecting longer-term diet, such as cadmium, carbon and nitrogen isotope ratios, and fatty acid signatures have also confirmed this foraging plasticity (Méndez-Fernandez et al. 2012, 2013, Monteiro 2013).
Distribution and Habitat
The long-finned pilot whale has a boreal distribution in the cold temperate and subpolar waters of all oceans except the North Pacific (Taylor et al. 2008), with a typical temperature range of 0-25° C (Martin et al. 1990). Globicephala melas melas occurs in the northern hemisphere and Globicephala melas edwardii inhabits the southern hemisphere (Olson 2009). This oceanic species occurs far offshore, but can also be found in coastal areas.
Distribution in the North Atlantic
Long-finned pilot whales are very widely distributed in the North Atlantic, from about 35°–65° N in the west and from about 40°–75° N in the east (ICES 1996; NAMMCO 1998ab, Abend and Smith 1999, Reid et al. 2003; Garrison et al. 2011; Roberts et al. 2016).
The 28-year long series of NASS and T-NASS summer sightings surveys, centered upon the three first weeks of July, provides a good understanding of the potential summer distribution of the species in the North Atlantic. There is an apparent gap in distribution in the area south of Greenland, however, this area has not been surveyed extensively so the gap may be an artefact.
Pilot whales can shift to and from oceanic and coastal habitats, as revealed by their feeding ecology (Desportes 1985, Desportes and Mouritsen 1993, Spitz et al. 2011, Méndez-Fernandez et al. 2012, 2013, Monteiro 2013). A recent spatial analysis of pilot whale distribution in the Northeast Atlantic (Rogan et al. 2017) indicated that summer numbers were highest in water depths >1,000 m and that they tended to be most abundant over areas of moderate slope. Abundance was also strongly associated with latitude, peaking at about 55° N and declining further north and south.
Pilot whale distribution does change from year to year, as is apparent from the distributions observed during the six NASS surveys (see sightings map). Although there is no indication that pilot whales undertake extensive seasonal migrations, their distribution also changes on a seasonal basis, with whales moving onto the slope, shelf and shelf edges over the summer months and moving back southwards into deeper offshore waters in winter (Sergeant and Fisher 1957, Sergeant 1962, Evans 1980, Payne & Heinemann 1993, Roberts et al. 2016). This also reflects in the July–August peak in the frequency of pilot whale drives in the Faroes (Zachariassen 1993).
The abundance and movements of preferred prey seem to drive pilot whale abundance and movements, as with the flying squid (Todarodes sagittatus) off the Faroes (Desportes and Mouritsen 1993, Zachariassen 1993, Jákopsstovu 2002), the northern shortfin squid (Illex illecebrosus) off Newfoundland (Mercer 1975) and the longfin inshore squid (Loligo pealei) and Atlantic mackerel (Scomber scombrus) off the United States (Smith et al. 1990, Payne and Heinemann 1993, Gannon et al. 1997b). The same pattern seems also present off the Iberian Peninsula, with the movements of the northern shortfin and lesser flying (Todaropsis eblanae) squids correlated with the distribution of pilot whales in the area (Santos et al. 2013).
North Atlantic Stocks
The stock structure of the North Atlantic population remains uncertain, despite genetic, morphometric, physiological and observational studies (ICES 1993, 1996; Fullard et al. 2000).
Studies analyzing differences in mitochondrial DNA (mtDNA) and allozymes in pilot whales across the North Atlantic have shown no significant differences between pilot whales from the western Atlantic, Iceland and the eastern Atlantic (Andersen 1993, Siemann 1994). This could be considered as evidence that there is only one stock of pilot whales in the North Atlantic. However, this uniformity may be related the social structure of pilot whales. If they occur in strong matrilineal (derived from mother) schools, as suspected, then the actual population unit is the school rather than the individual, making the genetically effective population size relatively small, in the order of several thousands rather than hundreds of thousands (ICES 1996, NAMMCO 1998b). This small effective population might be expected to have a low mtDNA variability. Andersen (1993) found that schools captured in the Faroes differed in their allozyme composition, suggesting that genetic differences between schools do exist.
More recently, however, a study using neutral microsatellite markers (Fullard 2000, Fullard et al. 2000) revealed significant genetic differentiation within the North Atlantic, and particularly between West Greenland and other both western and eastern regions (Cape Cod, Faroes and UK). This could not be explained by a simple isolation-by-distance model. Instead, the pattern of genetic differentiation suggested that population isolation occurs between areas of the ocean which differ in sea surface temperature, with 1) a cold-water population west of the Labrador/North Atlantic current, and 2) a warm-water population that extends across the Atlantic in the Gulf Stream.
Recently, Monteiro (2013) used both mitochondrial DNA (mitochondrial control region, neutral marker) and two loci of the Major Histocompatibility Complex (MHC, adaptive marker) on samples from USA, Faroes, Norway, UK and Northwest Iberia to revealed a level of genetic substructure in the North Atlantic, with consistent divergence patterns describing Northwest Iberia as a separate group.
Other lines of evidence suggest that there are at least two stocks in the North Atlantic. There are morphometric (body shape) differences between pilot whales caught in the Northwest and Northeast Atlantic (Bloch and Lastein 1993, ICES 1996). This indicates that pilot whales from the two areas are unlikely to be from the same stock. In addition, the depletion of pilot whales off Newfoundland from 1947 to 1972 apparently had no effect on pilot whale abundance elsewhere, indicating that there is probably little or no exchange between this area and others (Mercer 1975, Nelson and Lien 1996).
There may also be differences over smaller spatial and temporal scales. There were significant differences in pollutant concentrations (Aguilar et al. 1993, Caurant et al. 1993) and parasite burdens (Balbuena et al. 1993, 1994, 1995) between schools of whales landed in the Faroe Islands at different times and locations. This suggests that these schools spend different proportions of their time in different areas, which again may be indicative of stock differences and negate the hypothesis of just one resident Faroese population (ICES 1993).
In 1997, the Scientific Committee of NAMMCO concluded that, based on the evidence noted above, it was likely that there was more than one stock of pilot whales in the North Atlantic, and more than one stock subject to harvesting in the Faroe Islands (NAMMCO 1998b). It was apparent that further research was still required to resolve the stock delineation of pilot whales in the North Atlantic and this is still the case. However, the new genetic information strongly point to the existence of substructuring in the North Atlantic and the 2011 and 2012 satellite tagging clearly support that pilot whales caught in the Faroes do not belong to a resident population.
Current Abundance and Trends
Estimates of the abundance of pilot and other species of whales in the North Atlantic have been based largely on sightings surveys conducted from ships and airplanes. The North Atlantic Sightings Surveys (NASS) provide a time-series of abundance estimates from 1987 to 2015, covering a large part of the North Atlantic. Norwegian “mosaic” surveys cover most of the Northeast Atlantic, surveying a portion of the area annually on a six year rotation. In addition, the European CODA, American SNESSA (Southern New England to Scotian Shelf Abundance) and Canadian NAISS surveys have contributed to our knowledge of pilot whale abundance and distribution.
Abundance and trends in the North East Atlantic
The six NASS covered substantially different areas and, not surprisingly, yielded different population estimates for pilot whales. Year-to-year shifts in distribution are also apparent. The 1989 survey, conducted about two weeks later in the summer than the other surveys, extended farther south to cover the largest area of potential pilot whale habitat (1,279,741 nm²) and yielded the most reliable total estimate of 778,000 (CV=0.295) for the northeastern North Atlantic Ocean, although small numbers occur outside the area considered (Buckland et al. 1993). No sightings were made in the area North and northeast of the area, thus indicating that the joint survey covered the northernmost areas of pilot whale distribution.
The table below gives the abundance of pilot whales for the first five NASS for the Faroese and Icelandic areas with all data re-analysed similarly (Pike et al. 2013). It also presents an estimate from the NASS, SCANS and CODA areas combined from 2005-7, covering a very large area of the Northeast Atlantic. The 1989 estimate is significantly higher than the 1987, 2001 and 2007 estimates, but the 1989 survey had a substantially different timing and coverage (larger area, extending more to the south and west) than the others, with the possibility of more pilot whales having moved inside the area. The numbers suggest that the occupation or timing of occupation of the Northeast and Central Atlantic by pilot whales varies greatly from year to year. The table also provides estimates of pilot whales for West and East Greenland and Eastern Canada from 2007 and 2015. Taken together, these estimates suggest that up to 560,000 pilot whales occupy the Northeast and Central Atlantic area in some years, with somewhat smaller numbers in the Western Atlantic.
Trends in abundance
The estimates listed above are not directly comparable to one another because the area covered is not the same for all surveys. However, Pike et al. (2018) restricted the estimates to the area covered by all six surveys, and to the area covered by the three larger surveys (1989, 1995 and 2007). Because they cover exactly the same area, these “Survey Index Regions” are directly comparable between surveys. The Index Region covered by all six surveys shows a general decline in numbers from 1987 to 2007, followed by a recovery to the highest numbers yet observed in 2015. The Index Region covered by the three largest surveys shows a general decline from 1989 to 2007. However, the estimate from the smaller six-survey Index Region in 2015 is higher than most of those from the larger three-survey Index Region, indicating that a recovery would have been observed had the larger area been surveyed in 2015. This analysis therefore provides no evidence of any trend in pilot whale numbers in the Northeast Atlantic over the 28 year period from 1987 to 2015. The great variations in numbers between surveys within the Index Regions again confirms that the distribution of pilot whales differs greatly from year to year.
An indication of long term historical trends in the abundance of pilot whales around the Faroe Islands can be gained from analysis of catch data. Catch records from the Faroes go as far back as 1584, and are unbroken since 1709 (Bloch 1994). Catch, corrected for hunting effort, shows a cyclic pattern with a period of 100–120 years, with peaks in catch occurring in 1720–1730, 1840–1850, and 1935–1985 (Hoydal and Lastein 1993). There is no long-term indication of declining or increasing abundance over the period (Bloch and Lastein 1995). The local availability of pilot whales to the Faroese may be related to changes in sea temperature and the abundance of their favoured prey. See under ‘Life history and Ecology‘ for further detail.
Abundance and trends off the eastern U.S. and Canadian Atlantic coast
Pilot whales are common in the offshore waters of the northeastern USA and Canada (Mercer 1975, Lynch 1987, Nelson and Lien 1996, Gannon et al. 1997a, 1997b, Waring et al. 1999, Garrison et al. 2011, Roberts et al. 2016). However, the abundance and trends in abundance are uncertain, although several abundance estimates are available from selected regions for select time periods.
Long-finned and short-finned pilot whales overlap spatially along the mid-Atlantic shelf break between Cape Hatteras, North Carolina, and New Jersey. As the two species are difficult to distinguish at sea, sighting data during abundance surveys are reported as Globicephala sp. and thus combined abundance estimates for the two species have previously been derived from line-transect surveys. Sightings from shipboard and aerial surveys have been strongly concentrated along the continental shelf break; however, pilot whales are also observed over the continental slope in waters associated with the Gulf Stream (Roberts et al. 2016).
The best available abundance estimates are from surveys conducted during the summer of 2004 (Waring et al. 2012). These survey data have been combined with an analysis of the spatial distribution of the two species based on genetic analyses of biopsy samples to derive separate abundance estimates. The best resulting abundance estimate for long-finned pilot whales in U.S. waters is 12,619 (CV=0.37). More recently Roberts et al. (2016) estimated pilot whale abundance off the eastern USA as 18,977 (cv 0.11), however this included both short- and long-finned pilot whales.
Although there is no information on abundance trends, abundance is likely increasing because human-induced mortality has declined in recent years (Waring et al. 1999).
Pilot whales were subject to an intensive drive fishery in Newfoundland from 1947 to 1972, and this fishery apparently reduced the stock to very low levels (Mercer 1975, Hay 1982, Nelson and Lien 1996). Abundance at the onset of the fishery was likely about 60,000 animals (Mercer 1975). Hay (1982) conducted in 1980 an aerial survey in eastern Newfoundland and Labrador waters, and estimated 13,167 whales (95% C.I. 6,731 to 19,602, not corrected for diving whales or whales missed by observers). In July–August 2007, the Canadian part of the Trans-North Atlantic Sighting Survey (T-NASS) covered the area from northern Labrador to the Scotian Shelf, thus providing full coverage of the Atlantic Canadian coast (Lawson and Gosselin 2009, 2011, 2018). This aerial survey generated an abundance estimate of 32,999 pilot whales (95% CI approximately 14,468-75,265) (Lawson and Gosselin 2018). Almost all pilot whales were sighted off Nova Scotia in the southern part of the survey area (Lawson and Gosselin 2009). The survey was repeated in 2016, resulting in an estimate of similar magnitude (see table above). However, in this survey, which was conducted about 2 weeks later than in 2007, pilot whales had a more northerly distribution, suggesting seasonal movement in to the area (Lawson and Gosselin 2018). Taken together, these surveys suggest that pilot whale numbers are stable or recovering in the area.
A trend analysis incorporating all six NASS surveys covering the 28 year period from 1987 to 2017 found no trend in pilot whale numbers over the period (Pike et al. 2018). Given the minimum size of the population, as indicated by the 1989 survey, of over 500,000 animals in the Northeast and Central Atlantic, it seems very unlikely that an annual harvest of around 1,000 whales in the period 1987–2015 would cause a reduction in the population. The fact that the population has been subject to approximately the same level of harvest for at least 300 years, with apparently little change in availability (Hátún and Gaard 2010), also suggests that the Faroese harvest is likely not causing the stock to decline in numbers. In 1997, NAMMCO concluded that the drive hunt was sustainable (NAMMCO 1998c).
The effect of catches of pilot whales in the Faroe Islands depend critically about the geographic range of the population, which is affected by these catches (ICES 1996, see figure below). If the whales come from the Mid-Atlantic Ridge-Iceland Area (A+B+C) or the area covered by the NASS 1989 (A+B+C+D) sighting survey, then catches over the last 150 years have hardly any impact on the population trajectory. However the qualitative effect of the catches is very different if they have come from a population with a geographic range the size of the Rockall-Iceland Area (A+B) or the Faroese Islands Area (A).
Although the stock delineation of pilot whales remains uncertain, non-genetic evidence (pollutant concentrations and parasite burdens, see above) indicate that there is likely more than one stock subject to harvesting in the Faroe Islands (ICES 1996, NAMMCO 1998b) and that Faroese harvesting is not concentrated on a small resident population. The satellite tagging data also show that pilot whales caught off the Faroes moved well beyond the Faroe Islands Area. Indeed the satellite tagging data from 2012 indicate that the whales moved well beyond the Mid-Atlantic Ridge Area (A+B+C below), as well as beyond the extent of the 3-NASS Survey Eastern Index Region.
The abundance of pilot whales in the population contributing to the catch required to sustain an annual catch of 678 animals (the average annual Faroese catch 1997–2011) is between 50,000 and 80,000 whales (with a precision equivalent to that of the sightings survey in 2007) (NAMMCO 2013). The population in the Eastern Index Area, which is smaller than the range of the population affected by the catch, is alone over 100,000 pilot whales. That said, the last formal assessment (ICES 1996) is dated and the NAMMCO Scientific Committee is planning a new assessment tentatively scheduled for 2019, which will take into account all new information, including new estimates of abundance and trend analyses.
The average annual catch of long-finned pilot whales in West Greenland during 1993–2007 was 126 whales. The aerial NASS 2015 survey off west Greenland yielded an abundance of 8,133 pilot whales (95% CI = 3,635–23,234), but only partly covered the potential pilot whale habitat, as aggregations of pilot whales were encountered at the western edge of the survey area (Hansen et al. 2018). The estimate from a similar survey carried out in 2007 was of similar magnitude (Guldborg Hansen and Heide-Jørgensen 2013). The NAMMCO Scientific Committee (2013) suggested that a sustainable harvest level of pilot whales taken from this abundance would be between 50–70 whales per year. However, it seems likely that the size of the stock subject to the Greenlandic hunting is larger than that revealed by the survey, and that the summer aggregation off West Greenland cannot be considered an isolated stock. Instead, it is likely connected to pilot whales along Labrador and at Newfoundland, and the occurrence and abundance in West Greenland is probably influenced by the sea temperature regimes in the area (Fullard et al. 2000). For these reasons the stock status of West Greenland pilot whales remains uncertain.
The 2011 US assessment (Waring et al. 2012) concluded that the status of long-finned pilot whales in the U.S. Atlantic EEZ was unknown. There were insufficient data to determine population trends for this species. The total U.S. fishery-related mortality and serious injury for long-finned pilot whales was unknown, since it was not possible to partition mortality estimates between the long-finned and short-finned pilot whales. However, this mortality was most likely not less than 10% of the calculated PBR (Potential Biological Removal) and therefore could not be considered to be insignificant and approaching zero mortality and serious injury rate. Therefore, it was recommended that the stock should be considered a strategic stock. However, the inability to partition mortality estimates between the two pilot whale species limited the ability to adequately assess the status of the long-finned pilot whale stock.
Pilot whales were subject to an intensive drive fishery in Newfoundland from 1947 to 1972, and this fishery apparently reduced the stock to very low levels (Mercer 1975, Hay 1982, Nelson and Lien 1996). Abundance at the onset of the fishery was likely about 60,000 animals (Mercer 1975). Hay (1982) conducted in 1980 an aerial survey in eastern Newfoundland and southeastern Labrador waters, and estimated 13,167 whales (95% CI = 6,731-19,602, not corrected for diving whales or whales missed by observers).
Nelson and Lien (1996) concluded that the population had likely not yet recovered to its pre-exploitation size. This seems confirmed by the results of the 2015 Canadian NAISS survey part of the T-NASS survey (Lawson and Gosselin 2018), which provided a full coverage of the Atlantic Canadian coast and yielded a fully corrected abundance estimate of 28,218 (approximate 95% CI = 14,236–55,934). The estimate from the Canadian component of the 2007 T-NASS survey was of similar magnitude (Lawson and Gosselin 2011). Taken together, these surveys suggest that pilot whale numbers are stable or recovering in the area.
Pilot whales are likely one of the most abundant odontocetes in the North Atlantic. The harvesting of pilot whales that continues today in the Faroe Islands has proven sustainable over a period of more than 400 years. In 1997, NAMMCO concluded that the drive hunt was sustainable (NAMMCO 1998c). The population off Newfoundland is likely slowly recovering after a period of excessive harvesting.
In some other areas, by-catch of pilot whales in fisheries continues, but apparently at relatively low levels. While there is no indication at present that pilot whales are being affected by contaminants, their occupation of a relatively high trophic level and the high level of contaminants observed does make them susceptible to this threat.
Better information on the abundance and trends in abundance of pilot whales is required to ensure the long-term sustainability of these harvests. In addition, further information on stock delineation, and geographical range of any stock components found, would improve the ability to design and carry out effective surveys for this species. In the light of the new genetic information, the recent tagging data, as well as the new abundance estimates obtained from the 2015 NASS survey (analysis in progress) and the 2016 SCANS III survey, a new assessment is warranted. NAMMCO will conduct a full assessment of the species in 2019.
Conservation Status according to other international organisations
CITES – Convention on International Trade in Endangered Species of Wild Fauna and Flora
Long-finned pilot whales are currently listed on Appendix II of the CITES. CITES is a legally-binding multilateral environmental agreement that aims to ensure that international trade does not threaten the survival of species in the wild. Both Greenland and the Faroes are signatories to the convention through Denmark. A listing on Appendix II means that an export permit shall only be granted when the Scientific Authority of the State of export has advised that such export will not be detrimental to the survival of the species in the wild. There is however no export of pilot whale products from Greenland or the Faroes, except for a very small non-commercial export of meat and blubber for family consumption.
IUCN – International Union for Conservation of Nature
IUCN classify long-finned pilot whales, treated as one species, as Data Deficient, with the following justification: There is evidence that long-finned pilot whales may comprise a complex of two or more species. Because additional data should resolve this taxonomic uncertainty, the current species is listed as Data Deficient. Threats that could cause widespread declines include high levels of anthropogenic sound, especially from military sonar and seismic surveys, and by-catch. Primary threats that could cause widespread declines include entanglement in fisheries and competition with squid fisheries. The combination of possible declines driven by these factors is believed sufficient that a 30% global reduction over three generations (72 years; Taylor et al. 2007) cannot be ruled out (criterion A) (Taylor et al. 2008).
Long-finned pilot whales inhabit the waters of the four NAMMCO member countries: Faroe Islands, Greenland, Iceland and Norway.
The long finned pilot whale is not protected in Iceland, but pilot whales are not hunted there. However, mass strandings happen from time to time (see under Mass strandings).
Pilot whales are protected in Norway, both in Svalbard and on mainland Norway.
Pilot whales are taken in southwest Greenland on an opportunistic basis (a few hundreds a year, see under Recent harvests). There are no quotas for pilot whales in Greenland, however there are regulations pertaining to hunting methods and equipment.
Regulation of the Faroese pilot whale hunt is based on old Norse laws, and is regulated by government order which deals in detail with all aspects of the hunt, including driving procedures, beaching, killing methods and approved equipment, valuation, distribution and beach cleanup. These regulations are subject to regular review and have been updated and revised a number of times in recent years, both to keep them consistent with technological developments and to refine some of the organisational aspects of the drive and the distribution. A recently developed spinal lance has been introduced as mandatory for the killing of pilot whales. The spinal lance has been shown to reduce killing time to 1-2 seconds, while also improving accuracy and safety (Anonym 2013). A blowhole hook has also been developed and from May 2015, only persons having attended a certified course of instructions in the whaling regulations and killing methods will be permitted to kill whales. NAMMCO (2014) has recently published an Instruction Manual on Pilot Whaling (The manual exists in Faroese and English).
Only some specific bays, today numbering 23, which meet the requirements for suitable whale beaching conditions, are allowed for the slaughtering of the whales. The hunt is supervised by elected grindforemen, who are themselves under the supervision of the sýslumaður, or district sheriff. The sýslumaður also oversees the valuation and division of the catch, and is responsible for keeping records of the harvest (e.g. Bloch et al. 1990, Bloch 2007, Anonym 2013).
There are no quotas, but certain beaches or entire whaling districts can be closed when harvests are considered sufficient.
The catch is shared freely among those taking part in the drive and the local residents of the whaling bay and district in accordance with a complex, traditional community sharing system. The division of the catch is administered by the relevant sýslumaður. The catch is divided into shares known in Faroese as a skinn, which is a age-old measurement value that derives from agriculture practices. One skinn is roughly equivalent to 34 kilograms of blubber and 38 kilograms of meat. Whales in the cacth are numbered, their condition is assessed and they are valued using a traditional wooden pole calibrated in logarithmic division representing the value in skinn. Their value in skinn is marked in roman numerals on the flipper (e.g. Joensen 1976, Bloch et al. 1990, Bloch 2007).
Levels of PCB’s and mercury are relatively high in the blubber and meat of pilot whales taken in the Faroes (Borrell and Aguilar 1993, Caurant et al. 1993). In some cases, the level of consumption of pilot whale by Faroese may lead to intake of these substances that exceeds recommended levels. This is of particular concern given the documented neurotoxicity of methylmercury, in particularly to the developing foetus (Weihe et al. 1996; for more details see under Contaminants). Consequently, since 1998 the Faroese health authorities have been provided regular recommendations for the consumption of pilot whale meat and blubber, in response to most current research and based on the latest internationally applied standards for precautionary limits, the latest one in June 2011.
You can find more information on the Faroese pilot whaling here, as well as accessing the last executive order on the pilot whale drive (July 2013) in English translation.
Pilot whales have a long history of utilisation by humans in the North Atlantic. In the 20th century, they have been harvested in Greenland, Iceland, the Faroe Islands, western Ireland, Shetland and Orkney Islands and Norway, the eastern USA and Newfoundland in Canada (Mitchell 1975, Nelson and Lien 1996). They continue to be harvested in the Faroe Islands and Greenland. In most places, pilot whaling was conducted as drive fisheries. Meat and blubber were used for human consumption.
Pilot whales are taken in southwest Greenland on an opportunistic basis. They are usually hunted from small boats using rifles and hand harpoons. Recent catches have ranged between 0 and 365 animals (Table below).
Drive fisheries for pilot whales in the Faroe Islands—known in Faroese as grindadráp—date back to the Norse settlement in the 9th century with written descriptions from as early as 1632 (Sanderson 1992). It represents “a distinctive cultural characteristic for the Faroe Islands” (Joensen 1976) and “an established symbol of Faroese national identity” (Sanderson 1992). In addition to the objects of material culture it has produced, the grindadráp has inspired authors, poets and songwriters in the Faroe Islands for centuries (e.g. Sanderson 1992).
Catch statistics exist since 1584 and are unbroken from 1709 to today. They show and annual average catch of 850 pilot whales (range 0-4,480) with a cyclic variation correlated with North Atlantic climatic variations and oceanic events (Hoydal and Lastein 1993, Bloch and Lastein 1995. Block 1998, Jákupsstovu 2002, Hátún et al. 2009, Hátún and Gaard 2010).
From 1709 to 1999, a total of 246,434 pilot whales have been caught in 1,766 pods. There have been an average of 6.1 grinds (whale drives) per year in that period, and grind size has ranged from 1 to 1200 whales, with a mean of 139.5 whales per grind (Zachariassen 1993, Bloch 1994). Since 2000, the pilot whale catch at the Faroes has ranged between 0 and 1107, with a yearly average for the period 2000–2013 of 671 animals (Table below).
In the Faroes, harvesting of pilot whales has been an important source of food for the inhabitants since the islands were colonized (e.g. Williamson 1970). Pilot whales are taken in an organised drive hunt, or grind. When whales are sighted, local small fishing vessels cooperate to drive the whales into designated beaches. Once ashore, they are killed by severing the neck arteries and veins using a specialized knife. The catch is then evaluated by designated officials who measure and mark the whales. The catch is divided into shares and distributed free of charge following specified rules to hunt participants and residents in the district. Larger catches are distributed more widely (e.g. Bloch et al. 1990, Bloch 2007, Ministry of Fisheries).
USA and Canada
An important pilot whale drive fishery was active at Cape Cod from the mid-1700s to the 1920s. During the late 1800s the mean annual catch was in the order of 2–3,000 animals. A drive fishery was also active off the shores of Virginia and North Caroline (Mitchell 1975 a,b).
Newfoundland’s drive fishery was active from 1947 to 1964 and at its highest in 1956, with catches reaching almost 10,000 animals (Sergeant 1962, Mitchell 1975a). It declined shortly after and is now defunct.
Pilot whale meat is high in protein (higher than beef) and low in fat. Because a whale’s fat is contained in the layer of blubber beneath the skin, and the muscle is high in myoglobin, the meat has a dark red colour (e.g. Bloch 2007).
Both the meat and blubber of pilot whales have long been—and continue to be—a valued part of the national diet. Catches are shared largely without the exchange of money among the participants in a whale drive and residents of the local district where they are landed (e.g. Bloch 2007, Ministry of Fisheries).
On average, 54% of the total weight of a whale is consumed as meat and blubber, with up to 60% in larger whales, which have proportionally larger muscle mass than smaller whales. In comparison, in average 47% of a fish weight is consumed (Bloch 2007).
Whale meat and blubber are stored, prepared and eaten in a variety of ways (e.g., Bloch 2007, Ministry of Fisheries). When fresh, the meat is boiled or served as steaks, with blubber and potatoes. The meat and blubber can be frozen, or preserved using traditional Faroese methods such as dry-salting or storing in brine. Strips of whale meat are also hung to wind-dry for several weeks and then eaten raw in thin slices. Thin slivers of blubber are also a popular accompaniment to dried fish.
Catch statistics exist since 1584 and are unbroken from 1709 to today. They show an annual average catch of 850 pilot whales (range 0- 4,480) with a cyclic variation correlated with North Atlantic climatic variations and oceanic events (Hoydal and Lastein 1993, Bloch and Lastein 1995, Bloch 1998, Jákupsstovu 2002, Hátún et al. 2009, Hátún and Gaard 2010).
From 1709 to 1999, a total of 246,434 pilot whales have been caught in 1,766 pods. There have been an average of 6.1 grinds (whale drives) per year in that period, and grind size has ranged from 1 to 1200 whales, with a mean of 139.5 whales per grind (Zachariassen 1993, Bloch 1994).
Since 2000, the pilot whale catch at the Faroes has ranged between 0 and 1203, with a yearly average for the period 2000-2017 of 614 animals (see table of catches below).
Pilot whales are taken on an opportunistic basis and principally in southwest Greenland. Recent catches have ranged between 0 and 430 animals, with a yearly average for the period 2000-2013 of 204 animals (see table of catches above).
DID YOU KNOW?
A pilot whale stomach can be used as a buoy
Pilot whale stomachs were used as buoys until the 70s. Pilot whale stomachs have three compartments. The first one, called mechanical stomach, is made of very strong tissues and acts as a grinder. This part was emptied, placed in brine, then tanned and inflated for use as buoys with the long-lines (left). In former days, thongs of the dried skin were used in the boats to tie the oars to the wooden tollars which take the places of rowlock (right).
Other Human Impacts
Anthropogenic activities which may affect marine mammals generally and pilot whales specifically can be divided into two main categories: habitat degradation and oceanographic changes. Knowledge about pilot whale habitat use is limited and it is therefore difficult to assess the relative impact that such changes may represent for the species.
A range of human activities has the potential to degrade habitat important to pilot whale survival. The species occurs in coastal waters, but is essentially oceanic. Main threats include:
• changing water quality and pollution (e.g. runoff from agriculture, oil spills) • entanglement (e.g. in marine debris, fishing gear, etc.) • prey depletion due to over-harvesting • acoustic pollution with disturbance from low-frequency noise (vessels, seismic surveys, military activities)
In addition to their direct toxicity, anthropogenic contaminants may affect the resilience and increase susceptibility to disease in marine mammals (Reijnders and de Ruiter-Dijkman 1995). The accumulation of contaminants in pilot whales has been studied on both sides of the Atlantic (e.g. Aguillar et al. 1993, Borrell 1993; Borrell and Aguilar 1993, Borrell et al. 1995, Caurant et al. 1993, 1994, 1996, Caurant and Amiard-Triquet 1995, Tilbury et al. 1999, Dam and Bloch 2000, Weisbrod et al. 2000, 2001, Sonne et al. 2010, Méndez-Fernandez et al. 2014ab). Studies dating back to 1977 have shown an overall increase in contamination of the meat, blubber, liver and kidneys of pilot whales. Together with the killer whale (Orcinus orca), the long-finned pilot whale is one of the most polluted species in the world (AMAP 2004, 2005; Dam and Bloch 2000).
Faroese pilot whales have concentrations of organic contaminants in their blubber which are roughly in the mid-range of such concentrations in other species of toothed whales in the North Atlantic (Borrell and Aguilar 1993, Mendez-Fernandez et al. 2014b). It is not known if these contaminants are affecting the health of pilot whales in the North Atlantic.
The concentration of trace metals (other than copper) in the liver of pilot whales from the Faroe Islands is on the higher end of the range of what is found in other marine mammal species of the North Atlantic (Caurant et al. 1993) and pilot whales from other area of the North Atlantic (Méndez-Fernandez et al. 2014a). Cadmium levels, in particular, are very high and even higher than in species from highly industrialized areas (Caurant et al. 1993). This is probably related to their heavy consumption of squids (Bustamante et al. 1998).
The heavy metals mercury (Hg) and cadmium (Cd) produce adverse effects in various mammals, with risks of health impacts on internal organs, such as the liver and kidneys. Possible direct and indirect effects (e.g. immunodeficiency) of trace metals on pilot whales have been little studied. However, a recent study showed a high prevalence of histopathological changes in liver and renal tissues of Faroe Island pilot whales and suggested that age, heavy metal, and organic contaminants may be important factors in pathology development (Sonne et al. 2010).
The Faroe Islanders rely on pilot whales as an aboriginal and important wildlife food resource. However, the consumption of pilot whale meat is thought to representing a hazard to the health of consumers (e.g., Weihe et al. 1996, Steuerwald et al. 2000, Weihe and Joensen 2008, 2012, Choi et al. 2009, Grandjean et al. 2011). Pilot whales today contain contaminants (both organochlorines or metals) in concentrations such that neither meat nor blubber would comply with current limits for acceptable concentrations of toxic contaminants, and it has been recommended that pilot whales should no longer be used for human consumption (latest: Weihe and Joensen, 2012). As more developing nations industrialize, marine pollution is likely to increase. As the meat and blubber become more contaminated, their risk may increasingly outweigh their benefits (Fielding 2010).
Pilot whales are taken as by-catch in some fisheries on both sides of the Atlantic. They were taken in significant numbers in the Mediterranean driftnet fishery for swordfish (Xiphias gladius) in the 1980’s, however limitations on net size imposed in 1990 have probably ameliorated this problem (Notarbartolo-di-Sciara 1990, Natale and Notarboartolo-di-Sciara 1994). Currently, by-catch of pilot whales in the eastern Atlantic appears to be insignificant. For the period 2008–2012, the ICES Working Group on Bycatch of Protected Species reports only a few observed pilot whale by-catch in European Fisheries, all in the Atlantic: four in 2008 by a French midwater pair trawl; five in 2011 by a German midwater otter trawl; and one in in 2012 by a Dutch midwater otter trawl (ICES 2010, 2011, 2012, 2013, 2014).
In the western Atlantic, pilot whales have been taken as by-catch in several types of fisheries, including squid traps (Lien 1994), pelagic drift gillnets, trawls, purse seines and longlines (Waring et al. 1999). By-catches were highest in the pelagic drift gillnet fishery for swordfish, ranging from 9 to 135 whales per year between 1989 and 1996. This fishery was closed in 1997. By-catch of pilot whales in the western Atlantic was not considered to be causing stock decline or significantly impeding stock recovery (Nelson and Lien 1996, Waring et al. 1999), although there were probably more pilot whales taken incidentally than were documented (Bernard and Reilly 1999). The average annual estimated fishery-related mortality during 2000–2004 in the Northeast mid-water trawl fishery was 8.9 (CV=0.35) pilot whales and in the Atlantic herring mid-water trawl fishery 11 animals (Waring et al. 2007ab). The average annual mortality in the pelagic long-line fishery was 114 (CV=0.20) pilot whales during 2005–2009 (Waring et al. 2012). The 2005–2009 average mortality attributed to the mid-Atlantic bottom trawl was 30 animals (CV=0.16), to the northeast bottom trawl 12 animals (CV=0.14) and to the to the Mid-Atlantic mid-water trawl fishery was 2.4 (CV=0.99) (Waring et al. 2012). The total U.S. fishery-related mortality and serious injury for long-finned pilot whales is unknown, since it is not possible to partition mortality estimates between the long-finned and short-finned pilot whales, but it cannot be considered insignificant (Waring et al. 2012).
Competition with fisheries
Pilot whales prey on some commercially important invertebrate and fish species such as squid, shrimp, mackerel, blue whiting and herring. The availability of these for whales might therefore be reduced by commercial fisheries. Fisheries for squid are widespread on both side of the North Atlantic, targeting species which are the main prey eaten by pilot whales in the area: short-finned squid (Illex illecebrosus) off Newfoundland, long-finned squid (Loligo pealeii) off the US coast, European flying squid (Todarodes sagittatus) off the Faroe Islands, Norway and Portugal, curled octopus (Eledone cirrhosa) off Spain and Portugal. This raises the possibility of prey depletion for pilot whales.
The abundance of squid available to fisheries is known to exhibit dramatic yearly fluctuations, with no obvious pattern. Periods of either high or low abundance may last for several years. These changes would be determined by the interaction of fluctuating year-class strength and varying hydrographic conditions influencing natural mortality and the distribution of the early life stages (Arnold 1979, Fisheries and Oceans Canada 2013).
Long-finned pilot whales feed on a wide variety of prey, and appear to be able to adjust their diet in response to changes in prey abundance (Desportes and Mouritsen 1993; Santos et al. 2013). They are therefore likely less vulnerable to prey depletion than more specialised species. However, pilot whale diet includes several high quality species, the quality of food being dictated by the cost of living for each species; shifting to food of lower-quality species (species with lower energy densities per mass unit) may negatively affect the population dynamics of a species (Spitz et al. 2011, 2012). The intensified pelagic fishery targeting blue whiting (Micromesistius poutassou) west of the British Isles is likely one of the factors reinforcing the apparent decrease in abundance of pilot whales since the 1990s (Hátun and Gaard 2010). The blue whiting is preyed upon both by the flying squid and the pilot whale.
This species, like many beaked whales, is likely to be vulnerable to loud anthropogenic sounds, such as those generated by navy sonar and seismic exploration (Cox et al. 2006), and almost all behavioural responses are expected to result in a change in dive pattern (Sivle et al 2012). Indeed intense military sonar signals should be audible to cetaceans over large distances given the efficient propagation of sound and the sensitive hearing capabilities of cetaceans.
Exposure to military sonar pulses is associated with changes in behaviour in pilot whales, suggesting acoustic disturbance. Changes in vocalizations, traveling, surfacing and diving/foraging behaviours have been observed, the latter potentially reducing the foraging efficiency of the affected animals (Rendell and Gordon 1999, Miller et al. 2011, 2012, Sivle et al. 2012).
Pilot whales may, however, be less sensitive to sonar exposure, compared to species such as killer whales and beaked whales. They exhibit higher response thresholds to sonar exposure than these species, and an avoidance response restricted to the duration of sonar exposure, while the responses reported for killer whales and beaked whales may last longer than the sound exposure. There are however individual differences and the behavioral responses to sound stimuli are strongly affected by the context of the exposure (Antunes et al. 2014).
Predicted impacts of global climate change on the marine environment may affect long-finned pilot whales, and may induce changes in the species’ range, abundance and/or migration patterns (Learmont et al. 2006). In particular, pilot whales may be affected indirectly, through their prey, as the migration and survival of squid is very temperature-dependent.
MacLeod et al. (2005) suggest that the late 1980s warming of local waters has, indeed, led to changes in the cetacean community of north-west Scotland, with a decline in occurrence of cold water species, including pilot whales, an increase in the occurrence of existing warm water species and the addition of new warm water species to the community. They predicted that if the temperature rise continues, colder water species like the pilot whale might be entirely lost from the north-west Scottish cetacean community.
A clear link has been identified between the abundance of long-finned pilot whales and the marine climate in the northeastern Atlantic throughout the last three centuries (Hoydal and Lastein 1993, Hátun et al. 2009). During warm periods the whales are observed in high abundances while they can be completely absent from the region during cold periods. The linkage between the marine climate and the abundance of pilot whales probably involves their main prey items, the flying squid and the large but highly variable blue whiting stock (Hátun and Gaard 2010). This link, however, was broken post-1980s, when warming and an increase in the blue whiting stock were not followed by an increase in the abundance of flying squids and pilot whales. Hátun and Gaard (2010) identified potential causes rooted in global warming and an intensified pelagic fishery, which collectively might explain this apparent disruption.
Pilot whales have a tendency to mass-strand throughout their range in the North Atlantic (e.g. Sergeant 1962, Bloch et al. 1993a, Sigurjónsson et al. 1993, Waring et al. 1999, 2007ab, 2012). It is not known whether human activity influences these occurrences, and at present, such strandings must be considered a component of the natural mortality of the species. However Culik (2011) report on three mass stranding events in Tasmania, just prior to and after the arrival of naval vessels using high frequency (5–200 Kz) sonar, where a behavioural reaction to the sonar facilitating the second and third events could not be ruled out.
Research in NAMMCO Member Countries
All NAMMCO member countries as well as Canada have participated in the NASS and T-NASS surveys, and the pilot whale has been one of the target species (see under Current Abundance and Trends). These surveys are coordinated through the Scientific Committee of NAMMCO. In addition, the Faroe Islands conduct research on ecology, population structure, levels and trends in the accumulation of contaminants and impacts of climate change on pilot whale distribution and abundance.
An intensive international research programme on the ecology and status of the long-finned pilot whale off the Faroe Islands and the impact of the fishery on the population was initiated and supported by the Faroese Governement in 1986, under the auspices of the IWC and UNEP (Desportes 1988, 1990, Desportes et al. 1994c). Some of the results were compiled in the first monograph on Northern Hemisphere pilot whales (Donovan et al. 1993).
Following pilot whales movements through satellite tracking
Satellite transmitters have been successfully attached to pilot whales from different schools since July 2000 (see Table). In each case, the schools of whales were driven into a bay, the tags attached to the selected whales, and the entire school driven back out to sea again. The maps below shows the overall movements of the whales from the four last tracking events.
These tagging experiments are very important because they shed light on the extent of the population affected by the Faroese catch. As described under Stock status the effects of the catch are very different if the catch comes from a population restricted to the Faroe Island area or from a population spread over a wider geographical area.
Ongoing sampling of pilot whale catches
The measurement of skinn values, which has been used traditionally in Faroese whaling (see under Hunting and Utilisation), continue being recorded. This measure, together with the sex and total body length which have been recorded from most pilot whales caught since 1984, allows researchers to follow trends in the size of the whales landed. The Faroese Museum of Natural History also conducts a small-scale opportunistic sampling of the catch to monitor trends in life history parameters and feeding habits.
On-going biological sampling of pilot whales landed in the Faroe Islands, together with satellite tracking projects and regular sighting surveys are important tools that provide updated information for management to ensure that the pilot whale catch remains being sustainable.
Level of contaminants in pilot whales
Samples of pilot whale tissue are taken regularly by the Environment Agency to examine and follow the levels of heavy metals in the meat and organochlorines in the blubber of the whales.
The focus of the monitoring of muscle and blubber is to elucidate possible changes in concentrations over time in the exposure of the Faroese human population utilizing pilot whale blubber and meat for food. The focus of the monitoring of heavy metals in kidney and liver tissues is to follow the possible risk to the pilot whales of elevated tissue metal concentrations, which are known to impair reproduction in may species.
Since 2008, the monitoring data collected by the Environment Agency are part of the Arctic Monitoring and Assessment Programme (AMAP) and are available online, under the heading ENVOFAR). ENVOFAR is a cooperation of Faroese institutions that works actively to describe and study the environment in the AMAP and CAFF (Conservation of Arctic Flora and Fauna) working groups under the Arctic Council.
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- Atlas of cetacean distribution in the north-west European waters | <urn:uuid:a3e9d646-db53-4e8a-b0e8-f6f4f9514c2f> | 2.9375 | 26,208 | Knowledge Article | Science & Tech. | 66.865313 | 95,562,398 |
Researchers have discovered that some species of polychaete worms are able to modify their metabolic rates to better cope with and thrive in waters high in carbon dioxide (CO2), which is otherwise poisonous to other, often closely-related species.
The study sheds new light on the robustness of some marine species and the relative resilience of marine biodiversity should atmospheric CO2 continue to cause ocean acidification.
A team of scientists led by Plymouth University, and including colleagues from the Naples Zoological Station in Ischia; the Marine Ecology Laboratory ENEA in La Spezia, Italy; the University of Texas Galveston; and the University of Hull, conducted a three-year research project into the potential mechanisms that species of worm polychaetes use to live around the underwater CO2 vent of Ischia in Southern Italy.
The researchers collected specimens found in waters characterised by either elevated or low levels of CO2, and placed them in specially-constructed 'transplantation chambers', which were then lowered into areas both within and away from the volcanic vent.
They monitored the responses of the worms and found that one of the species that had been living inside the CO2 vent was physiologically and genetically adapted to the acidic conditions, whilst another was able to survive inside the vent by adjusting its metabolism.
Project leader Dr Piero Calosi, of Plymouth University's Marine Institute, said: "Previous studies have shown that single-cell algae can genetically adapt to elevated levels of carbon dioxide, but this research has demonstrated that a marine animal can physiologically and genetically adapt to chronic and elevated levels of carbon dioxide.
"Furthermore, we show that both plasticity and adaptation are key to preventing some species' from suffering extinction in the face of on-going ocean acidification, and that these two strategies may be largely responsible to defining the fate of marine biodiversity."
The results revealed that species normally found inside the CO2 vent were better able to regulate their metabolic rate when exposed to high CO2 conditions, whilst species only found outside the CO2 vent were clearly impaired by acidic waters. In fact, their metabolism either greatly decreased, indicating reduced energy production, or greatly increased, indicating a surge in the basic cost of living, in both cases making life inside the vent unsustainable.
Dr Maria-Cristina Gambi, of the Naples Zoological Station in Ischia, explained: "Despite some species showing the ability to metabolically adapt and adjust to the extreme conditions that are found inside the CO2 vents, others appear unable to physiologically cope with such conditions.
''In this sense, our findings could help to explain mass extinctions of the past, and potential extinctions in the future, as well as shed light on the resilience of some species to on-going ocean acidification."
The team also found that those species adapted to live inside the CO2 vent showed slightly higher metabolic rates and were much smaller in size – up to 80% smaller – indicating that adaptation came at a cost of energy for growth.
Dr Calosi concluded that: ''Ultimately, species' physiological responses to high CO2, as those reported by our study, may have repercussions on their abundance and distribution, and thus on the structure and dynamics of marine communities. This in turn will impact those ecosystem functions that humans rely upon to obtain goods and services from the ocean."
The research was funded by a Natural Environment Research Council UK Ocean Acidification Research Programme grant, and an Assemble Marine EU FP7 scheme, and is the first of its kind to bring together both the physiological and genetic evidence for adaptation to elevated pCO2 in a multicellular organism.
The findings are published in the Philosophical Transactions of the Royal Society B, online at 00.01BST on the 26th of August 2013, until which the information contained in this press release is embargoed.
Notes to Editors
The full report is available upon request. For more information please contact Andrew Merrington, Senior Press Officer, on 01752 588003.
Please find attached an image of the transplantation chambers in place at one of the vents. More images are available upon request.
Details: Calosi, P., Rastrick, S.P.S., Lombardi, C., de Guzman, H.J., Davidson, L., Jahnke, M., Giangrande, A, Hardege, J.D., Schulze, A., Spicer, J.I., Gambi, M.C., 2013. Adaptation and acclimatisation to ocean acidification in marine ectotherms: an in situ transplant experiment with polychaetes at a shallow CO2 vent system. Phil. Trans. Roy. Soc. London B special issue Ocean Acidification and Climate Change: Advances in Ecology and Evolution.
About Plymouth University
As one of the world's top modern universities and awarded a Queen's Anniversary Prize for Higher and Further Education in 2012, Plymouth has a strong record of excellence, enterprise and innovation across its teaching and research activities. Distinguished by its long-term engagement with business and the community, the University enjoys outstanding links with employers and plays a key role in civic and regional leadership. It is the only university in the world to have been awarded the Social Enterprise Mark in recognition of its work in support of the sector.
With around 30,000 students, including those studying higher education at its partner colleges throughout the South West, the University is one of largest in the UK. It enjoys a high rate of graduate employment and has recently invested more than £150 million in its estate and facilities to enhance the student experience and support world-class research.
Plymouth has embedded sustainability across its operations, and is the overall best performing university in the People & Planet Green League. It is the first modern university to found a medical and dental school – the Plymouth University Peninsula Schools of Medicine and Dentistry – and is the leading provider of Higher Education in Cornwall.
Andrew Gould | EurekAlert!
Global study of world's beaches shows threat to protected areas
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NSF-supported researchers to present new results on hurricanes and other extreme events
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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....
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“Yet more evidence that the great physicist got gravity right.”
From NBC News:
Einstein’s theory of general relativity has passed its toughest test with flying colors, a new study reports.
General relativity, which Einstein proposed in 1916, holds that gravity is a consequence of space-time’s inherent flexibility: Massive objects distort the cosmic fabric, creating a sort of well around which other bodies orbit.
Like all scientific theories, general relativity makes testable predictions. One of the most important is the “equivalence principle” — the notion that all objects fall in the same way, no matter how big they are or what they’re made of. [Einstein’s Theory of Relativity Explained (Infographic)]
Researchers have confirmed the equivalence principle many times on Earth — and, famously, on the moon. In 1971, Apollo 15 astronaut David Scott dropped a feather and a hammer simultaneously; the two hit the gray lunar dirt at the same time. (On Earth, of course, the feather would flutter to the ground much later than the hammer, having been held up by our atmosphere.)
But it’s tough to know if the equivalence principle applies in all situations — when the objects involved are incredibly dense or massive, for example. This wiggle room has given hope to adherents of alternative gravity theories, though such folks remain in the minority.
The new study could take some of the air out of their optimism. An international team of astronomers tested the equivalence principle under extreme conditions: a system composed of two superdense stellar corpses known as white dwarfs and an even denser neutron star. | <urn:uuid:6a05d0c6-2b7e-4396-806a-711704268c7b> | 3.515625 | 343 | News Article | Science & Tech. | 35.976656 | 95,562,416 |
Conservation of energy
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In physics, the law of conservation of energy states that the total energy of an isolated system remains constant, it is said to be conserved over time. This law means that energy can neither be created nor destroyed; rather, it can only be transformed or transferred from one form to another. For instance, chemical energy is converted to kinetic energy when a stick of dynamite explodes. If one adds up all the forms of energy that were released in the explosion, such as the kinetic energy of the pieces, as well as heat and sound, one will get the exact decrease of chemical energy in the combustion of the dynamite. Classically, conservation of energy was distinct from conservation of mass; however, special relativity showed that mass could be converted to energy and vice versa by E = mc2, and science now takes the view that mass–energy is conserved.
Scientifically speaking, conservation of energy can be rigorously proven by Noether's theorem as a consequence of continuous time translation symmetry; that is, from the fact that the laws of physics do not change over time.
A consequence of the law of conservation of energy is that a perpetual motion machine of the first kind cannot exist, that is to say, no system without an external energy supply can deliver an unlimited amount of energy to its surroundings. For systems which do not have time translation symmetry, it may not be possible to define conservation of energy. Examples include curved spacetimes in general relativity or time crystals in condensed matter physics.
Ancient philosophers as far back as Thales of Miletus c. 550 BCE had inklings of the conservation of some underlying substance of which everything is made. However, there is no particular reason to identify this with what we know today as "mass-energy" (for example, Thales thought it was water). Empedocles (490–430 BCE) wrote that in this universal system, composed of four roots (earth, air, water, fire), "nothing comes to be or perishes"; instead, these elements suffer continual rearrangement.
In 1638, Galileo published his analysis of several situations—including the celebrated "interrupted pendulum"—which can be described (in modern language) as conservatively converting potential energy to kinetic energy and back again. Essentially, he pointed out that the height a moving body rises is equal to the height from which it falls, and used this observation to infer the idea of inertia. The remarkable aspect of this observation is that the height to which a moving body ascends on a frictionless surface does not depend on the shape of the surface.
In 1669, Christian Huygens published his laws of collision. Among the quantities he listed as being invariant before and after the collision of bodies were both the sum of their linear momentums as well as the sum of their kinetic energies. However, the difference between elastic and inelastic collision was not understood at the time. This led to the dispute among later researchers as to which of these conserved quantities was the more fundamental. In his Horologium Oscillatorium, he gave a much clearer statement regarding the height of ascent of a moving body, and connected this idea with the impossibility of a perpetual motion. Huygens' study of the dynamics of pendulum motion was based on a single principle: that the center of gravity of a heavy object cannot lift itself.
The fact that kinetic energy is scalar, unlike linear momentum which is a vector, and hence easier to work with did not escape the attention of Gottfried Wilhelm Leibniz. It was Leibniz during 1676–1689 who first attempted a mathematical formulation of the kind of energy which is connected with motion (kinetic energy). Using Huygens' work on collision, Leibniz noticed that in many mechanical systems (of several masses, mi each with velocity vi),
was conserved so long as the masses did not interact. He called this quantity the vis viva or living force of the system. The principle represents an accurate statement of the approximate conservation of kinetic energy in situations where there is no friction. Many physicists at that time, such as Newton, held that the conservation of momentum, which holds even in systems with friction, as defined by the momentum:
was the conserved vis viva. It was later shown that both quantities are conserved simultaneously, given the proper conditions such as an elastic collision.
In 1687, Isaac Newton published his Principia, which was organized around the concept of force and momentum. However, the researchers were quick to recognize that the principles set out in the book, while fine for point masses, were not sufficient to tackle the motions of rigid and fluid bodies. Some other principles were also required.
The law of conservation of vis viva was championed by the father and son duo, Johann and Daniel Bernoulli. The former enunciated the principle of virtual work as used in statics in its full generality in 1715, while the latter based his Hydrodynamica, published in 1738, on this single conservation principle. Daniel's study of loss of vis viva of flowing water led him to formulate the Bernoulli's principle, which relates the loss to be proportional to the change in hydrodynamic pressure. Daniel also formulated the notion of work and efficiency for hydraulic machines; and he gave a kinetic theory of gases, and linked the kinetic energy of gas molecules with the temperature of the gas.
This focus on the vis viva by the continental physicists eventually led to the discovery of stationarity principles governing mechanics, such as the D'Alembert's principle, Lagrangian, and Hamiltonian formulations of mechanics.
Émilie du Châtelet (1706 – 1749) proposed and tested the hypothesis of the conservation of total energy, as distinct from momentum. Inspired by the theories of Gottfried Leibniz, she repeated and publicized an experiment originally devised by Willem 's Gravesande in 1722 in which balls were dropped from different heights into a sheet of soft clay. Each ball's kinetic energy - as indicated by the quantity of material displaced - was shown to be proportional to the square of the velocity. The deformation of the clay was found to be directly proportional to the height the balls were dropped from, equal to the initial potential energy. Earlier workers, including Newton and Voltaire, had all believed that "energy" (so far as they understood the concept at all) was not distinct from momentum and therefore proportional to velocity. According to this understanding, the deformation of the clay should have been proportional to the square root of the height from which the balls were dropped from. In classical physics the correct formula is , where is the kinetic energy of an object, its mass and its speed. On this basis, Châtelet proposed that energy must always have the same dimensions in any form, which is necessary to be able to relate it in different forms (kinetic, potential, heat…).
Engineers such as John Smeaton, Peter Ewart, Carl Holtzmann, Gustave-Adolphe Hirn and Marc Seguin recognized that conservation of momentum alone was not adequate for practical calculation and made use of Leibniz's principle. The principle was also championed by some chemists such as William Hyde Wollaston. Academics such as John Playfair were quick to point out that kinetic energy is clearly not conserved. This is obvious to a modern analysis based on the second law of thermodynamics, but in the 18th and 19th centuries the fate of the lost energy was still unknown.
Gradually it came to be suspected that the heat inevitably generated by motion under friction was another form of vis viva. In 1783, Antoine Lavoisier and Pierre-Simon Laplace reviewed the two competing theories of vis viva and caloric theory. Count Rumford's 1798 observations of heat generation during the boring of cannons added more weight to the view that mechanical motion could be converted into heat, and (as importantly) that the conversion was quantitative and could be predicted (allowing for a universal conversion constant between kinetic energy and heat). Vis viva then started to be known as energy, after the term was first used in that sense by Thomas Young in 1807.
The recalibration of vis viva to
which can be understood as converting kinetic energy to work, was largely the result of Gaspard-Gustave Coriolis and Jean-Victor Poncelet over the period 1819–1839. The former called the quantity quantité de travail (quantity of work) and the latter, travail mécanique (mechanical work), and both championed its use in engineering calculation.
In a paper Über die Natur der Wärme(German "On the Nature of Heat/Warmth"), published in the Zeitschrift für Physik in 1837, Karl Friedrich Mohr gave one of the earliest general statements of the doctrine of the conservation of energy in the words: "besides the 54 known chemical elements there is in the physical world one agent only, and this is called Kraft [energy or work]. It may appear, according to circumstances, as motion, chemical affinity, cohesion, electricity, light and magnetism; and from any one of these forms it can be transformed into any of the others."
Mechanical equivalent of heat
A key stage in the development of the modern conservation principle was the demonstration of the mechanical equivalent of heat. The caloric theory maintained that heat could neither be created nor destroyed, whereas conservation of energy entails the contrary principle that heat and mechanical work are interchangeable.
In the middle of the eighteenth century, Mikhail Lomonosov, a Russian scientist, postulated his corpusculo-kinetic theory of heat, which rejected the idea of a caloric. Through the results of empirical studies, Lomonosov came to the conclusion that heat was not transferred through the particles of the caloric fluid.
In 1798, Count Rumford (Benjamin Thompson) performed measurements of the frictional heat generated in boring cannons, and developed the idea that heat is a form of kinetic energy; his measurements refuted caloric theory, but were imprecise enough to leave room for doubt.
The mechanical equivalence principle was first stated in its modern form by the German surgeon Julius Robert von Mayer in 1842. Mayer reached his conclusion on a voyage to the Dutch East Indies, where he found that his patients' blood was a deeper red because they were consuming less oxygen, and therefore less energy, to maintain their body temperature in the hotter climate. He discovered that heat and mechanical work were both forms of energy and in 1845, after improving his knowledge of physics, he published a monograph that stated a quantitative relationship between them.
Meanwhile, in 1843, James Prescott Joule independently discovered the mechanical equivalent in a series of experiments. In the most famous, now called the "Joule apparatus", a descending weight attached to a string caused a paddle immersed in water to rotate. He showed that the gravitational potential energy lost by the weight in descending was equal to the internal energy gained by the water through friction with the paddle.
Over the period 1840–1843, similar work was carried out by engineer Ludwig A. Colding, although it was little known outside his native Denmark.
Both Joule's and Mayer's work suffered from resistance and neglect but it was Joule's that eventually drew the wider recognition.
In 1844, William Robert Grove postulated a relationship between mechanics, heat, light, electricity and magnetism by treating them all as manifestations of a single "force" (energy in modern terms). In 1846, Grove published his theories in his book The Correlation of Physical Forces. In 1847, drawing on the earlier work of Joule, Sadi Carnot and Émile Clapeyron, Hermann von Helmholtz arrived at conclusions similar to Grove's and published his theories in his book Über die Erhaltung der Kraft (On the Conservation of Force, 1847). The general modern acceptance of the principle stems from this publication.
In 1877, Peter Guthrie Tait claimed that the principle originated with Sir Isaac Newton, based on a creative reading of propositions 40 and 41 of the Philosophiae Naturalis Principia Mathematica. This is now regarded as an example of Whig history.
Matter is composed of such things as atoms, electrons, neutrons, and protons. It has intrinsic or rest mass. In the limited range of recognized experience of the nineteenth century it was found that such rest mass is conserved. Einstein's 1905 theory of special relativity showed that it corresponds to an equivalent amount of rest energy. This means that it can be converted to or from equivalent amounts of other (non-material) forms of energy, for example kinetic energy, potential energy, and electromagnetic radiant energy. When this happens, as recognized in twentieth century experience, rest mass is not conserved, unlike the total mass or total energy. All forms of energy contribute to the total mass and total energy.
For example, an electron and a positron each have rest mass. They can perish together, converting their combined rest energy into photons having electromagnetic radiant energy, but no rest mass. If this occurs within an isolated system that does not release the photons or their energy into the external surroundings, then neither the total mass nor the total energy of the system will change. The produced electromagnetic radiant energy contributes just as much to the inertia (and to any weight) of the system as did the rest mass of the electron and positron before their demise. Likewise, non-material forms of energy can perish into matter, which has rest mass.
Thus, conservation of energy (total, including material or rest energy), and conservation of mass (total, not just rest), each still holds as an (equivalent) law. In the 18th century these had appeared as two seemingly-distinct laws.
Conservation of energy in beta decay
The discovery in 1911 that electrons emitted in beta decay have a continuous rather than a discrete spectrum appeared to contradict conservation of energy, under the then-current assumption that beta decay is the simple emission of an electron from a nucleus. This problem was eventually resolved in 1933 by Enrico Fermi who proposed the correct description of beta-decay as the emission of both an electron and an antineutrino, which carries away the apparently missing energy.
First law of thermodynamics
For a closed thermodynamic system, the first law of thermodynamics may be stated as:
- , or equivalently,
where is the quantity of energy added to the system by a heating process, is the quantity of energy lost by the system due to work done by the system on its surroundings and is the change in the internal energy of the system.
The δ's before the heat and work terms are used to indicate that they describe an increment of energy which is to be interpreted somewhat differently than the increment of internal energy (see Inexact differential). Work and heat refer to kinds of process which add or subtract energy to or from a system, while the internal energy is a property of a particular state of the system when it is in unchanging thermodynamic equilibrium. Thus the term "heat energy" for means "that amount of energy added as the result of heating" rather than referring to a particular form of energy. Likewise, the term "work energy" for means "that amount of energy lost as the result of work". Thus one can state the amount of internal energy possessed by a thermodynamic system that one knows is presently in a given state, but one cannot tell, just from knowledge of the given present state, how much energy has in the past flowed into or out of the system as a result of its being heated or cooled, nor as the result of work being performed on or by the system.
Entropy is a function of the state of a system which tells of limitations of the possibility of conversion of heat into work.
For a simple compressible system, the work performed by the system may be written:
where is the pressure and is a small change in the volume of the system, each of which are system variables. In the fictive case in which the process is idealized and infinitely slow, so as to be called quasi-static, and regarded as reversible, the heat being transferred from a source with temperature infinitesimally above the system temperature, then the heat energy may be written
If an open system (in which mass may be exchanged with the environment) has several walls such that the mass transfer is through rigid walls separate from the heat and work transfers, then the first law may be written:
where is the added mass and is the internal energy per unit mass of the added mass, measured in the surroundings before the process.
The conservation of energy is a common feature in many physical theories. From a mathematical point of view it is understood as a consequence of Noether's theorem, developed by Emmy Noether in 1915 and first published in 1918. The theorem states every continuous symmetry of a physical theory has an associated conserved quantity; if the theory's symmetry is time invariance then the conserved quantity is called "energy". The energy conservation law is a consequence of the shift symmetry of time; energy conservation is implied by the empirical fact that the laws of physics do not change with time itself. Philosophically this can be stated as "nothing depends on time per se". In other words, if the physical system is invariant under the continuous symmetry of time translation then its energy (which is canonical conjugate quantity to time) is conserved. Conversely, systems which are not invariant under shifts in time (an example, systems with time dependent potential energy) do not exhibit conservation of energy – unless we consider them to exchange energy with another, external system so that the theory of the enlarged system becomes time invariant again. Conservation of energy for finite systems is valid in such physical theories as special relativity and quantum theory (including QED) in the flat space-time.
With the discovery of special relativity by Henri Poincaré and Albert Einstein, energy was proposed to be one component of an energy-momentum 4-vector. Each of the four components (one of energy and three of momentum) of this vector is separately conserved across time, in any closed system, as seen from any given inertial reference frame. Also conserved is the vector length (Minkowski norm), which is the rest mass for single particles, and the invariant mass for systems of particles (where momenta and energy are separately summed before the length is calculated—see the article on invariant mass).
The relativistic energy of a single massive particle contains a term related to its rest mass in addition to its kinetic energy of motion. In the limit of zero kinetic energy (or equivalently in the rest frame) of a massive particle, or else in the center of momentum frame for objects or systems which retain kinetic energy, the total energy of particle or object (including internal kinetic energy in systems) is related to its rest mass or its invariant mass via the famous equation .
Thus, the rule of conservation of energy over time in special relativity continues to hold, so long as the reference frame of the observer is unchanged. This applies to the total energy of systems, although different observers disagree as to the energy value. Also conserved, and invariant to all observers, is the invariant mass, which is the minimal system mass and energy that can be seen by any observer, and which is defined by the energy–momentum relation.
In general relativity, energy–momentum conservation is not well-defined except in certain special cases. Energy-momentum is typically expressed with the aid of a stress–energy–momentum pseudotensor. However, since pseudotensors are not tensors, they do not transform cleanly between reference frames. If the metric under consideration is static (that is, does not change with time) or asymptotically flat (that is, at an infinite distance away spacetime looks empty), then energy conservation holds without major pitfalls. In practice, some metrics such as the Friedmann–Lemaître–Robertson–Walker metric do not satisfy these constraints and energy conservation is not well defined. The theory of general relativity leaves open the question of whether there is a conservation of energy for the entire universe.
In quantum mechanics, energy of a quantum system is described by a self-adjoint (or Hermitian) operator called the Hamiltonian, which acts on the Hilbert space (or a space of wave functions) of the system. If the Hamiltonian is a time-independent operator, emergence probability of the measurement result does not change in time over the evolution of the system. Thus the expectation value of energy is also time independent. The local energy conservation in quantum field theory is ensured by the quantum Noether's theorem for energy-momentum tensor operator. Note that due to the lack of the (universal) time operator in quantum theory, the uncertainty relations for time and energy are not fundamental in contrast to the position-momentum uncertainty principle, and merely holds in specific cases (see Uncertainty principle). Energy at each fixed time can in principle be exactly measured without any trade-off in precision forced by the time-energy uncertainty relations. Thus the conservation of energy in time is a well defined concept even in quantum mechanics.
- Energy quality
- Energy transformation
- Eternity of the world
- Laws of thermodynamics
- Principles of energetics
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- Grossman, Lisa (18 January 2012). "Death-defying time crystal could outlast the universe". newscientist.com. New Scientist. Archived from the original on 2017-02-02.
- Cowen, Ron (27 February 2012). ""Time Crystals" Could Be a Legitimate Form of Perpetual Motion". scientificamerican.com. Scientific American. Archived from the original on 2017-02-02.
- Powell, Devin (2013). "Can matter cycle through shapes eternally?". Nature. doi:10.1038/nature.2013.13657. ISSN 1476-4687. Archived from the original on 2017-02-03.
- Gibney, Elizabeth (2017). "The quest to crystallize time". Nature. 543 (7644): 164–166. Bibcode:2017Natur.543..164G. doi:10.1038/543164a. ISSN 0028-0836. Archived from the original on 2017-03-13.
- Janko, Richard (2004). "Empedocles, "On Nature"" (PDF). Zeitschrift für Papyrologie und Epigraphik. 150: 1–26.
- Hagengruber, Ruth, editor (2011) Émilie du Chatelet between Leibniz and Newton. Springer. ISBN 978-94-007-2074-9.
- Arianrhod, Robyn (2012). Seduced by logic : Émilie du Châtelet, Mary Somerville, and the Newtonian revolution (US ed.). New York: Oxford University Press. ISBN 978-0-19-993161-3.
- Lavoisier, A.L. & Laplace, P.S. (1780) "Memoir on Heat", Académie Royale des Sciences pp. 4–355
- von Mayer, J.R. (1842) "Remarks on the forces of inorganic nature" in Annalen der Chemie und Pharmacie, 43, 233
- Mayer, J.R. (1845). Die organische Bewegung in ihrem Zusammenhange mit dem Stoffwechsel. Ein Beitrag zur Naturkunde, Dechsler, Heilbronn.
- Grove, W. R. (1874). The Correlation of Physical Forces (6th ed.). London: Longmans, Green.
- "On the Conservation of Force". Bartleby. Retrieved April 6, 2014.
- William John Macquorn Rankine (1853) "On the General Law of the Transformation of Energy," Proceedings of the Philosophical Society of Glasgow, vol. 3, no. 5, pages 276-280; reprinted in: (1) Philosophical Magazine, series 4, vol. 5, no. 30, pages 106-117 (February 1853); and (2) W. J. Millar, ed., Miscellaneous Scientific Papers: by W. J. Macquorn Rankine, ... (London, England: Charles Griffin and Co., 1881), part II, pages 203-208: "The law of the Conservation of Energy is already known—viz. that the sum of all the energies of the universe, actual and potential, is unchangeable."
- Hadden, Richard W. (1994). On the shoulders of merchants: exchange and the mathematical conception of nature in early modern Europe. SUNY Press. p. 13. ISBN 0-7914-2011-6., Chapter 1, p. 13
- Jensen, Carsten (2000). Controversy and Consensus: Nuclear Beta Decay 1911-1934. Birkhäuser Verlag. ISBN 3-7643-5313-9.
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History of ideas
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- Guillen, M. (1999). Five Equations That Changed the World. New York: Abacus. ISBN 0-349-11064-6.
- Hiebert, E.N. (1981). Historical Roots of the Principle of Conservation of Energy. Madison, Wis.: Ayer Co Pub. ISBN 0-405-13880-6.
- Kuhn, T.S. (1957) "Energy conservation as an example of simultaneous discovery", in M. Clagett (ed.) Critical Problems in the History of Science pp.321–56
- Sarton, G.; Joule, J. P.; Carnot, Sadi (1929). "The discovery of the law of conservation of energy". Isis. 13: 18–49. doi:10.1086/346430.
- Smith, C. (1998). The Science of Energy: Cultural History of Energy Physics in Victorian Britain. London: Heinemann. ISBN 0-485-11431-3.
- Mach, E. (1872). History and Root of the Principles of the Conservation of Energy. Open Court Pub. Co., Illinois.
- Poincaré, H. (1905). Science and Hypothesis. Walter Scott Publishing Co. Ltd; Dover reprint, 1952. ISBN 0-486-60221-4., Chapter 8, "Energy and Thermo-dynamics" | <urn:uuid:606ea6fe-764b-45ed-8108-da8d1d7a70de> | 3.59375 | 6,347 | Knowledge Article | Science & Tech. | 51.0353 | 95,562,427 |
Community Contributor | Jul 3, 2018 | 0
Understanding Weather – not predicting –
This past week an unusual synoptic pattern has held sway across the southern hemisphere. A major anticyclone with core pressures well above 1030hPa straddled the Date Line (180o) in the south Pacific while on our side, a complex low pressure pattern covered most of southern Africa and the southern oceans.
Both high and low pressure systems have been static for this period. Static in position but active within themselves: anticyclonic strength ensured a consistent flow to maintain La Nina’s, positive oscillation, and dominance of global weather.
The complexities of the vortex areas see one core deepen, drift somewhat eastward while in the cold, unstable polar air behind it a secondary vortex quickly forms, weakening the older core, then the same cycle is repeated. The effect of this pattern maintained a zonal flow throughout the troposphere (surface to 40000 feet) above southern Africa.
The unusual feature is that these differing systems have held their geographical placing while whatever else may be on the weather map either by-passes or collapses while these two major systems remain.
The other unusual feature is the global situation on either side of globe: the high and the low. Again, the effect saw a limited, if not absent, eastern Atlantic anticyclone, and similarly an absence of the western Indian Ocean anticyclone.
This departure from the norm means there is no lower level moisture input from the Indian Ocean, so with no push from the east, the heat-low pressure belt across southern Africa remains static ensuring that over Namibia there has been an advection of bone dry southerly air. This limits daytime temperatures but with no anticyclonic thrust it cannot undercut the heat-low. Without convergence, there is no cumulus cloud and no rain!
The thin layer of cloud visible has too little moisture but its presence offers hope for improvement as November wears on.
The vortex pattern persists. The weak South Atlantic anticyclone remains limited throughout the period and because there is little ability to ridge round the continent, any development of a cell away to the east is restricted. Any prospect of late Spring showers depends on the persistent heat-low generating an upward convective extension to tap the adjacent moister air mass gathering above much of Zambia, linking with the equally adjacent Congo air mass then to advect this combination into our Kavango area or further west.
Current outlooks show a mixed set of patterns across the northern mid-subcontinent. Much of the data available is based on satellite images showing cloud coverage and direction of movement. Other observational sources in that area are, largely, non-existent. This data provides the grist from which computer models are built. Otherwise, it is up to a weather observer to assess what is seen to be present and offer an outlook regarding what the current situation will be able to evolve. The heat factor is seen to be increasing and its effects, as outlined earlier, offer a prospect of showers into the new week. n the south west, temperatures will be considerably cooler with a fresh southwesterly wind as a result of the high ridging in from the south Atlantic. | <urn:uuid:f3a6f29f-8225-4900-8071-da6c8560369f> | 2.921875 | 659 | News Article | Science & Tech. | 33.475311 | 95,562,457 |
ANOVA. Dr. AJIT SAHAI Director – Professor Biometrics JIPMER, Pondicherry.
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Dr. AJIT SAHAI
Director – Professor
Analysis of Variance (ANOVA) - Is a technique whereby the total variation present in a data set is partitioned or segregated into several components - Usually each of these components of variation is associated with a specific source of variation - In any experimentation it is of interest to know the magnitude of the contributions of each of these sources to the total variation
HypothesesWe may test the null hypothesis that, - all population or treatment means are equal against thealternative that, - the members of at least one pair are not equal
- In situations warranting multiple comparisons of means -a global test like ANOVA is desirable - mainly to examine whether there are any differences in the data; - prior to testing various combinations of means to determine individual group differences
If a global test is not performed - multiple tests between different pairs of means will alter the alpha level, - not for each comparison but for the - experimentation as a whole
For example, if four drug levels with their six possible combinations are to be compared, and each comparison is made by using Alpha = .05, -there is a 5% chance that each comparison will falsely be called significant;
i.e. a type I error may occur six times; Overall, therefore, there is a 30% chance (6 * 5%) of declaring one of the comparisons incorrectly significant. Of course this 30% is only an approximation; it does not mean that all the comparisons are not independent.
So the recommended use of ANOVA protects the researcher againsterror inflation - by first asking if there are differences at all among means of the groups.
Some basic concepts in experimental designs are the minimum requirements to appreciate the approach of ANOVA in estimating and testing the hypotheses about - population means or about - population variances.
It may be pointed out that when experiments are designed with the analysis in mind, researchers can, before conducting experiments, identify those sources of variation that they consider important and choose a design that will allow them to measure the extent of the contribution of these sources to total variation.
The Completely Randomized Design (CRD) and the Randomized Complete Block Designs (RCBD) - are commonly used in Pharmacological experimentations, requiring the application of - One-way and - Two-way Analyses of Variance, respectively.
In case the crucial assumptions** of ANOVA are not met, one may wish to consider a parallel non-parametric test such as - Kruskal – Wallis procedure or - Friedman procedure, respectively,for One or Two-way ANOVA
Assumptions - Observed data constitute independent random sample from the respective populations. - Each of the populations from which the sample comes is normally distributed. - Each of the populations has the same variance.
Tests of significanceThe frequently used tests with there suitability to the situations are, - t-testfor the paired or independent groups (with or without adjusting the level downward); - Bonferroni’s t-method or - Dunn’s multiple-comparisonprocedure; - Posteriori, or Post Hoc, comparisons; Contd.
Tukey’s HSD(Honestly Significant Difference) - Scheffe’s Procedure; - Newman-Keuls Procedure;- Dunnett’s Procedure; - Duncan’s new multiple-range test and - Least Significant Difference (LSD) | <urn:uuid:2eb94224-9610-40c2-beca-5c8e7ab2570a> | 2.8125 | 794 | Knowledge Article | Science & Tech. | 12.840998 | 95,562,470 |
12 July 2018
Cactus-strophic extinction ahead
Published online 5 October 2015
Cacti may not have high water demands, but they are still among the most threatened groups of plants in the world.
Cacti are among the most threatened groups of plants assessed to date, with over 30% of species at risk of extinction, according to a study published online in Nature Plants1.
The likelihood of extinction among plant species remains poorly understood, with only 19,374 of an estimated 300,000 species having been evaluated. Cacti are a culturally significant group, distributed primarily in the arid environments of the Americas, with a long history of human use for ornamental horticulture, food and medicine. Despite the pressures these regions face, they have not attracted the conservation attention associated with other environments, such as tropical forests.
Barbara Goettsch and colleagues determined the risk of extinction of 1,478 of the 1,480 species of extant cacti. They find that cacti are the fifth most threatened taxonomic group of plants assessed to date. The greatest numbers of threatened species are found in southern Rio Grande do Sul, Brazil, and in northern Artigas, Uruguay. The most significant threats facing cacti are the appropriation of land for agriculture and aquaculture, the collection of cacti as biological resources, and residential and commercial development.
The authors suggest that their study demonstrates that global species assessments can be undertaken for major plant taxa (groups) with relatively moderate resources.
- Bárbara Goettsch et al. High proportion of cactus species threatened with extinction. Nature Plants dx.doi.org/10.1038/nplants.2015.142 (2015) | <urn:uuid:c5154953-73f3-4037-88a1-17053531dd43> | 3.796875 | 355 | Truncated | Science & Tech. | 40.459011 | 95,562,478 |
The very first and basic problem to solve in seismology is to locate of the seismic events. For that purpose we generally need at least 3 stations (Figure 8.1). We therefore define a seismic network as being a group of stations working together jointly for data collection and analysis.
Before 1960, there were in general only individual seismic stations operating independently. Each station made its observations, which were usually sent to some central location, if several stations were operating in a country or region. In that sense it was possible to talk about networks, however the time lag between recording and manual processing was so long that such networks are not considered as seismic networks in the modern sense. In the 1960's, ‘real’ seismic networks started operating. These were mainly networks made for micro earthquake recording and the distance between stations was a few kilometers to a couple of hundred kilometers. The key feature, used to define them as networks, was that the signals were transmitted in real time by wire or radio link to a central recording station where all data was recorded with central timing. This enabled very accurate relative timing between stations and therefore also made it possible to make accurate locations of local earthquakes. Recording was initially analog and has over the years evolved to be nearly exclusively digital. Lee and Stewart (1981) made a good general description of local networks. With the evolution of communication capabilities to cover the whole world, seismic networks are now not limited to local networks but can be either regional or global too. The distinction between them is primarily no longer the differences in data transfer, accuracy of timing, time lag between data acquisition and analysis, etc, but the scope of investigation, spatial resolution, and quality of data in terms of frequency content and dynamic range.
KeywordsSeismic Station Radio Link Forward Error Correction Seismic Network Virtual Network
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Oblique Backscatter Sounders
Having discussed sounders which transmit and receive RF energy at vertical incidence to the ionosphere in the previous chapter, we now turn our attention to a class of sounders which direct RF energy at oblique angles to the ionosphere. By Oblique Backscatter Sounders (OBS) we include any technique which uses HF through UHF radio waves coherently backscattered from ionospheric irregularities either directly or via reflection from the surface of the earth to deduce properties of ionospheric irregularities. Examples of recently or currently deployed OBS systems are the STARE (Scandinavian Twin Auroral Radar Experiment, Greenwald et al. 1978) the SABRE VHF radar (Nielsen et al. 1983), the HF phased array radar located at Goose Bay, Labrador (Greenwald et al. 1985), the Cornell University CUPRI Radar (Riggin et al. 1986) Swedish/French SAFARI radar in Scandinavia (Hanuise et al. 1981) and the PACE (Goose Bay and Antarctic HF radars Baker et al. 1989). Table 4.4 lists all the known currently operating OBS systems.
KeywordsRadar System Ionospheric Irregularity International Geophysical Year Virtual Height Radio Technique
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posted by UCI studebt
Which of the following is NOT true of colligative properties? Colligative properties are...
A. dependent on the mass of solute present.
B. independent of the chemical identity of the solute.
C. responsible for lowering the vapor pressure of a solution versus the vapor pressure of the pure solvent.
D. dependent on the molar mass of the solute.
E. all of these are true.
i was working on this with two friends, one tried E and the other tried B and they both got the answer wrong. I thought that colligative properties depended on whether a solute was volatile verses nonvolatile and not on if it is ionic or not.
I was thinking D, but I don't have a good reason to justify this answer, since colligative properties depend on the amount in grams of a solute, but not on the molar mass of the solute, and C is true because colligative properties are responsible for lowering the vapor pressure of the pure solvent
The answer is A. Let me legitimitize my answer; Since you can use the freezing point depression equation to find the molar mass of the solute, the molar mass obviously has an effect on the freezing point. I think its pretty clear that C is true. B is true by the definition of a colligative property (colligative properties are dependent on the number of molecules of solute in a solution, not on the identity of the solute) I go to UCI, just did this, and got it right.
its not a...i just did it right now n it said INCORRECT! :(
No you were right. Colligative properties are not dependent on the molar mass of solute, only on the mass of solute. I'm 10000% percent sure. Trust me. Molar mass of solute...the answer is D.
the answer is NOT d!!...i just did it and got it wrong -__- | <urn:uuid:2d761c80-6e3b-4d71-8ef1-ddfc69f76a27> | 2.5625 | 421 | Q&A Forum | Science & Tech. | 64.686562 | 95,562,504 |
Boyle's law (sometimes referred to as the Boyle–Mariotte law, or Mariotte's law) is an experimental gas law that describes how the pressure of a gas tends to increase as the volume of the container decreases. A modern statement of Boyle's law is
Mathematically, Boyle's law can be stated as
|Pressure is inversely proportional to the volume.|
|Pressure multiplied by volume equals some constant .|
where P is the pressure of the gas, V is the volume of the gas, and k is a constant.
The equation states that the product of pressure and volume is a constant for a given mass of confined gas and this holds as long as the temperature is constant. For comparing the same substance under two different sets of conditions, the law can be usefully expressed as
The equation shows that, as volume increases, the pressure of the gas decreases in proportion. Similarly, as volume decreases, the pressure of the gas increases. The law was named after chemist and physicist Robert Boyle, who published the original law in 1662.
This relationship between pressure and volume was first noted by Richard Towneley and Henry Power in the seventeenth century. Robert Boyle confirmed their discovery through experiments and published the results. According to Robert Gunther and other authorities, it was Boyle's assistant, Robert Hooke, who built the experimental apparatus. Boyle's law is based on experiments with air, which he considered to be a fluid of particles at rest in between small invisible springs. At that time, air was still seen as one of the four elements, but Boyle disagreed. Boyle's interest was probably to understand air as an essential element of life; for example, he published works on the growth of plants without air. Boyle used a closed J-shaped tube and after pouring mercury from one side he forced the air on the other side to contract under the pressure of mercury. After repeating the experiment several times and using different amounts of mercury he found that under controlled conditions, the pressure of a gas is inversely proportional to the volume occupied by it. The French physicist Edme Mariotte (1620–1684) discovered the same law independent of Boyle in 1679, but Boyle had already published it in 1662. Mariotte did, however, discover that air volume changes with temperature. Thus this law is sometimes referred to as Mariotte's law or the Boyle–Mariotte law. Later, in 1687 in the Philosophiæ Naturalis Principia Mathematica, Newton showed mathematically that if an elastic fluid consisting of particles at rest, between which are repulsive forces inversely proportional to their distance, the density would be directly proportional to the pressure, but this mathematical treatise is not the physical explanation for the observed relationship. Instead of a static theory a kinetic theory is needed, which was provided two centuries later by Maxwell and Boltzmann.
This law was the first physical law to be expressed in the form of an equation describing the dependence of two variable quantities.
The law itself can be stated as follows:
Or Boyle's law is a gas law, stating that the pressure and volume of a gas have an inverse relationship, when temperature is held constant. If volume increases, then pressure decreases and vice versa, when temperature is held constant.
Therefore, when the volume is halved, the pressure is doubled; and if the volume is doubled, the pressure is halved.
Relation with kinetic theory and ideal gases
Boyle's law states that at constant temperature for a fixed mass, the absolute pressure and the volume of a gas are inversely proportional. The law can also be stated in a slightly different manner, that the product of absolute pressure and volume is always constant.
Most gases behave like ideal gases at moderate pressures and temperatures. The technology of the 17th century could not produce high pressures or low temperatures. Hence, the law was not likely to have deviations at the time of publication. As improvements in technology permitted higher pressures and lower temperatures, deviations from the ideal gas behavior became noticeable, and the relationship between pressure and volume can only be accurately described employing real gas theory. The deviation is expressed as the compressibility factor.
Boyle (and Mariotte) derived the law solely on experimental grounds. The law can also be derived theoretically based on the presumed existence of atoms and molecules and assumptions about motion and perfectly elastic collisions (see kinetic theory of gases). These assumptions were met with enormous resistance in the positivist scientific community at the time however, as they were seen as purely theoretical constructs for which there was not the slightest observational evidence.
Daniel Bernoulli in 1737-1738 derived Boyle's law using Newton's laws of motion with application on a molecular level. It remained ignored until around 1845, when John Waterston published a paper building the main precepts of kinetic theory; this was rejected by the Royal Society of England. Later works of James Prescott Joule, Rudolf Clausius and in particular Ludwig Boltzmann firmly established the kinetic theory of gases and brought attention to both the theories of Bernoulli and Waterston.
The debate between proponents of Energetics and Atomism led Boltzmann to write a book in 1898, which endured criticism up to his suicide in 1906. Albert Einstein in 1905 showed how kinetic theory applies to the Brownian motion of a fluid-suspended particle, which was confirmed in 1908 by Jean Perrin.
The mathematical equation for Boyle's law is:
- P denotes the pressure of the system.
- V denotes the volume of the gas.
- k is a constant value representative of the temperature and volume of the system.
So long as temperature remains constant the same amount of energy given to the system persists throughout its operation and therefore, theoretically, the value of k will remain constant. However, due to the derivation of pressure as perpendicular applied force and the probabilistic likelihood of collisions with other particles through collision theory, the application of force to a surface may not be infinitely constant for such values of v, but will have a limit when differentiating such values over a given time. Forcing the volume V of the fixed quantity of gas to increase, keeping the gas at the initially measured temperature, the pressure p must decrease proportionally. Conversely, reducing the volume of the gas increases the pressure. Boyle's law is used to predict the result of introducing a change, in volume and pressure only, to the initial state of a fixed quantity of gas.
The initial and final volumes and pressures of the fixed amount of gas, where the initial and final temperatures are the same (heating or cooling will be required to meet this condition), are related by the equation:
Here P1 and V1 represent the original pressure and volume, respectively, and P2 and V2 represent the second pressure and volume.
Human breathing system
Boyle's law is often used as part of an explanation on how the breathing system works in the human body. This commonly involves explaining how the lung volume may be increased or decreased and thereby cause a relatively lower or higher air pressure within them (in keeping with Boyle's law). This forms a pressure difference between the air inside the lungs and the environmental air pressure, which in turn precipitates either inhalation or exhalation as air moves from high to low pressure.
Other gas laws in chemistry:
- Draper, John William (1861). A Textbook on chemistry. p. 46.
- Levine, Ira. N (1978). "Physical Chemistry" University of Brooklyn: McGraw-Hill
- Levine, Ira. N. (1978), p. 12 gives the original definition.
- In 1662, he published a second edition of the 1660 book New Experiments Physico-Mechanical, Touching the Spring of the Air, and its Effects with an addendum Whereunto is Added a Defence of the Authors Explication of the Experiments, Against the Obiections of Franciscus Linus and Thomas Hobbes; see J Appl Physiol 98: 31–39, 2005. (Jap.physiology.org Online.)
- Henry Power, Experimental Philosophy, in Three Books … (London, England: Printed by T. Roycroft for John Martin and James Allestry, 1663), pp. 126-130. Available on-line at: Early English Books Online. On page 130, Power presents (not very clearly) the relation between the pressure and the volume of a given quantity of air: "That the measure of the Mercurial Standard, and Mercurial Complement, are measured onely by their perpendicular heights, over the Surface of the restagnant Quicksilver in the Vessel: But Ayr, the Ayr's Dilatation, and Ayr Dilated, by the Spaces they fill. So that here is now four Proportionals, and by any three given, you may strike out the fourth, by Conversion, Transposition, and Division of them. So that by these Analogies you may prognosticate the effects, which follow in all Mercurial Experiments, and predemonstrate them, by calculation, before the senses give an Experimental [eviction] thereof." In other words, if one knows the volume V1 ("Ayr") of a given quantity of air at the pressure p1 ("Mercurial standard", i.e., atmospheric pressure at a low altitude), then one can predict the volume V2 ("Ayr dilated") of the same quantity of air at the pressure p2 ("Mercurial complement", i.e., atmospheric pressure at a higher altitude) by means of a proportion (because p1 V1 = p2 V2).
- Charles Webster (1965) "The discovery of Boyle's law, and the concept of the elasticity of air in seventeenth century," Archive for the History of Exact Sciences, 2 (6) : 441-502 ; see especially pp. 473-477.
- Charles Webster (1963) "Richard Towneley and Boyle's Law," Nature, 197 (4864) : 226-228.
- Robert Boyle acknowledged his debts to Towneley and Power in: R. Boyle, A Defence of the Doctrine Touching the Spring and Weight of the Air, … (London, England: Thomas Robinson, 1662). Available on-line at: Spain's La Biblioteca Virtual de Patrimonio Bibliográfico. On pages 50, 55-56, and 64, Boyle cited experiments by Towneley and Power showing that air expands as the ambient pressure decreases. On p. 63, Boyle acknowledged Towneley's help in interpreting Boyle's data from experiments relating the pressure to the volume of a quantity of air. (Also, on p. 64, Boyle acknowledged that Lord Brouncker had also investigated the same subject.)
- Gerald James Holton (2001). Physics, the Human Adventure: From Copernicus to Einstein and Beyond. Rutgers University Press. pp. 270–. ISBN 978-0-8135-2908-0.
- R. Boyle, A Defence of the Doctrine Touching the Spring and Weight of the Air, … (London, England: Thomas Robinson, 1662). Available on-line at: Spain's La Biblioteca Virtual de Patrimonio Bibliográfico. Boyle presents his law in "Chap. V. Two new experiments touching the measure of the force of the spring of air compress'd and dilated.", pp. 57-68. On p. 59, Boyle concludes that " … the same air being brought to a degree of density about twice as that it had before, obtains a spring twice as strong as formerly." That is, doubling the density of a quantity of air doubles its pressure. Since air's density is proportional to its pressure, then for a fixed quantity of air, the product of its pressure and its volume is constant. On page 60, he presents his data on the compression of air: "A Table of the Condensation of the Air." The legend (p. 60) accompanying the table states: "E. What the pressure should be according to the Hypothesis, that supposes the pressures and expansions to be in reciprocal relation." On p. 64, Boyle presents his data on the expansion of air: "A Table of the Rarefaction of the Air."
- The Boyle Papers BP 9, fol. 75v-76r at BBK.ac.uk Archived 2009-11-22 at the Wayback Machine.
- The Boyle Papers, BP 10, fol. 138v-139r at BBK.ac.uk Archived 2009-11-22 at the Wayback Machine.
- Britannica Educational Publishing 2012, p. 94.
- Mariotte, Essais de Physique, ou mémoires pour servir à la science des choses naturelles, … (Paris, France: E. Michallet, 1679); "Second essai. De la nature de l'air".
- (Mariotte, Edmé), Oeuvres de Mr. Mariotte, de l'Académie royale des sciences; … , vol. 1 (Leiden, Netherlands: P. Vander Aa, 1717); see especially pp. 151-153.
- Mariotte's essay "De la nature de l'air" was reviewed by the French Royal Academy of Sciences in 1679. See: (Anon.) (1733) "Sur la nature de l'air," Histoire de l'Académie Royale des Sciences, 1 : 270-278.
- Mariotte's essay "De la nature de l'air" was also reviewed in the Journal des Sçavans (later: Journal des Savants) on 20 November 1679. See: (Anon.) (20 November 1679) "Essais de physique, … ," Journal des Sçavans, pp. 265-269.
- Britannica Educational Publishing 2012, p. 95.
- Ley, Willy (June 1966). "The Re-Designed Solar System". For Your Information. Galaxy Science Fiction. pp. 94–106.
- Principia, Sec.V,prop. XXI, Theorem XVI
- Levine, Ira. N. (1978), p11 notes that deviations occur with high pressures and temperatures.
- Levine, Ira. N. (1978), p400 – Historical background of Boyle's law relation to Kinetic Theory
- Gerald J. Tortora, Bryan Dickinson, 'Pulmonary Ventilation' in Principles of Anatomy and Physiology 11th edition, Hoboken: John Wiley & Sons, Inc., 2006, pp. 863-867
- Britannica Educational Publishing (1 December 2012). Scientists and Inventors of the Renaissance. Britannica Educational Publishing. ISBN 978-1-61530-884-2. | <urn:uuid:1f5c5dfd-59b7-4d23-a9ae-53d96b04cec6> | 4.125 | 3,091 | Knowledge Article | Science & Tech. | 49.26088 | 95,562,514 |
(ab)c = a(bc), (associative law)
1a = a1 = a. (identity)
The function ϕ is called multiplication and the element 1 the identity. The associative law allows us to ignore parentheses in products a1a2⋯a n . The monoid is said to be abelian, or commutative, if ab = ba for all elements a and b. In an abelian monoid the function ϕ is often called addition and written as ϕ(a, b) = a + b; the identity element is then denoted by 0. In this case we speak of an additive monoid, as opposed to a multiplicative monoid. In a multiplicative monoid we write the n-fold product aa⋯a as a n for each positive integer n, and set a0 =1; in an additive monoid we write the n-fold sum a + a + ⋯ + a as na, and set 0a = 0.
KeywordsPrime Ideal Commutative Ring Left Ideal Free Module Division Ring
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In this section we shall obtain certain combinatorial properties of sequences of n integers, each integer one of 1, . . . , a. The motivation for our interest in these properties will become apparent in Chapter 3. By at once proving the necessary facts we gain in efficiency at the expense of a temporary lack of motivation. To avoid the trivial we assume, throughout this monograph, that a ≧ 2 and n ≧ 2 ; the main interest in application will usually be for large n.
KeywordsLagrange Multiplier Concave Function Entropy Function Prob Ability Unique Maximum
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May 2018, was warmer than normal in temperatures with below average relative humidities, precipitation and wind speed. The mean temperature of the month was 31.5°C which is 1.7°C above the long-term normal.
News from Members
On June 4, 433 weather stations in China were recognized as the first set of Chinese Centennial Observing Station list， said a spokesman at the monthly press conference of China Meteorological Administation (CMA). According to the plan, these stations will be added on the key protection list and received local government protection commitments to ensure long-term observation, accumulate climate data. It will play a big role in support of climate change research, ecological civilization construction and use of meteorological data.
On 21:07 p.m. BJT, June 5, the Fengyun-2H meteorological satellite, carried by a Long March-3A rocket, was launched from the Xichang Satellite Launch Center in southwest China's Sichuan Province. As the westernmost on-duty satellite in geostationary meteorological satellites layout of China, FY-2H can provide custom-made services for countries along “Belt and Road” territories, and data support for weather prediction and disaster prevention and mitigation.
The Tokyo Climate Center (TCC) of the Japan Meteorological Agency (JMA) has released the 52nd issue of the TCC News on the TCC website.
This issue covers: - El Nino Outlook (May - November 2018) - JMA's Seasonal Numerical Ensemble Prediction for Boreal Summer 2018 - Warm Season Outlook for Summer 2018 in Japan - Summary of the 2017/2018 Asian Winter Monsoon - Characteristics of climate conditions in Japan in winter 2017/2018 - World climate monitoring webpage revamp - TCC contributions to Regional Climate Outlook Forums in Asia
Low snow in low and middle altitudes and well below average precipitation resulted in drought condition appearing as soon as in the early May in the Czech Republic, while normally such conditions are typical for July or August. Significant number of water gauges reports lowest flows on record for this time of the year. Significant drought (defined as lowest 15 % of observations for given period of the year) has been observed at 62 % of all monitored objects. | <urn:uuid:94d5e207-18b1-44b3-9e46-74612882d073> | 2.625 | 469 | News (Org.) | Science & Tech. | 33.400791 | 95,562,547 |
The Mariana region, famed for boasting the deepest spot on the planet, is also home to the Mariana subduction system. This mash-up of tectonic plates includes a wide range of geological settings and marine habitats, including a very deep trench, a shallow volcanic arc, and a mid-depth back-arc spreading center. This great diversity of settings and habitats makes the Marianas a valuable natural laboratory for testing ideas about the distribution of animal species within hydrothermal vent ecosystems.
In the Mariana region, only the volcanic arc has been systematically explored for hydrothermal vents, resulting in the discovery of 20 hydrothermally active seamounts and over 20 new species. These remarkable discoveries directly inspired the establishment of the Marianas Trench Marine National Monument in 2009.
In contrast, more than 1000 kilometers of the Mariana back-arc remains almost completely unexplored.
Focusing on the Back-Arc
Last November, scientists aboard Falkor aimed to shed light on the Mariana Back-arc, expecting it to be teeming with activity and life. Principal Investigator Joseph Resing, of the University of Washington, led a team of researchers from the University of Washington, Oregon State University, and NOAA/PMEL, over the course of the 27 day mission at sea. Their goal was to explore the back-arc spreading center to find new sites of hydrothermal activity and to better understand the physical, chemical, and geological forces that shape biodiversity in these unique ecosystems.
Life in the Shadowy Depths
These researchers expected that the Mariana back-arc would host many sites of hydrothermal activity with chemosynthetic ecosystems. “Chemosynthesis” refers to organisms that transform carbon dioxide into organic matter in the same manner as plants, but, instead of using the energy from sunlight to do this — as in photosynthesis — they use chemical energy instead, mostly from hydrogen, methane, hydrogen sulfide, and iron. Chemosynthetic ecosystems exist in locations on the seafloor where chemical energy is present from seafloor hot springs, cold seeps, or other microbiological processes.
Shaping Earth, Shaping Life
The Mariana subduction system offers living organisms a range of conditions unlike any other region on the planet. During subduction, two of Earth’s tectonic plates collide. However, instead of crashing into each other and crumpling like a car wreck, one of the plates dives beneath the other, producing a deep trench. The down-going plate causes melting in the overlying mantle, creating magma that feeds the active volcanoes of the overlying arc. Further to the west, the back-arc is a zone of spreading in the overriding plate, where mantle magmas well up and new ocean crust is formed. For the chemosynthetic ecosystems, each of these tectonic environments create different geophysical and geochemical conditions. These differences seem to be reflected in the diversity of biological communities on the seafloor.
The Right Tools
Searching for hydrothermal vents is not an easy task due to the technical challenges of working in the deep ocean. The team used the Sentry Autonomous Underwater Vehicle (AUV), as well as instrument packages consisting of optical and chemical sensors to survey systematically for hydrothermally active areas. These sites could hold the answers to fundamental questions about the relationships between ecosystems, geologic settings, and fluid geochemistry.
Identifying vent sites
The research from this cruise helped test the idea that arc and back-arc sites have distinct ecosystems, controlled by each settings’ geology and unique fluid chemistry. In order to test this hypothesis, several tasks had to be accomplished. The science team began by finding and identifying active vent sites along the Mariana back-arc, and characterizing each site by its depth, geologic setting, temperature, chemical composition, and rise heights of hydrothermal plumes. During a follow-up expedition in 2016, the scientists will return with a remotely operated vehicle (ROV) to visually explore and sample the new vent sites on the seafloor.
The science team found some surprises given how little exploration had been done on the back-arc, including several new sites. We consider the Mariana system as a natural laboratory where hypotheses about the interrelations between tectonics, biodiversity, and biogeographic patterns can be tested. After constructing a geological and geochemical model of the back-arc vent settings, the team plans on combining the model with biodiversity data, to better define the relationships between geologic setting, chemical environment, and biological communities.
Partial support for this expedition comes from the NOAA Ocean Exploration and Research Program and the NOAA Pacific Marine Environmental Laboratory.
by Logan Mock-Bunting and Carlie Wiener
Data & Publications
The resulting shipboard dataset is being stored at the Rolling Deck to Repository.
Backscatter: Optical, Pressure, and Temperature acquired from MAPR device mounted on AUV Sentry are now available on the Marine Geoscience Data System repository.
Conductivity, Pressure, Temperature collected from AUV Sentry are now available on the Marine Geoscience Data System repository.
- Cruise Report: Hydrothermal Hunt at Mariana
- I-Poster: Exploring and Protecting the Marvelous Marianas Trench Marine National Monument
- Baker, E., Walker, S., Resing, J., Chadwick, W., Merle, S., and Anderson, M. (2016). Hydrothermal Plume Surveys of the Mariana Backarc (12.7°-18.3°N) by Surface-Ship and AUV Find an Unexpectedly High Spatial Frequency of Vent Sites, Oral Presentation, American Geophysical Union Fall Meeting, San Francisco, CA, USA.
- Resing, J., Chadwick, W., Baker, E., Butterfield, D., Baumberger, T., Buck, N., Walker, S., and Merle, S. (2016). Hydrothermal exploration of the Mariana Back Arc Basin: Chemical Characterization, Poster Presentation, American Geophysical Union Fall Meeting, San Francisco, CA, USA.
- Walker, S., Baker, E., Resing, J., Chadwick, W., Merle, S., and Kaiser, C. (2016). High Resolution Mapping of Hydrothermal Plumes in the Mariana Back-arc Relate Seafloor Sources to Above-bottom Plumes, Poster Presentation, American Geophysical Union Fall Meeting, San Francisco, CA, USA.
- Hirsh, H., Chadwick, Jr., W., Fryer, P., Villagomez, A., Beauregard, L., Cabrera, I., and Peterka, L. (2016). Exploring and Protecting the Marvelous Marianas Trench Marine National Monument, Poster Presentation, International Union for Conservation of Nature (IUCN) World Conservation Congress, Honolulu, HI, USA.
- 2017). Geological interpretation of volcanism and segmentation of the Mariana back-arc spreading center between 12.7°N and 18.3°N, Geochem. Geophys. Geosyst., 18, 2240–2274, doi:10.1002/2017GC006813. [This publication is available as OPEN ACCESS]. , C , , M., , S., , J., , E., , D., , S., and (
- Baker, E., Walker, S., Resing, J., Chadwick, Jr., W., Merle, S., Anderson, M., Butterfield, D., Buck, N., and S. Michael. (2017). The Effect of Arc Proximity on Hydrothermal Activity Along Spreading Centers: New Evidence from the Mariana Back-Arc (12.7° - 18.3°N). Geochem. Geophys. Geosyst.. Accepted Author Manuscript. doi:10.1002/2017GC007234. [This article has been published as OPEN ACCESS].
- Anderson, M., Chadwick, Jr., W., Merle, S., Resing, J., Baker, E., Walker, S., Hannington, M., and N. Augustin. (2017). Relationship between Tectonism, Volcanism, and Hydrothermal Venting along the Mariana Back-arc Spreading Center between 12.7N and 18.3N. Oral Presentation at AGU Chapman Conference on Submarine Volcanism, Hobart, Tasmania, AUS.
- Anderson, R., Reveillaud, J., Reddington, E., Delmont, T., Eren, A., McDermott, J., Seewald, J., and Huber, J. (2017). Genomic Variation in Microbial Populations Inhabiting the Marine Subseafloor at Deep-sea Hydrothermal Vents. Nature Communications 8, 1114 (2017), doi: 10.1038/s41467-017-01228-6. [This article is published as OPEN ACCESS].
- Chadwick, Jr., W., Merle, S., Kaiser, C., Baker, E., Walker, S., Resing, J., Butterfield, D., Baumberger, T., Anderson, M., Shore, P., Wiens, D., and Rubin, K. (2017). A Recent Volcanic Eruption Discovered on the Central Mariana Back-arc Spreading Center. Oral Presentation at IAVCEI 2017 General Assembly, Portland, OR, USA.
- Chadwick, Jr. W. From Galapagos to Mariana: Discovering the Diversity of Hydrothermal Vent Environments, Oral Presentation at OSU and Hydrothermal Vents: 40th Anniversary of the Discovery that Launched 1000 Ships, Corvallis, OR, USA.
- Chadwick, W., Tunnicliffe, V., Butterfield, D., Bates, A., Huber, J., Trembath-Reichert, E., Bobbitt, A., and Merle, S. (2018). Newly Discovered Hydrothermal Vent Sites Along the Mariana Back-arc Spreading Center Support Hypothesis of Geological and Chemical Control on Chemosynthetic Ecosystems. Poster Presentation at Ocean Sciences Meeting, Portland, OR, USA.
- Baker, E., Walker, S., Resing, J., Chadwick, W., Merle, S., Anderson, M., and D. Butterfield. (2018). Hydrothermal Activity Along Back-Arc Spreading Centers: The Importance of Arc Proximity. Poster Presentation at Ocean Sciences Meeting, Portland, OR, USA.
In the News
Sevenseas Marine Conservation & Travel • January 8th, 2016
Hydro International • January 4th, 2016
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Physics Today Magazine • August, 2016 | <urn:uuid:8fd25d6a-5801-49d3-8b27-1d9494505979> | 4.15625 | 2,311 | Knowledge Article | Science & Tech. | 44.643572 | 95,562,574 |
Once again, scientists report they have found evidence of ivory-billed woodpeckers, this time in Florida. But having observed the turbulent disputes among ornithologists and birders that followed the report last year that the bird had been found in Arkansas, these researchers are proceeding with caution.
Geoffrey Hill, of Auburn University in Alabama, and Daniel Mennill of the University of Windsor, in Ontario, both biologists and ornithologists, say 14 sightings and extensive sound recordings “provide evidence that ivory-billed woodpeckers may live along the Choctawhatchee River in the Florida Panhandle.”
The report appears online in a Canadian journal, Avian Conservation and Ecology (www.ace-eco.org).
The ivory bill, the largest woodpecker in the United States, was thought to have gone extinct until scientists at the Cornell Lab of Ornithology and others reported in Science that at least one had been seen and videotaped in the Cache River National Wildlife Refuge in Arkansas.
That claim was at first widely accepted and then vigorously disputed by bird experts and academic ornithologists who argued that the bird in a few seconds of blurry videotape cited in Science was a pileated woodpecker, a smaller, quite common bird. An extensive search in Arkansas last winter led by the Cornell lab did not produce conclusive evidence.
Dr. John Fitzpatrick, director of the Cornell lab, who had consulted with Dr. Hill about the findings before publication, said, “They’ve got a lot of intriguing evidence.”
“This is a perfect illustration of the fact that we need to get a multigroup multistate, comprehensive range-wide search for this bird undertaken,” Dr. Fitzpatrick said.Continue reading the main story
David Sibley, author of “The Sibley Guide to Birds,” a critic of the report on the Arkansas bird, called the Florida report “intriguing”, but said it “really provides very little evidence for the existence of Ivory-bills there.”
In a phone interview, Dr. Hill said only an indisputable photograph or DNA evidence would be scientifically conclusive. He said he knew how heated the subject of ivory bills had become, but asked, “Once we found them, what was I supposed to do?”
“The mistake,” he added dryly, “was ever looking for them.”Continue reading the main story | <urn:uuid:8231d892-e5bd-449a-ac85-dd33a1c0b305> | 2.671875 | 516 | Truncated | Science & Tech. | 34.396231 | 95,562,579 |
Server-side validation incorporates code validation into a form handler. NET application on the server that provides the functionality that your form needs for processing after a customer has submitted it.Because the code is stored on the server, server-side validation requires a roundtrip to the server.(16 printed pages) Introduction Getting Started Writing the Validation Script Connecting the Form to the Script Associating Form Fields with Custom Script Code Listing Conclusion When you create forms, providing form validation is useful to ensure that your customers enter valid and complete data.For example, you may want to ensure that someone inserts a valid e-mail address into a text box, or perhaps you want to ensure that someone fills in certain fields.Caution when using brackets () in scripts : Expression manager uses brackets () to enclose expressions.If you have to use brackets in your Java Script, you must add a space or line feed after the opening bracket () This is from a survey that is a invitation to a longer party, when the user clicks to the next page, the calculated results will be shown.The main problem is that it can't be accessed using ID because every checkbox will have different ID.But they share one common attribute which is "name". I live in World Wide Web and from there take care of this website.
This workaround is in case you need to do some validation involving more than one question, it implies a very little Java Script programming and the use of SGQA Identifiers; this should work on almost any version of Lime Survey.If you wonder what the stuff is, look at SGQA identifier and Using information from previous answers.As of version 1.92, this is easier to do using the min/max/equals_num_value attributes (to validate sums), or the em_validation_q function, which lets you refer to other variables when you validate the current question Expression Manager.We use return false; because when this function is called when the form is submitted and if this textbox is found empty the page shouldn’t be submitted so returning the boolean value false with prevent the form from being submitted.An HTML combobox shows a dropdown list of items from which one item is selected. | <urn:uuid:b2775bb7-a1fc-47b3-b86c-a0a0d45bfe99> | 2.671875 | 450 | Tutorial | Software Dev. | 41.631815 | 95,562,585 |
Acting as caps on the ends of each chromosome, telomeres are composed of repetitive DNA and shelterin, a protective protein complex protects. Titia de Lange's lab has identified many of the components of shelterin and studies how its components work together to ensure that chromosome ends are not recognized as DNA breaks.
Previous work from the de Lange lab showed that TRF2, a shelterin protein that binds to the duplex part of the telomere, is crucial for telomere protection. Without TRF2, telomeres activate a DNA damage signal and are repaired by the same pathways that act on DNA breaks. TRF2 brings a second shelterin protein, POT1, to the telomeres. Because POT1 binds to single-stranded telomeric DNA present at the very end of the chromosomes, the de Lange lab asked how POT1 contributes to the protection of telomeres.
"We had previously removed TRF2 from mouse cells and seen many dramatic phenotypes," says de Lange, "all of the telomeres ligate together; there is a massive DNA damage response and the cells basically die. We argued that if the function of TRF2 was to bring POT1 to the DNA, then we should observe the same phenotype if we removed POT1."
To determine if this was the case, graduate student Dirk Hockemeyer, the first author of the paper, decided to remove the POT1 gene from mice. Humans have one POT1 gene, so de Lange and Hockemeyer were more than a bit surprised when they found two POT1 genes in the mouse genome. "Both genes are ubiquitously expressed and both are at telomeres," says de Lange. "Nothing prepared us for the possibility that these two genes, which we called POT1a and POT1b, were doing different things at the telomere."
But the mice showed that POT1a and POT1b did indeed serve different functions. Without POT1a, the cells showed a massive DNA damage response, which did not happen in cells missing POT1b. In contrast, cells without POT1b had strangely altered telomere structures, something that didn't occur when POT1a was removed. "Wherever we looked, the two phenotypes were different," de Lange says. "To make it more extreme, the POT1b knock-out mouse was alive and well, but the POT1a knock-out mouse was embryonic lethal at a very early stage."
The other surprise came from the POT1a/b double knock-out mouse. While it had a very strong DNA damage response, similar to cells missing TRF2, there was hardly any chromosome end fusion. This result lead de Lange and Hockemeyer to realize that while POT1a and b are required for the protection of the telomeres from the DNA damage response, TRF2 is what is needed to protect against the repair pathway.
But this leaves an interesting dilemma for human telomere biology, which only has one POT1 gene. Does the human POT1 gene serve the functions of both POT1a and POT1b? How does the presence of the second POT1 protein affect the rest of the complex? "I've gone through hundreds of genes involved in chromosome biology and the genes from mouse to human are always there one to one," says de Lange. "We know that the telomeric complex evolves rapidly, but I had no idea that it was this rapid, that even within the mammalian lineage you can see big changes in evolution. We will have to be very careful now how we use rodent systems, bearing in mind this difference and the possibility that there might be others."
Kristine Kelly | 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:62c6b5c8-0c3b-4412-bf90-928b3b162a83> | 3.796875 | 1,434 | Content Listing | Science & Tech. | 43.857137 | 95,562,618 |
A meteoroid fell to Earth on February 15, streaking some 20 to 30 kilometers
above the city of Chelyabinsk, Russia at 9:20am local time. Initially traveling
at about 20 kilometers per second, its explosive deceleration after impact
with the lower atmosphere created a flash brighter than the Sun. This picture
of the brilliant bolide (and others of its persistent trail) was captured
by photographer Marat Ametvaleev, surprised during his morning sunrise
session creating panoramic images of the nearby frosty landscape. An estimated
500 kilotons of energy was released by the explosion of the 17 meter wide
space rock with a mass of 7,000 to 10,000 tons. Actually expected to occur
on average once every 100 years, the magnitude of the Chelyabinsk event
is the largest known since the Tunguska impact in 1908.
Russian meteor explosion: Spectacular dash cam video of meteorite fireball
Russia's Urals region has been rocked by a meteorite explosion in the stratosphere. The impact wave damaged several buildings, and blew out thousands of windows amid frigid winter weather.
The Great Russian Meteor of 2013
What in heaven's blazes is that? Thousands of people living near the Ural
Mountains in Russia saw last Friday morning one of the more spectacular
meteors of modern times streak across the sky. Forceful sound waves arrived
at the ground minutes later, knocking people over and breaking windows
for hundreds of kilometers. The above video is a compilation of several
car dashcams and includes real time footage of the meteor rampaging, smoke
trails drifting, shadows quickly shifting, and even the meteor's light
reflecting off the back of a bus. The fireball is thought to have been
caused by a car-sized chunk of ice and rock crashing into the Earth's atmosphere.
Since the event was captured from so many angles, the meteor's trajectory
has become determined well enough to indicate from where it came and to
where any resultant pieces might have landed. It is already certain that
this meteor had nothing to do with the several-times larger asteroid 2012
DA14 which passed the Earth from a different direction later the same day.
If pieces of the meteor are found, they might tell humanity more about
the early Solar System, when the meteor was likely formed.
ScienceCasts: What Exploded Over Russia?
Two weeks after an asteroid exploded over Russia's Ural mountains, scientists are making progress understanding the origin and make-up of the unexpected space rock. | <urn:uuid:b21124eb-4815-4587-8664-f976d47a9860> | 3.46875 | 532 | Content Listing | Science & Tech. | 37.352742 | 95,562,623 |
The endoplasmic reticulum is a system of interconnected tubes and pouches inside a cell, like a hollow funnel cake. There are two different specialized areas of the endoplasmic reticulum (ER), each with different functions. One is called the smooth ER and the other is called the rough ER. The two are connected, but produce different types of molecules for the cell. The smooth ER makes the lipid molecules that are the stuff of cell membranes, while the rough ER makes the protein machines of the cell.
Structure of Endoplasmic Reticulum
The endoplasmic reticulum is a system of interconnected tunnels. The tunnel walls are membranes that prevent water from freely moving in or out. Membranes are made of oily molecules called phospholipids. The special thing about phospholipids is that they form sheets -- membranes -- that separate water, salts, sugars and proteins on the outside from those that are on the inside. The rough ER is called rough because it has many protein machines called ribosomes that are attached to its surface. The smooth ER is called smooth because it does not have ribosomes on it and looked smooth to the person who first observed it under the microscope.
Smooth ER Function
The smooth ER has the special job of making lipids, or oily molecules, for the cell. There are two main types of lipids that come from the smooth ER. One is the phospholipids, which are molecules that have an electrically charged head and a water-fearing tail. This north pole and south pole nature is why phospholipids arrange themselves as membranes and make up the membranes of a cell. The other type of lipid that comes for the smooth ER is cholesterol. In addition to being part of cell membranes, cholesterol is modified by the smooth ER to make androgens and estrogens, the male and female sex steroids.
Rough ER Function
The rough ER has the job of making lots and lots of proteins. Ribosomes are the machines that make new proteins. Many ribosomes can be found on the outer surface of the rough ER because they are inserting the new proteins that they are making into the rough ER. Ever wonder how proteins on the surface of the cell can be stuck in the cell membrane? Well, those proteins got shoved into the membrane of the rough ER while their ribosomes were making them and inserting them into the rough ER’s inner chamber. The rough ER will eventually ship that part of its membrane to the surface of the cell, which is how that protein ends up on the surface of the cell.
Facing the Golgi
The rough ER makes proteins and ships them to the rest of the cell or out of the cell. However, it does this with the help of another organelle called the Golgi apparatus. The Golgi is also a system of tubed membrane tunnels. If the rough ER is the front desk of a UPS shipping office, the Golgi is the backdoor. The rough ER sends the proteins that were inserted into its inside or its membrane to the Golgi. The Golgi adds sugar molecules to these proteins, which serve as address labels. The Golgi then ships these proteins in small pouches called vesicles. The pouches deliver proteins to places throughout the cell or out of the cell. | <urn:uuid:99f564e4-43e9-4224-901f-cc3cb5eb45ab> | 3.703125 | 686 | Knowledge Article | Science & Tech. | 51.411852 | 95,562,641 |
by W.C. Martin, W.L. Wiese
Publisher: National Institute of Standards and Technology 2003
Number of pages: 31
This article outlines the main concepts of atomic structure, with some emphasis on terminology and notation. Atomic radiation is discussed, in particular the wavelengths, intensities, and shapes of spectral lines, and a few remarks are made regarding continuous spectra. We include updated tabulations of ionization energies for the neutral atoms and transition probabilities for persistent lines of selected neutral atoms.
Home page url
Download or read it online for free here:
by Michel Orrit - Universiteit Leiden
The field of optical spectroscopy covers: investigations of single nano-objects (molecules, nanocrystals, quantum dots, metal particles, etc.). The aim of these lectures is to present the experimental techniques giving access to single objects.
by Steve Marsden - chemtopics.com
Three principal methods of modern spectrographic analysis are to be examined here: Mass Spectroscopy, Nuclear Magnetic Resonance, and Infra-Red Spectroscopy. Used in concert, they allow the positive identification of many organic chemicals.
by A. C. Candler
Contents - Complex spectra: Combination of several electrons; Short periods; Long periods; Rare earths; Intensity relations; Sum rules and coupling; Series limit; Hyperfine structure; Quadripole radiation; Fluorescent crystals; etc.
by Niels Bohr - Cambridge University Press
Three essays deal with the application of the quantum theory to problems of atomic structure: On the spectrum of hydrogen - On the series spectra of the elements - The structure of the atom and the physical and chemical properties of the elements. | <urn:uuid:be18cfc0-8ec8-4b35-aa5e-aaca9e67d1dc> | 2.984375 | 353 | Content Listing | Science & Tech. | 22.603451 | 95,562,677 |
Genome rearrangements can make and break small RNA genes.
- Citation data:
Genome biology and evolution, ISSN: 1759-6653, Vol: 7, Issue: 2, Page: 557-66
- Publication Year:
- Repository URL:
- https://works.bepress.com/rahul-raghavan/40; https://pdxscholar.library.pdx.edu/bio_fac/103
- Agricultural and Biological Sciences; Biochemistry, Genetics and Molecular Biology; Escherichia coli.; Salmonella; RNA; Genomics; Biology; Genetics and Genomics
Small RNAs (sRNAs) are short, transcribed regulatory elements that are typically encoded in the intergenic regions (IGRs) of bacterial genomes. Several sRNAs, first recognized in Escherichia coli, are conserved among enteric bacteria, but because of the regulatory roles of sRNAs, differences in sRNA repertoires might be responsible for features that differentiate closely related species. We scanned the E. coli MG1655 and Salmonella enterica Typhimurium genomes for nonsyntenic IGRs as a potential source of uncharacterized, species-specific sRNAs and found that genome rearrangements have reconfigured several IGRs causing the disruption and formation of sRNAs. Within an IGR that is present in E. coli but was disrupted in Salmonella by a translocation event is an sRNA that is associated with the FNR/CRP global regulators and influences E. coli biofilm formation. A Salmonella-specific sRNA evolved de novo through point mutations that generated a σ(70) promoter sequence in an IGR that arose through genome rearrangement events. The differences in the sRNA pools among bacterial species have previously been ascribed to duplication, deletion, or horizontal acquisition. Here, we show that genomic rearrangements also contribute to this process by either disrupting sRNA-containing IGRs or creating IGRs in which novel sRNAs may evolve. | <urn:uuid:0000a382-051b-41c4-9c7e-4b2387da88ff> | 3.046875 | 433 | Academic Writing | Science & Tech. | 23.672454 | 95,562,693 |
Scheduled to arrive at NASA's Marshall Space Flight Center on Monday, July 25, six gold-coated mirrors for the James Webb Space Telescope (JWST) must be tested under extreme conditions to ensure that the mirrors will be smooth and focused when they are put to work most of a million miles from Earth.
A principal research scientist at The University of Alabama in Huntsville's Center for Applied Optics, Hadaway leads the optical testing of the Webb telescope's 18 primary mirrors. Subcontractors through Ball Aerospace, he and Dr. Patrick Reardon are part of a team working to ensure that the Webb telescope sees everything it should see. The observatory was designed to look at stars and galaxies on the distant edges of the universe.
The mirrors arriving next week are the second of three sets. The first six mirrors all passed their tests in April and May, despite Marshall Space Flight Center (MSFC) losing electric power following an outbreak of tornadoes in late April.
"We had six mirrors in the vacuum chamber and we were at the cold temperature -- 45 Kelvin (about 378° F below zero) -- and we had finished measurements on three mirrors by that Wednesday afternoon," recalled Hadaway. "It was a pretty critical time. It takes a lot to get and keep these mirrors cold.
"We knew something bad was happening outside, but we had to focus on what we were doing."
UAHuntsville's optical measurement team headed for home about 5:30 that afternoon, just before the power went out at MSFC. That included power to the X-Ray and Cryogenic Facility (XRCF) where the mirror testing is done.
"Fortunately, the XRCF has a diesel generator to keep things running in a power outage," Hadaway said. "That night they e-mailed us, 'We're still good,' so for the next three days we were out there taking data. They only had enough power for the instruments and to maintain the chamber, so by Saturday it was up to 85 inside the building. But we ended up getting all of our data as planned, on budget and on schedule.
"The real story on this is the people who run the facility. They're the ones who did the heroic job, arranging for enough diesel fuel, liquid nitrogen, liquid helium and all the other things needed to keep us running. They did a great job of keeping everything going."
Once they are cooled to the temperature of deep space, the extraordinarily smooth mirrors have to be warmed slowly over a period of several days to avoid damage, distortion or condensation, which could leave behind deposits on the polished gold surface.
Hadaway has been part of the Webb telescope program from its beginning, when he led the optical design team that came up with the initial layout for the telescope. More than two and a half times bigger than the Hubble space telescope, the Webb will collect infrared radiation (energy that our bodies sense as heat) from the most distant stars and galaxies ever viewed.
"The final optical design is basically the same as my original design," Hadaway said. "The optics weren't too difficult to design. The hard part was making lightweight mirrors that will survive launch loads and then deploy properly."
The next step would be building and testing mirrors, starting with engineering mockups and continuing with flight hardware.
What would have been routinely challenging was complicated by the observatory's working environment. Infrared energy includes the same wavelengths created when sunlight warms a spacecraft. To avoid polluting weak infrared radiation from galaxies on the edges of the universe with heat absorbed from sunlight, the Webb telescope will be shaded from the sun. Sitting in that shade, the mirrors will operate at temperatures about 45 degrees Celsius above absolute zero.
When the mission was proposed, no one knew how telescope mirrors built on Earth at room temperatures might bend and distort at temperatures that cold. During a meeting at NASA's Marshall Space Flight Center, officials wondered where they might find someone with the special knowledge and skills needed to organize and conduct a mirror testing program under those extreme conditions.
Hadaway stuck up his hand.
"We can do that," he said. After working with NASA to develop specialized mirrors used for X-ray telescopes, Hadaway was confident the CAO team could develop the tools needed to test mirrors designed to collect energy at the other end of the electromagnetic spectrum.
A house-sized cryogenic chamber in the XRCF, a facility built for testing the Chandra X-ray Observatory's optics, was adapted for testing Webb mirrors at extremely cold temperatures.
Using techniques that they developed, "we measured to see how each mirror deforms when it 'goes cold,'" Hadaway said. "We send what we find to Tinsley Laboratories in Richmond, California, which polishes opposite distortions into the mirrors. If it was a bump when it was cold, they polish in a hole. Now it looks bad at room temperature, but it's perfect in the cold."
Perfect? The average imperfection allowed is the height of about 200 hydrogen atoms.
Testing mirrors in a massive insulated chamber requires Hadaway and his team to be flexible. "If it gets cold at 3 a.m., you go in at 3 a.m.," he said. "You go when they're cold. We try to work with the guys at Marshall so things work out in the daytime, but you just have to be there when it's time."
The mirror-testing program is scheduled to end by the end of this year, although Hadaway expects to be involved in the Webb telescope's ongoing testing, development and preparations for a possible launch in 2015. In the 15 years he has been involved in the program, Hadaway's team has received more than $5 million in NASA funding to support UAHuntsville's work.
"I was part of this program from day one," he said. "My goal is to be there when it's on orbit and certified to be operational."Dr. James Hadaway, (256) 824-2533
Ray Garner | Newswise Science News
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:80edab8c-f58b-4527-bedb-d5dd1e2a1ff4> | 2.828125 | 1,881 | Content Listing | Science & Tech. | 50.003489 | 95,562,705 |
Species Detail - Great Black-backed Gull (Larus marinus) - 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).
Great Black-backed Gull
Protected Species: Wildlife Acts || Threatened Species: Birds of Conservation Concern || Threatened Species: Birds of Conservation Concern >> Birds of Conservation Concern - Amber List
1 January (recorded in 2003)
31 December (recorded in 2012)
National Biodiversity Data Centre, Ireland, Great Black-backed Gull (Larus marinus), accessed 21 July 2018, <https://maps.biodiversityireland.ie/Species/10043> | <urn:uuid:9aac2a3f-f80d-4b1c-a724-eb9c71e44a4d> | 3.25 | 179 | Structured Data | Science & Tech. | 33.974544 | 95,562,713 |
Temporal range: Middle Miocene - Recent
|Spheniscus demersus, the African penguin|
The banded penguins are penguins that belong to the genus Spheniscus. There are four living species of penguins known as banded penguins, and all have similar coloration. They are sometimes also known as "jack-ass penguins" due to their loud locator calls sounding similar to a donkey braying. Common traits include a band of black that runs around their bodies bordering their black dorsal coloring, black beaks with a small vertical white band, distinct spots on their bellies, and a small patch of unfeathered or thinly feathered skin around their eyes that can be either white or pink. All members of this genus lay eggs and raise their young in nests situated in burrows or natural depressions in the earth.
The banded penguins belong to the genus Spheniscus, which was established by Mathurin Jacques Brisson in 1760. The word Spheniscus is the diminutive of sphẽn or sphẽnos, meaning "wedge"; this is a reference to the penguin's thin, wedge-shaped flippers.
The four extant species of banded penguins (Spheniscus) are:
Image Common name Binomial name Magellanic penguin Spheniscus magellanicus Humboldt penguin Spheniscus humboldti Galapagos penguin Spheniscus mendiculus African penguin, black-footed or jackass penguin Spheniscus demersus
Several extinct species are known from fossils:
- Spheniscus muizoni (Pisco Middle/Late Miocene of Cerro La Bruja, Peru)
- Spheniscus chilensis (Late Miocene/Early Pliocene of Chile)
- Spheniscus megaramphus (Late Miocene/Early Pliocene of Peru and Chile)
- Spheniscus urbinai (Late Miocene/Early Pliocene of Peru and Chile)
The African, Humboldt, and Magellanic species all live in more temperate climates such as South Africa and the southern coasts of Chile and Argentina. The Humboldt and Magellanic penguins are partially sympatric, since their geographical dispersal overlaps along the Pacific ocean coast in south America. The Galápagos penguin is native to the Galápagos Islands, making it the most northerly of all banded penguin species. Ornithologists believe that the banded penguins originated in South America, even though the oldest penguin fossils from Antarctica belong to the genus.
Banded penguins use vocalizations for localization, socialization and to allow recognition for conspecifics or mates. Vocalizations in birds are produced by vibrations of the syrinx, located at the bottom of the trachea. These penguins are sometimes referred to as "jack-ass" penguins, since their vocalizations tend to sound similar to a donkey braying. Vocalizations in adult penguins can be classified into 4 distinct categories based on its acoustic properties and the behavioural context in which a vocalization is produced. The 4 categories of vocalizations include contact calls, agonistic calls, ecstatic display songs or mutual display songs.
Contact calls are vocalizations used primarily to maintain unity within a social group, to identify ones self and to maintain contact with a mate. Vocal individuality has evolved in banded penguins due to their large social group sizes. Contact calls are frequently used by banded penguins to form large flocks when foraging at sea. It is easy to become separated while diving for food, therefore these penguins use contact calls to stay in contact with each other when they are out of sight. A contact call can relay an excess of information about an individual penguin, including the penguins sex, age, social status within a group and emotional state.
Agonistic calls are vocalizations used when a banded penguin is demonstrating agonistic behaviour, which is characterized by aggressive interactions or fighting. Typically, banded penguins vocalize agonistic calls when defending a territory, such as their nest, against conspecifics. For nesting penguin species, such as banded penguins, the mating pair and their offspring are the only individuals allowed on their nest. Thus, any conspecific from the large colony that intrudes this territory will be a threat and a agonistic call will be produced.
There are two types of display songs vocalized by banded penguins; ecstatic display songs and mutual display songs. Ecstatic display songs are the loudest and most complex vocalization performed by banded penguins. They are composed of a sequence of distinct acoustic syllables that combine to form a complete phrase and are often displayed during their breeding season. Despite the close relatedness of banded penguin species, the ecstatic display calls of African, Humboldt and Magellanic penguins are distinctly recognizable, even to human listeners. Typically, females respond more strongly to ecstatic display calls from their mates than from other conspecifics. Furthermore, there is evidence to suggest that ecstatic display songs may convey vocal individuality through the type of syllables the song produces. This vocal individuality can convey information such as body size and weight, since heavier penguins typically emit longer and lower-pitched vocalizations. Mutual display songs are similar to ecstatic display songs in that they are also complex sequences of acoustic syllables. However, mutual display songs are performed by mates at their nesting site.
The source-filter theory is a framework used for studying the communication of mammalian animals through vocalizations. According to this theory, acoustic calls are produced by a source and then must be filtered to remove certain frequencies or leave others unchanged, which produces vocal individuality. In mammals, the source is the vibrations in the larynx and the filter is the super laryngeal vocal tract. However, birds use a different source and filter to produce vocalizations. They use a structure called the syrinx as their source of vibrations and their trachea acts as the filter. The source-filter theory has become increasingly popular to study birds, such as various species of banded penguins. This theory can be used to investigate how acoustic variation and individualilty within a set of closely related species is attributed to distinct morphological differences in their vocal organs. The equivalence of the source-filter theory in humans is the source-filter model of speech production.
- Favaro L; Ozella L; Pessani D (20 July 2014). "The Vocal Repertoire of the African Penguin (Spheniscus demersus): Structure and Function of Calls". PLoS ONE. 9 (7): e103460. doi:10.1371/journal.pone.0103460.
- Ellis, Richard (2004). No Turning Back: The Life and Death of Animal Species. New York: Harper Perennial. p. 69. ISBN 0-06-055804-0.
- Favaro, Livio; Gamba, Marco; Gili, Claudia; Pessani, Daniela (2017-02-15). "Acoustic correlates of body size and individual identity in banded penguins". PLOS ONE. 12 (2): e0170001. doi:10.1371/journal.pone.0170001. ISSN 1932-6203.
- "ITIS Report: Spheniscus". Integrated Taxonomic Information System. Retrieved 11 August 2014.
- Jobling, James A. (2010). The Helm Dictionary of Scientific Bird Names. London, UK: Christopher Helm. p. 361. ISBN 978-1-4081-2501-4.
- Favaro, Livio; Gili, Claudia; Rugna, Cristiano Da; Gnone, Guido; Fissore, Chiara; Sanchez, Daniel; McElligott, Alan G.; Gamba, Marco; Pessani, Daniela. "Vocal individuality and species divergence in the contact calls of banded penguins". Behavioural Processes. 128: 83–88. doi:10.1016/j.beproc.2016.04.010.
- Jadwiszczak, Piotr; Krajewski, Krzysztof P.; Pushina, Zinaida; Tatur, Andrzej; Zieliński, Grzegorz (2013-06-01). "The first record of fossil penguins from East Antarctica". Antarctic Science. 25 (3): 397–408. doi:10.1017/S0954102012000909. ISSN 0954-1020.
- Favaro, Livio; Gamba, Marco; Alfieri, Chiara; Pessani, Daniela; McElligott, Alan G. (2015-11-25). "Vocal individuality cues in the African penguin (Spheniscus demersus): a source-filter theory approach". Scientific Reports. 5 (1). doi:10.1038/srep17255. ISSN 2045-2322.
- Briefer, E.F., Te amanti, F., & McElligo, A.G. (2015). "Emotions in goats: mapping physiological, behavioural and vocal profiles". Animal Behaviour. 99: 131–143. doi:10.1016/j.anbehav.2014.11.002.
- Jouventin, Pierre; Aubin, Thierry. "Acoustic systems are adapted to breeding ecologies: individual recognition in nesting penguins". Animal Behaviour. 64 (5): 747–757. doi:10.1006/anbe.2002.4002. | <urn:uuid:33fd774d-95d2-4209-aad9-a1b6b982f90e> | 3.828125 | 2,052 | Knowledge Article | Science & Tech. | 43.45545 | 95,562,724 |
Chapter 56: Ecosystem and Global Ecology
56.2 How Does Energy Flow Through the Global Ecosystem?
Solar energy drives ecosystem processes
•Solar energy enters ecosystems by way of plants and other photosynthetic
•Only about 5 percent of the solar energy that arrives on Earth is captured by
photosynthesis; remaining energy is either radiated back into the atmosphere
as heat or taken up by the evaporation of water.
•Gross primary productivity (GDP) is the rate at which energy is
incorporated into the bodies of photosynthetic organisms.
•The accumulated energy is called gross primary production.
•Primary producer use some of this accumulated energy for their own
metabolism; the rest is stored in their bodies or used for their growth and
•The energy available to organisms that eat primary producer, called net
primary production (NPP), is gross primary production minus the energy
expended by the primary producers during their metabolism.
•Only the energy of an organism’s net production is available to other
organisms that consume it.
•The geographic distribution of the energy assimilated by primary producers
reflects the distribution of land masses, temperature, and moisture on Earth.
•Production in aquatic ecosystems in limited by light, which decreases rapidly
with depth; by nutrients, which sink and must be replaced by upwelling of
water; and by temperature.
Human activities modify flows of energy
•Some human activities decrease net global primary productivity (e.g.
conversion of forests).
56.4 What Services Do Ecosystem Provide?
•Ecosystems provide people with a variety of goods and services.
•The rapidly expanding human population has greatly modified Earth’s
ecosystems to increase their ability to provide some of the goods and
services it needs, particularly food, fresh water, timber, fiber, and fuel.
•The most important driver of alterations in ecosystems and the services they
provide has been changes in land use as natural ecosystem have been
converted to other, more intensive uses.
•The modifications of ecosystems to benefit human beings in one way has
often resulted in the degradation of other services.
56.5 What Options Exist to Manage Ecosystems Sustainably?
•Often the total economic value of a sustainably managed ecosystem is higher
than that of an intensively exploited ecosystem (e.g. land for clear cutting).
•A major barrier to achieving these greater long-term benefits is that many
ecosystem services are considered “public goods” that have no market value.
•More sustainable use of fresh water can be achieved by charging the full cost
of providing the water, by developing methods to use water more efficiently
in agriculture and by altering the allocation of water rights so that the
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Homing abilities of the Australian intertidal ant Polyrhachis sokolova
The pressure of returning to and locating the nest after a successful foraging trip is immense in ants. To find their way back home, ants use a number of different strategies (e.g. path integration, trail following) and rely on a range of cues (e.g. patte
|Collections||ANU Research Publications|
|Source:||Journal of Experimental Biology|
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The unexpected discovery was made by a team exploring a 12 billion-year-old cluster of stars in the Milky Way called M22.
It contains hundreds of thousands of stars and can be seen with the naked eye as a hazy patch of light.
Scientists at the International Centre for Radio Astronomy Research now believe there could be as many as 100 black holes inside the cluster.
Dr James Miller-Jones, who co-wrote a report that appears in the journal Nature, said: "Simulations of how globular clusters evolve show that many black holes are created early in a cluster's history.
"The many black holes then sink towards the middle of the cluster where they begin a chaotic dance. Most are thrown out until only one surviving black hole remains.
"We were searching for one large black hole in the middle of the cluster, but instead found two smaller black holes a little way out from the centre, which means all the theory and simulations need refinement."
Black holes are formed when a massive star reaches the end of its life and collapses in on itself.
They are so dense that even light cannot escape them.
The M22 cluster, which can be found in the constellation Sagittarius, was discovered almost 350 years ago.
It is 10,000 light years away, so astronomers on Earth only see it as it was 10,000 years ago.
The research involved scientists from the University of Southampton, as well as universities in the United States and Australia.
Life is like a penny, you can spend it on what you like, but you can ONLY spend it once. | <urn:uuid:9c3b45b5-4b7b-42aa-8335-9b3a0429dd54> | 4.03125 | 326 | News Article | Science & Tech. | 55.763091 | 95,562,782 |
Growth characteristics and nutrient removal capability of eco-ditch plants in mesocosm sediment receiving primary domestic wastewater
Eco-ditches are being explored to maximize their capability of capturing pollutants and mitigate any harmful side effects in rivers. In this study, mesocosm plastic drum sediment and field experiments were set up to screen 18 plant species found in ditches and identify those with potential for high biomass production and nutrients removal. Terrestrial plants grown in the mesocosm system were shown to be able to acclimate to aquatic conditions and to survive in primary domestic sewage. About 73–95% increase in plant biomass was recorded. Removal efficiencies for total nitrogen, total phosphorus, and ammonium-nitrogen from the sewage of 72–99%, 64–99%, and 75–100%, respectively, were recorded. Furthermore, complete removal of the applied nitrate-nitrogen load was achieved in mesocosm systems. Findings also show that all species, but especially Acorus calamus, Canna indica, Canna lily, Cyperus alternifolius, Colocasia gigantea, Eichhornia crassipes, Iris sibirica, and Typha latifolia had the highest efficiencies for nitrogen and phosphorous removal. The N and P mass balance analysis demonstrated that plant uptake and sediment N and P accumulation accounted for 41–86% and 18–49% of the total influent TN and TP loads, respectively. In addition, the amounts of nitrogen and phosphorous uptake by these plant species were influenced significantly by biomass. The field-culture experiment further identified Canna indica followed by Cyperus alternifolius as the most promising for high biomass production and nutrients uptake. Therefore, these plants may be recommended for extensive use in treating highly eutrophicated rivers. Outcomes of this work can be useful for model design specifications in eco-ditch mitigation of sewage pollution.
KeywordsAquatic and terrestrial plants Biomass Non-point source pollutants Vegetated drainage channel Uptake Untreated sewage
The authors are grateful to the Natural Science Foundation of China (Grant No. 41430750), the CAS Western Light Plan, and the Chinese Academy of Sciences—the Third World Academy of Sciences (CAS-TWAS) President’s Fellowship program for developing countries for financial support of this work.
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- Kumwimba MN, Zhu B, Zhixin D, Jialiang T, Wang T, Liwei X, Muyembe DK (2017b) Assessing nutrient, biomass, and sediment transport of drainage ditches in the Three Gorges Reservoir Area. CLEAN Soil Air Water 45(1). doi: 10.1002/clen.201501012
- Kumwimba MN, Dzakpasu M, Zhu B, Wang T, Lunda I, Muyembe DK (2017c) Nutrient removal in a trapezoidal vegetated drainage ditch used to treat primary domestic sewage in a small catchment of the upper Yangtze River. Water Environ J 31:72–79Google Scholar
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To combat the warming of Earth’s atmosphere, U.S. scientists are considering stratospheric climate geoengineering, or in other words, spraying sulfur dioxide into the atmosphere to form clouds.
Crafted clouds could be the cooling cure to slow planetary warming. They could also create some very serious problems in the atmosphere.
Much of this is speculative science proposed in study published yesterday in the journal Nature Ecology & Evolution.
“The idea behind this type of geoengineering would be to create a sulfuric acid cloud in the upper atmosphere,” climatologist Alan Robock told USA Today, “The clouds formed after airplanes spray sulfur dioxide, would reflect solar radiation and thereby cool the planet.”
It seems that because man was largely the cause of our planet’s warming, man should be the solution, as per the manners, “clean up after yourself.” However, this proposed solution may do more harm than good.
Unless airplanes are continuously maintaining the cloud, warming may exacerbate. In the study, the effects of creating clouds for 50 years and then suddenly stopping were alarming: the earth would warm up too quickly, likely causing a huge loss of animal and plant life.
The bottom line seems to be that there must be a way for stratospheric climate geoengineering to be sustained if it is deployed. If not, the damage it causes would be much worse than the positive effects it would create.
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Teen Who Urged Boyfriend’s Suicide Through Text Says It Was Free Speech
Apparently, the First Amendment extends to telling your boyfriend to get back into the truck and kill himself.
Build-A-Bear ‘Pay Your Age’ Deal Ends in Failure
Would you wait in a line for hours, for a $29.00 teddy? Many did, which ended in chaos. | <urn:uuid:dfb343b1-42b1-4bba-828a-0f34a302ef4b> | 3.25 | 437 | Truncated | Science & Tech. | 52.661251 | 95,562,788 |
A Puget Sound seaweed cultivation project aimed at investigating the ability of kelp to help mitigate ocean acidificaiton was recently featured on 60 Minutes. This project is a collaboration between researchers at the Puget Sound Restoration Fund, University of Washington, NOAA, and Department of Natural Resources, and has just entered it's second field season.
Field Engineer Zoë Parsons found this awesome video from the UW Media Center's archived 16 mm film...
The 6th annual report on marine water conditions in Puget Sound is now available. This report contains a comprehensive look at Puget Sound marine conditions for the year 2016, including physical, chemical, and biological information ranging from large-scale climate variations to local biota monitoring.
The new Real-Time HABs website provides timely information on toxic harmful algal blooms in the Pacific Northwest. View the latest harmful algal bloom measurements from the Environmental Sample Processor (ESP), an underwater robot located on the NEMO mooring 13 miles off La Push, Washington.
A comprehensive look at Puget Sound marine conditions for the year 2015 is now available. Physical, chemical, and biological information ranging from large-scale climate variations to local biota monitoring are summarized to provide a thorough overview of Puget Sound conditions for 2015.
Univerity of Washington News
Scientists with the University of Washington and the National Oceanic and Atmospheric Administration deployed a new tool this week that will constantly be on the lookout for harmful algal blooms and their toxins off the coast of La Push, Washington.
NOAA Ocean Service
NOAA, partners deploy experimental "robot" to measure paralytic shellfish toxins.
Oceanographers deployed a buoy in Bellingham Bay on Thursday that will chart the health of Puget Sound. It joins a half-dozen other buoys, but this is the only one in the north Puget Sound. It is equipped with several pieces of advanced technology that will monitor everything from salinity, temperature and weather changes.
UW School of Oceanography
The Center for Coastal Margin Observation and Prediction, through its education partner the University of Washington, is deploying an oceanographic observing buoy in Bellingham Bay this week that will allow Northwest Indian College students both hands-on experience with the technology as well as the ability to study the data from their computers, through the Northwest Association of Networked Ocean Observing Systems, NANOOS.
A new buoy about two miles out in Bellingham Bay is collecting streams of data around the clock that scientists and students will use to monitor the health of north Puget Sound and the Salish Sea. | <urn:uuid:d9181d54-b5e4-4a90-b4c7-ddde38670780> | 2.5625 | 530 | Content Listing | Science & Tech. | 27.245952 | 95,562,794 |
The statistics only keeps getting bleaker. Last November 8, 2016, the United Nations World Meteorological Organization or WMO published a report showcasing how the planet's global warming situation has only gotten worse in the last few years.
Republicans are still in the midst of celebrating the party's return to the White House. On the other hand, environmentalists from all over the world have already voiced out their concern over the appointment of the new president of the free world.
Donald Trump's victory on the US presidency over Hillary Clinton came as a shock not only to the US and economy but also to ongoing climate change negotiations. Trump, who has expressed his doubts on the truth behind climate change, says that he will "cancel" the Paris climate change agreement once elected.
After the landmark Paris Agreement entered into force, the world gathered in Morocco for the first meeting under the pact to iron out implementation details for participating countries.
A new research sheds light on how much damage one individual’s carbon dioxide emission could cause to the Arctic summer sea ice.
The 2015 Paris Agreement was made last December. But it was only this November that the agreement officially entered into force, and nations are starting to put together plans to cut greenhouse gas emissions.
Scientists have discovered that increasing temperatures can affect the dietary choices of frogs. Researchers at the Universities of Lisbon and Uppsala studied the behavior of three kinds of amphibians to discover what effect heat waves can have on their diets.
A new study reveals that soils could have a limited potential in countering the effects of climate and more likely to become a net source of atmospheric carbon dioxide in the next century.
Yes, you’ve caused a sizable chunk of the Arctic to melt into the warm ocean.
NASA IceBridge data shows the alarming retreat of ice sheets in the Antarctic region.
Is there a quick solution to stop climate change? Put A Price On It, a new movement, says that a faster climate solution is making carbon pollution expensive.
A new study reveales that the record low snowpack levels in the western-most region of the continental U.S. last 2015 were most likely caused by high temperature.
With the alarming news that Australia's Great Barrier Reef is in the brink of death, scientists are formulating live-saving techniques to prevent coral death and the declining population of marine life.
A new observation from NASA revealed that the oldest and thickest ice in the arctic has either melted or thinned away due to warming summers, leaving the sea ice cap more vulnerable to the increasing temperature of the ocean and atmosphere. | <urn:uuid:df41865f-afbd-44d4-aa1f-43ddb7405c3a> | 2.953125 | 522 | Content Listing | Science & Tech. | 39.332578 | 95,562,813 |
Big companies will have to report their energy use, carbon dioxide emissions and energy efficiency measures in their annual reports from next April under a new framework set out by the Br...
A heat wave is bringing unusually hot and dry conditions, fuelling wildfires within the Arctic Circle.
The iceberg - weighing between 8 and 10 million tons - came within just 100 metres of the shoreline.
Designers from the UN and Yale University have collaborated to create a piece of futuristic architecture.
Infrastructure, such as undersea cables, that is vital for global connectivity is likely to be at risk from rising sea levels, according to a new study.
Healthier for you and the planet.
As veganism grows in global popularity, tensions between militant animal welfare campaigners and French butchers are threatening to boil over.
The subspecies is still critically endangered, due to poaching and habitat destruction.
With coral reefs across the globe in crisis, communities are working with scientists to protect the ocean ecosystems.
Despite global progress, nearly a billion people still lack clean drinking water.
New MIT research shows that urban wetlands could reduce weather damage and improve the environment.
In 2048, the Antarctica Treaty becomes modifiable, leaving the fate of the continent up to the rest of the world.
China has made significant progress in battling the environmental catastrophes of the past century. What can other countries learn from them?
Bugs emit less harmful gas than mainstream farm animals, which could make them the food of the future.
On average, a woman in rural India walks between 5 and 20 kilometres a day to fetch water. | <urn:uuid:319a2fe5-b82e-4fd8-bb2a-97912a418a26> | 2.53125 | 325 | Content Listing | Science & Tech. | 41.590403 | 95,562,833 |
The Water Beneath Our Feet: New Study on California's Central Valley Groundwater Level Decline
SGS hydrologist Dr. Claudia Faunt discusses her new study about Calfornia's vast central valley groundwater system and the new study findings.
Location Taken: US
Hello and welcome to this U.S. Geological Survey PodCast. I'm Laurel Rogers and today, I am speaking with Dr. Claudia Faunt, a USGS hydrologist who has just completed an extensive study of groundwater in California's Central Valley. Hello Claudia. Thank you for talking with us today.
Claudia: Thanks, it's nice to talk with you.
Laurel: What does this study tell us about California's groundwater. Can you sort of paint a picture for us about the state of California's groundwater now?
Claudia: Well, competition for water supplies are intensifying, there are urban populations, agriculture, and the environment all needing water. Despite all the conservation efforts that have taken place over the last few years, the competing needs coupled with drought conditions have limited the availability of water. When there are limited supplies of surface water, Californian's turn towards groundwater. Groundwater is not directly observable except at springs and wells, so groundwater could be considered CA's hidden resource and also an important source of water during drought.
Laurel: What are some of the results of this study?
Claudia: In the Central Valley, like in all of California, the conditions vary. There are general trends, and exceptions to these general trends. In general, the system responds to climatic variations and changes. In wetter periods, water goes into storage, while in drier periods, or droughts, water is removed from storage. Take the Sacramento Valley for example. It has a cooler and wetter climate and much more surface water than the southern San Joaquin Valley. The groundwater system there is less stressed in general and groundwater levels there remain relatively constant. In the southern and southwestern San Joaquin Valley, there has been intense irrigation from surface water and groundwater. Irrigation from surface and groundwater has increased recharge to, and discharge from the groundwater system by a factor of 6.
Laurel: How far have groundwater levels dropped?
Claudia: It varies; it depends on where you are. In the lower pumped zone, in the southwestern part of the San Joaquin Valley like we talked about before, the decline has been as much as 400 feet from predevelopment conditions. These predevelopment conditions are like, from the 1800's. In the 1970's the water levels rose, with less pumping associated with the surface-water deliveries. Groundwater quality has changed and subsidence has occurred. Recent drought conditions have caused groundwater pumping to increase, and groundwater levels to approach their historic lows.
Laurel: And, land subsidence can cause problems?
Claudia: Yes, historically land subsidence in the Central Valley has cost the state millions of dollars, the land subsidence has resulted in damage to buildings, aqueducts, well casings, bridges and highways, and often causes flooding.
Laurel: Now, associated with this study you developed an extensive groundwater model of the Central Valley. What is a groundwater model?
A groundwater model is a hard thing to define. Usually, is it referred to as, like, a computer program the c(computer) program based on mathematical equations, and is often called a mathematical, or numerical model. It's used to predict aquifer behavior in responses to changes. These changes can be things like irrigation developments or groundwater pumping.
Laurel: So, I understand that when you develop a model like this, it’s available to the public, and anyone, theoretically, could use it, but realistically, who would use this model and how would they take advantage of it?
Claudia: Yes, in theory anyone could use the model. However, like any tool for a particular trade, to use it effectively a person would need some training and background. Realistically, the model is probably most useful to hydrologists and water resource managers and those familiar with numerical codes for looking at hydrogeologic resources. The model is released with a report that has several parts. The first two sections are oriented toward the lay reader and lay person. They pull information from the literature and the model to document the status of the Central Valley groundwater system, and hydrologic system, and how it responds to changing conditions. The final section and the appendix are oriented more towards an experienced modeler. They document the model: how it was set up and constructed, details of the input data, and the results.
Laurel: Claudia, how can people learn more about this study?
Claudia: There are several ways. A four page fact sheet giving an overview of the study is available online. Also, a full report documenting the study in detail is available. Both should be available online through the publications warehouse.
Laurel: Thank you Claudia. Dr. Claudia Faunt, thank you very much for talking with us today, and thank you to our listeners for tuning in to the podcast. This podcast is a production of the U.S. Geological Survey, the Department of the Interior. Until next time, I'm Laurel Rogers and thanks for tuning in. | <urn:uuid:91b30b45-5b26-42d1-abee-fdd1e057d777> | 3.21875 | 1,100 | Audio Transcript | Science & Tech. | 43.2089 | 95,562,841 |
What is Apache FOP?
Apache FOP is a print formatter driven by XSL formatting objects(XSL-FO). It is a library to read XSL FO objects and generate documents with specified output format. Here I have used pdf as the output format.
What is XSL?
XSL is a language for expressing stylesheets. It describes how to display data in an XML file.
What is XSL FO?
XSL FO is a part of XSL which is a markup language for XML document formatting. Follow W3school tutorial for XSL FO.
How Apache FOP generate PDFs.
I have generated javaFX form to enter the data and when I click the print button after filling data, PDF will be created in a folder called PDFs. source code for this available in https://github.com/laki88/PatientDischargeForm.
Following points are used 1. Check whether the last digit of the integer can be divided by 2 or not 2. Check whether the sum of all digit...
It can be white listed and black listed applications in WSO2 EMM 2.1.0 onwards. What is Application White List? White listed applications...
There are two separate cases for APPM and EMM integration 1. APPM and EMM on a single JVM. ex : EMM standalone pack. 2. APPM and EMM on s...
You can create OAuth applications using OAuthAdminService admin service. You can follow the below steps to see how mapping of existing OAu... | <urn:uuid:92a8e85e-b38e-4240-a3f7-057ee3aa0be1> | 2.578125 | 325 | Content Listing | Software Dev. | 75.323503 | 95,562,843 |
An experimental study on the cavitation of water with dissolved gases
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Cavitation inception is generally determined by the tensile strengths of liquids. Investigations on the tensile strength of water, which is essential in many fields, will help understand the promotion/prevention of cavitation and related applications in water. Previous experimental studies, however, vary in their conclusions about the value of tensile strength of water; the difference is commonly attributed to the existence of impurities in water. Dissolved gases, especially oxygen and nitrogen from the air, are one of the most common kinds of impurities in water. The influence of these gases on the tensile strength of water is still unclear. This study investigated the effects of dissolved gases on water cavitation through experiments. Cavitation in water is generated by acoustic method. Water samples are prepared with dissolved oxygen and nitrogen in different gas concentrations. Results show that under the same temperature, the tensile strength of water with dissolved oxygen or nitrogen decreases with increased gas concentration compared with that of ultrapure water. Under the same gas concentration and temperature, water with dissolved oxygen shows a lower tensile strength than that with dissolved nitrogen. Possible reasons of these results are also discussed.
Experiments in this work are supported by the National Natural Science Foundation of China (Grant Nos. 51476085 and 51621062).
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Time running out for Texas to play part in building world's largest telescope
UT, A&M have millions left to collect as partners aim to beginUpdated: January 13, 2014 11:41am
If the eyes of Texas want to gaze through the world's largest telescope, it's time to pay up.
After more than a decade of planning, a group of astronomers seeking to build the $1.05-billion Giant Magellan Telescope are aiming to begin construction later this year.
Time is running out. Competitors in California and Europe have also announced plans to build great astronomical instruments, each of which would be at least 10 times or more powerful than the Hubble Space Telescope.
The international partnership to build the Magellan telescope includes the University of Texas at Austin and Texas A&M University. The University of Texas is hoping to contribute $100 million to the project, and Texas A&M $50 million. The more money an institution pays, the more observing time its astronomers receive.
But of the $100 million the University of Texas hopes to contribute it thus far has only raised $3 million. Texas A&M, thanks to recently-deceased alumnus George Mitchell and his fascination with the stars, already has raised $25 million, half of its contribution.
"There's no official deadline to commit the funds, but the telescope is coming up on a time that's pretty critical," said Darren DePoy, a Texas A&M astronomer who is on the telescope's board of directors.
That's because telescope organizers plan to decide by this summer on whether, after a decade of raising funds, they're ready to begin construction atop a mountain in a Chilean desert. If so, construction of the first phase could be completed by 2020.
The project is Texas-sized in scope and ambition.
With seven, 28-foot-wide mirrors focusing the light collected from the faintest, farthest objects in the universe, the proposed telescope would be so large that its enclosure would tower above the Astrodome.
Scientists want to build this next generation of telescopes to see the universe's most distant and oldest galaxies. From these observations, they hope to better understand the nature of "dark energy," an unknown force that appears to be accelerating at the rate at which the universe expands. Closer to home, a tantalizing possibility exists of capturing pictures of Earth-like planets orbiting nearby stars and possibly the chemical signatures of life.
Tipping the balance
Like the Texas institutions, other Magellan partners including Harvard, the University of Arizona, the Smithsonian Institution, and universities in Australia and Korea, are at various states of raising the funds they've promised to the ambitious project.
To complete the first phase of the telescope - building a structure to house the telescope and four of the seven mirrors - will require between $600 and $700 million, organizers say. The telescope partners will discuss, likely sometime this summer, whether to formally proceed.
"It would absolutely help if UT would come up with some money," DePoy said. "If Texas steps up and commits at the sort of level that Texas A&M does, it tips the balance toward moving forward with construction."
Stepping up efforts
Texas astronomers are trying to do just that.
The Austin campus recently submitted a request to the UT System for $47 million for part of the university's contribution to the Giant Magellan Telescope (GMT). That would be half its goal.
According to UT system spokeswoman Jenny LaCoste-Caputo, the next opportunity for new agenda items would be the May meeting of the Board of Regents, unless a special meeting is called, as agenda items for the February meeting are in the last draft stages at this point.
The proposal has the full support of UT-Austin president William Powers.
"The GMT will be on the leading edge of major scientific research and it's important for UT to play a role in that," said Gary Susswein, director of media relations for UT-Austin.
The remainder of the university's contribution will come primarily through philanthropy, said astronomer David Lambert, director of UT's McDonald Observatory in west Texas, and also a member of the Magellan telescope's board of directors.
Efforts to raise the funds now are being stepped up, Lambert said.
"It's happened already," he said. "We haven't ramped up to the point where we have checks, but we have made presentations to good candidates. We're setting the groundwork. The key will be if the regents come through with $50 million."
So far, at least, the organization responsible for building the telescope hasn't begun to publicly apply pressure to Texas and other member institutions to make good on their promises.
"All partners have made progress towards this goal during the last twelve months, and, more specifically, (we are) pleased with the efforts made by UT, the scientific and financial support it has provided to the project so far and the future support it is working to finalize," said Michael Long, vice president of the Giant Magellan Telescope Organization.
Astronomer Lambert believes Texas and Texas A&M will be able to make good on their commitments in time to ensure that the Magellan telescope is the first of a new generation of very large telescopes built, ensuring it makes the greatest new discoveries.
"If you didn't think you could do it, you wouldn't be doing it," he said. | <urn:uuid:5b1d2378-ddf5-45bd-b3e7-1a0637391efa> | 2.765625 | 1,114 | News Article | Science & Tech. | 40.912106 | 95,562,852 |
A team of researchers that includes biologists from Washington University in St. Louis has discovered that a gene involved in the development and function of the fruit fly antenna also gives the organism its color vision.
Pretty fly - for a fruit fly. The areas stained blue are regions in the fruit fly where the spineless gene is expressed. WUSTL biologists Ian and Dianne Duncan have spent years making discoveries of how the gene is involved in making the fruit fly antenna. Now they are part of a team that has found that spineless plays a key role in the organisms color vision.
Claude Desplan, Ph.D., professor of biology at New York University, and his students made the discovery and provided the data. Ian Duncan, Washington University professor of biology, and his wife, research assistant Dianne Duncan, provided the Desplan laboratory fruit fly (Drosophila) clones and mutants and technical assistance that helped locate where the gene, called spineless, is expressed in the retina.
The Duncans have a long history with the spineless gene. Their interest has been in the role spineless plays in directing development of the antenna, Drosophila’s primary olfactory organ. Years ago, they deleted the spineless gene and found that the mutants then produced a leg instead of an antenna.
"Spineless plays a key role in the antenna and maxillary palp, the two major olfactory organs of the fly," said Ian Duncan. "It’s also important in mechanosensory bristles and in the taste receptors of the legs, wings, and mouth parts. There has been a sensory theme to the gene, and now we learn from Claude’s work that it plays a key role in color vision."
In humans the closest known homolog (counterpart) is the arylhydrocarbon (’dioxin’) receptor, a key protein in human health that senses a wide variety of synthetic compounds and then activates expression of detoxification genes. The dioxin receptor is studied closely in cancer biology and toxicology.
Recently, the Duncans had found a relationship between spineless and a gene called homothorax. Desplan’s group had shown that homothorax plays an important role in the Drosophila eye, and after hearing Ian Duncan make a presentation on the homothorax-spineless relationship in the antenna, the Desplan laboratory decided to study spineless in the eye.
The collaborators published their results in the March 9, 2006 issue of Nature.
The Drosophila retina is comprised of clusters of photosensitive cells called ommatidia. Two types of ommatidia are present: one is sensitive to long-wave light and the other to short-wave light. This difference is due to the expression of different light-sensitive pigments (rhodopsins) in the two central photoreceptor cells (R7 and R8) of each ommatidial cluster. Spineless determines the long-wave type by activating expression of rhodopsin-4 in R7 cells. In ommatidia where spineless is not expressed, R7 expresses the short-wave sensitive rhodopsin-3.
"The fascinating thing in this work is that the longer wave length sensitive ommatidia are randomly positioned," said Duncan. "About 70 percent of the ommatidia sense longer wavelength and 30 percent sense short-wave length. It’s been a mystery how you generate a random pattern like that and still have that ratio."
Using the tools that the Duncan laboratory provided, Desplan’s group mapped the regulatory region in the spineless gene that drives the random pattern mechanism.
"Nobody knew what controlled this random pattern," said Dianne Duncan. "Now we know it’s spineless. We’ve known for a while that spineless has several sensory functions and we thought it might be a bit underrated in developmental biology. Now we add color vision to its duties."
Spineless also appears to control communication between the R7 and R8 photoreceptors. "It has been known for some time that the expression of rhodopsin genes in R7 and R8 is coupled with the particular genes expressed in R8 being determined by the adjacent R7 cells," said Ian Duncan.
"An additional important finding in the paper is that spineless controls this signaling between R7 and R8."
Link to human odor perception
The Duncans will continue to look for other genes that spineless controls in making an antenna. They have shown that spineless acts together with two other factors, Homothorax and Distalless, and identified downstream target genes by virtue of their having clustered binding sites for these factors. And they are looking into similarities between spineless and the mammalian dioxin receptor. In a collaboration with a University of Wisconsin researcher, they have put the mammalian dioxin receptor gene into Drosophila, where, surprisingly, it specifies the making of an antenna.
"When you think about it, the antenna is quite special," Dianne Duncan said. "It contains many proteins not expressed anywhere else in the fly. These include many odor receptor proteins that are expressed in subsets of cells within the antenna. Our hope is that by unraveling how development of the Drosophila antenna is controlled, we will gain important insights into how human odor perception works."
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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.
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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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Example of using throws and do-catch and try to handle errors in Swift
Throwing functions in Swift
To indicate that a function can throw error you just add the word “throws” after its parameters and before its return type.
It is then called a throwing function. Continue reading “Error handling using throws and do-catch in Swift”
In fact Array and Dictionary are generic collections, this is why you can create an Array of Int , String or any other type
What are Generics
Generics are one of the most powerful features of Swift, It allows you to create flexible Functions and Types that can work with any type.
If you used Array or Dictionary before in Swift then you already knows about Generics.
In fact Array and Dictionary are generic collections, this is why you can create an Array of Int , String or any other type and the same with Dictionary. Continue reading “What exactly are Generics”
Also called Type Properties
What is Static property
We all know Instance Properties that belong to an instance of type and every time you create an instance of that type it has its own property value. Continue reading “Static properties in Swift”
Learn about private, fileprivate, public and internal
Use it to restrict access to parts of your code from code in another modules or files.
You can assign access levels to Classes, Structs, Enumerations in addition to their Properties, Initializers, Methods and Subscripts. Continue reading “Access control in Swift”
Easily detect the absence of value in variable or constant using Optionals
Optional is an enum that has 2 states, the first state is where there is a value and that value is of some type for example Int, and the other state is nil where there is no value at all. Continue reading “Optionals in Swift”
Observe and respond to property changes
What is Property Observer
Property Observer observe and respond to changes in property’s value.
It is called every time a property’s value is set, even if the new value is the same as the old value. Continue reading “Property Observer in Swift”
By default function parameters are constants in Swift.
If you attempt to change a parameter within a function you will get a compiler error.
To Solve this issue and enable a function to have an effect outside its scope we should use In-Out parameters. Continue reading “In-Out parameters in Swift” | <urn:uuid:9aa8c00e-3e1a-45da-b96e-d5c844fb4290> | 2.71875 | 517 | Tutorial | Software Dev. | 33.902439 | 95,562,883 |
It may seem like modern technology and meteorology should have a firm grip on future weather, but in reality, weather has too many variables to ever be fully predictable. Small changes in air currents, pressure, and heat can cause events to take surprising turns. But, even though chaos theory prevents us from becoming storm psychics, we can try to use our knowledge of it to develop more accurate prediction methods. For example, meteorologists now create ensemble forecasts, which are groups of several potential forecasts based on slight differences in factors at the start of each.
Share the knowledge!
Key Facts In This Video
Because of the universe's inherent chaos and quantum uncertainty, there will never be a perfectly accurate weather forecast. 00:35
The double-pendulum experiment is a reliable demonstration of chaos theory. 01:11
There are 10 to the 44th power air molecules on Earth. 02:04
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By creating and using the first optical attosecond pulse, scientists from the Laboratory for Attosecond Physics measured the time it takes electrons inside atoms to respond to the electromagnetic forces of light.
In the race to establish ever-faster electronics, light could play an important role. For instance, using light pulses of a precisely controlled waveform, physicists aim to switch electric currents in electronics circuits with light frequencies.
But will electrons in such circuits follow light oscillations instantaneously? How fast will electrons react to the push of a “light-based” button? Or, from a more fundamental perspective: how fast do electrons bound in atoms, molecules or solids respond to light?
Now, an international collaboration of physicists led by Dr. Eleftherios Goulielmakis, head of the research group “Attoelectronics” at the Max Planck Institute of Quantum Optics, researchers from Texas A&M University, USA, and the Lomonosov Moscow State University, have been able to track the effect of this delay for the first time. By creating the first optical attosecond pulse and using it to set electrons in krypton atoms in motion, they discovered that it takes as long as 100 attoseconds for electrons to respond to the electromagnetic forces of light. (Nature, 4 February 2016, DOI: 10.1038/nature16528)
Even for electrons, the lightest particles residing outside the atomic nucleus, quantum mechanics predicts that when exposed to light, a tiny but finite time interval to respond to the forces of light is necessary. But this time interval is predicted to be extremely brief – in the order of tens to hundreds of attoseconds, with one attosecond being one billionth of a billionth of a second. Owing to its brevity, such a phenomenon was considered by scientists immeasurably fast for many decades.
“A prerequisite for capturing such a brief event is a light flash which can pull electrons – or to use the scientific term, polarize them – extremely quickly, and thus probe their response,” said Dr. Mohammed Hassan, a researcher in the group of Dr. Goulielmakis.
With a light-field synthesizer, a device which can manipulate the properties of visible light and nearby infrared and ultraviolet frequencies, the scientists were able to compose visible light pulses as short as 380 attoseconds. These light pulses are so short that they entailed barely more than a half-oscillation of a light field in their time profile. This makes them the fastest pulses of visible light ever created. “We can now not only manipulate visible light with attosecond precision, but also confine its waves into attosecond time intervals,” said Dr. Tran Trung Luu, a researcher in the Attoelectronics group.
With this novel tool at hand, the researchers flashed krypton atoms with optical attosecond pulses. They performed several experiments, each time with a pulse that would apply a slightly different force to the electrons. To check how the electrons responded, they measured the ultraviolet radiation of the wiggling electrons in a vacuum. From the measurements, they were able to deduce that electrons would need some 100 attoseconds to react to the force of light.
“Our study closes a several-decades-long inquiry into the fundamental dynamic response of matter to light fields. From the rotation and the nuclear motion in molecules captured in the last decades with femtosecond technology, we are now able for the first time to track in real time the response of electrons bound in atoms,” Dr. Goulielmakis pointed out. “But at the same time, it opens up a new era of probing and manipulating matter on the electronic level,” he added.
As one of the next steps, Dr. Goulielmakis and his team plan to extend the studies of electron dynamics in solid materials. “Tracing and controlling electrons in solids will enable us to identify the most promising routes for novel ultrafast electronics and photonics operating on sub-fs time scales and at Petahertz clocking rates,” Goulielmakis said.
M. Th. Hassan, T. T. Luu, A. Moulet, O. Raskazovskaya, P. Zhokhov, M. Garg, N. Karpowicz, A. M. Zheltikov, V. Pervak, F. Krausz, and E. Goulielmakis
Optical attosecond pulses and tracking the nonlinear response of bound electrons
Nature, 4 February 2016, DOI: 10.1038/nature16528
Dr. Eleftherios Goulielmakis
ERC Research Group Attoelectronics
Max-Planck-Institute of Quantum Optics
Laboratory for Attosecond Physics
Hans-Kopfermann-Str. 1, 85748 Garching, Germany
Phone: +49(0)89 / 32 905 -632 /Fax: -200
Dr. Olivia Meyer-Streng
Press & Public Relations
Max Planck Institute of Quantum Optics, Garching, Germany
Phone: +49 (0)89 / 32 905 -213
Dr. Olivia Meyer-Streng | Max-Planck-Institut für Quantenoptik
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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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Water and Life on Mars
Mars perhaps first caught public interest in the late 1870s, when Italian astronomer Giovanni Schiaparelli reported using a telescope to observe canali, or channels, on Mars. By the turn of the century, popular songs told of sending messages between Earth and Mars by means of huge signal mirrors. On a darker side, H.G. Wells' 1898 novel The War of the Worlds portrayed an invasion of Earth by technologically superior Martians desperate for water. (1) In the early 1900s novelist Edgar Rice Burroughs, who is best known his creation of the jungle hero Tarzan, also entertained young readers with tales of adventures among the exotic inhabitants of Mars, which he called Barsoo. (2) It was hoped that Mars had ample liquid water and perhaps even irrigation channels of liquid water. Of all the planets in our solar system other than Earth, Mars is the most likely to have harbored liquid water and perhaps even life. Mars' rotational period and seasonal cycles are similar to those of Earth, although they are twice as long due to its greater rotational period around the sun. (see table 1) (3) Fact began to turn against such imaginings when the first robotic spacecraft was sent to Mars in 1965. Pictures from the first flyby and orbiter missions showed a desolate world, (see figure 1) blemished with craters like Earth's Moon. The first wave of Mars exploration ended after the Viking mission. This mission sent two orbiters and two landers to the Red Planet in 1975. The landers conducted experiments including chemical tests in search of life. Most scientists interpreted the results of these tests as negative, diminishing hopes of a world where life is widespread. (3) Several new developments in studies occurred over the next few decades and changed the way that scientists thought about life and Mars. One of these developments was the 1996 announcement by a team from Stanford University, NASA's Johnson Space Center and Quebec's McGill University that a meteorite, ALH84001, believed to have originated on Mars contained what might be the fossils of ancient microbes (see figure 2). This rock and other apparent Mars meteorites that were discovered on several continents on Earth are believed to have been blasted away from the red planet by asteroid or meteor impacts. They are thought to come from Mars because gases trapped in some of the rocks match the composition of Mars' atmosphere. Not all scientists agree with the conclusions of the team announcing the discovery of fossils, but it reopened the issue of life on Mars. (4) A fundamental requirement for life as we know it is liquid water. In the 1980s and 1990s, biologists found that microbial life has an amazing flexibility for surviving in extreme environments, areas of the world that are extraordinarily hot, or cold, or dry, or under immense pressure, conditions that could not sustain human life. In June of 2000, NASA announced that it had found evidence of water on Mars. The tremendous discovery fueled hope for finding microbiological life on the Red Planet. This discovery also made a human mission to Mars more practical. This discovery led many researchers to wonder if Red Planet could have ever supported life. (5) Many scientists believe that water may have thrived billions of years ago in an underground thermal spring, or it might still exist in some form in niches below the frigid, dry, windswept surface. Mars today is too cold, with an atmosphere that is too thin to support liquid water on its surface. Yet scientists who studied images from the Viking orbiters kept encountering features that appeared to be formed by flowing water, among them deep channels and canyons. There is conclusive evidence that liquid water existed at one time on the surface of Mars, even though some scientists dispute it. Key discoveries leading to this conclusion include the detection of various minerals such as hematite and goethite which usually only form in...
Citations: 1 – "H.G. Wells." Funk & Wagnalls New World Encyclopedia. 2002.
2 – "Edgar Rice Burroughs." Funk & Wagnalls New World Encyclopedia
3 – "Mars." Funk & Wagnalls New World Encyclopedia. 2002.
6 – NASA. "Mineral in Mars ‘Berries" Adds to Water Story." Press release. March 18, 2004.
8 – NASA. "Mars Rovers Spot Water-Clue Mineral, Frost, Clouds." Press release. Dec. 13, 2004.
9 – "Mars Water History Re-written." In the News
10 – "Olivine May Hold Clues About Water on Mars." October 19, 2006. http://science.monstersandcritics.com/news/article_1212666.php/Olivine_may_hold_clues_about_water_on_Mars
11 - "The Story of Water on Mars." CNN
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Pine's team discovered a planet an estimated 39 billion kilometers (24 million miles) from infant star HD 163296, while the other team, led by University of MI astronomer Richard Teague, located two planets roughly 12 billion and 21 billion kilometres (7.4 billion and 13 billion miles) from the star.
Scientists have found a trio baby planets using a new technique of spotting unusual gas motion around developing stars. They looked for a particular kind of light that is emitted by the movement of carbon monoxide - which allows them to understand how the gas in the disk is churning around.
It's the first time the $1.4 billion Atacama Large Millimeter/submillimeter Array (ALMA) telescope has discovered new planets, thanks to a special technique to help hunt them down.
With that idea, the group, which included two independent teams, analyzed the protoplanetary disk of a young star sitting in the constellation of Sagittarius named HD 163296.
These gaps in the rings of gas and dust could be used by forming planets. "Through ultra-high resolution work the image on ALMA, this completely new approach can help to detect some of the youngest planets in our Galaxy", says Richard Teague, an astronomer from the University of MI and principal author of the second article. Instead, they saw disturbances in the gas.
All three exoplanets reside within the protoplanetary disk, and that's how the researchers managed to find them. These discrete disturbances in a young star's gas-filled disk are caused by the presence of planets around it.
A team led by Pinte found a planet about 39 billion kilometres (24 billion miles) from the star while Teague's team found two planets 12 billion and 21 billion kilometres (7.5 billion and 13 billion miles) out. They are surrounded by a swirling disk of gas and dust, hiding objects like baby planets and making it hard for scientists to study how planetary systems form. A previous study of this particular star's disc shows that the gaps in the dust and gas overlap, suggesting that at least two planets have formed there.
Woman sues NASA to keep moon-dust gifted by Neil Armstrong
The federal agents believed the 74-year-old had stolen the artefacts (she was never charged and successfully sued the agents). "If you look at the Davis case, what Nasa is essentially saying is that lunar material in private hands is stolen property".
Other techniques for finding baby planets in the disks surrounding young stars are based on observations of the emission coming from a disk's dust particles.
"We still don't truly understand how planets form, so catching them at this earliest stage and being able to see what the actual mechanisms are that produce these giant planets is really going to help", Teague said.
"The precision is mind boggling", said co-author Dr Til Birnstiel of the University Observatory of Munich.
The technique used by Dr. Pinte and colleagues, which more directly measured the flow of the gas, is better suited to studying the outer portion of the disk.
These initial observations, however, merely provided circumstantial evidence and could not be used to accurately estimate the masses of the planets, noted Teague. Orbiting at distances of 83 and 137 times that between the sun and Earth, the planets' host star is actually significantly brighter than our own parent star.
This research was presented in two papers to appear in the same edition of the Astrophysical Journal Letters.
The system consists of three newly formed planets gravitating around a nearby star, dubbed HD 163296. "A Kinematic Detection of Two Unseen Jupiter Mass Embedded Protoplanets", by R. Teague et al. | <urn:uuid:79912a1e-8ed7-4854-a1e8-b9bffc80b900> | 3.296875 | 764 | News Article | Science & Tech. | 48.536272 | 95,562,921 |
Hearing Tornadoes Before They Form
New research suggests analyzing sounds in a storm could help detect tornado formation earlier. People who have experienced tornadoes frequently describe the sound being like that of a train. The sounds important in detecting tornadoes earlier can't be heart by human ears; it's called "infrasound." These infrasound signals could tell us information about the pressure, wind speed, and size of the tornado.
(image credit: Brian Elbing)
Brian Elbing teaches mechanical and aerospace engineering at Oklahoma State University. He and a team of students are working on this research and had some success with storms last May. He said, “We could look at radar data of the larger storm system, and when the rotation there was really strong, it produced almost no infrasound." He added, “And then 10 minutes before the tornado itself formed is when you start seeing this big increase in the sound levels. And then it lasted the duration of the tornado.” Tornadoes are not the only weather event or natural phenomenon to produce these infrasound waves which have frequencies lower than what humans can pick up on. This research is still in the early stages, but Elbing says he hopes this can improve false alarm rates of tornado warnings and provide more lead time. | <urn:uuid:430dbd03-92b4-4b77-b344-a07d6c92653b> | 3.9375 | 263 | News Article | Science & Tech. | 44.375552 | 95,562,924 |
Lone pair(Redirected from Lone electron pair)
In chemistry, a lone pair refers to a pair of valence electrons that are not shared with another atom and is sometimes called a non-bonding pair. Lone pairs are found in the outermost electron shell of atoms. They can be identified by using a Lewis structure. Electron pairs are therefore considered lone pairs if two electrons are paired but are not used in chemical bonding. Thus, the number of lone pair electrons plus the number of bonding electrons equals the total number of valence electrons around an atom.
Lone pair is a concept used in valence shell electron pair repulsion theory (VSEPR theory) which explains the shapes of molecules. They are also referred to in the chemistry of Lewis acids and bases. However, not all non-bonding pairs of electrons are considered by chemists to be lone pairs. Examples are the transition metals where the non-bonding pairs do not influence molecular geometry and are said to be stereochemically inactive. In molecular orbital theory (fully delocalized or otherwise), the concept of a lone pair is less distinct, but orbitals that are occupied but nonbonding (or mostly nonbonding) in character are frequently regarded as "lone pairs" as well.
A single lone pair can be found with atoms in the nitrogen group such as nitrogen in ammonia, two lone pairs can be found with atoms in the chalcogen group such as oxygen in water and the halogens can carry three lone pairs such as in hydrogen chloride.
In VSEPR theory the electron pairs on the oxygen atom in water form the vertices of a tetrahedron with the lone pairs on two of the four vertices. The H–O–H bond angle is with 104.5°, less than the 109° predicted for a tetrahedral angle, and this can be explained by a repulsive interaction between the lone pairs.
Various computational criteria for the presence of lone pairs have been proposed. While electron density ρ(r) itself generally does not provide useful guidance in this regard, the laplacian of the electron density is revealing, and one criterion for the location of the lone pair is where L(r) = –∇2ρ(r) is a local maximum. The minima of the electrostatic potential V(r) is another proposed criterion. Yet another considers the electron localization function (ELF).
Different descriptions of the lone pairs of waterEdit
In elementary chemistry courses, the lone pairs of water are described as "rabbit ears": two equivalent electron pairs of approximately sp3 hybridization, while the HOH bond angle is 104.5°, slightly smaller than the ideal tetrahedral angle of arccos(–1/3) ≈ 109.47°. The smaller bond angle is rationalized by VSEPR theory by ascribing a larger space requirement for the two identical lone pairs compared to the two bonding pairs. At a higher degree of sophistication, this basic picture is modified using the theory of isovalent hybridization, in which spx hybrids with nonintegral values of x are allowed. In this picture, the O–H bonds are considered to be constructed from O bonding orbitals of ~sp4.0 hybridization (~80% p character, ~20% s character), which leaves behind O lone pairs orbitals of ~sp2.3 hybridization (~70% p character, ~30% s character). These deviations from idealized sp3 hybridization are consistent with Bent's rule.
However, an alternative description of water treats the lone pairs of water as energetically and geometrically distinct and possessing different symmetry (σ and π). In this model, one lone pair is represented by a lower energy σ-symmetry in-plane hybrid orbital that mixes s and p character (σ(out)), while the other lone pair is represented by a higher energy π-symmetry orbital perpendicular to the plane of the molecule of pure 2p character (p). In the fully delocalized canonical molecular orbital picture, these orbitals are given the Mulliken labels a1 and b1, in which the "nonbonding" a1 orbital actually consists of σ(out) mixed with the in-phase symmetry-adapted linear combination of the H(1s) orbitals (the small back lobe of σ(out) is able to interact). Thus, a1 is actually weakly bonding in character while b1 is truly nonbonding.
Both models are of value, but one must be careful of their applicability. Since only the canonical MOs (as opposed to any variety of localized MOs) are eigenfunctions of the effective Hamiltonian, one must look at inequivalent, fully delocalized lone pair orbitals when interpreting the photoelectron spectrum of water (Koopmans' theorem), which does indeed show two signals corresponding to different energy levels for the lone pairs. However, any set of orbitals obtained by taking linear combination of symmetry-adapted orbitals via unitary transformations, as the equivalent lone pair hybrid orbitals are, result in the same electron density as the original set of orbitals. In this case, we can construct the two equivalent lone pair hybrid orbitals h and h' by taking linear combinations h = c1σ(out) + c2p and h' = c1σ(out) – c2p for an appropriate choice of coefficients c1 and c2. For chemical and physical properties of water that depend on the overall electron distribution of the molecule, the use of h and h' is just as valid as the use of σ(out) and p. In some cases, such a view is intuitively useful. For example, the hydrogen bonds of water form along the directions of the "rabbit ears" lone pairs, as a reflection of the increased availability of electrons in these regions. This view is supported computationally.
Because of the popularity of VSEPR theory, the treatment of the water lone pairs as equivalent is prevalent in introductory chemistry courses, and many practicing chemists continue to regard it as a useful model. A similar situation arises when describing the two lone pairs on the carbonyl oxygen of a ketone. However, the question of whether it is physically sound and conceptually useful to derive equivalent orbitals from symmetry-correct ones, from the standpoint of bonding theory and pedagogy and in light of modern experimental and computational data, is still a controversial one, with recent (2014 and 2015) articles opposing and supporting the practice.
The pairs often exhibit a negative polar character with their high charge density and are located closer to the atomic nucleus on average compared to the bonding pair of electrons. The presence of a lone pair decreases the bond angle between the bonding pair of electrons, due to their high electric charge which causes great repulsion between the electrons. They are also used in the formation of a dative bond. For example, the creation of the hydronium (H3O+) ion occurs when acids are dissolved in water and is due to the oxygen atom donating a lone pair to the hydrogen ion.
This can be seen more clearly when looked at it in two more common molecules. For example, in carbon dioxide (CO2), the oxygen atoms are on opposite sides of the carbon, whereas in water (H2O) there is an angle between the hydrogen atoms of 104.5º. Due to the repulsive force of the oxygen atom's lone pairs, the hydrogens are pushed further away, to a point where the forces of all electrons on the hydrogen atom are in equilibrium. This is an illustration of the VSEPR theory.
Lone pairs can make a contribution to a molecule's dipole moment. NH3 has a dipole moment of 1.47 D. As the electronegativity of nitrogen (3.04) is greater than that of hydrogen (2.2) the result is that the N-H bonds are polar with a net negative charge on the nitrogen atom and a smaller net positive charge on the hydrogen atoms. There is also a dipole associated with the lone pair and this reinforces the contribution made by the polar covalent N-H bonds to ammonia's dipole moment. In contrast to NH3, NF3 has a much lower dipole moment of 0.24 D. Fluorine is more electronegative than nitrogen and the polarity of the N-F bonds is opposite to that of the N-H bonds in ammonia, so that the dipole due to the lone pair opposes the N-F bond dipoles, resulting in a low molecular dipole moment.
Unusual lone pairsEdit
A stereochemically active lone pair is also expected for divalent lead and tin ions due to their formal electronic configuration of ns2. In the solid state this results in the distorted metal coordination observed in the litharge structure adopted by both PbO and SnO. The formation of these heavy metal ns2 lone pairs which was previously attributed to intra-atomic hybridization of the metal s and p states has recently been shown to have a strong anion dependence. This dependence on the electronic states of the anion can explain why some divalent lead and tin materials such as PbS and SnTe show no stereochemical evidence of the lone pair and adopt the symmetric rocksalt crystal structure.
In molecular systems the lone pair can also result in a distortion in the coordination of ligands around the metal ion. The lead lone pair effect can be observed in supramolecular complexes of lead(II) nitrate, and in 2007 a study linked the lone pair to lead poisoning. Lead ions can replace the native metal ions in several key enzymes, such as zinc cations in the ALAD enzyme, which is also known as porphobilinogen synthase, and is important in the synthesis of heme, a key component of the oxygen-carrying molecule hemoglobin. This inhibition of heme synthesis appears to be the molecular basis of lead poisoning (also called "saturnism" or "plumbism").
Computational experiments reveal that although the coordination number does not change upon substitution in calcium-binding proteins, the introduction of lead distorts the way the ligands organize themselves to accommodate such an emerging lone pair: consequently, these proteins are perturbed. This lone-pair effect becomes dramatic for zinc-binding proteins, such as the above-mentioned porphobilinogen synthase, as the natural substrate cannot bind anymore - in those cases the protein is inhibited.
In Group 14 elements (the carbon group), lone pairs can manifest themselves by shortening or lengthening single (bond order 1) bond lengths, as well as in the effective order of triple bonds as well. The familiar alkynes have a carbon-carbon triple bond (bond order 3) and a linear geometry of 180° bond angles (figure A in reference ). However, further down in the group (silicon, germanium, and tin), formal triple bonds have an effective bond order 2 with one lone pair (figure B) and trans-bent geometries. In lead, the effective bond order is reduced even further to a single bond, with two lone pairs for each lead atom (figure C). In the organogermanium compound (Scheme 1 in the reference), the effective bond order is also 1, with complexation of the acidic isonitrile (or isocyanide) C-N groups, based on interaction with germanium's empty 4p orbital.
Stereogenic lone pairsEdit
|Inversion of a generic organic amine molecule at nitrogen.|
A lone pair can contribute to the existence of chirality in a molecule, when three other groups attached to an atom all differ. The effect is seen in certain amines, phosphines, sulfonium and oxonium ions, sulfoxides, and even carbanions.
The resolution of enantiomers where the stereogenic center is an amine is usually precluded because the energy barrier for nitrogen inversion at the stereo center is low, which allow the two stereoisomers to rapidly interconvert at room temperature. As a result, such chiral amines cannot be resolved, unless the amine's groups are constrained in a cyclic structure (such as in Tröger's base).
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|Posted: Jun 27, 2018|
Composite material mimics color changes of living organisms(Nanowerk News) A range of creatures, including chameleons, octopuses, and frogs, can change color in response to changes in the environment. Some insights into the mechanisms behind this at the anatomical, cellular, and molecular levels have been obtained. However, much work is still required to obtain sufficient understanding of this phenomenon and to translate it into useful artificial applications.
|a) This is a photograph of the spherical colloidal crystals containing 0.20 wt% carbon black (CB). The size of the fine silica particles ranges from 200 to 300 nm, and 11 different sizes were used. b) This is a picture of a weevil drawn using spherical colloidal crystals prepared using monodispersed silica particles with various particle sizes and CB. The surroundings of the weevils are drawn with spherical colloidal crystals that do not contain CB and change with the color of the background. (© Wiley)|
|As reported in the journal Small ("Bioinspired Color Materials Combining Structural, Dye, and Background Colors"), researchers at Nagoya University's Department of Molecular Design and Engineering developed a material containing dyes and crystals that can change the colors and patterns it displays depending on the background color used within it and its exposure to visible or ultraviolet light.|
|The team was inspired to develop this material by findings obtained in the skin of certain frogs, in which different layers of cells with different properties combine to enable remarkable color changes.|
|This is color change in a picture of a morning glory created with the composite color material due to light irradiation and the background color. (© Wiley)|
|Each component of this novel material plays a key role in its color properties. For example, the dyes contribute their inherent colors to the material's appearance, which can be adjusted by mixing them to different extents. These dyes also include those that change color upon exposure to light.|
|Spherical crystals were also introduced into the system, which rather than influencing the color through their inherent pigmentation affect it through their microscopic structures that can directly interfere with light. Finally, a black pigment and different background colors were employed to alter the colors the other components of the system display.|
|"We examined the influences of the different components in the system, such as by changing the size of the crystals, switching the background from white to black, or performing exposure to visible or ultraviolet light," corresponding author Yukikazu Takeoka says. "We found these changes resulted in different colors being displayed across the material, resembling the way in which some organisms can change color in response to various factors in their environment."|
|This is electron micrographs of spherical colloidal crystals composed of fine silica particles with a particle diameter of 250 nm: (a) image showing one spherical colloidal crystal, (b) surface image of the spherical colloidal crystal, (c) a sectional image of the spherical colloidal crystal, and (d) spherical colloidal crystals maintained between the mesh sizes of 125 µm and 150 µm. (© Wiley)|
|"This is an exciting stage in this field of study, as we are increasingly able to adapt the color-changing mechanisms that some animals use to artificial devices," study first author Miki Sakai adds. "If these artificial color-changing materials can equal or surpass the vibrant displays that some animals such as octopuses and frogs make, it could have exciting applications in the development of new display technologies."|
|Source: Nagoya University|
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When comparing Scheme vs Pascal / Object Pascal, the Slant community recommends Scheme for most people. In the question“What is the best programming language to learn first?” Scheme is ranked 8th while Pascal / Object Pascal is ranked 15th. The most important reason people chose Scheme is:
Scheme syntax is extremely regular and easy to pick up. A *formal* specification of the syntax fits onto just a few pages; it can be introduced informally in a paragraph or two. Students are not distracted by remembering how to write if statements or loops or even operator precedence because every syntactic follows the same pattern. Ultimately, everything looks something like this: (func a b c) This includes not only user-defined functions but even control flow: (if cond then-clause else-clause) or even primitive operations like `define` and `set`: (define foo 10) (set! foo 11) This means that nothing really has special syntactic treatment in the language. There are essentially no weird edge-cases to memorize, and different concepts are given a more equal weight in the language. (Unlike Algol-like languages which tend to given undue weight to loops and assignment statements, for example.)
Ranked in these QuestionsQuestion Ranking
Pro Simple syntax
Scheme syntax is extremely regular and easy to pick up. A formal specification of the syntax fits onto just a few pages; it can be introduced informally in a paragraph or two. Students are not distracted by remembering how to write if statements or loops or even operator precedence because every syntactic follows the same pattern.
Ultimately, everything looks something like this:
(func a b c)
This includes not only user-defined functions but even control flow:
(if cond then-clause else-clause)
or even primitive operations like
(define foo 10) (set! foo 11)
This means that nothing really has special syntactic treatment in the language. There are essentially no weird edge-cases to memorize, and different concepts are given a more equal weight in the language. (Unlike Algol-like languages which tend to given undue weight to loops and assignment statements, for example.)
Pro No Magic - it's clear how everything works
Scheme has far less built into the language itself, helping students see that things like OOP are not magical: they are just patterns for organizing code. Everything in Scheme is built up from a very small set of primitives which compose in a natural and intuitive fashion.
Having a language that does not accord many things special status helps keep students open minded. This will help students later go between different languages and paradigms from procedural to object-oriented to functional.
Pro Great at teaching fundamental programming ideas
Scheme teaches the important, fundamental ideas immediately without the distraction of unnecessary syntax or language features.
Pro Great, well known textbooks
There is a set of very strong textbooks introducing CS and programming using Scheme. These books are available for free online.
The most famous example--and one of the most famous CS books full stop--is Structure and Interpretation of Computer Programs usually known as SICP. This book introduces fundamental ideas in computer science and covers an incredible amount of material quickly and clearly without requiring any prior knowledge.
However, some people find SICP a bit challenging as a first text. Happily, there are other more introductory texts as well. Simply Scheme is a book designed to be read before SICP, easing beginners into the language as well as CS and programming in general. How to Design Programs is another text used in introductory college courses.
Pro Robust metaprogramming
The quotation functionality of Lisp allow for extremely powerful, yet syntactically straightforward metaprogramming via macros. This is more powerful than the C preprocessor while being less involved than something like Template Haskell or F# quotations.
Using macros to properly decompose a problem domain teaches new developers good habits, improving composibility and reliability when tackling large programs. Scheme metaprogramming also serves as a gentle introduction to domain specific languages.
Unlike most languages, Scheme actually accords both functional programming and imperative programming roughly equal status. Many other languages like Python and Java are staunchly imperative while SML and Haskell are primarily functional; Scheme is a nice middle ground.
Additionally, since Scheme syntax is extremely flexible, it can easily be re-purposed for teaching non-deterministic and logic programming. There is no need to learn a new language like Prolog when the same ideas can easily be expressed with Scheme syntax.
This gives students a good perspective on different ways to think about and organize programs, which makes it much easier to move forward to other languages and technologies.
Pro Understanding of basics
Because of the verbosity and easy syntax, Pascal language is relatively easier to be learned and understood, even for someone who has no programming knowledge. It's said that Pascal code —if written well— is like reading pseudo code.
Pro Cross platform
Pascal / Object pascal was used in schools during the 2000's to teach kids the basics of object oriented programming.
Pro Clear syntax
Pascal's syntax is clear and concise, for example:
procedure test(); begin DoSomething(); end;
Pro Fast compilation
The compiler is fast, really fast. Compared to C/C++, the delphi compiler is designed to compile a decent sized desktop application in seconds rather than minutes.
Pro Enforces good programming practice
Numerous strong compile time checks with optional runtime checks ensure one doesn't do stupid things and even when one does (because the compiler can't prove it at compile time), the binary will check and report it at runtime.
Correct modular programming implementation with proper namespacing, no file inclusion hack.
Pro Tons of academic reading
Being known as the programming language for education, especially in the 90's, there many academic reading and tutorials available on the internet.
Pro Assembler Code and DLL/SO creation
You can put Assembler code in Intel or AT&T formats, to achieve great results of speed and accuracy. It is possible to create Dynamic Link Libraries or their equivalent in Unix-like systems so it's relatively easy to use and powerful.
Pro Rich existing libraries
Both shipped with implementations and spread all over the web. Both natively written or bindings to libraries written in other languages. Typically to build non-trivial applications there's no need to surf the web as many things are implemented already. Streaming, output templating, socket & networking, web, database, image manipulation, high performance graphics, (de)compression, (de|en)cryption, regex, unit testing, json manipulation, google API, indexing, multithreading, external process management, the list just goes on and on!
Using the Free Pascal Compiler (the main Pascal distribution) you can code in a language that can be procedural and imperative now, but it can became object-oriented simply adding a directive at the start of the source
Pro Easy GUI creation
Visual Basic may have predated Delphi but Delphi was the ground breaking visual designer which set the standards expected today by most GUI developers. Its rich component set was well designed, structured and extensible, it even has the ability to display live data from the attached database in its data controls.
Pro Well balanced for desktop development
For desktop development, Delphi is productive, the code is easy to understand, compilation speed is blazing, and it produces well performing applications that are easy to deploy. The perfect balance between C# and C++.
Pro Automatic Memory Management
The new Delphi compilers are powered by Automatic Reference Counting to ease development.
Pro Still active
From the early roots of Pascal, Delphi has been developed and is still actively supported. It is used in many desktop applications today, and even supports multi platform coding.
Pro Language depth
Object Pascal is being used to write custom kernels (Ultibo) and operating-systems for various ARM boards. So the way you work with the code scales from low-level to pure OOP high-level. Object Pascal has the same level of depth that you find in C/C++ but with added productivity.
Pro Extensive third party libraries
There are large collections of third party components, many free which enable developers to add wide ranging and complex functionality to their code with ease
Pro Fast execution
The compiler generates fast and optimized code. No stop-the-universe garbage collection.
Pro Suitably close to modern languages, without the pitfalls
It was developed as a teaching language and it shows. No syntax pitfalls and gently encourages good style.
Pro Reliable language and code base
Most code from the Turbo Pascal days in the 80s still compiles, yet the language has since been adapted and extended with modern concepts, introducing OOP and interfaces, exception handling, native Unicode support, anonymous methods, generics, ARC and more.
Con Little Job Market
There are little to none jobs searching for a Scheme programmer. The ones that exist are more related to Research in Maths or Artificial Intelligence.
Con Fragmented ecosystem
Scheme is an IEEE standard, not an implementation. Unfortunately, the standard is too minimal and practical implementations have diverged--they had to expand on the standard to get anything done, but did so in incompatible ways.
The later de facto standard R6RS tried to correct this, but lost Scheme's minimalist elegance in the process. The newer R7RS standard takes the best of both worlds with an elegant minimalist core and a practical standard library.
Con Very different semantics from mainstream programming languages
Con A language that is purely academic
If someone said "I am starting a project in Scheme" then they are either talking about their homework or they are starting a joke.
Con Niche language
Most use of this language will be found in jobs supporting legacy code. It will be hard to find things to do with this language outside of that niche.
Con No up-to-date version of language standards
In 1983, and update in 1990, the language was standardized with two standards: ISO/IEC 7185:1990 Pascal and ISO/IEC 10206:1990 Extended Pascal. However, Object Pascal extensions to the language have no official standards but in 1993, a draft proposal for object oriented Pascal standard was re; for review purposes only. There are no standards for modern features and enhancements, thus various Pascal dialects like Delphi or HP Pascal has their own enhancements and features. | <urn:uuid:a7a5fcf6-b391-4d23-ae68-c928b3242d54> | 2.515625 | 2,167 | Listicle | Software Dev. | 31.266725 | 95,562,986 |
The technicians will fix an underwater earthquake with a fiber optic connection, which consists of transoceanic cables. Minor signals of the network will allow researchers to detect the underlying fluctuations and to determine their epicenter.
A new method for the determination of earthquakes was invented by accident, reports mir24.tv.
Metrologist Giuseppe Marra engaged in the testing of fiber-optic lines that connect to atomic clock research centers of different States, and noticed that the noise level in the signal, which always occurs because of small vibrations of the cable, much higher than normal. The researcher decided that it is associated with earthquakes above five points.
Then, Giuseppe continued his observation of the cable which is laid under water between Malta and Sicily. He managed, together with colleagues to fix the fluctuations of a magnitude of 3.4 points, but to pinpoint the epicenter of the experts failed.
Then they concluded that if the start laser signal with opposite ends of the depth of the cable, the point of impact can be calculate by the difference in travel time of the pulse. The epicenter of the earthquake can be determined using the fiber optic network of several wires. | <urn:uuid:a59f6167-2559-4681-8e54-20ccc8a0b13a> | 3.78125 | 238 | Truncated | Science & Tech. | 39.019545 | 95,563,006 |
Stephen Hawking has held a news conference in London to announce his plans of investing $100 million into a project that aims to search for alien life.
The project, named Breakthrough Listen, will search for extraterrestrial life and will allow scientists to collect one year’s worth of data in just one day – in a move that Hawking hopes will speed up the search.
“We believe that life arose spontaneously on Earth,” Hawking said at Monday’s news conference, “So in an infinite universe, there must be other occurrences of life.”
Geoffrey Marcy, a University of California, Berkeley, astronomer who found most of our first exoplanets, also spoke at the event as part of the group’s brain trust.
“The universe is apparently bulging at the seams with the ingredients of biology,” Marcy explained. Indeed, Marcy and other scientists have found a surprising number of Earth-like exoplanets in recent years — rocky planets the right distance from their suns to support water — suggesting that life as we know it is at least possible, if not probable, all over the universe.
That being said, the group of esteemed scientists gathered on Monday didn’t make any bold claims about immediately hunting down intelligent life-forms — or ever finding them at all, for that matter. But the likelihood of success is about to shoot up exponentially, because right now we’re barely trying.
The Search for Extraterrestrial Intelligence (SETI) has been active since 1960, when scientist Frank Drake — another of the great minds joining Breakthrough Listen — sought out radio signals from neighboring stars. But even the largest group looking for life, the SETI Institute, doesn’t receive any government funding, and this particular aspect of space exploration now relies on dwindling support from universities and private organizations.
“We would typically get 24 to 36 hours on a telescope per year, but now we’ll have thousands of hours per year on the best instruments,” Andrew Siemion, a scientist at the University of California, Berkeley, and one of the group’s co-founders, said at the news conference. “It’s difficult to overstate how big this is. It’s a revolution.”
Milner, best known for investing in technology companies like Facebook and Alibaba, is footing the entire bill for the project. It’s the latest endeavor of his Breakthrough Prize Foundation, a Silicon Valley funded group that currently gives the biggest prize — $3 million per laureate — of any scientific award. The prize is funded by investors including Facebook’s Mark Zuckerberg and Google’s Sergey Brin, but Breakthrough Listen will start with a $100 million, 10-year budget from Milner’s own pocket.
According to Milner and the scientists joining him, the project will allow scientists to collect as much data on SETI in a day as they now do in a year. The data will be made available to the public, so anyone can help search for the radio signals that could be used to track down alien civilizations. Meanwhile, others at Breakthrough Listen will be working to improve our own signaling techniques, brainstorming the best way to send a message out into the cosmos.
“I’ve been thinking about this since I was a child, reading Carl Sagan’s book ‘Intelligent Life in the Universe,’ ” Milner told The Post. “The year that I was born, 1961, that was a big year in science — the first man was launched into space, and I was named for him. And Kennedy made his famous speech about putting man on the moon.”
As far as Milner is concerned, we owe it to ourselves to try to answer the question of whether or not humanity is alone.
“I don’t have high expectations, but the search itself will teach us quite a bit,” Milner said. “We could find something we’re not even looking for.”
And while his expectations aren’t high, he says he has a gut feeling we’re not alone.
“I think it’s a low probability but high impact event,” he said. “Irrespective of what the answer is, it’s a powerful answer. At any given time, we should apply the best technology and use the best instruments available to search for that answer.”
Latest posts by Sean Adl-Tabatabai (see all)
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- FBI Official Overseeing Russian Investigation Quits After Lack Of Evidence - July 17, 2018 | <urn:uuid:dcb50c9e-dcd9-4d03-8d97-af2c1183f802> | 2.609375 | 1,015 | News Article | Science & Tech. | 46.8042 | 95,563,012 |
International team of researchers, including Carnegie Mellon's Matthew Walker, devise precise method for calculating the mass of galaxies
Does the Milky Way look fat in this picture? Has Andromeda been taking skinny selfies? It turns out the way some astrophysicists have been studying our galaxy made it appear that the Milky Way might be more massive than it's neighbor down the street, Andromeda.
Not true, says a study published in the journal Monthly Notices of the Royal Astronomical Society by an international group of researchers, including Matthew Walker of Carnegie Mellon University's McWilliams Center for Cosmology.
In the paper, they demonstrate a new, more accurate method for measuring the mass of galaxies. Using this method, the researchers have shown that the Milky Way has only about half the mass of its neighbor, the Andromeda Galaxy.
In previous studies, researchers were only able to estimate the mass of the Milky Way and Andromeda based on observations made using their smaller satellite dwarf galaxies. In the new study, researchers culled previously published data that contained information about the distances between the Milky Way, Andromeda and other close-by galaxies — including those that weren't satellites — that reside in and right outside an area referred to as the Local Group.
Galaxies in the Local Group are bound together by their collective gravity. As a result, while most galaxies, including those on the outskirts of the Local Group, are moving farther apart due to expansion, the galaxies in the Local Group are moving closer together because of gravity. For the first time, researchers were able to combine the available information about gravity and expansion to complete precise calculations of the masses of both the Milky Way and Andromeda.
"Historically, estimations of the Milky Way's mass have been all over the map," said Walker, an assistant professor of physics at Carnegie Mellon. "By studying two massive galaxies that are close to each other and the galaxies that surround them, we can take what we know about gravity and pair that with what we know about expansion to get an accurate account of the mass contained in each galaxy. This is the first time we've been able to measure these two things simultaneously."
By studying both the galaxies in and immediately outside the Local Group, Walker was able to pinpoint the group's center. The researchers then calculated the mass of both the ordinary, visible matter and the invisible dark matter throughout both galaxies based on each galaxy's present location within the Local Group. Andromeda had twice as much mass as the Milky Way, and in both galaxies 90 percent of the mass was made up of dark matter.
The study was supported by the UK's Science and Technology Facilities Council and led by Jorge Peñarrubia of the University of Edinburgh's School of Physics and Astronomy. Co-authors include Yin-Zhe Ma of the University of British Columbia and Alan McConnachie of the NRC Herzberg Institute of Astrophysics.
About Carnegie Mellon University:
Carnegie Mellon is a private, internationally ranked research university with programs in areas ranging from science, technology and business, to public policy, the humanities and the arts. More than 12,000 students in the university's seven schools and colleges benefit from a small student-to-faculty ratio and an education characterized by its focus on creating and implementing solutions for real problems, interdisciplinary collaboration and innovation. A global university, Carnegie Mellon has campuses in Pittsburgh, Pa., California's Silicon Valley and Qatar, and programs in Africa, Asia, Australia, Europe and Mexico.
Jocelyn Duffy | Eurek Alert!
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 | Materials Sciences
19.07.2018 | Earth Sciences
19.07.2018 | Life Sciences | <urn:uuid:d7053355-f80c-495f-b3eb-b6df5470273e> | 3.796875 | 1,348 | Content Listing | Science & Tech. | 36.541759 | 95,563,028 |
Consider the following aqueous route to oxidize SO2:
SO2(aq) + H2O2(aq) -> H2SO4(aq) k = 1.1 X 10^3 L/mols
a. The partial pressure and Henry's law constants for SO2 and H2O2 are 2.7 ppm (KH = 1.2 mol L-1atm-1) and 4.9 ppb (KH = 1.0E5 mol L-1atm-1), respectively. Calculate the reaction rate of this process.
b. Calculate the reaction rate (per liter of air) if the amount of liquid water in the atmosphere is 0.008 g L-1.
Hint: Calculate volume of water contaminated, length of time to do this, distance
I downloaded a study guide and attempted it 3 times but was wrong.© BrainMass Inc. brainmass.com July 22, 2018, 12:13 pm ad1c9bdddf
I really do implore you to work your way through the thought process on the way to these answers.
Henry's Law is a an approximation of the amount of the gas in the vapor over the liquid that dissolves into the solvent . The molality of the solute gas is proportional in the limit of little solute gas in the solvent to the partial pressure of the gas in the vapor over the solvent The K's given in the relations of these gasses are the proportionality constants for the respective gasses in equilibrium with the solvent.
Also the total moles of things making up the liquid is the sum of the moles H2SO4 (aq) + moles SO2 (aq) + moles of H2O2 (aq) and the molality of a species is n moles species/total moles substance.
Also Henrys law is an ideal gas law such that the amount of solute in the overall atmospheric gas is dilute enough such that ideal gas relations apply. Thus PV=nRT for the partial pressures of the gasses in question.
Finally, in the case of gasses ppm and ppb are usually reported by volume rather than a mixed mass to volume as we see for liquids and as I have said before this can lead to some mass confusion when reporting calculated values.
I am pretty confused by this notation. I am going to look at a web site on environmental chemistry and see if I can shed light on this problem.
FIRST WEB SOURCE
The ultimate fate of all sulfur in the atmosphere is to be oxidized to the sulfate ion, usually as sulfuric acid (H2SO4). The most common base present in the ...
It shows how to calculate the reaction rate of the aqueous route to oxidize SO2. | <urn:uuid:27c92ea2-4da3-4646-b768-31b12427a029> | 3.515625 | 584 | Q&A Forum | Science & Tech. | 68.94 | 95,563,067 |
Rising costs from flooding and erosion are prompting Americans, military bases and government agencies to opt for more natural alternatives.
Air conditioning is becoming more vital as temperatures rise, pushing up utility bills and putting comfortable levels of cooling out of the reach of some.
As climate change fuels large wildfires, the pollution they're releasing is making Americans sick and undermining decades of progress in cleaning the air.
The federal government has provided less than half of what Louisiana says it needs to recover from last year's deadly rainstorm.
New Jersey's working class are forgotten as federal government funds fixes for wealthier neighbors.
Climate change is now a centerpiece of the National Park Service’s visitor outreach strategy (though that may change under president-elect Trump).
We have a huge stake in the present and future health of national parks because ultimately, these cherished places are a reflection of who we are as individuals, and as a nation.
Every National Park is already being impacted by climate change. Take this quiz to see which one you should visit before its irreparably harmed. | <urn:uuid:166c479c-4a3a-40ba-9e7e-5e9f662747ca> | 2.640625 | 214 | Content Listing | Science & Tech. | 30.032733 | 95,563,090 |