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Novelist and essayist Jonathan Franzen highlights the worldwide decline of seabirds, the threats they face, and how Island Conservation and other organizations are working to prevent extinctions on islands around the world.
Some might imagine that seabirds which nest on remote islands and spend the majority of their lifetime at sea would be safe from many environmental concerns. However, seabirds are one of the most threatened groups of birds worldwide. To understand what is threatening them, we must look at the habitats they depend on for survival—islands and oceans. For seabirds, invasive species on islands pose the largest threat of extinction. When this is compounded with pollution, climate change, plastics, and commercial fishing, it’s amazing seabirds are able to survive at all.
Jonathan Franzen, an award-winning novelist and conservationist, has delved into the impacts that invasive species and other environmental concerns pose to seabirds on islands around the world. From the Farallon Islands of the coast of San Francisco to Gough Island in the South Atlantic Ocean, Franzen points to dedicated conservation efforts and organizations such as Island Conservation that are striving to prevent extinctions of seabirds. Franzen explains:
Organizations such as Island Conservation, a nonprofit based in California, have perfected the use of helicopters and GIS technology to target predators with poisoned mammal-specific bait. Animal lovers may grieve at the mass killing of small furry mammals, but human beings have an even greater responsibility to the species they’ve threatened with extinction, however inadvertently, by introducing predators.”
The article is featured in National Geographic’s July issue and explores the issues that seabirds face and the hope that conservation efforts bring. Dr. Nick Holmes, Island Conservation’s Director of Science commented:
Seabirds respond well to restoration. Addressing the terrestrial threat bolsters their resistance to all the other threats.”
The article also features a map exploring the leading threats to seabirds which uses data from the Threatened Island Biodiversity Database.
Removal of invasive species is one of the most critical interventions for saving threatened plants and animals and restoring island ecosystems, with remarkable recovery of native species worldwide.
Read the full article at National Geographic
Featured photo: Invasive carnivorous mice are threatening Gough Island‘s native species, including Tristan and Yellow-nosed Albatross. The Royal Society for the Protection of Birds and Island Conservation are working together to remove invasive mice from Gough Island in 2019. Credit: Ben Dilley
- Study Shows 5000% Increase in Native Trees on Rat-free Palmyra Atoll - July 17, 2018
- WIRED: New Research Finds Invasive Rat Removal on Islands Benefits Coral Reefs - July 11, 2018
- Outcome Monitoring Results from Antipodes Island - July 3, 2018
- Jonathan Franzen features Island Conservation in National Geographic - June 26, 2018
- Getting to Know the Friends of Midway Atoll National Wildlife Refuge - June 21, 2018
- Detection Dogs Deployed to Try and Find Remaining Few Rats on Lehua - June 18, 2018
- The Top 5 Threats to Birds may Surprise You - June 13, 2018
- One Dog that Saved an Island of Penguins - June 11, 2018
- Poor Fliers Reluctant to Cross Water - June 8, 2018
- Con X Tech Competition: Prevent Extinctions, Win $20,000 - June 5, 2018 | <urn:uuid:aa7ba59b-fcd1-4ba3-9446-2e23703e807d> | 3.75 | 716 | News (Org.) | Science & Tech. | 24.379768 | 95,603,802 |
Anisotropic Stiffness Tensor Measurement for Standing Trees using Acoustics
Conference: Publication Date: 24 October 2016Testing Method:
Acoustic non-destructive testing techniques have been developed to measure properties, such as stiffness, of standing trees and logs. Standing tree stiffness measurements are commonly calculated by inserting two probes into the “same face” of the tree stem, hitting one with a hammer, and measuring the propagation time of the resulting acoustic signal between two probes. Studies have suggested that these time of flight measurements are biased to measure the outerwood stiffness rather than that of the tree stem as a whole and may vary between different hammer hit strengths and hence between users. In this paper, we explore a multipath acoustic technique for measuring components of the anisotropic stiffness matrix of tree stems, which describes the mechanical properties of wood. This technique uses anisotropic acoustic wave propagation velocity measurements made along the surface and through a standing tree. This technique was used to calculate an average stiffness through the tree’s cross-section. Different acoustic/ultrasonic excitation techniques are investigated which obtain velocity measurements that are independent of the user.
- Andrews, M., 2002. Which acoustic speed. In: Proceedings of the 13th International Symposium on Nondestructive Testing of Wood. pp.159–165.
- Bucur, V., 2006. Acoustics of wood. 2nd ed. New York: Springer.
- Carcione, J.M., 2007a. Anisotropic elastic media. In: Wave fields in real media: Wave propagation in anisotropic, anelastic, porous and electromagnetic media. Oxford, Elsevier.
- Chauhan, S. and Walker, J., 2006. Variations in acoustic velocity and density with age, and their interrelationships in radiata pine. Forest Ecology and Management, 229(1), pp.388–394.
- Dickson, R., Matheson, A., Joe, B., Ilic, J. and Owen, J., 2004. Acoustic Segregation of Pinus radiata logs for sawmilling. New Zealand Journal of Forestry Science, 34(2), pp.175–189.
- Dickson, R.L., Raymond, C.A., Joe, W. and Wilkinson, C.A., 2003. Segregation of Eucalyptus dunnii logs using acoustics. Forest Ecology and Management, 179(1), pp.243–251.
- Dikrallah, A., Hakam, A., Kabouchi, B., Brancheriau, L., Baillères, H., Famiri, A. and Ziani, M., 2006. Experimental analysis of acoustic anisotropy of green wood by using guided waves. Proceedings of the ESWM-COST Action E, 35, pp.149–154.
- Grabianowski, M., Manley, B. and Walker, J., 2006. Acoustic measurements on standing trees, logs and green lumber. Wood Science and Technology, 40(3), pp.205–216.
- Harris, P., Petherick, R. and Andrews, M., 2002. Acoustic resonance tools. In: Proceedings, 13th International Symposium on Nondestructive Testing of Wood. pp.195–201.
- Hsu, C.Y., 2003. Radiata pine wood anatomy structure and biophysical properties. PhD thesis, Forestry Department, University of Canterbury, New Zealand.
- Joe, B., Dickson, R., Raymond, C., Ilic, J. and Matheson, A., 2004. Prediction of Eucalyptus Dunnii and Pinus Radiata Timber Stiffness Using Acoustics: A Report for the RIRDC/Land and Water Australia/FWPRDC/MDBC Joint Venture Agroforestry Program. RIRDC.
- Lasserre, J.-P., Mason, E.G. and Watt, M.S., 2007. Assessing corewood acoustic velocity and modulus of elasticity with two impact based instruments in 11-year-old trees from a clonal-spacing experiment of Pinus radiata D. Don. Forest Ecology and Management, 239(1), pp.217–221.
- Legg, M and S Bradley. Measurement of stiffness of standing tress using acoustic velocity measurements made through tree stems. In 19th International Nondestructive Testing and Evaluation of Wood Symposium, pages 633–640. Rio de Janeiro, Brazil, 22–25 Sep. 2015.
- Li, G., Wang, X., Feng, H., Wiedenbeck, J. and Ross, R.J., 2014. Analysis of wave velocity patterns in black cherry trees and its effect on internal decay detection. Computers and Electronics in Agriculture, 104, pp.32–39.
- Mahon, J.M., 2007. The use of acoustics for the wood quality assessment of standing P. taeda trees. PhD Thesis. University of Georgia.
- Mahon, J.M., Jordan, L., Schimleck, L.R., Clark, A. and Daniels, R.F., 2009. A comparison of sampling methods for a standing tree acoustic device. Southern Journal of Applied Forestry, 33(2), pp.62–68.
- Matheson, A.C., Dickson, R.L., Spencer, D.J., Joe, B. and Ilic, J., 2002. Acoustic segregation of Pinus radiata logs according to stiffness. Annals of Forest Science, 59(5-6), pp.471–477.
- Maurer, H., Schubert, S.I., Bächle, F., Clauss, S., Gsell, D., Dual, J. and Niemz, P., 2006. A simple anisotropy correction procedure for acoustic wood tomography. Holzforschung, 60(5), pp.567–573.
- Mora, C.R., Schimleck, L.R., Isik, F., Mahon, J.M., Clark, A. and Daniels, R.F., 2009. Relationships between acoustic variables and different measures of stiffness in standing Pinus taeda trees. Canadian Journal of Forest Research, 39(8), pp.1421–1429.
- Ross, R.J. and Pellerin, R.F., 1994. Nondestructive testing for assessing wood members in structures. General Technical Report FPL-GTR-70, Forest Products Laboratory, US Department of Agriculture.
- Searles, G., 2012. Acoustic segregation and structural timber production. PhD thesis. Edinburgh Napier University.
- Su, J., Zhang, H. and Wang, X., 2009. Stress Wave Propagation on Standing Trees-Part 2. Formation of 3D Stress Wave Contour Maps. In: Series: Conference Proceedings.
- Svilainis, L. and Motiejunas, G., 2006. Power amplifier for ultrasonic transducer excitation. Ultragarsas, 1(58), pp.30–36.
- Wang, X., 2013. Acoustic measurements on trees and logs: a review and analysis. Wood Science and Technology, 47(5), pp.965–975.
- Wang, X., Ross, R.J. and Carter, P., 2007. Acoustic evaluation of wood quality in standing trees. Part I. Acoustic wave behavior. Wood and Fiber Science, 39(1), pp.28–38.
- Wang, X., Ross, R.J., McClellan, M., Barbour, R.J., Erickson, J.R., Forsman, J.W. and McGinnis, G.D., 2001. Nondestructive evaluation of standing trees with a stress wave method. Wood and Fiber Science, 33(4), pp.522–533.
- Wang, X.R.R.J., Brashaw, B.K., Punches, J., Erickson, J.R., Forsman, J.W. and Pellerin, R.F., 2004. Diameter effect on stress-wave evaluation of modulus of elasticity of logs. Wood and Fiber Science, 36(3), pp.368–377.
- Zhang, H., Thurber, C. and Rowe, C., 2003. Automatic P-wave arrival detection and picking with multiscale wavelet analysis for single-component recordings. Bulletin of the Seismological Society of America, 93(5), pp.1904–1912.
- Zhang, H., Wang, X. and Ross, R.J., 2009. Stress wave propagation on standing trees: Part 1. Time-of-flight measurement and 2D stress wave contour maps. In: 16th International Symposium on NDT/NDE of Wood. Beijing, China, pp.12–14.
- Zhang, H., Wang, X. and Su, J., 2011. Experimental investigation of stress wave propagation in standing trees. Holzforschung, 65(5), pp.743–748.
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Tokyo: Astronomers have found signs of a giant icy planet growing around TW Hydrae, one of the closest young stars to Earth.
Based on the distance from the central star and the distribution of tiny dust grains, the baby planet is thought to be an icy giant, similar to Uranus and Neptune in our solar system.
"Combined with the orbit size and the brightness of TW Hydrae, the planet would be an giant icy planet like Neptune," said lead researcher Takashi Tsukagoshi at Ibaraki University, Japan.
This result, to be published in the journal Astrophysical Journal Letters, is another step towards understanding the origins of various types of planets.
TW Hydrae is one of the most favourable targets for investigating planet formation.
Past observations have shown that TW Hydrae is surrounded by a disk made of tiny dust particles. This disk is the site of planet formation.
Recent Atacama Large Millimeter/submillimeter Array (ALMA) observations revealed multiple gaps in the disk. Some theoretical studies suggest that the gaps are evidence of planet formation.
The team observed the disk around TW Hydrae with ALMA in two radio frequencies. Since the ratio of the radio intensities in different frequencies depends on the size of the dust grains, researchers can estimate the size of dust grains.
The ratio indicates that smaller, micrometer-sized, dust particles dominate and larger dust particles are absent in the most prominent gap with a radius of 22 astronomical units.
Theoretical studies have predicted that a gap in the disk is created by a massive planet, and that gravitational interaction and friction between gas and dust particles push the larger dust out from the gap, while the smaller particles remain in the gap.
The current observation results match these theoretical predictions.
Researchers believe that the planet is probably a little more massive than Neptune. | <urn:uuid:40f05778-9ab0-42f2-8b59-ef6c9262e839> | 3.203125 | 378 | News Article | Science & Tech. | 35.026175 | 95,603,812 |
INSIGHTS INTO THE RING-OPENING MECHANISM OF BENZENE METABOLISM; AN INVESTIGATION OF THE OXIDATION OF MODEL OXEPINS BY CYTOCHROME P450
Benzene is a known human carcinogen and environmental pollutant. The mechanism of its metabolism by cytochrome P450 is well understood. Initial oxidation of benzene produces benzene oxide/oxepin, valence tautomers in rapid equilibrium. Most metabolites of benzene are derived from benzene oxide and include phenol, catechols, quinones, and bioconjugates. A small number of ring-opened metabolites are derived from oxidation of oxepin. Muconaldehyde is one such metabolite; it is toxic and is known to react with glutathione and cross-link DNA. It is unclear how muconaldehyde is formed from oxepin. In the 1970’s Davies and Whitham postulated that oxepin is epoxidized by cytochrome P450 to form 2,8-dioxabicyclo[5.1.0]octa-3,5-diene (2,3-epoxyoxepin) that rapidly rearranges to form muconaldehyde. While Davies and Whitham were not able to observe the 2,3-epoxyoxepin intermediate, they used model compounds to generate ring opened products. Later, Greenberg et al demonstrated that dimethyldioxirane (DMDO) could epoxidize model oxepins at low temperature to form 2,3-epoxyoxepin intermediates; the intermediates were observed using low temperature NMR. Alternatively, Golding proposed that oxepin was oxidized by consecutive one electron oxidations with cerium ammonium nitrate (CAN) to form a radical cation intermediate that ring-opened to form corresponding dicarbonyl compounds. It is still unclear which mechanism is utilized by cytochrome P450 to form ring-opened metabolites. The present study involves the synthesis of model oxepins 2,7-dimethyloxepin and 4,5-benzoxepin that are used in synthetic and enzymatic oxidation studies. The incubations with 2.7-dimethyloxepin did not produce ring-opened metabolites, but rather dimethylphenols. This is likely an application of the Curtin-Hammett principle where the dimethyl-1,6-benzene oxide tautomer is energetically accessible and the activation barrier for formation of phenol derived products is lower than that to produce ring opened compounds. Oxidation of 4,5-benzoxepin with DMDO produced 1H-2-benzopyran-1-carboxaldehyde, while oxidation with CAN gave a novel dimeric compound. The enzymatic oxidation of 4,5-benzoxepin revealed that the major oxidation pathway utilized by P450 is epoxidation of oxepin to a 2,3-epoxyoxepin; the major product observed was 1H-2-benzopyran-1-carboxaldehyde. This is the first time a 2,3-epoxyoxepin derivative has been shown as an intermediate in enzymatic oxidation and gives insight into the ring opening mechanism of benzene metabolism. A small amount of the dimeric compound was also observed, indicating a minor oxidation pathway of consecutive one electron oxidations. Much work has been done to fully characterize and identify the novel dimeric compound. | <urn:uuid:2aa247db-8e84-4303-a7cd-f3de7cbd2814> | 2.5625 | 741 | Academic Writing | Science & Tech. | 13.020988 | 95,603,816 |
Earlier in our inventory efforts, the Upper Columbia Basin Network focused on bats in the John Day Fossil Beds National Monument. Bats are hard to study because they are only out at night, hide during the day, and tend to be found in places where humans have a hard time getting to, like sheer cliffs or deep caves.
During 2002-2003 we found that the Fossil Beds hosted particularly high bat species diversity, including several very rare and declining species such as the pallid bat, a very large desert species known to eat scorpions and other tough desert invertebrates.
Another species, the spotted bat, virtually unknown in Oregon prior to our surveys, was found to be relatively common in the area, and was regularly heard (but not seen!) foraging in the John Day River canyon and tributaries where the park is located. This information and results from bat inventories done in other UCBN parks will be instrumental in helping these parks prepare for and respond to emerging threats to bats such as the disease known as white-nose syndrome.
The UCBN has published a number of technical reports and journal articles using bat inventory data and is assisting Craters of the Moon National Monument with long-term monitoring of hibernating bat populations in lava tubes(Rodhouse et al. 2012, Rodhouse et al. 2011, Rodhouse et al. 2008, Weller et al. 2007, and Rodhouse et al. 2005). | <urn:uuid:a166d5cb-1be7-4916-a9e2-47ff61b24247> | 3.40625 | 294 | Knowledge Article | Science & Tech. | 47.426723 | 95,603,819 |
- Open Access
Lunar cratering chronology: Statistical fluctuation of crater production frequency and its effect on age determination
© The Society of Geomagnetism and Earth, Planetary and Space Sciences (SGEPSS); The Seismological Society of Japan; The Volcanological Society of Japan; The Geodetic Society of Japan; The Japanese Society for Planetary Sciences. 2008
Received: 30 March 2007
Accepted: 31 October 2007
Published: 9 April 2008
The crater frequency is often used to determine ages of planetary surfaces. In this study, we evaluate the statistical fluctuation of the crater frequency and its effect on age determination using a Monte Carlo simulation prior to the SELENE (KAGUYA) / Terrain Camera acquiring extensive high-resolution images over the entire Moon. We found that the ages estimated between 2.5 and 3.5 Gyr tend to be too young when there are not enough craters. Age determination for Eratosthenian units is least accurate. The errors defined with 1σ are 0.7 Gyr for units of 100 km2, 0.5 Gyr for units of 1000 km2, and 0.4 Gyr for units of 2500 km2. The maximum error exceeds 20% and is comparable with the error due to the cratering asymmetry. | <urn:uuid:8a508b40-38dd-41bf-a58d-89fd1dacc1c8> | 2.84375 | 272 | Truncated | Science & Tech. | 41.66375 | 95,603,828 |
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Chicago Wilderness region urban forest vulnerability assessment and synthesis: a report from the Urban Forestry Climate Change Response Framework Chicago Wilderness pilot projectAuthor(s): Leslie A. Brandt; Abigail Derby Lewis; Lydia Scott; Lindsay Darling; Robert T. Fahey; Louis Iverson; David J. Nowak; Allison R. Bodine; Andrew Bell; Shannon Still; Patricia R. Butler; Andrea Dierich; Stephen D. Handler; Maria K. Janowiak; Stephen N. Matthews; Jason W. Miesbauer; Matthew Peters; Anantha Prasad; P. Danielle Shannon; Douglas Stotz; Christopher W. Swanston
Source: Gen. Tech. Rep. NRS-168. Newtown Square, PA: U.S. Department of Agriculture, Forest Service, Northern Research Station. 142 p.
Publication Series: General Technical Report (GTR)
Station: Northern Research Station
View PDF (9.0 MB)
DescriptionThe urban forest of the Chicago Wilderness region, a 7-million-acre area covering portions of Illinois, Indiana, Michigan, and Wisconsin, will face direct and indirect impacts from a changing climate over the 21st century. This assessment evaluates the vulnerability of urban trees and natural and developed landscapes within the Chicago Wilderness region to a range of future climates. We synthesized and summarized information on the contemporary landscape, provided information on past climate trends, and illustrated a range of projected future climates. We used this information to inform models of habitat suitability for trees native to the area. Projected shifts in plant hardiness and heat zones were used to understand how nonnative species and cultivars may tolerate future conditions. We also assessed the adaptability of planted and naturally occurring trees to stressors that may not be accounted for in habitat suitability models such as drought, flooding, wind damage, and air pollution. The summary of the contemporary landscape identifies major stressors currently threatening the urban forest of the Chicago Wilderness region. Major current threats to the region’s urban forest include invasive species, pests and disease, land-use change, development, and fragmentation. Observed trends in climate over the historical record from 1901 through 2011 show a temperature increase of 1 °F in the Chicago Wilderness region. Precipitation increased as well, especially during the summer. Mean annual temperature is projected to increase by 2.3 to 8.2 °F by the end of the century, with temperature increases across all seasons. Projections for precipitation show an increase in winter and spring precipitation, and summer and fall precipitation projections vary by model. Species distribution modeling for native species suggests that suitable habitat may decrease for 11 primarily northern species and increase or become newly suitable for 40 species. An analysis of tree species vulnerability that combines model projections, shifts in hardiness and heat zones, and adaptive capacity showed that 15 percent of the trees currently present in the region have either moderate-high or high vulnerability to climate change, and many of those trees with low vulnerability are invasive species. We developed a process for self-assessment of urban forest vulnerability that was tested by urban forestry professionals from four municipalities, three park districts, and three forest preserve districts in the region. The professionals generally rated the impacts of climate change on the places they managed as moderately negative, mostly driven by the potential effects of extreme storms and heavy precipitation on trees in the area. The capacity of forests to adapt to climate change ranged widely based on economic, social, and organizational factors, as well as on the diversity of species and genotypes of trees in the area. These projected changes in climate and their associated impacts and vulnerabilities will have important implications for urban forest management, including the planting and maintenance of street and park trees, management of natural areas, and long-term planning. will have important implications for urban forest management, including the planting and maintenance of street and park trees, management of natural areas, and long-term planning.
- Check the Northern Research Station web site to request a printed copy of this publication.
- Our on-line publications are scanned and captured using Adobe Acrobat.
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CitationBrandt, Leslie A.; Derby Lewis, Abigail; Scott, Lydia; Darling, Lindsay; Fahey, Robert T.; Iverson, Louis; Nowak, David J.; Bodine, Allison R.; Bell, Andrew; Still, Shannon; Butler, Patricia R.; Dierich, Andrea; Handler, Stephen D.; Janowiak, Maria K.; Matthews, Stephen N.; Miesbauer, Jason W.; Peters, Matthew; Prasad, Anantha; Shannon, P. Danielle; Stotz, Douglas; Swanston, Christopher W. 2017. Chicago Wilderness region urban forest vulnerability assessment and synthesis: a report from the Urban Forestry Climate Change Response Framework Chicago Wilderness pilot project. Gen. Tech. Rep. NRS-168. Newtown Square, PA: U.S. Department of Agriculture, Forest Service, Northern Research Station. 142 p. https://doi.org/10.2737/NRS-GTR-168.
Keywordsclimate change, vulnerability, adaptive capacity, urban forests, Climate Change Tree Atlas, expert elicitation, climate projections, impacts
- A framework for adapting urban forests to climate change
- Chicago's urban forest ecosystem: results of the Chicago Urban Forest Climate Project
- Characteristics of stewardship in the Chicago Wilderness Region
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The promise of the genomics revolution - the ability to compare important genes and proteins from many different organisms - is that such detailed knowledge will produce new scientific insights that will improve human quality of life. In work on a key human enzyme, PBGS (porphobilinogen synthase), the laboratory of Fox Chase Cancer Center scientist Eileen K. Jaffe, Ph.D., has characterized a rare mutation that results in an unprecedented rearrangement of the enzyme´s structure. The discovery provides a key into how tiny genetic changes can have a giant evolutionary impact and may even lead to the development of novel herbicides and antibacterial agents.
The report, "Control of Tetrapyrrole Biosynthesis by Alternate Quaternary Forms of Porphobilinogen Synthase," appears in the September 2003 issue of Nature Structure Biology and as an advance online publication on the journal´s web site starting August 3. PBGS is one of a group of enzymes found in every organism from bacteria through plants and humans.
Important roles for PBGS include formation of chlorophyll in plants and the heme component of hemoglobin, the protein that carries oxygen in the blood. A September 1999 report of a routine screen of newborn infants for metabolic defects identified a new mutation in PBGS, termed F12L, that causes the enzyme to lose activity, as reported by Shigeru Sassa, M.D., Ph.D., of Rockefeller University and co-authors in the British Journal of Haematology.
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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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13.07.2018 | Life Sciences | <urn:uuid:1311563e-3924-4f17-a415-35984b82ce3f> | 3.09375 | 959 | Content Listing | Science & Tech. | 38.100273 | 95,603,865 |
The spiral of Theodorus (which is also called the square root spiral, Einstein spiral, and Pythagorean spiral) was first devised by the Greek mathematician Theodorus of Cyrene during the 5th century BC. The spiral consists of a sequence of right triangles where the ith triangle has side lengths 1, √i, and √(i+1). Each triangle’s edge of length √(i+1) is shared with the next triangle as shown in the following picture from Wikipedia.
When you fill in the number of triangles that you want to draw and click Draw, the following code executes.
private void btnDraw_Click(object sender, EventArgs e)
// Get the spiral of Theodorus's points.
int num_triangles = int.Parse(txtNumTriangles.Text);
List<PointF> edge_points = FindTheodorusPoints(num_triangles);
// Draw the spiral of Theodorus.
picSpiral.Image = DrawTheodorusSpiral(
This code gets the number of triangles that you entered. It then calls the FindTheodorusPoints method described shortly to get the points on the outside of the spiral of Theodorus. It finishes by calling the DrawSpiral method (also described shortly) to draw the spiral.
The following sections describe the FindTheodorusPoints and DrawSpiral methods and their helper routines.
The following code shows the FindTheodorusPoints method.
// Find points on the spiral of Theodorus.
private List<PointF> FindTheodorusPoints(int num_triangles)
// Find the edge points.
List<PointF> edge_points = new List<PointF>();
// Add the first point.
float theta = 0;
float radius = 1;
for (int i = 1; i <= num_triangles; i++)
radius = (float)Math.Sqrt(i);
radius * (float)Math.Cos(theta),
radius * (float)Math.Sin(theta)));
theta -= (float)Math.Atan2(1, radius);
This method first creates an edge_points list to hold the triangles’ outer vertices.
The variable theta keeps track of the angle that the points make with respect to the spiral’s center. Variable radius keeps track of the length of the triangles’ side lengths.
The code sets theta = 0 and radius = 1, and then enters a loop to find the leading edge point for each triangle. Inside the loop, the code uses theta and radius to find the triangle’s point and adds it to the list.
Each triangle’s inner angle (the one by the spiral’s center) is the arc tangent of the opposite side (which always has length 1) and the adjacent side. The adjacent side for the ith triangle has length radius = √i, so the program subtracts Atan2(1, radius) from theta to prepare for the next point on the spiral. (The code subtracts this value instead of adding it so the angles increase counterclockwise for the triangles.)
After it finishes finding the edge points, the method returns them.
The following code shows the DrawTheodorusSpiral method, which draws the spiral.
// Draw the spiral of Theodorus.
private Bitmap DrawTheodorusSpiral(List<PointF> edge_points,
Size size, bool outline_triangles, bool fill_triangles)
// Make the bitmap and associated Graphics object.
int wid = size.Width;
int hgt = size.Height;
Bitmap bm = new Bitmap(wid, hgt);
using (Graphics gr = Graphics.FromImage(bm))
gr.SmoothingMode = SmoothingMode.AntiAlias;
// Make brushes.
Color colors = RainbowColors(255);
Brush brushes = ColorsToBrushes(colors);
// Scale and center.
float xmin, xmax, ymin, ymax;
GetBounds(edge_points, out xmin, out xmax,
out ymin, out ymax);
RectangleF drawing_rect = new RectangleF(
xmin, ymin, xmax - xmin, ymax - ymin);
RectangleF target_rect = new RectangleF(
5, 5, wid - 10, hgt - 10);
MapDrawing(gr, drawing_rect, target_rect, false);
using (Pen pen = new Pen(Color.Black, 0))
int num_brushes = brushes.Length;
for (int i = edge_points.Count - 1; i > 0; i--)
PointF points =
new PointF(0, 0),
edge_points[i - 1].X,
edge_points[i - 1].Y),
gr.FillPolygon(brushes[i % num_brushes],
This method draws the spiral of Theodorus on a bitmap of a specified size and returns the bitmap.
It starts by creating a bitmap of the correct size, making an associated Graphics object, and clearing it.
The method then calls the RainbowColors method to make some colors. It then uses the ColorsToBrushes method to convert those colors into an array of brushes. Both of those methods are described shortly.
The code then calls the GetBounds method (also described shortly) to get bounds for the spiral’s edge points. It uses the bounds to make a rectangle representing the drawing area. It then passes the drawing rectangle and a rectangle that represents the bitmap’s surface (minus a margin) to the MapDrawing method.
The MapDrawing method applies translation and scaling transformations to the Graphics object to make drawing commands it inside the target area. For more information on this method, see the post Scale a drawing to fit a target area in C#.
Now the method draws the spiral of Theodorus. It creates a black pen with thickness 0. (Pens with thickness 0 are not scaled even if the Graphics object includes a scaling transformation.)
The method then enters a loop that runs from the last triangle point to the first. The loops runs last-to-first instead of first-to-last because later triangles may overlap earlier ones. The picture on the right shows the spiral of Theodorus with 30 triangles. You can see that the outer ones overlap the inner ones. Drawing the triangles last-to-first lets you see pieces of all of the triangles.
After it fills a triangle, the method outlines it.
As it draws each triangle, the code checks the outline_triangles and fill_triangles values to see whether it should outline or fill the triangles. (Draw the spiral without filling it if you want to see the overlapping outlines of the triangles.)
The following code shows the RainbowColors method.
// Return an array of rainbow colors.
private Color RainbowColors(byte alpha)
return new Color
Color.FromArgb(alpha, 255, 0, 0),
Color.FromArgb(alpha, 255, 255, 0),
Color.FromArgb(alpha, 255, 128, 0),
Color.FromArgb(alpha, 0, 255, 0),
Color.FromArgb(alpha, 0, 255, 255),
Color.FromArgb(alpha, 0, 0, 255),
Color.FromArgb(alpha, 255, 0, 255),
This method simply builds an array holding a predefined set of colors. The method takes an alpha parameter in case you want to make the colors semi-transparent. (I originally thought that would be useful in this example, but it just made the result more cluttered.)
The following code shows the ColorsToBrushes helper method.
// Convert colors to brushes.
private Brush ColorsToBrushes(Color colors)
int num_colors = colors.Length;
Brush brushes = new Brush[num_colors];
for (int i = 0; i < num_colors; i++)
brushes[i] = new SolidBrush(colors[i]);
This method simply loops through an array of colors and makes a SolidBrush for each.
The following code shows the GetBounds method.
// Get the points' bounds.
private void GetBounds(List<PointF> points,
out float xmin, out float xmax,
out float ymin, out float ymax)
// Find the bounds.
xmin = points.X;
xmax = xmin;
ymin = points.Y;
ymax = ymin;
foreach (PointF point in points)
if (xmin > point.X) xmin = point.X;
if (xmax < point.X) xmax = point.X;
if (ymin > point.Y) ymin = point.Y;
if (ymax < point.Y) ymax = point.Y;
This method simply loops through an array of PointF and finds their minimum and maximum X and Y values. (You could use LINQ to do something similar, but it wouldn’t be any easier to read and it would be slightly slower.)
Download the example to see additional details and to experiment with the program. For example, you might try using semi-transparent colors, with or without the triangle outlines. If you fill around 10,000 or more triangles without outlining them, you can also see an interesting wave effect flowing through the spiral’s rings.
For more information on the spiral of Theodorus, see the Wikipedia article Spiral of Theodorus. | <urn:uuid:641ea82c-f24e-46b2-824a-0d5feb12e961> | 4.03125 | 2,094 | Documentation | Software Dev. | 64.401088 | 95,603,872 |
I have seen recently several articles about using magnetic fields to deflect plasma around a spaceship. The first was about deflecting "cosmic rays", such as protons being part of the stellar wind from the Sun. They all involve the use of super conducting magnets, similar in concept to those used in the Large Hadron Collider - essntially you get a hugely powerful magnetic field, without having to constantly generate fresh electric current.
Here is an article about a proposal do avoid the need for a physical heat shields.
In a very real sense it is a Force Field, though not in the way of Star Trek.
The Next Generation of Heat Shield: Magnetic
The next generation of heat shields to protect astronauts and payloads on their re-entry into the Earth's atmosphere may use superconducting magnets to deflect the plasma that forms in front of spacecraft as they travel at high speeds in the air. The first test of such a heat shield could happen as early as ten years from now, and the basic technology is already in development.
Rorting In The Auckland Property Market !
3 years ago | <urn:uuid:6eb74b4b-e28a-493b-b4d1-e0b122d6bdf3> | 2.859375 | 222 | Personal Blog | Science & Tech. | 48.569911 | 95,603,874 |
A material such as a salt or a drug is hygroscopic if it absorbs water vapour from the air when the relative humidity (RH) of the air is larger than a certain value specific for this material. A material is non-hygroscopic, if it doesn’t absorb water vapour at RH’s below saturation. According to this definition a salt or drug is hygroscopic, that is all soluble in water. Hygroscopic materials are widely used in medicine for therapeutic and diagnostic purposes. Hygroscopic materials are present in atmospheric aerosol particles. High concentrations, mainly NaCl, are found near to the sea (Keith and Arons, 1954; Winkler and Junge, 1972). Continental aerosols also have a hygroscopic fraction (Hänel, 1976; Hicks and Megaw, 1985; McMurry and Stolzenburg, 1989; Busch et al., 1994; Busch, 1995). Hygroscopic aerosols play an important role in the formation of clouds (Pruppacher and Klett, 1980).
Weitere Kapitel dieses Buchs durch Wischen aufrufen
- Deposition of Hygroscopic Aerosol Particles in the Lungs
George A. Ferron
- Springer Netherlands
Fallstudie Überschwemmungskarten/© Thaut Images | Fotolia | <urn:uuid:a8089c54-3374-4d96-b5ff-1f53668aeee0> | 3.328125 | 294 | Knowledge Article | Science & Tech. | 39.0785 | 95,603,880 |
It is tesitfied that the continental shelf of the East China Sea was exposed and covered with the huge wetland and grassland ecosystems during the the last two glacial periods.
This shows terrigenous palynomorphs of short-distance transportation: light microscope and scanning electron microscope photos of pollen and spore, plant debris and charcoals.
Credit: © Science China Press
They discovered that the variation of terrestrial sources is concordent with global glacial volume and sea-level changes at orbital-scale since 200 kyrs before present. Their work, entitled "A ~200 ka pollen record from Okinawa Trough: Paleoenvironment reconstruction of glacial-interglacial cycles", was published in SCIENCE CHINA Earth Sciences.2013, Vol 56 (doi: 10.1007/s11430-013-4619-0)
This research work concerns mainly the Quaternary environment and global chages based on pollen analysis from a deep-sea core in Okinawa Trough. The project was directed by Department of Earth Sciences, Sun Yat-sen University, with colaboration of University Claude Bernard-Lyon 1 and Laboratory of Climate and Environment Sciences in Gif-sur-Yvette. The first author is professor ZHENG Zhuo from Sun Yat-sen University. Their research work was supported by the National Natural Science Foundation of China (grant no. 40772113, 41072128).
The discoreries show that terrestrial-source materials vary greatly during the transition of glacial and interglacial periods, proving the sensitive response on the global ice volume and sea-level changes. This deep-sea record has firstly documented high percentage of sedge, grass and many freshwater algaes in the glacial interval, which indicates that the offshore distance of Okinawa Trough has obviously shortened due to the exposed continental shelf during the glacial stages.
The vegetation on the exposed continental shelf was dominated by intrazonal communities such as halophyte grasslands and freshwater wetlands. New evidence demonstrated that the fundamental changes of sediment sources in Okinawa Trough since ~200 ka BP were affected by combine factors including the offshore coastline distance, monsoon variability and sea-level changes.
This new research provides an oldest record of Quaternry environment reconstruction so far in the Okinawa Trough. It has a great scientific significance on highlighting the evolution history of continental shelf extension, the tracing of the sediment source areas of the Okinawa Trough and global climate changes since the last 200 kyrs.
See the article: Zheng Z, Huang K Y, Deng Y, Cao L L, Yu S H, Suc J P, Berne S, Guichard F., A ~200 ka pollen record from Okinawa Trough: Paleoenvironment reconstruction of glacial-interglacial cycles. SCI CHINA Earth Sci, 2013 Vol. 56 (doi: 10.1007/s11430-013-4619-0)
Science China Press Co., Ltd. (SCP) is a scientific journal publishing company of the Chinese Academy of Sciences (CAS). For 50 years, SCP takes its mission to present to the world the best achievements by Chinese scientists on various fields of natural sciences researches.
ZHENG Zhuo | EurekAlert!
New research calculates capacity of North American forests to sequester carbon
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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...
13.07.2018 | Event News
12.07.2018 | Event News
03.07.2018 | Event News
18.07.2018 | Life Sciences
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18.07.2018 | Health and Medicine | <urn:uuid:bffa40d0-4ca4-4848-a161-74cded3a4971> | 3.484375 | 1,297 | Content Listing | Science & Tech. | 40.761601 | 95,603,902 |
When the ants come marching in, having miles of linked habitats may not be such a good idea after all.
In a classic example of the law of unintended consequences, new University of Florida research suggests that wildlife corridors – strips of natural land created to reconnect habitats separated by agriculture or human activities -- can sometimes encourage the spread of invasive species such as one type of fire ant.
The findings are particularly important in Florida, where invasive species are a vexing problem. The Sunshine State plays host to animals such as Cuban tree frogs, green iguanas and feral hogs. In 2013, the Florida Fish and Wildlife Conservation Commission even sponsored a Burmese python hunting challenge.
The discovery also comes as a team of explorers prepares to embark this fall on its second 1,000-mile expedition to raise support for the Florida Wildlife Corridor. The organization’s goal is to create a corridor stretching from Everglades National Park to the Okefenokee National Wildlife Refuge in Georgia.
Could corridors be used by invasive species to spread across conservation lands? Sometimes, according to research by Julian Resasco, who led a study of red imported fire ants while he was a doctoral student in biology at UF. Resasco and his colleagues found that one type of fire ant used wildlife corridors to dominate recently created landscapes. Resasco’s paper is published in the August issue of Ecology.
"Although habitat corridors are usually beneficial, they occasionally have negative effects," he said. "Sometimes they can help invasive species spread in exactly the same way they help native species."
The challenge for ecologists is to figure out when invasive species are likely to benefit from corridors. Resasco's results initially surprised the researchers because invasive species are usually talented in their ability to invade new areas -- they shouldn't need corridors to get around. Fire ants turned out to be an exception that proves the rule.
They have two social forms: monogyne and polygyne. Monogyne fire ants fly high in the air to mate and disperse, raining down to create new colonies. Polygyne fire ants, on the other hand, mate low to the ground and sometimes crawl short distances to create new colonies. They don’t spread widely and their colonies are dense.
Resasco and his team went to South Carolina to study eight sections of land, each dominated by one of the two social forms. Each section consisted of five patches of regenerating habitat. Each patch was about the size of a football field. Some were connected by a corridor and others were not, allowing the researchers to study the influence of corridors.
The researchers found that corridors significantly increased the abundance of polygyne -- but not monogyne -- fire ants. In polygyne sections, native ant species’ diversity was lower in patches connected by corridors than in unconnected patches. That was most likely due to the higher fire ant abundance, according to the study.
Ultimately, Resasco said, whether corridors spread invasive species depends on dispersal ability: "It is not a coincidence that the readily dispersing monogyne form of fire ants doesn’t benefit from corridors, whereas the poorly dispersing polygyne form does." For better or worse, poorly dispersing invasive species are exceptional.
More analysis is necessary to determine whether the effects of corridors on invasive species are transient or permanent. In the meantime, Resasco’s paper urges land managers to consider animals’ traits when making decisions about land corridors. In rare cases, their best intentions could backfire by aiding invasive species.
Researchers from North Carolina State University, University of Wisconsin-Madison, Michigan State University, University of Washington and the USDA Agricultural Research Service in Gainesville also worked on the paper.
Resasco is now an NSF Postdoctoral Research Fellow in biology at the University of Colorado at Boulder.
Julia Glum | newswise
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...
13.07.2018 | Event News
12.07.2018 | Event News
03.07.2018 | Event News
18.07.2018 | Life Sciences
18.07.2018 | Materials Sciences
18.07.2018 | Health and Medicine | <urn:uuid:bc89edf9-af98-47ce-a85c-eca95867cdfe> | 3.46875 | 1,451 | Content Listing | Science & Tech. | 32.746136 | 95,603,903 |
“While gold nanoparticles are being used by so many researchers – chemists, materials scientists and biomedical engineers – no one understood their molecular and electronic structures until now,” said Robert Whetten, a professor in the Georgia Institute of Technology’s School of Physics and School of Chemistry and Biochemistry. “This research opens a new window for nanoparticle chemistry.”
Gold and sulfur atoms tend to aggregate in specific numbers and highly symmetrical geometries. Sometimes these clusters are called “superatoms” because they can mimic the chemistry of single atoms of a completely different element.
Researchers commonly use gold nanoparticles because they are stable and exhibit distinct optical, electronic, electrochemical and bio-labeling properties. However, understanding the physicochemical properties of such clusters is a challenge, according to Whetten, because that requires knowledge of their atomic structures.
A significant advance came in late 2007 though, when Stanford University researchers reported the first-ever total structure determination of a 102-atom gold cluster. The X-ray structure study revealed that pairs of organic sulfur (“thiolate”) groups extracted gold atoms from the gold layer to form a linear thiolate-gold-thiolate bridge while interacting weakly with the metal surface below. These gold–thiolate complexes formed a sort of protective crust around the nanoparticles.
“This discovery contradicted what most chemists believed was going on – which was that the sulfur atom merely sat atop the uppermost gold layer, bound to three adjacent metal atoms,” said Whetten.
With the experimentally determined structural coordinates, an international team of researchers from Georgia Tech, Stanford University, the University of Jyväskylä in Finland and Chalmers University of Technology in Sweden set out to determine the electronic principles underlying the 102-atom gold compound and others like it. The team conducted large-scale electronic structure calculations in supercomputing centers in Espoo, Finland; Stockholm, Sweden; and Juelich, Germany.
The researchers found that the 102-atom gold cluster was a “superatom” with a core of 79 gold atoms arranged into a truncated decahedron: two pyramids with pentagonal bases joined together into a faceted shape, but with the pyramids’ tips chopped off. Around the core, 23 gold atoms formed an unusual pattern, joining the thiolates in shapes that resemble handles.
The results confirmed the “divide and protect” structure first predicted by team member Hannu Häkkinen, a professor at the University of Jyväskylä and former senior research scientist at Georgia Tech in the laboratory of Uzi Landman. Häkkinen and Henrik Grönbeck of the Chalmers University of Technology previously proposed that a cluster of 38-atom gold contained a central metallic core of 14 gold atoms and a protective layer of 24 gold atoms bound to sulfur.
“In 2006, we predicted that gold atoms in this bonding motif were divided in two groups – those that made the metal core and those that helped to protected it,” explained Häkkinen. “Now there was evidence that this was true.”
In the study reported in PNAS, the researchers found that the clusters were stable because the surface gold atoms in the core each had at least one surface-chemical bond and the gold core exhibited a strong electron shell closing.
With the 102-atom gold cluster, each gold atom in the cluster donated one valence electron. Forty-four of those electrons were immobilized in bonds between gold atoms and thiolates, leaving 58 electrons to fill a shell around the “superatom.” In this configuration, the cluster wouldn’t benefit from adding or shedding electrons, which would destabilize its structure. This process is similar to what happens in noble gases, which are chemically inert because they have just the right number of electrons to fill a shell around each atom’s nucleus.
Associated with the filled electron shell, the gold-thiolate compound also had a major energy gap to unoccupied states. The calculated energy gap between the highest occupied molecular orbital and the lowest unoccupied molecular orbital states for the 102-atom compound was significant – 0.5 electron volts. Metals typically have a gap of zero, so this gap indicates an atypical electronic stability of the compound, explained Whetten.
Besides the 102-atom compound, the researchers also determined the electronic structures for 11-, 13- and 39-atom gold cluster compounds. They found that the 11- and 13-gold atom clusters form closed electronic shells with 8 electrons and the 39-atom gold clusters with 34.
“The theoretical concepts published in this paper provide a solid background for further understanding of the distinct electrical, optical and chemical properties of the stable mono-layer-protected gold nanoclusters,” said Whetten, whose funding for this research came from the National Science Foundation and the U.S. Department of Energy. Former Georgia Tech graduate student Ryan Price and current graduate student James Bradshaw also contributed to this work.
The study also shows that experimentally well-characterized, structure-resolved, thermodynamically stable species of thiolate-, phosphine-halide-, and phosphine-thiolate-protected gold nanoparticles share common factors underlying their stability.
Once this initial work was completed, the researchers started predicting the structures of other stable gold cluster compositions that are still awaiting a precise structure determination.
In the March 26 issue of the Journal of the American Chemical Society, the research team predicted the structure for a cluster containing 25 gold atoms. They determined that the structure was comprised of an icosahedron-like 13-atom gold core protected by six “V-shaped” long units, creating a “divide and protect” composition. The structural prediction was recently confirmed by another group’s experimental work.
“We now have a unified model that provides a solid background for nanoengineering ligand-protected gold clusters for applications in catalysis, sensing, photonics, bio-labeling and molecular electronics,” said Häkkinen.
Additional authors on the PNAS paper included Michael Walter, Jaakko Akola and Olga Lopez-Acevedo of the University of Jyväskylä; and Pablo Jadzinsky, Guillermo Calero and Christopher Ackerson of Stanford University.
Abby Vogel | Newswise Science News
Innovative genetic tests for children with developmental disorders and epilepsy
11.07.2018 | Christian-Albrechts-Universität zu Kiel
Oxygen loss in the coastal Baltic Sea is “unprecedentedly severe”
05.07.2018 | European Geosciences Union
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
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20.07.2018 | Materials Sciences | <urn:uuid:7b92d4d7-1c04-4dc2-834c-0c75136b44db> | 3.75 | 1,929 | Content Listing | Science & Tech. | 28.747673 | 95,603,934 |
A sample of nitrogen gas has a volume of 3.00 L at 25 degrees C. What volume will it occupy at each of the following temperatures if the pressure and number of moles are constant:
We will use the ideal gas law for solving this.
We know that, PV = nRT
Where R is the Universal gas constant and n is the number of ...
The solution employs the formula from the ideal gas law in each case given, showing all the calculation steps. | <urn:uuid:3a683d7b-6c22-470e-a944-d9662f0cf976> | 3.4375 | 98 | Tutorial | Science & Tech. | 75.544578 | 95,603,985 |
By Leticia Brambila-Paz,Peter Newstead,Richard P. W. Thomas,Oscar Garcia-Prada
Read Online or Download Moduli Spaces (London Mathematical Society Lecture Note Series) PDF
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Moduli Spaces (London Mathematical Society Lecture Note Series) by Leticia Brambila-Paz,Peter Newstead,Richard P. W. Thomas,Oscar Garcia-Prada | <urn:uuid:08ac0565-8e4d-42c7-93e8-43a284919d8b> | 2.625 | 444 | Product Page | Science & Tech. | 22.697453 | 95,604,019 |
The brown dwarf is named CFBDS J005910.83-011401.3 (it will be called CFBDS0059 in the following). Its temperature is about 350°C and its mass about 15-30 times the mass of Jupiter, the largest planet of our solar system . Located about 40 light years from our solar system, it is an isolated object, meaning that it doesn't orbit another star.
Brown dwarfs are intermediate bodies between stars and giant planets (like Jupiter). The mass of brown dwarfs is usually less than 70 Jupiter masses. Because of their low mass, their central temperature is not high enough to maintain thermonuclear fusion reactions over a long time. In contrast to a star like our Sun, which spends most of its lifetime burning hydrogen, hence keeping a constant internal temperature, a brown dwarf spends its lifetime getting colder and colder after its formation.
The first brown dwarfs were detected in 1995. Since then, this type of stellar object has been found to share common properties with giant planets, even though differences remain. For example, clouds of dust and aerosols, as well as large amounts of methane, were detected in their atmosphere (for the coldest ones), just as in the atmosphere of Jupiter and Saturn. However, there were still two major differences. In the brown dwarf atmospheres, water is always in gaseous state, while it condenses into water ice in giant planets; and ammonia has never been detected in the brown dwarf near-infrared spectra, while it is a major component of Jupiter's atmosphere. CFBDS0059, the newly-discovered brown dwarf, looks much more like a giant planet than the known classes of brown dwarfs, both because of its low temperature and because of the presence of ammonia.
To date, two classes of brown dwarfs have been known: the L dwarfs (temperature of 1200-2000°C), which have clouds of dust and aerosols in their high atmosphere; and the T dwarfs (temperature lower than 1200°C), which have a very different spectrum because of methane forming in their atmospheres. Because it contains ammonia and has a much lower temperature than do L and T dwarfs, CFBDS0059 might be the prototype of a new class of brown dwarfs to be called the Y dwarfs. This new class would then become the missing link in the sequence from the hottest stars to giant planets of less than -100°C, by filling the gap now left in the midrange.
This discovery also has important implications in the study of extrasolar planets. The atmosphere of brown dwarfs looks very much like that of giant planets, therefore the same models are used to reproduce their physical conditions. Such modeling needs to be tested against observations. Observing the atmospheres of extrasolar planets is indeed very hard because the light from the planets is embedded in the much stronger light from their parent stars. Because brown dwarfs are isolated bodies, they are much easier to observe. Thus, looking to brown dwarfs with a temperature close to that of the giant planets will help in testing the models of extrasolar planets' atmospheres.
The team of astronomers includes P. Delorme, X. Delfosse (Observatoire de Grenoble, France), L. Albert (CFHT, Hawaii), E. Artigau (Gemini Observatory, Chile), T. Forveille (Obs. Grenoble/France, IfA/Hawaii), C. Reylé (Observatoire de Besançon, France), F. Allard, A. C. Robin (CRAL, Lyon, France), D. Homeier (Göttingen, Germany), C.J. Willott (University of Ottawa, Canada), M. C. Liu, T. J. Dupuy (IfA, Hawaii).
CFBDS0059 was discovered in the framework of the Canada-France Brown-Dwarfs survey. The object was first identified in pictures from the wide-field camera Megacam installed on the CFHT (Canada France Hawaii Telescope). Infrared pictures were then obtained with the NTT telescope (La Silla, ESO, Chile) and confirmed the low temperature of the object. Finally, the spectrum showing the presence of ammonia was obtained using the Gemini North Telescope (Hawaii).
The mass of Jupiter is about 300 times the Earth's mass and about 1/1000e of the Sun's mass.
Jennifer Martin | alfa
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...
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The scientists observed twisting patterns in the polarization of the cosmic microwave background—light that last interacted with matter very early in the history of the universe, less than 400,000 years after the Big Bang.
These patterns, known as “B modes,” are caused by gravitational lensing, a phenomenon that occurs when the trajectory of light is bent by massive objects, much like a lens focuses light. Early today, Physics World magazine heralded the result as one of the top 10 physics breakthroughs of 2013.
A multi-institutional collaboration of researchers led by John Carlstrom, the S. Chandrasekhar Distinguished Service Professor in Astronomy & Astrophysics at the University of Chicago, made the discovery. They announced their findings in a paper published in the journal Physical Review Letters—using the first data from SPTpol, a polarization-sensitive camera installed on the telescope in January 2012.
“The detection of B-mode polarization by South Pole Telescope is a major milestone, a technical achievement that indicates exciting physics to come,” said Carlstrom, who also is deputy director of the Kavli Institute for Cosmological Physics. The cosmic microwave background is a sea of photons (light particles) left over from the Big Bang that pervades all of space, at a temperature of minus 270 degrees Celsius—a mere 3 degrees above absolute zero.
Measurements of this ancient light have already given physicists a wealth of knowledge about the properties of the universe. Tiny variations in temperature of the light have been painstakingly mapped across the sky by multiple experiments, and scientists are gleaning even more information from polarized light. Light is polarized when its electromagnetic waves are preferentially oriented in a particular direction. Light from the cosmic microwave background is polarized mainly due to the scattering of photons off of electrons in the early universe, through the same process by which light is polarized as it reflects off the surface of a lake or the hood of a car.
The polarization patterns that result are of a swirl-free type, known as “E modes,” which have proven easier to detect than the fainter B modes, and were first measured a decade ago by a collaboration of researchers using the Degree Angular Scale Interferometer, another UChicago-led experiment. Simple scattering can’t generate B modes, which instead emerge through a more complex process—hence scientists’ interest in measuring them. Gravitational lensing, it has long been predicted, can twist E modes into B modes as photons pass by galaxies and other massive objects on their way toward earth.
This expectation has now been confirmed. To tease out the B modes in their data, the scientists used a previously measured map of the distribution of mass in the universe to determine where the gravitational lensing should occur. They combined their measurement of E modes with the mass distribution to provide a template of the expected twisting into B modes.
The scientists are currently working with another year of data to further refine their measurement of B modes. The careful study of such B modes will help physicists better understand the universe. The patterns can be used to map out the distribution of mass, thereby more accurately defining cosmologically important properties like the masses of neutrinos, tiny elementary particles prevalent throughout the cosmos.
Similar, more elusive B modes would provide dramatic evidence of inflation, the theorized turbulent period in the moments after the Big Bang when the universe expanded extremely rapidly. Inflation is a well-regarded theory among cosmologists because its predictions agree with observations, but thus far there is not a definitive confirmation of the theory. Measuring B modes generated by inflation is a possible way to alleviate lingering doubt.
“The detection of a primordial B-mode polarization signal in the microwave background would amount to finding the first tremors of the Big Bang,” said the study’s lead author, Duncan Hanson, a postdoctoral scientist at McGill University in Canada. B modes from inflation are caused by gravitational waves. These ripples in space-time are generated by intense gravitational turmoil, conditions that would have existed during inflation. These waves, stretching and squeezing the fabric of the universe, would give rise to the telltale twisted polarization patterns of B modes.
Measuring the resulting polarization would not only confirm the theory of inflation—a huge scientific achievement in itself—but would also give scientists information about physics at very high energies—much higher than can be achieved with particle accelerators. The measurement of B modes from gravitational lensing is an important first step in the quest to measure inflationary B modes. In inflationary B mode searches, lensing B modes show up as noise.
“The new result shows that this noise can be accounted for and subtracted off so that scientists can search for and hopefully measure the inflationary B modes underneath,” Hanson said. “The lensing signal itself can also be used by itself to learn about the distribution of mass in the universe.” - See more at: http://news.uchicago.edu/article/2013/12/13/swirls-remnants-big-bang-may-hold-clues-universe-s-infancy#sthash.rpjjz1Yw.dpuf
Steve Koppes | 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....
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What's the Latest Development?
By studying the neurons inside rat brains, British neuroscientist Kathryn Jeffery has concluded that mammals most likely collapse the world into a two-dimensional map when navigating and calculating distances. Jeffrey's team enticed rats to climb up a spiral staircase while collecting electrical recordings from single cells. "The firing pattern encoded very little information about height. The finding adds evidence for the hypothesis that the brain keeps track of our location on a flat plane, which is defined by the way the body is oriented."
What's the Big Idea?
As humans and animals move over distances, two distinct types of neurons, divided into grid cells and space cells, switch on and off inside our brain, telling us how far we have come and how far we have left to go. The cells orient us on a flat plane, which is why astronauts report feeling disoriented when they stand on "ceilings", even though that distinction does not exist in zero-gravity environments. Neuroscientists say a two-dimensional map is all we have needed to survive so our brain has not evolved beyond its basic spatial outlook.
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Temporal range: Triassic–present 235–0 Ma
|A digger wasp, Sphex pensylvanicus|
Hymenoptera is a large order of insects, comprising the sawflies, wasps, bees, and ants. Over 150,000 living species of Hymenoptera have been described, in addition to over 2,000 extinct ones.
Females typically have a special ovipositor for inserting eggs into hosts or places that are otherwise inaccessible. The ovipositor is often modified into a stinger. The young develop through holometabolism (complete metamorphosis)—that is, they have a worm-like larval stage and an inactive pupal stage before they mature.
The name Hymenoptera refers to the wings of the insects, but the original derivation is ambiguous.:42 All references agree that the derivation involves the Ancient Greek πτερόν (pteron) for wing. The Ancient Greek ὑμήν (hymen) for membrane provides a plausible etymology for the term because species in this order have membranous wings. However, a key characteristic of this order is that the hind wings are connected to the fore wings by a series of hooks. Thus, another plausible etymology involves Hymen, the Ancient Greek god of marriage, as these insects have "married wings" in flight.
The cladogram of external relationships, based on a 2008 DNA and protein analysis, shows the order as a clade, most closely related to endopterygote orders including the Diptera (true flies) and Lepidoptera (butterflies and moths).
|part of Endopterygota||
Hymenoptera originated in the Triassic, with the oldest fossils belonging to the family Xyelidae. Social hymenopterans appeared during the Cretaceous. The evolution of this group has been intensively studied by Alex Rasnitsyn, Michael S. Engel, Gennady Dlussky, and others.
This clade has been studied by examining the mitochondrial DNA. Although this study was unable to resolve all the ambiguities in this clade, some relationships could be established. The Aculeata, Ichneumonomorpha, and Proctotrupomorpha were monophyletic. The Megalyroidea and Trigonalyoidea are sister clades as are the Chalcidoidea+Diaprioidea. The Cynipoidea was generally recovered as the sister group to Chalcidoidea and Diaprioidea which are each other's closest relations.
|Symphyta (red bar) are paraphyletic as Apocrita are excluded.|
Hymenopterans range in size from very small to large insects, and usually have two pairs of wings. Their mouthparts are adapted for chewing, with well-developed mandibles (ectognathous mouthparts). Many species have further developed the mouthparts into a lengthy proboscis, with which they can drink liquids, such as nectar. They have large compound eyes, and typically three simple eyes, ocelli.
The forward margin of the hind wing bears a number of hooked bristles, or "hamuli", which lock onto the fore wing, keeping them held together. The smaller species may have only two or three hamuli on each side, but the largest wasps may have a considerable number, keeping the wings gripped together especially tightly. Hymenopteran wings have relatively few veins compared with many other insects, especially in the smaller species.
In the more ancestral hymenopterans, the ovipositor is blade-like, and has evolved for slicing plant tissues. In the majority, however, it is modified for piercing, and, in some cases, is several times the length of the body. In some species, the ovipositor has become modified as a stinger, and the eggs are laid from the base of the structure, rather than from the tip, which is used only to inject venom. The sting is typically used to immobilise prey, but in some wasps and bees may be used in defense.
Hymenopteran larvae typically have a distinct head region, three thoracic segments, and usually nine or 10 abdominal segments. In the suborder Symphyta, the larvae resemble caterpillars in appearance, and like them, typically feed on leaves. They have large chewing mandibles, three pairs of thoracic limbs, and, in most cases, six or eight abdominal prolegs. Unlike caterpillars, however, the prolegs have no grasping spines, and the antennae are reduced to mere stubs. Symphytan larvae that are wood borers or stem borers have no abdominal legs and the thoracic legs are smaller than those of non-borers.
With rare exceptions larvae of the suborder Apocrita have no legs and are maggotlike in form, and are adapted to life in a protected environment. This may be the body of a host organism, or a cell in a nest, where the adults will care for the larva. In parasitic forms, the head is often greatly reduced and partially withdrawn into the prothorax (anterior part of the thorax). Sense organs appear to be poorly developed, with no ocelli, very small or absent antennae, and toothlike, sicklelike, or spinelike mandibles. They are also unable to defecate until they reach adulthood due to having an incomplete digestive tract (a blind sac), presumably to avoid contaminating their environment. The larvae of stinging forms (Aculeata) generally have 10 pairs of spiracles, or breathing pores, whereas parasitic forms usually have nine pairs present.
Among most or all hymenopterans, sex is determined by the number of chromosomes an individual possesses. Fertilized eggs get two sets of chromosomes (one from each parent's respective gametes) and develop into diploid females, while unfertilized eggs only contain one set (from the mother) and develop into haploid males. The act of fertilization is under the voluntary control of the egg-laying female, giving her control of the sex of her offspring. This phenomenon is called haplodiploidy.
However, the actual genetic mechanisms of haplodiploid sex determination may be more complex than simple chromosome number. In many Hymenoptera, sex is actually determined by a single gene locus with many alleles. In these species, haploids are male and diploids heterozygous at the sex locus are female, but occasionally a diploid will be homozygous at the sex locus and develop as a male, instead. This is especially likely to occur in an individual whose parents were siblings or other close relatives. Diploid males are known to be produced by inbreeding in many ant, bee, and wasp species. Diploid biparental males are usually sterile but a few species that have fertile diploid males are known.
One consequence of haplodiploidy is that females on average actually have more genes in common with their sisters than they do with their own daughters. Because of this, cooperation among kindred females may be unusually advantageous, and has been hypothesized to contribute to the multiple origins of eusociality within this order. In many colonies of bees, ants, and wasps, worker females will remove eggs laid by other workers due to increased relatedness to direct siblings, a phenomenon known as worker policing.
Another consequence is that hymenopterans may be more resistant to the deleterious effects of inbreeding. As males are haploid, any recessive genes will automatically be expressed, exposing them to natural selection. Thus, the genetic load of deleterious genes is purged relatively quickly.
Some hymenopterans take advantage of parthenogenesis, the creation of embryos without fertilization. Thelytoky is a particular form of parthenogenesis in which female embryos are created (without fertilisation). The form of thelytoky in hymenopterans is a kind of automixis in which two haploid products (proto-eggs) from the same meiosis fuse to form a diploid zygote. This process tends to maintain heterozygosity in the passage of the genome from mother to daughter. It is found in several ant species including the desert ant Cataglyphis cursor, the clonal raider ant Cerapachys biroi, the predaceous ant Platythyrea punctata, and the electric ant (little fire ant) Wasmannia auropunctata. It also occurs in the Cape honey bee Apis mellifera capensis.
Oocytes that undergo automixis with central fusion often have a reduced rate of crossover recombination, which helps to maintain heterozygosity and avoid inbreeding depression. Species that display central fusion with reduced recombination include the ants Platythyrea punctata and Wasmannia auropunctata and the honey bee Apis mellifera capensis. In A. m. capensis, the recombination rate during meiosis is reduced more than 10 fold. In W. auropunctata the reduction is 45 fold.
Single queen colonies of the narrow headed ant Formica exsecta illustrate the possible deleterious effects of increased homozygosity. Colonies of this species which have more homozygous queens will age more rapidly, resulting in reduced colony survival.
Different species of Hymenoptera show a wide range of feeding habits. The most primitive forms are typically herbivorous, feeding on leaves or pine needles. Stinging wasps are predators, and will provision their larvae with immobilised prey, while bees feed on nectar and pollen.
A huge number of species are parasitoids as larvae. The adults inject the eggs into a host, which they begin to consume after hatching. For example, the eggs of the endangered Papilio homerus are parasitized at a rate of 77%, mainly by Hymenoptera species. Some species are even hyperparasitoid, with the host itself being another parasitoid insect. Habits intermediate between those of the herbivorous and parasitoid forms are shown in some hymenopterans, which inhabit the galls or nests of other insects, stealing their food, and eventually killing and eating the occupant.
The Hymenoptera are divided into two groups; the Symphyta which have no waist, and the Apocrita which have a narrow waist.
The suborder Symphyta includes the sawflies, horntails, and parasitic wood wasps. The group may be paraphyletic, as it has been suggested that the family Orussidae may be the group from which the Apocrita arose. They have an unconstricted junction between the thorax and abdomen. The larvae are herbivorous, free-living eruciforms, with three pairs of true legs, prolegs (on every segment, unlike Lepidoptera) and ocelli. The prolegs do not have crochet hooks at the ends unlike the larvae of the Lepidoptera.
The wasps, bees, and ants together make up the suborder (and clade) Apocrita, characterized by a constriction between the first and second abdominal segments called a wasp-waist (petiole), also involving the fusion of the first abdominal segment to the thorax. Also, the larvae of all Apocrita lack legs, prolegs, or ocelli. The hindgut of the larvae also remains closed during development, with feces being stored inside the body, with the exception of some bee larvae where the larval anus has reappeared through developmental reversion. In general, the anus only opens at the completion of larval growth.
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- Gerstaecker, A (July 1867). "Ueber die Gattung Oxybelus Latr. und die bei Berlin vorkommenden Arten derselben". Zeitschrift für die gesammten Naturwissenschaft. 30 (VII): 1–144.
- Goulet, Henri; Huber, John T., eds. (1993). Hymenoptera of the world: An identification guide to families (PDF). Ottawa: Agriculture Canada. ISBN 0-660-14933-8. Archived from the original (PDF) on 2016-03-05.
- Gullan, P. J.; Cranston, P. S. (2014). The Insects: An Outline of Entomology (Fifth ed.). Wiley Blackwell.
- Günther, A.C.L.G., ed. (1867). The Record of Zoological Literature vol. iv. London: van Voorst. (see The Record of Zoological Literature)
- Grimaldi, D. and Engel, M.S. (2005). Evolution of the Insects. Cambridge University Press. ISBN 0-521-82149-5.
- Hennig, Willi (1969). Die Stammesgeschichte der Insekten. Frankfurt: Waldemar Kramer.
- Mao, Meng; Gibson, Tracey; Dowton, Mark (March 2015). "Higher-level phylogeny of the Hymenoptera inferred from mitochondrial genomes". Molecular Phylogenetics and Evolution. 84: 34–43. doi:10.1016/j.ympev.2014.12.009. PMID 25542648.
- Rasnitsyn, A.P. and Quicke, D.L.J. (2002). History of Insects. Kluwer Academic Publishers. pp. 242–254. ISBN 1-4020-0026-X.
- Rasnitsyn, A.P. (1988). "An outline of evolution of hymenopterous insects (order Vespida)". Oriental Insects. 22: 115–145.
- Seltmann, Katja Chantre ́ (December 2004). Building web-based interactive keys to the hymenopteran families and superfamilies (PDF). College of Agriculture, University of Kentucky. Archived from the original (M Sc Thesis) on 3 December 2011.
- Sharkey, Michael J (2007). "Phylogeny and Classification of Hymenoptera" (PDF). Zootaxa. 1668: 521–548.
- Sharkey, Michael J.; Carpenter, James M.; Vilhelmsen, Lars; Heraty, John; Liljeblad, Johan; Dowling, Ashley P.G.; Schulmeister, Susanne; Murray, Debra; Deans, Andrew R.; Ronquist, Fredrik; Krogmann, Lars; Wheeler, Ward C. (February 2012). "Phylogenetic relationships among superfamilies of Hymenoptera". Cladistics. 28 (1): 80–112. doi:10.1111/j.1096-0031.2011.00366.x.
- Song, Sheng-Nan; Tang, Pu; Wei, Shu-Jun; Chen, Xue-Xin (16 February 2016). "Comparative and phylogenetic analysis of the mitochondrial genomes in basal hymenopterans". Scientific Reports. 6: 20972. Bibcode:2016NatSR...620972S. doi:10.1038/srep20972. PMC . PMID 26879745.
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- Hymenoptera Anatomy Ontology project
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- Hymenoptera Forum German and International
- [permanent dead link] Hymenoptera Information System (German)
- Hymenoptera of North America – large format reference photographs, descriptions, taxonomy
- International Society of Hymenopterists
- Bees, Wasps and Ants Recording Society (UK)
- Ants Photo Gallery (RU)
- [permanent dead link] International Palaeoentomological Society
- Sphecos Forum for Aculeate Hymenopterra
- Hymenoptera images on MorphBank, a biological image database
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Calculate the area of masonry to build wall with dimensions of 9 m × 4 m with 4 windows of size 64 cm × 64 cm.
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Outlines of Statistical Mechanics
In this chapter, we start with certain principles and describe the general methods of statistical mechanics [2.1–17]. If we assume that every quantum-mechanical state (microscopic state) has the same weight (the principle of equal probability), then we can establish a standpoint where mechanical laws are combined with probability theory. By considering a system in contact with a larger system, we can describe a system with constant temperature or constant pressure. Thus, we develop the statistical mechanics for an equilibrium state (statistical mechanics in a narrow sense) and we can also find a microscopic interpretation of the laws in thermodynamics.
KeywordsQuantum State Density Matrix Statistical Mechanic State Density Canonical Ensemble
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- 2.3D. terHaar: Elements of Statistical Mechanics (Holt, Rinehart and Winston, New York 1961)Google Scholar
- 2.4D. terHaar: Elements of Thermostatics (Holt, Rinehart and Winston, New York 1966)Google Scholar
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- 2.18K. Husimi: Proc. Phys.-Math. Soc. Jpn. 22, 246 (1940)Google Scholar | <urn:uuid:a087083a-f9df-4f6e-b34c-179c7df94c6d> | 3.234375 | 417 | Truncated | Science & Tech. | 48.323352 | 95,604,093 |
All atoms of an element have the same number of protons. When an atom gives off radiation, it turns into a different kind of atom. Some atoms decay very quickly,..Some materials are radioactive. When an atom of a radioactive substance gives off radiation, it becomes a new type of atom. There are two..There is more nitrogen gas in the air than any other kind of gas.
For example, all hydrogen atoms have one proton, all carbon atoms have 6 protons, and all uranium..Carbon-14 is an isotope of the element carbon. Most carbon atoms also have 6 neutrons, giving them an atomic mass of 12 ( = 6 protons 6 neutrons). About 4/5ths of Earth's atmosphere is nitrogen gas!
Traditional radiocarbon dating is applied to organic remains between 500 and 50,000 years old and exploits the fact that trace amounts of radioactive carbon are found in the natural environment.
Carbon-14 dating (also called "radiocarbon dating") is used to determine the age of materials that contain carbon that was originally in living things.The amount of carbon-14 in the air has stayed the same for thousands of years.There is a small amount of radioactive carbon-14 in all living organisms because it enters the food chain.For some reason, which I have not yet figured out, at least one person per week has been asking me about the Carbon-14 Radiometric Dating Technique.They want to know if it is accurate or if it works at all. | <urn:uuid:0afa7b14-6e78-4a0e-9fae-23da19618b5c> | 3.59375 | 311 | Spam / Ads | Science & Tech. | 58.90276 | 95,604,145 |
Space bacteria found in British river could be new power source for the world
- Using microbial fuel cell Bacillus stratosphericus generates twice as much electricity as other bacteria
- Could be used to power appliances in developing countries
Bacteria usually found orbiting high above the Earth have been found in a British river - and could be a new power source for the world.
The mysterious organisms, found in the the mouth of the River Wear, in Sunderland, can generate electricity using a special battery called a microbial fuel cell.
The Bacillus stratosphericus - usually found 20 miles above the Earth - is believed to have been brought to the surface by atmospheric cycling, which causes evaporated water rise into the stratosphere and then fall again.
Powerful: Bacillus stratosphericus can generate twice as much electricity as other types of common bacteria
It is a particularly potent form of bacteria which can be used in a microbial fuel cell (MFC) to convert river waste into power and clean water.
It had double the electricity generating potential of other bacteria and scientists from Newcastle University believe they could be harvested and used in the developing world to power appliances.
Inside an MFC, the organisms produce carbon dioxide, protons and electrons when kept in a solution without oxygen.
Liberated electrons form a negatively charged anode while the protons create a positively charged cathode.
Source of power: The mouth of the River Wear in Sunderland where scientists found the bacteria
This produces both charges necessary to produce an electric current.
Microbial fuel cell: How bacteria can generate electricity
Publishing their findings in the American Chemical Society’s Journal of Environmental Science and Technology, Grant Burgess, Professor of Marine Biotechnology at Newcastle University, said the research demonstrated the 'potential power of the technique'.
He said: 'What we have done is deliberately manipulate the microbial mix to engineer a biofilm that is more efficient at generating electricity.
'This is the first time individual microbes have been studied and selected in this way.
'Finding B.stratosphericus was quite a surprise, but what it demonstrates is the potential of this technique for the future - there are billions of microbes out there with the potential to generate power.'
Prof Burgess said that, isolating 75 different species of bacteria from the River Wear, the team tested the power-generation of each one using a Microbial Fuel Cell (MFC).
By selecting the best species of bacteria, scientists were able to create an artificial biofilm, doubling the electrical output of the MFC from 105 watts per cubic metre to 200 watts per cubic metre.
While still relatively low, this would be enough power to run an electric light and could provide a much-needed power source in parts of the world without electricity.
The use of microbes to generate electricity is not a new concept and has been used in the treatment of waste water and sewage plants.
Prof Burgess said: 'This is a very interesting method of collecting energy from what would otherwise be a valueless resource.'
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|MLA Citation:||Bloomfield, Louis A. "Question 1582: Why does combining red, green, and blue light create white light?"|
How Everything Works 22 Jul 2018. 22 Jul 2018 <http://howeverythingworks.org/print1.php?QNum=1582>.
The color sensing cells in our eyes are known as cone cells and they can detect only three different bands of color. One type of cone cell is sensitive to light in the red portion of the spectrum, the second type is sensitive to the green portion of the spectrum, and the third type is sensitive to the blue portion of the spectrum.
Their sensitivities overlap somewhat, so light in the yellow and orange portions of the spectrum simultaneously affects both the red sensitive cone cells and the green sensitive ones. Our brains interpret color according to which of three cone cells are being stimulated and to what extent. When both our red sensors and our green sensors are being stimulated, we perceive yellow or orange.
That scheme for sensing color is simple and elegant, and it allows us to appreciate many of the subtle color variations in our world. But it means that we can't distinguish between certain groups of lights. For example, we can't distinguish between (1) true yellow light and (2) a carefully adjusted mixture of true red plus true green. Both stimulate our red and green sensors just enough to make us perceive yellow. Those groups of lights look exactly the same to us.
Similarly, we can't distinguish between (3) the full spectrum of sunlight and (4) a carefully adjusted mixture of true red, true green, and true blue. Those two groups stimulate all three types of cone cells and make us perceive white. They look identical to us.
That the primary colors of light are red, green, and blue is the result of our human physiology and the fact that our eyes divide the spectrum of light into those three color regions. If our eyes were different, the primary colors of light would be different, too.
Many things in our technological world exploit mixtures of those three primary colors to make us see every possible color. Computer monitors, televisions, photographs, and color printing all make us see what they want us to see without actually reproducing the full light spectrum of the original. For example, if you used a light spectrum analyzer to study a flower and a photograph of that flower, you'd discover that their light spectra are different. Those spectra stimulate our eyes the same way, but the details of the spectra are different. We can't tell them apart. | <urn:uuid:1fbe0752-440c-4ccc-bdbe-8a24f6261406> | 3.46875 | 525 | Knowledge Article | Science & Tech. | 58.428429 | 95,604,174 |
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Mitochondrial ATP synthase catalyzes ATP synthesis, utilizing an electrochemical gradient of protons across the inner membrane during oxidative phosphorylation. It is composed of two linked multi-subunit complexes: the soluble catalytic core, F1, and the membrane-spanning component, Fo, which comprises the proton channel. The catalytic portion of mitochondrial ATP synthase consists of five different subunits (alpha, beta, gamma, delta, and epsilon) assembled with a stoichiometry of 3 alpha, 3 beta, and single representatives of the gamma, delta, and epsilon subunits. The proton channel likely has nine subunits (a, b, c, d, e, f, g, F6 and 8). This gene encodes the f subunit of the Fo complex. Alternatively spliced transcript variants encoding different isoforms have been identified for this gene. This gene has multiple pseudogenes. Naturally occurring read-through transcription also exists between this gene and the downstream pentatricopeptide repeat domain 1 (PTCD1) gene.
ATP synthase subunit f, mitochondrial
, ATP synthase, H+ transporting, mitochondrial F0 complex, subunit f
, hypothetical protein, clone:2-31
, ATP synthase f chain, mitochondrial
, F1F0-type ATPase subunit f
, F1Fo-ATP synthase complex Fo membrane domain f subunit
, F1Fo-ATPase synthase f subunit
, ATP synthase, H+ transporting, mitochondrial F0 complex, subunit F2
, mitochondrial Atp5j2 | <urn:uuid:927de2b1-7d90-45ee-af02-ba5215dabf39> | 2.65625 | 376 | Knowledge Article | Science & Tech. | 22.48559 | 95,604,180 |
Foreshock migration preceded main Kumamoto earthquake in 2016 Slow slip spreads toward the main quake’s fault
A research group at the University of Tokyo found that the swarm of smaller quakes that acted as a precursor to the main Kumamoto earthquake in 2016 migrated in parallel and perpendicular directions—along the fault-strike and dip, respectively—to the main quake’s fault plane. The finding points out the foreshocks’ effect on the earthquake’s force and suggests the propagation of slow slip movements toward the main shock’s breaking point ultimately set it off.
A series of earthquakes struck the Kumamoto area in the southwestern Japanese island of Kyushu in April 2016. The main shock, defined as the largest quake, which struck on April 16, was a magnitude 7.0 earthquake. It was reported that this was preceded by a magnitude 6.2 foreshock on April 14 through routine observations made by the Japan Meteorological Agency, but details of the seismic events—related to both space and time, and in terms of stress interactions—leading to the main shock had not been fully understood.
The research group led by Associate Professor Aitaro Kato at the University of Tokyo’s Earthquake Research Institute compiled a hypocenter catalog containing highly accurate assessments of the series of seismic activities related to the foreshocks and main shock of the 2016 Kumamoto earthquake, and analyzed in detail changes in the spatiotemporal evolution of earthquakes over time. When the seismologists examined the earthquake catalog, they saw that after the magnitude 6.2 foreshock on April 14, the earthquakes migrated gradually over time.
The migration occurred both parallel to the fault-strike and along the slope of the dip (the upper end being close to the ground and the lower end deeper down), with indication of movement toward the rupture point of the April 16 main shock. Changes in the movement of the Earth’s crust detected by control stations, operated by the Geospatial Information Authority of Japan, situated close to where the foreshocks struck, have in fact indicated gradual movement in the same direction as the large foreshock rupture in the span of time between the magnitude 6.2 foreshock and the main shock.
Such changes were observed at only a few points, and accurately assessing the location and scale of the slip is quite difficult; however, the observed data supports the view that the slip occurred along the foreshocks’ fault plane, increasing the possibility that the slow slip actually occurred there. This suggests that the slow slip movement together with changes in stress brought on by the foreshocks added force to the main shock’s fault plane, causing it to rupture and bring on the earthquake.
It should be mentioned, though, that with the type of information observed in the current study on the migration of earthquakes and the slow slip, we have not yet reached the point where experts can accurately assess whether or not a big earthquake will strike anytime soon. Whether the fault plane of the main quake ultimately ruptures depends on how much stress has accumulated in areas around the main shock’s center. Moving forward, developing methods for assessing such degree of criticality in faults will become important for seismologic research.
“Similar migration of foreshocks over an extended area in subduction zones, the boundaries where oceanic plates are thrust under the continental plates, has been reported in the past,” says Kato. He continues, “The main finding in the current study is that such phenomena also occur, albeit on a small scale, at active faults situated inland.”
Foreshock migration preceding the 2016 Mw 7.0 Kumamoto earthquake, Japan", Geophysical Research Letters Online Edition: 2016/08/16 (Japan time), doi: 10.1002/2016GL070079.
Article link (Publication) | <urn:uuid:f4cc77aa-f3b3-4361-a4ed-f64ce75cab2f> | 3.234375 | 782 | Knowledge Article | Science & Tech. | 33.606118 | 95,604,184 |
First Characterization of a Sensory [FeFe] Hydrogenase
Hydrogenases are enzymes capable of making hydrogen gas (H2) using protons from water, a reaction with relevance to a potential future green energy economy based on H2.
Bacteria containing these enzymes often produce H2 as a waste product during sugar metabolism in the absence of oxygen. Meanwhile, other types of bacteria consume this H2 as an energy source.
Hydrogenases, the key enzymes in both these processes, are only required under specific conditions, and so their synthesis inside the bacterium must be regulated in response to the amount of H2 present. This regulation is achieved using sensory hydrogenases capable of sensing and signaling the concentration of H2 to the bacterial protein synthesis machinery.
One particular class of sensory hydrogenases, the so-called sensory [FeFe] hydrogenases (HydS), have remained completely uncharacterized so far. Now, a team from the Max Planck Institute for Chemical Energy Conversion in Mülheim an der Ruhr in Germany together with the Institute of Low Temperature Science at the University of Hokkaido in Japan, have produced and characterized a HydS enzyme from the thermophilic bacterium Thermotoga maritima.1
Using the recently developed technique of artificial maturation together with advanced spectroscopic methods, the researchers showed that the protein environment of the catalytic center is elegantly tuned to optimize this protein for its sensory function.
The researchers demonstrate that the catalytic center is very sensitive to low amounts of H2 allowing the enzyme to effectively signal the presence of H2 to the regulatory system of the bacterium. This research provides a key step forward for our understanding of how these sensory enzymes work. Furthermore, knowing which adaptations tailor the sensory enzymes for their function tells us about how the other [FeFe] hydrogenases that produce hydrogen work.
Ultimately, a complete picture of the enzyme mechanism may provide important clues for telling chemists how to build better catalysts for water electrolyzers and hydrogen fuel cells, allowing the dream of a future hydrogen energy economy to become a reality.
1. Chongdar N, Birrell JA, Pawlak K, Sommer C, Reijerse EJ, Rüdiger O, Lubitz W, Ogata H (in press) J. Am. Chem. Soc. DOI: 10.1021/jacs.7b11287
The work was supported by the Max Planck Society and in part by JSPS KAKENHI grant number 16K21748.
Nipa Chongdar, James A. Birrell, Krzysztof Pawlak, Constanze Sommer, Edward J. Reijerse, Olaf Rüdiger, Wolfgang Lubitz, Hideaki Ogata: Unique spectroscopic properties of the H-cluster in a putative sensory [FeFe] hydrogenase, Journal of the American Chemical Society, 2017, DOI: 10.1021/jacs.7b11287
Prof. Dr. Wolfgang Lubitz
Max Planck Institute for Chemical Energy Conversion
Dr. Hideaki Ogata
Institute of Low Temperature Science, Hokkaido University
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２８ Loop Quantum Gravity(LQG) 【What is the Universe？】Dialogue with the Universe
[Electromagnetic force + Weak interaction＋Strong interaction ＋ Gravity]
・LQG is an attempt to merge quantum mechanics and general relativity.
・Quantum gravity (QG) is a field of theoretical physics that seeks to describe the force of gravity according to the principles of quantum mechanics.
２８－１ Overview
○In the loop models, the basic structure of space-time turns out to be discrete. In such discrete space-times, there are smallest values for volumes and areas that are not divisible any farther.
○The granular structure of space-time gets rid of the infinities that plague quantum field theory.
○Elementary particles for each type, the rotational speed takes the value of the discrete, as the basic number of Planck constant. For example, an electron rotates at half the speed of Planck constant.
＜Decide the direction of the space from the spin direction of the particle＞
・In the 1950s, by utilizing this principles of the spin, "the Spin network" theory which defines the direction of each point in space from the direction of the electron spin published by Penrose.
・As a specific method, the theory represents a material at a point, and represents the direction at a line, and make a constant volume by planes perpendicular to the line.
・The predicted size of this structure is the Planck length, which is approximately 10－35 meters.
・Space can be viewed as an extremely fine fabric or network "woven" of finite loops. These networks of loops are called spin networks.
・This change in spin network indicates the presence of gravity and elementary particles.
・The granular structure of space-time that is implied by spin networks also gets rid of the infinities that plague quantum field theory.
<img src="https://image.space.rakuten.co.jp/d/strg/ctrl/9/f53b7eb0d5240f971550f3a78a6bb7deedf4df22.214.171.124.2.png" border=0 />
※Spin networks
＜Loop quantum gravity theory creates space, gravity and substance at a time＞
・The evolution of a spin network over time is called a spin foam.
・Spin form changes discretely.
• The time difference is 1 Planck seconds of the change (10-43 seconds), and the time that people feel is what this very short time is stacked.
・The main output of LQG is a physical picture of space where space is granular. It has the same nature as the granularity of the photons in the quantum theory of electromagnetism and the discrete levels of the energy of the atoms.
２８－２ Difference from super string theory
１）In string theory( a quantum theories of gravity) one generally starts with quantized excitations on top of a classically fixed background. LQG is thus described as background dependent. In contrast, LQG, like general relativity, is manifestly background independent.
２）Super string theory requires that space-time have 10 dimensions; LQG is formulated in 4 dimensions.
３）String theory also implies the existence of supersymmetry, in which all known particles have yet-undiscovered partners. Supersymmetry isn’t a feature of LQG.
４）In loop quantum gravity, there is no big bang singularity; instead, the universe´s history can be traced infinitely far into the past, step by step.
※An inflationary expansion might have been driven by quantum-gravitational effects.
・Quantum gravity effects are notoriously difficult to measure because the Planck length is so incredibly small. However recently physicists have started to consider the possibility of measuring quantum gravity effects.
・The Universe can be used as a laboratory to test quantum gravity effects. First, there are accelerators in distant galaxies that produced gamma burst, 10 billion years ago, particles with energies much higher than we can produce in even the largest man-made accelerators, 10 million times higher. Secondly, due to the long times and vast distances involved, effects such as the difference in speeds of these particles (speed of light is energy dependent according to LQG) can be detected over these long distances and times.
・In 2015, the Advanced LIGO team announced that they had detected gravitational waves from a pair of black holes merging.
1. Loop quantum gravity - Wikipedia
2. Loop quantum gravity — Einstein Online
3.String Theory Meets Loop Quantum Gravity | Quanta Magazine
4. Carol Rovelli“Loop quantum gravity”
5.Quantum gravity (QG) - Wikipedia
6.Duality of Spacetime and Matter - NCF.ca
7.Gravitational wave - Wikipedia
8.Ｎｏ．３０ Gravitational Wave
20170421 Split into 3 items | <urn:uuid:d968b9cc-5d8f-46e6-b426-726cf6877507> | 3.390625 | 1,128 | Knowledge Article | Science & Tech. | 45.625422 | 95,604,199 |
Researchers using supercomputer simulations have exposed a very violent and critical relationship between interstellar gas and dark matter when galaxies are born – one that has been largely ignored by the current model of how the universe evolved.
The findings, published today in Science, solve a longstanding problem of the widely accepted model – Cold Dark Matter cosmology – which suggests there is much more dark matter in the central regions of galaxies than actual scientific observations suggest.
“This standard model has been hugely successful on the largest of scales—those above a few million light-years—but suffers from several persistent difficulties in predicting the internal properties of galaxies,” says Sergey Mashchenko, research associate in the Department of Physics & Astronomy at McMaster University. “One of the most troublesome issues concerns the mysterious dark matter that dominates the mass of most galaxies.”
Supercomputer cosmological simulations prove that indeed, this problem can be resolved. Researchers modeled the formation of a dwarf galaxy to illustrate the very violent processes galaxies suffer at their births, a process in which dense gas clouds in the galaxy form massive stars, which, at the ends of their lives, blow up as supernovae.
“These huge explosions push the interstellar gas clouds back and forth in the centre of the galaxy,” says Mashchenko, the lead author of the study. “Our high-resolution model did extremely accurate simulations, showing that this ‘sloshing’ effect – similar to water in a bathtub— kicks most of the dark matter out of the centre of the galaxy.”
Cosmologists have largely discounted the role interstellar gas has played in the formation of galaxies and this new research, says Mashchenko, will force scientists to think in new terms and could lead to a better understanding of dark matter.
The simulations reported in the research paper were carried out on the Shared Hierarchical Academic Research Computing Network (SHARCNET).
Michelle Donovan | EurekAlert!
First machine learning method capable of accurate extrapolation
13.07.2018 | Institute of Science and Technology Austria
A step closer to single-atom data storage
13.07.2018 | Ecole Polytechnique Fédérale de Lausanne
For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.
To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...
For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.
Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...
Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.
A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...
Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.
"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....
Ultra-short, high-intensity X-ray flashes open the door to the foundations of chemical reactions. Free-electron lasers generate these kinds of pulses, but there is a catch: the pulses vary in duration and energy. An international research team has now presented a solution: Using a ring of 16 detectors and a circularly polarized laser beam, they can determine both factors with attosecond accuracy.
Free-electron lasers (FELs) generate extremely short and intense X-ray flashes. Researchers can use these flashes to resolve structures with diameters on the...
13.07.2018 | Event News
12.07.2018 | Event News
03.07.2018 | Event News
16.07.2018 | Physics and Astronomy
16.07.2018 | Life Sciences
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Cloning - Wikipedia
Cloning is the process of producing genetically identical individuals of an organism either naturally or artificially. In nature, many organisms produce clones ...
What is Cloning - Learn.Genetics
Many people first heard of cloning when Dolly the Sheep showed up on the scene in 1997. Artificial cloning technologies have been around for much longer than Dolly, though.
Cloning Fact Sheet - National Human Genome Research ...
Fact sheet published by the National Human Genome Research Institute (NHGRI) about cloning (human cloning, animal cloning, therapeutic cloning, etc.)
Cloning is the process of creating an exact genetic replica of a cell, tissue or organism. Learn about the types and uses in medicine.
cloning | Definition, Process, & Types | Britannica.com
Cloning: Cloning, the process of generating a genetically identical copy of a cell or an organism. Cloning happens often in nature, as when a cell replicates itself asexually without genetic alteration or recombination.
Cloning (Stanford Encyclopedia of Philosophy)
1. What is Cloning? Strictly speaking, cloning is the creation of a genetic copy of a sequence of DNA or of the entire genome of an organism. In the latter sense, cloning occurs naturally in the birth of identical twins and other multiples.
Cloning - Genetics Generation
Cloning A clone is a genetically identical copy of an organism, and it may be naturally occurring or created in the lab. Through the process of asexual reproduction, organisms such as bacteria (and some plants) create offspring that are genetically identical to the parent.
How Cloning Works | HowStuffWorks
Scientists have successfully cloned several animals. But this success has sparked fierce debates about the use and morality of cloning. Find out about cloning and discover some possible uses of this technology.
The Facts and Fiction of Cloning - WebMD
Understanding the real science of cloning behind the headlines and the hubbub.
Cloning - ScienceDaily
Cloning is the process of creating an identical copy of an original organism or thing. A cloning in the biological sense, therefore, is a molecule, single cell (like bacteria, lymphocytes etc.) or multi-cellular organism that has been directly copied from and is therefore genetically identical to another living organism. | <urn:uuid:948a735f-a91f-47b3-ad10-cc2f0b16df0f> | 3.5 | 474 | Content Listing | Science & Tech. | 29.252429 | 95,604,214 |
Showing 1-3 of 3 Resources
Click & LearnThis interactive explores the biology of sex determination and development in humans, set against the backdrop of the different sex testing policies implemented throughout sports history.
Scientists at Work(9 min 55 sec) Planarians have an amazing ability to regenerate lost tissues. In this video, scientists knock out two different genes in planaria to start to understand how the process works—and they generate animals with two heads and two tails!
Scientists at Work(11 min 47 sec) A mini-documentary discussing the remarkable regenerative capabilities of the planarian, and how HHMI researcher Alejandro Sánchez Alvarado uses them to study the biology of stem cells.
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Bigger is better, if you're a leatherback sea turtle.
For the first time, researchers at the University of Wisconsin-Madison, Florida Atlantic University (FAU), and the National Oceanic and Atmospheric Administration (NOAA) have measured the forces that act on a swimming animal and the energy the animal must expend to move through the water.
Scientists studied newborn leatherback sea turtles to create the first models of a swimming animal. Challenges to measuring forces like drag and thrust made this difficult before, but the research team overcame these, offering the opportunity for many more to benefit from their findings.
Credit: Photo courtesy of Jeanette Wyneken, Florida Atlantic University
A surprising finding: Longer, slender turtles are less efficient swimmers than more rotund turtles, which get better stroke for their buck.
By taking these measurements, the research team — led by UW-Madison's Warren Porter — built models of swimming turtles and, in doing so, have enabled others to "compute the energetics, behavior and distributions of a species anywhere on Earth now or in the future," says Porter, a professor of zoology. The findings are published today in the journal PLOS One.
As climate change shifts the habitable ranges of both land and sea animals, and as scientists and others try to reconstruct ancient habitats of long-ago species, the ability to assess and predict an animal's physical interactions with the environment is key. The researchers see their work as instrumental for everyone from land managers to paleoecologists, students and conservationists.
"If you've got mechanistic models, then whatever kind of scenarios you want to run for the environment, you can run these models and have a lot of confidence that they're giving you good numbers," says Porter, who previously developed a model for land animals.
But getting there wasn't easy.
Several labs have tried to model the movements of animals in water but "swimming animals are very, very difficult to measure experimentally," Porter says. "It's very difficult to get drag and thrust."
No one before had been able to measure the fluid dynamics of a swimming creature, or the energetics required to perform the work of moving through water. This allows scientists to measure critical aspects of biology, such as how much food an animal must eat to survive.
It was serendipity that connected Porter and the lead author of the study, Peter Dudley, a former graduate student in Porter's lab, to the scientists at FAU who would eventually help solve the problem.
Jeanette Wyneken, FAU professor of biological sciences, had developed methods to keep newborn leatherback sea turtles in the lab for study. She and her former students created a tether system that allows the turtles to swim freely while also staying safe; the turtles don't recognize barriers and can easily injure themselves in their enclosures.
Porter, Dudley and Todd Jones — Wyneken's former graduate student and now a NOAA physiologist — tethered the turtles to instruments that allowed them to measure the force they produced while swimming. They also measured the oxygen the turtles consumed (a direct measure of their metabolism) and the heat they exchanged with the environment. All the while, the scientists took video of the tiny turtles.
Then the team recreated a virtual environment with a swimming turtle, to see if they could predict how much energy the turtle was using. Dudley, whose background is in engineering, says Porter uses "on-the-ground" engineering tools in his lab.
They scaled this up to model the three-dimensional motion of swimming juvenile leatherback sea turtles , to find power and heat transfer rates during the larger animal's flipper strokes.
It was here, by playing with the parameters of their virtual reality turtles, that the researchers learned husky turtles were better swimmers than their leaner counterparts.
"That was a surprise and I thought it was a mistake when I originally did it," says Dudley, who eventually learned that the flippers of thinner turtles come closer together at the bottom of their stroke than those of larger turtles, causing them to lose power.
It is that question — how does body size interact with the physical environment to constrain evolutionary design — that lies at the crux of the study's findings.
"We can literally design animals now and ask how are they going to function, just like a car or a rocket ship," says Porter. He is currently engaged in a UW-Madison initiative called Climate Quest, a competition to solve climate-change problems, and is putting this expertise to use.
In his project, he is assessing the impact of climate change on milk production in dairy cows in order to "select for cows 50 or 100 years from now," to improve production both now and in the face of a different planet.
"Now that we have (models) for both marine and terrestrial environments, we can answer those types of questions and get back to the big mass extinctions and get some insights into how did animals live before and after those extinctions," Porter says. "Why were the animals that survived able to survive?"
The researchers collaborated with Riccardo Bonazza, a UW-Madison professor of engineering physics, to develop their swimming turtle models. And it was the art department, says Porter, that enabled them to create a virtual swimming turtle.
"When you're looking at a problem, the more different ways you can look at it, the more different perspectives you can get on it, the more ideas you can have on how to deal with it and ... on different directions you can go," says Porter.
The study was funded in part by the UW Foundation and a Disney Worldwide Conservation Fund grant.
CONTACT: Warren Porter, 608-262-1719, firstname.lastname@example.org; Peter Dudley, P.N.D.PhD@gmail.com
Warren Porter | 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...
13.07.2018 | Event News
12.07.2018 | Event News
03.07.2018 | Event News
18.07.2018 | Materials Sciences
18.07.2018 | Life Sciences
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Frog croaks in ultrasound
Thursday, 16 March 2006
The concave-eared torrent frog (Amolops tormotus) is the first non-mammalian species known to use the ultra-high frequencies that humans cannot hear.
It joins bats, dolphins and whales, and a small number of rodents, in the elite club of creatures that can communicate this way.
A US and Chinese team reports its find today in the journal Nature.
Professor Albert Feng of the University of Illinois and team found that male frogs of the species make high-pitched melodic bird-like calls.
The calls sometimes exceeded their recorder's maximum range of 128 kilohertz, more than six times the limit of human hearing.
The frogs inhabit Huangshan Hot Springs, a popular mountainous area west of Shanghai, where there are loud waterfalls and streams.
The high frequencies provide a channel of communication that cannot be disrupted by the lower-frequency rumble of the water, says Feng.
"Nature has a way of evolving mechanisms to facilitate communication in very adverse situations," he says.
"One of the ways is to shift the frequencies beyond the spectrum of the background noise. Mammals such as bats, whales and dolphins do this, and use ultrasound for their sonar system and communication. Frogs were never taken into consideration for being able to do this."
The discovery also answers a puzzle as to why the frogs do not have external eardrums.
"Thin eardrums are needed for detection of ultrasound," says Feng. "Recessed ears shorten the path between the eardrums and the ear, enabling the transmission of ultrasound to the ear."
Ultrasounds are high-pitched sounds with a frequency of more than 20 kilohertz, much higher than the frequency most birds, reptiles and amphibians can hear. | <urn:uuid:176f292a-1e34-424c-8e1a-868cc8c65700> | 3.515625 | 381 | News Article | Science & Tech. | 47.397245 | 95,604,244 |
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Edited By: G Baretta-Bekker, Egbert K Duursma and Bouwe R Kuipers
357 pages, 127 illus
The multidisciplinary character of this encyclopaedia brings together the basic items of marine biology, chemistry, geology, and physical oceanography, by way of 3,000 up-to-date, alphabetically listed keywords. The brief explanation of the concepts, terminology and methods make this book more than a pure glossary or dictionary.
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High diversity in an urban habitat: are some animal assemblages resilient to long-term anthropogenic change?
- 761 Downloads
Urbanization is thought to lead to the loss of biodiversity both because of habitat disturbance and the increased abundance of invasive species. However, most studies of biodiversity in cities are conducted on a short time scale, usually less than 3 years, and so miss the long-term dynamics of communities inhabiting these ecosystems. Here we use a study performed in the early 70’s on North Carolina State University (Raleigh, USA) as a baseline to evaluate the long term effects of disturbance and introduced species on native ant communities. Ant species were sampled almost 40 years later using a variety of sampling techniques in order to maximize species collection. Our results show that while the number of exotic species increased, including three major invasive ants, native ant species richness remained high. Furthermore, our survey was able to add several new records for the area considered, in comparison of the 70’s study, for a total of 89 species known from NCSU campus. After comparison with other studies, our results represent one of the most species-rich urban environments monitored and thus open encouraging perspective on how urban ecosystems could contribute to the preservation of the biodiversity of small-bodies organisms such as ants.
KeywordsUrban ecosystem Long term study Formicidae Disturbance Invasive species
The authors would like to thank Neil McCoy, Katherine Driscoll, Matthew Drew for their help in collecting. We would like to thank Terry Nuhn for discussion about his collection. Thank you also to Alex Wild for authorizing the use of his pictures. Finally, we’d like to thank two anonymous reviewers for their comments on a previous version of the manuscript. The work of RRD and BG was supported by a NASA Biodiversity Grant (ROSES-NNX09AK22G), support from a USGS grant to the Climate Science Center and an NSF-CAREER grant (09533390).
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- Wetterer JK (2009) Worldwide spread of the Penny ant, Tetramorium bicarinatum (Hymenoptera: Formicidae). Sociobiology 54:811–830Google Scholar | <urn:uuid:e07f8957-2424-47a7-839a-9ae6edde1e8d> | 3.1875 | 1,385 | Academic Writing | Science & Tech. | 40.192062 | 95,604,294 |
Emory University scientists have for the first time used a new class of luminescent "quantum dot" nanoparticles in living animals to simultaneously target and image cancerous tumors. The quantum dots were encapsulated in a highly protective polymer coating and attached to a monoclonal antibody that guided them to prostate tumor sites in living mice, where they were visible using a simple mercury lamp. The scientists believe the ability to both target and image cells in vivo represents a significant step in the quest to eventually use nanotechnology to target, image, and treat cancer, cardiovascular plaques, and neurodegenerative disease in humans. The findings were published on-line July 18 in the journal Nature Biotechnology and will appear in the journals August 1 print edition.
The research team was led by Shuming Nie, PhD, a nanotechnology expert and a professor in the Coulter Department of Biomedical Engineering at Emory and the Georgia Institute of Technology and in Emorys Winship Cancer Institute, and by Lelund Chung, PhD, professor of urology in Emory University School of Medicine and the Winship Cancer Institute. Quantum dots are nanometer-sized luminescent semiconductor crystals that have unique chemical and physical properties due to their size and their highly compact structure. Quantum dots can be chemically linked (conjugated) to molecules such as antibodies, peptides, proteins or DNA and engineered to detect other molecules, such as those present on the surface of cancer cells.
The researchers injected human prostate cancer cells under the skin of mice to promote growth of solid prostate tumors. They then encapsulated quantum dots, made from cadmium selenide, within a highly protective coating called an ABC triblock copolymer, and over-coated the particle-polymer composite with poly (ethylene glycol). They injected the quantum dots into the circulatory system of the mice first to test "passive" targeting of the tumor. Tumors grow extra blood vessels in a process called angiogenesis. These angiogenic vessels are very porous, which allowed the quantum dots to leak out and accumulate at the tumor sites, where they could be detected by fluorescence imaging.
Holly Korschun | EurekAlert!
World’s Largest Study on Allergic Rhinitis Reveals new Risk Genes
17.07.2018 | Helmholtz Zentrum München - Deutsches Forschungszentrum für Gesundheit und Umwelt
Plant mothers talk to their embryos via the hormone auxin
17.07.2018 | Institute of Science and Technology Austria
For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.
To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...
For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.
Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...
Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.
A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...
Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.
"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....
Ultra-short, high-intensity X-ray flashes open the door to the foundations of chemical reactions. Free-electron lasers generate these kinds of pulses, but there is a catch: the pulses vary in duration and energy. An international research team has now presented a solution: Using a ring of 16 detectors and a circularly polarized laser beam, they can determine both factors with attosecond accuracy.
Free-electron lasers (FELs) generate extremely short and intense X-ray flashes. Researchers can use these flashes to resolve structures with diameters on the...
13.07.2018 | Event News
12.07.2018 | Event News
03.07.2018 | Event News
16.07.2018 | Physics and Astronomy
16.07.2018 | Life Sciences
16.07.2018 | Earth Sciences | <urn:uuid:8c04a4a5-7f5b-4ed2-a6be-6620aa36f721> | 3.03125 | 1,116 | Content Listing | Science & Tech. | 32.401278 | 95,604,324 |
Large variation in mitochondrial DNA of sexual and parthenogenetic Dahlica triquetrella (Lepidoptera: Psychidae) shows multiple origins of parthenogenesis
Elzinga, Jelmer A.
Shama, Lisa N.S.
- Journal Article
Rights / licenseCreative Commons Attribution 2.0 Generic
Background Obligate parthenogenesis is relatively rare in animals. Still, in some groups it is quite common and has evolved and persisted multiple times. These groups may provide important clues to help solve the ‘paradox of sex’. Several species in the Psychidae (Lepidoptera) have obligate parthenogenesis. Dahlica triquetrella is one of those species where multiple transitions to parthenogenesis are postulated based on intensive cytological and behavioural studies. This has led to the hypothesis that multiple transitions from sexuals to diploid parthenogens occurred during and after the last glacial period, followed by transitions from parthenogenetic diploids to parthenogenetic tetraploids. Our study is the first to test these hypotheses using a molecular phylogeny based on mtDNA from multiple sexual and parthenogenetic populations from a wide geographic range. Results Parthenogenetic (and sexual) D. triquetrella are not monophyletic, and considerable sequence variation is present suggesting multiple transitions to parthenogenesis. However, we could not establish ancestral sexual haplotypes from our dataset. Our data suggest that some parthenogenetic clades have evolved, indicating origins of parthenogenesis before the last glacial period. Conclusions Multiple transitions to parthenogenesis have taken place in Dahlica triquetrella, confirming previous hypotheses. The number of different parthenogenetic clades, haplotypes and their apparent evolutionary age, clearly show that parthenogenesis has been a very successful reproductive strategy in this species over a long period Show more
Journal / seriesBMC Evolutionary Biology
Pages / Article No.
SubjectAsexual; Automixis; COI; COII; Phylogeny; Tetraploid
Organisational unit03705 - Jokela, Jukka
MoreShow all metadata | <urn:uuid:be850a7a-6091-400b-a9be-49c470ed037f> | 2.59375 | 454 | Academic Writing | Science & Tech. | -8.724047 | 95,604,325 |
How scientists discovered our first interstellar mystery visitor
The astronomy world has been abuzz recently with the discovery of a new object cutting through our solar system. Its path indicates it came from interstellar space — the first body of its kind ever observed.
When it was first discovered, astronomers thought this object was a comet and gave it the name C/2017 U1, but further observations revealed the fast-moving object did not have a tail of dust and gas as comets do. Instead, its image was seen as slightly extended due to its rapid motion across the sky.
Within hours of the discovery being announced in the early morning of Oct. 25, the world’s astronomers began to train their facilities on this unusual object.
I’m an astronomer with the National Research Council of Canada, a leader of the Outer Solar System Origins Survey (OSSOS) and member of the Colours for OSSOS (ColOSSOS) project that is measuring the surface colours of Kuiper belt objects discovered in OSSOS. The ColOSSOS team immediately began observing this unusual visitor.
What is this thing?
The initial discovery announcement includes information from 10 observatories, each with its own team of astronomers. These observatories would have been privately alerted to the existence of this unusual detection and asked to provide confirming observations. This is a common practice to avoid a false announcement of an object’s discovery when the orbit is significantly different than expectations.
The International Astronomical Union designated the the object A/2017 U1. It’s not the most romantic name conceivable but fascinating nonetheless.
The name A/2017 U1 is a code describing the object. A for asteroid, followed by the year, bi-weekly period U (astronomers break the year into 26 two-week periods) and the number 1 to indicate this is the first object in this class in 2017.
In reality, however, this is the first-ever known interstellar asteroid that humans have directly observed.
From early in the process of the formation of planetary systems there is a rather large surplus of material — debris — that remains, which is not taken up into major planets.
In our solar system, the asteroid belt is the nearest accessible remnant of such debris. The asteroid that killed the dinosaurs likely came from this belt of material.
But the asteroid belt is a tiny fraction of the debris that a typical planetary system produces. Looking out at nearby stars that appear to be forming planetary systems, such as Epislon Eridani, we can see rings of billions of particles of debris. These rings of dusty debris are themselves only remnants of the initial material.
Why so much debris? Once planets form, chaos takes over. Giant planets push and pull on each other with their massive gravity, scattering each other about and ejecting billions of smaller objects — some as large as thousands of kilometres across — into the depths of space.
In our solar system, some of the material forms a halo of objects orbiting the sun at distances of 10,000 to 100,000 astronomical units (the Oort Cloud). An astronomical unit is the average distance between the sun and earth — about 149,597,870 kilometres — which is the standard unit of measure in planetary science.
The physics of planet formation indicates that many billions of small objects — up to a few kilometres across — are formed for every object the size of Pluto. Some scientists argue that the large objects accrete from dust sizes and up, while others contend that large objects — 100 kilometres across or more — form in single events and then grind down to smaller pieces.
Regardless, these small objects can be held in very distant orbits or ejected from the influence of a star’s gravity entirely. Once ejected, they become free-floating planetary mass objects, drifting through our galaxy — if you can call 80,000 km/h drifting.
The existence of free floating planets that formed in orbit around a star and were then ejected has long been discussed and provided the first direct evidence for the existence of such planetary mass objects floating through space.
Given models of planet formation, astronomers understood that many asteroid-sized objects should be freely floating also, but would they ever be detected? Most agreed that was unlikely, but not impossible.
Discovering A/2017 U1 and its origins
The Panoramic Survey Telescope and Rapid Response System (PanSTARRS) survey of the sky is designed to discover and track objects that might be on a collision course with the Earth. PanSTARRS surveys the entire sky every few nights and has discovered thousands of asteroids, near and far, in our solar system.
One part of the mission is to alert supporting facilities, and the population of Earth, if an object with a high likelihood of Earth impact is detected. The massive data volumes produced by PanSTARRS are searched every morning and alerts to new and interesting discoveries are sent out to the world community. It is because of this machinery that astronomers were alerted to the existence of A/2017 U1.
Dr. Joe Masiero of NASA’s Jet Propulsion Laboratory had the 200-inch (5-metre) Hale telescope at Mount Palomar observatory in California trained on the object within hours of the public announcement after being alerted over Twitter. Two days later, the initial draft of an article describing his observations was online. These initial measurements are quite rough and the weather did not cooperate, but they show that the object is red in colour, much like members of the Kuiper belt — and unlike the much closer asteroid belt.
These facts, along with the asteroid’s trajectory, suggest it is of interstellar origin.
More details of the properties of this visitor will be analyzed in the coming days. The ColOSSOS group obtained observations of the object with the Gemini eight-metre telescope in Hawaii a few days ago. Details of those observations, along with those from other groups, will soon be published on arxiv.org.
One thing we are left to contemplate is the home from which this object made its journey to our region of space. The trajectory excludes the possibility that this object is from our solar system. This is a visitor from another star — a natural interstellar spaceship.
Eric Mamajek, deputy program schief scientist at NASA’s Exoplanet Exploration Program, reports that A/2017 U1’s motion velocity relative to the galactic centre makes stars in the group with Epsilon Eridani a plausible origin. If e-Eri was its home, then the object has come from just 10.5 light-years away, a journey of about 120,000 thousand years given its current speed — a mere blink in time.
A/2017 U1 is a visitor from another world. The question that remains: As with Arthur C. Clarke’s visitors, do they come in threes? | <urn:uuid:497f968a-68f6-4d29-8625-8ffd5e7da8f7> | 3.65625 | 1,404 | News Article | Science & Tech. | 42.584853 | 95,604,335 |
Imagine if every animal and plant on the planet collapsed into a single population each, says ecologist Gerardo Ceballos. If lions disappeared except from one small corner of Kenya, the prey they keep in check would run amok everywhere else. If sparrows were no more except in one Dutch forest, the seeds that sparrows disperse would stay in place everywhere else. If honeybees became isolated to one American meadow, the flowers that they pollinate would fail to reproduce everywhere else. None of those species would be extinct per se, “but we’d still be in very bad shape,” says Ceballos.
He uses this thought experiment to show that fixating on the concept of extinction can lead scientists to overestimate the state of the planet’s health. Extinction obviously matters. If a species is completely wiped out, that’s an important and irreversible loss. But that flip from present to absent, extant to extinct, is just the endpoint of a long period of loss. Before a species disappears entirely, it first disappears locally. And each of those local extinctions—or extirpations—also matters.
“If jaguars become extinct in Mexico, it doesn’t matter if there are still jaguars in Brazil for the role that jaguars play in Mexican ecosystems,” says Ceballos. “Or we might able to keep California condors alive forever, but if there are just 10 or 12 individuals, they won’t be able to survive without human intervention. We’re missing the point when we focus just on species extinction.”
He and his colleagues, Paul Ehrlich and Rodolfo Dirzo, have now tried to quantify those local losses. First, they analyzed data for some 27,600 species of land-based vertebrates, and found that a third of these are in decline. That doesn’t mean they are endangered: A third of these declining species are listed as “low concern” by the International Union for Conservation of Nature, meaning that they aren’t in immediate peril. But that, according to Ceballos’s team, provides a false sense of security. Barn swallows, for example, still number in the millions, but those numbers are going down, and the birds are disappearing from many parts of their range. “Even these common species are declining,” says Ceballos. “Eventually, they’ll become endangered, and eventually they’ll be extinct.”
The team also analyzed detailed historical data for 177 species of mammals. In the last century, every one of these species has lost at least 30 percent of its historical range, and almost half have lost more than 80 percent. Consider the lion. If you divide the world’s land into a grid of 22,000 sectors, each containing 10,000 square kilometers, around 2,000 of those would have been home to lions at the start of the 20th century. Now, just 600 of them are. These royal beasts, which once roamed all over Africa and all the way from southern Europe to northern India, are now confined to pockets of sub-Saharan Africa, and a single Indian forest. Their numbers have fallen by 43 percent in the last two decades.
Several other species that were once thought to be safe are also now endangered. Since the 1980s, the giraffe population has fallen by up to 40 percent, from at least 152,000 animals to just 98,000 in 2015. In the last decade, savanna elephant numbers have fallen by 30 percent, and 80 percent of forest elephants were slaughtered in a national park that was one of their last strongholds. Cheetahs are down to their last 7,000 individuals, and orangutans to their last 5,000.
All told, “as much as 50 percent of the number of animal individuals that once shared Earth with us are already gone, as are billions of populations,” Ceballos and his colleagues write. “While the biosphere is undergoing mass species extinction, it is also being ravaged by a much more serious and rapid wave of population declines and extinctions.”
Strong words, but “one has to be incredibly cautious to not be alarmist,” Ceballos tells me.
I point out that the paper in which he describes his new findings begins with the words “biological annihilation,” which sure sounds a little alarmist.
“It would be alarmist if we didn’t have the data,” he counters. “Now it would be irresponsible on our part to not use strong language. I wish we could say we are wrong but unfortunately, this is what is happening.”
These claims feed into a broader debate about whether the Earth is in the middle of a new mass extinction—a crisis in which the majority of living species blink out of existence. There have been five such catastrophes in the planet’s past, the most famous and recent of which wiped out most of the dinosaurs. Scientists like Ceballos, Ehrlich, and Dirzo argue that humans are kicking off the sixth such event.
That seems intuitively right, given what Ceballos and others have found. But other scientists—including many paleontologists who actually study the historical big five—think that the current crisis, though severe, comes nowhere close to those ancient Ragnaroks.
Their argument, as Peter Brannen recently recounted in The Atlantic, is that people underestimate how bad the earlier mass extinctions truly were. The worst of them—the so-called Great Dying at the end of the Permian period—claimed around 97 percent of all species on Earth. And all five mass extinctions killed off not just charismatic megafauna—the equivalents of lions and elephants—but hardy, ubiquitous species like insects and plants. Critically, they finished off widespread species like clams and hard-shelled plankton whose relatively sudden absence is plain to see in the fossil record.
But Ceballos argues that such species are under threat. Although he only looked at mammals and other vertebrates, other researchers have also documented striking declines among insects, snails, and more.
He also says that it’s a question of rates. Extinction may be a natural part of life, but in 2011, one team showed that mammals are going extinct at 3 to 80 times their usual pace. Four years later, Ceballos and his team confirmed that that number of vertebrate species that we’ve lost in the last century would normally have taken between 800 and 10,000 years to disappear. We may not be in a full-blown mass extinction yet, but we’re certainly in the earliest stages. “At the end of this, we’ll probably be able to say, yes, we were in the sixth mass extinction and we lost 75% of everything,” he says. “But we don’t have to wait until the end.”
The problem with this reasoning, says Doug Erwin from the Smithsonian Institution, is that it misleadingly compares what happened in the last century to what happened over the last several million years. “Any comparison of a long-term rate to a short term one almost inevitably comes up with a higher short-term rate,” he says, because the longer intervals average out a lot of fluctuations, while “short-term rates are generally only calculated when they are high.” Erwin isn’t downplaying the magnitude of the current crisis, but he says that Ceballos isn’t comparing like for like.
It’s an odd debate because both sides have a lot of common ground. Erwin says that mass extinctions are huge, runaway, snowballing events; if we were already in one, it’d be too late to do anything about it. Ceballos says that it’s important to recognize that we’re in the early stages, precisely because we still have a small window in which to avert it. They’re both ultimately saying the same thing, even though they disagree about how to label the emergency.
“The real trouble with mass extinctions, from a modern perspective, is that it's really hard to know you're in one before it’s too late,” says Jacquelyn Gill from the University of Maine. “By the time you compile the casualty list, the damage is done. What's really powerful about [Ceballos’s new] study is that it focuses not on the losses, but on the early warning signals. Population declines are a common precursor to extinction, and it's a process we can actually do something about.”
“At the end of the day, protecting biodiversity is the goal,” she adds. “Even if this isn't a mass extinction, we're clearly still losing species that we care about. The loss of the white rhino hurts even if wasn't geologically superlative.”
We want to hear what you think. Submit a letter to the editor or write to firstname.lastname@example.org. | <urn:uuid:85dfad4f-52b3-4809-b2e7-e8fec688379f> | 4 | 1,925 | News Article | Science & Tech. | 50.403299 | 95,604,337 |
The discovery, announced on March 28,, is forcing scientists to rethink their ideas about the formation of galaxies.
“We didn’t expect that this could happen,” said Yale University astronomer Pieter van Dokkum, lead author of the research published in the journal Nature.
Paradoxically, the discovery of a galaxy without dark matter may actually confirm that the stuff actually exists by contradicting hypotheses advanced by dark matter doubters.
Van Dokkum said the galaxy, called NGC1052-DF2 and located about 65 million light years away from Earth, also appears to be devoid of gas and is relatively sparsely populated by stars.
It is about the same size as the Milky Way, but has roughly 250 times fewer stars: 400 million compared to the Milky Way’s 100 billion stars. It is classified as an ultra-diffuse galaxy, a kind first recognized in 2015.
Dark matter, which is invisible, is thought to comprise about a quarter of the universe’s combined mass and energy and about 80 percent of its total mass, but has not been directly observed. Scientists believe it exists based on gravitational effects it seems to exert on galaxies.
The universe’s ordinary matter includes things like gas, stars, black holes and planets, not to mention shoes, umbrellas, platypuses and whatever else you might see on Earth.
“Dark matter is not something that galaxies can sort of swap in or out of, like it’s kind of an optional thing that galaxies sometimes have and sometimes don’t,” van Dokkum said.
“We really thought that this is the essence of what a galaxy is, that galaxies are built from, initially, a bunch of dark matter and that all the stars and all the planets and everything else is just a little frost on top,” van Dokkum added.
The scientists spotted NGC1052-DF2 using the Dragonfly Telephoto Array, a telescope in New Mexico. They do not know how it formed, but have some hypotheses, including the possibility that a cataclysm within NGC1052-DF2 swept away all its gas and dark matter or that a massive nearby galaxy played havoc with it.
Van Dokkum said NGC1052-DF2 is so sparse that “it is literally a see-through galaxy.” | <urn:uuid:aa6972a7-8d57-4111-ac36-f78764e6d73a> | 3.796875 | 498 | News Article | Science & Tech. | 44.683086 | 95,604,355 |
The Solar System is so complex! Just when climatologists think they have it figured out, they discover how little they understand. Here's an example:
The thermal structure and composition of the atmosphere is determined fundamentally by the incoming solar irradiance. Radiation at ultraviolet wavelengths dissociates atmospheric molecules, initiating chains of chemical reactions—specifically those producing stratospheric ozone—and providing the major source of heating for the middle atmosphere, while radiation at visible and near-infrared wavelengths mainly reaches and warms the lower atmosphere and the Earth’s surface1. Thus the spectral composition of solar radiation is crucial in determining atmospheric structure, as well as surface temperature, and it follows that the response of the atmosphere to variations in solar irradiance depends on the spectrum2. Daily measurements of the solar spectrum between 0.2 µm and 2.4 µm, made by the Spectral Irradiance Monitor (SIM) instrument on the Solar Radiation and Climate Experiment (SORCE) satellite3 since April 2004, have revealed4 that over this declining phase of the solar cycle there was a four to six times larger decline in ultraviolet than would have been predicted on the basis of our previous understanding. This reduction was partially compensated in the total solar output by an increase in radiation at visible wavelengths. Here we show that these spectral changes appear to have led to a significant decline from 2004 to 2007 in stratospheric ozone below an altitude of 45 km, with an increase above this altitude. Our results, simulated with a radiative-photochemical model, are consistent with contemporaneous measurements of ozone from the Aura-MLS satellite, although the short time period makes precise attribution to solar effects difficult. We also show, using the SIM data, that solar radiative forcing of surface climate is out of phase with solar activity. Currently there is insufficient observational evidence to validate the spectral variations observed by SIM, or to fully characterize other solar cycles, but our findings raise the possibility that the effects of solar variability on temperature throughout the atmosphere may be contrary to current expectations.
Correspondence to: Joanna D. Haigh1 Email: firstname.lastname@example.org
Appears in Nature 467, 696-699 (7 October 2010)
Published here on 6 Oct. 2010
Ken Ham’s Darwinism: On The Origin of Species by Means of Hyper-Evolution Following Noah’s Flood - Young life creationists, or baraminologists as they prefer to be called, have experienced a paradigm shift over the past three decades. During that time th...
3 days ago | <urn:uuid:300aba83-4ce9-49e2-87eb-1ca10563c45a> | 3.65625 | 527 | Personal Blog | Science & Tech. | 25.25251 | 95,604,368 |
Two Types of Inulin Fructotransferases
AbstractInulin is a polysaccharide contained in chicory, dahlia, and other plants. An oligosaccharide DFA III is produced from inulin using a microbial enzyme, inulin fructotransferase (DFA III producing) [EC 188.8.131.52]. The oligosaccharide DFAIII has a unique functionality that accelerates the assimilation of minerals (Ca, Fe, and so on) from intestines. Therefore, it has a potential for the improvement of osteoporosis and iron deficiency anemia. The production of DFA III was industrialized in 2004 in Japan. Another oligosaccharide DFA I is produced from inulin by another enzyme, inulin fructotransferase (DFA I producing) [EC 184.108.40.206]. The oligosaccharide DFA I has half the sweetness of sucrose. The genes of the two enzymes were cloned and the nucleotide sequences were determined. The deduced amino acid sequences of two enzyme genes had a homology of 49.8%. View Full-Text
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Haraguchi, K. Two Types of Inulin Fructotransferases. Materials 2011, 4, 1543-1547.
Haraguchi K. Two Types of Inulin Fructotransferases. Materials. 2011; 4(9):1543-1547.Chicago/Turabian Style
Haraguchi, Kazutomo. 2011. "Two Types of Inulin Fructotransferases." Materials 4, no. 9: 1543-1547. | <urn:uuid:dd140b68-670f-461c-96f2-b12b30b7fbc6> | 2.71875 | 355 | Academic Writing | Science & Tech. | 35.08125 | 95,604,393 |
Between now and the end of July, all five of the brightest planets can be spotted in Santa Barbara's evening skies, with the Moon acting as a convenient guidepost to help you find them
On dark evenings starting now through June 22, head for a spot with a dark southern horizon and try to spot the 4 Vesta asteroid.
Santa Barbara's evening skies for the first half of June will feature numerous visible passes by the International Space Station, weather permitting.
Last Tuesday afternoon, an asteroid estimated to be about 300 feet across made a close approach, passing Earth at about half the distance to the Moon, or roughly 126,000 miles.
With the Sun now well north of the equator, Santa Barbara will get some long and bright visible evening passes from the International Space Station to start this series, weather permitting.
On Thursday evening, weather permitting, we'll get some nice celestial views as the Sun sets.
On Saturday morning will be the first launch of an interplanetary mission from Vandenberg, NASA's InSight mission to Mars to gather information on the interior of the red planet.
Santa Barbara will get a very nice series of visible evening passes from the International Space Station over the next week or so, weather permitting.
The International Space Station will once again be visible in Santa Barbara's evening skies, assuming we get a break in the clouds.
The International Space Station will visit Santa Barbara's evening skies, weather permitting, in the week leading up to Valentine's Day.
Chuck shares photos of the Super Blue Blood Moon from the Bridge to Nowhere on Wednesday morning.
This Wednesday, January 31, we will experience a Super Blue Blood Moon.
To close out January, the International Space Station will once again be visible in Santa Barbara's evening skies, weather permitting.
Last Monday, November 28, was the 50th anniversary of the discovery of pulsars: highly magnetized, rotating neutron star or white dwarf, that emits a beam of electromagnetic radiation.
The International Space Station will be cruising through Santa Barbara's evening skies as we're eating turkey and leftovers.
If you want to see a spectacular dawn conjunction of the two brightest planets, Venus and Jupiter, look to the east on the mornings of November 12, 13, and 14.
Chuck points out some really really big stars that are brightening up our skies lately.
On Wednesday evening, an approximately 50-foot across Potentially Hazardous Asteroid named 2012 TC4 made a close flyby of the Earth, passing within about 32,000 miles.
The mid-October skies above Santa Barbara will feature several nice visible passes by the International Space Station.
The International Space Station is back in Santa Barbara’s skies to celebrate the beginning of Autumn and the latest loony prophecy for the end of the world.
Max shares an aerial photo of the Big Dipper.
A large Potentially Hazardous Asteroid named after Florence Nightingale will make a fairly close approach to the Earth on Friday.
An edhat reader shares an image of the total eclipse from Oregon.
More on the eclipse!
The International Space Station is back for some early August Santa Barbara appearances.
July and August are excellent times to view the Milky Way.
The friendly astronomers of the Santa Barbara Astonomical Unit are holding numerous free public star parties throughout the summer.
The International Space Station is back for some late July trips across the skies of Santa Barbara.
Chuck shares details of the International Space Station passing over Santa Barbara skies. | <urn:uuid:75ca6743-355a-4d06-a6a1-5c00caa63f15> | 2.625 | 716 | Content Listing | Science & Tech. | 40.664233 | 95,604,406 |
Functions of carbohydrates
The main role of carbohydrates is to provide energy.
Living organisms use monosaccharides to fuel metabolic reactions. They produce ATP in a process of aerobic cellular respiration.
Stored form of carbohydrates is polysaccharides such as starch and glycogen.
Besides this base task - to serve as a source of energy, carbohydrates are irreplaceable for other cell functions.
For example, plants use cellulose for structural support. Peptidoglycan forms cell walls of bacteria.
To enhance the functionality of biological molecules, cells attach carbohydrates to proteins and lipids. Modified structures of lipids in cell membranes improve cell signaling and immune responses.
In the human body, carbohydrates function as part of hormones such as follicle-stimulating hormone and luteinizing hormone.
Monosaccharides - ribose and deoxyribose - are important parts of nucleotides, which are building blocks of DNA and RNA.
3 different types of carbohydrates
General formula of carbohydrates can be represented by the stoichiometric formula (CH2O)n, where n is the number of carbons in the molecule.
In carbohydrate molecules the ratio of carbon to hydrogen to oxygen is 1:2:1.
The general formula of carbohydrates and the ratio of their atoms also explain the origin of the term “carbohydrate”: the components are carbon (“carbo”) and the components of water (hence, “hydrate”).
There are 3 different types of carbohydrates:
Monosaccharides are the simplest form of 3 types of carbohydrates.
They (mono- = “one”; sacchar- = “sweet”) are simple sugars, the most common of which is glucose.
Most monosaccharide names end with the suffix -ose.
- If the sugar has an aldehyde group (the functional group with the structure R-CHO), it is known as an aldose,
- if it has a ketone group (the functional group with the structure R-C(=O)-R'), it is known as a ketose.
In monosaccharides, the number of carbons usually ranges from three to seven.
Depending on the number of carbons in the sugar, they also may be known as trioses (three carbons), pentoses (five carbons), and hexoses (six carbons).
The two simplest monosaccharides are:
- dihydroxyacetone (a triose with a ketone group),
- glyceraldehyde (a triose with an aldehyde group).
Three common pentose sugars are:
- ribose (a component of RNA),
- deoxyribose (a sugar in DNA),
- ribulose (used in photosynthesis).
Three common hexoses are:
- glucose (source of energy for all cells),
- galactose (milk sugar),
- fructose (fruit sugar).
Although glucose, galactose, and fructose all have the same chemical formula (C6H12O6), they differ structurally and chemically (and are known as isomers) because of the different arrangement of functional groups around the asymmetric carbon; all of these monosaccharides have more than one asymmetric carbon.
Monosaccharides can exist as a linear chain or as ring-shaped molecules; in aqueous solutions they are usually found in ring forms.
Ring forms of monosaccharides serve as a monomer of carbohydrate polymers.
Ring structure of glucose
When a glucose molecule forms a six-membered ring, there is a 50 percent chance that the hydroxyl group at carbon one will end up below the plane of the ring.
Thus the ring structure of glucose can have two different arrangements of the hydroxyl group (-OH) around the anomeric carbon.
The anomeric carbon - carbon 1 that becomes asymmetric in the process of ring formation, stereocenter.
If the hydroxyl group is below carbon number 1 in the ring structure of glucose, it is said to be in the alpha (α) position, and if it is above the plane, it is said to be in the beta (β) position.
alpha (α) position and beta (β) position of the anomeric carbon of the ring structure of glucose
Oligosaccharides are second type of carbohydrates.
Usually oligosaccharides contain two or three simple sugars attached to one another by covalent bonds called glycosidic linkages.
Glycosidic bonds can be of the alpha or the beta type.
Examples of important disaсcharides are:
Chemical structure of maltose is composed of two α - ring structures of glucose molecules held together by a 1-4 glycosidic linkage.
Maltose can be found in grains which is used in the production of beer.
Sucrose molecular structure consists of α - ring structure of glucose and α - ring structure of fructose with a 1-2 glycosidic linkage between them.
Sucrose is the most known as common table sugar.
Molecular structure of lactose is composed of such monomers of carbohydrates as α - ring structure of glucose and α - ring structure of galactose.
Lactose is normally found in milk.
Polysaccharides are the type of carbohydrate polymers that are made up of several hundred to several thousand monomers of carbohydrates - monosaccharides held together by glycosidic linkages.
Some polysaccharides are straight chains, and some are branched.
Starch, glycogen, cellulose, and chitin are primary examples of polysaccharides.
Starch is the stored form of carbohydrate polymers in plants and is made up of a mixture of amylose and amylopectin (both polymers of glucose).
Starch is made up of monomer of carbohydrates - glucose that are joined by α 1-4 or α 1-6 glycosidic bonds.
The numbers 1-4 and 1-6 refer to the carbon number of the two residues that have joined to form the bond.
Amylose is starch formed by unbranched chains of glucose monomers (only α 1-4 linkages), whereas amylopectin is a branched polysaccharide (α 1-6 linkages at the branch points).
Glycogen is the storage form of glucose in humans and other vertebrates and is made up of monomers of glucose.
Cellulose is the primary structural polysaccharide in all plants, and is a major component in cell walls. It is a straight chain polymer of β - ring structure of glucose that is held together by 1-4 glycosidic linkages.
Every other glucose monomer in cellulose is flipped over, and the monomers are packed tightly as extended long chains. This gives cellulose its rigidity and high tensile strength - which is so important to plant cells.
While the β 1-4 linkage cannot be broken down by human digestive enzymes, herbivores such as cows, koalas, buffalos, and horses are able, with the help of the specialized flora in their stomach, to digest plant material that is rich in cellulose and use it as a food source.
A cellulose-like polymer exists in the hard exoskeleton of insects, crustaceans. This polymer is known as chitin, which is a polysaccharide-containing nitrogen.
It is made of repeating units of N-acetyl-β-d-glucosamine, a modified monomer of carbohydrates - glucose.
Chitin is also a major component of fungal cell walls.
Fungi are neither animals nor plants and form a kingdom of their own in the domain Eukarya.
Carbohydrates - naming and classification | <urn:uuid:7dc4107b-8143-49ef-b9b2-f71aac2631f2> | 3.953125 | 1,672 | Knowledge Article | Science & Tech. | 30.468869 | 95,604,455 |
Authors: Raji Heyrovska
During the synthesis of a deuteron nucleus from a neutron and a proton, an electron, positron pair and an antineutrino, neutrino pair are released. The electrostatic energy (order of MeV) of the former pair is released as gamma radiation and is equivalent to the mass defect. Based on the largest mass defect per nucleon (MDPN) as the criterion of nuclear stability, it. is estimated that, in general, for a nuclide X(Z,N) with a fractional mass defect f , the MDPN(nu) due to neutrinos/antineutrinos alone is equal to fk(n) (Z/(z+N)), where the proportionality constant k(n) = 0.7 micro atomic mass unit. Since f is of the order of 0.01, MDPN(nu) is in nano-atomic mass units, which is the right order of the mass of neutrinos. (This paper is reprinted with permission from Desktop publication (1998) by Arjun consultancy & publishing Inc.,Wayne N.J.(USA))
Comments: 13 pages. Text: pp 1-7; pages 8-13 (please ignore the handwritten numbers): Table 1, legends for Figs. and 3 Figures; Paper presented at 216th National Meeting of the American Chemical Society, Boston, Aug. 1998, short abstract no. 9.
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From: European Space Agency
Posted: Tuesday, November 3, 2009
The second satellite in ESA's Earth Explorer series - the Soil Moisture and Ocean Salinity (SMOS) mission - and the second demonstration satellite under ESA's Project for Onboard Autonomy (Proba-2) were launched into orbit last night from northern Russia.
SMOS will play a key role in the monitoring of climate change on a global scale. It is the first ever satellite designed both to map sea surface salinity and to monitor soil moisture on a global scale. It features a unique interferometric radiometer that will enable passive surveying of the water cycle between oceans, the atmosphere and land.
Travelling piggyback on the launch of SMOS, Proba-2 is a follow-on to the highly successful Proba-1 satellite launched in 2001. It will demonstrate 17 advanced satellite technologies -such as miniaturised sensors for ESA's future space probes and a highly sophisticated CCD camera with a wide angle view of about 120o - while carrying a set of four science instruments to observe the Sun and study the plasma environment in orbit.
Two satellites on two orbits
The satellites were launched atop a Rockot launch vehicle provided by Eurockot GmbH. Liftoff from the Plesetsk Cosmodrome in northern Russia took place at 01:50 UTC (02:50 CET) on Monday 2 November.
Some 70 minutes after launch, SMOS successfully separated from the Rockot's Breeze-KM upper stage. Shortly after, the satellite's initial telemetry was acquired by the Hartebeesthoek ground station, near Johannesburg, South Africa. The upper stage then performed additional manoeuvres to arrive at a slightly lower orbit and Proba-2 was released too, some 3 hours into flight.
Both satellites are currently circling the Earth on their respective sun-synchronous orbits, at an altitude of some 760 km in the case of SMOS and 725 km in that of Proba-2. The Proteus mission control centre operated by the Centre National d'Etudes Spatiales (CNES) in Toulouse, France, is in control of SMOS on behalf of ESA, while the Proba control centre, at ESA's tracking station in Redu, Belgium, has taken over Proba-2.
Early in-orbit operations have begun to check the satellites before commissioning them for operations. Proba-2 is planned to reach operational status in two months' time. The highly innovative payload onboard SMOS will take longer to check and calibrate, and the spacecraft will enter fully operational mode within six months.
"We are extremely pleased with this double 'lucky strike' that will provide Europe with new tools to better understand our planet and climate change, as well as new technology breakthroughs that will enhance the competitiveness of European industry on the world-wide market, thus contributing to the global economy," said Jean-Jacques Dordain, ESA's Director General, witnessing the launch from Plesetsk.
Looking for water exchanges
SMOS is a 658-kg satellite developed by ESA in cooperation with France's CNES and Spain's Centro para el Desarrollo Tecnologico Industrial (CDTI). It is based on the Proteus small satellite platform designed and built by Thales Alenia Space and its payload is composed of a single instrument, the Microwave Imaging Radiometer using Aperture Synthesis (MIRAS), developed by EADS CASA Espacio. MIRAS is an interferometer that connects together 69 receivers mounted on three deployable arms to measure the temperature of the reflection of the Earth's surface in the microwave frequency range. This temperature is linked to both the actual temperature of the surface and its conductive characteristics, which are in turn linked to soil moisture for land surface and to water salinity for sea surface.
"The data collected by SMOS will complement measurements already performed on the ground and at sea to monitor water exchanges on a global scale. Since these exchanges - most of which occur in remote areas - directly affect the weather, they are of paramount importance to meteorologists" said Volker Liebig, ESA's Director of Earth Observation Programmes. "Moreover, salinity is one of the drivers for the Thermohaline Circulation, the large network of currents that steers heat exchanges within the oceans on a global scale, and its survey has long been awaited by climatologists who try to predict the long-term effects of today's climate change," Liebig added, witnessing the launch from the Plesetsk Cosmodrome.
SMOS is the second satellite launched under the Earth Explorer programme conducted by ESA to foster the acquisition of new environmental data for the science community. It follows the Gravity and steady-state Ocean Circulation Explorer (GOCE), also launched on a Rockot, in March 2009. More Earth Explorers are already undergoing preparation. Cryosat-2, which will measure the thickness of the ice sheets, is due for launch in February 2010. It will be followed by ADM-Aeolus to study atmospheric dynamics and the Swarm mission to monitor the weakening of the Earth's magnetic field, in 2011, as well as by the EarthCARE mission on clouds and aerosols in 2013.
Technologies for tomorrow
With a launch mass of 135 kg, Proba-2 is a much smaller satellite, "but like its predecessor Proba-1, it is aimed at demonstrating a wide range of technologies, both for future satellite systems and for space science instruments. Among these is a demonstration model of a miniaturised startracker developed for ESA's BepiColombo mission to Mercury and the future Solar Orbiter probe," said Michel Courtois, ESA's Director of Technology and Quality Management, from Plesetsk.
Other technologies to be demonstrated include a digital sun sensor, miniaturised wide angle camera, fibre sensors, a high-precision magnetometer, a dual frequency GPS space receiver, a xenon-fed resistojet thruster, a cold gas generator and many more.
In addition, Proba-2 carries two Belgian solar physics instruments and two Czech plasma physics experiments.
Two more Proba missions are already in the design and development phase. Proba-V will carry a vegetation multispectral sensor to monitor vegetation cover, and Proba-3 is due to demonstrate formation flying.
// end // | <urn:uuid:9cf0eb5a-a8e6-47c4-9e6b-e0126289f0ab> | 2.765625 | 1,330 | News (Org.) | Science & Tech. | 25.49704 | 95,604,461 |
A View from Emerging Technology from the arXiv
The Amazing Physics of Spinning Graphene
Levitate a flake of graphene and set it spinning; then this wonder material begins to reveal its truly extraordinary properties
Graphene is one of the more extraordinary materials discovered in the last few years. This carbon chicken wire has properties that make it a superhero in the materials world. It is a superb thermal and electrical conductor, it has a high melting point and it is stronger than almost any other known substance.
And yet measuring these properties is tricky because graphene flakes inevitably have to sit on some kind of substrate and this interferes with the results.
What to do? Now Bruce Kane at the University of Maryland makes the case for suspending charged flakes of graphene in an electric field ion trap. That allows the graphene to sit in a vacuum while it is prodded and poked in whatever way physicists can think of and without the interfering effect of any substrate.
Kane has even achieved this feat by injecting flakes suspended in liquid into a quadropole electric field vacuum.
By shining polarised light on the flakes he can make them spin and accurately measure their rate of rotation.
This suggests some interesting experiments. Kane says that spinning them fast enough would test the strength of the flakes as centrifugal forces tear them apart. That will require rotation rates measured in GHz, much faster than the MHz rates he has been able to measure so far.
It should also be possible to measure a flake’s chemical and physical properties at high temperature. These measurements are difficult when the flake rests on a surface that has a different properties. “Very little is known about the melting of graphene or how defects will behave at high temperatures,” points out Kane.
Another possibility is to cool the flakes to their mechanical ground state and use them as spinning qubits.
That’ll be interesting. Is there anything this wonder material cannot do?
Ref: arxiv.org/abs/1006.3774: Levitated Spinning Graphene
Couldn't make it to EmTech Next to meet experts in AI, Robotics and the Economy?Go behind the scenes and check out our video | <urn:uuid:fd0627d9-9eae-46df-8f58-5e5f634896ce> | 3.6875 | 451 | Truncated | Science & Tech. | 42.726829 | 95,604,470 |
ASDF is the standard build system for Common Lisp. It is shipped in most Common Lisp implementations. It includes UIOP, “the Utilities for Implementation- and OS- Portability”. You can read its manual and the tutorial and best practices.
Loading a System
The most trivial use of ASDF is by calling
(asdf:make :foobar) (or
to load your library.
Then you can use it.
For instance, if it exports a function
some-fun in its package
then you will be able to call it with
(foobar:some-fun ...) or with:
(in-package :foobar) (some-fun ...)
You can also use Quicklisp:
Testing a System
To run the tests for a system, you may use:
The convention is that an error SHOULD be signalled if tests are unsuccessful.
Designating a system
The proper way to designate a system in a program is with lower-case strings, not symbols, as in:
(asdf:make "foobar") (asdf:test-system "foobar")
Trivial System Definition
A trivial system would have a single Lisp file called
That file would depend on some existing libraries,
alexandria for general purpose utilities,
trivia for pattern-matching.
To make this system buildable using ASDF,
you create a system definition file called
with the following contents:
(defsystem "foobar" :depends-on ("alexandria" "trivia") :components ((:file "foobar")))
Note how the type
is implicit in the name of the file above.
As for contents of that file, they would look like this:
(defpackage :foobar (:use :common-lisp :alexandria :trivia) (:export #:some-function #:another-function #:call-with-foobar #:with-foobar)) (in-package :foobar) (defun some-function (...) ...) ...
Using the system you defined
Assuming your system is installed under
~/quicklisp/local-projects/ or some other filesystem hierarchy
already configured for ASDF, you can load it with:
If your Lisp was already started when you created that file,
you may have to
(asdf:clear-configuration) to re-process the configuration.
Trivial Testing Definition
Even the most trivial of systems needs some tests, if only because it will have to be modified eventually, and you want to make sure those modifications don’t break client code. Tests are also a good way to document expected behavior.
The simplest way to write tests is to have a file
and modify the above
foobar.asd as follows:
(defsystem "foobar" :depends-on ("alexandria" "trivia") :components ((:file "foobar")) :in-order-to ((test-op (test-op "foobar/tests")))) (defsystem "foobar/tests" :depends-on ("foobar" "fiveam") :components ((:file "foobar-tests")) :perform (test-op (o c) (symbol-call :fiveam '#:run! :foobar)))
:in-order-to clause in the first system
allows you to use
which will chain into
:perform clause in the second system does the testing itself.
In the test system,
fiveam is the name of a popular test library,
and the content of the
perform method is how to invoke this library
to run the test suite
Obvious YMMV if you use a different library.
Create a project skeleton
cl-project can be used to generate a project skeleton. It will create a default ASDF definition, it generates a system for unit testing, etc.
Create a project:
(cl-project:make-project #p"lib/cl-sample/" :author "Eitaro Fukamachi" :email "firstname.lastname@example.org" :license "LLGPL" :depends-on '(:clack :cl-annot)) ;-> writing /Users/fukamachi/Programs/lib/cl-sample/.gitignore ; writing /Users/fukamachi/Programs/lib/cl-sample/README.markdown ; writing /Users/fukamachi/Programs/lib/cl-sample/cl-sample-test.asd ; writing /Users/fukamachi/Programs/lib/cl-sample/cl-sample.asd ; writing /Users/fukamachi/Programs/lib/cl-sample/src/hogehoge.lisp ; writing /Users/fukamachi/Programs/lib/cl-sample/t/hogehoge.lisp ;=> T
Page source: systems.md | <urn:uuid:49ecc437-e2f0-4dac-8a9d-232dabb49b60> | 2.765625 | 1,075 | Documentation | Software Dev. | 50.128775 | 95,604,476 |
- Gibbs Sampling
One of a number of computational methods collectively known as Markov chain Monte Carlo (MCMC) methods. In simulating a Markov chain, Gibbs sampling can be viewed as a special case of the Metropolis-Hastings algorithm. In statistical practice, the terminology Gibbs sampling most often refers to MCMC computations based on conditional distributions for the purpose of drawing inferences in multiparameter Bayesian models
- Bayesian Inference
Consider the parameter θ of a probability model as a random variable with the prior density function p(θ). The choice of a prior distribution may be based on previous experience or personal opinion. Then Bayesian inference combines information in the observed data x with information provided by the prior distribution to obtain a posterior distribution p(θ|x). The parameter θ may be a vector.
The likelihood function p(x|θ) is defined (up to a constant multiple) as the joint density function of the data x, now viewed as a function...
KeywordsMarkov Chain Posterior Distribution Markov Chain Monte Carlo Prior Distribution Bayesian Inference
- Chib S, Greenberg E (1994) Understanding the Metropolis-Hastings algorithm. Am Stat 49:327–335Google Scholar
- Diaconis P, Freedman D (1997) On Markov chains with continuous state spaces (Statistics Technical Report 501), University of California Berkeley Library. www.stat.berkeley.edu/tech-reports/501.pdf
- Donders FC (1868) Die Schnelligkeit psychischer Prozesse, Archiv für Anatomie und Physiologie und wissenschaftliche Medizin, pp. 657–681. English edition: Donders FC (1969) On the speed of mental processes, Attention and performance II (trans: Koster WG). North Holland, AmsterdamGoogle Scholar
- R Development Core Team (2012) R: a language and environment for statistical computing. R Foundation for Statistical Computing, Vienna, www.R-project.org. ISBN 3-900051-07-0Google Scholar
- Snedecor GW, Cochran WG (1980) Statistical methods, 7th edn. Iowa State University Press, AhmmmmesGoogle Scholar
- Speigelhalter D, Thomas A, Best N, Lunn D (2011) BUGS: Bayesian inference using Gibbs sampling. MRC Biostatistics Unit, CambridgeGoogle Scholar
- Trumbo BE (2002) Learning statistics with real data. Duxbury Press, BelmontGoogle Scholar | <urn:uuid:66f9bc64-6863-4efe-861a-0be45cc7c0a5> | 3.046875 | 539 | Academic Writing | Science & Tech. | 42.757607 | 95,604,480 |
What is less known is how much water occupied the red planet and what happened to it during its geological march to the present. Mostly, evidence has pointed to a period when clay-rich minerals were formed by water, followed by a drier time, when salt-rich, acidic water affected much of the planet. Assuming that happened, the thinking goes, it would have been difficult for life, if it did exist, to have survived and for scientists to find traces of it.
Now a research team led by Brown University has found evidence of carbonates, a long-sought mineral that shows Mars was home to a variety of watery environments — some benign, others harsh — and that the acidic bath the planet endured left at least some regional pockets unscathed.If primitive life sprang up in pockets that avoided the acidic transformation, clues for it may remain.
Finding carbonates indicates that Mars had neutral to alkaline waters when the minerals formed in the mid-latitude region more than 3.6 billion years ago. Carbonates dissolve quickly in acid, therefore their survival challenges suggestions that an exclusively acidic environment later cloaked the planet.
The carbonates showed up in the most detail in two-dozen images beamed back by the Compact Reconnaissance Imaging Spectrometer for Mars, an instrument aboard the NASA Mars Reconnaissance Orbiter. Scientists found the mineral near a trough system called Nili Fossae, which is 667 kilometers (414 miles) long, at the edge of the Isidis impact basin. Carbonates were seen in a variety of terrains, including the sides of eroded mesas, sedimentary rocks within Jezero crater and rocks exposed on the sides of valleys in the crater's watershed. The researchers also found traces of carbonates in Terra Tyrrhena and in Libya Montes.
NASA's Phoenix Mars Lander recently found carbonates in soil samples, and researchers had previously found them in Martian meteorites that fell to Earth and in windblown Mars dust observed from orbit. However, the dust and soil could be mixtures from many areas, so the origins of carbonates have been unclear. The latest observations indicate carbonates may have formed over extended periods on early Mars and also point to specific locations where future rovers and landers could search for possible evidence of past life.
"This is opening up a range of environments on Mars," said John "Jack" Mustard, a Brown professor of geological sciences and a co-author on the Science paper. "This is highlighting an environment that to the best of our knowledge doesn't experience the same kind of unforgiving conditions that have been identified in other areas."
The researchers, including Brown graduate student Leah Roach and scientists from NASA, the Johns Hopkins University Applied Physics Laboratory, the Institut d'Astrophysique Spatiale at the University of Paris, the U.S. Geological Survey, Cornell University and the University of Nevada, have multiple hypotheses for how the carbonate-bearing rocks were formed and the origin of the water that shaped them. They may have been formed by slightly heated groundwater percolating through fractures in olivine-rich rocks. Or, they may have been formed at the surface when olivine-rich rocks were exposed and altered by running water. Yet another theory is the carbonates precipitated in small, shallow lakes. Either way, such environments would have boded well for primitive life forms to emerge.
"We know there's been water all over the place, but how frequently have the conditions been hospitable for life?" Mustard said. "We can say pretty confidently that when water was present in the places we looked at, it would have been a happy, pleasant environment for life."
Richard Lewis | 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....
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Series: Alaska Park Science - Volume 17, Issue 1. Migration: On the Move in Alaska
Seasonal Sea Ice and Arctic Migrations of the Beluga Whale
Each spring to early summer, the continental shelves of the Chukchi and Beaufort seas north of Alaska emerge from a cloak of winter sea ice. Such seasonal phases of sea ice break-up in the spring and sea ice freeze-up in the fall govern the accessibility and productivity of Alaska’s Arctic Ocean for several migratory marine species. Open water in spring serves as a welcome mat for beluga whales (Delphinapterus leucas) and bowhead whales (Balaena mysticetus) that transit the Pacific’s only gateway into the Arctic through the narrow Bering Strait. Each year, these Arctic whales pass the coastal boundaries of Bering Land Bridge National Preserve and Cape Krusenstern National Monument, dispatched from their winter haunts in the Bering Sea. After passing through the Bering Strait each spring, they enter the southern Chukchi Sea, one of the most seasonally productive regions of the global oceans (Grebmeier 2012). Some belugas and most bowhead whales continue on their >1,500 mile (>2,500 km) migration north of Alaska to the Canadian Beaufort Sea for the summer.
For beluga whales, recent cooperative research has provided deeper insights into the relative distribution, movements, and behavior of two distinct populations. The Eastern Chukchi Sea and Eastern Beaufort Sea beluga populations (“Chukchi” and “Beaufort” populations) return each summer to the nearshore regions of Kasegaluk Lagoon in northwest Alaska and the Mackenzie River Estuary, Canada, respectively (Figure 1). A mixture of large, white adults and dark grey calves arrive around June-early July, presumably for an annual molt of their skin in the warmer, less saline coastal water (St. Aubin et al. 1990). These coastal regions also provide a more protected area to nurture their young. Scientists working collaboratively with local communities have tagged beluga whales from the Chukchi and Beaufort populations with satellite-linked transmitters since 1993.
Listen to beluga whale sounds.
- 2 minutes, 47 seconds
Location data from the transmitters reveal extensive movements around the Chukchi and Beaufort seas and deep (1.9 miles, or more than 3,000 m) Canada Basin, with some animals ranging to nearly ~80°N latitude (Richard et al. 2001, Suydam et al. 2001). Two decades of tracking data, combined, in some cases, with data on underwater diving behavior, help clarify why these populations use the Pacific Arctic as well as when and where they may overlap. Chukchi and Beaufort belugas are spatially segregated during July and August. However, both populations use the Alaskan Beaufort Sea and overlap during September when Beaufort belugas rapidly shift their distribution from the Canadian Beaufort Sea to the western Chukchi Sea, a month ahead of the Chukchi population’s westward migration (Figure 2; Hauser et al. 2014). There is also limited spatial overlap in fall months in the Chukchi Sea. Adult males generally separate from females during summer and use deeper water, farther from shore, and denser sea ice concentrations (Hauser et al. 2017a).
- 36 seconds
Figure 2. An animation of daily locations from Chukchi Sea (‘Chukchi’: purple dots) and Beaufort Sea (‘Beaufort’: green dots) beluga whales tagged from 1993-2007. Data were collected in collaboration with the Alaska Beluga Whale Committee, North Slope Borough, Village of Point Lay, Alaska Department of Fish and Game, National Marine Fisheries Service (for Chukchi Sea belugas) as well as Fisheries and Ocean Canada, Fisheries Joint Management Committee, and Hunter and Trapper Committees of villages in the Inuvialuit Settlement Region (for Beaufort Sea belugas). See Hauser et al. (2014) for more details and additional acknowledgements of the individuals, organizations, and funding sources that supported tagging and analysis efforts.
These complicated seasonal distributions beg the question of why migrate and what factors influence their movements? Belugas have encountered this highly seasonal and ephemeral sea ice environment since at least the Late Miocene (Harington 2008), so their population-specific fidelity to distinct summer areas, sexual segregation, and offset migration timing are presumably shaped by seasonal fluctuations in summer to fall conditions and sea ice in particular. Beluga philopatry (site fidelity) and migration patterns are also culturally transmitted, passed down from their mothers (O’Corry-Crowe et al. 2016). Belugas mediate their behavior to respond to patchily distributed prey, as illustrated by variations in diving behavior among Pacific Arctic regions. For example, both beluga populations dive to depths and portions of the water column that would presumably optimize foraging opportunities, based on the available information of prey distributions as well as oceanographic properties that concentrate prey (Hauser et al. 2015). Therefore, beluga distribution, movements, and behavior are ultimately driven by combined effects of genetic, social, and environmental influences.
Beluga Migrations in the Face of a Changing Pacific Arctic
The Arctic is undergoing rapid and unprecedent-ed change, with warming twice as fast as the rest of the planet (AMAP 2017). The Pacific Arctic ecosystem is transforming with an expanded open-water summer season, increased wind-forcing and upper-ocean heat content, more freshwater, and upwelling (Wood et al. 2015). How are belugas and other Arctic marine mammals mediating these changing conditions, and to what extent, given tradeoffs in social versus environmental forcing?
Tagging data are again useful in helping assess beluga responses to shifts in their environment. The annual spring ice break-up in both the Chukchi and Beaufort seas now occurs earlier while fall freeze-up has shifted later, meaning that the overall duration of the open-water season has increased (13-15 days/decade during 1979-2013; Laidre et al. 2015). Comparing tagging data from 1998-2002 to 2007-2012 (when sea ice cover significantly declined), Chukchi belugas delayed fall migration to allow for a prolonged presence in the Beaufort Sea as sea ice freeze-up also occurred later (Table 1; Hauser et al. 2017b). These results support the hypothesis that Chukchi belugas are coping with a changing Pacific Arctic environment by shifting migration timing. In contrast, there were few examples where migration timing of Beaufort belugas changed between the 1990s and 2000s, nor was there evidence that freeze-up timing cues migration for the Beaufort population. Rather, Beaufort beluga migration timing appears to be somewhat “pre-programmed” for a particular time each fall. More research is needed to determine how the migration strategies of Chukchi and Beaufort belugas affect their population dynamics, vital parameters, or potential for persistence. In the case of Pacific Arctic bowhead whales, current sea ice and oceanographic conditions seem to support enhanced foraging opportunities that have improved recent body condition and population growth (George et al. 2015), which may also be the case for belugas. However, later migration from the Beaufort Sea in the fall may expose Chukchi belugas to more variable freeze-up patterns and the potential for fatal ice entrapments. Ultimately, it seems that beluga responses to changing sea ice conditions vary among populations, which not only complicates predictions for future conditions, but also suggests some beluga populations may be more likely than others to persist in a changing climate.
|Migration Passage Location||Median Migration Day of the Year in
Early, Late Periods
|Days Between Median Dates
(Late - Early)
|Eastern Chukchi Sea belugas (tagged 1998-2002 and 2007-2012|
|Exit Beaufort Sea (first day west of 157°W)||6 Oct, 8 Nov||+33|
|Commence southward migration (last day north of 70°N)||22 Oct, 12 Nov||+21|
|Enter Bering Sea (first day south of Bering Strait, 65.9°N)
||11 Nov, 25 Nov||+14|
|Eastern Beaufort Sea belugas (tagged 1993-1997 and 2004-2005)|
|Exit Canada (first day west of 141°W)||8 Sept, 2 Sept||-6|
|Exit Beaufort Sea (first day west of 157°W)||17 Sept, 9 Sept||-8|
|Commence southward migration (last day north of 70°N)||16 Oct, 18 Oct||+2|
|Enter Bering Sea (first day south of Bering Strait, 65.9°N)||None tagged,
In the face of sea ice loss, belugas and other Arctic marine mammals are also likely to experience increased anthropogenic activities and changes in the marine mammal community. For example, Arctic marine mammals and the subsistence communities that rely on them are vulnerable as sea ice loss expands the navigability of Arctic sea routes (Huntington et al. 2015) and possibilities for oil and gas development (Reeves et al. 2014). An increasingly ice-free Pacific Arctic may also affect the more temperate marine mammal species that ply Alaska’s northern waters on a seasonal basis. Some baleen whales, such as fin and humpback whales (Balaenoptera physalus and Megaptera novaeangliae), are more commonly sighted now in the Chukchi Sea north of Bering Strait. This is either the result of a lack of sea ice or simply reflects the recovery of North Pacific populations following the cessation of commercial whaling (Clarke et al. 2013). Killer whales (Orcinus orca), a relatively novel Arctic predator, are also increasingly observed in the Pacific Arctic, similar to the Eastern Arctic. Overall, additional research is needed to understand the impacts of sea ice loss on Arctic marine mammals (Laidre et al. 2015).
For More Information
Arctic Monitoring and Assessment Program (AMAP). 2017.
Snow, Water, Ice and Permafrost. Summary for Policy-makers. Arctic Monitoring and Assessment Programme (AMAP), Oslo, Norway. 20 pp.
Citta, J. J., P. Richard, L. F. Lowry, G. O’Corry-Crowe, M. Marcoux, R. Suydam, L. T. Quakenbush, R. C. Hobbs, D. I. Litovka, K. J. Frost, T. Gray, J. Orr, B. Tinker, H. Aderman, and M. L. Druckenmiller. 2017.
Satellite telemetry reveals population specific winter ranges of beluga whales in the Bering Sea. Marine Mammal Science 33:236-250.
Clarke, J. T., K. M. Stafford, S. E. Moore, B. K. Rone, L. A. M. Aerts, and J. Crance. 2013.
Subarctic cetaceans in the southern Chukchi Sea: Evidence of recovery or response to a changing ecosystem. Oceanography 26:136-149.
Frost, K. J. and L. F. Lowry. 1990.
Distribution, abundance, and movements of beluga whales, Delphinapterus leucas, in coastal waters of western Alaska. Pages 39-57 in T. G. Smith, D. J. St. Aubin, and J. R. Geraci, editors. Advances in Research on the Beluga Whale, Delphinapterus leucas. Canadian Bulletin of Fisheries and Aquatic Sciences 224, Ottawa.
Frost, K. J., L. F. Lowry, and G. Carroll. 1993.
Beluga whale and spotted seal use of a coastal lagoon system in the northeastern Chukchi Sea. Arctic 46:8-16.
Garland, E., C. Berchok, and M. Castellote. 2015.
Temporal peaks in beluga whale (Delphinapterus leucas) acoustic detections in the northern Bering, northeastern Chukchi, and western Beaufort Seas: 2010–2011. Polar Biology 38:747-754.
George, J. C., M. L. Druckenmiller, K. L. Laidre, R. Suydam, and B. Person. 2015.
Bowhead whale body condition and links to summer sea ice and upwelling in the Beaufort Sea. Progress in Oceanography 136:250-262.
Grebmeier, J. M. 2012.
Shifting patterns of life in the Pacific Arctic and Sub-Arctic seas. Annual Review of Marine Science 4:63-78.
Harington, C. R. 2008.
The evolution of Arctic marine mammals. Ecological Applications 18:S23-S40.
Hauser, D. D. W. 2016.
Beluga whale distribution, migration, and behavior in a changing Pacific Arctic. University of Washington, Seattle, WA.
Hauser, D. D. W., K. L. Laidre, H. L. Stern, S. E. Moore, R. S. Suydam, and P. R. Richard. 2017a.
Habitat selection by two beluga whale populations in the Chukchi and Beaufort seas. Plos One 12:e0172755.
Hauser, D. D. W., K. L. Laidre, K. M. Stafford, H. L. Stern, R. S. Suydam, and P. R. Richard. 2017b.
Decadal shifts in autumn migration timing by Pacific Arctic beluga whales are related to delayed annual sea ice formation. Global Change Biology 23:2206-2217.
Hauser, D. D. W., K. L. Laidre, S. L. Parker-Stetter, J. K. Horne, R. S. Suydam, and P. R. Richard. 2015.
Regional diving behavior of Pacific Arctic beluga whales Delphinapterus leucas and possible associations with prey. Marine Ecology Progress Series 541:245-264.
Hauser, D. D. W., K. L. Laidre, R. S. Suydam, and P. R. Richard. 2014.
Population-specific home ranges and migration timing of Pacific Arctic beluga whales (Delphinapterus leucas). Polar Biology 37:1171-1183.
Huntington, H. P., R. Daniel, A. Hartsig, K. Harun, M. Heiman, R. Meehan, G. Noongwook, L. Pearson, M. Prior-Parks, M. Robards, and G. Stetson. 2015.
Vessels, risks, and rules: Planning for safe shipping in Bering Strait. Marine Policy 51:119-127.
Laidre, K. L., H. Stern, K. M. Kovacs, L. Lowry, S. E. Moore, E. V. Regehr, S. H. Ferguson, Ø. Wiig, P. Boveng, R. P. Angliss, E. W. Born, D. Litovka, L. Quakenbush, C. Lydersen, D. Vongraven, and F. Ugarte. 2015.
Arctic marine mammal population status, sea ice habitat loss, and conservation recommendations for the 21st century. Conservation Biology 29:724-737.
Lowry, L. F., J. J. Burns, and R. R. Nelson. 1987.
Polar bear, Ursus maritimus, predation on belugas, Delphinapterus leucas, in the Bering and Chukchi Seas. Canadian Field-Naturalist 101:141-146.
O’Corry-Crowe, G., A. R. Mahoney, R. Suydam, L. Quakenbush, A. Whiting, L. Lowry, and L. Harwood. 2016.
Genetic profiling links changing sea-ice to shifting beluga whale migration patterns. Biology Letters 12:20160404.
Reeves, R. R., P. J. Ewins, S. Agbayani, M. P. Heide-Jørgensen, K. M. Kovacs, C. Lydersen, R. Suydam, W. Elliott, G. Polet, Y. van Dijk, and R. Blijleven. 2014.
Distribution of endemic cetaceans in relation to hydrocarbon development and commercial shipping in a warming Arctic. Marine Policy 44:375-389.
Richard, P. R., M. P. Heide-Jorgensen, J. Orr, R. Dietz, and
T. G. Smith. 2001.
Summer and autumn movements and habitat use by belugas in the Canadian High Arctic and adjacent areas. Arctic 54:207-222.
St. Aubin, D. J., T. G. Smith, and J. R. Geraci. 1990.
Seasonal epidermal molt in beluga whales, Delphinapterus leucas. Canadian Journal of Zoology 68:359-367.
Suydam, R. S., L. F. Lowry, K. J. Frost, G. M. O’Corry-Crowe, and D. J. Pikok. 2001.
Satellite tracking of eastern Chukchi Sea beluga whales into the Arctic Ocean. Arctic 54:237-243.
Wood, K. R., N. A. Bond, S. L. Danielson, J. E. Overland, S. A. Salo, P. J. Stabeno, and J. Whitefield. 2015.
A decade of environmental change in the Pacific Arctic region. Progress in Oceanography 136:12-31. | <urn:uuid:1e6b5da4-7303-4cff-a14c-94ca33d3996f> | 3.59375 | 3,854 | Knowledge Article | Science & Tech. | 61.945397 | 95,604,488 |
Reynolds, D Poeppel, WJ Nichols. 2013. Your Brain On Nature: Communicating to change behavior: The need to understand neural processing and the effects of nature. 5th International Partners in Flight Conference and Conservation Workshop. August 25 – 28, 2013, Snowbird, Utah.
Traditional Communication Methods
The U.S. Fish and Wildlife Service and the broader conservation community prides itself on the foundation of sound science used to achieve the best conservation for the species and habitats we are entrusted to protect, restore and enhance.
To inform our diverse audiences and raise awareness that will illicit change, our communications tend to:
• provide information;
• use traditional tools (e.g., websites, newsletters);
• play on guilt; and
• scare people with dire messages.
Quite simply, we are sending the wrong message.
Science Needs Proposal: Your Brain on Nature
The Wave of the Future: Neuromarketing
Neuromarketing is a new form of market research, that uses neuroscience tools to measure the emotional impact of communication across all media, and translate the findings into actionable marketing recommendations.
For-profit companies have long used neuroscience to help develop their marketing strategies and campaigns. Companies like Coca Cola, Volkswagon, Frito Lay, all use neural studies to help them develop marketing campaigns that measure customer response to color, sounds, fonts, and emotions. Neural studies in the marketing world use technology to look inside our heads and show what consumers really feel, as opposed to what marketers think we feel.
Applying what we learn from this study to conservation messages offers great hope for motivating people to care about and act upon environmental issues.
Ninety-five percent of our decisions are made in the portion of our brains that control subconscious thought. While traditional marketing measures our external opinions, neuromarketing measures emotions as they happen.
Communicating for Conservation Change: Neuroconservation
To provide a stronger foundation for the communication and outreach we do and to enhance our capabilities of “selling” conservation, we propose to study how our brains respond to birds and coastal environments, landscapes, etc... in order to construct conservation campaigns that provide information that leads to conservation action.
Neural studies in the marketing world use technology to look inside our heads and show what consumers really feel, as opposed to what marketers think we feel. Applying what we learn from this study to conservation messages offers great hope for motivating people to care about and act upon environmental issues.
Pictures are more powerful than words, but environmentalists who show the horrific scope of a problem with a devastating photo often end up alienating the very people they wish to inspire. This is refered to as a “compassion collapse,” in which people wind up feeling powerless and then disengage from the issue.
Instead of focusing the spotlight on results of scientific studies that prove our planet is rapidly warming, or on statistics about alarming species extinction rates, we should be talking about how an ocean view will make us feel happy or standing among trees will arouse our feelings of peacefulness. This idea is called neuroconservation.
Using the tenets of neuroscience may boost the effort to gain support for conservation causes in a world that’s overrun with more scientific data than we know what to do with.
Debra Reynolds, U.S. Fish & Wildlife Service, Dr. David Poeppel, Professor of Psychology and Neural Science, New York University, Dr. Wallace J Nichols, Research Associate at California Academy of Sciences and co-founder of OceanRevolution.org
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Recent research has confirmed what many boaters already know – you experience emotional, behavioral... continue
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In recent years horizontal, or lateral, gene transfer has been seen frequently in prokaryotes and also occasionally in eukaryotes. This lateral transfer involves the movement of genetic material between species as opposed to the vertical transfer of genes from parent to progeny. Horizontal transfer has been observed between the mitochondrial DNA of different plant species. Until now, however, no one had found evidence for horizontal transfer in the nuclear DNA of plants.
In a new study published online in the open access journal PLoS Biology, Xianmin Diao, Michael Freeling, and Damon Lisch analyzed the genomes of millet and rice, two distantly related grasses that diverged 30–60 million years ago. They found evidence for a case of horizontal gene transfer; despite significant genetic divergence from millions of years of mutations, they carry some nuclear DNA segments that are surprisingly similar. These segments contain transposon-related sequences (MULEs); transposons are genetic elements capable of independently replicating and inserting the copy into new positions in DNA.
To dispel alternative explanations for these similar segments, the authors investigated whether they could have been the result of positive selection acting to preserve these sequences. However, similarity of non-coding regions of the sequences in millet and rice was as high as the coding regions, and even synonymous mutations, which do not alter the protein sequence, were very few. The authors discount another explanation—that these sequences might occur within a genomic region subject to a lower mutation rate in general—with the help of maize (as complete genomic sequence data for the surrounding region in millet is not available). The sequences did not show the similar degree of reduced variation predicted for below-average mutation rates.
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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posted by Mike Joseph
A 0.40-kg ball, attached to the end of a horizontal cord, is rotated in a circle of radius 2.0 m on a frictionless horizontal surface.
If the cord will break when the tension in it exceeds 75 N, what is the maximum speed the ball can have?
May someone please walk me through this problem step by step
ma = T
ma = mv²/R | <urn:uuid:35c3bf8c-d5f4-41c1-aeb6-c5f6ae06ac43> | 2.765625 | 89 | Q&A Forum | Science & Tech. | 83.926786 | 95,604,497 |
|시간 제한||메모리 제한||제출||정답||맞은 사람||정답 비율|
|5 초||512 MB||28||22||18||85.714%|
The kitchen at the Infinite House of Pancakes has just received an order for a stack of Kpancakes! The chef currently has N pancakes available, where N ≥ K. Each pancake is a cylinder, and different pancakes may have different radii and heights.
As the sous-chef, you must choose K out of the N available pancakes, discard the others, and arrange those K pancakes in a stack on a plate as follows. First, take the pancake that has the largest radius, and lay it on the plate on one of its circular faces. (If multiple pancakes have the same radius, you can use any of them.) Then, take the remaining pancake with the next largest radius and lay it on top of that pancake, and so on, until all K pancakes are in the stack and the centers of the circular faces are aligned in a line perpendicular to the plate, as illustrated by this example:
You know that there is only one thing your diners love as much as they love pancakes: syrup! It is best to maximize the total amount of exposed pancake surface area in the stack, since more exposed pancake surface area means more places to pour on delicious syrup. Any part of a pancake that is not touching part of another pancake or the plate is considered to be exposed.
If you choose the K pancakes optimally, what is the largest total exposed pancake surface area you can achieve?
The first line of the input gives the number of test cases, T. T test cases follow. Each begins with one line with two integers N and K: the total number of available pancakes, and the size of the stack that the diner has ordered. Then, N more lines follow. Each contains two integers Ri and Hi: the radius and height of the i-th pancake, in millimeters.
For each test case, output one line containing
Case #x: y, where
x is the test case number (starting from 1) and
y is the maximum possible total exposed pancake surface area, in millimeters squared.
y will be considered correct if it is within an absolute or relative error of 10-6 of the correct answer.
4 2 1 100 20 200 10 2 2 100 20 200 10 3 2 100 10 100 10 100 10 4 2 9 3 7 1 10 1 8 4
Case #1: 138230.076757951 Case #2: 150796.447372310 Case #3: 43982.297150257 Case #4: 625.176938064
In Sample Case #1, the "stack" consists only of one pancake. A stack of just the first pancake would have an exposed area of π × R02 + 2 × π * R0 × H0 = 14000π mm2. A stack of just the second pancake would have an exposed area of 44000π mm2. So it is better to use the second pancake.
In Sample Case #2, we can use both of the same pancakes from case #1. The first pancake contributes its top area and its side, for a total of 14000π mm2. The second pancake contributes some of its top area (the part not covered by the first pancake) and its side, for a total of 34000π mm2. The combined exposed surface area is 48000π mm2.
In Sample Case #3, all of the pancakes have radius 100 and height 10. If we stack two of these together, we effectively have a single new cylinder of radius 100 and height 20. The exposed surface area is 14000π mm2.
In Sample Case #4, the optimal stack uses the pancakes with radii of 8 and 9. | <urn:uuid:966fa55d-636c-469e-95be-3666e4841604> | 2.546875 | 861 | Tutorial | Science & Tech. | 72.862059 | 95,604,508 |
posted by Robin
A metal, , of atomic weight 96 reacts with fluorine to form a salt that can be represented as . In order to determine and therefore the formula of the salt, a boiling point elevation experiment is performed. A 9.18- sample of the salt is dissolved in 100.0 of water and the boiling point of the solution is found to be 374.38 . Find the formula of the salt.
See your other post. | <urn:uuid:7673e825-78eb-4d03-83bd-62b6b6b20835> | 3.59375 | 91 | Q&A Forum | Science & Tech. | 78.084605 | 95,604,510 |
Program transformation is used in a wide range of applications including compiler construction, optimization, program synthesis, refactoring, software renovation, and reverse engineering. Complex program transformations are achieved through a number of consecutive modifications of a program. Transformation rules define basic modifications. A transformation strategy is an algorithm for choosing a path in the rewrite relation induced by a set of rules. This paper surveys the support for the definition of strategies in program transformation systems. After a discussion of kinds of program transformation and choices in program representation, the basic elements of a strategy system are discussed and the choices in the design of a strategy language are considered. Several styles of strategy systems as provided in existing languages are then analyzed. © 2001 Published by Elsevier Science B. V.
Mendeley saves you time finding and organizing research
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Schmidt Fund Awards to Advance Innovations in Drug Therapy and Search for Planets
News Apr 26, 2013
The fund supports concepts with potential for broad impact in the natural sciences and engineering. It was created in 2009 through a $25 million endowment by Google executive chairman Eric Schmidt, a 1976 alumnus and former trustee, and his wife, Wendy, to encourage the development of new technologies that could transform entire fields of science.
The winning projects are a technology for attaching drug molecules to radioactive labels that enable detection of the drugs using brain imaging, led by Princeton chemistry professor John Groves; and a method for improving the image-correcting systems on telescopes to better detect far away objects including planets outside our solar system, led by Tyler Groff, Princeton postdoctoral researcher in mechanical and aerospace engineering.
"These are two truly innovative technologies that have tremendous potential to lead to breakthroughs in their areas of study and beyond," said A.J. Stewart Smith, dean for research, the Class of 1909 Professor of Physics, and chair of the committee that selected the winners. "The Schmidt fund has enabled Princeton University to make investments in ideas that have the potential to radically boost scientific and technical advancement."
New tools to visualize drug therapy in the brain
John Groves and his team will receive $600,000 from the fund to develop a system for labeling drugs with radioactive markers that make them visible using a brain-imaging method known as positron emission tomography (PET) scanning.
The rapid creation of these radiolabeled drugs could enable medical researchers to explore whether the experimental medicines are reaching their targets, and could aid in the development of drugs to treat disorders such as Alzheimer's disease and stroke, according to Groves, Princeton's Hugh Stott Taylor Chair of Chemistry.
The method for creating the radiolabeled drugs is based on a recent discovery in Groves' lab of a new process, published in Science last fall, for incorporating fluorine atoms into drug molecules. The process uses a synthetic liver enzyme to replace hydrogen with radioactive fluorine in the drug molecule. This new method avoids the toxic and corrosive agents in use for such processes today.
With the Schmidt funding, Groves and his team will develop an automated method to quickly attach radiolabeled fluorine to drug molecules. The major hurdle, Groves said, is finding a way to accelerate the chemical reaction between the fluorine and the drug so that the attachment can be completed before the compound degrades, which it does in about two hours. The group has already made substantial progress, Groves said.
"The Schmidt funding will enable us to explore ways to optimize the chemical reaction," Groves said, "as well as to create a prototype of an automated system that can carry out the reaction without the need for a human operator. This will allow us to create a rapid and noninvasive way to evaluate drug candidates and observe important metabolites within the human brain."
Aiding the search for planets
Inspired by the search for planets outside our solar system, Princeton postdoctoral researcher Tyler Groff conceived of a technology that could enhance the quality of images from telescopes. Groff will receive $300,000 in Schmidt funding to develop a new device for controlling the mirrors that telescopes use to correct blurring and distortion caused by atmospheric turbulence, heat and vibrations.
This technology, known as adaptive optics, involves measuring disturbances in the light coming into the telescope and making small deformations to the surface of a mirror in precise ways to correct the image.
These deformations are made using an array of mechanical devices, known as actuators, each of which can move a small area of the flexible reflective surface up and down. But existing actuators have limitations, such as requiring continuous power and being limited in the amount of correction they can provide. Additionally, the spaces between the actuators create dimples in the mirror, producing a visible pattern in the resulting images that astronomers call "quilting."
Groff envisioned replacing the array of rigidly attached actuators with flexible ones that can smoothly change shape as needed. Instead of actuators, attached to the back of the mirror is a packet containing iron particles suspended in a liquid, which is known as a ferrofluid. Just as iron filings can be moved by waving a magnet over them, applying varying magnetic fields to the ferrofluid creates changes in the shape of the fluid that in turn deforms the mirror.
The ferrofluid mirror enables high image quality while being more resistant to vibrations and potentially more power efficient, which will be important for future satellite-based telescopes, said Groff, who works in the laboratory of Jeremy Kasdin, professor of mechanical and aerospace
engineering. Ferrofluid mirrors do not have the size limits of the high actuator-density mirrors in use today, so they have the potential to be more easily integrated into the telescope. A ferrofluid mirror can also achieve something that a rigid actuator mirror cannot: it can assume a concave or bowl-like shape that aids the focusing of the telescope on objects in space.
"A telescope that uses ferrofluid mirrors would be able to see dim objects better, greatly enhancing our ability to probe other solar systems," Groff said. "The Eric and Wendy Schmidt Transformative Technology Fund will enable the studies needed to develop this technology, which has the potential to greatly expand our ability to find new planets in the universe."
Identical Twin Study Shows Impact of a Lifetime of Exercise on FItnessNews
When it comes to being fit, are genes or lifestyle more important? Researchers removed the nature part of the equation by studying a pair of identical twins who had taken radically different fitness paths over three decades. One became an Ironman triathlete while the other remained relatively sedentary over the last 30 years. | <urn:uuid:05ccc385-46f8-466c-8b66-6f0e16f9f032> | 2.59375 | 1,187 | News Article | Science & Tech. | 22.411459 | 95,604,515 |
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Published on May 23, 2012
OCEAN ACIDIFICATION AN ECOSYSTEM FACING DISSOLUTION
As a large sink, the ocean absorbs carbon dioxide from the atmosphere. But in sea water, the gas reacts to produce carbonic acid - a threat for organisms building their shells and skeletons from calcium carbonate.
CAMERA Maike Nicolai, GEOMAR Jens Klimmeck, realTVgroup | <urn:uuid:de11825d-57ec-46ac-a530-f2dcf8646ecb> | 2.71875 | 115 | Truncated | Science & Tech. | 39.040658 | 95,604,517 |
Solar Energy: Answers to Common Questions
What is the world energy consumption? What amount of solar energy incident on the earth?
Earth as seen from space
The sun produces an enormous amount of energy: about 1.1 x 1020 kW hours every second (1 kW-hour is the energy needed to light a 100-watt bulb for 10 hours). The outer atmosphere intercepts approximately about 1.5 trillion (1.500.000.000.000.000.000) kilowatt hours per year. However, due to reflection, scattering and absorption caused by atmospheric gasses, only 47% of this energy, or about 0.7 trillion (700.000.000.000.000.000) kW hours reach the surface of the earth.
This energy is what launches the “machinery” of the Earth. Warms the atmosphere, oceans and continents, it generates winds, moves the water cycle, makes plants grow, provides food to animals, and even (over a long period of time) produces fossil fuels.
The world each year is about 85 trillion (85,000,000,000,000) kilowatt hour. This is what can be measured, ie the energy that is bought, sold or traded. There is no way of knowing exactly how much non-commercial energy each person (eg how much wood is burned, or that amount of water is used in small waterfalls to produce electricity). According to some experts, this non-commercial energy may be as much a fifth of the total energy consumed. Even if this is the case, the total energy consumed by the world would mean only 1 / 7,000 of the solar energy that strikes the surface of the earth every year.
What is it and how a photovoltaic or wind system work?
A photovoltaic system is a device that, from solar radiation, produces electricity in a position to be exploited by man. The system consists of the following elements (see diagram):
A solar generator, consisting of a set of photovoltaic panels, which capture light radiation from the sun and transform it into direct current at low voltage (12-48 V).
If instead of a solar panel installed a wind turbine system is called the wind. If installed both be a mixed system. In this case, each one should carry his own regulator.
Is photovoltaic solar energy profitable?
The answer to this question depends on where in the world where we are. A large part of humanity in developing countries have no access to electricity for lacking a basic electrical infrastructure. In these countries solar photovoltaic energy turns out to be the most profitable for electricity source, and in some places only.
In developed countries, where there is a large electric infrastructure, the question is different. In this case, in purely economic terms, photovoltaic systems are profitable only in places far from the conventional network. However, the question will change a lot if, in addition to cost effectiveness, we also consider the environmental cost of each energy source.
Can you use photovoltaic solar energy for heating or for heating water?
Although technically it would be possible, from an economic point of view makes no sense. To produce hot water is best to use a solar thermal system, which uses collectors are filled with water and absorb heat. As for heating, the only possibility to implement solar energy is to use a solar thermal system with underfloor heating.
What is the lifespan of a photovoltaic solar panel?
Given that the panel has no moving parts and that cells and contacts are encapsulated in a robust synthetic resin with very good reliability is achieved with a long service life of the order of 30 years or more. Also, if one of the cells fails, this does not affect the operation of the others, and the current and voltage produced can be easily adjusted by adding or removing cells.
What maintenance requires a photovoltaic system?
Photovoltaic systems require minimal and simple maintenance, which is reduced to the following:
Panels: require no or very little maintenance due to it is advisable to make a general inspection 1 or 2 times a year to ensure that connections between panels and the regulator are tight and free of corrosion. In most cases, the action of rain eliminates the need for cleaning of the panels; if necessary, simply use water and a mild detergent.
Regulator: the simplicity of control equipment substantially reduces maintenance and makes faults are very slim. The operations that can be performed are: visual observation of the condition and operation of the regulator; check wiring and wiring equipment; observation of the instantaneous values of the voltmeter and ammeter provide an indication of the behavior of the installation.
Accumulator: is the element of the installation that requires further attention; their correct use and good maintenance depend largely on its duration. The usual operations to be performed are as follows:
Check the electrolyte level (approximately every 6 months) should be maintained within the range of brands of “Maximum” and “Minimum”. If no such marks, correct electrolyte level is 20 mm above the protector of separators. If a lower level is observed in any of the elements should be filled with distilled or demineralized water. It must never be filled with sulfuric acid.
By performing the above operation it must also check the status of the battery terminals; It must be cleaned of possible sulfate deposits and neutral Vaseline all connections.
What environmental impact of photovoltaic solar energy?
Photovoltaic solar energy, like other renewable energy sources, is compared to fossil fuels, an inexhaustible source, contributes to national energy self-sufficiency and is less damaging to the environment, avoiding the effects of direct use (air pollution, waste , etc) and derivatives of his generation (excavations, mines, quarries, etc.).
The effects of photovoltaic energy upon the main environmental factors are:
Climate: generation of electricity directly from sunlight does not require any kind of combustion, so no thermal pollution or CO2 emissions that favor the greenhouse effect.
Geology: Photovoltaic cells are made from silicon, element obtained from sand, very abundant in nature and that no significant quantities are required. Therefore, in the manufacture of photovoltaic modules no alterations in the lithological, topographical or structural characteristics of the terrain.
Floors: to not occur or contaminants, or discharges, or earthworks, the impact on the physical and chemical soil characteristics or credibility is zero.
surface and underground water: no alteration of aquifers or surface water or by consumption or pollution by waste or spillage occurs.
Landscape: solar panels have different possibilities for integration, which makes them easy to integrate and harmonize element in different types of structures, minimizing their visual impact. Moreover, as autonomous systems, not the landscape with poles and power lines altered.
Noises: the photovoltaic system is absolutely silent, which represents a clear advantage over motor generators in remote homes.
Moreover, photovoltaic solar energy is the best solution for those places that you want to provide electricity while preserving the environmental conditions; as is the case for example of Protected Natural Areas.
What is the peak power of a panel?
It is the output power, in watts, producing a photovoltaic panel under conditions of maximum solar lighting, with a radiation of about 1 kW / m2 (which occurs on a sunny day at solar noon).
As a photovoltaic panel manufactured?
A photovoltaic panel is formed by a set of solar cells electrically connected together in series and parallel to the required voltage for use.
Cross section of a photovoltaic panel
This group of cells is surrounded by elements that confer protection against external agents and rigidity to engage the structures that support them. The elements are:
Encapsulation, consisting of a material should have good radiation transmission and low degradability to the action of sunlight.
Tempered glass outer sheath, which, apart from providing maximum light transmission, must withstand the most adverse and sudden changes in temperature withstand weather conditions.
Rear cover, normally made up of several opaque layers that reflect light that has passed between the interstices of the cells, causing again influence on them again.
Setting of metal, usually aluminum, which ensures rigidity and tightness joint, and carries the elements needed (usually bores) for mounting the panel on the support structure.
Terminal box: incorporates the terminals for connecting the module.
Protection diode: preventing damage by partial shadows on the panel surface.
What is the difference between monocrystalline and polycrystalline panels?
Photovoltaic panels are composed of photovoltaic cells of monocrystalline or polycrystalline silicon. The difference between them lies in the manufacturing process. The monocrystalline silicon cells are obtained from very pure silicon, which is remelted in a crucible together with a small proportion of boron. Once the material is in liquid state it is inserted a rod with a “seed crystal” silicon, which is becoming regrow new atoms from the liquid, which are arranged following the crystal structure. Thus, a doped single crystal, which is then cut into wafers about 3 tenths of a millimeter thick is obtained. These wafers are then introduced in special furnaces, into which phosphorus atoms are deposited on one side and reach a certain depth in the surface spread. Subsequently, and before screen printing for surface interconnections, they are coated with an antireflective treatment of titanium dioxide or zirconium.
In polycrystalline cells, rather than from a single crystal, it is allowed to slowly solidify the paste on a silicon mold, whereupon a solid formed by many small silicon crystals, which can then be cut into thin multi crystalline wafers is obtained.
In what factors affect the efficiency of a photovoltaic panel?
Fundamentally the intensity of light radiation and temperature of the solar cells.
Current and voltage variation with radiation and temperature according to nominal power
The current intensity generated by the panel increases with radiation, remaining approximately constant voltage. In this connection it is very important placing panels (its orientation and inclination to the horizontal), as the radiation values vary throughout the day depending on sun angle relative to the horizon.
The temperature increase in the cells an increase in the current, but also a much greater decrease proportionally voltage. The overall effect is that the panel power decreases with increasing temperature of the same. A radiation 1000 W / m2 is capable of heating a panel about 30 degrees above the temperature of the surrounding air, which reduces the voltage at 2mV / (cell * degree) * 36 * 30 degrees cells = 2.16 Volts and thus the power by 15%. It is therefore important to place the panels in a place where they are well ventilated.
The incorporation of a solar tracking system does it improve the performance of photovoltaic capture?
It depends on the weather and the type of application. Ideally, system performance can be improved up to 40%, but the higher cost of not offset the increase is achieved. Its application is limited to cases where the highest performance coincides with increased demand (in the case of pumping systems for livestock in very dry regions).
What characteristics define the behavior of a battery?
Serves, in a photovoltaic system, how long the system can operate without light radiation recharge the batteries. This measure of the days of autonomy is one of the important parts in the design of the installation.
Theoretically, for example, 200 Ah battery can supply 200 A for an hour, or 50 A for 4 hours, or 4 A for 50 hours, or 1 A for 200 hours.
However, this is not exactly true, since some batteries, including automotive, are designed to produce fast downloads in short periods of time without damage. However, they are not designed for long periods of low discharge. This is why automotive batteries are not the most suitable for photovoltaic systems.
Factors that can vary the capacity of a battery:
Loading and unloading ratios. If the battery is charged or discharged to a different specified rate, the available capacity may increase or decrease. Generally, if the battery is discharged at a slower pace, its capacity will increase slightly. If the pace is faster, the capacity will be reduced.
Temperature. Another factor that influences the capacity is the temperature of the battery and its environment. The behavior of a battery is classified at a temperature of 27 degrees. Lower temperatures reduce capacity significantly. Higher temperatures produce a slight increase in capacity, but this can increase water loss and decrease the number of cycles of battery life.
Depth of discharge:
Batteries “shallow cycle” are designed to download 10 to 25% of its total capacity in each cycle. Most batteries “deep cycle” manufactured for photovoltaic applications are designed for downloads of up to 80% of capacity, without damage. Battery manufacturers NiCad say they can be fully discharged without harm.
The depth of discharge, however, even affects deep cycle batteries. The greater the discharge, the smaller the number of charge cycles the battery can have.
What is the composition of a solar lead acid battery?
These batteries are composed of several lead plates in a sulfuric acid solution. The plate consists of a grid of lead alloy with a lead oxide paste on the grid embedded. The solution of sulfuric acid and water is called electrolyte.
Construction of a monoblock battery (VARTA)
The grid material is an alloy of lead because the lead is a pure physically weak material and could break during transport and battery service.
Normally the alloy is lead with 2-6% antimony. The lower the antimony content is less resistant battery during the charging process. The lower amount of antimony reduces the production of hydrogen and oxygen during charging, and thus water consumption. Moreover, a higher proportion of antimony allows deeper discharges without damaging the plates, which implies a longer life of the batteries. This lead-antimony are the type of “deep cycle”.
Cadmium and strontium are used instead of antimony to strengthen the grid: offer the same advantages and disadvantages of antimony, but also reduce the rate of self-discharge the battery suffers when not in use.
Calcium also strengthens the grid and reduces the self-discharge. However, calcium reduces the recommended depth of discharge to no more than 25%, so the lead-calcium batteries are the type of “shallow cycle”.
The positive and negative plates are immersed in a solution of sulfuric acid and subjected to a load of “training” by the manufacturer. The direction of this loading results in the paste to the grid of the positive plates is lead dioxide transforms. Paste negative plates become spongy lead. Both materials are highly porous, allowing the sulfuric acid solution penetrates freely into plates.
The plates alternate in the battery, with separators between them, which are made of a porous material that allows the flow of electrolyte. electrically nonconductive. May be mixtures of silicone and plastics or rubbers.
The spacers may be individual sheets or “envelopes”. Envelopes are sleeves, open at the top, which are placed only on the positive plates.
Regardless of the size of the plates, a cell only a nominal supply voltage of 2 volts (for lead acid). A battery consists of several cells connected in series or elements, internally or externally, to increase the voltage to normal values to electric appliances. Therefore, a battery of 6 V is composed of three cells, and a 12 V 6.
Positive on one side and the negative plates on the other are interconnected by external terminals at the top of the battery.
What is the sulfation of battery Lead-acid?
If lead-acid battery is left in a state of deep discharge for a long period of time, sulphation will occur. Sulfur acid part will be combined with lead from the plates to form lead sulfate. If the battery is not filled with water periodically, part of the plates will be exposed to air, and the process will be accelerated.
The lead sulfate covering the plates so that the electrolyte can not penetrate them. This represents an irreversible loss of battery capacity that even with the addition of water, can not be recovered.
How can you find out the state of charge of a battery?
A hydrometer (unassembled) from those used in stationary batteries
Density is weight of the electrolyte as compared with the same amount of water and is measured with a densimeter or hydrometer. The most common densimeter is used for automotive, indicating charging in percent. It has the disadvantage that it is calibrated for the electrolyte used in starter batteries and non-stationary, so mark always less than the real (50% for a fully charged battery stationary).
Can I get to freeze the accumulators? What temperature?
Since lead-acid batteries use an electrolyte that carries water, they may freeze. However, sulfuric acid leading acts as an antifreeze. The higher the percent acid in water, lower the freezing temperature. However, even a fully charged battery to an extremely low-temperature freeze.
As shown in the table, an accumulator lead-acid, 50% load, it will freeze at a temperature of about -25 degrees.
As can be seen, the battery must be kept above -10 degrees, if you will be fully discharged. If you will not be able to keep a higher temperature, keep it charging status at a high enough level to prevent freezing. This can be achieved automatically with a charge controller capable of disconnecting consumption when the battery voltage falls below a preset level.
- State Density Volts / glass Volts / set Freezing
- Steeped 1,265 2,12 12,70 -57 ° C
- Steeped 75% -38 12.60 2.10 1.225
- Steeped 50% 1,190 2,08 12,45 -25 ° C
- Steeped 25% 1,155 2,03 12,20 -16 ° C
- Unloaded 1,120 11.70 1.95 -10
State of charge, density, voltage and freezing point of a lead-acid battery
What is the effect of rapidly discharging a battery?
First, all the energy that is capable of providing the battery is not obtained. For example, a discharged battery within 72 hours returns approximately twice the energy that if discharged in only 8 hours.
Furthermore, discharges produce fast deformation and premature disintegration of the plates of the elements, which are deposited on the bottom of containers in powder form to reach shorting both plates, disabling the battery.
What effect does heat in batteries?
The temperature rise is extremely detrimental to the batteries. If the temperature of the containers is greater than about 40 degrees, it is necessary to decrease the charging rate.
Where be the batteries installed?
Must be sought a place where the temperature is warm, avoid cold or exposed to low temperatures places. It should also avoid temperatures below 0 degrees because then the internal resistance of the batteries increases greatly.
What is the danger of leaving a battery discharged for a long time?
The lead sulfate covering the plates hardens when the battery is discharged; pores clogged, leave penetrate the electrolyte and therefore can not act on the active elements of the plates, reducing the effective capacity. This also makes it very difficult to recharge a battery that has been left sulfated.
What are the most common causes of battery sulfation?
The most common causes of sulfation of a battery are:
- Leave it empty for a long time.
- Pure Add acid electrolyte.
- Overloading too frequent.
- Not have added distilled water at the right time.
- The transfer of electrolyte few glasses other.
What are the symptoms of a battery element is sulfated?
The most obvious symptoms are:
- The densimeter always registers a low density of the electrolyte, even though the element always subjected to the same charge as the other elements.
- The voltage is lower than other elements during discharge and during charging top.
- It is impossible to charge the battery to full capacity.
- The two plates, positive and negative, have a clear color.
- In extreme cases, one of the terminals protrudes more than normal due to the deformation of the plates.
What is and how a fuel cell works?
A fuel cell is an electrochemical device that generates electricity directly from chemical energy. Its construction is very similar to the accumulators consist of an electrolyte (which may be alkaline, phosphoric acid, molten carbonate or solid oxide) and two electrodes. The anode is fed with fuel (typically hydrogen) and the cathode with the oxidant (usually oxygen). To increase the effective area of the electrodes they are constructed with these porous materials. Furthermore, high pressures and high temperatures are used to promote the reaction. The byproduct of the chemical reaction is steam. Fuel cells phosphoric acids are approximately 40% yield and a working temperature of 200C. Currently, they manufactured in units of about 200kW. To learn more about this technology click here. | <urn:uuid:88c2a4fe-9eb7-493d-9045-4e758ed954cc> | 3.1875 | 4,430 | Knowledge Article | Science & Tech. | 35.933008 | 95,604,521 |
I need help with this question. I just need some steps in figuring it out Im totally lost Recall that mRNA has one start codon and three codons. based on what you know about process of gene expression, hypothesize why it would be benefecial to have only one start codon but three stop codons in this process.© BrainMass Inc. brainmass.com July 17, 2018, 9:39 am ad1c9bdddf
The genetic code establishes which amino acids will be added to a growing polypeptide. It also specifies for the initiation of translation by the start codon (UAG) and termination of translation by the stop codons (UAG, UGA, and UAA). There is a degeneracy in the genetic code whereby an amino acid may correspond to more than one codon. With 4 bases and three positions there are 64 possible codons, but there are only 20 amino acids.
The ability for more than one codon to specific an amino acid allows for the system to accommodate a certain amount of somatic mutations. For example, serine is specified by the codons UCA, UCG, UCC, UCU, AGU, AGC. If the codon UCA is mutated to UCU the amino acid is preserved. Serine residues main be modified via phosphorylation as a means to regulate protein activity. In cases ...
Several paragraphs developing a hypothesis as to why there is only 1 start codon but 3 stop codons. Web references provided. | <urn:uuid:00d73c51-b9f7-4667-aca9-c6192cfe41ff> | 3.015625 | 313 | Q&A Forum | Science & Tech. | 48.620019 | 95,604,535 |
Collaborative project uncovers the role of a protein in the formation and maintenance of the inner membrane structures of photosynthetic systems
Chloroplasts are the solar cells of plants and green algae. In a process called photosynthesis, light energy is used to produce biochemical energy and the oxygen we breathe. Thus, photosynthesis is one of the most important biological processes on the planet.
A central part of photosynthesis takes place in a specialized structure within chloroplasts, the thylakoid membrane system. Despite its apparent important function, until now it was not clear how this specialized internal membrane system is actually formed.
In a collaborative project, researchers at Johannes Gutenberg University Mainz (JGU) in Germany have now identified how this membrane is generated. According to their findings, a protein called IM30 plays a major role by triggering the fusion of internal membranes. The study elucidating the role of IM30 involved biologists, chemists, biochemists, and biophysicists at Mainz University and the Max Planck Institute for Polymer Research. Their results have recently been published in the journal Nature Communications.
Chloroplasts are organelles found in higher plants and green algae. They contain an internal membrane system, so-called thylakoid membranes, where the key processes of photosynthesis take place. "A detailed understanding of photosynthesis and the associated molecular processes is essential to properly comprehend life on our planet," emphasized Professor Dirk Schneider of the Institute of Pharmaceutical Sciences and Biochemistry at JGU, who coordinated the study.
"Despite the significance of the process, we know almost nothing about how these special membranes are formed and maintained." It had not previously been possible to identify a single fusion-mediating protein in photosynthetic cells, even though it was perfectly clear that such proteins have to be involved in the development of thylakoid membranes.
With this in mind, the Mainz-based research team isolated and investigated the protein IM30 from a blue-green alga, which might be classified as a "free-living chloroplast." IM30 – the "IM" stands for "internal membrane" while 30 is its atomic mass (30 kilodaltons) – was first described in the mid-1990s and it was demonstrated that it binds to internal membranes.
Thanks to the combined expertise of the teams headed by Professor Dirk Schneider, Professor Jürgen Markl of the JGU Institute of Zoology, and Professor Tobias Weidner of the Max Planck Institute for Polymer Research it has now emerged that IM30 forms a ring structure that specifically interacts with phospholipids of the membranes.
"This binding alters the membrane structure and under certain conditions can lead to membrane fusion," explained Schneider. In absence of IM30, thylakoid membranes are noticeably deteriorated, which can subsequently lead to loss of cell viability. The IM30 fusion protein provides a starting point for future research, unraveling new types of membrane fusion mechanisms in chloroplasts and blue-green algae.
The interdisciplinary research project was primarily undertaken by doctoral candidates at the Max Planck Graduate Center (MPGC). The MPGC was founded in June 2009 to support joint projects and shared doctorates at Johannes Gutenberg University Mainz and the Max Planck Institutes for Polymer Research and for Chemistry, both of which are based in Mainz.
Raoul Hennig et al.
IM30 triggers membrane fusion in cyanobacteria and chloroplasts
Nature Communications, 8. Mai 2015
Professor Dr. Dirk Schneider
Institute of Pharmaceutical Sciences and Biochemistry – Therapeutic Life Sciences
Johannes Gutenberg University Mainz (JGU)
55099 Mainz, GERMANY
phone +49 6131 39-25833
fax +49 6131 39-25348
http://www.uni-mainz.de/presse/18298_ENG_HTML.php - press release ;
http://www.bio.chemie.uni-mainz.de/46.php – Prof. Dirk Schneider ;
http://www.bio.uni-mainz.de/zoo/312_DEU_HTML.php – Prof. Jürgen Markl ;
http://www.mpip-mainz.mpg.de/~weidner – Prof. Tobias Weidner ;
http://www.nature.com/naturecommunications – Nature Communications
Petra Giegerich | idw - Informationsdienst Wissenschaft
World’s Largest Study on Allergic Rhinitis Reveals new Risk Genes
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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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17.07.2018 | Power and Electrical Engineering | <urn:uuid:965de59c-8414-40d3-b5ce-677b7bc72aeb> | 3.609375 | 1,595 | Knowledge Article | Science & Tech. | 38.133419 | 95,604,542 |
Publisher: Wikipedia 2014
Gamma-ray bursts (GRBs) are flashes of gamma rays associated with extremely energetic explosions that have been observed in distant galaxies. They are the brightest electromagnetic events known to occur in the universe. Bursts can last from ten milliseconds to several minutes.
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by A. Biviano - arXiv
This is a review of the properties of galaxy systems as determined from optical and infrared measurements. Covered topics are: clusters identification, global cluster properties and their scaling relations, cluster internal structure, etc.
by Regina Schulte-Ladbeck, at al. - Hindawi Publishing
Dwarf galaxies provide opportunities for drawing inferences about the processes in the early universe by observing our Local Group and its vicinity. This issue is a snapshot of the current state of the art of dwarf-galaxy cosmology.
by F. Aharonian, A. Bykov, E. Parizot, V. Ptuskin, A. Watson - arXiv
We review sources of cosmic rays, their composition and spectra as well as their propagation in the galactic and extragalactic magnetic fields, both regular and fluctuating. A special attention is paid to the recent results of the observations.
by Alison L. Coil - arXiv
On large scales the Universe displays coherent structure, with galaxies residing in groups and clusters, which lie at the intersections of long filaments of galaxies. Vast regions of relatively empty space span the volume between these structures. | <urn:uuid:b399488f-7086-4579-a9be-0ccc8a6d4055> | 2.5625 | 321 | Content Listing | Science & Tech. | 34.450581 | 95,604,589 |
Ghost particles, otherwise known as neutrinos, are literally everywhere—trillions of them, each with barely any mass at all, are passing through your body right now. But we understand very little about how these particles work. That’s an absolute shame, since they might be key to explaining some of the biggest mysteries of the universe, including why there is a universe.
We just took a large step forward in answering those questions. In a pair of new papers published Thursday in Science, an international research team of hundreds announce they’ve discovered evidence of the origins of these tiny, elusive particles: giant, oval-shaped galaxies called blazars. The findings resolve more than a century’s worth of work in pinpointing what is thrusting subatomic particles like neutrinos as high-energy cosmic rays off through space.
“We have been observing cosmic neutrinos since 2013,” says Francis Halzen, a physicist at the University of Wisconsin-Madison and the lead scientist for the IceCube Neutrino Observatory that spearheaded the new findings. “We had no idea where they came from.”
The key to this latest discovery was in trying to figure out what other high-energy events neutrinos might be associated with. That’s where multi-messenger astronomy comes in: the study of astrophysical events through several different signals. For example, if you were trying to learn as much as possible about a dynamite explosion, you wouldn’t just make a recording with your phone. You’d want to make observations in different wavelengths of light, make audio recordings, and more. In astronomy, multi-messenger means observing signals relating to electromagnetic radiation, gravitational waves, neutrinos, and cosmic rays.
“Neutrinos point back at their sources,” says Halzen, “and so we were trying to associate their arrival directions with known sources, including blazers. This was not successful until we started this multi-messenger campaign.”
IceCube, a kilometer-sized telescope that sits under a mile of ice in the South pole, has been running since 2011, and has used its several thousand sensors to observe nearly 100,000 neutrinos a year. Its express purpose is to find neutrinos, near or far (and in the case of this latest observation, very far). It’s a powerhouse observatory for tracking elementary particles, but if we’re trying to connect neutrinos with other signals in order to find the origin point, we need to turn to other instruments for aid.
IceCube is equipped with an alert system that goes off when it detects extremely high-energy neutrinos. That alert system relays coordinates to other telescopes around the world and tells them to make follow-up observations.
For this investigation, IceCube found a really high neutrino event on September 22, 2017. NASA's orbiting Fermi Gamma-ray Space Telescope and the Major Atmospheric Gamma Imaging Cherenkov Telescope in the Canary Islands were put on alert, and they ended up detecting high-energy gamma rays coming from a galaxy called TXS 0506+056—a blazar—about 4 billion light-years from Earth, located off the upper-left corner of Orion. The gamma-ray activity, some of the strongest ever detected by Fermi from that source, lined up incredibly well with the neutrino coordinates sent by IceCube.
Although blazars weren’t the expected source for neutrinos, they make sense when you realize how well they live up to their wicked-sounding name. “In active galaxies, the supermassive black hole powers two massive jets, which shoot outwards from the galaxy carrying high-energy particles and powerful radiation and magnetic fields,” explains Marcos Santander, a physicist and astronomer at the University of Alabama and a coauthor of the new studies. “Blazars are a kind of active galaxy where one of these jets happens to be oriented towards the line of sight of the Earth, meaning that we’re looking at the jet ‘down the barrel of the gun.’” This alignment means we can observe very energetic radiation sprawled across the entire electromagnetic spectrum, from radio waves, to visible light, to gamma rays—energies that, for blazars, peak at more than 10 trillion times the energy of visible light. “The strong shock waves along the blazar jet are known to contain high-energy particles capable of producing gamma rays and may accelerate cosmic rays,” he says.
These jets are responsible for accelerating cosmic rays, which are made of mostly protons. When protons interact with photons and hydrogen from the blazar or the black hole jet, they produce neutrinos. “So, neutrinos trace cosmic rays,” says Halzen. “They are tied at the hip.”
If we understand that neutrinos are produced alongside cosmic rays, then that means they must have the same source of origin as the cosmic rays themselves. “While the cosmic rays that we detect do not point back to their sources—because their electric charge and their path are distorted by magnetic fields—the neutrinos point back to the site where they were created,” says Halzen. “The neutrinos allowed us to pinpoint this source along with some twenty other telescopes.”
So that was the first piece of evidence the team needed. Once they knew TXS 0506+056 was the source of the September 22 neutrino detection, the researchers looked back at about 10 years of archival data, finding high-energy neutrino bursts coinciding with more than a dozen other flares emanating from that blazar in just a short span in 2014 and 2015 alone. This was the second piece of evidence. “This clinched everything,” says Halzen.
There is, of course, reason to be cautious about the findings. Blazars have long been a candidate source for emitting neutrinos, but previous studies trying to tie neutrinos to blazars fell short. It’s not totally clear why TXS 0506+056—which isn’t even the brightest known gamma-ray blazar—fit the bill when others could not. Blazars can’t yet be labeled wholesale as neutrino factories.
“I don't think we're in a position either to say ‘it's all blazars,’” says University of Maryland physicist Erik Blaufuss, another coauthor of the papers. “I think it’s hard to draw too strong of conclusions about all blazers based on a sample of one. I think it’s still to be determined if this source is somehow special or just the first to ‘poke it’s head out of the grass’ and be bright enough in neutrinos for us to see.”
If high-energy action is key to explaining why blazars emit neutrinos, then we should pretty readily see the similar results arising from observations or starburst galaxies and gamma-ray bursts. If not, then it means there’s something much more specific and eccentric going on with blazars than we currently know.
And even if we just focus locally on this blazar itself, “this also certainly isn’t a gold plated discovery either,” says Blaufuss. Scientists typically use a 5-sigma threshold to label something as a “discovery,” And the analyses for both of these latest papers, according to Blaufuss, are 3-sigma, which signifies “evidence,” but not necessarily a discovery. A 3-sigma level still means you can allow for pretty high confidence the results aren’t due to random chance, but when it comes to particle physics, that sort of chance can still create wary feelings. It’s best to welcome the new findings with cautious enthusiasm.
For now, the team is also just basking in its hard efforts finally paying off. “Making a breakthrough on one of the oldest outstanding problems in astronomy is exciting,” says Halzen. “This is what IceCube was built for. That our first source is a blazar was somewhat surprising, but one cannot argue with facts.” | <urn:uuid:d6ba75f8-ae1f-4be1-a009-0d33c7364ff8> | 3.640625 | 1,743 | News Article | Science & Tech. | 41.783972 | 95,604,630 |
Graphene proves to be source of infinite energy: A revolution in energy
U.S. physicists accidentally discovered that graphene can generate energy with the help of the environment and will become a game changer in energy and bionics in the near future.
The existence of graphene in nature is a phenomenon that became possible due to the fact that scientists found a “loophole” in the laws of physics and forced a solid two-dimensional atomic sheet to behave like a three-dimensional material. More and more new studies have revealed useful applications of this material, and the forecasts sound very encouraging: it turns out that graphene can be used to obtain an almost infinite number of energy!
A team of physicists led by researchers from the University of Arkansas made the discovery entirely by accident. The original purpose of their tests was to study the vibration of graphene – but why?
We are all familiar with granular graphite, which is commonly used together with ceramic components to create a pencil rod. The black streak left behind after pencil lead is traced over paper is actually thin sheets of carbon atoms that slide easily over one another. For years physicists have wondered: could such a sheet be isolated and made into an independent two-dimensional plane?
In 2004, physicists from Manchester University succeeded in doing this. To exist separately from one another, the sheets of carbon atoms must behave like a three-dimensional material to ensure the necessary stability. The “loophole” in this case proved to be is the displacement of mobile atoms, which gives graphene the properties of a third dimension. In other words, graphene was never 100% flat – it vibrated at the atomic level so that its connections did not undergo spontaneous decay.
Physicist Paul Thibado recently led a group of graduate students in conducting a very simple study with the precise goal of measuring the level of this displacement and vibration. The scientists laid out graphene sheets on a special copper netting and observed changes in the positions of atoms with a microscope. However, the numbers did not match the expected model for some reason. Moreover, the data varied from test to test.
Graphene as a source of energy
Thibado decided to take the experiment in another direction in an attempt to find a suitable template and alter the method used to analyse the data. The researchers divided each image obtained during the measurement into sub-images. The strategy proved to be correct: a large-scale picture did not allow for studying the laws of atomic motion, however an analysis of its details resulted in an interesting discovery. It was assumed that the sheets of graphene moved according to the same principle as bent sheets of metal, but this assumption proved to be false.
It turned out that it was all a matter of so-called Levy flights – templates of small random oscillations combined with sudden, sharp shifts. Similar systems were previously observed in biological and climatic systems, but this marked the first time physicists had seen them on an atomic scale. Measuring the speed and scale of these graphene waves, Thibado suggested that they could be used to extract energy from the environment.
While the ambient temperature prevents the “comfortable” movement of graphene atoms relative to one another, they will continue to pulsate and flex. Place electrodes on both sides of a section of this graphene and you'll get a tiny generator. According to calculations, a 10x10 micron graphene graph has capacity of 10 microwatts. Given that as many as 20,000 such squares could fit on a pinhead, such a "power station" does not look very impressive, does it?
However, at room temperature this power would be enough to provide energy for a small gadget – for example, wrist watches. It is also interesting that in the future such a method of obtaining energy could lead to the creation of bioimplants that would not require bulky batteries.
At present, Thibado is already working with scientists from the U.S. Naval Research Laboratory to figure out if this strategy has a future. Perhaps graphene will become a source of “energy of the future”, which will make it possible to make a significant technological breakthrough in the near future.
During the panel discussion ‘Finding a New Balance on the Oil Market’ as part of REW 2017, Zarubezhneft General Director Sergey Kudryashov noted that the agreement with OPEC+ countries on reducing oil production has stabilized the situation in the industry.
The Berlin Energy Transition Dialogue (BETD) has presented its Green Sofa at REW 2017. BETD's trademark Green Sofa has made a name for itself by touring international events and hosting interviews on the subject of world energy among more than 500 leading politicians.
October 12, Moscow. – Several oil sector agreements were signed during Russian Energy Week. Cooperation between Irkutsk Oil Company and the Japanese company JOGMEC moved to the next phase of development with a new joint venture, INK-Krasnoyarsk. This agreement to expand the parameters of cooperation includes plans for geological exploration at five licensed sites in Krasnoyarsk Territory. “Our | <urn:uuid:22eba266-2f0a-4669-b5ac-c287084fa28e> | 3.3125 | 1,043 | News Article | Science & Tech. | 32.634437 | 95,604,639 |
Curriculum Subject Areas
→ Middle School
→ Investigations into Mathematics (IM)
Unit 1 - Ratios and Proportional Relationships - Overview
Unit 2 - Rational Number Operations - Overview
Unit 3 - Expressing Geometric Relationships - Overview
Unit 4 - Statistics and Probability - Overview
Unit 5 - The Real Number System - Overview
Unit 6 - Functional Relationships and Linear Equations - Overview
Unit 7 - Transformations and Geometric Measurement - Overview
Get an explanation of what your child will be learning in Investigations into Mathematics in the Middle School Course Bulletin.
The framework for Investigations into Mathematics is based on the Common Core State Standards for Mathematics. | <urn:uuid:4b88c139-694b-4793-9471-4fd2cd86566c> | 4.15625 | 138 | Tutorial | Science & Tech. | -21.928913 | 95,604,641 |
Filters: Tags: A1-Wildlife (X)29 results (40ms)
We studied the kill rate by wolves (Canis lupus) after a large-scale wolf removal when populations of wolves, moose (Alces alces), and woodland caribou (Rangifer tarandus caribou) were all increasing. We followed a total of 21 wolf packs for 4 winters, measuring prey selection, kill rates, and ecological factors that could influence killing behavior. Wolf predation was found to be mainly additive on both moose and caribou populations. Kill rates by individual wolves were inversely related to pack size and unrelated to prey density or snow depth. Scavenging by ravens decreased the amount of prey biomass available for wolves to consume, especially for wolves in smaller packs. The kill rate by wolves on moose calves...
We studied kill rates by wolves (Canis lupus) on a rapidly growing moose population in the east-central Yukon. We added these data to the cumulative functional response curve obtained in other North American wolf studies. Our kill rates are higher than those predicted at low moose densities. The kill rate increases rapidly, reaching 2.4 moose per wolf per 100 days at 0.26 moose/km2 and remains constant at this level. No data are available below 0.2 moose/km2 to indicate the shape of the ascending curve. Based on moose distribution and the low prey-switching ability of wolves, we suggest that the functional response curve is of type II. Our wolf predation rate model predicts that moose are held to a low density equilibrium...
Regional Assessment of Wildlife in the Yukon Southern Lakes Region: Volume 1: Context and Recommendations
The northern goshawk (Accipiter gentilis) is a rare to uncommon forest raptor that is widely distributed in boreal & temperate forests. This report first reviews the goshawk's distribution, taxonomy, biology, habitat, threats to its population, conservation status, and current conservation & research actions related to this species in British Columbia. It then sets out options for management of the goshawk's habitat and a strategy for conservation that would maintain or enhance the goshawk population. Finally, priorities for research are recommended and actions to evaluate the conservation initiative are outlined.
Short-term impacts of military jet overflights on the Fortymile caribou herd during the calving season
Regional Assessment of Wildlife in the Yukon Southern Lakes Region: Volume 2: Species Status Assessment
Prioritizing avian conservation areas for the Yellowstone to Yukon Region of North America [electronic resource] | <urn:uuid:2f205723-48a8-4102-b85d-4377fa7c2699> | 2.65625 | 549 | Content Listing | Science & Tech. | 32.629272 | 95,604,650 |
Apr 03, 2017 10:28 AM EDT
International Space Station crew members conducted research on how to improve the growth of crystals on Earth. The data is intended to improve the drug development process for humans all over the world.
These crystals are proteins that play an important role in the human body. They help the body regulate, repair and protect itself. Since they are too small to be studied under a microscope, they are crystallized to determine their 3D structures.
The structures reveal to researchers how a certain protein functions as well as its involvement in the development of disease. Once a model has been created, drug developers can use the structure to develop a drug that can safely interact with the protein. This process is called the structure-based drug design.
Phys.org reported that the ISS crew conducted two investigations: The Effect of Macromolecular Transport on Microgravity Protein Crystallization (LMM Biophysics 1) and Growth Rate Dispersion as a Predictive Indicator for Biological Crystal Samples Where Quality Can be Improved with Microgravity Growth (LMM Biophysics 3). They studied the formation of the crystals with regard to how microgravity-grown crystals usually have a higher-quality than Earth-grown ones as well as which types of crystals benefit most from being grown in space.
The first study will investigate whether the cause of high-quality in crystals is because they grow slower in microgravity due to a lack of buoyancy-induced convection or whether a higher level of purification can be achieved in microgravity. The data results will be gathered from improved X-ray diffraction.
The second study, according to News-Medical.net, will examine which crystals benefit from crystallization in space. It was noted that only some proteins crystallized in space benefit from microgravity growth. The protein's shape and surface that makes up a crystal defines its potential for success in microgravity.
The understanding of how these different proteins crystallize in microgravity can give researchers a better view of how these proteins function. It can also help to determine which crystals ought to be transported to the space station for growth.
See Now: Facebook will use AI to detect users with suicidal thoughts and prevent suicide© 2017 University Herald, All rights reserved. Do not reproduce without permission. | <urn:uuid:2d2edbe9-b8a8-476a-947c-6651f55b9a93> | 3.890625 | 463 | Truncated | Science & Tech. | 37.746754 | 95,604,652 |
There are two known ways that such silica-rich soil – which is 90% pure silicon dioxide – could have formed. Water heated by subsurface volcanic activity, with lots of silica dissolved in it, could have percolated up into the soil, and then as it evaporated left the silica behind.The find has resulted in the area where the silica was uncovered being christened "silica valley." The New Scientist says NASA is now working to figure out the composition of the remaining portion of the soil that isn't silica in order to determine how the mineral was formed.
Or hot, highly acidic steam from a volcanic eruption – essentially concentrated sulfuric acid – could have rained down on soil that contained a variety of minerals, and leached away everything except the silica. Both mechanisms occur on Earth: the action of acidic steam is seen around fumaroles in places such as Yellowstone, and the water percolating through volcanic soil is common around volcanoes in Hawaii.
Either way, there was a lot of water involved. "Both of these involve substantial interactions of water with hot volcanic material," [rover lead scientist Steven Squyres] said. | <urn:uuid:de02d6ca-281a-4b68-b1de-cd0065e14bb9> | 4.125 | 241 | News Article | Science & Tech. | 31.7825 | 95,604,662 |
Coronal mass ejection is an exploding bubble of plasma, charged particles, and magnetic fields that expands out into space from the Sun's corona. During this bursting of bubble-shaped solar plasma, the charged particles are sent out at the speed of light. The ejected plasma is composed mainly of protons and electrons, as well as quantities of elements. This phenomenon usually causes disruption in satellites and magnetic storms on Earth. Coronal mass ejection is caused by magnetic reconnection, which is the rearrangement of magnetic field lines in the Sun. | <urn:uuid:2881c081-e00b-40f2-9592-a8f72cba3877> | 3.78125 | 110 | Knowledge Article | Science & Tech. | 39.105 | 95,604,675 |
- Reason why raindrops and spilt coffee splash revealed by University of Warwick research
- New theory uncovers – for first time – what happens in space between liquid drop and surface to cause splash
- Microscopic layer of air – 50 times smaller than a human hair – trapped between liquid and surface can prevent liquid spreading on surface
- Scale comparable to a 1cm layer of air stopping a tsunami wave spreading across a beach
- Research published in top Physics & Mathematics journal
New research from the University of Warwick generates fresh insight into how a raindrop or spilt coffee splashes.
Dr James Sprittles from the Mathematics Institute has created a new theory to explain exactly what happens - in the tiny space between a drop of water and a surface - to cause a splash.
When a drop of water falls, it is prevented from spreading smoothly across a surface by a microscopically thin layer of air that it can’t push aside - so instead of wetting the surface, parts of the liquid fly off, and a splash is generated.
A layer of air 1 micron in size – fifty times smaller than the width of a human hair – can obstruct a 1mm drop of water which is one thousand times larger.
This is comparable to a 1cm layer of air stopping a tsunami wave spreading across a beach.
Dr Sprittles has established exactly what happens to this miniscule layer of air during the super-fast action by developing a new theory, capturing its microscopic dynamics – factoring in different physical conditions, such as liquid viscosity and air pressure, to predict whether splashes will occur or not.
The lower the air pressure, the easier the air can escape from the squashed layer – giving less resistance to the water drop - enabling the suppression of splashes. This is why drops are less likely to splash at the top of mountains, where the air pressure is reduced.
Understanding the conditions that cause splashing enables researchers to find out how to prevent it – leading to potential breakthroughs in various fields.
In 3D printing, liquid drops can form the building blocks of tailor-made products such as hearing aids; stopping splashing is key to making products of the desired quality.
Splashes are also a crucial part of forensic science - whether blood drops have splashed or not provides insight into where they came from, which can be vital information in a criminal investigation.
Dr Sprittles comments:
“You would never expect a seemingly simple everyday event to exhibit such complexity. The air layer’s width is so small that it is similar to the distance air molecules travel between collisions, so that traditional models are inaccurate and a microscopic theory is required.
“Most promisingly, the new theory should have applications to a wide range of related phenomena, such as in climate science – to understand how water drops collide during the formation of clouds or to estimate the quantity of gas being dragged into our oceans by rainfall.”
The research, ‘Kinetic Effects in Dynamic Wetting’, is published in Physical Review Letters. It is supported by grants from the Leverhulme Trust and the Engineering and Physical Sciences Research Council (EP/N016602/1).
Notes for editors:
The University of Warwick’s Mathematics Institute was ranked 3rd in the UK by the 2014 REF (Research Excellence Framework) - with more than 90% of research activity assessed as either internationally excellent or world leading.
The research environment at Warwick is rated by REF 2014 as the very best in the UK for mathematical sciences (achieving the maximum possible score of 100% at 4*).
Dr Sprittles is a part of Micro & Nano Flows for Engineering, a research partnership between the Universities of Warwick and Edinburgh, and Daresbury Laboratory.
17 March 2017 | <urn:uuid:02d207aa-9d3c-49c7-9c7b-ef13efc9c90b> | 3.515625 | 782 | News (Org.) | Science & Tech. | 31.548765 | 95,604,676 |
What property makes a given material a good conductor? What property makes a given material a good insulator?© BrainMass Inc. brainmass.com July 19, 2018, 1:41 pm ad1c9bdddf
Conductivity is the measure of the ability of a material to transfer electric charges from one point to another under the influence of an external electric field. Insulating is just the opposite, that is, the property by which the electron flow is limited or impeded.
<br>In a good conductor, there must be free electrons available to ... | <urn:uuid:192d0ef7-3f29-4d96-aac9-01535f055e05> | 3.359375 | 117 | Truncated | Science & Tech. | 52.529134 | 95,604,701 |
Astronomers, including the University of California, Riverside's Bahram Mobasher and his graduate student Hooshang Nayyeri, have discovered that one of the most distant galaxies known is churning out stars at a shockingly high rate. The researchers made the discovery using NASA's Spitzer and Hubble space telescopes. The blob-shaped galaxy, called GN-108036, is the brightest galaxy found to date at such great distances.
This image shows one of the most distant galaxies known, called GN-108036, dating back to 750 million years after the Big Bang that created our universe. The galaxy's light took 12.9 billion years to reach us. Credit: NASA/JPL-Caltech/STScI/University of Tokyo
The galaxy, which was discovered and confirmed using ground-based telescopes, is 12.9 billion light-years away. Data from Spitzer and Hubble were used to measure the galaxy's high star production rate, equivalent to about 100 suns per year. For reference, our Milky Way galaxy is about five times larger and 100 times more massive than GN-108036, but makes roughly 30 times fewer stars per year.
The discovery is surprising because previous surveys had not found galaxies this bright so early in the history of the universe. According to the researches, GN-108036 may be a special, rare object that they happened to catch during an extreme burst of star formation.
The international team of astronomers, led by Masami Ouchi of the University of Tokyo, Japan, first identified the remote galaxy after scanning a large patch of sky with the Subaru Telescope atop Mauna Kea in Hawaii. Its great distance was then carefully confirmed with the W.M. Keck Observatory, also on Mauna Kea.GN-108036 lies near the very beginning of time itself, a mere 750 million years after our universe was created 13.7 billion years ago in an explosive "Big Bang." Its light has taken 12.9 billion years to reach us, so we are seeing it as it existed in the very distant past.
Infrared observations from Spitzer and Hubble were crucial for measuring the galaxy's star-formation activity. Astronomers were surprised to see such a large burst of star formation because the galaxy is so small and from such an early cosmic era. Back when galaxies were first forming, in the first few hundreds of millions of years after the Big Bang, they were much smaller than they are today, having yet to bulk up in mass.
During this epoch, as the universe expanded and cooled after its explosive start, hydrogen atoms permeating the cosmos formed a thick fog that was opaque to ultraviolet light. This period, before the first stars and galaxies had formed and illuminated the universe, is referred to as the "dark ages." The era came to an end when light from the earliest galaxies burned through, or "ionized," the opaque gas, causing it to become transparent. Galaxies similar to GN-108036 may have played an important role in this event.
"The high rate of star formation found for GN-108036 implies that it was rapidly building up its mass some 750 million years after the Big Bang, when the universe was only about five percent of its present age," said Mobasher, a professor of physics and astronomy. "This was therefore a likely ancestor of massive and evolved galaxies seen today."
The researchers report their findings in the Astrophysical Journal.
Other authors include: Kyle Penner and Benjamin J. Weiner of the University of Arizona, Tucson; Yoshiaki Ono, Kazuhiro Shimasaku and Kimihiko Nakajima of the University of Tokyo; Mark Dickinson and Jeyhan S. Kartaltepe of the National Optical Astronomy Observatory, Ariz.; Daniel Stern of NASA's Jet Propulsion Laboratory (JPL), Pasadena, Calif.; Nobunari Kashikawa of the National Astronomical Observatory of Japan; and Hyron Spinrad of UC Berkeley.
JPL manages the Spitzer Space Telescope mission for NASA's Science Mission Directorate, Washington. Science operations are conducted at the Spitzer Science Center at the California Institute of Technology in Pasadena. Caltech manages JPL for NASA.
The University of California, Riverside (www.ucr.edu) is a doctoral research university, a living laboratory for groundbreaking exploration of issues critical to Inland Southern California, the state and communities around the world. Reflecting California's diverse culture, UCR's enrollment has exceeded 20,500 students. The campus will open a medical school in 2013 and has reached the heart of the Coachella Valley by way of the UCR Palm Desert Center. The campus has an annual statewide economic impact of more than $1 billion.
A broadcast studio with fiber cable to the AT&T Hollywood hub is available for live or taped interviews. UCR also has ISDN for radio interviews. To learn more, call (951) UCR-NEWS.
Iqbal Pittalwala | EurekAlert!
Computer model predicts how fracturing metallic glass releases energy at the atomic level
20.07.2018 | American Institute of Physics
What happens when we heat the atomic lattice of a magnet all of a sudden?
18.07.2018 | Forschungsverbund Berlin
A new manufacturing technique uses a process similar to newspaper printing to form smoother and more flexible metals for making ultrafast electronic devices.
The low-cost process, developed by Purdue University researchers, combines tools already used in industry for manufacturing metals on a large scale, but uses...
For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.
To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...
For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.
Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...
Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.
A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...
Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.
"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....
13.07.2018 | Event News
12.07.2018 | Event News
03.07.2018 | Event News
20.07.2018 | Power and Electrical Engineering
20.07.2018 | Information Technology
20.07.2018 | Materials Sciences | <urn:uuid:06390bac-6d1e-4b17-a079-36802075f13b> | 3.953125 | 1,591 | Content Listing | Science & Tech. | 42.447291 | 95,604,731 |
Progress in quantum computers and their threat to conventional public key infrastructure is driving new forms of encryption. Quantum Key Distribution (QKD) using entangled photons is a promising approach. A global QKD network can be achieved using satellites equipped with optical links. Despite numerous proposals, actual experimental work demonstrating relevant entanglement technology in space is limited due to the prohibitive cost of traditional satellite development. To make progress, we have designed a photon pair source that can operate on modular spacecraft called CubeSats. We report the in-orbit operation of the photon pair source on board an orbiting CubeSat and demonstrate pair generation and polarisation correlation under space conditions. The in-orbit polarisation correlations are compatible with ground-based tests, validating our design. This successful demonstration is a major experimental milestone towards a space-based quantum network. Our approach provides a cost-effective method for proving the space-worthiness of critical components used in entangled photon technology. We expect that it will also accelerate efforts to probe the overlap between quantum and relativistic models of physics.
R. Chandrasekara, Z. Tang, Y. C. Tan, C. Cheng, L. Sha, G. C. Hiang, D. Oi, and A. Ling, "Generation and analysis of correlated pairs of photons on board a nanosatellite," Proc. SPIE 9996, Quantum Information Science and Technology II, 99960E (Presented at SPIE Security + Defence: September 27, 2016; Published: 26 October 2016); https://doi.org/10.1117/12.2241491.
Conference Presentations are recordings of oral presentations given at SPIE conferences and published as part of the conference proceedings. They include the speaker's narration along with a video recording of the presentation slides and animations. Many conference presentations also include full-text papers. Search and browse our growing collection of more than 12,000 conference presentations, including many plenary and keynote presentations. | <urn:uuid:290f314b-1b3b-4d52-aebb-c82727dfffcc> | 2.796875 | 402 | Academic Writing | Science & Tech. | 31.131204 | 95,604,733 |
Natural convection of a nanofluid inside a vertical circular enclosure exposed to a non-uniform heat flux
- Habibi Matin Meisam, Vaziri Shadi
- International Communications in Heat and Mass Transfer SCI(E) SCOPUS
- Elsevier in 2016
- Cited Count
In the present study natural convection of Al2O3-water nanofluid inside a vertical circular enclosure is investigated. The enclosure is exposed to heat flux with a non-uniform distribution from the bottom. The objective is finding the heat flux distribution for which the heat transfer coefficient is optimum at different values of the governing parameters. For examining the effect of heat flux distribution on thermal transport phenomenon, 9 various flux distributions are considered as cases 1 to 9. The bottom side of the enclosure is divided to six annular strips each of which receives a portion of the total heat i.e., the flux applied on each strip is different. The side wall is kept at constant temperature and the top wall is assumed to be adiabatic. A numerical finite volume scheme is employed to solve non-dimensional conservative equations in cylindrical coordinates. In addition to the heat flux distribution, the effects of Rayleigh number (104
1.Three-dimensional numerical simulation of buoyancy driven convection in vertical cylinders heated from below. J. Fluid Mech.. Vol. 214. 559578(1990) Neumann G.
2.On the onset of convective instabilities in cylindrical cavities heated from below. I. Pure thermal case(1999) D. Henry et al. PHYSICS OF FLUIDSPhysics cited 0 times
3.Three-dimensional instability of axisymmetric buoyant convection in cylinders heated from below(1996) Wanschura, M. et al. Journal of Fluid MechanicsPhysics cited 11 times
4.Numerical studies on laminar natural convection inside inclined cylinders of unity aspect ratio. Int. J. Heat Mass Transf.. Vol. 52. 822838(2009) Kurian V. et al.
5.Steady and oscillatory convection in vertical cylinders heated from below, Numerical simulation of asymmetric flow regimes. Adv. Space Res.. Vol. 8. 281292(1988) Crespo del Arco E. et al.
6.Laminar natural convection in a cylindrical enclosure with different end temperatures. Int. J. Heat Mass Transf.. Vol. 35. 545557(1992) Schneider S. et al.
7.Natural convection in vertical Bridgman configurations. J. Cryst. Growth. Vol. 70. 7893(1984) Muller G. et al.
8.Transitions to turbulence in helium gas. Phys. Rev. A. Vol. 36. 58705873(1987) Heslot F. et al.
9.Steady natural convection in a tilted long cylindrical envelope with the side wall is kept at constant temperature and the top wall is adiabatic al adiabatic surface, Part 2, Heat transfer rate, flow patterns and temperature distributions. Numer. Heat Transfer A. Vol. 44. 399431(2003) He Y.L. et al.
10.Steady natural convection in a vertical cylindrical envelope with adiabatic lateral wall. Int. J. Heat Mass Transf.. Vol. 47. 31313144(2004) He Y.L. et al. | <urn:uuid:78266de2-0420-40f2-a839-c5279b812020> | 2.71875 | 730 | Academic Writing | Science & Tech. | 57.547023 | 95,604,737 |
1 Comparative Planetology Mercury, Venus, Earth, Moon, Mars Astronomy 100Comparative PlanetologyMercury, Venus, Earth, Moon, Mars
2 Now: How are planets formed. Why does Earth have water Now: How are planets formed? Why does Earth have water? How do rocks form?Main concepts: solar system formation, comparative planetology, Moon formation hypotheses, cratering, plate tectonics, volcanism, earthquakes, atmosphere, solar wind/auroras,Vocabulary: protoplanetary disk, crater, Heavy Bombardment, cratering, atmosphere, mantle, differentiation, plastic, greenhouse effect, albedo, ejecta, rays, solar wind, auroras
3 Formation of the Solar System The Solar Nebula was spinningProtostarProtoplanetary diskBits coalescedTa-da – planets!NOW:String represents 5 billion years (50 feet)Each foot is 100 million years.Place the events in order.You have 20 minutes ONLY
15 Martian North Pole and Terrestrial (Earth) South Pole Describe three things that are the same about the landforms.Describe three things that are different about the landforms.Why do both planets have ice caps?Why are the ice caps different sizes?Valles Majas & the Grand CanyonWhat force do you think formed the Grand Canyon?What force do you think formed Valles Majas?Do you think it is the same force? Why or why not? How do your observations support this conclusion?Olympus Mons and the Hawai’ian IslandsUsing the contour gauge, trace the profile of both Olympus Mons and Hawai’i. Draw your guess for what the internal structure might look like inside both volcanoes.
17 Answer Now:Why do the Moon and Mercury have more craters than the Earth?What types of planets are there in our Solar System?
18 Vocabulary: Apollo, MER, Altair, Constellation, Venera, MESSENGER Now: How many other worlds have humans walked on? How many “planets” have we “explored?”Main concepts:Mercury missions past and futureVenus missions past and futureMoon missions past and futureMars missions past and futureVocabulary: Apollo, MER, Altair, Constellation, Venera, MESSENGER
19 Answer Now:Why do the Moon and Mercury have more craters than the Earth?What types of planets are there in our Solar System? | <urn:uuid:8c0db239-ab3b-4343-84d7-62b27cbd81d2> | 3.65625 | 512 | Content Listing | Science & Tech. | 37.949449 | 95,604,744 |
Washington: Scientists have finally isolated magnon drag from other thermoelectric effects after a 50-year quest.
As electrons move past atoms in a solid, their charge distorts the nearby lattice and can create a wave. Reciprocally, a wave in the lattice affects the electrons motion, in analogy to a wave in the sea that pushes a surfer riding it.
This interaction results in a thermoelectric effect that was first observed during the 1950’s and has come to be known as phonon-drag, because it can be quantified from the flow of lattice-wave quanta (phonons) that occurs over the temperature gradient.
Soon after the discovery of the phonon drag, an analogous phenomenon was predicted to appear in magnetic materials: the so-called magnon drag.
In a magnetic material the intrinsic magnetic moment or spin of the electrons arrange in an organized fashion. In ferromagnets, the spins maintain a parallel orientation.
If a distortion in the preferred spin orientation occurs, a spin wave is created that could affect electron motion. It is therefore reasonable to expect that the flow of magnons (spin-wave quanta) could also drag the electrons.
Despite the similarities with phonon drag, the observation of the magnon drag has been elusive, and only a few indirect indications of its existence have been reported over the years. The main reason being the presence of other thermoelectric effects, most notably the phonon drag, that make it difficult to discriminate its contribution to the thermopower.
Now, researchers of ICN’s Physics and Engineering of Nanodevices Group, Marius V. Costache, German Bridoux, Ingmar Neumann and group leader ICREA Prof. Sergio O. Valenzuela have discriminated the magnon drag from other thermoelectric effects using a unique device geometry.
The device resembles a thermopile formed by a large number of pairs of ferromagnetic wires placed between a hot and a cold source and connected thermally in parallel and electrically in series.
By controlling the relative orientation of the magnetization in pairs of wires, the magnon drag can be studied independently of the electron and phonon drag thermoelectric effects.
This information is crucial to understand the physics of thermal spin transport. | <urn:uuid:75a24353-3a0e-46e1-84c4-70b2c4390b3e> | 3.34375 | 481 | News Article | Science & Tech. | 31.106061 | 95,604,756 |
Researchers from Durham University, UK, and the University of St Andrews, looking at grey seal colonies in Scotland, found that some seal mothers are flexible in the parenting style they adopt and 'gamble' on the outcome of their actions, whilst other play it safe and steady.
The study is the first to demonstrate how variation in personality traits in large marine mammals in the wild can persist, rather than a single, successful, personality type dominating the population.
The research shows that some seal mothers have a very fixed approach to looking after their pups, and tend to behave in a similar fashion whatever the local conditions on the breeding colony are; whether they are in a crowded and busy location, or in a less disturbed situation. These mums tend to achieve average success in terms of their pups' weight gain (crucial to the future survival of the pup), so that, by-and-large, they generally do well. These mums seem to have a 'play it safe' approach to life.
Some seal mothers have a very different approach. These mums are more flexible and try to adjust their mothering behaviour according to the local conditions. In potentially unpredictable situations, this can be risky; sometimes they get it right and their pups fare very well, but other times they might get it wrong and their pups do rather badly.
The findings, published in the journal PLoS One, show that individual animals can differ markedly in their ability to adjust their behaviour to their local environmental conditions and that large variations in behavioural strategies can persist within a species.
According to the researchers, the results for both extremes of personality show how different types can be maintained by selection. This retains behavioural diversity within a species, potentially making the species more resilient to environmental change.
The results are relevant to environment and conservation policies that use a one-size-fits-all approach, as these may need to be re-evaluated to take into account individual differences in animal personality, the researchers say.
Lead author, Dr Sean Twiss, School of Biological and Biomedical Sciences, Durham University, said: "Some mums have a very fixed way of caring for their pups, come what may, whilst others are more flexible. "Seals that 'gamble' and try to fit their behaviour to their immediate surroundings can do very well, if they get it right! However, being flexible can be risky - a mum might 'mis-judge' the conditions and fail to match her behaviour to the prevailing conditions.
"In either resting or disturbed situations, seal mums behaved in very individual ways, some showing high levels of maternal attentiveness, others showing low levels. Some behaved the same when disturbed as they did at rest while other individuals changed their behaviour dramatically when disturbed."
These differences in mothers' behaviour, either fixed or flexible, can have profound effects on their pups. After about 2 weeks of being looked after by their mothers, all pups are left to fend for themselves, and have to teach themselves to feed. The fatter a mum leaves her pup, the more time the pup has to learn, and its chances of surviving are better.
The scientists observed seals on the Scottish island of North Rona during the breeding season over two years. The team observed seals in their natural habitat to analyse responses to unusual stimuli (disturbances) and to assess seal behaviour at rest.
Co-author Dr Paddy Pomeroy said: "What's really interesting about these short term tests is the way behavioural types map onto individual measures of reproductive success. If more flexible mothers are better and worse pup rearers, one of our next tasks will be to see how breeding successes and failures are apportioned over lifetimes, which can only be done in this type of study."
The research has been part-funded by NERC, The Living With Environmental Change partnership, and the Esmée Fairburn Foundation.
How they did it: The researchers ran 30-minute observations on 14 females to see how they behaved at rest. The team measured the attentiveness of the mothers towards their pups during these periods by recording the number of pup checks made (where the mother raises her head off the ground and moves it in the direction of her young to check their well-being).
Repeating these observations twice on each seal showed that mothers varied considerably, and consistently, in their behaviour, with some showing low levels of maternal attentiveness, whilst others checked their pups much more often.The team then used a remote controlled vehicle (RCV) with a fitted video camera to test how seals reacted to mild disturbance, including approaches by the RCV and wolf calls played from the vehicle.
The team also measured and weighed each seal mum and pup before and after each test and observation. Comparing these measurements for the behaviourally 'fixed' and 'flexible' seals, the team found an intriguing pattern: All mums with the 'fixed' approach had very average pup growth rates, while some of the 'flexible' mums did really well, with their pups growing at twice the rate of others, but the rest did rather poorly, with pup growth rates well below average.
The researchers can identify individual seals using their unique and varied patterns on their fur and this allows them to observe maternal behaviour over multiple years as seals generally return to the same site to breed.
Carl Stiansen | 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...
13.07.2018 | Event News
12.07.2018 | Event News
03.07.2018 | Event News
13.07.2018 | Event News
13.07.2018 | Materials Sciences
13.07.2018 | Life Sciences | <urn:uuid:0e99de11-0520-4de0-9140-d63a8bdc155f> | 3.203125 | 1,759 | Content Listing | Science & Tech. | 40.616196 | 95,604,768 |
NASAs Stardust spacecraft marked its 12th anniversary in space on Monday, Feb. 7, with a rocket burn to further refine its path toward a Feb. 14 date with a comet.
Just over two weeks before its flyby of comet Tempel 1, NASAs Stardust spacecraft fired its thrusters to help refine its flight path toward the comet. The Stardust-NExT mission will fly past comet Tempel 1 on Valentines Day (Feb. 14, 2011).
A new Comet Observing Planner tool has been added to the COBS website.
NASAs NEOWISE mission has completed its survey of small bodies, asteroids and comets, in our solar system. The missions discoveries of previously unknown objects include 20 comets, more than 33,000 asteroids in the main belt between Mars and Jupiter, and 134 near-Earth objects (NEOs). The NEOs are asteroids and comets with orbits that come within 45 million kilometers (28 million miles) of Earths path around the sun.
NASAs Stardust spacecraft has downlinked its first images of comet Tempel 1, the target of a flyby planned for Valentines Day, Feb. 14. The images were taken on Jan. 18 and 19 from a distance of 26.3 million kilometers (16.3 million miles), and 25.4 million kilometers (15.8 million miles) respectively. On Feb. 14, Stardust will fly within about 200 kilometers (124 miles) of the comets nucleus.
NASAs Stardust-NExT spacecraft is nearing a celestial date with comet Tempel 1 at approximately 11:37 p.m. EST, on Feb. 14. The mission will allow scientists for the first time to look for changes on a comets surface that occurred following an orbit around the sun.
Comet C/2011 A3 (Gibbs) was discovered on 2011, Jan. 15.51 by Alex Gibbs (during the course of the Catalina Sky Survey) in four 22-sec exposures taken with the 0.68-m Schmidt on Mt.Bigelow.
The sun has just experienced a storm—not of explosive flares and hot plasma, but of icy comets.
On February 14, 2011, NASAs Stardust-NExT (New Exploration of Tempel 1) mission will encounter Comet Tempel 1, providing a unique opportunity to measure the dust properties of two separate comets (Wild 2 and Tempel 1) with the same instrument for accurate data comparison. The encounter will also provide a comparison between two observations of a single comet, Tempel 1, taken before and after a single orbital pass around the sun.
As people on Earth celebrate the holidays and prepare to ring in the New Year, an ESA/NASA spacecraft has quietly reached its own milestone: on December 26, the Solar and Heliospheric Observatory (SOHO) discovered its 2000th comet. | <urn:uuid:d666f468-7dd1-4b48-9d61-51666ebea2b2> | 3.203125 | 596 | Content Listing | Science & Tech. | 63.114207 | 95,604,818 |
Researchers from the Institute of Organic Chemistry and Biochemistry of the Czech Academy of Sciences (IOCB Prague) built a 2-dimensional organized array of light-driven molecular motors. At the molecular level, they have created a system of regularly spaced microscopic machines rotating when illuminated. The team headed by Dr. Jiří Kaleta (Prof. Josef Michl Group) collaborated with the 2016 Nobel laureate in chemistry Prof. Ben Feringa. Their research was published in the prestigious Journal of the American Chemical Society (JACS).
View more details.
Development of molecular motors is still in its early days and in the basic research realm, but it is clear that it has a great potential and is drawing a great deal of attention, as illustrated by the 2016 Nobel prize in chemistry awarded for the research in this field. The discovery by the IOCB Prague team and their colleagues shows how to move away from manipulating with individual motors to organized arrays of millions or billions of units with dramatically increased impact. This will enable us to study motors more conveniently and in an appropriately designed system could eventually lead to the transport of microscopic objects along the surface with the use of just light as a trigger and fuel of the process, CzechInvest government agency writes.
12th June 2018
15th February 2018 | <urn:uuid:a6605532-848f-4306-84b7-1a0844091a80> | 2.828125 | 261 | News Article | Science & Tech. | 37.311289 | 95,604,878 |
New catalyst upgrades greenhouse gas into renewable hydrocarbons
A new technology from U of T Engineering is taking a substantial step towards enabling manufacturers to create plastics out of two key ingredients: sunshine and pollution.
Today, non-renewable fossil fuels not only provide the raw material from which plastics are made, they are also the fuel burned to power the manufacturing process, producing climate-warming carbon dioxide (CO2) — the International Energy Agency estimates the production of the main precursors for plastics is responsible for 1.4 per cent of global CO2 emissions.
A team led by University of Toronto Professor Ted Sargent is turning this process on its head. They envision capturing CO2 produced by other industrial process and using renewable electricity — such as solar power — to transform it into ethylene. Ethylene is a common industrial chemical that is a precursor to many plastics, such as those used in grocery bags.
The system addresses a key challenge associated with carbon capture. While technology exists to filter and extract CO2 from flue gases, the substance currently has little economic value that can offset the cost of capturing it — it's a money-losing proposition. By transforming this carbon into a commercially valuable product like ethylene, the team aims to increase the incentives for companies to invest in carbon capture technology.
At the core of the team's solution are two innovations: using a counterintuitively thin copper-based catalyst and a reimagined experimental strategy.
"When we performed the CO2 conversion to ethylene in very basic media, we found that our catalyst improved both the energy efficiency and selectivity of the conversion to the highest levels ever recorded," said post-doctoral fellow Dr. Cao-Thang Dinh, the first author on the paper published today in the journal Science. In this context, efficiency means that less electricity is required to accomplish the conversion. The authors then used this knowledge to further improve the catalyst and push the reaction to favour the formation of ethylene, as opposed to other substances.
Next, the team addressed stability, which has long been a challenge with this type of copper-based catalyst. Theoretical modelling shows that basic conditions — that is, high pH levels — are ideal for catalyzing CO2 to ethylene. But under these conditions, most catalysts, and their supports, break down after less than 10 hours.
The team overcame this challenge by altering their experimental setup. Essentially, they deposited their catalyst on a porous support layer made of polytetrafluoroethylene (PTFE, better known as Teflon) and sandwiched their catalyst with carbon on the other side. This new setup protects the support and catalyst from degrading due to the basic solution, and enables it to last 15 times longer than previous catalysts. As an added bonus, this setup also improved efficiency and selectivity still further.
"Over the last few decades, we've known that operating this reaction under basic conditions would help, but no one knew how to take advantage of that knowledge and transfer it into a practical system," says Dinh. "We've shown how to overcome that challenge."
Currently their system is capable of performing the conversion on a laboratory scale, producing several grams of ethylene at a time. The team's long-term goal is to scale the technology up to the point where they are able to convert the multiple tonnes of chemicals needed for commercial application.
"We made three simultaneous advances in this work: selectivity, energy-efficiency and stability," says Sargent. "As a group, we are strongly motivated to develop technologies that help us realize the global challenge of a carbon-neutral future."
The multidisciplinary group, which also includes mechanical engineering professor David Sinton, combines strengths in materials science, chemical engineering, chemistry and mechanical engineering, is providing new perspectives on the field. Several members are also involved in CERT, the University of Toronto team that just advanced to the final round of the NRG COSIA Carbon XPRIZE. The Carbon XPRIZE competition challenges groups from industry and academia to capture carbon emissions from power plants and efficiently convert them into valuable chemical products. | <urn:uuid:df2459aa-6f7f-4a6a-9388-7770d9bf49f2> | 3.46875 | 843 | News Article | Science & Tech. | 24.274909 | 95,604,884 |
Scientists Make Plants Work Better by Making Them Bionic
Mar 18, 2014 11:08
Graphene is truly some magical material. So it's no surprise that a team of chemical engineers and biochemists have managed to change how plants work, using that. They made plants work better by embedding carbon nanotubes into the plants' leaves so that they can absorb more light.
The technique is not quite perfect. "We envisioned them as new hybrid biomaterials for solar energy harnessing, self-repairing materials [and] chemical detectors of pollutants, pesticides, [and] fungal and bacterial infections," said MIT chemical engineer Juan Pablo Giraldo.
The carbon nanotubes are sheets of graphene rolled into straw-like shapes, and it can absorb light and convert it into electron flow. The photosynthesis rates in these plants were three times higher than those without.
Could modifying plants with this technique give us cleaner air? Will bionic plants be the norm in the future?
If you are looking forward to rank your website on top, you might have asked SEO experts a common question – how much time does it take to reach the top rank on Google? The answer is complicated and can never be definite. Read more
It is, without doubt, evident that SEO has had a massive impact in the internet world today, so much that emerging website owners are already informed on techniques like keyword SERP tracking to give the ultimate SEO value to their site. Additionally, useful tools have come up, such as the social network checker that allows web owners, bloggers, small business owners as well as large enterprises check whether the content they share on social media have an impact on their overall digital marketing strategy, and it is affecting the overall ranking of their sites. Read more
Demand for 3D printing has exploded in recent years with hundreds of new 3D printer producers being developed to help meet this huge growth in demand. So, who are the new trailblazers in the industry? We take a look at the top five manufacturers of 3D printers, who are set to shape the industry with new products and innovations. Read more | <urn:uuid:f7712fcb-ab73-4e55-8796-f784c92c180f> | 3.421875 | 434 | Listicle | Science & Tech. | 43.330463 | 95,604,895 |
|Using the GNU Compiler Collection (GCC)|
FSF GCC on Darwin does not create “fat” object files; it will create an object file for the single architecture that it was built to target. Apple's GCC on Darwin does create “fat” files if multiple -arch options are used; it does so by running the compiler or linker multiple times and joining the results together with lipo.
The subtype of the file created (like ‘ppc7400’ or ‘ppc970’ or ‘i686’) is determined by the flags that specify the ISA that GCC is targetting, like -mcpu or -march. The -force_cpusubtype_ALL option can be used to override this.
The Darwin tools vary in their behavior when presented with an ISA mismatch. The assembler, as, will only permit instructions to be used that are valid for the subtype of the file it is generating, so you cannot put 64-bit instructions in a ‘ppc750’ object file. The linker for shared libraries, /usr/bin/libtool, will fail and print an error if asked to create a shared library with a less restrictive subtype than its input files (for instance, trying to put a ‘ppc970’ object file in a ‘ppc7400’ library). The linker for executables, ld, will quietly give the executable the most restrictive subtype of any of its input files.
A framework directory is a directory with frameworks in it. A
framework is a directory with a ‘"Headers"’ and/or
‘"PrivateHeaders"’ directory contained directly in it that ends
in ‘".framework"’. The name of a framework is the name of this
directory excluding the ‘".framework"’. Headers associated with
the framework are found in one of those two directories, with
‘"Headers"’ being searched first. A subframework is a framework
directory that is in a framework's ‘"Frameworks"’ directory.
Includes of subframework headers can only appear in a header of a
framework that contains the subframework, or in a sibling subframework
header. Two subframeworks are siblings if they occur in the same
framework. A subframework should not have the same name as a
framework, a warning will be issued if this is violated. Currently a
subframework cannot have subframeworks, in the future, the mechanism
may be extended to support this. The standard frameworks can be found
in ‘"/System/Library/Frameworks"’ and
‘"/Library/Frameworks"’. An example include looks like
#include <Framework/header.h>, where ‘Framework’ denotes
the name of the framework and header.h is found in the
‘"PrivateHeaders"’ or ‘"Headers"’ directory.
If the compiler was built to use the system's headers by default,
then the default for this option is the system version on which the
compiler is running, otherwise the default is to make choices that
are compatible with as many systems and code bases as possible.
Warning: The -mone-byte-bool switch causes GCC
to generate code that is not binary compatible with code generated
without that switch. Using this switch may require recompiling all
other modules in a program, including system libraries. Use this
switch to conform to a non-default data model.
.ofiles into already running programs. -findirect-data and -ffix-and-continue are provided for backwards compatibility. | <urn:uuid:0fbade97-7c84-488b-b5dc-0043080d4ac8> | 2.71875 | 788 | Documentation | Software Dev. | 43.696044 | 95,604,900 |
New study shows the vulnerability of the basin to future invaders – and calls for regulations to mitigate this threat
The Great Lakes have been invaded by more non-native species than any other freshwater ecosystem in the world. In spite of increasing efforts to stem the tide of invasion threats, the lakes remain vulnerable, according to scientists from McGill University and colleagues in Canada and the United States. If no new regulations are enforced, they predict new waves of invasions and identify some species that could invade the Lakes over the next 50 years.
Over the past two centuries, more than 180 non-native species have been recorded in the Great Lakes and the rivers that flow into them. Nearly 20% of these species are considered to be harmful ecologically and economically, posing threats to the Lakes’ native biodiversity and multibillion dollar fishery. New threats are emerging because of risks associated with trade in live organisms and climate change, the researchers caution in a study in the Journal of Great Lakes Research.
In recent years, the pace of species invasions appears to have slowed dramatically, as measures have been taken to protect the lakes. This is why the three scenarios (optimistic, pessimistic and status quo) the researchers considered for the next 50 years hinge on the implementation and effectiveness of regulations aimed at blocking current means of entry for invasive species.
Indeed, for many years, shipping was the primary pathway for new species to enter the basin, until the rules were tightened. Ballast water is taken on board and later discharged by ships to maintain a consistent weight as they receive and offload cargo. In 2006 and 2008, new regulations were mandated that required ships to discharge freshwater and fill their tanks with saltwater before entering the St. Lawrence Seaway. This means that ballast tank water should contain only saltwater animals, which are incapable of surviving and multiplying in the Great Lakes. “No new species have been recorded since 2006,” says Katie Pagnucco, PhD student at McGill and lead author of the study. “We may have closed the door on ballast water-mediated invasions. That remains to be seen. But other doors are still open.”
In the most pessimistic scenario, greater numbers of non-native species are introduced, as ballast water regulations prove to be ineffective in the long term, and live trade continues to expand. Live trade – the importation of live animals and plants for food markets or to be used as baitfish and aquarium pets – is largely unregulated. Consequently, in 50 years, the Great Lakes would be populated with many new invaders, most of which may come from inland waterways where Europe and Asia meet – the region around the Black Sea. This region is the source of some of the most disruptive invaders in the Great Lakes today, such as the zebra mussel, and still has many species at a high risk of invading the North American lakes and rivers, such as the killer shrimp or the monkey goby.
The status-quo scenario includes no additional protection policies. Ballast water regulations remain effective, and no new species arrive with overseas ships. The primary cause of invasions in this scenario becomes live trade. The main threat would be Asian carp species, which are well adapted to temperature conditions in much of the Great Lakes. They are voracious plankton-feeders, capable of diverting energy from the rest of the food web, and thus could impact the fishery.
In the most optimistic scenario, the risk of invasion is minimized by harmonized policies enforced by Canada and the United States. “Invasions are a transboundary issue,” says McGill professor Anthony Ricciardi, an invasive-species biologist who supervised the study. “In addition to harmonized regulations on live trade, the two countries must coordinate early detection and rapid response to new threats – before an invasion has progressed beyond control.”
Weakened temperature barrier
The researchers caution that climate change will complicate each of the scenarios. “For example, the Great Lakes have already had all the invasive species from the Mississippi that could survive there, as a temperature barrier is protecting us from others” notes Pagnucco. But warmer waters will facilitate the migration and establishment of southern species, most notably via the canal from the Mississippi to the Great Lakes.
Invasion risks are dynamic and management responses must evolve to cope with them, Ricciardi and Pagnucco caution.
The study will be published in a special issue of the Journal of Great Lakes Research that examines the history of the Great Lakes over the past few decades and forecasts their future.
This work was supported by the Great Lakes Futures Project, funded by the Transborder Research University Network, Environment Canada, Michigan Sea Grant, New York Sea Grant, and supporting universities. Additional funding was provided by the Canadian Aquatic Invasive Species Network and an NSERC Discovery
“The future of species invasions in the Great Lakes-St. Lawrence River basin”.
Journal of Great Lakes Research, available online December 3, 2014
Katie S. Pagnucco, George A. Maynard, Shannon A. Fera, Norman D. Yan,
Thomas F. Nalepa, Anthony Ricciardi
Melody Enguix | newswise
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...
13.07.2018 | Event News
12.07.2018 | Event News
03.07.2018 | Event News
17.07.2018 | Information Technology
17.07.2018 | Materials Sciences
17.07.2018 | Power and Electrical Engineering | <urn:uuid:da0f8a6e-765f-47ce-ae80-8c851bcf7e4d> | 3.515625 | 1,731 | Content Listing | Science & Tech. | 37.558357 | 95,604,921 |
When an asteroid the size of a city block zips past the Earth about 29,000 miles per hour on Nov. 8, it will seem like an encounter with an old acquaintance to Univeristy of Arizona astronomer Robert McMillan.
Six years ago, McMillan was taking images of the night sky with an 83-year-old telescope on Kitt Peak searching for asteroids, chunks of rock that weren't swept up into one of the nascent planets during the formation of our solar system and have traveled around the sun ever since. That is how he discovered 2005 YU55.
"2005 YU55 is one of the potentially hazardous asteroids that make close approaches from time to time because their orbits either approach or intersect the orbit of the Earth," said McMillan, who is an associate research scientist with the UA's Lunar and Planetary Laboratory with a joint appointment in the UA's Steward Observatory.
The asteroid or more correctly, minor planet will approach the Earth within about 202,000 miles, closer than the distance to the moon. No object of comparable size has come this close since 1976, and none is going to until 2028, when another asteroid dubbed 2001 WN5 will pass about halfway between the moon and the Earth.
Although 2005 YU55's orbit takes it into Earth's neighborhood every once in a while, there is no chance of it hitting our planet for at least another 100 years. However, because asteroids' trajectories change over time, there is a slight chance it may do so at some point in the future.
Enter SPACEWATCH and the Catalina Sky Survey, two research programs at the UA's Lunar and Planetary Laboratory dedicated to the study of small objects like asteroids and comets. Founded in 1980 by the late Tom Gehrels and McMillan, who is now its principal investigator, SPACEWATCH aims to find objects that might pose a hazard to Earth and gain a better understanding of how the solar system came to be.
Begun by LPL senior staff scientist Steve Larson and now led by senior staff scientist Ed Beshore, the Catalina Sky Survey is a NASA-supported project to discover and catalog Earth-approaching and potentially hazardous asteroids.
"We complement each other in what we focus on," McMillan said. "With SPACEWATCH, we spend a lot of our time doing follow-ups on objects that have already been discovered through other programs. Because we can go after fainter and dimmer objects, we can chase them longer after their time of discovery as they are hurtling out deeper into space."
SPACEWATCH was the first program dedicated to the discovery and tracking of asteroids that made use of charge-coupled devices, or CCDs, which are now found in many digital cameras, instead of photographic plates to scan the skies. The 0.9-meter telescope, built in 1921, was the first telescope the UA's Steward Observatory ordered. Originally housed on campus, it was moved to Kitt Peak in 1962, where it has been in operation ever since.
The search for asteroids is challenging and tedious."When you look through a telescope, asteroids don't look any different from stars," McMillan explained. "The only difference is that they're moving, and to detect that motion we have to take a series of images.
Usually we take three images spaced 20 or 30 minutes apart."
Next, the observers run specialized software to examine those images for any star-like images that are moving from one image to the next. The software compiles them into a list of candidates that is presented to the observer for their approval.
"We have to double-check the images, because the software is not perfect and sometimes picks up things that aren't really asteroids," McMillan said.
Objects that pass the review are then forwarded to the Minor Planet Center, or MPC, at the Smithsonian Astrophysical Observatory in Cambridge, Mass.
In determining which ones could potentially slam into Earth, asteroid hunters look for those that are traveling faster than the more common Main Belt Asteroids, which orbit the sun between the orbits of Mars and Jupiter and do not pose a threat. Objects meeting those criteria are sent to the MPC separately with special designations as candidates for Near Earth Objects, or NEOs. The MPC reviews them and decides which ones should be designated as NEOs.
That is how 2005 YU55 went from being a faint speck of light to a Potentially Hazardous Asteroid.
"The MPC posted it on their confirmation page, which is monitored by everybody who follows up newly discovered Near Earth Objects," McMillan said. "So we followed it up on subsequent nights and over the following month. Over time, we refined its orbit to the point that NASA's Jet Propulsion Laboratory listed a large number of potential close encounters with the Earth."
"Now, after 767 observations by ground-based observers, we have the orbit of that asteroid really nailed down, so we know it's not going to hit the Earth on Nov. 8."
In addition to observation with optical telescopes, radar measurements revealed 2005 YU55's distance, velocity and size. The coal-black asteroid, which is almost spherical in shape and measures about 1,300 feet in diameter, slowly spins as it travels through space, completing a rotation every 18 hours.
According to McMillan, the gravity of other planets, as well as the pressure of sunlight affect the paths of asteroids. In addition, a phenomenon known as the Yarkovsky Effect slight asymmetries in heat distribution that arise as the object soaks up sunlight and radiates it back into space as it turns plays a role. Those asymmetries exert forces that add up over time to cause the asteroid to veer off its orbit ever so slightly.
"We now know that 2005 YU55 is a carbonaceous chondrite asteroid that is relatively dark and contains carbon," McMillan said, "But long-range trajectories are very difficult to predict when you don't know the exact physical properties of the asteroid."To better understand the properties of Potentially Hazardous Asteroids, the Lunar and Planetary Laboratory is leading the OSIRIS-REx mission, an
By that time, 2005 YU55 will have long passed our planet and continue on its lonely journey through the cold, black void of the outer fringes of the solar system.
Robert S. McMillan (520-621-6968; email@example.com)Daniel Stolte, University Communications (520-626-4402;
Daniel Stolte | University of Arizona
What happens when we heat the atomic lattice of a magnet all of a sudden?
17.07.2018 | Forschungsverbund Berlin
Subaru Telescope helps pinpoint origin of ultra-high energy neutrino
16.07.2018 | National Institutes of Natural Sciences
For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.
To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...
For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.
Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...
Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.
A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...
Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.
"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....
Ultra-short, high-intensity X-ray flashes open the door to the foundations of chemical reactions. Free-electron lasers generate these kinds of pulses, but there is a catch: the pulses vary in duration and energy. An international research team has now presented a solution: Using a ring of 16 detectors and a circularly polarized laser beam, they can determine both factors with attosecond accuracy.
Free-electron lasers (FELs) generate extremely short and intense X-ray flashes. Researchers can use these flashes to resolve structures with diameters on the...
13.07.2018 | Event News
12.07.2018 | Event News
03.07.2018 | Event News
17.07.2018 | Information Technology
17.07.2018 | Materials Sciences
17.07.2018 | Power and Electrical Engineering | <urn:uuid:5b12c78b-0cab-4c15-b099-002fd10cac6d> | 3.328125 | 2,004 | Content Listing | Science & Tech. | 45.675771 | 95,604,922 |
Hormonal Tug-of-war Helps Plant Roots Navigate Their Journey Through the Soil
Image Caption: The balanced cross-talk between auxin and cytokinin positions the auxin minimum (indicated by *). This minimum determines the size of a root's meristem by triggering cells to transit from division to elongation. When cytokinin effects either dominate (left panel) or are reduced (right panel), the auxin minimum is repositioned (*), causing the meristem to either shrink (left panel) or extend (right panel). The hormonal tug-of-war underlying this repositioning takes place through modifications in auxin transport and degradation. Credit: PNAS doi: 10.1073/pnas.1705833114
Scientists from the John Innes Centre and Sapienza University, Rome, combined mathematical and computer modelling with molecular genetics to show how roots can regulate their growth via the interactions of two antagonistic hormones, auxin and cytokinin.
As the root grows and meristem cells at the tip continuously divide, they are left behind in relation to the moving root tip. When these cells reach a certain distance from the tip, called the transition position, they stop dividing and instead start elongating until reaching their maximum lengths.
But how do cells “know” when they have reached the transition position between division and elongation? What signal do they read out?
This, explains Dr Veronica Grieneisen of the John Innes Centre, is down to something called positional information, which is a common feature in all developing organisms:
“Cells, although initially all identical, need to change fate or behaviour according to where they are located in the embryo or organ. This is positional information.”
To solve the puzzle the teams of Dr Grieneisen and Dr Stan Marée from the John Innes Centre needed to discover what “positional information” is available at thetransition zone to enable cells to know they are at the right location to transit behaviour from dividing (meristem zone) to elongating (elongation zone), and how this information is established and positioned.
Other studies by Dr Grieneisen, Dr Marée and colleagues had shown that the hormone auxin was present at very high levels at the root tip to maintain certain cells as stem cells, and that this was the result of fast dynamics of auxin swirling around due to PINs (proteins that pump auxin through the root).
Their computational work had revealed how these currents of auxin allowed the auxin maximum and its associated gradient to move together with the growing root, providing part of the necessary positional information required to coordinate the meristem zone.
Further recent work, however, showed that auxin does not regulate the transition alone. Antagonistic cross-talk between auxin and another hormone, cytokinin, could both stabilise the size of the meristem zone, and even change it – thus, either stabilizing root growth, or changing its velocity.
Grieneisen and Sabatini joined forces, and together with the Marée lab developed a computerised root model in which the action of cytokinin on auxin transport and breakdown was examined.
They found that cytokinin’s influence generated a very typical pattern of auxin concentrations in the root: as before, with an auxin maximum at the tip, but they noticed that a dip in auxin appeared right at the transition zone of this computational root. This was then confirmed experimentally.
Dr Grieneisen explains: “It’s like a valley between two steep mountains. The cells in the root, as they move over the auxin landscape, transit from high auxin in the meristem into a region of low levels, and then rapidly again experience rises in auxin.”
“By merely sensing relative changes in auxin, cells robustly notice that they have reached the auxin minimum and thus the point of transition, triggering their switch in behaviour.”
Experiments using Arabidopsis roots demonstrated that a tug-of-war between cytokinin and auxin results in this auxin minimum being positioned either closer to the root tip (if cytokinin is “winning” the tug-of-war), or it being positioned further away from the tip (when auxin is “winning” the tug-of-war).
In nature this mechanism allows the root to respond to its environment, proliferating in favourable conditions while restricting growth in adversity.
Hay Fever Risk Genes Overlap with Autoimmune DiseaseNews
In a large international study involving almost 900,000 participants, researchers from the University of Copenhagen and COPSAC have found new risk genes for hay fever. It is the largest genetic study so far on this type of allergy, which affects millions of people around the world.READ MORE
You Thought Your Bread was Stale!News
At an archaeological site in northeastern Jordan, researchers have discovered the charred remains of a flatbread baked by hunter-gatherers 14,400 years ago. It is the oldest direct evidence of bread found to date, predating the advent of agriculture by at least 4,000 years.READ MORE
Hidden Signals in RNAs Regulate Protein SynthesisNews
Scientists have long known that RNA encodes instructions to make proteins. In a new study published in Nature, scientists describe how the protein-making machinery identifies alternative initiation sites from which to start protein synthesis.READ MORE | <urn:uuid:940fd16e-fadf-46c8-96eb-5e8f1e9c787b> | 3.78125 | 1,134 | News Article | Science & Tech. | 28.720231 | 95,604,925 |
How can we feed future colonists on Mars? Wrocław scientists are working on this problem by developing a wastewater treatment system. Its purpose is to help obtain water and nutrients for aeroponic plant crops in extraterrestrial colonies.
Knowledge of gladiators is common. Fewer people know that female gladiators also fought in ancient Rome. Some were forced to fight, others did it for money or fame, to become stars. Historian Prof. Dariusz Słapek talks about women fighters in an interview with PAP.
Physicists from the University of Lodz are the only team from Poland that participates in an international n_TOF research project at CERN. The objective of the project is to develop a safer way to produce nuclear energy, says the university spokesperson Paweł Śpiechowicz.
The white streak that the plane leaves behind it in the sky is simply a cloud of water droplets or ice crystals. It forms when hot steam from the engines liquefies, mixing with cold air at high altitude. Just like steam from a kettle - says cloud physicist Prof. Szymon Malinowski.
"RNA bricks" designed by Prof. Janusz Bujnicki`s team can be assembled into molecules and then used to create new drugs and nanotechnology materials. Computer modelling allows to analyse thousands of chemical compounds and choose those that can destroy bacteria and viruses by acting on RNA. | <urn:uuid:bb9bd34e-7a65-43d9-87b7-9af7c1647d20> | 2.640625 | 293 | Content Listing | Science & Tech. | 44.880615 | 95,604,929 |
Accurate gamma ray spectrum analysis
The problem of gamma ray spectrum analysis has been is studied. The difficulties encountered by different methods are explained. An empirical method which uses an experimental peak for the analysis of spectrum is developed. This method utilizes the simple algorithm of linear least squares and is able to analyze the multiplets. It gives more accurate results than other ones. It is well adapted for automatic treatment of gamma ray spectra by small computers.
KeywordsSpectrum Analysis Physical Chemistry Inorganic Chemistry Accurate Result Simple Algorithm
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Dad needs to improve the edges of the wooden boxes - to be reinforced with metal rails. How many cms of rails will he need if the box has the shape of a prism with the length of the edges 70cm 70cm and 120cm?
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These nanodiamonds, which are produced under high-temperature, high-pressure conditions created by cosmic impacts and have been found in meteorites, are concentrated in similarly aged sediments at Murray Springs, Ariz., Bull Creek, Okla., Gainey, Mich., and Topper, S.C., as well as Lake Hind, Manitoba, and Chobot, Alberta, in Canada. Nanodiamonds can be produced on Earth, but only through high-explosive detonations or chemical vaporization.
Last year a 26-member team from 16 institutions proposed that a cosmic impact event, possibly by multiple airbursts of comets, set off a 1,300-year-long cold spell known as the Younger Dryas, fragmented the prehistoric Clovis culture and led to the extinction of a large range of animals, including mammoths, across North America. The team's paper was published in the Oct. 9, 2007, issue of the Proceedings of the National Academy of Sciences. (News release on the 2007 paper is available at: http://tinyurl.com/82988t, with link to a copy of that paper.)
Now, reporting in the Jan. 2 issue of the journal Science, a team led by the University of Oregon's Douglas J. Kennett, a member of the original research team, report finding billions of nanometer-sized diamonds concentrated in sediments -- weighing from about 10 to 2,700 parts per billion -- in the six locations during digs funded by the National Science Foundation.
"The nanodiamonds that we found at all six locations exist only in sediments associated with the Younger Dryas Boundary layers, not above it or below it," said Kennett, a UO archaeologist. "These discoveries provide strong evidence for a cosmic impact event at approximately 12,900 years ago that would have had enormous environmental consequences for plants, animals and humans across North America."
The Clovis culture of hunters and gatherers was named after hunting tools referred to as Clovis points, first discovered in a mammoth's skeleton in 1926 near Clovis, N.M. Clovis sites later were identified across the United States, Mexico and Central America. Clovis people possibly entered North America across a land bridge from Siberia. The peak of the Clovis era is generally considered to have run from 13,200 to 12,900 years ago. One of the diamond-rich sediment layers reported sits directly on top of Clovis materials at the Murray Springs site.
The eight co-authors on the Science paper were: Kennett's father, James P. Kennett of the University of California, Santa Barbara; A. West of GeoScience Consulting in Dewey, Ariz.; C. Mercer of the National Institute for Materials Science in Tsukuba, Japan; Que Hee of the University of California, Los Angeles; L. Bement of the Oklahoma Archaeological Survey at the University of Oklahoma; T.E. Bunch and M. Sellers, both of Northern Arizona University; and W.S. Wolbach of DePaul University in Chicago.
Source: Doug Kennett, professor of archaeology, department of anthropology, email@example.com. (Kennett is on sabbatical. He may be reached by email. A phone number may be available through the media contact above.)
Links: Kennett faculty page: http://www.uoregon.edu/~dkennett/Welcome.html; anthropology department: http://www.uoregon.edu/~anthro/
Jim Barlow | Newswise Science News
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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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Nasa says big asteroid to pass safely by Earth on 1 September
Nasa says a large asteroid will pass safely by the Earth on 1 September at a distance of seven million kilometres or 18 Earth-Moon distances
Washington: A large near-Earth asteroid will pass safely by our planet on 1 September, at a distance of seven million kilometres, or about 18 Earth-Moon distances, according to the National Aeronautics and Space Administration (Nasa).
Asteroid Florence is among the largest near-Earth asteroids that are several miles is size.
Measurements from Nasa’s Spitzer Space Telescope and NEOWISE mission indicate it is about 4.4 kilometres in size.
“While many known asteroids have passed by closer to Earth than Florence will on 1 September, all of those were estimated to be smaller,” said Paul Chodas, manager of Nasa’s Center for Near-Earth Object Studies (CNEOS).
“Florence is the largest asteroid to pass by our planet this close since the Nasa programme to detect and track near-Earth asteroids began,” Chodas said.
This relatively close encounter provides an opportunity for scientists to study this asteroid up close. Florence is expected to be an excellent target for ground-based radar observations, Nasa said.
The resulting radar images will show the real size of Florence and also could reveal surface details as small as about 10 metres. Asteroid Florence was discovered by Schelte Bus at Siding Spring Observatory in Australia in March 1981.
It is named in honour of Florence Nightingale, the founder of modern nursing. This year’s encounter is the closest by the asteroid since 1890 and the closest it will ever be until after 2500, according to the US space agency.
Florence will brighten to ninth magnitude in late August and early September, when it will be visible in small telescopes for several nights as it moves through the constellations Piscis Austrinus, Capricornus, Aquarius and Delphinus.
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It could possibly be a groundbreaking yr — within the worst approach attainable.
Usually, when somebody tells you horrible issues are going to occur within the yr forward, it’s not price fretting about. In any case, from local weather change to quickly dwindling biodiversity to, properly, a chocolate crisis, we’ve already acquired a lot to fret about.
Why add one other dollop of despair?
However when that somebody is Roger Bilham, a outstanding geologist on the College of Colorado, it might be prudent to strap on our seismic seat belts.
In a paper published in August in the journal Geophysical Research Letters, Bilham and Rebecca Bendick of the College of Montana recommend we’re in for an unusually excessive variety of devastating earthquakes in 2018.
In fact, there’ll by no means be a day when the Earth stands nonetheless. This stressed rock is consistently in flux, due to the fixed shuffling between 15 to 20 tectonic plates within the Earth’s crust. They grind and scrape alongside, largely due to a wide range of radioactive actions within the molten mantle they skate on.
The truth is, our planet acquired even busier in 2014. Scientists famous these plates had doubled their exercise — moving faster than at any point in the last 2 billion years.
However these shifting plates could solely be a part of the table-setting for 2018. When the Earth’s rotation slows, the scientists be aware, it additionally correlates with extra lively seismic exercise.
Within the study, Bilham notes that previously 100 years, there have been 5 events when the slowing of the planet’s rotation was adopted by a spate of earthquakes, significantly on the extra extreme finish of the Richter scale.
The slowdown is imperceptible to most of us — primarily manifesting in days which can be just some milliseconds shorter. And the planet finally regains her stride. However not earlier than these tiny modifications register with the deep interior workings of our planet.
“In fact that appears type of loopy,” Bendick told Science. “However suppose by way of it a bit of, and it may not appear so outlandish. The Earth’s rotation is understood to undergo common decades-long intervals by which it slows down and hurries up. Even seasonal modifications, like a powerful El Niño, can have an effect on the planet’s rotation.”
And that, the workforce contends, could lead to an enormous quantity of vitality being launched — working these tectonic plates as much as a devastating fervor.
“The yr 2017 marks six years following a deceleration episode that commenced in 2011, suggesting that the world has now entered a interval of enhanced international seismic productiveness with a period of no less than 5 years,” Bilham notes.
Even when Bilham and Bendick’s concept proves true, there should still be purpose for optimism. It goes with out saying that one of the simplest ways to outlive an earthquake is to be ready for one.
“One thing that folks have all the time hoped to seek out … is a few type of a number one indicator for seismicity, as a result of that provides us a warning about these occasions,” Bendick told the Washington Post.
Sadly, because of the myriad complicated processes at work in tectonic shifts, scientists have but to give you a dependable means for predicting earthquakes.
Which will lastly change if certainly, as Bilham informed Science, “the Earth provides us a 5-years heads up on future earthquakes.” | <urn:uuid:c11f8d17-fd0a-4c5c-8c59-4041d924841c> | 2.6875 | 742 | Truncated | Science & Tech. | 44.407908 | 95,604,990 |
A rotation is a curler movement of an object around a center of rotation. A 3-D object rotates around an imaginary line called a rotation axis. It this axis is within the body and passes through its center of mass the body will rotate upon itself or spin. A rotation about an external point is called a revolution when it is produced by gravity.
A rotation is a rigid body movement which is unlike a translation which keeps a point fixed. All rigid body movements are rotations, translation or combination of the two. A rotation is a progressive radial orientation to a common point. The distinction between a rotation and an orbit is the location of the axis of the rotation.
Rotations around the x, y, and z axes are called principal rotations. Rotations around any axis can be performed by taking a rotation around the x axis, followed by a rotation around the y axis, followed by the rotation around the z axis.
The speed of rotation is given by angular frequency. The time-rate of change of angular frequency is angular acceleration. Said change is caused by torque. According to the right-hand rule, the direction away from the observer is associated with clockwise rotation and the direct towards the observer with counter-clockwise rotation.© BrainMass Inc. brainmass.com July 16, 2018, 10:26 pm ad1c9bdddf | <urn:uuid:42f140d1-95e3-4860-a166-8df3af05679b> | 4.0625 | 278 | Knowledge Article | Science & Tech. | 47.490345 | 95,605,013 |
Microscopy & Microtechniques
All You Need to Know About the Schiaparelli Space Probe
Oct 27 2016 Read 2291 Times
It’s no easy feat landing a spacecraft on Mars. As head engineers fronting the European-Russian ExoMars 2016 mission found out when they attempted to make spaceflight history and land the Schiaparelli Space Probe on the surface of the Red Planet.
The stakes were high, and the disappointment was even higher when the lander failed to touch down on the Martian surface on October 19. Had it gone ahead, the Schiaparelli landing would have marked the beginning of the first successful Red Planet surface mission powered by Europe and Russia.
Schiaparelli sent to a dusty grave
Though despite input from two of the most advanced space agencies on the planet, the landing technology didn’t deliver. The launch itself was a success, with two separate Proton rockets powering an orbiter, lander and rover into space. Though as it made its descent, data reveals that at 4 minutes and 41 seconds into its 6-minute fall, Schiaparelli’s heat shield and parachute ejected prematurely. This meant that the thrusters designed to decelerate the probe for 30 seconds were only able to engage for 3 seconds before the lander’s computer automatically commanded them to switch off. Analysts estimate that the crash landing saw the craft hit the planet’s surface at 300 kilometres per hour, with a NASA spacecraft later snapping images of its dusty gravesite.
The silver linings
Painful as it is, the ESA has been quick to stress that the ExoMars mission is still a triumph. Not only was Schiaparelli able to transmit test data from the majority of its descent, but its Trace Gas Orbiter sister craft managed to successfully manoeuvre into Martian orbit. From here, it will study the Red Planet’s atmosphere, and search for traces of biological or geological methane.
“As it is, we have one part that works very well and one part that didn’t work as we expected,” comments Jorge Vago, project scientist for ExoMars. “The silver lining is that we think we have in hand the necessary information to fix the problem.”
The team also asserts that they now have valuable insight into what went wrong, and how to ensure the success of the upcoming 2020 mission.
“That’s super important. I think it’s on everybody’s mind,” says Vago.
As well as cutting edge advancements in outer space, exciting new developments are also playing out on Planet Earth. ‘Electron Microscopy; A Platform Advancing Science at the Crick’ celebrates the long awaited opening of London’s new Francis Crick Institute, an iconic building that will host 1250 researchers working together to discover the basic biology underlying human health.
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A Faster and More Efficient Way to Convert Carbon Dioxide into Fuel
New catalysts turn carbon dioxide into fuels faster and more efficiently.
Reusing carbon dioxide emitted by power plants could reduce fossil-fuel consumption.
Making carbon dioxide by burning hydrocarbons is easy. A pair of novel catalysts recently made by researchers at the University of Illinois at Chicago could make it far more practical to do the reverse, converting carbon dioxide and water into fuel.
Because running this reaction normally requires large amounts of energy, it has been economical only in rare cases (see “Company Makes CO2 into Liquid Fuel, with Help from a Volcano”). But if the process could be done commercially, liquid fuels could be made from the exhaust gases of fossil-fuel power plants.
The new work, described this week in the journal Nature Communications, improves on a pair of catalysts discovered last year that more efficiently turn carbon dioxide into carbon monoxide, which can then be made into gasoline and other products. Those catalysts produce carbon monoxide slowly, however, and one is made of silver, so it’s expensive. But the Illinois researchers have demonstrated that it’s possible to replace the silver with relatively inexpensive carbon fibers while maintaining about the same efficiency. And the technique produces carbon monoxide about 10 times faster.
The work is still in early stages, says Amin Salehi-Khojin, a professor of mechanical engineering at the University of Illinois at Chicago, who led the work. Salehi-Khojin says it will be necessary to produce larger amounts of the catalysts and find a way to incorporate them into a membrane that helps keep them stable over long periods of time—development work that will require industrial partners.
Salehi-Khojin says it may be possible to incorporate the catalysts into an “artificial leaf.” Right now, if the process were to run on sunlight, it would require at least two pieces of equipment: a solar panel to generate electricity, and then a reactor to form the carbon monoxide. A leaf-inspired system would absorb energy from the sun and use it to drive the chemical reactions directly, rather than making electricity first (see “A Greener ‘Artificial Leaf,’” “Sun Catalytix Seeks Second Act with Flow Battery,” and “Artificial Photosynthesis Effort Takes Root”). This approach would make the process more economical.
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Original Research ARTICLE
Comparison of Seasonal Cycles of Phytoplankton Chlorophyll, Aerosols, Winds and Sea-Surface Temperature off Somalia
- 1Fishery Resources Assessment Division, Central Marine Fisheries Research Institute, Kochi, India
- 2School of Marine Sciences, Cochin University of Science and Technology, Kochi, India
- 3National Centre for Earth Observation, Plymouth Marine Laboratory, Plymouth, United Kingdom
- 4Plymouth Marine Laboratory, Plymouth, United Kingdom
In climate research, an important task is to characterize the relationships between Essential Climate Variables (ECVs). Here, satellite-derived data sets have been used to examine the seasonal cycle of phytoplankton (chlorophyll concentration) in the waters off Somalia, and its relationship to aerosols, winds and Sea Surface Temperature (SST). Chlorophyll-a (Chl-a) concentration, Aerosol Optical Thickness (AOT), Ångström Exponent (AE), Dust Optical Thickness (DOT), SST and sea-surface wind data for a 16-year period were assembled from various sources. The data were used to explore whether there is evidence to show that dust aerosols enhance Chl-a concentration in the study area. The Cross Correlation Function (CCF) showed highest positive correlation (r2 = 0.3) in the western Arabian Sea when AOT led Chl-a by 1–2 time steps (here, 1 time step is 8 days). A 2 × 2° box off Somalia was selected for further investigations. The correlations of alongshore wind speed, Ekman Mass Transport (EMT) and SST with Chl-a were higher than that of AOT, for a lag of 8 days. When all four variables were considered together in a multiple linear regression, the increase in r2 associated with the AOT is only about 0.02, a consequence of covariance among AOT, SST, EMT and alongshore wind speed. The AOT data show presence of dust aerosols most frequently during the summer monsoon season (June–September). When the analyses were repeated for the dust aerosol events, the correlations were generally lower, but still significant. Again, the inclusion of DOT in the multiple linear regression increased the correlation coefficient by only 2%, indicating minor enhancement in Chl-a concentration. Interestingly, during summer monsoon season, there is a higher probability of finding more instances of positive changes in Chl-a after one time step, regardless of whether there is dust aerosol or not. On the other hand, during the winter monsoon season (November–December) and rest of the year, the probability of Chl-a enhancement is higher when dust aerosol is present than when it is absent. The phase relationship in the 8-day climatologies of Chl-a and AOT (derived from NASA's SeaWiFS and MODIS-A ocean colour processing chain) showed that AOT led Chl-a for most of the summer monsoon season, except when Chl-a was very high, during which time, Chl-a led AOT. The phase shift in the Chl-a and AOT climatological relationship at the Chl-a peak was not observed when AOT from Aerosol Climate Change Initiative (Aerosol-CCI) was used.
Phytoplankton, Sea-Surface Temperature (SST), sea-surface winds and aerosols are all Essential Climate Variables (ECVs) identified by the Global Climate Observation System (GCOS, 2011) as being worthy of sustained global observations at high spatial resolution and over long time scales, to aid studies of Earth's climate and climate change. As we strive to understand how the Earth system might respond holistically to climate change, it is important to explore not only the behavior of individual ECVs, but also their inter-relationships and the feedbacks between them. In the western Arabian Sea, the relationships between phytoplankton, winds and SST are better understood than that between phytoplankton and aerosols.
Yet, there are known functional links between marine aerosols and phytoplankton. For example, dust aerosols, transported by winds over the ocean, can be an important source of micronutrients such as iron, essential for phytoplankton growth (Duce and Tindale, 1991; Martin et al., 1991, 1994; Prospero et al., 2002; Cropp et al., 2005; Jickells et al., 2005; Mahowald et al., 2005; Meskhidze et al., 2005; Gallisai et al., 2014), with the proviso that not all the iron contained in dust particles is usable by phytoplankton. Winds over the ocean are also responsible for the formation of aerosols through generation of sea salt sprays (O'Dowd et al., 1997; Smirnov et al., 2003; Satheesh et al., 2006; Mulcahy et al., 2008; Glantz et al., 2009; Huang et al., 2010; Meskhidze and Nenes, 2010) and the same winds also mix the surface layer of the ocean, dictating the entrainment of nutrients from the deeper waters into the surface layer and controlling the average light available for phytoplankton growth in the layer. In addition to sea salt sprays, biological particles (for example, fragments of phytoplankton) contained in sea spray can also aid aerosol formation (Leck and Bigg, 2005; Facchini et al., 2008; Hawkins and Russell, 2010; Quinn and Bates, 2011). Feedback mechanisms (both positive and negative) have been proposed between dimethyl sulphide in the atmosphere of phytoplanktonic origin and the Earth's radiation budget, via aerosols (Charlson et al., 1987; Lovelock, 2006).
Positive (Martin et al., 1994; Jickells et al., 2005; Patra et al., 2007; Banerjee and Prasanna Kumar, 2014) and negative (Mallet et al., 2009; Paytan et al., 2009; Jordi et al., 2012) correlations between marine aerosols and phytoplankton concentration have been reported for different parts of the world ocean. Some studies have also identified regions where no relationship exists between the two (Cropp et al., 2005; Gallisai et al., 2014). Possible explanations for the positive correlations include the fertilizing role of iron contained in dust aerosols, or phytoplankton themselves, acting as a source of marine aerosols. Negative correlations might arise from high winds causing production of wind-spray aerosols, while at the same time forming deep mixed layers that may be able to support only low concentrations of phytoplankton, because of low average light levels available in the layer.
Satellite-based measurements provide a valuable tool for studies of aerosols and phytoplankton. Aerosol Optical Thickness (AOT), amenable to remote sensing, is an often-used measure of aerosol concentration. The Ångström Exponent (AE), which defines the wavelength dependence of AOT, is indicative of the type of aerosols present, and is also available through remote sensing. Dust Optical Thickness (DOT) can be inferred from AOT and the AE. Satellite data have been used to track dust aerosols for thousands of kilometers away from their source (Myhre et al., 2005). Likewise, ocean colour measured from space provides information on the concentration of chlorophyll-a (Chl-a), which is a major photosynthetic pigment contained in phytoplankton. Furthermore, estimates of winds (speed and direction) and SST, essential for understanding phytoplankton dynamics, are also available through remote sensing. An advantage of remote sensing is that it provides data at large scales and over many years, allowing studies of time-series at multiple locations in a systematic manner. But some caution should be exercised when using ocean colour derived Chl-a concentration, AOT and AE. Sometimes they are all produced from the same processing chain, and one might argue that, in the extreme case, any relationships observed between the three are purely artifacts of the processing algorithm. Furthermore, the effects of clouds on satellite retrievals are significant and sometimes lead to biases by overestimation or underestimation of aerosol data, particularly for dust aerosols (Levy et al., 2007; Torres et al., 2007; Baddock et al., 2009; Kahn et al., 2010). However, some authors have used cloud-screening techniques to reduce such errors (Kaufman et al., 2005). Therefore, the processing chain issues should be verified to arrive at conclusive results.
In this paper, we examine the relationships of Chl-a with winds, SST, AOT and dust aerosols in the western Arabian Sea, at a selected site off Somalia. The region is characterized by a high dynamic range in Chl-a values that vary seasonally, in response to the reversing wind patterns and associated upwelling (Prasanna Kumar et al., 2001; Schott and McCreary, 2001; Schott et al., 2002; Shankar et al., 2002; Wiggert et al., 2005; Lévy et al., 2007; Wiggert and Murtugudde, 2007; Prakash et al., 2012). Diverse physical forcings of both oceanic and atmospheric origins drive biological production off Somalia region. During summer monsoon season, the Somalia coastal region is characterized by strong upwelling with high primary productivity due to the swift Somali current caused by strong south-westerlies along the coast (Smith and Codispoti, 1980; Schott, 1983; Hitchcock and Olson, 1992; Brock et al., 1994; Schott et al., 2002; deCastro et al., 2016). The anti-cyclonic eddies associated with the Somali current during the same season further enhance production by transporting and mixing upwelled water (Fischer et al., 1996; McCreary et al., 1996; Schott et al., 1997; Koning et al., 2001; Schott et al., 2002; Santos et al., 2015). The consequent nutrient enrichment in the mixed layer of the ocean leads to high phytoplankton production during summer monsoon season (Banse, 1987; Owens et al., 1993). Because of its proximity to the Arabian Peninsula, the region also receives seasonally-varying dust deposition (Pease et al., 1998; Li and Ramanathan, 2002; Prospero et al., 2002; Léon and Legrand, 2003; Zhu et al., 2007; Prasanna Kumar et al., 2010). Thus, the same winds that transport dust aerosols to the western Arabian Sea during the summer monsoon season also induce upwelling, favoring phytoplankton blooms. Hence the relationship between Chl-a and aerosols in this region would be incomplete, unless we examined the effect of winds on phytoplankton dynamics as well. Here, we use 16 years of satellite data (1998–2013) to make a systematic study of the relationship of Chl-a with AOT, winds and SST in the waters off Somalia.
2. Materials and Methods
Level-3 8-day composite Aerosol Optical Thickness (AOT) at 865 nm and Ångström Exponent (AE) from Sea-viewing Wide Field-of-view Sensor (SeaWiFS) during January 1998–December 2010 and Moderate Resolution Imaging Spectro-radiometer (MODIS) Aqua during January 2011–December 2013 downloaded from National Aeronautics and Space Administration's (NASA's) ocean colour website (https://oceancolor.gsfc.nasa.gov) were used in this work. The AOT and AE data from NASA are referred to here as NASA-AOT and NASA-AE respectively. The daily AOT at 550 nm and AE data from European Space Agency's (ESA's) Aerosol Climate Change Initiative (Aerosol-CCI) programme (de Leeuw et al., 2015; Popp et al., 2016, see also http://www.esa-aerosol-cci.org) were also used in this study, as an independent source of aerosol data, unconnected with ocean colour atmospheric correction routines. The AOT and AE data from the Aerosol-CCI website are referred to here as CCI-AOT and CCI-AE respectively. The data are available at 1° spatial resolution for the period from January 1998–December 2010.
The relationship between the AOT (τ) at any given wavelength λ0 and that at any other wavelength λ depends on the AE (α) through the equation:
In principle, if the optical thickness at one wavelength and the AE are known, the optical thickness can be computed at any other wavelength using Equation (1).
Chlorophyll-a (Chl-a) concentration, for the period January 1998–December 2013, was obtained from ESA's Ocean Colour-Climate Change Initiative (OC-CCI) website (Sathyendranath et al., 2016, see also https://www.oceancolour.org). One of the major reasons for the choice of the Chl-a data was the improved coverage provided by the OC-CCI data in the Arabian Sea, especially during the summer monsoon season. The 8-day composite AOT data from SeaWiFS are available at only 9 km resolution, so we used MODIS Aqua data at the same resolution (9 km) even though they are available at 4 km resolution. The Chl-a concentration from OC-CCI (version-2), which is available at 4 km resolution, was also re-gridded to 9 km resolution. Since the CCI-AOT data are available at 1° spatial resolution, the Chl-a concentration from OC-CCI was also re-gridded to 1° resolution to analyse the correlation between them. The daily value of AOT at 865 nm was calculated from daily CCI-AOT at 550 nm and CCI-AE using Equation (1). The data were merged to genereate 8-day composites and extracted for the region off Somalia. The daily 1° gridded Sea Surface Temperature (SST) data were obtained for the period January 1998–December 2013 from Woods Hole Oceanographic Institute's (WHOI's) objectively-analyzed air-sea heat fluxes available at Asia-Pacific Data-Research Centre (APDRC) website (http://apdrc.soest.hawaii.edu). The SST anomaly has been calculated using these data after merging into 8-day composites. In addition, the daily NCEP/NCAR reanalysis U-wind (zonal velocity) and V-wind (meridional velocity) data with 2.5 × 2.5° spatial resolution at 10 m above the sea surface were obtained for the same period from their official website (https://www.esrl.noaa.gov/psd). The data have been merged to generate 8-day composites and used to derive the south westerly wind component along the Somalia coast. All the above mentioned information is summarized in Table 1.
The methods used in this study are shown schematically in Figure 1, and described below.
2.2.1. Correlation between Chl-a and AOT in the Arabian Sea
Correlation between Chl-a and AOT concentration for the 1998–2013 period over the Arabian Sea was studied using the 8-day composites. The results showed areas of both positive and negative correlation. The western Arabian Sea showed strong positive correlation. A 2 × 2° box (54–56° E longitude and 10–12° N latitude) off Somalia coast, with high positive correlation, was chosen for further analyses.
2.2.2. CCF Analysis and Lagged Correlation
We studied the lags in the correlation between Chl-a and AOT using Cross Correlation Function (CCF). CCF analysis produces cross correlations in which the observations of one time series are correlated with the observations of another time series at different lags and leads, to identify the variables which are leading or lagging indicators of other variables. The basic premise is that, if the relationships between the variables were merely a processing artifact, the correlations would peak at zero lag. In instances where phytoplankton might be contributing biological material for aerosol formation, the correlation would be maximum when AOT lagged behind Chl-a concentration. On the other hand, if the oceans were fertilized by aerosols, then Chl-a would lag behind AOT.
The CCF analysis was also carried out between Chl-a concentration and alongshore component of wind speed. If wind-induced upwelling were a causative factor for the increment in Chl-a concentration in the Somalia coast, then we anticipate that the correlation between them would peak when Chl-a lagged behind wind (because of the finite time it takes for phytoplankton to bloom in response to the nutrients brought to the surface by upwelling). Though the alongshore wind speed over the Somalia coast is a fairly good indicator of upwelling strength, we have calculated the Ekman Mass Transport (EMT) as an upwelling index for the analysis. Since a surface signature of upwelling is a decrease of SST in the upwelling zone, we have also taken SST as another proxy for upwelling.
2.2.3. Ekman Mass Transport
For the Somalia region, the alongshore component of the wind stress is favorable for upwelling during summer monsoon season. A positive value for the EMT represents upwelling along the coast of Somalia. The alongshore wind stress for Somalia coast was calculated by the bulk aerodynamic formula from Koracin et al. (2004) as shown in Equation (2):
where τy is the alongshore wind stress; ρa is the density of air, which was taken to be 1.2 kg/m3; w is the magnitude of the wind speed; v is the alongshore component of wind speed in m/s; and Cd is the nonlinear drag coefficient based on Large and Pond (1981) and Trenberth et al. (1990) for low wind speeds. So, the EMT along the Somalia coast can be calculated using Equation (3):
where, Mev is mass transport by the alongshore wind, f is the Coriolis parameter (2 × Ω × sinϕ), Ω is the angular frequency of the Earth and ϕ is the latitude.
Multiple linear regression analysis with Chl-a as dependent variable and NASA-AOT (or DOT), alongshore wind speed, EMT and SST as independent variables was carried out. We used 8-day composites with lags of 1–2 time steps for this analysis (these lags correspond to the maximum correlation between Chl-a and NASA-AOT data). The analysis was repeated by replacing NASA-AOT with CCI-AOT (or DOT) with a lag of 3 time steps, corresponding to the maximum correlation between Chl-a and CCI-AOT. We have also calculated the 8-day climatologies of all these variables, and plotted against time of year, to study their phase relationships.
2.2.4. Derivation of Dust Optical Thickness (DOT)
The desert dust transported by winds over the ocean contains micronutrients such as iron, which can regulate phytoplankton activity (Martin et al., 1994; Lenes et al., 2001; Muhs et al., 2007; Donaghay et al., 2015). Since the seasonal monsoon winds bring large quantities of iron-containing dust aerosols to the study area (Li and Ramanathan, 2002; Banerjee and Prasanna Kumar, 2014), we investigated the effect of dust aerosols on Chl-a concentrations. The AE, which is often used as a qualitative indicator of aerosol particle size, and AOT, which indicates the aerosol load, can be used to differentiate dust aerosol from other types of aerosol. Generally, a higher value of AE (α>1) is indicative of fine, submicron aerosols, whereas lower values (α < 1) are representative of coarse, super-micron particles (Kaufman, 1993; Gobbi et al., 2007; Yoon et al., 2012). The AOT values are lower for fine aerosols and higher for coarse aerosols. In the literature, different criteria have been proposed to identify dust aerosols at different locations: for example, α < 0.6 (Dubovik et al., 2002; Brindley et al., 2015), α < 0.8 (Eck et al., 2005; Che et al., 2013), α < 1 (Eck et al., 1999; Schuster et al., 2006; Papaynannis et al., 2007; Yoon et al., 2012; Valenzuela et al., 2014; Zu et al., 2014; Pakszys et al., 2015) and α < 1.4 (Gobbi et al., 2007; Pereira et al., 2011; Shinozuka et al., 2011); similarly, AOT > 0.11 (Toledano et al., 2007; Balarabe et al., 2016), AOT > 0.2 (Salinas et al., 2009; Pakszys et al., 2015) and AOT > 0.25 (Guleria et al., 2012) have been recommended to identify dust aerosols. After considering all these studies, we have adopted the ranges of AOT and AE for off Somalia as follows: AE less than 1, and AOT at 440 nm (τ440) greater than 0.2 (i.e., α < 1 and τ440 > 0.2) are designated as DOT or dust aerosols. The NASA-AOT at 865 nm (τ865) and NASA-AE were used to calculate NASA-AOT at 440 nm (τ440), using Equation (1). Similarly, CCI-AOT at 550 nm (τ550) and CCI-AE were used to calculate CCI-AOT at 440 nm (τ440), using Equation (1).
3.1. Relationship between Chl-a and AOT in the Arabian Sea
The correlation between Chl-a and NASA-AOT using 8-day time series from 1998 to 2013 data for the Arabian Sea is mapped in Figure 2. The results are based on data for all the seasons rather than for specific seasons as in Patra et al. (2007) or in Banerjee and Prasanna Kumar (2014). The western Arabian Sea exhibits high positive correlations, whereas the south eastern Arabian Sea shows low to moderate positive correlations. There are also regions (south central) where no statistically-significant correlation is evident and extensive regions (north-central and north-eastern) of significant negative correlations. The region off Somalia shows high positive correlation between Chl-a and NASA-AOT and it is located along the path of winds carrying dust aerosols emanating from South Asia, South-West Asia, North Africa (Sahara) and the eastern Horn of Africa (Pease et al., 1998; Ginoux et al., 2001; Goudie and Middleton, 2001; Prospero et al., 2002; Léon and Legrand, 2003). Although there are several studies (Banzon et al., 2004; Kayetha et al., 2007; Patra et al., 2007; Singh et al., 2008; Nezlin et al., 2010; Banerjee and Prasanna Kumar, 2014) that have examined the relationship between Chl-a and AOT in various parts of the Arabian Sea, the region off Somalia has not yet been explored in detail, and it is the region selected for our investigation.
Figure 2. Correlation map between 8-day composited Chl-a and NASA-AOT during 1998–2013 for the Arabian Sea. Pale to dark red shading and pale to dark blue shading represent positive and negative correlation respectively. The black square box off Somalia shows the study area selected for further analyses.
3.2. Climatologies of Chl-a, Aerosols, Winds and SST off Somailia
The 16-year 8-day climatological seasonal cycles of Chl-a concentration, NASA-AOT, CCI-AOT, SST and along-shore wind speed are shown in Figure 3A, for the selected study area off Somalia. SST data are reported as anomalies from 8-day average. When the aerosols are identified as dust aerosols, they are indicated in the plot using black and purple filled circles. Out of 46 observations involved in both AOT data sets, for the 8-day climatology, 24 observations were dust aerosols for CCI-AOT data whereas 14 were identified as dust aerosols for NASA-AOT data. It was found that the CCI-AOT data showed the presence of dust aerosols not only during the summer monsoon season, but also during the winter monsoon season. The corresponding climatological wind vectors are shown in Figure 3B. During the first 100 days of the year, winds are north easterly, the wind speed decreasing with time. These conditions are unfavorable for upwelling off Somalia. During this period, SST increases steadily by some 3°C. At the same time, the Chl-a concentrations decrease, and AOT also remains low. After this, the winds reverse direction and intensify, resulting in upwelling (indicated by decreasing SST) that favors phytoplankton growth. We note that the initial response of phytoplankton to the intense south westerly winds is a decrease in concentration, perhaps a consequence of the phytoplankton being mixed into deeper layers. After this, the Chl-a increases, with a lag of a couple of time steps behind the increasing wind speed. Both AOT and Chl-a reach their respective maxima during the summer monsoon season.
Figure 3. Time series of 8-day climatology, (A) for Chl-a, NASA-AOT, CCI-AOT, SST anomaly and Wind speed and (B) for the wind vectors. The black and purple coloured dots in the NASA-AOT and CCI-AOT graph denote the presence of dust aerosols.
In Figure 3A, the NASA-AOT and Chl-a reach their respective maxima during the summer monsoon season. Although the seasonality of CCI-AOT is more or less similar to that of NASA-AOT, the occurrence of peak values is different. The maximum value for CCI-AOT occurred during early summer monsoon season (Day of Year, DoY 170) while the Chl-a is still increasing, whereas the NASA-AOT peak occurred at DoY 224 during the waning phase of summer monsoon season and after the Chl-a peaks at DoY 216. An interesting feature in the figure is that, towards the peak of the summer monsoon (around DoY 180), when Chl-a concentration reaches ≈ 0.8 mg m−3, there is a brief period when Chl-a continues to increase and leads NASA-AOT by up to 3 time steps until DoY ≈ 220. However, this feature was not found in CCI-AOT data. Just before the Chl-a peak is reached, the wind speed starts to drop, followed by Chl-a and NASA-AOT, until all variables reach minima toward DoY 300, at which point the wind direction again reverses. SST starts to increase when the south-westerly winds drop, reaching a secondary peak at around DoY 310.
The seasonal patterns are consistent with the known geography of the area. However, there is a tantalizing suggestion in Figure 3 that when the winds speed are at their highest, and Chl-a levels are high, the NASA-AOT concentrations may be enhanced by maritime aerosols, in addition to the dust aerosols, and that some of these aerosols may have a biological origin, as indicated by Chl-a leading NASA-AOT during this period. However, this observation is not supported by CCI-AOT, and in the absence of additional information, it would be premature to conclude that such is the case. But it would be a point worthy of further investigation.
3.3. The Relationship between Chl-a, AOT and DOT off Somalia
Since Figure 3 indicates that there is a lag in the relationships between Chl-a and the other variables studied here, further analysis has been made for the 2 × 2° box using Cross Correlation Function (CCF) between Chl-a and AOT. The result (Figure 4A) shows that the highest significant positive correlation (r = 0.55) between Chl-a and NASA-AOT in the study region occurred for Chl-a lagging NASA-AOT by 1 to 2 time steps (1 time step is 8 days). The CCF analysis was also carried out between CCI-AOT and Chl-a and shows a significant positive correlation. Further, the maximum correlation (r = 0.54) occurred when Chl-a lagged behind CCI-AOT by 3 time steps (Figure 4B). So the analysis using CCI-AOT data confirmed the results obtained using NASA-AOT on the existence of a significant correlation between Chl-a and AOT in the region off Somalia, the magnitude of the correlation and also the sign of the lag.
Figure 4. Cross Correlation Function between (A) Chl-a and NASA-AOT (B) Chl-a and CCI-AOT for study area off Somalia.Time step is 8 days.
The relationship between Chl-a and AOT (or DOT) with lag of 8 days is explored further in Figure 5 using NASA-AOT (or DOT). Scatter plot between Chl-a and AOT is shown in Figure 5A, with the fitted curve and the r value of 0.55 for the fit, consistent with the CCF. However, we recognize that the relationship of maritime and dust aerosols with Chl-a would be functionally different (for example, we do not anticipate that maritime aerosols could fertilize the oceans, whereas it would be plausible with dust aerosols). Dust aerosols are present more frequently during the summer monsoon season because of the favorable wind from adjacent land masses, compared with other seasons. Out of 736 observations over 16 years, around 203 observations were identified as dust aerosols. Figure 5B shows the relationship between Chl-a and DOT. We see that there is a general tendency for Chl-a to increase with DOT.
Figure 5. (A) The scatter plot between 8-day composite AOT (NASA-AOT) and Chl-a with lag of one time steps, for the study area. The straight line in red colour indicates the regression equation and the correlation coefficient (r) is shown in the top right side. (B) Scatter plot between DOT and Chl-a with lag of one time steps (subset of all the data points in (A). (C) Scatter plot between AOT and ΔChl-a with lag of one time step. The circles in red colour indicate dust aerosols. (D) Histogram for ΔChl-a during the presence of dust aerosols with lag of one time steps.
We checked further whether the presence of dust aerosols enhances the Chl-a concentration in the subsequent time steps by calculating the difference in Chl-a (ΔChl-a) in 1 time step after a dust event, and plotting it against NASA-AOT (Figure 5C). The presence of more positive ΔChl-a following high aerosol events would be indicative of a positive effect of aerosols on phytoplankton concentration. The data (Figure 5C) show no obvious relationship between aerosols and ΔChl-a either for all aerosols taken together or for dust aerosol events (circles in red colour) by themselves. However, for all the DOT events considered by themselves, the frequency of ΔChl-a is slightly skewed toward positive numbers, with some 114 values being positive out of 203 events (see histogram of ΔChl-a, Figure 5D). So the probability that Chl-a enhancement is associated with the presence of dust aerosols throughout the year is 56% (114 out of 203), compared with 238 out of 532 in the absence of dust aerosols (45%). The higher number of positive ΔChl-a observations is significant (p < 0.05) according to a binomial test. For the non-dust events, there is a higher number of negative values (294) compared with positive values (238) of ΔChl-a. These results are summarized in Table 2.
Table 2. The number of observations with enhancements in Chl-a (+ve ΔChl-a) or reductions in Chl-a (−ve ΔChl-a), for all data, and for the summer monsoon, for the non-monsoon and sorted according to whether the aerosols were identified as dust or not (here, dust aerosols were derived from NASA-AOT data).
We supplemented these calculations after splitting the data according to monsoon (summer monsoon) and non-monsoon seasons, recognizing the differences in oceanographic and meteorological conditions during these two parts of the year (Table 2). Out of 224 observations during the summer monsoon season, 140 are dust aerosol events and 84 are non-dust events. Within these 140 dust events, the number of positive ΔChl-a values is 82 (59%), compared with 58 (41%) negative values. However, for non-dust events during this season, we also find more positive ΔChl-a values (58 events, or 69%) than negative ones (26 events, or 31%). For the non-monsoon season, out of 511 total observations, 448 are non-dust aerosol events and 63 are dust events. Within these non-dust observations, there is higher number of negative values (268, or 60%) when compared with positive values (180 or 40%). But during dust events, the number of positive observations is slightly higher, with 32 (51%) positive values compared with 31 (49%) negative ones. We conclude from all of the above that the probability of Chl-a enhancement during the summer monsoon season does not depend much on the presence or absence of dust aerosols. In other words, during the summer monsoon season, there is a higher probability of finding positive ΔChl-a values, regardless of whether there is a dust event or not. On the other hand, during the rest of the year, the probability of chlorophyll enhancement is a little higher during dust events than during non-dust events.
The analysis was also repeated for CCI-AOT data to verify the above results and is presented in Table 3. For this dataset, the probability of Chl-a enhancement is again more in the presence of dust aerosols when the whole year is considered, at 53% (134 out of 251), compared with 142 out of 344 in the absence of dust aerosols (41%). Out of 208 observations during the summer monsoon season, 154 are dust aerosol events and 54 are non-dust events. Within these 154 dust events, the number of positive ΔChl-a values is 83 (54%), compared with 71 (46%) negative values. However, for non-dust events during this season, we also find more positive ΔChl-a values (31, or 57%) than negative ones (23, or 43%). The results from winter monsoon season indicate that, though the dust aerosol events are fewer in number (49) compared with non-dust (93) within 142 observations, there were more positive ΔChl-a values (28, or 57%) than negative values (21, or 43%) when dust aerosols were present in the region. But, during the absence of dust aerosols, there is a higher number of negative values (48, or 52%) compared with positive values (45 or 48%).
Table 3. The number of observations with enhancements in Chl-a (+ve ΔChl-a) or reductions in Chl-a (−ve ΔChl-a), for all data, and for the summer monsoon, for the winter monsoon and sorted according to whether the aerosols were identified as dust or not (here, dust aerosols were derived from CCI-AOT data).
Thus both NASA-AOT and CCI-AOT lead to the conclusion that the probability of Chl-a enhancement during the summer monsoon season does not depend on the presence or absence of dust aerosols. In other words, during the summer monsoon season, there is a higher probability of finding positive ΔChl-a values, regardless of whether there is a dust event or not. On the other hand, during the winter monsoon season and rest of the year, the probability that dust events may be associated with chlorophyll enhancement is higher than that during non-dust periods.
3.4. Relationship of Chl-a with Winds, SST, AOT, and DOT
To elucidate further the relationship between Chl-a and environmental conditions, we next examined the CCF between Chl-a and alongshore wind speed, since it is known that the alongshore winds determine upwelling, and hence influence phytoplankton dynamics in the area (Goes et al., 2005; Gregg et al., 2005; Wiggert et al., 2005; Prasanna Kumar et al., 2010); (see also Figure 3). The result (Figure 6) shows, similar to the CCF between Chl-a and NASA-AOT, that the correlation peaks with a lag of 1-2 time steps, with wind speed leading Chl-a, but with a higher correlation coefficient (r = 0.69, p < 0.05).
Figure 6. Cross Correlation Function between Chl-a and alongshore wind speed for study area off Somalia. Time step is 8 days.
Since the correlation coefficients of Chl-a with both aerosols and wind speed peak with a lag of 1–2 time steps, we chose a lag of 1 time step, for a linear step-wise multiple regression study with Chl-a as dependent variable, and NASA-AOT (or DOT), Ekman Mass Transport (EMT), alongshore wind speed and SST as independent variables. The upwelling indices, the wind speed and EMT both show more or less similar correlation with Chl-a. So, we excluded the EMT from the multiple linear regression analysis (but the results from the multiple linear regression including EMT are presented as Table S1). When the correlations with each of the independent variables are considered individually, the highest r2 values were found for alongshore wind speed (r2 = 0.47) for the ensemble of year-round data, with the corresponding r2 dropping to 0.17 when dust aerosol events are considered separately (140 dust events during the summer monsoon, and 63 outside of it, totalling 203), followed by SST (r2 = 0.33 and r2 = 0.20 for the same two cases respectively), and then by NASA-AOT (r2 = 0.30 and r2 = 0.08 for the corresponding cases). From the results of pair-wise regression analysis, we see that the addition of NASA-AOT (or DOT) as an independent variable, in addition to wind speed, increases r2 values by a modest 0.02. With all three variables taken together as independent variables, the explained variance (r2) is 0.52 for all data, and 0.25 for DOT events (Table 4). The results for a lag of 2 time steps (not shown) are similar to those for lag of 1 time step, but with lower correlation coefficients.
Table 4. Results of multiple linear regression analysis with Chl-a as the dependent variable and NASA-AOT or DOT, alongshore wind speed and SST as independent variables for 1 time step lag.
The multiple regression analysis was also repeated for CCI-AOT data with Chl-a as dependent variable and CCI-AOT (or DOT), alongshore wind speed and SST as independent variables (Table 5). Since the correlation coefficients of Chl-a with CCI-AOT peak with a lag of 3 time steps, we chose a lag of 3 time steps for this analysis. When the correlations with each of the independent variables are considered individually, the highest r2 values were again found for alongshore wind speed (r2 = 0.49) for year-round data and r2 = 0.38 for dust aerosol events (154 dust events during the summer monsoon, and 97 outside of it, totalling 251) considered separately, followed by SST (r2 = 0.32 and r2 = 0.15 for the same two cases respectively), and then by CCI-AOT (r2 = 0.29 and r2 = 0.09 for the corresponding cases). From the results of pair-wise regression analysis, the addition of CCI-AOT (or DOT) on wind speed as independent variables did not make any improvement in the r2 value of 0.49. However, a small increase in r2 value by 0.06 or 0.08 was found when adding CCI-AOT (or DOT) respectively to SST.
Table 5. Results of multiple linear regression analysis with Chl-a as the dependent variable and CCI-AOT or DOT, alongshore wind speed and SST as independent variables for 3 time step lag.
4.1. The Satellite Data Used
Much of the interpretation of results for the region off Somalia depends on the quality of the satellite data used for the analysis, especially during the summer monsoon season, since this is a highly dynamic season, with high winds, high AOT and high Chl-a concentrations. The OC-CCI Chl-a dataset (Sathyendranath et al., 2016) was selected because of the significantly-improved seasonal coverage that the data provide in the study area, compared with other datasets, especially during the summer monsoon season. But it is important to reassure ourselves that the data are of sufficient quality for the analysis presented. Though the OC-CCI data have been validated using a global dataset as part of the project, and also for the neighboring Red Sea (Brewin et al., 2015) and the Gulf of Aden (Gittings et al., 2016), we do not have in situ data from off Somalia region for local validation. However, the data are reassuring in some respects: the first one is that, if the relationship between Chl-a and AOT were an artifact of the processing, then one would anticipate that the relationship would peak at zero lag. In fact, we see that, typically, the maximum correlation occurred with a lag, suggesting a functional relationship between the two variables, rather than an artifact. The second is that the seasonal patterns in Chl-a are consistent with the known oceanography of the area, and appear as a consequence of the seasonal changes in the oceanographic conditions, as indicated by the winds and SST. The AOT and AE data from both NASA and CCI also show seasonal changes with high AOT values and low AE during summer monsoon season and vice versa for the rest of the year.
We have used aerosol data from the NASA ocean colour web site, partly to reassure ourselves that the aerosol and Chl-a products that are outputs of the same processing chain do not show inter-dependencies associated with the assumptions that underlie the processing. In the OC-CCI processing version-2 used here, SeaWiFS and MODIS-Aqua data were processed using NASA's SeaDAS software, consistent with the processing chain that generated the aerosol products at the NASA ocean colour website. That the analysis presented here has indicated that the patterns in Chl-a and in the aerosol properties are consistent with the known oceanography of the study area, and that the correlations vary with region (Figure 2) as oceanographic and meteorological conditions change, lends some confidence to the quality of the data, in the absence of direct validation data. To further substantiate the application of satellite data to studies of relationship between aerosol and phytoplankton, Aerosol-CCI data sets were also subjected to identical analysis and the data confirmed our findings.
4.2. Aerosols and Phytoplankton in the Western Arabian Sea off Somalia
There have been a few previous studies that dealt with the influence of aerosols on phytoplankton dynamics in the Arabian Sea. A recent study (Banerjee and Prasanna Kumar, 2014) has shown that episodic dust storms could generate phytoplankton blooms in the central Arabian Sea during the winter monsoon. Nezlin et al. (2010) reported a correlation between Chl-a and aerosols when studying inter-annual variations in the Persian Gulf area. Prasanna Kumar et al. (2010) reported an increasing trend in phytoplankton in the central Arabian Sea during winter months of 1997–2007, and attributed it to increasing supply of iron by dust aerosols. Singh et al. (2008) studied a series of dust storms in the northern Arabian Sea during a 3-year period, and reported chlorophyll enhancement within 1–4 days of dust events, but also pointed out other mechanisms that might be responsible for the relationship observed.
Our results for the western Arabian Sea off Somalia indicate only a possible minor role for dust aerosols enhancing Chl-a concentration during the summer monsoon, supplementing the major role of alongshore winds inducing upwelling favorable for phytoplankton growth. The upwelling component of winds off Somalia during summer monsoon season appears to be far stronger than the classic eastern coastal upwelling zones in the world ocean (Bakun et al., 1998). In the data used here, the wind speed was greater than 15 m/s during summer monsoon season over the Somalia coast. Recently, de Castro et al. (2016) studied the evolution of Somali coastal upwelling under future warming scenarios using models. When the intensity of Somali coastal upwelling during summer monsoon season was projected for the twenty first century, the trends showed that changes in coastal upwelling were mainly related to the wind-induced Ekman transport. Further, our findings are consistent with those of Gallisai et al. (2014) for the Mediterranean: they concluded that the main driver of phytoplankton dynamics is the supply of nutrients from the deep water to the surface layers through vertical mixing. However, the results of the multiple regression presented here do not necessarily imply that the effect of aerosols on Chl-a is only 2%, but only that, because AOT covaries with the other variables, especially wind speed, it is difficult to disentangle their individual effects on Chl-a concentration. Perhaps more interesting is the possibility that the effect of dust events on Chl-a enhancement might be a little stronger during the winter monsoon season and rest of the year than during the summer monsoon season (Tables 2, 3), consistent with the results of Prasanna Kumar et al. (2010) for the central Arabian Sea during winter monsoon season. The direction of the winds during the winter monsoon would suggest an origin in the Asian subcontinent for these dust aerosols, rather than the Arabian peninsula.
We used the cross correlation function to study the phase relationship between aerosol (AOT) and phytoplankton (Chl-a) dynamics. The correlation between the two variables peaked at a lag of 1–2 time steps, with AOT leading. However, since a similar lag was found in the CCF between Chl-a and alongshore winds, it is difficult to attribute a causal relationship to the aerosols by themselves. The phase relationship also throws light on whether or not the biological particles might be enhancing the production of aerosols in the study area. If such events were commonplace, then one would expect that Chl-a enhancement might occur prior to increase in aerosol concentration. The CCF results do not support this in general, but the climatologies of the studied variables (Figure 3A) do show that there is a reversal in the phase relationship for a brief period, with Chl-a leading NASA-AOT when Chl-a concentration approaches its peak during the summer monsoon season. However, this result is not confirmed by CCI-AOT data. Thus, conclusive evidence for biological enhancement of aerosols remains elusive. The intriguing result with the NASA-AOT certainly merits further investigation.
5. Concluding Remarks
Essential Climate Variables, or ECVs, are our sentinels for observation of climate change. However, to understand climate change, it is not sufficient to study individual ECVs in isolation. Instead, it is also important to study how they interact with each other, and to understand how these interactions might change in the future. Of the marine ECVs, Chl-a concentration is the only biological ECV that is currently amenable to routine observations by remote sensing.
In this paper, we have examined one piece of the puzzle, by studying how the variability of Chl-a in the western Arabian Sea is related to those in three other ECVs: aerosols, winds and SST, focussing more on aerosol- Chl-a interactions, using 16 years of satellite data. What emerges is a complex pattern of relationships, in an area where many ECVs co-vary with each other. While it is difficult to elucidate causal relationships from simple correlations, the phase relationships between the variables can throw some light on the underlying causes.
A question that had to be addressed first, when using satellite data for the analysis, was whether there were artifacts in the patterns in Chl-a, introduced by the atmospheric correction process, which depends to some extent on aerosol optical properties. The correlation between Chl-a and NASA-AOT (a by-product of ocean colour processing) peaking with a lag provided reassurance on this point, since the peak should have been observed at zero lag had processing artifacts been the cause of the correlation. This point was reinforced by repeating the analysis with data from Aerosol-CCI products, which are derived independently of the ocean colour processing chain.
Though the NASA aerosol properties and the CCI aerosol properties are generally consistent with each other, there is a significant phase shift in the time when they peak during the summer monsoon season. The underlying causes for this difference deserve to be investigated further, but fall outside the scope of this paper. In the Somali region, under upwelling regimes, the Chl-a concentration is strongly correlated with wind. Analysis of Ekman Mass Transport supports the hypothesis that wind-induced upwelling is the underlying cause of the high correlation between wind and Chl-a. According to the linear multiple regression analysis, aerosols have a modest effect on Chl-a, at best, with a lag of one to two time steps during this period. An unexpected outcome from this study is related to the importance of dust aerosols in stimulating Chl-a enhancement during the winter monsoon season, suggesting that the abundance of dust aerosols might enhance Chl-a in the absence of wind-induced upwelling.
MS carried out all the data analyses and produced the figures. MS and SS wrote the manuscript. SS conceived the scientific plan, with help from TP. TP provided scientific advice, and led the project. GG contributed to the planning and discussions, and along with AB, provided supervision.
Conflict of Interest Statement
The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.
The authors acknowledge Department of Science and Technology (DST), India for the Jawaharlal Nehru Science Fellowship (JNSF) awarded to TP. The authors thank the Director, CMFRI, Kochi for all support and encouragement. This work is a contribution to the Ocean Colour Climate Change Initiative of the European Space Agency, and to the activities of the National Centre for Earth Observations of UK. We also thank the two reviewers for their helpful comments, which have improved the manuscript.
The Supplementary Material for this article can be found online at: https://www.frontiersin.org/articles/10.3389/fmars.2017.00386/full#supplementary-material
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Keywords: essential climate variables, aerosol optical thickness, Ångström exponent, chlorophyll-a, ocean colour climate change initiative, climate change, remote sensing, dust aerosols
Citation: Shafeeque M, Sathyendranath S, George G, Balchand AN and Platt T (2017) Comparison of Seasonal Cycles of Phytoplankton Chlorophyll, Aerosols, Winds and Sea-Surface Temperature off Somalia. Front. Mar. Sci. 4:386. doi: 10.3389/fmars.2017.00386
Received: 30 March 2017; Accepted: 15 November 2017;
Published: 12 December 2017.
Edited by:Catherine Jeandel, Centre National de la Recherche Scientifique (CNRS), France
Reviewed by:Hubert Loisel, Université du Littoral Côte d'Opale, France
David Antoine, Curtin University, Australia
Copyright © 2017 Shafeeque, Sathyendranath, George, Balchand and Platt. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) or licensor are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.
*Correspondence: Shubha Sathyendranath, firstname.lastname@example.org | <urn:uuid:37cc5239-75a3-4486-b65d-b224a0ff66a6> | 2.546875 | 16,929 | Academic Writing | Science & Tech. | 67.147025 | 95,605,052 |
CHAR and VARCHAR are the datatypes of the MySQL.
This article is to cover similarity and difference of both datatypes. Both are almost same but for some aspects both behave slight different based on condition.
CHAR and VARCHAR are almost same but both are different at the stage of storing and retriving the data from the database.
For both the datatypes we have to pass the length specifier, it indicates that how much data that fields can hold. For example char(30) and varchar(30) this means fields with these datatypes can hold upto 30 characters.
For CHAR this length can be any from 0 to 255 and for VARCHAR can be from 0 to 65,535. But for VARCHAR this maximum limit depends on Maximum row size and character set you have used.
Storing of data is quite different in both types. First takes the case of the CHAR.
When values are stored in CHAR fields, remaining chars will be padded with the white spaces.
Say for example one fields is “name CHAR(5)” and you are about to store just “jack” then actual value stored will be “jack “.
VARCHAR will not add extra spaces to your data when you provide the less data than specified length. It will store the data as you have provide in the query.
For both the data types, If you pass the larger data than specified length then MySQL will truncate the data to fit the length specified at the time of creating a table and it will return a warning. But this will be the case if SQL Strict Mode is not enabled.
But if you want to restrict this truncation of the data you should enable the Strict Mode in MySQL. So it will generate error for the query.
Data retrival is also quite different for the both types.
As mentioned above CHAR will add the spaces to the data if less data is provided, so while retrival of the data it will remove the added spaces and provide the data.
VARCHAR will store only data which you pass on the query so like CHAR, it will not perform any space removal process on the data.
There is a bit difference in storage space required for both datatypes.
First of all, assuming that fields are using single byte character set like latin1.
As mentioned above CHAR will add the space to the remaining word count. So CHAR will always occupy the number of bytes based on the length specified. So CHAR(5) field will always occupy 5 bytes doesn’t matter what we have stored, like ‘a’, ‘abcd’ or ‘abcde’.
Unlike CHAR, VARCHAR will only occupy the space based on the data stored, So for example if we have fields with VARCHAR(30) then, this will occupy the space based on the data we are going to store.
One more thing with VARCHAR is, it also occupy the 1 or 2 bytes of length prefix. This 1 and 2 bytes are based on length of data we store. If data is less than 255 char then 1 Byte is used and for data larger than 255 char 2 bytes are occupies as the length prefix
So now the question is, which one to use? Use of these datatypes are purely depends on the need.
If you have fixed size of data, just like the flags of “Y” and “N”. Then it will better to use CHAR rather than VARCHAR. The reason is that length prefix used with VARCHAR.
So if you use VARCHAR then it will store 2 bytes for “Y” and “N”. (i.e. 1 byte for data and 1 byte for length prefix) and CHAR will store only 1 bytes which is of data only.
Avinash Zala is leading various projects which deals with the various technology involved with the web. A combination of perfect technical and management skills. Avinash would like to chat with you and convert your imagination into the working system. You can get in touch with him on Facebook and Twitter.
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This post is going to show about editing the hosts file. So first of all what is hosts file?
Hosts file is simple file which maps the host name and IP address. But this mapping is applicable for that machine only.
Location of this file can be vary based on the operating system. You can find full list of all OS with location of hosts files on each OS at this link.
You can edit the hosts file using any text editor but you will need administrator right for that.
You need to map ip address and host name as per below method.
You can use # to comment the line in hosts file.
Here is the real example of mapping the host name and ip address
So now after placing this in your hosts file, local.com will served form 127.0.0.1 means from local. It will load local site instead of actual site.
You can not specify port based IP address in hosts file. So below code will not work.
Note: You can not specify port based IP address in hosts file.
Once I had a great fun with this file. I have placed below code in hosts file of my friend’s machine.
So now whenever he types google.com in browser it will just load the local file of apache’s root. Really it was a great fun.
Have you done any fun like this with this file?
Avinash Zala is leading various projects which deals with the various technology involved with the web. A combination of perfect technical and management skills. Avinash would like to chat with you and convert your imagination into the working system. You can get in touch with him on Facebook and Twitter.
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This guide (which is also a Literate Haskell program) describes basic Hakyll metaphors in a way that I would have found useful when first learning Hakyll, using a working example site to illustrate the concepts. The mechanism described in this article are not necessarily the literal implementation Hakyll, but are rather a glimpse of the metaphors that I have found useful in practise when working with it. Also, it should probably be noted that I was using Hakyll 22.214.171.124 and GHC 7.8.1 when writing this article.
Hakyll is the static web site generator used to create this site. You use it by defining the behaviour and structure of your site as a Haskell program that uses various facilities exposed by the Hakyll modules, a style familiar to users of Xmonad. A number of tutorials are available on the Hakyll website, but when I was trying to learn Hakyll (some years ago), I was sorely missing a guide aimed at experienced Haskell programmers, one that defined the basic abstractions and metaphors in terms of the data types actually exposed by Hakyll. After much trial and error, I eventually came to understand what was going on, and decided to document it as the kind of tutorial that I would have found useful. I still recommend skimming the other tutorials, as I will probably skip things that I don’t find very interesting. In fact, this should probably be considered an “advanced tutorial” (that certainly sounds much better than “stream-of-consciousness snapshot”).
Hakyll is used by compiling and running a program in the directory containing the input files, which then generates the site as a set of output files. Hence, we define a
Main module that exports a
main function and imports all the modules we’ll need. The
OverloadedStrings language extension, as a small convenience, lets us write
"*.md" instead of
Fundamentally, Hakyll is extremely simple: it is an association between Identifiers and Compilers, and everything else is just scaffolding around that. An identifier is just that: a name consisting of an optional “group” and a mandatory “path”, which need not be a file path, but often is. A compiler is an action in the monad
Compiler. When the site is generated, the compiler for each identifier is executed. A compiler can in principle do anything to generate its output, but one interesting thing it can do is ask for the compilation result some other (known) identifier. Hakyll will automatically run the compilers in the proper order such that these requirements are satisfied, although cycles are forbidden. Since you cannot in general know the type of values generated by the compiler of some arbitrary identifier, you can get type error at runtime, if you ask for the compilation result as a different type than the compiler produces (there are some typeclass constraints that I’ll get into later).
The output from a compiler is not necessarily put anywhere unless another compiler asks for it, but it is possible to define a “route” for a compiler, which causes Hakyll to write the result to a file in the site directory. The route is not part of the compiler itself, but defined as an association of the identifier. Routes are the way we can map, for example, a Markdown file to the HTML file it should become in the generated site.
When working with Hakyll in practise, you will define compilers though a monadic DSL incarnated in the Rules monad. This monad makes it easy to apply similar compilers to all files matching some given pattern. For example, let us define a rule that copies the
style.css file verbatim into our site.
return () is to make the type
Rules, rather than
RulesM (Pattern CopyFile) –
Rules is just
RulesM (). The
match function runs the given rules for each file in its match, although the above will only match exactly one file, namely
style.css in the same directory as our Hakyll source file. In general terms, the
compile action associates the given compiler with each of the identifiers matching the current pattern. The set of possible identifiers (which are then filtered by the pattern) is taken from the files (not directories) in the directory from which Hakyll is run. The compiler given to
compile must take a
Resource as its input, which is really just a wrapper around an identifier guaranteed to refer to a file.
Let’s do something more complicated: we want our site to contain a bunch of pages, but all of them should contain a complete list (a menu) of all pages on the site. This sounds like a problem: in order to generate one page, we must already have seen every other page, which violates the requirement that compiler dependencies must be acyclic. The solution is to use two logical passes: first run a set of compilers that somehow generate a list of all pages, then actually generate the content for each page while including that information. This is possible since the menu does not need to know the content of each page, but only its eventual location on the site, which in Hakyll terms is the route for each identifier corresponding to an input file. So far, so good, but how do we easily generate such lists? To begin with, we define a pattern that matches all the content pages on our site.
This pattern matches all
.md files, including those in subdirectories to any depth. Our site may have other files - images and other resources - but we do not want these to show up in the menu anyway.
When we try to define rules for storing menu information, we may run into the problem that the compiler we pass to
compile is really quite restricted in its output type: it has to implement various type classes permitting serialisation, as it could in principle be asked to write its result to a file. In this case we’re in luck, as plain
Strings implement the required instances. A second problem is that we conceptually wish to associate two compilers with each input file - one that generates its data for the menu, and one that actually renders the page to HTML. The solution is to tag the identifiers related to the menu compilers with a version (here,
"menu"), which makes them different from the identifiers used for the actual content, which have no version.
For every file that matches the
content pattern, we create an identifier corresponding of the file path and the version
"menu". This identifier we associate with the compiler
destination. It is important to note that
match filters the input, whereas
version modifies the identifiers of the output.
destination compiler does not use its underlying file for anything, but instead obtains the identifier being compiled, setting the version of that identifier to
Nothing, getting the route for the resulting identifier, and if that identifier doesn’t exist (the route is
Nothing), returning the empty string. This is a a bit of a hack, but we don’t really expect getRouteFor to ever return
Nothing, as that would mean we have been asked to add a menu entry for a file that will not exist on the site. Since the only difference between the identifiers used for generating the menu and the content is that the latter have version
Nothing, this will compute the output path of the compiler responsible for generating the content for the respective file. The reason this works is because you do not need to run the compiler in order to determine where it will put its output - that is defined in the
Rules DSL, and hence available simply by querying the identifier.
The rule for defining our content pages is quite simple. We replace the existing extension (
md according to the
content pattern) with
html, then pass the page through a three-step compiler that first converts the page from Markdown to HTML, then applies an HTML template, then finally converts absolute URLs into relative URLs so the resulting files can be put anywhere (don’t worry about this last stage, it’s not important). To understand how
loadAndApplyTemplate works, we first have to understand Hakyll templates and contexts. Templates are simply files in which variables can be written as
$var$. When applying the template, each such instance is replaced with the value of the corresponding variable in the passed context. Our
template.html file will contain the text
$menu$ where we intend our menu to show up, and hence we need to create a context that contains a
menu field containing an HTML-rendering of the menu for that page.
Apart from the
menu field, the template also needs some standard fields like
"title". These are provided by
getMenu compiler is the one that actually produces the menu. The real trick here is the use of
loadAll, which lets us obtain a list of all compiler outputs for identifiers in the
"menu" group. That means a list of all routes for our content pages!
showMenu itself is just a plain Haskell function that produces an HTML list with the current page highlighted. In practice, we’d use a proper HTML combinator library, but let’s stick with strings for simplicity.
In order to use a template, we have to tell Hakyll it exists. That’s what the
templateCompiler is about. This is not a very interesting definition.
Finally, the Hakyll main function is written in a rather stylised manner, with
hakyll being given a
Rules () monadic action. Note that although I execute
compileContent for conceptual reasons, I could swap them around and it would still work.
That’s all there is to it. To try it out, download some input files, put this hakyll.lhs into the directory, then run
$ ghc --make hakyll.lhs && ./hakyll build && ./hakyll preview 8080
and point your web browser at
localhost:8080. The result should be something similar to this. If you change the code, remember to run
./hakyll clean as well, as Hakyll’s cache system might otherwise not realise that something is different.
You may also want to look at sigkill.lhs, the program generating my own website. | <urn:uuid:afe84cb6-0623-4994-8fb9-5d65f172f22e> | 2.734375 | 2,169 | Documentation | Software Dev. | 45.489047 | 95,605,061 |