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Pezizomycotina is the largest subphylum of phylum Ascomycota (also known as sac fungi). With well over 100, 000 species (over 30,000 of these species have been well described), subphylum Pezizomycotin…
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Diatoms are photosynthetic organisms referred to
as algae with a length/diameter of between 2 and 500 microns. They have a
transparent cell wall (frustule) made of silicon dioxide, which is itself
hydrated with a little amount of water. Therefore, diatoms are simply
aquatic organisms, which can be found in such environments as fresh and
marine (salty) waters and moist soils.
The hydrated silica that makes the cell wall of these organisms looks more like opal, which is transparent, forming what resembles a glass house for the algae. The cell wall (frustule) is composed of two halves (valves) that fit into each other like a pill capsule. Because silica is impervious (it does not let anything through) this system allows for the exchange of nutrients and waste in the environment where the organism resides.
The valves also play an important role in the identification and their classification. Although they grow as single cells, they can also form filaments or simple colonies in a group.
As algae, diatoms are protists. This means that
they are eukaryotic organisms that are not specifically defined as plants, animals
or fungus. Formally, they are classified under Division Chrysophyta in Class
Bacillariophyceae. This Class of organism is distinguished by the presence
of an inorganic cell wall that is composed of hydrated silica. Some of the
other characteristics of this Division (Chrysophyta) include:
An endoplasmic cysts
They store oils rather than
A bipartite cell wall
Secretion of silica
Diatoms are also divided in to two main Orders,
which include the Centrales and the Pennales.
Also referred to as Biddulphiales, Centrales
have the following characteristics:
Valve striae arranged in
relation to a point
An annulus (central areola)
Pennales are also known as Bacillariales and
have the following characteristics:
Valve triae arranged in
relation to a point
Typically, diatoms divide and reproduce by a
process referred to as vegetative division, which involves the division of a
single cell into two new cells. During the reproduction cycle, the new cell is
formed inside the parent cell. The new cell is smaller in size given that it
forms within the mother cell that has a rigid cell wall that does not expand.
During this process, the daughter cell also takes a valve of the parent
frustule as its epitheca before building its own hypotheca in a period of about
15 minutes. This process may be repeated a number of times a day (1 to 8
times). However, this largely depends on the availability of dissolved
The process also results in reduced size of the cells with each
division, which in turn results in a relative change in dimensions. This change
in size and shape of a population is commonly referred to as Size Reduction
Series. In this case therefore, one can expected to see a variation of shapes
and sizes of a given population of diatoms under the microscope.
As a result of the reducing average size of the
diatom frustule in a population, there comes a point where restoration of the
size of the frustule is necessary. It's at this point that auxospores are
These particular cells possess a different cell wall compared to the
former generation and lack the siliceous frustule as well. This allows for the
swelling of the frustule to the maximum size. The initial auxospore cell forms a
new frustule of maximum size, which then forms following an active vegetative
reproduction after nutrient levels have been depleted. Once the nutrient level
increases, the cycle continues.
Habitats and Morphology
Different types of diatoms have different
morphological adaptations that allow them to survive in their respective
habitats. For instance, diatoms that live in such aquatic habitats as ponds,
lakes and oceans possess morphological features that make it possible for them
to remain suspended in water.
By forming long chains that are linked to each
other by silica spines, these planktonic species are able to remain suspended
on water. Others will form zigzag/stellate colonies that keep them afloat.
These species are often star-shaped.
Other species grow and multiply on such surfaces
as rocks and other aquatic plants. For these species, their frustules are often
arched or curved in a manner that allows them to fit on stems of aquatic moss.
Other species need to attach them to surfaces and therefore form a stalk or
mucilage pads that allow them to achieve this.
Depending on their habitats
therefore, one can identify differences in their structures, which can help
identify where they come from.
When the aquatic diatoms die, they sink to the
bottom of whatever habitat they are found in and collect to form what is known
as diatomaceous earth. The shells (made of silica) cannot decay, and therefore
collect together at the bottom of the lake. In some cases, they collect to form
a soft, chalky light weight rock called diatomite.
This is commonly used as an
insulating material as well as making explosives, filters and abrasives among
other products. Most of the
diatomaceous earth available on earth is composed of silicon dioxide and may
contain lower levels of crystalline silicon dioxide. It is used in a wide variety
of products including wettable powders and pressurized liquids where it is used
in farms, buildings, skin care products and pet kennels among others.
In its dry form, Diatomaceous earth
causes insects to dry out and die by absorbing their oils and fats from their
cuticle. If a person is exposed to diatomaceous earth it
can cause nasal irritation or cough and shortness when inhaled in very large
amounts. Dust containing this substance can also be irritating to the eyes or
cause skin irritation and dryness. However, it is not poisonous.
Diatoms make for very interesting specimen under
the microscope. They show complex patterns with very fine punctures on their
surface. With some of the species, fine pores in the frustule are used for
testing the resolving power of the lens of a microscope.
Diatoms can be easily prepared for viewing under
the microscope by preparing wet mounts. Here, the sample is simply smeared on
the slide using such liquids as water. The slide can then be placed on the
microscope for viewing. This is the simplest method and can help determine how
In some cases, hydrogen peroxide (or other oxidizing agents) may be
used to remove the organic matter of the frustule for better viewing. Here, a
small amount of hydrochloric acid (HCL) may be used for the purposes of
removing calcium carbonate followed by rinsing in distilled water to remove all
the acid. The sample can then be dried and placed on a slide for viewing.
increase contrast, a mounting medium of higher refractive index can be used. Brightfield
and phase contrast microscopy can be used for observing diatoms. Here, phase
contrast is particularly preferred when viewing specimens that are lightly
silicified. For a dry specimen, 40X and 100X are commonly used.
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The material on this page is not medical advice and is not to be used for diagnosis or treatment. Although care has been taken when preparing this page, its accuracy cannot be guaranteed. Scientific understanding changes over time. | <urn:uuid:af0363f7-3ee7-49e5-95e5-f10cf77a5c25> | 3.015625 | 1,769 | Knowledge Article | Science & Tech. | 35.354505 | 95,597,319 |
Supernova Hunting with Supercomputers
Berkeley researchers provide “roadmap” and tools for finding and studying Type Ia supernovae in their natural habitat
May 20, 2015
Contact: Linda Vu, +1 510 495 2402, firstname.lastname@example.org
Type Ia supernovae are famous for their consistency. Ironically, new observations suggest that their origins may not be uniform at all. Using a “roadmap” of theoretical calculations and supercomputer simulations, astronomers observed for the first time a flash of light caused by a supernova slamming into a nearby star, allowing them to determine the stellar system from which the supernova was born. This finding confirms one of two competing theories about the birth of Type Ia supernovae. But taken with other observations, the results imply that there could be two distinct populations of these objects. The details of these findings will appear May 20 in an advance online issue of Nature.
“By calibrating the relative brightness of Type Ia supernovae to several percent accuracy, astronomers were able to use them to discover the acceleration of the Universe. But if we want to push further and constrain the detailed properties of the dark energy driving acceleration, we need more accurate measurements. If we don’t know where Type Ia supernovae come from, we can’t be totally confident that our cosmological measurements are correct,” says Daniel Kasen, an Associate Professor of Astronomy and Physics at UC Berkeley, who holds a joint appointment at the Lawrence Berkeley National Laboratory (Berkeley Lab).
In 2010, Kasen predicted a new way to test the origins of supernovae. Using theoretical arguments and simulations run on supercomputers at the Department of Energy’s National Energy Research Scientific Computing Center (NERSC), he showed that if a supernova is born in a binary star system, the collision of the debris with the companion star will produce a brief, hot flash of light. The challenge is then to find a Type Ia event shortly after it ignites, and quickly follow it up with ultraviolet telescopes. Using an automated supernova-hunting pipeline—the intermediate Palomar Transient Factory (iPTF), which uses machine-learning algorithms running on NERSC supercomputers—astronomers did just that. They found iPTF14atg just hours after it ignited in a nearby galaxy. Follow up observations with NASA’s Swift Space Telescope showed ultraviolet signals consistent with Kasen’s predictions.
“Kasen’s paper was very important to our work. Without it, we wouldn’t have known what to look for,” says Yi Cao, a graduate student at Caltech and lead author of the Nature paper. “With the help of NERSC’s Edison supercomputer, the iPTF pipeline can turn up supernova candidates 10-15 minutes after its initial detection. This is crucial to our work to search for the ephemeral signal predicted by Kasen.”
“We often talk about how computational science is the third pillar of the scientific
method, next to theory and experimentation, this finding really brings that point home. In this case, we can see how computational models and tools are driving discovery and transforming our knowledge about the cosmos,” says Peter Nugent, Berkeley Lab scientist and member of the iPTF collaboration.
Origin Theories for Type Ia Supernovae
Because the relative brightness of Type Ia supernovae can be measured so well no matter where they are located in the Universe, they make excellent distance markers. In fact, they were instrumental to measuring the accelerating expansion of the Universe in the 1990s—a finding that netted three scientists the 2011 Nobel Prize in Physics, including one for Berkeley Lab’s Saul Perlmutter. Yet, astronomers still do not fully understand where they come from.
There are currently two competing origin theories. In both theories, the white dwarf star that eventually becomes a Type Ia supernova is one of a pair of stars that orbits around a common center of mass. In the double-degenerate model the stellar companions are both white dwarfs and the supernova ignites when both stars merge.
In the competing single-degenerate model a white dwarf star orbits with a Sun-like star or a red giant star, which is essentially a dying Sun-like star. As these stars orbit, the white dwarf’s gravity pulls, or accretes, material from its stellar companion. As the white dwarf becomes more massive, the temperature and pressure in its core increases, eventually initiating a runaway nuclear reaction, which will end in a dramatic explosion or Type Ia supernova.
In the single-degenerate model, Kasen predicted that the material ejected from a Type Ia supernova would slam into its companion star, generating a shockwave that heats the surrounding material. According to his calculations, the collision should produce emissions detectable at ultraviolet wavelengths in the hours and days following the supernova explosion. And, that’s exactly what Cao and his team at Caltech saw in the Swift observations.
The Swift telescope measured a pulse of ultraviolet radiation that declined initially but then rose as the supernova brightened. Because such a pulse is short-lived, it can be missed by surveys that scan the sky less frequently than the iPTF does.
“We have never observed a white dwarf just before it went supernova, but if you can get data soon after ignition, it may be possible to infer the nature of the progenitor system,” says Kasen.
After Kasen made his prediction in 2010, he notes that a lot of people tried to look for the ultraviolet signature, but this is the first-time that anyone has seen it. “This discovery is a proof of principal that we can get images of Type Ia supernovae in their infancy. Now we can move forward and try to acquire a large number of these ‘baby pictures,’ which will tell us how the different channels for igniting stars affect the properties of the supernova,” says Kasen.
According to Shrinivas Kulkarni, Professor of Astronomy and Planetary Science at Caltech and principal investigator for the iPTF, the discovery "provides direct evidence for the existence of a companion star in a Type Ia supernova, and demonstrates that at least some type Ia supernovae originate from the single-degenerate channel."
Although the data from supernova iPTF14atg support the single-degenerate model, the double-degenerate model has not been disproven. In fact, previous data from the iPTF have provided credible evidence to support that alternative theory. And that means that both theories actually may be valid, says Caltech Professor of Theoretical Astrophysics Sterl Phinney. "The news is that it seems that both sets of theoretical models are right, and there are two very different kinds of Type Ia supernovae."
“It’s really exciting to learn that something that once only existed in your imagination, is actually out there in the real Universe. Automated surveys like iPTF have revolutionized the field by catching these events earlier and earlier. It opens up a new avenue for studying the life and death of stars,” says Kasen.
Kasen is not a member of the iPTF collaboration and was not involved in the Nature study. He developed his 2010 “roadmap” using codes developed and resources provided by DOE’s Computational Astrophysics Consortium SciDAC program, which was led by Stan Woosley at UC Santa Cruz.
iPTF is a scientific collaboration between Caltech; Los Alamos National Laboratory; the University of Wisconsin, Milwaukee; the Oskar Klein Centre in Sweden; the Weizmann Institute of Science in Israel; the TANGO Program of the University System of Taiwan; and the Kavli Institute for the Physics and Mathematics of the Universe in Japan. NERSC is a DOE Office of Science User Facility.
The Nature paper is entitled "Strong ultraviolet pulse from a newborn type Ia supernova." In addition to Cao and Kulkarni, the other authors are D. Andrew Howell, Avishay Gal-Yam, Mansi M. Kasliwal, Stefano Valenti, J. Johansson, R. Amanullah, A. Goobar, J. Sollerman, F. Taddia, Assaf Horesh, Ilan Sagiv, S. Bradley Cenko, Peter E. Nugent, Iair Arcavi, Jason Surace, P. R. Wozniak, Daniela I. Moody, Umaa D. Rebbapragada, Brian D. Bue, and Neil Gehrels.
For more information on Nature paper and observations, see the Caltech press release: http://www.caltech.edu/news/caltech-astronomers-observe-supernova-colliding-its-companion-star-46771
Read Kasen's 2010 paper "Seeing the Collision of a Supernova with its Companion Star": http://arxiv.org/abs/0909.0275
About Computing Sciences at Berkeley Lab
The Lawrence Berkeley National Laboratory (Berkeley Lab) Computing Sciences organization provides the computing and networking resources and expertise critical to advancing the Department of Energy's research missions: developing new energy sources, improving energy efficiency, developing new materials and increasing our understanding of ourselves, our world and our universe.
ESnet, the Energy Sciences Network, provides the high-bandwidth, reliable connections that link scientists at 40 DOE research sites to each other and to experimental facilities and supercomputing centers around the country. The National Energy Research Scientific Computing Center (NERSC) powers the discoveries of 6,000 scientists at national laboratories and universities, including those at Berkeley Lab's Computational Research Division (CRD). CRD conducts research and development in mathematical modeling and simulation, algorithm design, data storage, management and analysis, computer system architecture and high-performance software implementation. NERSC and ESnet are DOE Office of Science User Facilities.
Lawrence Berkeley National Laboratory addresses the world's most urgent scientific challenges by advancing sustainable energy, protecting human health, creating new materials, and revealing the origin and fate of the universe. Founded in 1931, Berkeley Lab's scientific expertise has been recognized with 13 Nobel prizes. The University of California manages Berkeley Lab for the DOE’s Office of Science.
DOE’s Office of Science is the single largest supporter of basic research in the physical sciences in the United States, and is working to address some of the most pressing challenges of our time. For more information, please visit science.energy.gov. | <urn:uuid:404448ad-e3ff-43de-adcf-c038a3763d20> | 3.109375 | 2,239 | News (Org.) | Science & Tech. | 31.497959 | 95,597,323 |
Original Research ARTICLE
At the brink of supercoloniality: genetic, behavioral, and chemical assessments of population structure of the desert ant Cataglyphis niger
- 1Department of Zoology, George S. Wise Faculty of Life Sciences, Tel Aviv University, Tel Aviv, Israel
- 2Department of Evolutionary Biology and Ecology, Université Libre de Bruxelles, Brussels, Belgium
- 3IRBI, UMR 7261, Université Francois Rabelais de Tours, Tours, France
The nesting habits of ants play an important role in structuring ant populations. They vary from monodomy, a colony occupies a single nest, via polydomy, a colony occupies multiple adjacent nests, to supercoloniality, a colony spans over large territories comprising dozen to thousands nests without having any boundaries. The population structure of the desert ant Cataglyphis niger, previously considered to form supercolonies, was studied using genetic, chemical, and behavioral tools in plots of 50 × 50 m at two distinct populations. At the Palmahim site, the plot comprised 15 nests that according to the genetic analysis constituted three colonies. Likewise at the Rishon Leziyyon site 14 nests constituted 5 genetic colonies. In both sites, both chemical analysis and the behavioral (aggression) tests confirmed the colony genetic architecture. The behavioral tests also revealed that aggression between colonies within a population was higher than that exhibited between colonies of different populations, suggesting the occurrence of the “nasty neighbor” phenomenon. In contrast to supercolony structure previously reported in another population of this species, the presently studied populations were composed of polydomous colonies. However, both the genetic and chemical data revealed that the inter-colonial differences between sites were larger than those within site, suggesting some within-site population viscosity. Thus, C. niger exhibits flexible nesting characteristics, from polydomy to supercoloniality, and can be considered at the brink of supercoloniality. We attribute the differences in population structure among sites to the intensity of intraspecific competition.
The diversity of spatial organization of ant populations is associated greatly with differences among species in life history, reproductive strategies and dispersion (Bourke and Franks, 1995; Crozier and Pamilo, 1996; Ross, 2001). The classical, possibly ancestral ant colony is composed of a single, monandrous (single mating) queen that is the sole reproducer and her sterile daughters that act as workers and tend to the brood and all other colony tasks. This basic colony kin structure, leading to high levels of relatedness among colony members, is believed to have evolved via kin selection (Hölldobler and Wilson, 1990; Hughes et al., 2008a; Boomsma, 2009). Typically, each colony-family occupies a nest around which it maintains a territory that it defends against intruders, con- and heterospecific alike.
Genetic studies, however, revealed that breeding systems that lower intracolony relatedness have evolved multiple times in ants (Hughes et al., 2008b). For example, both queen number and queen mating frequency may vary greatly between species, and even within species in a population. Colonies may be headed by a single queen (monogynous) or by two or more queens (polygynous) (Bourke and Franks, 1995; Crozier and Pamilo, 1996; Purcell and Chapuisat, 2013). Species may also vary in the number of males with which the queen(s) mate, from strict monandry to high levels of polyandry (Boomsma et al., 2009). This social polymorphism is the result of multiple selective pressures such as ecological constraints on nesting success, predation risks, or increased genetic diversity to better defend against pathogens or to enhance division of labor and colony task efficiency (Bourke and Franks, 1995; Keller, 1995; Crozier and Pamilo, 1996). Colony queen number is usually associated with profound changes in life history strategies and dispersal behavior (Bourke and Franks, 1995; Keller, 1995; Crozier and Pamilo, 1996; Ross, 2001; Chapuisat et al., 2004). Monogyny is generally (but see exceptions in Peeters and Molet, 2010; Cronin et al., 2013) associated with long-range nuptial flights and independent colony foundation. In contrast, under polygyny, mating occurs inside or in the vicinity of the natal nest, and colony reproduction proceeds by budding whereby the mated queen(s) leave their natal nest with a worker force to found a new colony nearby. At the population level, dispersion by budding usually results in a pattern of genetic isolation-by-distance (Sundstrom et al., 2005; Leniaud et al., 2009). In some ant species, the daughter colonies maintain exchanges of workers, brood, and food with the mother nest creating polydomous colonies, each composed of several nest units (Hölldobler and Wilson, 1990; Debout et al., 2007). In its most extreme form, polydomy can lead to the creation of supercolonies composed of several hundreds of nests, with no aggression between workers that belong to different units over a vast geographic scale (Pedersen et al., 2006; Thomas et al., 2006). Such unicoloniality is typical of many invasive ants, and possibly also the key to their success (Holway et al., 2002).
Supercoloniality poses an evolutionary challenge of understanding the selective forces that result in their prosperity, and whether or not kin selection operates despite the multiple genetic lineages that compose such supercolonies (Helantera et al., 2009; Moffett, 2012). Unicoloniality is also typified by the lack of aggression, even between very distant nests e.g., Linepithema humilis (Giraud et al., 2002; Brandt et al., 2009b; Blight et al., 2012), Wasmannia auropunctata (Errard et al., 2005; Vonshak et al., 2009; Foucaud et al., 2010) or Pheidole megacephala (Fournier et al., 2009). This is attributed to the relaxation or complete loss of nestmate recognition in these population, the mechanism of which is postulated to be either “genetic cleansing” following introduction (Giraud et al., 2002) or a “bottleneck” phenomenon (Suarez et al., 2008). Ample evidence indicate that hydrocarbons constitute at least part of the recognition system (reviewed in Hefetz, 2007), and that there is high degree of congruency in the hydrocarbon recognition cues within a supercolony and distinct compositions between supercolonies (Errard et al., 2005; Brandt et al., 2009a). Recently, it was shown in the unicolonial ant Formica yessensis that profile similarity/disparity as well as incomplete chemical discrimination via the hydrocarbon sensilla (Kidokoro-Kobayashi et al., 2012) are important factors in the establishment of unicoloniality.
Cataglyphis ants have evolved a remarkable number of life histories and reproduction strategies (Lenoir et al., 2009). Some species are strictly monogynous (Pearcy et al., 2004a; Timmermans et al., 2008) while others are facultatively or obligatory polygynous (Leniaud et al., 2011; Eyer et al., 2012). Monogynous species may be organized as independent colonies (Leniaud et al., 2011) while others are organized in polydomous colonies, with one central nest holding the queen and the rest of the nests function as queenless satellites (Dahbi et al., 1997). In contrast to the usual association between monogyny and long-range nuptial flights, young queens of the monogyne C. cursor and C. floricola mate close to their natal nest and colony reproduction proceeds by fission (Lenoir et al., 1988; Hardy et al., 2008; Amor et al., 2011; Chéron et al., 2011). Queens of some species are singly mated (Eyer et al., 2012; Leniaud et al., 2012), whereas in other species they are obligatory multiply mated (Timmermans et al., 2008, 2010; Pearcy et al., 2009). Finally, queens of several species use alternative reproductive pathways for the production of the queen and worker castes. New queens are produced asexually by thelytokous parthenogenesis, while workers are produced by normal sexual reproduction (Pearcy et al., 2004a; Leniaud et al., 2012; Eyer et al., 2013).
A recent population genetic study of Cataglyphis niger revealed that it is polygynous, that queens mate multiply and that the population sampled was supercolonial (Leniaud et al., 2011). However, this study encompassed only a single population and a limited sample size of 12 nests in an area of 4 square kilometers. Moreover, neither the chemistry or aggressive behavior of its nest constituents were studied to support the genetic data.
In the present study, we investigated the association between genetic architecture, chemical signature, and nestmate recognition in two, newly sampled populations of C. niger. First, we determined the structure of populations, using microsatellites markers. Second, we measured intra- and inter-population tolerance on the basis of aggression tests between workers. Finally, we examined the pattern of variation of worker cuticular hydrocarbon profiles in relation to population genetic structure and the spatial distribution of colonies within the population and nests within a colony.
Methods and Materials
Field Collection and Sampling
Ant samples were collected at two study sites, representing two disparate populations (~15 km apart), on the Israeli coastal plain in Rishon Leziyyon (31.98056, 34.742863) and Palmahim (31.935046, 34.705571). All nests at each site (14 and 15 nests for Rishon Leziyyon and Palmahim, respectively) were partially excavated and approximately 50 workers sampled. The spatial distribution and distances between nests and the distances between physical nests in each plot were carefully measured on a defined and marked 50 × 50 m area. A portion of the workers was immediately frozen for further molecular and chemical analysis and the remaining workers were brought back to the laboratory for behavioral bioassays. In the laboratory they were placed in artificial nests composed of a round plastic box 10 cm in diameter and 8.5 cm in height, with a plaster laid floor to obtain sufficient moister. The ants were kept in a rearing room under a controlled temperature of 29 ± 1°C and a photoperiod of 12L:12D, and were provided with an identical diet of sugar water and minced insects three times a week. The colonies from each site were kept in the laboratory for not longer than 1 week, during which the behavioral assays were conducted.
DNA extraction—Individual ants were ground in digestion solution (100 mM NaCl, 50 mM Tris, 1 mM EDTA, 0.5% SDS, and 200 μg/ml proteinase K) and incubated for 12 h at 55°C in 100 μl of solution. Genomic DNA was purified through phenol/chloroform extractions and ethanol precipitation following standard protocols (Sambrook and Russell, 2001). The DNA pellet was resuspended in 100 μl of sterile H2O.
Genomic DNA genotyping—Genotypes of ants were determined at 9 microsatellite loci: four loci previously described for C. cursor (Cc11, Cc51, Cc54, Cc99; Pearcy et al., 2004b), three for C. hispanica (Ch01, Ch11, Ch12; Darras et al., 2014), and two new markers developed for C. niger (Cn04, Cn08). PCR were performed with a MJ Research PTC-200 thermocycler. Annealing temperature and magnesium concentration were optimized for each locus individually (available upon request). PCR products were genotyped on a ABI 3100 automated sequencer (Applied Biosystems). The size of the different alleles was determined using the Peak Scanner version 1.0 analysis software (Applied Biosystems) and used to construct a multilocus genotype for each individual. Control for genotyping errors due to null alleles and allele drop-outs was performed with Micro-Checker (Van Oosterhout et al., 2004). Possible linkage disequilibrium were tested with GENEPOP ON THE WEB (Rousset, 2008).
Genetic analyses were performed on a sample of 168 workers (X ±SE = 11.2 ± 1.6, N = 14 nests) from Rishon Leziyyon, and 168 workers (12 ± 0, N = 15 nests) from Palmahim. The number of alleles, allele frequencies, observed (HO) and expected (HE) heterozygosities were calculated using FSTAT 184.108.40.206 (Goudet, 1995) and averaged across loci. F-statistics were estimated according to the method of Weir and Cockerham (1984) using GENEPOP ON THE WEB (Rousset, 2008). To determine if different nests belonged to the same genetic entity (i.e., polydomy), genotypic frequencies at all collection points were compared using a log-likelihood (G) based test of differentiation, from GENEPOP ON THE WEB (Rousset, 2008). Overall significance was determined using a Fisher's combined probability test; a Bonferroni correction was applied to account for multiple comparisons. Nests were considered as belonging to different colonies if genotypic differentiation was statistically significant (α < 0.0005 and α < 0.0006 after Bonferroni correction for Palmachim and Rishon Leziyyon, respectively). Population structure was investigated by plotting [Fst/(1–Fst)] coefficients between pairs of nests against the ln of the geographical distance (Slatkin, 1993). The correlation coefficients between genetic differentiation [Fst/(1–Fst)], ln of geographical distances and chemical distances were assessed with a Mantel test as implemented in GENEPOP ON THE WEB (Rousset, 2008). Genetic-distance based PCoA was performed with GENALEX v. 6.41. Relatedness coefficients among workers were estimated using the program FSTAT 220.127.116.11 (Goudet, 1995). The mean relatedness was estimated between workers of the same colony relative to the collection site.
Encounters were conducted in dyads using randomly selected workers from two randomly selected physical nests either within a site or between sites. Different workers were used for each trial, and the order of encounter types was random. Before each test, each of the workers was gently placed in an open glass tube (3 cm in diameter and 8 cm in height) within the neutral arena (10 cm in diameter and 8.5 cm in height) for 90 s for acclimatization. The test started by lifting the enclosing glass tubes and lasted for 3 min. The behavior of the ants was recorded in real time using the program JWatcher (version 0.9; http://www.jwatcher.ucla.edu), as well as videotaped, as backup, using a Logitech HD webcam pro C910 video camera. Encounters between individuals from the same nests were considered as nestmate control assays; encounters between individuals belonging to different physical nests, whether from the same or different sites, were considered as non-nestmate experimental assays. The arena was paved with a filter paper that was replaced every trial, to avoid residual odors.
Aggression was scored using a graded index from 0–4 as follows: 0, antennation; 1, mandibular threat; 2, short biting with jumping; 3, biting and /or seizing the opponent with mandibles; 4, curling the abdomen and spraying formic acid. The aggression index was calculated as follows:
where Ai and ti are the aggression score and duration of each act, respectively, and T is the total interaction time defined as the sum of times in which the ants were in physical contact (not necessarily equal to assay duration). For each encounter type (that is, involving workers from two specific nests), we performed 4–6 replicate tests and the average of which was defined as the aggression index. A total of 20 (13 involving different physical nests and 6 involving nestmates) and 17 (12 involving different physical nests and 5 involving nestmates) encounter types were done at the Palmahim and Rishon Leziyyon sites, respectively (For details of the physical nests assayed see Table 1). In addition we performed 9 encounters (37 replicates in total) between nests from the two sites.
Previous findings have shown that the cuticular hydrocarbon (CHCs) serve as the recognition cue in C. niger (Lahav et al., 1999) and that there is complete congruency in hydrocarbon composition between the epicuticle and those of the postpharyngeal glands (PPG) (Soroker et al., 1994, 1995). Since the PPG secretion is by far more copious than extractable cuticular hydrocarbons, it enables a much more accurate and fine tuned analysis, and can serve as representative of the CHC composition.
Fifteen workers from each nest were used for the chemical analysis. The PPG of individual workers was cleanly dissected and extracted in 100 μl pentane, containing 625 ng docosane and 6250 ng of tetratriacontane as internal standards. Compound identification was done by combined GC/MS (see also Soroker et al., 1995) and was based on their fragmentation patterns, as compared to authentic standards. Sample quantification was done by gas chromatography, using a VF-5ms capillary column that was temperature-programmed from 150°C (with 1 min initial hold) to 300°C at a rate of 5°C per min, with a final hold of 15 min. Peak integration was performed using the program Galaxie Varian 1.9. Compounds that constituted less than 1% across all samples were omitted from the analyses, because their quantification is unreliable. For assessing hydrocarbon profile-specificity we used multivariate statistics, i.e., discriminant analysis using the stepwise forward mode. This module of the program works initially as a principle component analysis for reducing the number of variables to fit the number of cases, and then perform the discriminant function.
Cartography of the nests revealed the occurrence of 14 and 15 nests, with a mean ±SD distance between nests of 7.52 ± 6.22 m and 12.56 ± 10.83 m in Palmahim and Rishon Leziyyon, respectively. In both sites, nests were not evenly distributed within the plot, but were clustered (Figures 1A,B). The index of aggregation R for the Plamahim site was 0.701 and for Rishon Leziyyon was 0.854. However, if we Exclude nest # 291 who was the only one that belonged to the genetic colony C5, the R value at Rishon Leziyyon was reduced to 0.506. Both indicate that nests were not randomly dispersed, but are aggregated (Clark and Evans, 1954).
Figure 1. Spatial distribution of nests at the Palmahim (A) and Rishon Leziyyon (B) sites. Each nest is represented by a number (e.g., 285; 286 etc.) and each genetic colony is represented by a different symbol, color and number (e.g., C1; C2 etc.).
None of the 9 microsatellite markers genotyped showed indication of null alleles. However, linkage disequilibrium was found between three marker loci (i.e., Ch01, Ch11, and Cc11), which were therefore removed from our analyses. The number of alleles at the six remaining microsatellite loci ranged from 4 to 15 in Palmahim, and from 5 to 22 in Rishon Leziyyon. Mean heterozygosity was HO = 0.78 (range: 0.59–0.87) and HE = 0.76 (range: 0.54–0.80) in Palmahim and HO = 0.78 (range: 0.40–0.94) and HE = 0.76 (range: 0.69–0.84) in Rishon Leziyyon. The fixation index (FIT) was slightly superior of zero in Palmahim and not different from zero in Rishon Leziyyon, indicative of random mating in both populations sampled (Palmahim: mean ±SEjackknife over loci = 0.055 ± 0.042; 95% CI: 0.017–0.132; permutation test P = 0.001; Rishon Leziyyon: mean ±SEjackknife over loci = 0.018 ± 0.023; 95% CI: 0.025–0.083; permutation test P = 0.23).
In Palmahim, the G-test showed that the 15 nests sampled clustered into 3 genetically distinct colonies, each comprising 4–7 nests that were not differentiated genetically (Figure 1A) (P > 0.00055 after Bonferroni correction; CI: 0.08–0.099): colony 1 (nests 285, 286, 287, 288), colony 2 (nests 212, 282, 283, 284) and colony 3 (nests 274, 275, 276, 277, 279, 280, 281). The Fst estimates between colonies were moderate and significantly different from zero (0.162 ± 0.022; 95% CI: 0.122–0.201; permutation test P = 0.0). The Similarly, in Rishon Leziyyon the G-test (P > 0.0006) indicated that the 14 nests clustered into 5 genetically distinct colonies comprising 1–5 nests (Figure 1B): colony 1 (nests 292, 293, 298, 299), colony 2 (nests 302, 289, 290, 295, 296), colony 3 (nests 297, 301), colony 4 (nests 300, 294) and colony 5 (nest 291). The FST estimate between colonies was moderate and significantly different from zero (0.156 ± 0.012; 95% CI: 0.131–0.174; permutation test P = 0.0).
In Palmahim, the mean within physical nest genetic relatedness among workers (nestmates) was 0.221 ± 0.025 and within-colony (colony-mates) was 0.31 (SEjackknife = 0.03, N = 15). For Rishon Leziyyon it was 0.259 ± 0.023 and 0.30 for nestmates and colony-mates, respectively (SEjackknife = 0.02, N = 14). These values are significantly lower than 0.75 expected under monogyny, monoandry and random mating in haplodiploid organisms (two-tailed t-tests, P < 0.005 for the two populations).
Effect of the workers' origin (nest, colony origin, site) on aggression levels was tested using dyadic encounters. The initial selection of nests for the dyadic encounters was done randomly, without knowledge of their genetic compositions. However, since we hypothesize that nests that are genetically indistinguishable show also high degree of tolerance, the analyses of the aggression tests proceeded according to colony classification using the molecular data as follows: nestmates (i.e., workers from the same physical nest); workers of different nests but within the same genetic colony; workers from nests belonging to different genetic colonies within a site; and workers from nests of the two sites. Figure 2A presents the results according to colony and Figure 2B present the pooled results as well as the result of the encounters between colonies of the different populations. The results of both types of analyses were in accordance with colony assignment using the molecular results. Both at the Palmahim and Rishon Leziyyon sites, level of aggression between workers from different nests belonging to the same genetic colony was low and not significantly different from that between nestmates. In contrast, the aggression between workers from nests belonging to different genetic colonies, within a site, was significantly higher than that between workers of different nests within a genetic colony or nestmates (for particular encounters, Figure 2A: Palmahim site One Way ANOVA, F = 19.2, df = 6, p < 0.001, followed by Tukey post hoc test p < 0.05; Rishon Leziyyon site (One Way ANOVA, F = 20.26, df = 9, p < 0.001, followed by Tukey post hoc test p < 0.05) (For pooled encounters, Figure 2B: One Way ANOVA, F = 54.75, df = 6, p < 0.01, followed by Tukey post hoc test p < 0.05). Interestingly, the aggression between workers belonging to colonies from the different sites was significantly lower than that between colonies of the same site.
Figure 2. Mean aggression (± standard error) between workers in the different encounter types from either Rishon Leziyyon (hatched bars) or Palmahim (dotted bars) sites. (A) Data of encounters between particular genetic colonies including (1) Nestmates; (2) workers from different nests belonging the same genetic colony (e.g., C2–C2); and (3) of nests belonging to different genetic colonies (e.g., C3-C2). For details of the physical nest assayed see Table 1. (B) Pooled data of the above 3 encounter types and encounters between colonies of the different populations. Statistical significance is denoted by letters above the columns [For (A); capital letters refer to the Palmahim site and small letters to the Rishon Leziyyon site]. The numbers above the columns indicate replications.
The chemical composition and compound identification of the PPG secretion is presented in Figure 3. The secretion is composed of hydrocarbons ranging from tetracosane to tritriacontane comprising linear, monomethyl, diemethyl, and trimethyl branched components. The secretion was dominated by 2 peaks comprising a mixture of 11- + 13- + 15-methylnoacosane and 11,15- + 13,15-dimethylnonacosane, similar to previous analyses (Soroker et al., 1995).
Figure 3. Chromatogram of the PPG secretion of a C. niger worker from Rishon Leziyyon site. Peaks identity is as follows: 1, Tetracosane; 2, 12-methyltetracosane; 3, pentacosane; 4, 11- + 13-methylpentacosane; 5, 7-methylpentacosane; 6, 5-methylpentacosane; 7, 5,17-dimethylpentacosane; 8, 3-methylpentacosane; 9, hexacosane; 10, 10- + 12- + 14-methylhexacosane; 11, 6–methylhexacosane; 12, heptacosene isomer 1; 13, heptacosene isomer 2; 14, heptacosene isomer 3; 15, heptacosane; 16, 11- + 13- methylheptacosane; 17, 7-methylheptacosane; 18, 5-methylheptacosane; 19, 11,15-dimethylheptacosane; 20, 7,11-dimethylheptacosane; 21, 3-methylheptacosane; 22, 5,9-dimethylheptacosane + 5,11-dimethylheptacosane; 23, 7, 11, 15-trimethylheptacosane; 24, 12-methyloctacosane; 25, 8,12-dimethyloctacosane + 12,16-dimethyloctacosane; 26, 6,12-dimethyloctacosane; 27, 4,12-dimethyloctacosane; 28, nonacosene; 29, nonacosane; 30, 11- + 13- + 15 methylnonacosane; 31, 11,15-dimethylnonacosane + 13,15 dimethylnonacosane; 32, 9,13 dimethylnonacosane; 33, 7,13 dimethylnonacosane; 34, 3-methylnonacosane + 5,13 dimethylnonacosane; 35, 7, 11, 15-trimethylnonacosane; 36, 4, 11, 13-trimethylnonacosane; 37, 14-methyltriacontane; 38, 10,14-dimethyltriacontane + 12,14-dimethyltriacontane; 39, 6,14-dimethyltriacontane; 40, 4,14-dimethyltriacontane; 41, 6,12,20-trimethyltriacontane; 42, x,y,z-trimethyltriacontane; 43, 4,12,20-trimethyltriacontane; 44, 13- + 15-methylhentriacontane; 45, 11,15-dimethylhentriacontane; 46, 7,15-dimethylhentriacontane; 47, 5,15-dimethylhentriacontane; 48, 7,11,15-trimethylhentriacontane; 49, 12- + 14-methyldotriacontane; 50, 12, 14-dimethyldotriacontane + 12,16 dimethyldotriacontane; 51, tritriacontane isomer 1; 52, tritriacontane; 53, 13- + 15-methyltritriacontane; 54, 11,15-dimethyltritriacontane; 55, 11,15,19-trimethyltritriacontane.
To examine whether differences in hydrocarbon profiles of workers match the behavioral and molecular data, we performed a disriminant analysis of the genetically defined colonies in Palmahim and Rishon Leziyyon (Figures 4A,B). For that purpose we used all the individuals that belong to a genetic colony irrespective of their nest origin. The analysis performed used the stepwise forwards module, which ranks the variables according to their impact and accordingly reduce their number to fit the appropriate number of cases. All three genetic colonies in Palmahim were completely chemically distinct (Figure 4A; Wilks' Lambda: 0.0090835, F(38, 96) = 23.98068 p < 0.005). Likewise, all five genetic colonies in Rishon Leziyyon were chemically distinct (Figure 4B; Wilks' Lambda: 0.0000376 F(100, 161) = 19.44184 p < 0.0000). Table 2 compares the Mahalanobis distances between nests, measured irrespective of their grouping, within a genetic colony to that between nests belonging to different genetic colonies. For both populations, the cuticular hydrocarbon profiles of nests within a genetic colony were significantly more similar to each other than to those of nests belonging to a different genetic colony (t-test Palmahim: n1 = 30, n2 = 41, t = −7.5779, df = 68, p < 0.0001; t-test Rishon Leziyyon: n1 = 16, n2 = 61, t = −6.8134, df = 35, p < 0.0001).
Figure 4. Discriminant analysis based on cuticular hydrocarbons of individuals from Palmahim (A) and Rishon Leziyyon (B) sites. For these analyses we considered all individuals of a specific genetic colony as colony-mates. Clear separation emerges from this analysis and divides the two populations: 3 colonies in Palmahim and 5 colonies in Rishon Leziyyon.
Table 2. Chemical (Mahalanobis) distances, using worker CHC composition, between nests of Cataglyphis niger either within a genetic colony or between genetic colonies.
Association between Variation of the Cuticular Profiles, Genetic Composition, and Spatial Distribution
Table 3 presents the results of the Mantel tests of the correlation between the genetic composition, cuticular hydrocarbon composition and the geographical distances between nests. In both populations, genetic differentiation between pairs of nests was significantly correlated with geographical distance, indicating a pattern of isolation-by-distance (rgen, geo = 0.68 and 0.57 in Rishon Leziyyon and Palmahim, respectively; both p < 0.0001). Likewise there was a significant correlation between the genetic differentiation and variation in cuticular hydrocarbon composition (rgen, chem = 0.53 and 0.66, for Rishon Leziyyon and Palmahim respectively; both p < 0.0001). The correlation between chemical composition and geographic distance was less pronounced albeit it was also significant (rgeo, chem = 0.48, p < 0.0001 and rgeo, chem = 0.24, p < 0.02, for Rishon Leziyyon and Palmahim respectively).
Table 3. Correlation between geographical (between-nest distances), genetic (microsatellite variation) and chemical (cuticular hydrocarbon composition) distances of workers of Cataglyphis niger.
Inspection of the CHC composition of nests from the two populations showed some more profound differences between populations. We therefore performed a discriminant analysis comprising nests from both populations. This revealed that colonies within a population were more similar to each other than between populations (Figure 5A; Wilks' Lambda: 0.0000014 F(174, 585) = 29.74149 p < 0.000). Consistent with these results, a PCoA based on the genetic distances (Eigen values) between nests belonging to the two populations showed that the two populations are mostly distinct genetically, with only some overlap involving colony 3 of Palmahim and colony 3 of Rishon Leziyyon (Figure 5B).
Figure 5. Chemical and genetic comparisons between colonies comprising the two populations studied, Palmahim and Rishon Leziyyon. Discriminant analysis of cuticular hydrocarbons (A) and Principal Coordinates Analysis (PCoA) based on the microsatellite analyses (B). R1–R4 denote the 4 colonies in Rishon Leziyyon population (colony 5 comprised only one nest and therefore excluded), and P1-P3 denote the 3 colonies of the Palmahim population.
Polydomy is a nesting habit whereby a colony is composed of several nests that extend over a large territory and is characterized by constant worker movement between nests. It enables the colony a larger foraging area, the extent of which (i.e., the number of nests per colony and their spatial distribution) is limited by competition with other colonies in the population (reviewed by Hölldobler and Wilson, 1990; Debout et al., 2007). Highly extended polydomy can comprise many nests and when it extends over very large geographic areas the species is considered supercolonial. Supercolonial population-structure typifies many invasive ant populations (Holway et al., 2002), but it may also occurs in native populations (Higashi and Yamauchi, 1979; Holzer et al., 2006; Buczkowski and Bennett, 2008; Buczkowski, 2010). Polydomy and supercoloniality can be detected genetically as well as behaviorally and chemically. Members of a supercolony are tolerant to each other even if they originate from different nests at the time of their testing, and exhibit chemical uniformity of cuticular hydrocarbon compositions (Errard et al., 2005; Brandt et al., 2009b; Vonshak et al., 2009; Blight et al., 2012; Kidokoro-Kobayashi et al., 2012). Therefore, assessing the population structure of an ant species is best done by encompassing all three parameters, genetic, behavior and recognition chemistry. Recently we have reported a genetic analysis of colonies of C. niger from a population (Ashqelon), located in the southern coastal plain of Israel. We found a genetic uniformity of 12 nests that span over 4 km2, suggesting that the species forms a supercolony (Leniaud et al., 2011). However, this study was based on a single population with limited sample size.
In contrast to our previous finding with the Ashqelon population (Leniaud et al., 2011), our present study combining genetic, behavioral assays and chemical analyses shows that both the Palmahim and Rishon Leziyyon populations are polydomous rather than supercolonial. Our genetic analysis revealed that average relatedness values among workers from the same colony are very similar in both Palmahim and Rishon Leziyyon (rw–w ≈ 0.30). Quite surprisingly, these values are 10 folds of that registered for the Ashqelon population (0.02). Despite the fact that both sites in the present study were somewhat smaller (50 × 50 m each) than that in Ashqelon we could detect 3 genetically different colonies in Palmahim, comprising 4,−7 nests, and 5 colonies in Rishon Leziyyon, comprising 1–5 nests. Since we limited our analyses to a 50 × 50 m plots it is hard to generalize on a mean number of nests per colony. Yet, together these results do not support supercoloniality in the two presently studied populations of C. niger. The marked difference in within-colony genetic relatedness between this work and the population of Ashqelon remains enigmatic. A research constraint we had in the current study was our inability to completely excavate the nests. As a consequence, no queen could be sampled; hence, the number of queens per nest/colony and their mating frequency, two primary factors on relatedness values within colonies, remain unknown. Therefore, our genetic data are limited to the analyses of workers only. Nevertheless comparing the within and between colony genetic similarity of the two populations indicate some genetic viscosity within each, facilitating high polydomy and perhaps bringing the population to the verge of supercoloniality. Thus the differences in population structure between Ashqelon and Palmahim and Rishon Leziyyon lend credence to the hypothesis that C. niger shows large plasticity in social structure, and what we may observe is a transition state from high polydomy to supercoloniality. Similar plasticity was also recorded for Formica truncorum where in certain sites the population is largely polydomus while in other sites it is unicolonial (Rosengren et al., 1985; Elias et al., 2005).
There is a good congruency between the genetic data and both the behavior and the chemistry. Workers from different nests but from the same genetic colony were as tolerant to each other as are nestmates. This was true for both populations and is depicted more pronouncedly when we compared nestmate vs colony-mate vs. between colonies, irrespective of colony identity (Figure 2B). Interestingly, aggression between colonies of the two populations was significantly lower than that between colonies within population. We consider this phenomenon as “nasty neighbor” (as opposed to the “dear enemy” phenomenon). Nasty neighbor phenomenon is common in social insects, in particular ants where the threat from neighboring nests is far greater than a wondering individual from a colony that is further away (Knaden and Wehner, 2003; Sanada-Morimura et al., 2003; Boulay et al., 2007; Thomas et al., 2007; Wilgenburg, 2007; Newey et al., 2010; Roux et al., 2013). Competition between colonies for space in polydomous species is predicted to be even higher compared to monodomous species due to their ability to create new satellite nests as strongholds in the new territory and by that facilitating the expansion of their foraging area.
Nestmate recognition in C. niger, and in all likelihood in other ant species, is mediated by cuticular hydrocarbons (Lahav et al., 1999). We therefore estimated their chemical similarity/disparity according to the genetic colonies. For both sites there was a clear segregation of profiles according to colony identity, with almost no overlap. Comparing the chemical (Mahalanobis) distances confirmed that the distance between workers of a colony, irrespective of their nest origin, was significantly lower than that between workers of different colonies. Given the moderate genetic viscosity within site, we were interested in comparing the sites also with respect to their CHC profiles. It is clear from Figure 5A that the two populations are markedly different, much more than that based on genetics. This suggests that both genetics and the environment, i.e., difference in locality, may affect the composition of the CHCs.
In summary, all three parameters investigated, genetics, behavior and chemistry point to the fact that colonies of C. niger in both Palmahim and Rishon Leziyyon are polydomous in nature. This is in contrast to a previous study in which the population of Ashqelon was indicated by genetics to be unicolonial. We tend to exclude the possibility that in Ashqelon the population is also polydomous rather than unicolonial. The total area that the 12 colonies occupied was 4 km2 and the mean distance between physical nests was over 50 m, in line with the phenomenon of unicoloniality. The present site span over a smaller area of 2.5 km2, and the mean distance between nests ranged between 7 and 12 m, in line with polydomy. These differences may be attributed to several factors, among which we consider intraspecific competition to be a major one. Adephic and climatic conditions among the 3 sites do not differ by much, but the populations in Palmahim and Rishon Leziyyon are situated sites that are highly visited by human, compared to the site in Ashqelon, which seemingly generate greater resources. If the existence and survival of a colony is a balance between foraging and fighting efforts, these conditions may be supportive for the establishment of new colonies and thus mutually limiting the expansion of each. If, on the other hand resources are more limited the establishment of new colonies become more difficult and may be prohibited by the already existing colonies. Since all population show isolation by distance, indicating reproduction by colony splitting, supercolonies may be formed in uncompetitive areas, but limited to polydomy in highly competitive area. The ant Cataglyphis niger thus merits the statement of “being at the brink of supercoloniality.”
Authors and Contributors
Maya Saar conducted the field studies, including the behavioral assays and the chemical analyses. Laurianne Leniaud conducted the molecular population genetic studies. Abraham Hefetz and Serge Aron conceived the idea and supervised the work. All authors contributed to the writing of the manuscript.
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.
We thank Tovit Simon (TAU) and L. Grumiau (ULB) for technical assistance. This work was supported by grants from Tel Aviv University internal grant (#2191) (Abraham Hefetz), the Belgian FRS-FNRS (Laurianne Leniaud and Serge Aron) and Action de Recherché Concertée Grant N°2010-2015#5 (Serge Aron)
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Thomas, M. L., Payne-Makrisa, C. M., Suarez, A. V., Tsutsui, N. D., and Holway, D. A. (2006). When supercolonies collide: territorial aggression in an invasive and unicolonial social insect. Mol. Ecol. 15, 4303–4315. doi: 10.1111/j.1365-294X.2006.03038.x
Thomas, M. L., Payne-Makrisâ, C. M., Suarez, A. V., Tsutsui, N. D., and Holway, D. A. (2007). Contact between supercolonies elevates aggression in Argentine ants. Insectes Soc. 54, 225–233. doi: 10.1007/s00040-007-0935-8
Timmermans, I., Hefetz, A., Fournier, D., and Aron, S. (2008). Population genetic structure, worker reproduction and thelytokous parthenogenesis in the desert ant Cataglyphis sabulosa. Heredity 101, 490–498. doi: 10.1038/hdy.2008.72
Van Oosterhout, C., Hutchinson, W., Wills, D., and Shipley, P. (2004). MICRO-CHECKER: software for identifying and correcting genotyping errors in microsatellite data. Mol. Ecol. Notes 4, 535–538. doi: 10.1111/j.1471-8286.2004.00684.x
Vonshak, M., Dayan, T., Foucaud, J., Estoup, A., and Hefetz, A. (2009). The interplay between genetic and environmental effects on colony insularity in the clonal invasive little fire ant Wasmannia auropunctata. Behav. Ecol. Sociobiol. 63, 1667–1677. doi: 10.1007/s00265-009-0775-9
Wilgenburg, E. V. (2007). The influence of relatedness, neighbourhood and overall distance on colony mate recognition in a polydomous ant. Ethology 113, 1185–1191. doi: 10.1111/j.1439-0310.2007.01431.x
Keywords: Cataglyphis, polydomy, supercoloniality, nestmate recognition, population genetic structure, cuticular hydrocarbons, “nasty neighbor effect”
Citation: Saar M, Leniaud L, Aron S and Hefetz A (2014) At the brink of supercoloniality: genetic, behavioral, and chemical assessments of population structure of the desert ant Cataglyphis niger. Front. Ecol. Evol. 2:13. doi: 10.3389/fevo.2014.00013
Received: 01 February 2014; Accepted: 09 April 2014;
Published online: 01 May 2014.
Edited by:Patrizia D'Ettorre, University Paris 13 - Sorbonne Paris Cité, France
Reviewed by:Jelle Stijn Van Zweden, KU Leuven, Belgium
Claudie Doums, Ecole Pratique des Hautes Etudes, France
Copyright © 2014 Saar, Leniaud, Aron and Hefetz. 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: Abraham Hefetz, Department of Zoology, George S. Wise Faculty of Life Sciences, Tel Aviv University, Tel Aviv 69978, Israel e-mail: email@example.com
† These authors have contributed equally to this work. | <urn:uuid:8099f101-c922-444c-8060-fb88a9efe30b> | 2.796875 | 12,656 | Academic Writing | Science & Tech. | 54.726443 | 95,597,332 |
Just Earth News | @JustEarthNews | 06 Dec 2017
New York, Dec 6(Just Earth News): Soil is a major carbon storage system, essential for sustainable agriculture and climate change mitigation, the United Nations agriculture agency said on Tuesday, launching on World Soil Day a comprehensive global map showing the amount of carbon stocks contained in soil.
“Soil is the foundation of agriculture , it is where food begins,” said Maria Helena Semedo, Deputy Director-General of the UN Food and Agriculture Organization (FAO).
“Maintaining the soil’s important functions and ecosystem services to support food production and increase resilience to a changing climate calls for sustainable soil management practices,” she added.
Soil organic matter, with carbon as its main component, is crucial to soil health and fertility, water infiltration and retention as well as food production.
The world’s soils act as the largest terrestrial carbon sink, reducing greenhouse gases. Intensifying its role could significantly offset the rapid rise of carbon dioxide in the atmosphere.
In an historic decision on agriculture, the 2017 UN Climate Change Conference in Bonn (COP23 ) recognized the need for improved soil carbon, soil health and soil fertility. The Global Soil Organic Carbon Map, the most comprehensive to date, illustrates the amount of organic carbon stock in the first 30 cm of soil – revealing natural areas with high carbon storage that require conservation along with regions where further sequestration would be possible.
This information can prove a powerful tool to guide decision-making on practices aimed to preserve and increase the current soil carbon stocks – helping win the fight against climate change.
The map shows that globally the first 30 cm of soil contains around 680 billion tons of carbon – almost double the amount present in our atmosphere.
The degradation of one third of the world’s soils has already prompted an enormous release of carbon into the atmosphere. Restoring these soils can remove up to 63 billion tons of carbon, significantly reducing the effects of climate change.
FAO's Intergovernmental Technical Panel on Soils supported the map’s development, including by putting together the national carbon maps of more than 100 countries, making a concrete contribution towards Sustainable Development Goal (SDG) 15, Life on Earth.
The next step is for countries to monitor their national soil information systems for organic carbon levels to make evidence-based decisions on how to manage and monitor their soils.
- Centre for Science and Environment urges global intervention to stop unregulated dumping of used vehicles in Africa and South Asia
- UN agriculture agency digs in to help forests and farms build resilience to climate change
- At least 94 dead as heavy rain inundates Japan
- NASA’s Kepler Spacecraft pauses science observations to download science data
- Canada: Heat wave in Quebec kills 33 people | <urn:uuid:374e3a31-889d-4d30-bd52-5bb9b19f2cc9> | 3.296875 | 576 | News Article | Science & Tech. | 20.728769 | 95,597,347 |
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Graze: the act of feeding on low-growing plants, like grasses.
Migration: movement of an animal or a group of animals from one place to another.
Nitrogen: a chemical that is important for all organisms to build tissues. Nitrogen makes up 78% of the Earth's atmosphere.
Protein: a type of molecule found in the cells of living things, made up of special building blocks called amino acids.
Swarm: a large, dense group; or to move somewhere in a large group.
Telecoupling: when places that are far apart are connected by an event or other occurrence.
The sky darkens with moving sheets pushing across the horizon. What looks like a cloud of dense dust is something entirely different: locusts. Your first thought is to avoid being hit by the flying grasshoppers. But then you realize they are also under your feet.
They are landing everywhere—on the ground, on your crops, and even on your stored food. That's when you realize your biggest problem. The locusts are eating everything.
Around the world, there are many people whose lives depend upon the food they grow on their own land. If locusts eat it all, then people either go hungry or are forced to buy expensive food. Usually a little of both.
Hunger and higher food costs can affect communities in many ways. They may have to spend money meant for school, or healthcare, or other things that a community needs. This is what happened in the West African village in Senegal, where senior sustainability scientist Arianne Cease first encountered locusts.
Locusts are a special kind of grasshopper that can form a swarm. These grasshoppers gather in groups and migrate when exposed to certain conditions, such as a crowded population.
A locust swarm might have almost 100 billion hungry insects in it. A swarm with that many bugs would be almost as big as the entire city of Los Angeles. And an adult locust can eat its weight in food in a single day. Could you eat your weight in food in a single day? No way. Locusts are really, really hungry insects.
And all that hunger can destroy all the plants or crops in an area. All those locusts could eat 423 million pounds of plants in one day. When all the food is gone, the locusts just fly or march along to the next place, leaving a wasteland behind them.
During an outbreak year, locusts could cover one-fifth of all the land on Earth. When that happens, one out of every 10 people on the planet suffers. That’s why Cease studies locusts – to find a way to help the people who have to deal with locust outbreaks.
Locust outbreaks have been happening for thousands of years. Locust swarms are even written about in the Bible. In all that time, people have not found out exactly what causes locusts to swarm and migrate. A crowded population is an important trigger, but there are other environmental factors involved that have yet to be uncovered.
Cease's research team focuses in part on some of the causes of locust migration. Grasshoppers usually like to be alone. So what makes them form hungry swarms and migrate from place to place?
Animals and plants, including insects, need protein to grow. And locust swarms often happen in places where the soil is low in nitrogen – a nutrient necessary to make proteins. In low nitrogen areas, plants can’t make as much protein. Low-protein plants are a favorite snack of locusts.
For some locust species, if they have only high-protein plants to eat, they actually grow more slowly and some even get sick or die. Locusts depend on low-protein food. Low-protein food is often found in areas where cattle or other livestock graze heavily…and even more so, where they graze too much. So overgrazing seems to be one potential cause of locust swarms.
When livestock animals eat too much grass from one place over a long time period, it makes the soil less healthy. Nitrogen washes away, and the grasses get low in protein.
That’s when locusts start to grow stronger, group together and form a swarm. But these locusts don't just affect the overgrazed communities. They migrate to nearby or distant locations, eating crops and food stores wherever they go.
Linking distant communities with such environmental effects is called telecoupling, and it's an important focus for Cease. If locust swarms are going to be lessened in the future, scientists must look at the problem broadly across the landscape and from many different angles.
They must take into account the actions of the farmers, ranchers, and community members, in addition to the biology of the locusts. And they must do this across different countries with separate governments. By getting many of these groups to work together, Cease is hoping to help prevent some of these swarms.
Using an approach like this, Cease and her colleagues just might turn locust management on its head. Working with people from China, Australia, Senegal, Canada, and the United states, they are tackling this worldwide issue so that one day, people won't have to lose so much to locusts.
Learn more about locust research at livingwithlocusts.com.
Additional images via Wikimedia Commons.
Karla Moeller, Michelle Schwartz. (2015, September 15). On the Lookout for Locusts. ASU - Ask A Biologist. Retrieved July 16, 2018 from https://askabiologist.asu.edu/explore/lookout-locusts
Karla Moeller, Michelle Schwartz. "On the Lookout for Locusts". ASU - Ask A Biologist. 15 September, 2015. https://askabiologist.asu.edu/explore/lookout-locusts
Karla Moeller, Michelle Schwartz. "On the Lookout for Locusts". ASU - Ask A Biologist. 15 Sep 2015. ASU - Ask A Biologist, Web. 16 Jul 2018. https://askabiologist.asu.edu/explore/lookout-locusts | <urn:uuid:fa1def48-5648-4677-b404-e2def3fa4443> | 3.375 | 1,337 | Knowledge Article | Science & Tech. | 60.159218 | 95,597,359 |
hath: Hath manipulates network blocks in CIDR notation.
Hath is a Haskell program for working with network blocks in CIDR notation. When dealing with blocks of network addresses, there are a few things that one usually wants to do with them:
Create a regular expression matching the CIDR block(s). This is because grep will throw up if you feed it CIDR.
Combine small blocks into larger ones. For example, if you have two consecutive /24s, they might combine into a larger /23.
View the result of block combination in a useful way.
Find their associated PTR records.
Hath has several modes to perform these functions:
- This computes a (Perl-compatible) regular expression matching the input CIDR blocks. It's the default mode of operation.
- This combines small blocks into larger ones where possible, and eliminates redundant blocks. The output should be equivalent to the input, though.
- Shows only the blocks that would be removed by reduce; that is, it shows the ones that would get combined into larger blocks or are simply redundant.
- Shows what would change if you used reduce. Uses diff-like notation.
- List the IP addresses contained within the given CIDRs.
- Perform reverse DNS (PTR) lookups on the IP addresses contained within the given CIDRs.
Combine two /24s into a /23:
$ hath reduced <<< "10.0.0.0/24 10.0.1.0/24" 10.0.0.0/23
Create a perl-compatible regex to be fed to grep:
$ grep -P `hath regexed -i cidrs.txt` mail.log
List the addresses in 192.168.0.240/29:
$ hath listed <<< "192.168.0.240/29" 192.168.0.240 192.168.0.241 192.168.0.242 192.168.0.243 192.168.0.244 192.168.0.245 192.168.0.246 192.168.0.247
Perform PTR lookups on all of 18.104.22.168/30:
hath reversed <<< "22.214.171.124/30" 126.96.36.199: a.root-servers.net. 188.8.131.52: 184.108.40.206: rs.internic.net. 220.127.116.11:
|Versions||0.0.1, 0.0.2, 0.0.3, 0.0.4, 0.0.5, 0.1.0, 0.1.1, 0.1.2, 0.2.0, 0.2.1, 0.2.2, 0.2.3, 0.3.0, 0.4.1, 0.4.2|
|Dependencies||base (==4.6.*), bytestring (==0.10.*), dns (==0.3.*), HUnit (==1.2.*), MissingH (==1.2.*), parallel-io (==0.3.*), QuickCheck (==2.6.*), split (==0.2.*), test-framework (==0.8.*), test-framework-hunit (==0.3.*), test-framework-quickcheck2 (==0.3.*) [details]|
|Maintainer||Michael Orlitzky <firstname.lastname@example.org>|
|Source repo||head: git clone http://michael.orlitzky.com/git/hath.git -b master|
|Uploaded||by MichaelOrlitzky at Mon Aug 19 22:15:27 UTC 2013|
|Downloads||4854 total (18 in the last 30 days)|
|Rating||2.0 (votes: 1) [estimated by rule of succession]|
|Status||Docs not available [build log]
All reported builds failed as of 2016-12-20 [all 7 reports]
Hackage Matrix CI
For package maintainers and hackage trustees | <urn:uuid:0c3cd55f-16a6-4855-9d12-fd6d67d88b64> | 2.75 | 912 | Documentation | Software Dev. | 110.37401 | 95,597,374 |
Panda love spreads to benefit the planet
Recent MSU work shows China’s decades of defending panda turf have been good not just for the beloved bears, but also protects habitat for other valuable plants and animals, boosts biodiversity and fights climate change.
June 26, 2017 - Author: Sue Nichols, firstname.lastname@example.org, 517-282-1093
Loving pandas isn’t just a feel-good activity. Recent Michigan State University (MSU) work shows China’s decades of defending panda turf have been good not just for the beloved bears, but also protects habitat for other valuable plants and animals, boosts biodiversity and fights climate change.
The study points to a path going beyond pandas to even more benefits of conservation.
“Hidden roles of protected areas in the conservation of biodiversity and ecosystem services” was published in this week’s journal Ecosphere.
“Sometimes unintended consequences can be happy ones – and give us ways to do even better as we work toward sustainability,” said Jianguo “Jack” Liu, MSU’s Rachel Carson Chair in Sustainability and director of Center for Systems Integration and Sustainability (CSIS). “Pandas are leading us to even greater ways to care for nature, and health of humans and the planet.”
Many of those answers came from above. Andrés Viña specializes in remote sensing – carefully examining tree cover from satellite images. A big part of conservation in China has been restoring and protecting forests. Over several decades, the government there has introduced sweeping programs to convert farmlands back to forests, ban logging and harvesting of wood products and replant acres of trees.
They’ve also established nature reserves specifically to protect habitat suitable for pandas.
What Viña and Liu discovered in analyzing data was that not only are the forests in the reserves thriving, and in ways that benefit more than the iconic pandas.
“Reserves are created thinking about the pandas – but we wanted to see if they provide more benefits than just the pandas,” Viña said. “A lot of work is focused in regards to the pandas, but we wanted to ask about other animal and plant species. How are these nature reserves doing for biodiversity and for carbon sequestration?”
The answer: Extra points scored for benefits to both people and the environment. The forests inside reserves, and in areas outside the reserves’ borders, are providing critical canopy materials – the leaves and branches – that soak up carbon dioxide, a greenhouse gas which contributes to climate change.
Forests outside of reserves, the study shows, are often growing faster than in the reserves. But that isn’t a downfall of reserves, Viña said. Rather, reserves usually had a head start in forest preservation, and in many cases have reached their maximum growth and density.
The researchers also have found that not all forests are created equal – both in panda appeal and for biodiversity.
Many of those forests come with an understory rich with bamboo – a necessity for pandas. The study notes that the types of forest present opportunities to improve. In some areas, the original goal of reforestation was to retain soil and water. That meant planting fast-growing conifers close together. Years later, that strategy has blocked the sun from reaching the ground, suppressing plant diversity – including not much bamboo.
Viña said in the future it would be good to allow more spacing between planted trees and include different varieties to allow for more robust forests. The researchers also discovered that forests in lower elevations – areas not generally targeted for panda habitat – are not being protected in the same way.
“We are seeing efforts that are moving in the right direction and showing positive results for nature and for humans,” Viña said. “Now it’s time to continue those efforts, and fine tune them to continue to get even more benefits.”
The research was supported by the National Science Foundation. | <urn:uuid:c91a1d13-33a4-4786-9c84-08112032214c> | 3.1875 | 839 | News (Org.) | Science & Tech. | 36.696999 | 95,597,380 |
By downloading free open-source software, you could be using data from space to monitor global deforestation and land-use in general in just a matter of minutes.
Land use, forests and agriculture are at the core of the Paris Agreement on climate change, not least because they account for almost a quarter of the world’s greenhouse gas emissions.
Preventing deforestation – forests absorb carbon dioxide – is a vital part of the commitment countries have made under the accord. Their ability to reliably measure, report and verify the state of deforestation within their borders is mission critical.
With Collect Earth, anyone who has an internet connection can now evaluate the state of forests and land-use around the world using state of the art satellite imagery.
The tool relies on a collaboration between Google and the UN’s Food and Agriculture Organisation (FAO) that was announced at the COP22 climate summit.
“Satellite images and products that used to take days to download and process can now be produced and visualised in a fraction of that time,” said Giulio Marchi, a forestry officer at the United Nations.
This type of data used to be collected by large government and business departments and required specialised equipment and training, making this type of monitoring more complicated for developing nations.
— FAO Forestry (@FAOForestry) December 8, 2016
The software provides easy access to archives with very high-resolution imagery including Google Earth and Bing Maps.
With Collect Earth, users can specify the type of information they want to track and search a vast set of satellite images of different resolutions, including an archive of images from the pioneering Landsat Earth observation programme dating back to 1972, the UN’s food and agriculture website explains.
“The FAO Collect Earth application brilliantly builds on top of Google Earth and Earth Engine to provide a simple but powerful global and national forest carbon monitoring tool,” explains Rebecca Moore, a director at Google
Users can zoom in on the images to mark small areas as, for example, forest, crop or grassland, and compare them to the same areas in the past, building up an exportable data set in the process.
“For FAO, this is not just a partnership. This is a strategic alliance,” said FAO director-general José Graziano da Silva, noting it combines FAO’s global effort to combat climate change with Google’s commitment to help on the climate data science and awareness fronts.
Ruth Turia of the Papua New Guinea Forest Authority told the UN that the software has already allowed foresters in her country to gather their own data for national forest monitoring. “For us, Collect Earth has been really useful, and this time we want to do that monitoring work ourselves” Turia said.
Collect Earth is one of the open source tools developed by the Open Foris initiative, a UN project funded by the governments of Finland, Germany and Norway.
Forestry is also a major focus for Climate-KIC, the European Union’s climate innovation initiative. The Fully Optimized and Reliable EmissionS Tool (FOREST), a project supported by Climate-KIC, provides users with an integrated service that combines optical and radar data, measurements through ground stations and vegetation models.
Anyone can give the tool a try through the online demo on the website of the project partners, Airbus. The platform puts information about the size and structure of forested areas, including analysis of their evolution over time as well as carbon stock estimations, at your fingertips.
Learn more about how Climate-KIC is working to make land use more sustainable. | <urn:uuid:fbea1d48-ff66-4096-af4f-4caaf8263e13> | 3.59375 | 749 | News Article | Science & Tech. | 25.294105 | 95,597,402 |
Alchemy was a precursor to chemistry. The word is derived from the Arabic الكيمية (Al Kimia), meaning "the art of transformation". The key pursuit of alchemy was to create what was known as the philosopher's stone, which was reputed to turn any base metal into gold; additionally alchemists searched for the elixir of life, which could cure any ailment and extend life indefinitely. This was as much a spiritual quest as it was a scientific one. Unbeknownst to alchemists at the time, gold is an element, and therefore cannot be produced by combining any other elements except through nuclear fission or fusion. Sir Issac Newton, in addition to his scientific endeavors, was a devoted alchemist.
Symbolism of alchemy
The symbolism of alchemy is rich and employs many western and eastern traditions. Some of the important symbols of alchemy are Solomons seal, the hermaphrodite, and the four Elements of wind, fire, earth and, water. These symbols are said to be from the period of the legendary alchemist Hermes Trismegistus, founder of the Hermetic arts. These and the other symbols of alchemy are regarded as having psychological significance by Carl Jung, contemporary of Sigmund Freud.
Why it failed
- Medieval alchemists wanted to turn lead into gold. It was a fruitless endeavor because they used chemical reactions. Nowadays, we know why: Chemical reactions cannot change one element into another. Only nuclear processes, which involve intense energies not available until the 20th century, can accomplish this. | <urn:uuid:eb1dd26c-5bca-46cc-b930-f1ca05297aca> | 3.109375 | 330 | Knowledge Article | Science & Tech. | 34.291574 | 95,597,445 |
Find the volume of the following region in space: The first octant region bounded by the coordinate planes and the surfaces y=1-x^2, z=1-x^2.
This question is #12 (section 9.3) in Advanced engineering mathmatics (8th ed.) by Kreyszig.
This section deals with the evaluation of double integrals.© BrainMass Inc. brainmass.com July 23, 2018, 1:53 pm ad1c9bdddf
Double inegrals are used to find the volume of a region. | <urn:uuid:e816ab53-454c-457f-a1b7-edbafa912c13> | 3.015625 | 119 | Q&A Forum | Science & Tech. | 82.263375 | 95,597,448 |
Evapotranspiration (ET) is a major component of the energy and water balances over land. Many studies of long-term averages have shown that more than half of the net solar energy and two thirds of precipitation go to ET over land. Evaporation of water from soil surfaces (ES) is a major component in the soil water balance for field crops with incomplete cover and for bare soil conditions. Most crop, hydrology, and water quality models require the simulation of evaporation from the soil surface. Quantification of ES is necessary in evaluating the water balance of soils for use in environmental and hydrologic studies and for crop management. | <urn:uuid:cc4de271-2daa-42e0-8b92-5ab70c46f930> | 2.84375 | 131 | Knowledge Article | Science & Tech. | 26.983159 | 95,597,455 |
Fourwing saltbush, Atriplex canescens (Pursh) Nutt., is an ecologically important range plant in arid south-western U.S.A. rangelands. Native populations of this chenopodiacious shrub are more extensively colonized by melanized dark septate fungi (DS) than by conventional mycorrhizal fungi. Seedling radicles of A. canescens are colonized at germination by a DS fungus identified as Aspergillus ustus that cannot be removed by heat or sterilization. The association of A. canescens with A. ustus was evaluated by comparing naturally colonized control seedlings receiving no P (0P) or adequate plant available P (AAP) receiving 30 p.p.m. supplied as KH2PO4in the root zone to seedlings whose roots were separated from plant unavailable P (as rock phosphate (RP) or tricalcium phosphate (TCP)) by a barrier that only allowed access by the fungus. A. ustus penetrated A. canescens roots with hyaline septate hyphae, formed melanized runner hyphae at the root surface, and extended through the root exclusion barrier into RP and TCP. In these treatments A. ustus obtained plant carbon, increased shoot and root biomass, and phosphorus use efficiency. A. ustus grew well in culture on RP and TCP and internally colonized in vitro Ri-T DNA D. carota roots. The mutualistic association of DS fungi in arid ecosystems is discussed. © 2002 Elsevier Science Ltd.
Mendeley saves you time finding and organizing research
Choose a citation style from the tabs below | <urn:uuid:5ea59fc1-6205-4534-88c5-7ed4c4e95119> | 2.65625 | 352 | Academic Writing | Science & Tech. | 42.358069 | 95,597,484 |
Sight, hearing, smell, taste, touch, …and magnetoreception? While we are quite used to our five basic senses, there has always been a search for a sixth sense. Many have connected this sense to the ability to see the future, see distant objects, or read minds.
However, an American scientist has found something else. Magnetoreception, or the ability to sense and navigate through the invisible magnetic fields of our planet, is commonly present among different kinds of animals.
Birds use this kind of ability to travel south during wintertime; some species of mice and rats locate their nests along magnetic field lines; and dogs relieve themselves along a north-south axis.
Until now, no one has been aware that this kind of subconscious awareness of Earth’s magnetic fields exists in humans. However, Joe Kirschvink of the California Institute of Technology claims to have found this same ability in humans.
Although Kirshcvink’s study is only in its early stages, with a small sample and without any peer-reviews, his finds are extraordinary.
This possibility of magnetoreception in humans could help us understand the human evolution better, and perhaps we could learn how to consciously use this ability?
Using a Faraday cage, Kirschvink managed to isolate the participants from magnetic interferences that come from computers, mobiles, elevators, and other everyday objects. This interference may be the same which prevented previous studies from a relevant result.
While in the isolated magnetic field, the participants’ brainwave activity was constantly monitored, and Kirschvink rotated the magnetic field to see if there would be any changes in the brainwaves.
Whenever Kirschvink rotated the magnetic field counterclockwise (the same way the Earth’s magnetic field does), he noticed a sharp drop in the participants’ brainwaves. This drop suggests a natural response to the shifting magnetic field.
He notes that the brainwave drop occurred only when the magnetic field rotated counterclockwise, and not the other way around, which is a strong indicator that our brains might be subconsciously connected to Earth’s magnetic field.
While this ‘sixth sense’ has no vital implications on human survival nowadays, understanding its existence and its uses could lead to a better scientific understanding of ourselves.
Kirschvink compares this ability in humans to the wings of an ostrich – magnetoreception is a remnant of our evolutionary past. However, the very fact that our brainwaves are constantly responding to Earth’s magnetic field is fascinating.
Do you think you can sense where North is if you tried?
Source: Science Alert
A professional writer with over a decade of incessant writing skills. Her topics of interest and expertise range from psychology, to all sorts of disciplines such as science and news. | <urn:uuid:20b7cb32-b66f-4f92-a727-5f0f6203d5f8> | 3.3125 | 583 | Truncated | Science & Tech. | 31.474325 | 95,597,506 |
More of the United States is in moderate drought or worse than at any other time in the 12-year history of the U.S. Drought Monitor, officials from the National Drought Mitigation Center at the University of Nebraska-Lincoln said today.
Analysis of the latest drought monitor data revealed that 46.84 percent of the nation's land area is in various stages of drought, up from 42.8 percent a week ago. Previous records were 45.87 percent in drought on Aug. 26, 2003, and 45.64 percent on Sept. 10, 2002.
Looking only at the 48 contiguous states, 55.96 percent of the country's land area is in moderate drought or worse – also the highest percentage on record in that regard, officials said. The previous highs had been 54.79 percent on Aug. 26, 2003, and 54.63 percent on Sept. 10, 2002.
"The recent heat and dryness is catching up with us on a national scale," said Michael J. Hayes, director of the National Drought Mitigation Center at UNL. "Now, we have a larger section of the country in these lesser categories of drought than we've previously experienced in the history of the Drought Monitor."
The monitor uses a ranking system that begins at D0 (abnormal dryness) and moves through D1 (moderate drought), D2 (severe drought), D3 (extreme drought) and D4 (exceptional drought).
Moderate drought's telltale signs are some damage to crops and pastures, with streams, reservoirs or wells getting low. At the other end of the scale, exceptional drought includes widespread crop and pasture losses, as well as shortages of water in reservoirs, streams and wells, creating water emergencies. So far, just 8.64 percent of the country is in either extreme or exceptional drought.
"During 2002 and 2003, there were several very significant droughts taking place that had a much greater areal coverage of the more severe and extreme drought categories," Hayes said. "Right now we are seeing pockets of more severe drought, but it is spread out over different parts of the country.
"It's early in the season, though. The potential development is something we will be watching."
The U.S. Drought Monitor is a joint endeavor by the National Drought Mitigation Center at UNL, the National Oceanic and Atmospheric Administration, the U.S. Department of Agriculture and drought observers across the country.
To examine the monitor's current and archived national, regional and state-by-state drought maps and conditions, go to http://droughtmonitor.unl.edu.
Mike Hayes | EurekAlert!
Global study of world's beaches shows threat to protected areas
19.07.2018 | NASA/Goddard Space Flight Center
NSF-supported researchers to present new results on hurricanes and other extreme events
19.07.2018 | National Science Foundation
A new manufacturing technique uses a process similar to newspaper printing to form smoother and more flexible metals for making ultrafast electronic devices.
The low-cost process, developed by Purdue University researchers, combines tools already used in industry for manufacturing metals on a large scale, but uses...
For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.
To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...
For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.
Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...
Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.
A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...
Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.
"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....
13.07.2018 | Event News
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20.07.2018 | Materials Sciences | <urn:uuid:495d921a-258c-4c9b-bb16-5b52f85d3f5c> | 3.234375 | 1,123 | Content Listing | Science & Tech. | 51.549814 | 95,597,565 |
doi:10.1038/nindia.2018.62 Published online 21 May 2018
Using table sugar, researchers have synthesised carbon dots that can be used as a sensitive sensor for detecting minute traces of lead ions in drinking water1.
Carbon dots are carbon nanoparticles that are widely used to make light-emitting diodes, solar cells and even supercapacitors. Existing methods to make such nanodots are complex and time-consuming.
To find a simple green process, scientists from the University of Calicut, Kerala, in India heated a mixture of table sugar and diluted ammonia solution, and then exposed it to microwave irradiation. The solution was then cooled, filtered and freeze-dried to yield carbon nanodots.
Adding a solution of lead ions to the carbon nanodot solution turned the nanodot solution turbid, a state that can be detected by the naked eye.
When a mixture of metal ions such as those of cadmium, mercury, copper, potassium and sodium –without the lead ions – was added to the nanodot solution, the nanodot solution remained clear. When lead ions were added, the nanodot solution became turbid, showing that the nanodots are sensitive only to lead ions.
On being exposed to lead ions, the nanodots formed an aggregation that scattered light, turning the solution turbid. It was possible to measure the levels of lead ions in any water sample by measuring the turbidity of the solution.
The carbon nanodots successfully detected lead ion concentrations as low as 14 parts per billion in lead-containing real water samples.
1. Ansi, V. A. et al. Table sugar derived carbon dot – a naked eye sensor for toxic Pb2+ions. Sensor. Actuator. B. Chem. 264, 67-75 (2018) | <urn:uuid:190256e8-c5c0-4ae3-ac7b-2d529d1bce85> | 3.71875 | 386 | Truncated | Science & Tech. | 48.750652 | 95,597,572 |
Temporal range: Neoproterozoic - Recent
|Ammonia tepida (Foraminifera)|
The Rhizaria are a species-rich supergroup of mostly unicellular eukaryotes. A multicellular form has also been described. This supergroup was proposed by Cavalier-Smith in 2002. Being described mainly from rDNA sequences, they vary considerably in form, having no clear morphological distinctive characters (synapomorphies), but for the most part they are amoeboids with filose, reticulose, or microtubule-supported pseudopods. Many produce shells or skeletons, which may be quite complex in structure, and these make up the vast majority of protozoan fossils. Nearly all have mitochondria with tubular cristae.
The three main groups of Rhizaria are:
- Cercozoa – various amoebae and flagellates, usually with filose pseudopods and common in soil
- Foraminifera – amoeboids with reticulose pseudopods, common as marine benthos
- Radiolaria – amoeboids with axopods, common as marine plankton
A few other groups may be included in the Cercozoa, but on some trees appear closer to the Foraminifera. These are the Phytomyxea and Ascetosporea, parasites of plants and animals, respectively, and the peculiar amoeba Gromia. The different groups of Rhizaria are considered close relatives based mainly on genetic similarities, and have been regarded as an extension of the Cercozoa. The name Rhizaria for the expanded group was introduced by Cavalier-Smith in 2002, who also included the centrohelids and Apusozoa.
Historically, many rhizarians were considered animals because of their motility and heterotrophy. However, when a simple animal-plant dichotomy was superseded by a recognition of additional kingdoms, taxonomists generally placed rhizarians in the kingdom Protista. When scientists began examining the evolutionary relationships among eukaryotes using molecular data, it became clear that the kingdom Protista was paraphyletic. Rhizaria appear to share a common ancestor with Stramenopiles and Alveolates forming part of the SAR (Stramenopiles+Alveolates+Rhizaria) super assemblage. Rhizaria has been supported by molecular phylogenetic studies as a monophyletic group.
- Christopher Taylor (2004). "Rhizaria". Archived from the original on 2009-04-20.
- Nikolaev SI, Berney C, Fahrni JF, et al. (May 2004). "The twilight of Heliozoa and rise of Rhizaria, an emerging supergroup of amoeboid eukaryotes". Proc. Natl. Acad. Sci. U.S.A. 101 (21): 8066–71. doi:10.1073/pnas.0308602101. PMC . PMID 15148395.
- Brown; et al. (2012). "Aggregative Multicellularity Evolved Independently in the Eukaryotic Supergroup Rhizaria". Current Biology. 22: 1123–1127. doi:10.1016/j.cub.2012.04.021. PMID 22608512.
- Moreira D, von der Heyden S, Bass D, López-García P, Chao E, Cavalier-Smith T (July 2007). "Global eukaryote phylogeny: Combined small- and large-subunit ribosomal DNA trees support monophyly of Rhizaria, Retaria and Excavata". Mol. Phylogenet. Evol. 44 (1): 255–66. doi:10.1016/j.ympev.2006.11.001. PMID 17174576.
- Cavalier-Smith, Thomas (2002). "The phagotrophic origin of eukaryotes and phylogenetic classification of Protozoa". International Journal of Systematic and Evolutionary Microbiology. 52 (2): 297–354. doi:10.1099/00207713-52-2-297. ISSN 1466-5026. PMID 11931142. Retrieved 2007-06-08.
- Hartikainen, H; Stentiford, GD; Bateman, KS; Berney, C; Feist, SW; Longshaw, M; Okamura, B; Stone, D; Ward, G; Wood, C; Bass, D (2014). "Mikrocytids are a broadly distributed and divergent radiation of parasites in aquatic invertebrates". Curr Biol. 24 (7): 807–12. doi:10.1016/j.cub.2014.02.033. PMID 24656829.
- Burki, F; Shalchian-Tabrizi, K; Minge, M; Skjaeveland, A; Nikolaev, SI; Jakobsen, KS; Pawlowski, J (2007). Butler, Geraldine, ed. "Phylogenomics Reshuffles the Eukaryotic Supergroups". PLoS ONE. 2 (8): e790–. doi:10.1371/journal.pone.0000790. PMC . PMID 17726520. Retrieved 2008-01-24.
- Burki, Fabien; Shalchian-Tabrizi, Kamran; Pawlowski, Jan (August 23, 2008). "Phylogenomics reveals a new 'megagroup' including most photosynthetic eukaryotes". Biology Letters. 4 (4): 366–9. doi:10.1098/rsbl.2008.0224. PMC . PMID 18522922. Retrieved 15 January 2015.
- Bass D, Chao EE, Nikolaev S, et al. (February 2009). "Phylogeny of Novel Naked Filose and Reticulose Cercozoa: Granofilosea cl. n. and Proteomyxidea Revised". Protist. 160 (1): 75–109. doi:10.1016/j.protis.2008.07.002. PMID 18952499.
- Howe; et al. (2011), "Novel Cultured Protists Identify Deep-branching Environmental DNA Clades of Cercozoa: New Genera Tremula, Micrometopion, Minimassisteria, Nudifila, Peregrinia", Protist, 162: 332–372, doi:10.1016/j.protis.2010.10.002, PMID 21295519
- Silar, Philippe (2016), "Protistes Eucaryotes: Origine, Evolution et Biologie des Microbes Eucaryotes", HAL archives-ouvertes: 1–462 | <urn:uuid:8bfecd6e-8389-45ce-8e82-0977eb27a769> | 3.28125 | 1,485 | Knowledge Article | Science & Tech. | 51.365735 | 95,597,573 |
Reactor Irradiations at 15°K
Early attempts to describe the basic nature of radiation damage were based upon measurement of physical changes occurring in materials, which were bombarded at or near room temperature. Almost at the outset of research in this field, it was recognized that some radiation induced defects might be mobile below room temperature. Observation of these defects could be made only if they were frozen into the material during bombardment and subsequently studied under controlled low temperature conditions.
KeywordsSample Chamber Braze Alloy Graphite Reactor Cryogenic Engineer Vacuum Jacket
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Suppose I made a compass with a pencil on a string attached to a stick. If the string did not move freely around the stick the length between the stick and pencil would get shorter causing a spiral as the string winds up around the stick. Is there a certain radius of stick that would cause a golden ratio spiral?
Assume the string is infinitely thin. Or like fishing line or something. I don’t have an answer just wondering. Thanks
I am trying to figure out how much more dense a point cloud is taking the same geometry using 2 different programs. In program V, the points cannot be closer than 1.5mm; while in program P the points cannot be closer than 0.5mm. Obviously program P will have a higher point density for a given geometry, however I am having trouble determining how much so.
For example: taking a 1.5mm Cube, program V will have taken 4 points (one for each vertex) while program P will have taken 64 points, leading you to believe program P will take 8x as many points as program V for a given geometry.
However, for a 3mm cube, program V will take 27 points while program P will take 343 leading to 12.7x as many points as program V.
How can I represent how many more points program P will take than program V if it keeps changing for different volumes? Is my problem that I need to be thinking about it in spheres rather than cubes?
Here’s an equation
f(x) = sin(x) - x/2 + 10
• df/dx = cos(x) -1/2
Objective: find two points, that is [x, f(x)] and [x+2 π, f(x+2 π)] that share the same tangent line.
Note: the function has the same tangent line every 2 π
Note 2: find between 0<x<2 for your [x, f(x)]
I tried this for fun and I’m getting stuck right at the end. I boiled it down to this
f(x) -x(cos(x)-1/2) = f(x + 2 π) -(x+ 2 π)(cos(x)-1/2)
I know I need to find an x here and then proceed to plug it in to the original f(x)
I’m trying something here. It’s been a while since i’m working on this and just realize something about the principle.
Let me tell you the basics first,
In music an octave is an interval who double the frequencies. (128hz,256hz,etc...)
There is something called musical temperament, who divide the octave in different intervals (it was invented a long time ago and there are few concrete information about it).
What make the music is also the rhythm witch also mean dividing the octaves.
Now, in my software I have a rhythmical grid. I would like to divide the octave by different division such as 1/4, 1/3, 1/8 with my equal division octave.
If anyone interested by the question just show up. I know that my explanation aren’t very clear. | <urn:uuid:7f4dbb4d-ed79-4619-9a8c-450474e53436> | 3.34375 | 683 | Q&A Forum | Science & Tech. | 80.747138 | 95,597,585 |
Fuel cells are devices which electrochemically convert the chemical free energy of gaseous or liquid reactants into electrical energy in a continuous way. As in a battery the reactants are prevented from chemically reacting by separating them with an electrolyte, which is in contact with electro-catalytically active porous electrode structures. Apart from effectively separating the anode and cathode gases and/or liquids, in other words the fuel and air, the electrolyte mediates the electrochemical reactions taking place at the electrodes by conducting a specific ion at very high rates during the operation of the fuel cell. In the simplest case of a fuel cell, operating with hydrogen (fuel) and oxygen (air) as reacting gases, a proton or oxide ion current equivalent to the electronic current passing through the external load is driven through the electrolyte and parts of the heterogeneous electrode structures (Fig.1.1).
KeywordsFuel Cell Life Cycle Assessment Solid Oxide Fuel Cell Fuel Cell System Polymer Electrolyte Membrane Fuel Cell
I thank Giuliano Gregori and Linas Vilciauskas (both from Max-Planck-Institut für Festkörperforschung) for reading the proofs.
- 1.Schöenbein CF (1839) X. On the voltaicpolarization of certain solid and fluid substances, Philosophical Magazine Series 3, 14:85, 43–45. http://dx.doi.org/10.1080/14786443908649658
- 2.Grove WR Esq.M.A.M.R.I. (1839) XLII. On a small voltaic battery of great energy; some observations on voltaic combinations and forms of arrangement; and on the inactivity of a copper positive electrode in nitro-sulphuric acid, Philosophical Magazine Series 3, 15:96, 287–293. http://dx.doi.org/10.1080/14786443908649881
- 3.Baur E, Preis H (1937) Über Brennstoff-Ketten Mit Festleitern, Ztschr. Elektrochem. Bd. 43, Nr. 9 727–732Google Scholar | <urn:uuid:4aa249f9-3195-4f33-8643-4193fdf9e333> | 3.078125 | 475 | Academic Writing | Science & Tech. | 54.581044 | 95,597,590 |
Greenhouse Gas Emissions Factsheet: Tunisia
This factsheet provides information on 2011 greenhouse gas emissions (GHG) in Tunisia. Included is an overview of emissions by sector, changes in emissions, information on carbon intensity, as well as climate change mitigation targets and plans.
Tunisia emitted 33 million metric tons (MtCO2e) of greenhouse gases in 2011. The energy sector was the primary emitter, contributing 72 percent to overall emissions. Within the sector, electricity and heat production and transportation comprised the majority of energy emissions.
From 1990 - 2011, Tunisia’s gross domestic product (GDP) increased more than total greenhouse gas emissions, demonstrating that carbon intensity in 2011 decreased relative to 1990.
Tunisia’s Intended Nationally Determined Contribution (INDC) pledges to achieve an unconditional carbon intensity target to reduce carbon intensity by 13 percent in 2030, compared to 2010 levels. Tunisia plans to achieve the 13 percent goal exclusively through energy sector actions. A conditional target of an additional 28 percent reduction in carbon intensity is contingent upon international funding, capacity building and technology transfer.
Find other country and regional climate risk management resources here.
Download File 475.56 KB
About this Resource | <urn:uuid:f6757a4e-b8fe-43a7-a576-8401fb13b1d7> | 3.15625 | 251 | Knowledge Article | Science & Tech. | 20.287727 | 95,597,602 |
Im no expert on this, but Im deckie on a scientific research vessel, and we have deployed Tsunami warning buoys off the coast of Chile and Thailand, and survey fault lines around the world. If the scientists arent too full of themselves I pick their brain a bit, cuz its pretty interesting work. Anyhow, I think the answer to your question is YES and NO.<br><br>Yes, because a Tsunami (Japanese word for “harbor wave”) is a high frequency shock wave from an earthquake, sometimes over 200 knots per hour! The Tsunami slows as it reaches shallower water, but builds in amplitude. So in a sense, people hundreds of miles away from the epicenter are feeling the EFFECTS of the the earthquake, not the earthquake itself, and I am quite certain people on boats in shallow water are in danger of its damage. <br>Ive had to heave anchor several time because of Tsunami warnings when I was working in the Aleutian Islands. We just sail to deep water until the danger passes. But in deep water, you feel nothing at all. The water compresses and releases so quickly it doesnt move at a frequency slow enough to move a ship or boat. It takes fairly sophisticated doppler sonar to detect this on the warning buoys.<br>But then again, I imagine if you were in 50 feet of water over the epicenter of an earthquake, youd feel something, but 3000 meters? no.<br>I also worked on a seismic vessel, and we would “make earthquakes” by firing powerful air cannons into the water in order to image what lies beneath the sea floor. As we would get near shallow areas the stern of the 270 foot ship would “jump” out of the sea. A shock strong enough to maybe knock over a Bic lighter sitting on a table every minute or so. nothing spectacular, but REAL annoying on a month-long cruise. We would hope to survey a deep area so we could get some sleep at night. <br>Anyhow, To answer your question, The answer is YES and NO.<br>Sort of like the theory of if a butterfly beats its wings in Africa, does it eventually cause a typhoon in Asia? | <urn:uuid:92236c84-cec5-4633-a030-792c9465d09f> | 2.53125 | 471 | Comment Section | Science & Tech. | 62.14455 | 95,597,619 |
The many threats facing bumblebees can be tested using a “virtual safe space” created by scientists at the University of Exeter. Bumble-BEEHAVE provides a computer simulation of how colonies will develop and react to multiple factors including pesticides, parasites and habitat loss.
The tool lets researchers, farmers, policymakers and other interested parties test different land management techniques to find out what will be most beneficial for bees. Field experiments can be very timely and costly, so results from Bumble-BEEHAVE can help refine and reduce the number of experiments needed.
Bumble-BEEHAVE – which is freely available online – is a powerful tool that can make predictions, according to a new study.
“We know that pollinator decline is a really big problem for crops and also for wildflowers,” said Dr Grace Twiston-Davies, of the Environment and Sustainability Institute at the University of Exeter’s Penryn Campus in Cornwall.
“Bumble-BEEHAVE takes into account the many complicated factors that interact to affect bumblebees.
“This provides a virtual safe space to test the different management options.”
“It’s a free, user-friendly system and we’re already starting to work with land managers and wildlife groups on the ground.”
Disentangling the many factors that affect bumblebee colonies is incredibly complicated, meaning real-word testing of different methods by land managers is often not feasible.
This problem prompted the Exeter scientists to create the BEEHAVE (honeybees) and Bumble-BEEHAVE computer models. Bumble-BEEHAVE can simulate the growth, behaviour and survival of six UK bumblebee species living in a landscape providing various nectar and pollen sources to forage on.
“The Bumble-BEEHAVE model is a significant step towards predicting bumblebee population dynamics,” said Professor Juliet Osborne, who leads the BEEHAVE team.
“It enables researchers to understand the individual and interacting effects of the multiple stressors affecting bumblebee survival and the feedback mechanisms that may buffer a colony against environmental stress, or indeed lead to spiralling colony collapse.
“The model can be used to aid the design of field experiments, for risk assessments, to inform conservation and farming decisions and for assigning bespoke management recommendations.”
Professor Osborne and team won the BBSRC Social Innovator of the Year 2017 award for creating the BEEHAVE models.
“We really hope that researchers and landowners will use the model and give us feedback so we can improve it further in future” said model developer Dr Matthias Becher.
The new study, published in the Journal of Applied Ecology, is entitled: “Bumble-BEEHAVE: a systems model for exploring multifactorial causes of bumblebee decline at individual, colony, population and community level.”
Source: University Of Exeter | <urn:uuid:0fb7dbf5-8144-4734-8445-7b947c77fdba> | 3.859375 | 629 | News Article | Science & Tech. | 19.275424 | 95,597,636 |
C#: Why you should use ConfigureAwait(false) in your library code
Writing asynchronous code after the introduction of async/await in .NET4.5 became relatively easy. Async/await keywords improve code readability and programmer productivity as code resembles synchronous code and it's easy to follow, thanks to the compiler taking care of the most difficult part of asynchronous programming.
Let’s create an example to see how easy it is to write async code to curl a specific URL and return its content as a string.
We have our asynchronous call that does not block the calling thread while it fetches the content of Bynder.
In an ideal world people would always use our library in the following way:
However, the programming world is far from ideal and some people might use it in the following way:
This way curl is done in a synchronous way, blocking the calling thread until curl finishes. If this is executed in a Console Application, most of the time our code will run as expected (not necessarily always).
However, if that code is run in a UI Application, for example when a button is clicked like in the following example:
Then the application will freeze and stop working, we have a deadlock. Of course, users of our library will complain because it makes the application unresponsive.
To solve the problem and make our library work in this situation we will have to rewrite our function as follows:
In fact, only adding the first ConfigureAwait(false) would be enough to solve the problem.
In conclusion, it is good practice to always use ConfigureAwait(false) in your library code to prevent unwanted issues.
Now, we will analyse why a deadlock occurs in an UI application (and not in most console applications) and why ConfigureAwait(false) solves this issue.
First we need to understand how most UI applications work:
- There is one thread that is responsible for the UI: the UI Thread. The UI can only be updated if called from this thread, so if this thread is blocked, the application becomes unresponsive.
- The UI Thread has a message queue to receive notifications/actions to perform. In Win32 this translates into something like this:
- The UI Thread has a SynchronizationContext by default.
If there is a SynchronizationContext (i.e. we are in the UI thread) the code after an await will run in the original thread context. This is the default and expected behaviour.
If we were to modify a UI component from a thread other than the UI Thread, a ‘System.InvalidOperationException’ would be thrown, like in the following example:
Back to our working example, our async DoCurlAsync call is conceptually equivalent to:
NOTE: this snippet is a simplified version of what actually takes place when using await. It also does not take care of the using keyword for closing resources.
The Post call sends a message to the UI Thread message pump to be processed, so to finish DoCurlAsync it is mandatory that the UI Thread executes await httpResonse.Content.ReadAsStringAsync().
However, in the following scenario:
UI Thread cannot process that instruction because it's blocked. We have a deadlock because DoCurlAsync will never finish. ConfigureAwait(false) configures the task so that continuation after the await does not have to be run in the caller context, therefore avoiding any possible deadlocks.
Updated: July 20, 2015 For the latest documentation on Visual Studio 2017 RC, see Visual Studio 2017 RC Documentation…msdn.microsoft.com
When I discuss the new async language features of C# and Visual Basic, one of the attributes I ascribe to the await…blogs.msdn.microsoft.com | <urn:uuid:60a69f16-a367-4851-9829-e109e961e874> | 2.609375 | 789 | Personal Blog | Software Dev. | 44.001736 | 95,597,640 |
The first part of an investigation into how to represent numbers using geometric transformations that ultimately leads us to discover numbers not on the number line.
Arrow arithmetic, but with a twist.
How can you use twizzles to multiply and divide?
Introduces the idea of a twizzle to represent number and asks how one can use this representation to add and subtract geometrically.
First or two articles about Fibonacci, written for students.
A loopy exploration of z^2+1=0 (z squared plus one) with an eye on winding numbers. Try not to get dizzy!
Make the twizzle twist on its spot and so work out the hidden link.
Where we follow twizzles to places that no number has been before.
This article looks at how models support mathematical thinking about numbers and the number system
Can you explain how Galley Division works?
Have you seen this way of doing multiplication ?
Using balancing scales what is the least number of weights needed to weigh all integer masses from 1 to 1000? Placing some of the weights in the same pan as the object how many are needed?
This article for the young and old talks about the origins of our number system and the important role zero has to play in it. | <urn:uuid:c313657e-164f-402d-bf1f-4f5fc06058ec> | 4.25 | 262 | Content Listing | Science & Tech. | 58.579151 | 95,597,665 |
University of Delaware marine scientists are now working aboard the 420-foot U.S. Coast Guard icebreaker Healy on a National Science Foundation project to track the fresh water flowing out of the Arctic Ocean into the Atlantic. This fresh water, from melting ice and rivers, affects the salinity and circulation of the ocean and thus has a major influence on the Earth’s climate.
The 420-foot U.S. Coast Guard icebreaker Healy will be home to research teams from the University of Delaware, Oregon State University, and the Institute of Ocean Sciences in British Columbia during a month-long expedition to begin tracking the fresh water flowing out of the Arctic Ocean into the Atlantic
“Freshwater discharge from the Arctic to the North Atlantic is a crucial factor controlling global climate,” says Andreas Muenchow, associate professor of Physical Ocean Science and Engineering in the UD College of Marine Studies and one of the lead investigators on the project.
The five-year study involves over 35 scientists from Oregon State University, the Institute of Ocean Sciences in British Columbia, and the University of Delaware. The scientists will be using tools ranging from underwater current profilers to satellite sensors to determine the volume and timing of freshwater flows through Nares Strait, a narrow channel between northern Greenland and Canada’s Ellesmere Island.
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
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
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This chapter demonstrates how linear systems can be used to model biochemical networks. Such models give predictable power that can be used to generate hypotheses, which in turn can be (in)validated experimentally. The advantages of linear systems are that they are relatively simple, efficient to obtain and simulate, and have been studied in great detail. In spite of inherent nonlinearities in real world applications, linear systems have been successfully used in control theory as a tool to model, analyse and control technological systems. In contrast, although at the molecular level reactions are nonlinear, modelling of key behaviours important to predict new features of a system can in many instances be captured by linear dynamics. Guided by a simple example, this chapter explains step-by-step how to use linear system identification (SId) to obtain causal relationships between different biological species in complex networks. We will cover key aspects of model estimation, validation and selection. The corresponding MatlabTM codes will be also be introduced. The chapter ends with illustrations of practical applications through two case studies, where SId has been used to further our understanding of biological networks. | <urn:uuid:e7b16541-aaf9-441e-89c4-bf83ac1e742b> | 2.9375 | 223 | Truncated | Science & Tech. | 20.032778 | 95,597,678 |
An article in todays Lincoln Journal Star states
...nine whooper chicks now sport high-tech bling thanks to the work of two avian scientists from The Crane Trust, a conservation organization headquartered on the Platte River near Alda.
And the project marks the first time in 22 years whooping cranes have been banded on their breeding grounds in the Northwest Territories.
The global positioning system transmitters will allow biologists to track the endangered birds as they migrate up and down the continent, revealing new information about where whoopers roost, rest and, more importantly, die.
Researchers know little about the causes of premature death for a species that can live 30 years in the wild. About 80 percent of annual crane mortality occurs during the 2,500-mile spring and fall migrations.
Much more in the article | <urn:uuid:14f4c373-5af6-464a-b77b-122791708249> | 3.09375 | 168 | Truncated | Science & Tech. | 52.727059 | 95,597,685 |
Scientists from Spectrolab, Inc., a subsidiary of Boeing, have recently published their research on the fabrication of solar cells that surpass the 40% efficiency milestone—the highest efficiency achieved for any photovoltaic device. Their results appear in a recent edition of Applied Physics Letters.
Most conventional solar cells used in today’s applications, such as for supplemental power for homes and buildings, are one-sun, single-junction silicon cells that use only the light intensity that the sun produces naturally, and have optimal efficiency for a relatively narrow range of photon energies.
The Spectrolab group experimented with concentrator multijunction solar cells that use high intensities of sunlight, the equivalent of 100s of suns, concentrated by lenses or mirrors. Significantly, the multijunction cells can also use the broad range of wavelengths in sunlight much more efficiently than single-junction cells.
"These results are particularly encouraging since they were achieved using a new class of metamorphic semiconductor materials, allowing much greater freedom in multijunction cell design for optimal conversion of the solar spectrum," Dr. Richard R. King, principal investigator of the high efficiency solar cell research and development effort, told PhysOrg.com. "The excellent performance of these materials hints at still higher efficiency in future solar cells."
In the design, multijunction cells divide the broad solar spectrum into three smaller sections by using three subcell band gaps. Each of the subcells can capture a different wavelength range of light, enabling each subcell to efficiently convert that light into electricity. With their conversion efficiency measured at 40.7%, the metamorphic multijunction concentrator cells surpass the theoretical limit of 37% of single-junction cells at 1000 suns, due to their multijunction structure.
While Spectrolab's primary business is supplying PV cells and panels to the aerospace industry (many of their solar cells are used on satellites currently in orbit), the company envisions that this breakthrough will also have applications in commercial terrestrial solar electricity generation.
The research that led to the discovery of the high efficiency concentrator solar cell was funded partly by the U.S. Department of Energy’s National Renewable Energy Laboratory, and will play a significant role in the government’s Solar America Initiative, which aims to make solar energy cost-competitive with conventional electricity generation by 2015. The company has said that these solar cells could help concentrator system manufacturers produce electricity at a cost that is competitive with electricity generated by conventional methods today.
The Spectrolab scientists also predict that with theoretical efficiencies of 58% in cells with more than three junctions using improved materials and designs, concentrator solar cells could achieve efficiencies of more than 45% or even 50% in the future.
Citation: King, R. R., Law, D. C., Edmondson, K. M., Fetzer, C. M., Kinsey, G. S., Yoon, H., Sherif, R. A., and Karam, N. H. “40% efficient metamorphic GaInP/GaInAs/Ge multijunction solar cells.” Applied Physics Letters 90, 183516 (2007).
Copyright 2007 PhysOrg.com.
All rights reserved. This material may not be published, broadcast, rewritten or redistributed in whole or part without the express written permission of PhysOrg.com.
Explore further: Organic solar cells reach record efficiency, benchmark for commercialization | <urn:uuid:db99b164-1c6d-4e2f-81c8-dd40b664e2d2> | 3.390625 | 712 | News (Org.) | Science & Tech. | 35.598987 | 95,597,710 |
As film buffs queue to watch the new Spider-man movie, geography students from the University of Sussex have gone one better by discovering a new species of spider in the wild.
The second year undergraduates were taking part in a field course to the Seychelles, one of the most biologically diverse places on the planet. As part of this trip the students were responsible for helping to set insect traps in the Vallée de Mai, a UNESCO World Heritage Site on Praslin, the second-largest island in the main Seychelles group.
An undisturbed tract of palm forest, the area is renowned for being home to the remarkable Coco de Mer double coconut, as well as vanilla orchids and a host of rare birds and lizards. Because of its fame, the site is frequently visited by biologists and, as a result, is one of the most-sampled places on the islands.
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....
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:bf9fabe5-1f09-4a78-a8c7-7227da9eaf3b> | 2.6875 | 766 | Content Listing | Science & Tech. | 40.891695 | 95,597,742 |
The Voyager 1 probe, which launched 40 years ago today (Sept. 5), is humankind's most distant physical emissary, at almost 13 billion miles (21 billion kilometers) from Earth. Voyager 1 and its sister-spacecraft, Voyager 2, which launched two weeks earlier in 1977, gave scientists their first close-up views of Jupiter, Saturn, Uranus and Neptune. And the spacecraft famously carried with them what could be aliens' first views of Earth, its inhabitants and their culture: copies of the Golden Record.
The astronomer and science popularizer Carl Sagan curated the record selections, and it carried sounds and music from Earth as well as greetings in 55 languages. But the record also contains encoded photos seeking to teach aliens the mathematics — or really, the measurements — needed to understand humans' lives and their place in the universe.
"Whatever number of pictures we were going to be able to send, I thought it should be a coherent story, not a grab bag of unrelated things," Jon Lomberg, the Golden Record's design director, told Space.com. "What the sequence of pictures afforded us was the opportunity to tell a story about Earth … the sequencing, the subject matter, the repeated motifs, the symbology that we invented so we could tell them a lot more quantitative information about things in the pictures — the idea was to make it a coherent whole." [The Golden Record in Pictures: Voyager Probes' Message to Space Explained]
"And within that whole, there were substories," Lomberg added. "A story of how we eat, and a story of how we're born, and a story of how we travel. Also, there were some recurrent kinds of tutorial aspects."
Part of that tutorial, Lomberg said, was pairing images with silhouettes that told nonhuman viewers which parts of the photos were significant, or even how to interpret perspective (that more distant images appeared smaller). And another was to build a sense of scale — of time, measurement and composition — to give the images context.
Seth Shostak, the director of the Center for SETI (Search for Extraterrestrial Intelligence) Research at California's SETI Institute, put it this way: "If you have a representation of the Earth, you have a photo of the Earth from space, and the aliens say, 'OK, that's good, but will it fit in a bread box? Or is it 100,000 miles [160,000 km] across? What is it?'
"You always need the numbers to set scale," he told Space.com.
The Golden Record's cover, facing outward from where the record was placed on the two spacecraft's sides, gets straight to the point in depicting how the media is to be used — the top diagrams show how the record should be placed on its player and how images can be decoded from a certain portion of the disk. If decoded properly, the first image seen should be a circle.
The two bottom-most images are more interesting. One is a map of Earth's location in space compared to 14 rapidly rotating, ultradense neutron stars the size of cities called pulsars; the dashes and lines along each encode how quickly the stars pulse with radiation (more on that code later). Pulsars, which can form when a dying star collapses, can serve as handy waypoints in space, because their rapid blinking can be extremely regular and distinctive. No matter where aliens are looking from, if they're close enough, they could triangulate the sun's location using its position relative to those pulsars.
The second diagram is of the second-lowest and lowest energy states for a hydrogen atom. Hydrogen takes a specific amount of time to transition from one state to the other, producing a specific wavelength of light — both of which are used as basic units of measurement within the record.
"A lot of people look at this — the cover diagram I made, for example, [on] how to play the record — and they can't figure it out in a couple of minutes, so they conclude that extraterrestrials will never be able to figure it out," Lomberg said. "Well, if we found something that was an artifact, we'd spend more than a few minutes, and we'd bring in people from all kinds of disciplines, because you don't know who's going to have the insight.
"The issue is how much time do you devote to it and how many smart friends do you bring in on the project," he added. [NASA's Epic Voyager Mission at 40: Q&A with Lead Scientist Ed Stone]
Into the photos
If the spacecraft's alien interceptors understand the instructions to play the record, and therefore recover the sounds of Earth as well as the photos encoded at the end, the first image they would see would be a circle. This shape's there so the aliens can make sure their calibrations were correct and they're seeing the photos correctly.
Second, they'd see another view of that map from the record's cover, along with a photo of the Andromeda galaxy where one of the pulsars is located. Andromeda and its satellite galaxies' positioning tells viewers when, on a cosmic scale, the record was sent, Lomberg said. Physical aspects like the amount that the probe's nuclear battery has decayed could give aliens some understanding of how long it had been traveling. However, if visitors came upon the spacecraft after thousands or millions of years, the galaxy's configuration could provide a more long-lasting clue.
Then, the record gets to the nitty-gritty: how to interpret numbers.
Count on it
The Golden Record committee chose to start by illustrating numbers in the simplest way — a number of dots, which the aliens should be able to count in any number system. Then, the record equates those values with numbers written in binary as well as base 10, which is our ordinary number system.
Binary writes every number using powers of two. In the Golden Record's version, a vertical line fills in for "1" and a horizontal line for "0" — 5 is represented as "| – |," which comes out to (1 x 2^2) + (0 x 2^1) + (1 x 2^0) = 4 + 0 + 1 = 5. As numbers get longer, binary representations quickly grow unwieldy — look at "| | | | – | – – –" for 1,000, the largest number shown on the image.
The diagram then goes on to show how our number system works: adding, multiplying and denoting fractions.
While astronomer Frank Drake, who masterminded the images' addition to the record, had experience considering how to communicate with extraterrestrial intelligence, its exact implementation here was done very quickly, according to Lomberg. The Golden Record came together at a frenetic pace.
"The background of this, of course, is that the whole project took six weeks," Lomberg said. "From the time I got the phone call to the time we had to send our finished design [of the Golden Record] out to be fabricated was six weeks. So, we didn't have a heck of a lot of time to really have thorough discussions and explore alternatives; it was very much shoot from the hip.
"For any one of these decisions, you could have had a panel talking about the way to show [for example] the structure of the Earth, and they could have met several times and taken a month to come up with something — and we did it in an afternoon," he added. "In retrospect, the thing I'm most amazed by is that most people seem to think we did a fairly good job." [Photos from NASA's Voyager 1 and 2 Probes]
Space and time
Now, back to those hydrogen atoms, seen at the top left of this next diagram. Atomic hydrogen has one proton and one electron, and each of those components can have a particular spin. When the two are spinning in the same direction, the atom has slightly more energy than when they spin in opposite directions, so the electron will eventually flip to that configuration, releasing radiation. That radiation is a particular wavelength of light 21 centimeters (8.3 inches) long, detectable coming from wherever hydrogen gas congregates in space.
So, the most common element in the universe, combined with a signature wavelength of light it releases, offered the Golden Record's designers a valuable chance to build up a measurement system.
You can see the hydrogen atom with its electron and proton spinning in one configuration, then the other, in the diagram at the top. From there, the image derives 1 M (the weight of an atom of hydrogen) and 1 ↑ (the time it takes for that electron flip). The image converts M to grams, kilograms and "e" (based on Earth's mass) and converts the time measurement to seconds, days and years.
Then, on the right, the image uses the wavelength — 21 cm — released by the flip to explain centimeters, angstroms, meters and kilometers.
The Earth and us
Those units come in handy soon afterward, because the record next goes through the sun and the solar system planets to give their diameters, distance from the sun, mass compared to Earth (using the "e" unit from before) and how long each planet takes to complete a full rotation, compared to an Earth day.
All that established, the record's framers can get into the good stuff — images of the planets, with their sizes and masses, the proportions of different elements and the key ingredients to life on Earth (shown as atoms and molecules) and even how DNA is built.
The viewer is plunged into a deeper look at humanity — how our bodies are built, how babies form, the many cultures on Earth and activities that fill people's lives. Throughout, diagrams provide the sizes and durations of what's depicted.Another key element the measurements could add to photos was a sense of time, Lomberg said. "How long does it take for a certain activity to happen? How long does it take to form a baby, to do a routine on a balance beam, to grow and die? How old do people live to be? It gave a fuller picture of human life by being able to include things like that as well."
Lomberg is currently spearheading a project to upload a "Golden Record 2.0" to the hard drive of the New Horizons probe, which flew by Pluto in 2015 and is the farthest-traveling probe after the Voyager duo. On the crowdfunding site Kickstarter, he's raising money to build a platform for people to submit photos, sound and more to fill that record. On that project, like with the Golden Record, the main goal is providing a view of humanity to two audiences: extraterrestrials, and humans themselves.
This article's discussion focuses on the measurements and diagrams on the Golden Record, but the key goal of the audio and photographic parts was always to convey the less directly measurable aspects of human life and society, Lomberg said.
"The spacecraft itself tells a lot about our engineering and technology; you want the record to tell about the rest of us — the other parts of being human," Lomberg said.
You can view more of the photos and diagrams on the Golden Record here: https://voyager.jpl.nasa.gov/galleries/images-on-the-golden-record/
One Earth Message's Kickstarter is online here: www.kickstarter.com/projects/31060842/one-earth-message-a-digital-voyager-golden-record
Email Sarah Lewin at firstname.lastname@example.org or follow her @SarahExplains . Follow us @Spacedotcom , Facebook and Google+ . Original article on Space.com . | <urn:uuid:fdeedfb5-a0f8-4114-9654-80f29ab56d27> | 3.78125 | 2,446 | Truncated | Science & Tech. | 50.884426 | 95,597,746 |
Vacuum state(Redirected from Quantum vacuum)
In quantum field theory, the quantum vacuum state (also called the quantum vacuum or vacuum state) is the quantum state with the lowest possible energy. Generally, it contains no physical particles. Zero-point field is sometimes used as a synonym for the vacuum state of an individual quantized field.
According to present-day understanding of what is called the vacuum state or the quantum vacuum, it is "by no means a simple empty space". According to quantum mechanics, the vacuum state is not truly empty but instead contains fleeting electromagnetic waves and particles that pop into and out of existence.
The QED vacuum of quantum electrodynamics (or QED) was the first vacuum of quantum field theory to be developed. QED originated in the 1930s, and in the late 1940s and early 1950s it was reformulated by Feynman, Tomonaga and Schwinger, who jointly received the Nobel prize for this work in 1965. Today the electromagnetic interactions and the weak interactions are unified in the theory of the electroweak interaction.
The Standard Model is a generalization of the QED work to include all the known elementary particles and their interactions (except gravity). Quantum chromodynamics is the portion of the Standard Model that deals with strong interactions, and QCD vacuum is the vacuum of quantum chromodynamics. It is the object of study in the Large Hadron Collider and the Relativistic Heavy Ion Collider, and is related to the so-called vacuum structure of strong interactions.
Non-zero expectation valueEdit
If the quantum field theory can be accurately described through perturbation theory, then the properties of the vacuum are analogous to the properties of the ground state of a quantum mechanical harmonic oscillator, or more accurately, the ground state of a measurement problem. In this case the vacuum expectation value (VEV) of any field operator vanishes. For quantum field theories in which perturbation theory breaks down at low energies (for example, Quantum chromodynamics or the BCS theory of superconductivity) field operators may have non-vanishing vacuum expectation values called condensates. In the Standard Model, the non-zero vacuum expectation value of the Higgs field, arising from spontaneous symmetry breaking, is the mechanism by which the other fields in the theory acquire mass.
In many situations, the vacuum state can be defined to have zero energy, although the actual situation is considerably more subtle. The vacuum state is associated with a zero-point energy, and this zero-point energy has measurable effects. In the laboratory, it may be detected as the Casimir effect. In physical cosmology, the energy of the cosmological vacuum appears as the cosmological constant. In fact, the energy of a cubic centimeter of empty space has been calculated figuratively to be one trillionth of an erg (or 0.6 eV). An outstanding requirement imposed on a potential Theory of Everything is that the energy of the quantum vacuum state must explain the physically observed cosmological constant.
For a relativistic field theory, the vacuum is Poincaré invariant, which follows from Wightman axioms but can be also proved directly without these axioms. Poincaré invariance implies that only scalar combinations of field operators have non-vanishing VEV's. The VEV may break some of the internal symmetries of the Lagrangian of the field theory. In this case the vacuum has less symmetry than the theory allows, and one says that spontaneous symmetry breaking has occurred. See Higgs mechanism, standard model.
In principle, quantum corrections to Maxwell's equations can cause the experimental electrical permittivity ε of the vacuum state to deviate from the defined scalar value ε0 of the electric constant. These theoretical developments are described, for example, in Dittrich and Gies. In particular, the theory of quantum electrodynamics predicts that the QED vacuum should exhibit nonlinear effects that will make it behave like a birefringent material with ε slightly greater than ε0 for extremely strong electric fields. Explanations for dichroism from particle physics, outside quantum electrodynamics, also have been proposed. Active attempts to measure such effects have yielded negative results so far.
The presence of virtual particles can be rigorously based upon the non-commutation of the quantized electromagnetic fields. Non-commutation means that although the average values of the fields vanish in a quantum vacuum, their variances do not. The term "vacuum fluctuations" refers to the variance of the field strength in the minimal energy state, and is described picturesquely as evidence of "virtual particles". It is sometimes attempted to provide an intuitive picture of virtual particles, or variances, based upon the Heisenberg energy-time uncertainty principle:
(with ΔE and Δt being the energy and time variations respectively; ΔE is the accuracy in the measurement of energy and Δt is the time taken in the measurement, and ħ is the Reduced Planck constant) arguing along the lines that the short lifetime of virtual particles allows the "borrowing" of large energies from the vacuum and thus permits particle generation for short times. Although the phenomenon of virtual particles is accepted, this interpretation of the energy-time uncertainty relation is not universal. One issue is the use of an uncertainty relation limiting measurement accuracy as though a time uncertainty Δt determines a "budget" for borrowing energy ΔE. Another issue is the meaning of "time" in this relation, because energy and time (unlike position q and momentum p, for example) do not satisfy a canonical commutation relation (such as [q, p] = i ħ). Various schemes have been advanced to construct an observable that has some kind of time interpretation, and yet does satisfy a canonical commutation relation with energy. The very many approaches to the energy-time uncertainty principle are a long and continuing subject.
Physical nature of the quantum vacuumEdit
According to Astrid Lambrecht (2002): "When one empties out a space of all matter and lowers the temperature to absolute zero, one produces in a Gedankenexperiment [mental experiment] the quantum vacuum state." According to Fowler & Guggenheim (1939/1965), the third law of thermodynamics may be precisely enunciated as follows:
Photon-photon interaction can occur only through interaction with the vacuum state of some other field, for example through the Dirac electron-positron vacuum field; this is associated with the concept of vacuum polarization. According to Milonni (1994): "... all quantum fields have zero-point energies and vacuum fluctuations." This means that there is a component of the quantum vacuum respectively for each component field (considered in the conceptual absence of the other fields), such as the electromagnetic field, the Dirac electron-positron field, and so on. According to Milonni (1994), some of the effects attributed to the vacuum electromagnetic field can have several physical interpretations, some more conventional than others. The Casimir attraction between uncharged conductive plates is often proposed as an example of an effect of the vacuum electromagnetic field. Schwinger, DeRaad, and Milton (1978) are cited by Milonni (1994) as validly, though unconventionally, explaining the Casimir effect with a model in which "the vacuum is regarded as truly a state with all physical properties equal to zero." In this model, the observed phenomena are explained as the effects of the electron motions on the electromagnetic field, called the source field effect. Milonni writes:
The basic idea here will be that the Casimir force may be derived from the source fields alone even in completely conventional QED, ... Milonni provides detailed argument that the measurable physical effects usually attributed to the vacuum electromagnetic field cannot be explained by that field alone, but require in addition a contribution from the self-energy of the electrons, or their radiation reaction. He writes: "The radiation reaction and the vacuum fields are two aspects of the same thing when it comes to physical interpretations of various QED processes including the Lamb shift, van der Waals forces, and Casimir effects.
This point of view is also stated by Jaffe (2005): "The Casimir force can be calculated without reference to vacuum fluctuations, and like all other observable effects in QED, it vanishes as the fine structure constant, α, goes to zero."
References and notesEdit
- Astrid Lambrecht (2002). Hartmut Figger; Dieter Meschede; Claus Zimmermann, eds. Observing mechanical dissipation in the quantum vacuum: an experimental challenge; in Laser physics at the limits. Berlin/New York: Springer. p. 197. ISBN 3-540-42418-0.
- Christopher Ray (1991). Time, space and philosophy. London/New York: Routledge. Chapter 10, p. 205. ISBN 0-415-03221-0.
- AIP Physics News Update,1996
- Physical Review Focus Dec. 1998
- Walter Dittrich & Gies H (2000). Probing the quantum vacuum: perturbative effective action approach. Berlin: Springer. ISBN 3-540-67428-4.
- For an historical discussion, see for example Ari Ben-Menaḥem, ed. (2009). "Quantum electrodynamics (QED)". Historical Encyclopedia of Natural and Mathematical Sciences. 1 (5th ed.). Springer. pp. 4892 ff. ISBN 3-540-68831-5. For the Nobel prize details and the Nobel lectures by these authors see "The Nobel Prize in Physics 1965". Nobelprize.org. Retrieved 2012-02-06.
- Jean Letessier; Johann Rafelski (2002). Hadrons and Quark-Gluon Plasma. Cambridge University Press. p. 37 ff. ISBN 0-521-38536-9.
- Sean Carroll, Sr Research Associate - Physics, California Institute of Technology, June 22, 2006 C-SPAN broadcast of Cosmology at Yearly Kos Science Panel, Part 1
- Bednorz, Adam (November 2013). "Relativistic invariance of the vacuum". The European Physical Journal C. 73 (12): 2654. arXiv: . Bibcode:2013EPJC...73.2654B. doi:10.1140/epjc/s10052-013-2654-9. Retrieved 26 November 2013.
- David Delphenich (2006). "Nonlinear Electrodynamics and QED". arXiv: .
- Klein, James J. and B. P. Nigam, Birefringence of the vacuum, Physical Review vol. 135, p. B1279-B1280 (1964).
- Mourou, G. A., T. Tajima, and S. V. Bulanov, Optics in the relativistic regime; § XI Nonlinear QED, Reviews of Modern Physics vol. 78 (no. 2), 309-371 (2006) pdf file[permanent dead link].
- Holger Gies; Joerg Jaeckel; Andreas Ringwald (2006). "Polarized Light Propagating in a Magnetic Field as a Probe of Millicharged Fermions". Physical Review Letters. 97 (14): 140402. arXiv: . Bibcode:2006PhRvL..97n0402G. doi:10.1103/PhysRevLett.97.140402. PMID 17155223.
- Davis; Joseph Harris; Gammon; Smolyaninov; Kyuman Cho (2007). "Experimental Challenges Involved in Searches for Axion-Like Particles and Nonlinear Quantum Electrodynamic Effects by Sensitive Optical Techniques". arXiv: [hep-th].
Myron Wyn Evans; Stanisław Kielich (1994). Modern nonlinear optics, Volume 85, Part 3. John Wiley & Sons. p. 462. ISBN 0-471-57548-8.
For all field states that have classical analog the field quadrature variances are also greater than or equal to this commutator.
- David Nikolaevich Klyshko (1988). Photons and nonlinear optics. Taylor & Francis. p. 126. ISBN 2-88124-669-9.
Milton K. Munitz (1990). Cosmic Understanding: Philosophy and Science of the Universe. Princeton University Press. p. 132. ISBN 0-691-02059-0.
The spontaneous, temporary emergence of particles from vacuum is called a "vacuum fluctuation".
- For an example, see P. C. W. Davies (1982). The accidental universe. Cambridge University Press. p. 106. ISBN 0-521-28692-1.
A vaguer description is provided by Jonathan Allday (2002). Quarks, leptons and the big bang (2nd ed.). CRC Press. pp. 224 ff. ISBN 0-7503-0806-0.
The interaction will last for a certain duration Δt. This implies that the amplitude for the total energy involved in the interaction is spread over a range of energies ΔE.
- This "borrowing" idea has led to proposals for using the zero-point energy of vacuum as an infinite reservoir and a variety of "camps" about this interpretation. See, for example, Moray B. King (2001). Quest for zero point energy: engineering principles for 'free energy' inventions. Adventures Unlimited Press. pp. 124 ff. ISBN 0-932813-94-1.
- Quantities satisfying a canonical commutation rule are said to be noncompatible observables, by which is meant that they can both be measured simultaneously only with limited precision. See Kiyosi Itô (1993). "§ 351 (XX.23) C: Canonical commutation relations". Encyclopedic dictionary of mathematics (2nd ed.). MIT Press. p. 1303. ISBN 0-262-59020-4.
- Paul Busch; Marian Grabowski; Pekka J. Lahti (1995). "§III.4: Energy and time". Operational quantum physics. Springer. pp. 77 ff. ISBN 3-540-59358-6.
- For a review, see Paul Busch (2008). "Chapter 3: The Time–Energy Uncertainty Relation". In J.G. Muga; R. Sala Mayato; Í.L. Egusquiza. Time in Quantum Mechanics (2nd ed.). Springer. pp. 73 ff. arXiv: . Bibcode:2002tqm..conf...69B. ISBN 3-540-73472-4.
- Fowler, R., Guggenheim, E.A. (1965). Statistical Thermodynamics. A Version of Statistical Mechanics for Students of Physics and Chemistry, reprinted with corrections, Cambridge University Press, London, page 224.
- Partington, J.R. (1949). An Advanced Treatise on Physical Chemistry, volume 1, Fundamental Principles. The Properties of Gases, Longmans, Green and Co., London, page 220.
- Wilks, J. (1971). The Third Law of Thermodynamics, Chapter 6 in Thermodynamics, volume 1, ed. W. Jost, of H. Eyring, D. Henderson, W. Jost, Physical Chemistry. An Advanced Treatise, Academic Press, New York, page 477.
- Bailyn, M. (1994). A Survey of Thermodynamics, American Institute of Physics, New York, ISBN 0-88318-797-3, page 342.
- Jauch, J.M., Rohrlich, F. (1955/1980). The Theory of Photons and Electrons. The Relativistic Quantum Field Theory of Charged Particles with Spin One-half, second expanded edition, Springer-Verlag, New York, ISBN 0-387-07295-0, pages 287–288.
- Milonni, P.W. (1994). The Quantum Vacuum. An Introduction to Quantum Electrodynamics, Academic Press, Inc., Boston, ISBN 0-12-498080-5, page xv.
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- Schwinger, J.; DeRaad, L.L.; Milton, K.A. (1978). "Casimir effect in dielectrics". Annals of Physics. 115: 1–23. Bibcode:1978AnPhy.115....1S. doi:10.1016/0003-4916(78)90172-0.
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- Free pdf copy of The Structured Vacuum - thinking about nothing by Johann Rafelski and Berndt Muller (1985) ISBN 3-87144-889-3.
- M.E. Peskin and D.V. Schroeder, An introduction to Quantum Field Theory.
- H. Genz, Nothingness: The Science of Empty Space
- Puthoff, H. E.; Little, S. R.; Ibison, M. (2001). "Engineering the Zero-Point Field and Polarizable Vacuum for Interstellar Flight". arXiv: .
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Sterile neutrinos (or inert neutrinos) are a hypothetical particle (neutral leptons – neutrinos) that interact only via gravity and do not interact via any of the fundamental interactions of the Standard Model. The term sterile neutrino is used to distinguish them from the known active neutrinos in the Standard Model, which are charged under the weak interaction.
|Interactions||gravity; other potential unknown interactions|
|Weak isospin projection||0|
|B − L||depends on L charge assignment|
This term usually refers to neutrinos with right-handed chirality (see right-handed neutrino), which may be added to the Standard Model. Occasionally it is used in a more general sense for any neutral fermion.
The existence of right-handed neutrinos is theoretically well-motivated, as all other known fermions have been observed with left and right chirality, and they can explain the observed active neutrino masses in a natural way. The mass of the right-handed neutrinos themselves is unknown and could have any value between 1015 GeV and less than one eV.
The number of sterile neutrino types (should they exist) is not yet theoretically established. This is in contrast to the number of active neutrino types, which has to equal that of charged leptons and quark generations to ensure the anomaly freedom of the electroweak interaction.
The search for sterile neutrinos is an active area of particle physics. If they exist and their mass is smaller than the energies of particles in the experiment, they can be produced in the laboratory, either by mixing between active and sterile neutrinos or in high energy particle collisions. If they are heavier, the only directly observable consequence of their existence would be the observed active neutrino masses. They may, however, be responsible for a number of unexplained phenomena in physical cosmology and astrophysics, including dark matter, baryogenesis or dark radiation. In May 2018, physicists of the MiniBooNE experiment reported a stronger neutrino oscillation signal than expected, a possible hint of sterile neutrinos.
Sterile neutrinos may be neutral heavy leptons (NHLs), also called heavy neutral leptons (HNLs).
Experimental results show that all produced and observed neutrinos have left-handed helicities (spin antiparallel to momentum), and all antineutrinos have right-handed helicities, within the margin of error. In the massless limit, it means that only one of two possible chiralities is observed for either particle. These are the only helicities (and chiralities) included in the Standard Model of particle interactions.
Recent experiments such as neutrino oscillation, however, have shown that neutrinos have a non-zero mass, which is not predicted by the Standard Model and suggests new, unknown physics. This unexpected mass explains neutrinos with right-handed helicity and antineutrinos with left-handed helicity: since they do not move at the speed of light, their helicity is not relativistic invariant (it is possible to move faster than them and observe the opposite helicity). Yet all neutrinos have been observed with left-handed chirality, and all antineutrinos right-handed. Chirality is a fundamental property of particles and is relativistic invariant: it is the same regardless of the particle's speed and mass in every inertial reference frame, even though chirality is not conserved in the propagation of a free particle (a particle that starts out left-handed can evolve a right-handed component). The question, thus, remains: can neutrinos and antineutrinos be differentiated just by chirality? Or do right-handed neutrinos and left-handed antineutrinos exist as separate particles?
Such particles would belong to a singlet representation with respect to the strong interaction and the weak interaction, having zero electric charge, zero weak hypercharge, zero weak isospin, and, as with the other leptons, no color, although they do have a B-L of −1. If the standard model is embedded in a hypothetical SO(10) grand unified theory, they can be assigned an X charge of −5. The left-handed anti-neutrino has a B-L of 1 and an X charge of +5.
Due to the lack of charge, sterile neutrinos would not interact electromagnetically, weakly, or strongly, making them extremely difficult to detect. They have Yukawa interactions with ordinary leptons and Higgs bosons, which via the Higgs mechanism lead to mixing with ordinary neutrinos. In experiments involving energies larger than their mass they would participate in all processes in which ordinary neutrinos take part, but with a quantum mechanical probability that is suppressed by the small mixing angle. That makes it possible to produce them in experiments if they are light enough. They would also interact gravitationally due to their mass, however, and if they are heavy enough, they could explain cold dark matter or warm dark matter. In some grand unification theories, such as SO(10), they also interact via gauge interactions which are extremely suppressed at ordinary energies because their gauge boson is extremely massive. They do not appear at all in some other GUTs, such as the Georgi–Glashow model (i.e. all its SU(5) charges or quantum numbers are zero).
All particles are initially massless under the Standard Model, since there are no Dirac mass terms in the Standard Model's Lagrangian. The only mass terms are generated by the Higgs mechanism, which produces non-zero Yukawa couplings between the left-handed components of fermions, the Higgs field, and their right-handed components. This occurs when the SU(2) doublet Higgs field acquires its non-zero vacuum expectation value, , spontaneously breaking its SU(2)L × U(1) symmetry, and thus yielding non-zero Yukawa couplings:
Such is the case for charged leptons, like the electron; but within the standard model, the right-handed neutrino does not exist, so even with a Yukawa coupling neutrinos remain massless. In other words, there are no mass terms for neutrinos under the Standard Model: the model only contains a left-handed neutrino and its antiparticle, a right-handed antineutrino, for each generation, produced in weak eigenstates during weak interactions. See neutrino masses in the Standard Model for a detailed explanation.
In the seesaw mechanism, one eigenvector of the neutrino mass matrix, which includes sterile neutrinos, is predicted to be significantly heavier than the other.
A sterile neutrino would have the same weak hypercharge, weak isospin, and mass as its antiparticle. For any charged particle, for example the electron, this is not the case: its antiparticle, the positron, has opposite electric charge, among other opposite charges. Similarly, an up quark has a charge of + 2⁄3 and (for example) a color charge of red, while its antiparticle has an electric charge of − 2⁄3 and a color charge of anti-red.
Dirac and Majorana termsEdit
Sterile neutrinos allow the introduction of a Dirac mass term as usual. This can yield the observed neutrino mass, but it requires that the strength of the Yukawa coupling be much weaker for the electron neutrino than the electron, without explanation. Similar problems (although less severe) are observed in the quark sector, where the top and bottom masses differ by a factor of 40.
Unlike for the left-handed neutrino, a Majorana mass term can be added for a sterile neutrino without violating local symmetries (weak isospin and weak hypercharge) since it has no weak charge. However, this would still violate total lepton number.
It is possible to include both Dirac and Majorana terms: this is done in the seesaw mechanism (below). In addition to satisfying the Majorana equation, if the neutrino were also its own antiparticle, then it would be the first Majorana fermion. In that case, it could annihilate with another neutrino, allowing neutrinoless double beta decay. The other case is that it is a Dirac fermion, which is not its own antiparticle.
To put this in mathematical terms, we have to make use of the transformation properties of particles. For free fields, a Majorana field is defined as an eigenstate of charge conjugation. However, neutrinos interact only via the weak interactions, which are not invariant under charge conjugation (C), so an interacting Majorana neutrino cannot be an eigenstate of C. The generalized definition is: "a Majorana neutrino field is an eigenstate of the CP transformation". Consequently, Majorana and Dirac neutrinos would behave differently under CP transformations (actually Lorentz and CPT transformations). Also, a massive Dirac neutrino would have nonzero magnetic and electric dipole moments, whereas a Majorana neutrino would not. However, the Majorana and Dirac neutrinos are different only if their rest mass is not zero. For Dirac neutrinos, the dipole moments are proportional to mass and would vanish for a massless particle. Both Majorana and Dirac mass terms however can appear in the mass Lagrangian.
In addition to the left-handed neutrino, which couples to its family charged lepton in weak charged currents, if there is also a right-handed sterile neutrino partner (a weak isosinglet with zero charge) then it is possible to add a Majorana mass term without violating electroweak symmetry. Both neutrinos have mass and handedness is no longer preserved (thus "left or right-handed neutrino" means that the state is mostly left or right-handed). To get the neutrino mass eigenstates, we have to diagonalize the general mass matrix :
where is big and is of intermediate size terms.
Apart from empirical evidence, there is also a theoretical justification for the seesaw mechanism in various extensions to the Standard Model. Both Grand Unification Theories (GUTs) and left-right symmetrical models predict the following relation:
According to GUTs and left-right models, the right-handed neutrino is extremely heavy: MNHL ≈ – 1051012 GeV, while the smaller eigenvalue is approximately equal to
This is the seesaw mechanism: as the sterile right-handed neutrino gets heavier, the normal left-handed neutrino gets lighter. The left-handed neutrino is a mixture of two Majorana neutrinos, and this mixing process is how sterile neutrino mass is generated.
The production and decay of sterile neutrinos could happen through the mixing with virtual ("off mass shell") neutrinos. There were several experiments set up to discover or observe NHLs, for example the NuTeV (E815) experiment at Fermilab or LEP-l3 at CERN. They all led to establishing limits to observation, rather than actual observation of those particles. If they are indeed a constituent of dark matter, sensitive X-ray detectors would be needed to observe the radiation emitted by their decays.
Sterile neutrinos may mix with ordinary neutrinos via a Dirac mass after electroweak symmetry breaking, in analogy to quarks and charged leptons. Sterile neutrinos and (in more-complicated models) ordinary neutrinos may also have Majorana masses. In the type 1 seesaw mechanism both Dirac and Majorana masses are used to drive ordinary neutrino masses down and make the sterile neutrinos much heavier than the Standard Model's interacting neutrinos. In some models[which?] the heavy neutrinos can be as heavy as the GUT scale (). In other models[ ≈1015 GeVwhich?] they could be lighter than the weak gauge bosons W and Z as in the so-called νMSM model where their masses are between GeV and keV. A light (with the mass ) sterile neutrino was suggested as a possible explanation of the results of the ≈1 eVLiquid Scintillator Neutrino Detector experiment. On April 11, 2007, researchers at the MiniBooNE experiment at Fermilab announced that they had not found any evidence supporting the existence of such a sterile neutrino. More-recent results and analysis have provided some support for the existence of the sterile neutrino. Two separate detectors near a nuclear reactor in France found 3% of anti-neutrinos missing. They suggested the existence of a 4th neutrino with a mass of 0.7 keV. Sterile neutrinos are also candidates for dark radiation. Daya Bay has also searched for a light sterile neutrino and excluded some mass regions. Daya Bay Collaboration measured the anti-neutrino energy spectrum, and found that anti-neutrinos at an energy of around 5 MeV are in excess relative to theoretical expectations. It also recorded 6% missing anti-neutrinos. This could suggest that sterile neutrinos exist or that our understanding of neutrinos is not complete.
The number of neutrinos and the masses of the particles can have large-scale effects that shape the appearance of the cosmic microwave background. The total number of neutrino species, for instance, affects the rate at which the cosmos expanded in its earliest epochs: more neutrinos means a faster expansion. The Planck Satellite 2013 data release is compatible with the existence of a sterile neutrino. The implied mass range is from 0 to 3 eV.[not in citation given (See discussion.)] In 2016, scientists at the IceCube Neutrino Observatory did not find any evidence for the sterile neutrino. However, in May 2018, physicists of the MiniBooNE experiment reported a stronger neutrino oscillation signal than expected, a possible hint of sterile neutrinos.
- MiniBooNE at Fermilab
- A major physics experiment just detected a particle that shouldn't exist Live Science (2018)
- Marco Drewes (2013). "The Phenomenology of Right Handed Neutrinos". International Journal of Modern Physics E. 22 (8): 1330019. arXiv: . Bibcode:2013IJMPE..2230019D. doi:10.1142/S0218301313300191.
- Letzter, Rafi (1 June 2018). "A Major Physics Experiment Just Detected A Particle That Shouldn't Exist". LiveScience. Retrieved 3 June 2018.
- Collaboration, MiniBooNE; Aguilar-Arevalo, A. A; Brown, B. C; Bugel, L; Cheng, G; Conrad, J. M; Cooper, R. L; Dharmapalan, R; Diaz, A; Djurcic, Z; Finley, D. A; Ford, R; Garcia, F. G; Garvey, G. T; Grange, J; Huang, E. -C; Huelsnitz, W; Ignarra, C; Johnson, R. A; Karagiorgi, G; Katori, T; Kobilarcik, T; Louis, W. C; Mariani, C; Marsh, W; Mills, G. B; Mirabal, J; Monroe, J; Moore, C. D; et al. (2018). "Observation of a Significant Excess of Electron-Like Events in the MiniBooNE Short-Baseline Neutrino Experiment". arXiv: [hep-ex].
- Battison, Leila (2011-09-16). "Dwarf galaxies suggest dark matter theory may be wrong". BBC News. Retrieved 2011-09-18.
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- The Reactor Antineutrino Anomaly
- An, F. P; Balantekin, A. B; Band, H. R; Beriguete, W; Bishai, M; Blyth, S; Butorov, I; Cao, G. F; Cao, J; Chan, Y. L; Chang, J. F; Chang, L. C; Chang, Y; Chasman, C; Chen, H; Chen, Q. Y; Chen, S. M; Chen, X; Chen, X; Chen, Y. X; Chen, Y; Cheng, Y. P; Cherwinka, J. J; Chu, M. C; Cummings, J. P; De Arcos, J; Deng, Z. Y; Ding, Y. Y; Diwan, M. V; et al. (1 October 2014). "Search for a Light Sterile Neutrino at Daya Bay". Phys. Rev. Lett. 113 (14): 141802. arXiv: . Bibcode:2014PhRvL.113n1802A. doi:10.1103/PhysRevLett.113.141802.
- Ade, P.A.R.; et al. (Planck Collaboration) (2013). "Planck 2013 results. XVI. Cosmological parameters". Astronomy & Astrophysics. 571: A16. arXiv: [astro-ph.CO]. Bibcode:2014A&A...571A..16P. doi:10.1051/0004-6361/201321591.
- "Icy telescope throws cold water on sterile neutrino theory". Nature. 8 August 2016. Retrieved 12 August 2016.
- M. Drewes (2013). "The Phenomenology of Right Handed Neutrinos". International Journal of Modern Physics E. 22 (8): 1330019. arXiv: . Bibcode:2013IJMPE..2230019D. doi:10.1142/S0218301313300191.
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Gaseous molecules and ions, and even dust grains, can accumulate charge in the interstellar medium (ISM) by harvesting the energy of UV photons, cosmic rays, helium ions and metastable atoms. This Perspective views the various modes of gas-phase formation of multiply-charged cations and the possible impact of their reactions on the chemical and ionization structure of the ISM, in the light of what is still very limited knowledge. Emphasis is given to gas-phase reactions of multiply-charged cations with atoms, molecules and electrons that lead to charge reduction, charge separation and chemical bond formation and these are examined for multiply-charged atoms, small molecules, hydrocarbons, polycyclic aromatic hydrocarbons and fullerenes, primarily as dications but also as a function of charge state. The increased electrostatic interaction due to multiple charge is seen to promote bonding to individual charge sites on large molecules (e. g. fullerenes) and allow ensuing "surface'' chemistry under the influence of Coulomb repulsion. The unique ability of multiply charged cations to undergo charge separation reactions, either unimolecular or bimolecular, can feature in the production in the ISM of internally cold, but translationally hot, cations of lower charge state or hot atoms that may provide the driving force for subsequent chemical reactions in what is otherwise an ultracold environment. Available chemical kinetic models that account for the role of multiply-charged ions in the ISM are few and of limited scope and the observation of these ions in the ISM has remained elusive.
Mendeley saves you time finding and organizing research
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A solar flare is a sudden flash of increased Sun's brightness, usually observed near its surface. Powerful flares are often, but not always, accompanied by a coronal mass ejection, with the most powerful ones barely detectable in the total solar irradiance.
Solar flares occur in a power-law spectrum of magnitudes; an energy release of typically 1020 joules of energy is considered to be the median for a well-observed event, while a major event can emit up to 1025 joules
The flare ejects clouds of electrons, ions, and atoms along with the electromagnetic waves through the Sun's corona into outer space. The phenomenon therefore provides an early example of multi-messenger astronomy. If ejection is in the direction of the Earth the particles hitting the upper atmosphere can cause bright auroras, and may even disrupt long range radio communication. It usually takes a day or two for these clouds to reach Earth. The term is also used to refer to similar phenomena in other stars, where the term stellar flare applies.
- 1 Physics
- 2 Cause
- 3 Classification
- 4 Hazards
- 5 Observations
- 6 Flare spray
- 7 Prediction
- 8 See also
- 9 References
- 10 External links
Solar flares affect all layers of the solar atmosphere (photosphere, chromosphere, and corona), when the plasma medium is heated to tens of millions of kelvin, while the cosmic-ray-like electrons, protons, and heavier ions are accelerated to near the speed of light. They produce radiation across the electromagnetic spectrum at all wavelengths, from radio waves to gamma rays, although most of the energy is spread over frequencies outside the visual range and for this reason the majority of the flares are not visible to the naked eye and must be observed with special instruments. Flares occur in active regions around sunspots, where intense magnetic fields penetrate the photosphere to link the corona to the solar interior. Flares are powered by the sudden (timescales of minutes to tens of minutes) release of magnetic energy stored in the corona. The same energy releases may produce coronal mass ejections (CME), although the relation between CMEs and flares is still not well established.
X-rays and UV radiation emitted by solar flares can affect Earth's ionosphere and disrupt long-range radio communications. Direct radio emission at decimetric wavelengths may disturb the operation of radars and other devices that use those frequencies.
Solar flares were first observed on the Sun by Richard Christopher Carrington and independently by Richard Hodgson in 1859 as localized visible brightenings of small areas within a sunspot group. Stellar flares can be inferred by looking at the lightcurves produced from the telescope or satellite data of variety of other stars.
The frequency of occurrence of solar flares varies, from several per day when the Sun is particularly "active" to less than one every week when the Sun is "quiet", following the 11-year cycle (the solar cycle). Large flares are less frequent than smaller ones.
On July 23, 2012, a massive, and potentially damaging, solar superstorm (solar flare, coronal mass ejection, solar EMP) barely missed Earth, according to NASA. According to NASA, there may be as much as a 12% chance of a similar event occurring between 2012 and 2022, although because this particular figure was based on an extreme extrapolation of the calculated frequency of future storms, the actual probability of this is quite uncertain.
Flares occur when sped up charged particles, mainly electrons, interact with the plasma medium. Abundant evidence implicates that the phenomenon of magnetic reconnection, also describable as magnetic flux transfer, leads to this copious acceleration of charged particles. On the Sun, magnetic reconnection may happen on solar arcades – a series of closely occurring loops following magnetic lines of force. These lines of force quickly reconnect into a low arcade of loops leaving a helix of magnetic field unconnected to the rest of the arcade. The sudden release of energy in this reconnection is the origin of the particle acceleration. The unconnected magnetic helical field and the material that it contains may violently expand outwards forming a coronal mass ejection. This also explains why solar flares typically erupt from what are known as the active regions on the Sun where magnetic fields are much stronger on average.
Although there is a general agreement on the source of a flare's energy, the mechanisms involved are still not well known. It is not clear how the magnetic energy is transformed into the particle kinetic energy, nor is it known how some particles can be accelerated to the GeV range (109 electron volt) and beyond. There are also some inconsistencies regarding the total number of accelerated particles, which sometimes seems to be greater than the total number in the coronal loop. Scientists are unable to forecast flares, even to this day.
The classification system for solar flares uses the letters A, B, C, M or X, according to the peak flux in watts per square metre (W/m2) of X-rays with wavelengths 100 to 800 picometre, as measured at the Earth's orbital distance by the GOES spacecraft.
|Classification||Peak flux range at 100–800 picometre|
|B||10−7 – 10−6|
|C||10−6 – 10−5|
|M||10−5 – 10−4|
The strength of an event within a class is noted by a numerical suffix ranging from 1 to 9, which is also the factor for that event within the class. Hence, an X2 flare is twice the strength of an X1 flare, an X3 flare is three times as powerful as an X1, and only 50% more powerful than an X2. An X2 is four times more powerful than an M5 flare.
An earlier flare classification is based on Hα spectral observations. The scheme uses both the intensity and emitting surface. The classification in intensity is qualitative, referring to the flares as: faint (f), normal (n) or brilliant (b). The emitting surface is measured in terms of millionths of the hemisphere and is described below. (The total hemisphere area AH = 15.5 × 1012 km2.)
(millionths of hemisphere)
A flare then is classified taking S or a number that represents its size and a letter that represents its peak intensity, v.g.: Sn is a normal sunflare.
Solar flares strongly influence the local space weather in the vicinity of the Earth. They can produce streams of highly energetic particles in the solar wind or stellar wind, known as a solar proton event. These particles can impact the Earth's magnetosphere (see main article at geomagnetic storm), and present radiation hazards to spacecraft and astronauts. Additionally, massive solar flares are sometimes accompanied by coronal mass ejections (CMEs) which can trigger geomagnetic storms that have been known to disable satellites and knock out terrestrial electric power grids for extended periods of time.
The soft X-ray flux of X class flares increases the ionization of the upper atmosphere, which can interfere with short-wave radio communication and can heat the outer atmosphere and thus increase the drag on low orbiting satellites, leading to orbital decay. Energetic particles in the magnetosphere contribute to the aurora borealis and aurora australis. Energy in the form of hard x-rays can be damaging to spacecraft electronics and are generally the result of large plasma ejection in the upper chromosphere.
The radiation risks posed by solar flares are a major concern in discussions of a manned mission to Mars, the Moon, or other planets. Energetic protons can pass through the human body, causing biochemical damage, presenting a hazard to astronauts during interplanetary travel. Some kind of physical or magnetic shielding would be required to protect the astronauts. Most proton storms take at least two hours from the time of visual detection to reach Earth's orbit. A solar flare on January 20, 2005 released the highest concentration of protons ever directly measured, giving astronauts as little as 15 minutes to reach shelter.
Flares produce radiation across the electromagnetic spectrum, although with different intensity. They are not very intense at white light, but they can be very bright at particular atomic lines. They normally produce bremsstrahlung in X-rays and synchrotron radiation in radio.
Richard Carrington observed a flare for the first time on 1 September 1859 projecting the image produced by an optical telescope through a broad-band filter. It was an extraordinarily intense white light flare. Since flares produce copious amounts of radiation at Hα, adding a narrow ( ≈1 Å) passband filter centered at this wavelength to the optical telescope, allows the observation of not very bright flares with small telescopes. For years Hα was the main, if not the only, source of information about solar flares. Other passband filters are also used.
During World War II, on February 25 and 26, 1942, British radar operators observed radiation that Stanley Hey interpreted as solar emission. Their discovery did not go public until the end of the conflict. The same year Southworth also observed the Sun in radio, but as with Hey, his observations were only known after 1945. In 1943 Grote Reber was the first to report radioastronomical observations of the Sun at 160 MHz. The fast development of radioastronomy revealed new peculiarities of the solar activity like storms and bursts related to the flares. Today ground-based radiotelescopes observe the Sun from c. 15 MHz up to 400 GHz.
Since the beginning of space exploration, telescopes have been sent to space, where they work at wavelengths shorter than UV, which are completely absorbed by the atmosphere, and where flares may be very bright. Since the 1970s, the GOES series of satellites observe the Sun in soft X-rays, and their observations became the standard measure of flares, diminishing the importance of the Hα classification. Hard X-rays were observed by many different instruments, the most important today being the Reuven Ramaty High Energy Solar Spectroscopic Imager (RHESSI). Nonetheless, UV observations are today the stars of solar imaging with their incredible fine details that reveal the complexity of the solar corona. Spacecraft may also bring radio detectors at extremely long wavelengths (as long as a few kilometers) that cannot propagate through the ionosphere.
- Big Bear Solar Observatory, located in Big Bear Lake, California and operated by the New Jersey Institute of Technology, is a solar dedicated observatory with different instruments, as well as a huge data bank of full disk Hα images.
- Swedish 1-m Solar Telescope, operated by the Institute for Solar Physics (Sweden), is located in the Observatorio del Roque de los Muchachos on the island of La Palma (Spain).
- McMath-Pierce Solar Telescope, located at Kitt Peak National Observatory in Arizona, is the world's largest solar telescope.
- Nançay Radioheliographe (NRH) is an interferometer composed of 48 antennas observing at meter-decimeter wavelengths. The radioheliographe is installed at the Nançay Radio Observatory, France.
- Owens Valley Solar Array (OVSA) is a radio interferometer operated by the New Jersey Institute of Technology consisting of 7 antennas, observing from 1 to 18 GHz in both left and right circular polarization. OVSA is located in Owens Valley, California. It is now being improved, increasing to 15 the total number of antennas and upgrading its control system.
- Nobeyama Radioheliograph (NoRH) is an interferometer installed at the Nobeyama Radio Observatory, Japan, formed by 84 small (80 cm) antennas, with receivers at 17 GHz (left and right polarization) and 34 GHz operating simultaneously. It continuously observes the Sun, producing daily snapshots.
- Siberian Solar Radio Telescope (SSRT) is a special-purpose solar radio telescope designed for studying solar activity in the microwave range (5.7 GHz) where the processes occurring in the solar corona are accessible to observation over the entire solar disk. It is a crossed interferometer, consisting of two arrays of 128x128 parabolic antennas 2.5 meters in diameter each, spaced equidistantly at 4.9 meters and oriented in the E-W and N-S directions. It is located in a wooded valley separating two mountain ridges of the Eastern Sayan Mountains and Khamar-Daban, 220 km from Irkutsk, Russia.
- Nobeyama Radio Polarimeters are a set of radio telescopes installed at the Nobeyama Radio Observatory that continuously observes the full Sun (no images) at the frequencies of 1, 2, 3.75, 9.4, 17, 35, and 80 GHz, at left and right circular polarization.
- Solar Submillimeter Telescope is a single dish telescope, that observes continuously the Sun at 212 and 405 GHz. It is installed at Complejo Astronomico El Leoncito in Argentina. It has a focal array composed by 4 beams at 212 GHz and 2 at 405 GHz, therefore it can instantaneously locate the position of the emitting source SST is the only solar submillimeter telescope currently in operation.
- Polarization Emission of Millimeter Activity at the Sun (POEMAS) is a system of two circular polarization solar radio telescopes, for observations of the Sun at 45 and 90 GHz. The novel characteristic of these instruments is the capability to measure circular right- and left-hand polarizations at these high frequencies. The system is installed at Complejo Astronomico El Leoncito in Argentina. It started operations in November 2011. In November 2013 it went offline for repairs. It is expected to return to observing in January 2015.
- Bleien Radio Observatory is a set of radio telescopes operating near Gränichen (Switzerland). They continuously observe the solar flare radio emission from 10 MHz (ionospheric limit) to 5 GHz. The broadband spectrometers are known as Phoenix and CALLISTO.
The following spacecraft missions have flares as their main observation target.
- Yohkoh – The Yohkoh (originally Solar A) spacecraft observed the Sun with a variety of instruments from its launch in 1991 until its failure in 2001. The observations spanned a period from one solar maximum to the next. Two instruments of particular use for flare observations were the Soft X-ray Telescope (SXT), a glancing incidence low energy X-ray telescope for photon energies of order 1 keV, and the Hard X-ray Telescope (HXT), a collimation counting instrument which produced images in higher energy X-rays (15-92 keV) by image synthesis.
- WIND – The Wind spacecraft is devoted to the study of the interplanetary medium. Since the Solar Wind is its main driver, solar flares effects can be traced with the instruments aboard Wind. Some of the WIND experiments are: a very low frequency spectrometer, (WAVES), particles detectors (EPACT, SWE) and a magnetometer (MFI).
- GOES – The GOES spacecraft are satellites in geostationary orbits around the Earth that have measured the soft X-ray flux from the Sun since the mid-1970s, following the use of similar instruments on the Solrad satellites. GOES X-ray observations are commonly used to classify flares, with A, B, C, M, and X representing different powers of ten – an X-class flare has a peak 1-8 Å flux above 0.0001 W/m2.
- RHESSI – The Reuven Ramaty High Energy Solar Spectral Imager is designed to image solar flares in energetic photons from soft X rays (c. 3 keV) to gamma rays (up to c. 20 MeV) and to provide high resolution spectroscopy up to gamma-ray energies of c. 20 MeV. Furthermore, it has the capability to perform spatially resolved spectroscopy with high spectral resolution.
- SOHO – The Solar and Heliospheric Observatory is collaboration between the ESA and NASA which is in operation since December 1995. It carries 12 different instruments, among them the Extreme ultraviolet Imaging Telescope (EIT), the Large Angle and Spectrometric Coronagraph (LASCO) and the Michelson Doppler Imager (MDI). SOHO is in a halo orbit around the earth-sun L1 point.
- TRACE – The Transition Region and Coronal Explorer is a NASA Small Explorer program (SMEX) to image the solar corona and transition region at high angular and temporal resolution. It has passband filters at 173 Å, 195 Å, 284 Å, 1600 Å with a spatial resolution of 0.5 arc sec, the best at these wavelengths.
- SDO – The Solar Dynamics Observatory is a NASA project composed of 3 different instruments: the Helioseismic and Magnetic Imager (HMI), the Atmospheric Imaging Assembly (AIA) and the Extreme Ultraviolet Variability Experiment (EVE). It has been operating since February 2010 in a geosynchronous earth orbit.
- Hinode –The Hinode spacecraft, originally called Solar B, was launched by the Japan Aerospace Exploration Agency in September 2006 to observe solar flares in more precise detail. Its instrumentation, supplied by an international collaboration including Norway, the U.K., the U.S., and Africa focuses on the powerful magnetic fields thought to be the source of solar flares. Such studies shed light on the causes of this activity, possibly helping to forecast future flares and thus minimize their dangerous effects on satellites and astronauts.
- ACE – The Advanced Composition Explorer was launched in 1997 into a halo orbit around the earth-sun L1 point. It carries spectrometers, magnetometers and charged particle detectors to analyze the solar wind. The Real Time Solar Wind (RTSW) beacon is continually monitored by a network of NOAA-sponsored ground stations to provide early warning of earth-bound CMEs.
- MAVEN – The Mars Atmosphere and Volatile EvolutioN (MAVEN) mission, which launched from Cape Canaveral Air Force Station on November 18, 2013, is the first mission devoted to understanding the Martian upper atmosphere. The goal of MAVEN is to determine the role that loss of atmospheric gas to space played in changing the Martian climate through time. The Extreme Ultraviolet (EUV) monitor on MAVEN is part of the Langmuir Probe and Waves (LPW) instrument and measures solar EUV input and variability, and wave heating of the Martian upper atmosphere.
In addition to these solar observing facilities, many non-solar astronomical satellites observe flares either intentionally (e.g., NuSTAR), or simply because the penetrating hard radiations coming from a flare can readily penetrate most forms of shielding.
Examples of large solar flares
The most powerful flare ever observed was the first one to be observed, on September 1, 1859, and was reported by British astronomer Richard Carrington and independently by an observer named Richard Hodgson. The event is named the Solar storm of 1859, or the "Carrington event". The flare was visible to a naked eye (in white light), and produced stunning auroras down to tropical latitudes such as Cuba or Hawaii, and set telegraph systems on fire. The flare left a trace in Greenland ice in the form of nitrates and beryllium-10, which allow its strength to be measured today. Cliver and Svalgaard reconstructed the effects of this flare and compared with other events of the last 150 years. In their words: "While the 1859 event has close rivals or superiors in each of the above categories of space weather activity, it is the only documented event of the last ∼150 years that appears at or near the top of all of the lists."
In modern times, the largest solar flare measured with instruments occurred on November 4, 2003. This event saturated the GOES detectors, and because of this its classification is only approximate. Initially, extrapolating the GOES curve, it was estimated to be X28. Later analysis of the ionospheric effects suggested increasing this estimate to X45. This event produced the first clear evidence of a new spectral component above 100 GHz.
Other large solar flares also occurred on April 2, 2001 (X20), October 28, 2003 (X17.2 and 10), September 7, 2005 (X17), February 17, 2011 (X2), August 9, 2011 (X6.9), March 7, 2012 (X5.4), July 6, 2012 (X1.1). On July 6, 2012, a solar storm hit just after midnight UK time, when an X1.1 solar flare fired out of the AR1515 sunspot. Another X1.4 solar flare from AR 1520 region of the Sun, second in the week, reached the Earth on July 15, 2012 with a geomagnetic storm of G1–G2 level. A X1.8-class flare was recorded on October 24, 2012. There has been major solar flare activity in early 2013, notably within a 48-hour period starting on May 12, 2013, a total of four X-class solar flares were emitted ranging from an X1.2 and upwards of an X3.2, the latter of which was one of the largest year 2013 flares. Departing sunspot complex AR2035-AR2046 erupted on April 25, 2014 at 0032 UT, producing a strong X1.3-class solar flare and an HF communications blackout on the dayside of Earth. NASA's Solar Dynamics Observatory recorded a flash of extreme ultraviolet radiation from the explosion. The Solar Dynamics Observatory recorded an X9.3-class flare at around 1200 UTC on September 6, 2017.
Flare sprays are a type of eruption associated with solar flares. They involve faster ejections of material than eruptive prominences, and reach velocities of 20 to 2000 kilometers per second.
Current methods of flare prediction are problematic, and there is no certain indication that an active region on the Sun will produce a flare. However, many properties of sunspots and active regions correlate with flaring. For example, magnetically complex regions (based on line-of-sight magnetic field) called delta spots produce the largest flares. A simple scheme of sunspot classification due to McIntosh, or related to fractal complexity. is commonly used as a starting point for flare prediction. Predictions are usually stated in terms of probabilities for occurrence of flares above M or X GOES class within 24 or 48 hours. The U.S. National Oceanic and Atmospheric Administration (NOAA) issues forecasts of this kind.
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- Solar Flares NASA Video from 2003
- Solar Flares Solar & Heliospheric Observatory Video from 2002 Miracle of the Sun (speculated)
|Wikimedia Commons has media related to Solar flares.|
- Real-time space weather on the iPhone, iPad, and Android from 150 data streams and 19 institutions.
- Live Solar Images and Data Site Includes x-ray flare, geomagnetic, space weather information detailing current solar events.
- Solar Cycle 24 and VHF Aurora Website (www.solarcycle24.com)
- Solar Weather Site
- Current Solar Flare – and geomagnetic activity in dashboard style (www.solar-flares.info)
- STEREO Spacecraft Site
- BBC report on the November 4, 2003 flare
- NASA SOHO observations of flares
- 'The Sun Kings', lecture by Dr Stuart Clark on the discovery of solar flares given at Gresham College, 12 September 2007 (available as a video or audio download as well as a text file).
- NASA Astronomy Picture of the Day: An X Class Flare Region on the Sun (6 November 2007)
- Sun trek website An educational resource for teachers and students about the Sun and its effect on the Earth
- NASA – Carrington Super Flare NASA May 6, 2008
- Archive of the most severe solar storms
- Animated explanation of Solar Flares from the Photosphere (University of South Wales)
- 1 min. 35 sec. Mini documentary: How big are solar flares' prominences? A simplified explanation of the size of solar flares' prominences as compared to Earth.
- The Most Powerful Solar Flares Ever Recorded – spaceweather.com (X9+ summary)
- Most Energetic Flares since 1976 (X5.7+ details)
- Davis, Chris. "Tracking the X Flare". Backstage Science. Brady Haran.
- Study solar flares with Sunspot Data. ()
- Solar Flare Monitoring Network by DLR Projectlab Neustrelitz. () | <urn:uuid:246ce649-0798-4eda-92c9-446585822a29> | 4.5 | 7,026 | Knowledge Article | Science & Tech. | 53.667322 | 95,597,781 |
Theory behind radiocarbon dating
Free 5-day trial Ever wondered how scientists know the age of old bones in an ancient site or how old a scrap of linen is?
Radiocarbon is not suitable for this purpose because it is only applicable: a) on a time scale of thousands of years and b) to remains of once-living organisms (with minor exceptions, from which rocks are excluded).As a member, you'll also get unlimited access to over 55,000 lessons in math, English, science, history, and more.Plus, get practice tests, quizzes, and personalized coaching to help you succeed.The field of radiocarbon dating has become a technical one far removed from the naive simplicity which characterized its initial introduction by Libby in the late 1940's.It is, therefore, not surprising that many misconceptions about what radiocarbon can or cannot do and what it has or has not shown are prevalent among creationists and evolutionists - lay people as well as scientists not directly involved in this field.In living organisms, which are always taking in carbon, the levels of carbon 14 likewise stay constant.
But in a dead organism, no new carbon is coming in, and its carbon 14 gradually begins to decay.
The technique hinges on carbon-14, a radioactive isotope of the element that, unlike other more stable forms of carbon, decays away at a steady rate.
Organisms capture a certain amount of carbon-14 from the atmosphere when they are alive.
In the following article, some of the most common misunderstandings regarding radiocarbon dating are addressed, and corrective, up-to-date scientific creationist thought is provided where appropriate. Radiocarbon is used to date the age of rocks, which enables scientists to date the age of the earth.
Radiocarbon is not used to date the age of rocks or to determine the age of the earth.
The clock was initially calibrated by dating objects of known age such as Egyptian mummies and bread from Pompeii; work that won Willard Libby the 1960 Nobel Prize in Chemistry. | <urn:uuid:2438605c-6d34-4360-bad7-88bb788e7943> | 4 | 428 | Knowledge Article | Science & Tech. | 38.365 | 95,597,793 |
The chemical composition of the environment, including gases and particles (aerosols), are continually altering on account of natural events equivalent to volcanic eruptions and because of human actions, including the results of emissions from fossil gas burning. The definitions in this glossary had been initially generated by the students in a senior-degree class learning air high quality and atmospheric chemistry at Sam Houston State College throughout the spring of 1995 in a course entitled Environmental Science 440/Chemistry 442, AIR HIGH QUALITY.
The traditional Greeks regarded air as one of the four components The primary scientific studies of atmospheric composition started in the 18th century, as chemists corresponding to Joseph Priestley , Antoine Lavoisier and Henry Cavendish made the first measurements of the composition of the environment.
This leads to the rain water attaining an acidic pH of 5.6 As a result of this, the purest form of rain reaches the earth as an acidic solution of pH 5.6 Acidity causes Environmental issues like Destruction of vegetation Marine life Corrosion and Etching of buildings that are exposed to ambiance.
This meeting will particularly give attention to aerosol-cloud interactions, ice nucleation, biosphere-ambiance feedbacks, integration of measurements and models, indoor air high quality, … | <urn:uuid:d35fc6be-a610-4fd6-a46f-101a18349a98> | 3.34375 | 259 | Knowledge Article | Science & Tech. | 10.384126 | 95,597,821 |
AN ancient virus could be responsible for human consciousness, giving you the ability to think for yourself.
New research has linked a human gene responsible for conscious thought to a virus that was spread in the early days of humanity.
Two papers published in the Cell journal discuss the origins of the Arc gene, which packages up genetic information and sends it around nerve cells in little virus-style capsules.
These packages of information are believed to be critical to how our nerves communicate, and could be responsible for our thoughts.
Elissa D. Pastuzyn, who authored one of the studies, said: “Evolutionary analysis indicates that Arc is derived from a vertebrate lineage of Ty3/gypsy retrotransposons, which are also ancestors to retroviruses.”
It’s believed that between 40 per cent and 80 per cent of the human genome was developed thanks to ancient viruses.
What is a virus?
Here's what you need to know...
- A virus is a small, infectious “agent”
- It can only replicate inside the living cells of other creatures, like humans
- Viruses can infect anything that lives, including plants, animals and bacteria
- There are believed to be millions of different types of virsuses around the world
- They’re so common that they’re believed to be the most abundant biological entity
- Viruses can spread in lots of ways, including through body contact and exposure to infected blood
- Some antiviral drugs exist, but antibiotics have no effect on a virus
Unlike bacteria, which simply live in the body, viruses make active changes to your cells, injecting their own genetic code.
This can often be entirely useless – and sometimes causes harm, including through the reproduction of more viruses – but occasionally we end up with useful modifications.
And it seems an ancient virus may have given rise to all human thought – thanks to the Arc gene.
Pastuzyn says that the virus was “repurposed during evolution, to mediate intercellular communication in the nervous system”.
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James Ashley, who authored one of the studies, said: “The neuronal gene Arc is essential for long-lasting information storage in the mammalian brain, mediates various forms of synaptic plasticity, and has been implicated in neurodevelopmental disorders.”
He adds that mutations in the gene have been “linked to autism and schizophrenia”, which suggests that Arc has a pivotal role to play in how we perceive and react to the world around us. | <urn:uuid:512218a6-3d8c-43cb-b5bc-e52a59d31de0> | 3.5625 | 557 | News Article | Science & Tech. | 31.291387 | 95,597,845 |
The month-long launch window for NASA’s new Mars lander, InSight opens this weekend. InSight will be the first spacecraft to use a robotic arm to place its instruments on another planet’s soil—effectively unraveling the innards of the Red Planet. It’s also the first interplanetary mission to launch from the West Coast instead of Cape Canaveral, and it may not be the last. InSight isn’t a rover, like Curiosity or Opportunity, but a stationary lander. Its mission is to peer deep into Mars with two main instruments. One is a probe that’ll hammer 16 feet deep to take the planet’s temperature and determine how much heat it’s losing. (That heat comes from the violent formation of a planet, but also the decay of radioactive elements.) The other is a seismometer for sensing marsquakes. Together, the instruments, which the robot arm will pluck from the deck of the spacecraft, will ideally show what Mars is made of, lending insight (sorry) into not … [Read more...] about Why Is NASA’s InSight Mars Mission Launching from California?
Spacex mars mission
The heat shield for NASA's next Mars spacecraft just cracked open. Luckily, engineers found this out during testing here on Earth, long before the Mars 2020 rover missionleaves for the Red Planet in search of habitable environments there. In preparation for landing, both the rover and the craft's landing gear will be encapsulated in a protective material — a heat shield — to keep them safe during the scalding trip through the Martian atmosphere. Engineers discovered the fracture on April 12, after a week of structural testing at Lockheed Martin. The crack was unexpected, but NASA's Jet Propulsion Laboratory – which manages the mission development – said the mission should still lift off in 2020, as anticipated. [Interstellar Space Travel: 7 Futuristic Spacecraft to Explore the Cosmos] The damage happened after the heat shield was subjected to forces up to 20 percent greater than what the Mars 2020 rover should encounter when it plows through Mars' … [Read more...] about Heat Shield for NASA’s Next Mars Mission Breaks During Testing
SpaceX has released a tear-jerking new video of the historic first flight of its Falcon Heavy rocket, which launched Elon Musk's Tesla Roadster and a dummy named Starman on a journey into the solar system on Feb. 6. Set to David Bowie's 1971 hit "Life on Mars," the video chronicles Starman's journey into space, starting from SpaceX's Horizontal Integration Facility at Kennedy Space Center in Florida, where the cherry-red electric car and its passenger were packed inside the rocket's payload fairing. The video shows the enormous rocket rolling out to the launchpad and blasting off into space, where live views of Starman were beamed down to Earth. [In Photos: SpaceX's 1st Falcon Heavy Rocket Launch Success!] The video shows the impressive double-booster landing and the crash of the third booster, which narrowly missed SpaceX's Drone ship "Of Course I Still Love You." This is the first time SpaceX has shown the crash footage (look for it at the 1:12 mark). But the … [Read more...] about Relive the Historic SpaceX Falcon Heavy Launch with ‘Starman’ in This Inspiring Video
Elon Musk and his space company recently received a lot of attention for putting a space suit-wearing dummy, dubbed Starman, into a Tesla car and shooting the two into space. While that is exciting, their plans for an internet-beaming satellite network are far more intriguing.Musk isn't a stranger to far-out ideas: He helped make electric cars sexy; he's open-sourced a wild "hyperloop" transit system that could revolutionise the way we get from A to B; his space company, SpaceX, is developing reusable rockets and planning to colonise Mars; and, through an initiative called Starlink, he's trying to blanket the Earth in high-speed internet. Here's what you need to know about it.What is Starlink? Starlink is a SpaceX initiative currently in testing Consists of a network of satellites that beam internet down These will be put into low-Earth orbit by 2020 First two experimental satellites will launch in February 2018 SpaceX's Starlink initiative consists of a huge network - aka a … [Read more...] about Starlink explained: How SpaceX will blanket Earth with superfast internet
Main image: NASA's Space Launch System will be an essential component of missions to Mars. Credit: NASA/MSFCEver since the dawn of science fiction we’ve been fascinated by Mars. Our planetary neighbour has been the subject of some of the greatest space stories in history, from the invasion of Martians in The War of the Worlds to humans going the other way in The Martian. Now, after more than a century of dreaming about the Red Planet, developing scientific breakthroughs, and researching its potential for exploration and sustaining life, we’re ready to go. Well, nearly. Earlier this year, NASA released a progress report on its plans for deep space exploration, including a mission to Mars, while US president Donald Trump pledged $19.1 billion in funding to help NASA get to Mars. And getting there is about more than simply staking a claim on Mars and fulfilling our sci-fi-fuelled dreams. Many experts believe that if we don’t start looking for other … [Read more...] about This is how we’ll get to Mars | <urn:uuid:3d008c4d-f8d6-4575-be3d-6df1df108e5a> | 3.328125 | 1,140 | Content Listing | Science & Tech. | 54.444678 | 95,597,863 |
Authors: Edward G. Lake
Paul Langevin’s so-called “Twin Paradox,” based upon Albert Einstein’s Special Theory of Relativity, seems to be by far the most argued topic in physics. Many hundreds of articles have been written about the “Twin Paradox,” but all they seem to accomplish is to make the subject even more confusing. This is an attempt to simplify the subject by identifying the causes of the confusion. And it proposes a relatively simple experiment to clarify how time dilation works.
Comments: 9 Pages.
[v1] 2018-07-09 11:05:25
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The Solar System
If you knew exactly where to look with a powerful telescope -- and took pictures several days, weeks, or months apart -- you might be able to find the four giant planets moving against the background of fixed stars. From the inside out we are looking at the orbits of Jupiter, Saturn, Uranus, and Neptune. The highly elliptical orbit belongs to Pluto.
You may notice that the Sun is no longer exactly in the center of the image. We have moved close enough to Earth to be able to tell that we are not headed directly toward the Sun. The Sun is much too bright at this distance to be able to discern any of the small, inner, rocky planets.
In the last few years, four spacecraft have passed beyond the orbit of Pluto on their own journeys to the stars: Pioneers 10 and 11, and Voyagers 1 and 2. Pioneer 10 is farthest away at a distance of 10.3 terameters (over nine light hours). It is headed in the direction of Taurus toward the bright star of Aldebaran, 68 light years away -- arriving in about two million years....
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In chemistry, racemization is the conversion of an enantiomerically pure mixture (one where only one enantiomer is present) into a mixture where more than one of the enantiomers are present. If the racemization results in a mixture where the D and L enantiomers are present in equal quantities, the resulting sample is described as a racemic mixture or a racemate. Racemization can proceed through a number of different mechanisms, and it has particular significance in pharmacology as different enantiomers may have different pharmaceutical effects.
Chiral molecules have two forms (at each point of asymmetry), which differ in their optical characteristics: The levorotatory form (the (−)-form) will rotate the plane of polarization of a beam of light to the left, whereas the dextrorotatory form (the (+)-form) will rotate the plane of polarization of a beam of light to the right. The two forms, which are non-superimposable when rotated in 3-dimensional space, are said to be enantiomers. The notation is not to be confused with D and L naming of molecules which refers to the similarity in structure to D-glyceraldehyde and L-glyceraldehyde. Also, (R)-(+) and (S)-(−) refer to the chemical structure of the molecule based on Cahn–Ingold–Prelog priority rules of naming rather than rotation of light.
Racemization occurs when one pure form of an enantiomer is converted into equal proportion of both enantiomers, forming a racemate. When there are both equal numbers of dextrorotating and levorotating molecules, the net optical rotation of a racemate is zero. Enantiomers should also be distinguished from diastereomers which are a type of stereoisomer that have different molecular structures around a stereocenter and are not mirror images.
Racemate may have different physical properties from either of the pure enantiomers because of the differential intermolecular interactions (see Biological Significance section). The change from a pure enantiomer to a racemate can change its density, melting point, solubility, heat of fusion, refractive index, and its various spectra. Crystallization of a racemate can result in separate (+) and (−) forms, or a single racemic compound.
In general, most biochemical reactions are stereoselective, so only one stereoisomer will produce the intended product while the other simply does not participate or can cause side-effects. Of note, the L form of amino acids and the D form of sugars (primarily glucose) are usually the biologically reactive form. This is due to the fact that many biological molecules are chiral and thus the reactions between specific enantiomers produce pure stereoisomers. Also notable is the fact that all amino acid residues exist in the L form. However, bacteria produce D-amino acid residues that polymerize into short polypeptides which can be found in bacterial cell walls. These polypeptides are less digestible by peptidases and are synthesized by bacterial enzymes instead of mRNA translation which would normally produce L-amino acids.
The stereoselective nature of most biochemical reactions meant that different enantiomers of a chemical may have different properties and effects on a person. Many psychotropic drugs show differing activity or efficacy between isomers, e.g. amphetamine is often dispensed as racemic salts while the more active dextroamphetamine is reserved for refractory cases or more severe indications; another example is methadone, of which one isomer has activity as an opioid agonist and the other as an NMDA antagonist.
Racemization of pharmaceutical drugs can occur in vivo. Thalidomide as the (R) enantiomer is effective against morning sickness, while the (S) enantiomer is teratogenic, causing birth defects when taken in the first trimester of pregnancy. If only one enantiomer is administered to a human subject, both forms may be found later in the blood serum. The drug is therefore not considered safe for use by women of child-bearing age, and while it has other uses, its use is tightly controlled. Thalidomide can be used to treat multiple myeloma. Another commonly used drug is ibuprofen which is only anti-inflammatory as one enantiomer while the other is biologically inert. Likewise, the (S) stereoisomer is much more reactive than the (R) enantiomer in citalopram (Celexa), an antidepressant which inhibits serotonin reuptake, is active. The configurational stability of a drug is therefore an area of interest in pharmaceutical research. The production and analysis of enantiomers in the pharmaceutical industry is studied in the field of chiral organic synthesis.
Formation of racemic mixtures
Racemization can be achieved by simply mixing equal quantities of two pure enantiomers. Racemization can also occur in a chemical interconversion. For example, when (R)-3-phenyl-2-butanone is dissolved in aqueous ethanol that contains [NaOH] or HCl, a racemate is formed. The racemization occurs by way of an intermediate enol form in which the former stereocenter becomes planar and hence achiral. An incoming group can approach from either side of the plane, so there is an equal probability that protonation back to the chiral ketone will produce either an R or an S form, resulting in a racemate.
Racemization can occur through some of the following processes:
- Substitution reactions that proceed through a free carbocation intermediate, such as unimolecular substitution reactions, lead to non-stereospecific addition of substituents which results in racemization.
- Although unimolecular elimination reactions also proceed through a carbocation, they do not result in a chiral center. They result instead in a set of geometric isomers in which trans/cis (E/Z) forms are produced, rather than racemates.
- In an unimolecular aliphatic electrophilic substitution reaction, if the carbanion is planar or if it cannot maintain a pyramidal structure, then racemization should occur, though not always.
- In a free radical substitution reaction, if the formation of the free radical takes place at a chiral carbon, then racemization is almost always observed.
The rate of racemization (from L-forms to a mixture of L-forms and D-forms) has been used as a way of dating biological samples in tissues with slow rates of turnover, forensic samples, and fossils in geological deposits. This technique is known as amino acid dating.
Discovery of optical activity
In 1843, Louis Pasteur discovered optical activity in paratartaric, or racemic, acid found in grape wine. He was able to separate two enantiomer crystals that rotated polarized light in opposite directions.
- Streitwieser & Heathcock (1985) pp. 122–124
- Nelson, D. L.; Cox, M. M. (2013). Lehninger Principles of Biochemistry (6th ed.). New York: W. H. Freeman. ISBN 1429234148.
- Voet, D.; Voet, J. G.; Pratt, C. W. (2013). Fundamentals of Biochemistry: Life at the Molecular Level (4th ed.). Hoboken, NJ: John Wiley & Sons. ISBN 0470547847.
- Arnold, L. E.; Wender, P. H.; McCloskey, K.; Snyder, S. H. (1972). "Levoamphetamine and Dextroamphetamine: Comparative Efficacy in the Hyperkinetic Syndrome: Assessment by Target Symptoms". Arch. Gen. Psychiatry. 27 (6): 816–822. doi:10.1001/archpsyc.1972.01750300078015. PMID 4564954.
- Teo, S. K.; Colburn, W. A.; Tracewell, W. G.; Kook, K. A.; Stirling, D. I.; Jaworsky, M. S.; Scheffler, M. A.; Thomas S. D.; Laskin, O. L. (2004). "Clinical pharmacokinetics of thalidomide". Clin. Pharmacokinet. 43 (5): 311–327. doi:10.2165/00003088-200443050-00004. PMID 15080764.
- Stolberg, S. G. (17 July 1998). "Thalidomide Approved to Treat Leprosy, With Other Uses Seen". The New York Times. Retrieved 8 January 2012.
- "Use of thalidomide in leprosy". WHO:leprosy elimination. World Health Organisation. Retrieved 22 April 2010.
- Reddy, K. C. S.; Kasiviswanath, I. V. (2013). "Racimisation of (R)–Alpha–Ethyl-2-Oxo-1-Pyrrolidine Acetic acid with Thionyl Chloride". International Journal for Pharmaceutical Research Scholars. 2 (1): 45–48.
- Jacquot, C.; David, D. J.; Gardier, A. M.; Sánchez, C. (2007). "Escitalopram and citalopram: the unexpected role of the R-enantiomer". Encéphale. 33 (2): 179–187. PMID 17675913.
- M. Reist, B. Testa, P.-A. Carrupt. "Drug Racemization and Its Significance in Pharmaceutical Research". In Michel F. Eichelbaum, Bernard Testa, Andrew Somogyi. Stereochemical Aspects of Drug Action and Disposition. Handbook of Experimental Pharmacology. 153. pp. 91–112. doi:10.1007/978-3-642-55842-9_4.
- Streitwieser & Heathcock (1985) p. 373
- March (1985) pp. 517–518
- March (1985) p. 610 | <urn:uuid:461c878a-5018-4a9a-930b-a0d2d821e234> | 3.765625 | 2,156 | Knowledge Article | Science & Tech. | 42.416191 | 95,597,897 |
Artificial intelligence (AI). It’s in the walls, the toaster, and even the label on your favourite brand of wine.
In addition to the weird and wacky solutions peddled by Silicon Valley, AI also has a number of actual uses… ones that are, in themselves, useful. Chatbots, smart cars and heuristic programming are all examples of AI in the wild.
AI, otherwise known as Artificial Intelligence, can be simply understood as intelligence that is exhibited by machines. Defined by the Oxford Dictionary, intelligence is confirmed to be: “The ability to acquire and apply knowledge and skills”.
By this definition, artificial intelligence is a non-organic means of acquiring and applying knowledge… but ask a computer a question it has not been programmed to answer, and it will stumble, sputter and spark. AI, at least our definition of it, is often seen to exceed the creative ability of the technological world today.
AI is, by the traditional understanding, a thinking, feeling computer. A robot that’s able to empathise; something that is required to obey Asimov’s laws of robotics. AI, and by this we mean the singularity event, is still some time away. Scientists in China are making great leaps towards this with quantum computing, but the dream of true AI however, is still a long way off.
Inc.com included their own timeline around the lifecycle of AI:
• 1950: Alan Turing predicts a computer will emulate human intelligence (it will be impossible to tell whether you're texting with a human or a computer) "by the end of the century."
• 1970: Life Magazine quotes several distinguished computer scientists saying "we will have a machine with the general intelligence of a human being" within three to fifteen years.
• 1983: The bestseller The Fifth Generation predicts Japan will create intelligent machines within ten years.
• 2002: MIT scientist Rodney Brooks predicts machines will have "emotions, desires, fears, loves, and pride" in 20 years.
There’s an argument to be made for reaching for the stars. Fiction is often found to mimic reality… we would suggest that the opposite is true. Think of the flatscreen TV, mobile phones and wearable technology. Back when Star Trek first aired, these were firmly set in the realm of future tech… but today, they’re a normal part of everyday life (and some would say the iPhone mimics the Star Trek communicator itself).
In business, however, the reality of AI is some way from that seen in science fiction. Machine learning can’t be classified as a form of intelligence - instead, it’s more similar to clever coding, a means to allow a machine to do more for us, automate actions, and do what a computer does best – compute.
It’s true, yes, that a large number of AI projects have failed… but each failure has acted as a building block for bigger and better things. A remarkably human trait.
One AI system, built by Northpointe, was designed to predict the chances a previous offender would commit a crime… but the software was accused of a racial bias as non-white offenders were marked as a higher risk.
In healthcare, however, we have a greater amount of data – cold hard facts with which AI can be fed. Indeed, AI is now available to turn standard fitness trackers into “life-saving medical devices”. A wearable EKG monitor, designed to assess heart health, was recently noted as the first ever (official) medical use of wearables and the AI algorithms that power the benefit.
The opportunity for AI to spot trends, crunch big data and replace our traditional input processes is very much here. The ability of AI to replace what hundreds of humans could do is very much at the forefront of AI today… Just ask Alexa, Siri, Google home or Cortana to translate something.
AI isn’t the iRobot pinnacle of computing… but it is a remarkably effective tool for specific and well-defined challenges. If there’s one thing for certain, it’s that if people can think of something, then with enough time they can make it happen.
What’s your experience been of AI so far? Does it live up to the hype? Get in touch with us and let us know
Read more like this | <urn:uuid:9281ecdc-a44a-49c1-be5b-c048590cb1a2> | 3.4375 | 906 | Personal Blog | Science & Tech. | 46.048911 | 95,597,902 |
+44 1803 865913
Series: Advances in Natural and Technological Hazards Research Volume: 31
Edited By: Yamada Y
715 pages, 227 colour & 67 b/w illustrations
Submarine mass movements represent major offshore geohazards due to their destructive and tsunami-generation potential. This potential poses a threat to human life as well as to coastal, nearshore and offshore engineering structures. Recent examples of catastrophic submarine landslide events that affected human populations (including tsunamis) are numerous
This volume consists of the latest scientific research by international experts in geological, geophysical, engineering and environmental aspects of submarine mass failure, focused on understanding the full spectrum of challenges presented by submarine mass movements and their consequences.
Section I: Physical Properties of Sediments and Slope Stability Assessment
Section II: Seafloor Geomorphology for Trigger Mechanisms and Landslide Dynamics
Section III: Role of Fluid Flow in Slope Instability
Section IV: Mechanics of Mass Wasting in Subduction Margins
Section V: Post-Failure Dynamics
Section VI: Landslide Generated Tsunamis
Section VII: Witnessing and Quasi-Witnessing of Slope Failures
Section VIII: Architecture of Mass Transport Deposits/Complexes
Section IX: Relevance of Natural Climate Change in Triggering Slope Failures
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The Kentucky Seismic and Strong Motion Network
The Kentucky Seismic and Strong Motion Network, run by the Kentucky Geological Survey, is made up of 24 stations across the state. Eleven of those stations have strong-motion sensors (accelerometers) and 18 have weak-motion sensors (seismometers). Five stations have both. Data from these stations has helped Kentucky develop better building codes. | <urn:uuid:9dca353f-ad9d-4ed9-a985-bcd02d958ef9> | 2.9375 | 80 | Knowledge Article | Science & Tech. | 36.51 | 95,597,962 |
UDP-based Data Transfer
UDT is a reliable UDP based application level data transport protocol for distributed data intensive applications over wide area high-speed networks. UDT uses UDP to transfer bulk data with its own reliability control and congestion control mechanisms. The new protocol can transfer data at a much higher speed than TCP does. UDT is also a highly configurable framework that can accommodate various congestion control algorithms.
|_service||000000005858 Bytes||1408656098almost 4 years ago|
|libudt.changes||0000000634634 Bytes||1409933205almost 4 years ago|
|libudt.spec||00000028852.82 KB||1409933205almost 4 years ago| | <urn:uuid:31e00e1b-20fd-4d1c-9312-836baa1ae530> | 2.5625 | 151 | Content Listing | Software Dev. | 47.405 | 95,597,974 |
Mission Areas L2 Landing Page Tabs
The Bird Banding Laboratory (BBL) is an integrated scientific program established in 1920 supporting the collection, archiving, management and dissemination of information from banded and marked birds in North America. This information is used to monitor the status and trends of resident and migratory bird populations. Because birds are good indicators of the health of the environment, the...
USGS provides fisheries research information to restore and enhance fish habitat and understand fish diseases. Endangered species and those that are imperiled receive special research interest. Aquatic Invasive Species research is aiding in early detection and control measures, as well as understanding impacts these invaders have on aquatic environments.
USGS research in advanced technologies, use of remote sensing, and research and monitoring in large river systems across the U.S. uniquely positions the USGS Fisheries Program to contribute to practical applications of landscape science.
As part of the USGS Fisheries program, ecological flows, or the relationships between quality, quantity, and timing of water flows and ecological response of aquatic biota and ecosystems; and related ecosystem services are being investigated.
Climate change is an additional stressor in a complex suite of threats facing freshwater ecosystems. Climate change is already stressing many freshwater species by warming water temperatures, shifting streamflow regimes, increasing extreme events (e.g., floods, drought, wildfire), and facilitating species invasions.
USGS fisheries scientists study the complex...
USGS scientists conduct studies to understand how aquatic species interact with each other and their environment in a wide range of aquatic habitats, including streams, rivers, lakes, wetlands, and coastal areas. USGS scientists quantify and describe functional relationships among aquatic species and habitats to describe aquatic community structure, function, adaptation, and sustainability....
The USGS Fisheries Program develops valuable tools for assessing species’ vulnerability to environmental stressors, focusing on 3 critical elements: exposure (magnitude of change), sensitivity (likelihood of adverse impacts), and adaptive capacity (species’ ability to cope with change). For example, our scientists develop the tools and science to help water managers evaluate tradeoffs in...
The USGS investigates pathogens and other environmental factors that affect aquatic organism health to support the management, conservation, and restoration of aquatic species.
USGS investigates pathogen discovery, causes, and drivers; researches disease ecology and immunology; and develops advanced tools for surveillance, risk assessment, and control of diseases that impact aquatic organism health to support the management, conservation, and restoration of aquatic species.
USGS research focuses on fish physiology and behavioral characteristics, vulnerability assessments, and development of indicator tools that can be used to inform decisions with the goal of sustaining and enhancing fisheries resources in concert with human uses.
Forty percent of all fish species in North America are at risk of extinction. USGS research is crucial to protect and manage at-risk species and healthy fish populations into the future. Species management research encompasses threatened and endangered species, Interior trust species protected by law, sensitive species that are declining, rare, or uncommon that may be candidates for future...
This site provides data and tools to help answer the question of how well we are protecting common plants and animals (GAP Analysis). Choose a state or the entire United States. Download data for land cover, species, protected areas and more or view online, using the interactive GAP Data Viewers.
This tool produces and provides information on the characteristics, extent, and status of the Nation's wetlands and deepwater habitats and other wildlife habitats.
At this website, one can view lists of native freshwater snails by state or province boundary, and plot distributions of snails by political boundaries. Lists can be downloaded for use in reports or analyses. Data file last updated 12/17/2013.
The 2008 AFS Endangered Species Committee list of imperiled freshwater and diadromous fishes of North America
At this website, one can view lists of imperiled fishes by freshwater ecoregion, by state or province boundary, and plot distributions of imperiled fishes by ecoregions or political boundaries. Data file last updated 4/25/2013.
The 2007 AFS Endangered Species Committee list of common and imperiled freshwater crayfishes of the United States and Canada
At this website, one can view lists of crayfishes by freshwater ecoregion, by state or province boundary, and plot distributions of crayfishes by ecoregions or political boundaries. Data file last updated 3/17/2011.
Modulators of mercury risk to wildlife and humans in the context of rapid global change
Environmental mercury (Hg) contamination is an urgent global health threat. The complexity of Hg in the environment can hinder accurate determination of ecological and human health risks, particularly within the context of the rapid global changes that are altering many ecological processes, socioeconomic patterns, and other factors like...Eagles-Smith, Collin A.; Silbergeld, Ellen K.; Basu, Niladri; Bustamante, Paco; Diaz-Barriga, Fernando; Hopkins, William A.; Kidd, Karen A.; Nyland, Jennifer F.
Spatial patterns in occupancy and reproduction of Golden Eagles during drought: Prospects for conservation in changing environments
We used a broad-scale sampling design to investigate spatial patterns in occupancy and breeding success of territorial pairs of Golden Eagles (Aquila chrysaetos) in the Diablo Range, California, USA, during a period of exceptional drought (2014–2016). We surveyed 138 randomly selected sample sites over 4 occasions each year and identified 199...Wiens, David; Kolar, Patrick; Hunt, W. Grainger; Hunt, Teresa; Fuller, Mark R.; Bell, Douglas A.
Survey of beaver-related restoration practices in rangeland streams of the western USA
Poor condition of many streams and concerns about future droughts in the arid and semi-arid western USA have motivated novel restoration strategies aimed at accelerating recovery and increasing water resources. Translocation of beavers into formerly occupied habitats, restoration activities encouraging beaver recolonization, and instream...Pilliod, David S.; Rohde, Ashley T.; Charnley, Susan; Davee, Rachael R; Dunham, Jason B.; Gosnell, Hannah; Grant, Gordon E.; Hausner, Mark B.; Huntington, Justin L.; Nash, Caroline
The effect of isolation, fragmentation, and population bottlenecks on song structure of a Hawaiian honeycreeper
Little is known about how important social behaviors such as song vary within and among populations for any of the endemic Hawaiian honeycreepers. Habitat loss and non‐native diseases (e.g., avian malaria) have resulted in isolation and fragmentation of Hawaiian honeycreepers within primarily high elevation forests. In this study, we examined how...Pang-Ching, Joshua M.; Paxton, Kristina L.; Paxton, Eben H.; Pack, Adam A.; Hart, Patrick J.
Development and release of phenological data products—A case study in compliance with federal open data policy
In Autumn 2015, USA National Phenology Network (USA-NPN) staff implemented new U.S. Geological Survey (USGS) data-management policies intended to ensure that the results of Federally funded research are made available to the public. The effort aimed both to improve USA-NPN data releases and to provide a model for similar programs within the USGS....Rosemartin, Alyssa H.; Langseth, Madison L.; Crimmins, Theresa M.; Weltzin, Jake F.
Using a food web model to inform the design of river restoration—An example at the Barkley Bear Segment, Methow River, north-central Washington
With the decline of Chinook salmon (Oncorhynchus tshawytscha) and steelhead (O. mykiss), habitat restoration actions in freshwater tributaries have been implemented to improve conditions for juveniles. Typically, physical (for example, hydrologic and engineering) based models are used to design restoration alternatives with the assumption that...Benjamin, Joseph R.; Bellmore, J. Ryan; Dombroski, Daniel
Land use diversification and intensification on elk winter range in Greater Yellowstone: A framework and agenda for social-ecological research
Amenity migration describes the movement of peoples to rural landscapes and the transition toward tourism and recreation and away from production-oriented land uses (ranching, timber harvesting). The resulting mosaic of land uses and community structures has important consequences for wildlife and their management. This research note examines...Haggerty, Julia Hobson; Epstein, Kathleen; Stone, Michael; Cross, Paul
Rapid colonization of a Hawaiian restoration forest by a diverse avian community
Deforestation of tropical forests has led to widespread loss and extirpation of forest bird species around the world, including the Hawaiian Islands which have experienced a dramatic loss of forests over the last 200–800 years. Given the important role birds play in forest ecosystem functions via seed dispersal and pollination, a bird community's...Paxton, Eben H.; Yelenik, Stephanie G.; Borneman, Tracy E.; Rose, Eli; Camp, Richard J.; Kendall, Steve J.
Evaluating trade-offs in bull trout reintroduction strategies using structured decision making
Structured decision making allows reintroduction decisions to be made despite uncertainty by linking reintroduction goals with alternative management actions through predictive models of ecological processes. We developed a decision model to evaluate the trade-offs between six bull trout (Salvelinus confluentus) reintroduction decisions with the...Brignon, William R.; Peterson, James T.; Dunham, Jason B.; Schaller, Howard A.; Schreck, Carl B.
Lack of observed movement response to lead exposure of California condors
Lead poisoning is an important conservation concern for wildlife, and scavenging birds are especially at risk from consumption of carcasses of animals killed with lead ammunition. Because current methods to identify lead exposure require animal capture and blood collection, management would benefit from the development of a less costly and...Poessel, Sharon; Brandt, Joseph; Uyeda, Linda; Astell, Molly; Katzner, Todd E.
Estimating vegetation biomass and cover across large plots in shrub and grass dominated drylands using terrestrial lidar and machine learning
Terrestrial laser scanning (TLS) has been shown to enable an efficient, precise, and non-destructive inventory of vegetation structure at ranges up to hundreds of meters. We developed a method that leverages TLS collections with machine learning techniques to model and map canopy cover and biomass of several classes of short-stature vegetation...Anderson, Kyle E.; Glenn, Nancy F.; Spaete, Lucas P.; Shinneman, Douglas; Pilliod, David S.; Arkle, Robert; McIlroy, Susan; Derryberry, DeWayne R.
Meteorological and environmental variables affect flight behaviour and decision-making of an obligate soaring bird, the California Condor Gymnogyps californianus
The movements of animals are limited by evolutionary constraints and ecological processes and are strongly influenced by the medium through which they travel. For flying animals, variation in atmospheric conditions is critically influential in movement. Obligate soaring birds depend on external sources of updraft more than do other flying species...Poessel, Sharon; Brandt, Joseph; Miller, Tricia A.; Katzner, Todd
American pika in the Northern Cascades. American pikas occupy talus slopes in mountain ecosystems throughout western North America.
Curt Storlazzi of the USGS explains how the water cycle pulled him into oceanography, and how his personal interests parallel his profession.
Chart showing changes in vegetation density in the Mississippi River delta in Louisiana, May 2015-May 2016. From a USGS Open File Report published in July 2017 by co-authors Elijah Ramsey III and Amina Rangoonwala,
Metolius River, Smiling River Campground, Deschutes National Forest
USGS ecologists Molly McCormick (left) and Katie Laushman (right) conducting a seeding experiment that is a part of RAMPS, a new USGS-led initiative to improve restoration outcomes in the Southwest....
An aerial view of southeast Louisiana coastal marshes.
Satellite images of the same wetland taken in 2008 and 2016 show a wetland restoration project has produced some gains in marsh area.
Hot new imagery from temperature-sensing cameras suggests that bats who warm up from hibernation together throughout the winter may be better at surviving white nose syndrome, a disease caused by a cold-loving fungus ravaging insect-eating bat populations in the United States and Canada.
Adding milkweeds and other native flowering plants into midwestern agricultural lands is key to restoring monarch butterflies, with milkweed sowers from all sectors of society being critically needed for success.
Scientists recently reconstructed the skin of endangered green turtles, marking the first time that skin of a non-mammal was successfully engineered in a laboratory, according to a recently published U.S. Geological Survey study. In turn, the scientists were able to grow a tumor-associated virus to better understand certain tumor diseases.
Harvests from freshwater fisheries such as the Great Lakes could total more than 12 million tons a year globally and contribute more to global food supplies and economies than previous estimates indicate, according to a study published today by Michigan State University and the U.S. Geological Survey.
Prairie dogs in the wild are less likely to succumb to plague after they ingest peanut-butter-flavored bait that contains a vaccine against the disease, according to a U.S. Geological Survey study published today in the journal EcoHealth.
Sudden flooding hit islands of global importance for Pacific birds highlighting threats and opportunities for conservation planning
Europe’s wild snakes could face a growing threat from a fungal skin disease that has contributed to wild snake deaths in North America, according to an international collaborative study, led by conservation charity Zoological Society of London alongside partners including the U.S. Geological Survey. The new study is published in the journal Scientific Reports.
Exploring the Role of Non-Native American Shad in the Columbia River Basin
Researchers from the U.S. Geological Survey, Taronga Conservation Society Australia, The National Trust of Fiji and NatureFiji-MareqetiViti have discovered a new species of banded iguana.
A new study led by the U.S. Geological Survey and the University of Wyoming found that increased westward ice drift in the Beaufort and Chukchi seas requires polar bears to expend more energy walking eastward on a faster moving “treadmill” of sea ice.
On June 6, 1944, thousands of men rained down from the skies onto the battlegrounds of Normandy. After five grueling years of war that shook the globe, D-Day’s victory swept the Allied nations into a wave of celebration.
New USGS Science Plan Designed to Help Plan for Drought Effects on People, Communities, and Ecosystems
The U. S. Geological Survey is poised to bring a dynamic array of science and tools to help decision-makers manage and offset effects of increased drought across the United States, according to a drought plan report released today. | <urn:uuid:b633507d-deb1-4ddb-9bb3-62e6601e2224> | 2.859375 | 3,163 | Content Listing | Science & Tech. | 27.855583 | 95,597,981 |
posted by Bruce
A sinusoidal wave traveling on a string is moving in the positive x-direction. The wave has a wavelength of 8 m, a frequency of 60 Hz, and an amplitude of 9 cm. What is the wave function for this wave? (Use any variable or symbol stated above as necessary.)
I think the function follows this format:
y(x,t)=A*sin(kx-wt+phase shift), but im not sure how apply it to this problem. Any help or suggestions is appreciated, thank you! | <urn:uuid:940c118f-74f8-41f8-bd7a-54d64e3bb4db> | 2.984375 | 113 | Q&A Forum | Science & Tech. | 70.565776 | 95,598,032 |
Facts Summary: Austrofolium equatorianum is a species of concern belonging in the species group "plants" and found in the following area(s): Ecuador (Galapagos Islands). This species is also known by the following name(s): Bartoniella equatoriana.
Austrofolium equatorianum Facts Last Updated: January 1, 2016
To Cite This Page:
Glenn, C. R. 2006. "Earth's Endangered Creatures - Austrofolium equatorianum Facts" (Online).
Accessed 7/19/2018 at http://earthsendangered.com/profile.asp?sp=15793&ID=11.
Need more Austrofolium equatorianum facts?
Twelve Incredibly Odd Endangered Creatures
1. Solenodon The solenodon is a mammal found primarily in Cuba and Hispanola. The species was thought to be extinct until scientists found a few still alive in 2003. Solenodons only prefer to come out at night. They eat primarily insects and they are one of the few mammal species that are venomous, delivering a very powerful toxin. Symptoms of a solenodon bite are very similar to a snake bite, including swelling and severe pain, lasting several days. | <urn:uuid:93545e44-add8-4d86-92e5-dcf7e3efe582> | 3.515625 | 267 | Knowledge Article | Science & Tech. | 43.473493 | 95,598,048 |
The movement of the 2 flagella of Oxyrrhis marina was examined with respect to their individual waveforms and the swimming behaviour of the organism. The longitudinal flagella propagated helicoidal waves whose amplitude decreased toward the tip of the flagellum. Their beat frequencies were 50-60 Hz. The transverse flagella beat helicoidally within a furrow. Sudden changes in the direction of the cell trajectories were generated by transient arrests of the longitudinal flagellum beat, which were accompanied by a switch from the backward orientation to a forward one. This sweeping motion generated the rotation of the cell body. Ca2+ions highly stimulated the frequencies of this arrest response, which compared to the "walking-stick" behaviour of sea urchin spermatozoa. Isolated flagella were ATP-reactivated after detergent treatment. They exhibited 2 types of motion within the same experimental conditions. A progressive helicoidal motion was generated upon longitudinal flagellum reactivation, whereas a rolling motion with little progression characterized transverse flagellum reactivation. The differences motile behaviour reflect regulations of flagellar movement which were not destroyed by the isolation procedure and may be indicative of regulation of accessory structures. © 1988.
Mendeley saves you time finding and organizing research
Choose a citation style from the tabs below | <urn:uuid:3b717db4-c894-4bbf-bad6-af51eec6843e> | 2.59375 | 277 | Academic Writing | Science & Tech. | 13.478526 | 95,598,066 |
How many distinct triangles can be constructed by choosing three vertices from among the corners of a unit cube?
Source: NCTM Mathematics Teacher, February 2008
We construct four triangles from three corners of a face for a total of triangles.
In the plane formed by the the two diagonals and and the two sides, we construct four triangles. Similarly, the diagonals C and D produce four more triangles. Thus, the Top/Bottom, Front/Back and Left/Right faces make total of triangles.
Take corner as the top and form a tetrahedron with the three diagonals as the base. The tetrahedron produces four triangular faces – three are repeat, one is distinct. Hence, eight corners make distinct triangles.
The number of distinct triangles constructed by choosing three vertices from among the corners of a unit cube = .
We construct a triangle from any three corners of the cube because they are not collinear. The number of ways to choose three corners from a set of eight = . | <urn:uuid:3138ca9c-5659-4dc1-97ee-ac482f6a1698> | 3.953125 | 211 | Knowledge Article | Science & Tech. | 59.444852 | 95,598,076 |
We need a few C functions created for us (Using GCC):
1) Small Database System
- We need a few functions that would simulate a small database written. I think a double linked list would be perfect. We need a function to add to the database, remove a record from the database, a function to read from the database and a function to re-sort the database. The Read/Write/Delete functions should all accept the following parameters Filename, KEY, Data. The filename specifies the "file" to work with, the "KEY" would be some sort of Unique key that will be passed in, and the DATA will be the data we want saved. So for instance, if I were to have a cars database, and I wanted to write to the cars database I would do somthing like this... Call the function to write to the database with the filename "Cars.dat", pass in "BMW" as my key and the data "This is a BMW Car record". When I read the file using the read function I would pass in the filename and key of "BMW" and it would return "This is a BMW Car record". The Delete function would be similar to the read function in that it would require the filename and key only, but delete the record instead of return the data. Inserting a record should "insert" the data in the correct link list spot based on the key. If its inserted in the correct spot, there will be no need to resort later... If at anypoint in time a duplciate record comes up it should overwrite the current Key and data.
The functions must be written, tested and compiled with GCC (Cross platform C). We will test the functions using Cygwin GCC and also Linux GCC. These functions must be platform independant.
Code must be commented, and clean.
26 freelanceria on tarjonnut keskimäärin %project_bid_stats_avg_sub_26% %project_currencyDetails_sign_sub_27% tähän työhön
Hello ! I can offer you much better implementation as double linked list. If you will leave me to do it my own way you will get really fast and reliable small database. Thanks. skirn
Hi, We are highly expert in C/C++ programming in GNU/Linux environment. We can provide you a very efficient function in C for this project. Please have a look at PMB for more details. Best Regards ... ccpplinux | <urn:uuid:c57d9e95-1166-47ad-988c-58603e3bdc33> | 2.625 | 521 | Comment Section | Software Dev. | 66.452712 | 95,598,092 |
Can plants and animals evolve to keep pace with climate change? A study published May 19 in the journal Proceedings of the National Academy of Sciences shows that for at least one widely-studied plant, the European climate is changing fast enough that strains from Southern Europe already grow better in the north than established local varieties.
Small and fast-growing, Arabidopsis thaliana is widely used as the “lab mouse” of plant biology. The plant grows in Europe from Spain to Scandinavia and because Arabidopsis is so well-studied, there is a reference collection of seeds derived from wild stocks across its native range. Originally collected from 20 to 50 years ago, these plants have since been maintained under controlled conditions in the seed bank.
Johanna Schmitt, formerly at Brown University and now a distinguished professor in the UC Davis Department of Evolution and Ecology, and colleagues took banked seed samples originally from Spain, England, Germany and Finland and raised all the plants in gardens in all four locations.
“The southern imports do better across the range than locals,” Schmitt said.
“This shows that the adaptive optimum has moved really fast.”
Seed stocks banked decades ago may no longer be the best for their locations of origin, she said, although they still may be critical for preserving genetic diversity, especially from warmer parts of the species range that may facilitate adaptation to future climates.
Whether wild Arabidopsis can evolve fast enough to thrive in warming conditions, or southern varieties move north fast enough to replace northern strains, remains an open question, Schmitt said.
Arabidopsis is a fast-growing, short-lived species. For forest managers, there is another question: can trees that sprouted 30 or 40 years ago adapt in place to a rapidly changing climate?
“This is a concern for foresters — trees live a long time, but will they die if the climate rug is pulled out from under them?” Schmitt said.
Coauthors on the study are Amity Wilczek, Martha Cooper and Tonia Korves, all at Brown University. The study was supported by the National Science Foundation.
Andy Fell | Eurek Alert!
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
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:60ccfdde-f8ca-42fd-9bad-dcc379b4359f> | 3.734375 | 1,040 | Content Listing | Science & Tech. | 38.885768 | 95,598,093 |
Developed programs should be documented at multiple levels, from code comments, through API documentation, to installation and usage documentation. Comments at each level should take into account different target audience, from experienced developers, to end users with no programming skills.
Example of good documentation: A Guide to NumPy/SciPy Documentation
Markdown is a lightweight markup language that allows you to create webpages, wikis and user documentation with a minimum of effort. Documentation written in markdown looks exactly like a plain-text document and is perfectly human-readable. In addition, it can also be automatically converted to HTML, latex, pdf, etc. More information about markdown can be found here:
Retext is a markdown aware text editor, that can be used to edit markdown files and convert them into HTML or PDF. It can be found at:
Alternatively, 'pandoc' is a command line utility that can convert markdown documents to into several other formats (including latex):
An Eclipse plugin for previewing the HTML generated by markdown is available on this page:
Clear explanation of the goal of the project with pointers to other documentation resources.
Use GitHub flavoured markdown for, e.g., syntax highlighting. (If reStructuredText or another format that GitHub renders is idiomatic in your community, use that instead.) README is targeted towards developers, it is more technical than home page. Keeping basic documentation in README.md can be even useful for lead developer, to track steps and design decisions. Therefore it is convenient to create it from the beginning of the project, when initialising git repository.
- StackOverflow on good readme
- short gist with README.md template
- The art of README from nodejs community
Well defined functionality
Ideally in README.md
Source code documentation
Code comments, can be block comments or inline comments. They are used to explain what is the piece of code doing. Those should explain why something is done in the domain language and not programming language - why instead of what.
API documentation should explain function arguments and outputs, or the object methods. How they are formulated will depend on the language.
- User manual (as PDF) in the "doc" directory. This is the real manual, targeted at your users. Make sure this is readable by domain experts, and not only software developers. Make sure to include:
- Netherlands eScience Center logo.
- Author name(s).
- Versions numbers of the software and documentation.
- References to:
- The eScience Center web site.
- The project web site.
- The Github page of the project.
- Location of the issue tracker.
- More information (e.g. research papers).
Documented development setup
(good example is Getting started with khmer development) It should be made available once there is more than one developer working on the codebase. If your development setup is very complicated, please consider providing a Dockerfile and docker image.
Contribution guidelines make it easier for collaborators to contribute, and smooth the process of collaboration.
Guidelines should be made available once the code is available online and there is a process for contributions by other people. Good guidelines will save time of both lead developer and contributor since things have to be explained only once. A good CONTRIBUTING.md file describes at least how to perform the following tasks:
- How to install the dependencies
- How to run (unit) tests
- What code style to use
- Reference to code of conduct
- When using a git branching model, the choice of branching model An extensive example can be found here. Note that GitHub has built in support for a CONTRIBUTING.md file.
Code of conduct
A code of conduct is a set of rules outlining the social norms, religious rules and responsibilities of, and or proper practices for an individual. Such a document is advantagous for collaberation, for several reasons:
- It shows your intent to work together in a positive way with everyone.
- It reminds everyone to communicate in a welcoming and inclusive way.
- It provides a set of guidelines in case of conflict.
CofC should be attached from the beginning of the project. There is no gain from having it with one developer, but it does not cost anything to include it in the project and will be handy when more developers join.
Documented code style
From the beginning of the project, a decision on the code style has to be made and then should be documented. Not having a documented code style will highly increase the chance of inconsistent style across the codebase, even when only one developer writes code. The Netherlands eScience Center should have a sane suggestion of coding style for each programming language we use. Coding styles are about consistency and making a choice, and not so much about the superiority of one style over the other. A sane set of guides can be found on in google documentation.
How to file a bug report
Describing how to properly report a bug will save a lot of developers's time. It is also useful to point users to good bug report guide like one from Simon Tatham
Explained meaning of issue labels
Once users start submitting issues labels should be documented.
DOI or PID
Identifiers should be associated with releases and should be created together with first release.
To get credit for your work, it should be as easy as possible to cite your software.
Your software should contain sufficient information for others to be able to cite your software, such as: authors, title, version, journal article (if there is one) and DOI (as described in the DOI section). It is recommended that this information is contained on a single file.
You can use the CITATION file format to provide this information on a human- and machine-readable format.
Read more in the post by Robin Wilson.
Print software version
Make it easy to see which version of the software is in use.
- if it's a command line tool: print version on the command line
- if it's a website: print version within the interface
- if the tool generates the output: output file should contain the version of software that generated the output | <urn:uuid:8ff76264-cc5d-47a7-8cd9-dc2d576875c1> | 3.21875 | 1,291 | Documentation | Software Dev. | 37.930893 | 95,598,105 |
If you have ever grabbed the metal handle of pot being heated over a campfire, you have painfully experienced heat transfer. There are four ways in which heat is transferred from one object to another: conduction, radiation, convection and advection. Heat almost always flows from the higher temperature object to the lower, changing the internal energy of both objects in the process. The primary difference between convection and advection heat transfers is the direction of the exchange.
Convection Heat Transfer
Convection heat transfer involves the transfer of heat through the movement of the medium’s particles. This medium must be a gas or liquid, thereby allowing for movement. Convection always transfers heat in the vertical plane. This movement is driven by variations in the medium’s density and, therefore, buoyancy. Heated particles expand, causing them to decrease in density; these particles become more buoyant than surrounding particles, causing them to rise. As they rise, their heat is transferred to cooler portions of the medium located above them.
Examples of Convection
Convection heat transfer takes place when a pot of water is heated. As the water molecules closest to the heat source warm, they expand. This expansion lowers their density and they begin to rise; this is what causes water in a pot to boil. The atmosphere also provides an example of convection heat transfer. When a packet of air is warmed by solar energy -- radiation heat transfer -- the air packet expands, lowering its density. This increases its buoyancy and causes it to rise in the atmosphere. This produces an unstable atmosphere with a vertical flow of air.
Advection Heat Transfer
Advection heat transfer differs from convection in that the movement of heat is confined to the horizontal plane. This type of heat transfer is not powered by variations in density, but rather requires an outside force, such as wind or currents, to displace the particles of the medium. As the particles move horizontally into systems that are hotter or colder, heat is transferred.
Examples of Advection
The primary example of advection heat transfer is the movement of meteorological fronts. These fronts represent air masses of cold or warm air that are moved horizontally over the surface by winds; as these air masses encounter warmer or cooler air, heat is exchanged between the systems. Ocean currents are another example of advection heat transfer. Rather than vertically, currents move warm or cold water in horizontal directions. As these waters interact with warmer or cooler areas of water, heat is exchanged between them.
Other Types of Heat Transfer
The remaining types of heat transfers are conduction and radiation. Conduction transfers heat from one object to another with no movement; teat is transferred from molecule to molecule. This type of heat transfer only occurs in solids; the handle of a hot pot is an example of conduction. Radiation heat transfer involves the transfer of heat by electromagnetic waves of energy. An example of radiation is sunlight; when these waves strike other particles, they cause them to vibrate, or warm. | <urn:uuid:6b4cf4fb-344a-45bb-9bd6-32a0f72d916b> | 4.15625 | 621 | Knowledge Article | Science & Tech. | 39.144414 | 95,598,107 |
Numbers and Ratios
- Category: Numbers and Ratios
- Hits: 1818
37 is a remarkable number for many reasons but for our purposes the astronomical utility and its connections, as an invariant, to anciently developed concepts involving it are highlighted. The number within mathematics can be studied at https://en.wikipedia.org/wiki/37_(number).
We have observed in a number of articles (click on tab 37 above to view them), that the number 37 is
- The approximate number of lunar months in three solar years.
- The length of three Saturnian years, of 364 days each, equals 37 lunar months.
- The counting of 37 lunar months six times can generate 222 lunar months, one short of the 223 in the Saros eclipse period and 13 short of the 235 in the Metonic periods anniversary of sun, moon and stars.
- Two lunar years of 12 lunar months could and were alternated with a lunar year of 13 lunar months to achieve 37 lunar months.
3. The counting of 37 lunar months to count Saros and Metonic periods
In the late 1990s I drew a pattern of counting which shows the whole idea without reference to any ancient monument. A scane of this is below:
Figure 3.1 of a drawing made in late 1990s of the idea of counting sixe sets of 37 lunar months as 12 + 13 + 12 lunar month years equalling 222 lunar months | <urn:uuid:c7cab827-56bf-4f98-acc4-dbcc815a257b> | 2.9375 | 295 | Knowledge Article | Science & Tech. | 62.610991 | 95,598,111 |
Scientists of the Max Planck Institute (MPI) of Biochemistry in Martinsried near Munich, Germany, have now decoded the structure of a protein complex (Ski complex) which plays an essential role in the process of degrading ribonucleic acids (RNAs).
The ski complex plays an important role in the quality management of the cell.
Grafic: Felix Halbach © MPI of Biochemistry
“The Ski complex we investigated feeds RNA molecules to the degradation machinery,” says Felix Halbach, scientist at the MPI of Biochemistry. The study has now been published in the journal Cell.
RNAs are ubiquitous and abundant molecules with multiple functions in the cell, such as allowing the translation of the genomic information into proteins. Any errors that occur during the synthesis of RNA molecules or unwanted accumulation of RNAs can be harmful for the cell. The elimination of defective RNAs or of RNAs that are no longer needed is therefore a key step in the metabolism of a cell. This task is carried out by a protein complex called Exosome, one of the research objects in the department “Structural Cell Biology” headed by Elena Conti. The molecular mechanism of how the Exosome is regulated, however, is not very clear yet.
The Max Planck scientists have now elucidated the atomic structure and the operating mechanism of a protein complex (Ski complex) which is involved in the activation of the cytoplasmic Exosome. The Ski complex contains several subunits and can be found in all eukaryotes – from yeast to humans. “We could show that the Ski complex and the Exosome interact directly and that they jointly form a channel for the RNA which is supposed to be degraded,” says Felix Halbach. Like DNA, RNA molecules are often folded. To be degraded by the Exosome, RNA molecules have to be unfolded first – this task is executed by the Ski complex. The unfolded RNA molecules can then be guided through the joint channel to the Exosome. “The Ski complex feeds RNA molecules to the Exosome,” explains the biochemist.
The results also reveal additional parallels between the Exosome and the Proteasome. The Proteasome is the protein complex responsible for the degradation of proteins in a cell. “It becomes clear that these two complexes are not only structurally and functionally similar,” says Elena Conti, “also their regulatory subunits work in a similar manner.” They unwind RNA molecules or, respectively, proteins and guide them to the active centers of the specific degradation machinery.Original Publication
Anja Konschak | Max-Planck-Institut
Further reports about: > Biochemistry > Klopferspitz > Max Planck Institute > Molecular machines > RNA > RNA molecule > Ski > Ski complex > Structural Biology Laboratory > atomic structure > cell death > defective macromolecules > exosome > molecular mechanism > proteasome > protein complex > ribonucleic acid > ribonucleic acids
NYSCF researchers develop novel bioengineering technique for personalized bone grafts
18.07.2018 | New York Stem Cell Foundation
Pollen taxi for bacteria
18.07.2018 | Technische Universität München
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:90b08ec3-212b-4370-8232-422bf8d608ed> | 3.171875 | 1,266 | Content Listing | Science & Tech. | 34.315936 | 95,598,153 |
We often hear that great crested newts are bad news for developers, but what about the ecology of this native protected species?
What’s their range?
In Britain, the great crested newt (Triturus cristatus) is widely distributed throughout England, Wales and southern Scotland, but is patchy in its distribution. Britain is the most westerly country supporting populations of the species with its range extending to Finland in the north, the Russian border with Kazakhstan to the east and southern France in the south.
Where might you find one?
To survive, they require both aquatic and terrestrial habitat. They are usually found in ponds but other standing water bodies such as ditches may also support the species. The ideal pond size is between 100 and 300m2, but they can be found in smaller ponds, particularly if there are a series of ponds in close proximity. For the newts to breed, the ponds should have suitable submerged plant cover to allow eggs to be laid in the leaves for protection. Unvegetated areas within the pond are also helpful as it allows males space to display to females during the breeding season. The species has been known to occur in both acid and alkaline waterbodies but seems to prefer either close to neutral or slightly alkaline ponds. Around the edge of the waterbody, areas of refuge would allow them to withstand extreme weather conditions such as cold in the winter and drought in the summer. There should be suitable areas for foraging habitat to allow them to catch prey, as well as suitable features that could be used for hibernation, including underground crevices, tree root systems, mammal burrows, rubble piles or old walls.
What do they eat and what eats them?
They are mainly active at night and feed during this time, taking refuge at the bottom of ponds or hiding in refugia during the day. They have a wide variety of prey, which they hunt both on land and in the water. Their diet will depend on the availability of prey; when they are foraging on land, crane flies, worms, spiders, slugs and snails could be on the menu, whereas in water, shrimps, lesser water boatmen, mayfly nymphs, and leeches all make for a tasty snack. They will also eat other newt larvae, tadpoles and frog spawn! They suffer predation themselves from larger predators such as herons, fish and dragonfly larvae.
What does a year in the life of an adult great crested newt look like?
Their active period begins between February and April, depending on the temperature and rainfall, when adults emerge from hibernation and migrate from their overwintering sites on land to the ponds where they will breed and the females will lay their eggs. They typically arrive at ponds gradually rather than simultaneously, with males tending to arrive earlier than their female counterparts. The breeding season takes place between April and May with males developing the distinctive crest that gives the species its common name. After mating, the females lay their eggs singly on submerged leaves, with the leaf folded over the egg for protection, with each breeding female typically laying around 250 eggs each season.
The amount of time that newts stay in the breeding ponds varies hugely between individuals. While some will begin leaving from as early as May, others leave as late as October and in some cases will even overwinter in the pond. Having left the pond, they will live and forage on land over the rest of the summer and autumn and begin hibernation around October time, depending on the temperature in any given year.
What about the development of juveniles?
After the female lays her eggs, they take between 2 and 6 week to hatch, but this varies depending on environmental conditions such as shade and temperature. An unusual and unfortunate feature of their development is that they have a chromosomal abnormality which means that around 50% of the young die within 1-2 weeks of embryonic development. The larvae predate on small invertebrates, with the rate of development influenced by prey availability. Typically, it takes around 16 weeks for the newly hatched larvae to complete metamorphosis into an adult. However, it takes around 2-4 years for a juvenile to mature and begin breeding. In this period, they leave the pond and tend to live and forage predominantly on land but may sometimes return to ponds before they are mature. | <urn:uuid:034f10db-a5c4-4acf-a474-1c08157d10e0> | 3.703125 | 898 | Knowledge Article | Science & Tech. | 44.491334 | 95,598,165 |
Consider two imaginary cells. Both are cube shaped (the same dimension in all directions) The first cell has a side length of 10 micrometers. The second has a side length of 100 micrometers. Calculate the surface areas and volumes of both of these cells then calculate the sa/v for each of them. The SA, V and Sa/V dived out of each of theses cells. which one of these would be most efficeint at feeding itself? Why? If we added a third cell with a side length of 50 micrometers how would its feeding efficiency compare to our first two cells ( no calculations needed) Why ?
Finally if our least efficient cell needed to increase its feeding effiency to match the most efficient cell what is one way it might do it? Oh - that's without actually changing its volume. Be specific about how the cell must change.© BrainMass Inc. brainmass.com July 21, 2018, 9:46 am ad1c9bdddf
please see the attachment for the solution to this problem.
--------- Text below for searching only-------
The side length of the first cell = 10 micrometers.
Since the cell is of cubic shape, its surface area (SA) is given by 6a2 where a is the side length of the cube.
Therefore, the SA of the first cube = 6x(10x10-6 )2 (1 micrometer =10-6 meter )
Volume of the cell (V) = a3 = (10x10-6 )3 = 10-15 m3
for the first cell , Surface Area/Volume = SA/V =6x10-10 /10-15
= 6x105 per meter
Similarly, for the second cell whose side length = 100 micrometers,
Surface Area = 6x(100x10-6 )2 = 6x10-8 m2 ...
The solution shows all mathematical steps to arrive at the final answer. This will enable you to solve similar problems yourself. More than 350 word explanation as a Word attachment. | <urn:uuid:a99ee69f-b801-4447-8c51-3157016c9246> | 3.953125 | 432 | Tutorial | Science & Tech. | 75.400091 | 95,598,196 |
The Syntax member of a data structure describes the type of data stored in the value member. The Syntax member is a CLUSPROP_SYNTAX union that describes data in one of two ways:
- As two WORD values with one value describing the format of the data and the other describing the data type. When Syntax is specified this way, the values are combined into a single DWORD at run time.
- As a single DWORD value combining the format and type at compile time.
If there is no single DWORD value defined that describes the data, you must use a combination of format and type. For example, user-defined types must be described as a combination of format and type. Otherwise you can use either method of describing the data. | <urn:uuid:9d91be30-3d33-4c15-9a86-8f15a9acfd2b> | 2.953125 | 160 | Documentation | Software Dev. | 44.851563 | 95,598,238 |
The Grotthuss mechanism (also known as proton jumping) is the process by which an 'excess' proton or proton defect diffuses through the hydrogen bond network of water molecules or other hydrogen-bonded liquids through the formation and concomitant cleavage of covalent bonds involving neighboring molecules.
In his 1806 publication "Theory of decomposition of liquids by electrical currents", Theodor Grotthuss proposed a theory of water conductivity. Grotthuss envisioned the electrolytic reaction as a sort of 'bucket line' where each oxygen atom simultaneously passes and receives a single hydrogen ion. It was an astonishing theory to propose at the time, since the water molecule was thought to be OH not H2O and the existence of ions was not fully understood. On its 200th anniversary, his article was reviewed by Cukierman.
Although Grotthuss was using an incorrect empirical formula of water, his description of the passing of protons through the cooperation of neighboring water molecules proved prescient.
The Grotthuss mechanism is now a general name for the proton-hopping mechanism. In liquid water the solvation of the excess proton is idealized by two forms: the H9O4+ (Eigen cation) or H5O2+ (Zundel cation). While the transport mechanism is believed to involve the inter-conversion between these two solvation structures, the details of the hopping and transport mechanism is still debated. Currently there are two plausible mechanisms:
The calculated energetics of the hydronium solvation shells were reported in 2007 and it was suggested that the activation energies of the two proposed mechanisms do not agree with their calculated hydrogen bond strengths, but mechanism 1 might be the better candidate of the two.
By use of conditional and time-dependent radial distribution functions (RDF), it was shown that the hydronium RDF can be decomposed into contributions from two distinct structures, Eigen and Zundel. The first peak in g(r)[clarification needed] of the Eigen structure is similar to the equilibrium, standard RDF, only slightly more ordered, while the first peak of the Zundel structure is actually split into two peaks. The actual proton transfer (PT) event was then traced (after synchronizing all PT events so that t=0 is the actual event time), revealing that the hydronium indeed starts from an Eigen state, and quickly transforms into the Zundel state as the proton is being transferred, with the first peak of g(r) splitting into two.
The Grotthuss mechanism, along with the relative lightness and small size of the proton, explains the unusually high diffusion rate of the proton in an electric field, relative to that of other common cations (Table 1) whose movement is due simply to random thermal motion, i.e. Brownian motion. Quantum tunnelling becomes more probable the smaller the mass of the cation is, and the proton is the lightest possible stable cation. Thus there is a minor effect from quantum tunnelling also, although it dominates at low temperatures only.
|Cation||Mobility / cm2 V−1 s−1| | <urn:uuid:85c9c900-0ab7-47cf-bfcf-0c670d49d7aa> | 3.328125 | 672 | Knowledge Article | Science & Tech. | 30.869482 | 95,598,248 |
Researcher James Morris is rethinking what happens to the enormous number of mollusk shells that end up in landfills every year, according to Popular Science. Morris's team Calcium in a Changing Environment or CACHE, wants to recycle the waste produced by seafood lovers. Oysters on the half shell may seem like a special treat, but enough people eat them for the deterioration of oyster beds and waste management to be have become a serious issue. CACHE is proposing that the shells be recycled, by either being restored to oyster reef systems or crushed for their potential as bio material.
“Reusing shell waste is a perfect example of a circular economy, particularly as shells are a valuable biomaterial,” Morris told Popular Science. “Not only does it improve the sustainability of the aquaculture industry moving forwards, but it can also provide secondary economic benefits to shellfish growers and processors as well.”
The shells of mollusks serve an important purpose in the aquatic eco-system. Climate change has been a blow to oyster reefs, as the water heats and pollution rises. Oyster larvae needs a hard place to settle in order to grow, and the disposed shells could be the perfect place—if they're not destroyed.
“For oysters, particularly, overfishing and disease have reduced the amount of living and dead shells present, and subsequently the amount of hard surfaces available for the young to settle on,” Morris explained.
'If done properly, these structures quickly get covered in living oysters, which in turn attracts other species," he added, meaning that supporting healthy oyster reefs will lead to diversity of species and ocean health generally.
The other value in an oyster shell is the material calcium carbonate, which is generally found through the unsustainable practice of limestone mining. Calcium carbonate is used for lots of things, like in cement mix or even as a dietary supplement for hens.
“In Galicia, Northern Spain, where the biggest mussel farming industry in the European Union is, shells are cleaned and used to treat acid soils in the local area,” Morris said. “This practice has been going on for a long time. There are also examples of shells being used in basic aggregate mixes: oyster shells in France, for instance. But these applications represent a small portion of the shells produced.”
These possibilities may be well-known in some places, but one of CACHE's most challenging works is just connecting engineers and industries that rely on calcium carbonate with venues that produce oysters, or mollusk shell waste. And they're not the only ones struggling with getting the word out. Earlier this summer, Fast Company reported on an organization called the Alabama Coastal Foundation, which had also launched an oyster shell recycling program.
The group had connected with almost 30 restaurants, diverting their oyster shells to repair oyster beds in the Gulf Coast. They in turn had been inspired by a similar program run by the Coalition to Restore Coastal Louisiana, which has been in place since 2014. A great idea will always catch on, and hopefully grown into a firm foundation for saving marine life, and a tasty appetizer.
Sweden's aggressive target of generating over 40 terawatt-hours of renewable energy by 2030 could be reached nearly a decade early. A massive amount of wind power projects could hit a snag in market value with subsidies, but SWEA could push to close those up by the end of the year.
It's challenging and laborious to detect this bacteria that decimates bee populations, so an apiary inspector trained a dog to do it. They're amazing.
New technologies means that instead of sucking power off the energy grid, buildings can feed back into it, powering other buildings and even cars.
A sixth-grader in Massachusetts has begun developing a robot that's able to detect microplastics in our ocean after wanting to make a difference at the Boston Harbor. Her ultimate goal is to create a way to also pick up trash and cut costs in the process. | <urn:uuid:930f959d-b997-4f32-b13e-ebab8e3b4012> | 3.9375 | 838 | News Article | Science & Tech. | 40.562787 | 95,598,252 |
Importance of Solubility in Everyday First
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Keywords: examples of solubility in everyday life
For my science project I'll be researching the solubility of various substances. Solubility is an interesting subject because it's very important for everyday life and I knew very little of it before I started my project. My experiment will give me insight on how the rate of solubility is affected by certain factors and if certain liquids struggle to mix together well. For this essay I needed to understand what solubility is, what affects the rate of solubility, where it can be found in nature, how it's used every day, and how solubility works.
The measure of solubility determines how substances dissolve into one another. The substance dissolving into the other is the solute and the substance being dissolved into is the solvent. When you mix salt into water the salt is the solute and the water is the solvent. Though the salt won't dissolve into the water immediately and if a large portion of salt is being dissolved into water, then there will be a portion of salt left over.Nevertheless, when salt and water do mix a new substance is formed that can have many practical uses. Solubility isn't limited to just liquids mixing with other liquids, however, solids and gases can also mix into liquids.A solution is created when the solute's molecules form intermolecular bonds with the solvent's molecules as they merge. First the solute's molecules drift into the solvent and are surrounded by the solvent's molecules, then the molecular bonds of the solute are broken so that intermolecular bonds can be made with the solvent. This process can be compared to dropping a clod of dirt into a puddle of water.
There are numerous factors that affect solubility such as temperature, stirring, and the substances themselves. These factors can accelerate the rate of solubility or they can prevent certain substances from being soluble. Temperature is an important factor when it comes to experiments of solubility because the rate of solubility increases with temperature. Solutions are affected by temperature because it causes the molecules to speed up when hotter or slow down when colder and when molecules are moving around quickly they can merge into the other solvent's molecules quickly and vice-versa. Solubility among gases, however, works better when the gases are colder because they're more dense when cold. Stirring is also important when mixing substances for faster solubility because it has a similar affect on molecules that heat has. The ocean's tides and waves stir the dirt and salt in the water, thus causing the substances to quickly mix together.
Certain substances are composed in a way that negates them from being soluble with other substances. This can be caused by the density of a substance and whether the solute's and solvent's molecules are polar. The density of a substance, such as oil, causes it to sink to the bottom of a cup of water rather than mix with the water because the molecules of oil are larger and heavier. The water simply sits on top of the oil and if more oil is added, then it'll just pass through the water. Solids won't mix with other solids because their molecules are too dense, but solids can mix with liquids. Gases can mix with liquids too if the gas's molecules are dense enough. The polar alignment of a substance also prevents it from merging with something of the opposite alignment unless one substance is both polar and non-polar, such as alcohol. Chemists use the phrase "like dissolves like" to describe this circumstance.
Solutions can be found almost everywhere on the earth, from the oceans to the sky. Every ocean and every lake on Earth is a solution. This is because the water has mixed with dirt, salt, and various substances to become a new substance that, though still water, isn't healthy to drink. When rain touches the ground it mixes with dirt, rocks, and so on that it becomes a solution upon contact with the earth. Dirt and rocks are too dense to mix with each other, but when they're small enough they can mix with various substances. Smoke can mix with clouds and create a solution of acid rain that can be very dangerous and carbon dioxide can create the unhealthy phenomenon of smog. Because gases diffuse, the earth's atmosphere isn't a giant solution.
Solubility has many practical applications in our lives such as purifying water, making drinks, and vitamin storage. Because every ocean in the world is a solution of water mixed with dirt, salt, and various substances the water isn't healthy to drink, so it's purified by chemicals that remove the harmful products of the water. Almost everything we drink is a solution because it's had chemicals added to it that make it taste better or make it safer to drink. This process is used on most of the food we eat and liquids we drink to prevent people from getting sick. Chemicals are added to eggs to prevent food poisoning from salmonella and to certain products to increase shelf life.
When you stir sugar in a cup of coffee you're making a solution. The stirring and heat make the process of the sugar dissolving in the coffee faster and afterward you have a tastier cup of coffee. When you make coffee you're making a solution because the coffee beans are added to water and blended until they become a liquid. Blending drinks and making martinis are both ways of making solutions that taste better or worse than their individual components. Drinks can be carbonated for an interesting taste that is caused by mixing a liquid and a gas under pressure. Most vitamins can be categorized as fat-soluble, which means that the vitamins are stored in our bodies, and water-soluble, which means that the vitamins pass through our bodies and are excreted as urine. Because fat-soluble vitamins are stored in our bodies, they shouldn't be taken in large doses. The names "fat-solubles" and "water-solubles" refer to how they should be used by our bodies.
I learned a lot from my essay about solubility, but I namely learned how often solubility occurs, its uses & limitations, and that solutions are very practical. Solubility is all around us in nature and God implemented it so that we could be healthier and enjoy interesting tastes. Our world would be vastly different if there were no solubility, in fact no living creatures could exist.
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Visual scanning behaviour in honeybees
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Freely flying bees were rewarded with sugar solution on a variety of black-and-white shapes as well as on coloured gratings in various training situations (Table 1). In subsequent dualchoice tests, the bees' discrimination between the various shapes was measured. In addition, the bees were video-filmed while flying in front of the shapes. The scanning patterns thus obtained were then quantified in order to (i) characterize scanning behaviour and its relationship to the geometrical parameters of the scanned shapes, (ii) investigate whether scanning plays a role in pattern discrimination and (iii) examine the influence of training on the characteristics of scanning.
The scanning patterns clearly mirror the contours of the scanned shape in all cases (Fig. 3), i.e. the bees fly along the contours contained in the shape. This behaviour does not depend on whether the scanned shape is one that was previously rewarded, or one that is completely novel to the bees.
Comparison of the results of quantifying the scanning patterns with the results of dual-choice tests (Fig. 5) reveals that scanning behaviour is independent of discrimination performance.
On the average, horizontal scanning directions occur more often than vertical directions (Fig. 4).
Variations of the training situation produce measurable differences in scanning behaviour (Fig. 4). However, except in the case of vertical scanning on a vertical grating (Fig. 4), these differences are quite small, indicating that following contours is a largely stereotyped behaviour.
Horizontal gratings are very well discriminated from vertical ones even if they offer contrast to only one receptor type, i.e. blue or green (Fig. 8), demonstrating that the direction of contours is visible to the pattern recognition system even under these conditions. However, vertical and horizontal coloured gratings offering only blue-contrast do not elicit contour-following (Fig. 9 c and d), whereas gratings offering only green-contrast do (Fig. 9 a and b). Thus, the bees' scanning behaviour is colour-blind and most probably governed by the green receptors.
We suggest that contour-following is the byproduct of a behavioural mode which serves to prevent retinal image movement during flight in front of a contoured visual pattern.
KeywordsRetinal Image Stereotyped Behaviour Discrimination Performance Scanning Direction Pattern Discrimination
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Researchers at EPFL have built a matchbox-sized device that can test for the presence of bacteria in a couple of minutes, instead of up to several weeks. A nano-lever vibrates in the presence of bacterial activity, while a laser reads the vibration and translates it into an electrical signal that can be easily read—the absence of a signal signifies the absence of bacteria.
Thanks to advances in laser and optical technology, the EPFL team of physicists has reduced this time to a couple of minutes. To do so, Giovanni Dietler, Sandor Kasas and Giovanni Longo have exploited the microscopic movements of a bacterium's metabolism.
The researchers are currently evaluating the tool's potential in other fields, notably oncology. They are looking into measuring the metabolism of tumor cells that have been exposed to cancer treatment to evaluate the efficiency of the treatment. "If our method also works in this field, we really have a precious tool on our hands that can allow us to develop new treatments and also test both quickly and simply how the patient is reacting to the cancer treatment," says Sandor Kasas.
Lionel Pousaz | EurekAlert!
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To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...
For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.
Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...
Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.
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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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20.07.2018 | Power and Electrical Engineering
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Scientists have found how fluids, such as water, become sealed within the earth’s fault planes for a long period of time. This fluid pressure makes it easier for the earth’s plates to move alongside each other, eventually resulting in an earthquake.
Dr Dan Faulkner explains: “The difficulty with predicting earthquakes is that we know so little about how fault planes work. Over the years we have found that even small stresses acting on the earth’s plates can cause large earthquakes. For example the Loma Prieta earthquake in 1989 caused massive devastation, yet there was very little stress acting on the plate boundary to cause the quake in the first place.
“In theory, high stresses are needed to cause slip along a fault plane, but if something like pressurised water or gas gets inside the fault then it should act as a kind of cushion, making movement between plates easier and an earthquake more likely. Until now a problem with this theory was that as fluid pressures increased the rocks would crack and the fluids could escape through the cracks, reducing the ‘cushion’ effect. Our recent study, however, found that much smaller cracks surrounding the fault plane change the stresses acting on the rock, reducing the likelihood of significant cracks forming and allowing the fluid to escape.”
The team measured the density of ‘microcracks’ in the rock near the Chile fault line and applied varying amounts of stress to the rock to see how it responded. They found the ‘microcracks’ changed the elasticity of the rock, which meant stresses that might normally occur at almost right angles to the fault line rotated to a 45 degree angle instead.
Under normal stresses fluid would build up to such as extent that the rock would break and the fluid would escape, reducing the risk of an earthquake. When stress, however, occurs at a 45 degree angle the rock is less likely to break and the low fluid pressures inside can cause earthquakes.
Dr Faulkner added: “We now need to conduct further study into where these fluids and gases are coming from. Scientists are currently drilling of the San Andreas Fault in California, to help us understand more fully the mechanics of fault zones and how earthquakes occur.”
The San Andreas Fault Observatory at Depth (SAFOD) is a deep borehole observatory that will measure the physical conditions under which plate boundary earthquakes occur. Dr Faulkner is one of only two UK scientists who currently have access to rock drilled from the San Andreas Fault, which will be analysed in order to understand fault behaviour.
Dr Faulkner’s research is published in Nature Magazine.
Samantha Martin | alfa
Global study of world's beaches shows threat to protected areas
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NSF-supported researchers to present new results on hurricanes and other extreme events
19.07.2018 | National Science Foundation
A new manufacturing technique uses a process similar to newspaper printing to form smoother and more flexible metals for making ultrafast electronic devices.
The low-cost process, developed by Purdue University researchers, combines tools already used in industry for manufacturing metals on a large scale, but uses...
For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.
To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...
For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.
Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...
Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.
A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...
Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.
"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....
13.07.2018 | Event News
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A Continuing Enigma of Geology
Jelte P. Harnmeijer, University of Washington
Banded Iron Formations (‘BIFs’) are highly controversial chemical precipitates characterized by the presence of alternating layers of iron-rich and amorphous silica-rich layers. This dichotomous compositional layering is usually expressed on several scales at anygiven outcrop, from fine sub-millimetre-scale varve-like laminae to metre-scale bands. Even on a microscopic scale, the boundary between the ferruginous and siliceous layers is distinctly abrupt.
This paper sets out to explore the key aspects of BIFs pertinent to their role in the study of early earth evolution, and outline the major controversies surrounding their interpretation. The focusrests on BIF classification, temporal- and spatial-distribution, behavior in solution, depositional environment, and origin.
An understanding of the origin of BIFs provides useful insight into conditions existing on, and governing, the early lithosphere, hydrosphere and atmosphere. BIFs have proved particularly useful to studies of the early earth due to their intimate coupling with oxygenconcentration. Researchers have benefited tremendously from the narrow temporal-, depositional-, and tectonic- niches inhabited by BIFs in our geological record.
In the context of early earth evolution, it is the possible link to an evolving biosphere that makes BIFs particularly interesting. Iron is used as a metabolic agent by numerous microorganisms. Some of these, including specific species ofoxygenic- and anoxygenic- photoautotrophs and chemoferrotrophs, lend credit to the theory of BIF-deposition being, at least in part, a microbially mediated process. Direct evidence for a microbial role in Archaean BIF deposition remains elusive.
The dominant enigma surrounding BIFs is the spectacular alternating BIF banding. A distal hydrothermal source for iron is favored, while recent workutilizing Ge/Si ratios (Hamade et al., 2003) suggests a continental component in silica flux. Various mechanisms for primary Fe2+ oxidation are explored, including diffusive, photochemical and biological processes.
The favorable characteristics of hydrothermal settings as sites for the emergence of life are well recognized (eg., Russell and Hall, 1997). Likewise, the catalytic role that surfaces ofclay minerals may have played has much support (Cairns-Smith, 1982). Given their presence at the very beginning of the rock record, association with hydrothermal activity, diverse mineralogy, hydrous clay mineral content and probable biogenicity, I propose BIFs as a candidate-site for the emergence of life on Earth.
Table of Contents
1. Observations of BIFs in Australia, southern Africa 4
2.1. Literature Classification and Definition 5
2. BIF Distribution 7
1. Temporal Distribution 7
2. Spatial Distribution 9
3. BIF Chemistry and Metamorphism 10
4. The Behaviour of BIF Components in Solution12
4.1. Fe2+ and Fe3+ in Solution 12
2. Silica in Solution 12
5. Depositional Environment 13
6. Origin of Precambrian BIFs 15
1. Sources of Iron and Silica 15
2. Primary Oxidation 16
1. Near-surface Oxidation 16
2. Photochemical Processes 17
3. Biological Processes 174. Tectonic Origin 21
7. Conclusions 22
iron formation a chemical sedimentary rock, typically thin-bedded and/or finely laminated, containing at least 15% iron of sedimentary origin, and commonly but not necessarily containing layers of chert
- American Geological Institute Glossary of Geology (after...
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The Interior of the Earth
The interior of the Earth (and, a fortiori, of the other planets) is much less known than the interior of the Sun, and also of stars light years away. The physics and chemistry of solid and liquid phases at high pressures, essential for the understanding of terrestrial planets and the core of the outer planets, are much more complex than those of nearly perfect gases (which form stars) and very little known. For the Earth, the detailed study of seismic propagation has provided, especially for the mantle, excellent measurements of its density distribution and is discussed in this chapter. The model of its interior so obtained is quite relevant for the study of its geological history, as well as for other planets. Planetary interiors are characterized by two major features: a fluid, conductive core, which generally produces a global magnetic held by the dynamo process (Ch. 6); and the interaction between the crust and the slow motion of convective eddies in the mantle. Due to this interaction, the crust undergoes continuous deformations, responsible for continental drifts, earthquakes and the uplifting of mountain chains. They are called plate tectonics and are discussed in some detail here, also in view of the fact that they can be measured directly from space.
KeywordsSolar System Seismic Wave Rayleigh Wave Inner Core Plate Motion
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Haploid yeast cells bud next to the site of the previous division (axial pattern), but diploid yeast cells bud from their poles (bipolar pattern). In the 8 December Science, Chen et al. propose that the Rax2 protein marks the cortex to provide a landmark for bipolar budding (Science 2000, 290:1975-1978). Rax2 is an integral membrane protein, discovered following a hunt for mutants defective in bipolar budding. Late in the cell cycle, Rax2 protein localizes to rings associated with division sites. These rings persist long after production of the protein has ceased. Induction and repression experiments show that the marks are stable, and that existing, localized protein does not shift to new poles or division sites. Rax2 therefore represents a form of long-lasting, epigenetic inheritance. Its discovery suggests that heritable protein marks at the cell cortex may contribute to the development of tissue architecture in higher eukaryotes. | <urn:uuid:3af7abae-ca81-4d1e-87a1-45ab7ee1c1d1> | 3.078125 | 193 | Knowledge Article | Science & Tech. | 40.703594 | 95,598,329 |
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Antonie van Leeuwenhoek was a Dutch draper who needed a better way to examine the tiny threads of cloth. His ingenious solution gave birth to the modern science of microbiology!
We must be clear-eyed about the security threats presented by climate change, and we must be proactive in addressing them.
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A bipolar neuron is a nerve cell which has two processes; a dendrite and an axon. Bipolar neurons are sensory nerve cells specialized for the transmission of special nerve impulses. As such, they are part of the sensory pathways for smell, sight, taste, hearing and vestibular functions. The most common examples are the bipolar neuron of the retina, and the ganglia of the vestibulocochlear nerve. When used without further detail, the term usually refers to the retinal cells.
The bipolar neuron of the retina exists between photoreceptors (rod cells and cone cells) and ganglion cells. Their function is the transmission signals from the photoreceptors to the ganglion cells. Bipolar cells receive synaptic input from either rods or cones, but not both, and they are designated rod bipolar or cone bipolar cells respectively. There are roughly 10 distinct forms of cone bipolar cells, however, only one rod bipolar cell, due to the rod receptor arriving later in the evolutionary history than the cone receptor.
Bipolar neurons are also found in the spinal ganglia, when the cells are in an embryonic condition. They are best demonstrated in the spinal ganglia of fish. Sometimes the processes, come off from opposite poles of the cell, and the cell then assumes a spindle shape; in other cells both processes emerge at the same point. In some cases where two fibers are apparently connected with a cell, one of the fibers is really derived from an adjoining nerve cell and is passing to end in a ramification around the ganglion cell, or, again, it may be coiled spirally around the nerve process which is issuing from the cell. | <urn:uuid:ba9d99c4-ea52-4562-be25-bb51e2910ba6> | 3.609375 | 342 | Knowledge Article | Science & Tech. | 38.170136 | 95,598,335 |
Beyond the Basics in CSS and Scripting
In Chapters 5, 6, and 7, you learned how to use CSS to make your website attractive and easy to maintain with styles. In this chapter, we will look at styling your content for different media. In several places in this book, I have pointed out that you have more control over how pages display when printed than over how they display on the screen. Using a print media stylesheet allows you to specify how a page should print. You can reformat a page so that only the parts of the page you choose are printed and so that you use print measurements, such as margins in inches or centimeters and type in points.
KeywordsRegular Expression Error Message Form Field Form Validation Screen Reader
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Hibernate is a Object-relational mapping (ORM) tool for Java. It was initiated by Gavin King in 2001. ORM methodology is used to map classes to tables, class instances is mapped to rows and attributes are mapped to table columns. It also map data types of Java to SQL data types.
Hibernate is a persistence framework which used to store and fetch data from Java environment to database table. Persistence is a storing process of data to permanent storing medium like SQL database and fetching back to any time which may be after ending the process which stores data to this table.
Hibernate 4 was released in December 2011. The newly added features are : support for initial multi-tenancy, ServiceRegistry Introduction, SessionFactory session clean up, Improvement in Integration through org.hibernate.integrator.spi.Integrator and auto discovery, Improvement in logging due to i18n support and message codes, more clear separation between API, SPI and implementation classes, deprecated functions, classes clean up.
Given below the complete list of topics on Hibernate 4 :
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|MLA Citation:||Bloomfield, Louis A. "How Everything Works" How Everything Works 17 Jul 2018. Page 131 of 160. 17 Jul 2018 <http://www.howeverythingworks.org/prints.php?topic=all&page=131>.|
This tungsten recycling process dramatically slows the filament's decay. Although the filament gradually develops thin spots that eventually cause it to fail, the filament can operate at a higher temperature and still last two or three times as long as the filament of a regular bulb. The hotter filament of a halogen bulb emits relatively more blue light and relatively less infrared light than a regular bulb, giving it a whiter appearance and making it more energy efficient.
The amount of each force is determined by how fast the cars approach one another before they hit and by how stiff their surfaces and frames are. If the cars are approaching rapidly and are extremely stiff and rigid, they will exert enormous forces on one another when they collide and will do so for a very short period of time. During that time, the cars will accelerate violently and their velocities will change radically. If you happened to be in one of the cars, you would also accelerate violently in response to severe forces and would find the experience highly unpleasant.
If, on the other hand, the cars are soft and squishy, they will exert much weaker forces on another and they will accelerate much more gently for a long period of time. That will be true even if they were approaching one another rapidly before impact. When the collision period is over, the cars will again have changed velocities significantly but the weaker forces will have made those changes much more gradual. If you have to be in a collision, chose the soft squishy cars over the stiff ones—the accelerations and forces are much weaker and less injurious. That's why cars have crumple zones and airbags: they are trying to act squishy so that you don't get hurt as much.
In effect, the charged particle "plays" with the photon of light, trying to see if it can absorb that photon. As it plays, the charged particle begins to shift into a new quantum state—a "virtual" state. This virtual state may or may not be permanently allowed. If it is, it's called a real state and the charged particle may remain in it indefinitely. In that case, the charged particle can truly absorb the photon and may never reemit it at all. But if the virtual state turns out not to be a permanently allowed quantum state, the charged particle can't remain in it long and must quickly return to its original state. In doing so, this charged particle reemits the photon it was playing with. The closer the photon is to one that it can absorb permanently, meaning the closer the virtual quantum state is to one of the real quantum states, the longer the charged particle can play with the photon before recognizing that it must give the photon up.
A colored material is one in which the charged particles can permanently absorb certain photons of visible light. Because this material only absorbs certain photons of light, it separates the components of white light and gives that material a colored appearance.
A transparent material is one in which the charged particles can't permanently absorb any photons of visible light. While these charged particles all try to absorb the visible light photons, they find that there are no permanent quantum states available to them when they do. Instead, they play with the photons briefly and then let them continue on their way. This playing process slows the light down. In general blue light slows down more than red light in a transparent material because blue light photons contain more energy than red light photons. The charged particles in the transparent material do have real permanent states available to them, but to reach those states, the charged particles would have to absorb high-energy photons of ultraviolet light. While blue photons don't have as much energy as ultraviolet photons, they have more energy than red photons do. As a result, the charged particles in a transparent material can play with a blue photon longer than they can play with a red photon—the virtual state produced by a blue photon is closer to the real states than is the virtual state produced by a red photon. Because of this effect, the speed at which blue light passes through a transparent material is significantly less than the speed at which red light passes through that material.
Finally, about quantum states: you can think of the real states of one of these charged particles the way you think about the possible pitches of a guitar string. While you can jiggle the guitar string back and forth at any frequency you like with your fingers, it will only vibrate naturally at certain specific frequencies. You can hear these frequencies by plucking the string. If you whistle at the string and choose one of these specific frequencies for your pitch, you can set the string vibrating. In effect, the string is absorbing the sound wave from your whistle. But if you whistle at some other frequency, the string will only play briefly with your sound wave and then send it on its way. The string playing with your sound waves is just like a charged particle in a transparent material playing with a light wave. The physics of these two situations is remarkably similar.
Modern studies of glass show that below the glass transition temperature, which is well above room temperature, molecular rearrangement effectively vanishes altogether. The glass stops behaving like a viscous liquid and becomes a solid. Its heat capacity and other characteristics are consistent with its being a solid as well.
You'll notice that I keep saying "relative to the earth's center of mass" when I discuss motion. I do that because there is no special "absolute" frame of reference. Any inertial frame is as good as any other frame and your current inertial frame is just as good as anyone else's. In fact, you are quite justified in declaring that your frame of reference is stationary and that everyone else's frames of reference are moving. After all, you don't detect any motion around you so why not declare that your frame is officially stationary. Since the air is also stationary in that frame of reference, flying about in the air doesn't make things any more complicated. You are flying through stationary air in your old stationary frame of reference. The only way in which the 950 mph speed appears now is in comparing your frame of reference to the rest of the earth: in your frame of reference, the earth's center of mass is moving westward at 950 mph.
When two atoms exchange an electron, they form an ionic bond that again lowers the overall energy of the atoms and sticks them together. Although moving the electron from one atom to the other requires some energy, the two atomic ions that are formed by the transfer have opposite charges and attract one another strongly. The reduction in energy that accompanies their attraction can easily exceed the energy needed to transfer the electron so that the two atoms become permanently stuck to one another.
While you're looking at your image, the reversed direction is the forward-backward direction. But it's natural to imagine yourself in the place of your image. To do this you imagine turning around to face in the direction that your image is facing. When you turn in this manner, you mentally eliminate the forward-backward reversal but introduce a new reversal in its place: a left-right reversal. If you were to imagine standing on your head instead, you would still eliminate the forward-backward reversal but would now introduce an up-down reversal. Since it's hard to imagine standing on your head in order to face in the direction your image is facing, you tend to think only about turning around. It's this imagined turning around that leads you to say that your image is reversed horizontally.
When the pole-vaulter stands ready to begin his jump, he is motionless on the ground and he has no kinetic energy (energy of motion), minimal gravitational potential energy (energy of height), and no elastic energy in his pole. All he has is chemical potential energy in his body, energy that he got by eating food. Now he begins to run down the path toward the jump. As he does so, he converts chemical potential energy into kinetic energy. By the time he plants his pole at the jump, his kinetic energy is quite large.
But once he plants the pole, the pole begins to bend. As it does, he slows down and his kinetic energy is partially transferred to the pole, where it becomes elastic potential energy. The pole then begins to lift the vaulter upward, returning its stored energy to him as gravitational potential energy. By the time the vaulter clears the bar, 5 or 6 meters above the ground, almost all of the energy in the situation is in the form of gravitational potential energy. The vaulter has only just enough kinetic energy to carry him past the bar before he falls. On his way down, his gravitational potential energy becomes kinetic energy and he hits the pit at high speed. The pit's padding extracts his kinetic energy from him gently and converts that energy into thermal energy. This thermal energy then floats off into the air as heat.
One interesting point about jumping technique involves body shape. The vaulter bends his body as he passes over the bar so that his average height (his center of gravity) never actually gets above the bar. Since his gravitational potential energy depends on his average height, rather than the height of his highest part, this technique allows him to use less overall energy to clear the bar.
Physical science, particularly physics itself, is completely self-consistent. By that I mean that the same set of physical rules applies to every possible situation in the universe and that this set of rules never leads to paradoxical results. Despite its complicated behavior, the universe is orderly and predictable. It's precisely this order and predictability that is the basis for the whole field of physics.
In contrast, pseudo-science is eclectic—it draws from physics and magic as it sees fit. It uses the laws of physics when it finds those laws useful and it ignores the laws of physics when they conflict with its interests. But the laws of physics only make sense if they apply universally—if there were even one situation in which a law of physics didn't apply, physics would lose its self-consistency and predictive power. That's just what happens with pseudo-science when it begins to ignore the laws of physics on occasion. Moreover, the new rules that pseudo-science introduces to replace the ones it ignores make the trouble even worse. Overall, pseudo-science is inconsistent and can't be counted on to predict anything.Pseudo-science might argue that the laws of physics are correct as far as they go, but that they're incomplete. No doubt the laws of physics are incomplete; physicists have frequently discovered improvements to the laws of physics that have allowed them to make even more accurate predictions of the universe's behavior. But in the years since the discoveries of relativity and quantum physics, the pace of such discoveries has slowed and what remains to be understood is at a very deep and subtle level. It's extraordinarily unlikely that the laws of physics as they're currently understood are wrong at a level that would allow a person to bend a spoon with their thoughts alone or predict the order of a deck of cards without assistance. Just because I haven't dropped a particular book doesn't prevent me from predicting that it will fall when I let go of it. I understand the laws that govern its motion and I know that having it fly upward would violate those laws. Similarly, I don't have to watch someone try to bend a spoon with their thoughts to know that it can't be done legitimately. Again, I understand the laws that govern the spoon's condition and I know that having it bend without an identifiable force acting on it would violate those laws. I also don't have to watch someone try to predict cards to know that it, too, can't be done legitimately. Without a clear physical mechanism for transporting information from the cards to the person, a mechanism that must involve forces or exchanges of particles, there is no way for the person to predict the cards.
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In an array all elements are of the same type. In contrast to the array, the record structure offers the possibility to declare a collection of elements as a unit even if the elements are of different types. The following examples are typical cases where the record is the appropriate choice of structuring method. A date consists of three elements, namely day, month, and year. A description of a person may consist of the person’s names, sex, identification number, and birthdate. This is expressed by the following type declarations
KeywordsStatement Sequence Array Element Record Field Individual Field Concise Notation
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One third of us globally cannot see the Milky Way in the night sky because of light pollution – artificial light that brightens the night sky – says an international team of scientists who created the ‘New World Atlas of Artificial Night Sky Brightness’.
The scientists, from Israel, Germany, Italy and the USA, published the new atlas in the open-access journal Science Advances (citation below). It documents the degree to which different parts of the world are illuminated by artificial skyglow.
Artificial skyglow is the diffuse luminance of the night sky originating from light we produce, as opposed to the natural night light from the Moon and other celestial bodies.
Polar graph showing the 3 different light intensity distributions used to compute the three map versions: the Lambertian distribution with a peak toward the zenith (blue), the function with peak intensity at low angles above the horizon plane (green), and the function with peak at intermediate angles, 30° above the horizon plane (yellow). The red line shows the overall best-fitting function. (Image: Science Advances)
Light pollution also affects wildlife
Study leader, Fabio Falchi from the Italian Light Pollution Science and Technology Institute (ISTIL), and colleagues explained that light pollution is not only a nuisance for astronomers and amateur skygazers, it also affects nocturnal organisms and our ecosystems.
“The new atlas provides a critical documentation of the state of the night environment as we stand on the cusp of a worldwide transition to LED technology.”
“Unless careful consideration is given to LED color and lighting levels, this transition could unfortunately lead to a 2-3 fold increase in skyglow on clear nights.”
The map above shows the artificial sky brightness as a ratio to the natural sky brightness (assumed to be 174 μcd/m2). (Image: Science Advances)
Our skies have changed significantly
The atlas maps a world which has changed considerably over the past 200 years – today much of it is awash with light. In Western Europe, for example, there are just a handful of small areas left where the night sky is relatively unaffected by light pollution, including regions in Austria, Spain, Scotland, Sweden and Norway.
Apart from the world map, the researchers also provide tables showing the areas of each nation and what proportion of its population lives under skies with high concentrations of skyglow.
The scientists specifically gathered and analysed data from the G20 nations – the twenty largest economies in the world – and found that in terms of area, the most light-polluted are South Korea and Italy, while Australia and Canada have the lowest concentrations of artificial skyglow.
Citizens of Germany and India are most likely to be able to see our galaxy (Milky Way) from their home, while those in South Korea and Saudi Arabia are least likely.
Thanks to a new satellite and the recent development of cheap sky radiance meters, major advances over the 2001 atlas were possible.
Maps of Europe’s artificial sky brightness, in twofold increasing steps. Map ‘A’ shows artificial night brightness in V-band, map ‘B’ shows the forecast in the perceived sky brightness for a dark-adapted eye after a transmission toward 4000K CCT LED technology, without increasing the photopic flux of lamps that are currently installed. (Image: Science Advances)
Citizen scientists vital for whole project
The researchers calibrated the atlas using Sky Quality Meters at 20,865 different locations across the globe. They were especially grateful for the participation of citizen scientists in gathering calibration data, which they described as ‘critical’.
Co author Dr. Christopher Kyba, who works at GFZ German Research Centre for Geosciences as a researcher, said:
“Citizen scientists provided about 20% of the total data used for the calibration, and without them we would not have had calibration data from countries outside of Europe and North America.”
Night brightness in North America and the Caribbean. (Image: Science Advances)
Dr. Sibylle Schroer, who coordinates the EU funded ‘Loss of the Night Network’ and was not a study author, said: “The community of scientists who study the night have eagerly anticipated the release of this new Atlas.”
Scott Feierabend, Director of the International Dark-Sky Association, said:
“The new atlas acts as a benchmark, which will help to evaluate the success or failure of actions to reduce light pollution in urban and natural areas.”
In an Abstract that precedes the main paper in the journal, the researchers wrote:
“This atlas shows that more than 80% of the world and more than 99% of the U.S. and European populations live under light-polluted skies.”
“The Milky Way is hidden from more than one-third of humanity, including 60% of Europeans and nearly 80% of North Americans. Moreover, 23% of the world’s land surfaces between 75°N and 60°S, 88% of Europe, and almost half of the United States experience light-polluted nights.”
Citation below: “The new world atlas of artificial night sky brightness,” Fabio Falchi, Pierantonio Cinzano, Dan Duriscoe, Christopher C. M. Kyba, Christopher D. Elvidge, Kimberly Baugh, Boris A. Portnov, Nataliya A. Rybnikova and Riccardo Furgoni. Science Advances, Vol. 2, no. 6, e1600377. 10 June 2016. DOI: 10.1126/sciadv.160037.
Video – Light pollution in our night skies
In this Science News video (no sound) you can see an image of the Earth rotating with different colours on its surface representiing various intensities of artificial light. | <urn:uuid:1f830e17-ec9c-4d2d-a97a-905c3b29130b> | 3.890625 | 1,240 | News Article | Science & Tech. | 41.605579 | 95,598,414 |
An ultra fast meteor came in from space and hit our atmosphere earlier this month at an incredible speed of 29000 miles per hour (46,600 km/h), says the American space agency NASA, which estimated the object weighed at least 150 pounds (68 kg) and was approximately 16 inches (40.6 cm) in diameter. NASA scientists believe it was a piece of an asteroid.
29000 miles per hour is equivalent to 8 miles per second.
According to NASA, all its six sky meteor cameras in the Southeast of the US detected a meteor fifty miles above the Earth’s surface over the town of Georgia, about 140 miles southeast of Atlanta.
NASA scientists were able to calculate the meteor’s weight and dimensions by measuring its brightness.
An image of the meteor burning up in the sky, taken by one of NASA’s six cameras in the area. (Image: blogs.nasa.gov)
When it hit the atmosphere it had been travelling due south at a speed of 29,000 miles per hour.
Slowed to 9,000 mph and stopped burning
The NASA cameras continued tracking it to an altitude of 17 miles above Locust Grove, a city in Henry County, Georgia, where it had slowed to 9,000 miles per hour. By this time the meteor was no longer producing light.
NASA scientists say some fragments of this meteor may have survived and reached the ground as meteorites.
We call it a meteor when it is flying, but as soon as it hits the ground it is called a meteorite.
NASA says its scientists will be carrying out a more detailed analysis.
In a separate alert of sightings, the American Meteor Society (AMS) received over fifty-five reports of a bright object whizzing across the skies of California, Arizona and Nevada on Tuesday, 22nd December, at around 18:10 PST.
According to AMS, this was not a fireball. It was Russian space debris – parts from an SL-4 rocket body that had reentered the atmosphere somewhere above Arizona.
What is a fireball?
The American Meteor Society says a fireball is a bright meteor, usually brighter than magnitude -4, which is approximately the same magnitude of the planet Venus as seen in the evening or morning sky.
A fireball that explodes in a bright terminal flash at the end, sometimes with visible fragmentation, is called a bollide.
NASA Video – Bright Fireball Spotted by 6 NASA All Sky Cameras | <urn:uuid:aa4d5134-23d7-4324-9da3-c7f324e9acbe> | 3.34375 | 508 | News Article | Science & Tech. | 54.616471 | 95,598,415 |
Toxin proteins are genetically engineered into our food because they kill insects by perforating body cell walls, and Professor Rikard Blunck of the University of Montreal's Group for the study of membrane proteins (GÉPROM) has detected the molecular mechanism involved.
In recognition of his breakthrough, he received the Traditional Paul F. Cranefield Award of the Society of General Physiologists yesterday evening. "This study is about gaining a better understanding of the basic functioning of the toxin proteins in order to judge the risks of using them as pesticides for our nutrition," Dr. Blunck explained.
The Cry1Aa toxin of B. thuringiensis that was investigated is a member of the class of proteins which are called "pore-forming toxins" because they perforate the walls, or membranes, of cells. Cry toxins kill insect larvae if ingested by them and are, therefore, genetically engineered into a number of transgenic crops, including those for human consumption, to make them resistant against these insects.
The pores in the membranes cause minerals necessary for the cell to live to break out and collapse the energy household of the cell. While these toxins could be studied outside of cell membranes through existing techniques that provide images of the 3D structure, the toxins rapidly change their architecture once in contact with the membrane, where the traditional approaches cannot be applied.
Dr. Blunck and his co-workers found a way of using fluorescent light to analyze the architecture and mechanism of the proteins in an artificial cell wall environment. Planar lipid bilayer (PLB) are artificial 0.1 mm-wide systems that mimic the cell membrane. The researchers developed a chip to investigate proteins introduced into these artificial cell walls with fluorescent light waves. Molecular fluorescent probes are coupled to the toxin proteins. If the proteins now enter the artificial membranes and change their structure, their architecture and movement and even their distribution can be followed – thanks to the developed technique - by the fluorescent light they are emitting.
"By watching the toxin in both its active and inactive state, and by measuring the dynamic changes of the light emitted by the molecular probes, we were able to determine which parts of it were interacting with the membrane to cause the pores." Dr. Blunck explained. "We expect the technique to be applied to a wide range of disease-causing toxins in future."
About the study:
"Rapid topology probing using fluorescence spectroscopy in planar lipid bilayer: the pore-forming mechanism of the toxin Cry1Aa of Bacillus thuringiensis" was published in the Journal of General Physiology by Rikard Bunck, Nicolas Groulx and Marc Juteau of the University of Montreal. The study received funding from the Natural Sciences and Engineering Research Council, the Canada Research Chairs, the Canadian Foundation for Innovation, the Fonds de la recherché en santé du Québec and the Fonds québécois de la recherché sur la nature et les technologies. The University of Montreal is officially known as Université de Montréal.
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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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Fast Facts: What is phenology monitoring?
Your day-to-day observations of nature can contribute to citizen science! Plant and animal life stages that occur in an annual cycle, in rhythm with the changing seasons, are called phenophases. Phenology is the study of the timing of these changes. Scientists have found that phenological changes are some of the most sensitive indicators of local effects of global climate change. Monitoring these changes can provide knowledge of how species respond to climate change, and can help predict future changes to better prepare ourselves and our environment for the changing climate.
The challenge is that long-term data on phenophases can take a lot of time and effort to collect. In fact, it is nearly impossible to gather many types of phenology data without the help of citizen scientists - so the work you do is very important!
Rockweed, or knotted rack, is an especially important species to monitor. Observing rockweed throughout its seasonal reproductive cycle can provide a lot of information about water quality conditions during the rockweed’s life. CRV works with Maine Sea Grant's Coastal Signs of the Seasons program to equip volunteers to contribute important data about seasonal changes in rockweed throughout the spring and summer.
Volunteer Description: What do rockweed phenology monitors do?
Volunteer Experience: Rockweed monitors attend a two-hour training. After that, they will be responsible for taking weekly observations of rockweed at one coastal location throughout the late spring and early summer. They will upload their observations into an online database. CRV will provide all needed materials and training.
Time Frame: Volunteers will take observations once per week, on their own schedule.
Project Impacts: Our partners at Maine Sea Grant have been monitoring rockweed phenology through the Coastal Signs of the Seasons program for many years. Coastal Research Volunteers’ data will be combined with Maine volunteers’ data to contribute to a long-term database, which is analyzed by Dr. Jessie Muhlin of Maine Maritime Academy. This type of multi-year database is essential for study of phenology, but hard to obtain because it requires many years of data collection - it couldn’t be done without volunteers like you!
- Interest in visiting the coastline approximately once every two weeks and taking observations
- Ability to upload data on a computer after completing observations
- Learn about, visit, and contribute to knowledge of the local coastline
- Contribute to a long-term phenological dataset
Questions? For more information or if you want to become a rockweed phenology monitor, contact Caitlin.
Upcoming Opportunities: Join our rockweed phenology monitoring efforts!
Contact Caitlin if you'd like to learn how to be involved!
Learn More: Links, resources, and partner organizations
You can read all about the rockweed phenology program conducted by our partners at Maine Sea Grant, and learn more about nationwide citizen science phenology monitoring by browsing the National Phenology Network website. Finally, check out this article about rockweed monitoring on the Gundalow Company blog, written by one of our own Coastal Research Volunteers. | <urn:uuid:5fc55266-98ae-4131-9ba8-d19281da74ee> | 3.5 | 638 | Product Page | Science & Tech. | 28.706546 | 95,598,438 |
Deakin research highlights global sea turtle conservation success storiesMedia release
New Deakin University research is pointing to signs of recovery in global sea turtle populations thanks to long-term conservation efforts, contrasting with a trend that’s seen most endangered vertebrates continue to decline in numbers.
The research, completed in partnership with Aristotle University of Thessaloniki in Greece, looked at hundreds of nesting surveys from breeding sites around the world and found a greater trend towards increases in population size, as well as some worrying population declines.
Of the 299 time series examined, 95 showed significant increases in turtle abundance, while 35 showed significant decreases.
Alfred Deakin Postdoctoral Research Fellow in Deakin's School of Life and Environmental Sciences Dr Gail Schofield said the data, published in Science Advances today, showed efforts to protect nesting and foraging habitat were safeguarding some sea turtle populations.
"This study demonstrates the long-term benefits of sea turtle conservation efforts globally, and the need for continued funding to maintain recovery," Dr Schofield said.
"Positive trends in abundance are likely linked to the effective protection of eggs and nesting females, as well as reduced harvesting and bycatch in fishing."
Six of the world’s seven sea turtle species are currently listed as vulnerable, endangered, or critically endangered.
Historically, adult females were harvested for food while nesting onshore, along with their eggs, as well as being harvested at sea or incidentally caught by fisheries (bycatch). This led to a rapid decline in sea turtle populations by the 1950s.
Eggs and hatchlings emerging on the beaches are also consumed by various predators, including crabs, foxes and racoons.
Dr Schofield said most conservation efforts focussed on reducing illegal harvesting, and caging or relocating nests to hatcheries to maximise protection, with these actions being reinforced by the establishment of marine protected areas.
But she said there was still a lot of work to be done.
"While the news in this study is encouraging, long-term support for conservation is hard to obtain but is essential to deliver sustained conservation success," she said.
"Many populations remain under threat, especially as there may be lags of several decades in detecting survival rates based on nesting data, because of the time required for offspring to reach maturity.
"The positive trends we found should not be interpreted as sea turtle populations being out of the woods; rather, we are highlighting the value of long-term sea turtle conservation efforts globally, and the need to continue these efforts into the future."
Dr Schofield said that in Australia some positive trends were detected, but conservation concerns remained.
"Australia supports the nesting grounds and foraging habitat of five of the seven sea turtle species, along with important foraging habitat for leatherbacks," she said.
"Of note, conservation efforts continue to try and improve the nesting habitat for the green turtle nesting beaches at Raine Island, which is the largest green turtle rookery in the world.
"Challenges remain to document abundance trends across the massive amount of the Australian coast used by nesting turtles."
Victoria's inland wetlands lock away the annual emissions of 185,000 people, or roughly the population of Geelong, according to the state's first ever tally of the valuable environmental resources.
Deakin University will collaborate with a group of French research institutions and the University of Tasmania on a new international cancer research laboratory, after a special agreement signed by French President Emmanuel Macron and Australian Prime Minister Malcolm Turnbull at Admiralty House today.
The removal of rabbits could be good or bad for Australia’s native species depending on how many rabbits are removed and for how long, according to new research from Deakin University’s Centre for Integrative Ecology. | <urn:uuid:0b06b55e-5fd4-4232-b26d-69b46d28fd2f> | 3.046875 | 772 | News (Org.) | Science & Tech. | 19.663504 | 95,598,448 |
Dialysis tubing, also known as Visking tubing, is an artificial semi-permeable membrane tubing used in separation techniques, that facilitates the removal or exchange of small molecules from macromolecules in solution based on differential diffusion. In the context of life science research, dialysis tubing is typically used in the sample clean-up and processing of proteins and DNA samples or complex biological samples such as blood or serums. Dialysis tubing is also frequently used as a teaching aid to demonstrate the principles of diffusion, osmosis, Brownian motion and the movement of molecules across a restrictive membrane. For the principles and usage of dialysis in a research setting, see Dialysis (biochemistry).
History, properties and composition
Dialysis occurs throughout nature and the principles of dialysis have been exploited by humans for thousands of years using natural animal or plant based membranes. The term dialysis was first routinely used for scientific or medical purposes in the late 1800s and early 1900s, pioneered by the work of Thomas Graham. The first mass-produced man-made membranes suitable for dialysis were not available until the 1930s based on materials used in the food packaging industry such as Cellophane. In the 1940s, Willem Kolff constructed the first dialyzer (artificial kidney), and successfully treated patients with renal failure using dialysis across semi-permeable membranes. Today, dialysis tubing for laboratory applications comes in a variety of dimensions and molecular-weight cutoffs (MWCO). In addition to tubing, dialysis membranes are also found in a wide range of different preformatted devices, significantly improving the performance and ease of use of dialysis.
Different dialysis tubing or flat membranes are produced and characterized as differing molecular-weight cutoffs (MWCO) ranging from 1-1,000,000 kDa. The MWCO determination is the result of the number and average size of the pores created during the production of the dialysis membrane. The MWCO typically refers to the smallest average molecular mass of a standard molecule that will not effectively diffuse across the membrane upon extended dialysis. Thus, a dialysis membrane with a 10K MWCO will generally retain >90% of a protein having a molecular mass of at least 10 kDa. Pore sizes typically range from ~10-100 Angstroms for 1K to 50K MWCO membranes.
It is important to note that the MWCO of a membrane is not a sharply defined value. Molecules with mass near the MWCO of the membrane will diffuse across the membrane slower than molecules significantly smaller than the MWCO. In order for a molecule to rapidly diffuse across a membrane it typically needs to be at least 20-50 times smaller than the membranes MWCO rating. Therefore, it is not practical to try separating a 30kDa protein from a 10kDa protein using dialysis across a 20K rated dialysis membrane. Dialysis tubing for laboratory use is typically made of a film of regenerated cellulose or cellulose ester. However; dialysis membranes made of polysulfone, polyethersulfone (PES), etched polycarbonate, or collagen are also extensively used for specific medical, food, or water treatment applications.
Membranes, composed of either regenerated cellulose or cellulose esters, are manufactured through distinct processes of modifying and cross-linking cellulose fibers (derived from wood pulp or cotton fibers) to form films with differing properties and pore sizes. Variations in the manufacturing process significantly change the properties and pore sizes of the films; depending on the cross-linkages introduced in cellulose, the size of pores can be modulated. While similar in composition, most of the cellulose-based membranes currently manufactured are not necessarily useful for dialysis. Cellulose-based membranes are also widely used for applications ranging from food wrapping, film stock, or “plastic” wrap.
For dialysis applications, regenerated cellulose-based membranes are extruded as tubing or sheets and then dried. Glycerol is frequently added as a humectant to prevent cracking during drying and to help maintain the desired pore structure. Regenerated cellulose membranes are very hydrophilic and hydrate rapidly when introduced to water. Due to their additional crosslinking, regenerated cellulose membranes have better chemical compatibility and heat stability than membranes made from cellulose esters. Regenerated cellulose membranes are more resistant to organic solvents and to the weak or dilute acids and bases that are commonly used in protein and molecular biology applications. Membranes based on cellulose esters are typically supplied wet and come in a greater range of MWCOs. Pore sizes are typically more consistent across cellulose acetate membranes.
- Dialysis Tubing, York High School
- "Separation characteristics of dialysis membranes".
- "Fundamentals of membrane Dialysis".
- Ing, Todd S. (2012). Dialysis: History, Development and Promise. World Scientific Publishing Co Pte Ltd. ISBN 9789814289757.
- Klemm, Dieter; Brigitte Heublein; Hans-Peter Fink; Andreas Bohn (2005). "Cellulose: Fascinating Biopolymer and Sustainable Raw Material". Angewandte Chemie International Edition. 44 (22): 3358–3393. doi:10.1002/anie.200460587. PMID 15861454. | <urn:uuid:1df423bb-b86e-4136-b2ef-4471538d6ce9> | 3.421875 | 1,116 | Knowledge Article | Science & Tech. | 21.087532 | 95,598,450 |
Common name: blue acara
available through www.itis.gov
Identification: Kullander (1983) considered genus Aequidens, like genus Cichlasoma, a catch-all for several different phylogenetic lineages. According to Kullander (1983, 1986), "Aequidens" pulcher represents a species complex consisting of "A." pulcher, "A." coeruleopunctatus, "A." latifrons, and "A." rivulatus, belonging to a genus distinct from Aequidens as now restricted by Kullander. Although a modern systematic review of the "A." pulcher complex has not been completed, the genus was recently reviewed by Kullander (2003). Color photographs of Aequidens pulcher, or a closely related form, appeared in Axelrod (1993).
Size: 15 cm TL.
Native Range: Tropical America. The genus is native to Panama, and to the Orinoco, Amazon, Parnaiba, and Paraguay basins, and the Guianas of South America (Kullander and Nijssen 1989).
Interactive maps: Point Distribution Maps
Puerto Rico &
This species was formerly considered common, reportedly reproducing in canals and ditches around fish farms in the Tampa Bay, Florida, area, in Hillsborough and Manatee counties, during the 1960s; it was not collected in that area during 1970-1972 surveys or since; therefore, the species is considered extirpated (Courtenay et al. 1974; Courtenay and Hensley 1979; Courtenay and Stauffer 1990; Courtenay and Williams 1992).
Table 1. States with nonindigenous occurrences, the earliest and latest observations in each state, and the tally and names of HUCs with observations†. Names and dates are hyperlinked to their relevant specimen records. The list of references for all nonindigenous occurrences of Aequidens pulcher are found here.
Table last updated 5/25/2018
† Populations may not be currently present.
Means of Introduction: Probable release or escape from local ornamental-fish farms.
Status: Formerly established in Florida but now considered extirpated (Courtenay et al. 1974; Courtenay and Hensley 1979); disappearance possibly the result of low winter temperatures (Courtenay and Stauffer 1990).
Impact of Introduction: Unknown.
References: (click for full references)
Axelrod, H.R. 1993. The most complete colored lexicon of cichlids. Tropical Fish Hobbyist Publications, Inc., Neptune City, NJ.
Courtenay, W.R., Jr., and D.A. Hensley. 1979. Survey of introduced non-native fishes. Phase I Report. Introduced exotic fishes in North America: status 1979. Report Submitted to National Fishery Research Laboratory, U.S. Fish and Wildlife Service, Gainesville, FL.
Courtenay, W.R., Jr., and J.R. Stauffer, Jr. 1990. The introduced fish problem and the aquarium fish industry. Journal of the World Aquaculture Society 21(3):145-159.
Courtenay, W.R., Jr., and J.D. Williams. 1992. Dispersal of exotic species from aquaculture sources, with emphasis on freshwater fishes. 49-81 in A. Rosenfield, and R. Mann, eds. Dispersal of living organisms into aquatic ecosystems. Maryland Sea Grant Publication, College Park, MD.
Courtenay, W.R., Jr., H.F. Sahlman, W.W. Miley, II, and D.J. Herrema. 1974. Exotic fishes in fresh and brackish waters of Florida. Biological Conservation 6(4):292-302.
Kullander, S.O. 1983. A revision of the South American cichlid genus Cichlasoma (Teleostei: Cichlidae). Swedish Museum of Natural History, Stockholm, Sweden.
Kullander, S.O. 1986. Cichlid fishes of the Amazon River drainage of Peru. Swedish Museum of Natural History, Stockholm, Sweden.
Kullander, S.O. 2003. Cichlidae (Cichlids). 605-654 in R.E. Reis, S.O. Kullander, and C.J. Ferraris, Jr., eds. Checklist of the freshwater fishes of South and Central America. Porto Alegre: EDIPUCRS, Brasil.
Kullander, S.O., and H. Nijssen. 1989. The cichlids of Surinam, Teleostei: Labroidei. E. J. Brill, New York, NY.
Leo Nico, and Bill Loftus
Revision Date: 4/30/2018
Peer Review Date: 2/9/2016
Leo Nico, and Bill Loftus, 2018, Aequidens pulcher (Gill, 1858): U.S. Geological Survey, Nonindigenous Aquatic Species Database, Gainesville, FL, https://nas.er.usgs.gov/queries/FactSheet.aspx?SpeciesID=435, Revision Date: 4/30/2018, Peer Review Date: 2/9/2016, Access Date: 7/22/2018
This information is preliminary or provisional and is subject to revision. It is being provided to meet the need for timely best science. The information has not received final approval by the U.S. Geological Survey (USGS) and is provided on the condition that neither the USGS nor the U.S. Government shall be held liable for any damages resulting from the authorized or unauthorized use of the information. | <urn:uuid:5129751e-7353-4139-8aea-e0d4e1aaa17e> | 2.875 | 1,232 | Knowledge Article | Science & Tech. | 56.288397 | 95,598,453 |
List sort method orders a list in place.
By default sorts in ascending order.
You can modify sort behavior by passing in keyword arguments.
A special "name=value" syntax in function calls that specifies passing by name and is often used for giving configuration options.
In sorts, the reverse argument sorts list in descending order.
The key argument gives a one-argument function that returns the value to be used in sorting.
The string object's standard lower case converter in the following convert string to lower case during sorting:
L = ['abc', 'ABD', 'aBe'] L.sort() # Sort with mixed case print( L ) L = ['abc', 'ABD', 'aBe'] L.sort(key=str.lower) # Normalize to lowercase print( L ) L = ['abc', 'ABD', 'aBe'] L.sort(key=str.lower, reverse=True) # Change sort order print( L )
The sort key argument is useful when sorting lists of dictionaries to pick out a sort key by indexing each dictionary.
Sorting is also available in recent Pythons as a built-in function, which sorts any collection and returns a new list for the result instead of in-place changes:
L = ['abc', 'ABD', 'aBe'] print( sorted(L, key=str.lower, reverse=True) ) # Sorting built-in # from w w w .j a v a 2 s . com L = ['abc', 'ABD', 'aBe'] print( sorted([x.lower() for x in L], reverse=True) ) # Pretransform items: differs!
Here, the last example here converts to lowercase prior to the sort with a list comprehension.
The result does not contain the original list's values as it does with the key argument.
The latter is applied temporarily during the sort, instead of changing the values to be sorted altogether. | <urn:uuid:018899cb-a553-4c9f-bb1f-e0836db33121> | 3.65625 | 413 | Documentation | Software Dev. | 68.286023 | 95,598,471 |
But weather forecasting on the Red Planet is likely to be even trickier than on Earth
Weather, which changes day-to-day due to constant fluctuations in the atmosphere, and climate, which varies over decades, are familiar to those of us here on Earth. More recently, a third regime, called “macroweather,” has been used to describe the relatively stable period between short-term weather and long-term climate.
A new study finds that this same three-part pattern applies to atmospheric conditions on Mars. The results, published today in Geophysical Research Letters, a journal of the American Geophysical Union, also show that the sun plays a major role in determining macroweather.
The research promises to advance scientists’ understanding of the dynamics of Earth’s own atmosphere – and could provide insights into the weather of Venus, Saturn’s moon Titan, and possibly the gas giants Jupiter, Saturn, Uranus and Neptune.
The scientists chose to study Mars for its wealth of data with which to test their theory that a transitional “macroweather” regime exists on other planets. They used information collected from Viking—a Mars lander mission during the 1970s and 1980s—and more recent data from a satellite orbiting Mars.
By taking into account how the sun heats Mars, as well as the thickness of the planet’s atmosphere, the scientists predicted that Martian temperature and wind would fluctuate similarly to Earth’s – but that the transition from weather to macroweather would take place over 1.8 Martian days (about two Earth days), compared with a week to 10 days on Earth.
“Our analysis of the data from Mars confirmed this prediction quite accurately,” said Shaun Lovejoy, a physics professor at McGill University in Montreal, Canada, and lead author of the paper. “This adds to evidence, from studies of Earth’s atmosphere and oceans, that the sun plays a central role in shaping the transition from short-term weather fluctuations to macroweather.”
The findings also indicate that weather on Mars can be predicted with some skill only two days in advance, compared to 10 days on Earth.
Co-author Professor Jan-Peter Muller from the University College London Mullard Space Science Laboratory in the United Kingdom, said: “We’re going to have a very hard time predicting the weather on Mars beyond two days given what we have found in weather records there, which could prove tricky for the European lander and rover.”
The American Geophysical Union is dedicated to advancing the Earth and space sciences for the benefit of humanity through its scholarly publications, conferences, and outreach programs. AGU is a not-for-profit, professional, scientific organization representing more than 62,000 members in 144 countries. Join our conversation on Facebook, Twitter, YouTube, and other social media channels.
Notes for Journalists
Journalists and public information officers (PIOs) of educational and scientific institutions who have registered with AGU can download a PDF copy of this article by clicking on this link: http://onlinelibrary.wiley.com/doi/10.1002/2014GL061861/abstract?campaign=wlytk-41855.5282060185
Or, you may order a copy of the final paper by emailing your request to Kate Wheeling at firstname.lastname@example.org. Please provide your name, the name of your publication, and your phone number.
Neither the paper nor this press release is under embargo.
“On Mars too, expect macroweather”
Shaun Lovejoy: McGill University, Montreal, Quebec, Canada;
J.P. Muller: Mullard Space Science Laboratory, Surrey, UK;
J.P. Boisvert: McGill University, Montreal, Quebec, Canada
Contact information for the authors:
Shaun Lovejoy: email@example.com
+1 (202) 777-7516
+1 (514) 398-4201
+44 (0)20 3108 3846
Kate Wheeling | American Geophysical Union
New research calculates capacity of North American forests to sequester carbon
16.07.2018 | University of California - Santa Cruz
Scientists discover Earth's youngest banded iron formation in western China
12.07.2018 | University of Alberta
For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.
To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...
For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.
Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...
Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.
A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...
Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.
"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....
Ultra-short, high-intensity X-ray flashes open the door to the foundations of chemical reactions. Free-electron lasers generate these kinds of pulses, but there is a catch: the pulses vary in duration and energy. An international research team has now presented a solution: Using a ring of 16 detectors and a circularly polarized laser beam, they can determine both factors with attosecond accuracy.
Free-electron lasers (FELs) generate extremely short and intense X-ray flashes. Researchers can use these flashes to resolve structures with diameters on the...
13.07.2018 | Event News
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03.07.2018 | Event News
16.07.2018 | Physics and Astronomy
16.07.2018 | Life Sciences
16.07.2018 | Earth Sciences | <urn:uuid:5ed4204c-b737-40f1-89c0-9083c601a8d8> | 3.953125 | 1,479 | Content Listing | Science & Tech. | 43.165856 | 95,598,479 |
Friday, October 21, 2011
The ABC facts of Environmental issues
Here are some interesting information on the ABC facts and terms used when we talk about the environment and climate change issues.
Environment - current issues: air pollution from industrial and vehicular emissions; water pollution from raw sewage; deforestation; smoke/haze from Indonesian forest fires
Definition: This entry lists the most pressing and important environmental problems. The following terms and abbreviations are used throughout the entry:
Acidification - the lowering of soil and water pH due to acid precipitation and deposition usually through precipitation; this process disrupts ecosystem nutrient flows and may kill freshwater fish and plants dependent on more neutral or alkaline conditions (see acid rain).
Acid rain - characterized as containing harmful levels of sulfur dioxide or nitrogen oxide; acid rain is damaging and potentially deadly to the earth's fragile ecosystems; acidity is measured using the pH scale where 7 is neutral, values greater than 7 are considered alkaline, and values below 5.6 are considered acid precipitation; note - a pH of 2.4 (the acidity of vinegar) has been measured in rainfall in New England.
Aerosol - a collection of airborne particles dispersed in a gas, smoke, or fog.
Afforestation - converting a bare or agricultural space by planting trees and plants; reforestation involves replanting trees on areas that have been cut or destroyed by fire.
Asbestos - a naturally occurring soft fibrous mineral commonly used in fireproofing materials and considered to be highly carcinogenic in particulate form.
Biodiversity - also biological diversity; the relative number of species, diverse in form and function, at the genetic, organism, community, and ecosystem level; loss of biodiversity reduces an ecosystem's ability to recover from natural or man-induced disruption.
Bio-indicators - a plant or animal species whose presence, abundance, and health reveal the general condition of its habitat.
Biomass - the total weight or volume of living matter in a given area or volume.
Carbon cycle - the term used to describe the exchange of carbon (in various forms, e.g., as carbon dioxide) between the atmosphere, ocean, terrestrial biosphere, and geological deposits.
Catchments - assemblages used to capture and retain rainwater and runoff; an important water management technique in areas with limited freshwater resources, such as Gibraltar.
DDT (dichloro-diphenyl-trichloro-ethane) - a colorless, odorless insecticide that has toxic effects on most animals; the use of DDT was banned in the US in 1972.
Defoliants - chemicals which cause plants to lose their leaves artificially; often used in agricultural practices for weed control, and may have detrimental impacts on human and ecosystem health.
Deforestation - the destruction of vast areas of forest (e.g., unsustainable forestry practices, agricultural and range land clearing, and the over exploitation of wood products for use as fuel) without planting new growth.
Desertification - the spread of desert-like conditions in arid or semi-arid areas, due to overgrazing, loss of agriculturally productive soils, or climate change.
Dredging - the practice of deepening an existing waterway; also, a technique used for collecting bottom-dwelling marine organisms (e.g., shellfish) or harvesting coral, often causing significant destruction of reef and ocean-floor ecosystems.
Drift-net fishing - done with a net, miles in extent, that is generally anchored to a boat and left to float with the tide; often results in an over harvesting and waste of large populations of non-commercial marine species (by-catch) by its effect of "sweeping the ocean clean."
Ecosystems - ecological units comprised of complex communities of organisms and their specific environments.
Effluents - waste materials, such as smoke, sewage, or industrial waste which are released into the environment, subsequently polluting it.
Endangered species - a species that is threatened with extinction either by direct hunting or habitat destruction.
Freshwater - water with very low soluble mineral content; sources include lakes, streams, rivers, glaciers, and underground aquifers.
Greenhouse gas - a gas that "traps" infrared radiation in the lower atmosphere causing surface warming; water vapor, carbon dioxide, nitrous oxide, methane, hydrofluorocarbons, and ozone are the primary greenhouse gases in the Earth's atmosphere.
Groundwater - water sources found below the surface of the earth often in naturally occurring reservoirs in permeable rock strata; the source for wells and natural springs.
Highlands Water Project - a series of dams constructed jointly by Lesotho and South Africa to redirect Lesotho's abundant water supply into a rapidly growing area in South Africa; while it is the largest infrastructure project in southern Africa, it is also the most costly and controversial; objections to the project include claims that it forces people from their homes, submerges farmlands, and squanders economic resources.
Inuit Circumpolar Conference (ICC) - represents the 145,000 Inuits of Russia, Alaska, Canada, and Greenland in international environmental issues; a General Assembly convenes every three years to determine the focus of the ICC; the most current concerns are long-range transport of pollutants, sustainable development, and climate change.
Metallurgical plants - industries which specialize in the science, technology, and processing of metals; these plants produce highly concentrated and toxic wastes which can contribute to pollution of ground water and air when not properly disposed.
Noxious substances - injurious, very harmful to living beings.
Overgrazing - the grazing of animals on plant material faster than it can naturally regrow leading to the permanent loss of plant cover, a common effect of too many animals grazing limited range land.
Ozone shield - a layer of the atmosphere composed of ozone gas (O3) that resides approximately 25 miles above the Earth's surface and absorbs solar ultraviolet radiation that can be harmful to living organisms.
Poaching - the illegal killing of animals or fish, a great concern with respect to endangered or threatened species.
Pollution - the contamination of a healthy environment by man-made waste.
Potable water - water that is drinkable, safe to be consumed.
Salination - the process through which fresh (drinkable) water becomes salt (undrinkable) water; hence, desalination is the reverse process; also involves the accumulation of salts in topsoil caused by evaporation of excessive irrigation water, a process that can eventually render soil incapable of supporting crops.
Siltation - occurs when water channels and reservoirs become clotted with silt and mud, a side effect of deforestation and soil erosion.
Slash-and-burn agriculture - a rotating cultivation technique in which trees are cut down and burned in order to clear land for temporary agriculture; the land is used until its productivity declines at which point a new plot is selected and the process repeats; this practice is sustainable while population levels are low and time is permitted for regrowth of natural vegetation; conversely, where these conditions do not exist, the practice can have disastrous consequences for the environment .
Soil degradation - damage to the land's productive capacity because of poor agricultural practices such as the excessive use of pesticides or fertilizers, soil compaction from heavy equipment, or erosion of topsoil, eventually resulting in reduced ability to produce agricultural products.
Soil erosion - the removal of soil by the action of water or wind, compounded by poor agricultural practices, deforestation, overgrazing, and desertification.
Ultraviolet (UV) radiation - a portion of the electromagnetic energy emitted by the sun and naturally filtered in the upper atmosphere by the ozone layer; UV radiation can be harmful to living organisms and has been linked to increasing rates of skin cancer in humans.
Water-born diseases - those in which bacteria survive in, and are transmitted through, water; always a serious threat in areas with an untreated water supply.
Source: CIA World Factbook - Unless otherwise noted, information in this page is accurate as of October 14, 2011 | <urn:uuid:2722f707-892d-4959-82f4-e84d6e784e52> | 3.453125 | 1,682 | Structured Data | Science & Tech. | 14.024327 | 95,598,483 |
U. BUFFALO (US) — Scientists can produce hydrogen—a potential power source for portable devices—on demand by adding water to nanosized silicon.
In a series of experiments, scientists created spherical silicon particles about 10 nanometers in diameter. When combined with water, these particles reacted to form silicic acid (a nontoxic byproduct) and hydrogen—a potential source of energy for fuel cells.
The reaction didn’t require any light, heat, or electricity, and also created hydrogen about 150 times faster than similar reactions using silicon particles 100 nanometers wide, and 1,000 times faster than bulk silicon.
Scientists were able to verify that the hydrogen they made was relatively pure by testing it successfully in a small fuel cell that powered a fan. The findings appeared online in the journal Nano Letters.
“When it comes to splitting water to produce hydrogen, nanosized silicon may be better than more obvious choices that people have studied for a while, such as aluminum,” says researcher Mark T. Swihart, professor of chemical and biological engineering at the University at Buffalo.
“With further development, this technology could form the basis of a ‘just add water’ approach to generating hydrogen on demand,” says researcher Paras Prasad, a professor in the Departments of Chemistry, Physics, Electrical Engineering and Medicine. “The most practical application would be for portable energy sources.”
The speed at which the 10-nanometer particles reacted with water surprised the researchers. In under a minute, these particles yielded more hydrogen than the 100-nanometer particles yielded in about 45 minutes. The maximum reaction rate for the 10-nanometer particles was about 150 times as fast.
Swihart says the discrepancy is due to geometry. As they react, the larger particles form nonspherical structures whose surfaces react with water less readily and less uniformly than the surfaces of the smaller, spherical particles.
Though it takes significant energy and resources to produce the super-small silicon balls, the particles could help power portable devices in situations where water is available and portability is more important than low cost. Military operations and camping trips are two examples of such scenarios.
“It was previously unknown that we could generate hydrogen this rapidly from silicon, one of Earth’s most abundant elements,” Erogbogbo says.
“Safe storage of hydrogen has been a difficult problem even though hydrogen is an excellent candidate for alternative energy, and one of the practical applications of our work would be supplying hydrogen for fuel cell power. It could be military vehicles or other portable applications that are near water.”
“Perhaps instead of taking a gasoline or diesel generator and fuel tanks or large battery packs with me to the campsite (civilian or military) where water is available, I take a hydrogen fuel cell (much smaller and lighter than the generator) and some plastic cartridges of silicon nanopowder mixed with an activator,” Swihart says, envisioning future applications.
“Then I can power my satellite radio and telephone, GPS, laptop, lighting, etc. If I time things right, I might even be able to use excess heat generated from the reaction to warm up some water and make tea.”
Source: University at Buffalo | <urn:uuid:8da24873-a77e-4c76-9fef-7f207ede575c> | 4.25 | 679 | News Article | Science & Tech. | 25.506224 | 95,598,491 |
A View from Katherine Bourzac
Making a Black Hole with Metamaterials
The materials might one day be used to make “optical black holes” in the lab.
Metamaterials interact with light in weird ways. They can bend it around an object as if the object weren’t there, or narrow the resolution of microscopes down to a few nanometers.
It could soon be possible to use metamaterials to study the laws of physics, too.
Last week, Xiang Zhang, professor of materials science at the University of California, Berkeley, and a leader in metamaterials research, published a paper in Nature Physics explaining the idea. He suggests that just as the movement of celestial bodies has provided important evidence for Einstein’s theory of relativity, so the movement of light through metamaterials that mimic curved space-time might be used to study the laws of physics.
However, unlike celestial bodies, metamaterials can be studied in controlled experiments. One design the researchers propose would act as an “optical black hole”–an object that has the same effect on light that a gravitational black hole has on matter.
Physicists have been working on ways to make objects analogous to black holes to study in the lab, and most of them require complex experimental setups. Zhang’s design, it seems, would not. Metamaterials that behave like black holes might find applications down the road in devices that slow and trap light.
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:a502ac16-d873-4bc2-9600-b96e7bd49002> | 4.125 | 340 | Truncated | Science & Tech. | 40.372564 | 95,598,531 |
Activation and stabilization of gallium arsenide anode in an aqueous photoelectrochemical cell
MetadataShow full item record
The formation of a porous layer on the surface of gallium arsenide anode, n-GaAs, increases photogenerated currents significantly. This layer was formed as a result of an anodic polarization of illuminated n-GaAs in acidified chloride electrolytes. The formation of the porous layer was confirmed by scanning electron microscopy micrographs. The porous layer increases the reflectivity of GaAs to light, thus enhances the photogenerated current density. In addition, the formation of the porous layer enriches GaAs surface with arsenic. As a result of this enrichment, the positions of the energy levels on the semiconductor surface might have been changed in favor of oxidizing the electrolyte rather than consuming electron–hole pairs in recombination processes within surface states. The n-GaAs with porous surface layer was employed as the working electrode in a photoelectrochemical cell with dimethylviologen as a reversible electrolyte. The rates of the anodic reaction, at GaAs, and cathodic reaction, at a Pt counter electrode, are about equal, only when the surface area of the Pt counter electrode is approximately 20 times greater than that of the n-GaAs. Equal rates of reduction and oxidation of the dimethlviologen redox couples reveals that the number of the photogenerated electrons and holes getting into the electrolyte are the same. Therefore, the photogenerated holes formed at GaAs surface are consumed totally as a result of the electrolyte oxidation rather than GaAs corrosion. The deposition of a thin layer of gold on the top of the porous surface doubles the magnitude of the photocurrent density due to suppressing electron–hole recombination process.
- Chemistry & Earth Sciences [102 items ] | <urn:uuid:289bc481-5b37-4be5-8bdc-da31ac83f0c8> | 2.875 | 384 | Academic Writing | Science & Tech. | 10.201026 | 95,598,543 |
By attaching short sequences of single-stranded DNA to nanoscale building blocks, researchers can design structures that can effectively build themselves.
The building blocks that are meant to connect have complementary DNA sequences on their surfaces, ensuring only the correct pieces bind together as they jostle into one another while suspended in a test tube.
The spheres that make up the crystal follow each other in slipstreams, making some patterns more likely to form. (Ian Jenkins)
Now, a University of Pennsylvania team has made a discovery with implications for all such self-assembled structures.
Earlier work assumed that the liquid medium in which these DNA-coated pieces float could be treated as a placid vacuum, but the Penn team has shown that fluid dynamics play a crucial role in the kind and quality of the structures that can be made in this way.
As the DNA-coated pieces rearrange themselves and bind, they create slipstreams into which other pieces can flow. This phenomenon makes some patterns within the structures more likely to form than others.
The research was conducted by professors Talid Sinno and John Crocker, alongside graduate students Ian Jenkins, Marie Casey and James McGinley, all of the Department of Chemical and Biomolecular Engineering in Penn’s School of Engineering and Applied Science.
It was published in the Proceedings of the National Academy of Sciences.
The Penn team’s discovery started with an unusual observation about one of their previous studies, which dealt with a reconfigurable crystalline structure the team had made using DNA-coated plastic spheres, each 400 nanometers wide. These structures initially assemble into floppy crystals with square-shaped patterns, but, in a process similar to heat-treating steel, their patterns can be coaxed into more stable, triangular configurations.
Surprisingly, the structures they were making in the lab were better than the ones their computer simulations predicted would result. The simulated crystals were full of defects, places where the crystalline pattern of the spheres was disrupted, but the experimentally grown crystals were all perfectly aligned.
While these perfect crystals were a positive sign that the technique could be scaled up to build different kinds of structures, the fact that their simulations were evidently flawed indicated a major hurdle.
“What you see in an experiment,” Sinno said, “is usually a dirtier version of what you see in simulation. We need to understand why these simulation tools aren’t working if we’re going to build useful things with this technology, and this result was evidence that we don’t fully understand this system yet. It’s not just a simulation detail that was missing; there’s a fundamental physical mechanism that we’re not including.”
By process of elimination, the missing physical mechanism turned out to be hydrodynamic effects, essentially, the interplay between the particles and the fluid in which they are suspended while growing. The simulation of a system’s hydrodynamics is critical when the fluid is flowing, such as how rocks are shaped by a rushing river, but has been considered irrelevant when the fluid is still, as it was in the researchers’ experiments. While the particles’ jostling perturbs the medium, the system remains in equilibrium, suggesting the overall effect is negligible.
“The conventional wisdom,” Crocker said, “was that you don't need to consider hydrodynamic effects in these systems. Adding them to simulations is computationally expensive, and there are various kinds of proofs that these effects don’t change the energy of the system. From there you can make a leap to saying, ‘I don’t need to worry about them at all.’”
Particle systems like ones made by these self-assembling DNA-coated spheres typically rearrange themselves until they reach the lowest energy state. An unusual feature of the researchers’ system is that there are thousands of final configurations — most containing defects — that are just as energetically favorable as the perfect one they produced in the experiment.
“It’s like you’re in a room with a thousand doors,” Crocker said. “Each of those doors takes you to a different structure, only one of which is the copper-gold pattern crystal we actually get. Without the hydrodynamics, the simulation is equally likely to send you through any one of those doors.”
The researchers’ breakthrough came when they realized that while hydrodynamic effects would not make any one final configuration more energy-favorable than another, the different ways particles would need to rearrange themselves to get to those states were not all equally easy. Critically, it is easier for a particle to make a certain rearrangement if it’s following in the wake of another particle making the same moves.
“It’s like slipstreaming,” Crocker said. “The way the particles move together, it’s like they’re a school of fish.”
“How you go determines what you get,” Sinno said. “There are certain paths that have a lot more slipstreaming than others, and the paths that have a lot correspond to the final configurations we observed in the experiment.”
The researchers believe that this finding will lay the foundation for future work with these DNA-coated building blocks, but the principle discovered in their study will likely hold up in other situations where microscopic particles are suspended in a liquid medium.
“If slipstreaming is important here, it’s likely to be important in other particle assemblies,” Sinno said. It’s not just about these DNA-linked particles; it’s about any system where you have particles at this size scale. To really understand what you get, you need to include the hydrodynamics.”
The research was supported by the National Science Foundation through its Chemical, Bioengineering, Environmental and Transport Systems Division.
Evan Lerner | EurekAlert!
Scientists uncover the role of a protein in production & survival of myelin-forming cells
19.07.2018 | Advanced Science Research Center, GC/CUNY
NYSCF researchers develop novel bioengineering technique for personalized bone grafts
18.07.2018 | New York Stem Cell Foundation
A new manufacturing technique uses a process similar to newspaper printing to form smoother and more flexible metals for making ultrafast electronic devices.
The low-cost process, developed by Purdue University researchers, combines tools already used in industry for manufacturing metals on a large scale, but uses...
For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.
To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...
For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.
Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...
Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.
A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...
Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.
"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....
13.07.2018 | Event News
12.07.2018 | Event News
03.07.2018 | Event News
20.07.2018 | Power and Electrical Engineering
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The researchers produced cadmium sulphide particles in microscopically small membrane bubbles. Depending on which of the construction manuals they follow, the particles can be 4 or 50 nanometres in size.
Because the membrane bubbles have the same size as living cells, the scientists' work also provides an indication as to how nanostructures could arise in nature. (Small, published online: June 8, 2009/DOI: 10.1002/smll.200900560)
Cells and microorganisms are absolute masters when it comes to working in the smallest possible dimensions. Like particularly efficient micro-factories, they produce particles and structures from inorganic material, for example pieces of chalk, that are only a few nanometres in size, that is, millionths of a millimetre. Cells have two different factors to thank for this capability. First, they have peptides, a biological tool at their disposal that may shape the chalk into a desired form. Second, the fact that they are very small themselves is convenient: the chalk particles cannot grow boundlessly - the end is reached when the calcium carbonate, the building block of chalk, runs out in the cell.
"We used the fact that cells represent a closed reaction container as a model for the synthesis of nanoparticles," says Rumiana Dimova. Her group at the Max Planck Institute of Colloids and Interfaces studies membranes - the cell envelope. The scientist and her colleagues form bubbles that are around 50 micrometres in size from lecithin membranes, which are similar to biological membranes. Like cells, membrane bubbles - or vesicles as scientists refer to them - also provide a closed reaction container. The scientists load the membrane bubbles with one of two reactants for the nanoparticles.
From this point, the researchers have developed two different sets of protocols. In one case, they produce bubbles loaded with one of the two reactants, sodium sulphide or cadmium chloride. The scientists then bring the bubbles with the different loads together and fuse two vesicles to form a bigger vesicle - this is done by subjecting the bubble cocktail to a short but very strong electrical pulse. The electric shock fuses the membranes of two adjacent bubbles.
In many cases, this results in the fusion of two bubbles containing different reactants. These then react to form cadmium sulphide, which is not water soluble and thus precipitates in the form of nanoparticles. "Because the reactants are only present to a limited extent in the fused bubbles, the particles only grow to a size of four nanometres," explains Rumiana Dimova. The scientists were able to track the entire process directly under the microscope because they had added different fluorescent molecules to the membranes of the differently loaded vesicles. The researchers were also able to see the nanoparticles forming as the particles shone like tiny lamps.
In the second process, the researchers only produce vesicles with one of the reactants. When the vesicles have formed, unlike in the first procedure, the researchers do not remove them from the production chamber. Instead, the bubbles remain attached to their substrate via small membrane channels, like balloons tied to strings, and stand in a solution that is the same as the one inside them. The researchers working with Rumiana Dimova then altered this situation: they substituted the solution with the first ingredient for the nanoparticles with a second component. This causes no change inside the vesicles at first. The second ingredient only creeps gradually between the substrate and membrane into the channel and to the vesicle. In the vesicle, where the other ingredient is already waiting, the nanoparticles grow again - this time to a size of 50 nanometres.
"With our method, we succeeded for the first time in producing particles with a certain diameter in vesicles whose size corresponds to that of cells," says Rumiana Dimova. Previously, biologists thought that cells depended on the help of peptides for the synthesis of nanoparticles. However, as Rumiana Dimova and her colleagues have discovered, it can also be done without them.
Original work:Peng Yang, Reinhard Lipowsky, and Rumiana Dimova
Dr. Rumiana Dimova | EurekAlert!
First evidence on the source of extragalactic particles
13.07.2018 | Technische Universität München
Simpler interferometer can fine tune even the quickest pulses of light
12.07.2018 | University of Rochester
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
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Recent reporting on the discovery and enhancement of plastic-dissolving enzymes in bacteria made me stop and think about what this might mean for the plastic pollution problem that is plaguing oceans and choking the world’s coral reefs.
While this development is interesting and draws necessary focus to an immense environmental challenge, it is premature to guess whether these kinds of enzymes might provide an effective silver bullet for treating plastics floating in the five great gyres of the sea.
There is so much more we need to understand about the complex relationships between plastics and marine ecosystems before we can take drastic action such as spraying the ocean with so-called plastic-eating bacteria.
“Plastic-eating” bacteria already at work
The untold millions of tons of plastic that ends up in the sea – and in landfills – have created an absolutely huge new food source for naturally existing, and very hungry, microbes.
In fact, some scientists think microbes eating plastic are already an important reason that the plastics numbers do not add up – the amount of plastic we see in the ocean is much less than the total amount of plastic calculated to have been piled and poured into it.
”Enhanced enzyme” wasn’t designed for this
So what’s my hesitation with this new discovery? For one, the enhanced enzyme that made headlines this spring was actually not developed to eat plastic.
In fact, the main goal of the researchers was to identify and empower it for industrial application. The enzyme facilitates plastic recycling by breaking down some plastics – such as PET #1, for all of you recyclers – into chemical intermediates that can be recovered and turned back into plastic products.
This concept is a big deal from a global solid waste and landfill point of view, and I’m excited to see such research grow to help solve this problem. The better we can manage waste on land, the less will end up in the ocean.
Making the leap to enzymes to try to tackle waste that’s already in the ocean could be risky, however.
Unknown and potentially hazardous side effects
It is also not clear that this enzyme, or similar enzymes, could safely be used in widespread environmental remediation.
Using direct enzyme spraying – or microbes engineered to deliver environmentally active enzymes – widely in the sea presents all kinds of unassessed hazards. In general, such interventions have a long history of inducing underappreciated side effects, and we would be well-served to take it slow.
Plastics could be even more deadly than we realize today, which should also give us pause. Many types of plastics actively absorb highly toxic persistent pollutants such as PCBs, for example.
We know from our own work on reefs that floating plastics deliver disease-causing microbes to corals. Ecosystem and human health risks related to both floating and sinking plastics should be considered before any large-scale plan is employed to deal with floating or sunken plastics problems.
Meanwhile, we have work to do
The first order of the day must therefore be to reduce our reliance on single-use plastics and to improve solid waste management systems globally. Once we tackle the problem at the source, we can start thinking about directly addressing the remaining plastic pollution accumulated in ocean gyres and on the bottom of the sea.
Until then, we still have a lot to learn and do.
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Researchers from the University of Hawai'i at Mānoa (UHM) Department of Botany have discovered hundreds of potentially new species of fungi in the deep coral ecosystem in the 'Au'au channel off Maui, Hawai'i. Mesophotic coral ecosystems (MCE) are generally found at depths between 130 - 500 feet and possess abundant plant (algal) life as well as new fish species. The mysteries of these reefs are only recently being revealed through technological advances in closed circuit rebreather diving. Previously overlooked--being too precarious for conventional SCUBA and too shallow to justify the cost of frequent submersible dives--mesophotic reefs continuously disclose breathtaking levels of biodiversity with each dive, yielding species and behavioral interactions new to science.
The UHM Hawai'i Undersea Research Laboratory (HURL) used the Pisces V submersible to collect native algae from the mesophotic reefs in the 'Au'au channel. Using the DNA sequencing facility at the UHM Hawai'i Institute of Marine Biology, Benjamin Wainwright, lead author of the study and UHM Botany postdoctoral researcher, and colleagues determined which species of fungus were associated with the native algae.
Fungi have been documented in almost all habitats on Earth, although marine fungi are less studied in comparison to their terrestrial counterparts. Scientists have found fungi in deep and shallow water corals, marine sponges and other invertebrates. The recently discovered fungi, however, were found living in association with algae.
"To the best of our knowledge, this is the first documented evidence confirming fungi in MCEs," said Wainwright.
Additionally, the research team discovered that 27% of the species detected in these deep dark environments are also found on terrestrial rainforest plants in Hawai'i.
"Finding such high overlap of fungal diversity on terrestrial plants was surprising. Mesophotic reefs are as dark as it gets where photosynthesis is still possible, so to find the same species of fungi on forest plants illustrates the remarkable ability of some fungi to tolerate, and thrive, in extremely different habitats," said Anthony Amend, senior author of the study and UHM associate professor of botany. "This ecological breadth is something that seemingly sets fungi apart from other organisms."
Plant-associated fungi provide many benefits to society. For example, Taxol, a chemotherapy medication used to treat cancers, is produced by a fungus found inside tree bark and leaves. Additionally, research has shown that fungi are useful in bioremediation efforts (for example, oil spill and industrial waste treatment) and capable of breaking down plastic waste.
It is currently not known whether the newly discovered fungal species are pathogens, helpful symbionts or unimportant to their algae hosts.
"Further, we don't currently know what metabolic capabilities they have that may prove to have medical or environmental applications," said Wainwright. "We know other undiscovered species are present in these ecosystems. Unfortunately, if we do not look now we may miss our opportunity to benefit from them and conserve them."
Deep reefs, like those in the 'Au'au channel, may act as a refuge as Earth's climate changes, providing habitat for any marine creatures that can take advantage of this deeper habitat. If this is indeed the case, understanding how this habitat functions and how the corals, algae and fungi interact with one another will be vital to preserving the refuge in the deep.
Marcie Grabowski | EurekAlert!
Barium ruthenate: A high-yield, easy-to-handle perovskite catalyst for the oxidation of sulfides
16.07.2018 | Tokyo Institute of Technology
The secret sulfate code that lets the bad Tau in
16.07.2018 | American Society for Biochemistry and Molecular Biology
For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.
To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...
For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.
Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...
Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.
A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...
Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.
"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....
Ultra-short, high-intensity X-ray flashes open the door to the foundations of chemical reactions. Free-electron lasers generate these kinds of pulses, but there is a catch: the pulses vary in duration and energy. An international research team has now presented a solution: Using a ring of 16 detectors and a circularly polarized laser beam, they can determine both factors with attosecond accuracy.
Free-electron lasers (FELs) generate extremely short and intense X-ray flashes. Researchers can use these flashes to resolve structures with diameters on the...
13.07.2018 | Event News
12.07.2018 | Event News
03.07.2018 | Event News
16.07.2018 | Physics and Astronomy
16.07.2018 | Life Sciences
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Calculating x^y, 2^x, etc.
If y is an integer, we can repeatedly multiply (or use even faster algorithms that repeatedly square and multiply).
If y is not an integer, we generally make the substitution
x^y = e^(y ln( x )) or x^y = 2^(y log2( x ))
and use some subroutine to calculate ln(x) and e^b -- or, alternatively, calculate log2(x) and 2^b.
(Is there a page somewhere on massmind describing logarithms and exponentials? Move the following text there.)
"Richard Feynman and The Connection Machine" by W. Daniel Hillis 1989 briefly describes Richard Feyman and the algorithm:
An Algorithm For Logarithms
Feynman worked out ... the subroutine for computing logarithms. I mention it here not only because it is a clever algorithm, but also because it is a specific contribution Richard made to the mainstream of computer science. He invented it at Los Alamos.
Consider the problem of finding the logarithm of a fractional number between 1.0 and 2.0 (the algorithm can be generalized without too much difficulty). Feynman observed that any such number can be uniquely represented as a product of numbers of the form 1 + 2-k, where k is an integer. Testing each of these factors in a binary number representation is simply a matter of a shift and a subtraction. Once the factors are determined, the logarithm can be computed by adding together the precomputed logarithms of the factors. The algorithm fit especially well on the Connection Machine.... The entire computation took less time than division.
Scott Dattalo has written a far more detailed explanation of Feynman's log2(x) algorithm, with worked-out examples .
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A room-temperature superconductor is a hypothetical material that would be capable of exhibiting superconductivity at operating temperatures above 0 °C (273.15 K). While this is not strictly "room temperature", which would be approximately 20–25 °C, it is the temperature at which ice forms and can be reached and easily maintained in an everyday environment. The highest temperature known superconducting material is highly pressurized hydrogen sulfide, the transition temperature of which is 203 K (−70 °C), the highest accepted superconducting critical temperature as of 2015. By substituting a small part of sulfur with phosphorus and using even higher pressures, it has been predicted that it may be possible to raise the critical temperature to above 0 °C and achieve room-temperature superconductivity. Previously the record was held by the cuprates, which have demonstrated superconductivity at atmospheric pressure at temperatures as high as 138 K (−135 °C), and 164 K (−109 °C) under high pressure.
Although some researchers doubt whether room-temperature superconductivity is actually achievable, superconductivity has repeatedly been discovered at temperatures that were previously unexpected or held to be impossible.
Claims of "near-room temperature" transient effects date from the early 1950s and some suggest that in fact the breakthrough might have been made more than once but could not be made stable enough and/or reproducible as the relationship between isotope number and Tc was not known at the time.
Finding a room temperature superconductor "would have enormous technological importance and, for example, help to solve the world’s energy problems, provide for faster computers, allow for novel memory-storage devices, and enable ultra-sensitive sensors, among many other possibilities."
In 2000, while extracting electrons from diamond during ion implantation work, Johan Prins claimed to have observed a phenomenon that he explained as room-temperature superconductivity within a phase formed on the surface of oxygen-doped type IIa diamonds in a 10−6 mbar vacuum.
In 2003, a group of researchers published results on high-temperature superconductivity in palladium hydride (PdHx: x>1) and an explanation in 2004. In 2007 the same group published results suggesting a superconducting transition temperature of 260 K. The superconducting critical temperature increases as the density of hydrogen inside the palladium lattice increases. This work has not been corroborated by other groups.
In 2012, an Advanced Materials article claimed superconducting behavior of graphite powder after treatment with pure water at temperatures as high as 300 K and above.[Unreliable source] So far, the authors have not been able to demonstrate the occurrence of a clear Meissner phase and the vanishing of the material's resistance.
In 2015, an article published in Nature by researchers of the Max Planck Institute suggested that under certain conditions such as extreme pressure H2S transitioned to a superconductive form H3S at around 1.5 million times atmospheric pressure in a diamond anvil cell. The critical temperature is 203 K which would be the highest Tc ever recorded and their research suggests that other hydrogen compounds could superconduct at up to 260 K which would match up with the original research of Ashcroft.
Other research also suggests a link between the palladium hydride containing small impurities of sulfur as a plausible explanation for the anomalous resistance drops noticed by other researchers, and hydrogen absorption by cuprates has been suggested in light of the recent results in H2S as a plausible explanation for transient resistance drops or "USO" noticed in the 1990s during research after the discovery of YBCO.
Theoretical work by Neil Ashcroft predicted that solid metallic hydrogen at extremely high pressure (~500 GPa) should become superconducting at approximately room-temperature because of its extremely high speed of sound and expected strong coupling between the conduction electrons and the lattice vibrations (phonons). This prediction is yet to be experimentally verified, as yet the pressure to achieve metallic hydrogen is not known but may be of the order of 500 GPa.
A team at Harvard has claimed to make metallic hydrogen and reports a pressure of 495 GPa. Though the exact critical temperature has not yet been determined, weak signs of a Meissner effect at 250K may have appeared in magnetometer tests.
In 1964, William A. Little proposed the possibility of high temperature superconductivity in organic polymers. This proposal is based on the exciton-mediated electron pairing, as opposed to phonon-mediated pairing in BCS theory.
- Cartlidge, Edwin (18 August 2015). "Superconductivity record sparks wave of follow-up physics". Nature News. Retrieved 18 August 2015.
- Dai, P.; Chakoumakos, B.C.; Sun, G.F.; Wong, K.W.; Xin, Y.; Lu, D.F. (1995). "Synthesis and neutron powder diffraction study of the superconductor HgBa2Ca2Cu3O8+δ by Tl substitution". Physica C. 243 (3–4): 201–206. Bibcode:1995PhyC..243..201D. doi:10.1016/0921-4534(94)02461-8.
- "Workshop on the Road to Room Temperature Superconductivity" (PDF). dtic.mil.
- "Almaden Institute 2012 : Superconductivity 297 K – Synthetic Routes to Room Temperature Superconductivity". researcher.watson.ibm.com.
- NOVA. Race for the Superconductor. Public TV station WGBH Boston. Approximately 1987.
- Prins, JF (2003). "The diamond–vacuum interface: II. Electron extraction from n-type diamond: evidence for superconduction at room temperature" (PDF). Semiconductor Science and Technology. 18 (3): S131. Bibcode:2003SeScT..18S.131P. doi:10.1088/0268-1242/18/3/319.
- Tripodi, P.; Di Gioacchino, D.; Borelli, R.; Vinko, J. D. (May 2003). "Possibility of high temperature superconducting phases in PdH". Physica C: Superconductivity. 388–389: 571–572. Bibcode:2003PhyC..388..571T. doi:10.1016/S0921-4534(02)02745-4.
- Tripodi, P.; Di Gioacchino, D.; Vinko, J. D. (August 2004). "Superconductivity in PdH: Phenomenological explanation". Physica C: Superconductivity. 408–410: 350–352. Bibcode:2004PhyC..408..350T. doi:10.1016/j.physc.2004.02.099.
- Tripodi, P.; Di Gioacchino, D.; Vinko, J. D. (2007). "A review of high temperature superconducting property of PdH system". International Journal of Modern Physics B. 21 (18&19): 3343–3347. Bibcode:2007IJMPB..21.3343T. doi:10.1142/S0217979207044524.
- Scheike, T.; Böhlmann, W.; Esquinazi, P.; Barzola-Quiquia, J.; Ballestar, A.; Setzer, A. (2012). "Can Doping Graphite Trigger Room Temperature Superconductivity? Evidence for Granular High-Temperature Superconductivity in Water-Treated Graphite Powder". Advanced Materials. 24 (43): 5826. arXiv: . doi:10.1002/adma.201202219. PMID 22949348.
- Mankowsky, R.; Subedi, A.; Först, M.; Mariager, S. O.; Chollet, M.; Lemke, H. T.; Robinson, J. S.; Glownia, J. M.; Minitti, M. P.; Frano, A.; Fechner, M.; Spaldin, N. A.; Loew, T.; Keimer, B.; Georges, A.; Cavalleri, A. (2014). "Nonlinear lattice dynamics as a basis for enhanced superconductivity in YBa2Cu3O6.5". Nature. 516 (7529): 71–73. arXiv: . Bibcode:2014Natur.516...71M. doi:10.1038/nature13875.
- Ge, Y. F.; Zhang, F.; Yao, Y. G. (2016). "First-principles demonstration of superconductivity at 280 K in hydrogen sulfide with low phosphorus substitution". Phys. Rev. B. 93 (22): 224513. arXiv: . Bibcode:2016PhRvB..93v4513G. doi:10.1103/PhysRevB.93.224513.
- Ashcroft, N. W. (1968). "Metallic Hydrogen: A High-Temperature Superconductor?". Physical Review Letters. 21 (26): 1748–1749. Bibcode:1968PhRvL..21.1748A. doi:10.1103/PhysRevLett.21.1748.
- Little, W. A. (1964). "Possibility of Synthesizing an Organic Superconductor". Physical Review. 134 (6A): A1416–A1424. Bibcode:1964PhRv..134.1416L. doi:10.1103/PhysRev.134.A1416. | <urn:uuid:29368473-bc8e-45fb-95bb-1a2a78ba6cfd> | 3.953125 | 2,064 | Knowledge Article | Science & Tech. | 57.598632 | 95,598,597 |
Falling sulfur dioxide emissions in the United States are expected to substantially increase rainfall in Africa’s semi-arid Sahel, while bringing slightly more rain to much of the United States, according to a recent study in the Journal of Geophysical Research: Atmospheres.
Pollution filters placed on coal-fired power plants in the United States starting in the 1970s have dramatically cut emissions of sulfur dioxide, a toxic gas that contributes to acid rain and premature deaths from respiratory and cardiovascular diseases. If U.S. sulfur dioxide emissions are cut to zero by 2100, as some researchers have projected, rainfall over the Sahel could increase up to 10 percent from 2000 levels, computer simulations published in the study suggest.
“Reducing emissions in one region can influence rainfall far away because our global atmosphere is interconnected,” said the study’s lead author, Dan Westervelt, an atmospheric scientist at Columbia University’s Lamont-Doherty Earth Observatory. “We show that the health and environmental benefits of U.S. clean air policies extend to global climate as well.”
Sulfur dioxide simultaneously cools and dries earth’s climate by reflecting sunlight back to space and suppressing heat-driven evaporation near the ground. Though prior research has linked high sulfur emissions in Europe and Asia to the Sahel’s severe droughts of the 1970s and 1980s, this study is the first to look at how U.S. emissions influence precipitation in various regions globally.
Land at the northern edge of Africa’s Sahel could become suitable for farming if sulfur emissions in the United States continue to rapidly decline, says a new study. Here, farmers near Segou, Mali, plant maize at the start of the rainy season. (credit: Francesco Fiondella/International Research Institute for Climate and Society, Columbia University)
The researchers ran three independent global climate models to compare the relative impact of the United States cutting its human-caused sulfur emissions to zero and keeping its emissions at 2000-2005 levels. In the zero-emissions scenario, all three models showed a slight increase in average global rainfall, with higher levels in the United States and other northern-hemisphere regions. In the Sahel, two models found that wet-season rainfall increased by 5 to 10 percent, with one producing a rainy season two-and-a-half days longer.
“We were surprised to find that removing sulfur emissions in just one country would significantly influence rainfall on another continent, thousands of miles away,” said study coauthor Arlene Fiore, an atmospheric scientist at Lamont-Doherty.
The added rainfall came as the tropical rain belt returned to its normal, northernmost position above the equator during northern hemisphere summer, the models showed, consistent with earlier research. The rain belt ordinarily shifts north when the northern hemisphere heats up during summer, but when sulfur emissions are high, cooler temperatures in the north stop the rain belt from migrating as far.
Cutting U.S. emissions to zero was enough to move the rain belt roughly 35 kilometers north, placing more of the Sahel in its path, the researchers found. “We did not expect to see such a clear, significant influence on the Sahel,” said Westervelt. “This northern shift of the tropical rain belt could mean that cropland at the Sahel’s northern edge could become more productive in the future.”
Though two of the three models were generally consistent, they disagree on exactly how much rain different regions can expect as U.S. sulfur emissions go to zero, says study coauthor Drew Shindell, an atmospheric scientist at Duke University. “We have just one real-world example — historic data — to rely on, making it very challenging to quantitatively link emissions to response,” he said.
The influence of rising carbon emissions is another complicating factor. The technology to trap carbon dioxide, unlike sulfur dioxide, is still far from being cost-effective. So while carbon dioxide levels continue to climb, falling sulfur emissions impose a climate “penalty” — less human-caused cooling to offset human-caused warming from carbon dioxide.
“It’s still a good idea to cut SO2 with pollution control equipment on coal-fired power plants for the sake of public health, but even better would be to move away from coal-fired power plants entirely to reap the benefits of public health and climate change mitigation,” said Shindell.
The study’s other authors are Andrew Conley and Jean-François Lamarque of the National Center for Atmospheric Research; Michael Previdi and Gus Correa of Lamont-Doherty; Greg Faluvegi of NASA Goddard Institute for Space Studies and Columbia’s Center for Climate Systems Research; and Larry Horowitz of Princeton’s Geophysical Fluid Dynamics Laboratory.
This article was originally published by Columbia University’s Earth Institute. Read the original. | <urn:uuid:63cee672-98e9-4b3d-a74c-727279a3a95b> | 3.53125 | 1,033 | Truncated | Science & Tech. | 32.68644 | 95,598,604 |
|White witch moth |
Thysania agrippina is a species of moth in the Erebidae family. The species has numerous common names, including white witch, birdwing moth, ghost moth, great grey witch, and great owlet moth. It is the lepidopteran with the biggest wingspan, which typically is reported as being up to 27–29 centimetres (10.6–11.4 in) and one Brazilian specimen had a wingspan of almost 30 cm (12 in). The Atlas moth and Hercules moth, however, have greater wing areas. The species occurs in Mexico, Central and South America, and appears as a stray as far north as Texas in the U.S.
The species is generally widespread, but is considered endangered in the state of Rio Grande do Sul, Brazil, where it reaches the southern limit of its distribution.
No confirmed rearing records are available for this species. Based on reports for sister species Thysania zenobia that feeds on Senna and Cassia, the larval host plants for the White Witch are probably also woody members of Fabaceae (subfamily Caesalpinioideae).
- Ascalapha odorata, the black witch moth
- Hugo Kons, Jr. (17 May 1998). "Chapter 32 — Largest Lepidopteran Wing Span". Book of Insect Records. University of Florida. Archived from the original on 1 July 2011. Retrieved 21 October 2013.
- Host information
- "Robinson, G. S., P. R. Ackery, I. J. Kitching, G. W. Beccaloni & L. M. Hernández, 2010. HOSTS – A Database of the World's Lepidopteran Hostplants. Natural History Museum, London."
|Wikimedia Commons has media related to Thysania agrippina.|
- White Witch, Texas Entomology page authored by Mike Quinn]
- White Witch Watch, documentation of ongoing effort to determine T. agrippina life history
|This Erebinae-related article is a stub. You can help Wikipedia by expanding it.| | <urn:uuid:034ffc1b-c3ad-4259-b16a-8695ed0231ef> | 2.640625 | 452 | Knowledge Article | Science & Tech. | 55.613085 | 95,598,613 |
- Proceedings of the National Academy of Sciences of the United States of America
- Published 6 months ago
Centipedes can subdue giant prey by using venom, which is metabolically expensive to synthesize and thus used frugally through efficiently disrupting essential physiological systems. Here, we show that a centipede (Scolopendra subspinipes mutilans, ∼3 g) can subdue a mouse (∼45 g) within 30 seconds. We found that this observation is largely due to a peptide toxin in the venom, SsTx, and further established that SsTx blocks KCNQ potassium channels to exert the lethal toxicity. We also demonstrated that a KCNQ opener, retigabine, neutralizes the toxicity of a centipede’s venom. The study indicates that centipedes' venom has evolved to simultaneously disrupt cardiovascular, respiratory, muscular, and nervous systems by targeting the broadly distributed KCNQ channels, thus providing a therapeutic strategy for centipede envenomation.
Centipedes are among the oldest extant venomous predators on the planet. Armed with a pair of modified, venom-bearing limbs, they are an important group of predatory arthropods and are infamous for their ability to deliver painful stings. Despite this, very little is known about centipede venom and its composition. Advances in analytical tools, however, have recently provided the first detailed insights into the composition and evolution of centipede venoms. This has revealed that centipede venom proteins are highly diverse, with 61 phylogenetically distinct venom protein and peptide families. A number of these have been convergently recruited into the venoms of other animals, providing valuable information on potential underlying causes of the occasionally serious complications arising from human centipede envenomations. However, the majority of venom protein and peptide families bear no resemblance to any characterised protein or peptide family, highlighting the novelty of centipede venoms. This review highlights recent discoveries and summarises the current state of knowledge on the fascinating venom system of centipedes.
Retracing the evolutionary history of arthropods has been one of the greatest challenges in biology. During the past decade, phylogenetic analyses of morphological and molecular data have coalesced towards the conclusion that Mandibulata, the most diverse and abundant group of animals, is a distinct clade from Chelicerata, in that its members possess post-oral head appendages specialized for food processing, notably the mandible. The origin of the mandibulate body plan, however, which encompasses myriapods, crustaceans and hexapods, has remained poorly documented. Here we show that Tokummia katalepsis gen. et sp. nov., a large bivalved arthropod from the 508 million-year-old Marble Canyon fossil deposit (Burgess Shale, British Columbia), has unequivocal mandibulate synapomorphies, including mandibles and maxillipeds, as well as characters typically found in crustaceans, such as enditic, subdivided basipods and ring-shaped trunk segments. Tokummia and its closest relative, Branchiocaris (in Protocarididae, emended), also have an anteriormost structure housing a probable bilobed organ, which could support the appendicular origin of the labrum. Protocaridids are retrieved with Canadaspis and Odaraia (in Hymenocarina, emended) as part of an expanded mandibulate clade, refuting the idea that these problematic bivalved taxa, as well as other related forms, are representatives of the basalmost euarthropods. Hymenocarines now illustrate that the subdivision of the basipod and the presence of proximal endites are likely to have been ancestral conditions critical for the evolution of coxal and pre-coxal features in mandibulates. The presence of crustaceomorph traits in the Cambrian larvae of various clades basal to Mandibulata is reinterpreted as evidence for the existence of distinct ontogenetic niches among stem arthropods. Larvae would therefore have constituted an important source of morphological novelty during the Cambrian period, and, through heterochronic processes, may have contributed to the rapid acquisition of crown-group characters and thus to greater evolutionary rates during the early radiation of euarthropods.
The interrelationships of the four classes of Myriapoda have been an unresolved question in arthropod phylogenetics and an example of conflict between morphology and molecules. Morphology and development provide compelling support for Diplopoda (millipedes) and Pauropoda being closest relatives, and moderate support for Symphyla being more closely related to the diplopod-pauropod group than any of them are to Chilopoda (centipedes). In contrast, several molecular datasets have contradicted the Diplopoda-Pauropoda grouping (named Dignatha), often recovering a Symphyla-Pauropoda group (named Edafopoda). Here we present the first transcriptomic data including a pauropod and both families of symphylans, allowing myriapod interrelationships to be inferred from phylogenomic data from representatives of all main lineages. Phylogenomic analyses consistently recovered Dignatha with strong support. Taxon removal experiments identified outgroup choice as a critical factor affecting myriapod interrelationships. Diversification of millipedes in the Ordovician and centipedes in the Silurian closely approximates fossil evidence whereas the deeper nodes of the myriapod tree date to various depths in the Cambrian-Early Ordovician, roughly coinciding with recent estimates of terrestrialisation in other arthropod lineages, including hexapods and arachnids.
Myriapods (e.g., centipedes and millipedes) display a simple homonomous body plan relative to other arthropods. All members of the class are terrestrial, but they attained terrestriality independently of insects. Myriapoda is the only arthropod class not represented by a sequenced genome. We present an analysis of the genome of the centipede Strigamia maritima. It retains a compact genome that has undergone less gene loss and shuffling than previously sequenced arthropods, and many orthologues of genes conserved from the bilaterian ancestor that have been lost in insects. Our analysis locates many genes in conserved macro-synteny contexts, and many small-scale examples of gene clustering. We describe several examples where S. maritima shows different solutions from insects to similar problems. The insect olfactory receptor gene family is absent from S. maritima, and olfaction in air is likely effected by expansion of other receptor gene families. For some genes S. maritima has evolved paralogues to generate coding sequence diversity, where insects use alternate splicing. This is most striking for the Dscam gene, which in Drosophila generates more than 100,000 alternate splice forms, but in S. maritima is encoded by over 100 paralogues. We see an intriguing linkage between the absence of any known photosensory proteins in a blind organism and the additional absence of canonical circadian clock genes. The phylogenetic position of myriapods allows us to identify where in arthropod phylogeny several particular molecular mechanisms and traits emerged. For example, we conclude that juvenile hormone signalling evolved with the emergence of the exoskeleton in the arthropods and that RR-1 containing cuticle proteins evolved in the lineage leading to Mandibulata. We also identify when various gene expansions and losses occurred. The genome of S. maritima offers us a unique glimpse into the ancestral arthropod genome, while also displaying many adaptations to its specific life history.
The arthropodium is the key innovation of arthropods. Its various modifications are the outcome of multiple evolutionary transformations, and the foundation of nearly endless functional possibilities. In contrast to hexapods, crustaceans, and even chelicerates, the spectrum of evolutionary transformations of myriapod arthropodia is insufficiently documented and rarely scrutinized. Among Myriapoda, Chilopoda (centipedes) are characterized by their venomous forcipules-evolutionarily transformed walking legs of the first trunk segment. In addition, the posterior end of the centipedes' body, in particular the ultimate legs, exhibits a remarkable morphological heterogeneity. Not participating in locomotion, they hold a vast functional diversity. In many centipede species, elongation and annulation in combination with an augmentation of sensory structures indicates a functional shift towards a sensory appendage. In other species, thickening, widening and reinforcement with a multitude of cuticular protuberances and glandular systems suggests a role in both attack and defense. Moreover, sexual dimorphic characteristics indicate that centipede ultimate legs play a pivotal role in intraspecific communication, mate finding and courtship behavior. We address ambiguous identifications and designations of podomeres in order to point out controversial aspects of homology and homonymy. We provide a broad summary of descriptions, illustrations, ideas and observations published in past 160 years, and propose that studying centipede ultimate legs is not only essential in itself for filling gaps of knowledge in descriptive morphology, but also provides an opportunity to explore diverse pathways of leg transformations within Myriapoda.
Myriapods, including the diverse and familiar centipedes and millipedes, are one of the dominant terrestrial arthropod groups. Although molecular evidence has shown that Myriapoda is monophyletic, its internal phylogeny remains contentious and understudied, especially when compared to those of Chelicerata and Hexapoda. Until now, efforts have focused on taxon sampling (e.g., by including a handful of genes from many species) or on maximizing matrix size (e.g., by including hundreds or thousands of genes in just a few species), but a phylogeny maximizing sampling at both levels remains elusive. In this study, we analyzed forty Illumina transcriptomes representing three of the four myriapod classes (Diplopoda, Chilopoda and Symphyla); twenty-five transcriptomes were newly sequenced to maximize representation at the ordinal level in Diplopoda and at the family level in Chilopoda. Ten supermatrices were constructed to explore the effect of several potential phylogenetic biases (e.g., rate of evolution, heterotachy) at three levels of gene occupancy per taxon (50%, 75% and 90%). Analyses based on maximum likelihood and Bayesian mixture models retrieved monophyly of each myriapod class, and resulted in two alternative phylogenetic positions for Symphyla, as sister group to Diplopoda + Chilopoda, or closer to Diplopoda, the latter hypothesis having been traditionally supported by morphology. Within centipedes, all orders were well supported, but two deep nodes remained in conflict in the different analyses despite dense taxon sampling at the family level. Relationships among centipede orders in all analyses conducted with the most complete matrix (90% occupancy) are at odds not only with the sparser but more gene-rich supermatrices (75% and 50% supermatrices) and with the matrices optimizing phylogenetic informativeness or most conserved genes, but also with previous hypotheses based on morphology, development or other molecular data sets. Our results indicate that a high percentage of ribosomal proteins in the most complete matrices, in conjunction with distance from the root, can act in concert to compromise the estimated relationships within the ingroup. We discuss the implications of these findings in the context of the ever more prevalent quest for completeness in phylogenomic studies.
Centipede venoms have emerged as a rich source of novel bioactive compounds. However, most centipede species are commonly considered too small for venom extraction and transcriptomics is likely to be an attractive way of probing the molecular diversity of these venoms. Examining the venom composition ofScolopendra subspinipes, we test the accuracy of this approach. We compared the proteomically determined venom profile with four common toxin transcriptomic toxin annotation approaches: BLAST search against toxins in UniProt, lineage-specific toxins, or species-specific toxins and comparative expression analyses of venom and non-venom producing tissues. This demonstrated that even toxin annotation based on lineage-specific homology searches is prone to substantial errors compared to a proteomic approach. However, combined comparative transcriptomics and phylogenetic analysis of putative toxin families substantially improves annotation accuracy. Furthermore, comparison of the venom composition ofS. subspinipeswith the closely relatedS. subspinipes mutilansrevealed a surprising lack of overlap. This first insight into the intraspecific venom variability of centipedes contrasts the sequence conservation expected from previous findings that centipede toxins evolve under strong negative selection. Our results highlight the importance of proteomic data in studies of even comparably well-characterized venoms and warrants caution when sourcing venom from centipedes of unknown origin.
Given the numerous hypotheses concerning arthropod phylogeny, independent data are needed to supplement knowledge based on traditional external morphology and modern molecular sequence information. One promising approach involves comparisons of the structure and development of the nervous system. Along these lines, the morphology of serotonin-immunoreactive neurons in the ventral nerve cord has been investigated in numerous tetraconate taxa (Crustacea and Hexapoda). It has been shown that these neurons can be identified individually due to their comparably low number, characteristic soma position, and neurite morphology, thus making it possible to establish homologies at the single cell level. Within Chilopoda (centipedes), detailed analyses of major branching patterns of serotonin-immunoreactive neurons are missing, but are crucial for developing meaningful conclusions on the homology of single cells.
Recently, myriapods have attracted the attention of engineers because mobile robots that mimic them potentially have the capability of producing highly stable, adaptive, and resilient behaviors. The major challenge here is to develop a control scheme that can coordinate their numerous legs in real time, and an autonomous decentralized control could be the key to solve this problem. Therefore, we focus on real centipedes and aim to design a decentralized control scheme for myriapod robots by drawing inspiration from behavioral experiments on centipede locomotion under unusual conditions. In the behavioral experiments, we observed the response to the removal of a part of the terrain and to amputation of several legs. Further, we determined that the ground reaction force is significant for generating rhythmic leg movements; the motion of each leg is likely affected by a sensory input from its neighboring legs. Thus, we constructed a two-dimensional model wherein a simple local reflexive mechanism was implemented in each leg. We performed simulations by using this model and demonstrated that the myriapod robot could move adaptively to changes in the environment and body properties. Our findings will shed new light on designing adaptive and resilient myriapod robots that can function under various circumstances. | <urn:uuid:36d759c6-0654-4b4d-83bc-e76bca761a44> | 2.875 | 3,157 | Academic Writing | Science & Tech. | 1.492216 | 95,598,622 |
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Language: Chinese with scientific nomenclature
This series of books describes the morphology and biology of chrysomelids (i.e. leaf beetles) in Taiwan. The first issue includes 100 common and special species. This issue contains more than 500 full colour plates and live photos, and is written as an in-depth identification guide and biology reference for entomologists and nature lovers.
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These Breath-Taking Bubbles Shine Below A Canadian Lake... And They're Surprisingly Dangerous
This amazing spectacle below Lake Abraham, Alberta could cause quite the explosion
One look at the frozen Lake Abraham, in Alberta, Canada, and you know something special is going on below the ice.
At first glance it looks a bit like pillars of ice have formed below the water, but the natural phenomenon is actually caused by bubbles of frozen Methane – and they’re surprisingly dangerous.
The Methane bubbles form when dead organic matter from plants or animals falls into the water and is consumed by the bacteria below.
The resulting methane is the waste (of sorts) of this bacterium, and it’s highly flammable, so probably best not to light up if you’re skating over the lake.
Watching the video above will give you just a little bit of an idea of the damage this stuff can do, and scientists also point out that it’s a significantly more potent threat to the world’s climate than even carbon dioxide.
So that’s not great.
On the bright side though, at least the bubbles do look pretty awesome when they’re frozen below. Let’s just hope they don’t come back to cause the end of the world! | <urn:uuid:30521d90-5a57-47ca-b5b7-b4fee88ac38f> | 2.984375 | 270 | News Article | Science & Tech. | 53.603805 | 95,598,646 |
1. Write an Matlab m-file to solve this problem with Runge-Kutta method. Solve the concentration of T1 and T2 (or salt content) as function of time (up to 100 minutes). Both T1 and T2 are mixing tanks (assume immediate mixing). T1's capacity is 100 gallon and T2's capacity is 200 gallon. Initially, T1 contains full tank of salt solution which has 100 pounds of salt, T2 has full tank of pure water. When the input valve on T1 is turned on, the input flow rate (F1) is 10 gallon per minute with concentration of salt 0.6 pound per gallon flows into T1, and 15 gallons per minute (R1) of solution flows into T2, and 5 gallons per minute of solution flows from T2 to T1 (R2), and 20 gallons of solution (R3) flows out of T2. Also there is input (F2) flows into T2 at 10 gallons per minute. F2's concentration is 1 pound per gallon.© BrainMass Inc. brainmass.com July 21, 2018, 9:24 pm ad1c9bdddf
This problem is about dynamic of amount of salt flowing through the solution in two compartment (two tank) system. This dynamic system can be solved by Runge-Kutta method using ode45 solver in MATLAB programing. The Matlab code is attached with this post. Doc file named "548485_Problem 1_Solutin_updated.docx" ...
The Runge-Kutta method is solved using Matlab m-files. F2 concentrations for one pound per gallons are given. | <urn:uuid:a877ed6a-21ab-44b2-a754-ae97d5da6198> | 2.78125 | 353 | Tutorial | Science & Tech. | 80.046418 | 95,598,654 |
Web Date: April 19, 2012
The genetic basis for life on Earth may be stored in RNA and DNA, but scientists have now made six synthetic mimics of genetic material that are capable of recording, propagating, and evolving genetic information (Science, DOI: 10.1126/science.1217622).
The mimics could form a rudimentary basis for synthetic life and may have applications in materials science, molecular diagnostics, and therapeutics, comments Gerald F. Joyce, a chemist at Scripps Research Institute in La Jolla, Calif. They may also inform the search for life on other planets and for the origin of life on our own, he says.
A team led by Philipp Holliger, a chemist at the Medical Research Council Laboratory of Molecular Biology in Cambridge, England, prepared RNA and DNA mimics from six existing analogs of ribose and deoxyribose, the sugars that form the polymer backbones of RNA and DNA, respectively.
Like ribo- and deoxyribonucleotides, the nucleotide versions of these analogs can be strung together to form six different polymer backbones that the researchers call xeno-nucleic acids (XNAs). These are versions of nucleic acids containing nonnatural ring structures in place of ribose or deoxyribose. Each XNA can present sequences of the four genetic bases in DNA—cytosine, guanine, adenine, and thymine.
The team spent three years engineering and evolving polymerases that can copy a genetic code from DNA to an XNA and then back to DNA, a feat that mimics heredity, Holliger says. The team also showed that the synthetic genetic polymers could undergo Darwinian evolution when subjected to selection pressure. For example, the researchers evolved genetic polymer sequences based on 1,5-anhydrohexitol to bind to specific protein and RNA targets.
“In the longer run, it may be possible to design and build new forms of life that are based on one or more of these nonnatural genetic polymers,” comments Jack W. Szostak, who studies the origin of life at Harvard Medical School.
“Synthetic biologists are beginning to frolic on the worlds of alternative genetics but must not tread into areas that have the potential to harm our biology,” Joyce cautions. However, before the synthetic genetic polymers could form life, “the XNA must be able to catalyze its own replication without the aid of biological molecules,” and this would be a challenging task, Joyce notes.
For now, Holliger says his group is focused on biomedical and biotechnical applications. For example, he hopes to evolve the XNAs so that they fold into three-dimensional structures that can perform a task, such as delivering a drug to a cancer cell. Because the XNAs are synthetic polymers, “they can’t be degraded by nucleases, which would target RNA and DNA,” he says.
Furthermore, the team hopes to make use of the fact that the XNAs can be evolved to exhibit certain functions. In principle, Holliger says, “if you want the XNAs to deliver a drug inside cells, you could just select them to go into cells.”
Finally, the synthetic genetic polymers could be used as tools to figure out why, in the primordial soup, ribonucleic acids succeeded in becoming the first molecules of life, when many molecules were competing for the job. “Phil’s work will certainly make it possible to compare the functional abilities of a wide range of synthetic nonbiological nucleic acids” with those of RNA and DNA to answer this question, Szostak notes.
- Chemical & Engineering News
- ISSN 0009-2347
- Copyright © American Chemical Society | <urn:uuid:a8968917-d7b7-49ab-b2eb-578943086f15> | 3.859375 | 802 | Knowledge Article | Science & Tech. | 32.227733 | 95,598,655 |