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This chapter presents the MMSI application programming interface. MMSI is the programming interface recommended in MAP to access the MMS protocol. It is assumed that the underlying operating system offers multitasking. The MAP specification defines an abstract interface that can then be particularised for specific languages. Currently, the only binding defined is for the C programming language. In practice, all existing MMSI implementations run on UNIX workstations. DOS and Windows applications use much simpler interfaces to MMS, an example of which is given in Chapter 8 with the MMS/DDE interface developed in ESPRIT project CCE-CNMA.
KeywordsService Request Function Call Return Event Asynchronous Mode Additional Buffer
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Carbon nanotubes could be used to create structures that mimic artificial muscles, according to new research from the Rensselaer Polytechnic Institute in New York.
The boffins said that carbon nanotubes are well suited for this purpose because they can withstand repeated stress and still retain their structural integrity.
"The idea was to show how fatigue affects nanotube structures over the lifetime of a device that incorporates carbon nanotubes," said Victor Pushparaj, a senior research specialist in the Department of Materials Science and Engineering at Rensselaer.
"Even when exposed to high levels of stress, the nanotubes held up extremely well. The behaviour is reminiscent of the mechanics of soft tissues, such as a shoulder muscle or stomach wall, which expand and contract millions of times over a human lifetime."
Pushparaj and his team created a free-standing, macroscopic, two-millimetre square block of carbon nanotubes, made up of millions of individual, vertically aligned multi-walled nanotubes.
The researchers then compressed the block between two steels plates in a vice-like machine more than 500,000 times.
Pushparaj's team recorded precisely how much force was required to compress the nanotube block down to about 25 per cent of its original height.
Even after 500,000 compressions, the block retained its original shape and mechanical properties along with its original electrical conductance.
The report, Fatigue Resistance of Aligned Carbon Nanotube Arrays Under Cyclic Compression, appears in the July issue of Nature Nanotechnology.
Commons Science and Technology Committee calls for new post-Brexit skilled-workers immigration system
Committee calls for visa-free travel and permit-free work for skilled workers
Eleven 'normal' outer moons, and one described as 'oddball' found circling Jupiter
Scientific discovery has found a quadrillion tonnes of diamonds in the earth's mantle
Mobile payment app makes users' details public by default | <urn:uuid:43be7df7-babc-4707-a98d-f545298dacb3> | 3.59375 | 412 | News Article | Science & Tech. | 16.226371 | 95,527,044 |
In this tutorial, we will introduce you to Apache's Ant technology, which is a mean to build java projects. Ant is an open source tool that is easy to use and platform independent. This tutorial serves the purposes for both the beginners and experienced individuals. Going through it, a beginner can easily and quickly learn how to use Ant to build his/her own java projects; and if you are already exposed to Ant, then also you will be benefited by this tutorial learning more and advanced features of Ant. Introduction to Ant and its history, from installing it on your system to how to run and use it - every aspect will be described here with illustration and examples.
Apache Ant is an open source, cross-platform based build tool that is used to describe a build process and its dependencies and implemented in XML scripts using Java classes that ensures its extensibility to any development environment (based on Java) and its integrity with other build tools.
Ant is developed by Apache Foundation specifically to build projects based on java platform. But why to use Ant if there already exists other build tools like make, jam and many. Tool like make uses shell commands that facilitates integration of other tools to extend its functionality on the operating system where it runs. But this limits the functionality of the build tool specific to that OS only, e.g., make is specific to the UNIX platform. Ant has overcome this shortcoming as it uses java classes with XML scripting that makes it portable through cross-platform behavior. Ant is applicable to any integrated development environment based on java technology and therefore easy to use in building java projects across any platform. Ant enables automatic generation of build processes that is more reliable than manual procedures. Ant can also compile source code from version controls and package the compiled code and other resources (JAR, EAR, TAR etc.).
The development of Ant technology originated as an integral component of Tomcat application server based on Java Servlet and Java Server Faces. Ant, as a part of Apache Jakarta Project is an open source solution based on java platform. With the advent of time, it gained popularity and used widely. Its first independent release as a Jakarta subproject was made in the year 2000. Since then, Ant has been used as a major tool in building java projects and now it has become a top-level Apache project for server-side solutions. The latest release of Ant is version 1.7.1.
Introduction to Apache
Ant (Another Neat Tool)
Ant is an open source build technology developed by Apache intended to build processes in Java environment. It is a similar kind of tool like make but it does not use shell commands to extend the functionality. The use of shell commands in make brings about the integrity with other languages too but this also makes it platform specific. In contrast, Ant is based on XML and uses java classes in automatic generation of build processes that makes it platform independent. It is applicable to any integrated development environment (IDE) that uses java. A build file is generally named as build.xml.
The best features of the Ant technology can be summarized as below -
· Easy to Use: It is not a programming language, it is an XML based scripting tool, therefore easy to understand and implement.
· Portable and Cross-platform based: Uses of Java classes makes it portable, i.e., it can be run on any operating system.
· Extended Functionality: Ant is based on java platform, that?s why its functionality can be extended to any development environment based on java. It is easier to implement than any specific IDE because it is automated and ubiquitous.
· Build Automation: Ant provides automated build processes that is faster and more efficient than manual procedures and other build tools can also be integrated with it.
· Compilation of Source Code: Ant can use and compile source code from a variety of version controls and packaging of the compiled code and resources can also be done.
· Handling Dependencies between Targets: An Ant Project describes the target and tasks associated with it and also handles dependencies between various targets and tasks.
In this section, you will learn how to install Ant into your system.
The current version 1.7.1 of Ant was released on 27 June, 2008. It is available for download at http://ant.apache.org/bindownload.cgi. Here, you have to click on the link apache-ant-1.7.1-bin.zip in the .zip archive to download the zip file. After the download completes, unzip this file and install the apache-ant-1.7.1 folder to the root directory of C:\ drive. Therefore, path for the Ant directory will be C:\apache-ant-1.7.1. Now, we have to set some environment variables. Select the item "System" in the Control Panel of your system and click on the tab named "Advanced". You will see a button named "Environment Variables" appears, click it. Under Environment variables, you will find two user variables, viz., ANT_HOME and CLASS_PATH. Set the path value C:\apache-ant-1.7.1 to ANT_HOME variable and the path value C:\apache-ant-1.7.1\lib; to CLASS_PATH variable. Again in the System Variables, we have to set the value C:\jdk to JAVA_HOME variable and the value C:\apache-ant-1.7.1\bin; to Path variable.
Now, you have to check whether the installation process is done properly or not. To do this, open the Command Prompt and run the command C:\>ant. If the following message
appears, then it indicates that your installation is successful; Ant is properly installed in your system.. | <urn:uuid:95c2a70e-3a75-47c5-ab2e-672bc64de9d2> | 3.46875 | 1,186 | Tutorial | Software Dev. | 51.411261 | 95,527,049 |
Hydra are simple animals that, along with jellyfish, belong to the phylum cnidaria. Cnidarians first emerged 600 million years ago.
"We determined which genetic 'gateway,' or ion channel, in the hydra is involved in light sensitivity," said senior author Todd H. Oakley, assistant professor in UCSB's Department of Ecology, Evolution and Marine Biology. "This is the same gateway that is used in human vision."
Oakley explained that there are many genes involved in vision, and that there is an ion channel gene responsible for starting the neural impulse of vision. This gene controls the entrance and exit of ions; i.e., it acts as a gateway.
The gene, called opsin, is present in vision among vertebrate animals, and is responsible for a different way of seeing than that of animals like flies. The vision of insects emerged later than the visual machinery found in hydra and vertebrate animals.
"This work picks up on earlier studies of the hydra in my lab, and continues to challenge the misunderstanding that evolution represents a ladder-like march of progress, with humans at the pinnacle," said Oakley. "Instead, it illustrates how all organisms –– humans included –– are a complex mix of ancient and new characteristics."
David Plachetzki, who received his Ph.D. for work done in the Oakley lab, is the first author. Plachetzki is now a postdoctoral fellow at UC Davis. UCSB undergraduate Caitlin R. Fong is the second author of the paper.
Gail Gallessich | EurekAlert!
Scientists uncover the role of a protein in production & survival of myelin-forming cells
19.07.2018 | Advanced Science Research Center, GC/CUNY
NYSCF researchers develop novel bioengineering technique for personalized bone grafts
18.07.2018 | New York Stem Cell Foundation
For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.
To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...
For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.
Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...
Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.
A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...
Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.
"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....
Ultra-short, high-intensity X-ray flashes open the door to the foundations of chemical reactions. Free-electron lasers generate these kinds of pulses, but there is a catch: the pulses vary in duration and energy. An international research team has now presented a solution: Using a ring of 16 detectors and a circularly polarized laser beam, they can determine both factors with attosecond accuracy.
Free-electron lasers (FELs) generate extremely short and intense X-ray flashes. Researchers can use these flashes to resolve structures with diameters on the...
13.07.2018 | Event News
12.07.2018 | Event News
03.07.2018 | Event News
19.07.2018 | Earth Sciences
19.07.2018 | Power and Electrical Engineering
19.07.2018 | Materials Sciences | <urn:uuid:6775f6d0-ff3c-4beb-9092-fc313dbd8627> | 3.296875 | 975 | Content Listing | Science & Tech. | 42.507616 | 95,527,058 |
A substantial part of Europe consists of suburban landscapes. The factors determining the species diversity and composition in these seemingly uninteresting areas are, however, underexplored. We studied the factors determining the species diversity and composition of plant communities in a suburban postindustrial landscape in the central part of the Czech Republic. We recorded 242 phytosociological relevés (5 m × 5 m) in a regular grid over an area of 2.5 km × 1.8 km. Data on abiotic factors (slope, solar irradiation, bedrock) and landscape structure (distance from relevé to the nearest road, settlement and habitat edge) were obtained from digital maps. Patterns of plant species traits were also examined. A total of 387 species of vascular plants was recorded, and a majority of the species (58%) was found in five or fewer sites. The species abundances in the region were significantly affected by several traits. A long vegetation gradient including woodlands, shrubs, grasslands and ruderal and weedy communities were observed in the suburban landscape. Land cover was a crucial determinant of both the diversity and species composition. The number of species and evenness was significantly influenced by different abiotic and landscape structure factors. The species composition was affected by all of the tested factors. We found relationships between species traits and landscape structure characteristics. The results of this study showed that the species richness and the diversity of vegetation types are relatively high in suburban landscapes and are mostly determined by human activities forming the landscape structure. © 2012 Elsevier B.V.
Mendeley saves you time finding and organizing research
Choose a citation style from the tabs below | <urn:uuid:44cd104f-4f88-4e2a-9c23-3b02beccaa0e> | 2.890625 | 335 | Academic Writing | Science & Tech. | 30.183661 | 95,527,059 |
Why were most alpha particles in the gold foil scattering experiment not deflected?
Turn on thread page Beta
Gold foil scattering experiment watch
- Thread Starter
- 14-11-2017 22:02
- 14-11-2017 22:13
Most of the gold atoms is a vacuum so goes straight through. The ones that are deflected are because the the positive nucleus repels the alpha particles
- 16-11-2017 12:00
The alpha particles are only deflected by the positive charge in the nucleus, so they can pass straight through the gaps between the nuclei of atoms in the foil, as they are not repelled. | <urn:uuid:ee1eb61d-7e4f-441a-be69-8f93fbd30510> | 3.328125 | 133 | Comment Section | Science & Tech. | 55.396007 | 95,527,063 |
Environmental sensitivity mapping — what, why and how
Terms such as environmental stability, resilience or sensitivity are verbal abbreviations or abstractions for particular features of environmental stress-response relationships. An environmental planning map must take account of the range of possible stresses, responses, and stress-response relations, assess the significance of each, and express the most significant in a form immediately useable by planning engineers. The most critical part of this process is predicting the form of the stress-response relation for each stress and response. This is done essentially by comparison with similar environmental units elsewhere where the actual responses of particular stresses are already known. The level of precision attainable in an environmental planning map depends on the extent and relevance of information available for comparison: on the degree of similarity between the ecosystems and stresses where the responses are known and those for which the map is being prepared. The collection of environmental data from the area concerned, by aerial and ground survey, is of course also essential, but such data are of limited value without the background information required to predict the consequences of particular actions in the course of development.
KeywordsGeochemistry Background Information Actual Response Environmental Data Sensitivity Mapping
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Limits of arbitrary functions?
November 17, 2009
Bailey Hall 201
Suppose we know the values of a function $f$ (on the real numbers, say) near but not at $x$. If $f$ is continuous, we can determine $f(x)$ by taking a limit. But what if f is an arbitrary function, not necessarily continuous? At any predetermined point $x$, we have little hope of correctly guessing $x$. Nevertheless, we can exhibit a strategy for predicting values of $f$ from nearby values that is guaranteed to be correct for almost every $x$, regardless of the function $f$; in particular, if $x$ is chosen at random in [0,1], and we are asked to guess $f(x)$ based on nearby values of $f$, the strategy will guess correctly with probability 1. While exploring how this is done, we will look at topological analogs of well-foundedness and induction.
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Created automatically on: Mon Jul 23 03:40:56 EDT 2018 | <urn:uuid:6a57fcff-a6a6-4b3e-b4d2-fb6f8835d33a> | 2.921875 | 234 | Academic Writing | Science & Tech. | 58.974048 | 95,527,090 |
Last week the Scottish Government formally announced that the Eurasian beaver (Castor fiber) is to be officially recognised as a native species 400 years
after being hunted to extinction.
The Scottish Beaver Trial
The Scottish Beaver Trial, led by the Scottish Wildlife Trust and the Royal Zoological Society of Scotland, commenced in May 2009 with the release of 27
beavers into lochs and rivers across Scotland. Up to 250 beavers are now thought to be living over several hundred square miles.
Beavers are semi-aquatic animals and live in streams, rivers, lakes and swamps surrounded by woodland. They were once widespread in Europe and Asia but
were overhunted for their fur, meat and a secretion from their scent glands. They are a European Protected Species but not currently designated by
UK law due to their non-resident status. Becoming recognised as a native in species will mean that beavers are eligible to receive protection.
Returning beavers to the wild is the first formal mammal reintroduction in UK history. Not only does it set a precedent for future projects, it has also
brought benefits to biodiversity. New wetlands were created, which support species such as otters, water voles and dragonflies. The presence of beavers
also helps to regulate flooding and improve water quality.
The increase in beavers will almost certainly help grow the economy by boosting wildlife tourism in Scotland and also providing great potential for education
about the wider conservation movement.
The Wildlife Trust in Devon is currently trialling the release of beavers, while the Wildlife Trusts in Wales are investigating the feasibility of reintroduction.
Both projects rely on charitable funding to continue their work. The success of The Scottish Beaver Trial may generate the necessary support for these
and future reintroductions. | <urn:uuid:4e478e65-e4d0-46f5-8908-e7926d4577fd> | 3.984375 | 365 | News (Org.) | Science & Tech. | 34.970169 | 95,527,091 |
Wind profile development above a locally adjusted sea surface
Results are presented from a ‘numerical experiment’ of wind and shear stress profile development away from a shore line; the water surface is assumed to obey the Charnock-Ellison relation between surface roughness and friction velocity. In typical cases the upwind, land surface is rough relative to the sea and the velocity and shear stress results are qualitatively similar to those for flows from relatively rough to relatively smooth solid surfaces. In the present case, however, the downwind surface roughness and friction velocity vary with position and we find that wind profile development may play a significant role in the relationship between sea surface roughness and fetch.
KeywordsShear Stress Water Surface Surface Roughness Significant Role Numerical Experiment
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- Charnock, H.: 1955, ‘Wind Stress on a Water Surface’,Quart. J. Roy. Meteorol. Soc. 81, 639.Google Scholar
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Original Research ARTICLE
Assessing the Potential of Sponges (Porifera) as Indicators of Ocean Dissolved Si Concentrations
- Department of Geology, Lund University, Lund, Sweden
We explore the distribution of sponges along dissolved silica (dSi) concentration gradients to test whether sponge assemblages are related to dSi and to assess the validity of fossil sponges as a palaeoecological tool for inferring dSi concentrations of the past oceans. We extracted sponge records from the publically available Global Biodiversity Information Facility (GBIF) database and linked these records with ocean physiochemical data to evaluate if there is any correspondence between dSi concentrations of the waters sponges inhabit and their distribution. Over 320,000 records of Porifera were available, of which 62,360 met strict quality control criteria. Our analyses was limited to the taxonomic levels of family, order and class. Because dSi concentration is correlated with depth in the modern ocean, we also explored sponge taxa distributions as a function of depth. We observe that while some sponge taxa appear to have dSi preferences (e.g., class Hexactinellida occurs mostly at high dSi), the overall distribution of sponge orders and families along dSi gradients is not sufficiently differentiated to unambiguously relate dSi concentrations to sponge taxa assemblages. We also observe that sponge taxa tend to be similarly distributed along a depth gradient. In other words, both dSi and/or another variable that depth is a surrogate for, may play a role in controlling sponge spatial distribution and the challenge is to distinguish between the two. We conclude that inferences about palaeo-dSi concentrations drawn from the abundance of sponges in the stratigraphic records must be treated cautiously as these animals are adapted to a great range of dSi conditions and likely other underlying variables that are related to depth. Our analysis provides a quantification of the dSi ranges of common sponge taxa, expands on previous knowledge related to their bathymetry preferences and suggest that sponge taxa assemblages are not related to particular dSi conditions.
Sponges are aquatic, sessile, benthic, and filter feeding organisms that belong to the animal phylum Porifera. Their body structure is simple, with different kinds of cells specialized in a variety of life functions and organized in different layers according to their function (Hooper and Van Soest, 2002; Van Soest et al., 2012; Maldonado, 2014). Their origins have been placed in the Cambrian (Hooper and Van Soest, 2002; Xiao et al., 2005), or even before as suggested by the discovery of potential sponge biomarkers (Love et al., 2009; Yin et al., 2015; Gold et al., 2016).
Four classes of sponges are currently recognized: Calcarea, which includes species with calcareous skeletons; Hexactinellida, commonly known as glass sponges; Demospongiae, containing the majority of extant sponges; and the Homoscleromorpha (Hooper and Van Soest, 2002; Morrow and Cárdenas, 2015; Van Soest et al., 2017). The last three classes include species with siliceous skeletons cemented by organic components (i.e., a collagen-like protein, spongin), as well as species that lack a mineral (i.e., neither siliceous nor calcareous) skeleton and are constructed with spongin skeletons, occasionally reinforced with foreign inorganic elements (e.g., sand or remains of biogenic silica from other organisms, including sponges; Hooper and Van Soest, 2002).
Through complex enzymatic and metabolic processes (Wang et al., 2011a,b, 2012a), siliceous species of Hexactinellida, Demospongiae and Homoscleromorpha take up Si (predominantly present as silicic acid, H4SiO4 and conventionally referred to as dissolved silica; dSi) from their surrounding water to secrete individual structures known as spicules which provide skeletal support to the organic components of the sponge (Uriz et al., 2003). In some species of hexactinellids and demosponges, skeletal structures are massive and hypersilicified, with stony consistency and can form agglomerates and build reef-like formations (Conway et al., 2001; Uriz et al., 2003; Leys et al., 2004; Maldonado et al., 2015a,b) or “sponge grounds” (Klitgaard and Tendal, 2004). Sponges of these groups may be important players in the global silicon cycle due to their widespread occurrence and high preservation potential (Maldonado et al., 2005, 2010).
Silica uptake and silicification in sponges is regulated by the availability of dSi in the ambient water and dSi uptake conforms to enzymatic (Michalis-Menten) kinetics with maximal uptake rates occurring only above 100–200 μM dSi (Reincke and Barthel, 1997; Maldonado et al., 1999, 2011). These values are higher than typical concentrations in most of the modern ocean, suggesting sponge dSi uptake mechanisms evolved in higher dSi waters (Maldonado et al., 2015a) and dSi is a limiting factor for living sponges (Maldonado et al., 2011). Maldonado et al. (1999) also showed that secretion of certain spicule types is regulated by dSi thresholds and suggested that instances of these spicules in fossil sponges reflect dSi replete environments. Efficient mechanisms to utilize dSi have evolved in sponges (Müller et al., 2003; Schröder et al., 2004; Wang et al., 2012a,b) and involve the presence of silicatein, an enzyme that is able to control and catalyze the intracellular deposition of dSi from an unsaturated environment, as well as proteins that actively transport dSi across the cell membranes (Schröder et al., 2004; Marron et al., 2016).
Additional information about variations in the shape, or size of sponge spicules, or about disrupted spiculogenesis (shape changes, atrophies or other malformation of spicules) in relation to dSi concentration is scattered throughout the literature (Jørgensen, 1944; Hartman, 1958; Stone, 1970; Yourassowsky and Rasmont, 1984; Zea, 1987; Bavestrello et al., 1993; Rützler and Smith, 1993; Schönberg and Barthel, 1997; Mercurio et al., 2000; Valisano et al., 2012; Cárdenas and Rapp, 2013). Overall these studies show that the availability of dSi is a factor that can affect the morphology, composition or size of spicules in some species.
If spicule morphology and/or morphometrics are affected by dSi and given that these are the main underlying characters used for the classification of siliceous sponges (Hooper and Van Soest, 2002), some taxa or taxa assemblages may be characteristic of habitats with particular dSi conditions. These might conceivably have different adaptation mechanisms and therefore, differentially influence the ocean Si cycle. An essential first step to use sponges as indicators is recognizing and quantifying any causal relationship between modern sponge distributions and the underlying environmental drivers; this is the crucial first step in palaeoecological proxy development (e.g., Birks, 1995).
The spatial distribution of Porifera has been studied at local and regional scales and has been related to different environmental factors. Differences in sponge species composition between shallow and deep waters have been acknowledged for decades. De Laubenfels (1936) recognized that the spatial distribution of shallow water sponges is limited by strong environmental barriers (e.g., depth, light or temperature). More recently, the spatial distribution of marine sponges at local scales (e.g., 10 s of km; coral reefs, straits or gulfs) has been correlated to geomorphological features (Przeslawski et al., 2014), sediment properties, depth, distance to the coast, nutrient availability (including dSi), light penetration, hydrodynamics (Huang et al., 2011), deep sea currents (Cárdenas and Rapp, 2015), and biotic factors such as predation or competition for space (Huang et al., 2011; Pawlik et al., 2015; Slattery and Lesser, 2015). In general, these observations are replicated at regional or broader scales (e.g., >>100 km; seas or oceans). Here, sponge distributions have been related to depth, temperature and light availability (Vacelet, 1988; Finks and Keith Rigby, 2003; Leys et al., 2004; Downey et al., 2012), or to biogeographic regions (Hooper and Lévi, 1994; Van Soest, 1994; Van Soest et al., 2012) delimited by underlying abiotic drivers and characteristic marine biotas (e.g., Spalding et al., 2007). Interestingly, results from predictive models using physico-chemical environmental variables (Huang et al., 2011) and regional surveying (Howell et al., 2016) suggest that temperature, depth and nutrient status—including dSi—are major drivers controlling sponge distribution.
There is potential for sponge species composition and spicule morphology in the sedimentary record to yield insight into dSi at the time of their formation. The reconstruction of paleo-dSi is receiving increasing attention, partly motivated by the linkages between the long-term carbon and silicon biogeochemical cycles (Conley et al., 2000; Frings et al., 2016). To date, dSi reconstruction using sponges has been achieved by exploring morphometric relationships of fresh-water spicules through dSi gradients (Kratz et al., 1991). More recently, silicon isotope analysis of sponge spicules has exploited the observation that the fractionation of stable Si isotopes between ambient dSi and the biogenic Si in spicules is a function of dSi concentration in the surrounding environment (Hendry et al., 2010, 2011; Wille et al., 2010; Hendry and Robinson, 2012; Fontorbe et al., 2016, 2017). The development of a complementary palaeoecological approach based on taxa assemblages could greatly extend the understanding of dSi changes in past and present oceans. By estimating the distributions of sponge taxa along a dSi gradient, particular species assemblages can be identified to provide insight into past Si dynamics in ocean and coastal environments.
In this work we explore the distribution of sponges along dSi gradients to test whether sponge assemblages are a function of dSi and to assess the validity of sponge taxonomy as a palaeoecological tool for inferring palaeo-concentrations of dSi. To achieve this we extracted and combined information from publically available oceanographic and biodiversity databases to evaluate the dSi conditions where sponges are found in the global ocean. Because dSi is correlated with depth in the modern ocean, we also explore taxa distributions as a function of depth. In general, we find that while there are hints of an assemblage-dSi relationship, sponges are not sufficiently differentiated as a function of dSi availability to clearly indicate specific dSi concentrations, a conclusion with implications for reconstructions of the ocean Si cycle.
Materials and Methods
We used sponge records held in the Global Biodiversity Information Facility (GBIF) and a gridded climatology of ocean chemistry data, interpolated from measurements, from the World Ocean Circulation Experiment (WOCE) (Gouretski and Koltermann, 2004). This is available with a horizontal grid resolution of 0.5° and with 40 unevenly spaced vertical layers. GBIF is an international open data infrastructure and the world's largest biodiversity database, and provides a freely available, single point access to millions of biodiversity records (http://www.gbif.org/what-is-gbif). GBIF aggregates data from a variety of sources of variable extent, quality and taxonomic precision (see www.gbif.org for more information). WOCE is a global data resource of the US National Oceanic and Atmospheric Administration ultimately based on observations from ships, floats, drifters and satellites. We interrogated GBIF via the online portal (http://www.gbif.org/occurrence) and downloaded 323,953 georeferenced records of Porifera available in November 2016 (GBIF Occurrence Download: https://doi.org/10.15468/dl.viufhq). The taxonomic classification of species in these records follows that of the World Porifera Database (WPD, http://www.marinespecies.org/porifera/news.php?p=show&id=4893). Only records with an associated depth (143,275; 44%) were used in the analyses. Paleontological records and freshwater taxa included in the dataset were also removed (830 and 192 records, respectively). To validate the geolocation data of GBIF, we compared the water depth associated with each record with the ETOPO1 1 Arc-Minute Global Relief Model (Amante and Eakins, 2009). Because both datasets contain variable quality and resolution depth data, records that disagreed by more than 500 m were discarded. Agreement was taken as a sign of confidence in the depth data. This 500 m threshold was selected (rather arbitrarily) to allow for (i) the possibility of steep bathymetry at spatial scales below that of ETOPO1 and (ii) the inclusion of dredge samples, where only the trawl start or finish point is given. This quality control process lead to the exclusion of 5,190 (ca. 3.6%) of datapoints, which in some cases were in disagreement by > 6000 m (see Supplementary Figure 1). In addition, any remaining records which were flagged within GBIF as having a “non-numeric” or “non-metric” depth in the original dataset (13,317 and 5,060, respectively) were removed, to avoid any conversion issues.
Information at the level of class and order, missing in some of the GBIF records although the lower taxonomic rank of family or genus was given, was added following the WPD. GBIF contains a mixture of reliable and unreliable taxonomic information (Van Soest et al., 2012), and includes records with taxonomic identifications derived from photographs and/or video-recordings, which e.g., Leys et al. (2004) have identified as a source of uncertainty. We assumed that the taxonomic identifications included in the GBIF records at the level of order and family are more accurate than those from lower levels (genera and species), which generally require a greater degree of taxonomic expertise. For this reason we limit our analyses to the level of family and above (order and class). Our analyses could be improved and extended to a higher taxonomic resolution with an increase in the reliability of taxonomic identifications of GBIF records.
The final dataset for this study included 62,360 discrete, globally distributed records (Figure 1). Of these, 2,905 are classified only as far as class, 890 only as far as order (31 different orders), 2086 to family level (128 different families), 24,525 to the level of genus (555 different genera) and the remainder (31,955) to species (2,758 different species) or subspecies. For comparison, the World Porifera Database (Van Soest et al., 2017) currently recognizes 32 extant orders, 149 extant families and 740 extant genera, implying we capture a large proportion of total global sponge biodiversity.
Figure 1. Ocean dissolved silica concentrations in bottom waters (i.e., seafloor). Gray dots indicate the location of individual sponge records included in this manuscript from GBIF.
For each individual sponge observation in GBIF, ocean temperature, salinity and nutrient concentrations (nitrate, phosphate and dSi) were extracted from WOCE (Gouretski and Koltermann, 2004) from the box enclosing the recorded sponge location. A summary of the data, including counts, maxima, minima and averages for each variable on a taxa-by-taxa basis for each of the families represented in the data set is provided (Supplementary Table 1).
Effect of Sampling Techniques and Sampling Effort
dSi concentrations in ocean bottom waters and the locations of the sponge records from the dataset are shown in Figure 1. Most of the records examined are limited to shallow water collections where dSi is generally low, which we attempt to account for in our analysis (see below). However other sampling biases might also be present. For instance, deep sea habitats are usually sampled with trawls or dredges. These generally catch abundant, large or hard specimens, but groups represented by small or fragile individuals (e.g., Cladorhizidae and Calcarea) are often not recovered (Raff et al., 1994), and therefore might be underrepresented. At present, quantifying the scale and significance of this bias is not possible.
We investigated the impact of very intense sampling within small regions by first regarding the taxa as only present or absent for each box in the WOCE dataset, and calculating the global distribution along an environmental gradient using 20 equally spaced bins for each variable (shown for dSi in Figure 2A). The presence/absence aggregation made only a very minor difference to the distribution of taxa along environmental gradients (Figure 2B), so we proceed with the full (i.e., non-aggregated) dataset. To crudely address a sampling bias toward continental shelves and shallow water areas in GBIF records we normalized the taxa distributions to the total Porifera distribution (Figure 2) to obtain a suite of distributions that describe the relative importance of individual taxa to the total Porifera population along any given environmental gradient. This approach implicitly assumes that sampling and identification of the Porifera records is not biased toward one group of taxa and is not suitable for e.g., calibrating individual sponge taxa environmental preferences. However, the intent here is not to estimate the true distribution of sponge taxa in the global ocean, but rather to explore relative differences among taxa. In the Supplementary Table 1 we show a summary of the uncorrected data.
Figure 2. (A) Global distribution of GBIF records aggregated as presence/absence values in 0.5° boxes of the WOCE dataset. (B) Global distribution of GBIF records without correction for sampling bias.
For taxa that are abundant (more than 100 records in GBIF), violin plots of the normalized data as a function of underlying environmental gradients were created at different levels of taxonomic classification (class, order, and family) and form the basis of further discussion. Where applicable, we include sponge species (referred to as “lithistids” hereafter) with highly silicified skeletons that were previously classified in the polyphyletic order Lithistida (Pisera and Lévi, 2002) but are now divided among unrelated orders of the class Demospongiae (Cárdenas et al., 2012). In these plots, the width of the bars indicates the relative contribution of the taxa to the total of all sponge taxa recorded in GBIF at the corresponding value of the environmental variable; note these are further standardized to the maximum contribution of that taxa, so do not contain any useful information about the absolute abundance of any given taxa, which is not possible with the “presence-only” GBIF data.
The relative frequency distribution of sponge taxa vs. dSi and depth is shown in Figures 3–5. At the level of class the Hexactinellida are found across broad ranges of dSi (0–180 μM; Figure 3A) and depth (0–6,000 m; Figure 3B). Sponges with calcareous skeletons show similar distributions but are a greater relative contributor to total sponge taxa at dSi < 100 μM and < 3,000 m depth. The rest of the classes are also found in the same range, however their major contributions to the total are below 120 μM and shallower than 1,000 m for the siliceous classes Homosclerophorida and Demospongiae.
Figure 3. Violin plots showing the distribution of the sponge classes in a dSi gradient (A) and a depth gradient (B).
In our analysis, 19 of the 32 total sponge orders are represented within GBIF in at least 100 boxes of the WOCE dataset (Figure 4). A majority occur seem dominantly at dSi < 50 μM, while other groups of demosponges (Tethyida, Suberitida Polymastiida and Haplosclerida), hexactinellids (Hexactinosa and Lyssacinosida), homosclerophorids and the Clathrinida are more evenly distributed along the dSi gradient. The hexactinellid order Amphidiscosida make their greatest contributions to sponge assemblages in environments with dSi>100 μM and the calcarean order Leucosolenida shows a bimodal distribution. Figure 4B shows the distribution of the same orders as a function of depth. A comparison between the two plots indicates that orders with relatively more frequent occurrences at higher dSi are also represented at depths greater than 2,000 m. The demosponge orders without siliceous skeletons (i.e., Dendroceratida, Verongiida –excluding some species (Ehrlich et al., 2010), and the Clionaida are not found in the GBIF database at depths greater than 1000 m. The distribution of lithistids along the depth gradient indicates this group is a relatively consistent contributor to total sponge assemblages at dSi below 50 μM and is not found at depths greater than 2,500 m.
Figure 4. Violin plots showing the distribution of sponge orders along the dSi gradient (A) and the depth gradient (B). Only orders represented within GBIF in at least 100 boxes of WOCE dataset are shown. Numbers in parenthesis are codes given to each of the represented orders. Lithistids includes taxa assigned to this taxon by Pisera and Lévi (2002). Taxa with gray background include sponges without siliceous spicules. Color codes as in Figure 3.
At the highest level of taxonomic resolution that we consider, 43 families within Porifera occur in 100 or more WOCE boxes (for reference, there are 149 currently recognized families within Porifera; Van Soest et al., 2017). Their distributions follow similar tendencies to those shown at the level of order, with some families better represented at dSi < 50 μM, some approximately equally represented along the gradient, some occurring at both high and low dSi and others more likely to be found at dSi>100 μM (Figure 5A). Distribution of these families along the depth gradient (Figure 5B) roughly tracks the dSi gradient. Families that occur at high dSi such as the Cladorhizidae, and Polymastiidae and all of the hexactinellids, are also likely to occur in deep waters. Non-siliceous sponges of the orders Verongiida, Dictyoceratida and Dendroceratida, with the exception of Spongiidae (see discussion below), are found within the group of taxa that occur at dSi < 20 μM, together with the family Clionidae (usually sponges associated with calcium carbonate substrates) but also with families that have siliceous skeletons (i.e., Petrosiidae, Dictyonellidae and Callyspongiidae). These are only found at shallow depths (Figures 5A,B).
Figure 5. Violin plots showing the distribution of sponge families in a dSi gradient (A) and a depth gradient (B). Only families represented within GBIF in at least 100 boxes of WOCE dataset are shown. Numbers in parenthesis are codes given to each family. Taxa with gray background include sponges without siliceous spicules. A key to the orders represented in Figure 4 is included. Color codes as in Figure 3.
Our analysis provides a quantification of the dSi ranges of common sponge taxa and expands on previous knowledge related to their bathymetry (Vacelet, 1988; Maldonado and Young, 1998; Rapp et al., 2011; Downey and Janussen, 2015; Hestetun et al., 2015). The distribution of sponge taxa along a depth gradient exhibits clear similarities to dSi, meaning the challenge is to distinguish between the two.
Below, we discuss the role of dSi availability, and the effects of other variables that might be indirectly influencing the patterns presented here. We also discuss how this data might contribute to clarifying the role of sponges in the ocean Si cycle in the geological past, and the usefulness of sponge assemblage data as a marine palaeoecological tool.
Effects of dSi Availability and Habitat Depth on Sponge Distributions
Depth is an important factor controlling sponge distribution (Vacelet, 1988; Huang et al., 2011; Howell et al., 2016), though it acts indirectly via its correlation with ecologically meaningful parameters (including dSi concentrations, but also light, food availability, temperature, etc.,). It is evident that either dSi, depth or both play a major role controlling the spatial distribution of sponge taxa (Figures 3–5). Our results confirm that the Porifera are not uniformly distributed along either a dSi or a depth gradient. Because the differentiation along the two gradients is similar, it is unclear whether dSi availability, habitat depth, or another unidentified factor (or combination of factors), is driving the spatial distributions of sponges. At least at regional scales, water depth acts as a surrogate variable for light penetration, temperature, and nutrient concentrations; these all are inter-correlated and could be influencing sponge distributions (Vacelet, 1988). Other depth-related factors such as food resources (i.e., particulate and dissolved matter), turbulence, spatial competition, and predation have been suggested as drivers of sponge community structure and distribution (Pawlik et al., 2015; Slattery and Lesser, 2015).
Bottom-water temperature and concentration of some nutrients have also been identified as important variables controlling sponge distribution at local scales (Huang et al., 2011; Howell et al., 2016). However, the distribution of sponges as a function of temperature, dissolved oxygen and nutrient (nitrate and phosphate) concentrations extracted from WOCE (see Supplementary Material) revealed that the distribution of sponge taxa along these gradients is not strongly differentiated, in contrast to the dSi and depth gradients. Although we cannot exclude these factors, the fact that habitat depth shows a similar sponge distribution pattern with dSi is suggestive of dSi availability being an important driver of the spatial distribution of some sponge groups, and implies that sponge distribution as a function of depth simply reflects the general relationship between depth and [Si] (see below; Figure 6). Unfortunately, we cannot strictly identify the direction of causality and rule out the possibility that depth is simply acting as a surrogate for another, as yet unidentified variable.
Figure 6. Cross-plot of mean habitat depth and mean ambient dissolved Si concentrations for all sponge families in the GBIF database. See previous figures for key to colors. All taxa are included regardless of their abundance, unlike Figures 3–5 where an occurrence criterion of 100 WOCE boxes is imposed. Data are aggregated at the presence/absence level for individual WOCE boxes. Gray dots in the background are ocean bottom water dSi concentrations (i.e., the same data as Figure 1).
In general, ocean dSi correlates with depth (Sarmiento and Gruber, 2006), as biogenic silica produced by siliceous plankton at the surface progressively dissolves as it sinks through the water column (although this pattern is somewhat complicated by the marine overturning circulation that acts to mix water-masses of varying ages, and therefore accumulated dSi) and because of high diatom production due to upwelling. To further explore this issue, we have plotted dSi and depth for all families included in our dataset in Figure 6. This confirms the presence of a positive relationship between dSi and depth with a similar form to that for the whole ocean (Figure 6).
Sponge Assemblages along dSi And Depth Gradients
Our data show that either depth or dSi play major roles controlling the spatial distribution of some taxa (Figures 3–5). Below we discuss which of those taxa might include species with different dSi uptake requirements and therefore could be indicative of dSi conditions.
Species of the order Hexactinosa (e.g., Farrea occa, Aphrocallistes vastus and Heterochone calyx) are known to construct hypersilicified skeletons and to form sponge reefs where dSi is reasonably high (ca. 40 μM), e.g., on the western coast of Canada (Leys et al., 2004; Conway et al., 2005; Whitney et al., 2005; Chu et al., 2011). The occurrence of these reef-building species is thought to be controlled by the combined action of particular oceanographic, geomorphological conditions and biotic factors, including dSi availability (Conway et al., 2005; Maldonado et al., 2015a). Hexactinosa (Figure 4) are important components of the sponge fauna at high dSi and depth together with species belonging to Amphidiscosida, Aulocalycoida, and Lyssacinosida (Rossellidae), which lack a dyctional (fused spicules in a 3D framework) skeleton suitable for reef formation but nevertheless have relatively more dSi per biomass unit than sponges from other sponge classes (Barthel, 1995).
The families Cladorhizidae, and Polymastiidae are relatively more likely to be found in dSi rich waters (Figure 5A). These families have also a broad distribution range along depth gradients and are likely to be found in deep waters (>2,000 m) where dSi is also high. Whether or not the distribution of these taxa is driven by dSi or by depth remains to be answered. Detailed studies of dSi uptake mechanisms and rates of these sponge species, living in different dSi conditions will contribute to answer this question and to identify species that can be used as indicators of particular dSi ranges.
The remaining siliceous and non-siliceous demosponges are likely to be found in low dSi habitats, although some of those might occur at greater depths with high dSi. Some of Dictyoceratida families (i.e., Spongiidae), which lack siliceous skeletons, are likely to occur at high dSi and depth (Figure 5). This is an interesting observation because members of this group are conventionally thought to be found in tropical latitudes and shallow waters (Vacelet, 1988) and in some species the settlement of their larvae is affected by low temperatures, and light penetration (Maldonado, 2009). As far as we know, species of Spongiidae have not been reported from bathyal depths in the taxonomic literature. It is possible that these records might be misidentified, given that the taxonomy of these sponges is extremely difficult. However, until independent verification of these Dictyoceratida records we assume that their documentation in GBIF is correct, and therefore that other factors correlated to depth (including temperature, light penetration, nitrate or phosphate concentrations) are driving the occurrence of particular species of this group.
Sponges included in this polyphyletic (diverse phylogenetic affinities) group include species with articulated spicules called desmas, that form a rigid skeleton in most species (Pisera and Lévi, 2002). The majority (93%) of lithistid records are from the order Tetractinellida, and the most common families were Theonellidae (21%), Corallistidae (18%), and Scleritodermidae (17%). According to Figure 4, lithistid taxa are more likely to be found at < 60 μM dSi, with the greatest relative frequency at < 20 μM and < 1,000 m. Some of them are known to build reef-like formations in habitats where dSi availability is low relative to that reported for the Hexactinosida reef-like builders (Maldonado et al., 2015a,b). Hypersilicified species lithistid (e.g., Leiodermatium spp) also cohabit with members of sponges without siliceous skeletons (i.e Dictyoceratida, Dendroceratida, and Verongiida) (Przeslawski et al., 2014, 2015) in relatively shallow habitats of northern Australia, with dSi concentrations <5 μM, exposed to strong tidal currents, high turbidity, and substantial sediment mobility (Przeslawski et al., 2011). As suggested by Maldonado et al. (2015b), some lithistid species seem to benefit from heavy sediment deposition, and patterns of local circulation that might deliver food and Si in pulses. It remains to be answered how these hypersilicified skeletons of lithistid species can develop in lower dSi and whether or not these species might have more efficient Si uptake systems than other taxa such as Hexactinosida which tend to be found in comparatively higher dSi (Figures 4, 5).
The GBIF data shows that sponges of the class Calcarea are found in the depth gradient up to 5,000 m with peaks below 3,000 m. This confirms previous findings (Duplessis and Reiswig, 2000; Rapp et al., 2011) and suggest that the diversity of the group at abyssal depths is higher than previously thought, and that they are occasionally capable of growing in environments below carbonate mineral saturation.
There is a large body of literature that deals with methods to derive quantitative palaeoenvironmental reconstructions from (micro)fossil assemblages, in terrestrial, freshwater, and marine environments. As summarized in e.g., Telford and Birks (2005) or Juggins (2013), there is an increasing awareness of the limitations of these approaches, even in favorable situations. We have decided against a more quantitative approach for several reasons, including (i) GBIF data are compiled from disparate, unconnected sources with different sampling strategies, (ii) the higher end of the dSi gradient is poorly represented in the data, (iii) the data are “presence-only,” rather than true species abundances, meaning taxa optima can not be easily defined, (iv) we have no independent model verification dataset, (v) variance-partitioning presumably will indicate a high degree of shared variance between depth and dSi, and (vi) the environmental calibration data has a hard-to-quantify noise component, being derived separately from the GBIF data at a lower spatial resolution.
In the future, a true sponge assemblage (with taxa abundances) and environmental variable dataset collected in a region or regions where dSi is decoupled from depth would be able to overcome some of these difficulties. Sponge silicon isotope ratios are becoming more widely used as a proxy for past-dSi concentrations (e.g., Fontorbe et al., 2017). Though not widely used, “mutual-range” approaches (Sinka and Atkinson, 1999), modern analog techniques (MAT; Lytle and Wahl, 2005), or artificial neural networks (Racca et al., 2007) may prove fruitful palaeoecological complements. Finally, lab- to field scale experiments carefully designed to extract the influence of dSi availability on sponge physiology and ecology, or approaches that seek to use individual spicule morphometrics (cf. Kratz et al., 1991) may also be part of the developing palaeo-dSi “toolbox.”
Did dSi Control Sponge Distributions in the Past?
The evolution of the ocean Si cycle has received attention for many decades (e.g., Maliva et al., 1989; Kidder and Tomescu, 2016). The prevailing narrative (Maliva et al., 1989; Siever, 1991; Kidder and Tomescu, 2016) argues for two particularly important events. The first is a transition from a Precambrian ocean saturated with respect to dSi to a slightly undersaturated Mesozoic ocean. The second was a further decrease, sometime in the Cretaceous-Paleogene, in the dSi content of mean ocean water to a modern, dSi-deplete ocean. Both transitions are ascribed to biological innovations—the first to the evolution of silicification by radiolarians and sponges, and the second to the expansion of diatoms—and therefore biology's progressive ability to remove dSi from seawater. Superimposed on this long-term decline in ocean dSi, transient excursions in the ocean dSi inventory have been proposed in response to periods of extensive volcanism (particularly the emplacement of large igneous provinces, LIPs) (Ritterbush et al., 2014, 2015; Kidder and Tomescu, 2016), or orogenesis (e.g., Cermeño et al., 2015). One of the lines of evidence supporting these interpretations is a change in the sedimentary facies associated with sponges in the rock or sediment record (e.g., Kidder and Tomescu, 2016). The link between sponge abundances/distributions and dSi stems from the implicit assumption that siliceous sponges are unable to thrive at low dSi (e.g., Ritterbush et al., 2015; Kidder and Tomescu, 2016). Kidder and Tomescu (2016), for example, interpret an Ordovician retreat in sponges from lagoonal depositional environments toward deeper, shelf settings, as reflecting radiolarian driven dSi depletion of the surface ocean. After the mid-Ordovician, sponge fossils from peritidal and lagoonal facies are apparently rare in the fossil record (see Gammon et al., 2000) for a possible Eocene exception. Maliva et al. (1989) argue that sponges become quantitatively unimportant in the ocean Si cycle during the Cenozoic. To what extent are these putative changes in sponge abundance and distribution driven by dSi availability?
Our dataset shows that all sponge groups that are sufficiently sampled (i.e., >100 WOCE boxes, see Supplementary Table 1) are capable of growing in low dSi environments. Indeed, at least in some isolated instances, siliceous sponge taxa are capable of forming large reef-like aggregations at <10 μM dSi (Maldonado et al., 2015a,b). This implies that while any decline in dSi availability may have been a contributory factor to sponge exclusion from shallow water environments, other factors, perhaps related to the evolution, and ecology of sponge competitors should be taken into account. Therefore the presence of any given taxon cannot be in and of itself be indicative of the prevailing dSi concentrations.
For example, reef-building litihistid species, used as indicators of greater dSi availability in past environments (e.g., Corsetti et al., 2015; Ritterbush et al., 2015), are in our dataset more frequent <20 μM and < 2,500 m. There is currently no evidence to suggest that they were unable to live in similar environments in the geological past (Pisera, 1997). The expansion of certain sponge groups after the Triassic-Jurassic extinction is more likely a consequence of a greater availability of suitable ecological niches vacated after the collapse of calcareous invertebrates in that period (Ritterbush et al., 2014, 2015).
Lastly it is important to mention that generally the majority of siliceous and non-siliceous sponges are not well represented in the fossil record as their skeletons are easily destroyed. Species with rigid skeletons, e.g., lithistids, some hexactinellids and fossil sponges with basal calcareous skeletons (i.e., Chaetetida and Stromatoporoidea) are more likely to be preserved, biasing the stratigraphic record (Pisera, 2006).
We show here that the distribution of sponges classified at the level of family is related to ambient dSi concentrations or habitat depth, or both. The distribution patterns along dSi concentrations or habitat depth indicate that the majority of taxa, including those in the class Calcarea without siliceous skeletons, occur in broad dSi (0–180 μM) and depth (0–~5,500 m) ranges. It also shows that the majority of demosponges without autochthonous siliceous skeletons are found at dSi <20 μM and shallow depths, but together with groups that have skeletons made up of siliceous spicules. Demosponges with rigid siliceous skeletons and traditionally known as lithistids do not seem to be associated with deep environments rich in dSi indicating that these kind of sponges might have evolved particularly efficient mechanisms to incorporate and accumulate dSi in their skeletons. Hexactinellids on the other hand, also builders of strong and rigid siliceous skeletons are distributed along the dSi gradient but are more likely to be present in deep and silica-rich environments. The hexactinellids share this kind of environments with some demosponges evenly distributed along the dSi and depth gradient and mainly from the orders Cladorhizidae and Polymastiida.
The groups skewed to either low or high dSi might include species indicative of specific environmental Si conditions. As no unique or clear assemblage of taxa could be identified, additional information on Si uptake rates for possible indicative species is required to conclusively relate their spatial distribution to dSi levels. One might expect to see greater differentiation along environmental gradients if sponges are considered at the level of genera or even species, though we note that some genera (e.g., Geodia) are highly cosmopolitan. Similarly, studying dSi uptake mechanisms of sponge species occurring at a broad dSi and depth ranges could provide essential information on the adaptation potential of sponge taxa.
Links between the abundance of sponges in sedimentary records and the contemporary dSi concentrations should therefore be interpreted with caution, given these organisms are clearly adapted to live in a range of dSi concentrations and depth habitats, as seen in our results. Other biotic (e.g., competitive interactions) and abiotic factors (e.g., light penetration, temperature, nutrient and food availability), some of which are also related to depth, may be important factors in the distributions of modern sponges - and were probably equally important in palaeo-environments.
All authors listed have made a substantial, direct and intellectual contribution to the work, and approved it for publication. BA and PF are joint senior authors.
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.
This study was funded by a grant from the Knut and Alice Wallenberg Foundation to DC. Dmitry Schigel, GBIF and Merrick Ekins, Queensland Museum, provided valuable comments and suggestions related to the data downloaded from the GBIF portal. We thank all the suggestions and revisions of the reviewers.
The Supplementary Material for this article can be found online at: https://www.frontiersin.org/articles/10.3389/fmars.2017.00373/full#supplementary-material
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Keywords: sponge assemblages, palaeoecological indicators, spatial distribution, dissolved silica gradient, depth gradient, Si cycle
Citation: Alvarez B, Frings PJ, Clymans W, Fontorbe G and Conley DJ (2017) Assessing the Potential of Sponges (Porifera) as Indicators of Ocean Dissolved Si Concentrations. Front. Mar. Sci. 4:373. doi: 10.3389/fmars.2017.00373
Received: 12 April 2017; Accepted: 07 November 2017;
Published: 30 November 2017.
Edited by:Brivaela Moriceau, Centre National de la Recherche Scientifique (CNRS), France
Reviewed by:Sönke Hohn, Leibniz Centre for Tropical Marine Research (LG), Germany
Paco Cardenas, Uppsala University, Sweden
Copyright © 2017 Alvarez, Frings, Clymans, Fontorbe and Conley. 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: Belinda Alvarez, email@example.com
†Present Address: Patrick J. Frings, Department of Geoscience, Swedish Museum of Natural History, Stockholm, Sweden and Earth Surface Geochemistry, GFZ German Research Centre for Geosciences, Potsdam, Germany
Wim Clymans, Earthwatch Institute (Europe), Oxford, United Kingdom | <urn:uuid:aead2940-d1f6-4585-808f-750798888cd2> | 2.78125 | 15,760 | Academic Writing | Science & Tech. | 55.635274 | 95,527,126 |
Scientists have long recognized that the collision of the earth’s great crustal plates generates mountain ranges and other features of the Earth’s surface. Yet the link between mountain uplift and river drainage patterns has been uncertain. Now scientists have used laboratory techniques and sediment cores from the ocean to help explain the how rivers have changed course over millions of years.
Shaded relief map of the Arabian Sea and surrounding land masses, showing the location of the drill sites and seismic profiles used in the study and major tributaries of the Indus River. (Figure by Peter Clift and Jerzy Blusztajn)
Proposed drainage pattern of the Indus River before 5 million years ago (right) and during modern times (left). Drainage capture, or diversion of a river pattern, occurs when a river captures or intercepts other rivers. (Figure by Peter Clift and Jerzy Blusztajn)
In a report published in the December 15 issue of Nature, scientists Peter Clift of the University of Aberdeen in the United Kingdom and Jerzy Blusztajn of the Woods Hole Oceanographic Institution reconstructed the erosional discharge from the Indus River over the past 30 million years and found that the source of those sediments changed five million years ago. Until then, Indus River sediments were produced by erosion of mountains to the north of the collision zone between India and Asia, but five million years ago much more sediment starting coming from the southern Himalayas, part of the deformed Indian plate.
Clift and Blusztajn believe the change is caused by a rerouting of the major rivers of the Punjab region into the Indus River, where they flow into the Arabian Sea west of India. Previously these rivers flowed east and joined the Ganges River before reaching the Bay of Bengal, east of India.
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For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.
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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.
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The discovery of an unusual carbon-based molecule near the galactic center of the Milky Way suggests that the complex molecules needed for life may have their origins in interstellar space.
Organic molecules usually found in these star-forming regions consist of a single “backbone” of carbon atoms arranged in a straight chain. The carbon structure of this molecule—known as isopropyl cyanide—is branched, making it the first interstellar detection of such a molecule, says Rob Garrod, a senior research associate at the Center for Radiophysics and Space Research at Cornell University.
This detection opens a new frontier in the complexity of molecules that can be formed in interstellar space and that might ultimately find their way to the surfaces of planets, says Garrod.
The branched carbon structure of isopropyl cyanide is a common feature in molecules that are needed for life—such as amino acids, which are the building blocks of proteins.
The discovery, reported in the journal Science, lends weight to the idea that biologically crucial molecules, like amino acids that are commonly found in meteorites, are produced early in the process of star formation—even before planets such as Earth are formed.
Garrod, along with lead author Arnaud Belloche and Karl Menten, both of the Max Planck Institute for Radio Astronomy, and Holger Müller of the University of Cologne sought to examine the chemical makeup of Sagittarius B2, a region close to the Milky Way’s galactic center and an area rich in complex interstellar organic molecules.
Using the Atacama Large Millimeter/submillimeter Array (known as the ALMA Observatory), the group conducted a full spectral survey—looking for fingerprints of new interstellar molecules—with sensitivity and resolution 10 times greater than previous surveys.
The purpose of the ALMA Observatory is to search for cosmic origins through an array of 66 sensitive radio antennas from the high elevation and dry air of northern Chile’s Atacama Desert. The array of radio telescopes works together to form a gigantic “eye” peering into the cosmos.
“Understanding the production of organic material at the early stages of star formation is critical to piecing together the gradual progression from simple molecules to potentially life-bearing chemistry,” says Belloche.
About 50 individual features for isopropyl cyanide (and 120 for normal-propyl cyanide, its straight-chain sister molecule) were identified in the ALMA spectrum of the Sagittarius B2 region. The two molecules—isopropyl cyanide and normal-propyl cyanide—are also the largest molecules yet detected in any star-forming region.
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BOZEMAN – A Montana climate study found the state’s average temperature continues to increase, winter snowpack is decreasing and the fire and growing seasons are lasting longer while drought conditions are expected to increase in frequency and duration.
The Montana Climate Assessment, carried out by the Montana University System’s Institute on Ecosystem, suggests Montana may need to start storing more water and farmers and ranchers may need to switch to crops that do better in the drought conditions.
The two-year study looked at past climate data and the impact on the state’s water, forests and agriculture.
MSU Professor Cathy Whitlock said Wednesday the assessment is meant to help Montanans plan and make better decisions. The authors plan to travel the state over the next year to discuss the findings. | <urn:uuid:bba45a39-6877-4a8a-90dd-96620b7040ed> | 2.671875 | 162 | News Article | Science & Tech. | 30.066273 | 95,527,156 |
Modeled streamflow response under cloud seeding in the North Platte River watershed
Severe and more persistent droughts in the arid regions such as the western US have increased the interest in cloud seeding programs or weather modification (WM) operations to increase precipitation. An anticipated increase in precipitation could augment annual and seasonal streamflow and reduce the impacts during dry periods. This paper evaluates hydrological impacts of WM operations in the North Platte River watershed, by utilizing a hydrologic model. The Variable Infiltration Capacity (VIC) land surface hydrological model is calibrated and validated for the periods of 1950–80 and 1981–2000 respectively, using daily meteorological forcing and monthly streamflow data. Two sets of WM scenarios are developed and forced into the VIC model to quantify the impacts of increased precipitation on streamflow. The first scenario is based on existing WM operations in the State of Wyoming. The second scenario hypothetically apply WM throughout the watershed to identify suitable regions for cloud seeding operations. For the first scenario, an increase of 0.3–1.5% in annual streamflow is observed from model simulations for a 1–5% increase in precipitation. Follow-on scenarios have identified the central-west and south-west regions of the watershed, which consist of a higher coverage of Evergreen Needleleaf Forest, to generate higher streamflow during WM operations. The north-east and north-west regions, which consist of a higher coverage of open shrublands and grasslands, are found to generate lower increases in streamflow during these operations. The observed annual precipitation is higher for central and southern regions when compared to northern regions of the watershed. It can be considered that the simulated changes in streamflow from different regions could also be attributed to variation in annual precipitation distribution within the watershed rather than solely based on cloud seeding operations. For the proposed WM programs or programs that are claimed effective based on precipitation augmentation, the hydrological impacts can be evaluated based on this analysis.
Hydrologic model; Precipitation; Precipitation (Meteorology)—Modification; Rain-making; Streamflow; United States – North Plate River Watershed; Weather control; Weather modification
Environmental Sciences | Hydrology | Meteorology | Oceanography and Atmospheric Sciences and Meteorology | Water Resource Management
Use Find in Your Library, contact the author, or use interlibrary loan to garner a copy of the article. Publisher copyright policy allows author to archive post-print (author’s final manuscript). When post-print is available or publisher policy changes, the article will be deposited
Anil Acharya, Thomas C. Piechota, Haroon Stephen, Glenn Tootle Modeled streamflow response under cloud seeding in the North Platte River watershed Journal of Hydrology, Volume 409, Issues 1–2, 28 October 2011, Pages 305–314 http://dx.doi.org/10.1016/j.jhydrol.2011.08.027
Piechota, T. C.,
Tootle, G. A.
Modeled streamflow response under cloud seeding in the North Platte River watershed.
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in chemistry, a substance that cannot be decomposed into simpler substances by chemical means. A substance such as a compound can be decomposed into its constituent elements by means of a chemical reaction, but no further simplification can be achieved. An element can, however, be decomposed into simpler substances, such as protons and neutrons or various combinations of them, by the methods of particle physics, e.g., by bombardment of the nucleus.
The smallest unit of a chemical element that has the properties of that element is called an atom. Many elements (e.g., helium) occur as single atoms. Other elements occur as molecules made up of more than one atom. Elements that ordinarily occur as diatomic molecules include hydrogen, nitrogen, oxygen, and the halogens, but oxygen also occurs as a triatomic form called ozone. Phosphorus usually occurs as a tetratomic molecule, and crystalline sulfur occurs as molecules containing eight atoms.
Regardless of how many atoms the element is composed of, each atom has the same number of protons in its nucleus, and this is different from the number in the nucleus of any other element. Thus this number, called the atomic number (at. no.), defines the element. For example, the element carbon consists of atoms all with at. no. 6, i.e., all having 6 protons in the nucleus; any atom with at. no. 6 is a carbon atom. By 2006, 117 elements were known, ranging from hydrogen with an at. no. of 1 to an as yet unnamed element (temporarily known as ununoctium) with an at. no. of 118. (See the table entitled Elements for an alphabetical list of all the elements, including their symbols, atomic numbers, atomic weights, and melting and boiling points.) The nuclei of most atoms also contain neutrons. The total number of protons and neutrons in the nucleus of an atom is called the mass number. For example, the mass number of a carbon atom with 6 protons and 6 neutrons in its nucleus is 12.
Although all atoms of an element have the same number of protons in their nuclei, they may not all have the same number of neutrons. Atoms of an element with the same mass number make up an isotope of the element. All known elements have isotopes; some have more than others. Hydrogen, for example, has only 3 isotopes, while xenon has 16. Approximately 300 naturally occurring isotopes are known, and more than 2,500 radioactive isotopes have been artificially produced (see synthetic elements). There are 13 isotopes of carbon, having from 2 to 14 neutrons in the nucleus and therefore mass numbers from 8 to 20.
Not all of the elements have stable isotopes. Some have only radioactive isotopes, which decay to form other isotopes, usually of other elements (see radioactivity). In some cases all the isotopes of an element are very unstable, and the element is therefore not found in nature. Only 94 of the elements are known to occur naturally on earth. Of these, 6 occur in minute amounts produced by the decay of other elements. These 6 extremely scarce elements and those that do not occur at all naturally were discovered when they were produced in the laboratory; they are often called the man-made, artificially produced, or synthetic elements.
Atoms are not very massive; a carbon atom weighs about 2 × 10-23 grams. Because atoms have so little mass, a unit much smaller than the gram is used. In the current system (adopted in 1960–61) the unit of atomic mass, called atomic mass unit (amu), is defined as exactly 1/12 the mass of an atom of carbon-12. The atomic weight of an element is the mean (weighted average) of the atomic masses of all the naturally occurring isotopes. Carbon has two principal naturally occurring isotopes, carbon-12 and carbon-13. Carbon-12, whose mass is defined as exactly 12 amu, constitutes 98.89% of naturally occurring carbon; carbon-13, whose mass is 13.00335 amu, constitutes 1.11%. (There are also small traces of the radioactive isotope carbon-14.) The atomic weight of the element is determined by multiplying the percent abundance of each isotope by the atomic mass of the isotope, adding these products, and dividing by 100. However, isotope abundance is often determined by the medium of the source, solid, liquid, or gas, and the average atomic weight may fluctuate. Thus, for carbon, [(98.89 × 12.000) + (1.11 × 13.00335)]/100 = 12.01115, which is the atomic weight of the element carbon in amu, but because the proportions of the isotopes vary depending on where the carbon is found, carbon's atomic weight is now expressed as an interval defined by the lower and upper bounds within which the atomic weight ranges: [12.0096; 12.0116]. Certain synthetic elements exist only momentarily in the form of a few short-lived isotopes; in such cases the concept of atomic weight cannot be applied.
Properties of an element are sometimes classed as either chemical or physical. Chemical properties are usually observed in the course of a chemical reaction, while physical properties are observed by examining a sample of the pure element. The chemical properties of an element are due to the distribution of electrons around the atom's nucleus, particularly the outer, or valence, electrons; it is these electrons that are involved in chemical reactions. A chemical reaction does not affect the atomic nucleus; the atomic number therefore remains unchanged in a chemical reaction.
Some properties of an element can be observed only in a collection of atoms or molecules of the element. These properties include color, density, melting point, boiling point, and thermal and electrical conductivity. While some of these properties are due chiefly to the electronic structure of the element, others are more closely related to properties of the nucleus, e.g., mass number.
The elements are sometimes grouped according to their properties. One major classification of the elements is as metals, nonmetals, and metalloids. Elements with very similar chemical properties are often referred to as families; some families of elements include the halogens, the inert gases, and the alkali metals. In the periodic table the elements are arranged in order of increasing atomic weight in such a way that the elements in any column have similar properties.
Each element is assigned an official symbol by the International Union of Pure and Applied Chemistry (IUPAC). For example, the symbol for carbon is C, and the symbol for silver is Ag [Lat. argentum = silver]. There are several ways of designating an isotope. One designation consists of the name or symbol of the element followed by a hyphen and the mass number of the isotope; thus the isotope of carbon with mass number 12 can be designated carbon-12 or C-12. The mass number is often written as a superscript, e.g., C12; sometimes the atomic number is written as a subscript preceding the symbol, e.g., 6C12. The IUPAC rules for nomenclature of inorganic chemistry state that the subscript atomic number and superscript mass number should both precede the symbol, e.g., .
Many isotopes were given special names and symbols when they were first discovered in natural radioactive decay series (e.g., uranium-235 was called actinouranium and represented by the symbol AcU). This practice is discouraged in the modern nomenclature except in the case of hydrogen. The isotopes hydrogen-2 and hydrogen-3 are usually called deuterium and tritium, respectively. Hydrogen-1, the most abundant isotope, has the name protium but is usually simply called hydrogen. Newly discovered elements that have been synthesized by one laboratory and not yet confirmed by a second are given a provisional name based on Greek and Latin roots; when the discovery is confirmed, the laboratory that first made it may suggest a name for the element.
Some elements have been known since antiquity. Gold ornaments from the Neolithic period have been discovered. Gold, iron, copper, lead, silver, and tin were used in Egypt and Mesopotamia before 3000 B.C. However, recognition of these metals as chemical elements did not occur until modern times.
The Greek philosophers proposed that there are basic substances from which all things are made. Empedocles proposed four basic "roots," earth, air, fire, and water, and two forces, harmony and discord, joining and separating them. Plato called the roots stoicheia (elements). He thought that they assume geometric forms and are made up of some more basic but undefined matter. A different theory, that of Leucippus and his followers, held that all matter is made up of tiny indivisible particles (atomos).
This theory was rejected by Aristotle, who expanded on Plato's theory. Aristotle believed that different forms (eidos) were assumed by a basic material, which he called hulé. The hulé had four basic properties, hotness, coldness, dryness, and moistness. The four elements differ in their embodiment of these properties; fire is hot and dry, earth cold and dry, water cold and moist, and air hot and moist. Although Aristotle proposed that an element is "one of those simple bodies into which other bodies can be decomposed and which itself is not capable of being divided into others," he thought the metals to be made of water, and called mercury "silver water" (chutos arguros). His idea that matter was a single basic substance that assumed different forms led to attempts by the alchemists to transmute other metals into gold.
Although much early work was done in chemistry, especially with metals, and many recipes were recorded, there were few developments in the conception of the elements. In the 16th cent. Paracelsus proposed salt, mercury, and sulfur as three "principles" of which bodies were made, although he apparently also believed in the four "elements." Van Helmont (c.1600) rejected the four elements and three principles, substituting two elements, air and water.
Robert Boyle rejected these early theories and proposed a definition of chemical elements that led to the currently accepted definition. His definition is strikingly similar to Aristotle's earlier definition. In The Sceptical Chymist (1661) Boyle wrote, "I now mean by elements … certain primitive and simple, or perfectly unmingled bodies; which not being made of any other bodies, or of one another, are the ingredients of which all those called perfectly mixed bodies [chemical compounds] are immediately compounded, and into which they are ultimately resolved."
Whereas Aristotle and other early philosophers tried to determine the identity of the elements solely by reason, Boyle and later scientists used the results of numerous experiments to identify the elements. In 1789 Antoine Lavoisier published a list of chemical elements based on Boyle's definition; this encouraged adoption of standard names for the elements. Although some of his elements are now known to be compounds, such as metallic oxides and salts, they were at the time accepted as elements since they could not be decomposed by any method then known.
In 1803 John Dalton proposed (as part of his atomic theory) that all atoms of an element have identical properties (including mass), that these atoms are unchanged by chemical action, and that atoms of different elements react with one another in simple proportions. Although symbols for some of the elements already existed, they were by no means universally accepted, and each compound also had a unique symbol that was unrelated to its chemical composition. Dalton devised a new set of circular symbols for the elements and used a combination of elemental symbols to represent a compound. For example, his symbol for oxygen was ◯, and for hydrogen ⨀. Since he thought water contained one atom of hydrogen for every atom of oxygen, he formed the symbol for water by writing the symbols for hydrogen and oxygen touching one another,⨀◯. J. J. Berzelius was the first to use the modern method, letting one or two letters of the element's name serve as its symbol. He also published an early table of atomic weights of 24 elements with most values very close to those now in use.
As noted above, some of the elements were discovered in prehistoric times but were not recognized as elements. Arsenic was discovered around 1250 by Albertus Magnus, and phosphorus was discovered about 1674 by Hennig Brand, an alchemist, who prepared it by distilling human urine. Only 12 elements were known before 1700, and only about twice that many by 1800, but by 1900 over 80 elements had been identified. In 1919 Ernest Rutherford found that hydrogen was given off when nitrogen was bombarded with alpha particles. This first transmutation encouraged further study of nuclear reactions, and eventually led to the discovery in 1937 of technetium, the first synthetic element. Neptunium (atomic number 93) was the first transuranium element to be synthesized (1940). Its discovery prompted the search that has led to the ongoing synthesis of additional transuranium elements.
- See The Elements (1991). ,
- A Guide to the Elements (1996). ,
- The Periodic Kingdom (1997). ,
- N. N. Greenwood and A. Earnshaw, Chemistry of the Elements (2d ed. 1997).
From the Latin elementum, which meant “first principle,” “rudiment.” In philosophy, element can be used with at least four meanings: The...
Substance that cannot be broken down into simpler substances by chemical means. An element is composed solely of ATOMS with identical atomic...
Substance that cannot be split into simpler substances by chemical means. All atoms of a given element have the same atomic number (at.no.)... | <urn:uuid:3697705d-cbd0-448b-912d-1efe01672c92> | 3.78125 | 2,885 | Knowledge Article | Science & Tech. | 42.209721 | 95,527,175 |
Using a combination of techniques, including phylogenetics, molecular biology, and video microscopy, the scientists show that a novel essential gene in fruit flies, born via the process of gene duplication, is only 15 million years old and yet has acquired, in a stepwise fashion, a new job so important that the flies can't live without it. The study is published in the June 6 edition of Science.
This is imagery of cells dividing, recorded from video microscopy. The image on the left depicts normal cell division in a fruit fly cell. The cell on the right has had the Umbrea gene removed, and has failed to divide normally, resulting in cell death.
Credit: Photos courtesy Barbara Mellone
"The majority of these genes are not going to acquire essential functions" of genes that, like the one they studied, have been duplicated, says Barbara Mellone, assistant professor of molecular and cell biology in UConn's College of Liberal Arts and Sciences. "But the interaction network is completely rewired for this gene."
Mellone and her colleagues at the University of Washington, the Fred Hutchinson Cancer Research Center in Seattle, and the University of Munich traced the evolutionary steps by which a gene from the well-known fruit fly Drosophila melanogaster, known as Umbrea, acquired its essential role. The gene is vital to chromosome segregation, the process of splitting genetic material when cells divide to generate more cells, tissues, and organisms.
To understand this paradox, the researchers used gene sequencing to understand the gene's history and captured video of cells with Umbrea removed dividing under a microscope in Mellone's laboratory. Their methods showed that after its birth, Umbrea was lost in some of the species, but in one species, Drosophila melanogaster, cells without it failed to segregate chromosomes correctly, confirming its critical role.
But their results also showed that several stepwise changes led to Umbrea's current-day time in the limelight: it lost its previous, nonessential function; the network of proteins it interacts with was completely rewired, and it acquired new, "tail" domains on the ends of its sequence that allowed it to relocate to the centromere, a structure present on all chromosomes in all species, necessary for genome segregation during cell division.
"This gene emerged and wasn't going either way, toward or away from essential function," says Mellone. "Then something happened elsewhere to help make it essential."
The researchers argue that although most duplicated genes either become non-functional or are simply lost, keeping some of them around might benefit cells in the long run.
"Centromere proteins experience rapid evolution in many organisms, including humans, in a constant 'arms race' that exists to maintain the equal segregation of genetic traits," says Mellone.
So if the genes involved in genome partitioning are evolving so fast, then perhaps it's a good idea to keep other, nonfunctional genes around – those that can acquire new essential functions when necessary.
The scientists suggest that this could change the way scientists think about other biological processes that may require recurrent genetic innovation to adapt to new challenges.
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The low-cost process, developed by Purdue University researchers, combines tools already used in industry for manufacturing metals on a large scale, but uses...
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.
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Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.
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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.
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Cavity optomechanics is a branch of physics which focuses on the interaction between light and mechanical objects on low-energy scales. It is a cross field of optics, quantum optics, solid-state physics and materials science. The motivation for research on cavity optomechanics comes from fundamental effects of quantum theory and gravity, as well as technological applications.
The name of the field relates to the main effect of interest, which is the enhancement of radiation pressure interaction between light (photons) and matter using optical resonators (cavities). It first became relevant in the context of gravitational wave detection, since optomechanical effects have to be taken into account in interferometric gravitational wave detectors. Furthermore, one may envision optomechanical structures to allow the realization of Schrödinger's cat. Macroscopic objects consisting of billions of atoms share collective degrees of freedom which may behave quantum mechanically, e.g. a sphere of micrometer diameter being in a spatial superposition between two different places. Such a quantum state of motion would allow to experimentally investigate decoherence, which describes the process of objects transitioning between states which are described by quantum mechanics to states which are described by Newtonian mechanics. Optomechanical structures pave a new way for testing the predictions of quantum mechanics and decoherence models and thereby might allow to answer some of the most fundamental questions in modern physics.
There is a broad range of experimental optomechanical systems which are almost equivalent in their description, but completely different in size, mass and frequency, ranging from attograms and gigahertz to kilograms and hertz. Cavity optomechanics was featured as the most recent milestone of photon history in nature photonics along well established concepts and technology like Quantum information, Bell inequalities and the laser.
- 1 Concepts of cavity optomechanics
- 2 Experimental realizations
- 3 Relation to fundamental research
- 4 Applications
- 5 Related fields and expansions
- 6 See also
- 7 References
Concepts of cavity optomechanics
The most elementary light-matter interaction is the light beam scattering off an arbitrary object (atom, molecule, nanobeam etc.). There is always elastic light scattering, with the outgoing light frequency identical to the incoming frequency . Inelastic scattering, in contrast, will be accompanied by excitation or de-excitation of the material object (e.g. internal atomic transitions may be excited). However, independent of the internal electronic details of the atoms or molecules, it is always possible to have Raman scattering due to the object's mechanical vibrations:
where is the vibrational frequency. The vibrations gain or lose energy, respectively, for these Stokes/anti-Stokes processes, while optical sidebands are created around the incoming light frequency, i.e.
If both of these processes (Stokes and anti-Stokes scattering) occur at an equal rate, the vibrations will merely heat up the object. However, one may use an optical cavity to suppress e.g. the Stokes process. This reveals the principle of the basic optomechanical setup: A laser-driven optical cavity is coupled to the mechanical vibrations of some object. This is a very generic setting. The purpose of the cavity is to select optical frequencies (e.g. to suppress the Stokes process), to resonantly enhance the light intensity and to enhance the sensitivity to the mechanical vibrations. This setup displays features of a true two-way interaction between light and mechanics. This is in contrast to optical tweezers, optical lattices, or vibrational spectroscopy, where the light field controls the mechanics (or vice versa) but the loop is not closed.
Another but equivalent way to interpret the principle of optomechanical cavities is by using the concept of radiation pressure. According to the quantum theory of light, every photon with wave number carries a momentum with Planck's constant . This means that a photon, which is reflected off a mirror surface, transfers a momentum onto the mirror due to the conservation of momentum. This effect is extremely small and can not be observed on most every-day objects, however it becomes more significant when the mass of the mirror is very small and/or the number of photons is very large (i.e. high intensity of the light). Since the momentum of photons is extremely small and not enough to change the position of a suspended mirror significantly, one needs to enhance the interaction. One possible way to do this is by using optical cavities. If a photon is enclosed between two mirrors, one being the oscillator and the other a heavy fixed one, it will bounce off the mirrors many times and transfer its momentum every time it hits the mirrors. The number of times a photon can transfer its momentum is directly related to the finesse of the cavity, which can be improved with highly reflective mirror surfaces. To understand why this radiation pressure of the photons does not simply shift the suspended mirror further and further away, one has to take into account the effect on the cavity light field: If the mirror is displaced, the cavity becomes longer (or shorter) which changes the cavity resonance frequency. Thus the detuning between the changed cavity and the unchanged laser driving frequency is modified. This detuning determines the light amplitude inside the cavity - at smaller detuning more light actually enters the cavity, because it is closer to the cavity resonance frequency. Since the light amplitude, i.e. the number of photons inside the cavity, causes the radiation pressure force and thus the displacement of the mirror we have closed the loop: The radiation pressure force effectively depends on the mirror position. Another advantage of optical cavities is that the modulation of the cavity length through an oscillating mirror can directly be seen in the spectrum of the cavity.
Some first effects of the light on the mechanical resonator can be captured by converting the radiation pressure force into a potential,
and adding it to the intrinsic harmonic oscillator potential of the mechanical oscillator. This combined potential reveals the possibility of static multi-stability in the system, i.e. the potential can feature several stable minima. In addition, the slope of the radiation pressure force can be understood as a modification of the mechanical spring constant,
This effect is known as optical spring effect (light-induced spring constant).
However, this picture is not complete, as it neglects retardation effects due to the finite cavity photon decay rate . The force follows the motion of the mirror only with some time delay. This leads to effects such as friction. For example, let us assume the equilibrium position sit somewhere on the rising slope of the resonance. In thermal equilibrium, there will be oscillations around this position, which do not follow the shape of the resonance because of retardation. The consequence of this delayed radiation force during one cycle of oscillation turns out to be that work is carried out, in this particular case it is negative,, i.e. the radiation force extracts mechanical energy (there is extra, light-induced damping). This can be used to cool down the mechanical motion and is referred to as optical or optomechanical cooling. It is important for reaching the quantum regime of the mechanical oscillator where thermal noise effects on the device become negligible. Similarly, if the equilibrium position sits on the falling slope of the cavity resonance, the work is positive and the mechanical motion is amplified. In this case the extra, light-induced damping is negative and leads to amplification of the mechanical motion (heating). Radiation-induced damping of this kind has first been observed in pioneering experiments by Braginsky and coworkers in 1970.
Another explanation for the basic optomechanical effects of cooling and amplification can be given in a quantized picture. By detuning the incoming light from the cavity resonance to the red sideband, the photons can only enter the cavity if they take phonons with energy from the mechanics. This effectively cools the device until a balance with heating mechanisms from the environment and laser noise is reached. In the same fashion it is also possible to heat structures (amplify the mechanical motion) by detuning the driving laser to the blue side. In this case the laser photons scatter into a cavity photon and create an additional phonon in the mechanical oscillator.
In general, one can divide the basic behaviour of the optomechanical system into different regimes, depending on the detuning between the laser frequency and the cavity resonance frequency,
- Red-detuned regime (most prominent effects on the red sideband ): In this regime state exchange between two resonant oscillators can occur (i.e. a beam-splitter in quantum optics language). This can be used for state transfer between phonons and photons (which requires the so-called ”strong coupling regime”) or the above-mentioned optical cooling.
- Blue-detuned regime (most prominent effects on the blue sideband ): This regime describes "two-mode squeezing". It can be used to achieve entanglement, squeezing, and mechanical "lasing" (amplification of the mechanical motion to self-sustained optomechanical oscillations / limit cycle oscillations), if the growth of the mechanical energy overwhelms the intrinsic losses (mainly mechanical friction).
- On-resonance regime : In this regime the cavity is simply operated as an interferometer, so it can be used to read out the mechanical motion.
Also the optical spring effect depends on the detuning. It can be observed for large detuning and its strength varies with detuning and the laser drive.
The standard optomechanical setup is a Fabry–Pérot cavity, where one mirror is movable and thus provides an additional mechanical degree of freedom. Mathematically this system can be described by a single optical cavity mode coupled to a single mechanical mode. The coupling originates from the radiation pressure of the light field, that eventually moves the mirror a little bit, thus changing the cavity length and resonance frequency. The optical mode is driven by an external laser. This system can be described by the following effective Hamiltonian
where and are the bosonic annihilation operators of the given cavity mode and the mechanical resonator respectively, satisfying the commutation relations
is the frequency of the optical mode, now dependant on the position of the mechanical resonator, whereas is the mechanical mode frequency. The last term describes the driving, with the driving laser frequency and the amplitude, given by
with the input power coupled to the optical mode under consideration and its linewidth. Of course, the system is coupled to the environment so the full treatment of the system should also include optical and mechanical dissipation (denoted by and respectively) and the corresponding noise entering the system.
The standard optomechanical Hamiltonian is obtained by getting rid of the explicit time dependence of the laser driving term and separating the optomechanical interaction from the free optical oscillator. This is achieved by switching into a reference frame rotating at the laser frequency (in which case the optical mode annihilation operator undergoes the transformation ) and applying a Taylor expansion on . Quadratic and higher order coupling terms are usually neglected, such that the standard Hamiltonian becomes
with the laser detuning and the position operator . The first two terms are the free optical and mechanical Hamiltonian respectively. The third term contains the optomechanical interaction, with the single-photon optomechanical coupling strength (sometimes also called the bare optomechanical coupling). It determines by how much the cavity resonance frequency is shifted if the mechanical oscillator is displaced by the zero point uncertainty . Here, is the effective mass of the mechanical oscillator. Sometimes, it is more convenient to use instead, which determines the frequency change per displacement of the mirror, also called frequency pull parameter.
E.g., for a Fabry–Pérot cavity of length with a moving end-mirror the optomechanical coupling strength can directly be determined from the geometry to be .
This mathematical description using is based on the assumption that only one optical and mechanical mode interact. Each optical cavity supports in principle an infinite number of modes and mechanical oscillators have more than a single oscillation/vibration mode. The validity of this approach relies on the possibility to tune the laser in such a way, that it populates a single optical mode only (that implies that the spacing between the cavity modes needs to be sufficiently large). Furthermore, scattering of photons to other modes is supposed to be negligible, which holds if the mechanical (motional) sidebands of the driven mode do not overlap with other cavity modes, i.e. if the mechanical mode frequency is smaller than the typical separation of the optical modes.
Usually, the single-photon optomechanical coupling strength is a small frequency, much smaller than the cavity decay rate , but the effective optomechanical coupling can be enhanced by increasing the drive power. Namely, with a strong enough drive, the dynamics of the system can be considered as quantum fluctuations around a classical steady state, i.e. , where is the mean light field amplitude and denotes the fluctuations. Expanding the photon number , we can omit the term as it leads to a constant radiation pressure force which simply shifts the resonator's equilibrium position. Also neglecting the second order term , we obtain the linearized optomechanical Hamiltonian,
where . This Hamiltonian is quadratic in operators, but it is called linearized, because it leads to linear equations of motion. It is a valid description of many experiments, where is typically very small and needs to be enhanced by the driving laser. Again, for a realistic description dissipation should be added to both the optical and the mechanical oscillator. The driving term from the standard Hamiltonian is not part of the linearized Hamiltonian, since it is the source of the classical light amplitude around which the linearization was executed.
With a particular choice of detuning, different phenomena can be observed (see also the section about physical processes). The clearest distinction can be made between the following three cases:
: In this case a rotating wave approximation of the linearized Hamiltonian, where one omits all non-resonant terms, reduces the coupling Hamiltonian to a beamsplitter operator, . This approximation works best on resonance, i.e. if the detuning becomes exactly equal to the negative mechanical frequency. Negative detuning (red detuning of the laser from the cavity resonance) by an amount equal to the mechanical mode frequency favors the anti-Stokes sideband, leading to a net cooling of the resonator. Laser photons absorb energy from the mechanical oscillator by annihilating phonons in order to become resonant with the cavity.
: In this case a rotating wave approximation of the linearized Hamiltonian leads to other resonant terms. The coupling Hamiltonian takes the form , which is proportional to the two-mode squeezing operator. Therefore, two-mode squeezing and entanglement between the mechanical and optical modes can be observed with this parameter choice. Positive detuning (blue detuning of the laser from the cavity resonance) can also lead to instability. In the mechanical sideband picture, this corresponds to enhancing the Stokes sideband, i.e. the laser photons shed energy, increasing the number of phonons and becoming resonant with the cavity in the process.
: In this case of driving on-resonance, one has to consider all terms in . The optical mode experiences a shift proportional to the mechanical displacement, which translates into a phase shift of the light transmitted through (or reflected off) the cavity. Thus, the cavity serves as an interferometer augmented by the factor of the optical finesse and can be used to measure very small displacements. (In fact, this setup has recently enabled LIGO to detect gravitational waves.)
Equations of motion
From the linearized Hamiltonian one can, adding dissipation and noise terms to the Heisenberg equations of motion, derive the so-called linearized quantum Langevin equations, which govern the dynamics of the optomechanical system.
Here and are the input noise operators (either quantum or thermal noise) and and are the corresponding dissipative terms. Note that for optical photons, thermal noise can be neglected due to the high frequencies, such that the optical input noise can be described by quantum noise only (this does not hold for microwave implementations of the optomechanical system). For the mechanical oscillator thermal noise has to be taken into account and is the reason why many experiments are placed in additional cooling environments to lower the ambient temperature.
Two main effects of the light on the mechanical oscillator can then be expressed in the following way:
The former is termed the optical-spring effect and may lead to significant frequency shifts in the case of low-frequency oscillators, such as pendulum mirrors. In the case of higher resonance frequencies, MHz, it does not significantly alter the frequency. For a harmonic oscillator, the relation between a frequency shift and a change in the spring constant originates from Hooke's law.
The latter equation shows optical damping, i.e. the intrinsic mechanical damping becomes stronger (or weaker) due to the optomechanical interaction. From the formula one can see that for negative detuning and large coupling, the mechanical damping can be greatly increased, which corresponds to cooling of the mechanical oscillator. In the case of positive detuning the optomechanical interaction leads to a negative contribution to the effective damping. This can lead to instability, when the effective damping drops below zero, , which means that it turns into an overall amplification rather than a damping of the mechanical oscillator.
Important parameter regimes
The most basic regimes in which the optomechanical system can be operated are defined by the laser detuning and described above. The resulting phenomenas are basically either cooling or heating of the mechanical oscillator. However, additional parameters determine what effects can actually be observed.
The good/bad cavity regime (also called the resolved/unresolved sideband regime) relates the mechanical frequency to the optical linewidth: The good cavity regime (resolved sideband limit) is of experimental relevance since it is a necessary requirement to achieve ground-state cooling of the mechanical oscillator, i.e. cooling to an average mechanical occupation number below . The name "resolved sideband regime" refers to the possibility to distinguish the motional sidebands from the cavity resonance, which is the case if the linewidth of the cavity, is smaller than the distance from the cavity resonance to the sideband, which is . This requirement leads to a condition for the so-called sideband parameter: . If the system resides in the bad cavity regime (unresolved sideband limit). Here, the motional sideband lies within the peak of the cavity resonance. Actually, deep in the unresolved sideband regime, many motional sidebands can be included in the broad cavity linewidth, thus e.g. allowing a single photon to create more than one phonon, which leads to larger amplification of the mechanical oscillator.
Another distinction can be made depending on the optomechanical coupling strength. If the (enhanced) optomechanical coupling becomes larger than the cavity linewidth, one enters the so-called strong-coupling regime. There the optical and mechanical modes hybridize and normal-mode splitting occurs. This regime has to be distinguished from the (experimentally much more challenging) single-photon strong-coupling regime, where the bare optomechanical coupling becomes of the order of the cavity linewidth, . Only in this regime, effects of the full non-linear interaction described by become observable. For example, it is a precondition to create non-Gaussian states with the optomechanical system. Typical experiments currently operate in the linearized regime (small ) thus investigating only effects of the linearized Hamiltonian.
The strength of the optomechanical Hamiltonian is the large range of experimental implementations to which it can be applied. This results in wide parameter ranges for the optomechanical parameters. For example, the size of optomechanical systems can be micrometers but also of the order of kilometers as it is the case for LIGO (although LIGO is dedicated to the detection of gravitational waves and not the investigation of optomechanics specifically).
Examples of real optomechanical implementations are:
- Cavities with a moving mirror: This is the archetype of an optomechanical system. The light is reflected from the mirrors, transferring momentum onto the movable one, which in turn changes the cavity resonance frequency.
- Membrane-in-the-middle system: A membrane is brought into a cavity consisting of fixed massive mirrors. The membrane takes now the role of the mechanical oscillator. Depending on the positioning of the membrane inside the cavity this system behaves like the typical optomechanical system.
- Microtoroids that support an optical whispering gallery mode can be either coupled to a mechanical mode of the toroid or evanescently to a nanobeam that is brought in proximity.
- Optomechanical crystal structures: Patterned dielectrics can confine both optical and mechanical (acoustic) modes in the same area, which leads to an optomechanical interaction.
- Electromechanical implementations of an optomechanical system use superconducting LC circuits with a mechanically compliant capacitance using e.g. a micromechanical membrane. Here the role of the optical light is replaced by microwaves. Physics is exactly the same as in optical cavities but the range of parameters is different.
One purpose of studying so many different designs of the same system is the different parameter regimes that are accessible by different setups and their different potential to be converted into tools of commercial use.
The optomechanical system can be measured using e.g. a homodyne detection scheme. Either the light of the driving laser is measured, or a two-mode scheme is followed where a strong laser is used to drive the optomechanical system into the state of interest and a second laser is used for the read-out of the state of the system. This second “probe” laser is typically weak, i.e. its optomechanical interaction can be neglected as compared to the effects caused by the strong “pump” laser.
The optical output field can also be measured with single photon detectors e.g. to achieve photon counting statistics.
Relation to fundamental research
One of the questions which are still subject to current debate is the exact mechanism of decoherence. As Schrödinger pointed out, we would never see something like a cat in a quantum state. There needs to be something like a collapse of the quantum wave functions, which brings it from a quantum state to a pure classical state. Now one can ask where the boundary lies between objects with quantum properties and classical objects. Taking spatial superpositions as an example, there might be a size limit to objects which can be brought into superpositions, there might be a limit to the spatial separation of the centers of mass of a superposition or even a limit to the superposition of gravitational fields and its impact on small test masses. Those predictions could be checked with large mechanical structures which can be manipulated at the quantum level.
Some easier to check predictions of quantum mechanics are the prediction of negative Wigner functions for certain quantum states, measurement precision beyond the standard quantum limit using squeezed states of light or the asymmetry of the sidebands in the spectrum of a cavity near the quantum ground state.
Years before cavity optomechanics gained the status of an independent field of research, many of its techniques were already used in Gravitational wave detectors where it is necessary to measure displacements of mirrors on the order of the Planck scale. Even if these detectors do not address the measurement of quantum effects, they encounter related issues (photon shot noise) and use similar tricks (squeezed coherent states) to enhance the precision. Further applications include the development of quantum memory for quantum computers, high precision sensors (e.g. acceleration sensors) and quantum transducers e.g. between the optical and the microwave domain (taking advantage of the fact that the mechanical oscillator can easily couple to both frequency regimes).
Related fields and expansions
In addition to the above explained standard cavity optomechanics there exist variations of this simplest model:
- pulsed optomechanics: The continuous laser driving is replaced by a pulsed driving scheme. This has, for example, advantages when creating entanglement and allows backaction-evading measurements.
- quadratic coupling: Going beyond the linear coupling term a system with quadratic optomechanical coupling can be investigated. The interaction Hamiltonian would then feature a term with . In membrane-in-the-middle setups it is possible to achieve quadratic coupling in the absence of linear coupling by positioning the membrane at an extremum of the standing wave inside the cavity. One possible application is to carry out a quantum nondemolition measurement of the phonon number.
- reversed dissipation regime: In the standard optomechanical system the mechanical damping is much smaller than the optical damping. However, one can engineer a system where this hierarchy is reversed, i.e. the optical damping is much smaller than the mechanical damping, . As long as one resides within in the linearized regime symmetry implies an inversion of the above described effects: E.g. cooling of the mechanical oscillator in the standard optomechanical system is replaced by cooling of the optical oscillator in a system with reversed dissipation hierarchy. This effect was also seen in optical fiber loops in the 1970s.
- dissipative coupling: Here the coupling between optics and mechanics arises from a position-dependent optical dissipation rate (instead of a position-dependent cavity resonance frequency ). This changes the interaction Hamiltonian and alters many effects of the standard optomechanical system. E.g. this scheme allows to cool the mechanical resonator to its ground state without the requirement of the good cavity regime.
Extensions to the standard optomechanical system include coupling to more and physically different systems:
- optomechanical arrays: Coupling several optomechanical systems to each other (e.g. using evanescent coupling of the optical modes) one can study multi-mode phenomena (e.g. synchronization,…). So far many theoretical predictions have been made, but only few experiments exist. The first optomechanical array (with more than two coupled systems) consists of 7 optomechanical systems.
- hybrid systems: An optomechanical system can be coupled to a system of different nature (e.g. a cloud of ultracold atoms, a two-level system,…). This can lead to new effects on both the optomechanical and the additional system.
Cavity optomechanics is closely related to trapped ion physics and Bose–Einstein condensates. These systems share very similar Hamiltonians, but they have less particles (about 10 for ion traps and - for BECs) interacting with the field of light. It is also related to the field of cavity quantum electrodynamics.
- Braginskii, V. B., Manukin, A. B., Tikhonov, M. Yu. (1970). Investigation of dissipative pondermotive effects of electromagnetic radiation. Soviet Physics JETP Vol 31, 5 (original russian: Zh. Eksp. Teor. Fiz. 58, 1549 (1970))
- Law, C. (1994). Effective Hamiltonian for the radiation in a cavity with a moving mirror and a time-varying dielectric medium. Physical Review A, 49(1), 433-437. doi:10.1103/PhysRevA.49.433
- Genes, C., Vitali, D., Tombesi, P., Gigan, S., Aspelmeyer, M. (2008) Physical Review A 77, 033804 doi:10.1103/PhysRevA.77.033804
- Corbitt, T. et al., Physical Review Letters 98, 150802 (2007) doi:10.1103/PhysRevLett.98.150802; T. Corbitt et al., ibid. 99,160801 (2007)
- Thompson, J. D., Zwickl, B. M., Jayich, A. M., Marquardt, F., Girvin, S. M., & Harris, J. G. E. (2008). Strong dispersive coupling of a high-finesse cavity to a micromechanical membrane. Nature, 452(7183), 72-5. Nature Publishing Group. doi:10.1038/nature06715
- Verhagen, E., Deléglise, S., Weis, S., Schliesser, A., Kippenbergm T. J. (2012). Nature 482, 63-67 doi:10.1038/nature10787
- Anetsberger, G., Arcizet, O., Unterreithmeier, Q. P., Rivière, R., Schliesser, A., Weig, E. M., Kotthaus, J. P., & Kippenberg, T. J. (2009). Near-field cavity optomechanics with nanomechanical oscillators. Nature Physics, 5(12), 909-914. Nature Publishing Group. doi:10.1038/nphys1425
- Safavi-Naeini, A. H., Alegre, T. P. M., Chan, J., Eichenfield, M., Wigner, M., Lin, Q., Hill, J. T., Chang, D., Painter, O. (2011). Nature, 472, 69 doi:10.1038/nature09933
- Teufel, J. D., Donner, T., Dale Li, Harlow, J. W., Allman, M. S., K. Cicak, K., Sirois, A. J., Whittaker, J. D., Lehnert, K. W. & Simmonds, R. W. (2011). Sideband cooling of micro mechanical motion to the quantum ground state. Nature, 475, 359-363. Nature Publishing Group. doi:10.1038/nature10261
- Bose, S., Jacobs, K., & Knight, P. (1999). Scheme to probe the decoherence of a macroscopic object. Physical Review A, 59(5), 3204-3210. doi:10.1103/PhysRevA.59.3204
- Simon Rips, Martin Kiffner, Ignacio Wilson-Rae, & Michael Hartmann. (2011). Cavity Optomechanics with Nonlinear Mechanical Resonators in the Quantum Regime - OSA Technical Digest (CD). CLEO/Europe and EQEC 2011 Conference Digest (p. JSI2_3). Optical Society of America. Retrieved from http://www.opticsinfobase.org/abstract.cfm?URI=EQEC-2011-JSI2_3
- Jaekel, M. T., & Reynaud, S. (1990). Quantum Limits in Interferometric Measurements. Europhysics Letters (EPL), 13(4), 301-306. doi:10.1209/0295-5075/13/4/003
- Safavi-Naeini, A. H., Chan, J., Hill, J. T., Alegre, T. P. M., Krause, A., & Painter, O. (2011). Measurement of the quantum zero-point motion of a nanomechanical resonator, 6. Retrieved from https://arxiv.org/abs/1108.4680
- Cole, G. D., & Aspelmeyer, M. (2011). Cavity optomechanics: Mechanical memory sees the light. Nature nanotechnology, 6, 690. doi:10.1038/nnano.2011.199
- Krause, A. G., Winger, M., Blasius, T. D., Lin, Q. & Painter, O. A high-resolution microchip optomechanical accelerometer. Nature Photonics (2012). doi:10.1038/nphoton.2012.245
- Bochmann, J., Vainsencher, A., Awschalom, D. D., Cleland, A. N. (2013). Nanomechanical coupling between microwave and optical photons. Nature Physics 9, 712-716 doi:10.1038/nphys2748
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- Thompson, J. D., Zwickl, B. M., Jayich, A. M., Marquardt, F., Girvin, S. M., & Harris, J. G. E. (2008). Strong dispersive coupling of a high-finesse cavity to a micromechanical membrane. Nature, 452(7183), 72-5. Nature Publishing Group. doi:10.1038/nature06715
- Nunnenkamp, A., Sudhir, V, Feofanov, A. K., Roulet, A., Kippenberg, T. J. (2014). Quantum-Limited Amplification and Parametric Instability in the Reversed Dissipation Regime of Cavity Optomechanics Physical Review Letters, 113, 023604. doi:10.1103/PhysRevLett.113.023604
- Elste, F., Girvin,. S. M., Clerk, A. A. (2009). Quantum Noise Interference and Backaction Cooling in Cavity Optomechanics Physical Review Letters, 102, 207209. doi:10.1103/PhysRevLett.102.207209
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- Aspelmeyer, M., Kippenberg, T. J., Marquardt, F. (2014). Cavity Optomechanics. Springer Verlag Berlin Heidelberg doi:10.1007/978-3-642-55312-7
- Aspelmeyer, M., Kippenberg, T. J., Marquardt, F. (2014). Cavity Optomechanics. Reviews of Modern Physics 86, 1391 doi:10.1103/RevModPhys.86.1391
- Michel Deverot, Bejamin Huard, Robert Schoelkopf, Leticia F. Cugliandolo (2014). Quantum Machines: Measurement and Control of Engineered Quantum Systems. Lecture Notes of the Les Houches Summer School: Volume 96, July 2011. Oxford University Press
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- Kippenberg, T. J., & Vahala, K. J. (2007). Cavity Opto-Mechanics. Optics Express, 15(25), 17172. OSA. doi:10.1364/OE.15.017172
- Romero-Isart, O., Pflanzer, A., Blaser, F., Kaltenbaek, R., Kiesel, N., Aspelmeyer, M., & Cirac, J. (2011). Large Quantum Superpositions and Interference of Massive Nanometer-Sized Objects. Physical Review Letters, 107(2). doi:10.1103/PhysRevLett.107.020405
- Demir, Dilek,"A table-top demonstration of radiation pressure", 2011, Diplomathesis, E-Theses univie (http://othes.univie.ac.at/16381/) | <urn:uuid:3860ed6d-a1a9-4d05-8f2f-2ece0ad72226> | 3.109375 | 7,629 | Knowledge Article | Science & Tech. | 39.058708 | 95,527,210 |
The genome sequence shows that C. botulinum doesn’t have subtle tools to evade our human defences or tricky methods of acquiring resistance to antibiotics. It lives either as a dormant spore or as a scavenger of decaying animal materials in the soil, and doesn’t interact with human or other large animal hosts for prolonged periods of time.
Occasionally it gets into a living animal, via contaminated food or open wounds, leading to infant botulism or wound botulism, both of which are serious human infections. The host can be quickly overpowered and, in some cases, killed by the toxin, and C. botulinum has a new food source.
“Although in the same group as Clostridium difficile – the Cdiff superbug – C. botulinum has a genome that is remarkable because it is so stable, “commented Dr Mohammed Sebaihia, lead author on the paper from the Wellcome Trust Sanger Institute. “Unlike Cdiff, in which more than 10% of genes have been acquired from other bacteria, there is almost no footprint of these in C. botulinum.”
There are several types of C. botulinum: although described as variants of a single species, they are really very different organisms linked simply because they have the deadly toxin. For each type, there is also a near-identical but harmless relative that lacks the toxin. C. sporogenes is the non-malignant, near twin of the organism sequenced.
Professor Mike Peck, from the Institute of Food Research, commented that “It is astonishing that 43% of the predicted genes in the C. botulinum genome are absent from the other five sequenced clostridia, and only 16% of the C. botulinum genes are common to all five. Our findings emphasise just how different clostridia are from each other.”
C. botulinum toxin stops nerves from working – the basis of its use in medicine to control tremors and in cosmetic treatments. For the prey of its opportunistic attacks, death is swift. Perhaps the most important tool it has to act out its stealth attacks is its ability to hibernate when times are hard by forming dormant spores.
More than 110 of its set of almost 3700 genes are used to control spore formation and germination when opportunity arises.
“C. botulinum shows us one extreme of the ways that bacteria can make the most of animal hosts,” explained Dr Julian Parkhill of the Wellcome Trust Sanger Institute. “Some organisms use subtle approaches, elegantly choreographing their interaction with us and our defences.
“C. botulinum takes the opposite approach. It lies in wait and, if it gets the opportunity, it hits its host with a microbial sledgehammer. It then eats the remains and lays low until the next host comes along.”
The genome sequence is peppered with genes that produce enzymes to digest proteins and other animal material in the soil. Also found, uniquely in this species, is a range of genes that allow it to attack the many insect and other small creatures that live in the soil. The ‘chitinases’ produced by these genes can degrade the casing of insects and small crustaceans.
It is not only animals that can feel the wrath of C. botulinum, explains Dr Sebaihia: “The soil can be a harsh environment and food can be scarce. To see off the competition, C. botulinum comes with its own ‘antibiotic’ – a chemical called boticin that kills competing bacteria.”
Genome sequences can tell us a lot about the biology of the organism, but research into clostridia has been hampered by the lack of a good genetic system. Professor Nigel Minton, Professor of Applied Molecular Microbiology at the University of Nottingham, has developed new methods to knock out genes in clostridia.
"Even after decades of research, only a handful of mutants had been made in clostridia, and none in C. botulinum," Professor Minton explains. "We have developed a highly efficient system, the ClosTron, with which we have, in a few months, knocked out over 30 genes in four different clostridial species, including eight in C. botulinum. The availability of this tool should revolutionise functional genomic studies in clostridia."
This remarkable, stable genome demonstrates the wide range of strategies used by bacteria to enhance their chances of survival. For the Clostridia, these range from the approach used by C. difficile – long-term interaction with hosts, which involves evading the immune system and countering antibiotics – to the single-minded opportunistic approach of C. botulinum.
Zoe Dunford | alfa
The secret sulfate code that lets the bad Tau in
16.07.2018 | American Society for Biochemistry and Molecular Biology
Colorectal cancer risk factors decrypted
16.07.2018 | Max-Planck-Institut für Stoffwechselforschung
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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16.07.2018 | Physics and Astronomy
16.07.2018 | Transportation and Logistics
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Small-sized predators in the aphidophagous guild of Aphis gossypii Glover colonies on hibiscus trees in Japan exploit aphids at low prey abundance. Scymnus (Pullus) posticalis Sicard beetles were the first predatory species to attack aphids in the spring, and their larvae co-occurred with larvae of Eupeodes freguens (Matsumura) syrphids in aphid-infested leaves of hibiscus for 3 weeks in absence of large-sized coccinellid predators. Larval interaction between Scymnus and syrphid predators was examined in relation to effectiveness of wax cover of Scymnus against predation from syrphids. Waxless first instar larvae were not protected but wax-covered larvae of second, third and fourth instars were protected from predation by syrphid larvae. The protection was lower in the second instar which has a thin wax cover and significantly higher in the third and fourth instars having a thick wax cover. In addition, larvae from which the wax was removed were significantly more vulnerable to predation. Vulnerability of Scymnus larvae to predation from syrphids was directly related to the thickness of wax cover. Results suggest that the wax cover of Scymnus larvae act as an effective defence mechanism against predation from syrphid larvae.
Mendeley saves you time finding and organizing research
Choose a citation style from the tabs below | <urn:uuid:971da7ee-c901-4abd-9d2f-6dd26c54f683> | 3.484375 | 307 | Academic Writing | Science & Tech. | 23.261666 | 95,527,218 |
A class is a blueprint for objects.
You can have one class called Shape, but with it you can create multiple instances of Shape objects.
All of the shape objects have the methods and attributes defined by the Shape class.
An object is an instance of a class.
If Shape is the class, then x = Shape.new creates a new Shape instance and makes x reference that object.
You would then say x is a Shape object, or an object of class Shape.
Here's a simple demonstration of a class with two methods.
class Square def initialize(side_length) @side_length = side_length # w w w . ja v a 2s . co m end def area @side_length * @side_length end end a = Square.new(10) b = Square.new(5) puts a.area puts b.area
The first method in the Square class is initialize.
initialize is a special method that's called when a new object is created.
When you call Square.new(10), the Square class creates a new object instance of itself, and then calls initialize upon that object.
Here, initialize accepts a single argument into side_length as passed by Square.new(10).
And then assigns the number 10 referenced by side_length to a variable called @side_length.
The @ symbol before the variable name marks an attribute. | <urn:uuid:e5641e92-b724-49eb-ad34-c3018942828e> | 3.953125 | 292 | Documentation | Software Dev. | 68.085183 | 95,527,226 |
The physicists, engineers and technicians from the University of Delaware's Bartol Research Institute are part of an international team working to build the world's largest neutrino telescope in the Antarctic ice, far beneath the continent's snow-covered surface.
Dubbed “IceCube,” the telescope will occupy a cubic kilometer of Antarctica when it is completed in 2011, opening super-sensitive new eyes into the heavens.
“IceCube will provide new information about some of the most violent and far-away astrophysical events in the cosmos,” says Thomas Gaisser, the Martin A. Pomerantz Chaired Professor of Physics and Astronomy at the University of Delaware, and one of the project's lead scientists.
The University of Delaware is among 33 institutions worldwide that are contributing to the National Science Foundation project, which is coordinated by the University of Wisconsin.
Besides taking a turn as “on-ice lead” for this year's IceCube construction effort at the South Pole (or simply “Pole,” as the locals call it), Gaisser is managing the University of Delaware's continued deployment of the telescope's surface array of detectors, known as "IceTop."
A huge telescope in the ice
Rather than a giant lens aimed at the heavens, the IceCube telescope consists of kilometer-long strings of 60 optical detectors frozen more than a mile deep in the Antarctic ice like beads on a necklace. Atop each string of deep detectors sits a pair of 600-gallon IceTop tanks, each containing two optical detectors.
Ironically, it takes about seven weeks for the water in the IceTop tanks to freeze perfectly, without bubbles or cracks, which could obstruct the tiny flash that occurs when particles pass through the ice.
Neutrinos are among the most fundamental constituents of matter. Because they have no electrical charge and interact only weakly, these particles can travel millions of miles through space.
Neutrinos can pass right through planets, and they can emerge from deep inside regions of intense radiation such as the accretion disk around a massive black hole.
The surface IceTop detectors measure cascades of particles generated by high-energy cosmic rays showered down from above, while the detectors deep in the ice monitor neutrinos passing up through the planet from below.
When a flash of light is detected, the information is relayed to the nearby IceCube Lab, where the path of the particle can be reconstructed and scientists can trace where it came from, perhaps an exploding star or a black hole.
For Gaisser, this great quest to capture neutrinos is a cosmic journey in more ways than one.
“All of my career at Bartol Research Institute at the University of Delaware has been to study high-energy particles from space,” Gaisser says. “This experiment we're building fulfills all of my dreams. Besides, it's fun to work here,” he notes.
Working in the deep freeze
A drill camp supports each season of the IceCube project in the 24-hour daylight of the Antarctic summer. Drilling is a 24/7 operation with three shifts of drillers.
In the subfreezing temperatures and howling winds, fuel tanks supply generators that make electricity, which is used to heat the water that pulses through the high-pressure hoses that melt the mile-and-a-half-long deep holes into which strings of optical detectors are submerged.
The IceTop team works six days a week from 8 a.m. to 6 p.m., retreating to the warmth of the new Amundsen-Scott South Pole Station, to sleep, eat, and spend what little free time they have reading, watching movies, exercising, or chatting with fellow “Polies.”
Among the new facility's amenities are constant e-mail communication, a recreation room with enough musical instruments for a band, and a greenhouse where lettuce, cucumbers and tomatoes are grown.
Gaisser and senior electronics instrument specialist James Roth, electronics engineer Leonard Shulman, and physicist Paul Evenson will all work on location at the South Pole over the next several weeks, assisted by Hermann Kolanoski, a colleague who is a professor of physics at the Humboldt University in Berlin.
Ten other scientists and graduate students from the University of Delaware Department of Physics and Astronomy also are involved in the effort, from deployment to data analysis. They include David Seckel, John Clem, Chris Elliott, Shahid Hussain, Takao Kuwabara, Bakhtiyar Ruzybayev, Todor Stanev, Serap Tilav and Chen Xu.
Log on to this Web site (http://www.expeditions.udel.edu/antarctica/) through Dec. 21 to read the research team's “Dispatches from the Frozen Frontier.”
Tracey Bryant | Newswise Science News
What happens when we heat the atomic lattice of a magnet all of a sudden?
18.07.2018 | Forschungsverbund Berlin
Subaru Telescope helps pinpoint origin of ultra-high energy neutrino
16.07.2018 | National Institutes of Natural Sciences
For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.
To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...
For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.
Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...
Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.
A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...
Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.
"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....
Ultra-short, high-intensity X-ray flashes open the door to the foundations of chemical reactions. Free-electron lasers generate these kinds of pulses, but there is a catch: the pulses vary in duration and energy. An international research team has now presented a solution: Using a ring of 16 detectors and a circularly polarized laser beam, they can determine both factors with attosecond accuracy.
Free-electron lasers (FELs) generate extremely short and intense X-ray flashes. Researchers can use these flashes to resolve structures with diameters on the...
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12.07.2018 | Event News
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18.07.2018 | Health and Medicine | <urn:uuid:6dcf53e8-3ccc-42c0-b4d0-96cb03bbf7a8> | 3.8125 | 1,655 | Content Listing | Science & Tech. | 40.942246 | 95,527,248 |
London: Migration between different communities of bacteria is the key to the type of gene transfer that can lead to the spread of traits such as antibiotic resistance, said researchers from Oxford University.
While horizontal gene transfer - also known as bacterial sex - has long been acknowledged as central to microbial evolution, why it is able to exert such a strong effect has remained a mystery till date.
Now, Oxford scientists have demonstrated that the secret is migration.
It is well known that bacteria are able to swap little pieces of DNA which is crucial for them to be able to evolve and adapt to new environments, including responding to antibiotics.
"It is different to sex in humans but the effect - swapping genetic material - is similar," said Kevin Foster, professor of evolutionary biology.
However, sex in bacteria is a very rare event, with only one cell among millions swapping DNA.
"In theory, any resistant strain will rapidly divide and take over the community, shutting down any opportunity to share the resistance gene with others," Foster added.
But it does keep happening, and genes are often able to hop through diverse groups of different bacteria. Until now, the mystery has been why.
This migration between communities of bacteria can take place anywhere, from the human body to soil.
While antibiotic resistance is a good example of a beneficial trait passed horizontally between microbes, it could also involve being able to survive in an environmental toxin or on a particular nutrient.
The study, published in the journal Nature Communications, sheds new light on how the spread of traits such as antibiotic resistance happens.
"Our model offers a theoretical framework for understanding the processes behind the bacterial spread," added study co-author Rene Niehus. | <urn:uuid:e4eb2969-0537-46e6-a9b3-0eaaa4d90436> | 3.921875 | 344 | News Article | Science & Tech. | 27.828554 | 95,527,263 |
Green lifeforms on our planet are able to create energy utilizing sunlight and CO2 in order to survive and thrive. Scientists are researching the ability to create an artificial Photosynthesis that can be used to produce liquid fuel from CO2 and water. The goal has become closer when the U.S. Department of Energy's Lawerence Berkeley National Laboratory made a discovery that nano-sized crystals of cobalt oxide can effectively carry out the crucial Photosynthesis reaction of splitting water molecules.
The following video shows an aqueous solution contains silica particles that have been embedded with photooxidizing cobalt oxide nanocrystals plus a sensitizer to allow the water-splitting reaction to be driven by visible light. When laser light hits the solution it turns from gold to blue as the sensitizer absorbs light. Bubbles soon begin to form as oxygen gas is released from the spilt water molecules.
To read more about the Subject, check the link: The Berkeley Lab Views | <urn:uuid:586aebe8-efab-4c62-9590-5f532afff5a3> | 3.921875 | 197 | Truncated | Science & Tech. | 31.0825 | 95,527,271 |
A Common-Sense Guide to Data Structures and Algorithms
Level Up Your Core Programming Skills
|Price||$38.06 - $39.99
|Publisher||The Pragmatic Programmers|
|Format||Paper book / ebook|
Use Big O notation, the primary tool for evaluating algorithms, to measure and articulate the efficiency of your code, and modify your algorithm to make it faster. Find out how your choice of arrays, linked lists, and hash tables can dramatically affect the code you write. Use recursion to solve tricky problems and create algorithms that run exponentially faster than the alternatives. Dig into advanced data structures such as binary trees and graphs to help scale specialized applications such as social networks and mapping software. You'll even encounter a single keyword that can give your code a turbo boost. Jay Wengrow brings to this book the key teaching practices he developed as a web development bootcamp founder and educator.
Use these techniques today to make your code faster and more scalable.
4 5 62 | <urn:uuid:2e02361e-dbac-4e62-9507-4ab2c92d9f4b> | 2.75 | 207 | Product Page | Software Dev. | 40.012958 | 95,527,274 |
Did you know that seaweed is an indicator for the ocean’s health and biodiversity? As primary producers, they support entire communities of species through photosynthesis and provide nutrition to herbivores. They may also act as ecosystem engineers, providing a habitat for faunal species, a refuge for prey, and a nursery for juveniles. Any changes to seaweed communities tend to influence organisms at higher trophic levels, resulting in ecosystem-wide effects. They are therefore considered to be good indicators of water quality.
Veronica Farrugia Drakard will talk about her research on algae with the aim to investigate the influence of different degrees of anthropogenic impact on the structure and function of seaweed communities on artificial structures. | <urn:uuid:57d5eae1-cf0a-417e-8e26-f75303001b5c> | 3.328125 | 147 | News (Org.) | Science & Tech. | 17.282356 | 95,527,304 |
Asian elephants don’t carry photo identification, so scientists from the Wildlife Conservation Society and India’s Nature Conservation Foundation are providing the service free of charge by creating a photographic archive of individual elephants, which can help save them as well.
The researchers have developed a unique “photographic capture-recapture” survey method that identifies individual male elephants, specifically by the shape and size of their tusks, ears, and other features. This in turn can be used to monitor their survival rates and movement, according to a new study published in the current issue of the Journal Animal Conservation (10: 391-399).
“Unlike African elephants where both males and females have tusks, only male Asian elephants have valuable tusks, so they are specifically targeted by poachers,” said WCS researcher Varun Goswami, the study’s lead author. “In light of this fact, just counting all elephants with generic techniques isn’t enough. Our new method allows specific tracking of male elephant population dynamics, so it is a powerful conservation tool.”
Working in collaboration with the Karantaka State Forest Department in Nagarahole and Bandipur reserves, researchers systematically took more than 2400 photographs of individual elephants, sampling game roads and waterholes over an 80-day period. Male elephants in particular were given special treatment, with the scientists recording data such as tusk length, thickness, angle, arrangement, as well as other characteristics ear shape, shoulder height, tail length, and scars. These data revealed some 134 individual male elephants in a population of 991 elephants, with an adult male/female ratio of 1 to 4.33. The data were analyzed using advanced ‘open capture-recapture models’.
The new method complements traditional survey techniques, which can gauge overall elephant densities and sex ratios at population levels, but are unable to monitor demographics of male elephants with a degree of rigor attained by studies that focus on data from individual animals. More importantly, such accurate assessments of male elephants can help conservationists monitor poaching rates over the long term. Also, elephant carcasses can be compared with archival photos to identify individuals and even to aid in law enforcement efforts.
In addition to poaching, another threat to male elephants comes from human farmers defending their food resources from crop-raiders. Recognizing individual males that are prone to crop-raiding can inform better management interventions. At present, exactly how many male elephants engage in crop-raiding is unknown.
“The rigor of this technique can help us achieve real conservation success with the Asian elephants, which are threatened across their 13 country range,” said Dr. Ullas Karanth, a co-author of the study who pioneered the use of the photographic capture-recapture method to study tigers earlier. “We believe this method can be expanded to answer other questions relevant to Asian elephant conservation across their entire range.”
John Delaney | EurekAlert!
Upcycling of PET Bottles: New Ideas for Resource Cycles in Germany
25.06.2018 | Fraunhofer-Institut für Betriebsfestigkeit und Systemzuverlässigkeit LBF
Dry landscapes can increase disease transmission
20.06.2018 | Forschungsverbund Berlin e.V.
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
23.07.2018 | Health and Medicine
23.07.2018 | Earth Sciences
23.07.2018 | Science Education | <urn:uuid:f0b2e289-2c4e-43e3-b946-a54fb544faa2> | 3.359375 | 1,215 | Content Listing | Science & Tech. | 31.577312 | 95,527,312 |
Python 3.7's dataclasses reduce repetition in your class definitions.
Newcomers to Python often are surprised by how little code is required to accomplish quite a bit. Between powerful built-in data structures that can do much of what you need, comprehensions to take care of many tasks involving iterables, and the lack of getter and setter methods in class definitions, it's no wonder that Python programs tend to be shorter than those in static, compiled languages.
However, this amazement often ends when people start to define classes
in Python. True, the class definitions generally will be pretty
short. But the
__init__ method, which adds attributes to a new object,
tends to be rather verbose and repetitive—for example: | <urn:uuid:d482d3a6-9687-4468-8a5e-e9b6db6cfad0> | 2.609375 | 157 | Truncated | Software Dev. | 40.238561 | 95,527,314 |
In this Java simulation the hydrostatic pressure of a liquid is measured with an U-tube manometer. On the upper side of the red coloured chamber there is a membrane which is deformed more or less, depending on the pressure. Consequently the pressure of the air in the connected tube (pink) increases so that the liquid sinks in the left part of the U-shaped tube and rises in its right part. The displacement of the liquid's level measures the hydrostatic pressure.
Remark 1: It is supposed that the liquids in the U-shaped tube and in the container are the same.
Remark 2: Note that only the hydrostatic pressure of the liquid is registered, not the pressure of the air!
The problem of this simulated experiment is the relation between hydrostatic pressure and depth. You can raise or lower the manometer with pressed mouse button. On the right side it is possible to select one of several liquids. In addition, you can write the values of density and depth directly into the text fields. On the lower right the applet will indicate the measured hydrostatic pressure (in hPa).
(1 hPa = 1 Hektopascal = 100 Pa = 100 N/m2)
You can see that the hydrostatic pressure of water increases by about 1 hPa for each cm of depth.
The following formula is more general:
|p = g ρ h|
p ... hydrostatic pressure of the liquid
g ... gravitational acceleration
ρ ... density of the liquid
h ... depth
Walter Fendt, February 3, 1999
Translation: Kaido Reivelt, 2007
Last modification: July 24, 2007 | <urn:uuid:4de4a3c5-4c1e-4614-801b-fbac03a08127> | 3.859375 | 342 | Documentation | Science & Tech. | 59.842355 | 95,527,321 |
Using five years of data from NASA's Ice, Cloud and land Elevation Satellite (ICESat), a team of NASA and university scientists made the first basin-wide estimate of the thickness and volume of the Arctic Ocean ice cover between 2003 and 2008. The scientists found that younger, thinner ice has replaced older, thicker ice as the dominant type over the past five years. Until recently, the majority of Arctic ice survived at least one summer and often several. That balance has now flipped. Seasonal ice, or ice that melts and re-freezes every year, now comprises about 70 percent of the Arctic sea ice in wintertime, up from 40 to 50 percent in the 1980s and 1990s. Thicker ice - surviving two or more years - now comprises just 10 percent of ice cover, down from 30 to 40 percent in years past.Sea ice thickness has been hard to measure directly so scientists have typically used estimates of ice age to approximate thickness. With ICESat, NASA scientists were for the first time able to monitor the ice thickness and volume changes over the entire Arctic Ocean. The Arctic ice cap grows each winter as the sun sets for several months and intense cold sets in. The total volume of winter Arctic ice is equal to the volume of fresh water in Lake Superior and Lake Michigan combined. Some of that ice is naturally pushed out of the Arctic by winds, while much of it melts in place.
But not all of the ice in the Arctic melts each summer, and the thicker, older ice that survives one or more summers is more likely to persist through the next summer. This older, thicker ice is declining thinner ice that is more vulnerable to summer melt. Seasonal sea ice usually reaches about 2 meters (6 feet) in thickness, while ice that has lasted through more than one summer averages 3 meters (9 feet), though it can grow much thicker in some locations near the coast. From 2003 to 2008, multi-year ice has thinned by an average of 60 centimeters (2 feet). The total ice volume in winter has decreased by 6,300 cubic kilometers, or 40 percent. The maximum extent of multi-year ice is now one-third of what it was in the 1990s.
This sequence shows Arctic sea ice thickness derived from fall campaigns from the ICESat satellite. While the sea ice extent might look similar from year to year this thickness data shows dramatic thinning especially near the North Pole (shown in dark blue). This image was generated with data acquired between Oct 4 - Oct 19, 2008.
Please give credit for this item to: NASA/Goddard Space Flight Center Scientific Visualization Studio The Next Generation Blue Marble data is courtesy of Reto Stockli (NASA/GSFC).
Science Paper: Zwally, H. J., D. H. Yi, et al. 2008. ICESat Measurements of Sea Ice Freeboard and Estimates of Sea Ice Thickness in the Weddell Sea. Journal of Geophysical Research-Oceans 113(C2). http://adsabs.harvard.edu/abs/2007AGUFM.C11B0421Z
Short URL to share this page: http://svs.gsfc.nasa.gov/3592
GCMD keywords can be found on the Internet with the following citation:
Olsen, L.M., G. Major, K. Shein, J. Scialdone, S. Ritz, T. Stevens, M. Morahan, A. Aleman, R. Vogel, S. Leicester, H. Weir, M. Meaux, S. Grebas, C.Solomon, M. Holland, T. Northcutt, R. A. Restrepo, R. Bilodeau, 2013. NASA/Global Change Master Directory (GCMD) Earth Science Keywords. Version 184.108.40.206.0 | <urn:uuid:5eb2138e-e609-40e5-93ae-97f226aa7051> | 4.1875 | 793 | Knowledge Article | Science & Tech. | 68.018815 | 95,527,325 |
Students often are given questions that require them to find basic and conditional probabilities for a 2×2 matrix such as this problem:
You can work this problem using StatCrunch using the Stat>Tables>Contingency path, but some students get confused by the cluttered output. I have developed an Excel worksheet that makes this much easier for a 2×2 table. You can use the online version below, or you can contact me and I will send you my workbook. When you put your data and the column and row labels in the blue cells, the table below will populate including the correct wording for the probability statements.
Here is a link to a video on how to use the calculator to solve this type of problem: https://youtu.be/_n6TAmWJFoM
You may download a copy of the calculator workbook here: Basic Probabilities Calculator | <urn:uuid:53000318-85fd-4dff-8d67-aea65da5fc26> | 2.625 | 181 | Tutorial | Science & Tech. | 41.8905 | 95,527,327 |
Nautiluses are the last surviving members of a 500 million year old animal lineage. Their continued existence, however, is under threat from unregulated fisheries and world-wide trade for the nautilus shell. For nearly a decade, the Save the Nautilus team has been assessing the current state of nautilus populations across the Indo-Pacific to support conservation initiatives. Utilizing a combination of methods, including underwater video surveillance and community outreach, the group’s work has led to the first international regulation of the nautilus shell trade, enacted in 2017. In his lecture Gregory Jeff Barord, Ph.D., will discuss monitoring nautilus populations and studying nautiluses and the deep-sea ecosystem as a whole. Barord is a conservation biologist for Save the Nautilus and the marine biology instructor for Des Moines Public Schools’ Central Campus.
|When||Thu, July 19, 2018 00:00:00 Tuesday, Aug 14, 2018 | 7:00 PM–8:30 PM|
|Cost||$5 for public; FREE for Aquarium members, seniors age 62 and up, teachers, and students with valid ID and advanced reservations.|
You can purchase tickets online for this lecture. You will need to select the option from the menu, correct time, and date on the following pages. Seniors age 62 and up, teachers, and students attending for free can also reserve seats online.
|Links||View past lecture videos| | <urn:uuid:bf3622e1-fa45-42f8-95a8-affea5fe3baf> | 2.828125 | 303 | News (Org.) | Science & Tech. | 44.207242 | 95,527,356 |
WASHINGTON (AP) - December's wild El Nino pushed 2015 in the United States to near-record levels for heat, moisture and downright extreme conditions, federal weather officials said Thursday.
The year that just ended was the second warmest and third wettest in 121 years of record-keeping for the lower 48 states, the National Oceanic and Atmospheric Administration announced.
The 54.4 degree average last year was second only to 2012.
"The combination of El Nino plus climate change clearly has brought the U.S. some weirdly memorable, highly unusual, and quite troubling weather," said climate scientist Michael Oppenheimer of Princeton University. "As for the influence of climate change, it's just the beginning."
These are just U.S. statistics. Globally, it's almost certain to be hottest on record with exact figures coming out later this month, and the U.S. near-record is emblematic of that, said Deke Arndt, NOAA's climate monitoring chief.
"We live in a warming world and a warming world is bringing more big heat and more big rain events to the United States," Arndt said during a NOAA press conference.
For much of the spring and summer, climate change was the big factor pushing U.S. temperatures above normal. But in November and December, El Nino took over and supercharged the global warming effect while turning on the heavy rains, said Victor Gensini, a meteorology professor at DuPage College outside Chicago.
El Nino is the natural warming of the central Pacific that changes weather worldwide. It occurs every two to seven years or so with one of its most noticeable affects being heavy downpours in California.
Going into December, it was just the fifth warmest and ninth wettest year in the United States. Then a record-setting December pushed everything up a few notches.
At 38.6 degrees - 6 degrees warmer than the 20th century average - December was nearly a full degree warmer than the record set in 1939. And the 3.93 inches of precipitation in December surpassed the old record by more than a sixth of an inch.
This was the first time that a month was both the warmest and wettest on record, said NOAA climate scientist Jake Crouch.
Last year, the U.S. lurched from one extreme to another. Going into December, the U.S. was flirting with a record low number of tornado deaths. Then a series of nasty tornadoes killed 24 people in four days, making it the second deadliest December for tornadoes on record.
December storms, featuring flooding in the Mississippi River and snowfall in the Southwest, killed at least 50 people, making it the deadliest weather event of 2015.
NOAA compiles a climate extremes index that puts all sorts of extreme weather - hot and cold, wet and dry - into one lump statistic. It showed 2015 was 70 percent more extreme than the average over 106 years. It was the fourth most extreme year in the United States.
Ten weather disasters last year caused $1 billion or more in damage - ranking fourth highest for number of billion-dollar disasters in 35 years of record-keeping. Dollar figures are adjusted for inflation.
Michael Mann, a Pennsylvania State University climate scientist, said the issue is not so much records but how lasts year's dramatic weather affected Americans, including record rainfall in South Carolina in early October and a balmy Christmas Eve in the East.
"These events weren't 'caused' by climate change, but each of them was made worse by climate change," Mann said in an email. "2015 was the year where climate change impacts in the U.S. weren't just detectable - they were obvious."
NOAA's state of the climate: http://www.ncdc.noaa.gov/sotc/summary-info/national/2015/12
Follow Seth Borenstein at http://twitter.com/borenbears and his work can be found at http://bigstory.ap.org/content/seth-borenstein
Copyright 2016 The Associated Press. All rights reserved. This material may not be published, broadcast, rewritten or redistributed. | <urn:uuid:e14a342a-b020-4d09-9b73-40fb3541c565> | 2.71875 | 867 | News Article | Science & Tech. | 59.387516 | 95,527,358 |
The Hertzsprung–Russell diagram is a stars scatter graph that shows the relationship between the stars' absolute magnitudes or luminosities versus their spectral types and effective temperatures. Hertzprung-Russell diagrams are not pictures or maps of the locations of the stars. Rather, they plot each star on a graph measuring the star's absolute brightness against its temperature and color. The diagram was created circa 1910 by Ejnar Hertzsprung and Henry Norris Russell and represents a major step towards an understanding of stellar evolution or "the lives of stars".
The Hertzsprung-Russell (H-R) diagram is simple. It plots two basic properties of stars: their luminosity (intrinsic brightness) and their surface temperature (as revealed by their color). In doing so, it anchors stellar astronomy just as the periodic table anchors chemistry. Whereas the periodic table groups together similar chemical elements—for example, placing all noble gases, such as helium, neon and argon, into one column—the H-R diagram groups together stars passing through similar stages of life. When astronomers invented the diagram, no one knew why the sun and other stars shine. No one knew how stars are born or how they die. No one could even assure the public that the sun would never explode. Nor did anyone know that the stars had forged most of the elements that make up Earth and our bodies.
Contemplation of the diagram led astronomers to speculate that it might demonstrate stellar evolution, the main suggestion being that stars collapsed from red giants to dwarf stars, then moving down along the line of the main sequence in the course of their lifetimes. Stars were thought therefore to radiate energy by converting gravitational energy into radiation through the Kelvin-Helmholtz mechanism. This mechanism resulted in an age for the sun of only tens of millions of years, creating a conflict over the age of the solar system between astronomers, and biologists and geologists who had evidence that the earth was far older than that. This conflict was only resolved in the 1930s when nuclear fusion was identified as the source of stellar energy. | <urn:uuid:76f68e35-d397-49c0-a529-9a0fd991546e> | 4.15625 | 426 | Personal Blog | Science & Tech. | 41.295304 | 95,527,363 |
+44 1803 865913
By: KR Reddy and RD DeLaune
774 pages, Col figs, tabs, illus
About a fourth of the plants, half of the fish, two-thirds of the birds, and three-fourths of the amphibians categorized as threatened or endangered in the United States are associated with wetlands. These areas can help control flooding, reduce wave action, slow down the flow of water, and improve water quality. Covering freshwater and coastal wetlands and their role in global climate change, "Biogeochemistry of Wetlands" is the first comprehensive book on biogeochemical cycling in these critical habitats. It offers an in-depth look at the chemical and biological cycling of nutrients, trace elements, and toxic organic compounds in wetland soils and water.
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How are animals used in science? Why do we use some animals and not others? What are the benefits and problems with using animals in science? You will explore these questions with others, and decide: Is it appropriate to use animals in science?
Participants must also be able to attend follow-on workshops on Tue 12, Wed 13 and Thu 14 July 10am-11am in the same location.
Suitable for kids aged 10-14 years.
Dunningham Suite, Dunedin City Library, 230 Moray Place
or call 027 389 1923
If you have any questions, email firstname.lastname@example.org or call 027 3891923.
This event is wheelchair accessible. | <urn:uuid:98146511-b4f5-488f-965c-eeb29b8573e6> | 2.6875 | 146 | News (Org.) | Science & Tech. | 63.144593 | 95,527,370 |
The idea of studying probability measures on spheres in Euclidean space ℝ p rather than on the Euclidean space itself is as old as the beginnings of probability theory and statistics. In 1734 Daniel Bernoulli looked at the orbital planes of the planes known at his time as random points on the surface of a sphere and asserted their uniform distribution. In the first quarter of this century Rayleigh and Karl Pearson started investigations on the resultant length of normal vectors, in connection with approximation problems for large samples, within the framework of random walks on spheres. Until then the distributions appearing in the work of the pioneers were all uniform.
KeywordsProbability Measure Compact Group Gauss Measure Compact Abelian Group Topological Semigroup
Unable to display preview. Download preview PDF. | <urn:uuid:a1134685-2230-4c4f-9c27-cf1e66d50886> | 2.921875 | 158 | Truncated | Science & Tech. | 30.896221 | 95,527,373 |
It is, of course, necessary to know the output of the laser. In the biomedical field it is much more important to be precise and accurate. The laser reaction in living tissue changes with but small changes in the various parameters of the laser output, whether it be changes in power, energy outputs or pulse duration. The findings of laser research at various centers cannot be compared unless accurate outputs of laser radiation are made. This important field is in a very much confused state at the present time because of the difficulty of measurement of laser output, especially of high outputs. Exit energies above 1500 joules exit energy have been used in biomedical applications with the pulsed solid-state lasers, 0.5–10 watts power outputs are to be used for the argon laser and 25 watts for the carbon dioxide laser. It would seem, at first glance, that the problem of measurements should be simple, for it is merely the detection of classical changes in electromagnetic fields. Many studies of this problem have been done in our laboratory by Hornby and Rockwell.
KeywordsLaser Output Copper Sulfate Confuse State Carbon Dioxide Laser Copper Cone
Unable to display preview. Download preview PDF. | <urn:uuid:24c09612-3305-4a81-86f3-d3e6bd3832d2> | 2.71875 | 241 | Truncated | Science & Tech. | 39.098879 | 95,527,374 |
In their search for the fundamental building blocks of matter, physicists have found smaller and smaller constituents which in their turn have proven to themselves be composite systems. By the end of the 19th century, it was known that all matter is composed of atoms. However, the existence of close to 100 elements showing periodically recurring properties was a clear indication that atoms themselves have an internal structure, and are not indivisible.
KeywordsElectromagnetic Interaction Colour Charge Elementary Particle Physic Fundamental Building Block Weak Charge
Unable to display preview. Download preview PDF. | <urn:uuid:63d1db13-6d83-4d14-8f2f-8c984d0fde36> | 3.328125 | 113 | Truncated | Science & Tech. | 23.810352 | 95,527,375 |
A Note on the Source of Interstellar Interference
Further consideration of the data obtained during observations on interstellar interference has shown that these radiations are received any time the antenna system is directed towards some part of the Milky Way system, the greatest response being obtained when the antenna points towards the center of the system. This fact leads to the conclusion that the source of these radiations is located in the stars themselves or in the interstellar matter distributed throughout the Milky Way.
Because of the similarity in the sound produced in the receiver headset, it is suggested that these radiations might be due to the thermal agitation of charged particles.
KeywordsSingle Direction Thermal Agitation Interstellar Matter Bell Telephone Laboratory Extraterrestrial Origin
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- K. G. Jansky, “Directional studies of atmospherics at high frequencies,” Proc. I.R.E., vol. 20, p. 1920; December, (1932)Google Scholar
- K. G. Jansky, “Electrical disturbances apparently of extraterrestrial origin,” Proc. I.R.E., vol. 21, p. 1387; October, (1933)Google Scholar
- Reprinted, with permission, from the ‘Proceedings of the Institute of Radio Engineers’ 23, 1158–1163 (1935)Google Scholar
- F. B. Llewellyn, “A study of noise in vacuum tubes and attached circuits,” Proc. I.R.E., vol. 18, p. 243; February (1930)Google Scholar
- A. S. Eddington, “Stars and Atoms,” pp. 66–69, Yale University Press, 1927.Google Scholar | <urn:uuid:83ae2c16-1fe6-4b0a-b04f-c7259e107ccc> | 2.953125 | 367 | Truncated | Science & Tech. | 53.236494 | 95,527,376 |
The Bitmap::LockBits method locks a rectangular portion of this bitmap and provides a temporary buffer that you can use to read or write pixel data in a specified format. Any pixel data that you write to the buffer is copied to the Bitmap object when you call Bitmap::UnlockBits.
Status LockBits( IN const Rect *rect, IN UINT flags, IN PixelFormat format, OUT BitmapData *lockedBitmapData );
Type: const Rect*
Pointer to a rectangle that specifies the portion of the bitmap to be locked.
Set of flags that specify whether the locked portion of the bitmap is available for reading or for writing and whether the caller has already allocated a buffer. Individual flags are defined in the ImageLockMode enumeration.
Integer that specifies the format of the pixel data in the temporary buffer. The pixel format of the temporary buffer does not have to be the same as the pixel format of this Bitmap object. The PixelFormat data type and constants that represent various pixel formats are defined in Gdipluspixelformats.h. For more information about pixel format constants, see Image Pixel Format Constants. GDI+ version 1.0 does not support processing of 16-bits-per-channel images, so you should not set this parameter equal to PixelFormat48bppRGB, PixelFormat64bppARGB, or PixelFormat64bppPARGB.
Pointer to a BitmapData object. If the ImageLockModeUserInputBuf flag of the flags parameter is cleared, then lockedBitmapData serves only as an output parameter. In that case, the Scan0 data member of the BitmapData object receives a pointer to a temporary buffer, which is filled with the values of the requested pixels. The other data members of the BitmapData object receive attributes (width, height, format, and stride) of the pixel data in the temporary buffer. If the pixel data is stored bottom-up, the Stride data member is negative. If the pixel data is stored top-down, the Stride data member is positive. If the ImageLockModeUserInputBuf flag of the flags parameter is set, then lockedBitmapData serves as an input parameter (and possibly as an output parameter). In that case, the caller must allocate a buffer for the pixel data that will be read or written. The caller also must create a BitmapData object, set the Scan0 data member of that BitmapData object to the address of the buffer, and set the other data members of the BitmapData object to specify the attributes (width, height, format, and stride) of the buffer.
Type: Type: Status
If the method succeeds, it returns Ok, which is an element of the Status enumeration.
If the method fails, it returns one of the other elements of the Status enumeration.
|Windows version||Windows XP, Windows 2000 Professional [desktop apps only] Windows 2000 Server [desktop apps only]|
|Header||gdiplusheaders.h (include Gdiplus.h)| | <urn:uuid:8fbd838e-a09e-41a4-afd0-68d1c4a7a259> | 2.78125 | 638 | Documentation | Software Dev. | 37.43911 | 95,527,406 |
Marine mammal beachings along the French coast have been recorded by scientists since 1972. According to Nicolas Keck, a veterinary surgeon with the Hérault Departmental Laboratory, "beached dolphins are regularly found along the Mediterranean coast, for various reasons, primarily due to accidents and infections. The death rate is occasionally higher, generally as a result of the morbillivirus".
As Geneviève Libeau, a CIRAD researcher, explains: "dolphins are susceptible to the morbillivirus and develop the disease. Their high density in the Mediterranean and their gregariousness favour the spread of the morbillivirus. We have observed epidemic peaks linked to the number of births, since it is generally young dolphins and adults without immunity that are affected". In the main, the disease causes nervous, respiratory and digestive problems in contaminated cetaceans.
Assessing the epidemic
Since 2003, the Departmental Veterinary Laboratory (overseen by the Hérault Departmental Council) and CIRAD have been studying morbilliviruses. They are currently the only organizations conducting such analyses in France.
The fact that a morbillivirus was responsible was demonstrated by viral analyses of tissue samples from infected animals. By isolating genome fragments, CIRAD traced the origin of the virus: it stemmed from the epidemic that began in Spain.
Analyses are continuing, and will do so for some time. The aim is to monitor the evolution of the disease and identify the risk factors, so as to control the epidemic. However, there are no plans to develop a vaccine, given the difficulty of vaccinating wild animals.
Helen Burford | alfa
Upcycling of PET Bottles: New Ideas for Resource Cycles in Germany
25.06.2018 | Fraunhofer-Institut für Betriebsfestigkeit und Systemzuverlässigkeit LBF
Dry landscapes can increase disease transmission
20.06.2018 | Forschungsverbund Berlin e.V.
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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To improve the water environment, manual water diversion projects were scheduled to bring freshwater to an urban artificial lake to dilute and divert pollutants out of the lake. A three-dimensional numerical model was used to study the effect of diversion schemes on the transport of dissolved substances by using concepts of water renewal time and water age. The model results showed that the impact of diversion schemes on transport processes was strongly influenced by hydrodynamic conditions induced by inflow/outflow discharges. Shorter water timescales occupied the west and east lake, implying a faster water renewal occurrence therein. Water ages were highly variable, both spatially and temporally. Longer water age was exhibited in the inner lake and bays. An exchange rate of 89.3% was obtained at the 5 m3/s discharge condition under 60 days' duration, with integral renewal time of approximately 50 days. The distribution of water age showed that it only took less than 10 days for the substance discharged at the inlets to be transported to the outlets. The results offer useful information for understanding the efficiency of water exchange by diversion projects and can be used to estimate the water renewal capacity for environmental assessment purposes.
Modelling the effect of water diversion projects on renewal capacity in an urban artificial lake in China
Xueping Gao, Liping Xu, Chen Zhang; Modelling the effect of water diversion projects on renewal capacity in an urban artificial lake in China. Journal of Hydroinformatics 11 November 2015; 17 (6): 990–1002. doi: https://doi.org/10.2166/hydro.2015.004
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in mathematics, assignment of a number as a measure of the "chance" that a given event will occur. There are certain important restrictions on such a probability measure. In any experiment there are certain possible outcomes; the set of all possible outcomes is called the sample space of the experiment. To each element of the sample space (i.e., to each possible outcome) is assigned a probability measure between 0 and 1 inclusive (0 is sometimes described as corresponding to impossibility, 1 to certainty). Furthermore, the sum of the probability measures in the sample space must be 1.
A simple illustration of probability is given by the experiment of tossing a coin. The sample space consists of one of two outcomes—heads or tails. For a perfectly symmetrical coin, the likely assignment would be 1/2 for heads, 1/2 for tails. The probability measure of an event is sometimes defined as the ratio of the number of outcomes. Thus if weather records for July 1 over a period of 40 years show that the sun shone 32 out of 40 times on July 1, then one might assign a probability measure of 32/40 to the event that the sun shines on July 1.
Probability computed in this way is the basis of insurance calculations. If, out of a certain group of 1,000 persons who were 25 years old in 1900, 150 of them lived to be 65, then the ratio 150/1,000 is assigned as the probability that a 25-year-old person will live to be 65 (the probability of such a person's not living to be 65 is 850/1,000, since the sum of these two measures must be 1). Such a probability statement is of course true only for a group of people very similar to the original group. However, by basing such life-expectation figures on very large groups of people and by constantly revising the figures as new data are obtained, values can be found that will be valid for most large groups of people and under most conditions of life.
In addition to the probability of simple events, probabilities of compound events can be computed. If, for example, A and B represent two independent events, the probability that both A and B will occur is given by the product of their separate probabilities. The probability that either of the two events A and B will occur is given by the sum of their separate probabilities minus the probability that they will both occur. Thus if the probability that a certain man will live to be 70 is 0.5, and the probability that his wife will live to be 70 is 0.6, the probability that they will both live to be 70 is 0.5×0.6=0.3, and the probability that either the man or his wife will reach 70 is 0.5+0.6-0.3=0.8.
In many probability problems, sophisticated counting techniques must be used; usually this involves determining the number of permutations or combinations. The number of permutations of a set is the number of different ways in which the elements of the set can be arranged (or ordered). A set of 5 books in a row can be arranged in 120 ways, or 5×4×3×2×1=5!=120 (the symbol 5!, denoting the product of the integers from 1 to 5, is called factorial 5). If, from the five books, only three at a time are used, then the number of permutations is 60, or
In general the number of permutations of n things taken r at a time is given by
On the other hand, the number of combinations of 3 books that can be selected from 5 books refers simply to the number of different selections without regard to order. The number in this case is 10:
In general, the number of combinations of n things taken r at a time is
The application of probability is fundamental to the building of statistical forms out of data derived from samples (see statistics). Such samples are chosen by predetermined and arbitrary selection of related variables and arbitrary selection of intervals for sampling; these establish the degree of freedom. Many courses are given in statistical method. Elementary probability considers only finite sample spaces; advanced probability by use of calculus studies infinite sample spaces. The theory of probability was first developed (c.1654) by Blaise Pascal, and its history since then involves the contributions of many of the world's great mathematicians.
- See Probability and Measure (1979). ,
- I. Hacking, The Emergence of Probability (1984, rev. ed. 2006).
- Probability (1986). ,
- Introduction to Probability (1988). ,
- Introduction to Probability Theory (1989). ,
In the history of empiricism, probability has been a central and distinctive concern, but the understanding of it has proved elusive. It is, of...
From the Latin probabilitas, and this from the Latin probabilis (“capable of standing a test”) and the particle -tas, where probabilis ...
Dale Andrew I. , A History of Inverse Probability: From Thomas Bayes to Karl Pearson , New York : Springer , 1991 Daston ... | <urn:uuid:b5921986-abf9-410a-a2da-d5d5e2835d9f> | 3.96875 | 1,064 | Knowledge Article | Science & Tech. | 56.176223 | 95,527,429 |
More than 60 people were killed and thousands left homeless in the worst forest fires to hit Greece in decades. According to data from ESA’s ERS-2 and Envisat satellites, which continuously survey fires burning across the Earth’s surface with onboard sensors, Greece experienced more wildfire activity this August than other European countries experienced over the last decade.
In an effort to aid authorities responding to disasters such as this, ESA and other national space agencies established the International Charter on Space and Major Disasters in 2000 to provide rush access to a broad range of satellite data.
The Charter, activated by the Department of Emergency Planning and Response of the Greek Civil Protection Agency, processed this request and recruited the German Aerospace Centre (DLR) and the Strasbourg-based rapid mapping specialist company (SERTIT) to produce the maps using satellite images provided by the space agencies.
As a result, the Greek Civil Protection Agency received a series of Earth Observation (EO)-based crisis/damage mapping products generated using a variety of EO sensors. The first EO-based maps, delivered while the fires were still active, were overview products based on the Medium Resolution Imaging Spectrometer (MERIS) instrument aboard ESA’s Envisat satellite. French and German Civil Protections active in Greece to support fire fighting teams also received the maps.
These maps were used for fighting active fires across Greece, particularly those in the region of the Parnonas Mountains, which rise to almost 2000 metres on the eastern side of the Peloponnese peninsula that makes up southern Greece.
"These map products proved to be very helpful for managing the severe fires that Greece suffered," Fivos Theodorou, Director for Emergency Planning and Response of the General Secretariat for Civil Protection, said. "The General Secretariat for Civil Protection intends to use these maps for post-fire management purposes, such as burnt area mapping, reforestation and the construction of flood prevention projects and supply them to the Greek authorities, such as the Greek Forest Service, responsible for consequence management."
DLR performed this service under the scope of the Risk-EOS service network. Risk-EOS, part of ESA's initial Services Element of Global Monitoring for Environment and Security (GMES), offers EO-based operational services for rapid mapping of major disasters as well as other geo-information services to support risk management of hazards such as floods and forest fires.
The Risk EOS service network and its Greek partner, National Observatory of Athens (NOA), are now working closely with Greek authorities to consolidate further the work done by the Charter on the affected areas.
Other satellites used to produce the maps include NASA’s Landsat, the SAC-C (an international cooperative mission between NASA and the Argentine Commission on Space Activities (CONAE), CNES, the Brazilian Space Agency, the Danish Space Research Institute and the Italian Space Agency), CNES’s SPOT satellite and Taiwan’s FORMOSAT satellite.
Other Charter members currently include the Indian Space Research Organisation (ISRO), the US National Oceanic and Atmospheric Administration (NOAA), the Argentine Space Agency (CONAE), the Japan Aerospace Exploration Agency (JAXA), the British National Space Centre/Disaster Monitoring Constellation (BNSC/DMC), the U.S. Geological Survey (USGS) and the China National Space Administration (CNSA).
Mariangela D'Acunto | alfa
Upcycling of PET Bottles: New Ideas for Resource Cycles in Germany
25.06.2018 | Fraunhofer-Institut für Betriebsfestigkeit und Systemzuverlässigkeit LBF
Dry landscapes can increase disease transmission
20.06.2018 | Forschungsverbund Berlin e.V.
For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.
To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...
For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.
Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...
Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.
A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...
Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.
"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....
Ultra-short, high-intensity X-ray flashes open the door to the foundations of chemical reactions. Free-electron lasers generate these kinds of pulses, but there is a catch: the pulses vary in duration and energy. An international research team has now presented a solution: Using a ring of 16 detectors and a circularly polarized laser beam, they can determine both factors with attosecond accuracy.
Free-electron lasers (FELs) generate extremely short and intense X-ray flashes. Researchers can use these flashes to resolve structures with diameters on the...
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From methanol to formaldehyde - this reaction is the starting point for the synthesis of many everyday plastics. Using catalysts made of gold particles, formaldehyde could be produced without the environmentally hazardous waste generated in conventional methods.
Gold/titanium dioxide catalyst in action: At the interface between a gold particle (Au, gold) and the titanium dioxide surface (TiO2, red and light blue), an oxygen molecule (O2, dark blue spheres) is activated by a charge transfer and becomes catalytically active. Thus, methanol (CH3OH) can be efficiently and selectively oxidized to formaldehyde (CH2O); water (H2O) is produced as well. The researchers made the charge transfer visible using vibrational spectroscopy of adsorbed carbon monoxide (CO; middle of the figure): In the presence of oxygen, a new band (CO@Au(delta+)O2(delta-) appears in the spectrum.
Image: M. Farnesi Camellone, D. Marx
Dr. Josef König | idw
World’s Largest Study on Allergic Rhinitis Reveals new Risk Genes
17.07.2018 | Helmholtz Zentrum München - Deutsches Forschungszentrum für Gesundheit und Umwelt
Plant mothers talk to their embryos via the hormone auxin
17.07.2018 | Institute of Science and Technology Austria
For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.
To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...
For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.
Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...
Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.
A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...
Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.
"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....
Ultra-short, high-intensity X-ray flashes open the door to the foundations of chemical reactions. Free-electron lasers generate these kinds of pulses, but there is a catch: the pulses vary in duration and energy. An international research team has now presented a solution: Using a ring of 16 detectors and a circularly polarized laser beam, they can determine both factors with attosecond accuracy.
Free-electron lasers (FELs) generate extremely short and intense X-ray flashes. Researchers can use these flashes to resolve structures with diameters on the...
13.07.2018 | Event News
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Benjamin Franklin wrote in his 1750 Poor Richard’s Almanac that "There are three things extremely hard: steel, a diamond, and to know one’s self." The problem of achieving accurate self-knowledge hasn’t gotten any easier in 250 years; and, as shown in a new research report, there are major real-world consequences to this very human attribute.
In "Flawed Self-Evaluation: Implications for Health, Education, and the Workplace," investigators David Dunning (Cornell), Chip Heath (Stanford), and Jerry M. Suls (University of Iowa) summarized current psychological research on the accuracy (or rather inaccuracy) of self-knowledge, across a wide range of studies in a range of spheres. Their report is published in the December 2004 issue of Psychological Science in the Public Interest, a journal of the American Psychological Society.
A consistent and sobering picture emerged from the team’s analysis: On the job, at school, or even in managing our own health, it is as though we all live in Garrison Keillor’s fictional Lake Wobegon, "where all the children are above average." People’s opinions of themselves, their abilities, and their health outlooks are generally skewed quite strongly in a positive direction.
David Dunning | EurekAlert!
05.07.2018 | Institute of Science and Technology Austria
Research project: EUR 3.3 million for improved quality of life in shrinking cities
02.07.2018 | Technische Universität Kaiserslautern
For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.
To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...
For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.
Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...
Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.
A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...
Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.
"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....
Ultra-short, high-intensity X-ray flashes open the door to the foundations of chemical reactions. Free-electron lasers generate these kinds of pulses, but there is a catch: the pulses vary in duration and energy. An international research team has now presented a solution: Using a ring of 16 detectors and a circularly polarized laser beam, they can determine both factors with attosecond accuracy.
Free-electron lasers (FELs) generate extremely short and intense X-ray flashes. Researchers can use these flashes to resolve structures with diameters on the...
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The Hubble Space Telescope: From Concept to Success by David J. Shayler
English | PDF,EPUB | 2016 | 438 Pages | ISBN : 1493928260 | 34.85 MB
The highly successful Hubble Space Telescope was meant to change our view and understanding of the universe. Within weeks of its launch in 1990, however, the space community was shocked to find out that the primary mirror of the telescope was flawed. It was only the skills of scientists and engineers on the ground and the daring talents of astronauts sent to service the telescope in December 1993 that saved the mission. | <urn:uuid:f1807625-ed8d-4a6e-a9dc-80637cf469bb> | 2.90625 | 119 | Product Page | Science & Tech. | 59.314211 | 95,527,478 |
This web page contains an interactive simulation on conservation of momentum. Users may choose from two views: a pair of ice skaters pushing off from each other or a model of two blocks exerting a force on each other. The user can adjust the masses of the two objects and observe their velocities, momenta, and kinetic energies as they move away from each other. This resource was developed to enhance understanding of the law of momentum conservation. It includes, the simulation help, a detailed lesson with related problems/solutions, learning outcomes, and instructions for use.
This item is part of a larger collection of simulation-based physics modules sponsored by the MAP project (Modular Approach to Physics).
Modular Approach to Physics: Skaters and Blocks. (2004, February 11). Retrieved July 21, 2018, from University of Calgary: http://canu.ucalgary.ca/map/content/force/newton3/exploding_blocks/applet.html
University of Calgary. Modular Approach to Physics: Skaters and Blocks. Calgary: University of Calgary, February 11, 2004. http://canu.ucalgary.ca/map/content/force/newton3/exploding_blocks/applet.html (accessed 21 July 2018).
%T Modular Approach to Physics: Skaters and Blocks %D February 11, 2004 %I University of Calgary %C Calgary %U http://canu.ucalgary.ca/map/content/force/newton3/exploding_blocks/applet.html %O application/java
%0 Electronic Source %D February 11, 2004 %T Modular Approach to Physics: Skaters and Blocks %I University of Calgary %V 2018 %N 21 July 2018 %8 February 11, 2004 %9 application/java %U http://canu.ucalgary.ca/map/content/force/newton3/exploding_blocks/applet.html
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Remote sensing is a critical but expensive tool for verifying and validating the impact of land-use improvement projects, especially when using airplanes and other low-flying machines. Environmental consultant Steve Apfelbaum, however, says he’s found a way to deliver cost-effective surveillance using 1970s technology.
18 February 2013 | Steve Apfelbaum knew the technology existed. He’d even tested it himself in the 1970s – but only with the permission of the US Department of Defense.
The airborne camera was, he knew, the perfect tool for tracking and surveying the kinds of changes in land use that he was looking for as chairman and chief ecologist for Applied Ecological Systems (AES), an ecological consulting firm that provides scientific solutions to land-use problems. But it also utilized remote-sensing technologies that he feared would never be licensed for civilian use – until four years ago, when he read about the Leica RCD30.
Like the model he tested in the 1970s, this one is also a military tool, primarily deployed for surveillance work in Iraq and Afghanistan. However, Apfelbaum wasn’t about to let that stop him. He approached the producers with a different proposal: how about opening up the cameras for science? His persistence paid off; and AES was ultimately able to test and compare these quality cameras from two manufacturers.
In the end, AES decided to jointly purchase a single digital imaging camera from Leica Geosystems with Aryes Associates. The camera takes pictures both in color and using near-infrared imagery. These capabilities, combined with resolutions as high as 1 inch, means that the Leica RCD30 can be used for a variety of ecological projects – from measuring and mapping plant species disease outbreaks and amount of invasive spreading, to even identifying water quality and erosion issues in clear bodies of water. The work can be accomplished under most weather conditions; while near-infrared imagery is capable of being used in low light and cloudy conditions, this is often a key limiting factor for color imagery.
To utilize the camera, the two companies had to purchase their own plane, certified with a camera-sized hole so that it can take pictures from the bottom of the aircraft. Since the plane was custom-built, they made sure it was capable of flying beneath the clouds – a sharp difference from most commercial planes, which fly high and fast in order to produce more volume of digital images.
AES stresses that its plane and camera are ideally suited for research – and if it couldn’t get any better, they also argue that the cost is cheaper than most industry alternatives. Expenses are linked closely to resolution, with 1-2 inch resolutions costing a couple of hundred dollars less than leading competitors.
While the camera has come a long way from its military purposes in the 70’s, it has not been completely dissociated with its beginnings. Currently, the companies need Department of State permission for any projects taking place outside of the United States. Apfelbaum, however, doesn’t believe this permission will be difficult to obtain and hopes to see AES’s technology expand beyond the borders. He believes it could prove a unique addition to the remote sensing options available for current researchers studying forest carbon offsets and other REDD-related activities in tropical countries. In an ideal world, Apfelbaum would buy another camera and set up an international base to meet increased demand – but for now, he’s content with merely spreading the word. | <urn:uuid:b5963ae5-4c97-48ea-a469-c59b24809972> | 3.5625 | 715 | Truncated | Science & Tech. | 30.993355 | 95,527,510 |
FOR CENTURIES, seahorses have held our curiosity. They appear in scrolls from ancient Greece and seaside tales from the Victorian era. The seahorse form even appears in the folds of our brains, in the shape of the hippocampus – the component of our limbic system responsible for consolidating memories and for spatial navigation.
However, the popular image of this peculiar creature dancing- in swaying sea grass and mangrove forests might not be in tune with reality. Overfishing and disruption to coastal seas, where the majority- of seahorses live, are threatening their populations. According to the World Conservation Union, nine of the planet’s 33 seahorse species are listed as vulnerable and one is endangered. Meanwhile, 25 million seahorses are traded annually, primarily for use in traditional Chinese medicine as a cure for a variety of ailments-, including impotence, poor blood circulation and wheezing.
The epicenter of the rallying cry for more protection is Project Seahorse, a BC-based organization run by two of the world’s most prolific seahorse researchers, Canadian marine biologist and conservationist Amanda Vincent and her British counterpart Heather Koldewey. Obviously they’re not the first to tackle marine conservation and target awareness about the impacts of overfishing on our oceans, but they certainly are the first to pick the highly charismatic seahorse as their protagonist.
“Ultimately, seahorses are flagship species for a wide range of marine conservation issues,” says Vincent. “Their dwindling numbers- suggest larger problems, including the depletion of other fish species and destruction of vital marine habitats, such as coral reefs and sea grasses. Saving seahorses means saving their threatened- marine ecosystems, and in turn, improving food security for the human communities that depend on them for survival.”
Overfishing and unsustainable practices – like those that resulted in the collapse of Newfoundland’s cod industry – illustrate the intrinsic link between human enterprise and nature. The Project Seahorse team’s diverse fields of expertise show a healthy bias towards continuing to drive home that link.
One research associate, Sarah Foster, focuses on bycatch (unintentionally caught fish) and trade of seahorses. Two others, Phil Molloy and Mai Yasue, have worked tirelessly to examine the connection between human actions, conservation efforts and delicate ecosystems. Vincent says they wholeheartedly believe that solutions will be found if both the public and policy makers appreciate this symbiosis.
“In our view, a hierarchy of concentric pressures bears down on individual animals, creating ‘an onion world’ effect,” says Vincent, noting that each layer effects the other. “By working to protect seahorses, Project Seahorse supports marine conservation more broadly.”
The project’s origins trace back to Vincent’s PhD research at Cambridge University in the 1980s. “At the time, most of what was known about syngnathids [the family of fuse-jawed fish that seahorses belong to] was decades old,” she says. “I was one of the first scientists to document seahorses’ unusual mating habits.”
Their bizarre behaviour intrigued Vincent. A three-day courtship is followed by the female depositing her eggs in the male’s pouch, where he nourishes and fertilizes them, ultimately giving birth two to four weeks later through contractions. During the gestation period, the female visits the male for daily “morning greetings,” five- to ten-minute interactions where they may link tails and change colours. What compelled Vincent even more was that despite the male’s specialized parental function, he still retained the conventional sex role of greater competitiveness, manifesting as male-to-male competition for access to mates. (Many seahorse pairs are monogamous and remain together during the entire breeding season.)
Vincent was hooked. She continued to study seahorses at Cambridge’s zoology department and in the wild. “Through my work, I discovered the trade in seahorses was much larger than previously suspected,” she says. “By the early 1990s, it was clear that many species were facing extreme pressure from overexploitation, pressure that was also damaging entire marine ecosystems.”
It was then that Vincent connected with the like-minded Koldewey, who was researching seahorse genetics at the Zoological Society of London (where she would later become the program manager for international marine and freshwater conservation). In 1996, the duo launched Project Seahorse at McGill University in Montreal. “We established an international team of researchers and community development specialists dedicated to finding ways to reduce those pressures, protect seahorse populations and ensure sustainable livelihoods for those who depend on seahorse fishing,” says Vincent.
The team wasted no time, turning their focus towards the community of Handumon in the Philippines, where seahorse fishing plays a vital role in the local economy. Vincent and her team helped to establish a community-managed marine sanctuary there, promoting traditional fishing techniques and “no-take” areas, as well as encouraging a unified organization of small scale fishers.
The project quickly spread to other countries, attracting scientists and other interested professionals. By late 2002, Project Seahorse had grown to include nearly 40 researchers, community development specialists and support staff, with project alumni working on every continent.
The team uprooted and moved headquarters from McGill to the Fisheries Centre at the University of British Columbia in Vancouver in late 2002. There are no known seahorse species native to Canada (although the Hippocampus erectus, or lined seahorse, occasionally drifts north from the Gulf of Mexico’s warmer waters) so the project focuses on conservation efforts abroad. Post-graduate students have conducted field research in Portugal, Central America, Sri Lanka and Vietnam under Project Seahorse’s guidance. The Philippines is still the project’s largest contingent, with about 16 full-time students, scientists, researchers and community development specialists.
Although the organization has garnered many awards and partnerships, Vincent says one of their proudest moments was helping to generate a landmark global agreement in 2002 under the Convention on the International Trade in Endangered Species (CITES), forbidding countries to export more seahorses than wild populations could bear. Only Indonesia, Japan, Norway and South Korea chose to opt out of the trade rules.
“This, the first-ever global agreement on trade in marine fishes of commercial importance, created a new international tool for fisheries management,” says Vincent, who serves as lead scientific advisor and chair of the seahorse working group at CITES, and is the Canada Research Chair in Marine Conservation. “[CITES] also effectively acknowledged that marine fish are wildlife as well as economic commodities.”
While mutually agreeable conservation efforts are certainly being built, Vincent says the implementation of the convention still presents challenges, “largely because countries don’t know how to proceed” while following trade rules and keeping their economy thriving.
Nonetheless, Vincent hopes the seahorse can be a game changer. “We will continue to work tirelessly to make the trade in seahorses sustainable, and we have a number of other seahorse- and marine-conservation focused projects underway.”
Shouldn’t the curious little creature that has held our attention for centuries be an apt metaphor for our oceans’ health? Vincent and Koldewey may be on to something.
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SCIENTISTS may have finally worked out how dinosaurs evolved into birds.
Experts have isolated a genetic sequence which they believe was present in dinosaurs before and during their evolution into birds.
Modern birds descended from a group of two-legged dinosaurs called theropods, whose members included the fearsome T-Rex and smaller Velociraptors.
Fossils show bird-like traits including feathers, light bones, air sacs and three-digit forelimbs.
But identifying genomic DNA changes during this evolutionary transition has remained a challenge.
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Tohoku University researchers have isolated a gene sequence they believe was present in dinosaurs before and during their transition to the feathered creatures we recognise today.
The international group of researchers have found a specific gene sequence which could be associated with the evolution of flight feathers in the dinosaur era.
In a journal published in Nature Communications, lead author Ryohei Seki wrote: “Flight feathers are one of the most prominent evolutionary innovations in the avian lineage, conferring not only the ability for flight but also, in some species, important roles in other biological functions, such as territorial displays and courtship ritual.
“Birds have two regions that have flight feathers: along the posterior edges of the wings and in the tail.
“Feathered dinosaur fossils have provided significant new information on the evolutionary origin of flight feathers.”
A new species of enormous dinosaur that was as long as two-and-a-half double decker buses was recently discovered.
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What seems to be missed on these answers is our motion through spacetime. Spacetime is the "web" of both space and time. Our galaxy is hurdling through the universe at tens/hundreds of thousands of mph as we are also hurdling through time, - and again space and time are part the same "matrix". So we are constantly hurdling through spacetime, and that is why when mass compresses and curves spacetime, we have a tendency to "move" toward mass. There is no such thing as a force of gravity, it is not a force, it is an observed effect. We feel as if we are constantly being pushed to the ground because of us flying through space and time so fast, and that spacetime that we are flying through is curved toward the mass of the earth. Actually, the earth is pushing, and exerting force on us. | <urn:uuid:cf76a77b-c42b-46da-b02c-fbf303ee7106> | 2.703125 | 180 | Q&A Forum | Science & Tech. | 57.606096 | 95,527,588 |
The image below illustrates the problem being solved here: a user is clicking the mouse hoping to select one of the several geometric shapes, but the place they are clicking is close to several entities, so a different entity is highlighted with each mouse click until the user is happy.
You can see that the user moves the mouse a little which makes the selection set change, but the order of the selected entities doesn't change radically: the entities that were available before and after the move are iterated in the same order.
This class encapsulates complex selection behaviour with a simple interface. It is also useful wherever data is acquired slowly but needs to end up in a sorted Array, or where an Array will be filtered a lot.
Two code sections will talk to a Selection object:
The slow side is the user clicking things, which manipulates Linked Lists in the Selection object.
Once the user has completed the selection, the renderer must re-draw the screen with some objects potentially drawn differently to show that they are selected.
So for every object the renderer is going to draw (and for many applications there could be millions) it must ask if that object is selected...
The renderer simply needs if(Selection.Has(ID)) ? DrawSelected(ID) : Draw(ID); because once selection is complete, the Linked Lists are Cached to a sorted Array which is searched with Binary Chop via the Has method.
Multiple Selection Mode is the default, and the simplest process:
The user can click on multiple objects to select them,
you add a Long Identifier (ID) representing each item they selected to the SelectionSet object,
and it holds the array for you.
Querying the SelectionSet to see if an ID is selected is very fast (Binary Chop algorithm).
Single Selection Mode allows the user to click the mouse over multiple items.
Each time they click the mouse, a different item is highlighted.
You simply add all the items to the SelectionSet and ask it to pick one to highlight.
Each time the user clicks the mouse in the same area,
you add all the items as before and ask the SelectionSet to pick one,
and it will pick a different one.
If the mouse moves a little and some of the objects are no longer close enough to the mouse,
the SelectionSet will still loop sensibly through the available objects.
It uses a 'History' Linked List to figure out what IDs are new.
The renderer can know if it is supposed to draw an entity in it's selected state or not with as little overhead as possible.
Separating the Single and Multi select as classes derived from a SelectionBase class has been tried, but the final polymorphic class is slower than this.
Normally, for Multiple Selection:
Toggle(i) would be called when the user has clicked on an entity.
Has(i) would be called by the renderer when deciding how to draw an Entity (selected or not).
You can get at the Selection Array with GetArray() or access individual elements with operator.
For Single Selection:
The user clicks (once) and it is possible that many overlapping Entities are selectable.
Add(i) would be called many times, once for each overlapping Entity.
When all the Entities are added, OnSelChanged() is called which chooses one of the Entities to select.
Has(i) would be called by the renderer when deciding how to draw an entity (selected or not).
If the user didn't get the Entity they wanted, they may click again and the next call to OnSelChanged() will select a different Entity.
The order of cyclic selection is the reverse order of the ID integer and is unlikely to relate to the topology.
If the user clicks where nothing is selectable, OnSelChanged() is called with Entites Empty which clears the selection.
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(1695) Last modified: Fri, 04 Oct 2013 18:57:40 +0100 | <urn:uuid:edff7a4f-f0a8-4b87-85f3-21ddfe770adf> | 2.78125 | 1,066 | Documentation | Software Dev. | 39.746009 | 95,527,605 |
Eleven light-years from Earth, orbiting a dim red star, there’s an exoplanet called Ross 128b that, as we recently reported, has some the best prospects for life of any known distant world. New results may help astronomers figure out what the planet is made of—and they offer more evidence that it might be inside its…
Following an independent review, NASA’s planned James Webb Space Telescope has received yet another delay in its mission schedule. This time, NASA has moved the target launch from May 2020 to March 2021.
Is this dang telescope ever going to launch?
President Donald Trump’s 2019 budget request would nix the Wide Field Infrared Survey Telescope (WFIRST), and scientists aren’t happy.
There’ve been some incredible images of the James Webb Space Telescope, the next generation telescope and successor to the Hubble. But we’re not really here to look at images of telescopes. We’re here to learn some dope space stuff.
The Hubble Space Telescope is incredible and has done some truly remarkable science, but it’s getting old. After all, it was launched in 1990. Taking its place is the James Webb Space Telescope, an $8 billion-plus experiment that was scheduled to launch in October 2018.
Like a dandelion reaching up to the sky on a warm spring day, the James Webb Telescope peers upwards in this stunning new photo released today by NASA. Still under construction, the powerful space-bound telescope will soon be shipped across the country for the next phase of its development.
We’re openly obsessed with the assembly of the segmented origami mirror for the James Webb Space Telescope. A gorgeous photo released today reveals the secret of an enormous robotic arm used to place the mirror segments to within a paper’s width of perfection.
The James Webb Space Telescope construction team doesn’t waste time! After hitting the halfway-point in December, they’re now up to 12 of 18 mirrors installed. Check out the livestream from the cleanroom for building this fantastic telescope now, or forever hold your peace!
What better way to spend the holidays than watching NASA technicians scurry around assembling mirror segments on the James Webb Space Telescope? With the 9th of 18 segments installed last week, we’re that much closer to hunting for signs of life on alien worlds and making our universe a little less lonely.
NASA has announced that they’ve installed the first of the James Webb Space Telescope’s mirrors. The part is one of eighteen that will eventually be bolted to the satellite, which is set to launch in 2018.
When it launches in October 2018, the James Webb Space Telescope will become the largest optical telescope in space. With its 6.5 meter wide mirror, it will gather infrared light from up to 13.5 billion light years away, giving astronomers a look at the earliest moments of the universe. But the mirror is too big to…
The James Webb Space Telescope (JWST), which will be “in many ways a hundred times” more capable than Hubble, isn’t launching until 2018, but already astrophysicists are thinking about its successor. They’re calling it the High Definition Space Telescope (HDST). That’s it on the far right, towering over both its…
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The James Webb Space Telescope is the most powerful space telescope ever built, and its mirrors must be kept squeaky clean. Any debris, even tiny flecks of dust, could impact its science. Ergo, “snow cleaning:” the use of carbon dioxide snow to clean the mirrors thoroughly yet gently.
Here are two engineers practicing “snow cleaning” on a test telescope mirror for the James Webb Space Telescope. I’m not exaggerating when I say this is the coolest way to dust off any surface without scratching it.
The James Webb Space Telescope takes carefully packing parts to new extremes: the packaging for the latest shipment weighted more than fifty times the actual part! This is the Space Telescope Transporter for Air Road and Sea, the shipping container for telescopes.
Behold, the GIANT GOLDEN SPIDER! Ok, this shiny marvel is actually a 2012 look at the James Webb Space Telescope under construction at NASA's Goddard Space Flight Center:
The James Webb Space Telescope is about to be tucked into a massive space simulator as part of its testing to ensure it can survive the harsh orbital environment. The telescope is the next-generation planet-hunter, intended to check exoplanetary atmospheres for signs of life.
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New technique tracks RNAs associated with the protein responsible for Fragile X
The process of turning genes into protein makes the insides of cells terribly crowded and complicated places. Signals tell machinery to transcribe the DNA of genes into messenger RNA (mRNA) whose translation into protein has to be coordinated with everything else that is happening within the cell. Fortunately, there are RNA binding proteins to organize mRNAs. These proteins are so critical that the loss of one particular RNA binding protein, FMRP, leads to Fragile X syndrome, the most common inherited forms of mental retardation.
Researchers based at the University of Pennsylvania School of Medicine invented a technique called Antibody Positioned RNA Amplification (APRA) to determine the identity of RNA molecules associated with RNA binding proteins. Their findings on FMRP, presented in the February 6th issue of the journal Neuron, further define the complex basis of Fragile X syndrome.
Greg Lester | EurekAlert!
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The earth's structure can be compared to an orange: its crust is the peel supported by the earth's heavy mantle. That peel is made up of a continental crust 30 to 40 kilometers thick. It is much lighter than the thinner oceanic crust and protrudes from the earth's mantle because of its lower density, like an iceberg in the sea.
"According to the current theory, the first continental crusts were formed when tectonic plates would collide, submerging oceanic crusts into the earth's mantle, where they would partially melt at a depth of approximately 100 kilometers. That molten rock then ascended to the earth's surface and formed the first continents," says adjunct professor Dr. Thorsten Nagel of the Steinmann Institute of Geosciences at the University of Bonn, lead author of the study. The theory has been supported by the oldest known continental rocks – approximately 3.8 billion years old – found in western Greenland.Following trace elements
Researchers from Bonn and Cologne have now analyzed the Greenlandic rocks for different elements occurring at various high concentrations, also know as trace elements. "Trace elements provide geologists with a window to the origin of continental crust," says Prof. Münker. "With their help, we can identify minerals in the residual rock that were deposited in the depths by the molten rock."
Before the magma separated from the bedrock, the semifluid rock and the leftover solid minerals actively exchanged trace elements. "Different minerals have characteristic ways of separating when trace elements are smelted. In other words, the concentration of trace elements in the molten rock provide a fingerprint of the residual bedrock," explains Dr. Elis Hoffmann from Bonn, coauthor of the study. The concentration of trace elements in the oldest continental rock allows geoscientists to reconstruct possible bedrock based on their minerals and thus determine at what depth the continental crust originated.The oceanic crust did not have to descend
Publication: Generation of Eoarchean tonalite-trondhjemite-granodiorite series from thickened mafic arc crust, Geology, DOI: 10.1130/G32729.1A photo for this press release can be found at:
Professor Dr. Thorsten Nagel | EurekAlert!
Global study of world's beaches shows threat to protected areas
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6 customer reviews
Save additional 15% OFF with coupon code: JULYXMAS
The vanes, or wings, in this solar radiometer are alternately dark and light in color. When the light strikes these wings it transfers heat to each one - but not at the same degree. The lighter wing reflects the rays and the darker wing absorbs. The stronger the light, the more energy there is to heat up the darker side of the wing causing the wings to spin faster. It spins under the solar light or a regular light bulb. Great for science projects, as a gift or as a desk amusement!
Uses heat transfer to spin
No batteries required; the radiometer is powered entirely by light
Either solar or indoor light works
Great desk toy
Great for solar science lessons
5.25 x 3.25 x 3.25 inches
13.34cm x 8.26cm x 8.26cm
0 lb 3 oz
directly observable interesting physics
Mark ODell from USA, CA, Los Angeles
Motion directly from light never gets old. This motion, however, is not due to photon momentum radiation pressure, or the direct pressure from gas warmed by the black faces. Such simple explanations turn out to be wrong. This is a light-driven heat engine. Even James Clerk Maxwell initially disagreed with Osborne Reynolds about the mechanism, so we are in good company watching and wondering. See Wikipedia Radiometer references for a lucid discussion, but know there is much more going on than the common explanations most of us learned when first seeing a Crookes Radiometer ("light-mill"). Cooling causes direction reversal. Improving the vacuum stops motion altogether. Radiation pressure is real, but the effect is too small here. The important mechanism has more in common with the flow of heat or superfluid helium than the momentum of photons or the pressure of bulk hot gas. The black sides do get hotter, but the ultimate magic of motion apparently happens at the edges of the vanes, not the faces.
Good Classroom Tool
Cynthia from USA, UT, Draper
This is an awesome way for students to learn that solar radiation is a form of energy.
Maria from Cedar Rapids, IA
Love to watch this work and think about the science behind it. Great tool for teaching about energy.
Great Conversation Piece!
Eric Holmes from Moose Jaw, Canada
Everyone that sees it will stop and look at it rotating and then will have a theory on what makes it rotate.
Joan from Tulsa, Oklahoma
This is so fun. I broke my mother's radiometer, so had to replace it. A good price for a great product. | <urn:uuid:48c57866-571a-4ad9-aff7-f525f505f55c> | 3.296875 | 544 | User Review | Science & Tech. | 62.554929 | 95,527,630 |
It covers many python concepts in depth. Python latest version tutorial pdf also teaches you some advance constructs of python like lambda expression, regular expression.
If you want a more traditional book, Python For You and Me is an excellent resource for learning all aspects of the language. Each tutorial is supplemented with logically added coding snippets and equips with a follow-up quiz on the subject learned. Online Python Tutor gives you a visual step by step representation of how your program runs. Python Tutor helps people overcome a fundamental barrier to learning programming by understanding what happens as the computer executes each line of a program’s source code. This beginner’s book is for those with no programming experience at all.
This book teaches Python programming and basic cryptography for absolute beginners. The chapters provide the source code for various ciphers, as well as programs that can break them. This is an excellent beginner programmer’s guide to Python. Also known as Python for Programmers with 3 Hours, this guide gives experienced developers from other languages a crash course on Python.
Dive Into Python 3 is a good book for those ready to jump in to Python 3. It’s a good read if you are moving from Python 2 to 3 or if you already have some experience programming in another language. Think Python attempts to give an introduction to basic concepts in computer science through the use of the Python language. While exploring the various features available in the Python language the author weaves in various design patterns and best practices. The book also includes several case studies which have the reader explore the topics discussed in the book in greater detail by applying those topics to real-world examples. Case studies include assignments in GUI and Markov Analysis.
Python Koans is a port of Edgecase’s Ruby Koans. It uses a test-driven approach, q. TEST DRIVEN DESIGN SECTION to provide an interactive tutorial teaching basic Python concepts. By fixing assertion statements that fail in a test script, this provides sequential steps to learning Python. For those used to languages and figuring out puzzles on their own, this can be a fun, attractive option.
For those new to Python and programming, having an additional resource or reference will be helpful. A free introductory book that teaches Python at the beginner level, it assumes no previous programming experience. A Byte of Python for Python 2. A Byte of Python for Python 3. A Codeacademy course for the absolute Python beginner.
Python programming whilst testing the user’s knowledge in between progress. Code the blocks provides free and interactive Python tutorials for beginners. The tutorials teach you how to use Python to create progressively elaborate 3D structures, making the process of learning Python fun and engaging. This book contains 59 specific ways to improve writing Pythonic code. This book is for intermediate to advanced Python programmers who are looking to understand how and why Python works the way it does and how they can take their code to the next level.
Expert Python Programming deals with best practices in programming Python and is focused on the more advanced crowd. It has a detailed, multi-chapter case study on writing and releasing a package and eventually an application, including a chapter on using zc. Later chapters detail best practices such as writing documentation, test-driven development, version control, optimization and profiling. Numerical Methods in Engineering with Python, written by Jaan Kiusalaas, puts the emphasis on numerical methods and how to implement them in Python. Programming Collective Intelligence introduces a wide array of basic machine learning and data mining methods. The exposition is not very mathematically formal, but rather focuses on explaining the underlying intuition and shows how to implement the algorithms in Python. Transforming Code into Beautiful, Idiomatic Python is a video by Raymond Hettinger.
Fullstack Python offers a complete top-to-bottom resource for web development using Python. As the name suggests, it covers everything you need to build and run a complete web app from scratch. Python in a Nutshell, written by Alex Martelli, covers most cross-platform Python’s usage, from its syntax to built-in libraries to advanced topics such as writing C extensions. This is Python’s reference manual, it covers the syntax and the core semantics of the language. Python Essential Reference, written by David Beazley, is the definitive reference guide to Python.
Flask and Green Unicorn on Ubuntu 16. This command creates an exact copy of your repo, we’ll also discuss the difference between equality and identity and we’ll likely take a look at how many of these operators are “deep” operations in Python. That it is natural or shows fluency in the language, python is always available if you get stuck. Numerical Methods in Engineering with Python — add a urlpattern for the new view. That can create too much of a mess.
Has said: “I wanted a scripting language that was more powerful than Perl, as well as for others to understand when we share it with them. While still mostly working on it in my own time, installation Do I need to install pip? The yield statement, he is comfortable creating polished products as a full stack developer. If there’s another sharing window open, this module will create a pool of 8 threads, idiomatic Python is a video by Raymond Hettinger. Fullstack Python offers a complete top, as measured by the TIOBE index. If you look at the state of the system now, the first two lines of the output are the key to decoding the rest of the text. | <urn:uuid:702c9d00-44a3-478b-99da-90be0147154e> | 2.921875 | 1,136 | Content Listing | Software Dev. | 42.934502 | 95,527,647 |
Chemtrail conspiracy theory
The chemtrail conspiracy theory is the false claim that long-lasting condensation trails, called "chemtrails" by proponents, consist of chemical or biological agents left in the sky by high-flying aircraft and deliberately sprayed for purposes undisclosed to the general public. Believers in the theory argue that normal contrails dissipate relatively quickly and contrails that do not dissipate must contain additional substances. Those who subscribe to the theory speculate that the purpose of the chemical release may be solar radiation management, weather modification, psychological manipulation, human population control, or biological or chemical warfare and that the trails are causing respiratory illnesses and other health problems.
The arguments have been dismissed by the scientific community; these are normal water-based contrails that are routinely left by high-flying aircraft under certain atmospheric conditions. Although proponents have tried to prove that the chemical spraying does take place, their analyses have been flawed or based on misconceptions. Because of the persistence of the conspiracy theory and questions about government involvement, scientists and government agencies around the world have repeatedly explained that the supposed chemtrails are in fact normal contrails.
Chemtrail conspiracy theories began to circulate after the United States Air Force (USAF) published a 1996 report about weather modification. Following the report, in the late 1990s the USAF was accused of "spraying the U.S. population with mysterious substances" from aircraft "generating unusual contrail patterns." The theories were posted on Internet forums by people including Richard Finke and William Thomas; the theories were also discussed by late-night radio host Art Bell, starting in 1999. As the chemtrail conspiracy theory spread, federal officials were flooded with angry calls and letters.
A multi-agency response attempting to dispel the rumors was published in 2000 by the Environmental Protection Agency (EPA), the Federal Aviation Administration (FAA), the National Aeronautics and Space Administration (NASA) and the National Oceanic and Atmospheric Administration (NOAA). Many chemtrail believers interpreted agency fact sheets as further evidence of the existence of a government cover-up. The EPA refreshed its posting in 2015.
In the early 2000s the USAF released an undated fact sheet that stated the conspiracy theories were a hoax fueled in part by citations to a 1996 strategy paper drafted within their Air University titled Weather as a Force Multiplier: Owning the Weather in 2025. The paper was presented in response to a military directive to outline a future strategic weather modification system for the purpose of maintaining the United States' military dominance in the year 2025, and identified as "fictional representations of future situations/scenarios." The USAF further clarified in 2005 that the paper "does not reflect current military policy, practice, or capability," and that it is "not conducting any weather modification experiments or programs and has no plans to do so in the future." Additionally, the USAF states that the "'Chemtrail' hoax has been investigated and refuted by many established and accredited universities, scientific organizations, and major media publications."
The conspiracy theories are seldom covered by the mainstream media, and when they are, they are usually cast as an example of anti-government paranoia. For example, in 2013, when it was made public that the CIA, NASA, and NOAA intended to provide funds to the National Academy of Sciences to conduct research into methods to counteract global warming with geoengineering, an article in the International Business Times anticipated that "the idea of any government agency looking at ways to control, or manipulate, the weather will be met with scrutiny and fears of a malign conspiracies" [sic], and mentioned chemtrail conspiracy theories as an example.
Proponents of the chemtrail conspiracy theory find support for their theories in their interpretations of sky phenomena, videos posted to the internet, and reports about government programs; they also have certain beliefs about the goals of the alleged conspiracy and the effects of its alleged efforts and generally take certain actions based on those beliefs.
Interpretation of evidence
Proponents of the chemtrail conspiracy theory say that chemtrails can be distinguished from contrails by their long duration, asserting that the chemtrails are those trails left by aircraft that persist for as much as a half day or transform into cirrus-like clouds. The proponents claim that after 1995 contrails had a different chemical composition and lasted a lot longer on the sky; proponents fail to acknowledge evidence of long-lasting contrails shown in World War II era photographs.
Proponents of the theory of the existence of chemtrails characterize contrails as streams that persist for hours and that, with their criss-cross, grid-like or parallel stripe patterns, eventually blend to form large clouds. Proponents view the presence of visible color spectra in the streams, unusual concentrations of sky tracks in a single area, or lingering tracks left by unmarked or military airplanes flying at atypical altitudes or locations as markers of chemtrails.
Photographs of barrels installed in the passenger space of an aircraft for flight test purposes have been claimed to show aerosol dispersion systems. The real purpose of the barrels is to simulate the weight of passengers or cargo. The barrels are filled with water, and the water can be pumped from barrel to barrel in order to test different centers of gravity while the aircraft is in flight.
Jim Marrs has cited a 2007 Louisiana television station report as evidence for chemtrails. In the report the air underneath a crosshatch of supposed chemtrails was measured and apparently found to contain unsafe levels of barium: at 6.8 parts per million, three times the US nationally recommended limit. A subsequent analysis of the footage showed, however, that the equipment had been misused, and the reading exaggerated by a factor of 100—the true level of barium measured was both usual and safe.
In May 2014 a video that went viral showed a commercial passenger airplane landing on a foggy night, which was described as emitting chemtrails. Discovery News pointed out that passengers sitting behind the wings would clearly see anything being sprayed, which would defeat any intent to be secretive, and that the purported chemical emission was normal air disruption caused by the wings, visible due to the fog. In October 2014, Englishman Chris Bovey filmed a video of a plane jettisoning fuel on a flight from Buenos Aires to London, which had to dump fuel to lighten its load for an emergency landing in São Paulo. The clip went viral on Facebook, with over three million views and more than 52,000 shares, cited as evidence of chemtrails. He later disclosed that the video post was done as a prank, and consequently he was subjected to some vitriolic abuse and threats from several conspiracy believers.
Various versions of the chemtrail conspiracy theory have been propagated via the Internet and radio programs. There are websites dedicated to the conspiracy theory, and it is particularly favored by right-wing groups because it fits well with deep suspicion of government.
A 2014 paper presented results of reviewing 20 chemtrail websites found that believers appeal to science in some of their arguments, but do not believe what academic or government-employed scientists say; scientists and federal agencies have consistently denied that chemtrails exist, explaining the sky tracks are simply persistent contrails.
The 2014 paper also found that chemtrail believers generally hold that chemtrails are evidence of a global conspiracy; people who believe in the conspiracy allege various goals which include profit (for example, manipulating futures prices or making people sick to benefit drug companies), population control, or weapons testing (use of weather as a weapon, or testing bioweapons). One of these ideas, is that clouds are being seeded with electrically conductive materials as part of a massive electromagnetic superweapons program based around the High Frequency Active Auroral Research Program (HAARP).
Those who believe in the conspiracy say the chemtrails are toxic; the 2014 review found that chemtrail believers generally hold that every person is under attack and found that believers often express fear, anxiety, sadness and anger about this.
In a 2011 study of people from the US, Canada, and the UK, 2.6% of the sample entirely believed in the conspiracy theory, and 14% believed it partially. An analysis of responses given to the 2016 Cooperative Congressional Election Study showed that 9% of the 36,000 respondents believed it was "completely true" that "...the government has a secret program that uses airplanes to put harmful chemicals into the air..." while a further 19% believed this was "somewhat true".
Chemtrail conspiracy theorists often describe their experience as being akin to a religious conversion experience. When they "wake up" and become "aware" of chemtrails, the experience motivates them to advocacy of various forms. For example, they often attend events and conferences on geoengineering, and have sent threats to academics working in the geoengineering field.
In 2001 in response to requests from constituents, US Congressman Dennis Kucinich introduced (but did not author) H.R. 2977 (107th), the Space Preservation Act of 2001 that would have permanently prohibited the basing of weapons in space, listing chemtrails as one of a number of "exotic weapons" that would be banned. Proponents have interpreted this explicit reference to chemtrails as official government acknowledgment of their existence. Skeptics note that the bill in question also mentions "extraterrestrial weapons" and "environmental, climate, or tectonic weapons." The bill received an unfavorable evaluation from the United States Department of Defense and died in committee, with no mention of chemtrails appearing in the text of any of the three subsequent failed attempts by Kucinich to enact a Space Preservation Act.
In 2003, in a response to a petition by concerned Canadian citizens regarding "chemicals used in aerial sprayings are adversely affecting the health of Canadians," the Government House Leader responded by stating, "There is no substantiated evidence, scientific or otherwise, to support the allegation that there is high altitude spraying conducted in Canadian airspace. The term 'chemtrails' is a popularised expression, and there is no scientific evidence to support their existence." The house leader went on to say that "it is our belief that the petitioners are seeing regular airplane condensation trails, or contrails."
In the United Kingdom, in 2005 Elliot Morley, a Minister of State for the Department for Environment, Food and Rural Affairs was asked "what research [the] Department has undertaken into the polluting effects of chemtrails for aircraft," and responded that "the Department is not researching into chemtrails from aircraft as they are not scientifically recognised phenomena," and that work was being conducted to understand "how contrails are formed and what effects they have on the atmosphere."
Some chemtrail believers adopt the notions of Wilhelm Reich (1897–1957) who devised a "cloudbuster" device from pipework. Reich claimed this device would influence weather and remove harmful energy from the atmosphere. Some chemtrail believers have built cloudbusters filled with crystals and metal filings, which are pointed at the sky in an attempt to clear it of chemtrails.
Chemtrail believers sometimes gather samples and have them tested, rather than rely on reports from government or academic laboratories, but their experiments are usually flawed; for example collecting samples in jars with metal lids contaminates the sample and is not done in scientific testing.
Contrails, or condensation trails, are "streaks of condensed water vapor created in the air by an airplane or rocket at high altitudes." Fossil fuel combustion (as in piston and jet engines) produces carbon dioxide and water vapor. At high altitudes the air is very cold. Hot humid air from the engine exahust mixes with the colder surrounding air, causing the water vapor to condense into droplets or ice crystals that form visible clouds. The rate at which contrails dissipate is entirely dependent on weather conditions and altitude. If the atmosphere is near saturation, the contrail may exist for some time. Conversely, if the atmosphere is dry, the contrail will dissipate quickly.
It is well established by atmospheric scientists that contrails can persist for hours, and that it is normal for them to spread out into cirrus sheets. The different-sized ice crystals in contrails descend at different rates, which spreads the contrail vertically. Then the differential in wind speeds between altitudes (wind shear) results in horizontal spreading of the contrail. This mechanism is similar to the formation of cirrus uncinus clouds. Contrails between 25,000 and 40,000 feet (7,600 and 12,200 m) can often merge into an "almost solid" interlaced sheet. Contrails can have a lateral spread of several kilometers, and given sufficient air traffic, it is possible for contrails to create an entirely overcast sky that increases the ice budget of individual contrails and persists for hours.
Experts on atmospheric phenomena say chemtrails do not exist, and that the characteristics attributed to them are simply features of contrails responding differently in diverse conditions in terms of the sunlight, temperature, horizontal and vertical wind shear, and humidity levels present at the aircraft's altitude. In the US, the gridlike nature of the National Airspace System's flight lanes tends to cause crosshatched contrails, and in general it is hard to discern from the ground whether overlapping contrails are at similar altitudes or not. The jointly published fact sheet produced by NASA, the EPA, the FAA, and NOAA in 2000 in response to alarms over chemtrails details the science of contrail formation, and outlines both the known and potential impacts contrails have on temperature and climate. The USAF produced a fact sheet as well that described these contrail phenomena as observed and analyzed since at least 1953. It also rebutted chemtrail theories more directly by identifying the theories as a hoax and disproving the existence of chemtrails.
Patrick Minnis, an atmospheric scientist with NASA's Langley Research Center in Hampton, Virginia, has said that logic does not dissuade most chemtrail proponents: "If you try to pin these people down and refute things, it's, 'Well, you're just part of the conspiracy'," he said.
Astronomer Bob Berman has characterized the chemtrail conspiracy theory as a classic example of failure to apply Occam's razor, writing in 2009 that instead of adopting the long-established "simple solution" that the trails consist of frozen water vapour, "the conspiracy web sites think the phenomenon started only a decade ago and involves an evil scheme in which 40,000 commercial pilots and air traffic controllers are in on the plot to poison their own children."
A 2016 study surveying 77 atmospheric scientists concluded that "76 out of 77 (98.7%) of scientists that took part in this study said there was no evidence of a [secret large-scale atmospheric program (SLAP)], and that the data cited as evidence could be explained through other factors, such as typical contrail formation and poor data sampling instructions presented on SLAP websites."
- Fraser, Stephen (2009). "Phantom menace? Are conspirators using aircraft to pollute the sky?". Current Science. 94 (14): 8–9.
Some theorists speculate that the goal is population control; some say it's climate modification; others say it's military weapons testing.(subscription required)
- Watson, Traci (7 March 2001). "Conspiracy theorists read between lines in the sky". USA Today. p. A.04.
Exasperated by persistent questions, the Environmental Protection Agency, NASA, the Federal Aviation Administration and the National Oceanic and Atmospheric Administration joined forces last fall to publish a fact sheet explaining the science of contrail formation. A few months earlier, the Air Force had put out its own fact sheet, which tries to refute its opponents' arguments point by point. "If you try to pin these people down and refute things, it's, 'Well, you're just part of the conspiracy,' " says atmospheric scientist Patrick Minnis of NASA's Langley Research Center in Hampton, Va. "Logic is not exactly a real selling point for most of them."
- James, Nigel (2003). Knight, Peter, ed. Contrails. Conspiracy Theories in American History: An Encyclopedia. ABC-CLIO. pp. 197–199. ISBN 978-1-57607-812-9.
there are no books on the subject to date. Reports on contrails are carried by dedicated websites...Mainstream news agencies rarely report on concerns over contrails, and when they do it is in terms of anti-government “paranoia.” When USA Today ran a contrail story it likened the story to something out of The X-Files, arguing that it was only those who are suspicious of the government who believe that lines in the sky are evidence of malfeasance.Some suggested that they are trying to slow down global warming with compounds that reflect sun-light into the sky.
- Schlatter, Thomas (9 March 2001). "Weather Queries: Chemtrail Controversy". Weatherwise. Archived from the original on 9 March 2001.
- "Contrails Facts" (PDF). US Air Force. 13 October 2005. Archived from the original (PDF) on 6 March 2013.
- Radford, Benjamin (March–April 2009). "Curious contrails: death from the sky?". Skeptical Inquirer. 33 (2): 25.
- Thomas, Dave (September 2008). "The 'Chemtrail Conspiracy'". Skeptical Inquirer. 18 (3).
- Cama, Timothy (March 13, 2015). "EPA confronts 'chemtrails' conspiracy talk". the Hill. Retrieved December 10, 2016.
Conspiracy theorists say that government officials or others are using jets to spray harmful chemicals into the atmosphere. They cite the contrails left by jets as evidence of the chemicals. The EPA has added a new notice to its website, which links to a fact sheet explaining that the trails left by jets in the atmosphere are only ice particles and contain no harmful chemicals. “Contrails are line-shaped clouds or ‘Condensation trails’ composed of ice particles that are visible behind jet aircraft engines under certain atmospheric conditions and at times can persist,” says the notice, posted to the EPA’s website Friday. “EPA is not aware of any deliberate actions to release chemical or biological agents into the atmosphere.” Theorists have posited that the chemicals are meant to control the climate, to harm humans or to kill them. The fact sheet from the EPA and other federal agencies like the Federal Aviation Administration and the National Oceanic and Atmospheric Administration was first published in 2000, when the chemtrails conspiracy became popular on the Web. An EPA spokeswoman said the agency frequently receives questions about chemtrails.
- Smith, Oliver (September 24, 2013). "'Chemtrails' and other aviation conspiracy theories". telegraph.co.uk. the Telegraph. Retrieved December 11, 2016.
So persistent is the chemtrail theory that US government agencies regularly receive calls from irate citizens demanding an explanation...The conspiracy theory took root in the Nineties, with the publication of a US Air Force research paper about weather modification...Governments and scientific institutions have of course dismissed the theories, and claim those vapour trails which persist for longer than usual, or disperse to cover a wide area, are just normal contrails.
- "chemtrail". Oxford English Dictionary (Third ed.). Oxford University Press. December 2011.(subscription required)
- Paul Simons (27 September 2013). "Weather Eye: contrail conspiracy". The Times.
This conspiracy idea took hold in 1996 when the US Government was accused of trying to modify the weather for military means(subscription required)
- Reynolds, Jay (March 1, 1999). "Those Mysterious Lines in the Sky". Veritas. Archived from the original on August 17, 2000., cited in USAF Contrails page.
- "Aircraft Contrails Factsheet" (PDF). United States Environmental Protection Agency. September 2000.
- Knickerbocker, Brad (14 March 2015). "EPA debunks 'chemtrails,' further fueling conspiracy theories (+video)". Christian Science Monitor.
- Cama, Timothy (13 March 2015). "EPA confronts 'chemtrails' conspiracy talk". TheHill.
- "The "Chemtrail" Hoax". Air Force. Archived from the original on 2 December 2002. Retrieved 7 May 2010.
- "Weather as a Force Multiplier: Owning the Weather in 2025". Fas.org. 1996. Archived from the original on July 16, 2009.
- "Aircraft Contrails Factsheet" (PDF). United States Environmental Protection Agency. Retrieved 30 August 2008.
- Poladian, Charles (22 July 2013). "CIA Exploring Geoengineering, Ways To Control Weather, To Reverse Globing Warming: Report". International Business Times.
- Thomas, William (Summer 2002). "Stolen Skies: The Chemtrail Mystery". Earth Island Journal. Retrieved 30 August 2008.
- Hamilton, Dan (7 April 2009). "Contrails vs. Chemtrails". Fox12 news at nine. Fox12 Idaho KTRV-TV. Retrieved 11 April 2009.
- Ferrell, Jeff (21 December 2007). "Chemtrails: Is U.S. Gov't. Secretly Testing Americans 'Again'?". Shreveport, LA. Archived from the original on 31 August 2011. Retrieved 28 July 2009.
- Haenggi, Michael (2003). Boeing Widebodies. Zenith Press. p. 15. ISBN 1610607074.
- Benjamin Radford for Discovery. May 1, 2014. Viral Video Claims to Prove 'Chemtrails' Conspiracy
- "The Man Who Tricked Chemtrails Conspiracy Theorists - VICE". Vice. Retrieved 2017-02-06.
- "Chris Bovey - What are they spraying? - Facebook".
- Cairns, Rose (March 2016). "Climates of suspicion: 'chemtrail' conspiracy narratives and the international politics of geoengineering". The Geographical Journal. 182 (1): 70–84. doi:10.1111/geoj.12116. Preprint available here
- "Scientists Just Say No to 'Chemtrails' Conspiracy Theory". nytimes.com. Retrieved 26 August 2016.
- "Chemtrails Conspiracy Theory". David Keith Lab, Harvard. Retrieved 16 December 2016.
- Poladian, Charles (July 22, 2013). "CIA Exploring Geoengineering, Ways To Control Weather, To Reverse Globing Warming: Report". International Business Times. Retrieved March 15, 2014.
- Hodapp, Christopher; von Kannon, Alice (2008). "Conspiracy Theories & Secret Societies for Dummies".
- Perlingieri, Ilya; Dr. Ilya Sandra Perlingieri (11 February 2009). "The Worldwide Environmental Crisis Gone Missing: The Precautionary Principle". Global Research. Retrieved 7 March 2009.
- Mercer, A. M.; Keith, D. W. & Sharp, J. D. (2011). "Public understanding of solar radiation management". Environmental Research Letters. 6 (4): 044006. Bibcode:2011ERL.....6d4006M. doi:10.1088/1748-9326/6/4/044006.
- Tingley, Dustin; Wagner, Gernot (31 October 2017). "Solar geoengineering and the chemtrails conspiracy on social media". Palgrave Communications. 7. doi:10.1057/s41599-017-0014-3. Retrieved 20 December 2017.
- Bill Text - 107th Congress (2001-2002) - THOMAS (Library of Congress)
- "Space Preservation Act of 2001 (2001 - H.R. 2977)".
- "Many Kucinich backers are out there – way out". Cleveland.com. 13 March 2001. Archived from the original on 4 November 2007. Retrieved 26 November 2010.
- Bethel, Brian (1 July 2008). "Abilene man wants to warn you about the dangers of 'chemtrails'". Abilene Reporter-News. Archived from the original on 26 March 2014. Retrieved 20 October 2008.
- "H.R.2977, The Library of Congress". Thomas.loc.gov.
- "H.R.2977, The Library of Congress". Thomas.loc.gov. Retrieved 24 July 2009.
- "A Petition to the Canadian House of Commons: The Government's Response". Response. Holmestead.ca. Retrieved 13 April 2009.
- "37th Parliament, 2nd Sessions Edited Hansard; Number 110 Contents". Publications: Debates: Committees of the House: Petitions: The Environment 1030. Parliament of Canada. 3 June 2003. Retrieved 13 April 2009.
Mr. John Herron (Fundy—Royal, PC): Mr. Speaker, I am presenting a petition on behalf of Mr. Brian Holmes of Ontario regarding aerial spraying. Mr. Holmes has collected signatures from across the country from concerned Canadians who believe that chemicals used in aerial sprayings are adversely affecting the health of Canadians. The petitioners call upon Parliament to stop this type of high altitude spraying. The petition has been duly certified by the clerk and I present it at this time.
- "Points to Ponder: Access to Information Act". Chemtrails - spraying in our sky. Holmestead.ca/. Retrieved 13 April 2009.
- "A Petition to the Canadian House of Commons". Chemtrails - spraying in our sky. Holmestead.ca/. Retrieved 13 April 2009.
- "Elliot Morley, former MP, Scunthorpe - TheyWorkForYou". TheyWorkForYou. Retrieved 2017-04-16.
- "House of Commons Hansard - 8 November 2005: Column 314W-315W". United Kingdom Parliament. 8 November 2005. Retrieved 12 March 2009.
Mr. Morley: The Department is not researching into chemtrails from aircraft as they are not scientifically recognised phenomena.
- Fleming JR (2010). Fixing the Sky: The Checkered History of Weather and Climate Control. Columbia Studies in International and Global History. Columbia University Press. p. 103. ISBN 9780231144131.
- Bowerman, Mary (August 16, 2016). "Scientists disprove airplane 'chemtrail' theory". USA Today.
- Kuhn, P. M. (September 1970). "Airborne Observations of Contrail Effects on the Thermal Radiation Budget". Journal of the Atmospheric Sciences. 27 (6): 937–942. Bibcode:1970JAtS...27..937K. doi:10.1175/1520-0469(1970)027<0937:AOOCEO>2.0.CO;2.
- R.G. Knollenberg (October 1972). "Measurements of the Growth of the Ice Budget in a Persisting Contrail" (PDF). Journal of the Atmospheric Sciences. 29 (7): 1367–1374. Bibcode:1972JAtS...29.1367K. doi:10.1175/1520-0469(1972)029<1367:MOTGOT>2.0.CO;2
- Laakso, A.; Partanen, A. I.; Kokkola, H.; Laaksonen, A.; Lehtinen, K. E. J.; Korhonen, H. (2012). "Stratospheric passenger flights are likely an inefficient geoengineering strategy". Environmental Research Letters. 7 (3): 034021. Bibcode:2012ERL.....7c4021L. doi:10.1088/1748-9326/7/3/034021.
- Berman, Bob (2009). "Applying Occam's razor: problem solving isn't always a clean shave". Astronomy. 37 (9): 14. (subscription required)
- Shearer, Christine; West, Mick; Caldeira, Ken; Davis, Steven J. (1 January 2016). "Quantifying expert consensus against the existence of a secret, large-scale atmospheric spraying program". Environ. Res. Lett. 11 (8): 084011. Bibcode:2016ERL....11h4011S. doi:10.1088/1748-9326/11/8/084011 – via Institute of Physics.
- Fritz, Angela (16 August 2016). "Scientists tell the world: 'Chemtrails' are not real". The Washington Post.
- Talbot, Margaret (30 August 2002). "The H-Word". The Guardian. London.
- "'Chemtrails' not real, say leading atmospheric science experts", Carnegie Institution for Science
- "Lake Oroville Runoff Enhancement Project" Final Report submitted to California Dept. of Water Resources Division of Operations and Maintenance (September 1995); published by US Department of the Interior's Bureau of Reclamation Technical Service Center, River Systems and Meteorology Group.
- Abstract: "Bureau of Reclamation cooperated with California Department of Water Resources to design and implement a snowpack augmentation program to increase runoff to Oroville Reservoir. The program involves collection of data to document physical processes leading to increased precipitation. This report summarizes main results from 3 yr of in-situ physical studies and statistical analysis of precipitation data collected during 87 randomized seeding cases. Liquid propane released from high elevation sites has proven to be a viable, reliable method of seeding wintertime clouds in the Sierra Nevada."
- Media related to Chemtrail conspiracy theory at Wikimedia Commons | <urn:uuid:928e7e3e-d909-4782-ae37-1475f91c0b37> | 2.859375 | 6,173 | Knowledge Article | Science & Tech. | 49.417433 | 95,527,651 |
Ewald summation, named after Paul Peter Ewald, is a method for computing long-range interactions (e.g., electrostatic interactions) in periodic systems. It was first developed as the method for calculating electrostatic energies of ionic crystals, and is now commonly used for calculating long-range interactions in computational chemistry. Ewald summation is a special case of the Poisson summation formula, replacing the summation of interaction energies in real space with an equivalent summation in Fourier space. In this method, the long-range interaction is divided into two parts: a short-range contribution, and a long-range contribution which does not have a singularity. The short-range contribution is calculated in real space, whereas the long-range contribution is calculated using a Fourier transform. The advantage of this method is the rapid convergence of the energy compared with that of a direct summation. This means that the method has high accuracy and reasonable speed when computing long-range interactions, and it is thus the de facto standard method for calculating long-range interactions in periodic systems. The method requires charge neutrality of the molecular system in order to calculate accurately the total Coulombic interaction. A study of the truncation errors introduced in the energy and force calculations of disordered point-charge systems is provided by Kolafa and Perram.
Ewald summation rewrites the interaction potential as the sum of two terms,
where represents the short-range term whose sum quickly converges in real space and represents the long-range term whose sum quickly converges in Fourier (reciprocal) space. The long-ranged part should be finite for all arguments (most notably r = 0) but may have any convenient mathematical form, most typically a Gaussian distribution. The method assumes that the short-range part can be summed easily; hence, the problem becomes the summation of the long-range term. Due to the use of the Fourier sum, the method implicitly assumes that the system under study is infinitely periodic (a sensible assumption for the interiors of crystals). One repeating unit of this hypothetical periodic system is called a unit cell. One such cell is chosen as the "central cell" for reference and the remaining cells are called images.
The long-range interaction energy is the sum of interaction energies between the charges of a central unit cell and all the charges of the lattice. Hence, it can be represented as a double integral over two charge density fields representing the fields of the unit cell and the crystal lattice
where the unit-cell charge density field is a sum over the positions of the charges in the central unit cell
and the total charge density field is the same sum over the unit-cell charges and their periodic images
where the Fourier transform of the lattice function is another sum over delta functions
where the reciprocal space vectors are defined (and cyclic permutations) where is the volume of the central unit cell (if it is geometrically a parallelepiped, which is often but not necessarily the case). Note that both and are real, even functions.
For brevity, define an effective single-particle potential
Since this is also a convolution, the Fourier transformation of the same equation is a product
where the Fourier transform is defined
The energy can now be written as a single field integral
Using Parseval's theorem, the energy can also be summed in Fourier space
where in the final summation.
This is the essential result. Once is calculated, the summation/integration over is straightforward and should converge quickly. The most common reason for lack of convergence is a poorly defined unit cell, which must be charge neutral to avoid infinite sums.
Particle mesh Ewald (PME) method
Ewald summation was developed as a method in theoretical physics, long before the advent of computers. However, the Ewald method has enjoyed widespread use since the 1970s in computer simulations of particle systems, especially those whose particles interact via an inverse square force law such as gravity or electrostatics. Recently, PME has also been used to calculate the part of the Lennard-Jones potential in order to eliminate artifacts due to truncation. Applications include simulations of plasmas, galaxies and molecules.
In the particle mesh method, just as in standard Ewald summation, the generic interaction potential is separated into two terms . The basic idea of particle mesh Ewald summation is to replace the direct summation of interaction energies between point particles
with two summations, a direct sum of the short-ranged potential in real space
(that is the particle part of particle mesh Ewald) and a summation in Fourier space of the long-ranged part
where and represent the Fourier transforms of the potential and the charge density (that's the Ewald part). Since both summations converge quickly in their respective spaces (real and Fourier), they may be truncated with little loss of accuracy and great improvement in required computational time. To evaluate the Fourier transform of the charge density field efficiently, one uses the Fast Fourier transform, which requires that the density field be evaluated on a discrete lattice in space (that's the mesh part).
Due to the periodicity assumption implicit in Ewald summation, applications of the PME method to physical systems require the imposition of periodic symmetry. Thus, the method is best suited to systems that can be simulated as infinite in spatial extent. In molecular dynamics simulations this is normally accomplished by deliberately constructing a charge-neutral unit cell that can be infinitely "tiled" to form images; however, to properly account for the effects of this approximation, these images are reincorporated back into the original simulation cell. The overall effect is called a periodic boundary condition. To visualize this most clearly, think of a unit cube; the upper face is effectively in contact with the lower face, the right with the left face, and the front with the back face. As a result, the unit cell size must be carefully chosen to be large enough to avoid improper motion correlations between two faces "in contact", but still small enough to be computationally feasible. The definition of the cutoff between short- and long-range interactions can also introduce artifacts.
The restriction of the density field to a mesh makes the PME method more efficient for systems with "smooth" variations in density, or continuous potential functions. Localized systems or those with large fluctuations in density may be treated more efficiently with the fast multipole method of Greengard and Rokhlin.
The electrostatic energy of a polar crystal (i.e., a crystal with a net dipole in the unit cell) is conditionally convergent, i.e., depends on the order of the summation. For example, if the dipole-dipole interactions of a central unit cell with unit cells located on an ever-increasing cube, the energy converges to a different value than if the interaction energies had been summed spherically. Roughly speaking, this conditional convergence arises because (1) the number of interacting dipoles on a shell of radius grows like ; (2) the strength of a single dipole-dipole interaction falls like ; and (3) the mathematical summation diverges.
This somewhat surprising result can be reconciled with the finite energy of real crystals because such crystals are not infinite, i.e., have a particular boundary. More specifically, the boundary of a polar crystal has an effective surface charge density on its surface where is the surface normal vector and represents the net dipole moment per volume. The interaction energy of the dipole in a central unit cell with that surface charge density can be written
where and are the net dipole moment and volume of the unit cell, is an infinitesimal area on the crystal surface and is the vector from the central unit cell to the infinitesimal area. This formula results from integrating the energy where represents the infinitesimal electric field generated by an infinitesimal surface charge (Coulomb's law)
The negative sign derives from the definition of , which points towards the charge, not away from it.
- Kolafa, Jiri; Perram, John W. (September 1992). "Cutoff Errors in the Ewald Summation Formulae for Point Charge Systems". Molecular Simulation. 9 (5): 351–368. doi:10.1080/08927029208049126.
- Di Pierro, M.; Elber, R.; Leimkuhler, B. (2015), "A Stochastic Algorithm for the Isobaric-Isothermal Ensemble with Ewald Summations for all Long Range Forces.", Journal of Chemical Theory and Computation, doi:10.1021/acs.jctc.5b00648, PMC .
- Herce, HD; Garcia, AE; Darden, T (28 March 2007). "The electrostatic surface term: (I) periodic systems". The Journal of Chemical Physics. 126 (12): 124106. Bibcode:2007JChPh.126l4106H. doi:10.1063/1.2714527. PMID 17411107.
- J. Chem. Phys. 98, 10089 (1993); doi:10.1063/1.464397
- Ewald, P (1921). "Die Berechnung optischer und elektrostatischer Gitterpotentiale". Ann. Phys. 369 (3): 253–287. Bibcode:1921AnP...369..253E. doi:10.1002/andp.19213690304.
- Darden, T; Perera, L; Li, L; Pedersen, L (1999). "New tricks for modelers from the crystallography toolkit: the particle mesh Ewald algorithm and its use in nucleic acid simulations". Structure. 7 (3): R55–R60. doi:10.1016/S0969-2126(99)80033-1.
- Frenkel, D., & Smit, B. (2001). Understanding molecular simulation: from algorithms to applications, Academic press. | <urn:uuid:97171680-768d-4f42-9ac7-87fcafcfa717> | 2.875 | 2,100 | Knowledge Article | Science & Tech. | 40.680214 | 95,527,652 |
Many scientists have developed models to predict the total number of species on Earth—including those not yet discovered—of an animal or plant group, but University of Chicago researchers have developed the first such model that breaks the number down by region, providing a valuable new tool for biodiversity inventory and analysis.
Using data about marine bivalves, the model estimates the number of undiscovered species living in a region based on the past rates of discovery and description of the species now known from that region. Regions with accelerating rates of discovery get higher projections for the number of species likely to live there, while regions with decreasing rates are likely to contain fewer undiscovered species. These models, broken down by region, take into account inconsistencies and disruptions in discovery efforts, cultural bias, warfare, uneven funding and other irregularities.
The research is described in a paper published in the Early Edition of the Proceedings of the National Academy of Sciences. The model aims to allow comparisons of species richness between regions that can be more useful than global numbers because the more specific and refined results help scientists establish more informed conservation priorities and understand ecological and evolutionary dynamics.
“This is the first time anyone has been able to predict in a robust, quantitative way the number of species that live in a specific region, and then rank those regions,” said David Jablonski, a study co-author and the William R. Kenan Jr. Distinguished Service Professor of Geophysical Sciences. “There's a huge range of biological questions where it helps to have a strong picture of where the most biodiverse places are, and how they compare to the less biodiverse places. We wanted to put some numbers on how reliable the differences among regions are. And would they stack up in the same way 20 or 50 years from now, given past discovery patterns?”
While scientists have described about 1.6 million extinct and living species, some estimate that Earth could be home to 10 or even 100 times as many. The number of undescribed species is “staggering,” Jablonski said, so this new model could help scientists figure out “how the natural world works.”
Living bivalves constitute an ideal starting place for the model because they are widely dispersed and have been well studied over centuries. “Global distribution of bivalves, as well as extensive data on the living species, was critical,” said Stewart Edie, a PhD student in geophysical sciences and lead author of the paper. “Bivalves have a long history of taxonomic study, which allowed us to demonstrate that the model’s predictions are accurate through the many different eras of species discovery.”
For a baseline on marine bivalves, the authors started with the 220 species that Carl Linnaeus—the botanist whose statue overlooks the Midway Plaisance—described in 1758. Linnaeus wrote Systema Naturae, which laid out the classification system for life on Earth that is still used today.
For subsequent numbers, the authors turned to Jablonski’s vast marine bivalve database of 5,744 species, with more than 62,000 records of where they are found. From this information, the researchers were able to establish patterns that they used to estimate the number of species of bivalves that live in 18 different geographic regions. They concluded that for the foreseeable future most of the newly described species would probably come from coastlines in the Indo-West Pacific region, a region that already has a massive level of biodiversity, but has far more to come, according to the model.
Knowing something about the underlying reasons why the history of bivalve discovery looks the way it does allowed the researchers to see how the model, which was built on the general statistical principles of discovery, performed across the pulses of discovery and quiet stretches of no discovery.
“As a result, we have a high level of confidence in the model and will continue to develop it so we can help to fill in gaps in our knowledge of biodiversity,” Edie said. “In the meantime, we can pinpoint which diversity patterns that we are most, and least, confident in—given the data we have on hand right now.”
The model is readily applicable to any biological group, he added. “Nearly all groups, from palm trees to tortoises, have a documented record of where and when their species were discovered. We can run those numbers through the model and predict how their biodiversity status will change, or not, with ongoing discoveries.”
“This is a significant step forward because our model can be used to answer fundamental questions that conservationists and evolutionary biologists have regarding the spatial deployment of biodiversity, worldwide,” Jablonski said.
Next steps will involve revising the model so it can account for more factors that influence discovery and description, such as body size, geographic range size, local abundance, water depth and other factors that make one animal more difficult to detect and collect than another. In addition, the model will be designed to take into account how such factors overlap and interact. | <urn:uuid:90dabecc-a929-427f-a264-29097a0e5b5e> | 4.0625 | 1,053 | News (Org.) | Science & Tech. | 27.254101 | 95,527,713 |
The genome encoding for all information to build an entire organism is made of DNA. This molecule is a very thin thread of about 2 m in length. The DNA has to fit into a cell nucleus with a diameter that is 100.000 times smaller than the length of the DNA. In order to stow and to protect the fragile DNA molecule inside, it is wrapped around molecular spools consisting of proteins.
Microscopic picture displaying the distribution of DNA and RNA in human cells: Cellular DNA (blue) and RNA (green) were stained with specific dyes and visualized by fluorescence microscopy. In control cells containing RNA, the DNA is distributed homogenously within the cell nucleus. After specific RNA depletion (lower panel) the DNA aggregates into compact and inactive higher order structures of chromatin.
Image: University of Regensburg
About 30 millions of such spools, arranged like pearls on a string, are required to package the DNA molecule. The pearls on a string undergo further coiling and compacting to safely store DNA that is called chromatin in its packaged form. However, for cell function and daily use the DNA information of specific genomic regions have to be rendered accessible. Therefore active mechanisms must have evolved to unpackage the genome and allow the readout of the underlying genetic information.Researchers belonging to the groups of the biochemist Gernot Längst from the University of Regensburg and Axel Imhof, a molecular biologist at the LMU in Munich, could now show that small RNA molecules regulate the accessibility and structure of the DNA in chromatin. They identified and characterized snoRNAs (a specific class of RNA molecules) as key regulators of chromatin organisation. In combination with an RNA and chromatin binding protein (the adapterprotein Df31) the RNA binds to specific regions of the genome. This complex interferes with the regular packaging of chromatin and locally decondenses this structure, thereby allowing the readout of the genetic information.
Alexander Schlaak | idw
Scientists uncover the role of a protein in production & survival of myelin-forming cells
19.07.2018 | Advanced Science Research Center, GC/CUNY
NYSCF researchers develop novel bioengineering technique for personalized bone grafts
18.07.2018 | New York Stem Cell Foundation
For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.
To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...
For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.
Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...
Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.
A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...
Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.
"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....
Ultra-short, high-intensity X-ray flashes open the door to the foundations of chemical reactions. Free-electron lasers generate these kinds of pulses, but there is a catch: the pulses vary in duration and energy. An international research team has now presented a solution: Using a ring of 16 detectors and a circularly polarized laser beam, they can determine both factors with attosecond accuracy.
Free-electron lasers (FELs) generate extremely short and intense X-ray flashes. Researchers can use these flashes to resolve structures with diameters on the...
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Diatoms are abundant and important biological components of the marine environment that biosynthesize diverse natural products. These microalgae are rich in various lipids, carotenoids, sterols and isoprenoids, some of them containing toxins and other metabolites. Several groups of diatom natural products have attracted great interest due to their potential practical application as energy sources (biofuel), valuable food constituents, and prospective materials for nanotechnology. In addition, hydrocarbons, which are used in climate reconstruction, polyamines which participate in biomineralization, new apoptotic agents against tumor cells, attractants and deterrents that regulate the biochemical communications between marine species in seawaters have also been isolated from diatoms. However, chemical studies on these microalgae are complicated by difficulties, connected with obtaining their biomass, and the influence of nutrients and contaminators in their environment as well as by seasonal and climatic factors on the biosynthesis of the corresponding natural products. Overall, the number of chemically studied diatoms is lower than that of other algae, but further studies, particularly those connected with improvements in the isolation and structure elucidation technique as well as the genomics of diatoms, promise both to increase the number of studied species with isolated biologically active natural products and to provide a clearer perception of their biosynthesis.
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The coral fungus Clavaria zollingeri in Babcock State Park, West Virginia, USA. The fungi are a separate kingdom of living things, different from animals and plants. Their cell walls contain chitin, unlike the cell walls of plants, which the kingdom of fungi pdf cellulose.
Some of these relationships are so absolutely important that if you took away the fungus, the importance of the distinction between prokaryotes and eukaryotes gradually became apparent. If you toss debris into relatively clean water, the version published in 2009 is shown below. It’s a remarkably sophisticated feat for a small, a review article by Simpson and Roger noted that the Protista were “a grab, can be found just 250 miles from the South Pole in Antarctica. Haeckel had moved the fungi out of Plantae into Protista after his original classification, certain types of cheese need a fungal species to be added.
Their basic mode of life is saprophytic: a fungus breaks down dead organic matter around it, and uses it as food. Fungi reproduce both sexually and asexually. Some fungi grow mushrooms: these are fruiting bodies. Fungi may be single celled or multicellular. Yeast is single-celled, and reproduces either sexually or asexually.
Hyphae look like threads, or rootlets. The mat of hyphae may be very thickly woven. The fungus uses them to extract nutrients. Lichens are a symbiosis between a fungus and an alga or bacterium. In this partnership the algal cells live inside the fungus tissue. The end result is a new mat-like life-form which clings to rock and other surfaces. | <urn:uuid:3e1b22b3-29d2-45de-9793-ea59e75835ca> | 3.4375 | 355 | Knowledge Article | Science & Tech. | 44.958879 | 95,527,728 |
In this page we have NCERT Solutions for Class 10 Maths Chapter 10:Circle for
EXERCISE 1 . Hope you like them and do not forget to like , social share
and comment at the end of the page.
Points to Remember
- The tangent to a circle is a special case of the secant, when the two end points of its corresponding chord coincide.
- The common point of the tangent and the circle is called the point of contact
- The tangent at any point of a circle is perpendicular to the radius through the point of contact
How many tangents can a circle have?
A circle can have infinite tangents.
Fill in the blanks:
(i) A tangent to a circle intersects it in ............... point(s).
(ii) A line intersecting a circle in two points is called a .............
(iii) A circle can have ............... parallel tangents at the most.
(iv) The common point of a tangent to a circle and the circle is called ............
(iv) point of contact
A tangent PQ at a point P of a circle of radius 5 cm meets a line through the centre O at a point Q so that OQ = 12 cm. Length PQ is :
(A) 12 cm
(B) 13 cm
(C) 8.5 cm
(D) √119 cm
We know that the line drawn from the centre of the circle to the tangent is perpendicular to the tangent.
So OP ⊥ PQ
Now By Pythagoras theorem in ΔOPQ,
PQ = √119 cm
(D) is the correct option.
Draw a circle and two lines parallel to a given line such that one is a tangent and the other, a secant to the circle.
AB and XY are two parallel lines where AB is the tangent to the circle at point C while XY is the secant to the circle.
Class 10 Maths
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Meteorites are fragments of extraterrestrial material that fall on the Earth’s surface. Most meteorites are parts of asteroids propelled into Earth-crossing orbits by relatively recent collisions in the asteroid belt, initiated by the gravitational effects of Jupiter’s orbit. Relatively small numbers of meteorites originate from larger objects such as the Moon and Mars. The Earth acquires 102 to 103 t of such material each day, but only 1% or less arrives in pieces large enough for identification and recovery (Dodd, 1981). The surface of the meteorite usually melts and emits a glowing tail and a trail of smoke, but the interior of the meteorite is unaffected by passage through the Earth’s atmosphere and remains at the temperature of interplanetary space.
Collection of meteorites
“Falls” are meteorites that have been observed to fall and were subsequently collected; “finds” are meteorites that were not seen to fall. Before the 1970s, the total number of known meteorites...
KeywordsPolycyclic Aromatic Hydrocarbon Carbonaceous Chondrite Normal Alkane Nonprotein Amino Acid Interstellar Space
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|Natural abundance||1 part per trillion|
|Half-life||5,730 ± 40 years|
|Isotope mass||14.003241 u|
|Decay mode||Decay energy (MeV)|
|Complete table of nuclides|
Carbon-14, 14C, or radiocarbon, is a radioactive isotope of carbon with an atomic nucleus containing 6 protons and 8 neutrons. Its presence in organic materials is the basis of the radiocarbon dating method pioneered by Willard Libby and colleagues (1949) to date archaeological, geological and hydrogeological samples. Carbon-14 was discovered on February 27, 1940, by Martin Kamen and Sam Ruben at the University of California Radiation Laboratory in Berkeley, California. Its existence had been suggested by Franz Kurie in 1934.
There are three naturally occurring isotopes of carbon on Earth: 99% of the carbon is carbon-12, 1% is carbon-13, and carbon-14 occurs in trace amounts, i.e., making up about 1 or 1.5 atoms per 1012 atoms of the carbon in the atmosphere. Carbon-12 and carbon-13 are both stable, while the half-life of carbon-14 is 5,730±40 years. Carbon-14 decays into nitrogen-14 through beta decay. A gram of carbon containing 1 atom of carbon-14 per 1012 atoms will emit ~0.2 beta particles per second. The primary natural source of carbon-14 on Earth is cosmic ray action on nitrogen in the atmosphere, and it is therefore a cosmogenic nuclide. However, open-air nuclear testing between 1955–1980 contributed to this pool.
The different isotopes of carbon do not differ appreciably in their chemical properties. This resemblance is used in chemical and biological research, in a technique called carbon labeling: carbon-14 atoms can be used to replace nonradioactive carbon, in order to trace chemical and biochemical reactions involving carbon atoms from any given organic compound.
- 1 Radioactive decay and detection
- 2 Radiocarbon dating
- 3 Origin
- 4 Occurrence
- 5 See also
- 6 References
- 7 Further reading
- 8 External links
Radioactive decay and detection
Carbon-14 goes through radioactive beta decay:
By emitting an electron and an electron antineutrino, one of the neutrons in the carbon-14 atom decays to a proton and the carbon-14 (half-life of 5700 ± 40 years) decays into the stable (non-radioactive) isotope nitrogen-14.
The emitted beta particles have a maximum energy of 156 keV, while their weighted mean energy is 49 keV. These are relatively low energies; the maximum distance traveled is estimated to be 22 cm in air and 0.27 mm in body tissue. The fraction of the radiation transmitted through the dead skin layer is estimated to be 0.11. Small amounts of carbon-14 are not easily detected by typical Geiger–Müller (G-M) detectors; it is estimated that G-M detectors will not normally detect contamination of less than about 100,000 disintegrations per minute (0.05 µCi). Liquid scintillation counting is the preferred method. The G-M counting efficiency is estimated to be 3%. The half-distance layer in water is 0.05 mm.
Radiocarbon dating is a radiometric dating method that uses (14C) to determine the age of carbonaceous materials up to about 60,000 years old. The technique was developed by Willard Libby and his colleagues in 1949 during his tenure as a professor at the University of Chicago. Libby estimated that the radioactivity of exchangeable carbon-14 would be about 14 disintegrations per minute (dpm) per gram of pure carbon, and this is still used as the activity of the modern radiocarbon standard. In 1960, Libby was awarded the Nobel Prize in chemistry for this work.
One of the frequent uses of the technique is to date organic remains from archaeological sites. Plants fix atmospheric carbon during photosynthesis, so the level of 14C in plants and animals when they die approximately equals the level of 14C in the atmosphere at that time. However, it decreases thereafter from radioactive decay, allowing the date of death or fixation to be estimated. The initial 14C level for the calculation can either be estimated, or else directly compared with known year-by-year data from tree-ring data (dendrochronology) up to 10,000 years ago (using overlapping data from live and dead trees in a given area), or else from cave deposits (speleothems), back to about 45,000 years before the present. A calculation or (more accurately) a direct comparison of carbon-14 levels in a sample, with tree ring or cave-deposit carbon-14 levels of a known age, then gives the wood or animal sample age-since-formation.
Natural production in the atmosphere
Carbon-14 is produced in the upper layers of the troposphere and the stratosphere by thermal neutrons absorbed by nitrogen atoms. When cosmic rays enter the atmosphere, they undergo various transformations, including the production of neutrons. The resulting neutrons (1n) participate in the following reaction:
- n + 14
The highest rate of carbon-14 production takes place at altitudes of 9 to 15 km (30,000 to 49,000 ft) and at high geomagnetic latitudes.
The rate of 14C production can be modelled and is between 16,400 and 18,800 atoms 14C m−2s−1, which agrees with the global carbon budget that can be used to backtrack, but attempts to directly measure the production rate in situ were not very successful. Production rates vary because of changes to the cosmic ray flux caused by the heliospheric modulation (solar wind and solar magnetic field), and due to variations in the Earth's magnetic field. The latter can create significant variations in 14C production rates, although the changes of the carbon cycle can make these effects difficult to tease out. Occasional spikes may occur; for example, there is evidence for an unusually strong increase of the production rate in AD 774–775, caused by an extreme solar energetic particle event, strongest for the last ten millennia. Another "extraordinarily large" 14C increase (20‰) has been recently (2017) associated with the 5480 BC event, which is however unlikely to be a solar energetic particle event.
Other carbon-14 sources
Carbon-14 can also be produced by other neutron reactions, including in particular 13C(n,γ)14C and 17O(n,α)14C with thermal neutrons, and 15N(n,d)14C and 16O(n,3He)14C with fast neutrons. The most notable routes for 14C production by thermal neutron irradiation of targets (e.g., in a nuclear reactor) are summarized in the table.
|Parent isotope||Natural abundance, %||Cross section for thermal neutron capture, b||Reaction|
Formation during nuclear tests
The above-ground nuclear tests that occurred in several countries between 1955 and 1980 (see nuclear test list) dramatically increased the amount of carbon-14 in the atmosphere and subsequently in the biosphere; after the tests ended, the atmospheric concentration of the isotope began to decrease.
One side-effect of the change in atmospheric carbon-14 is that this has enabled some options (e.g., bomb-pulse dating) for determining the birth year of an individual, in particular, the amount of carbon-14 in tooth enamel, or the carbon-14 concentration in the lens of the eye.
Emissions from nuclear power plants
Carbon-14 is produced in coolant at boiling water reactors (BWRs) and pressurized water reactors (PWRs). It is typically released to the atmosphere in the form of carbon dioxide at BWRs, and methane at PWRs. Best practice for nuclear power plant operator management of carbon-14 includes releasing it at night, when plants are not photosynthesizing.
Dispersion in the environment
After production in the upper atmosphere, the carbon-14 atoms react rapidly to form mostly (about 93%) 14CO (carbon monoxide), which subsequently oxidizes at a slower rate to form 14CO2, radioactive carbon dioxide. The gas mixes rapidly and becomes evenly distributed throughout the atmosphere (the mixing timescale in the order of weeks). Carbon dioxide also dissolves in water and thus permeates the oceans, but at a slower rate. The atmospheric half-life for removal of 14CO2 has been estimated to be roughly 12 to 16 years in the northern hemisphere. The transfer between the ocean shallow layer and the large reservoir of bicarbonates in the ocean depths occurs at a limited rate. In 2009 the activity of 14C was 238 Bq per kg carbon of fresh terrestrial biomatter, close to the values before atmospheric nuclear testing (226 Bq/kg C; 1950).
- Global inventory: ~8500 PBq (about 50 t)
- Atmosphere: 140 PBq (840 kg)
- Terrestrial materials: the balance
- From nuclear testing (till 1990): 220 PBq (1.3 t)
In fossil fuels
Many man-made chemicals are derived from fossil fuels (such as petroleum or coal) in which 14C is greatly depleted. 14CO2--or rather, its relative absence—is therefore used to determine the relative contribution (or mixing ratio) of fossil fuel oxidation to the total carbon dioxide in a given region of the Earth's atmosphere.
Dating a specific sample of fossilized carbonaceous material is more complicated. Such deposits often contain trace amounts of carbon-14. These amounts can vary significantly between samples, ranging up to 1% of the ratio found in living organisms, a concentration comparable to an apparent age of 40,000. This may indicate possible contamination by small amounts of bacteria, underground sources of radiation causing the 14N(n,p) 14C reaction, direct uranium decay (although reported measured ratios of 14C/U in uranium-bearing ores would imply roughly 1 uranium atom for every two carbon atoms in order to cause the 14C/12C ratio, measured to be on the order of 10−15), or other unknown secondary sources of carbon-14 production. The presence of carbon-14 in the isotopic signature of a sample of carbonaceous material possibly indicates its contamination by biogenic sources or the decay of radioactive material in surrounding geologic strata. In connection with building the Borexino solar neutrino observatory, petroleum feedstock (for synthesizing the primary scintillant) was obtained with low 14C content. In the Borexino Counting Test Facility, a 14C/12C ratio of 1.94×10−18 was determined; probable reactions responsible for varied levels of 14C in different petroleum reservoirs, and the lower 14C levels in methane, have been discussed by Bonvicini et al.
In the human body
Since many sources of human food are ultimately derived from terrestrial plants, the carbon that comprises our bodies contains carbon-14 at almost the same concentration as the atmosphere. The rates of disintegration of potassium-40 and carbon-14 in the normal adult body are comparable (a few thousand disintegrated nuclei per second). The beta-decays from external (environmental) radiocarbon contribute approximately 0.01 mSv/year (1 mrem/year) to each person's dose of ionizing radiation. This is small compared to the doses from potassium-40 (0.39 mSv/year) and radon (variable).
Carbon-14 can be used as a radioactive tracer in medicine. In the initial variant of the urea breath test, a diagnostic test for Helicobacter pylori, urea labeled with approximately 37 kBq (1.0 μCi) carbon-14 is fed to a patient (i.e., 37,000 decays per second). In the event of a H. pylori infection, the bacterial urease enzyme breaks down the urea into ammonia and radioactively-labeled carbon dioxide, which can be detected by low-level counting of the patient's breath. The 14C urea breath test has been largely replaced by the 13C urea breath test, which has no radiation issues.
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All other atmospheric carbon dioxide comes from young sources–namely land-use changes (for example, cutting down a forest in order to create a farm) and exchange with the ocean and terrestrial biosphere. This makes 14C an ideal tracer of carbon dioxide coming from the combustion of fossil fuels. Scientists can use 14C measurements to determine the age of carbon dioxide collected in air samples, and from this can calculate what proportion of the carbon dioxide in the sample comes from fossil fuels.
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- Bonvicini, G, Harris, N and Paolone, V, "The chemical history of 14C in deep oilfields", August 2003. (arXiv:hep-ex/0308025)
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- Kamen, Martin D. (1985). Radiant Science, Dark Politics: A Memoir of the Nuclear Age. Berkeley: University of California Press. ISBN 0-520-04929-2.
|Carbon-14 is an
isotope of carbon
|Decay product of:
|Decays to: | | <urn:uuid:b64d42be-df10-4c3e-834e-4fe97dcb252a> | 3.578125 | 5,440 | Knowledge Article | Science & Tech. | 68.475517 | 95,527,803 |
Images from the Gates research group
These panels show the localization of actin filaments (red) and nuclei (blue) during the process of border cell migration during Drosophila oogenesis. One of the major functions of the follicle cells is to produce the eggshell that will surround and protect the mature egg. The border cells are a subset of follicle cells that will contribute to the anterior-most portion of the eggshell (A, arrow). Partway through oogenesis the border cells break away from the follicle cell layer and migrate as a small group to the border between the nurse cells and the oocyte. This migration is delayed when border cells have reduced levels of a potential regulator of the actin binding protein Ena (B, *). Egg chambers shown are of a similar stage. Images taken by Lindsay Regruto '12. | <urn:uuid:aa6d3a01-4672-4dec-8981-8887da3fa021> | 3.609375 | 174 | Truncated | Science & Tech. | 45.285588 | 95,527,807 |
Feat probes light-matter interplay, phenomena of potential technological interest
Light and matter are typically viewed as distinct entities that follow their own, unique rules. Matter has mass and typically exhibits interactions with other matter, while light is massless and does not interact with itself. Yet, wave-particle duality tells us that matter and light both act sometimes like particles, and sometimes like waves.
These three false-color images represent the quantum Hall state that University of Chicago physicists created by shining infrared laser light at specially configured mirrors. Achieving this state with light instead of matter was an important step in developing computing and other applications from quantum phenomena. In this quantum Hall state, particles of light mimic the orbital action of electrons in more standard experiments that involve powerful magnetic fields and ultra-cold conditions of near absolute zero (minus 459.6 degrees Fahrenheit).
Credit: Nathan Schine, Albert Ryou, Andrey Gromov, Ariel Sommer, and Jonathan Simon
Harnessing the shared wave nature of light and matter, researchers at the University of Chicago led by Neubauer Family Assistant Professor of Physics Jonathan Simon have used light to explore some of the most intriguing questions in the quantum mechanics of materials. The topic encompasses complex and non-intuitive phenomena that are often difficult to explain in non-technical language, but which carry important implications to specialists in the field.
In work published online June 6, 2016, in the journal Nature, Simon's group presents new experimental observations of a quantum Hall material near a singularity of curvature in space.
Quantum effects give rise to some of the most useful and promising properties of materials: they define standard units of measurement, give rise to superconductivity, and describe quantum computers. The quantum hall materials are one prominent example in which electrons are trapped in non-conducting circular orbits except at the edges of the material. There, electrons exhibit quantized resistance-free electrical conduction that is immune to disorder such as material impurities or surface defects.
Furthermore, electrons in quantum Hall materials do not transmit sound waves but instead have particle-like excitations, some of which are unlike any other particles ever discovered. Some of these materials also exhibit simultaneous quantum entanglement between millions of electrons, meaning that the electrons are so interconnected, the state of one instantly influences the state of all others. This combination of properties makes quantum Hall materials a promising platform for future quantum computation.
Researchers worldwide have spent the past 35 years delving into the mysteries of quantum Hall materials, but always in the same fundamental way. They use superconducting magnets to make very powerful magnetic fields and refrigerators to cool electronic samples to thousandths of a degree above absolute zero.
In a new approach, Simon and his team demonstrated the creation of a quantum Hall material made up of light. "Using really good mirrors that are pointed at each other, we can trap light for a long time while it bounces back and forth many thousands of times between the mirrors," explained graduate student Nathan Schine.
In the UChicago experiment, photons travel back and forth between mirrors, while their side-to-side motion mimics the behavior of massive particles like electrons. To emulate a strong magnetic field, the researchers created a non-planar arrangement of four mirrors that makes the light twist as it completes a round trip. The twisting motion causes the photons to move like charged particles in a magnetic field, even though there is no actual magnet present.
"We make the photons spin, which leads to a force that has the same effect as a magnetic field," explained Schine. While the light is trapped, it behaves like the electrons in a quantum Hall material.
First, Simon's group demonstrated that they had a quantum Hall material of light. To do so, they shined infrared laser light at the mirrors. By varying the laser's frequency, Simon's team could map out precisely at which frequencies the laser was transmitted through the mirrors. These transmission frequencies, along with camera images of the transmitted light, gave a telltale signature of a quantum Hall state.
Next, the researchers took advantage of the precise control that advanced optical systems provide to place the photons in curved space, which has not been possible so far with electrons. In particular, they made the photons behave as if they resided on the surface of a cone.
...near a singularity
"We created a cone for light much like you might do by cutting a wedge of paper and taping the edges together," said postdoctoral fellow Ariel Sommer, also a co-author of the paper. "In this case, we imposed a three-fold symmetry on our light, which essentially divides the plane into three wedges and forces the light to repeat itself on each wedge."
The tip of a cone has infinite curvature--the singularity--so the researchers were able to study the effect of strong spatial curvature in a quantum Hall material. They observed that photons accumulated at the cone tip, confirming a previously untested theory of the quantum Hall effect in curved space.
Despite 20 years of interest, this is the first time an experiment has observed the behavior of quantum materials in curved space. "We are beginning to make our photons interact with each other," said Schine. "This opens up many possibilities, such as making crystalline or exotic quantum liquid states of light. We can then see how they respond to spatial curvature."
The researchers say this could be useful for characterizing a certain type of quantum computer that is built of quantum Hall materials.
"While quantum Hall materials were discovered in the eighties, they continue to reveal their fascinating secrets to this day," said Simon. "The final frontier is exploring the interplay of these beautiful materials with the curvature of space. That is what we've begun to explore with our photons."
Steve Koppes | EurekAlert!
Machine-learning predicted a superhard and high-energy-density tungsten nitride
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In borophene, boundaries are no barrier
17.07.2018 | Rice University
For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.
To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...
For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.
Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...
Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.
A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...
Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.
"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....
Ultra-short, high-intensity X-ray flashes open the door to the foundations of chemical reactions. Free-electron lasers generate these kinds of pulses, but there is a catch: the pulses vary in duration and energy. An international research team has now presented a solution: Using a ring of 16 detectors and a circularly polarized laser beam, they can determine both factors with attosecond accuracy.
Free-electron lasers (FELs) generate extremely short and intense X-ray flashes. Researchers can use these flashes to resolve structures with diameters on the...
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18.07.2018 | Health and Medicine | <urn:uuid:7dd2d985-944a-41c2-9b47-76abf23428d4> | 3.453125 | 1,818 | Content Listing | Science & Tech. | 35.603513 | 95,527,819 |
Laravel Eloquent Relationships Tutorial From ScratchBy Hardik Savani | July 7, 2018 | | 1785 Viewer | Category : PHP Laravel
ORM stands for Object-relational mapping. Laravel introduce ORM from Laravel 5 framework version. We used and see the foreign key for database relationship. but in this relation laravel created relationships between model.
As we know database table is almost related to another database table. but when you are working on retrieve data, create data or etc task. you have to use a join or something on every SQL query. So it takes time and also we have to write lots of database query. But in laravel Eloquent Model Relationship we can easily make in relation by using their types.
Why we should use laravel model relationship, So I want to give one example for this. If you have a "users" table and also you have "user_addresses" table. both tables are connected with each other using a foreign key. There are several records in users table and also more records in your address table. If you didn't use laravel eloquent relationship then you can get all address using "join" like as below:
Basic Model Query:
$userAddresses = User::select("users.*", "user_addresses.*")
->join("user_addresses", "user_addresses.id_user", "=", "users.id")
As you can above laravel query, you have to write long query, right now it is not big, but when you have more tables connected with users table then it can be more complected, so if we use laravel Relationship then you can do it just simple and you don't require to write every time join and anything, laravel will manage it. So you can write this way:
Model Query Using Relationship:
$userAddresses = User::find(1);
As you can see how it is simple, so i can say, we have to use laravel relationship.
In this tutorial, i will explain every types with how to insert data with relation model and how to get records from database table using model. i will also give example with table migration, model, retrieve and create new records. You have to just read and you will understand how it is working on all types of relationships in laravel. You can easily use order by, filter, where condition, delete, create, update, group by, get all, get count, save etc laravel methods.
Now as bellow i listed all laravel model relationships types and you can click on it and read in details of each types.
*** Click On it and Read in Details of RelationShip types:
I hope you found your best tutorials. | <urn:uuid:fc88b0eb-1bb6-4245-9cd8-6387d2021be6> | 2.84375 | 585 | Tutorial | Software Dev. | 43.747286 | 95,527,836 |
The old adage tells that oil doesn't mix with water. It doesn't do much for creatures in the water either, as demonstrated by new research on the effects of water-borne oil on seabirds along the Atlantic Coast in Brazil, Uruguay and Argentina.
Chronic oil pollution has been a long-standing problem along a 4,200-mile stretch of coast from southern Brazil to northern Argentina. Existing laws are not solving the problem, said University of Washington biologist Dee Boersma, co-author of a paper detailing how the oil pollution is affecting Magellanic penguins, appearing in the February edition of the Marine Pollution Bulletin, published by Elsevier.
The negative effects of oil on penguins could be a barometer for less-hardy species, she said.
"There are a lot of groups rehabilitating oiled birds, some for more than two decades, and that says that for more than 20 years there's been a big problem along this part of the South American coastline," Boersma said. "That's the prime wintering grounds for Magellanic penguins."
Unlike a major oil spill that causes problems for a time and can be cleaned up, chronic oil pollution is continuous and hard to track or clean up because it comes bit by bit, sometimes in ballast water from passing ships, sometimes in seepage from offshore oil rigs.
To gauge the scope of the problem, Boersma and fellow Wildlife Conservation Society scientist Pablo García-Borboroglu of the Argentine research center Centro Nacional Patagónico assembled a team to see how many organized groups are working to save oiled seabirds along the coast from central Argentina to central Brazil. The scientists found there were 19 groups dedicated to rehabilitating oiled seabirds, three that survey beaches looking for oiled birds and four groups that do both.
Boersma said the research team expected to find only four or five groups dealing with oiled birds and was surprised to encounter so many. The groups are not evenly distributed along the coast but are clustered near ports, oil terminals and offshore oil-drilling platforms.
The scientists found that the most commonly treated living birds were Magellanic penguins, which made up nearly 64 percent of the seabirds rehabilitated by the groups from 1995 to 2005. Live oiled penguins were most common in northern Argentina and less common farther north, along the coasts of Uruguay and Brazil. That finding correlates with Argentina's oil exportation, which grew rapidly in the 1990s.
But while oil pumping and loading take place only at specific places in northern Argentine waters, oiled penguins are found all along that coastline, leading researchers to wonder how the birds became oiled in areas where there is not petroleum activity.
Previous research estimated that 40,000 Magellanic penguins were killed by chronic oil pollution off the coast of Chubut Province in Argentina each year from 1982 to 1991. In 1994, oil tanker shipping lanes were moved 60 miles farther off the coast and few penguins are now found dead from petroleum along that coast.
But oil remains an issue because, as Boersma noted, Magellanic penguins can swim 60 miles a day and on foraging trips during breeding season they can swim hundreds of miles without coming ashore. Their physical condition can deteriorate quickly if they run afoul of oil in the water. She likened a healthy penguin that gets lightly oiled to a diver in a wet suit with just a few holes - there's not much difficulty and the swimmer can keep going. But heavy oil ruins the bird's insulation, like a wet suit with lots of holes, and the swimmer wants to get out of the water immediately.
"We know when penguins get heavily oiled they tend to seek the shore because that's their thermal neutral zone," Boersma said. "But when they are on shore they can't feed and so they starve to death."
Magellanic penguins are hardy creatures that can survive for as long as a month without food during courtship and egg incubation. But among long-lived seabirds such as penguins, which reach maturity late and lay small numbers of eggs, even a small decrease in adult survival can cause overall populations to decline. Northern Argentina had more oiled penguins than other areas studied, and that also was where the largest concentration of adult birds was found, which suggests that chronic oil pollution there could be reducing the adult population, Boersma said.
In addition, even a small amount of oil reduces penguins' reproductive success. Female penguins lay two eggs per breeding season and the male and female take turns sitting on the nest while the other goes to sea foraging for small fish. A penguin that becomes oiled might not be in any condition to return to the nesting grounds to change places with its partner. The remaining adult could be forced to abandon the nest to find food.
Because the sources of chronic oil pollution are not obvious, Boersma said, the birds could be getting oiled as far as 900 miles away from their nesting grounds along the Argentine coast.
"It's been going on for decades and it's having a long-term negative effect on wildlife," Boersma said. "Penguins can live a long time with oil, but that's not true of most seabirds. Our findings appear to be just the tip of the iceberg."
Other authors are Valeria Ruoppolo and Rudolfo Pinho da Silva of the International Fund for Animal Welfare Emergency Relief Team, Laura Reyes of Universidad Nacional de la Patagonia in Argentina, Ginger Rebstock of the UW, Karen Griot of Fundación Mar del Plata Aquarium in Argentina, Sergio Rodrigues Heredia of Fundación Mundo Marino in Argentina, and Andrea Corrado Adornes of Centro de Recuperacão de Animais Marinhos in Brazil.
The work was funded by the Wildlife Conservation Society, the Wadsworth Endowment for Conservation Science, Friends of the Penguins, Centro Nacional Patagónico and the University of Washington.
For more information, contact Boersma at (206) 616-2185, (206) 616-4054 or firstname.lastname@example.org | <urn:uuid:625ae0fd-4785-4668-855f-baabe243ea51> | 3.53125 | 1,300 | Knowledge Article | Science & Tech. | 41.110276 | 95,527,846 |
Group: VII: Halogens, Halides and Chlorine
Edited by Jamie (ScienceAid Editor), Taylor (ScienceAid Editor), SmartyPants, MaxScience
Properties of Halogens
- 1The electronegativity of halogens decrease down the group. Fluorine is very reactive and is the most electronegative element.Electronegativity.Advertisement
- 2A further physical property is the halogen's boiling point, which increase down Group 7. This is because the atoms get bigger and so the Van der Waals forces get larger as well.Boiling Point.
- 3And now a chemical property. The oxidizing power of the halogens decreases from Fluorine to Iodine. This property can be demonstrated by displacement reactions.This means if halogen ions are dissolved in water. If a halogen higher up the group is added; this higher halogen will replace it. For example, when chlorine is added to Br-(aq), the following reaction takes place.Oxidization.
2Br-(aq) + Cl2 ® 2Cl-(aq) + Br2
A halide is simply the ion of a halogen. Their ability to reduce increases down the group from F to I. This ability is shown in the reactions of NaX (where X is a halogen) with sulphuric acid, or as chemists like to call it: H2SO4. The table below shows the results of the reactions of NaX with sulphuric acid.
|Bromine|| Steamy fume
Colourless gas Brown fumes
|Iodine|| Steamy fumes
Colourless gas Yellow solid Rotten eggs smell A black solid a purple fumes
SO2 S H2S I2
What this demonstrates is that more products are formed with the sodium halides further down the group, therefore reducing the ability of these halides is greater at the bottom of the group.
How to Test for Halides
Now - how to test for the presence of the different halides. A classic test is to add silver nitrate, and it produces a precipitate of different colors depending on the halide. However, as you can see below, the difference in color is not very distinct. Therefore, we add another substance: ammonia. First, a few drops of dilute ammonia are added to the precipitate to see how much it dissolves. Chlorine will dissolve quite well. Bromine will dissolve sparingly and Iodine not at all. Then we add concentrated ammonia and the precipitate in both the chloride and bromide solutions will dissolve and the iodide precipitate turns white. The diagram below outlines this testing procedure.
The ionic equation for this reaction is as follows (using Br as the halide).
Cl-(aq) + Ag+(aq) ® AgCl(s)
Halogens will react with metals to form salts. For example, if chlorine gas is passed over a heated iron wire, you will see a brown solid upon cooling.
iron + chlorine ® iron (III) chloride 2Fe(s) + 3Cl2 (g) ® 2FeCl2 (s)
The most reactive halogen is fluorine, and they become less reactive as you go down. Due to this, a more reactive halogen will displace a less reactive one. For example, when chlorine gas is bubbled through potassium bromide solution...
2KBr(aq) + Cl2 (g) ® 2KCl (aq) + Br2 (aq)
Chlorine and Chlorides
Chlorine has a very interesting reaction with water. It's a reversible reaction and also shows something called disproportionation [dis-pro-por-shon-ay-shon].
Disproportionation defines a reaction where one species (in this case chlorine) is simultaneously oxidized and reduced. If you have a look at chlorine in HCl, it has an [chemistry/physical/redox.html|oxidation number] of -1 and in hydrogen chlorate. This reaction has been used in water treatment to destroy bacteria, however this practice has been replaced by granular calcium hypochlorite Ca(ClO)2 which is less dangerous.
Another reaction we are going to look at is chlorine with cold, dilute sodium hydroxide (NaOH). This causes the following reaction to take place.
Cl2 + 2OH- ® Cl- + ClO- + H2O
This reaction is very important because it is used commercially to produce bleach!
Questions and Answers
I read that fluorine is the most reactive but I thought it was the least?
Small atom so electrons closer to nucleus- doesn't that mean it's less reactive??
- The reason Fluorine is the (most) reactive is that it's at the top of the Halogen group or 2nd to the right on the periodic table. The higher an element is, the more reactive it is.
- Outer shells that orbit the nucleus lack electrons which makes them enthusiastically grab electrons. Fluorine is a massively reactive element, is nonmetal and halogen, it's atomic weight is 18.9984032, it's atomic number is 9 and contains 10 neurons in the nucleus.
Referencing this Article
If you need to reference this article in your work, you can copy-paste the following depending on your required format:
APA (American Psychological Association)
Group: VII: Halogens, Halides and Chlorine. (2017). In ScienceAid. Retrieved Jul 22, 2018, from https://scienceaid.net/chemistry/inorganic/halogens.html
MLA (Modern Language Association) "Group: VII: Halogens, Halides and Chlorine." ScienceAid, scienceaid.net/chemistry/inorganic/halogens.html Accessed 22 Jul 2018.
Chicago / Turabian ScienceAid.net. "Group: VII: Halogens, Halides and Chlorine." Accessed Jul 22, 2018. https://scienceaid.net/chemistry/inorganic/halogens.html.
Categories : Inorganic
Recent edits by: SmartyPants, Taylor (ScienceAid Editor), Jamie (ScienceAid Editor) | <urn:uuid:0d6778e6-a7ee-407c-8f49-b456aa85c44d> | 3.5 | 1,305 | Knowledge Article | Science & Tech. | 49.32512 | 95,527,862 |
The cloudscape threw us a curveball on June 20 when donut-shaped clouds wafted over the Inland Northwest. The unusual display prompted citizen observers to snap photographs and the Spokane office of the National Weather Service to post an explanation with satellite images on social media.
What people witnessed that morning were cavums, or “hole punch clouds” until the World Meteorological Organization officially recognized them with a Latin name less than four months ago.
Cavums are distinguished by circular – and sometimes cigar-shaped – gaps within waferlike cloud layers. And though we’re still learning about the exact atmospheric conditions that shape them, recent studies conclude that aircraft are largely responsible.
Picture a low-altitude jet flying through a thin cloud layer made of super-cooled water molecules. This disturbance causes the water droplets to freeze into ice crystals that fall from the sky like snow, leaving a void in the thin cloud blanket.
In a 2010 study led by Andrew Heymsfield of the National Center for Atmospheric Research, scientists found that commercial and private aircraft, military jets and turbo props all produce holes in certain types of clouds. What’s more, the size of the opening grows for hours.
If a plane climbs through the cloud layer, a hole is punched. If it flies more level to the cloud, an oblong, cigar shape is formed, researchers observed.
For several hours in June, wispy clouds over the Inland Northwest were pocketed with holes and cigar shapes. Most likely, cirrocumulus and altocumulus clouds were abundant that morning, setting up the right conditions for cavums to form along paths of low-altitude aircraft.
Nic Loyd is a meteorologist with Washington State University’s AgWeatherNet. Linda Weiford is a WSU news writer and weather geek. Contact: email@example.com or firstname.lastname@example.org. | <urn:uuid:c11df068-4e5b-432f-bf51-52ccdc1634e8> | 3.1875 | 406 | News Article | Science & Tech. | 41.630684 | 95,527,887 |
Sporulation in the mold Neurospora crassa can proceed along three very different pathways, leading to the production of three types of spores. Two asexual sporulation pathways that lead to the formation of macroconidia and microconidia involve budding from hyphae by two different mechanisms. A much more complex sexual reproductive pathway involves the formation of a fruiting body called a perithecium, in which meiosis takes place and ascospores are formed in sac-like cells called asci. Numerous mutations exist that affect these developmental pathways and genes have been isolated that are expressed preferentially during sporulation. The Neurospora sporulation pathways offer a simple system with which to study mechanisms and regulation of development that are usually obscured by complex cell-cell interactions involved in animal and plant development.
Mendeley saves you time finding and organizing research
Choose a citation style from the tabs below | <urn:uuid:797109cd-e0f9-4b6c-8196-bf6de0bfb60d> | 3.515625 | 182 | Academic Writing | Science & Tech. | 5.234352 | 95,527,937 |
(Schaeffer, 1916) Schaeffer, 1926
Polychaos dubium is a freshwater amoeboid and one of the larger species of single-celled eukaryote. Like other amoebozoans, P. dubium moves by means of temporary projections called pseudopods. P. dubium reportedly has one of the largest genome size of any organism known, though the authors of a 2004 study suggest treating that measurement with caution.
Polychaos dubium was previously known as Amoeba dubia. The author who named the species later recognized it as different from species of Amoeba, and so designated it the type species of the genus Polychaos. Unlike species of Amoeba, P. dubium lacks longitudinal ridges on its pseudopods.
A few characteristics distinguish Polychaos dubium from other species of Polychaos. The crystals floating in its cytoplasm take the shape of flat bipyramids, flat plates, or clustered platelets. The nucleus is ellipsoid in shape, has granules next to the membrane, and lacks an endosome. The cell is usually polypodal (has many pseudopodia), and the endoplasm and ectoplasm of the cytoplasm are clear. During rapid locomotion, P. dubium may become monopodial (present only one pseudopod), but there are an average of 12 pseudopodia.
Polychaos dubium has one of the largest genomes known for any organism, consisting of 670 billion base pairs or 670 Gbp, which is over 200 times larger than the human genome (3.2 Gbp). The authors of one 2004 study, however, suggest treating that measurement with caution, because it was taken before the advent of modern genomic methods.
Ecology and range
- Schaeffer, Asa Arthur (1926a). "Taxonomy of the amebas, with descriptions of thirty-nine new marine and freshwater species". Papers from the Department of Marine Biology of the Carnegie Institution of Washington. 24: 115 pp. 12 plates.
- Schaeffer, Asa A. (1916). "Notes on the specific and other characters of Amoeba proteusPall. (Leidy), A. discoides spec. nov., and A. dubia spec. nov". Archiv für Protistenkunde. 37: 204–228.
- Laura Wegener Parfrey; et al. (2008). "The Dynamic Nature of Eukaryotic Genomes". Molecular Biology and Evolution. 25: 787–794. doi:10.1093/molbev/msn032. PMC . PMID 18258610.
- McGrath, Casey, L, & Katz, Laura A. (2004). "Genome diversity in microbial eukaryotes". Trends in Ecology & Evolution. 19 (1): 32–38. doi:10.1016/j.tree.2003.10.007. PMID 16701223.
- Lee, J.J., Hutner, S.H. & Bovee, E.C., eds. (1985). Illustrated Guide to the Protozoa. Lawrence, Kansas: Society of Protozoologists. pp. ix + 630 pages.
- "Polychaos dubium". micro*scope - version 6.0. Archived from the original on 2010-07-25. Retrieved 2009-10-01.
- "Polychaos dubium". Protist Information Server. Retrieved 2009-10-01.
- "Polychaos dubium". Amoebae on the Web. Retrieved 2009-10-01.
- Leidy, Joseph (1878). "Amoeba proteus". The American Naturalist. 12 (4): 235–238. doi:10.1086/272082. | <urn:uuid:c4fde402-d377-4e87-b56d-76324ff43977> | 3.09375 | 820 | Knowledge Article | Science & Tech. | 62.19872 | 95,527,962 |
Impact of North Korean nuclear weapons test on 3 September, 2017 on inland China traced by 14C and 129I
Environmental impact of North Korea nuclear weapons testing on 3 Sept, 2017, is of key concern. In order to investigate whether there is radioactive leakage and whether it can be transported to inland China, 14C and 129I are determined in aerosol samples collected in a Chinese inland city before and after the test. Aerosol Δ14C values before and after the test do not show any significant difference. In contrast, a four-fold increase of 129I/127I ratios was found after the test. The possible sources of 129I in these atmospheric samples and the impact of the North Korea nuclear test are discussed.
KeywordsNorth Korea underground nuclear weapons test 14C 129I Environmental impact Aerosol
This work was supported by the National Natural Science Foundation of China (Nos. 11605207 and 91643206), the Technology Foundation for Selected Overseas Chinese Scholar, Department of Human Resources and Social Security of Shaanxi Province, China, and the Ministry of Science and Technology of China (No. 2015FY110800).
- 1.Wen L (2017) University of Science and Technology of China accurately determines the location and yield of North Korea underground nuclear detonation on September 3 2017. http://seis.ustc.edu.cn/2017/0903/c10094a191087/page.htm?from=timeline&isappinstalled=0. Accessed 27 Oct 2017 (in Chinese)
- 2.Zhao L, Xie X, He X, Zhao X, Yao Z (2017) Preliminary investigations on the seismic identification, depth and yield estimate of North Korea underground nuclear test on September 3, 2017. http://www.igg.cas.cn/xwzx/kyjz/201709/t20170904_4854427.html. Accessed 27 Oct 2017 (in Chinese)
- 3.Ministry of Environmental Protection of the People’s Republic of China (2017) Environmental radiation monitoring results of the sixth North Korean nuclear test in the northeast border and surrounding areas. http://www.zhb.gov.cn/gkml/. Accessed 3 Nov 2017
- 4.The Nuclear Regulation Authority of Japan (2017) Estimated and measured 1 m height environmental radioactivity level at monitoring posts in 47 prefectures all over Japan. http://www.nsr.go.jp/english/. Accessed 3 Nov 2017
- 11.Zhou WJ et al (2010) Preliminary study of radioisotope 129I application in China using Xi’an accelerator mass spectrometer. ICNS News 25:8–23Google Scholar
- 17.Toyama C, Muramatsu Y, Igarashi Y, Aoyama M, Matsuzaki H (2013) Atmospheric fallout of 129I in Japan before the Fukushima accident: regional and global contributions (1963–2005). Environ Sci Technol 47:8383–8390Google Scholar
- 20.Persio SL (2017) North Korean soldiers are being treated for radiation exposure after nuclear test: report newsweek. http://www.newsweek.com/north-korean-soldiers-being-treated-radiation-exposure-after-nuclear-test-698246. Accessed 27 Nov 2017
- 21.Draxler RR, Rolph GD (2003) HYSPLIT (HYbrid SingleParticle Lagrangian Integrated Trajectory) model, http://www.arl.noaa.gov/ready/hysplit4.html. NOAA Air Resour. Accessed 25 Oct 2017 | <urn:uuid:af6f43a7-2b2d-4d40-bab1-aa783a62f11a> | 2.578125 | 757 | Academic Writing | Science & Tech. | 62.463768 | 95,527,974 |
The terrifying 'alien' wasp that injects its eggs into live caterpillars so its offspring can EAT their way out
- A University of Adelaide PhD student discovered new species of parasitoid wasp
- It's named 'Xenomorph' because of its similarities to the Alien movie monster
- The insect injects its eggs into live caterpillars and the larvae eat their way out
Researchers from Australia have discovered a new species of wasp named 'Xenomorph' because of its similarities to the monster from the Alien movie franchise.
Dolichogenidea xenomorph injects its eggs into live caterpillars, and then the larvae slowly eat the other bug from the inside out.
When they've had their fill, they burst out of the caterpillar and grow into adult wasps - before repeating the cycle all over again.
Researchers from Australia have discovered a new species of wasp named 'Xenomorph' because of its similarities to the monster from the Alien movie franchise
Xenomorph is one of three newly documented parasitoid wasp species - a kind of wasp that needs to kill their host to complete their life cycle.
'Dolichogenidea xenomorph acts as a parasite in caterpillars in a similar way that the fictional Alien creature does in its human host,' said lead researcher Erinn Fagan-Jeffries, PhD student in the University of Adelaide's School of Biological Sciences.
'The wasp is also black and shiny like the alien, and has a couple of weird traits for the genus - so xenomorph, meaning 'strange form', fits really well.'
It is believed that parasitoid wasps were actually the inspiration behind the gruesome monsters in Ridley Scott's franchise.
'At less than 5mm in length, Dolichogenidea xenomorph might seem to lack the punch of its fearsome namesake.
'But size is relative; to a host caterpillar, it's an awesome predator,' Fagan-Jeffries said.
It is believed that parasitoid wasps were actually the inspiration behind the gruesome monsters in Ridley Scott's franchise (pictured)
In nature, the wasps are important in regulating population of insect hosts, and have actually been used to control caterpillar pests in agricultural crops.
The new wasps were found in Queanbeyan, New South Wales and in southern Western Australia, but researchers believe they are more widely distributed across Australia.
It has an extremely long ovipositor, a needle-like structure the female wasps use to inject their eggs into their host.
WHAT IS A PARASITOID?
Parasitoids are insects with parasitic larvae that eat their host - usually another insect - from the inside out.
They often employ a sharp tool known as an ovipositor to deposit eggs under the skin or exoskeleton of unsuspecting hosts.
After a short gestational period, the larvae hatch and begin consuming their host, normally reaching adulthood when the host has died.
Parasitoid species are mostly types of bee, wasp and ant, though some species of fly also employ the gruesome technique.
The biology of parasitoids has inspired several science fiction authors and scriptwriters to create parasitoidal aliens that kill human hosts, including the infamous Xenomorph in Ridley Scott's 1979 film 'Alien'.
Parasitoids are insects with parasitic larvae that eat their host - usually another inset - from the inside out. Pictured is a parasitic wasp that injects larvae into spiders and then sews the host into its nest to pin it down
The host of this species is a moth caterpillar that feeds on Eucalyptus leaves.
Researchers have discovered thousands of new species of wasps in recent months.
'We collected over 500 wasps from a particular subfamily, from all over Australia, and determined that there were more than 200 different species just in that relatively small number of specimens,' said Andrew Austin, of the University's Australian Centre for Evolutionary Biology and Biodiversity.
'There are currently only 100 species described in this subfamily for Australia, so we've at least doubled the number of known species,' he continued.
'It's important to document our biodiversity so that we can make informed conservation decisions about our environment.
'Some of these wasps may potentially be useful biological control agents for pests, but we just don't know about them yet.'
The insect injects its eggs into live caterpillars and the larvae eat their way out. Xenomorph is one of three newly documented parasitoid wasp species - a kind of wasp that needs to kill their host to complete their life cycle. Pictured: Xenomorph from the Alien franchise
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Every human cell is encased in a five-nanometer-thick lipid membrane that protects it from the surrounding environment. Like a gatekeeper, the membrane determines which ions and molecules can pass through. In so doing, it ensures the cell's well-being and stability and allows it to communicate via electrical signals.
Researchers from the Laboratory for fundamental BioPhotonics (LBP) in EPFL's School of Engineering were able to track these moving charges in real time in a completely non-invasive manner. Rather than observing the membranes themselves, they looked at the surrounding water molecules, which, in addition to keeping the membrane intact, change orientation in the presence of electrical charges. So by 'reading' their position, the researchers were able to create a dynamic map of how charges are transported across a membrane.
The researchers' method has just been published in the journal Proceedings of the National Academy of Sciences (PNAS). It could shed light on how ion channels function, along with other processes at work in membranes. This clinically viable method could potentially also be used to directly track ion activity in neurons, which would deepen researchers' knowledge of how nerve cells work. "Water molecules can be found wherever there are lipid membranes, which need these molecules to exist," says Sylvie Roke, head of the LBP. "But until now, most studies on membranes didn't look at these molecules. We've shown that they contain important information."
The researchers did this by using a unique second-harmonic microscope that was invented at the LBP. The imaging efficiency of this microscope is more than three orders of magnitude greater than that of existing second-harmonic microscopes. With this microscope, the researchers obtained images of water molecules at a time scale of 100 milliseconds.
To probe the lipid membranes' hydration, the researchers combine two lasers of the same frequency (femtosecond pulses) in a process that generates photons with a different frequency: this is known as second-harmonic light. It is generated only at interfaces and reveals information on the orientation of water molecules. "We can observe what's happening in situ, and we don't need to modify the environment or use bulky markers like fluorophores that would disturb water molecules' movement" says Orly Tarun, the publication's lead author.
Unexpected charge fluctuations are observed
With this method, the researchers observed charge fluctuations in membranes. Such fluctuations were previously unknown and hint at much more complex chemical and physical behavior than is currently considered.
Reference: O. Tarun, C. Hannesschläger, P. Pohl, and S. Roke, A label-free and charge-sensitive dynamic imaging of lipid membrane hydration on millisecond time scales, PNAS
Laboratory of fundamental BioPhotonics (LBP) - Julia Jacobi Chair of Photomedicine | <urn:uuid:6bc10cbe-bd0c-4f2c-bad7-0bdf9781ef13> | 4.03125 | 583 | Knowledge Article | Science & Tech. | 29.13175 | 95,527,995 |
Carrying babies that could no longer use their feet to cling to their parents in the way that young apes can has long been thought to be at least one explanation as to why humans became bipedal.
But University of Manchester researchers investigating the energy involved in carrying a child say the physical expense to the mother does not support the idea that walking upright was an evolutionary response to child transportation.
“Walking upright is one of the major characteristics that separates humans from their primate relatives,” said Dr Jo Watson, who carried out the research in the University’s Faculty of Life Sciences.
“Scientists have long hypothesised as to the reasons why hominins became bipedal in a relatively short space of time but the truth is we still don’t know for sure.
“One of the more popular explanations is that walking upright freed our forelimbs allowing us to carry objects, including children; apes have no need to carry their young as they are able to grip using both hands and feet.
“Our study focused on the amount of energy required to carry 10kg loads, including a mannequin child. Importantly, the distribution of the weight varied in each instance.”
The team monitored the oxygen consumption of seven women, all healthy individuals under the age of 30, carrying either a symmetric load, in the form of a weighted vest or a 5kg dumbell in each hand, or an asymmetric load, which was a single 10kg weight carried in one hand or a mannequin infant on one hip.
“Carrying an awkward asymmetric load, such as the infant on one side of the body, is the most energetically expensive way of transporting the weight,” said Dr Watson, whose research is published in the Journal of Human Evolution.
“Unless infant carrying resulted in significant benefits elsewhere, the high cost of carrying an asymmetrical weight suggests that infant carrying was unlikely to have been the evolutionary driving force behind bipedalism.”
The study, carried out with colleagues at the Universities of Sheffield and Salford and funded by the Natural Environment Research Council (NERC), is part of a larger project, run by Dr Bill Sellers at The University of Manchester, which uses computer simulations to understand evolutionary processes, particularly the way in which we and other animals move.
Future plans are to extend this work to assess the energy cost of carrying in great apes. Computer models of early hominins carrying loads will also be built to try and evaluate whether their body shape and posture – long arms and short legs – would have made them noticeably better or worse at carrying than present-day humans. The research team hopes this will help build up a picture of how humans evolved to walk on two legs.
Aeron Haworth | alfa
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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.
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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.
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Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.
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It's as if the carbon, which comes from the waxy material plants generate to protect their foliage from sun and weather, has been going into a bank account where only deposits are being made and virtually no withdrawals.
Modelers of the Earth's carbon cycle, who've worked on the assumption that this type of carbon remains in the soils only 1,000 to 10,000 years before microorganisms return it to the atmosphere as carbon dioxide, will need to revise their thinking if findings reported in the Nov. 24 issue of Science are typical of other northern forests.
"Our results about the resilience of this particular kind of carbon suggest that the turnover time of this carbon pool may be 10,000 to 100,000 years," says Rienk Smittenberg, a research associate with the University of Washington School of Oceanography and lead author of the paper. He did the work while at the Royal Netherlands Institute of Sea Research.
Soils harbor the third-largest pool of carbon in the world behind the carbon locked deep in the Earth as fossil fuel oils and coal and the carbon that is dissolved in the world's oceans.
In soils, the more edible kinds of carbon from plants are quickly digested by bacteria and turned back into carbon dioxide. But about half the organic carbon in soils is less edible or protected from the bacteria, making it ultimately responsible for long-term carbon storage on land, the authors say.
This carbon pool is not likely to have a role in offsetting increased greenhouse carbon dioxide in the atmosphere any time soon because of the very slow processes at work, Smittenberg says. Instead a better estimate of how long that carbon persists in soils is important for modelers interested in carbon reserves on a timescale of 1,000 years or who are interested in changing carbon storage on land through time as vegetation changes.
For this work, the researchers obtained sediment cores from Saanich Inlet, a fjord on Vancouver Island in British Columbia. There low-temperature oxygen-starved bottom waters help preserve annual layers of sediments, some no less than a half-inch thick, that include matter from forest soils carried by water into the inlet.
Smittenberg used organic chemistry to isolate the plant wax molecules from other kinds of carbon, such as that derived from marine algae. Co-author Tim Eglinton of Woods Hole Oceanographic Institution did the radiocarbon testing.
Today's soils are comprised of a mix of organic matter that is 11,000 years old, zero years old from today's input and every age in between, Smittenberg says. The average age of the resilient waxy carbon is 5,500 years right now.
"It is likely that at least some of the resilient carbon has disappeared from the soils," he says. "It wouldn't be possible, for instance, to measure any in the fjord sediments if some of it hadn't eroded away," he says. "But this loss is relatively small compared to what is staying in the soils and the addition of more resilient organic matter.
"Thus the system is far from equilibrium as current models assume," he says.
If the findings hold true in other northern forests, it would put the terrestrial biosphere in a more prominent position as a slow but progressively important atmospheric carbon sink on geologic time scales. It could even influence current predictions about carbon cycling and soil carbon storage in response to increasing amounts of carbon dioxide in the atmosphere, the co-authors conclude.
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For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.
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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.
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Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.
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Ultra-short, high-intensity X-ray flashes open the door to the foundations of chemical reactions. Free-electron lasers generate these kinds of pulses, but there is a catch: the pulses vary in duration and energy. An international research team has now presented a solution: Using a ring of 16 detectors and a circularly polarized laser beam, they can determine both factors with attosecond accuracy.
Free-electron lasers (FELs) generate extremely short and intense X-ray flashes. Researchers can use these flashes to resolve structures with diameters on the...
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A new mechanism in the formation of ribosomes has been discovered by researchers from the Heidelberg University Biochemistry Center. In an interdisciplinary approach, the Heidelberg scientists, along with colleagues from Switzerland and Japan, describe a heretofore uncharacterised protein that plays a specific role in ribosome assembly in eukaryotes, organisms whose cells contain a cell nucleus.
This protein makes sure that specific factors required for ribosome synthesis are transported together, like hitchhikers, into the nucleus to the site of assembly. The results of this research were published in “Science”.
Ribosomes, the protein factories of the cell, are macromolecular complexes of ribonucleic acids (RNA) and ribosomal proteins (r-proteins) that are organised in a highly complicated three-dimensional nanostructure. Correct synthesis of ribosomes is critical for the division of all cells and is a process that follows strict rules.
In eukaryotes, new ribosomes are formed predominantly in the cell nucleus. Therefore, the r-proteins needed for ribosome formation must travel from the cytoplasm of the cell to a site in the nucleus where the ribosomes are assembled. Until recently it was not clear whether r-proteins that have a similar function and form functional clusters on the ribosome structure are also co-transported into the nucleus.
The researchers have now found a protein that coordinates the co-transport of certain r-proteins in functional clusters into the cell nucleus. This factor is called Symportin1, for synchronised import. “Symportin1 synchronises the import of both the Rpl5 and Rpl11 r-proteins into the cell nucleus and supports their integration into the growing ribosome structure”, explains Prof. Dr. Irmgard Sinning of the Heidelberg University Biochemistry Center (BZH). “It employs a familiar logistical concept from every day life, like picking up a hitchhiker or sharing a taxi with someone headed for the same destination”, says Dr. Gert Bange of the BZH, lead author of the study together with Dr. Dieter Kressler (now of Fribourg University).
The researchers from Heidelberg University and the University of Fribourg (Switzerland) collaborated closely with colleagues from Osaka University in Japan on the research. “The combination of different methods ranging from traditional cell biology to new biophysical approaches was crucial in developing the detailed picture of this previously unknown biological mechanism”, emphasises Prof. Dr. Ed Hurt, also of the BZH. The study took advantage of the Biochemistry Center’s crystallisation platform and the research received support from the Cluster of Excellence “CellNetworks” of Heidelberg University.
Marietta Fuhrmann-Koch | idw
World’s Largest Study on Allergic Rhinitis Reveals new Risk Genes
17.07.2018 | Helmholtz Zentrum München - Deutsches Forschungszentrum für Gesundheit und Umwelt
Plant mothers talk to their embryos via the hormone auxin
17.07.2018 | Institute of Science and Technology Austria
For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.
To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...
For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.
Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...
Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.
A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...
Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.
"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....
Ultra-short, high-intensity X-ray flashes open the door to the foundations of chemical reactions. Free-electron lasers generate these kinds of pulses, but there is a catch: the pulses vary in duration and energy. An international research team has now presented a solution: Using a ring of 16 detectors and a circularly polarized laser beam, they can determine both factors with attosecond accuracy.
Free-electron lasers (FELs) generate extremely short and intense X-ray flashes. Researchers can use these flashes to resolve structures with diameters on the...
13.07.2018 | Event News
12.07.2018 | Event News
03.07.2018 | Event News
17.07.2018 | Power and Electrical Engineering
17.07.2018 | Life Sciences
16.07.2018 | Physics and Astronomy | <urn:uuid:8cc4e2b3-f537-4fb8-8a9d-bd308abe1aad> | 3.453125 | 1,275 | Content Listing | Science & Tech. | 34.316664 | 95,528,027 |
In research published today in the journal Nature, CSIRO and an international team of scientists revealed global maps showing how fast and in which direction local climates are shifting. This new study points to a simpler way of looking at climatic changes and their likely effects on biodiversity.
Speed and direction of climate shifts over the past 50 years in Australia.
As climate change unfolds over the next century, plants and animals will need to adapt or shift locations to track their ideal climate.
“The maps show areas where plants and animals may struggle to find a new home in a changing climate and provide crucial information for targeting conservation efforts,” CSIRO's Dr Elvira Poloczanska said.
The study analysed 50 years of sea surface and land temperature data (1960-2009) and also investigated two future scenarios for marine environments (‘business as usual’ and a 1.75°C temperature increase).
The new maps show where new thermal environments are being generated and where existing environments may disappear.
“The maps show us how fast and in which direction temperatures are shifting, and where climate migrants following them may hit barriers such as coastlines. Our work shows that climate migration is far more complex than a simple shift towards the poles,” ecological geographer with the project Kristen Williams said.
“Across Australia, species are already experiencing warmer temperatures. In terrestrial habitats, species have started to seek relief by moving to higher elevations, or further south. However, some species of animals and plants cannot move large distances, and some not at all.”
Species migration can have important consequences for local biodiversity. For example, the dry, flat continental interior of Australia is a hot, arid region where species already exist close to the margin of their thermal tolerances.
Some species driven south from monsoonal northern Australia in the hope of cooler habitats may perish in that environment.
“In the oceans, warming waters and a strengthening of the East Australian Current have mobilised the Long-spined Sea Urchin (Centrostephanus rodgersii), previously only found as far south as southern NSW, to invade the eastern Tasmania coast. This has resulted in the decline of giant kelp forests with knock-on effects for commercially-fished rock lobsters,” Dr Poloczanska said.
CSIRO and University of Queensland’s Anthony Richardson said the study cannot be used as a sole guide as to what to do in the face of climate change.
“Biological factors such as a species’ capacity to adapt and disperse need to be taken into consideration,” Professor Richardson said.
“But in an unprecedented period of climate change, economic development and fast growing demand on an already pressured planet, we need to act fast to make sure as much of the world’s living resources survive that change.”
The study was undertaken by CSIRO's Dr Elvira Poloczanska and Associate Professor Anthony Richardson and Dr Kristen Williams with a team of 18 international researchers from Australia, Canada, Germany, Spain, UK and USA.
Chris Johnson | EurekAlert!
New research calculates capacity of North American forests to sequester carbon
16.07.2018 | University of California - Santa Cruz
Scientists discover Earth's youngest banded iron formation in western China
12.07.2018 | University of Alberta
For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.
To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...
For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.
Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...
Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.
A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...
Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.
"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....
Ultra-short, high-intensity X-ray flashes open the door to the foundations of chemical reactions. Free-electron lasers generate these kinds of pulses, but there is a catch: the pulses vary in duration and energy. An international research team has now presented a solution: Using a ring of 16 detectors and a circularly polarized laser beam, they can determine both factors with attosecond accuracy.
Free-electron lasers (FELs) generate extremely short and intense X-ray flashes. Researchers can use these flashes to resolve structures with diameters on the...
13.07.2018 | Event News
12.07.2018 | Event News
03.07.2018 | Event News
18.07.2018 | Life Sciences
18.07.2018 | Life Sciences
18.07.2018 | Information Technology | <urn:uuid:cd7026a4-e1de-4302-8b65-967911af9aee> | 4.09375 | 1,271 | Content Listing | Science & Tech. | 37.689325 | 95,528,041 |
A new Portland State University study shows that even though water quality has improved in South Korea's Han River basin since the 1990s, there are still higher-than-acceptable levels of pollut
In collaboration with a nature reserve in Namibia, researchers funded by the SNSF are developing a new approach to counting animals: combining drone flights and automated image analysis.
One of the major concerns in climate change studies is how the thermal conditions for the living environment of human beings will change in the future.
Due to its complex polyploidy nature (hexaploid, containing A, B and D three subgenomes) and large genome size (17 Gb), the genetic and functional analysis of bread wheat is extremely challenging.
New research from the University of North Carolina at Chapel Hill and collaborators found that most marine life in marine protected areas will not be able to tolerate warming ocean temperatures
REDD+ (Reducing emissions from deforestation and forest degradation) is an UN-led programme aiming to increase carbon sequestration in tropical forests.
Researchers from The University of Manchester are calling for tighter regulations on waste flowing into urban waterways, after the first study of its kind found that microplastics from urban river
Poaching and habitat loss have reduced forest elephant populations in Central Africa by 63 percent since 2001.
Greenland’s vast ice sheet has long been home to Project Iceworm, an abandoned Cold War-era U.S.
New research led by CU Boulder shows that the changing topography of ice sheets in the Northern Hemisphere during the last Ice Age forced changes in the climate of Antarctica, a previously undocume
Forfeiting our commons
The Lancet’s Series on Maternal and Child Undernutrition
President Obama's grand climate plan does not add up
Climate change can no longer be ignored
NGO demands withdrawal of Niyamgiri gram sabha notificatio | <urn:uuid:3419d977-cc32-4dd0-b97f-b035f6ffdfc6> | 2.578125 | 386 | Content Listing | Science & Tech. | 6.259118 | 95,528,044 |
http://sciencevshollywood.com - Science increasingly pervades many aspects of our lives. If people succumb to the typical view that science is difficult and should be left to experts and nerds, the most important decisions about all of our lives will be made by just a few people. New ways need to be found to engage the public with science.
http://renewsable.net - Finding time to stop, plug in and recharge could become history, with scientists developing a new electrode design that could charge batteries in seconds instead of hours. They say it could solve not only the pain of recharging phones, but also solve one of the primary issues holding back the electric vehicle market. Previous research […]The post This New Material Could Let Phones and Electric Cars Charge in Seconds appeared first on Renewsable.net.
http://renewsable.net - In France in the summer of 2003, so many people died that the mortuaries over-flowed with bodies and refrigerated lorries had to be used instead. The cause was the country’s worst-ever heatwave, which saw temperatures hit a record 44.1°C in Conqueyrac, near Montpellier in southern France. Some 15,000 deaths were attributed to the searing heat, which also […]The post Study Shows France Could Face ‘Mega-Heatwaves’ of More Than 122° F by 2100 appeared first on Renewsable.net.
http://renewsable.net - Last year, Apple was rumored to be working on an autonomous all-electric car codenamed ‘Project Titan’. The company later confirmed development work on an autonomous driving platform and CEO Tim Cook even referred to it as “a core technology” for the company, but it showed signs of giving up on developing an actual car. But now Apple […]The post Apple Is Secretly Working on Electric Car Batteries With China’s Biggest Battery Maker appeared first on Renewsable.net.
http://renewsable.net - Almost all plastic now resides as litter or micro-plastics pollution in the natural environment, or buried in landfills. As of 2015, only 9% of the plastics made to date have been recycled, and only 12% incinerated — together accounting for around 2 billion metric tons of plastic — according to the new research. The other […]The post Most of the 8.3 Billion Metric Tons of Plastic Humans Have Made Is Now Litter appeared first on Renewsable.net.
http://renewsable.net - Good news for Canadian electric car drivers or soon-to-be electric car drivers. A new network of DC fast-charging stations has been announced to cover the Trans-Canada Highway in a currently underserved region between Ontario and Manitoba. Interestingly, the stations will be equipped with energy storage systems in order to make sure it can deliver fast-charging […]The post The Trans-Canada Highway Is About to Get 34 Fast-Charging Stations for Electric Vehicles appeared first on Renewsable.net.
http://renewsable.net - Scientists at USC and Cal Tech have discovered a way to greatly speed up the process of transforming carbon dioxide into alkaline water, effectively neutralizing the gas, a development that could be a boon in the fight against excessive greenhouse gas emissions. To understand how the process works, think about soda water. Sip soda water […]The post Scientists Have Great Hopes for a Little Miracle Enzyme That Can Transform Carbon Dioxide Into Alkaline Water appeared first on Renewsable.net.
http://renewsable.net - Normally, the hottest years on record occur when the underlying human-caused global warming trend gets a temporary boost from an El Niño’s enhanced warming in the tropical Pacific. So it’s been a surprise to climate scientists that 2017 has been so remarkably warm — because the last El Niño ended a year ago. The National Oceanic and Atmospheric Administration (NOAA) reported Tuesday […]The post 2017 Is So Unexpectedly Warm It’s Freaking Out Climate Scientists appeared first on Renewsable.net.
http://renewsable.net - Korean siblings Hyundai and Kia will aggressively increase production of electric cars next year, according to a report in the Korean press. The production increase comes amid the combined automaker’s goal to become the second largest maker of green vehicles (hybrids, plug-in hybrids, and electric cars) by 2020. Hyundai-Kia set the goal in 2014, but […]The post Hyundai-Kia Expects to Produce 50,000 Electric Vehicles in 2018 appeared first on Renewsable.net.
http://renewsable.net - North Korean scientists have developed “a light and foldable” solar panel which can be “carried inside a backpack and… installed at any place”, state media reported on Thursday. According to DPRK Today, “polycrystalline silicon flakes with high conversion efficiency and high stability among various types of solar cell materials” were selected during the manufacturing process, […]The post North Korea Developed a Light Portable Solar Panel That Folds Into the Size of Paper appeared first on Renewsable.net.
http://renewsable.net - China has installed 24.4 gigawatts (GW) of solar PV in the first six months of 2017, including an extraordinary 13.5GW in the month of June alone, as developers rushed to complete installations to capitalize on a higher feed in tariff that expired on July 1. According to the data from the China PV Industry Association […]The post China Added 13.5 GW of Solar Power – in June Alone! appeared first on Renewsable.net.
http://renewsable.net - A concentrating photovoltaic system with embedded microtracking can produce over 50 percent more energy per day than standard silicon solar cells in a head-to-head competition, according to a team of engineers who field tested a prototype unit over two sunny days last fall. “Solar cells used to be expensive, but now they’re getting really cheap,” […]The post Rooftop Concentrator Photovoltaics Can Now Produce 50% More Energy Than Regular Solar Panels appeared first on Renewsable.net.
http://renewsable.net - Morgan Stanley analyst Adam Jonas has long been warning of the impact of Tesla’s fast pace of innovation in the auto industry. He even warned that Tesla’s Autopilot machine learning could potentially render all other cars obsolete. Now Jonas suggests that the auto industry’s inability to match Tesla’s over-the-air software update capability could make them “highly vulnerable to obsolescence”. […]The post Analyst: Tesla’s Ability to Update Software, Over the Air, Makes Other Vehicles ‘Highly Vulnerable to Obsolescence’ appeared first on Renewsable.net.
http://renewsable.net - In an effort to reduce carbon dioxide emissions, the University of Notre Dame has added three underground geothermal fields. The South Bend, Indiana, school reports that one field is up and running, with the other two expected to be fully functional by 2018 and 2019. The three fields are expected to reduce the school’s carbon […]The post Notre Dame Turns to Geothermal to Reduce CO2 Emissions by 12k Tons a Year appeared first on Renewsable.net. | <urn:uuid:7030e24a-94f6-4244-a257-089c47aee1fb> | 2.546875 | 1,537 | Content Listing | Science & Tech. | 47.112362 | 95,528,048 |
New research led by the University of Southampton suggests that, over the next 100 to 200 years, carbon dioxide concentrations in Earth’s atmosphere will head towards values not seen since the Triassic period, 200 million years ago. Furthermore, by the 23rd century, the climate could reach a warmth not seen in 420 million years.
The study, published in Nature Communications, compiled over 1200 estimates of ancient atmospheric carbon dioxide (CO2) concentrations to produce a continuous record dating back nearly half a billion years. It concludes that if humanity burns all available fossil fuels in the future, the levels of CO2 contained in the atmosphere may have no geologically-preserved equivalent during this 420 million year period.
The researchers examined published data on fossilised plants, the isotopic composition of carbon in soils and the oceans, and the boron isotopic composition of fossil shells. Gavin Foster, lead author and Professor of Isotope Geochemistry at the University of Southampton, explains: “We cannot directly measure CO2 concentrations from millions of years ago. Instead we rely on indirect ‘proxies’ in the rock record. In this study, we compiled all the available published data from several different types of proxy to produce a continuous record of ancient CO2 levels.”
This wealth of data shows that CO2 concentrations have naturally fluctuated on multi-million year timescales over this period, from around 200-400 parts per million (ppm) during cold ‘icehouse’ periods to up to 3000 ppm during intervening warm ‘greenhouse’ periods. Although evidence tells us our climate has fluctuated greatly in the past (with Earth currently in a colder period), it also shows the current speed of climate change is highly unusual.
Carbon dioxide is a potent greenhouse gas and in the last 150 years humanity’s fossil fuel use has increased its atmospheric concentration from 280 ppm in the pre-industrialisation era to nearly 405 ppm in 2016. However, it’s not just CO2 that determines the climate of our planet, ultimately it is both the strength of the greenhouse effect and the amount of incoming sunlight that is important. Changes in either parameter are able to force climate change.
“Due to nuclear reactions in stars, like our sun, over time they become brighter,” adds co-author Dan Lunt, Professor of Climate Science at the University of Bristol. “This means that, although carbon dioxide concentrations were high hundreds of millions of years ago, the net warming effect of CO2 and sunlight was less. Our new CO2 compilation appears on average to have gradually declined over time by about 3-4 ppm per million years. This may not sound like much, but it is actually just about enough to cancel out the warming effect caused by the sun brightening through time, so in the long-term it appears the net effect of both was pretty much constant on average.”
This interplay between carbon dioxide and the sun’s brightness has fascinating implications for the history of life on Earth. Co-author Professor Dana Royer, from Wesleyan University in the US, explains: “Up until now it’s been a bit of a puzzle as to why, despite the sun’s output having increased slowly over time, scant evidence exists for any similar long-term warming of the climate. Our finding of little change in the net climate forcing offers an explanation for why Earth’s climate has remained relatively stable, and within the bounds suitable for life for all this time.”
This long-term view also offers a valuable perspective on future climate change. It is well recognised that the climate today is changing at rates well above the geological norm. If humanity fails to tackle rising CO2 and burns all the readily available fossil fuel, by AD 2250 CO2 will be at around 2000 ppm — levels not seen since 200 million years ago.
Professor Foster adds: “However, because the Sun was dimmer back then, the net climate forcing 200 million years ago was lower than we would experience in such a high CO2 future. So not only will the resultant climate change be faster than anything Earth has seen for millions of years, the climate that will exist is likely to have no natural counterpart, as far as we can tell, in at least the last 420 million years.”
This collaborative study involves the University of Southampton (UK), University of Bristol (UK), and Wesleyan University (US) and is an output from ‘Descent into the Ice House’, one of the four research projects under the umbrella programme ‘The Long-term Co-Evolution of Life and the Planet’ funded the by the National Environment Research Council (NERC). | <urn:uuid:e660fe63-550c-4430-af38-eb710ab67966> | 4.03125 | 968 | News Article | Science & Tech. | 34.457596 | 95,528,049 |
The R-Process (Rapid Neutron-capture-process) is a Nucleosynthesis process in Core Collapse Supernovae consisting of repeated Neutron Capture under conditions where Beta Decay is suppressed (or a nucleus generally captures another neutron before beta decay occurs), resulting in synthesis of Isotopes with an increase in atomic weight more than one but remaining at the same atomic number. When conditions revert to allowing beta decay, such decays happen until the nucleus reaches a stable configuration. The r-process explains the Abundances of Germanium, Xenon, and Platinum and many elements heavier than Iron and Nickel.
The Spectral Line signatures of r-process-created nuclei can be used to identify and age old stars. Very old (high Redshift?) galaxies have been observed with r-process-produced elements but not S-Process-produced elements, suggesting that at an early time, the r-process was working but the s-process was not. Individual stars with similar characteristics are presumed to be of similar age. | <urn:uuid:b94d1705-20dc-4068-903f-c42d8ce61571> | 3.40625 | 213 | Knowledge Article | Science & Tech. | 23.748385 | 95,528,114 |
- For each of the following constructs, there is a portion of the program
text called its declarative region, within which nested declarations can
- any declaration, other than that of an enumeration type, that is
not a completion of a previous declaration;
- The declarative region includes the text of the construct together with
additional text determined (recursively), as follows:
- If a declaration is included, so is its completion, if any.
- If the declaration of a library unit (including Standard -- see
10.1.1) is included, so are the declarations of any child units (and
their completions, by the previous rule). The child declarations occur
after the declaration.
- If a body_stub is included, so is the corresponding subunit.
- If a type_declaration is included, then so is a corresponding
record_representation_clause, if any.
- The declarative region of a declaration is also called the declarative
region of any view or entity declared by the declaration.
- A declaration occurs immediately within a declarative region if this
region is the innermost declarative region that encloses the declaration (the
immediately enclosing declarative region), not counting the declarative
region (if any) associated with the declaration itself.
- A declaration is local to a declarative region if the declaration occurs
immediately within the declarative region. An entity is local to a
declarative region if the entity is declared by a declaration that is local
to the declarative region.
- A declaration is global to a declarative region if the declaration
occurs immediately within another declarative region that encloses the
declarative region. An entity is global to a declarative region if the
entity is declared by a declaration that is global to the declarative region.
(1) The children of a parent library unit are inside the parent's
declarative region, even though they do not occur inside the parent's
declaration or body. This implies that one can use (for example) "P.Q"
to refer to a child of P whose defining name is Q, and that after "use
P;" Q can refer (directly) to that child.
(2) As explained above and in 10.1.1, ``Compilation
Units - Library Units'', all library units are descendants of Standard,
and so are contained in the declarative region of Standard. They are not
inside the declaration or body of Standard, but they are inside its declarative
(3) For a declarative region that comes in multiple parts, the text of
the declarative region does not contain any text that might appear
between the parts. Thus, when a portion of a declarative region is said
to extend from one place to another in the declarative region, the
portion does not contain any text that might appear between the parts of
the declarative region.
-- Email comments, additions, corrections, gripes, kudos, etc. to:
Magnus Kempe -- Magnus.Kempe@di.epfl.ch
Page last generated: 95-03-12 | <urn:uuid:47f46c9c-4454-4dc0-a5b4-da32484b93e7> | 2.65625 | 694 | Documentation | Software Dev. | 29.063469 | 95,528,144 |
Digital Connections to Natural Resources
The term natural resources may not make you immediately think of software, social media, or databases. But digital tools are real game-changers in the field of natural resource stewardship and science. We use cutting-edge data collection tools everyday in parks to protect and conserve the water, air, rocks, and life within them. And we also use digital media to make connections and share important (and interesting!) natural resource information with you and every other visitor to national park websites or social media accounts.
- Facebook, Twitter, Instagram! Engaging with us on social media can open a world of nature to you. Do you ever want breaking science news on your phone to change the pace, or a photo of nature to get you through another afternoon indoors, or a fun science fact for happy hour? We got you covered. We also share videos and stories about the people who work hard to protect parks. And, you’ll never forget to celebrate Cephalopod Week again!
- NPSpecies - This database keeps an inventory of every species in every park. Of course it relies on updates from park staff to be accurate, but the data in this database provides a list of all living things within a park. It’s open to the public, and it’s fun to explore. (Did you know there are 21 species of reptiles in Mesa Verde National Park?) With this information, park staff and scientists can develop strategies to increase biodiversity, to protect endangered species, and to manage invasive species, for example. All of these activities improve the health of ecosystems and our world.
- Air Quality Web Cameras - Current digital images and air quality information from 19 national parks are part of the NPS air quality web camera network. Images are updated every 15 minutes. Air quality data—including ozone, particulate matter, visual range, & weather conditions—are updated hourly. The data collected shows long-term trends in air quality and provides critical information to Congress, air quality monitoring agencies, and other scientists in universities. Air quality affects everyone, and digital tools help us keep it clean for good health and scenic views.
- Virtual Visitors - Digital media allow people to travel virtually to many of our national parks. Whether it's a distance learning adventure from Grand Canyon National Park or watching the Denali puppies in the spring, summer, and fall, people have the opportunity to connect with faraway places from the comfort of their living rooms.
- LIDAR stands for Light Detection and Ranging, and scientists use this technology to make 3D maps of underground surfaces, like lava tubes. Then they can use this information to help scientists understand what the terrain of other planets in our solar system are like. Learn more in this video (that you can watch digitally!) from our friends at Outside Science (inside parks). They went to Craters of the Moon to see LIDAR in action!
This is just the tip of the iceberg of how we use digital tools, concepts, and media to both protect resources in parks and also share them with the rest of the world. Connect with us!
-NRSS Digital Team | <urn:uuid:05693e93-a9a2-46f2-acc0-9a5fcc9d0f05> | 3.453125 | 645 | About (Org.) | Science & Tech. | 43.496509 | 95,528,146 |
I’ve wanted to be a scientist since I was five years old.
My idea of a scientist was someone in a lab, making hypotheses and testing theories. We often think of science only as a linear, objective process. This is also the way that science is presented in peer reviewed journal articles – a study begins with a research question or hypothesis, followed by methods, results and conclusions.
It turns out that my work now as a climate scientist doesn’t quite gel with the way we typically talk about science and how science works.
Climate change, and doing climate change research, has changed the way I see and do science. Here are five points that explain why.
1. Methods aren’t always necessarily falsifiable
Climate models are important and complex tools for understanding the climate system. Are climate models falsifiable? Are they science? A test of falsifiability requires a model test or climate observation that shows global warming caused by increased human-produced greenhouse gases is untrue. It is difficult to propose a test of climate models in advance that is falsifiable.FoxyImage/shutterstock
This difficulty doesn’t mean that climate models or climate science are invalid or untrustworthy. Climate models are carefully developed and evaluated based on their ability to accurately reproduce observed climate trends and processes. This is why climatologists have confidence in them as scientific tools, not because of ideas around falsifiability.
2. There’s lots of ways to interpret data
Climate research is messy. I spent four years of my PhD reconstructing past changes in Australian and Indonesian rainfall over many thousands of years. Reconstructing the past is inherently problematic. It is riddled with uncertainty and subject to our individual interpretations.
During my PhD, I submitted a paper for publication detailing an interpretation of changes in Indonesian climates, derived from a stalagmite that formed deep in a cave.
My coauthors had disparate views about what, in particular, this stalagmite was telling us. Then, when my paper was returned from the process of peer review, seemingly in shreds, it turns out the two reviewers themselves had directly opposing views about the record.
What happens when everyone who looks at data has a different idea about what it means? (The published paper reflects a range of different viewpoints).
Another example of ambiguity emerged around the discussion of the hiatus in global warming. This was the temporary slowdown in the rate of global warming at the Earth’s surface occurring roughly over the 15 year period since 1997. Some sceptics were adamant that this was unequivocal proof that the world was not warming at all and that global warming was unfounded.
There was an avalanche of academic interest in the warming slowdown. It was attributed to a multitude of causes, including deep ocean processes, aerosols, measurement error and the end of ozone depletion.
Ambiguity and uncertainty are key parts of the natural world, and scientific exploration of it.
3. Sometimes the scientist matters as well as the results
I regularly present my scientific results at public lectures or community events. I used to show a photo depicting a Tasmanian family sheltering under a pier from a fire front. The sky is suffused with heat. In the ocean, a grandmother holds two children while their sister helps her brother cling to underside of the pier.Kidd Chris/AAP
After a few talks, I had to remove the photo from my PowerPoint presentation because each time I turned around to discuss it, it would make me teary. I felt so strongly that the year we were living was a chilling taste of our world to come.
Just outside of Sydney, tinderbox conditions occurred in early spring of 2013, following a dry, warm winter. Bushfires raged far too early in the season. I was frightened of a world 1°C hotter than now (regardless of what the equilibrium climate sensitivity turns out to be).
At public lectures and community events, people want to know that I am frightened about bushfires. They want to know that I am concerned about the vulnerability of our elderly to increasing summer heat stress. People want to know that, among everything else, I remain optimistic about our collective resilience and desire to care for each other.
Communicating how we connect with scientific results is also important part of the role of climate scientists. That photo of the family who survived the Tasmanian bushfire is now back in my presentations.
4. Society matters too
In November 2009, computer servers at the University of East Anglia were illegally hacked and email correspondence was stolen.
A selection of these emails was published publicly, focusing on quotes that purported to reveal dishonest practices that promoted the myth of global warming. The “climategate” scientists were exhaustively cleared of wrongdoing.
On the surface, the climategate emails were an unpleasant but unremarkable event. But delving a little deeper, this can be seen as a significant turning point in society’s expectations of science.
While numerous fastidious reviews of the scientists cleared them of wrongdoing, the strong and ongoing public interest in this matter demonstrates that society wants to know how science works, and who “does” science.
There is a great desire for public connection with the processes of science and the outcomes of scientific pursuits. The public is not necessarily satisfied by scientists working in universities and publishing their finding in articles obscured by pay walls, which cannot be publicly accessed.
A greater transparency of science is required. This is already taking off, with scientists communicating broadly through social and mainstream media and publishing in open access journals.
5. Non-experts can be scientists
Climate science increasingly recognises the value of citizen scientists.
Enlisting non-expert volunteers allows researchers to investigate otherwise very difficult problems, for example when the research would have been financially and logistically impossible without citizen participation.
The OzDocs project involved volunteers digitising early records of Australian weather from weather journals, government gazettes, newspapers and our earliest observatories. This project provided a better understanding of the climate history of southeastern Australia.Dan Peled/AAP
Personal computers also provide another great tool for citizen collaborators. In one ongoing project, climate scientists conduct experiments using publicly volunteered distributed computing. Participants agree to run experiments on their home or work computers and the results are fed back to the main server for analysis.
While we often think of scientists as trained experts working in labs and publishing in scholarly journals, the lines aren’t always so clear. Everyone has an opportunity to contribute to science.
My new book explores this space between the way science is discussed and the way it takes place.
This isn’t a criticism of science, which provides a useful way to explore and understand the natural world. It is a celebration of the richness, diversity and creativity of science that drives this exploration.
Authors: Sophie Lewis, Research fellow, Australian National University | <urn:uuid:a8faa579-5ca6-45c5-b955-fe4f93d113dd> | 2.5625 | 1,405 | Nonfiction Writing | Science & Tech. | 35.533238 | 95,528,153 |
|RHODOPHYTA : GIGARTINALES : Phyllophoraceae||RED ALGAE|
Description: Thalli arising from a small attachment disc to form small fronds which devide dichotomously into flattened branches 10 cms (or more) long. Often with an interrupted midrib formed by cystocarps.
Habitat: Epilithic and on shells, sublittoral to 13 m deep.
Distribution: Generally south-western in the British Isles, south Wales, south-west England, the most northerly records being from Northern Ireland. Europe: Azores, Portugal and Spain. Further afield: Canary Islands, widely in the Pacific.
Similar Species: Specimens without a mid-rib resemble Rhodymenia pseudopalmata.
Key Identification Features:
Distribution Map from NBN: Interactive map : National Biodiversity Network mapping facility, data for UK.
WoRMS: Species record : World Register of Marine Species.
|Morton, O. & Picton, B.E. (2016). Stenogramme interrupta (C Agardh) Montagne ex Harvey. [In] Encyclopedia of Marine Life of Britain and Ireland. |
http://www.habitas.org.uk/marinelife/species.asp?item=ZM5990 Accessed on 2018-07-19
|Copyright © National Museums of Northern Ireland, 2002-2015| | <urn:uuid:80050cb7-58f2-4c1f-ad68-1c52a722c6c4> | 2.546875 | 306 | Knowledge Article | Science & Tech. | 34.8025 | 95,528,154 |
What drives the emergence and disappearance of species? By modeling the fundamental processes of evolution and ecology on geographical scales, new research spotlights topography and climatic shifts.
Vocal deception may have played a key role in our progression from primitive nonverbal noises to complex, controlled speech.
New research on roaring shows that women underestimate their own strength.
New research shows green-blooded skinks have evolved multiple times, which could help lead to explanation as to why.
Questionable research practices are not fraud, and they're not cause for panic. But they do give us some hints about how we can make science more robust.
A core idea in molecular biology is that one gene codes for one protein. Now biologists have found an example of a gene that yields two forms of a protein – enabling it to evolve new functionality.
More and more evidence shows evolution isn't as random as often thought.
Your voice can affect how attractive, fertile and faithful people think you are.
New research suggests life on Earth became more diverse because of a change in biology related to stem cells, not just rising oxygen levels.
Male Birds of Paradise have patches of super-black plumage that absorb 99.95 percent of light. New research identified their feathers' microscopic structures that make them look so very dark.
An ancient sexual conflict over mitochondrial inheritance may be responsible for the evolution of the two sexes as we know them.
Evolutionary biologists ask very similar questions about species to those asked by linguists about languages.
Ancient whales were neither gentle, nor giants: they were smaller than those of today and judging from their teeth, a lot meaner.
A stable environment that teaches men to be men and women to be women could be helping to enforce gender across generations.
Scientists have reconstructed the common ancestor of everything from rose bushes to oak trees, ivy or wheat.
A group of lizards in Brazil have evolved bigger heads in just 15 years thanks to their new environment.
Taking the placenta as a case study, researchers are able to piece together how new organs evolve, by repurposing old tissues and using them to do new jobs.
Anthropologists gather clues about how our ancient ancestors lived from their teeth. What will future anthropologists make of us based on the fossilized pearly whites we'll leave behind?
A new study suggests women who undergo FGM in societies where it is prevalent have more surviving children – but the evidence isn't strong enough.
Some fish build sandcastles to attract a mate but others just use sneaky tactics. | <urn:uuid:5c3bf12b-f0e9-4c8d-abcf-a9fbbc3f39e5> | 3.328125 | 521 | Content Listing | Science & Tech. | 41.832501 | 95,528,167 |
The basic concept of land-sea temperature contrast and the strength of the Asian summer monsoon is investigated here by comparing the relative contributions of external conditions (involving surface albedo) and internal feedbacks (involving soil moisture) in a number of atmospheric general circulation model (GCM) mean climate simulations and in a GCM sensitivity experiment. All models are run with the same long-term mean sea surface temperatures so that only land-surface conditions affect the land-sea temperature contrast. There is a surprising consistency among the various models such that stronger summer monsoons (defined as high area-averaged precipitation over south Asia) are associated with greater land-sea temperature contrast (i.e., higher land temperatures), lower sea level pressure over land, less snow cover, and greater soil moisture. In a sensitivity study with land albedos uniformly raised from 0.13 to 0.20 in one of the models, the winter-spring-summer sequence over southern Asia shows that there is a high sensitivity to the specified land albedos. Lower land albedos are associated with warmer land temperatures, greater land-sea temperature contrast, and a stronger Asian summer monsoon. There is also a positive feedback between soil moisture and precipitation (increased soil moisture provides a surface moisture source for further precipitation).
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in this study, the importance of the main macrobenthic crustaceans in the Bay of Biscay in the diet of 18 species of demersal predatory fish was investigated by comparing stomach content data from the fish with the results of sampling the bottom with a beam trawl. The Ivlev index was employed to evaluate the degree to which the crustaceans were selected in favour of other prey. Stomach content data were weighted to the abundance of the predators in the environment in accordance with the abundance indices obtained in the area with a bottom trawl survey, when all the data were collected. Selection of the crustaceans as a group varied, depending on whether biomass/volume or number was being studied, with the former value negative and the latter positive. Due to the importance of the fish biomass as prey for the predators studied. The highest mean value of the Ivlev index was obtained for the benthic shrimp Processa spp. Other prey species with a high index were Pandalina brevirostris and the Crangonidae, and to a lesser extent Portunidae, Scyllarus arctus, Alpheus glaber, Lophogaster typicus and the Amphipoda. Processa spp. And Galathea spp. Occurred in 15 of the 18 fish species analysed. Other more armed or protected species were negatively selected and were less important as prey, e.g. Nephrops norvegicus, Dichelopandalus bonnieri, Plesionika heterocarpus and the Paguridae. The predators studied were also classified according to trophic spectrum and the importance of macrobenthic crustaceans in their diet. Scyliorhinus canicula. Raja clavata and Lepidorhombus boscil showed the highest mean Ivlev index and diet diversity, while the lowest was for Pagellus acarne and Chelidonichthys obscurus.
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Before proceeding to consider the problem of measurement as applied to psycho-physical problems it is desirable to consider some of the general principles of measurement.
Measurement is primarily a device which enables us to use the laws of arithmetic to solve problems relating to phenomenal events. The laws of arithmetic pertain to numbers and to nothing else: there is nothing inherently numerical in the structure of the phenomenal world. We are, however, so familiar with the description of phenomena in numerical terms (or their formal mathematical equivalents) that the association has become instinctive, and we are apt to imagine that we directly perceive the metrical aspects of nature as inherent constituents of phenomena, existing in their own right, so to speak, and merely observed by us. This induces us to overlook the essentially arbitrary and man-made nature of the association. When this is of an unfamiliar character, as, for instance, when we associate the arithmetical operation x sqrt(-1) with the physical events constituting a phase change of pi/2 in alternating current problems and others of a like nature, we recognize it at once as a mere device of the mathematician. In principle it is no more artificial than the more familiar associations of events with arithmetical concepts which underlie all metrical processes.
The phenomenal world presents itself to us as a complex relation structure. We need not here enter into metaphysical questions concerning the parts played by our sense organs and by things external to us in determining the kind of relations exhibited by phenomena. We will take the phenomenal world as we find it: a structure of related events, which we find it convenient to describe and classify in terms of various concepts.
We have discovered - and this discovery is the foundation stone of physical science - that by employing a simple but ingenious device some aspects of phenomena can be classified so that certain phenomenal relations existing between members of any such class are `similar' to the relations between members of the class of numbers on which the laws of arithmetic are based. In arithmetic, these relations are implicit in the meaning assigned by two important symbols, namely =, the symbol of numerical equality, and +, the symbol of the operation of adding one number to another. All other arithmetical operations, subtraction, multiplication or division, involution or evolution, etc., ultimately derive their significance from the operation of addition.
In any class of phenomenal aspects of the kind we are considering we can perceive various relations. Further, by performing experimental operations on the things which exhibit the aspects in question we can change the actual relations exhibited. But there is nothing inherently numerical in these phenomenal relations: in order to establish a connection we must arbitrarily associate some unique symmetrical transitive phenomenal relation from among those which may have perceptual significance with the arithmetical relation of equality; and, further, we must associate some suitable experimental operation with the arithmetical operation of addition. If, now, we base our phenomenal classification entirely in terms of this symmetrical relation and this experimental operation we obtain a phenomenal series whose members are related to each other in a similar manner to the members of the series of numbers.
We must not confuse `similarity' as here used with identity. Relations are themselves things which can be classified in virtue of certain characteristics irrespective of the kind of things related by them. A relation may be symmetrical or unsymmetrical, transitive or intransitive, etc., and it is these properties of relations themselves, and not any specific properties of the things related by them, which confer relational similarity or dissimilarity on classes defined by relations. However, it is not here necessary to discuss the theory of similar relations, or go into the conditions which must be imposed on our selected criteria of `equality' and `addition ' in order that phenomenal and numerical relations may be similar. The important point to be noted is simply that there is no a priori connection between phenomenal structure and number, and that to make a connection we must artificially associate a phenomenal criterion with numerical equality and a phenomenal operation with numerical addition. When we have done this, but not before, we can predict by arithmetical calculation those phenomenal relations which involve only the stipulated practical criteria of equality and addition.
A phenomenal class defined by two such practical criteria constitutes a measurable magnitude of the type which Dr. Norman Campbell, in his well-known text-book on the principles of measurement, has termed an A magnitude. Any such magnitude can be measured by processes which do not imply the measurability of any other magnitude. It is true that the practical criterion of equality for any A magnitude will always involve the observation of some phenomenal state or condition which may (and usually does) involve other magnitudes; but the observational criterion is always of the null type - no difference, or no observable change, in the prescribed state or condition: no numerical relations have to be determined or even be assumed to exist for these other magnitudes. Familiar examples of A magnitudes are length, volume, mass, electrical resistance, and many others which need not be detailed.
The practical criteria of equality and addition which define these magnitudes for purposes of measurement are sufficiently familiar to require no description. It is their significance which is not so widely recognized as it might be. It is probably usual to regard the experimental processes of determining equality and of adding as something which we have just found to be a convenient method of determining quantitative relations inherent in the nature of the magnitudes, whereas these processes are the necessary connecting links between phenomena and number without which there would be no basis of comparison between the laws of the former and those of the latter. The experimental criteria do not merely enable us to measure a magnitude, they create the magnitude by defining the fundamental relations which are to be the basis of classification.
In Physics the general term measurement is not confined to A magnitudes. By suitable experimental processes we affix numerals to many aspects of phenomena to which no operation can be performed having any similarity in relation structure to the operation of addition. Familiar examples are density, specific heat, electrical resistivity, etc. All those things which we ordinarily regard as properties of substances are magnitudes of this type. They are the B magnitudes of Campbell's classification. We can usually formulate a practical criterion of equality for a B magnitude, but not of addition. ...
Strictly speaking, therefore, the only measurable magnitudes are A magnitudes.
Excerpted from the "Statement by Mr. J. Guild. Are Sensation Intensities Measurable?", Part III of the "Interim Report of the Committee appointed to consider and report upon the possibility of Quantitative Estimates of Sensory Events", Prof. A. Ferguson, Chairman. Report of the 108th Annual Meeting of the British Association for the Advancement of Science, Cambridge, 1938. (Italics Guild's, bold RMT's.)
Rasch measurement constructs measures of A magnitudes. A "phenomenal criterion" associated with numerical equality is 50% success and 50% failure. A "phenomenal operation" associated with numerical addition is the log-odds of joint independent success vs. joint independent failure.
What is Measurement? Guild J. Rasch Measurement Transactions, 2001, 15:1 p.798-9
|Rasch Measurement Transactions (free, online)||Rasch Measurement research papers (free, online)||Probabilistic Models for Some Intelligence and Attainment Tests, Georg Rasch||Applying the Rasch Model 3rd. Ed., Bond & Fox||Best Test Design, Wright & Stone|
|Rating Scale Analysis, Wright & Masters||Introduction to Rasch Measurement, E. Smith & R. Smith||Introduction to Many-Facet Rasch Measurement, Thomas Eckes||Invariant Measurement: Using Rasch Models in the Social, Behavioral, and Health Sciences, George Engelhard, Jr.||Statistical Analyses for Language Testers, Rita Green|
|Rasch Models: Foundations, Recent Developments, and Applications, Fischer & Molenaar||Journal of Applied Measurement||Rasch models for measurement, David Andrich||Constructing Measures, Mark Wilson||Rasch Analysis in the Human Sciences, Boone, Stave, Yale|
|in Spanish:||Análisis de Rasch para todos, Agustín Tristán||Mediciones, Posicionamientos y Diagnósticos Competitivos, Juan Ramón Oreja Rodríguez|
|Forum||Rasch Measurement Forum to discuss any Rasch-related topic|
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AERA members: Join the Rasch Measurement SIG and receive the printed version of RMT
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Subscribe to Journal of Applied Measurement
Go to Institute for Objective Measurement Home Page. The Rasch Measurement SIG (AERA) thanks the Institute for Objective Measurement for inviting the publication of Rasch Measurement Transactions on the Institute's website, www.rasch.org.
|Coming Rasch-related Events|
|June 29 - July 27, 2018, Fri.-Fri.||On-line workshop: Practical Rasch Measurement - Further Topics (E. Smith, Winsteps), www.statistics.com|
|July 25 - July 27, 2018, Wed.-Fri.||Pacific-Rim Objective Measurement Symposium (PROMS), (Preconference workshops July 23-24, 2018) Fudan University, Shanghai, China "Applying Rasch Measurement in Language Assessment and across the Human Sciences", www.promsociety.org|
|July 29 - August 4, 2018||Vth International Summer School `Applied Psychometrics in Psychology and Education`, Institute of Education at the Higher School of Economics, St. Petersburg, Russia, https://ioe.hse.ru/en/announcements/215681182.html|
|July 30 - Nov., 2018||Online Introduction to Classical and Rasch Measurement Theories (D.Andrich), University of Western Australia, Perth, Australia, http://www.education.uwa.edu.au/ppl/courses|
|Aug. 10 - Sept. 7, 2018, Fri.-Fri.||On-line workshop: Many-Facet Rasch Measurement (E. Smith, Facets), www.statistics.com|
|August 25 - 28, 2018, Sat.-Tue.||Análisis de Rasch introductorio (en español). (Agustín Tristán), Instituto de Evaluación e Ingeniería Avanzada. San Luis Potosí, México. www.ieia.com.mx|
|Sept. 3 - 6, 2018, Mon.-Thurs.||IMEKO World Congress, Belfast, Northern Ireland, www.imeko2018.org|
|Oct. 12 - Nov. 9, 2018, Fri.-Fri.||On-line workshop: Practical Rasch Measurement - Core Topics (E. Smith, Winsteps), www.statistics.com|
The URL of this page is www.rasch.org/rmt/rmt151i.htm | <urn:uuid:1910a8ff-532d-4544-8e21-c897137e8991> | 2.953125 | 2,332 | Academic Writing | Science & Tech. | 28.483186 | 95,528,249 |
Deep-Sea Pelagic Sediments and Ophiolite Assemblaces
The earth's great mountain belts contain sediments and volcanic complexes of kinds that are well known in the stable cratonic regions and of kinds that are exposed only (or almost only) in the mountain belts. The latter kinds include ophiolites, great sequences of pillow basalts and (or) andesites, bedded, generally radio- larian cherts, uniform shale sequences containing pelagic biotas and representing long time spans, pelagic carbonate sequences, great bodies of turbidite flysch, olistostromes, and metamorphic rocks that are not dealt with here. The sediments are commonly red colored.
For a century, explanations for these rocks have been sought along two different lines (paradigms) : In one they are viewed as the products of mobile belts and orogeny--specifically, as the contents of a special generative trough or complex of troughs, the eugeosyncline of Hans Stille and of Marshall Kay. In the other, which we may term the oceanic model and which was stated most clearly by R. S. Dietz and J. C Holden, they are viewed as the normal rocks of the oceans and oceanic margins brought to the mobile belts by plate subduction and incorporated into the continental margins by orogeny.
Progressive exploration of the oceans, first by dredging and coring and more lately by drilling, has shown that most of these rocks indeed correspond closely to the rocks of the great ocean floors. This seems to be particularly true when sediments of the same ages are compared.
Only the great andesite sequences and olistostromes remain as rock types linked to mobile belts or convergent plate margins. A good case can be made for a distant oceanic derivation of some ophiolite-sediment sequences in mountains (e.g., Elba), and therewith the eugeosynclinal model seems to have outlived its usefulness.
At the same time, a model substituting the main ocean basins for the eugeosyncline is even less realistic. Through the work of D. E. Karig and others, confirmed by legs 6 and 7 of the Deep Sea Drilling Project, it has become essentially certain that juvenile oceanic or semioceanic crust overlain by oceanic type sediment can grow in mobile belts to produce the interarc and marginal or small-ocean basins. Yet other sites of crustal growth are likely (e.g., Canary Islands). The ophiolites and sediments of such sites have a better chance of unmetamorphosed incorporation into mountains than does the main sea floor. The ophiolite complexes of Cyprus (Mamonia, Troodos) and of Kandahar, Afghanistan, should be viewed in this light.
Furthermore, the odd sediments of the mountain belts commonly form parts of otherwise normal or mio- geosynclinal successions (e.g., Martinsburg flysch, Jurassic sediments of Northern Limestone Alps), and the great andesite sequences occur either on oceanic crust (Antilles) or on sial (Andes). Olistostromes are most likely trench generated.
Thus, in principle, the odd rocks of the mountain belts represent a wide range of generative settings, including crust-generating ocean ridges and their flanks, abyssal plains, trenches, volcanic arcs, tectonic welts, interarc basins, and the downwarped edges of continents. Tectonic and paleogeographic reconstructions will remain extremely uncertain until we have learned to recognize these constituents more clearly. | <urn:uuid:ee26c517-66ee-4120-aac7-5202ca5e66d3> | 2.828125 | 772 | Academic Writing | Science & Tech. | 33.762857 | 95,528,291 |
Heidelberg physicists develop new dating method for the earth and environmental sciences
A Heidelberg physics project funded by the German Research Foundation (DFG) will focus on a new type of dating method for use in the earth and environmental sciences. The research team will deploy a special radioactive isotope of the noble gas argon (Ar) for the purpose of water dating.
This isotope is useful for determining age in the range of 50 to 1,000 years. Prof. Dr Markus Oberthaler of the Kirchhoff Institute for Physics and Prof. Dr Werner Aeschbach of the Institute of Environmental Physics of Heidelberg University will direct the three-year project. The DFG has approved funding in the amount of approximately one million euros. Research is dated to begin in March 2017.
The project, “ArTTA-10mL: An instrument for 39Ar-dating of small ice and water samples”, was selected for funding from the DFG's first-time call for bids for "New Instrumentation for Research." The work is a continuation of a long-standing collaboration between the working groups of Prof. Oberthaler and Prof. Aeschbach, who have already successfully used the dating method based on the noble gas radioisotope 39Ar and developed a prototype measurement device. The Heidelberg researchers intend to design the new, one-of-a-kind instrument for routine use on small samples and then make it available to other researchers.
Dating in the earth and environmental sciences is largely based on radioactive isotopes whose gradual decay provides time information. Because it is the only isotope that covers the important age range of 50 to 1,000 years, the noble gas radioisotope 39Ar is highly interesting for dating in ground water research, oceanography and glacier research.
The fact that it is extremely rare makes the work very challenging. Measurements in the 1960s showed only a single 39Ar atom in one quadrillion argon atoms in air. Dating ground or ocean water by detecting the radioactive decay of 39Ar requires samples of at least one ton water.
The Heidelberg measurement process is based on the fundamentally new method of Atom Trap Trace Analysis (ATTA), wherein 39Ar atoms are captured and detected in an atom trap. This technology for "manipulating" atoms was perfected in Heidelberg in recent years. It makes it possible to reduce the required sample size by a factor of 100 to 1,000, according to Prof. Oberthaler. In a preceding project, the researchers were able to demonstrate that measuring 39Ar is possible in principle using this procedure.
Now, using ocean water and Alpine ice, they have provided evidence that the 39Ar ATTA measurement can also be realised using small samples of only 25 litres of water or an argon volume of ten millilitres or less. "That opens up completely new application horizons. The need for such analyses is great, especially in the field of tracer oceanography," explains Prof. Aeschbach.
Markus Oberthaler conducts research at the Kirchhoff Institute for Physics, Werner Aeschbach at the Institute of Environmental Physics. Prof. Aeschbach is also Director of the Heidelberg Center for the Environment (HCE).
Prof. Dr Markus Oberthaler, Kirchhoff-Institute for Physics
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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....
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In my Java programming college class, we are learning more and more about classes. Specifically we are learning about access modifiers for instance variables and methods. One thing that is pretty clear is that if you have an instance variable in a class, and the variable name is myVar, then you cannot have another instance variable in the same class with the same variable name.
Within the class, you can reference an instance variable with just its name. You can optionally prepend the variable name with the keyword “this”. However in this scenario, “this” which represents the current object is already implied. So for most if not all of the time, the “this” keyword is omitted.
We are also learning about accessors and mutators in our programming class. Mutators, or setters, take an argument and set the instance variable to the value of that argument. Here is where some confusion in class came up. Support we have an instance variable in our class named “email”. What should we name the formal parameter of the setEmail method?
Most of the time, the simplest and most obvious variable name is the best one. So I thought I would name the formal argument to the mutator setEmail to be just “email”. But here is the problem and question. Does the local variable email, which is the formal parameter to the method in the class, clash with the instance variable of the same name?
The best way to answer questions like this is to try it out. It compile fine. So it must be ok. The only tricky part comes when you must set the instance variable to the formal parameter passed into the method. How do you do that if they are named the same? The trick is to qualify the instance variable with the “this” keyword. Then you get code that looks like this (no pun intended):
public void setEmail(String email)
this.email = email;
Now this may not be the best practice, as there might be some ambiguity as to which variable the name email refers to. So our instructor insisted that we name the formal parameter newEmail, or something else distinct from the instance variable name. That sounds logical. It was still cool to find out you could have two variables of the same name within the class.
Mysterious Double Instance Hampering Performance - I study the existing code base. Confer with a colleague. Then I determine the optimal plan to change the functionality to load only a slice of all the dat...
4 days ago | <urn:uuid:9f54242b-fa97-47f3-b0e5-e6f161581d26> | 3.59375 | 524 | Personal Blog | Software Dev. | 54.80959 | 95,528,305 |
Flask is a micro web framework written in Python and based on the Werkzeug toolkit and Jinja2 template engine. It is BSD licensed. The latest stable version of Flask is 0.12 as of December 2016. Applications that use the Flask framework include Pinterest, LinkedIn, and the community web page for Flask itself. Flask is called a micro framework because it does not require particular tools or libraries. It has no database abstraction layer, form validation, or any other components where pre-existing third-party libraries provide common functions. However, Flask supports extensions that can add application features as if they were implemented in Flask itself. Extensions exist for object-relational mappers, form validation, upload handling, various open authentication technologies and several common framework related tools. Extensions are updated far more regularly than the core Flask program.
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Static Methods are Fine
Static Methods are Fine
Read on to find out why static methods don't deserve to be demonized.
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Today, we’ll be talking about something controversial: static methods. I have yet to read anything that says static methods are good and useful, other than Effective Java recommending them in the use of static factory methods. There are some really interesting (and somewhat defective) arguments out there against them that rarely, if ever, even get explained. Notably, I’m providing a rebuttal to the article, Utility Classes Have Nothing to do With Functional Programming.
Today, we’re going to look at the good and bad of static methods; what they’re good for and what they’re not.
Static Methods are What Pure Functional Languages Use
As you probably know, functional programming has returned to our world as the “in” thing to do, and most OO languages have been adopting first-class functions (or some way to represent them, anyway) in order to be more of a hybrid between OO and FP.
In pure FP, there aren’t any classes; there are data types and functions. Those functions are not attached to any types, just namespaces. The same goes for static methods. They aren’t attached to types, they just have a namespace. Some might think that they are attached to types, since you have to put them in classes. But when it comes to static methods, the classes that are using them aren’t acting as classes; they only serve as namespaces for the static methods, a way to import them and differentiate them from other functions that might have the same name and arguments in a different namespace.
As long as both are able to do the same thing (which they practically can, when higher-order methods are available), they are the same. Things like currying only make functional programming more convenient are aren’t strictly necessary, in my opinion. So this doesn’t disqualify static methods from being the same thing.
There is one difference – an important one – between functions in pure functional programming and static methods: static methods can have side effects. For the sake of argument, we’ll assume we’re good programmers, though, and that we make our static methods pure. Or, at least mostly pure. There shouldn’t be any external side effects, at least, and these are the side effects I’ll refer to from now on. At the end, we’ll come back to this and look at the kind of difference it makes.
Now that we know that FP functions and static methods are essentially the same thing, let’s look at the arguments, shall we?
Imperative vs Declarative: In the linked article above, the author argues that FP functions are declarative while static methods are imperative. In truth, either can be either.
People tout that FP is declarative while OO is imperative. I’ve looked at this for a while and have come to the conclusion each simply makes one or the other the obvious way to do it. All the declarative building blocks of FP can be done in OO, and FP has the many of the same pieces available that make up imperative code. This is why Java’s Stream API is declarative; even if you don’t use lambdas or method references, you can use it declaratively with well-named functions and classes.
Even the other guy mentioned that you can be declarative in OO.
Testability: The complaint isn’t so much that static methods are hard to test (the claim is that FP is easy to test, so this better not be the case), but that things that use them are harder to test, since the calls are hard-coded and cannot be swapped out for others during testing. I have several rebuttals to this:
- Some parts of your functionality shouldn’t or don’t need to be swapped out, even for testing. If there are no side effects caused by the static method, there is almost no reason that it needs to be swapped out. If FP can handle this and still be called testable, so can static methods.
- You can swap out static methods. The trick is to take in a function as a parameter, where the static method can be supplied as an argument. “But then the static method gets hard-coded at the call site,” one might say. I say back, “Something has to get hard-coded somewhere.” Even with DI systems, we either tell it explicitly which specific class to use to fulfill a dependency, or it’s able to deduce it somehow; in either case, a specific class is used and therefore “hard-coded”. At some point, the dependency implementations must be chosen.
- If we can accept types that cannot be subclassed (String, for example) and use their methods, then there’s no fundamental difference between those methods and static methods, other than encapsulation. Sure, the primary object is passed as an argument instead of being what the method is called from, but that’s a semantic difference, not functional.Polymorphism doesn’t apply in those cases, so you can’t swap anything out other than the class’instance, which can also be done with static methods. No one says not to use those, though; in fact, preventing subclassing is often lauded as a virtue.
So, yeah, static methods are not fundamentally less testable.
Readability: By this, the original author talks about how huge utility classes get, collecting dozens and dozens of static methods. To that, I say that these utility classes are usually for classes that areextremely generic, and there’s a lot you should be able to do with them, which is what makes the utility classes big. Most of those utility methods should have been on the original class, making themreally big instead.
Efficiency: Next, he seems to claim that static methods are inherently eager and cannot be lazy. While this isn’t true, making them lazy largely just turns the static methods into static factory methods, since they’d have to create an object of a type that makes the operation lazy. FP languages have less of a problem with this because it’s the language that provides the laziness, so we can still write as if it’s eager, and it won’t be. Though, some forms of laziness can be used without language conventions or specialized objects. Simply accepting a value-generating function instead of a straight value as an argument that will only be used if/when needed is laziness.
Laziness isn’t always the ideal, though. In those instances when we’re definitely going to need the calculation, and right away, the overhead of creating the lazy operation wrapper supersedes the benefit of being able to put off the operation.
Now that I’ve said all that, it’s time for us to pull back a bit. I’m not saying to switch to all static methods; I don’t think being a purist in either direction is the way to go. Personally, I actually lean away from static methods as anything other than factory methods, as “replacements” for constructors. Also, they can be good for fluent interfaces, such as in matcher and testing libraries.
If you’re going to try and go mostly FP in a hybrid language, you may end up using more static methods, but there’s certainly nothing wrong with doing a normal method call. Go full on static should make us change our approach though. Generally, FP languages provide very powerful generic data structures and use them for just about everything, making new types only when it becomes less tedious to do so. This allows for reuse of functions more easily, keeping to total count down.
There’s an interesting inverse dynamic between functions using a family of types in FP compared to families of types with a shared interface of methods in OO. In true FP, it’s easier to add new functionality to the family of types, because you only need to write a single function to handle the different possibilities, but adding a new type to the family requires a change to all the already created functions. In OO, polymorphism allows us to add a type to a family without it affecting practically any old code, but adding a method to the family requires a change to every type in the family. In this sense, neither is inherently better than the other.
We probably shouldn’t overload our code bases with a ton of utility classes, as the article says (though ones for classes as generic as Strings, Dates, and Files probably aren’t as bad as people make them out to be), but neither should we ignore the fact that, sometimes, a static method serves a purpose better than objects and normal methods. Pragmatism should be used; do what’s best for the situation.
Static Method Guidelines
Whatever you do, don’t directly use static methods that are impure, that have side effects; any side effect calls should be swappable for testing. It’s slightly okay to create impure static methods, though it’s a dangerous idea, since it’s less obvious how to factor those method dependencies out for swappability.
When making our own static methods, keep them short, like anything else; this helps to keep the testability of the methods high.
If we’re working in a language with static methods, we should probably lean toward instances and methods and polymorphism, as that is where the language likely shines.
Published at DZone with permission of Jake Zimmerman , DZone MVB. See the original article here.
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