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10,807,068 | https://en.wikipedia.org/wiki/Journal%20of%20Systems%20and%20Software | The Journal of Systems and Software is a computer science journal in the area of software systems, established in 1979 and published by Elsevier.
Content and scope
The journal publishes research papers, state-of-the-art surveys, and practical experience reports. It includes papers covering issues of programming methodology, software engineering, and hardware/software systems. Topics include: "software systems, prototyping issues, high-level specification techniques, procedural and functional programming techniques, data-flow concepts, multiprocessing, real-time, distributed, concurrent, and telecommunications systems, software metrics, reliability models for software, performance issues, and management concerns."
Abstracting and indexing
According to the 2021 Journal Citation Reports, the Journal of Systems and Software has an impact factor of 3.514.
According to Google Scholar, the journal has an h5-index of 61, which ranks third among international publication venues in software systems, after ICSE and IEEE Transactions on Software Engineering.
Past and present editors-in-chief
John Manley and Alan Salisbury (1979–1983)
Richard E. Fairley (1984–1985)
Robert L. Glass (1986–2001)
David N. Card (2002–2008)
Hans van Vliet (2009–2017)
Paris Avgeriou and David Shepherd (2018–current)
Notable articles
A few of the most notable (downloaded) articles are:
Software defect prediction based on enhanced metaheuristic feature selection optimization and a hybrid deep neural network
A software engineering perspective on engineering machine learning systems: State of the art and challenges
MeTeaM: A method for characterizing mature software metrics teams
References
External links
Online access
Academic journals established in 1979
Computer science journals
Software engineering publications
Systems engineering
Elsevier academic journals
English-language journals
Monthly journals | Journal of Systems and Software | [
"Technology",
"Engineering"
] | 360 | [
"Software engineering publications",
"Works about computing",
"Systems engineering",
"Software engineering"
] |
10,807,783 | https://en.wikipedia.org/wiki/Allotype%20%28immunology%29 | The word allotype comes from two Greek roots, allo meaning 'other or differing from the norm' and typos meaning 'mark'. In immunology, allotype is an immunoglobulin variation (in addition to isotypic variation) that can be found among antibody classes and is manifested by heterogeneity of immunoglobulins present in a single vertebrate species. The structure of immunoglobulin polypeptide chain is dictated and controlled by number of genes encoded in the germ line. However, these genes, as it was discovered by serologic and chemical methods, could be highly polymorphic. This polymorphism is subsequently projected to the overall amino acid structure of antibody chains. Polymorphic epitopes can be present on immunoglobulin constant regions on both heavy and light chains, differing between individuals or ethnic groups and in some cases may pose as immunogenic determinants. Exposure of individuals to a non-self allotype might elicit an anti- allotype response and became cause of problems for example in a patient after transfusion of blood or in a pregnant woman. However, it is important to mention that not all variations in immunoglobulin amino acid sequence pose as a determinant responsible for immune response. Some of these allotypic determinants may be present at places that are not well exposed and therefore can be hardly serologically discriminated. In other cases, variation in one isotype can be compensated by the presence of this determinant on another antibody isotype in one individual. This means that divergent allotype of heavy chain of IgG antibody may be balanced by presence of this allotype on heavy chain of for example IgA antibody and therefore is called isoallotypic variant. Especially large number of polymorphisms were discovered in IgG antibody subclasses. Which were practically used in forensic medicine and in paternity testing, before replaced by modern day DNA fingerprinting.
Definition and organisation of allotypes in humans
Human allotypes nomenclature was first described in alphabetical system and further systematized in numerical system, but both could be found in the literature. For example, allotype expressed on constant region of heavy chain on IgG are designated by Gm which stands for ‘genetic marker ‘ together with IgG subclass (IgG1 àG1m, IgG2 àG2m) and the allotype number or letter [ G1m1/ G1m (a) ]. Polymorphisms within IgA are denoted in the same way as A2m (eg. A2m1/2) and kappa light chains constant region polymorphisms as Km (eg. Km1). Despite the fact, that there are multiple known lambda chain isotypes, there have not been reported any lambda chain serological polymorphisms.
All these before mentioned allotypes are expressed on constant regions of the immunoglobulin. Genes responsible for encoding structure of constant regions of heavy chains are closely linked and therefore inherited together as one haplotype with low number of crossovers. Although some crossovers did occur during human evolution resulting in the creation of current populations characteristic haplotypes and importance of allotype system in population studies.,
Implications for monoclonal antibody therapy
Antibody allotypes came back to spotlight due to development and use of therapies based on monoclonal antibodies. These recombinant human glycoproteins and proteins are now well established in clinical practise, but sometimes leads to adverse effects such as generation of antitherapeutic antibodies that negates therapy or even cause severe reactions to the therapy. This reaction may be attributed to differences between therapeutics itself or may arise between same therapeutics produced by different companies or even between different lots produced by the same company. To prevent production of such antitherapeutic antibodies, ideally, all clinical used proteins and glycoproteins should poses same allotype as natural patient’s product, this way the presence of ‘altered self‘ which poses a potential target for immune system, is limited. Whilst many parameters connected to developing and manufacturing process that might predispose monoclonal antibodies to cause immune response are well known and appropriate steps are taken to monitor and control these unwanted effects, complications linked with administration of monoclonal antibodies to genetically diverse human population are less well described. Humans exhibit abundance of genotypes and phenotypes, however all currently licensed IgG therapeutic immunoglobulins are developed as single allotypic/ polymorphic form. Patients that are homozygous for alternative phenotype are therefore at higher risk of developing potential immune response to the therapy.
See also
Allotype (disambiguation)
Idiotype
Isotype
References
External links
Genetics
Transplantation medicine | Allotype (immunology) | [
"Biology"
] | 1,000 | [
"Genetics"
] |
10,807,821 | https://en.wikipedia.org/wiki/Idiotype | In immunology, an idiotype is a shared characteristic between a group of immunoglobulin or T-cell receptor (TCR) molecules based upon the antigen binding specificity and therefore structure of their variable region. The variable region of antigen receptors of T cells (TCRs) and B cells (immunoglobulins) contain complementarity-determining regions (CDRs) with unique amino acid sequences. They define the surface and properties of the variable region, determining the antigen specificity and therefore the idiotope of the molecule. Immunoglobulins or TCRs with a shared idiotope are the same idiotype. Antibody idiotype is determined by:
Gene rearrangement
Junctional diversity
P-nucleotides (palindromic nucleotides at sites of single-strand breaks)
N-nucleotides
Somatic hypermutations
Etymology and usage
The word idiotype comes from two Greek roots, idio meaning 'private, distinctive, peculiar' and typos meaning 'mark.' Thus, idiotype describes the distinctive sequence and region that makes any immunoglobulin/TCR unique from others of the same type which is its variable region.
The term "idiotype" is sometimes used to describe the collection of multiple idiotopes, and therefore overall antigen binding capacity, possessed by an antibody.
The word "idiotype" became influential in immunology when Niels Jerne formulated his immune network theory. Jerne was awarded the Nobel Prize in Physiology or Medicine in 1984 largely for being the father of immune network theory. He defined idiotype as the set of epitopes on the V region of an antibody molecule, where epitope means an antigenic determinant. He also defined the "paratope" to be that part of an antibody variable region that binds to an antigen. The best developed version of immune network theory is called the symmetrical network theory, in which the distinction between idiotype and paratope plays no role.
See also
Allotype (immunology)
Isotype (immunology)
Immune network theory
External links
Overview at Medical University of South Carolina
Overview at Southern Illinois University Carbondale
Immune system | Idiotype | [
"Biology"
] | 450 | [
"Immune system",
"Organ systems"
] |
10,807,859 | https://en.wikipedia.org/wiki/Isotype%20%28immunology%29 | In immunology, antibodies (immunoglobulins (Ig)) are classified into several types called isotypes or classes.
The variable (V) regions near the tip of the antibody can differ from molecule to molecule in countless ways, allowing it to specifically target an antigen (or more exactly, an epitope).
In contrast, the constant (C) regions only occur in a few variants, which define the antibody's class.
Antibodies of different classes activate distinct effector mechanisms in response to an antigen (triggering different elements of the innate immune system).
They appear at different stages of an immune response, differ in structural features, and in their location around the body.
Isotype expression reflects the maturation stage of a B cell. Naive B cells express IgM and IgD isotypes with unmutated variable genes, which are produced from the same initial transcript following alternative splicing. Expression of other antibody isotypes (in humans: IgG, IgA, and IgE) occurs via a process of class switching after antigen exposure. Class switching is mediated by the enzyme AID (activation-induced cytidine deaminase) and occurs after the B cell binds an antigen through its B cell receptor. Class-switching usually requires interaction with a T helper cell.
In humans, there are five heavy chain isotypes α,δ,γ,ε,μ, corresponding to five antibody isotypes:
α – IgA, further divided into subclasses IgA1 and IgA2
δ – IgD
γ – IgG, further divided into subclasses IgG1 to IgG4
ε – IgE
μ – IgM
There are also two light chain isotypes κ and λ; however, there is no significant difference in function between the two. Thus an antibody isotype is determined by the constant regions of the heavy chains only.
IgM is first expressed as a monomer on the surface of immature B cells. Upon antigenic stimulation, IgM+ B cells secrete pentameric IgM antibody formed by five Ig monomers which are linked via disulfide bonds. The pentamer also contains a polypeptide J-chain, which links two of the monomers and facilitates secretion at mucosal surfaces. The pentameric structure of IgM antibodies makes them efficient at binding antigens with repetitive epitopes (e.g. bacterial capsule, viral capsid) and activation of complement cascade. As IgM antibodies are expressed early in a B cell response, they are rarely highly mutated and have broad antigen reactivity thus providing an early response to a wide range of antigens without the need for T cell help.
IgD isotypes are expressed on naive B cells as they leave bone marrow and populate secondary lymphoid organs. The levels of surface expression of IgD isotype has been associated with differences in B cell activation status but their role in serum is poorly understood.
The IgG, IgE and IgA antibody isotypes are generated following class-switching during germinal centre reaction and provide different effector functions in response to specific antigens. IgG is the most abundant antibody class in the serum and it is divided into 4 subclasses based on differences in the structure of the constant region genes and the ability to trigger different effector functions. Despite the high sequence similarity (90% identical on the amino acid level), each subclass has a different half-life, a unique profile of antigen binding and distinct capacity for complement activation. IgG1 antibodies are the most abundant IgG class and dominate the responses to protein antigens. Impaired production of IgG1 is observed in some cases of immunodeficiency and is associated with recurrent infections. The IgG responses to bacterial capsular polysaccharide antigens are mediated primarily via IgG2 subclass, and deficiencies in this subclass result in susceptibility to certain bacterial species. IgG2 represents the major antibody subclass reacting to glycan antigens but IgG1 and IgG3 subclasses have also been observed in such responses, particularly in the case of protein-glycan conjugates.
IgG3 is an efficient activator of pro-inflammatory responses by triggering the classical complement pathway. It has the shortest half-life compared to the other IgG subclasses and is frequently present together with IgG1 in response to protein antigens after viral infections. IgG4 is the least abundant IgG subclass in the serum and is often generated following repeated exposure to the same antigen or during persistent infections.
IgA antibodies are secreted in the respiratory or the intestinal tract and act as the main mediators of mucosal immunity. They are monomeric in the serum, but appear as a dimer termed secretory IgA (sIgA) at mucosal surfaces. The secretory IgA is associated with a J-chain and another polypeptide chain called the secretory component. IgA antibodies are divided into two subclasses that differ in the size of their hinge region. IgA1 has a longer hinge region which increases its sensitivity to bacterial proteases. Therefore, this subclass dominates the serum IgA, while IgA2 is predominantly found in mucosal secretions. Complement fixation by IgA is not a major effector mechanism at the mucosal surface but IgA receptor is expressed on neutrophils which may be activated to mediate antibody-dependent cellular cytotoxicity. sIgA has also been shown to potentiate the immune response in intestinal tissue by uptake of antigen together with the bound antibody by dendritic cells.
IgE antibodies are present at lowest concentrations in peripheral blood but constitute the main antibody class in allergic responses through the engagement of mast cells, eosinophils and Langerhans cells. Responses to specific helminths are also characterised with elevated levels of IgE antibodies.
See also
Idiotype
References
External links
Overview at University of South Carolina School of Medicine
Overview at Southern Illinois University Carbondale
Immunology | Isotype (immunology) | [
"Biology"
] | 1,264 | [
"Immunology"
] |
10,807,945 | https://en.wikipedia.org/wiki/Odd%E2%80%93even%20sort | In computing, an odd–even sort or odd–even transposition sort (also known as brick sort or parity sort) is a relatively simple sorting algorithm, developed originally for use on parallel processors with local interconnections. It is a comparison sort related to bubble sort, with which it shares many characteristics. It functions by comparing all odd/even indexed pairs of adjacent elements in the list and, if a pair is in the wrong order (the first is larger than the second) the elements are switched. The next step repeats this for even/odd indexed pairs (of adjacent elements). Then it alternates between odd/even and even/odd steps until the list is sorted.
Sorting on processor arrays
On parallel processors, with one value per processor and only local left–right neighbor connections, the processors all concurrently do a compare–exchange operation with their neighbors, alternating between odd–even and even–odd pairings. This algorithm was originally presented, and shown to be efficient on such processors, by Habermann in 1972.
The algorithm extends efficiently to the case of multiple items per processor. In the Baudet–Stevenson odd–even merge-splitting algorithm, each processor sorts its own sublist at each step, using any efficient sort algorithm, and then performs a merge splitting, or transposition–merge, operation with its neighbor, with neighbor pairing alternating between odd–even and even–odd on each step.
Batcher's odd–even mergesort
A related but more efficient sort algorithm is the Batcher odd–even mergesort, using compare–exchange operations and perfect-shuffle operations.
Batcher's method is efficient on parallel processors with long-range connections.
Algorithm
The single-processor algorithm, like bubblesort, is simple but not very efficient. Here a zero-based index is assumed:
function oddEvenSort(list) {
function swap(list, i, j) {
var temp = list[i];
list[i] = list[j];
list[j] = temp;
}
var sorted = false;
while (!sorted) {
sorted = true;
for (var i = 1; i < list.length - 1; i += 2) {
if (list[i] > list[i + 1]) {
swap(list, i, i + 1);
sorted = false;
}
}
for (var i = 0; i < list.length - 1; i += 2) {
if (list[i] > list[i + 1]) {
swap(list, i, i + 1);
sorted = false;
}
}
}
}
Proof of correctness
Claim: Let be a sequence of data ordered by <. The odd–even sort algorithm correctly sorts this data in passes. (A pass here is defined to be a full sequence of odd–even, or even–odd comparisons. The passes occur in order pass 1: odd–even, pass 2: even–odd, etc.)
Proof:
This proof is based loosely on one by Thomas Worsch.
Since the sorting algorithm only involves comparison-swap operations and is oblivious (the order of comparison-swap operations does not depend on the data), by Knuth's 0–1 sorting principle, it suffices to check correctness when each is either 0 or 1. Assume that there are 1s.
Observe that the rightmost 1 can be either in an even or odd position, so it might not be moved by the first odd–even pass. But after the first odd–even pass, the rightmost 1 will be in an even position. It follows that it will be moved to the right by all remaining passes. Since the rightmost one starts in position greater than or equal to , it must be moved at most steps. It follows that it takes at most passes to move the rightmost 1 to its correct position.
Now, consider the second rightmost 1. After two passes, the 1 to its right will have moved right by at least one step. It follows that, for all remaining passes, we can view the second rightmost 1 as the rightmost 1. The second rightmost 1 starts in position at least and must be moved to position at most , so it must be moved at most steps. After at most 2 passes, the rightmost 1 will have already moved, so the entry to the right of the second rightmost 1 will be 0. Hence, for all passes after the first two, the second rightmost 1 will move to the right. It thus takes at most passes to move the second rightmost 1 to its correct position.
Continuing in this manner, by induction it can be shown that the -th rightmost 1 is moved to its correct position in at most passes. Since , it follows that the -th rightmost 1 is moved to its correct position in at most passes. The list is thus correctly sorted in passes. QED.
We remark that each pass takes steps, so this algorithm has complexity.
References
Comparison sorts
Stable sorts
Articles with example pseudocode
Articles containing proofs | Odd–even sort | [
"Mathematics"
] | 1,040 | [
"Articles containing proofs"
] |
10,809,455 | https://en.wikipedia.org/wiki/46%C2%B0%20halo | A 46° halo is a rare atmospheric optical phenomenon that consists of a halo with an apparent radius of approximately 46° around the Sun. At solar elevations of 15–27°, 46° halos are often confused with the less rare and more colourful supralateral and infralateral arcs, which cross the parhelic circle at about 46° to the left and right of the sun.
The 46° halo is similar to, but much larger and fainter than, the more common 22° halo. The 46° halo forms when sunlight enters randomly oriented hexagonal ice crystals through a prism face and exits through a hexagonal base.
The 90° inclination between the two faces of the crystals causes the colours of the 46° halo to be more widely dispersed than those of the 22° halo. In addition, as many rays are deflected at larger angles than the angle of minimum deviation, the outer edge of the halo is more diffuse.
To tell the difference between a 46° halo and the infralateral or supralateral arcs, one should carefully observe sun elevation and the fluctuating shapes and orientations of the arcs. The supralateral arc always touches the circumzenithal arc, while the 46° halo only achieves this when the sun is located 15–27° over the horizon, leaving a gap between the two at other elevations. In contrast, supralateral arcs cannot form when the Sun is over 32°, so a halo in the region of 46° is always a 46° halo at higher elevations. If the Sun is near the zenith, however, circumhorizontal or infralateral arcs are located 46° under the Sun and can be confused with the 46° halo.
References
External links
Atmospheric Optics - 46° Radius Halo - including a HaloSim computer simulation and an Antarctica fish eye photo.
Atmospheric optical phenomena | 46° halo | [
"Physics"
] | 392 | [
"Optical phenomena",
"Physical phenomena",
"Atmospheric optical phenomena",
"Earth phenomena"
] |
10,810,026 | https://en.wikipedia.org/wiki/Methylcyclohexane | Methylcyclohexane (cyclohexylmethane) is an organic compound with the molecular formula is CH3C6H11. Classified as saturated hydrocarbon, it is a colourless liquid with a faint odor.
Methylcyclohexane is used as a solvent. It is mainly converted in naphtha reformers to toluene. A special use is in PF-1 priming fluid in cruise missiles to aid engine start-up when they run on special nonvolatile jet fuel like JP-10. Methylcyclohexane is also used in some correction fluids (such as White-Out) as a solvent.
History
While researching hydrogenation of arenes with hydroiodic acid in 1876 as part of his doctoral dissertation, first prepared the hydrocarbon from toluene. He determined its boiling point to be 97°C, its density at 20°C to by 0.76 g/cc and named it hexahydrotoluene. It was soon identified in oil from Baku and obtained by other synthetic methods.
Production and use
Most methylcyclohexane is extracted from petroleum but it can be also produced by catalytic hydrogenation of toluene:
CH3C6H5 + 3 H2 → CH3C6H11
The hydrocarbon is a minor component of automobile fuel, with its share in US gasoline varying between 0.3 and 1.7% in early 1990s and 0.1 to 1% in 2011. Its research and motor octane numbers are 75 and 71 respectively.
As a component of a mixture, it is usually dehydrogenated to toluene, which increases the octane rating of gasoline.
It is also one of a host of substances in jet fuel surrogate blends, e.g., for Jet A fuel.
Solvent
Methylcyclohexane is used as an organic solvent, with properties similar to related saturated hydrocarbons such as heptane. It is also a solvent in many types of correction fluids.
Structure
Methylcyclohexane is a monosubstituted cyclohexane because it has one branching via the attachment of one methyl group on one carbon of the cyclohexane ring. Like all cyclohexanes, it can interconvert rapidly between two chair conformers. The lowest energy form of this monosubstituted methylcyclohexane occurs when the methyl group occupies an equatorial rather than an axial position. This equilibrium is embodied in the concept of A value. In the axial position, the methyl group experiences steric crowding (steric strain) because of the presence of axial hydrogen atoms on the same side of the ring (known as the 1,3-diaxial interactions). There are two such interactions, with each pairwise methyl/hydrogen combination contributing approximately 7.61 kJ/mol of strain energy. The equatorial conformation experiences no such interaction, and so it is the energetically favored conformation.
Flammability and toxicity
Methylcyclohexane is flammable.
Furthermore, it is considered "very toxic to aquatic life". Note, while methylcyclohexane is a substructure of 4-methylcyclohexanemethanol (MCHM), it is distinct in its physical, chemical, and biological (ecologic, metabolic, and toxicologic) properties.
References
Hydrocarbons
Hydrocarbon solvents
Cyclohexyl compounds
Methyl compounds | Methylcyclohexane | [
"Chemistry"
] | 718 | [
"Organic compounds",
"Hydrocarbons"
] |
10,810,064 | https://en.wikipedia.org/wiki/Methylenecyclohexane | Methylenecyclohexane (IUPAC name: methylidenecyclohexane) is an organic compound with the molecular formula C7H12.
Synthesis
It can be produced by a Wittig reaction or a reaction with a Tebbe's reagent from cyclohexanone. It can also be synthesized as a side product of the dehydration of 2-methylcyclohexanol into 1-methylcyclohexene.
Structure
Methylenecyclohexane is an unsaturated hydrocarbon, containing a cyclohexane ring with a methylene (methylidine) group attached.
See also
Methylcyclohexane
Methylenecyclopropane
References
Vinylidene compounds
Hydrocarbons | Methylenecyclohexane | [
"Chemistry"
] | 163 | [
"Organic compounds",
"Hydrocarbons"
] |
10,810,380 | https://en.wikipedia.org/wiki/Propylamphetamine | Propylamphetamine (code name PAL-424; also known as N-propylamphetamine or NPA) is a psychostimulant of the amphetamine family which was never marketed. It was first developed in the 1970s, mainly for research into the metabolism of, and as a comparison tool to, other amphetamines.
Propylamphetamine is inactive as a dopamine releasing agent in vitro and instead acts as a low-potency dopamine reuptake inhibitor with an of 1,013nM. The drug can be N-dealkylated to form amphetamine (10–20% excreted in urine after 24hours). A study in rats found propylamphetamine to be approximately 4-fold less potent than amphetamine.
See also
Methamphetamine
Ethylamphetamine
Isopropylamphetamine
Butylamphetamine
Phenylpropylaminopentane
References
Norepinephrine-dopamine releasing agents
Prodrugs
Substituted amphetamines | Propylamphetamine | [
"Chemistry"
] | 226 | [
"Chemicals in medicine",
"Prodrugs"
] |
10,810,905 | https://en.wikipedia.org/wiki/Post%20Irradiation%20Examination | Post Irradiation Examination (PIE) is the study of used nuclear materials such as nuclear fuel. It has several purposes. It is known that by examination of used fuel that the failure modes which occur during normal use (and the manner in which the fuel will behave during an accident) can be studied. In addition information is gained which enables the users of fuel to assure themselves of its quality and it also assists in the development of new fuels. After major accidents the core (or what is left of it) is normally subject to PIE in order to find out what happened. One site where PIE is done is the ITU which is the EU centre for the study of highly radioactive materials.
Materials in a high radiation environment (such as a reactor) can undergo unique behaviors such as swelling and non-thermal creep. If there are nuclear reactions within the material (such as what happens in the fuel), the stoichiometry will also change slowly over time. These behaviors can lead to new material properties, cracking, and fission gas release:
Fission gas release
As the fuel is degraded or heated the more volatile fission products which are trapped within the uranium dioxide may become free.
Fuel cracking
As the fuel expands on heating, the core of the pellet expands more than the rim which may lead to cracking. Because of the thermal stress thus formed the fuel cracks, the cracks tend to go from the centre to the edge in a star shaped pattern.
In order to better understand and control these changes in materials, these behaviors are studied. . Due to the intensely radioactive nature of the used fuel this is done in a hot cell. A combination of nondestructive and destructive methods of PIE are common.
In addition to the effects of radiation and the fission products on materials, scientists also need to consider the temperature of materials in a reactor, and in particular, the fuel. Too high fuel temperatures can compromise the fuel, and therefore it is important to control the temperature in order to control the fission chain reaction.
The temperature of the fuel varies as a function of the distance from the centre to the rim. At distance x from the centre the temperature (Tx) is described by the equation where ρ is the power density (W m−3) and Kf is the thermal conductivity.
Tx = TRim + ρ (rpellet2 - x2) (4 Kf)−1
To explain this for a series of fuel pellets being used with a rim temperature of 200 °C (typical for a BWR) with different diameters and power densities of 250 Wm−3 have been modeled using the above equation. Note that these fuel pellets are rather large; it is normal to use oxide pellets which are about 10 mm in diameter.
Further reading
Radiochemistry and Nuclear Chemistry, G. Choppin, J-O Liljenzin and J. Rydberg, 3rd Ed, 2002, Butterworth-Heinemann,
References
External links
IAEA (International Atomic Energy Agency) - Post Irradiation Examination Facilities Database
Nuclear materials
Nuclear reprocessing
Nuclear technology
Nuclear chemistry
Radioactive waste
Actinides | Post Irradiation Examination | [
"Physics",
"Chemistry",
"Technology"
] | 632 | [
"Nuclear chemistry",
"Radioactive waste",
"Nuclear technology",
"Materials",
"Nuclear materials",
"Hazardous waste",
"nan",
"Nuclear physics",
"Radioactivity",
"Environmental impact of nuclear power",
"Matter"
] |
10,811,164 | https://en.wikipedia.org/wiki/Terry%20Lovejoy | Terry Lovejoy (born 20 November 1966) is an information technologist from Thornlands, Queensland, Australia, most widely known as an amateur astronomer. He has discovered six comets, including C/2011 W3 (Lovejoy), the first Kreutz Sungrazing comet discovered by ground-based observation in over 40 years. He is also known for popularizing procedures for modifying consumer-grade digital cameras so that they can be used for digital camera astrophotography.
Astrophotography
Lovejoy is known among amateur astronomers for identifying modifications to digital cameras needed for astrophotography. Such cameras come configured with built-in filters that cut off infrared light. They also cut off some of the red light that many deep space objects emit. After he published procedures to modify those filters, many amateur astronomers were able to improve their deep space photography.
Gordon J. Garradd named 61342 Lovejoy in honor of Lovejoy after discovering it on 3 August 2000.
On 15 March 2007, Lovejoy used a standard camera to discover the comet C/2007 E2 (Lovejoy). Two months later, he discovered another comet, designated C/2007 K5 (Lovejoy) using the modified camera.
On 27 November 2011, with his discovery of C/2011 W3 (Lovejoy), he became the first astronomer in over 40 years to discover a Kreutz Sungrazing comet from a ground-based observation. The discovery was made using a Celestron C8 Schmidt–Cassegrain telescope working at f/2.1 with a QHY9 CCD camera.
On 7 September 2013, Lovejoy discovered comet C/2013 R1 (Lovejoy) which became visible to the naked eye in November 2013.
On 17 August 2014, Lovejoy discovered comet C/2014 Q2 (Lovejoy) in the constellation Puppis.
His most recent discovery, C/2017 E4 (Lovejoy), was confirmed on 13 March 2017.
Gallery
References
Living people
People from South East Queensland
21st-century Australian astronomers
People in information technology
Australian computer specialists
Discoverers of comets
1966 births
People from Redland City | Terry Lovejoy | [
"Technology"
] | 434 | [
"People in information technology",
"Information technology"
] |
10,811,867 | https://en.wikipedia.org/wiki/Inorganic%20polymer | In polymer chemistry, an inorganic polymer is a polymer with a skeletal structure that does not include carbon atoms in the backbone. Polymers containing inorganic and organic components are sometimes called hybrid polymers, and most so-called inorganic polymers are hybrid polymers. One of the best known examples is polydimethylsiloxane, otherwise known commonly as silicone rubber. Inorganic polymers offer some properties not found in organic materials including low-temperature flexibility, electrical conductivity, and nonflammability. The term inorganic polymer refers generally to one-dimensional polymers, rather than to heavily crosslinked materials such as silicate minerals. Inorganic polymers with tunable or responsive properties are sometimes called smart inorganic polymers. A special class of inorganic polymers are geopolymers, which may be anthropogenic or naturally occurring.
Main group backbone
Traditionally, the area of inorganic polymers focuses on materials in which the backbone is composed exclusively of main-group elements.
Homochain polymers
Homochain polymers have only one kind of atom in the main chain. One member is polymeric sulfur, which forms reversibly upon melting any of the cyclic allotropes, such as S8. Organic polysulfides and polysulfanes feature short chains of sulfur atoms, capped respectively with alkyl and H. Elemental tellurium and the gray allotrope of elemental selenium also are polymers, although they are not processable.
Polymeric forms of the group IV elements are well known. The premier materials are polysilanes, which are analogous to polyethylene and related organic polymers. They are more fragile than the organic analogues and, because of the longer bonds, carry larger substituents. Poly(dimethylsilane) is prepared by reduction of dimethyldichlorosilane. Pyrolysis of poly(dimethylsilane) gives SiC fibers.
Heavier analogues of polysilanes are also known to some extent. These include polygermanes, and polystannanes,
Heterochain polymers
Si-based
Heterochain polymers have more than one type of atom in the main chain. Typically two types of atoms alternate along the main chain. Of great commercial interest are the polysiloxanes, where the main chain features Si and O centers: . Each Si center has two substituents, usually methyl or phenyl. Examples include polydimethylsiloxane (PDMS, ), polymethylhydrosiloxane (PMHS, ) and polydiphenylsiloxane ). Related to the siloxanes are the polysilazanes. These materials have the backbone formula . One example is perhydridopolysilazane PHPS. Such materials are of academic interest.
P-based
A related family of well studied inorganic polymers are the polyphosphazenes. They feature the backbone . With two substituents on phosphorus, they are structurally similar related to the polysiloxanes. Such materials are generated by ring-opening polymerization of hexachlorophosphazene followed by substitution of the groups by alkoxide. Such materials find specialized applications as elastomers.
B-based
Boron–nitrogen polymers feature backbones. Examples are polyborazylenes, polyaminoboranes.
S-based
The polythiazyls have the backbone . Unlike most inorganic polymers, these materials lack substituents on the main chain atoms. Such materials exhibit high electrical conductivity, a finding that attracted much attention during the era when polyacetylene was discovered. It is superconducting below 0.26 K.
Ionomers
Usually not classified with charge-neutral inorganic polymers are ionomers. Phosphorus–oxygen and boron-oxide polymers include the polyphosphates and polyborates.
Transition-metal-containing polymers
Inorganic polymers also include materials with transition metals in the backbone. Examples are Polyferrocenes, Krogmann's salt and Magnus's green salt.
Polymerization methods
Inorganic polymers are formed, like organic polymers, by:
Step-growth polymerization: Polysiloxanes;
Chain-growth polymerization: Polysilanes;
Ring-opening polymerization: Poly(dichlorophosphazene).
Reactions
Inorganic polymers are precursors to inorganic solids. This type of reaction is illustrated by the stepwise conversion of ammonia borane to discrete rings and oligomers, which upon pyrolysis give boron nitrides.
References | Inorganic polymer | [
"Chemistry"
] | 936 | [
"Inorganic polymers",
"Inorganic compounds"
] |
10,812,281 | https://en.wikipedia.org/wiki/Alternaria%20alternata | Alternaria alternata is a fungus causing leaf spots, rots, and blights on many plant parts, and other diseases. It is an opportunistic pathogen on over 380 host species of plant.
It can also cause upper respiratory tract infections and asthma in humans with compromised immunity.
Hosts and symptoms
Alternaria alternata has many different hosts depending on its forma specialis.
A. a. f. sp. (AAL) infects only certain cultivars of tomato plants and is often referred to as Alternaria stem canker of tomato. AALs main symptom is cankers in the stem. It resides in seeds and seedlings, and is often spread by spores as they become airborne and land on plants. It can also spread throughout other plants. Under severe infection, lesions enlarge and become coalesced causing blighting of the leaves. This symptom progression occurred in research done in Pakistan: the symptoms on affected tomatoes started with yellowing and browning of the lower leaves, then began developing on the leaf tips and along the margins of the leaf petiole. This progression continued until the entire leaves were covered in diseased tissue and then fell off. In addition to necrotic leaves and petioles, plants are found to have severe defoliation, with considerable yield losses when it occurs before flowering. The tomato fruit can also be infected as well, with brown cankers dotting them and making them inedible. Once the disease has spread to a certain point, little can be done to save the tomato plant.
There are several host factors that affect disease development. For example, various signaling pathways in tomato plants affect their susceptibility to AAL. Salicylic acid promotes resistance to AAL and antagonizes the ethylene response. Ethylene controls the synthesis of jasmonic acid, which is a necessary pathway for immunity. Independently of each other, salicylic acid, ethylene, and jasmonic acid can influence the susceptibility of tomato to AAL. Diagnosis of AAL is often from observing signs and symptoms from this fungal pathogen. In addition, a tomato cultivar's resistance to a toxin produced by AAL also affects disease development.
Environment
In order to survive, Alternaria alternata needs a moist warm environment. It is often found in areas with humid climates, or where there has been significant rainfall. The fungus lives in seeds and seedlings, and is also spread by spores. This disease flourishes in dead plants that have been left in gardens over winter. Additionally, when dead infected debris is added to compost pile it can spread to other vegetables throughout the garden.
There are no insect vectors for this disease. This means that using insecticides has no effect on the spread of this pathogen. However, there are several cultural practices that can be followed to suppress this fungal pathogen's impact. The disease first occurs in the host's exposed leaves. Plants planted with rows in an east–west direction have more severe disease than do plants planted north–south. This implies that if one plants tomato plants in a north–south manner they will be less susceptible. It is also suggested to highly monitor plants in April through June. This is when the pathogen is most prevalent. If monitoring indicates the presence of AAL, it is suggested to begin late-spring treatments of fungicide about mid-April. However, if a garden has a history of disease, it is advised to take extra measures. This can be done by treating tomatoes in mid to late April and 2 to 3 weeks later by applying a fungicide. Because this is a fungal pathogen that thrives off of wet environments, overhead irrigation is never advised when irrigating. This causes the moisture to remain on the leaf tissue and increase susceptibility to the disease and provides an optimal environment for the fungus to survive and grow. Furrow irrigation or drip irrigation systems allow the plant to remain dry.
Overall, AAL thrives in moist warm environments. Cultural practices for preventing this disease include planting tomatoes in a row north to south, monitoring plants heavily April through June, and using a drip irrigation system to keep as much plant tissue dry and free of favorable environments for this pathogen.
While γ-aminobutyric acid (GABA) has no direct fungicidal activity on A. alternata, it does induce resistance in tomato (Solanum lycopersicum). Some or all of that resistance is by activation of the tomato's own enzymes exerting an antioxidant effect.
Disease cycle
Teleomorph of Alternaria alternata is thought to be Clathrospora diplospora: this has yet to be confirmed. If this is correct, as a result this pathogen would be propagating itself via asexual spores called conidia. These conidia are produced in lesions on mature or dying leaves. Their production can begin in as few as ten days after the first symptoms appear, and can continue for to up to fifty days. A. alternata's conidia disperse via air currents, and their release from the lesions can be triggered by rainfall, or even just a sudden drop in humidity. When the conidium lands on a leaf, it will wait until the nighttime dew, and then germinate. It can either enter through the stomata, or penetrate directly through the top of the leaf, using its appressorium, infecting the leaf within 12 hours.
Pathogenesis
At the cellular level, AAL produces toxins that are essential for pathogenicity on tomato. This host specific mycotoxin is called fumonisin B1. It was identified and confirmed by research conducted on fast atom bombardment and ion spray mass spectrometry. Thus, tomatoes that are resistant to this pathogen may be resistance to this specific toxin. Resistance to the pathogen in tomato is inherited as a single gene expressing complete dominance. However, sensitivity to the fumonisin B1 gene is controlled by a single locus with two alleles expressing incomplete dominance when heterozygous. In addition to resistance to the specific gene, resistance can be found from signaling pathways.
At the organismal level, AAL grows very slowly. This makes it so its presence is often not known until seedlings become larger and are transplanted into the garden. A fungicide may be used to save the plants once they are infected; however, the disease cannot be completely eradicated.
Ultimately, pathogenicity of this organism depends on a specific tomato cultivar's resistance to an AAL strain's specific fumonisin B1 variant. Additionally, the best way to prevent this pathogen from producing disease on tomato plants is to ensure the tomatoes are resistant cultivars.
Identification
Teleomorph
Thought to be Clathrospora diplospora (to be confirmed).
Anamorph
Conidiophore
Pale brown to olive brown
25–60 x 3–3.5 μm
Straight or flexuous
Individual conidiophores arise directly from substrate forming bushy heads consisting of 4–8 large catenate conidia chains
Secondary conidiophores are generally short and 1-celled
Conidia
Pale brown to light brown
Obclavate to obpyriform orellipsoid, short conical beak at the tip, or beakless
Surface smooth to verruculose
Size
20–63 x 9–18 μm in size
(on PCA) mature conidia typically 10–30 x 5–12 μm
Septa
Several vertical and −8 transverse septa
(on PCA) 3–7 transepta, 1–5 longisepta
Chains
Produced in an often branched, long chain more than 5 conidia.
(on PCA) individual chains of 5–15 conidia, complex of branching chains may contain up to 50–60 conidia
References
External links
Index Fungorum
USDA ARS Fungal Database
Japanese Fungi on Plants: Alternaria alternata
Mycology Online: Alternaria alternata
alternata
Cereal diseases
Fungal grape diseases
Fungal plant pathogens and diseases
Fungal citrus diseases
Fungi described in 1817
Fungus species | Alternaria alternata | [
"Biology"
] | 1,679 | [
"Fungi",
"Fungus species"
] |
10,813,212 | https://en.wikipedia.org/wiki/SPC%20file%20format | The SPC file format is a file format for storing spectroscopic data.
The SPC file format is a file format in which all kinds of spectroscopic data, including among others infrared spectra, Raman spectra and UV/VIS spectra. The format can be regarded as a database with records of variable length and each record stores a different kind of data (instrumental information, information on one spectrum of a dataset, the spectrum itself or extra logs). It was invented by Galactic Industries as generic file format for its programs. Their original specification was implemented in 1986, but a more versatile format was created in 1996.
Galactic Industries was purchased by Thermo Fisher Scientific who now maintain and develop the GRAMS Software Suite for which the format was defined. They provide free tools and libraries to allow developers to create and maintain SPC files consistently.
This file format is not in plaintext, such as XML or CSV, but is a binary format and is therefore not readable with a standard text editor but requires a special reader or software to interpret the file data. The Environmental Protection Agency publishes a free spectra reader called ShowSPC that is open to the public for reading spectra data. Additionally, a company AnalyzeIQ produces a free SPC to CSV converter aptly titled SPC2CSV, an open-source project OpenSpectralWorks is an alternative free reader, as well as SpectraGryph which has analytic and display capabilities for reading SPC files. The Essential FTIR software offers a file reader that can read, display, analyze and export .spc files as well as many other spectroscopy file formats.
References
External links
Python module to read and convert SPC files on GitHub
hyperSpec R (programming language) package on GitHub
Computer file formats
Spectroscopy | SPC file format | [
"Physics",
"Chemistry"
] | 363 | [
"Instrumental analysis",
"Molecular physics",
"Spectroscopy",
"Spectrum (physical sciences)"
] |
10,813,277 | https://en.wikipedia.org/wiki/Upper-atmospheric%20lightning | Upper-atmospheric lightning and ionospheric lightning are terms sometimes used by researchers to refer to a family of short-lived electrical-breakdown phenomena that occur well above the altitudes of normal lightning and storm clouds. Upper-atmospheric lightning is believed to be electrically induced forms of luminous plasma. The preferred usage is transient luminous event (TLE), because the various types of electrical-discharge phenomena in the upper atmosphere lack several characteristics of the more familiar tropospheric lightning.
Transient luminous events have also been observed in far-ultraviolet images of Jupiter's upper atmosphere, high above the altitude of lightning-producing water clouds.
Characteristics
There are several types of TLEs, the most common being sprites. Sprites are flashes of bright red light that occur above storm systems. C-sprites (short for "columniform sprites") is the name given to vertical columns of red light. C-sprites exhibiting tendrils are sometimes called "carrot sprites". Other types of TLEs include sprite halos, ghosts, blue jets, gigantic jets, pixies, gnomes, trolls, blue starters, and ELVESs. The acronym ELVES (“emission of light and very low frequency perturbations due to electromagnetic pulse sources”) refers to a singular event which is commonly thought of as being plural. TLEs are secondary phenomena that occur in the upper atmosphere in association with underlying thunderstorm lightning.
TLEs generally last anywhere from less than a millisecond to more than 2 seconds. The first video recording of a TLE was captured accidentally on July 6, 1989 when researcher R.C Franz left a camera running overnight to view the night sky. When reviewing the video taken, two finger-like vertical images appeared in two frames of the film. The next known video recordings of a TLE were taken in 1989, when the Space Shuttle mission STS-34 was conducting the Mesoscale Lightning Observation Experiment. On October 21, 1989 TLEs were recorded during orbits 44 and 45.
TLEs have been captured by a variety of optical recording systems, with the total number of recent recorded events (early 2009) estimated at many tens-of-thousands. The global rate of TLE occurrence has been estimated from satellite (FORMOSAT-2) observations to be several million events per year.
History
In the 1920s, the Scottish physicist C.T.R. Wilson predicted that electrical breakdown should occur in the atmosphere high above large thunderstorms. In ensuing decades, high altitude electrical discharges were reported by aircraft pilots and discounted by meteorologists until the first direct visual evidence was documented in 1989. Several years later, the optical signatures of these events were named 'sprites' by researchers to avoid inadvertently implying physical properties that were, at the time, still unknown. The terms red sprites and blue jets gained popularity after a video clip was circulated following an aircraft research campaign to study sprites in 1994.
Sprites
Sprites are large-scale electrical discharges which occur high above a thunderstorm cloud, or cumulonimbus, giving rise to a quite varied range of visual shapes. They are triggered by the discharges of positive lightning between the thundercloud and the ground. The phenomena were named after the mischievous sprite, e.g., Shakespeare's Ariel or Puck, and is also a backronym for stratospheric/mesospheric perturbations resulting from intense thunderstorm electrification. They normally are colored reddish-orange or greenish-blue, with hanging tendrils below and arcing branches above. They can also be preceded by a reddish halo, known as a sprite halo. They often occur in clusters, reaching to above the Earth's surface. Sprites have been witnessed thousands of times. Sprites have been held responsible for otherwise unexplained accidents involving high-altitude vehicular operations above thunderstorms.
Jets
Although jets are considered to be a type of upper-atmospheric lightning, it has been found that they are components of tropospheric lightning and a type of cloud-to-air discharge that initiates within a thunderstorm and travels upwards. In contrast, other types of TLEs are not electrically connected with tropospheric lightning—despite being triggered by it. The two main types of jets are blue jets and gigantic jets. Blue starters are considered to be a weaker form of blue jets.
Blue jets
Blue jets are believed to be initiated as "normal" lightning discharges between the upper positive charge region in a thundercloud and a negative "screening layer" present above this charge region. The positive end of the leader network fills the negative charge region before the negative end fills the positive charge region, and the positive leader subsequently exits the cloud and propagates upward. It was previously believed that blue jets were not directly related to lightning flashes, and that the presence of hail somehow led to their occurrence. They are also brighter than sprites and, as implied by their name, are blue in color. The color is believed to be due to a set of blue and near-ultraviolet emission lines from neutral and ionized molecular nitrogen. They were first recorded on October 21, 1989, on a monochrome video of a thunderstorm on the horizon taken from the Space Shuttle as it passed over Australia. Blue jets occur much less frequently than sprites. By 2007, fewer than a hundred images had been obtained. The majority of these images, which include the first color imagery, are associated with a single thunderstorm. These were taken in a series of 1994 aircraft flights to study sprites. More recently, the source and formation of blue jets has been observed from the International Space Station.
Blue starters
Blue starters were discovered on video from a night time research flight around thunderstorms and appear to be "an upward moving luminous phenomenon closely related to blue jets." They appear to be shorter and brighter than blue jets, reaching altitudes of only up to 20 km. "Blue starters appear to be blue jets that never quite make it," according to Dr. Victor P. Pasko, associate professor of electrical engineering.
Gigantic jets
Where blue jets are believed to initiate between the upper positive charge region and a negative screening layer directly above this region, gigantic jets appear to initiate as an intracloud flash between the middle negative and upper positive charge regions in the thundercloud. The negatively charged leader then escapes upward from the cloud toward the ionosphere before it can discharge within the cloud. Gigantic jets reach higher altitudes than blue jets, terminating at 90 km. While they may appear to be visually similar to carrot-type sprites, gigantic jets differ in that they are not associated with cloud to ground lightning and propagate upward from the cloud at a slower rate.
Observations
On September 14, 2001, scientists at the Arecibo Observatory photographed a gigantic jet—double the height of those previously observed—reaching around into the atmosphere. The jet was located above a thunderstorm over an ocean, and lasted under a second. The jet was initially observed to be traveling up at around at a speed similar to typical lightning, increased to , but then split in two and sped upward with speeds of at least to the ionosphere where it then spread out in a bright burst of light.
On July 22, 2002, five gigantic jets between in length were observed over the South China Sea from Taiwan, reported in Nature. The jets lasted under a second, with shapes likened by the researchers to giant trees and carrots.
On November 10, 2012, the Chinese Science Bulletin reported a gigantic jet event observed over a thunderstorm in mainland China on August 12, 2010. "GJ event that was clearly recorded in eastern China (storm center located at 35.6°N,119.8°E, near the Huanghai Sea)".
On February 2, 2014, the Oro Verde Observatory of Argentina reported ten or more gigantic jet events observed over a thunderstorm in Entre Ríos south. The storm center was located at 33°S, 60°W, near the city of Rosario.
On August 13, 2016, photographer Phebe Pan caught a clear wide-angle photo of a gigantic jet on a wide-angle lens while shooting Perseid meteors atop Shi Keng Kong peak in Guangdong province and Li Hualong captured the same jet from a more distant location in Jiahe, Hunan, China.
On March 28, 2017, photographer Jeff Miles captured four gigantic jets over Australia.
On July 24, 2017, the Gemini Cloudcam at the Mauna Kea Observatory in Hawaii captured several gigantic jets as well as ionosphere-height gravity waves during one thunderstorm.
On October 16, 2019, pilot Chris Holmes captured a high-resolution video of a gigantic jet from 35,000 feet (10.6 km) above the Gulf of Mexico near the Yucatán Peninsula. From 35 miles (56 km), Holmes's video shows a blue streamer reach up from the top of a thunderstorm to the ionosphere, becoming red at the top. Only then does a brilliant white lightning leader crawl slowly from the top of the cloud, reaching about 10% of the height of the gigantic jet before fading.
On September 20, 2021, at 10:41 pm (02:41 UTC) facing NE from Cabo Rojo, Puerto Rico, photographer Frankie Lucena recorded a video of a gigantic jet plasma event which occurred over a thunderstorm in the area.
On 15 February 2024, photographer JJ Rao (Nature by JJ) captured a gigantic jet in high-resolution slow-motion video from Derby, in the Kimberley Region of Western Australia.
Other types
Elves
ELVES often appear as a dim, flattened, expanding glow around in diameter that lasts for, typically, just one millisecond. They occur in the ionosphere above the ground over thunderstorms. Their color was unknown for some time, but is now known to be red. ELVES were first recorded on another shuttle mission, this time recorded off French Guiana on October 7, 1990. That ELVES was discovered in the Shuttle Video by the Mesoscale Lightning Experiment (MLE) team at Marshall Space Flight Center, AL led by the Principal Investigator, Otha H."Skeet" Vaughan, Jr.
ELVES is a whimsical acronym for emissions of light and very Low frequency perturbations due to electromagnetic pulse sources. This refers to the process by which the light is generated; the excitation of nitrogen molecules due to electron collisions (the electrons possibly having been energized by the electromagnetic pulse caused by a discharge from an underlying thunderstorm).
Trolls
TROLLs (transient red optical luminous lineaments) occur after strong sprites, and appear as red spots with faint tails, and on higher-speed cameras, appear as a rapid series of events, starting as a red glow that forms after a sprite tendril, that later produces a red streak downward from itself. They are similar to jets.
Pixies
Pixies were first observed during the STEPS program during the summer of 2000, a multi-organizational field program investigating the electrical characteristics over thunderstorms on the High Plains. A series of unusual, white luminous events atop the thunderstorm were observed over a 20-minute period, lasting for an average of 16 milliseconds each. They were later dubbed 'pixies'. These pixies are less than 100 meters across, and are not related to lightning.
Ghosts
Ghosts (greenish optical emission from sprite tops) are faint, green glows that appear within the footprint of a red sprite, remaining after the red has dissipated, and fading away in milliseconds. Though possible examples of ghosts can be seen in historical images, ghosts were first noted as an exclusive phenomenon by storm chasers Hank Schyma and in 2019.
The first spectroscopy study to analyze the dynamics and chemistry of ghosts was led by the Atmospheric Electricity group of the Institute of Astrophysics of Andalusia (IAA). This experimental campaign reported the main contributors to the greenish hue of a single event recorded in 2019 to be atomic iron and nickel, molecular nitrogen and ionic molecular oxygen. A weak -but certain- contribution of atomic oxygen, and atomic sodium and ionic silicon were also detected.
Gnomes
A gnome is a type of lightning that is a small, brief spike of light that points upward from a thunderstorm cloud's anvil top, caused as strong updrafts push moist air above the anvil. It lasts for only a few microseconds. It is about 200 meters wide, and is a maximum of 1 kilometer in height. Its color is unknown as it has only been observed in black-and-white footage. Most sources unofficially refer to them as "Gnomes".
See also
Aurora
Heat lightning
Schumann resonances
Sprite (lightning)
St. Elmo's fire
Steve (atmospheric phenomenon)
References
External links
Homepage of the Eurosprite campaign, itself part of the CAL (Coupled Atmospheric Layers) research group
March 2, 1999, University of Houston: UH Physicists Pursue Lightning-Like Mysteries Quote: "...Red sprites and blue jets are brief but powerful lightning-like flashes that appear at altitudes of 40–100 km (25–60 miles) above thunderstorms..."
Ground and Balloon-Borne Observations of Sprites and Jets
Barrington-Leigh, C. P., "ELVES : Ionospheric Heating By the Electromagnetic Pulses from Lightning (A primer)". Space Science Lab, Berkeley.
"Darwin Sprites '97". Space Physics Group, University of Otago.
Gibbs, W. Wayt, "Sprites and ELVES : Lightning's strange cousins flicker faster than light itself". San Francisco. ScientificAmerican.com.
Barrington-Leigh, Christopher, "VLF Research at Palmer Station".
Sprites, jets and TLE pictures and articles
High speed video (10,000 frame/s) taken by Hans Stenbaek-Nielsen, University of Alaska
Video Reveals 'Sprite' Lightning Secrets, Livescience article, 2007.
Video evidence
Pictures and video of two separate gigantic jets above Oklahoma
Gigantic jets between a thundercloud and the ionosphere.
Huge Mystery Flashes Seen In Outer Atmosphere
Sprite Gallery
http://webarchive.loc.gov/all/20020914103454/http://elf.gi.alaska.edu/
The Endless, Short film inspired by Sprite
Cloud Flashes ZT Research
Electrical phenomena
Lightning
Terrestrial plasmas
Space plasmas
Weather hazards
Light sources | Upper-atmospheric lightning | [
"Physics"
] | 2,960 | [
"Space plasmas",
"Physical phenomena",
"Weather hazards",
"Weather",
"Astrophysics",
"Electrical phenomena",
"Lightning"
] |
10,813,955 | https://en.wikipedia.org/wiki/Male%20egg | Male egg can refer to either:
An egg that artificially contains genetic material from a male.
An egg from a haplodiploid species such as an ant or bee that is unfertilized and will hatch a male
A fertilized egg that a male organism is developing in
This article focuses on the first definition.
Male eggs are the result of a process in which the eggs of a female would be emptied of their genetic contents (a technique similar to that used in the cloning process), and those contents would be replaced with male DNA. Such eggs could then be fertilized by sperm. The procedure was conceived by Calum MacKellar, a Scottish bioethicist. With this technique, two males could be the biological parents of a child. However, such a procedure would additionally require an artificial womb or a female gestational carrier.
In 2023, male eggs from male mice cells were developed and used to create bi-paternal mice that grew into adulthood; bi-paternal mice had been obtained in 2008, but they only survived for a few days.
See also
Female sperm
Male pregnancy
LGBT reproduction
Genomic imprinting
References
Applied genetics
Biological engineering
Biotechnology
Genetic engineering
Medical ethics
Sexuality | Male egg | [
"Chemistry",
"Engineering",
"Biology"
] | 244 | [
"Biological engineering",
"Behavior",
"Sex",
"Genetic engineering",
"Biotechnology",
"nan",
"Molecular biology",
"Sexuality"
] |
10,813,956 | https://en.wikipedia.org/wiki/Female%20sperm | Female sperm can refer to either:
A sperm which contains an X chromosome, produced in the usual way in the testicles, referring to the occurrence of such a sperm fertilizing an egg and giving birth to a female.
A sperm which artificially contains genetic material from a female.
Since the late 1980s, scientists have explored how to produce sperm where all of the chromosomes come from a female donor.
Artificial female sperm production
Creating female sperm was first raised as a possibility in a patent filed in 1991 by injecting
a female's cells into a male's testicles, though the patent focused mostly on injecting altered male cells into a male's testes to correct genetic diseases. In 1997, Japanese scientists partially confirmed such techniques by creating chicken female sperm in a similar manner. "However, the ratio of produced W chromosome-bearing (W-bearing) spermatozoa fell substantially below expectations. It is therefore concluded that most of the W-bearing PGC could not differentiate into spermatozoa because of restricted spermatogenesis." These simple transplantation methods follow from earlier observations by developmental biologists that germ stem cells are autonomous in the sense that they can begin the processes to become both sperm and eggs.
One potential roadblock to injecting a female's cells into a male's testicles is that the male's immune system might attack and destroy the female's cells. In usual circumstances, when foreign cells (such as cells or organs from other people, or infectious bacteria) are put into a human body, the immune system will reject such cells or organs. However, a special property of testicles is that they are immune-privileged, that is, a male's immune system will not attack foreign cells (such as a female's cells) injected into the sperm-producing part of the testicles. Thus, a female's cells will remain in the male's testicles long enough to be converted into sperm.
However, there are more serious challenges. Biologists have well established that male sperm production relies on certain genes on the Y chromosome, which, when missing or defective, lead to such males producing little to no sperm in their testicles. An analogy, then, is that XX cells have complete Y chromosome deficiency. While many genes on the Y chromosome have backups (homologues) on other chromosomes, a few genes such as RBMY on the Y chromosome do not have such backups, and their effects must be compensated to convert a female's cells from into sperm. In 2007, a patent application was filed on methods for creating human female sperm using artificial or natural Y chromosomes and testicular transplantation. Key to successful creation of female sperm (and male eggs) will be inducing male epigenetic markings for female cells that initially have female markings, with techniques for doing so disclosed in the patent application.
In 2018, Chinese research scientists produced 29 viable mice offspring from two female mice by creating sperm-like structures from haploid embryonic stem cells using gene editing to alter imprinted regions of DNA. Experts noted that there was little chance of these techniques being applied to humans in the near future.
See also
LGBT reproduction
Male egg
References
Sex
Applied genetics
Biological engineering
Biotechnology
Genetic engineering
Medical ethics | Female sperm | [
"Chemistry",
"Engineering",
"Biology"
] | 662 | [
"Biological engineering",
"Sex",
"Genetic engineering",
"Biotechnology",
"nan",
"Molecular biology"
] |
10,814,534 | https://en.wikipedia.org/wiki/Assemblage%20%28journal%29 | Assemblage was an architectural theory journal published by MIT Press from 1986 to 2000.
History
K. Michael Hays and Alicia Kennedy served as the main editors for all 41 issues. The original consulting editors were Mary McLeod, Mark Rakatansky, and Ellen Shapiro. Other editors included Catherine Ingraham, Stan Allen, Sarah Whiting, Mark Pasnik and Monica Ponce de Leon.
Contributors
The journal's advisory and editorial board included many architectural theorists and writers, including Stanford Anderson (vol. 1–14), Francoise Choay (vol. 1–5), Mario Gandelsonas (all volumes), Jorge Silvetti (all volumes), Werner Oechslin (vol. 1–16), Beatriz Colomina (vol. 14–41), Mark Rakatansky (vol. 14–33), Mark Wigley (vol. 14–41), Sanford Kwinter (vol. 16–41), Robert McAnulty (vol. 17–41), Jennifer Bloomer (vol. 17–41), and Lauren Kogod (vol 33–41).
References
External links
All volumes on JSTOR
Architecture journals
MIT Press academic journals
Academic journals established in 1986
1986 establishments in Massachusetts | Assemblage (journal) | [
"Engineering"
] | 256 | [
"Architecture stubs",
"Architecture"
] |
10,814,713 | https://en.wikipedia.org/wiki/Levi%27s%20lemma | In theoretical computer science and mathematics, especially in the area of combinatorics on words, the Levi lemma states that, for all strings u, v, x and y, if uv = xy, then there exists a string w such that either
uw = x and v = wy (if |u| ≤ |x|)
or
u = xw and wv = y (if |u| ≥ |x|)
That is, there is a string w that is "in the middle", and can be grouped to one side or the other. Levi's lemma is named after Friedrich Wilhelm Levi, who published it in 1944.
Applications
Levi's lemma can be applied repeatedly in order to solve word equations; in this context it is sometimes called the Nielsen transformation by analogy with the Nielsen transformation for groups. For example, starting with an equation xα = yβ where x and y are the unknowns, we can transform it (assuming |x| ≥ |y|, so there exists t such that x=yt) to ytα = yβ, thus to tα = β. This approach results in a graph of substitutions generated by repeatedly applying Levi's lemma. If each unknown appears at most twice, then a word equation is called quadratic; in a quadratic word equation the graph obtained by repeatedly applying Levi's lemma is finite, so it is decidable if a quadratic word equation has a solution. A more general method for solving word equations is Makanin's algorithm.
Generalizations
The above is known as the Levi lemma for strings; the lemma can occur in a more general form in graph theory and in monoid theory; for example, there is a more general Levi lemma for traces originally due to Christine Duboc.
Several proofs of Levi's Lemma for traces can be found in The Book of Traces.
A monoid in which Levi's lemma holds is said to have the equidivisibility property. The free monoid of strings and string concatenation has this property (by Levi's lemma for strings), but by itself equidivisibility is not enough to guarantee that a monoid is free. However an equidivisible monoid M is free if additionally there exists a homomorphism f from M to the monoid of natural numbers (free monoid on one generator) with the property that the preimage of 0 contains only the identity element of M, i.e. . (Note that f simply being a homomorphism does not guarantee this latter property, as there could be multiple elements of M mapped to 0.) A monoid for which such a homomorphism exists is also called graded (and the f is called a gradation).
See also
String operations
String functions (programming)
Notes
Combinatorics on words
Lemmas | Levi's lemma | [
"Mathematics"
] | 596 | [
"Combinatorics",
"Mathematical problems",
"Mathematical theorems",
"Lemmas",
"Combinatorics on words"
] |
10,815,113 | https://en.wikipedia.org/wiki/Institute%20of%20Problems%20of%20Chemical%20Physics | The Institute of Problems of Chemical Physics (IPCP) () of the Russian Academy of Sciences (RAS) consists of 10 scientific departments and about 100 laboratories each one held by an independent research groups.
IPCP was established in 1956 as branch of the Moscow Institute of Chemical Physics.
See also
Mathematical chemistry
Aizik Isaakovich Vol'pert
Notes
References
. "The Institute of Chemical Physics. Historical essays" (English translation of the title) is an historical book on the Institute of Problems of Chemical Physics, written by Fedor Ivanovich Dubovitskii, one of his founders and leading directors for many years. It gives many useful details on the lives and the achievements of many scientists who worked there, including Aizik Isaakovich Vol'pert.
. "Institute of Problems of Chemical Physics. Fifty years in the trenches" (English translation of the title) is a brief historical sketch of the institute, published in the first volume of the 2004 yearbook.
External links
Official Website
Research institutes in the Soviet Union
Institutes of the Russian Academy of Sciences
Chemical research institutes
Moscow Institute of Physics and Technology
Nuclear weapons program of the Soviet Union
Research institutes established in 1956 | Institute of Problems of Chemical Physics | [
"Chemistry"
] | 237 | [
"Chemical research institutes"
] |
10,815,131 | https://en.wikipedia.org/wiki/Trace%20theory | In mathematics and computer science, trace theory aims to provide a concrete mathematical underpinning for the study of concurrent computation and process calculi. The underpinning is provided by an algebraic definition of the free partially commutative monoid or trace monoid, or equivalently, the history monoid, which provides a concrete algebraic foundation, analogous to the way that the free monoid provides the underpinning for formal languages.
The power of trace theory stems from the fact that the algebra of dependency graphs (such as Petri nets) is isomorphic to that of trace monoids, and thus, one can apply both algebraic formal language tools, as well as tools from graph theory.
While the trace monoid had been studied by Pierre Cartier and Dominique Foata for its combinatorics in the 1960s, trace theory was first formulated by Antoni Mazurkiewicz in the 1970s, in an attempt to evade some of the problems in the theory of concurrent computation, including the problems of interleaving and non-deterministic choice with regards to refinement in process calculi.
References
Volker Diekert, Grzegorz Rozenberg, eds. The Book of Traces, (1995) World Scientific, Singapore
Volker Diekert, Yves Metivier, "Partial Commutation and Traces", In G. Rozenberg and A. Salomaa, editors, Handbook of Formal Languages, Vol. 3, Beyond Words. Springer-Verlag, Berlin, 1997.
Volker Diekert, Combinatorics on traces, LNCS 454, Springer, 1990,
Concurrent computing
Formal languages
Trace theory | Trace theory | [
"Mathematics",
"Technology"
] | 338 | [
"Computing platforms",
"IT infrastructure",
"Formal languages",
"Mathematical logic",
"Concurrent computing"
] |
10,815,888 | https://en.wikipedia.org/wiki/Palladium%28II%29%20bis%28acetylacetonate%29 | Palladium(II) bis(acetylacetonate) is a compound with formula Pd(C5H7O2)2. This yellow solid is the most common palladium complex of acetylacetonate. This compound is commercially available and used as a catalyst precursor in organic synthesis. The molecule is relatively planar with idealized D2h symmetry.
See also
Platinum(II) bis(acetylacetonate)
Nickel(II) bis(acetylacetonate)
References
Palladium compounds
Acetylacetonate complexes
Catalysts | Palladium(II) bis(acetylacetonate) | [
"Chemistry"
] | 118 | [
"Catalysis",
"Catalysts",
"Chemical process stubs",
"Organic compounds",
"Chemical reaction stubs",
"Chemical kinetics",
"Organic compound stubs",
"Organic chemistry stubs"
] |
10,816,739 | https://en.wikipedia.org/wiki/Minimum%20bactericidal%20concentration | The minimum bactericidal concentration (MBC) is the lowest concentration of an antibacterial agent required to kill a particular bacterium. It can be determined from broth dilution minimum inhibitory concentration (MIC) tests by subculturing to agar plates that do not contain the test agent. The MBC is identified by determining the lowest concentration of antibacterial agent that reduces the viability of the initial bacterial inoculum by ≥99.9%. The MBC is complementary to the MIC; whereas the MIC test demonstrates the lowest level of antimicrobial agent that inhibits growth, the MBC demonstrates the lowest level of antimicrobial agent that results in microbial death. This means that even if a particular MIC shows inhibition, plating the bacteria onto agar might still result in organism proliferation because the antimicrobial did not cause death. Antibacterial agents are usually regarded as bactericidal if the MBC is no more than four times the MIC. Because the MBC test uses colony-forming units as a proxy measure of bacterial viability, it can be confounded by antibacterial agents which cause aggregation of bacterial cells. Examples of antibacterial agents which do this include flavonoids and peptides.
References
Microbiology terms | Minimum bactericidal concentration | [
"Biology"
] | 264 | [
"Microbiology terms"
] |
10,818,212 | https://en.wikipedia.org/wiki/Psilocybe%20caerulipes | Psilocybe caerulipes, commonly known as blue-foot, is a rare psilocybin mushroom of the family Hymenogastraceae, having psilocybin and psilocin as main active compounds. An older synonym is Agaricus caerulipes.
It is in the section Semilanceatae, other members of the section include Psilocybe bohemica, Psilocybe callosa, Psilocybe carbonaria, Psilocybe cyanofibrillosa, Psilocybe fimetaria, Psilocybe indica, Psilocybe liniformans var. liniformans, Psilocybe liniformans var. americana, Psilocybe pelliculosa, Psilocybe semiinconspicua, Psilocybe semilanceata, Psilocybe serbica, Psilocybe silvatica, Psilocybe subfimetaria and Psilocybe venenata.
Etymology
From the Latin words (blue) and (foot).
Description
Psilocybe caerulipes has a farinaceous taste and a no to slightly farinaceous odor.
The cap is 1 — 3.5 cm in diameter, obtusely conic to convex, and the margin is initially turned inwards, later becoming broadly convex to flattened or somewhat umbilicate while retaining a slight umbo, and at times quite irregular. The surface is viscid when moist from a gelatinous pellicle, but soon becomes dry and shiny, translucent-striate, and decorated with fine fibrillose veil remnants, often with greenish stains near the margin or a greenish tinge overall . It is cinnamon brown to caramel brown when fresh, hygrophanous, and soon fading to dingy ochraceous buff during dry conditions. The flesh is thin, pliant, bruising blue, sometimes slowly.
The gills are close but not crowded, narrow with adnate to sinuate to uncinate attachment. They are nearly white at first, becoming dark brown as the spores mature; the edges are whitish and slightly fimbriate.
The spores are dark brown, ellipsoid, 7—10 x 4—5 μm from 4-spored basidia, thick-walled, and with a broad germ pore. The spores from 2-spored basidia are larger.
The stipe is 3–6 cm long, 1.5–3 mm thick, equal to enlarging downwards, tough(ropey), and is whitish to brown at first. The stipe is pallid to bluish when dried, becoming dingy brown towards the base with age, and bruises blue, sometimes slowly. The surface is powdered at the apex, and covered with whitish to grayish fibrils downwards. The flesh is stuffed with a pith and is solid at first but becomes hollow. It lacks an annulus but sometimes remnants of the thin cortinate partial veil form a soon disappearing fibrillose annular zone in the upper region of the stem.
Microscopic features: The basidia are 2- and 4-spored. Pleurocystidia are absent. The cheilocystidia are 18—35 x 4.5—7.5 μm, langeniform (swollen at the base, narrowed at the top), and with a thin neck, sometimes forked, 1–2.5 μm broad at apices.
Habitat
Psilocybe caerulipes may be found growing solitary to cespitose, in deciduous forests on hardwood slash and debris, plant matter, on or about decaying hardwood logs, birch, beech and maple.
Season
Psilocybe caerulipes grows from late May through December.
Distribution
Psilocybe caerulipes grows in eastern North America, from Nova Scotia to North Carolina, and west to Michigan. It has also been found as far south as Mexico in the states of Hidalgo and Veracruz. In Mexico it is found in cloud forests on Fagus. It is often overlooked as just another little brown mushroom, and although widely distributed, it is not found often. It is sometimes confused with the larger Psilocybe ovoideocystidiata.
References
Further reading
Guzmán, G. The Genus Psilocybe: A Systematic Revision of the Known Species Including the History, Distribution and Chemistry of the Hallucinogenic Species. Beihefte zur Nova Hedwigia Heft 74. J. Cramer, Vaduz, Germany (1983) [now out of print].
Entheogens
Psychoactive fungi
caerulipes
Psychedelic tryptamine carriers
Fungi of North America
Fungus species
Taxa named by Charles Horton Peck | Psilocybe caerulipes | [
"Biology"
] | 985 | [
"Fungi",
"Fungus species"
] |
7,152,070 | https://en.wikipedia.org/wiki/Dagger%20category | In category theory, a branch of mathematics, a dagger category (also called involutive category or category with involution) is a category equipped with a certain structure called dagger or involution. The name dagger category was coined by Peter Selinger.
Formal definition
A dagger category is a category equipped with an involutive contravariant endofunctor which is the identity on objects.
In detail, this means that:
for all morphisms , there exists its adjoint
for all morphisms ,
for all objects ,
for all and ,
Note that in the previous definition, the term "adjoint" is used in a way analogous to (and inspired by) the linear-algebraic sense, not in the category-theoretic sense.
Some sources define a category with involution to be a dagger category with the additional property that its set of morphisms is partially ordered and that the order of morphisms is compatible with the composition of morphisms, that is implies for morphisms , , whenever their sources and targets are compatible.
Examples
The category Rel of sets and relations possesses a dagger structure: for a given relation in Rel, the relation is the relational converse of . In this example, a self-adjoint morphism is a symmetric relation.
The category Cob of cobordisms is a dagger compact category, in particular it possesses a dagger structure.
The category Hilb of Hilbert spaces also possesses a dagger structure: Given a bounded linear map , the map is just its adjoint in the usual sense.
Any monoid with involution is a dagger category with only one object. In fact, every endomorphism hom-set in a dagger category is not simply a monoid, but a monoid with involution, because of the dagger.
A discrete category is trivially a dagger category.
A groupoid (and as trivial corollary, a group) also has a dagger structure with the adjoint of a morphism being its inverse. In this case, all morphisms are unitary (definition below).
Remarkable morphisms
In a dagger category , a morphism is called
unitary if
self-adjoint if
The latter is only possible for an endomorphism . The terms unitary and self-adjoint in the previous definition are taken from the category of Hilbert spaces, where the morphisms satisfying those properties are then unitary and self-adjoint in the usual sense.
See also
*-algebra
Dagger symmetric monoidal category
Dagger compact category
References | Dagger category | [
"Mathematics"
] | 535 | [
"Dagger categories",
"Mathematical structures",
"Category theory"
] |
7,152,162 | https://en.wikipedia.org/wiki/Bed%20frame | A bed frame or bedstead is the part of a bed used to position the bed base, the flat part which in turn directly supports the mattress(es). The frame may also stop the mattress from sliding sideways, and it may include means of supporting a canopy above. There are several types of Bed Frames found around the globe. They are typically made of wood or metal. A bed frame includes head, foot, and side rails. The majority of double (full) beds and all queen- and king-sized beds necessitate a central support rail, often accompanied by additional feet that extend towards the floor for stability. The concept of a "bed frame" was initially introduced and referred to between 1805 and 1815. This foundational support system not only reinforces the structure of the bed but also ensures its durability and longevity, distributing weight evenly to prevent sagging and enhance overall comfort. Not all beds include frames: see bed base.
Early bed frames
Some of the earliest bed frames are known from the Sumerian culture. Ancient Egyptian beds have been found in well-preserved condition, dating to well over 6000 years before the present time. The bed frames of the early dynastic period are made of wood and can vary in craftsmanship from mere branches lashed together, to fine works of art.
Brass beds
Brass beds are beds in which the headboard and footboard are made of brass; the frame rails are usually made of steel. The ratio of metals may vary between manufacturers.
Initially, brass beds boasted a minimalist and straightforward design. Throughout the centuries, designs have become increasingly elaborate and can contain extensive ornamentation, such as porcelain finials. Some brass bed styles include traditional, Art Deco, Victorian, transitional, Edwardian and contemporary.
Iron beds
Iron beds are beds in which the headboard and footboard are made of iron; the frame rails are usually made of steel. Iron beds were developed in 17th century Italy to address concerns about infestation by bed bugs and moths. An iron cradle (with dangerously pointed corner posts) has been dated to 1620–1640. From the start of their production in the 1850s until World War I, iron beds were handmade. The manufacturing process included hand pouring and polishing intricately detailed casting and hand applying finishes. In the many small foundries of the time that employed only a handful of employees, it could take days to produce a single bed.
Following the conclusion of World War I, the methodologies employed for mass production during the war had a substantial impact on the iron industry. The erstwhile handmade craftsmanship gradually yielded to the adoption of cost-efficient mass production techniques.
Today's iron beds are constructed of cold roll, heavy-gauge steel tubing and solid bar stock.
Almost all iron beds now have a beech wood sprung slatted base in a steel framework which gives support to all types of mattresses.
Wooden drawer beds
These beds have a wooden framework resembling a box, designed to accommodate the mattress within a carved-out space, and have wooden drawers beneath the mattress area.
See also
Storage bed, a bed with built in storage, usually as part of the bed frame
References
Further reading
Beds | Bed frame | [
"Biology"
] | 643 | [
"Beds",
"Behavior",
"Sleep"
] |
7,152,206 | https://en.wikipedia.org/wiki/Parser%20Grammar%20Engine | The Parser Grammar Engine (PGE, originally the Parrot Grammar Engine) is a compiler and runtime system for Raku rules for the Parrot virtual machine. PGE uses these rules to convert a parsing expression grammar into Parrot bytecode. It is therefore compiling rules into a program, unlike most virtual machines and runtimes, which store regular expressions in a secondary internal format that is then interpreted at runtime by a regular expression engine. The rules format used by PGE can express any regular expression and most formal grammars, and as such it forms the first link in the compiler chain for all of Parrot's front-end languages.
When executed, the bytecode generated by PGE will parse text as described in the input rules, generating a parse tree. The parse tree can be manipulated directly, or fed into the next stage of the Parrot compiler toolchain to generate an abstract syntax tree (AST) from which code can be generated; if the grammar describes a programming language.
History
Originally named P6GE and written in C, PGE was translated to native Parrot and renamed not long after its initial release in November 2004. Its author is Patrick R. Michaud. PGE was written to reduce the amount of work needed to implement a compiler on Parrot. It was also written to allow Perl 6 to easily self-host, though current Pugs development no longer uses PGE as its main rules back-end in favor of a native engine named PCR.
Internals
PGE combines three styles of parsing:
Raku rules
an operator-precedence parser
custom parse subroutines
The primary form is Raku rules, so a PGE rule might look like this for an addition-only grammar:
rule term { <number> | \( <expr> \) }
rule number { \d+ }
rule expr { <term> ( '+' <term> )* }
The operator precedence parser allows an operator table to be built and used directly in a Perl 6 rule style parser like so:
rule expr is optable { ... }
rule term { <number> | \( <expr> \) }
rule number { \d+ }
proto term: is precedence('=')
is parsed(&term) {...}
proto infix:+ is looser('term:') {...}
This accomplishes the same goal of defining a simple, addition-only grammar, but does so using a combination of a Raku style regex/rules for term and number and a shift-reduce optable for everything else.
Code generation
Though PGE outputs code which will parse the grammar described by a rule, and can be used at runtime to handle simple grammars and regular expressions found in code, its main purpose is to parse high-level programming languages.
The Parrot compiler toolchain is broken into several parts, of which PGE is the first. PGE converts source code to parse trees. The tree grammar engine (TGE) then converts these into a Parrot abstract syntax trees (PAST). A second TGE pass then converts a PAST into Parrot opcode syntax trees (POST) which can be directly transformed into executable bytecode.
References
External links
Perl
Formal languages
Pattern matching
Beta software
Compilers
Interpreters (computing) | Parser Grammar Engine | [
"Mathematics"
] | 695 | [
"Formal languages",
"Mathematical logic"
] |
7,152,596 | https://en.wikipedia.org/wiki/Sham%20peer%20review | Sham peer review or malicious peer review is a name given to the abuse of a medical peer review process to attack a doctor for personal or other non-medical reasons. The American Medical Association conducted an investigation of medical peer review in 2007 and concluded that while it is easy to allege misconduct and 15% of surveyed physicians indicated that they were aware of peer review misuse or abuse, cases of malicious peer review able to be proven through the legal system are rare.
Legal basis
Those who maintain that sham peer review is a pervasive problem suggest that the Healthcare Quality Improvement Act (HCQIA) of 1986 allows sham reviews by granting significant immunity from liability to doctors and others who participate in peer reviews. This immunity extends to investigative activities as well as to any associated peer review hearing, whether or not it leads to a disciplinary (or other) action.
The definition of a peer review body can be broad, including not only individuals but also (for example, in Oregon), "tissue committees, governing bodies or committees including medical staff committees of a [licensed] health care facility...or any other medical group in connection with bona fide medical research, quality assurance, utilization review, credentialing, education, training, supervision or discipline of physicians or other health care providers."
The California legislature framed its statutes so as to allow "aggrieved physicians the opportunity to prove that the peer review to which they were subject was in fact carried out for improper purposes, i.e., for purposes unrelated to assuring quality care or patient safety". These statutes allow that a peer review can be found in court to have been improper due to bad faith or malice, in which case the peer reviewers' immunities from civil liability "fall by the wayside".
Those who practice sham peer review could draw out the process by legal maneuvering, and the fairness of a peer review that has been unduly delayed has been called into question. Many medical staff laws specify guidelines for the timeliness of peer review, in compliance with JCAHO standards.
Medical peer review process
The medical peer review system is a quasi-judicial one. It is modeled in some ways on the grand jury / petit jury system. After a complainant asks for an investigation, a review body is assembled for fact-finding. This fact-finding body, called an ad hoc committee, is appointed by the medical Chief of Staff and is composed of other physician staff members chosen at the Chief of Staff's discretion. This ad hoc committee then conducts an investigation in the manner it feels is appropriate. This may include a review of the literature or an outside expert. Thus, there is no standard for impartiality and specifically no standard for due process in the "peer-review 'process' ."
Physicians that are indicted (and sanctioned) have the right to request a hearing. At the hearing, counsel is allowed. A second independent panel of physicians is chosen as the petit jury, and a hearing officer is chosen. The accused physician has the option to demonstrate conflicts of interest and attempt to disqualify jurors based on reasonable suspicions of bias or conflicts of interest in a voir dire process.
Although some medical staff bodies utilize the hospital attorney and accept hospital funds to try peer review cases, the California Medical Association discourages this practice. California has enacted legislation formally requiring the separation of the hospital and medical staff.
Alleged cases
Some physicians allege that sham peer review is often conducted in retaliation for whistleblowing, although one study in 2007 suggested that such events were rare.
Khajavi v. Feather River Anesthesiology Medical Group
Those who disagree with the AMA point to the case of Nosrat Khajavi. In 1996, Khajavi, an anesthesiologist in Yuba City, California, disagreed with a surgeon over the appropriateness of cataract surgery for a patient and refused to attend during the procedure. Khajavi was subsequently terminated from his anesthesia group. He sued for wrongful termination under California Business & Professions' Code Section 2053, and the suit was allowed by the California Court of Appeals. In 2000, the court held that Khajavi was not protected from termination on the basis of advocating for what he felt was medically appropriate care. The court did not rule on the merits of the dispute.
Mileikowsky v. Tenet
A doctor was allegedly subject to multiple hearings for the same charges, and his rights to an expedited hearing were allegedly denied while a suspension was in place. On May 15, 2001, the California Medical Association filed an amicus curiae brief to emphasize legal protections meant to prevent physicians being arbitrarily excluded from access to healthcare facilities based on mechanisms such as summary suspension without a speedy hearing. This case was decided on April 18, 2005. The court ruled that the hearing officer in the case could indeed terminate the physician's peer review hearing based on grounds that the physician refused to cooperate on procedural and other matters necessary for the good conduct of the proceedings. Thus, the physician lost his membership and privileges at the hospital. Ironically, the same physician was brought into a peer review hearing at another facility a short time later. The hearing officer in that case also terminated the proceedings, this time due to the physician's failure to turn over certain evidence for use in the hearing. The physician challenged the termination through the court system arguing, contrary to the Tenet appellate court ruling, that California's peer review statutes never intended the hearing officer in peer review hearings to have such powers of termination. The California Supreme Court reviewed the case and agreed in April 2009. The High Court ruled, among other things, that peer review hearing officers must defer the question of termination to the panel of physicians who sit in judgment of each peer review hearing.
Roland Chalifoux
Roland Chalifoux, member of an advocacy organisation called the Semmelweis Society, had his medical license revoked in Texas in 2004 after numerous incidents including the death of a patient. The Texas State Board of Medical Examiners stated that Chalifoux's practices "constitute such a deviation from the standard of care that revocation of his license is the only sanction that will adequately protect the public". Chalifoux subsequently secured permission to practice in West Virginia, and alleges that the Texas board's actions constitute sham peer review.
Charles Williams, MD
Six years after Charles Williams, MD, an anesthesiologist was summarily suspended by University Medical Center of Southern Nevada, a federal jury in Las Vegas awarded Dr. Williams $8.8 million as compensation for the due process violations he experienced in his sham peer review. Before the trial, which began May 16, U.S. District Judge Philip Pro made a finding that Ellerton and UMC's medical staff had violated Williams' due process rights. That left only the question of damages for the jury. This case appears to be the highest jury verdict in the nation for sham peer review which has not been overturned.
Richard Chudacoff, MD
On May 28, 2008, without any notice or opportunity to be heard, the Medical Staff of UMC suspended Dr. Chudacoff's clinical privileges. As a result of this, UMC filed a report against Dr. Chudacoff with the National Practitioner Data Bank claiming that Dr. Chudacoff was a risk to patient safety and had inadequate skills. This led to the virtual destruction of Dr. Chudacoff's career. Dr. Chudacoff sued. U.S. District Court Judge Edward Reed opined that, in Nevada, a physician's hospital privileges are a constitutionally protected property right. The Ninth Circuit Court of Appeals then affirmed that Dr. Chudacoff's due process rights were violated by UMC. As well, the Medical Executive members lost their immunity under the HCQIA for failure to follow their bylaws. The case was settled out of court in favor of Dr. Chudacoff, under the cloak of confidentiality.
Development of the Patient Safety Organization (PSO)
The Patient Safety and Quality Improvement Act of 2005 (Public Law 109-41) allows for the creation of Patient Safety Organizations, quality of care committees that can act in parallel with peer review boards. PSOs were authorized to gather information to be analyzed by hospital administrators, nurses, and physicians as a tool for systems failure analysis. They may be used by any healthcare entity except insurance companies, but must be registered with the AHRQ wing of the US Department of Health and Human Services.
In PSOs, root cause analysis and "near misses" are evaluated in an attempt to avert major errors. Participants in PSOs are immune from prosecution in civil, criminal, and administrative hearings.
See also
False accusations
Subpoena duces tecum
References
Further reading
Abuse
Medical sociology
Human resource management
Deception
Peer review
Workplace harassment and bullying
Criticism of academia | Sham peer review | [
"Biology"
] | 1,820 | [
"Abuse",
"Behavior",
"Aggression",
"Human behavior"
] |
7,153,071 | https://en.wikipedia.org/wiki/Stem%20cell%20research%20policy | Stem cell research policy varies significantly throughout the world. There are overlapping jurisdictions of international organizations, nations, and states or provinces. Some government policies determine what is allowed versus prohibited, whereas others outline what research can be publicly financed. Of course, all practices not prohibited are implicitly permitted. Some organizations have issued recommended guidelines for how stem cell research is to be conducted.
International bodies
The United Nations adopted a declaration on human cloning that can be interpreted as calling on member states to prohibit somatic cell nuclear transfer, or therapeutic cloning. In 2005, in a divided vote, "Member States were called on to adopt all measures necessary to prohibit all forms of human cloning in as much as they are incompatible with human dignity and the protection of human life."
The World Health Organization has opposed a ban on cloning techniques in stem cell research.
The Council of Europe's Convention on Human Rights and Biomedicine seems to ban the creation of embryos solely for research purposes. It has been signed by 31 countries and ratified by 19: Bulgaria, Croatia, Cyprus, the Czech Republic, Denmark, Estonia, Georgia, Greece, Hungary, Iceland, Lithuania, Moldova, Portugal, Romania, San Marino, Slovakia, Slovenia, Spain, and Turkey.
The Hinxton Group
Researchers, ethicists and assorted spokespersons from 14 different countries have published a set of legal and ethical guidelines relating to stem cell research, in an effort to address conflicting international laws in this area. The ‘Hinxton Group’ met recently for the first time, in Cambridge, and published a consensus statement calling for a ‘flexible’ regulatory framework, which can simultaneously accommodate rapid scientific advance and at the same time accommodate the diversity of international approaches towards stem cell science. It also recommends that, in countries which oppose embryonic stem cell research, scientists should be free to pursue their research elsewhere.
In light of the controversy surrounding Hwang Woo-Suk, the Hinxton Group has additionally recommended a number of measures intended to prevent fraud in stem cell research. The group has requested that all authors of embryonic stem cell papers submit a statement of authenticity of any new cell-lines and that the source of stem cells be clearly specified.
On the ethical issues surrounding embryonic stem cell research, the group has additionally recommended that an international database be created, containing guidelines for ethical practice, research protocols, consent forms, and the information provided to donors.
However, the potential for an international consensus on these matters seems remote given the complexity and diversity of regulatory frameworks in this controversial area of science, both within nations and between nations.
ISSCR
The International Society for Stem Cell Research is developing guidelines for the conduct of stem cell research.
Nations
Embryonic stem cell research has divided the international community. In the European Union, stem cell research using the human embryo is permitted in Ireland, Sweden, Finland, Belgium, Greece, Britain, Denmark and the Netherlands; however it is illegal in Germany, Austria, Italy, and Portugal. The issue has similarly divided the United States, with several states enforcing a complete ban and others giving financial support. Elsewhere, Japan, India, Iran, Israel, South Korea, and China are supportive, Australia is partially supportive (exempting reproductive cloning yet allowing research on embryonic stem cells that are derived from the process of IVF); however New Zealand, most of Africa (excepting South Africa) and most of South America (excepting Brazil) are restrictive.
References
External links
The Hinxton Group
European Molecular Biology Organization publication
United Nations Declaration on Human Cloning
Council of Europe's Convention on Human Rights and Biomedicine
World Stem Cell Policy Map
World map of stem cell research centers
World Stem Cell Report
Stem Cell Research Reveals Clues to Disease's Origins
International Cellular Medicine Society
International Society for Stem Cell Research
Stem Cell Information from the United States National Academies
Federal Policy Verbatim on the Use of Stem Cells in the U.S.
The Hinxton Group: An International Consortium on Stem Cells, Ethics & Law
World Stem Cell Policies
Johns Hopkins Stem Cell Policy
Policy
Science policy | Stem cell research policy | [
"Chemistry",
"Biology"
] | 822 | [
"Translational medicine",
"Tissue engineering",
"Stem cell research"
] |
7,153,075 | https://en.wikipedia.org/wiki/Congenic | In genetics, two organisms that differ in only one locus and a linked segment of chromosome are defined as congenic. Similarly, organisms that are coisogenic differ in one locus only and not in the surrounding chromosome. Unlike congenic organisms, coisogenic organisms cannot be bred and only occur through spontaneous or targeted mutation at the locus.
Generating congenic strains
Congenic strains are generated in the laboratory by mating two inbred strains (usually rats or mice), and back-crossing the descendants 5–10 generations with one of the original strains, known as the recipient strain. Typically selection for either phenotype or genotype is performed prior to each back-cross generation. In this manner either an interesting phenotype, or a defined chromosomal region assayed by genotype, is passed from the donor strain onto an otherwise uniform recipient background. Congenic mice or rats can then be compared to the pure recipient strain to determine whether they are phenotypically different if selection was for a genotypic region, or to identify the critical genetic locus, if selection was for a phenotype.
Speed congenics can be produced in as little as five back-cross generations, through the selection at each generation of offspring that not only retain the desired chromosomal fragment, but also 'lose' the maximum amount of background genetic information from the donor strain. This is also known as marker-assisted congenics, due to the use of genetic markers, typically microsatellite markers, but now, more commonly, single nucleotide polymorphism markers (SNPs). The process can be further aided by the superovulation of females, to produce many more eggs.
See also
Gene knockout
Notes and references
Further reading
Congenic strains are discussed in detail in Lee Silver's online book Mouse Genetics: Concepts and Applications:
Genetics | Congenic | [
"Biology"
] | 383 | [
"Genetics"
] |
7,153,598 | https://en.wikipedia.org/wiki/Richards%20equation | The Richards equation represents the movement of water in unsaturated soils, and is attributed to Lorenzo A. Richards who published the equation in 1931. It is a quasilinear partial differential equation; its analytical solution is often limited to specific initial and boundary conditions. Proof of the existence and uniqueness of solution was given only in 1983 by Alt and Luckhaus. The equation is based on Darcy-Buckingham law representing flow in porous media under variably saturated conditions, which is stated as
where
is the volumetric flux;
is the volumetric water content;
is the liquid pressure head, which is negative for unsaturated porous media;
is the unsaturated hydraulic conductivity;
is the geodetic head gradient, which is assumed as for three-dimensional problems.
Considering the law of mass conservation for an incompressible porous medium and constant liquid density, expressed as
,
where
is the sink term [T], typically root water uptake.
Then substituting the fluxes by the Darcy-Buckingham law the following mixed-form Richards equation is obtained:
.
For modeling of one-dimensional infiltration this divergence form reduces to
.
Although attributed to L. A. Richards, the equation was originally introduced 9 years earlier by Lewis Fry Richardson in 1922.
Formulations
The Richards equation appears in many articles in the environmental literature because it describes the flow in the vadose zone between the atmosphere and the aquifer. It also appears in pure mathematical journals because it has non-trivial solutions. The above-given mixed formulation involves two unknown variables: and . This can be easily resolved by considering constitutive relation , which is known as the water retention curve. Applying the chain rule, the Richards equation may be reformulated as either -form (head based) or -form (saturation based) Richards equation.
Head-based
By applying the chain rule on temporal derivative leads to
,
where is known as the retention water capacity . The equation is then stated as
.
The head-based Richards equation is prone to the following computational issue: the discretized temporal derivative using the implicit Rothe method yields the following approximation:
This approximation produces an error that affects the mass conservation of the numerical solution, and so special strategies for temporal derivatives treatment are necessary.
Saturation-based
By applying the chain rule on the spatial derivative leads to
where , which could be further formulated as , is known as the soil water diffusivity . The equation is then stated as
The saturation-based Richards equation is prone to the following computational issues. Since the limits and , where is the saturated (maximal) water content and is the residual (minimal) water content a successful numerical solution is restricted just for ranges of water content satisfactory below the full saturation (the saturation should be even lower than air entry value) as well as satisfactory above the residual water content.
Parametrization
The Richards equation in any of its forms involves soil hydraulic properties, which is a set of five parameters representing soil type. The soil hydraulic properties typically consist of water retention curve parameters by van Genuchten: (), where is the inverse of air entry value [L−1], is the pore size distribution parameter [-], and is usually assumed as . Further the saturated hydraulic conductivity (which is for non isotropic environment a tensor of second order) should also be provided. Identification of these parameters is often non-trivial and was a subject of numerous publications over several decades.
Limitations
The numerical solution of the Richards equation is one of the most challenging problems in earth science. Richards' equation has been criticized for being computationally expensive and unpredictable because there is no guarantee that a solver will converge for a particular set of soil constitutive relations. Advanced computational and software solutions are required here to over-come this obstacle. The method has also been criticized for over-emphasizing the role of capillarity, and for being in some ways 'overly simplistic' In one dimensional simulations of rainfall infiltration into dry soils, fine spatial discretization less than one cm is required near the land surface, which is due to the small size of the representative elementary volume for multiphase flow in porous media. In three-dimensional applications the numerical solution of the Richards equation is subject to aspect ratio constraints where the ratio of horizontal to vertical resolution in the solution domain should be less than about 7.
References
See also
Infiltration (hydrology)
Water retention curve
Finite water-content vadose zone flow method
Soil Moisture Velocity Equation
Soil physics
Hydrology
Partial differential equations | Richards equation | [
"Physics",
"Chemistry",
"Engineering",
"Environmental_science"
] | 924 | [
"Environmental engineering",
"Hydrology",
"Applied and interdisciplinary physics",
"Soil physics"
] |
7,153,778 | https://en.wikipedia.org/wiki/Hydrologic%20Evaluation%20of%20Landfill%20Performance | The Hydrologic Evaluation of Landfill Performance (HELP) model is a quasi-two-dimensional hydrologic numerical model for conducting water balance analysis of landfills, cover systems, and other solid waste containment facilities; it was developed for the United States Environmental Protection Agency.
Versions
Public domain (free) version:
HELP v4.0 – Microsoft Excel-based version developed by EPA ORD's Center for Environmental Solutions and Emergency Management, HELP 4 user manual and further documentation for HELP v3.0
Commercial versions:
Visual HELP – based on the HELP version 3.07, offers a Microsoft Windows GUI to view and edit soil profiles and to generate weather data.
HELP 3.95 D – by Dr. Klaus Berger at the University of Hamburg; offers a Microsoft Windows UI and includes the model HELP 3.07 and the enhanced model HELP 3.95 D.
References
Landfill
Hydrology models | Hydrologic Evaluation of Landfill Performance | [
"Biology",
"Environmental_science"
] | 178 | [
"Hydrology",
"Environmental modelling",
"Hydrology models",
"Biological models"
] |
7,153,781 | https://en.wikipedia.org/wiki/Michael%20Coey | John Michael David Coey (born 24 February 1945), known as Michael Coey, is a Belfast-born experimental physicist working in the fields of magnetism and spintronics. He is an Emeritus professor at the Trinity College Dublin (TCD).
Life
Education
Michael Coey got a BA in Physics at Jesus College, Cambridge (1966), and a PhD from University of Manitoba (1971) for
a thesis on "Mössbauer Effect of 57Fe in Magnetic Oxides" with advisor Allan H. Morrish.
He has been in the physics department of Trinity College Dublin (TCD) since 1978. He obtained his ScD in 1987 and passed his Habilitation from the University of Grenoble in 1986, and an honorary doctorate in 1994. He served as Erasmus Smith's Professor of Natural and Experimental Philosophy at TCD from 2007 to 2012.
Career
Michael Coey has been a Professor of Physics at TCD since 1987, and was the last appointed Erasmus Smith's Professor of Natural and Experimental Philosophy (2007–2012), a chair that dates from 1724.
In 1994 Coey founded Magnetic Solutions and went on to be the cofounder of CRANN Ireland's Nanoscience Research institute (2002) and conceived Dublin's unique Science Gallery (2006). He has published over 700 scientific articles on diverse aspects of magnetism, many of which have had significant impact on the scientific community.
His textbook Magnetism and Magnetic Materials has been well received.
He delivered a public lecture on the History of Magnetism in Paris in 2010. Currently, Coey holds positions at National University Singapore and the Max Planck Institute for Chemical Physics of Solids in Dresden.
He has been part of numerous collaborations including: IBM Yorktown Heights (1979), Institute of Physics Peking (1980), McGill University (1982), University of Bordeaux (1984), CEN-Grenoble (1985), Johns Hopkins APL (1986), Universite de Paris IV (1992), University of California, San Diego (1997), Florida State University (1998), University of Paris XI (1998), Leman University Geneva (2001/3), University of Strasbourg (2006).
Coey pioneered a co-operation project between academic and industrial laboratories in the Concerted European Action on Magnets (1985–95). Throughout his career he has strongly identified himself with the European spirit and tradition of collaboration.
Honours and awards
Mike Coey is a member of the Royal Irish Academy (1987), a Fellow of the Royal Society (2003) and a Foreign Associate of the US National Academy of Sciences (2005). He is also a fellow of the Institute of Physics, the Mineralogical Society of America and the American Physical Society. His numerous awards include a Fulbright Fellowship, the Charles Chree Medal of the Institute of Physics (1997), the Gold Medal of the Royal Irish Academy (2005) the RDS INTEL Prize Lecture on Nanoscience (2012) in addition to being the recipient of the Humboldt (2013), Gutenberg (2015) and Max Born Medal and Prize (2019) awards. He has an honorary doctorate from the Institute Institute National Polytechnique Grenoble (1994) and has been a Distinguished Lecturer, IEEE Magnetics Study (2006) and the Albert Einstein Professor of the Chinese Academy of Sciences (2010). He received the Max Born Medal and Prize from the Institute of Physics in 2012.
Books
Magnetism and Magnetic Materials (Cambridge University Press, 2010)
(with R. Skomski) Permanent Magnetism (IOP 1999)
(with K Moorjani) Magnetic Glasses (Elsevier 1984)
(edited) Rare Earth Iron Permanent Magnets (Oxford 1996)
(edited) Concerted European Action on Magnets (Elsevier 1989)
(edited) Structural and Magnetic Phase Transitions in Minerals (Springer 1988)
(edited) Current Topics in Magnetism (CJP 1987)
Personal life
Since 1973, Coey has been married to poet Wong May Coey and has two sons.
References
Sources
1945 births
Living people
Academics of Trinity College Dublin
Alumni of Jesus College, Cambridge
Fellows of the Royal Society
Grenoble Institute of Technology alumni
Irish physicists
Foreign associates of the National Academy of Sciences
Spintronics
20th-century British physicists
21st-century British physicists
University of Manila alumni
Fellows of the American Physical Society | Michael Coey | [
"Physics",
"Materials_science"
] | 881 | [
"Spintronics",
"Condensed matter physics"
] |
7,154,332 | https://en.wikipedia.org/wiki/Skewness%20risk | Skewness risk in forecasting models utilized in the financial field is the risk that results when observations are not spread symmetrically around an average value, but instead have a skewed distribution. As a result, the mean and the median can be different. Skewness risk can arise in any quantitative model that assumes a symmetric distribution (such as the normal distribution) but is applied to skewed data.
Ignoring skewness risk, by assuming that variables are symmetrically distributed when they are not, will cause any model to understate the risk of variables with high skewness.
Skewness risk plays an important role in hypothesis testing. The analysis of variance, one of the most common tests used in hypothesis testing, assumes that the data is normally distributed. If the variables tested are not normally distributed because they are too skewed, the test cannot be used. Instead, nonparametric tests can be used, such as the Mann–Whitney test for unpaired situation or the sign test for paired situation.
Skewness risk and kurtosis risk also have technical implications in calculation of value at risk. If either are ignored, the Value at Risk calculations will be flawed.
Benoît Mandelbrot, a French mathematician, extensively researched this issue. He feels that the extensive reliance on the normal distribution for much of the body of modern finance and investment theory is a serious flaw of any related models (including the Black–Scholes model and CAPM). He explained his views and alternative finance theory in a book: The (Mis)Behavior of Markets: A Fractal View of Risk, Ruin and Reward.
In options markets, the difference in implied volatility at different strike prices represents the market's view of skew, and is called volatility skew. (In pure Black–Scholes, implied volatility is constant with respect to strike and time to maturity.)
Skewness for bonds
Bonds have a skewed return. A bond will either pay the full amount on time (very likely to much less likely depending on quality), or less than that. A normal bond does not ever pay more than the "good" case.
See also
Skewness
Kurtosis risk
Taleb distribution
Stochastic volatility
References
Mandelbrot, Benoit B., and Hudson, Richard L., The (mis)behaviour of markets : a fractal view of risk, ruin and reward, London : Profile, 2004,
Johansson, A. (2005) "Pricing Skewness and Kurtosis Risk on the Swedish Stock Market", Masters Thesis, Department of Economics, Lund University, Sweden
Premaratne, G., Bera, A. K. (2000). Modeling Asymmetry and Excess Kurtosis in Stock Return Data. Office of Research Working Paper Number 00-0123, University of Illinois
Statistical deviation and dispersion
Investment
Risk analysis
Mathematical finance
Applied probability | Skewness risk | [
"Mathematics"
] | 597 | [
"Applied mathematics",
"Mathematical finance",
"Applied probability"
] |
7,154,355 | https://en.wikipedia.org/wiki/Twist%20tie | A twist tie is a fastener made of one or more metal wires encased in a thin strip of paper or plastic, in such a way that it can bend and retain its shape. Wireless polymeric twist ties have also been developed.
Use
It is used to tie the openings of containers including bags, such as garbage bags or bread bags. It is also called garden twist wire. A twist tie is used by wrapping it around the item to be fastened, then twisting the ends together. They are often included with boxes of plastic food bags or trash bags, and are commonly available individually in pre-cut lengths, on large spools, or in perforated sheets called gangs.
The outer covering can be in a variety of colors with or without printing. Plain paper, metallic paper, plastic, poly, or custom coatings are popular for different applications. The plastic, poly, or metallic paper twist ties withstand water better than the uncoated paper versions. Different sizes and strengths are used for different applications, from a small closure for a bag of bread to a large, heavy tie to hold unwieldy garden hoses in place. A twist tie with a broad paper covering may also be used for labeling.
The wire is often made of stainless steel or galvanized steel with a diameter between 19 and 31 AWG (0.2 and 0.9 mm).
They were invented by Charles E. Burford in 1961.
Application
Twist ties can be applied manually. They can be reapplied several times, facilitating reusable packaging.
Twist ties are often found in grocery stores in the United States for customers to use to secure their purchases into bags.
Banner/flag style twist ties have a large portion extended out from the twist tie that allows user to write and identify PLU/BIN numbers when purchasing things like trail mix, granola, hardware, and more.
Automatic and semi-automatic twist-tying equipment is also available; The US Patent Office has listed several hundred patents for automation methods.
History
Before the invention of the twist-tie, small cuts of sheep or cow intestine were used as a rubber band. Before the use of the intestinal rubber band, thin pieces of metal would be hammered into a wire-like shape. These were called wire-twisties and were used by wrapping it around the item to be fastened, then twisting the ends together. According to the 1938 Food, Drug, and Cosmetic Act, twist ties are not allowed to hold candies together. After 1938, all licorice factories began binding their candies together with small pieces of twine or thin pieces of other licorice.
See also
Zip tie
Pipe cleaner
References
American inventions
Fasteners
Packaging | Twist tie | [
"Engineering"
] | 550 | [
"Construction",
"Fasteners"
] |
7,154,495 | https://en.wikipedia.org/wiki/Four-terminal%20sensing | In electrical engineering, four-terminal sensing (4T sensing), 4-wire sensing, or 4-point probes method is an electrical impedance measuring technique that uses separate pairs of current-carrying and voltage-sensing electrodes to make more accurate measurements than the simpler and more usual two-terminal (2T) sensing. Four-terminal sensing is used in some ohmmeters and impedance analyzers, and in wiring for strain gauges and resistance thermometers. Four-point probes are also used to measure sheet resistance of thin films (particularly semiconductor thin films).
Separation of current and voltage electrodes eliminates the lead and contact resistance from the measurement. This is an advantage for precise measurement of low resistance values. For example, an LCR bridge instruction manual recommends the four-terminal technique for accurate measurement of resistance below 100 ohms.
Four-terminal sensing is also known as Kelvin sensing, after William Thomson, Lord Kelvin, who invented the Kelvin bridge in 1861 to measure very low resistances using four-terminal sensing. Each two-wire connection can be called a Kelvin connection. A pair of contacts that is designed to connect a force-and-sense pair to a single terminal or lead simultaneously is called a Kelvin contact. A clip, often a crocodile clip, that connects a force-and-sense pair (typically one to each jaw) is called a Kelvin clip.
Operating principle
When a Kelvin connection is used, current is supplied via a pair of force connections (current leads). These generate a voltage drop across the impedance to be measured according to Ohm's law V=IR. A pair of sense connections (voltage leads) are made immediately adjacent to the target impedance, so that they do not include the voltage drop in the force leads or contacts. Since almost no current flows to the measuring instrument, the voltage drop in the sense leads is negligible.
It is usual to arrange the sense wires as the inside pair, while the force wires are the outside pair. If the force and sense connections are exchanged, accuracy can be affected, because more of the lead resistance is included in the measurement. The force wires may have to carry a large current when measuring very small resistances, and must be of adequate gauge; the sense wires can be of a small gauge.
The technique is commonly used in low-voltage power supplies, where it is called remote sensing, to measure the voltage delivered to the load independent of the voltage drop in the supply wires.
It is common to provide 4-wire connections to current-sensing shunt resistors of low resistance operating at high current.
3-wire sensing
A variant uses three wires, with separate load and sense leads at one end, and a common wire on the other. Voltage drop in the common wire is compensated for by assuming that it is the same as in the load wire, of the same gauge and length. This technique is widely used in resistance thermometers, also known as resistance temperature detectors or RTDs. It is not as accurate as 4-wire sensing but can remove most of the error caused by cable resistance and is accurate enough for most applications.
Another example is in the ATX power supply standard, which includes a remote sense wire connected to the 3.3 V supply line at connector pin 13, but no sense connection for the ground wires.
See also
Electrode array
Wenner array configuration
Schlumberger array configuration
Electrical measurements
References
External links
DC Metering Circuits chapter from Lessons In Electric Circuits Vol 1 DC free ebook and Lessons In Electric Circuits series.
Four-Point Techniques for Measuring Electrical Conductivity and Resistivity
Explanatory Video about Four Wire Resistance Measurement in Energy Systems using Kelvin Clamps
Scientific techniques
Impedance measurements | Four-terminal sensing | [
"Physics"
] | 755 | [
"Impedance measurements",
"Physical quantities",
"Electrical resistance and conductance"
] |
7,155,027 | https://en.wikipedia.org/wiki/Pyrrolizidine%20alkaloid | Pyrrolizidine alkaloids (PAs), sometimes referred to as necine bases, are a group of naturally occurring alkaloids based on the structure of pyrrolizidine. Their use dates back centuries and is intertwined with the discovery, understanding, and eventual recognition of their toxicity on humans and animals.
History
PAs were first discovered in plants in the 19th century, but their toxic effects were not immediately recognized. Instead, many PA-containing plants were traditionally used for medicinal purposes in various cultures around the world. For example, herbs containing PAs were used in traditional Chinese medicine and by Native American tribes for their purported therapeutic properties. It has been estimated that 3% of the world's flowering plants contain pyrrolizidine alkaloids. Honey can contain pyrrolizidine alkaloids, as can grains, milk, offal and eggs. To date (2011), there is no international regulation of PAs in food, unlike those for herbs and medicines.
In the early to mid-20th century, researchers began to observe and document cases of livestock poisoning linked to the consumption of PA-containing plants. These observations led to the recognition of PAs as potent hepatotoxic and genotoxic compounds.
In response to growing concerns about PA exposure, regulatory agencies around the world began to establish guidelines and regulations to limit PA levels in food, herbal products, and animal feed. These regulations aim to protect human and animal health by minimizing PA exposure and mitigating the risk of toxicity.
Despite regulatory efforts, the issue of PA exposure remains relevant today. Ongoing research continues to explore various aspects of PA toxicity, including the identification of new PA-containing plants, the development of sensitive analytical methods, and the assessment of human health risks associated with PA exposure. Additionally, efforts to raise awareness among healthcare professionals, herbal product manufacturers, and the general public about the risks of PA exposure are ongoing.
Natural occurrence
PAs are a group of naturally occurring compounds found in a wide range of plant species. These alkaloids are secondary metabolites synthesized by plants primarily as a defense mechanism against herbivores, insects, and pathogens.
The biosynthesis of PAs was discovered to occur through the first pathway-specific enzyme homospermidine synthase.
The polyamines putrescine and spermidine are derived from the basic amino acid arginine. Subsequently, homospermidine synthase exchanges the 1,3-diaminopropane by putrescine and forms symmetric homospermidine. Oxidation of homospermidine by copper-dependent diamine oxidases initiates cyclization to pyrrolizidine-1-carbaldehyde, which is reduced, to 1-hydroxymethylpyrrolizidine. Desaturation and hydroxylation ultimately form retronecine, which is acylated with an activated necic acid, for instance with senecyl-CoA2 as in the example shown below.
PAs are preferably found in the plant families Asteraceae (tribes Eupatorieae and Senecioneae), Boraginaceae (many genera), Fabaceae (mainly the genus Crotalaria), and Orchidaceae (nine genera). More than 95% of the PA-containing species investigated thus far belong to these four families.
Structure and reactivity
PAs are compounds made up of a necine base, a double five-membered ring with a nitrogen atom in the middle, and one or two carboxylic esters called necic acids. Four major necine bases are described, with retronecine and its enantiomer Heliotridine being the largest group, and highly toxic. Another group is the platynecine, the difference between these groups is its saturated base, which makes it less toxic. Most bases have a 1,2-unsaturated base. Another difference in the groups is with Otonecine, which cannot form N-oxides, due to the methylation of the nitrogen atom.
The alcohol groups on the necine bases can make esters in a wide variety of forms. Among the possibilities are mono-esters, like Floridine and Heliotrine, and di-esters either with an open or closed ring structure, like Usaramine and Lasiocarpine. In total more than 660 PAs and PA N-oxides have been identified in over 6000 plants.
Synthesis
There are multiple ways to synthesize PAs and their derivatives. A flexible strategy would be to start with a Boc (tert-Butoxycarbonyl) protected pyrrole molecule and use specific reaction for synthesis into the desired compound.
Mechanisms of actions and metabolism
PAs are commonly introduced into the body via oral ingestion through contaminated food or traditional medicine, notably borage leaf, comfrey and coltsfoot. It can readily form salts with nitrates, chlorides and sulphates, which facilitate the uptake in the gastrointestinal tract. After which they travel to the liver via the portal vein.
Metabolites form mostly in the liver. Here esterases can hydrolyze the PAs to reduce the compound into its necine acids and bases, both forms are non-toxic for humans and do not damage the body. However, cytochrome P450 (CYP450) also metabolizes PAs, this enzyme can form pyrrolic esters (EPy), these are hepatotoxic due to their high reactivity. The EPy can also be hydrolyzed into alcoholic pyrroles, which are mutagenic and carcinogenic.
Since this mostly happens in the liver, this is the most affected organ. Other affected organs are the lungs and kidneys. The EPy can escape the liver, and travel through the Disse space into the bloodstream.
The electrophilic nature of pyrroles makes it an easy target for nucleophilic attack from nucleic acids and protein. If bound by glutathione it can become a non-toxic conjugate and be excreted via the kidneys.
A second detoxifying pathway is the formation of the N-oxide In the liver and lungs of certain mammal species enzymes called monooxygenase can prevent aromatization of the double 5-ring and in turn prevent the formation of the pyrrole-protein adduct.
Toxicological effects
The toxicity consequences resulting from the metabolism of PAs in humans primarily revolve around hepatotoxicity and genotoxicity.
PAs are metabolized in the liver through CYP450-mediated pathways. This metabolic process leads to the formation of reactive intermediates, such as pyrrolic metabolites, which can covalently bind to proteins in the liver, forming pyrrole-protein adducts. These adducts impair the function of essential liver proteins, leading to hepatotoxicity. The severity of liver damage correlates with the level of pyrrole-protein adduct formation. Hepatotoxicity induced by PAs can manifest as liver injury, inflammation, necrosis, HSOS (Hepatic Sinusoidal Obstruction Syndrome) and even liver failure in severe cases. The pathogenesis of PAs-induces HSOS is shown by Xu.
Genotoxicity is another consequence of PA metabolism. The reactive metabolites formed during PA metabolism can also bind to DNA, leading to the formation of DNA adducts. These adducts can induce mutations and DNA damage, increasing the risk of cancer development and other adverse health effects. Genotoxicity is particularly concerning as it can lead to long-term health consequences, including carcinogenesis.
The toxicity of PA metabolites can vary depending on the specific PA compound and its chemical structure. Different PAs may undergo metabolic activation to varying degrees, resulting in differences in toxicity. For example, retronecine-type PAs like monocrotaline are known to be highly hepatotoxic, while other types may exhibit lower toxicity or different toxicological profiles.
Pharmacological effects
Next to its toxicological effects, PAs have long been researched for their potential beneficial effects. Traditional medicinal plants have long been known to contain PAs, the exact effect of the PAs regarding beneficial effect of the plants is debated. Among these traditional medicines is the root of Ligularia achyrotricha of Tibet. Several pharmacological effects have been found. Among these effects are antimicrobial activity, antiviral activity and antineoplastic activity, acetylcholinesterase inhibition, and gastric ulcers treatment.
Antimicrobial activity of several PAs have been identified as having mild to strong effect against bacteria: E. coli and P. chrysogenum. In particular Lasiocarpine and 7-angeloyl heliotrine were found to have significant activity against these microbes. Derivatives of PAs have been found to induce cell death in these bacteria by attacking bacterial cell membranes. Retronecine derivatives have been found slow the growth rate of several strains of the fungus Fusarium oxysporum.
Antiviral activity has been found in haliotridine derivates. However, effects are not consistent across PA compounds, derivates significantly differ in activity between different viral pathogens. As a result, it is difficult to determine an exact PA with an effect on a specific virus. Several PAs have been found with significant inhibition of growth in the following viruses: coxsackie, poliomyelitis, measles, and vesicular stomatitis.
Antineoplastic activity, specifically against leukemia, has been found in retronecine derivatives such as indicine. A 1984 study by L. Letendre treated 22 leukaemia patients with indicine, this resulted in a significant observed antineoplastic response with four complete remissions and five partial remissions. An observed adverse side effect of the treatment was observed in 5 patients who died of hepatic toxicity likely caused by the medication. Two different dose levels were tested on children: 2 g/m2/ day for 5 consecutive days (14 patients) and 2,5 g/m2/ day for 5 consecutive days (17 patients). Therapeutic effect was determined based on these doses and deemed to have a limited antileukemic effect below a dose of 3 g/m2/ day. However, this study also found severe hepatotoxic responses to be common at these doses.
Four known PAs, 7-O-angeloyllycopsamine N-oxide, echimidine N-oxide, echimidine, and 7-O-angeloylretronecine have been clinically shown to inhibit acetylcholinesterase (AChE) . AChE inhibitors have been used as one of the treatments for Alzheimer's disease. The effect of these compounds was significant in the reduction of AChE production and thus a potential alternative in the fight against Alzheimer's.
PAs like senecionine, integerrimine, retrorsine, usaramine and seneciphylline have been shown to cause an increase in both the levels of gastrin and the expression of epidermal growth factor (EGF). These two compounds aid in the repair of the stomach after gastric ulcers. A high concentration of said compounds can reduce lesions in the stomach. This may aid in treatment after operation to the stomach.
Effects on animals
The toxicological effects of PAs have been studied on animals. Retronecine derivatives are known to cause a toxic response in the livers of livestock like cows. Symptoms tend to start with a change in rough hair coat and depression. When Pregnant livestock is exposed to PAs an effect can be seen on the foetus, mainly stillbirth and accumulation in the foetus. The main lethal responses in adult livestock exhibit necrosis, HSOS and megalacytosis. Additional to the short-term effect PAs have been found to lead to carcinogenic growths on the long term. The carcinogenic effect is caused by formation of DNA adducts, because of metabolic reactions. No minimum dosage for the carcinogenic effect is currently known. However, there have been studies to determine the lowest dose for an adverse effect, also known as LOAEL. LOAEL and (oral) for 40 PAs have been experimentally found out. These values can be seen in the Table below. The found low LD50 values clearly show the relatively high toxicity of PAs, however no significant relation was found between the LD50 and LOAEL.
PAs are also used as a defense mechanism by some organisms such as Utetheisa ornatrix. Utetheisa ornatrix caterpillars obtain these toxins from their food plants and use them as a deterrent for predators. PAs protect them from most of their natural enemies. The toxins stay in these organisms even when they metamorphose into adult moths, continuing to protect them throughout their adult stage.
Plants species containing pyrrolizidine alkaloids
This is a dynamic list and may never be able to satisfy particular standards for completeness. You can help by adding missing items with reliable sources
|-
|
Adenostyles alliariae
Adenostyles glabra
Ageratum conyzoides
Ageratum houstonianum
Anchusa officinalis
Arnebia euchroma
Borago officinalis
Cacalia hastata
Cacalia hupehensis
Chromolaena odorata
Cordia myxa
Crassocephalum crepidioides
Crotalaria albida
Crotalaria assamica
Crotalaria crispat
Crotalaria dura
Crotalaria globifera
Crotalaria mucronata
Crotalaria sesseliflora
Crotalaria spectabilis
Crotalaria tetragona
Crotalaria retusa
Cynoglossum amabile
Cynoglossum lanceolatum
Cynoglossum officinale
Cynoglossum zeylanicum
Echium plantagineum
Echium vulgare
Emilia sonchifolia
Eupatorium cannabinum
Eupatorium chinense
Eupatorium fortunei
Eupatorium japonicum
Eupatorium perfoliatum
Eupatorium purpureum
Farfugium japonicum
Gynura bicolor
Gynura divaricata
Gynura segetum
Heliotropium amplexicaule
Heliotropium europaeum
|
Heliotropium indicum
Heliotropium popovii
Lappula intermedia
Ligularia cymbulifera
Ligularia dentata
Ligularia duiformis
Ligularia heterophylla
Ligularia hodgsonii
Ligularia intermedia
Ligularia lapathifolia
Ligularia lidjiangensis
Ligularia platyglossa
Ligularia tongolensis
Ligularia tsanchanensis
Ligularia vellerea
Liparis nervosa
Lithospermum erythrorhizon
Neurolaena lobata
Petasites japonicus
Senecio alpinus
Senecio argunensis
Senecio brasiliensis
Senecio chrysanthemoides
Senecio cineraria
Senecio glabellus
Senecio integrifolius var. fauriri
Senecio interggerrimus
Senecio jacobaea
Senecio lautus
Senecio linearifolius
Senecio madagascariensis
Senecio nemorensis
Senecio quadridentatus
Senecio riddelli
Senecio scandens
Senecio vulgaris
Syneilesis aconitifolia
Symphytum officinale
Tussilago farfara
References
Plant toxins
Hepatotoxins | Pyrrolizidine alkaloid | [
"Chemistry"
] | 3,275 | [
"Pyrrolizidine alkaloids",
"Alkaloids by chemical classification",
"Chemical ecology",
"Plant toxins"
] |
7,155,145 | https://en.wikipedia.org/wiki/Dagger%20compact%20category | In category theory, a branch of mathematics, dagger compact categories (or dagger compact closed categories) first appeared in 1989 in the work of Sergio Doplicher and John E. Roberts on the reconstruction of compact topological groups from their category of finite-dimensional continuous unitary representations (that is, Tannakian categories). They also appeared in the work of John Baez and James Dolan as an instance of semistrict k-tuply monoidal n-categories, which describe general topological quantum field theories, for n = 1 and k = 3. They are a fundamental structure in Samson Abramsky and Bob Coecke's categorical quantum mechanics.
Overview
Dagger compact categories can be used to express and verify some fundamental quantum information protocols, namely: teleportation, logic gate teleportation and entanglement swapping, and standard notions such as unitarity, inner-product, trace, Choi–Jamiolkowsky duality, complete positivity, Bell states and many other notions are captured by the language of dagger compact categories. All this follows from the completeness theorem, below. Categorical quantum mechanics takes dagger compact categories as a background structure relative to which other quantum mechanical notions like quantum observables and complementarity thereof can be abstractly defined. This forms the basis for a high-level approach to quantum information processing.
Formal definition
A dagger compact category is a dagger symmetric monoidal category which is also compact closed, together with a relation to tie together the dagger structure to the compact structure. Specifically, the dagger is used to connect the unit to the counit, so that, for all in , the following diagram commutes:
To summarize all of these points:
A category is closed if it has an internal hom functor; that is, if the hom-set of morphisms between two objects of the category is an object of the category itself (rather than of Set).
A category is monoidal if it is equipped with an associative bifunctor that is associative, natural and has left and right identities obeying certain coherence conditions.
A monoidal category is symmetric monoidal, if, for every pair A, B of objects in C, there is an isomorphism that is natural in both A and B, and, again, obeys certain coherence conditions (see symmetric monoidal category for details).
A monoidal category is compact closed, if every object has a dual object . Categories with dual objects are equipped with two morphisms, the unit and the counit , which satisfy certain coherence or yanking conditions.
A category is a dagger category if it is equipped with an involutive functor that is the identity on objects, but maps morphisms to their adjoints.
A monoidal category is dagger symmetric if it is a dagger category and is symmetric, and has coherence conditions that make the various functors natural.
A dagger compact category is then a category that is each of the above, and, in addition, has a condition to relate the dagger structure to the compact structure. This is done by relating the unit to the counit via the dagger:
shown in the commuting diagram above. In the category FdHilb of finite-dimensional Hilbert spaces, this last condition can be understood as defining the dagger (the Hermitian conjugate) as the transpose of the complex conjugate.
Examples
The following categories are dagger compact.
The category FdHilb of finite dimensional Hilbert spaces and linear maps. The morphisms are linear operators between Hilbert spaces. The product is the usual tensor product, and the dagger here is the Hermitian conjugate.
The category Rel of Sets and relations. The product is, of course, the Cartesian product. The dagger here is just the opposite.
The category of finitely generated projective modules over a commutative ring. The dagger here is just the matrix transpose.
The category nCob of cobordisms. Here, the n-dimensional cobordisms are the morphisms, the disjoint union is the tensor, and the reversal of the objects (closed manifolds) is the dagger. A topological quantum field theory can be defined as a functor from nCob into FdHilb.
The category Span(C) of spans for any category C with finite limits.
Infinite-dimensional Hilbert spaces are not dagger compact, and are described by dagger symmetric monoidal categories.
Structural theorems
Selinger showed that dagger compact categories admit a Joyal-Street style diagrammatic language and proved that dagger compact categories are complete with respect to finite dimensional Hilbert spaces i.e. an equational statement in the language of dagger compact categories holds if and only if it can be derived in the concrete category of finite dimensional Hilbert spaces and linear maps. There is no analogous completeness for Rel or nCob.
This completeness result implies that various theorems from Hilbert spaces extend to this category. For example, the no-cloning theorem implies that there is no universal cloning morphism. Completeness also implies far more mundane features as well: dagger compact categories can be given a basis in the same way that a Hilbert space can have a basis. Operators can be decomposed in the basis; operators can have eigenvectors, etc.. This is reviewed in the next section.
Basis
The completeness theorem implies that basic notions from Hilbert spaces carry over to any dagger compact category. The typical language employed, however, changes. The notion of a basis is given in terms of a coalgebra. Given an object A from a dagger compact category, a basis is a comonoid object . The two operations are a copying or comultiplication δ: A → A ⊗ A morphism that is cocommutative and coassociative, and a deleting operation or counit morphism ε: A → I . Together, these obey five axioms:
Comultiplicativity:
Coassociativity:
Cocommutativity:
Isometry:
Frobenius law:
To see that these relations define a basis of a vector space in the traditional sense, write the comultiplication and counit using bra–ket notation, and understanding that these are now linear operators acting on vectors in a Hilbert space H:
and
The only vectors that can satisfy the above five axioms must be orthogonal to one-another; the counit then uniquely specifies the basis. The suggestive names copying and deleting for the comultiplication and counit operators come from the idea that the no-cloning theorem and no-deleting theorem state that the only vectors that it is possible to copy or delete are orthogonal basis vectors.
General results
Given the above definition of a basis, a number of results for Hilbert spaces can be stated for compact dagger categories. We list some of these below, taken from unless otherwise noted.
A basis can also be understood to correspond to an observable, in that a given observable factors on (orthogonal) basis vectors. That is, an observable is represented by an object A together with the two morphisms that define a basis: .
An eigenstate of the observable is any object for which
Eigenstates are orthogonal to one another.
An object is complementary to the observable if
(In quantum mechanics, a state vector is said to be complementary to an observable if any measurement result is equiprobable. viz. an spin eigenstate of Sx is equiprobable when measured in the basis Sz, or momentum eigenstates are equiprobable when measured in the position basis.)
Two observables and are complementary if
Complementary objects generate unitary transformations. That is,
is unitary if and only if is complementary to the observable
References
Monoidal categories
Dagger categories | Dagger compact category | [
"Mathematics"
] | 1,639 | [
"Dagger categories",
"Monoidal categories",
"Mathematical structures",
"Category theory"
] |
7,156,065 | https://en.wikipedia.org/wiki/Dagger%20symmetric%20monoidal%20category | In the mathematical field of category theory, a dagger symmetric monoidal category is a monoidal category that also possesses a dagger structure. That is, this category comes equipped not only with a tensor product in the category theoretic sense but also with a dagger structure, which is used to describe unitary morphisms and self-adjoint morphisms in : abstract analogues of those found in FdHilb, the category of finite-dimensional Hilbert spaces. This type of category was introduced by Peter Selinger as an intermediate structure between dagger categories and the dagger compact categories that are used in categorical quantum mechanics, an area that now also considers dagger symmetric monoidal categories when dealing with infinite-dimensional quantum mechanical concepts.
Formal definition
A dagger symmetric monoidal category is a symmetric monoidal category that also has a dagger structure such that for all , and all and in ,
;
;
;
and
.
Here, and are the natural isomorphisms that form the symmetric monoidal structure.
Examples
The following categories are examples of dagger symmetric monoidal categories:
The category Rel of sets and relations where the tensor is given by the product and where the dagger of a relation is given by its relational converse.
The category FdHilb of finite-dimensional Hilbert spaces is a dagger symmetric monoidal category where the tensor is the usual tensor product of Hilbert spaces and where the dagger of a linear map is given by its Hermitian adjoint.
A dagger symmetric monoidal category that is also compact closed is a dagger compact category; both of the above examples are in fact dagger compact.
See also
Strongly ribbon category
References
Dagger categories
Monoidal categories | Dagger symmetric monoidal category | [
"Mathematics"
] | 328 | [
"Dagger categories",
"Monoidal categories",
"Mathematical structures",
"Category theory"
] |
7,156,461 | https://en.wikipedia.org/wiki/Default%20password | Where a device needs a username and/or password to log in, a default password is usually provided to access the device during its initial setup, or after resetting to factory defaults.
Manufacturers of such equipment typically use a simple password, such as admin or password on all equipment they ship, expecting users to change the password during configuration. The default username and password are usually found in the instruction manual (common for all devices) or on the device itself.
Default passwords are one of the major contributing factors to large-scale compromises of home routers. Leaving such a password on devices available to the public is a major security risk. There are several Proof-of-Concept (POC), as well as real world worms running across internet, which are configured to search for systems set with a default username and password. Voyager Alpha Force, Zotob, and MySpooler are a few examples of POC malware which scan the Internet for specific devices and try to log in using the default credentials.
In the real world, many forms of malware, such as Mirai, have used this vulnerability. Once devices have been compromised by exploiting the Default Credential vulnerability, they can themselves be used for various harmful purposes, such as carrying out Distributed Denial of Service (DDoS) attacks. In one particular incident, a hacker was able to gain access and control of a large number of networks including those of University of Maryland, Baltimore County, Imagination, Capital Market Strategies L, by leveraging the fact that they were using the default credentials for their NetGear switch.
Some devices (such as wireless routers) will have unique default router usernames and passwords printed on a sticker, which is more secure than a common default password. Some vendors will however derive the password from the device's MAC address using a known algorithm, in which case the password can also be easily reproduced by attackers.
See also
Backdoor (computing)
Internet of things
Cyber-security regulation
References
Password authentication
Computer security exploits | Default password | [
"Technology"
] | 417 | [
"Computer security exploits"
] |
7,156,760 | https://en.wikipedia.org/wiki/L.A.%20Noire | L.A. Noire is a 2011 action-adventure video game developed by Team Bondi and published by Rockstar Games. Set in 1947 Los Angeles, the game follows the rise of detective Cole Phelps among the ranks of the Los Angeles Police Department as he solves a range of cases across various bureaus. When he is tasked with investigating a morphine distribution ring involving several of his former squadmates from World War II, Phelps finds both his personal and professional life falling into turmoil, and reluctantly joins forces with his estranged former comrade, Jack Kelso, as they uncover a major conspiracy involving prominent Los Angeles figures.
The game is played from a third-person perspective. The player may freely roam its interactive open world, primarily in a vehicle or on foot. As the game progresses, the player advances through several police department bureaus—Patrol, Traffic, Homicide, Vice, and Arson. The story is divided into multiple "cases", during which players must investigate crime scenes for clues, follow up leads, and interrogate suspects and witnesses; the player's success at these activities impacts how much of each case's story is revealed and their overall rating. The game features fast-paced action sequences, including chases, combat, and gunfights. Outside of cases, the player can complete optional street crimes and collect items found around the game world.
The development of L.A. Noire began following Team Bondi's founding in 2004, and was assisted by multiple Rockstar studios worldwide. L.A. Noire uses the proprietary motion capture technology MotionScan, which captures actors' facial expressions from every angle, resulting in a realistic recreation of a human face essential for the game's interrogations. As part of their research for the open world, the development team conducted field research in Los Angeles. The game features an original score inspired by 1940s films, and contains licensed music of songs from the era. The game was delayed numerous times through its seven-year development, which included a change of publisher and platforms. The working hours and managerial style of the studio was met with public complaints from staff members, and Team Bondi closed shortly after the game's initial release.
L.A. Noire was the first video game honoured as an official selection at the Tribeca Film Festival. The game was released for the PlayStation 3 and Xbox 360 consoles in May 2011, and for Windows in November; an enhanced version was released for Nintendo Switch, PlayStation 4, and Xbox One in November 2017. The game received positive reviews from critics, with praise directed at the facial animation, narrative, characters, performances, music, world design, and interrogation gameplay, though responses to the shooting and driving mechanics were mixed. It shipped four million units in its first month and 7.5 million by September 2017, and received multiple year-end nominations from gaming publications. L.A. Noire: The VR Case Files, a subset of cases playable in virtual reality, was released in December 2017.
Gameplay
L.A. Noire is an action-adventure neo-noir crime game. Played from a third-person perspective, the game is set in an open-world environment featuring Los Angeles in 1947. The player completes cases to progress through the story, fulfilling objectives in a generally linear order; as they roam the open world, the player can also complete optional street crimes—short, linear scenarios with set objectives—and collect items such as golden film reels, vehicles, novels, and golden records. The player can also discover multiple landmarks based on real monuments from Los Angeles in the 1940s. For most of the game, the player controls Cole Phelps, a Los Angeles Police Department (LAPD) patrolman who advances through the police department bureaus (desks) of Traffic, Homicide, Vice, and Arson; in some cases during the final desk, the player controls investigator Jack Kelso. The player has the option to play the game in black and white to imitate film noir.
While solving cases, the player discovers evidence, including information from non-player characters or physical clues found in or around crime scenes, locations of interest, or dead bodies; several pieces of physical evidence can be manipulated or further investigated to discover more information. When all key clues are discovered at a crime scene, the investigation music concludes. The player can also use telephones or gamewells to contact the police radio and access additional information. During cases, the player interrogates suspects and witnesses to discover information. When the interviewee responds, the player is given the option to either believe them, doubt them, or accuse them of lying. If the player accuses them of lying, they must submit evidence to prove it. The player's in-game notebook is used to list evidence, locations, and people involved in the case, as well as to select questions during interrogations.
When interrogating two suspects at the police station, the player may decide whom to charge with the crime; charging the wrong suspect affects the case's end rating—a five-star scale determined based on the player's performance in investigations, interrogations, and behaviour while driving. The player can use Intuition points during investigations to locate remaining clues, or during interrogation by removing an answer or discovering the most popular answer among players via the Rockstar Games Social Club. Progressing through the game will increase the player's Rank, which unlocks outfits and hidden vehicles, and earns an additional Intuition point; the maximum rank is 20. In some cases, while searching for clues, the player can discover newspapers, which provide access to a short cinematic covering a part of the game's overarching plot.
The game's world is primarily traversed on foot or in a vehicle. The player can climb over fences and up pipes and ladders to access different areas. While driving, the player can turn on the siren, allowing them clearer passage through streets. The game also allows the player to skip travel sequences: as Phelps, they can nominate their partner as the driver and select the destination; as Kelso, who lacks a partner, they select the destination and arrive after a loading screen. As Phelps, the player can also ask their partner for directions. The game features fast-paced action sequences, including chases, combat, and gunfights. The player uses melee attacks and firearms to fight enemies; weapons can be swapped by opening the boot of the player's police vehicle. In combat, auto-aim and a cover system can be used as assistance against enemies. Should the player take damage, the colour will begin to fade to black and white; when free from damage, the character's health will gradually regenerate. Weapons can only be used in appropriate circumstances, such as during firefights; in some chase sequences, the player has the option to fire a warning shot against fleeing suspects. The player's partner will sometimes shoot at suspect vehicles during driving chase sequences. The player is presented with the option to skip action sequences and continue through the narrative upon failing three times.
Synopsis
Characters
For most of the game, the player takes on the role of Cole Phelps (Aaron Staton), a decorated United States Marine Corps veteran from the Sixth Marines. Phelps begins the game as an LAPD patrol officer alongside his partner Ralph Dunn (Rodney Scott), another new recruit. When Phelps is promoted to the Traffic desk, led by Captain Gordon Leary (Ned Vaughn), he is partnered with Stefan Bekowsky (Sean McGowan), a Polish American whom Phelps eventually befriends. Upon his promotion to Homicide, led by James Donnelly (Andrew Connolly), Phelps is partnered with Rusty Galloway (Michael McGrady), a weary and cynical detective who often challenges Phelps's theories and opinions. In the Vice bureau, led by Lieutenant Archie Colmyer (Steve Rankin), Phelps becomes partners with Roy Earle, a sardonic and corrupt detective with whom Phelps repeatedly clashes over morality, behaviour, and technique. During his time in Vice, Phelps begins an extramarital affair with Elsa Lichtmann (Erika Heynatz), a German jazz singer. As a detective, Phelps frequently works with coroner Dr. Malcolm Carruthers (Andy Umberger) and technical crime scene investigator Ray Pinker (JD Cullum).
Following his demotion to the Arson desk, led by Captain Lachlan McKelty (Randy Oglesby), Phelps is partnered with Herschel Biggs (Keith Szarabajka), a former Marine and proficient detective who is reclusive and opposed to partners. For some cases during Arson, the player assumes control of Jack Kelso (Gil McKinney), a former Marine with whom Phelps developed an intense rivalry. Kelso, initially a claims investigator at California Fire and Life and later a District Attorney Investigator, helps Phelps and Elsa discover the truth behind the Suburban Redevelopment Fund (SRF)—a program founded under the pretense of providing affordable housing for returning veterans. Members of the SRF include real estate magnate Leland Monroe (John Noble), California Fire and Life vice-president Curtis Benson (Jim Abele), and psychiatrist Harlan Fontaine (Peter Blomquist). Fontaine's mentee is medical student Courtney Sheldon (Chad Todhunter)—a former Marine with whom Phelps and Kelso were stationed—who becomes involved in the city's drug trade through a partnership with gangster Mickey Cohen (Patrick Fischler). One of Fontaine's patients is Ira Hogeboom (J. Marvin Campbell), a former flamethrower operator from the Sixth Marines who became severely traumatised after unintentionally burning out a cave of civilians on Phelps's orders.
Plot
In 1947, after successfully solving a major murder case as a patrol officer, Phelps is promoted to detective. His tenure at the Traffic desk results in solving multiple cases of murder and fraud. Six months later, after a stint on the Burglary desk, Phelps is promoted to the Homicide desk. He and Galloway investigate various cases containing similarities to the Black Dahlia murder, arresting numerous suspects. However, Phelps is doubtful they are apprehending the actual murderers; his theories are ultimately proven correct. They eventually track down and kill the real murderer but are unable to publicly disclose his identity due to his relation to a powerful government official.
Upon being promoted to the Vice division, Phelps investigates the distribution of military surplus morphine, stolen from the ship that had brought home his former Marine unit from the war. He learns that several members had stolen and distributed the morphine, only to be assassinated on the orders of Cohen. During this time, Phelps begins his affair with Elsa. Earle helps several prominent figures in the city draw attention away from a major prostitution scandal by exposing Phelps's adultery before he is able to draw a confession from Sheldon over his involvement with the stolen morphine. In exchange, Earle is given a place in the SRF. Phelps's marriage ends, he becomes disgraced in the LAPD, and he is demoted to the Arson desk, where he is tasked with investigating several suspicious house fires. Despite noting a solid connection between them and a housing development the SRF operates, Phelps is warned off by Earle from pursuing the syndicate and its founder Monroe. Seeking help, Phelps prompts Kelso to look into the matter.
Kelso discovers the development uses unsuitable building materials, and his boss Benson is knowingly insuring them. Following a shootout at Monroe's mansion, Kelso learns the syndicate used one of Fontaine's patients to burn down the homes of those who would not agree to sell their property to the fund while the occupants were on vacation; eventually, his patient accidentally killed four people in one such fire and became irreversibly traumatised. The patient confronts and murders Fontaine at his clinic and kidnaps Elsa. Investigating the clinic, Phelps discovers the syndicate was a front to defraud the Federal Government: knowing the government would later purchase the plots through eminent domain for a planned highway, Monroe would acquire land with money invested by the syndicate and build surreptitiously cheap houses to increase their value. Phelps also discovers that Sheldon, overcome with guilt, had provided Fontaine with the stolen morphine under the pretense that Fontaine would legally provide the morphine to medical facilities with the profits being reinvested into the SRF; Fontaine later murdered Sheldon after gaining knowledge of Kelso's investigation into the SRF.
Kelso realises Fontaine's patient was Hogeboom. Phelps and Kelso pursue Hogeboom and Elsa into the Los Angeles River Tunnels. The pair rescue Elsa, and Kelso shoots Hogeboom to end his suffering. As the water rises within the tunnels following intense rainfall, Elsa and Kelso manage to escape, but a violent current kills Phelps. At Phelps's funeral, Earle delivers a eulogy, claiming Phelps was wrongly accused of wrongdoings and that he had exposed the corruption of Fontaine and Monroe. After Elsa leaves in disgust, Kelso asks Biggs to comfort her; Biggs confirms to Kelso while Kelso and Phelps were not friends, they were never enemies. In a closing epilogue flashback, Kelso is revealed to have known about the stolen morphine but refused to be involved in its distribution, knowing the trouble it would cause.
Development
After the release of The Getaway (2002), writer and director Brendan McNamara left developer Team Soho and moved from London to his native Sydney. In mid-2003, he founded the six-person development studio Team Bondi alongside former Team Soho developers. The development of L.A. Noire began shortly thereafter, in 2004. The studio had signed an exclusive deal with Sony Computer Entertainment to develop a game for the , though the publishing rights were handed to Rockstar Games by September 2006. The development team visited Rockstar's headquarters in New York every few months to exhibit progress. Development was assisted by multiple studios owned by Rockstar Games worldwide. Analyst estimations place the game's combined development and marketing budget at more than , which would make it one of the most expensive video games to develop.
Unlike other games by Rockstar, which run on the Rockstar Advanced Game Engine, L.A. Noire uses a proprietary engine from Team Bondi. McNamara led the founding of Depth Analysis, a sister company to Team Bondi that developed the motion capture technology MotionScan, which records actors at 1,000 frames per second with 32 surrounding cameras to capture facial expressions from every angle, resulting in a realistic recreation of a human face. The technology is central to the interrogation mechanic as players are required to use reactions to judge whether the interviewee is lying. Its precise requirements demanded extensive preparation, including hairstyling for performers. Rockstar was doubtful about the process and the team considered using the same technique as other Rockstar games like Red Dead Redemption (2010) as a fallback. The game uses Havok as its physics engine. Eleven cases across two desks—Bunko and Burglary—were cut as the team suspected they would not fit on one Blu-ray for PlayStation 3; the Xbox 360 version utilised three discs, though it originally used up to six prior to compression. A version of Grand Theft Autos wanted system—wherein the player would evade and attack other police officers—was removed as it felt out of character for Phelps.
McNamara had been interested in 1940s Los Angeles for some time—while working on The Getaway, he had a screensaver of the first freeway being built in Los Angeles—and felt the improvement in lighting systems from the PlayStation 2 to PlayStation 3 allowed the possibility to explore the film noir genre. He began with writing a 4–5-page outline before reading stories from the Los Angeles Public Library to use as inspiration. The team spent the first year-and-a-half of development researching Los Angeles by using newspapers and magazines, organising research trips, and capturing photographs; a total of 180,000 photographs were available as resources throughout development, and over 1,000 newspapers were used for research. The open world of 1947 Los Angeles was modelled using aerial photographs taken by photographer Robert Spence, which helped to create traffic patterns and public transport routes, as well as the location and condition of buildings. Jay Leno's collection of vintage vehicles were photographed for reference.
Building interiors were based on real Los Angeles buildings; the team extensively studied the Barclay Hotel for an accurate recreation in-game. While striving for an accurate recreation, the team took some artistic licence, including the appearance of Intolerances Babylon film set, which was destroyed prior to the 1940s but included to celebrate its history. The team created over 140 production bibles during development, acting as style guides with information about floorplans, dressing, signs, graphics, lighting, and reference material. Several in-game cases were inspired by real-life crimes reported by the city's media at the time; for example, "The Red Lipstick Murder" is based on the unsolved murder of Jeanne French in February 1947. When creating the themes, narrative, visuals, and sounds, McNamara and the team were inspired by several films, albums, television and radio shows, and books.
L.A. Noire has over twenty hours of voice work, and over 400 actors performed for the game. McNamara felt the technology allows players to connect with the characters in a way games had not achieved; he aimed "to go on a personal journey with characters". The team engaged Michael Uppendahl to direct the actors due to his experience. Secretive auditions were held for casting by Schiff/Audino, leading to several shared actors with Mad Men (2007–2015). Rockstar Vice President of Creativity Dan Houser suggested Staton for the role of Phelps. Staton joined production after McNamara pitched him the character, world, and technology. He worked on the project for about 18 months; unable to read the entire 2,200-page script, he received a 12-page document outlining the story and Phelps's history. Regarding the switch in player character from Phelps to Kelso, McNamara explained the player had to "go outside the realm of being a cop to bend the rules". He found the ending akin to A Tale of Two Cities (1859), with the characters coming "full circle" where "[Phelps] could do something for [Kelso] for once"; Phelps's death was partly inspired by the ending of the film Chinatown (1974). A gameplay sequence was originally meant to take place after Phelps's death but was cut as it "never really worked".
Characters' physical movements were recorded using motion capture. McGowan felt Bekowsky, initially jealous of Phelps, eventually warmed up to him and treated him like a younger brother. McGrady felt his own introverted personality helped him connect to Galloway, who he felt convinced to play after reading the script. McNamara and Harrington considered Earle true to the genre, citing his dated attitudes and sense of entitlement. Harrington compared the motion capture performance to live acting, though found the MotionScan process "a little restricting". McNamara contacted Noble early in development and he regularly visited the studio; he was later offered a role, and began performing in early 2010. Some characters are based on real people, such as Mickey Cohen, while others are inspired; Captain Donnelly is loosely based on both LAPD Captain Jack Donahue and McNamara's father.
The game features an original score composed by Andrew Hale and Simon Hale. Recorded at Abbey Road Studios, the music was inspired by orchestral scores from 1940s films. The composers attempted to create music that felt accessible to players, avoiding an exclusive focus on swing or jazz. Andrew Hale found composing the score a flexible process "about setting a mood", as opposed to a "mechanical" process in which the music was specifically composed to fit the time period. To assist, Rockstar engaged Woody Jackson, who had previously collaborated with the team on the music of Red Dead Redemption; he re-orchestrated one of the themes and wrote much of the in-game music. While the score largely uses a live orchestra, Jackson found this led to difficulties with interactive music as the player can hear the loop; inspired by film noir and the works of musicians like Bernard Herman, Jackson departed from the existing music and wrote original tracks in about a month. The game contains licensed music provided by the in-game radio from artists such as Ella Fitzgerald, Dizzy Gillespie, and Billie Holiday. The developers engaged the Real Tuesday Weld to create three original vocal tracks to authentically suit the period's musical identity, performed by Claudia Brücken and sung in-game by Elsa.
Staff complaints
Shortly after release, a group of former Team Bondi employees launched a website called lanoirecredits.com, containing over 100 names excluded or incorrectly listed in the official credits. An anonymous employee claimed he was asked to work 10–12 hours every day, including weekends. Following this, in a report by IGN, several anonymous members of the team publicly discussed the studio's managerial, staff turnover rates, and working hours and conditions associated with L.A. Noire; some claimed McNamara had been controlling and verbally abusive, and others spoke about their increased workload as a result of high turnover. Several referenced the ongoing crunch throughout development; one claimed to occasionally work between 80 and 110 hours per week to meet milestones. Some ex-employees claimed they were not paid for overtime, which McNamara refuted.
Following the publication of IGNs report, the International Game Developers Association launched an investigation against Team Bondi to verify the claims made. Lead gameplay programmer David Heironymus and senior gameplay programmer Charles Lefebvre rebutted the claims, acknowledging crunch was unfortunate but inevitable and stating they were not aware of any unpaid overtime or abusive working conditions. McNamara felt he had been unfairly maligned by many ex-employees, noting other artists and businessmen in other industries—such as Steve Jobs, Sam Peckinpah, and Werner Herzog—had performed worse actions than he had with much less vilification. He claimed the studio had improved its working conditions in the months after release, including the introduction of flexitime.
In July 2011, a series of confidential emails were leaked along with further comments from staff members who claimed they highlight the contentious relationship between Team Bondi and Rockstar. McNamara questioned how the confidential emails were allowed to be shared, noting it sets a "pretty dangerous precedent". Speaking to GamesIndustry.biz, an anonymous source from the development team claimed Rockstar "saved the project" but the relationship between Rockstar and Team Bondi was "badly damaged" and it was "quite clear" further collaborations were unlikely. The source claimed Rockstar was frustrated with the direction at Team Bondi, and as a result management at Team Bondi "resented Rockstar for taking lots of creative control". They added Rockstar "used to be very keen on making Team Bondi something like 'Rockstar Sydney but "the more they worked with Team Bondi management, the more they came to understand that this was a terrible idea". McNamara remained optimistic about his relationship with Rockstar and said "hopefully it doesn't have any hard feelings about us".
Release and promotion
L.A. Noire was officially announced in 2005, to be released by Sony for the PlayStation 3; the publishing rights were handed to Rockstar Games by September 2006, though no platforms were specified. An early cinematic trailer was released in October 2006. Rockstar's parent company Take-Two Interactive acknowledged the game in June 2007, listing it for release in the 2008 fiscal year (October 2007 – September 2008) for the PlayStation 3; the game subsequently received several delays: first to the 2009 fiscal year, then to September 2010, and later to the first half of 2011, which was later narrowed down to 17 May 2011 for North America, and 20 May for Australia and Europe.
The game was the subject of Game Informers cover story for its March 2010 issue. The debut trailer was released in November 2010, revealing the game would release in early 2011 for PlayStation 3 and Xbox 360. A development video was released in December 2010, demonstrating MotionScan and featuring interviews with the cast and developers. The game's cover art was unveiled on 23 February 2011. The game was exhibited at PAX East in March 2011 with an exclusive theatre presentation. The final pre-launch trailer was released on 11 May 2011. To spur pre-order game sales, Rockstar collaborated with several retail outlets to provide pre-order bonuses. Rockstar also ran a competition to win a trip to Los Angeles to attend the Festival of Film Noir at the Grauman's Egyptian Theatre, and play the game a month before its release. In April 2011, L.A. Noire was honoured as an official selection at the Tribeca Film Festival, the first video game to do so.
Rockstar partnered with Mulholland Books to publish L.A. Noire: The Collected Stories on 6 June 2011, featuring a collection of eight short stories in the L.A. Noire universe written by noted crime authors, including Lawrence Block, Joe R. Lansdale, Joyce Carol Oates, Francine Prose, and Andrew Vachss. The collection, edited and curated by Jonathan Santlofer, was completed in six weeks. Some of the writers—including Megan Abbott, Duane Swierczynski, and Santlofer—previewed an hour of the game for inspiration at Rockstar's headquarters in New York. Rockstar originally rejected Santlofer's story as it spoiled some of the game's narrative; he began to write a second story before deciding to rewrite the first without spoilers. Rockstar released an excerpt and five full stories before the game's release in May 2011.
Rockstar announced a re-release of the game in September 2017 for Nintendo Switch, PlayStation 4, and Xbox One; it was released on 14 November 2017. Developed by Virtuos, the enhanced version features finer texture details, upgraded weather effects, and new camera angles; the Switch version also features gyroscopic controls with the Joy-Con. Rockstar also announced L.A. Noire: The VR Case Files, a subset of seven of the game's cases for virtual reality support through the HTC Vive. Developed by Videogames Deluxe, a new studio founded by McNamara, the game was released on 15 December 2017, following a delay from November; support for Oculus Rift devices was added on 4 April 2018, and the game was released for PlayStation VR on 25 September 2019.
Additional content
Rockstar announced it would release several pieces of downloadable content for L.A. Noire shortly following its release in May 2011; all content could be pre-purchased in the "Rockstar Pass", one of the first examples of a season pass in video games. Five cases were released as downloadable content, the first two also as pre-order bonuses: "The Naked City" on 31 May 2011, a Vice case inspired by the 1948 film of the same name; "A Slip of the Tongue" on 31 May 2011, a Traffic case focusing on motor vehicle theft; "Nicholson Electroplating" on 21 June 2011, an Arson case based on the 1947 explosion of the O'Connor Electro-Plating company; "Reefer Madness" on 12 July 2011, a Vice case surrounding illegal reefer operations; and "The Consul's Car" on 26 July 2011, a Traffic case originally exclusive to PlayStation 3. All in-game items initially available as pre-order content were also made available as part of the Rockstar Pass. Rockstar announced L.A. Noire: The Complete Edition for Windows in September 2011, containing all downloadable content and featuring some gameplay and technical enhancements; it was released on 8 November 2011 in North America, and on 11 November in Australia and Europe, followed by a release on PlayStation 3 and Xbox 360 on 15 November.
Reception
Critical response
L.A. Noire received "generally favorable reviews" from critics, according to review aggregator Metacritic. It was praised for its facial animation, narrative, characters and performances, music, world design, and interrogation gameplay, though responses to the shooting and driving mechanics were mixed. The Guardians Steve Boxer described it as a "breakthrough for games"; Edge felt most elements are achieved better by other games but "few developers have brought such a diffuse set of genres together so atmospherically, stylishly or cohesively". GameTrailers wrote it "sets a new standard for storytelling in video games", though noted some overall limitations compared to other games.
Reviewers praised the game's facial animation, with several calling it the best in any video game. GameTrailers wrote "it allows a level of emoting that's never been seen in interactive entertainment". Matt Liebl of GameZone felt the interrogation mechanic would have been unrealistic without the use of MotionScan. Joystiqs Justin McElroy considered the technology "nothing short of revolutionary", noting it allowed the player to view "an actor's entire performance"; Edge found it added a "human element" to the interrogations. Some reviewers found the body animations failed to match the faces—sometimes failing to bridge the uncanny valley—but felt the effect added to the realism and subtlety of performances.
GameSpys Ryan Scott considered L.A. Noire to be "one of the strongest stories Rockstar's ever published", and Giant Bombs Brad Shoemaker called it "among the best in the business", citing its cohesiveness and tension near its climax. Liebl of GameZone thought the focus on narrative and performances excelled the game over Rockstar's action-oriented titles. Boxer of The Guardian praised the narrative's pacing and arc; Carolyn Petit of GameSpot found the game's later chapters made the slower pace of the early story more worthy. GamePros Will Herring similarly lauded the game's final act, noting the narrative's accuracy in its portrayal of Los Angeles; conversely, some reviewers felt the game became less interesting towards the end and some found it became repetitive. Hilary Goldstein of IGN wrote the cases that strayed from the formula—particularly the Homicide desk—were among the best, though noted the game failed to reach the emotional heights of Heavy Rain.
Petit of GameSpot found Phelps's character development "fascinating", and Herring of GamePro wrote his rapport with his partners made the game more interesting. GamesRadars Mikel Reparaz considered Phelps more likable as the game progressed. Giant Bombs Shoemaker felt the characters' dialogue made them feel appropriate to the setting. Polygons Owen S. Good found Biggs's moral code and reignited interest in justice a crucial personification of the noir theme. Critics lauded the cast's performances, with particular praise for Aaron Staton, John Noble, Andrew Connolly, and Michael McGrady; Edge felt Connolly "dominated any scene he's in". Some reviewers found the performances made the characters feel more believable and convincing; IGNs Goldstein praised the actors' mannerisms. Ryan McCaffrey of Official Xbox Magazine (OXM wrote the performances made it "a hell of a great drama to watch unfold"; similarly, McElroy of Joystiq felt they made it one of the "most compelling video game stories ever". Eurogamers Oli Welsh wrote Staton "does his best with a dry character".
Many reviewers found Los Angeles to be the "star" of the game, with praise directed at the generally accurate recreation of the city in 1947. Eurogamers Welsh compared it to Rockstar's Grand Theft Auto: San Andreas (2004) and Midnight Club: Los Angeles (2008), noting "it's the fastidious period detail that really impresses this time". Shoemaker of Giant Bomb wrote the historical elements greatly benefited the overall tone and atmosphere, granting authenticity to the narrative. GamePros Herring called it "one of the richest and most impressively rendered video game environments". Matt Helgeson of Game Informer lauded the attention to detail but felt it lacked the feeling of interactivity of Liberty City from Rockstar's Grand Theft Auto IV (2008). Petit of GameSpot said the "outstanding" art direction made the game more memorable but the believability of the open world was marred by the awkward dialogue of the non-playable pedestrians.
Reviewers lauded the game's original score. Welsh of Eurogamer opined it contributed to the overall atmosphere, comparing it favourably to the "ominous swells" of Taxi Driver (1976) and the "signature muted brass" of L.A. Confidential (1997). GameSpots Petit concurred it successfully evoked some of the best music of film noir, and Joystiqs McElroy praised its authenticity to the time period. Helgeson of Game Informer felt the game effectively balances jazz tracks from the 1940s with a "mournful score". Giant Bombs Shoemaker wrote the "big-orchestra score feels completely appropriate for the setting and subject matter", and appreciated the music notes used during investigations.
Game Informers Helgeson considered the interrogations "the most compelling aspect of L.A. Noire"; IGNs Goldstein concurred, comparing them to dialogue-heavy scenes from role-playing games. Shoemaker of Giant Bomb favourably compared the interrogations to the dialogue choices of Mass Effect 2, noting they provide new energy to each case. Petit of GameSpot found the interrogations became more interesting once the player received more autonomy. OXMs McCaffrey appreciated the "vigor" brought to the game by the interrogations but criticised their passive nature of simply listening and pressing a single button. Some reviewers considered the system flawed due to its vague and sometimes illogical choices. Critics were divided on the game's investigation elements: GameSpots Petit called it "compelling" and praised the rich details, while Eurogamers Welsh called it "clunky" and "laborious"; Helgeson of Game Informer felt they became repetitive over the course of the game, feeling "more like an Easter egg hunt than an actual investigation", while Liebl of GameZone criticised the lack of significant penalty.
Several critics commented on the game's action sequences and driving controls. Eurogamers Welsh found the foot-chases to be "memorable and fun", comparing them to police television shows, while Game Informers Helgeson wrote they became "predictable and repetitive". Most reviewers considered the core gameplay simple to understand, though GameZones Liebl felt this lessened the experience, and GameTrailers described the controls as "floaty" and "imprecise". Petit of GameSpot found the cars to be "responsible and swift", and Shoemaker of Giant Bomb called the car chases his favourite aspect of the action sequences; other reviewers generally concurred, though some felt the driving was less impressive outside of car chases. Critics generally agreed the game's shooting mechanics were competent but simple; some found the controls awkward or repetitive, while others considered it lacklustre compared to Rockstar's Grand Theft Auto and Red Dead Redemption. GamePros Herring, however, called it "memorable" and "rewarding".
L.A. Noires Windows release also received "generally favorable reviews", according to Metacritic. GameSpots Petit considered it the best version of the game due to the inclusion of all DLC cases. Carlos Leiva of Vandal lauded the higher resolution textures, increased draw distances, additional environmental designs, and stable performance. Nathan Grayson of GameSpy appreciated the improvements but ultimately considered it "a pretty bare-bones PC port"; Tommaso Pugliese of Multiplayer.it echoed this sentiment, feeling the changes from the console release were minimal and the controls were made worse with a keyboard and mouse. Anthony Gallegos of IGN felt the port could use additional optimisation, citing some technical problems; Matthieu Hurel of Gamekult was similarly disappointed by the lack of improvements in the Windows version. Will Garrido of FiringSquad criticised the port's performance, controls, lack of graphical improvements, and required installation of the Rockstar Games Social Club, and wrote the game crashed several times.
Re-release
L.A. Noires re-release on Nintendo Switch, PlayStation 4, and Xbox One received "generally favorable reviews", according to Metacritic. Sam Brooke of Push Square wrote the re-release was "certainly worth its asking price", and Matt Espineli of GameSpot declared "it's well worth replaying or experiencing for the first time". Gameplanets Toby Berger considered the Switch version an effective showcase for the console.
The graphical upgrades divided critics—some felt the re-release had significantly upgraded the original game, while others felt it contained few differences, especially on the Nintendo Switch version—though most concurred the Switch version suffered from some dips in frame rate or other performance issues; Berger of Gameplanet felt it "doesn't occur often enough to detract much from the overall experience". Push Squares Brooke appreciated the upgraded visuals, particularly praising the new lighting engine. Some critics noted the sharper textures and increased draw distances had emphasised the game's outdated visuals; Ben Tyrer of PlayStation Official Magazine – UK (OPM) felt the facial capture looked "low-res when compared to the rest of the world", and Dave Meikleham of OXM said the increased visuals "can't disguise" the poor character design.
The addition of Joy-Con controls and touchscreen support for the Nintendo Switch also divided critics. Cody Perez of GameRevolution considered the Joy-Con controls a "welcome addition" and felt the touchscreen support made the investigations more user friendly; Simone Pettine of Multiplayer.it corroborated the latter, stating the game's existence on the Switch proved it was possible for other games. Destructoids Chris Carter was intrigued by the touchscreen controls, while IGNs Alanah Pearce found the motion controls "precise enough" to correspond with the in-game animations. Conversely, Chris James of Pocket Gamer called the Switch controls "lazy and pointless", questioning why Rockstar highlighted them in the game's marketing. Some reviewers noted a preference for the original controller setup.
Some critics commented on the additions and changes to the re-releases. Push Squares Brooke considered the change of the interrogation responses to be "more fitting" to Phelps's dialogue. Damien McFerran of Nintendo Life and Espineli of GameSpot found the change was an improvement but they remained too vague; several other critics concurred the responses were ambiguous. OPMs Tyrer named the addition of the Photo Mode a highlight of the re-release, while Multiplayer.its Tommaso Pugliese found it misplaced.
The VR Case Files
L.A. Noire: The VR Case Files received "generally favorable reviews", according to Metacritic. Dan Stapleton of IGN concluded it felt "less like a port and more like something that was always meant to be played this way", while Jimmy Thang of GameSpot said it "raises the bar for what a good VR port should look like". The Telegraphs Tom Hoggins called it an "interesting, reactive, and largely accomplished virtual reality adaption" of the game, and Gamer.nls Wilbert Meetsma compared it to a greatest hits album.
Several critics praised the control scheme in virtual reality. GameSpots Thang found it made the player reconsider the evidence they discover, and The Telegraphs Hoggins felt the exploration "makes a great deal more sense". Meetsma of Gamer.nl considered the walking mechanic an effective illusion; Alfonso Arribas of Vandal appreciated the control scheme's realism. Conversely, some critics found the movement controls were unreliable or imprecise; Lukas Schmid and Rebecca Döllner of PC Games criticised the HTC Vive controllers and the game's unpredictable object physics.
GameSpots Thang found the driving controls "works as well as you'd hope", particularly applauding the chase sequences. Meetsma of Gamer.nl similarly felt the driving controls were well-designed, and Alfonso Arribas of Vandal wrote they were precise and the sensitivity appropriate. In contrast, IGNs Stapleton found them to be "imprecise but goofy fun to pantomime"; Daniel Feith of GameStar said it was realistic but ultimately felt like a gimmick he eventually skipped. The Telegraphs Hoggins considered the driving to be the least successful feature of The VR Case Files, though praised its detail, and PC Gamess Schmid and Döllner criticised it as uncomfortable.
Meetsma of Gamer.nl described the fistfights as one of the better elements of the game, despite taking up a small portion. GameStars Feith similarly found them enjoyable due to the simulated areas. GameSpots Thang favourably compared the fistfights to a boxing minigame, deeming it appropriate and satisfying. Hoggins of The Telegraph found them "pleasingly physical" but "a little clumsy", noting a preference for the gunfights. Vandals Arribas considered the shooting mechanics to be credible and precise, while IGNs Stapleton called it "pretty simple shooting gallery stuff" but respected the smaller details and gameplay features; GameSpots Feith felt that the aiming was "imprecise".
IGNs Stapleton praised the visuals of The VR Case Files, noting the new perspective grants more appreciation of the development and design and the facial animations are enhanced by the closer angle. GameSpots Thang wrote "the graphics and artstyle work wonderfully in VR". Meetsma of Gamer.nl felt the facial animations remained effective but the overall design was less impressive, especially with the game's demanding system requirements; Feith of GameStar found the faces had weakened in virtual reality. Vandals Arribas opined the graphics had worsened with age, emphasised by the perspective of virtual reality; PC Gamess Schmid and Döllner similarly felt the game looked worse than the recent re-release, citing poor textures and performance issues.
Accolades
L.A. Noire received nominations and awards from gaming publications. It was nominated for Ultimate Game of the Year and Best Action/Adventure at the Golden Joystick Awards, and for Best Graphics at the Spike Video Game Awards. The game received nine nominations at the 15th Annual Interactive Achievement Awards, and three at the 12th Game Developers Choice Awards. It was nominated for four awards at the 10th Annual Game Audio Network Guild Awards, of which it won Music of the Year. Along with Batman: Arkham City, it received the most nominations at the 8th British Academy Games Awards with eight, including Best Game and Performer for Staton; it ultimately won for Original Music. Andrew and Simon Hale were nominated for Best Original Score for a Video Game or Interactive Media at the International Film Music Critics Association Awards. The game was nominated for four awards by GameSpot, and won Best Atmosphere. L.A. Noire appeared on some lists of the best games of 2011, including Ars Technica, CNET, CNN, GameSpot, The Guardian, Kotaku Australia, and NPR. The game's 2017 re-release was nominated for Best Remake/Remaster from IGN, and for the Freedom Tower Award for Best Remake at the 7th Annual New York Game Awards. The VR Case Files was nominated for Best VR Audio at the 16th Annual Game Audio Network Guild Awards.
Sales
On the day of the North American release, Take-Two Interactive's shares closed up 7.75%—a three-year high for the company—which was attributed to the game's positive reception. The game shipped four million units across both platforms in its first month. In the United States, L.A. Noire was the best-selling game in May 2011, selling 899,000 copies across both platforms, which Wedbush Securities considered lower than its estimate of one million units. It was the best-selling game in June 2011, but had dropped out of the top ten by July. McNamara felt pressure for the game to sell well—The Getaway sold four million units—and he was ultimately satisfied with its commercial performance. The game had shipped almost five million copies by December 2011, and approximately 7.5 million copies by September 2017.
The game topped the charts in the United Kingdom following its release, becoming the fastest-selling new intellectual property; 58% of copies sold on Xbox 360, and 42% on PlayStation 3. It remained atop the chart for three weeks, pushed to second place upon the release of Duke Nukem Forever in June 2011; it remained within the top ten of the weekly charts until mid-July. It was the eighth-best-selling game of 2011 in the United Kingdom. In Australia, video game retailers in major cities reported the game was out of stock within a week. Within its first week on sale in Japan, L.A. Noire sold over 71,000 copies; the PlayStation 3 topped the charts with 58,436 copies, while the Xbox 360 version placed 11th with 12,621 copies.
Future
Following L.A. Noires release in May 2011, McNamara claimed future games from Team Bondi would take less than five years to develop due to the existing technology and the team had started expanding MotionScan for full body performance. In August 2011, Team Bondi's assets were acquired by film production company Kennedy Miller Mitchell. Team Bondi was placed into administration on 30 August, and entered liquidation on 5 October. McNamara's next game, Whore of the Orient, was announced in November 2011; it was in development by KMM Interactive Entertainment, a studio set up by Kennedy Miller Mitchell, and described as a "spiritual successor" to L.A. Noire. By June 2016, the game had been cancelled. McNamara and some Team Bondi alumni worked on The VR Case Files at Videogames Deluxe; in July 2020, the studio claimed to be developing a "AAA open-world title in VR for Rockstar", revealed in 2021 to be a virtual reality version of Grand Theft Auto: San Andreas.
In May 2011, Take-Two CEO Strauss Zelnick called L.A. Noire "another strong franchise for this company"; in November, he said the game was Take-Two's "most successful new release" in the past fiscal year and reiterated its importance to the company. Rockstar said in February 2012 it was "considering what the future may hold for L.A. Noire as a series" but said not to "count out" a possible sequel. The following year, in March 2013, Take-Two COO Karl Slatoff reiterated L.A. Noire was an important franchise to the company. In May 2021, Aaron Staton said he "never heard word about a sequel" but "would be curious what they would tell" due to Phelps's death.
Notes
References
Bibliography
External links
2011 video games
Action-adventure games
BAFTA winners (video games)
Detective video games
Fiction about adultery
Fiction about child sexual abuse
Fiction about police misconduct
Fictional portrayals of the Los Angeles Police Department
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Video games produced by Dan Houser
Video games set in 1947
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Virtuos games
Windows games
Works about atonement
Works about prostitution in the United States
Works about the Black Dahlia case
Xbox 360 games
Xbox One games
Xbox One X enhanced games | L.A. Noire | [
"Biology"
] | 9,837 | [
"Behavior",
"Works about atonement",
"Works about behavior"
] |
7,156,954 | https://en.wikipedia.org/wiki/Algebraically%20closed%20group | In group theory, a group is algebraically closed if any finite set of equations and inequations that are applicable to have a solution in without needing a group extension. This notion will be made precise later in the article in .
Informal discussion
Suppose we wished to find an element of a group satisfying the conditions (equations and inequations):
Then it is easy to see that this is impossible because the first two equations imply . In this case we say the set of conditions are inconsistent with . (In fact this set of conditions are inconsistent with any group whatsoever.)
Now suppose is the group with the multiplication table to the right.
Then the conditions:
have a solution in , namely .
However the conditions:
Do not have a solution in , as can easily be checked.
However, if we extend the group to the group with the adjacent multiplication table:
Then the conditions have two solutions, namely and .
Thus there are three possibilities regarding such conditions:
They may be inconsistent with and have no solution in any extension of .
They may have a solution in .
They may have no solution in but nevertheless have a solution in some extension of .
It is reasonable to ask whether there are any groups such that whenever a set of conditions like these have a solution at all, they have a solution in itself? The answer turns out to be "yes", and we call such groups algebraically closed groups.
Formal definition
We first need some preliminary ideas.
If is a group and is the free group on countably many generators, then by a finite set of equations and inequations with coefficients in we mean a pair of subsets and of the free product of and .
This formalizes the notion of a set of equations and inequations consisting of variables and elements of . The set represents equations like:
The set represents inequations like
By a solution in to this finite set of equations and inequations, we mean a homomorphism , such that for all and for all , where is the unique homomorphism that equals on and is the identity on .
This formalizes the idea of substituting elements of for the variables to get true identities and inidentities. In the example the substitutions and yield:
We say the finite set of equations and inequations is consistent with if we can solve them in a "bigger" group . More formally:
The equations and inequations are consistent with if there is a group and an embedding such that the finite set of equations and inequations and has a solution in , where is the unique homomorphism that equals on and is the identity on .
Now we formally define the group to be algebraically closed if every finite set of equations and inequations that has coefficients in and is consistent with has a solution in .
Known results
It is difficult to give concrete examples of algebraically closed groups as the following results indicate:
Every countable group can be embedded in a countable algebraically closed group.
Every algebraically closed group is simple.
No algebraically closed group is finitely generated.
An algebraically closed group cannot be recursively presented.
A finitely generated group has a solvable word problem if and only if it can be embedded in every algebraically closed group.
The proofs of these results are in general very complex. However, a sketch of the proof that a countable group can be embedded in an algebraically closed group follows.
First we embed in a countable group with the property that every finite set of equations with coefficients in that is consistent in has a solution in as follows:
There are only countably many finite sets of equations and inequations with coefficients in . Fix an enumeration of them. Define groups inductively by:
Now let:
Now iterate this construction to get a sequence of groups and let:
Then is a countable group containing . It is algebraically closed because any finite set of equations and inequations that is consistent with must have coefficients in some and so must have a solution in .
See also
Algebraic closure
Algebraically closed field
References
A. Macintyre: On algebraically closed groups, ann. of Math, 96, 53-97 (1972)
B.H. Neumann: A note on algebraically closed groups. J. London Math. Soc. 27, 227-242 (1952)
B.H. Neumann: The isomorphism problem for algebraically closed groups. In: Word Problems, pp 553–562. Amsterdam: North-Holland 1973
W.R. Scott: Algebraically closed groups. Proc. Amer. Math. Soc. 2, 118-121 (1951)
Properties of groups | Algebraically closed group | [
"Mathematics"
] | 948 | [
"Mathematical structures",
"Algebraic structures",
"Properties of groups"
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7,156,988 | https://en.wikipedia.org/wiki/Electric%20water%20boiler | An electric water boiler, also called a thermo pot or tea urn in British English, is a consumer electronics small appliance used for boiling water and maintaining it at a constant temperature in an enclosed reservoir. It is typically used to provide an immediate source of hot water for making tea, hot chocolate, coffee, instant noodles, or baby formula, or for any other household use where clean hot water is required. They are a common component of Japanese kitchens and the kitchens of many East Asian countries but are found in varying use globally. Smaller units are portable. Some thermo pots are designed with a feature that can purify water.
Components
An electric water boiler is a device comprising a water reservoir equipped with a heating element positioned at the bottom. While some models offer the convenience of multiple temperature settings, others are integrated into larger water systems capable of boiling water and dispensing it in various forms: hot, cold, or lukewarm. Dispensing methods vary and can include pouring, utilizing an electric pump, or pressing a large button that acts as a diaphragm pump. Additionally, electric water boilers are typically equipped with a built-in thermostat that senses when the water has reached its boiling point of 100°C (212°F), automatically shutting off to prevent overheating.
Sedimentation
Sedimentation refers to the gradual accumulation of natural minerals within the water reservoir, typically found in trace amounts in municipal water mains. These minerals, predominantly calcium carbonate, tend to settle at the bottom of the reservoir as the water is heated. Over time, this sediment buildup can lead to several issues. Firstly, it can generate various noises within gas boilers due to the disturbance caused by the sediment. Additionally, the accumulation can impair the efficiency of the unit, as the sediment acts as an insulating layer, hindering the transfer of heat. Moreover, the presence of sediment can result in the development of an unpleasant sulfur or rotten-egg smell in the water.
To address sediment buildup in electric kettles, descaling agents such as vinegar or citric acid are commonly used. These substances effectively dissolve and remove the accumulated minerals, restoring the kettle's performance and eliminating any associated odors.
Uses
Some electric water boiler models enable tea to be steeped at a desired, adjustable temperature.
See also
Samovar
Electric kettle
Electric steam boiler
Immersion heater
Instant hot water dispenser
Thermoelectricity
Joule heating
References
Further reading
Retrieved on 2014-03-25.Ashby, M. F. (2012-03-28). Materials and the Environment: Eco-informed Material Choice. Butterworth-Heinemann. pp. 198–199. ISBN 978-0-12-385971-6.
External links
Home appliances
Boilers (cookware) | Electric water boiler | [
"Physics",
"Technology"
] | 577 | [
"Physical systems",
"Machines",
"Home appliances"
] |
7,156,992 | https://en.wikipedia.org/wiki/Zojirushi | The is a Japanese multinational manufacturer and marketer of vacuum flasks, beverage dispensers, and consumer electronics including bread machines, electric kettles, hot water dispensers, electric water boilers and rice cookers. It has a branch in South Korea and subsidiary companies in Taiwan, China, Hong Kong, and the United States. Zojirushi is listed on the Tokyo Stock Exchange.
The company was founded in 1918 as the Ichikawa Brothers Trading Company in Osaka and in 1948 was changed to Kyowa Manufacturing Co., Ltd. In 1961, its name was changed again from Kyowa Manufacturing Co., Ltd to the Zojirushi Corporation and its corporate logo, including an elephant (Zōjirushi means "elephant mark"), was adopted.
Some Zojirushi rice cooker models include a coating of , a self-cleaning fluoropolymer-aluminium composite developed by Sumitomo Electric.
References
External links
Zojirushi Worldwide corporate website
Zojirushi America Corporation website
Zojirushi South East Asia website
Companies listed on the Tokyo Stock Exchange
Home appliance brands
Home appliance manufacturers of Japan
Companies based in Osaka Prefecture
Japanese companies established in 1918
Electronics companies established in 1918
Manufacturing companies established in 1918
Japanese brands
Multinational companies headquartered in Japan
Midori-kai
Vacuum flasks | Zojirushi | [
"Physics"
] | 272 | [
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"Matter",
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7,156,993 | https://en.wikipedia.org/wiki/Tiger%20Corporation | Tiger Corporation () is a Japanese manufacturer that applies vacuum insulation and heat control technology to consumer electronic appliances. Their headquarters are located in Kadoma City in Osaka, Japan. The company manufactures and sells appliances such as household and commercial vacuum insulated containers and stainless-steel bottles, along with cooking appliances such as rice cookers. The company also manufactures industrial parts and products used in automobiles, homes, air conditioners, space, and medical care in 60 countries around the world.
In 2018, Tiger Corporation collaborated with Japan Aerospace Exploration Agency (JAXA) on jointly developing a “Double-Layered Vacuum Insulation Container,” a small collection capsule. It has successfully re-entered Earth’s atmosphere without harming the experimental samples from the International Space Station (ISS), opening a new plan for taking samples from space.
History
The company was founded in February 1923 as Kikuchi Manufacturing Company in Nishi-ku, Osaka and manufactured Tiger brand vacuum flasks. In 1953, the company's name was changed to Tiger Vacuum Bottle Ind, Co., Ltd., and in 1983 to Tiger Vacuum Bottle Co., Ltd., and from 1999 to its present name, Tiger Magic-jar Corporation.
In 1923, Tiger Corporation was established in Osaka by Takenori Kikuchi.
At the time, most vacuum bottles were made of glass and very fragile. With much trial and error, Takenori thought of placing a layer of cardboard between the inner and outer containers to protect the glass.
When Japan suffered the Great Kanto Earthquake also in 1923, only Tiger vacuum bottles remained intact among the different products on shop shelves.
Tiger’s thermos bottle technology was also used in space experiments. Tiger was in charge of the development of vacuum double insulated containers storing precious space experiment samples in a HTV Small Re-entry Capsule (developed for installation in the space station refueling machine Kounotori 7) bringing supplies from the International Space Station (ISS) to the Earth.
On November 11, 2018, the HTV Small Re-entry Capsule returned to the Earth withstanding the strong impact during landing while keeping the experimental samples from the International Space Station at about 4°C.
Products
, Tiger produces and markets rice cookers, vacuum flasks (thermoses), electric barbecue grills, insulated jugs, insulated lunch boxes, ice buckets (pails), electric mochi makers, mochi cutters, and air purifiers with ionizers.
References
External links
Tiger Worldwide corporate website
Home appliance brands
Home appliance manufacturers of Japan
Manufacturing companies established in 1923
Companies based in Osaka Prefecture
Multinational companies headquartered in Japan
Japanese companies established in 1923
Japanese brands
Vacuum flasks
Kadoma, Osaka | Tiger Corporation | [
"Physics"
] | 554 | [
"Vacuum",
"Matter",
"Vacuum flasks"
] |
7,157,316 | https://en.wikipedia.org/wiki/Attack%20rate | In epidemiology, the attack rate is the proportion of an at-risk population that contracts the disease during a specified time interval. It is used in hypothetical predictions and during actual outbreaks of disease. An at-risk population is defined as one that has no immunity to the attacking pathogen, which can be either a novel pathogen or an established pathogen. It is used to project the number of infections to expect during an epidemic. This aids in marshalling resources for delivery of medical care as well as production of vaccines and/or anti-viral and anti-bacterial medicines.
The rate is arrived at by taking the number of new cases in the population at risk and dividing by the number of persons at risk in the population.
See also
Incidence (epidemiology)
Compartmental models in epidemiology
Herd immunity
Risk assessment in public health
Vaccine-naive
References
External links
The International Biometric Society
The Collection of Biostatistics Research Archive
Guide to Biostatistics (MedPageToday.com)
Epidemiology
Medical statistics
Statistical ratios
Bioinformatics | Attack rate | [
"Engineering",
"Biology",
"Environmental_science"
] | 218 | [
"Bioinformatics",
"Biological engineering",
"Epidemiology",
"Environmental social science"
] |
7,157,635 | https://en.wikipedia.org/wiki/Geminin | Geminin, DNA replication inhibitor, also known as GMNN, is a protein in humans encoded by the GMNN gene. A nuclear protein present in most eukaryotes and highly conserved across species, numerous functions have been elucidated for geminin including roles in metazoan cell cycle, cellular proliferation, cell lineage commitment, and neural differentiation. One example of its function is the inhibition of Cdt1.
History
Geminin was originally identified as an inhibitor of DNA replication and substrate of the anaphase-promoting complex. Coincidentally, geminin was also shown to expand the neural plate in the developing Xenopus embryo.
Structure
Geminin is a nuclear protein made up of about 200 amino acids, with a molecular weight of approximately 25 kDa. It contains an atypical leucine zipper coiled-coil domain. It has no known enzymatic activity nor DNA binding motifs.
Function
Cell cycle control
Geminin is absent during G1 phase and accumulates through S, G2 phase and M phases of the cell cycle. Geminin levels drop at the metaphase-anaphase transition of mitosis when it is degraded by the anaphase-promoting complex.
S phase
During S phase, geminin is a negative regulator of DNA replication. In many cancer cell lines, inhibition of geminin by RNA interference results in re-replication of portions of the genome, which leads to aneuploidy. In these cell lines, geminin knockdown leads to markedly slowed growth and apoptosis within several days. However, the same is not true for primary and immortalized human cell lines, where other mechanisms exists to prevent DNA re-replication. Since geminin knockdown leads to cell death in many cancer cell lines but not primary cell lines, it has been proposed as a potential therapeutic target for cancer treatment.
Mitosis
At the start of the S-phase until late mitosis, geminin inhibits the replication factor Cdt1, preventing the assembly of the pre-replication complex. In early G1, the anaphase promoting complex triggers its destruction through ubiquitination.
Geminin, therefore, is an important player in ensuring that exactly one round of replication occurs during each cell cycle.
Developmental control
Geminin promotes early neural fate commitment by hyperacetylating chromatin. This effect allows neural genes to be accessible for transcription, promoting the expression of these genes. Ultimately, geminin allows cells uncommitted to any particular lineage to acquire neural characteristics.
Geminin has also been shown to interact with the SWI/SNF chromatin remodeling complex. In neural precursor cells, high levels of geminin prevent terminal differentiation. When the interaction between geminin and SWI/SNF is eliminated, geminin's inhibition to this process is eliminated and neural precursors are allowed to differentiate.
Clinical significance
Geminin has been found to be overexpressed in several malignancies and cancer cell lines, while there is data demonstrating that geminin acts as a tumor suppressor by safeguarding genome stability.
References
Further reading
External links
Proteins
Genes mutated in mice | Geminin | [
"Chemistry"
] | 635 | [
"Proteins",
"Biomolecules by chemical classification",
"Molecular biology"
] |
7,158,257 | https://en.wikipedia.org/wiki/Streaking%20%28microbiology%29 | In microbiology, streaking is a technique used to isolate a pure strain from a single species of microorganism, often bacteria. Samples can then be taken from the resulting colonies and a microbiological culture can be grown on a new plate so that the organism can be identified, studied, or tested.
The modern streak plate method has progressed from the efforts of Robert Koch and other microbiologists to obtain microbiological cultures of bacteria in order to study them. The dilution or isolation by streaking method was first developed in Koch's laboratory by his two assistants Friedrick Loeffler and Georg Theodor August Gaffky. This method involves the dilution of bacteria by systematically streaking them over the exterior of the agar in a Petri dish to obtain isolated colonies which will then grow into quantity of cells, or isolated colonies. If the agar surface grows microorganisms which are all genetically same, the culture is then considered as a microbiological culture.
Technique
Streaking is rapid and ideally a simple process of isolation dilution. The technique is done by diluting a comparatively large concentration of bacteria to a smaller concentration. The decrease of bacteria should show that colonies are sufficiently spread apart to affect the separation of the different types of microbes. Streaking is done using a sterile tool, such as a cotton swab or commonly an inoculation loop. Aseptic techniques are used to maintain microbiological cultures and to prevent contamination of the growth medium. There are many different types of methods used to streak a plate. Picking a technique is a matter of individual preference and can also depend on how large the number of microbes the sample contains.
The three-phase streaking pattern, known as the T-Streak, is recommended for beginners. The streaking is done using a sterile tool, such as a cotton swab or commonly an inoculation loop. The inoculation loop is first sterilized by passing it through a flame. When the loop is cool, it is dipped into an inoculum such as a broth or patient specimen containing many species of bacteria. The inoculation loop is then dragged across the surface of the agar back and forth in a zigzag motion until approximately 30% of the plate has been covered. The loop then is re-sterilized and the plate is turned 90 degrees. Starting in the previously streaked section, the loop is dragged through it two to three times continuing the zigzag pattern. The procedure is then repeated once more being cautious to not touch the previously streaked sectors. Each time the loop gathers fewer and fewer bacteria until it gathers just single bacterial cells that can grow into a colony. The plate should show the heaviest growth in the first section. The second section will have less growth and a few isolated colonies, while the final section will have the least amount of growth and many isolated colonies.
Growth medium
The sample is spread across one quadrant of a Petri dish containing a growth medium. Bacteria need different nutrients to grow. This includes water, a source of energy, sources of carbon, sulfur, nitrogen, phosphorus, certain minerals, and other vitamins and growth factors. A very common type of media used in microbiology labs is known as agar, a gelatinous substance derived from seaweed. The nutrient agar has a lot of ingredients with unknown amounts of nutrients in them. On one hand, this can be a very selective media to use because as mentioned bacteria are particular. If there is a certain nutrient in the media the bacteria could most certainly not grow and could die. On the other hand, this media is very complex. Complex media is important because it allows for a wide range of microbial growth. The bacteria growth can be supported by this media greatly due in part to the high amounts of nutrients. Choice of which growth medium is used depends on which microorganism is being cultured, or selected for.
Incubation
Dependent on the strain, the plate may then be incubated, usually for 24 to 36 hours, to allow the bacteria to reproduce. At the end of incubation there should be enough bacteria to form visible colonies in the areas touched by the inoculation loop. From these mixed colonies, single bacterial or fungal species can be identified based on their morphological (size/shape/colour) differences, and then sub-cultured to a new media plate to yield a pure culture for further analysis.
Automated equipment is used at industrial level for streak plating the solid media in order to achieve better sterilization and consistency of streaking and for reliably faster work. While streaking manually it is important to avoid scratching the solid medium as subsequent streak lines will be damaged and non-uniform deposition of inoculum at damaged sites on the medium yield clustered growth of microbes which may extend into nearby streak lines.
Importance
Bacteria exist in water, soil and food, on skin, and intestinal tract normal flora. The assortment of microbes that exist in the environment and on human bodies is enormous. The human body has billions of bacteria which creates the normal flora fighting against the invading pathogens. Bacteria frequently occur in mixed populations. It is very rare to find a single occurring species of bacteria. To be able to study the cultural, morphological, and physiological characteristics of an individual species, it is vital that the bacteria be divided from the other species that generally originate in the environment. This is important in determining a bacterium in a clinical sample. When the bacteria is streaked and isolated, the causative agent of a bacterial disease can be identified.
See also
Bacterial lawn
References
External links
Streaking agar plate method for getting isolated colonies (video).
Microbiology techniques
Bacteriology | Streaking (microbiology) | [
"Chemistry",
"Biology"
] | 1,161 | [
"Microbiology techniques"
] |
7,159,060 | https://en.wikipedia.org/wiki/Tetrasaccharide | A tetrasaccharide is a carbohydrate which gives upon hydrolysis four molecules of the same or different monosaccharides. For example, stachyose upon hydrolysis gives one molecule each of glucose and fructose and two molecules of galactose. The general formula of a tetrasaccharide is typically C24H42O21.
References | Tetrasaccharide | [
"Chemistry"
] | 83 | [
"Organic chemistry stubs"
] |
7,159,553 | https://en.wikipedia.org/wiki/Teleavia | Teleavia was a French manufacturer of televisions in the mid-20th century, it was created by aviation company "Sud Aviation" as a diversification operation to employ redundant workforce. It was later absorbed by Thomson SA.
The brand was best known for the innovative television set designs created by the French designer Roger Tallon in the 1950s and 1960s. The 1968 edition, known as the Portavia 111, was the year's most photographed appliance.
Tallon later said, in explanation of the trademark's success and longevity: "It was the first time the shape, the function and the material absolutely intertwined".
The brand's motto, from 1963, was "TELEAVIA, design also matters".
References
Television technology | Teleavia | [
"Technology"
] | 152 | [
"Information and communications technology",
"Television technology"
] |
7,159,903 | https://en.wikipedia.org/wiki/Automated%20vacuum%20collection | An automated vacuum waste collection system, also known as pneumatic refuse collection, or automated vacuum collection (AVAC), transports waste at high speeds through underground pneumatic tubes to a collection station where the waste is compacted and sealed in containers. Full containers are transported away to be emptied. The AVAC system helps facilitate the separation and recycling of waste material.
The process begins by disposing of trash into intake hatches, also known as portholes, which are usually specialized for waste, recycling, or compost. Portholes are often located in public areas, and on private property where the owner has opted in. Through the use of air pressure differentials created by large industrial fans, waste is pulled into an underground pipeline system; this process is facilitated by the use of porthole sensors that indicate when the trash needs to be emptied and help ensure that only one type of waste material travels through the pipe at a time. The pipelines converge in a central processing facility which directs the waste to the appropriate containers so it could be transported to its final location, such as a landfill or composting plant.
History
The first system was created in Sweden in the 1960s, designed by the Swedish corporation Envac AB (formerly known as Centralsug AB). The first installation was in 1961 at Sollefteå Hospital. The first vacuum system for household waste, was installed in the new residential district of Ör-Hallonbergen, Sweden in 1965.
Overview
Pneumatic waste collection systems provide a number of environmental benefits. These systems can decrease emissions from transit of waste by up to 90%. Systems in Europe provide separate outlets for food, recycling, and non-recycling, making waste separation and recycling more efficient. Some systems require household ID cards to use, and limit the amount of non-recyclable waste allowed per month, issuing a tax if the threshold is crossed. In Bergen, Norway, this system resulted in a 29% increase in plastic recycling, and an 85% decrease in non-recyclable waste, plus a $2 million saving in waste collection costs.
These systems also decrease the risk of fire and prevent animals from accessing waste.
Issues with budgeting and logistics have prevented a more widespread adoption of these systems. Upfront costs can reach into the hundreds of millions, and it is difficult to build the system into existing infrastructure. Pneumatic waste collection is optimal for high density development areas rather than existing urban areas. Maintenance may be difficult, and damage or blockages from inappropriate use requires engineers to enter the pipes to fix them.
Current systems
, there are close to a thousand systems in operation all over the world - in China, South East Asia, South Korea, the Middle East, the United States, Australia, and Europe.
Notable manufacturers include:
Envac Pneumatic Waste Collection System, used in more than 30 countries.
Stream Automated Waste Collection System from Malaysia, with many installations in Asia.
MetroTaifun, with over a thousand system in over 40 countries.
United States
In the U.S., this type of system is installed in several places, but the most well known are built by AVAC and located in the Magic Kingdom in Disney World, Orlando, Florida; and Roosevelt Island in New York City. The Magic Kingdom uses special Disney utility corridors.
The Roosevelt Island system, serving nearly 10,000 people, is said to be the largest in the United States and the only system in the U.S. in a residential complex.
Europe
Notable examples in Europe include Copenhagen, Barcelona, London, and Stockholm, and Leganés and Barakaldo in Spain.
An automated vacuum collection system called Rööri started operation in early 2014 in the new Jätkäsaari residential neighbourhood of Helsinki, Finland. All housing cooperatives and other apartment buildings were obliged to join the network. Each building has a collection point with up to five wastebins or tubes, each for different types of waste and with the capacity to store several parcels of waste. The underground tube network acts like a packet switched telecommunication network, transporting one kind of waste at a time. Once an input bin is filled, or capacity is available, it is transferred to the central collection site and combined with the same class of waste.
Also in Finland, in the suburb of Vuores in the city of Tampere, a vacuum collection system was included in a new suburban development planned for 13,000 inhabitants. It has a total of 124 collection points, 368 waste inlets, and 13 km of pipe. The system's daily collection capacity for dry waste, biowaste, paper, and recyclable cardboard comes to a combined total of 13 tonnes, and it became operational in 2012.
In Bergen, Norway, a system covers most of the city center.
Israel
, in Israel there are 5 systems - 2 operational in Yavne and Ra'anana, and 3 planned in Bat Yam, Tel Aviv and Rishon LeZion. In a techno-economic analysis conducted by the Ministry of Environmental Protection, it was found that the cost of intra-urban treating in pneumatic collection in neighborhoods with multiple units and under funding contractors is 25% lower in comparison to conventional methods, and this is without internalizing the external benefits arising from it (value of time and pollution). It was also found that for neighborhoods with higher buildings (with the same number of housing units), the cost of a pneumatic system was even cheaper (at least approximately 20%)
In 2006, Yavne municipality issued a tender for the establishment of a pneumatic evacuation of household waste for the residential project "Green Neighborhood" which comprises 4,700 household units in around 200 buildings. In September 2012, the system began operating in residential use. In February 2014, the municipality began replacing the neighborhood's street trash cans with pneumatic cans. Now there are also around 30 waste collection points in public areas - parks, schools and the streets. The system is also planned to be connected to all future neighborhoods and serve 10,660 house units.
In May 2012, Ra'anana municipality approved the residential project "Neve Zemer" which is planned to include around 3,550 housing units in around 235 buildings with a pneumatic evacuation system of household waste. The pneumatic evacuation system became operational in 22018.
Bat Yam municipality published in 2017 a tender for planning, construction, and operation of pneumatic evacuation system for 5,000 residential neighborhood units (approximately 60 high-rise buildings) and 2,000 hotel rooms.
In 2009, Tel Aviv municipality's head of the city's construction and infrastructure manager, Dr. Benny Maor, said the city planned to install a pneumatic evacuation system in planned northwestern neighborhoods. In 2013, the municipality requested the preparation of a plan for a pneumatic evacuation system as a condition for a building permit in part of a development plan of 11,446 square meters land plots located in Rothschild Boulevard and Ahad Ha'am streets.
Australia
In 2020, the first system in Australia became operational in Maroochydore, Queensland. The system was installed as part of the city center development project - the largest greenfield central business district development in the country.
Planned systems
North America
A system is planned for a new City Center development in Carmel, Indiana. It would service condominiums, businesses, and a hotel.
In March 2015, the city of Montreal abandoned its $3 million investment in a plan to install an automated vacuum collection system in the Quartier des Spectacles entertainment district.
Another installation is planned for Hudson Yards, Manhattan.
Middle East
The world's largest AWCS is being built by MetroTaifun in the vicinity of Islam's holiest mosque in Mecca, Saudi Arabia, to keep trash collection out of sight. During the Ramadan and Hajj, 600 tonnes (or 4,500 cubic meters) of waste is generated each day; it will be collected at 74 waste feeding points spread out across the area and then transferred via a 20-kilometre pipe network to a central collection point.
See also
Pneumatic tube
Dustpan
Central vacuum cleaner
Transfer station
Waste collection vehicle
Waste collection
Waste collector
References
External links
Article about the first automated vacuum collection system ever.
History about the invention of automated vacuum collection system.
Waste collection
Networks
Transport systems
Pneumatics | Automated vacuum collection | [
"Physics",
"Technology"
] | 1,695 | [
"Physical systems",
"Transport",
"Transport systems"
] |
7,159,994 | https://en.wikipedia.org/wiki/TosMIC | TosMIC (toluenesulfonylmethyl isocyanide) is an organic compound with the formula CH3C6H4SO2CH2NC. The molecule contains both sulfonyl and isocyanide groups. It is a colourless solid that, unlike many isocyanides, is odorless. It is prepared by dehydration of the related formamide derivative. It is used in the Van Leusen reaction which is used to convert ketones to nitriles or in the preparation of oxazoles and imidazoles. The versatility of TosMIC in organic synthesis has been documented. It is a fairly strong carbon acid, with an estimated pKa of 14 (compared to 29 for methyl tolyl sulfone), the isocyano group acting as an electron acceptor of strength comparable to an ester group.
References
Further reading
Isocyanides
Reagents for organic chemistry
p-Tosyl compounds | TosMIC | [
"Chemistry"
] | 205 | [
"Isocyanides",
"Functional groups",
"Reagents for organic chemistry"
] |
7,160,204 | https://en.wikipedia.org/wiki/List%20of%20eukaryotic%20picoplankton%20species | List of eukaryotic species that belong to picoplankton, meaning one of their cell dimensions is smaller than 3 μm.
Autotrophic species
Chlorophyta
Chlorophyceae
Stichococcus cylindricus Butcher, 3 – 4.5 μm, brackish
Pedinophyceae
Marsupiomonas pelliculata Jones et al., 3 – 3 μm, brackish-marine
Resultor micron Moestrup, 1.5 – 2.5 μm, marine
Prasinophyceae
Bathycoccus prasinos Eikrem et Throndsen, 1.5 – 2.5 μm, marine
Crustomastix stigmatica Zingone, 3 – 5 μm, marine
Dolichomastix lepidota Manton, 2.5 – 2.5 μm, marine
Dolichomastix eurylepidea Manton, 3 μm, marine
Dolichomastix tenuilepis Throndsen et Zingone, 3 – 4.5 μm, marine
Mantoniella squamata Desikachary, 3 – 5 μm, marine
Micromonas pusilla Manton et Parke, 1 – 3 μm, marine
Ostreococcus tauri Courties et Chrétiennot-Dinet, 0.8 – 1.1 μm, marine
Picocystis salinarum Lewin, 2 – 3 μm, hypersaline
Prasinococcus capsulatus Miyashita et Chihara, 3 – 5.5 μm, marine
Prasinoderma coloniale Hasegawa et Chihara, 2.5 – 5.5 μm, marine
Pseudoscourfieldia marina Manton, 3 – 3.5 μm, marine
Pycnococcus provasolii Guillard, 1.5 – 4 μm, marine
Pyramimonas virginica Pennick, 2.7 – 3.5 μm, marine
Trebouxiophyceae
Chlorella nana Andreoli et al., 1.5 – 3 μm, marine
Picochlorum oklahomensis Henley et al., 2 – 2 μm, hypersaline
Picochlorum atomus Henley et al., 2 – 3 μm, brackish
Picochlorum eukaryotum Henley et al., 3 – 3 μm, marine
Picochlorum maculatus Henley et al., 3 – 3 μm, brackish
Cryptophyta
Cryptophyceae
Hillea marina Butcher, 1.5 – 2.5 μm, marine
Haptophyta
Prymnesiaceae
Chrysochromulina tenuisquama Estep et al., 2 – 5 μm, marine
Chrysochromulina minor Parke et Manton, 2.5 – 7.5 μm, marine
Chrysochromulina apheles Moestrup et Thomsen, 3 – 4 μm, marine
Dicrateria inornata Parke, 3 – 5.5 μm, marine
Ericiolus spiculiger Thomsen, 3 – 3.8 μm, marine
Imantonia rotunda Reynolds, 2 – 4 μm, marine
Phaeocystis cordata Zingone, 3 – 4 μm, marine
Phaeocystis pouchetii Lagerheim, 3 – 8 μm, marine
Trigonaspis minutissima H.A.Thomsen, 2 – 3.6 μm, marine
Heterokontophyta (Stramenopiles)
Bacillariophyceae
Minidiscus comicus Takano, 2 – 7 μm, marine
Minidiscus trioculatus Hasle, 2.5 – 3.8 μm, marine
Minidiscus spinulosus Gao, Chang et Chin, 3 – 5 μm, marine
Minidiscus chilensis Rivera, 3 – 7.5 μm, marine
Minutocellus polymorphus Hasle, von Stosch et Syverstsen, 2 – 30 μm, marine
Minutocellus scriptus Hasle, von Stosch et Syverstsen, 3 – 36 μm, marine
Skeletonema menzelii Guillard, Carpenter et Reimann, 2 – 7 μm, marine
Skeletonema pseudocostatum Medlin, 2 – 9 μm, marine
Skeletonema japonicum Zingone et Sarno, 2 – 10 μm, marine
Skeletonema grethae Zingone et Sarno, 2 – 10.5 μm, marine
Skeletonema marinoi Sarno et Zingone, 2 – 12 μm, marine
Thalassiosira pseudonana Hasle et Heimdal, 2.3 – 5.5 μm, marine
Bolidophyceae
Bolidomonas pacifica Guillou et Chrétiennot-Dinet, 1 – 1.7 μm, marine
Bolidomonas mediterranea Guillou et Chrétiennot-Dinet, 1 – 1.7 μm, marine
Chrysophyceae
Ollicola vangoorii Conrad (Vors), 2.5 – 5 μm, marine
Tetraparma pelagica Booth et Marchant, 2.2 – 2.8 μm, marine
Tetraparma insecta Bravo-Sierra et Hernández-Becerril, 2.8 – 3.8 μm, marine
Triparma laevis Booth, 2.2 – 3.1 μm, marine
Triparma columacea Booth, 2.3 – 4.7 μm, marine
Triparma retinervis Booth, 2.7 – 4.5 μm, marine
Dictyochophyceae
Florenciella parvula Eikrem, 3 – 6 μm, marine
Eustigmatophyceae
Nannochloropsis granulata Karlson et Potter, 2 – 4 μm, marine
Nannochloropsis salina Hibberd, 3 – 4 μm, brackish
Nannochloropsis oceanica Suda et Miyashita, 3 – 5 μm, marine
Pelagophyceae
Aureococcus anophagefferens Hargraves et Sieburth, 1.5 – 2 μm, marine
Aureoumbra lagunensis Stockwell et al., 2.5 – 5 μm, marine
Pelagococcus subviridis Norris, 2.5 – 5.5 μm, marine
Pelagomonas calceolata Andersen et Saunders, 2 – 3 μm, marine
Pinguiophyceae
Pinguiochrysis pyriformis Kawachi, 1 – 3 μm, marine
Pinguiococcus pyrenoidosus Andersen et al., 3 – 8 μm, marin
Heterotrophic species
Cercozoa
Cercomonadida
Massisteria marina Larsen et Patterson, 2.5 – 6.5 μm, marine
Plasmodiophorida
Phagomyxa odontellae Kühn, Schnepf & Bulman, 3 – 4 μm, marine
Stramenopiles
Bicosoecida
Caecitellus parvulus Patterson et al., 3 – 10 μm, marine
Pseudobodo minima Ruinen, 2 μm, marine
Symbiomonas scintillans Guillou et Chrétiennot-Dinet, 1.2 – 1.5 μm, marine
Chrysophyceae
Paraphysomonas imperforata Lucas, 1.7 – 5.1 μm, marine
Paraphysomonas corbidifera Pennick and Clarke, 2 – 3.25 μm, marine
Paraphysomonas antarctica Takahashi, 2 – 4.3 μm, marine
Paraphysomonas caelifrica Preisig and Hibberd, 2.5 – 5 μm, marine
Paraphysomonas cribosa Lucas, 3 – 4 μm, marine
Paraphysomonas sideriophora Thomsen, 3 – 5 μm, marine
Paraphysomonas capreolata Preisig and Hibberd, 3 – 6.5 μm, marine
Paraphysomonas gladiata Preisig and Hibberd, 3 – 8 μm, marine
Picophagus flagellatus Guillou et Chrétiennot-Dinet, 1.4 – 2.5 μm, marine
Biological oceanography
Planktology
Aquatic ecology
Picoplankton | List of eukaryotic picoplankton species | [
"Biology"
] | 1,801 | [
"Aquatic ecology",
"Ecosystems"
] |
7,160,638 | https://en.wikipedia.org/wiki/Matita | Matita
is an experimental proof assistant under development at the Computer Science Department of the University of Bologna. It is a tool aiding the development of formal proofs by man–machine collaboration, providing a programming environment where formal specifications, executable algorithms and automatically verifiable correctness certificates naturally coexist.
Matita is based on a dependent type system known as the calculus of (co)inductive constructions (a derivative of the calculus of constructions), and is compatible, to some extent, with Coq.
The word "matita" means "pencil" in Italian (a simple and widespread editing tool). It is a reasonably small and simple application, whose architectural and software complexity is meant to be mastered by students, providing a tool particularly suited for testing innovative ideas and solutions. Matita adopts a tactic-based editing mode; (XML-encoded) proof objects are produced for storage and exchange.
Main features
Existential variables are native in Matita, allowing a simpler management of dependent goals.
Matita implements a bidirectional type inference algorithm exploiting both inferred and expected types.
The power of the type inference system (refiner) is further augmented by a mechanism of
hints
that helps in synthesizing unifiers in particular situations specified by the user.
Matita supports a sophisticated disambiguation strategy
based on a dialog between the parser and the typechecker.
At the interactive level, the system implements a small step execution of structured tactics
allowing a much better management of the proof development, and naturally leading
to more structured and readable scripts.
Applications
Matita has been employed in CerCo (Certified Complexity): a
FP7 European Project
focused on the development of a formally verified, complexity preserving compiler from a large subset of C to the assembly language of a MCS-51 microprocessor.
Documentation
The Matita tutorial provides a pragmatic introduction to the main functionalities of the Matita interactive theorem prover, offering a guided tour through a set of non-trivial examples in the field of software specification and verification.
See also
Curry–Howard correspondence
Interactive theorem proving
Intuitionistic type theory
List of proof assistants
References
External links
Proof assistants
Free theorem provers
Dependently typed languages
Educational math software
OCaml software
Free software programmed in OCaml
Functional languages | Matita | [
"Mathematics"
] | 471 | [
"Educational math software",
"Mathematical software"
] |
7,160,712 | https://en.wikipedia.org/wiki/Proclus%20of%20Laodicea | Proclus () or Proculeius, son of the physician Themison, was a hierophant at Laodiceia in Syria. He wrote, according to the Suda, the following works:
On the gods (θεολογία)
On the myth of Pandora in Hesiod (εἰς τὴν παρ' Ἡσιόδῳ τῆς Πανδώρας μῦθον)
On golden words (εἰς τὰ χρυσᾶ ἔπη)
On Nicomachus' introduction to number theory (εἰς τὴν Νικομάχου εἰσαγωγὴν τῆς ἀριθμητικῆς)
some geometrical treatises
He is also mentioned by Damascius in a commentary on Plato.
Although a commentary on the Pythagorean Golden Verses, known through a translation into Arabic (in the El Escorial library as manuscript 888) has sometimes been attributed to this Proclus (following a theory promoted by ), this is disputed, and a more widely accepted theory is that the commentary is instead by Proclus Diadochus.
See also
Proculeia gens
References
Year of birth missing
Year of death missing
Ancient Greek mathematicians
Ancient Greek writers
People from Latakia
Philosophers of mathematics | Proclus of Laodicea | [
"Mathematics"
] | 285 | [] |
7,160,942 | https://en.wikipedia.org/wiki/Filesystem-level%20encryption | Filesystem-level encryption, often called file-based encryption, FBE, or file/folder encryption, is a form of disk encryption where individual files or directories are encrypted by the file system itself.
This is in contrast to the full disk encryption where the entire partition or disk, in which the file system resides, is encrypted.
Types of filesystem-level encryption include:
the use of a 'stackable' cryptographic filesystem layered on top of the main file system
a single general-purpose file system with encryption
The advantages of filesystem-level encryption include:
flexible file-based key management, so that each file can be and usually is encrypted with a separate encryption key
individual management of encrypted files e.g. incremental backups of the individual changed files even in encrypted form, rather than backup of the entire encrypted volume
access control can be enforced through the use of public-key cryptography, and
the fact that cryptographic keys are only held in memory while the file that is decrypted by them is held open.
General-purpose file systems with encryption
Unlike cryptographic file systems or full disk encryption, general-purpose file systems that include filesystem-level encryption do not typically encrypt file system metadata, such as the directory structure, file names, sizes or modification timestamps. This can be problematic if the metadata itself needs to be kept confidential. In other words, if files are stored with identifying file names, anyone who has access to the physical disk can know which documents are stored on the disk, although not the contents of the documents.
One exception to this is the encryption support being added to the ZFS filesystem. Filesystem metadata such as filenames, ownership, ACLs, extended attributes are all stored encrypted on disk. The ZFS metadata relating to the storage pool is stored in plaintext, so it is possible to determine how many filesystems (datasets) are available in the pool, including which ones are encrypted. The content of the stored files and directories remain encrypted.
Another exception is CryFS replacement for EncFS.
Cryptographic file systems
Cryptographic file systems are specialized (not general-purpose) file systems that are specifically designed with encryption and security in mind. They usually encrypt all the data they contain – including metadata. Instead of implementing an on-disk format and their own block allocation, these file systems are often layered on top of existing file systems e.g. residing in a directory on a host file system. Many such file systems also offer advanced features, such as deniable encryption, cryptographically secure read-only file system permissions and different views of the directory structure depending on the key or user ...
One use for a cryptographic file system is when part of an existing file system is synchronized with 'cloud storage'. In such cases the cryptographic file system could be 'stacked' on top, to help protect data confidentiality.
See also
Steganographic file system
List of cryptographic file systems
Disk encryption
Full disk encryption
References
Disk encryption
Special-purpose file systems
Cryptographic software
Utility software types | Filesystem-level encryption | [
"Mathematics"
] | 669 | [
"Cryptographic software",
"Mathematical software"
] |
7,160,955 | https://en.wikipedia.org/wiki/Langley%20extrapolation | Langley extrapolation is a method for determining the Sun's irradiance at the top of the atmosphere with ground-based instrumentation, and is often used to remove the effect of the atmosphere from measurements of, for example, aerosol optical thickness or ozone. It is based on repeated measurements with a Sun photometer operated at a given location for a cloudless morning or afternoon as the Sun moves across the sky. It is named for American astronomer and physicist Samuel Pierpont Langley.
Theory
It is known from Beer's law that, for every instantaneous measurement, the direct-Sun irradiance I is linked to the solar extraterrestrial irradiance I0 and the atmospheric optical depth by the following equation:
where m is a geometrical factor accounting for the slant path through the atmosphere, known as the airmass factor.
For a plane-parallel atmosphere, the airmass factor is simple to determine if one knows the solar zenith angle θ: m = 1/cos(θ). As time passes, the Sun moves across the sky, and therefore θ and m vary according to known astronomical laws.
By taking the logarithm of the above equation, one obtains:
and if one assumes that the atmospheric disturbance does not change during the observations (which last for a morning or an afternoon), the plot of ln I versus m is a straight line with a slope equal to . Then, by linear extrapolation to m = 0, one obtains I0, i.e. the Sun's radiance that would be observed by an instrument placed above the atmosphere.
The requirement for good Langley plots is a constant atmosphere (constant ). This requirement can be fulfilled only under particular conditions, since the atmosphere is continuously changing. Needed conditions are in particular: the absence of clouds along the optical path, and the absence of variations in the atmospheric aerosol layer. Since aerosols tend to be more concentrated at low altitude, Langley extrapolation is often performed at high mountain sites. Data from NASA Glenn Research Center indicates that the Langley plot accuracy is improved if the data is taken above the tropopause.
Solar cell calibration
A Langley plot can also be used as a method to calculate the performance of solar cells outside the Earth's atmosphere. At the Glenn Research Center, the performance of solar cells is measured as a function of altitude. By extrapolation, researchers determine their performance under space conditions.
Low cost LED-based photometers
Sun photometers using low cost light-emitting diode (LED) detectors in place of optical interference filters and photodiodes have a relatively wide spectral response. They might be used by a globally distributed network of students and teachers to monitor atmospheric haze and aerosols, and can be calibrated using Langley extrapolation. In 2001, David Brooks and Forrest Mims were among many to propose detailed procedures to modify the Langley plot in order to account for Rayleigh scattering, and atmospheric refraction by a spherical Earth.
Di Justo and Gertz compiled a handbook for using Arduino to develop these photometers in 2012. The handbook refers to in equations () and (), as the AOT (Atmospheric Optical Thickness), and the handbook refers to I0 as the EC (extraterrestrial constant). The manual suggests that once a photometer is constructed, the user waits for a clear day with few clouds, no haze and constant humidity. After the data is fit to equation () to find I0, the handbook suggests a daily measurement of I. Both I0 and I are obtained from the LED current (voltage across sensing resistor) by subtracting the dark current:
where is the voltage while the LED is pointing at the Sun, and is the voltage while the LED is kept dark. There is a misprint in the manual regarding the calculation of from this single data point. The correct equation is:
where was calculated on that clear and stable day using Langley extrapolation.
References
Radiometry | Langley extrapolation | [
"Engineering"
] | 822 | [
"Telecommunications engineering",
"Radiometry"
] |
7,161,023 | https://en.wikipedia.org/wiki/Argentium%20sterling%20silver | Argentium silver (patented in 1998) is a brand of modern tarnish-resistant silver alloys, containing either 93.5%, 94% or 96% silver. Argentium alloys replace some of the copper in the traditional sterling silver (92.5% silver + 7.5% copper) with the metalloid germanium.
Argentium 935, Argentium 940 and Argentium 960 alloys exceed the standard required for hallmarking as sterling silver, and Argentium 960 silver meets the standard for hallmarking as Britannia silver (95.84% silver).
Origins and description
Argentium silver is the result of research at the Art and Design Research Institute (ADRI), School of Art & Design, Middlesex University, by Peter Johns and colleagues. The project began in 1990 with research on the effects of germanium additions to silver alloys. Germanium was discovered to impart the following properties to sterling silver:
firescale elimination
high tarnish resistance
precipitation hardening and simple heat-hardening properties
increased ductility
increased thermal and electrical resistance
environmental advantages
Many of these properties significantly affect the traditional methods of working silver. For instance the absence of firescale eliminates tedious and time-consuming steps required by the silver worker using traditional sterling silver. It also eliminates the need for plating the final product which is often done on manufactured items because of the problems introduced by firescale. Tarnish resistance is of significant importance to both silver workers and the wearer of silver jewellery.
Argentium silver was patented and is trademarked by Argentium Silver Company, UK.
Physical properties
{| class="wikitable";
|+
!rowspan=2| Silveralloy
!colspan=2| Solidusmelting temperature
!colspan=2| Liquidusflow point temperature
|- style="text-align:center;"
| °C || °F || °C || °F
|- style="text-align:right;"
| || 802 °C || 1475 °F || 899 °C || 1650 °F
|-
| || 860 °C ||1580 °F ||895 °C ||1643 °F
|- style="text-align:right;"
| || 890 °C || 1634 °F || 920 °C || 1688 °F
|}
Footnotes
References
Further reading
External links
Silver
Precious metal alloys
Jewellery making | Argentium sterling silver | [
"Chemistry"
] | 487 | [
"Precious metal alloys",
"Alloys"
] |
9,301,973 | https://en.wikipedia.org/wiki/Ozone%20monitoring%20instrument | The ozone monitoring instrument (OMI) is a nadir-viewing visual and ultraviolet spectrometer aboard the NASA Aura spacecraft, which is part of the satellite constellation A-Train. In this group of satellites Aura flies in formation about 15 minutes behind Aqua satellite, both of which orbit the Earth in a polar Sun-synchronous pattern, and which provides nearly global coverage in one day. Aura satellite was launched on July 15, 2004, and OMI has collected data since August 9, 2004.
From a technical point of view, OMI instrument use hyperspectral imaging to observe solar-backscatter radiation to the space with an spectral range that covers the visible and ultraviolet. Its spectral capabilities were designed to achieve specific requirements of total ozone amounts retrievals in terms of accuracy and precision. Also its characteristics provide accurate radiometric and wavelength self calibration over the long-term project requirements.
OMI project
The OMI project is a cooperation between the Netherlands Agency for Aerospace Programmes (NIVR), the Finnish Meteorological Institute (FMI) and the National Aeronautics and Space Agency (NASA).
The OMI project was carried out under the direction of the NIVR and financed by the Dutch Ministries of Economic Affairs, Transport and Public Works and the Ministry of Education and Science. The instrument was built by Dutch Space in co-operation with Netherlands Organisation for Applied Scientific Research Science and Industry and Netherlands Institute for Space Research. The Finnish industry supplied the electronics. The scientific part of the OMI project is managed by KNMI (principal investigator Prof. Dr. P. F. Levelt now at the Delft University of Technology), in close co-operation with NASA and the Finnish Meteorological Institute.
Scientific objectives and atmospheric monitoring
One of the scientific objectives of OMI is to measure trace gases: ozone (O3), nitrogen dioxide (NO2), sulfur dioxide (SO2), formaldehyde (HCHO), BrO, and OClO. However, OMI sensors can distinguish between aerosol types, such as smoke, dust, and sulfates, and can measure cloud pressure and cloud coverage, which provide data to derive tropospheric ozone. In that regard OMI follows in the heritage of TOMS, SBUV, GOME, SCIAMACHY, and GOMOS. On top of that, OMI aims to detect emissions in volcanic eruptions with up to at least 100 times more sensitivity than TOMS. The Ozone Monitoring Instrument has been proved an useful platform to monitor other traces gases like Glyoxal, variables like surface UV radiation, or total column estimations like the water vapor, NO2 and Ozone. Has been uses in operational services by European Centre for Medium-range Weather Forecasts (ECMWF), the US National Oceanic and Atmospheric Administration (NOAA) for ozone and air quality forecasts, and the Volcanic Ash Advisory Centers (VAACs) for the rerouting of aircraft in case of a volcanic eruption.
Instrument Information
The instrument observes Earth's backscattered radiation and uses two imaging grating spectrometers, and each grating spectrometer is coupled to a CCD detector with 780x576 (spectral x spatial) pixels. The instrument can operate in two different modes: the normal operational mode where a single pixel in the observation has an spatial resolution 13x24 km2 at nadir (straight down), and the zoom mode where this resolution is increased to 13x12 km2.
Spectral Information
OMI measurements cover a spectral region of 264–504 nm (nanometers) with a spectral resolution between 0.42 nm and 0.63 nm and a nominal ground footprint of 13 × 24 km2 at nadir. This spectral coverage is divided in three different channels two of them in the ultraviolet range, and one in the visible spectrum. Note that the ground pixel size of the UV-1 channel is twice as large in the swath direction compared to the other two channels, this optical design of the UV channel were done to reduce straylight in this wavelength range.
Orbital Information
The Aura satellite orbits at an altitude of 705 km in a sun-synchronous polar orbit with an exact 16-day repeat cycle and with a local equator crossing time of 13. 45 ( 1:45 P.M.) on the ascending node. The orbital inclination is 98.1 degrees, providing latitudinal coverage from 82° N to 82° S. It is a wide-field-imaging spectrometer with a 114° across-track viewing angle range that provides a 2600 km wide swath, enabling measurements with a daily global coverage.
Calibration and Validation
The discussion of the calibration and validation processes began before the launch of Aura Satellite. Once the instrument was in orbit the information of these calibration was published, showing specific details of the absolute radiometric calibration, the bi-directional scattering distribution function (BSDF) calibration and the spectral calibration carried on. Note also that the instrument is equipped with an internal white light source for detector calibration purposes. The validation, which aim to assess the inherent uncertainties in satellite data products of the instrument together with retrieval algorithms used for each data product, was carried on continuously since the launch of Aura satellite. The validation include products like: total ozone column, NO2, ozone vertical profiles.
In-flight performance
One important aspect of satellite instruments for scientific measurements is the evolution of the performance during the life-cycle of the sensors, as well as, the continuous evaluation of the quality of the data products. In the case of an instrument like OMI the main aspects to consider are: the radiometric and spectral stability, the row anomaly, and detector degradation. In the first aspect: the radiometric degradation of OMI ranges from ∼2% in the UV channels to ∼0.5% in the VIS channel, which is much lower than any other similar satellite instrument. Regarding the wavelength calibration of the instrument it remains stable to 0.005–0.020 nm which indicates a high wavelength stability. It was detected a row anomaly due, probably, to a partial cover of the instrument, warning flags were included in the raw products to avoid the use of these specific rows and keep the quality of the retrieval products. Further information of the long-term calibration indicated in 2017 that the instrument will be able to provide useful science data for another 5 to 10 years.
Scientific relevance
The OMI project has been monitoring the atmospheric composition and providing measurements widely used in the field of atmospheric chemistry research. The fact that it has been operational for more than a decade makes it also useful for trend monitoring. The reference describing the first 14 years of the OMI details the research data products provided by NASA, KNMI, FMI and SAO, also according to these authors, beyond the initial goals, OMI has been important due the high-resolution NO2 and SO2 measurements (OMI is the first instrument that is able to obtain daily global coverage combined with such spatial resolution), and the fact that top-down studies allowed for source attribution analyses.
Awards
The International Team of the Ozone Monitoring Instrument has received several awards for its contributions to a better understanding of the Earth system:
USGS 2018 Pecora Award The Pecora award is annual to recognize individuals or teams using remote sensing in the field of Earth Science. It consider not only the scientific role but also its role informing decision makers and supporting natural or human-induced disaster responses.
2021 AMS Special Award A broad description of this award to OMI International Team is given as an AMS video.
Contributions to scientific research
Assessment of the Montreal Protocol: the instrument has proved stability to provide long-term data record for monitoring the ozone layer, which is the particular interest to evaluate the possible recovery of the ozone depletion in the southern hemisphere.
Global concentrations of trace gases: the OMI data show a steady decline in concentrations of NO2 in the United States, Europe, and Japan, whereas in China, first strong increases were observed, followed by decreases after 2014.
Absorbing aerosol that can cause warming: OMI can provide information as from its ultraviolet (UV) channel it is possible to derive such absorbing capacity.
Long-term data record of tropospheric ozone has been established: Tropospheric ozone assessment is important as it is the third main anthropogenic greenhouse gas, and the fraction of ozone in the troposphere can be derived from the OMI data, either by itself alone or in combination with other instruments
OMI formaldehyde retrievals indicate increases of this trace gas over India and China, and a downward trend over the Amazonian forest, spatially correlated with areas affected by deforestation
OMI has been the first satellite instrument to be used for daily monitoring of volcanic emissions
References
External links
OMI webpage at NASA.gov
OMI webpage at KNMI.nl
Tropospheric Emission Monitoring Internet Service (TEMIS)
https://docserver.gesdisc.eosdis.nasa.gov/repository/Mission/OMI/3.3_ScienceDataProductDocumentation/3.3.2_ProductRequirements_Designs/README.OMI_DUG.pdf
Scientific instruments
Spectrometers
Ozone depletion
Weather imaging satellite sensors | Ozone monitoring instrument | [
"Physics",
"Chemistry",
"Technology",
"Engineering"
] | 1,914 | [
"Spectrum (physical sciences)",
"Scientific instruments",
"Measuring instruments",
"Spectrometers",
"Spectroscopy"
] |
9,302,182 | https://en.wikipedia.org/wiki/Watson%20interferometer | The Watson interferometer is a vintage microscope accessory (for use only in reflected light microscopy) which was manufactured by the Watson Company in Great Britain. It is a variant of Michelson interferometer that can be installed on a conventional microscope. It consists of a beam splitter and varying the distance between the specimen surface and the image of the reference mirror creates interference fringes. For transmitted light investigations in biology, the C. Watson company produced the Smith/Baker system in the 1950s.
References
Interferometers | Watson interferometer | [
"Technology",
"Engineering"
] | 105 | [
"Interferometers",
"Measuring instruments"
] |
9,302,344 | https://en.wikipedia.org/wiki/European%20Nuclear%20Energy%20Tribunal | The European Nuclear Energy Tribunal (ENET) is an international tribunal, established 1 January 1960, that operates under the auspices of the Organisation for Economic Co-operation and Development (OECD). Its member states are Austria, Belgium, Denmark, France, Germany, Ireland, Italy, Luxembourg, Netherlands, Norway, Portugal, Spain, Sweden, Switzerland, Turkey, and the United Kingdom. The tribunal was established by the Convention on the Establishment of the Security Control in the Field of Nuclear Energy, signed in 1957.
The purpose of the tribunal is to hear cases concerning liability over nuclear accidents. Formerly it also had the role of hearing cases concerning the violation of the European regional nuclear safeguards system operated by the OECD but that jurisdiction was suspended in the 1970s due to its duplication of the IAEA and the Euratom systems.
The tribunal consists of seven judges appointed to five-year terms.
The OECD Council appointed judges for a term from 1 January 2020 to 31 December 2024, with Mr. Francis Delaporte serving as the President of the Tribunal. The appointed judges come from Finland, Italy, Luxembourg, Norway, Portugal, Spain, and the United Kingdom.
The Registrar of the Tribunal is currently Ximena Vásquez-Maignan, Head of Legal Affairs at the Nuclear Energy Agency. Located at the OECD headquarters in Paris, France, the Tribunal's seat is established by Article 7(b) of its Protocol.
In the over fifty years of its existence the tribunal has never been presented with a case.
References
External links
European Nuclear Energy Tribunal page at the OECD Nuclear Energy Agency
International nuclear energy organizations
International courts and tribunals
OECD
Nuclear liability
Tribunals | European Nuclear Energy Tribunal | [
"Engineering"
] | 348 | [
"International nuclear energy organizations",
"Nuclear organizations"
] |
9,304,399 | https://en.wikipedia.org/wiki/Equilibrium%20selection | Equilibrium selection is a concept from game theory which seeks to address reasons for players of a game to select a certain equilibrium over another. The concept is especially relevant in evolutionary game theory, where the different methods of equilibrium selection respond to different ideas of what equilibria will be stable and persistent for one player to play even in the face of deviations (and mutations) of the other players. This is important because there are various equilibrium concepts, and for many particular concepts, such as the Nash equilibrium, many games have multiple equilibria.
Equilibrium Selection with Repeated Games
A stage game is an n-player game where players choose from a finite set of actions, and there is a payoff profile for their choices. A repeated game is playing a number of repetitions of a stage game in discrete periods of time (Watson, 2013). A player's reputation affects the actions and behavior of the other players. In other words, how a player behaves in preceding rounds determines the actions of their opponents in subsequent rounds. An example is the interaction between an employee and an employer where the employee shirks their responsibility for a short-term gain then loses on the bonus that the employer discontinues after observing the employee's behavior (Watson, 2013). The dynamics of equilibrium selection for repeated games can be illustrated with a two-period game. With every action from the players in one period, a new subgame is initiated based on that action profile. For the Nash Equilibrium of the entire game, a subgame perfect equilibrium of every game is required. Hence, in the last period of a repeated game, the players will choose a stage game Nash Equilibrium. Equilibria stipulation actions that are not Nash Equilibrium strategies in the stage game are still supported. This can be achieved by establishing a reputation of "cooperation" in the preceding periods that leads to the opponent selecting a more favorable Nash Equilibrium strategy in the final period. If a player builds a reputation of deviating instead of co-operating, then the opponent can "punish" the player by choosing a less favorable Equilibrium in the final period of the repeated game.
Focal point
Another concept that can help to select an equilibrium is focal point. This concept was first introduced by Thomas Schelling, a Nobel-winning game theorist, in his book The Strategy of Conflict in 1960 (Schelling, 1960). When the participants are in a coordinate game where the players do not have a chance to discuss their strategies beforehand, focal point is a solution that somehow stands out as the natural answer.
For example, in an experiment conducted in 1990 by Mehta et al. (1994), the researchers let the participants answer a questionnaire, which contained the question "name a year" or "name a city in England". The participants were asked to provide the first answer that came to their minds, and many provided their birth year or hometown city.
However, when they had the incentive to coordinate - the participants were told they would be paid if they managed to answer the question the same way as an anonymous partner - most of them chose 1990 (the year at the time) and London (the largest city in the UK). These are not the first answers that came to their minds, but they are the best bets after deliberation while trying to find a partner without prior discussion. In this case, the year 1990, or the city of London, is the focal point of this game, to help the players to select the best equilibrium in this coordinate game.
Besides, even in the situation where the game players are allowed to communicate with each other, such as negotiation, focal point can still be useful for them selecting an appropriate equilibrium: When the negotiation is about to the end, each player must make the last-minute decision about how aggressive they should be and to what extent they should trust their opponents (Hyde, 2017).
Symmetries
Various authors have studied games with symmetries (over players or actions), especially in the case of fully cooperative games. For example, the team game Hanabi has been considered, in which the different players and suits are symmetric. Relatedly, some authors have considered how equilibrium selection relates between isomorphic games. Generally, it has been argued that a group of players shouldn't choose strategies that arbitrarily break these symmetries, i.e., should play symmetric strategies to aim for symmetric equilibria. Similarly they should play isomorphic games isomorphically. For example, in Hanabi, hints corresponding to the different suits should have analogous (symmetric) meanings. In team games, the optimal symmetric strategy is also a (symmetric) Nash equilibrium. While breaking symmetries may allow for higher utilities, it results in unnatural, inhuman strategies. Every finite symmetric game (including non-team games) has a symmetric Nash equilibrium.
Examples of equilibrium selection concepts
Risk & Payoff dominance
Definition: Consider a situation where a game has multiple Nash equilibria (NE), the equilibrium can be classified into two categories:
A Nash equilibrium is considered risk dominant if it has the largest basin of attraction (i.e. is less risky).
A Nash equilibrium is considered payoff dominant if it is Pareto superior to all other Nash equilibria in the game.
Explanation: A risk dominant NE is chosen when the player wants to avoid big losses while a payoff dominant NE is considered for an optimal payoff solution. Note that either the risk dominant or payoff dominant is a typical type of NE.
Example: Take the normal form payoff matrix of a game as an example:
There are two NEs in this game, i.e. (U, L) and (D,R). Here (U, L) is a payoff dominant NE since such a strategy can return an optimal overall payoff. However, given the uncertainty of an opponent's action, one of the players may consider a more conservative strategy (D for player 1 and R for player two), which can avoid the situation of "a great loss", i.e. getting 0 payoff once the opponent deviates. Hence the (D, R) is a risk dominant NE.
1/2 dominance
See also
Pareto efficiency
Equilibrium refinement
References
Harsanyi, John C. and Selten, Reinhard, A General Theory of Equilibrium Selection in Games, MIT Press (1988)
Watson, J. (2013). Repeated Games and Reputation. In Strategy: An introduction to game theory (3rd ed., pp. 291–305). essay, Norton & Company.
Hyde, T., 2017. Can Schelling's focal points help us understand high-stakes negotiations?. [online] Aeaweb.org. Available at: <https://www.aeaweb.org/research/can-schellings-focal-points-help-us-understand-high-stakes-negotiations> [Accessed 9 December 2021].
Mehta, J., Starmer, C., & Sugden, R. (1994). The Nature of Salience: An Experimental Investigation of Pure Coordination Games. The American Economic Review, 84(3), 658–673.
Schelling, T. C. (1960). The strategy of conflict. Cambridge, Mass.
Game theory equilibrium concepts | Equilibrium selection | [
"Mathematics"
] | 1,499 | [
"Game theory",
"Game theory equilibrium concepts"
] |
9,304,834 | https://en.wikipedia.org/wiki/Pointclass | In the mathematical field of descriptive set theory, a pointclass is a collection of sets of points, where a point is ordinarily understood to be an element of some perfect Polish space. In practice, a pointclass is usually characterized by some sort of definability property; for example, the collection of all open sets in some fixed collection of Polish spaces is a pointclass. (An open set may be seen as in some sense definable because it cannot be a purely arbitrary collection of points; for any point in the set, all points sufficiently close to that point must also be in the set.)
Pointclasses find application in formulating many important principles and theorems from set theory and real analysis. Strong set-theoretic principles may be stated in terms of the determinacy of various pointclasses, which in turn implies that sets in those pointclasses (or sometimes larger ones) have regularity properties such as Lebesgue measurability (and indeed universal measurability), the property of Baire, and the perfect set property.
Basic framework
In practice, descriptive set theorists often simplify matters by working in a fixed Polish space such as Baire space or sometimes Cantor space, each of which has the advantage of being zero dimensional, and indeed homeomorphic to its finite or countable powers, so that considerations of dimensionality never arise. Yiannis Moschovakis provides greater generality by fixing once and for all a collection of underlying Polish spaces, including the set of all naturals, the set of all reals, Baire space, and Cantor space, and otherwise allowing the reader to throw in any desired perfect Polish space. Then he defines a product space to be any finite Cartesian product of these underlying spaces. Then, for example, the pointclass of all open sets means the collection of all open subsets of one of these product spaces. This approach prevents from being a proper class, while avoiding excessive specificity as to the particular Polish spaces being considered (given that the focus is on the fact that is the collection of open sets, not on the spaces themselves).
Boldface pointclasses
The pointclasses in the Borel hierarchy, and in the more complex projective hierarchy, are represented by sub- and super-scripted Greek letters in boldface fonts; for example, is the pointclass of all closed sets, is the pointclass of all Fσ sets, is the collection of all sets that are simultaneously Fσ and Gδ, and is the pointclass of all analytic sets.
Sets in such pointclasses need be "definable" only up to a point. For example, every singleton set in a Polish space is closed, and thus . Therefore, it cannot be that every set must be "more definable" than an arbitrary element of a Polish space (say, an arbitrary real number, or an arbitrary countable sequence of natural numbers). Boldface pointclasses, however, may (and in practice ordinarily do) require that sets in the class be definable relative to some real number, taken as an oracle. In that sense, membership in a boldface pointclass is a definability property, even though it is not absolute definability, but only definability with respect to a possibly undefinable real number.
Boldface pointclasses, or at least the ones ordinarily considered, are closed under Wadge reducibility; that is, given a set in the pointclass, its inverse image under a continuous function (from a product space to the space of which the given set is a subset) is also in the given pointclass. Thus a boldface pointclass is a downward-closed union of Wadge degrees.
Lightface pointclasses
The Borel and projective hierarchies have analogs in effective descriptive set theory in which the definability property is no longer relativized to an oracle, but is made absolute. For example, if one fixes some collection of basic open neighborhoods (say, in Baire space, the collection of sets of the form {x∈ωω s is an initial segment of x} for each fixed finite sequence s of natural numbers), then the open, or , sets may be characterized as all (arbitrary) unions of basic open neighborhoods. The analogous sets, with a lightface , are no longer arbitrary unions of such neighborhoods, but computable unions of them. That is, a set is lightface , also called effectively open, if there is a computable set S of finite sequences of naturals such that the given set is the union of the sets {x∈ωω s is an initial segment of x} for s in S.
A set is lightface if it is the complement of a set. Thus each set has at least one index, which describes the computable function enumerating the basic open sets from which it is composed; in fact it will have infinitely many such indices. Similarly, an index for a set B describes the computable function enumerating the basic open sets in the complement of B.
A set A is lightface if it is a union of a computable sequence of sets (that is, there is a computable enumeration of indices of sets such that A is the union of these sets). This relationship between lightface sets and their indices is used to extend the lightface Borel hierarchy into the transfinite, via recursive ordinals. This produces the hyperarithmetic hierarchy, which is the lightface analog of the Borel hierarchy. (The finite levels of the hyperarithmetic hierarchy are known as the arithmetical hierarchy.)
A similar treatment can be applied to the projective hierarchy. Its lightface analog is known as the analytical hierarchy.
Summary
Each class is at least as large as the classes above it.
References
Descriptive set theory
General topology | Pointclass | [
"Mathematics"
] | 1,216 | [
"General topology",
"Topology"
] |
9,304,980 | https://en.wikipedia.org/wiki/Jus%20post%20bellum | Jus post bellum ( ; Latin for "Justice after war") is a concept that deals with the morality of the termination phase of war, including the responsibility to rebuild. The idea has some historical pedigree as a concept in just war theory. In modern times, it has been developed by a number of just war theorists and international lawyers. However, the concept means different things to the contributors in each field. For lawyers, the concept is much less clearly defined, and many have rejected the usefulness of the concept altogether. The concept continues to attract scholarly interest in the field of international humanitarian law. A famous example of Jus post bellum is the reconstruction of Germany by the Allies post World War 2.
Background
Brian Orend cites Immanuel Kant as the first to consider a three-pronged approach to the morality of armed conflict and concluded that a third branch of just war theory, the morality of the termination phase of war, had been overlooked. Part of this morality, according to Michael Walzer, is that we have a moral obligation to not leave the regimes intact that caused the war in the first place. However, the actual duty of the role of jus post bellum remains unclear. To achieve a lasting peace, the goal is to find a balance between transitional justice and order. A related concept to the jus post bellum is the lex pacificatoria, the law of peacemaking by treaty to introduce the jus post bellum phase.
Purpose
The purpose of the concept and its usefulness depends on whether it is considered as a moral or a legal concept. As a concept in just war theory, the jus post bellum debate considers a number of issues:
Provide terms for the end of war; once the rights of a political community have been vindicated, further continuation of war becomes an act of aggression.
Provide guidelines for the construction of peace treaties.
Provide guidelines for the political reconstruction of defeated states.
Prevent draconian and vengeful peace terms; the rights a just state fights for in a war provide the constraints on what can be demanded from the defeated belligerent.
Thus, the areas within which jus post bellum applies can include restraining conquest; political reconstruction, especially in the case of genocide and war crimes; and economic reconstruction, including restoration and reparations.
Criticisms
When a state does help reconstruct another state after winning a war, they (as well as other international actors) have their own incentives to create new power structures that favor their state. Additionally, if the population doesn't accept the reconstruction or otherwise feel their grievances have been met, the very act of reconstruction can be seen as violence, and further conflict, just appearing in a different form.
James Pattison argues that the idea that the belligerent shouldn't have a responsibility to rebuild to justify the morality of a war. Jus post bellum should only play a role in determining post war justice. There are many problems with the assumption that only the belligerent should rebuild:
The defeated actor may not need rebuilding, but the victor.
Third parties may be adversely affected by the externalities of the conflict that would not be ordinarily considered during the typical idea of post war rebuilding, and so they are left out of the equation.
It is unfair to a state that wages a defensive war where they had no other choice but to defend themselves.
The belligerents aren't always the best choice for helping rebuild, for instance if they are occupying post-war and the population is hostile to them, sparking more conflict, or if the belligerents don't have the money to rebuild the loser of the conflict and they fought a just war in self defense.
See also
Jus ad bellum
Jus in bello
Just War Theory
Lex pacificatoria
Peace treaty
References
Allman, Mark J. and Winright, Tobias L. "Jus Post Bellum: Extending the Just War Theory" in Faith in Public Life, College Theology Society Annual Volume 53, 2007 (Maryknoll, NY: Orbis Books, 2008), 241–264.
Allman, Mark J. and Winright, Tobias L. After the Smoke Clears: The Just War Tradition and Post War Justice (Maryknoll, NY: Orbis Books, 2010).
DiMeglio, Richard P. "The Evolution of the Just War Tradition: Defining Jus Post Bellum" Military Law Review (2006), Vol. 186, pp. 116–163.
Kwon, David C. Justice after War: Jus Post Bellum in the 21st Century (Washington, D.C.: The Catholic University of America, 2023).
Orend, Brian. War in Stanford Encyclopedia of Philosophy, 2000/2005.
Specific
Just war theory
Aftermath of war
Concepts in ethics | Jus post bellum | [
"Biology"
] | 979 | [
"Just war theory",
"Behavior",
"Aggression"
] |
9,305,752 | https://en.wikipedia.org/wiki/Fanno%20flow | In fluid dynamics, Fanno flow (after Italian engineer Gino Girolamo Fanno) is the adiabatic flow through a constant area duct where the effect of friction is considered. Compressibility effects often come into consideration, although the Fanno flow model certainly also applies to incompressible flow. For this model, the duct area remains constant, the flow is assumed to be steady and one-dimensional, and no mass is added within the duct. The Fanno flow model is considered an irreversible process due to viscous effects. The viscous friction causes the flow properties to change along the duct. The frictional effect is modeled as a shear stress at the wall acting on the fluid with uniform properties over any cross section of the duct.
For a flow with an upstream Mach number greater than 1.0 in a sufficiently long duct, deceleration occurs and the flow can become choked. On the other hand, for a flow with an upstream Mach number less than 1.0, acceleration occurs and the flow can become choked in a sufficiently long duct. It can be shown that for flow of calorically perfect gas the maximum entropy occurs at M = 1.0.
Theory
The Fanno flow model begins with a differential equation that relates the change in Mach number with respect to the length of the duct, dM/dx. Other terms in the differential equation are the heat capacity ratio, γ, the Fanning friction factor, f, and the hydraulic diameter, Dh:
Assuming the Fanning friction factor is a constant along the duct wall, the differential equation can be solved easily. One must keep in mind, however, that the value of the Fanning friction factor can be difficult to determine for supersonic and especially hypersonic flow velocities. The resulting relation is shown below where L* is the required duct length to choke the flow assuming the upstream Mach number is supersonic. The left-hand side is often called the Fanno parameter.
Equally important to the Fanno flow model is the dimensionless ratio of the change in entropy over the heat capacity at constant pressure, cp.
The above equation can be rewritten in terms of a static to stagnation temperature ratio, which, for a calorically perfect gas, is equal to the dimensionless enthalpy ratio, H:
The equation above can be used to plot the Fanno line, which represents a locus of states for given Fanno flow conditions on an H-ΔS diagram. In the diagram, the Fanno line reaches maximum entropy at H = 0.833 and the flow is choked. According to the Second law of thermodynamics, entropy must always increase for Fanno flow. This means that a subsonic flow entering a duct with friction will have an increase in its Mach number until the flow is choked. Conversely, the Mach number of a supersonic flow will decrease until the flow is choked. Each point on the Fanno line corresponds with a different Mach number, and the movement to choked flow is shown in the diagram.
The Fanno line defines the possible states for a gas when the mass flow rate and total enthalpy are held constant, but the momentum varies. Each point on the Fanno line will have a different momentum value, and the change in momentum is attributable to the effects of friction.
Additional Fanno flow relations
As was stated earlier, the area and mass flow rate in the duct are held constant for Fanno flow. Additionally, the stagnation temperature remains constant. These relations are shown below with the * symbol representing the throat location where choking can occur. A stagnation property contains a 0 subscript.
Differential equations can also be developed and solved to describe Fanno flow property ratios with respect to the values at the choking location. The ratios for the pressure, density, temperature, velocity and stagnation pressure are shown below, respectively. They are represented graphically along with the Fanno parameter.
Applications
The Fanno flow model is often used in the design and analysis of nozzles. In a nozzle, the converging or diverging area is modeled with isentropic flow, while the constant area section afterwards is modeled with Fanno flow. For given upstream conditions at point 1 as shown in Figures 3 and 4, calculations can be made to determine the nozzle exit Mach number and the location of a normal shock in the constant area duct. Point 2 labels the nozzle throat, where M = 1 if the flow is choked. Point 3 labels the end of the nozzle where the flow transitions from isentropic to Fanno. With a high enough initial pressure, supersonic flow can be maintained through the constant area duct, similar to the desired performance of a blowdown-type supersonic wind tunnel. However, these figures show the shock wave before it has moved entirely through the duct. If a shock wave is present, the flow transitions from the supersonic portion of the Fanno line to the subsonic portion before continuing towards M = 1. The movement in Figure 4 is always from the left to the right in order to satisfy the second law of thermodynamics.
The Fanno flow model is also used extensively with the Rayleigh flow model. These two models intersect at points on the enthalpy-entropy and Mach number-entropy diagrams, which is meaningful for many applications. However, the entropy values for each model are not equal at the sonic state. The change in entropy is 0 at M = 1 for each model, but the previous statement means the change in entropy from the same arbitrary point to the sonic point is different for the Fanno and Rayleigh flow models. If initial values of si and Mi are defined, a new equation for dimensionless entropy versus Mach number can be defined for each model. These equations are shown below for Fanno and Rayleigh flow, respectively.
Figure 5 shows the Fanno and Rayleigh lines intersecting with each other for initial conditions of si = 0 and Mi = 3. The intersection points are calculated by equating the new dimensionless entropy equations with each other, resulting in the relation below.
The intersection points occur at the given initial Mach number and its post-normal shock value. For Figure 5, these values are M = 3 and 0.4752, which can be found the normal shock tables listed in most compressible flow textbooks. A given flow with a constant duct area can switch between the Fanno and Rayleigh models at these points.
See also
Rayleigh flow
Mass injection flow
Isentropic process
Isothermal flow
Gas dynamics
Compressible flow
Choked flow
Enthalpy
Entropy
Isentropic nozzle flow
References
External links
Purdue University Adiabatic and Isothermal Fanno flow calculators
University of Kentucky Fanno flow Webcalculator
Maurice W. Downey, Gino Fanno
Flow regimes
Aerodynamics | Fanno flow | [
"Chemistry",
"Engineering"
] | 1,396 | [
"Aerospace engineering",
"Aerodynamics",
"Flow regimes",
"Fluid dynamics"
] |
9,306,272 | https://en.wikipedia.org/wiki/Shock%20%28fluid%20dynamics%29 | Shock is an abrupt discontinuity in the flow field and it occurs in flows when the local flow speed exceeds the local sound speed. More specifically, it is a flow whose Mach number exceeds 1.
Explanation of phenomena
Shock is formed due to coalescence of various small pressure pulses. Sound waves are pressure waves and it is at the speed of the sound wave the disturbances are communicated in the medium. When an object is moving in a flow field the object sends out disturbances which propagate at the speed of sound and adjusts the remaining flow field accordingly. However, if the object itself happens to travel at speed greater than sound, then the disturbances created by the object would not have traveled and communicated to the rest of the flow field and this results in an abrupt change of property, which is termed as shock in gas dynamics terminology.
Shocks are characterized by discontinuous changes in flow properties such as velocity, pressure, temperature, etc. Typically, shock thickness is of a few mean free paths (of the order of 10−8 m). Shocks are irreversible occurrences in supersonic flows (i.e. the entropy increases).
Normal shock formulas
Where, the index 1 refers to upstream properties, and the index 2 refers to down stream properties. The subscript 0 refers to total or stagnation properties. T is temperature, M is the mach number, P is pressure, ρ is density, and γ is the ratio of specific heats.
See also
Mach number
Sound barrier
supersonic flow
References
Fluid dynamics | Shock (fluid dynamics) | [
"Chemistry",
"Engineering"
] | 309 | [
"Piping",
"Chemical engineering",
"Fluid dynamics"
] |
9,307,303 | https://en.wikipedia.org/wiki/Generalised%20likelihood%20uncertainty%20estimation | Generalized likelihood uncertainty estimation (GLUE) is a statistical method used in hydrology for quantifying the uncertainty of model predictions. The method was introduced by Keith Beven and Andrew Binley in 1992. The basic idea of GLUE is that given our inability to represent exactly in a mathematical model how nature works, there will always be several different models that mimic equally well an observed natural process (such as river discharge). Such equally acceptable or behavioral models are therefore called equifinal.
The methodology deals with models whose results are expressed as probability distributions of possible outcomes, often in the form of Monte Carlo simulations, and the problem can be viewed as assessing, and comparing between models, how good these representations of uncertainty are. There is an implicit understanding that the models being used are approximations to what might be obtained from a thorough Bayesian analysis of the problem if a fully adequate model of real-world hydrological processes were available.
GLUE is equivalent to Approximate Bayesian computation for some choices of summary statistic and threshold.
References
Hydrology
Probability assessment
Bayesian statistics | Generalised likelihood uncertainty estimation | [
"Chemistry",
"Engineering",
"Environmental_science"
] | 214 | [
"Hydrology",
"Hydrology stubs",
"Environmental engineering"
] |
9,307,355 | https://en.wikipedia.org/wiki/Practical%20Common%20Lisp | Practical Common Lisp is an introductory book on the programming language Common Lisp by Peter Seibel. It features a fairly complete introduction to the language interspersed with practical example chapters, which show developing various pieces of software such as a unit testing framework, a library for parsing ID3 tags, a spam filter, and a SHOUTcast server.
At the Jolt Product Excellence and Productivity Awards in 2006, it won a Productivity Award in the technical book category.
The full text is available online. In a 2006 Google TechTalk, Seibel presented the book's main points in the context of linguistic relativity (the Sapir–Whorf hypothesis).
See also
Common Lisp the Language
References
External links
Practical Common Lisp
Common Lisp publications | Practical Common Lisp | [
"Technology"
] | 152 | [
"Computing stubs",
"Computer book stubs"
] |
9,307,607 | https://en.wikipedia.org/wiki/Planar%20laser-induced%20fluorescence | Planar laser-induced fluorescence (PLIF) is an optical diagnostic technique widely used for flow visualization and quantitative measurements. PLIF has been shown to be used for velocity, concentration, temperature and pressure measurements.
Working
A PLIF setup consists of a source of light (usually a laser), an arrangement of lenses to form a sheet, fluorescent medium, collection optics and a detector. The light from the source, illuminates the medium, which then fluoresces. This signal is captured by the detector and can be related to the various properties of the medium.
The typical lasers used as light sources are pulsed, which provide a higher peak power than the continuous-wave lasers. Also the short pulse time is useful for good temporal resolution. Some of the widely used laser sources are Nd:YAG laser, dye lasers, excimer lasers, and ion lasers. The light from the laser (usually a beam) is passed through a set of lenses and/or mirrors to form a sheet, which is then used to illuminate the medium. This medium is either made up of fluorescent material or can be seeded with a fluorescent substance. The signal is usually captured by a CCD or CMOS camera (sometimes intensified cameras are also used). Timing electronics are often used to synchronize pulsed light sources with intensified cameras.
Basic principles
Comparison with other techniques
Advantages
- Unlike several other flow imaging techniques, PLIF may be combined with particle image velocimetry (PIV). This allows for the simultaneous measurement of a fluid velocity field and species concentration.
Limitations
flowfield must contain molecular species with an optical resonance wavelength that can be accessed by laser
temperature measurements typically require two laser sources
velocity measurements typically practical only for high Mach number flows (near sonic or supersonic)
signal-to-noise ratio often limited by detector shot-noise
fluorescence interferences from other species, especially from hydrocarbons in high pressure reacting flows
attenuation of laser sheet across flow field or reabsorption of fluorescence before it reaches detector can lead to systematic errors
Applications
See also
Fluorescence
Laser-induced fluorescence
Flow visualization
Particle image velocimetry (PIV)
References
Measurement
Fluid dynamics | Planar laser-induced fluorescence | [
"Physics",
"Chemistry",
"Mathematics",
"Engineering"
] | 448 | [
"Physical quantities",
"Chemical engineering",
"Quantity",
"Measurement",
"Size",
"Piping",
"Fluid dynamics"
] |
9,307,728 | https://en.wikipedia.org/wiki/Calcium%20aluminate%20cements | Calcium aluminate cements are cements consisting predominantly of hydraulic calcium aluminates. Alternative names are "aluminous cement", "high-alumina cement", and "Ciment fondu" in French. They are used in a number of small-scale, specialized applications.
History
The method of making cement from limestone () and low-silica bauxite () was patented in France in 1908 by Bied of the Pavin de Lafarge Company. The initial development was as a result of the search for a cement offering sulfate resistance. The cement was known as "Ciment fondu" and "Ciment électro-fondu" in French.
As indicated by Bied (1922), who was the inventor of this type of cement, the terms "Ciment fondu" ("fused cement") and "Ciment électro-fondu" ("electro-fused cement") refer only to the manufacturing process involving the melting of the base materials (CaO obtained after the decarbonation of , and ). This is because there is no temperature range in which it is possible to observe the gradual softening and clinkerization of these materials, as is the case with Portland cement at around 1450 °C. In the absence of a softening temperature, calcium aluminates are obtained directly by fusion of the precursor materials, and Bied (1922) clearly indicated his preference for the appellation "ciment alumineux" ("aluminous cement") referring to its composition rather than to a manufacturing process.
Subsequently, its other special properties were discovered, and these led to its future in niche applications.
By the 2010s, the product was found in the US market under the name FONDAG cement (FOND Aluminous Aggregate), sometimes referred to as ALAG (ALuminous AGgregate). FONDAG cement is a mix of up to 40 percent alumina, and is stable at high temperatures and thermal cycling from
Composition
CAC cement invented in 1908 by Bied is sulfate-free and hardens to give mainly hydrated calcium aluminates or carboaluminates (AFm phases: Aluminium Ferrite mono-substituted phases), sometimes accompanied with C–S–H as a minor component, while (portlandite) is absent. So, CAC cement must not be confused with calcium sulfo-aluminate (CSA) cement containing calcium sulfate and invented later in 1936.
The main constituent, and also the most reactive phase, of calcium aluminate cements is the monocalcium aluminate ( = , also written as CA in the cement chemist notation). It usually contains other calcium aluminates as well as a number of less reactive phases deriving from impurities in the raw materials. Rather a wide range of compositions is encountered, depending on the application and the purity of aluminium source used. Constituents of some typical formulations include:
The mineral phases all take the form of solid solutions with somewhat variable compositions.
Manufacture
The cement is made by fusing together a mixture of a calcium-bearing material (normally calcium oxide from limestone) and an aluminium-bearing material (normally bauxite for general purposes, or refined alumina for white and refractory cements).
The melting of the mixture is achieved at 1600 °C and is energy demanding. The more elevated temperature explains a part of its higher production costs than for the clinker of ordinary Portland cement sintered at 1450 °C.
The liquified mixture cools to a vesicular, basalt-like clinker which is ground alone to produce the finished product. Because complete melting usually takes place, raw materials in lump-form can be used. A typical kiln arrangement comprises a reverberatory furnace provided with a shaft preheater in which the hot exhaust gases pass upward as the lump raw material mix passes downward. The preheater recuperates most of the heat in the combustion gases, dehydrates and de-hydroxylates the bauxite and de-carbonates the limestone. The calcined material drops into the "cool end" of the melt bath. The melt overflows the hot end of the furnace into molds in which it cools and solidifies. The system is fired with pulverized coal or oil. The cooled clinker ingots are crushed and ground in a ball mill. In the case of high-alumina refractory cements, where the mix only sinters, a rotary kiln can be used.
Hydration reactions
CAC cements gain strength more rapidly than ordinary Portland cement (OPC). Sometimes, a retarder is needed to ensure a longer workability.
In contrast to Portland cements, calcium aluminate cements do not release calcium hydroxide (, portlandite, or lime) during their hydration.
The hydration reactions of calcium aluminate cements are very complex. The strength-developing phases are monocalcium aluminate (), dodeca-calcium hepta-aluminate (), and belite (), a dicalcium silicate. Calcium aluminoferrite (), monocalcium dialuminate (), gehlenite, and pleochroite contribute little to the concrete strength.
During the cement setting, the reactive aluminates react with water initially to form a mixture of hydrated phases expressed hereunder in normal oxide notation and also abbreviated in the more compact cement chemist notation (CCN) (CaO = C; = A; = H; and = S):
(),
(),
(), and gel,
the amounts of each is depending upon the curing temperature.
The first two hydrates subsequently decompose to a mixture of gel, and water, this process being called "conversion". Because of the loss of water, conversion causes an increase in porosity, which can be accompanied by a decrease in concrete strength. This need not be a problem in structural concrete provided that a sufficiently high cement content and a sufficiently low water/cement ratio are employed.
Structural stability issues: inappropriate use for general construction
The inappropriate use of calcium aluminate cements as a common construction material without special precautions has led to structural stability problems in buildings.
On 8 February 1974, the roof of a swimming pool collapsed in the UK. In 1984, the roof of a factory building in Uherské Hradiště in Czechoslovakia (built 1952) collapsed, killing 18 people. In Madrid, Spain, a large housing block nicknamed Korea (because it was built to house Americans during the Korean War), built was affected and had to be torn down in 2006. Also in Madrid the Vicente Calderón soccer stadium was affected and had to be partially rebuilt and reinforced.
Special applications
Because of their relatively high cost and delicate implementation, calcium aluminate cements are used in a number of restricted applications where performance achieved justifies costs:
for some concrete components, for which a rapid strength development is required, even at low temperatures. In this case, a sufficiently high cement content and a sufficiently low water/cement ratio are mandatory to minimize any possible structural stability problems and to increase the concrete durability.
as a component in blended cement formulations, for various properties such as ultra-rapid strength development and controlled expansion are required.
in refractory concretes, where strength is required at high temperatures.
as a protective liner (and repair material) against microbial corrosion such as in sewer infrastructures because of their high resistance to biogenic sulfide corrosion.
Sewer networks applications
The biogenic corrosion resistance of calcium aluminate cements is used today in three main applications:
Ductile iron pipe for waste water have an internal lining made of calcium aluminate cement mortar.
Concrete pipes for sewerage can be made either with full mass calcium aluminate cement concrete or with an internal liner of calcium aluminate cement mortar.
Rehabilitation of man-accessible sewer infrastructures with 100% calcium aluminate mortar using one of the following placing methods: low pressure wet spray, spinning head wet spray, or high pressure dry spray (gunite, shotcrete).
References
Bibliography
Cement
French inventions
Building materials | Calcium aluminate cements | [
"Physics",
"Engineering"
] | 1,687 | [
"Building engineering",
"Construction",
"Materials",
"Building materials",
"Matter",
"Architecture"
] |
9,307,899 | https://en.wikipedia.org/wiki/Ice%20pier | An ice pier or ice wharf is a man-made structure used to assist the unloading of ships in Antarctica. It is constructed by pumping seawater into a contained area and allowing the water to freeze. By repeating this procedure several times, additional layers are built up. The final structure is many metres in thickness, and strong enough to support container trucks. Operation Deep Freeze personnel constructed the first floating ice pier at Antarctica’s southernmost sea port at McMurdo Station in 1973. Ice piers have been in use each summer season since, at McMurdo's natural harbor at Winter Quarters Bay located at . The harbor is positioned on the southern tip of Ross Island.
Historically, two supply ships, a freighter and a tanker, arrive at the ice pier each summer, after an icebreaker opens a ship channel through pack ice. The ice pier's key function is to provide a platform for freight trucks to come alongside a supply ship to receive or offload cargo. Steel cables attached to shoreline hold the dock in a fixed position.
Port officials distribute freight arriving at the dock to McMurdo Station, nearby Scott Base, and to field camps as far away as the South Pole. Imports include virtually any materials needed to support personnel living and working in Antarctica. Exports range from items such as scientific ice core samples and human waste collected from field camps to broken equipment and recyclables for return to the United States for processing.
Ice piers typically have a lifespan of three to five years. Once an ice pier is no longer usable, icebreakers tow the pier to sea to be cast adrift.
Annual break-in opens ship channel
Ships docking at the McMurdo Station ice pier rely upon icebreakers opening a ship channel from Upper McMurdo Sound to Winter Quarters Bay. One or more icebreakers, depending upon seasonal conditions, will typically open a channel from long.
However, in 2005 icebreakers encountered more than of pack ice blocking entry to McMurdo Sound. The ice buildup occurred when a long iceberg (B15A) ran aground near Upper McMurdo Sound. Two icebreakers eventually broke a ship channel through to Winter Quarters Bay.
The ship channel provides a seaway for the few annual re-supply vessels and research ships which call upon the extraordinarily remote seaport at McMurdo Station. Preparation for the supply ships’ arrival includes icebreakers maintaining a uniform edge on the seaward side of the pier. The ship's skipper maneuvers the icebreaker to use its bow as a giant battering ram to scarf or shave jagged edges from the pier to facilitate ships tying up at the dock.
Ice pier expedites shipping
U.S. ships discharged cargo at temporary iceports in McMurdo Sound prior to the military's invention of the ice pier. Ships during that time moored alongside seasonal pack ice where military longshoremen offloaded cargo onto large snow sleds. Equipment operators then used snow cats and tractors to tow the freight over ice to McMurdo, a difficult and potentially dangerous operation. Tankers arriving with oil, diesel fuel, and gasoline were forced to dock as far away as from the harbour and pump their fuel ashore.
Beginning in 1964, icebreakers started opening a ship channel to Winter Quarters Bay where ships tied off to fast ice, a form of sea ice attached to the coast or ice wall such as Antarctica's Ross Ice Shelf. However, mooring to fast ice produced undesirable results. Warm water discharged from ships eroded ice at the rate of some three square kilometres every year.
Consequently, port authorities built a steel dock in 1972, which waves from a storm destroyed soon after. Builders came up with an alternative that same season. They constructed a block of ice, covered it with matting and straw and used it as a fender for a tanker that docked at the harbor in fall 1973. The ice fender became the forerunner to the contemporary ice pier.
McMurdo's dock is not without comparison. In 1987 workers constructed a similar pier in Mys Shmidta, a small seaport located in Chukotka, a far-eastern territory adjacent to Alaska on the Arctic Sea. And, like McMurdo, the Arctic ice pier facilitated getting ships to get closer to shore for loading cargo. The pier built in the former Soviet Union measured more than long.
Seawater construction
The ice piers deployed at McMurdo Station have grown in sophistication and size since the ice fender prototype. A contemporary pier is approximately long by wide and thick. Fleet operations personnel make the floating pier during the winter. They build upon naturally occurring frozen seawater in McMurdo Sound after the pack ice reaches approximately in thickness.
Subsequently, workers construct a snow berm to a depth of several feet along the perimeter of the soon-to-be ice pier. High-volume pumps then flood the pack ice with seawater to a depth of about . The seawater typically freezes solid within 24 hours. Personnel repeat the flooding until they achieve a thickness of .
Next a reinforcement mat of approximately of steel cable is secured to steel pipe embedded in the ice pier. The pier overall requires approximately of steel cable for construction, according to National Science Foundation permit documentation.
Workers repeat the entire process three more times until the ice pier is approximately thick. Wooden utility poles drilled about four deep into the final ice pier support electrical and telephone service to the pier. Moreover, during the final construction phase, personnel mount shorter poles in the ice edge to serve as bollards to secure the pier to the shore at McMurdo. A layer of volcanic gravel tops off the pier to provide a non-slip surface and to insulate the ice from the summer sun.
Experience has shown that ice piers have a lifespan of three to five years. Factors such as stress cracking and erosion shorten the duration. In addition, storm surges, wave action, contact with vessels, and the warm water discharge from ships contribute to degradation of the pier's seaward edge.
Ice pier limits discovered
Ice pier operations at the world's most southern port have not been without mishap. The principal threat is onshore winds with accompanying high seas and ocean swells, which can severely damage the ice pier. For example, in 1993, high winds and heavy swells caused major cracks in the wharf. Rough seas produced movements of several feet between individual sections of the pier, according to a National Science Foundation (NSF) report. The resulting damage prevented vehicles from traveling onto the pier for repairs.
Conditions worsened the following week when additional storms pushed ice, slush, and sea water onto the pier, flooding about one-half of the dock. The inundation on the pier's seaward side reached high and froze nearly immediately, according to the NSF report. The strategy to repair the storm damage included adding additional restraining cables followed by routine flooding to build up the ice thickness.
Notable incidents with damaged ice piers at McMurdo Station include an event 10 years earlier. The ice pier had been in use four seasons in 1983 when the freighter USNS Southern Cross docked at Winter Quarters Bay. Operation Deep Freeze officials pressed the pier into extended service in order for the freighter to make an unprecedented two supply runs in one season from Port Lyttelton, New Zealand, to McMurdo. However, efforts to extend the ice pier's lifespan resulted in a cargo truck breaking through the ice. The driver of the truck standing atop the container leapt to safety, receiving minor injuries.
The most recent incident in 2010 occurred when a 10-year storm blew in causing white cap waves to wash the pier out to sea. It was assumed to be lost with the Jamesway hut, telephone pole, bollards, and other equipment still on it. Found during the austral summer in 2011, the equipment was ferried by helicopter back to McMurdo. A tracking beacon was left on the Ice Pier as it drifted out to sea.
Maintenance gives way to disposal
Maintenance on the ice pier begins at the end of the austral summer. Equipment operators remove the gravel and store it for the next season. Removing the gravel prevents the gravel's insulating qualities from inhibiting further thickening of the ice during winter. Winter operations include plowing insulating snow from the dock and flooding the pier with seawater to help sustain the ice strength.
However, when the pier is no longer usable, a permit from the Antarctic Conservation Act allows for an icebreaker to tow the ice pier out to McMurdo Sound and cast it adrift. Preparations for dumping include:
Pumice surface is removed
Wooden poles are cut off just above the surface of the ice
All equipment, materials, and debris are removed
After release at sea, currents and southerly winds drive the ice pier north towards the Ross Sea and into the circumpolar currents of the Southern Ocean. A beacon mounted on the pier allows for tracking and serves as a warning to ships. The pier mixes with pack ice and eventually melts, a process that can take years, according to NSF estimates. Consequently, some of steel cable and of pipe used in its construction sink to the ocean floor
U.S. government reports vary regarding the fate of the untreated wooden bollards used in the ice pier. The wood in some instances is reported as weighted so as to sink. Yet a 1999 ocean dumping permit notes that: "the short lengths of wooden poles will float in the ocean for several months before becoming waterlogged and eventually sinking to the ocean floor."
See also
Icebreaker
Iceport
Ice road
McMurdo Sound
McMurdo Station
Operation Deep Freeze
Sea ice
Scott Base
Winter Quarters Bay
Notes
References
Antarctic Sun.
Federal Register Environmental Documents
The Press; Christchurch, New Zealand.
Seattle Post-Intelligencer.
USA Today
Transport in Antarctica
Ross Island
Piers
Pier
Pier
Buildings and structures made of snow or ice | Ice pier | [
"Physics"
] | 1,997 | [
"Ice in transportation",
"Physical phenomena",
"Earth phenomena",
"Sea ice",
"Physical systems",
"Transport"
] |
9,308,170 | https://en.wikipedia.org/wiki/Tapesia%20yallundae | Tapesia yallundae is the causal agent for a variety of cereal and forage grass diseases. The anamorph of T. yallundae is the W-type strain of Pseudocercosporella herpotrichoides. The R-type strain of Pseudocercosporella herpotrichoides is now known as Tapesia acuformis.
Morphology
Produces two types of mycelium - one vegetative, yellow-brown, linear, and branching, the other dark and stromalike. Conidiophores are simple or sparingly branched. Conidia (1.5-3.5 x 37-70 μm) are hyaline, curved, and mostly five- to seven-celled. Sclerotia or sclerotialike stromatic mycelium, at first white to yellow-brown but later dark brown, may also be found on the lesions of infected plants.
Black apothecia, 0.2 to 0.5 mm of diameter, form at the base of host culms. Apothecium contain cylindric to fusoid asci, of 35 to 38 μm x 5.9 to 7.4 μm. Ascospores are hyaline, fusoid, 0-1 septate, with a rounded end and an average size of 8.9 μm (7.4 to 10.3) x 2.07 μm (1.95 to 2.34).
Growth media
Tapesia yallundae can be grown on a moist, sterile wheat and barley straw, oat kernels, and a variety of simple agar media, preferably supplemented with wheat extract. Sporulation in vitro tends to originate from loose sporodochai. Young colonies on potato-dextrose agar are gray, compact and mounded.
Molecular characterization
Polymerase chain reaction (PCR) combined with restriction enzyme digestion of an amplified ribosomal DNA fragment, are now used to characterize T. yallundae isolates. Novartis produces a polymerase chain reaction (PCR) diagnostic tool that provides cereal growers with an efficient means for checking the progression of eyespot disease in cereals. The tool reveals the presence and extent of disease before symptoms develop and can identify the different eyespot strains including the W-type (Tapesia yallundae''') and R-type (Tapesia acuformis).
Host speciesAegilops cylindrica1,, Aegilops ovata1,, Aegilops sp.1,, Aegilops triuncialis1,, Agropyron cristatum1,, Agropyron dasystachyum1,, Agropyron inerme1,, Agropyron repens1,, Agropyron riparium1,, Agropyron sp.1,, Avena fatua1,, Avena sativa1,, Avena sp.1,, Balsamorhiza sp.1,, Bromus carinatus1,, Bromus inermis1,, Bromus japonicus1,, Bromus sterilis1,, Bromus tectorum1,, Delphinium sp1,., Festuca idahoensis1,, Hordeum distichon1,, Hordeum vulgare1,, Koeleria cristata1,, Lithospermum ruderale1,, Lomatium triternatum1,, Poa sandbergii1,, Poa secunda, Secale cereale, Sitanion hystrix1,, Trisetum aestivum1,, Triticum aestivum1,, Triticum dicoccum1,, Triticum durum1,, Triticum monococcum1,, Triticum sp.1,, Triticum spelta1,, Triticum vulgare''1,
Notes
1. USDA ARS Fungal Database
Main diseases
Eyespot of wheat; eyespot of barley; eyespot of rye.
Geographical distribution
Notes
1. USDA ARS Fungal Database
2.
3.
4.
5.
Sources
Index Fungorum
USDA ARS Fungal Database
References
Fungal plant pathogens and diseases
Barley diseases
Wheat diseases
Dermateaceae
Fungus species | Tapesia yallundae | [
"Biology"
] | 907 | [
"Fungi",
"Fungus species"
] |
9,308,202 | https://en.wikipedia.org/wiki/Mutilated%20chessboard%20problem | The mutilated chessboard problem is a tiling puzzle posed by Max Black in 1946 that asks:
Suppose a standard 8×8 chessboard (or checkerboard) has two diagonally opposite corners removed, leaving 62 squares. Is it possible to place 31 dominoes of size 2×1 so as to cover all of these squares?
It is an impossible puzzle: there is no domino tiling meeting these conditions. One proof of its impossibility uses the fact that, with the corners removed, the chessboard has 32 squares of one color and 30 of the other, but each domino must cover equally many squares of each color. More generally, if any two squares are removed from the chessboard, the rest can be tiled by dominoes if and only if the removed squares are of different colors. This problem has been used as a test case for automated reasoning, creativity, and the philosophy of mathematics.
History
The mutilated chessboard problem is an instance of domino tiling of grids and polyominoes, also known as "dimer models", a general class of problems whose study in statistical mechanics dates to the work of Ralph H. Fowler and George Stanley Rushbrooke in 1937. Domino tilings also have a long history of practical use in pavement design and the arrangement of tatami flooring.
The mutilated chessboard problem itself was proposed by philosopher Max Black in his book Critical Thinking (1946), with a hint at the coloring-based solution to its impossibility. It was popularized in the 1950s through later discussions by Solomon W. Golomb (1954), George Gamow and Marvin Stern (1958), Claude Berge (1958), and Martin Gardner in his Scientific American column "Mathematical Games" (1957).
The use of the mutilated chessboard problem in automated reasoning stems from a proposal for its use by John McCarthy in 1964. It has also been studied in cognitive science as a test case for creative insight, Black's original motivation for the problem. In the philosophy of mathematics, it has been examined in studies of the nature of mathematical proof.
Solution
The puzzle is impossible to complete. A domino placed on the chessboard will always cover one white square and one black square. Therefore, any collection of dominoes placed on the board will cover equal numbers of squares of each color. But any two opposite squares have the same color: both black or both white. If they are removed, there will be fewer squares of that color and more of the other color, making the numbers of squares of each color unequal and the board impossible to cover. The same idea shows that no domino tiling can exist whenever any two squares of the same color (not just the opposite corners) are removed from the chessboard.
Several other proofs of impossibility have also been found. A proof by Shmuel Winograd starts with induction. In a given tiling of the board, if a row has an odd number of squares not covered by vertical dominoes from the previous row, then an odd number of vertical dominoes must extend into the next row. The first row trivially has an odd number of squares (namely, 7) not covered by dominoes of the previous row. Thus, by induction, each of the seven pairs of consecutive rows houses an odd number of vertical dominoes, producing an odd total number. By the same reasoning, the total number of horizontal dominoes must also be odd. As the sum of two odd numbers, the total number of dominoes—vertical and horizontal—must be even. But to cover the mutilated chessboard, 31 dominoes are needed, an odd number. Another method counts the edges of each color around the boundary of the mutilated chessboard. Their numbers must be equal in any tileable region of the chessboard, because each domino has three edges of each color, and each internal edge between dominoes pairs off boundaries of opposite colors. However, the mutilated chessboard has more edges of one color than the other.
If two squares of opposite colors are removed, then the remaining board can always be tiled with dominoes; this result is Gomory's theorem, after mathematician Ralph E. Gomory, whose proof was published in 1973. Gomory's theorem can be proven using a Hamiltonian cycle of the grid graph formed by the chessboard squares. The removal of any two oppositely colored squares splits this cycle into two paths with an even number of squares each. Both of these paths are easy to partition into dominoes by following them. Gomory's theorem is specific to the removal of only one square of each color. Removing larger numbers of squares, with equal numbers of each color, can result in a region that has no domino tiling, but for which coloring-based impossibility proofs do not work.
Application to automated reasoning
Domino tiling problems on polyominoes, such as the mutilated chessboard problem, can be solved in polynomial time, either by converting them into problems in group theory, or as instances of bipartite matching. In the latter formulation, one obtains a bipartite graph with a vertex for each available chessboard square and an edge for every pair of adjacent squares; the problem is to find a system of edges that touches each vertex exactly once. As in the coloring-based proof of the impossibility of the mutilated chessboard problem, the fact that this graph has more vertices of one color than the other implies that it fails the necessary conditions of Hall's marriage theorem, so no matching exists. The problem can also be solved by formulating it as a constraint satisfaction problem, and applying semidefinite programming to a relaxation.
In 1964, John McCarthy proposed the mutilated chessboard as a hard problem for automated proof systems, formulating it in first-order logic and asking for a system that can automatically determine the unsolvability of this formulation. Most considerations of this problem provide solutions "in the conceptual sense" that do not apply to McCarthy's logic formulation of the problem. Despite the existence of general methods such as those based on graph matching, it is exponentially hard for resolution to solve McCarthy's logical formulation of the problem, highlighting the need for methods in artificial intelligence that can automatically change to a more suitable problem representation and for knowledge representation systems that can manage the equivalences between different representations. Short proofs are possible using resolution with additional variables, or in stronger proof systems allowing the expression of avoidable tiling patterns that can prune the search space. Higher-level proof assistants are capable of handling the coloring-based impossibility proof directly; these include Isabelle, the Mizar system, and Nqthm.
Related problems
A similar problem asks if a wazir starting at a corner square of an ordinary chessboard can visit every square exactly once, and finish at the opposite corner square. The wazir is a fairy chess piece that can move only one square vertically or horizontally (not diagonally). Using similar reasoning to the mutilated chessboard problem's classic solution, this wazir's tour does not exist. For example, if the initial square is white, as each move alternates between black and white squares, the final square of any complete tour is black. However, the opposite corner square is white. This sort of tour of a chessboard also forms the basis of a type of puzzle called Numbrix, which asks for a tour in which the positions of certain squares match given clues. The impossibility of a corner-to-corner tour shows the impossibility of a Numbrix puzzle with the clues 1 in one corner and 64 in the opposite corner.
De Bruijn's theorem concerns the impossibility of packing certain cuboids into a larger cuboid. For instance, it is impossible, according to this theorem, to fill a box with cuboids. The proof uses a similar chessboard-coloring argument to the mutilated chessboard problem.
References
External links
Gomory's Theorem by Jay Warendorff, The Wolfram Demonstrations Project.
Tiling puzzles
Logic puzzles
Mathematical chess problems
Unsolvable puzzles | Mutilated chessboard problem | [
"Physics",
"Mathematics"
] | 1,675 | [
"Mathematical chess problems",
"Unsolvable puzzles",
"Tessellation",
"Recreational mathematics",
"Tiling puzzles",
"Mathematical problems",
"Symmetry"
] |
9,309,401 | https://en.wikipedia.org/wiki/Architecture%20of%20Yemen | The architecture of Yemen dates back to ancient times, when it was part of a tradition of South Arabian architecture. Developments continued during the Islamic period, displaying both local characteristics and external influences. The historic cities and towns of Yemen are known for their traditional tower-houses.
Ancient Yemen
In Antiquity, Yemen was home to several wealthy city-states and an indigenous tradition of South Arabian architecture. Historical texts and archeological evidence indicate that large and richly-decorated palaces existed in several cities, such as the Ghumdan Palace in Sanaa. Most of these structures have not been preserved, although the remains of Shabwa, the former capital of Ḥaḍramawt, provide some evidence of their structure.
In the first millennium BCE, the first large South Arabian kingdom, Saba', was created by the Sabaeans with its center at Marib, alongside other kingdoms in the region. Its influence reached as far as Ethiopia. The oases of this region grew their agriculture with the help of floodwaters. Marib city and some constructions in the Wadi Dhana valley were likely established as early as the 2nd millennium BCE and artificial irrigation may date as far back as the third millennium BCE. The ancient Marib Dam was first built in the 6th century BCE and repaired up until the 5th or 6th century CE. It was a major feat of engineering in the ancient world and was used to harness the water of biannual floods, allowing for more systematic irrigation. The first dam was a basic earth-built structure around long and probably about high, situated between two rock formations. A second dam was built towards 500 BC as a sloping rampart with a triangular cross section. It stood about high and was faced with stone and mortar. The next major reconstruction was undertaken by the Himyarites in or after the late 2nd century CE, who rebuilt it as another earthen structure faced with stone, this time long, high, and complete with more sophisticated hydraulic systems.
Classical Sabaean temples were structures with an inner courtyard in peristyle form (surrounded by porticoes). An example of this is the Awwam Temple or Mahram Bilqis, which was erected at the edge of a large, roughly oval, walled enclosure. Some temples in the Jawf region had a hypostyle form. In both the Jawf and Hadramawt regions, there were also temples consisting of an interior space divided by two rows of three or four pillars, which in Hadramawt often had bent entrances. The art of these temples is characterized by their abstractness, as exemplified by their distinctive ibex friezes. Aside from temple architecture, it also appears that the traditional Yemeni tower-house emerged around this period, built with stone foundations and upper sections in wood and clay.
In the first century BCE, the Romans arrived in the Red Sea region, resulting in a shift in power and trade networks. A new Himyarite kingdom took control of Yemen. In the same century, the Palace of Shaqir (the "Towering One") was built in Shabwa. It was destroyed circa 230 CE but subsequently rebuilt and restored. The building, made of mudbrick and wood on stone foundations, consisted of a towering multi-story structure attached to a courtyard surrounded by two-story galleries. The galleries had octagonal pillars covered with carved vine motifs and capitals carved with images of griffins. Wall frescoes depicted scenes with women and other decorative motifs. The ornamental repertoire displays links with late Hellenistic art of the time.
As the Himyarite kingdom grew stronger, it cultivated a period of peace and cultural exchanges. The capital was at Zafar (near Yarim), which was enclosed by double walls and nine gates. It had a citadel, the Raidan fortress or Raydan Palace, which was the seat of the Himyarite kings. Other stone castles were built in various locations. By the 5th century AD, there is evidence that the indigenous styles were being influenced by Byzantine and Late Antique Mediterranean art. In the 5th and 6th centuries, Christianity spread in the region and churches were built. Abraha, a local Aksumite ruler who made Sanaa his capital, built a cathedral there circa 567, allegedly with the help of two architects provided by Byzantine emperor Justinian I. The Ghumdan Palace, which was probably first built around 200 CE, was preserved in collective memory and probably influenced the architecture of future palaces. It apparently had many stories, a transparent roof of alabaster, coloured stone inlay decorating its façades, and animal statues.
Islamic period
7th to 13th centuries
Yemen was Islamized in the 7th century, but few buildings from the early Islamic period have been preserved intact today. It is only from the 10th century onward that distinctive Islamic architectural styles can be documented. Yemeni architecture can be characterized as "conservative", as the Yemeni people combine their pre-Islamic and Islamic past. This philosophy is demonstrated in the construction of the Mosque of Sulayman ibn Dawud in Marib, which was built directly on top of an old temple.
The oldest mosque in Yemen is believed to be either the Great Mosque of Janad (located in Janad, northeast of Ta'izz) or the Great Mosque of Sanaa. The mosque in Janad was reportedly founded in 627–8 (6 AH) by Mu'adh ibn Jabal. Traditional Muslim sources claim the Great Mosque of Sanaa was originally built on the orders of Muhammad, carried out by one of his companions. A study by 'Abd al-Muhsin al-Mad'aj suggests that it was most likely built in 633.
After the early caliphal period, the region was ruled by various dynasties including the Sulayhids (11th–12th centuries). One type of mosque attested around this time consists of a large cubic chamber with one entrance, which had antecedents in the pre-Islamic temple architecture of the region. Examples include the al-Abbas Mosque in Asnaf (1126, near Sanaa) and the Mosque of Sarha (13th century, near Ibb), which both have richly-decorated ceilings carved and painted with interlacing star-like patterns. Another type consisted of a rectangular chamber, with a transverse orientation, with multiple entrances and supporting columns inside, sometimes preceded by a courtyard. Examples of this include the Mosque of Sulayman ibn Dawud (1089, reusing ancient remains) at Marib and the congregational mosque of Damar (12th–13th century). This type also had pre-Islamic antecedents.
The hypostyle mosque with courtyard, which was more common throughout much of the Islamic world at the time, was comparatively rare in early Islamic Yemen. The Great Mosque of Sanaa was one of the few mosques of this type in the region. After its foundation, it was rebuilt in larger form on the orders of the Umayyad caliph al-Walid (). It was reconstructed again in 753–4 and after 875. On the latter occasion it was rebuilt with stone and gypsum walls and a teak roof, though these too have been repaired and restored over the centuries. The mosque's decoration reflects the multiple restorations but also exemplifies the best artistic techniques in Yemen over the centuries, including carved and painted wood, carved stone, and carved stucco. The earliest known example of a monumental entrance portal in Yemen was also added to the Great Mosque of Sanaa at an entrance along the qibla wall in 1158.
Other examples of early hypostyle courtyard mosques in the region are the Great Mosque of Shibam Kawkaban (9th–10th century) and the Mosque of Arwa bint Ahmad (1087–9) in Jibla. The Great Mosque of Janad also has a courtyard form, but it was rebuilt in its present form circa 1200 and it's unclear what its original layout would have been. The Great Mosque of Shibam, like the Great Mosque of Sanaa, has a richly-painted ceiling, though its columns and their capitals resemble pre-Islamic forms. The Mosque of Arwa bint Ahmad was reportedly part of a Sulayhid palace before being converted to a mosque. Unlike other local hypostyle mosques at the time, it features a dome over the space in front of its mihrab, which is likely due to Fatimid architectural influence via the Sulayhids (who acknowledged the Fatimids as caliphs). Its mihrab is the oldest surviving well-decorated mihrab in Yemen, covered in carved arabesques and featuring a rectangular frame with a Kufic inscription. This design was imitated in later mihrabs in the region.
For many centuries, one of the most important cites in the regions was Zabid, which was the capital under several successive dynasties, starting with the Ziyadids (9th to 11th centuries). It has the highest concentration of historic religious buildings of any city in Yemen aside from Sanaa. Two of the most important mosques are the Great Mosque of Zabid and the al-Asha'ir Mosque, both hypostyle courtyard mosques built by the Ziyadid ruler al-Husayn ibn Salamah (). The brick minaret of the Great Mosque of Zabid is one of the oldest surviving minarets in Yemen, though it was added later under the Ayyubids ().
13th century and after
Mosques and madrasas
The Ayyubids introduced domed mosque types as well as Sunni-syle madrasas to the region, but none of their buildings in Yemen have survived. However, the Rasulids after them (13th–15th centuries) were prolific patrons of architecture and perpetuated these new building types, influenced by their political links with Egypt. The Rasulids were based in Ta'izz and several of their buildings survive there, including the Muẓaffariyya Mosque (built by Sultan al-Malik al-Muẓaffar Yusuf sometime between 1249 and 1295) and several madrasas that also incorporate mosques.
The domed mosque type was a significant innovation in the history of religious architecture in Yemen and demonstrates a greater integration of architectural ideas from the surrounding Islamic world. One of its earliest examples was the Mosque of al-Mahjam. Its minaret, which is very similar to that of the Great Mosque of Zabid, is all that remains of the mosque, but records indicate that its prayer hall had many domes. While Ayyubid structures in Yemen have not survived, it's possible that some of them served as prototypes for later domed mosques in the region. Art historian Barbara Finster also suggests that the Asadiyya Madrasa in Ibb, built in the first half of the 13th century, may have been the model for later domed mosques, as it has a prayer hall consisting of a central dome flanked by pairs of domes on either side.
Most of the Rasulid religious buildings were characterized by a domed prayer hall that is wider than it is deep. This layout was also continued in the architecture of the Tahirids who succeeded the Rasulids in the 15th century. Aside from the major dynastic constructions, similar but smaller domed mosques appeared throughout the areas occupied by a Sunni population. This transversal domed layout thus distinguished Sunni sanctuaries from those built in areas controlled by the contemporary Zaydi imams, who were Shi'a. This floor plan is exemplified by the Muẓaffariyya Mosque, which has a large central dome flanked by two consecutive pairs of smaller domes to the west and three to the east, each of these leading to another large domed chamber at the western and eastern ends of the hall. The design of this mosque was innovative in its inclusion of large windows in the qibla wall, thus introducing much more light to the interior than in more traditional mosque designs. The exterior façade of the qibla wall is also decorated with friezes of interlacing motifs.
The oldest madrasas in Yemen also date from the Rasulid period, including the aforementioned Asadiyya Madrasa (before 1258), the Mu'tabiyya Madrasa in Ta'izz (1392), and the Ashrafiyya Madrasa (built by Sultan al-Malik al-Ashraf in 1397–1401) also in Ta'izz. Unlike contemporary madrasas in Egypt, the Rasulid madrasas do not follow the four-iwan layout. The Mu'tabiyya and Ashrafiyya madrasas both have rectangular floor plans with a domed prayer hall to the north and a courtyard to the south flanked by smaller domed and vaulted chambers on either side which were used for teaching.
Barbara Finster considers the Mu'tabiyya to be a high point of Yemeni architecture thanks to its meticulous and deliberate planning. It has a prayer hall of six equal domed bays which is surrounded by a U-shaped passage to the west, south, and east. The west and east wings of this passage are open to the outside via an arcade and terminate with small domed chambers at their north ends. On the south side of it is a rectangular courtyard flanked by teaching rooms to the east and west, with the projecting entrance gate and its vestibule are located south of the courtyard. The slightly later Ashrafiyya represents essentially a larger-scale version of the same design, further distinguished by imposing twin minarets near its southern corners. It also has an entrance portal built with stones of different colour carved with scallopped motifs and a multifoil arch, a style most likely borrowed from Upper Mesopotomia. Most of the many small madrasas across Yemen simply imitated the traditional design of local mosques while adding an additional lecture hall across the courtyard from the prayer hall. An example that features exceptionally rich stucco decoration on the courtyard façades is the Farhaniyya Madrasa in Zabid (before 1432).
The mosques built under the early Zaydi imams include the Mosque of Zafar Dhibin () and the Mosque of al-Hadi (1339–40) in Sa'da. The Mosque of Zafar Dhibin, which was part of a palace complex, looks superficially like a courtyard mosque but its courtyard lacks a covered gallery (riwaq) on the south side and it is dominated by two attached tombs. The tomb of Imam al-Mansur Billah sits opposite the prayer hall on the same axis as the mosque's mihrab. The prayer hall's courtyard façade is decorated with carved stucco highlighted with gray-green faience tiles and an arcade of mixtilinear or trefoil-like arches that could reflect a distant Maghebi influence via Egypt. Inside, the prayer hall has richly-decorated coffered ceilings and its three central naves leading towards the mihrab are taller than the others. This rich and particular decorative is program is not known in other courtyard-type mosques in Yemen. The al-Hadi Mosque has two parts, one of which has a wide but shallow courtyard with a prayer hall to the north and a series of tombs around the other sides, similar in conception to the Zafar Dhibin Mosque. The second part is a larger extension to the north, which includes a rectangular courtyard with a freestanding minaret inside it. The prayer hall has both longitudinal and transversal rows of arches (i.e. running perpendicular and parallel to the qibla wall. Unlike the Zafar Dhibin Mosque, decoration is absent in most of the hall except for the domed bay in front of the mihrab.
Minarets in the later Rasulid period were strongly influenced by Egyptian Mamluk minarets, with shafts divided into multiple levels with differing designs. The minarets built under the early Zaydi imams were generally simpler, with a mostly smooth circular shaft set on a square base.
With the advent of Ottoman rule in Yemen from 1538 to 1636, Rasulid-style architecture continued to be the local norm in Sunni-controlled areas, but elements of Ottoman architecture began to be introduced in the late 16th century. The clearest monument of Ottoman inspiration is the Bakiriyya Mosque in Sanaa from 1597, which has a large dome and four corner turrets, but this design does not seem to have inspired later buildings.
Tombs
In this same period, Zaydi imams in northern Yemen were buried in richly-decorated domed tombs which were among the only significant examples of this type of building in Yemen at the time. The tombs at Zafar Dhibin are one of the earliest examples of prominent Zaydi tombs, dating to the early 13th century. Another major complex of Zaydi domed tombs, dating generally from the 14th and 15th centuries, is the one attached to the Mosque of al-Hadi in Sa'da. The domed structures have been built up next to each other and are now interconnected. They were usually open on three sides, with a mihrab on the qibla side, and covered by either simple domes or more ornate gadrooned domes. The interiors are very richly decorated with inscription bands and carved stucco, in contrast with the mostly plain mosque. A more expansive but exceptional layout is found in the tomb of Imam Salah ad-Din (d. 1391) in Sanaa, where the domed chamber is also flanked to the north by an iwan with a mihrab, to the south by an apse, and to the west by another rectangular chamber. Richly carved and painted wooden cenotaphs were added over the graves of some 18th-century imams.
Unlike the Zaydi imams, the Rasulid rulers were normally buried in more modest tombs attached to their madrasas. The graves inside the mausoleum of Sultan al-Ashraf and his family (attached to the Ashrafiyya Mosque) are nonetheless marked by lavish cenotaphs built as domed baldaquin-style elements with carved and gilded stucco decoration.
Domed mausoleums are also a tradition in the Hadramawt valley, where they usually covered the graves of local Muslim saints (awliya), such as the local Saiyids. These are often built as open kiosks consisting of domes resting on four pillars, with the space between the pillars later closed with walls or screens. The graves themselves were often covered by a wooden or bronze sarcophagus, which could be embellished with carved decoration and inscriptions. The most important tombs, which also acted as religious sanctuaries that received pilgrims, were typically rebuilt and expanded over time to become some of the most important monuments in the area. Among the most notable sanctuaries is Qabr Hud. In nearby Tarim, the oldest domed tomb is that of Mas'ud ibn Yamani (circa 1250). The town of Mashhad also hosts several large domed mausoleums of high quality construction. The oldest of the Mashhad tombs may be dated to 1591, though all the mausoleums were probably rebuilt in the 19th century.
Domestic architecture
Overview
Yemen is notable for its historic tower-houses, built on two or more floors. These houses vary in form and materials from region to region. They are typically built of mud (either rammed earth or sun-dried mud-brick), stone, or a combination of both, with timber used for roofs and floors. In some cases, as at Sanaa, the lower floors are built in heavier stone and the upper floors are built in lighter brick. Mud is sometimes mixed with straw and the walls are sometimes finished with lime. Coral stone is also used in coastal towns. Traditionally, the ground floor could be used for practical functions such as agriculture, the middle floors consisted of various multi-functional rooms, and the top floor often had a large reception room (mafraj) which enjoyed the best views.
Decoration of houses is often executed with gypsum, lime or some other plaster. At Sanaa, typical designs consist of bands of geometric motifs on the exterior created with protruding bricks that are whitewashed. Plasterwork is also found around the windows, and geometric or floral motifs can be used in coloured glass within the semicircular fanlights. This style can be seen also be seen at Dar al-Hajar, a palace built on a rocky outcrop in Wadi Dahr (15 kilometres north of Sanaa), dating to the 1930s, which features rich gypsum decoration and coloured glass fanlights.
Some villages and towns, such as Rada'a, were built around a fortified citadel (e.g. the Citadel of Rada'a), others were encircled by a high mud-brick wall (e.g. Shibam), and some were built so that the houses themselves formed an outer wall along an elevated position (e.g. Khawlan).
While these structures are repaired and restored over time, this architectural style has remained generally unchanged for hundreds of years. The old city of Sanaa is a prominent example which preserves many of these houses. Since 1986 it is a UNESCO World Heritage Site, although its conservation is threatened by the ongoing Yemeni Civil War. The oldest house in the city is believed to one of stone and earth located in the Harat al-'Alami area, as its existence is documented as early as the 14th century.
Regional variations
Various different styles of houses are found across different regions of Yemen. The mud-brick houses in the Hadramawt valley are especially tall, with Shibam being among the most famous. Locals were likely motivated to build their houses tall both as protection from the frequent tribal warfare in the region as well as to maximize the amount of land that could be preserved for agriculture in the dry valley. Generally, houses were entered via a single external door leading to a central passage and staircase. In tall houses, the first two floors had very few windows, if any, and were occupied by storage rooms for goods and animals, while the habitable rooms occupied the third level and above. The first habitable level included reception rooms for visitors while the private family areas were located on the floors above. Some of the largest rooms on the upper floors had external terraces.
Shibam has a unique concentration of very tall houses, which are built in mud-brick with stone foundations. Their walls taper from nearly thick at the bottom to less than at the top. Their exterior was usually covered with a plaster made of mud mixed with straw, giving them a warm brown colour, except for the highest stories, which were covered with a white lime plaster.
At Say'un (or Seiyun), the Say'un Palace is the largest single building in the Hadramawt valley and one of the largest mud-brick structures in the world. It was the royal residence of the Kathiris, who ruled an autonomous sultanate in the region up to 1967. In both Say'un and nearby Tarim, the houses incorporate Southeast Asian, Indian, or colonial European influences due to the history of local notables working in Indonesia and other parts of the world from the 19th century onward, returning with knowledge of foreign styles and new amenities. Some of the mansions and villas they built had outer walled enclosures. Tarim includes a number of large square-plan palaces from the Kathiri period. The most impressive is that built for Sayyid Umar ibn Shaykh al-Kaf, which has tall windows, an overall South Asian or Indonesian appearance, and whose exterior was once painted in deep blue.
At Sa'da and nearby villages, traditional houses are built with a mud and straw mixture and have a tapered shape, with the top of the house marked by pointed protrusions of gypsum. Some houses have window panes made of alabaster.
In the Tihama plain along the coast, including towns like Zabid, the buildings are instead built low, with one or two stories. They tend to be built of reeds and palm wood in the north or of rubble stone and brick in the south. Houses in Zabid tend to also omit exterior decoration and focus on interior decoration instead.
References
Citations
Bibliography
Further reading
Architectural history | Architecture of Yemen | [
"Engineering"
] | 4,936 | [
"Architectural history",
"Architecture"
] |
9,309,794 | https://en.wikipedia.org/wiki/Coset%20construction | In mathematics, the coset construction (or GKO construction) is a method of constructing unitary highest weight representations of the Virasoro algebra, introduced by Peter Goddard, Adrian Kent and David Olive (1986). The construction produces the complete discrete series of highest weight representations of the Virasoro algebra and demonstrates their unitarity, thus establishing the classification of unitary highest weight representations.
References
Conformal field theory
Lie algebras | Coset construction | [
"Physics"
] | 87 | [
"Quantum mechanics",
"Quantum physics stubs"
] |
9,309,912 | https://en.wikipedia.org/wiki/Calyculin | Calyculins are natural products originally isolated from the marine sponge Discodermia calyx. Calyculins have proven to be strong serine/threonine protein phosphatase inhibitors and based on this property, calyculins might be potential tumor-promoting agents.
A laboratory synthesis of calyculin A has been reported.
Biosynthesis
Calyculin A is biosynthesized as a pyrophosphate containing phosphocalyculin A protoxins by a hybrid PKS-NRPS pathway within the sponge bacterial symbiont, "Candidatus Entotheonella" sp.
References
Organophosphates
Nitriles
Spiro compounds | Calyculin | [
"Chemistry"
] | 150 | [
"Functional groups",
"Organic compounds",
"Nitriles",
"Organic compound stubs",
"Organic chemistry stubs",
"Spiro compounds"
] |
9,310,254 | https://en.wikipedia.org/wiki/Multilevel%20queue | Multi-level queueing, used at least since the late 1950s/early 1960s, is a queue with a predefined number of levels. Items get assigned to a particular level at insert (using some predefined algorithm), and thus cannot be moved to another level (unlike in the multilevel feedback queue). Items get removed from the queue by removing all items from a level, and then moving to the next. If an item is added to a level above, the "fetching" restarts from there. Each level of the queue is free to use its own scheduling, thus adding greater flexibility than merely having multiple levels in a queue.
Process Scheduling
Multi-level queue scheduling algorithm is used in scenarios where the processes can be classified into groups based on property like process type, CPU time, IO access, memory size, etc. One general classification of the processes is foreground processes and background processes. In a multi-level queue scheduling algorithm, there will be 'n' number of queues, where 'n' is the number of groups the processes are classified into. Each queue will be assigned a priority and will have its own scheduling algorithm like Round-robin scheduling or FCFS. For the process in a queue to execute, all the queues of priority higher than it should be empty, meaning the process in those high priority queues should have completed its execution. In this scheduling algorithm, once assigned to a queue, the process will not move to any other queues.
Consider the following table with the arrival time, execute time and type of the process (foreground or background - where foreground processes are given high priority) to understand non pre-emptive and pre-emptive multilevel scheduling in depth with FCFS algorithm for both the queues:
See also
Fair-share scheduling
Lottery scheduling
References
Scheduling algorithms | Multilevel queue | [
"Technology"
] | 376 | [
"Computing stubs",
"Computer science",
"Computer science stubs"
] |
9,311,082 | https://en.wikipedia.org/wiki/Tapesia%20acuformis | Tapesia acuformis is the causal agent for a variety of cereal and forage grass diseases. The anamorph of T. acuformis was formerly known as the R-type strain of Pseudocercosporella herpotrichoides. The W-type strain of P. herpotrichoides is now known as T. yallundae.
Management
Agropyron elongatums genetic resistance to this disease is useful to introgress into wheat.
See also
List of rye diseases
List of wheat diseases
References
Fungal plant pathogens and diseases
Rye diseases
Wheat diseases
Dermateaceae
Fungus species | Tapesia acuformis | [
"Biology"
] | 127 | [
"Fungi",
"Fungus species"
] |
9,311,172 | https://en.wikipedia.org/wiki/Drug | A drug is any chemical substance other than a nutrient or an essential dietary ingredient, which, when administered to a living organism, produces a biological effect. Consumption of drugs can be via inhalation, injection, smoking, ingestion, absorption via a patch on the skin, suppository, or dissolution under the tongue.
In pharmacology, a drug is a chemical substance, typically of known structure, which, when administered to a living organism, produces a biological effect. A pharmaceutical drug, also called a medication or medicine, is a chemical substance used to treat, cure, prevent, or diagnose a disease or to promote well-being. Traditionally drugs were obtained through extraction from medicinal plants, but more recently also by organic synthesis. Pharmaceutical drugs may be used for a limited duration, or on a regular basis for chronic disorders.
Classification
Pharmaceutical drugs are often classified into drug classes—groups of related drugs that have similar chemical structures, the same mechanism of action (binding to the same biological target), a related mode of action, and that are used to treat the same disease. The Anatomical Therapeutic Chemical Classification System (ATC), the most widely used drug classification system, assigns drugs a unique ATC code, which is an alphanumeric code that assigns it to specific drug classes within the ATC system. Another major classification system is the Biopharmaceutics Classification System. This classifies drugs according to their solubility and permeability or absorption properties.
Psychoactive drugs are substances that affect the function of the central nervous system, altering perception, mood or consciousness. These drugs are divided into different groups such as: stimulants, depressants, antidepressants, anxiolytics, antipsychotics, and hallucinogens. These psychoactive drugs have been proven useful in treating a wide range of medical conditions including mental disorders around the world. The most widely used drugs in the world include caffeine, nicotine and alcohol, which are also considered recreational drugs, since they are used for pleasure rather than medicinal purposes. All drugs can have potential side effects. Abuse of several psychoactive drugs can cause addiction or physical dependence. Excessive use of stimulants can promote stimulant psychosis. Many recreational drugs are illicit; international treaties such as the Single Convention on Narcotic Drugs exist for the purpose of their prohibition.
Etymology
In English, the noun "drug" is thought to originate from Old French "", possibly deriving from " ()" from Middle Dutch meaning "dry (barrels)", referring to medicinal plants preserved as dry matter in barrels.
In the 1990s however, Spanish lexicographer Federico Corriente Córdoba documented the possible origin of the word in {ḥṭr} an early romanized form of the Al-Andalus language from the northwestern part of the Iberian peninsula. The term could approximately be transcribed as حطروكة or hatruka.
The term "drug" has become a skunked term with negative connotation, being used as a synonym for illegal substances like cocaine or heroin or for drugs used recreationally. In other contexts the terms "drug" and "medicine" are used interchangeably.
Efficacy
Drug action is highly specific and their effects may only be detected in certain individuals. For instance, the 10 highest-grossing drugs in the US may help only 4-25% of people. Often, the activity of a drug depends on the genotype of a patient. For example, Erbitux (cetuximab) increases the survival rate of colorectal cancer patients if they carry a particular mutation in the EGFR gene. Some drugs are specifically approved for certain genotypes. Vemurafenib is such a case which is used for melanoma patients who carry a mutation in the BRAF gene. The number of people who benefit from a drug determines if drug trials are worth carrying out, given that phase III trials may cost between $100 million and $700 million per drug. This is the motivation behind personalized medicine, that is, to develop drugs that are adapted to individual patients.
Medication
A medication or medicine is a drug taken to cure or ameliorate any symptoms of an illness or medical condition. The use may also be as preventive medicine that has future benefits but does not treat any existing or pre-existing diseases or symptoms. Dispensing of medication is often regulated by governments into three categories—over-the-counter medications, which are available in pharmacies and supermarkets without special restrictions; behind-the-counter medicines, which are dispensed by a pharmacist without needing a doctor's prescription, and prescription only medicines, which must be prescribed by a licensed medical professional, usually a physician.
In the United Kingdom, behind-the-counter medicines are called pharmacy medicines which can only be sold in registered pharmacies, by or under the supervision of a pharmacist. These medications are designated by the letter P on the label. The range of medicines available without a prescription varies from country to country. Medications are typically produced by pharmaceutical companies and are often patented to give the developer exclusive rights to produce them. Those that are not patented (or with expired patents) are called generic drugs since they can be produced by other companies without restrictions or licenses from the patent holder.
Pharmaceutical drugs are usually categorised into drug classes. A group of drugs will share a similar chemical structure, have the same mechanism of action or the same related mode of action, or target the same illness or related illnesses. The Anatomical Therapeutic Chemical Classification System (ATC), the most widely used drug classification system, assigns drugs a unique ATC code, which is an alphanumeric code that assigns it to specific drug classes within the ATC system. Another major classification system is the Biopharmaceutics Classification System. This groups drugs according to their solubility and permeability or absorption properties.
Spiritual and religious use
Some religions, particularly ethnic religions, are based completely on the use of certain drugs, known as entheogens, which are mostly hallucinogens,—psychedelics, dissociatives, or deliriants. Some entheogens include kava which can act as a stimulant, a sedative, a euphoriant and an anesthetic. The roots of the kava plant are used to produce a drink consumed throughout the cultures of the Pacific Ocean.
Some shamans from different cultures use entheogens, defined as "generating the divine within," to achieve religious ecstasy. Amazonian shamans use ayahuasca (yagé), a hallucinogenic brew, for this purpose. Mazatec shamans have a long and continuous tradition of religious use of Salvia divinorum, a psychoactive plant. Its use is to facilitate visionary states of consciousness during spiritual healing sessions.
Silene undulata is regarded by the Xhosa people as a sacred plant and used as an entheogen. Its roots are traditionally used to induce vivid (and according to the Xhosa, prophetic) lucid dreams during the initiation process of shamans, classifying it a naturally occurring oneirogen similar to the more well-known dream herb Calea ternifolia.
Peyote, a small spineless cactus, has been a major source of psychedelic mescaline and has probably been used by Native Americans for at least five thousand years. Most mescaline is now obtained from a few species of columnar cacti in particular from San Pedro and not from the vulnerable peyote.
The entheogenic use of cannabis has also been widely practised for centuries. Rastafari use marijuana (ganja) as a sacrament in their religious ceremonies.
Psychedelic mushrooms (psilocybin mushrooms), commonly called magic mushrooms or shrooms have also long been used as entheogens.
Smart drugs and designer drugs
Nootropics, also commonly referred to as "smart drugs", are drugs that are claimed to improve human cognitive abilities. Nootropics are used to improve memory, concentration, thought, mood, and learning. An increasingly used nootropic among students, also known as a study drug, is methylphenidate branded commonly as Ritalin and used for the treatment of attention deficit hyperactivity disorder (ADHD) and narcolepsy. At high doses methylphenidate can become highly addictive. Serious addiction can lead to psychosis, anxiety and heart problems, and the use of this drug is related to a rise in suicides, and overdoses. Evidence for use outside of student settings is limited but suggests that it is commonplace. Intravenous use of methylphenidate can lead to emphysematous damage to the lungs, known as Ritalin lung.
Other drugs known as designer drugs are produced. An early example of what today would be labelled a 'designer drug' was LSD, which was synthesised from ergot. Other examples include analogs of performance-enhancing drugs such as designer steroids taken to improve physical capabilities; these are sometimes used (legally or not) for this purpose, often by professional athletes. Other designer drugs mimic the effects of psychoactive drugs. Since the late 1990s there has been the identification of many of these synthesised drugs. In Japan and the United Kingdom this has spurred the addition of many designer drugs into a newer class of controlled substances known as a temporary class drug.
Synthetic cannabinoids have been produced for a longer period of time and are used in the designer drug synthetic cannabis.
Recreational drug use
Recreational drug use is the use of a drug (legal, controlled, or illegal) with the primary intention of altering the state of consciousness through alteration of the central nervous system in order to create positive emotions and feelings. The hallucinogen LSD is a psychoactive drug commonly used as a recreational drug.
Ketamine is a drug used for anesthesia, and is also used as a recreational drug, both in powder and liquid form, for its hallucinogenic and dissociative effects.
Some national laws prohibit the use of different recreational drugs; medicinal drugs that have the potential for recreational use are often heavily regulated. However, there are many recreational drugs that are legal in many jurisdictions and widely culturally accepted.
Cannabis is the most commonly consumed controlled recreational drug in the world (as of 2012). Its use in many countries is illegal but is legally used in several countries usually with the proviso that it can only be used for personal use. It can be used in the leaf form of marijuana (grass), or in the resin form of hashish. Marijuana is a more mild form of cannabis than hashish.
There may be an age restriction on the consumption and purchase of legal recreational drugs. Some recreational drugs that are legal and accepted in many places include alcohol, tobacco, betel nut, and caffeine products, and in some areas of the world the legal use of drugs such as khat is common.
There are a number of legal intoxicants commonly called legal highs that are used recreationally. The most widely used of these is alcohol.
Administration of drugs
All drugs have a route of administration, and many can be administered by more than one.
A bolus is the administration of a medication, drug or other compound that is given to raise its concentration in blood rapdily to an effective level, regardless of the route of administration
Control of drugs
Numerous governmental offices in many countries deal with the control and supervision of drug manufacture and use, and the implementation of various drug laws. The Single Convention on Narcotic Drugs is an international treaty brought about in 1961 to prohibit the use of narcotics save for those used in medical research and treatment. In 1971, a second treaty the Convention on Psychotropic Substances had to be introduced to deal with newer recreational psychoactive and psychedelic drugs.
The legal status of Salvia divinorum varies in many countries and even in states within the United States. Where it is legislated against, the degree of prohibition also varies.
The Food and Drug Administration (FDA) in the United States is a federal agency responsible for protecting and promoting public health through the regulation and supervision of food safety, tobacco products, dietary supplements, prescription and over-the-counter medications, vaccines, biopharmaceuticals, blood transfusions, medical devices, electromagnetic radiation emitting devices, cosmetics, animal foods and veterinary drugs.
In India, the Narcotics Control Bureau (NCB), an Indian federal law enforcement and intelligence agency under the Ministry of Home Affairs, is tasked with combating drug trafficking and assisting international use of illegal substances under the provisions of Narcotic Drugs and Psychotropic Substances Act.
See also
Club drug
Controlled Substances Act
Drug checking
Drug development
Inverse benefit law
Lifestyle drug
Medical cannabis
Nonsteroidal anti-inflammatory drug
Pharmacognosy
Placebo
Prodrug
Specialty drugs (United States)
United Nations Office on Drugs and Crime
Lists of drugs
List of drugs
List of pharmaceutical companies
List of psychoactive plants
List of Schedule I drugs (US)
References
Further reading
External links
DrugBank, a database of 13,400 drugs and 5,100 protein drug targets
"Drugs", BBC Radio 4 discussion with Richard Davenport-Hines, Sadie Plant and Mike Jay (In Our Time, May 23, 2002) | Drug | [
"Chemistry"
] | 2,729 | [
"Pharmacology",
"Chemicals in medicine",
"Drugs",
"Products of chemical industry"
] |
9,311,900 | https://en.wikipedia.org/wiki/On%20Lisp | On Lisp: Advanced Techniques for Common Lisp is a book by Paul Graham on macro programming in Common Lisp. Published in 1993, it is currently out of print, but can be freely downloaded as a PDF file.
See also
Anaphoric macro
References
External links
On Lisp home page
Free versions of "On Lisp"
On Lisp in pdf-format
On Lisp in multiple HTML files
On Lisp in multiple HTML files (white on black)
On Lisp in a single HTML file
Piecing Together a Printed Copy of "On Lisp" -- includes the nine missing diagrams.
Common Lisp publications | On Lisp | [
"Technology"
] | 127 | [
"Computing stubs",
"Computer book stubs"
] |
1,522,385 | https://en.wikipedia.org/wiki/Alphard | Alphard , designated Alpha Hydrae (α Hydrae, abbreviated Alpha Hya, α Hya), is the brightest star in the constellation of Hydra. It is a single giant star, cooler than the Sun but larger and more luminous. It is about 177 light-years away.
Nomenclature
α Hydrae (Latinised to Alpha Hydrae) is the star's Bayer designation.
The traditional name Alphard is from the Arabic الفرد (al-fard), "the individual", there being no other bright stars near it. It was also known as the "backbone of the Serpent" to the Arabs. In the catalogue of stars in the Calendarium of Al Achsasi Al Mouakket, it was designated Soheil al Fard, which was translated into Latin as Soheil Solitarius, meaning the bright solitary one. In 2016, the International Astronomical Union organized a Working Group on Star Names (WGSN) to catalog and standardize proper names for stars. The WGSN's first bulletin of July 2016 included a table of the first two batches of names approved by the WGSN; which included Alphard for this star. It is now so entered in the IAU Catalog of Star Names.
The European astronomer Tycho Brahe dubbed it Cor Hydræ, Latin for 'the heart of Hydra'.
In Chinese, (), meaning Star, refers to an asterism consisting of Alphard, τ1 Hydrae, τ2 Hydrae, ι Hydrae, 26 Hydrae, 27 Hydrae, HD 82477 and HD 82428. Consequently, Alphard itself is known as (), "the First Star of Star". In ancient China it formed part of an asterism called the "red bird".
Properties
Alphard has three times the mass of the Sun. Its estimated age is 420 million years and it has evolved away from the main sequence to become a giant star with a spectral classification of K3 and luminosity class III. The angular diameter has been measured using interferometry, after correction for limb darkening, it yields a value of . Assuming the distance of , it yields a physical size of .
Alphard's spectrum shows a mild excess of barium, an element that is normally produced by the s-process of nucleosynthesis. Typically a barium star belongs to a binary system and the anomalies in abundances are explained by mass transfer from a companion white dwarf star.
Precise radial velocity measurements have shown variations in the stellar radial velocities and spectral line profiles. The oscillations are multi-periodic with periods from several hours up to several days. The short-term oscillations were assumed to be a result of stellar pulsations, similar to the solar ones. A correlation between the variations in the asymmetry of the spectral line profile and the radial velocity has also been found. The multi-periodic oscillations make HD 81797 (Alphard) an object of interest for asteroseismologic investigations.
Modern legacy
Alphard appears on the flag of Brazil, symbolising the state of Mato Grosso do Sul.
The Toyota Alphard is a minivan named after this star.
The character Roy Alphard from Japanese light novel series Re:Zero is named after this star.
Notes
References
Hydrae, Alpha
Hydra (constellation)
K-type bright giants
K-type giants
Alphard
Hydrae, 30
046390
081797
BD-08 2680
3748 | Alphard | [
"Astronomy"
] | 734 | [
"Hydra (constellation)",
"Constellations"
] |
1,522,415 | https://en.wikipedia.org/wiki/Sigma%20Sagittarii | Sigma Sagittarii, Latinized from σ Sagittarii; formally named Nunki , is the second-brightest star in the constellation of Sagittarius. It has an apparent magnitude of +2.05, making it readily visible to the naked eye. The distance to this star, determined using parallax measurements from the Hipparcos astrometry satellite, yields a value of approximately from the Sun.
Properties
Sigma Sagittarii has a spectrum matching a stellar classification of B2.5 V, which indicates this is a B-type main-sequence star. Its total luminosity is 3300 times that of the Sun while it has a surface temperature of 18,890 K. X-ray emission has been detected from this star, which has an estimated X-ray luminosity of .
It has a 10th magnitude optical companion located 5.2 arcminutes away.
It is 3.45 degrees south of the ecliptic, so it can be occulted by the Moon and rarely by planets. The last occultation by a planet took place on November 17, 1981, when it was occulted by Venus. This is the brightest star that can be principally occulted by an exterior planet between 5000 BC and 5000 AD. However, only Mars can do this, and only rarely; the last time was on September 3, 423.
Nomenclature
σ Sagittarii (Latinised to Sigma Sagittarii) is the star's Bayer designation. In his Uranometria star atlas, Johann Bayer placed this star in the fourth magnitude class, although it is a second-magnitude star by modern measurements.
It bore the traditional name of Nunki, which was an Assyrian or Babylonian name recovered by archaeologists and made public by R. H. Allen. In 2016, the International Astronomical Union organized a Working Group on Star Names (WGSN) to catalogue and standardize proper names for stars. The WGSN approved the name Nunki for this star on 21 August 2016 and it is now so included in the List of IAU-approved Star Names.
This star, together with :
Gamma Sagittarii, Delta Sagittarii, Epsilon Sagittarii, Zeta Sagittarii, Lambda Sagittarii, Tau Sagittarii and Phi Sagittarii, comprised the Teapot asterism.
Phi Sagittarii, Zeta Sagittarii, Chi Sagittarii and Tau Sagittarii were the Arabic Al Naʽām al Ṣādirah (النعم السادرة), the Returning Ostriches.
Zeta Sagittarii and Pi Sagittarii may have been the Akkadian Gu-shi-rab‑ba, the Yoke of the Sea.
In the catalogue of stars in the Calendarium of Al Achsasi al Mouakket, this star was designated Thanih al Sadirah, which was translated into Latin as Secunda τού al Sadirah, meaning second returning ostrich.
In Chinese, (), meaning Dipper, refers to an asterism consisting of Sigma Sagittarii, Phi Sagittarii, Lambda Sagittarii,
Mu Sagittarii, Tau Sagittarii and Zeta Sagittarii. Consequently, the Chinese name for Sigma Sagittarii itself is (, .)
References
B-type main-sequence stars
Binary stars
Sagittarius (constellation)
Sagittarii, Sigma
Durchmusterung objects
Sagittarii, 34
175191
092855
7121
Nunki | Sigma Sagittarii | [
"Astronomy"
] | 740 | [
"Sagittarius (constellation)",
"Constellations"
] |
1,522,419 | https://en.wikipedia.org/wiki/Alpha%20Ophiuchi | Alpha Ophiuchi (α Ophiuchi, abbreviated Alpha Oph, α Oph), also named Rasalhague , is a binary star and the brightest star in the constellation of Ophiuchus.
Nomenclature
The name Alpha Ophiuchi is a Romanisation of the star's Bayer designation, α Ophiuchi. It is also known by the traditional name Rasalhague, from the Arabic رأس الحواء raʼs al-ḥawwāʼ "the head of the serpent collector". In 2016, the International Astronomical Union organized a Working Group on Star Names (WGSN) to catalog and standardize proper names for stars. The WGSN's first bulletin of July 2016 included a table of the first two collections of approved names, formally listing Alpha Ophiuchi as Rasalhague.
Properties
Alpha Ophiuchi is a binary star system with an orbital period of about 8.62 years. The orbital parameters were only poorly known until 2011 when observations using adaptive optics produced a better orbital fit, allowing the individual masses of the two components to be determined. The primary component, Alpha Ophiuchi A, has a mass of about 2.4 times the mass of the Sun, while the secondary, Alpha Ophiuchi B, has 0.85 solar masses. Estimates of the mass of the primary by other means range from a low of 1.92 to 2.10 solar masses, up to 2.84 or even 4.8 solar masses. The mass of the secondary suggests that it has a stellar classification in the range K5V to K7V, which indicates it is a main sequence star that is still generating energy by the thermonuclear fusion of hydrogen at its core. The pair reached periastron passage, or closest approach, around April 19, 2012, when they had an angular separation of 50 milliarcseconds.
This star system has a combined apparent magnitude of +2.08 and is located at a distance of about from the Earth. The stellar classification of A5IVnn indicates that the primary is a bluish-white subgiant star that has evolved away from the main sequence after consuming the hydrogen at its core. It is radiating about 25 times the luminosity of the Sun and has an effective temperature of about 8,000 K, giving it the characteristic white hue of an A-type star.
The spectrum of Alpha Ophiuchi shows an anomalously high level of absorption of the lines for singly-ionized calcium (Ca II). However, this is likely the result of interstellar matter between the Earth and the star, rather than a property of the star or circumstellar dust.
Rotation
Alpha Ophiuchi A is a rapidly rotating star with a projected rotational velocity of 240 km s−1. It is spinning at about 88.5% of the rate that would cause the star to break up. This gives it an oblate spheroid shape with an equatorial bulge about 20% larger than the polar radius. The polar radius is calculated to be and the equatorial radius .
Because of the oblateness and rapid spin, the surface gravity at the pole is higher than at the equator. An effect known as gravity darkening means that the temperature at the poles is also higher than at the equator. The polar temperature is calculated to be and the equatorial temperature .
The energy radiated by an oblate star is higher along its axis of rotation because of the larger projected area and the Stefan–Boltzmann law. The axis of rotation of α Ophiuchi is inclined about to the line of sight from the Earth, so that it is being observed from nearly equator-on. The apparent bolometric luminosity seen at this angle is , but the true luminosity of the star is thought to be . Since a star's effective temperature is simply the temperature which would produce its total energy output from a black body, the true effective temperature of is different from the apparent effective temperature of .
References
External links
Ophiuchi, Alpha
Ophiuchus
Rasalhague
Ophiuchi, 55
086032
K-type main-sequence stars
Binary stars
6556
159561
BD+12 3252
A-type subgiants | Alpha Ophiuchi | [
"Astronomy"
] | 873 | [
"Ophiuchus",
"Constellations"
] |
1,522,428 | https://en.wikipedia.org/wiki/Theta%20Centauri | Theta Centauri or θ Centauri, officially named Menkent (), is a single star in the southern constellation of Centaurus, the centaur. With an apparent visual magnitude of +2.06, it is the fourth-brightest member of the constellation. Based on parallax measurements obtained during the Hipparcos mission, it is about distant. It has a relatively high proper motion, traversing the celestial sphere at the rate of . This suggests that Menkent may have originated in the outer disk of the Milky Way and is merely passing through the solar neighborhood.
Nomenclature
θ Centauri, Latinised to Theta Centauri, is the star's Bayer designation.
It bore the traditional name of Menkent derived from the Arabic word مَنْكِب (mankib) for "shoulder" (of the Centaur), apparently blended with a shortened form of "kentaurus" (centaur). In 2016, the International Astronomical Union organized a Working Group on Star Names (WGSN) to catalog and standardize proper names for stars. The WGSN approved the name Menkent for this star on 21 August 2016 and it is now so included in the List of IAU-approved Star Names.
In Chinese, (), meaning arsenal, refers to an asterism consisting of Theta Centauri, Zeta Centauri, Eta Centauri, 2 Centauri, HD 117440, Xi¹ Centauri, Gamma Centauri, Tau Centauri, D Centauri and Sigma Centauri. Consequently, the Chinese name for Theta Centauri itself is (, ).
Properties
This is an evolved giant star with a stellar classification of K0 III and 1.27 times the mass of the Sun. It is believed to be fusing helium into carbon and heavier elements within its core, qualifying it as a red clump star. It is a southern analog to Pollux, the brightest star in Gemini and the closest giant to the Sun. It is over ten times larger than the Sun and 60 times more luminous. The outer envelope has an effective temperature of 4,853 K, giving it the orange-hued glow of a cool, K-type star. Soft X-ray emission has been detected from this star, which has an estimated X-ray luminosity of .
See also
List of nearest giant stars
Notes
References
K-type giants
Centaurus
Centauri, Theta
Durchmusterung objects
Centauri, 5
0539
123139
068933
5288
Menkent | Theta Centauri | [
"Astronomy"
] | 530 | [
"Centaurus",
"Constellations"
] |
1,522,473 | https://en.wikipedia.org/wiki/Alpha%20Cassiopeiae | Alpha Cassiopeiae or α Cassiopeiae, also named Schedar (), is a second-magnitude star in the northern constellation of Cassiopeia. Though listed as the "alpha star" by Johann Bayer, α Cas's visual brightness closely matches the 'beta' (β) star in the constellation (Beta Cassiopeiae) and it may appear marginally brighter or dimmer, depending on which passband is used. However, recent calculations from NASA's WISE telescope confirm that α Cas is the brightest in Cassiopeia, with an apparent magnitude of 2.240. Its absolute magnitude is 18 times greater than β Cas, and it is located over four times farther away from the Sun.
Nomenclature
α Cassiopeiae (Latinised to Alpha Cassiopeiae) is the star's Bayer designation.
It bore the traditional name Schedar, which was first encountered in the Alfonsine tables of the thirteenth century. It derives from the Arabic word صدر şadr, meaning "breast" (as in chest), a word which is derived from its relative position in the heart of the mythological queen Cassiopeia. Johannes Hevelius used the name Schedir in his writings, although there were additional traditional spellings of this Arabic transliteration such as Shedar, Shadar, Sheder, Seder, Shedis, and Shedir. In 2016, the International Astronomical Union organized a Working Group on Star Names (WGSN) to catalogue and standardize proper names for stars. The WGSN approved the name Schedar for this star on 21 August 2016 and it is now so included in the List of IAU-approved Star Names.
Al-Sufi and Ulug Beg named the star Al Dhāt al Kursiyy (Arabic ذات الكرسي, meaning "the lady in the chair"), which Giovanni Battista Riccioli changed to Dath Elkarti.
In Chinese, () refers to the Chinese asterism Wang Liang, a famous charioteer during the Spring and Autumn period. The stellar pattern consists of Alpha, Beta, Kappa, Eta and Lambda Cassiopeiae. Consequently, the Chinese name for Alpha Cassiopeiae itself is (, ).
Visibility
With a declination of 56° 32' North, α Cassiopeiae is principally visible in the northern hemisphere. The star is detectable to most observers across the globe reaching as far south as Perth, Australia, Santiago, Chile and other settlements north ± 33° South latitude, albeit close to the horizon. α Cassiopeiae is located in line-of-sight of the Milky Way galaxy, so there are other notable celestial objects one can view close to this star—the Pacman Nebula, NGC 436 and NGC 457 being a few.
Alpha Cas reaches its zenith above cities like Edinburgh, Copenhagen and Moscow. It is circumpolar throughout Europe, Russia, and as far south as Los Angeles, California on the North American continent as well as other locations around the globe having a latitude greater than ± 33° North. Since α Cassiopeiae is listed as a second-magnitude star (equal to Beta Cas), it is easily observable to the naked eye as long as one's stargazing is not hindered by the light pollution common to most cities.
The best time for observation is during the late autumn months of the northern hemisphere, when Cassiopeia passes the meridian at midnight, but given its circumpolar nature in many northern localities, it is visible to many of the world's inhabitants throughout the year.
Angular analysis
With the advances in optical interferometry in the 1990s, α Cassiopeiae's angular diameter was measured in 1998 at various wavelengths ranging from 500 to 850 nm. The result was a limb darkened angular measurement of 5.62 ± 0.06 milliarcseconds (mas), a diameter which equates to roughly 0.393 AU or , assuming a parallax of 14.29 mas. With the planet Mercury orbiting the Sun at approximately 0.4 AU, α Cassiopeiae's photosphere extends to roughly half the mercurial orbit.
Properties
α Cassiopeiae is a red giant star whose spectral classification is K0-IIIa, notably cooler than the Sun. However, because it is nearing the final stages of its evolution, the photosphere has expanded substantially, yielding a bolometric luminosity that is approximately . It is considered 98% likely to be a horizontal branch star fusing helium in its core.
According to Hipparcos, the New Reduction (van Leeuwen, 2007), the estimated distance to the star is about 70 parsecs or 228 light-years. Like all giant stars, α Cassiopeiae rotates slowly with an approximate velocity of —a speed which takes the star approximately 102 days to make one complete revolution on its axis.
α Cassiopeiae has been sometimes classified as a variable star, but no variability has been detected since the 19th century. Also, three companions to the star have been listed in the Washington Double Star Catalog, but it seems that all of them are just distant line-of-sight optical components.
α Cassiopeiae is thought to be around 100 to 200 million years old, having spent much of its time as a blue-white B-type main-sequence star.
Depiction
In 1551, Gerardus Mercator, a Flemish cartographer, produced a celestial globe portraying the 48 traditional Ptolemaic constellations in addition to two others, Coma Berenices and Antinous. On this globe, he represents Cassiopeia as the Queen of Ethiopia, punished for her boasting by being chained to a chair hanging upside-down. α Cassiopeiae is found near her left breast, reflecting its Arabic etymological origin.
References
External links
Harvard Map Collection The Mercator Globes
The Internet Encyclopedia of Science: Shedar (Alpha Cassiopeiae)
K-type giants
Suspected variables
Cassiopeia (constellation)
Cassiopeiae, Alpha
Durchmusterung objects
Cassiopeiae, 18
003712
003179
0168
Schedar
TIC objects | Alpha Cassiopeiae | [
"Astronomy"
] | 1,292 | [
"Cassiopeia (constellation)",
"Constellations"
] |
1,522,483 | https://en.wikipedia.org/wiki/Alpha%20Coronae%20Borealis | Alpha Coronae Borealis (α Coronae Borealis, abbreviated Alpha CrB, α CrB), officially named Alphecca , is an eclipsing binary star in the constellation of Corona Borealis. It is located about 75 light years from the Sun and contains two main sequence stars, one class A and one class G.
Properties
Alpha Coronae Borealis is a binary system, its stars orbiting each other in an eccentric orbit every 17.36 days. Because the plane of this orbit is inclined at an angle of 88.2° to the line of sight to the Earth, the pair form a detached eclipsing binary system similar to Algol (β Per). The periodic eclipses result in a magnitude variation of +2.21 to +2.32, which is hardly noticeable to the unaided eye.
The primary component is a white main sequence star that has a stellar classification of A0V and 2.6 times the mass of the Sun. Estimates of the star's radius range from 2.89 to 3.04 times the radius of the Sun. An excess of infrared radiation at 24 μm and 70 μm has been detected about the primary star by the IRAS. This suggests the presence of a large disc of dust and material around the star, prompting speculation of a planetary or proto-planetary system similar to that currently assumed around Vega. The disk extends out to a radius of around 60 astronomical units (AU).
The secondary component is a yellow main sequence star with an estimated stellar class of G5, 0.92 times the Sun's mass and 0.90 times the Sun's radius. The X-ray luminosity of this star is , which is 30 times greater than the peak activity level of the Sun. This higher activity level is expected for a young star of this class. The corona has a temperature of about 5 MK, which is much hotter than the Sun's corona. The upper limit of 14 km/s for the equatorial rotation velocity is equivalent to a rotation period of 3 days. More likely, the rotation period is 7–9 days.
The space velocity components of this star system are U =, V = and W =. α CrB is believed to be a member of the Ursa Major Moving Group of stars that have a common motion through space.
Nomenclature
α Coronae Borealis (Latinised to Alpha Coronae Borealis) is the star's Bayer designation.
It bore the traditional names Alphecca, Gemma, and Gnosia Stella Coronae. Alphecca is Arabic, short for نير الفكّة nayyir al-fakka "the bright (star) of the broken (ring of stars)". Gemma is Latin for "jewel". Also Latin in origin is Gnosia Stella Coronae "Cretan star of the Crown" (specifically from Vergil's Georgics), from Gnōsus or Gnōsos ("Knossos"), referencing the birthplace of Ariadne, whose wedding diadem became in some myths the constellation of Corona Borealis, following her marriage to Bacchus. As the brightest star in Corona Borealis, it lent its name to Alphekka Meridiana, the brightest in the constellation of Corona Australis. The International Astronomical Union Working Group on Star Names (WGSN) has chosen Alphecca as the formal name for this star.
The term nayyir al-fakka or Nir al Feccah appeared in the Al Achsasi Al Mouakket catalogue.
In Chinese, (), meaning Coiled Thong, refers to an asterism consisting of Alpha Coronae Borealis, Pi Coronae Borealis, Theta Coronae Borealis, Beta Coronae Borealis, Gamma Coronae Borealis, Delta Coronae Borealis, Epsilon Coronae Borealis, Iota Coronae Borealis and Rho Coronae Borealis. Consequently, the Chinese name for Alpha Coronae Borealis itself is (, .).
In culture
Under the name Alphecca, this is one of the medieval Behenian fixed stars.
References
G-type main-sequence stars
A-type main-sequence stars
Eclipsing binaries
Ursa Major moving group
Alphecca
Corona Borealis
Coronae Borealis, Alpha
Durchmusterung objects
Coronae Borealis, 05
139006
076267
5793 | Alpha Coronae Borealis | [
"Astronomy"
] | 912 | [
"Corona Borealis",
"Constellations"
] |
1,522,501 | https://en.wikipedia.org/wiki/Gamma%20Draconis | Gamma Draconis (γ Draconis, abbreviated Gamma Dra, γ Dra), formally named Eltanin , is a star in the northern constellation of Draco. Contrary to its gamma-designation (historically third-ranked), it is the brightest object in Draco at magnitude 2.2, outshining Beta Draconis by nearly half a magnitude and Alpha Draconis by over a magnitude.
Gamma Draconis is at a distance of from the Sun, as determined by parallax measurements from the Hipparcos astrometry satellite. In 1728, while unsuccessfully attempting to measure the parallax of this star, the English astronomer James Bradley discovered the aberration of light resulting from the relative movement of the Earth. Bradley's discovery apparently confirmed Copernicus' theory that the Earth revolved around the Sun. It is drifting closer to the Solar System with a radial velocity of about –28 km/s.
In 1.5 million years, Gamma Draconis will pass within 28 light-years of Earth. For a period, if its current absolute magnitude does not change, it will be the brightest star in the night sky, nearly as bright as Sirius is at present. It is by far the brightest star having a zenith above a point near London which led to its vaunting in these places as the "zenith star". Nearby this red star to the south-southeast is Vega, a bright, well-known star in Lyra.
Properties
Gamma Draconis is an evolved giant star with a stellar classification of K5 III. Since 1943, the spectrum of this star has served as one of the stable anchor points by which other stars are classified. It has about two times more mass than the Sun and it has expanded to around 50 times its size. It is radiating about 600 times as much luminosity as the Sun from its outer atmosphere at an effective temperature of 3,964 K. This is cooler than the Sun, giving this star the orange-hued glow of a K-type star.
Gamma Draconis has six companions listed in double star catalogues. All were discovered by the American astronomer Sherburne Wesley Burnham. The closest may be physically associated and would be separated by about . The luminosity of this object suggests it is a red dwarf star. The others are all much more distant stars unrelated to Gamma Draconis.
Nomenclature
γ Draconis (Latinised to Gamma Draconis) is the star's Bayer designation.
It bore the traditional name Eltanin derived from the Arabic التنين At-Tinnin 'The great serpent'. The name Rastaban was formerly used for Gamma Draconis, and the two terms share an Arabic root meaning "serpent" or "dragon". In 2016, the International Astronomical Union organized a Working Group on Star Names (WGSN) to catalogue and standardize proper names for stars. The WGSN approved the name Eltanin for this star on 21 August 2016 and it is now so entered in the IAU Catalog of Star Names.
Gamma Draconis, along with Beta Draconis, Mu Draconis, Nu Draconis, and Xi Draconis were Al ʽAwāïd "the Mother Camels", which was later known as the Quinque Dromedarii.
In Chinese, (), meaning Celestial Flail, refers to an asterism consisting of Gamma Draconis, Xi Draconis, Nu Draconis, Beta Draconis and Iota Herculis. Consequently, the Chinese name for Gamma Draconis itself is (, .)
Namesake
USS Etamin was a United States Navy Crater class cargo ship named after the star.
See also
List of stars in Draco
Notes and references
References
Notes
Draconis, Gamma
Draco (constellation)
K-type giants
Eltanin
087833
Draconis, 33
6705
164058
Durchmusterung objects | Gamma Draconis | [
"Astronomy"
] | 810 | [
"Constellations",
"Draco (constellation)"
] |
1,522,504 | https://en.wikipedia.org/wiki/Iota%20Carinae | Iota Carinae (ι Carinae, abbreviated Iota Car, ι Car), officially named Aspidiske , is a star in the southern constellation of Carina. With an apparent visual magnitude of 2.2, it is one of the brighter stars in the night sky.
Appearance and location
The star and rest of southern Carina never sets on places from about 34° S southwards including Cape Town; its northernmost viewpoints are unobstructed southern horizons near to the 30th parallel north, once a day.
The False Cross is an asterism formed from Iota Carinae, Delta Velorum, Kappa Velorum and Epsilon Carinae. It is so called because it is sometimes mistaken for the Southern Cross, causing errors in astronavigation.
The star appears 46.0' (0.7668°) WSW of V357 Carinae, a mid-third-magnitude star, also forming part of the asterism and leading to its long, narrow projection which culminates in Canopus.
Nomenclature
ι Carinae (Latinised to Iota Carinae) is the star's Bayer designation.
It has the traditional cognate names Aspidiske (not be confused with Asmidiske, the proper name of Xi Puppis), Scutulum and Turais (or Tureis, a name shared with Rho Puppis). Turais is the Arabic تُرَيْس turais "small shield" (diminutive), while Aspidiske and Scutulum are Greek and Latin translations from ασπίδα and scūtum. In 2016, the International Astronomical Union formed its Working Group on Star Names (WGSN) to catalog and standardize proper names for stars. The WGSN's first bulletin of July 2016 included a table of the first two batches of names it approved which included Aspidiske for this star.
In Chinese, (), meaning Sea Rock, refers to an asterism consisting of Iota Carinae, Epsilon Carinae, HD 83183, HD 84810 and Upsilon Carinae. Consequently, Iota Carinae itself is known as (, ).
Properties
Based on parallax measurements this star is about from the Earth. It has a stellar classification of A7 Ib, with the luminosity class of 'Ib' indicating it has reached the stage of its evolution where it has expanded to become a lower-luminosity supergiant. It is just entering the Hertzsprung gap of the Hertzsprung–Russell diagram, and is evolving towards a red supergiant phase.
Iota Carinae has around seven times the Sun's mass and has expanded to roughly 50 times the Sun's radius. It is radiating about 4,900 times the luminosity of the Sun. However, this luminosity appears to vary, causing the star's apparent magnitude to range between 2.23–2.28. This energy is being radiated into space from the star's outer envelope at an effective temperature of 7,500 K, giving Iota Carinae the white hue typical of an A-type star. Being short of the rough initial mass limit above which stars collapse and explode as supernovae, Iota Carinae will likely end its life as a white dwarf with roughly the current mass of the Sun, similar to Sirius B today (which was also estimated to have an initial mass of up to 7 solar masses).
Due to precession of the Earth's axis of rotation, in the next 7,500 years the south celestial pole will pass close to this star and Upsilon Carinae and it will become the South Star around 8100 CE.
References
A-type supergiants
Carina (constellation)
Carinae, Iota
Durchmusterung objects
080404
045556
3699
Aspidiske
Suspected variables | Iota Carinae | [
"Astronomy"
] | 814 | [
"Carina (constellation)",
"Constellations"
] |
1,522,510 | https://en.wikipedia.org/wiki/Beta%20Cassiopeiae | Beta Cassiopeiae (β Cassiopeiae, abbreviated Beta Cas or β Cas), officially named Caph , is a Delta Scuti variable star in the constellation of Cassiopeia. It is a giant star belonging to the spectral class F2. The white star of second magnitude (+2.28 mag, variable) has an absolute magnitude of +1.3 mag.
Nomenclature
Beta Cassiopeiae is the star's Bayer designation. It also bore the traditional names Caph (from the Arabic word , "palm" – i.e. reaching from the Pleiades), Chaph and Kaff, as well as al-Sanam al-Nakah "the Camel's Hump". In 2016, the International Astronomical Union organized a Working Group on Star Names (WGSN) to catalog and standardize proper names for stars. The WGSN's first bulletin of July 2016 included a table of the first two batches of names approved by the WGSN; which included Caph for this star.
Originally, the pre-Islamic Arabic term al-Kaff al-Khadib "the stained hand" referred to the five stars comprising the 'W' of the constellation Cassiopeia, and depicted a hand stained with henna. The term was abbreviated and somehow came to signify β Cassiopeiae alone. The old "stained hand" was part of an asterism called Thuraya stretching from the Pleiades, which signified the "head" through Taurus and Perseus and into Cassiopeia, while the other "hand" was in Cetus.
In Chinese, (), in the Legs (Chinese constellation), refers to an asterism consisting of β Cassiopeiae, κ Cassiopeiae, η Cassiopeiae, α Cassiopeiae and λ Cassiopeiae. Consequently, the Chinese name for β Cassiopeiae itself is (, .)
Together with Alpha Andromedae (Alpheratz) and Gamma Pegasi (Algenib), Beta Cassiopeiae was one of three bright stars known as the "Three Guides" marking the equinoctial colure. This is an imaginary line running due south from Beta Cassiopeiae through Alpha Andromedae to the celestial equator, at a point where the Sun's path (the ecliptic) crosses it each autumn and spring equinox.
Visibility
With a mean apparent magnitude (V-band) of +2.28, it is one of the five stars which make up the 'W' of Cassiopeia, adjacent to the just brighter Schedar (Alpha Cassiopeiae). SN 1572, traditionally known as Tycho's Star, appeared about 5 degrees to the northwest of Caph in 1572.
As a star in the deep northern hemisphere of the sky, Beta Cassiopeiae is prominent to viewers in the northern hemisphere but not often seen by those in the southern hemisphere. The constellation of Cassiopeia does not rise above the horizon to viewers in Tasmania, and only low if one were in Cairns.
System
Beta Cassiopeiae is a yellow-white hued giant of stellar class F2 III with a surface temperature around . More than three times the size of and 28 times brighter than the Sun, Caph has an absolute magnitude of +1.3. It was once an A-type star with about double the Sun's mass. It is now in the process of cooling and expanding to become a red giant. Its core is likely to have used up its hydrogen and is shrinking and heating, while its outer envelope of hydrogen is expanding and cooling. Stars do not spend much time in this state and are relatively uncommon. Caph's corona is unusually weak.
Beta Cassiopeiae is a variable star of the Delta Scuti type; in fact, the fourth brightest of such stars in the sky after Denebola, Vega and Altair. It is a monoperiodic pulsator, with a brightness that ranges from magnitude +2.25 to +2.31 with a period of 2.5 hours. This type of variable includes subgiant or main-sequence stars of spectral classes F5–A0, having masses between 1.5–2.5 solar masses and nearing the end of their core hydrogen fusion lifetime. Their pulsations are related to the same helium instability strip on the Hertzsprung–Russell diagram as that of classical Cepheids. Delta Scuti stars are located at the intersection of the strip with the main sequence.
This star is rotating at about 92% of its critical velocity, completing 1.12 rotations every day. This is giving the star an oblate spheroid shape with an equatorial bulge that is 24% larger than the polar radius. This shape is causing the polar region to have a higher temperature than the equator: the temperature difference is about 1,000 K. The axis of rotation is inclined about 20 degrees to the line of sight from the Earth.
Beta Cassiopeiae was once considered to be a spectroscopic binary with a faint companion in a 27-day orbit, but it is now thought to be a single star.
References
External links
Cassiopeiae, Beta
Cassiopeiae, 11
Cassiopeia (constellation)
Delta Scuti variables
F-type giants
Caph
0021
000432
000746
BD+58 0003
0008 | Beta Cassiopeiae | [
"Astronomy"
] | 1,132 | [
"Cassiopeia (constellation)",
"Constellations"
] |
1,522,529 | https://en.wikipedia.org/wiki/Delta%20Scorpii | Delta Scorpii (Latinised from δ Scorpii, abbreviated Delta Sco, δ Sco) is a binary star (the presence of a third star in the system is being debated) in the constellation of Scorpius. The primary star is named Dschubba .
Observation
Delta Scorpii is 2.0 degrees south of the ecliptic. It is a binary star with two components of magnitudes 2.4 and 4.6 separated by . In 1981 it was occulted by Saturn's rings as seen by Voyager 2, with starlight unexpectedly blocked even by the apparently empty gaps, indicating that "there is very little empty space anywhere in the main ring system."
Variability
Delta Scorpii A is a Gamma Cassiopeiae variable star. This type of star shows irregular slow brightness variations of a few hundredths of a magnitude due to material surrounding the star.
In June 2000 Delta Scorpii was observed by Sebastian Otero to be 0.1 magnitudes brighter than normal; its brightness has varied since then and has reached at least as high as magnitude 1.6, altering the familiar appearance of Scorpius. Spectra taken after the outburst began have shown that the star is throwing off luminous gases from its equatorial region. The companion passed close by in 2011, again resulting in the star peaking at 1.65 between 5 and 15 July 2011.
Nomenclature
δ Scorpii (Latinised to Delta Scorpii) is the system's Bayer designation. The two components are designated Delta Scorpii A and B.
Delta Scorpii bore the traditional name Dschubba, which comes from Arabic جبهة العقرب jabhet al-aqrab meaning 'the forehead of the scorpion'. In 2016 the International Astronomical Union organized a Working Group on Star Names (WGSN) to catalogue and standardize proper names for stars. The WGSN approved the name Dschubba for δ Scorpii A on 21 August 2016 and it is now so entered in the IAU Catalog of Star Names.
In Chinese, (), meaning Room, refers to an asterism consisting of δ Scorpii, β1 Scorpii, β2 Scorpii, π Scorpii, and ρ Scorpii. Consequently, the Chinese name for δ Scorpii itself is (), "the Third Star of Room".
Properties
δ Scorpii was once used as a spectroscopic standard for the B0 IV classification, but is now considered too unusual and variable.
The primary, δ Scorpii A, is a B class subgiant surrounded by a disc of material spun off by the rapidly rotating star. The secondary, δ Scorpii B, orbits every 10.5 years in a highly elongated elliptical orbit; it appears to be a normal B class main sequence star. There have been reports that Delta Scorpii A is itself a very close spectroscopic binary, but this does not appear to be the case.
δ Scorpii is a proper motion member of the Upper Scorpius subgroup of the Scorpius–Centaurus OB association, the nearest such co-moving association of massive stars to the Sun. The Upper Scorpius subgroup contains thousands of young stars with mean age 11 million years at average distance of 470 light years (145 parsecs).
References
External links
Jim Kaler's Stars, University of Illinois: Dschubba
Delta Scorpii brighter than ever (Sky and Telescope, February 4, 2002)
Delta Scorpii still showing off (Sky and Telescope, June 25, 2003)
Delta Scorpii: the birth of a Be star (AAVSO article)
Scorpius
Scorpii, Delta
B-type subgiants
Dschubba
Upper Scorpius
B-type main-sequence stars
Binary stars
Gamma Cassiopeiae variable stars
Be stars
BD-22 4068
5953
078401
143275
Scorpii, 07 | Delta Scorpii | [
"Astronomy"
] | 847 | [
"Scorpius",
"Constellations"
] |
1,522,535 | https://en.wikipedia.org/wiki/Epsilon%20Pegasi | Epsilon Pegasi (Latinised from ε Pegasi, abbreviated Epsilon Peg, ε Peg), formally named Enif , is the brightest star in the northern constellation of Pegasus.
With an average apparent visual magnitude of 2.4, this is a second-magnitude star that is readily visible to the naked eye. The distance to this star can be estimated using parallax measurements from the Hipparcos astrometry satellite, yielding a value of around .
Nomenclature
ε Pegasi (Latinised to Epsilon Pegasi) is the star's Bayer designation.
It bore the traditional name Enif derived from the Arabic word for 'nose', due to its position as the muzzle of Pegasus. In 2016, the International Astronomical Union organized a Working Group on Star Names (WGSN) to catalog and standardize proper names for stars. The WGSN's first bulletin of July 2016 included a table of the first two batches of names approved by the WGSN; which included Enif for this star.
Other traditional names for the star include Fom al Feras, Latinised to Os Equi. In Chinese, (), meaning Rooftop (asterism), refers to an asterism consisting of Epsilon Pegasi, Alpha Aquarii and Theta Pegasi. Consequently, the Chinese name for Epsilon Pegasi itself is (, .)
Physical characteristics
Epsilon Pegasi is a red supergiant star, as indicated by the stellar classification of K2 Ib. It is estimated to be between seven and twelve times the Sun's mass. The angular diameter of Epsilon Pegasi has been measured many times, giving values between and . At the estimated distance of this star, this yields an enormous physical size of 169 to 185 times the radius of the Sun. Another estimate gives a radius of . From this expanded envelope, it is radiating roughly 8,500 times the luminosity of the Sun at an effective temperature of . This temperature is cooler than the Sun, giving it the orange-hued glow of a K-type star.
Epsilon Pegasi is a slow irregular variable star that usually has a brightness between magnitudes 2.37 and 2.45. However, it was once observed very briefly at magnitude 0.7, giving rise to the theory that it (and possibly other supergiants) erupt in massive flares that dwarf those of the Sun. It has also been observed as faint as magnitude 3.5.
The spectrum shows an overabundance of the elements strontium and barium, which may be the result of the s-process of nucleosynthesis in the outer atmosphere of the star. It has a relatively high peculiar velocity of .
Evolution
Epsilon Pegasi has exhausted its core hydrogen and expanded away from the main sequence. It is almost certainly on the horizontal branch fusing helium in its core. If it loses more mass in the supergiant phase in its evolution, it may shed its outer layers and leave behind an unusual high mass oxygen–neon white dwarf near the Chandrasekhar limit, otherwise it may be able to produce a supernova, albeit an electron capture supernova.
Based on its position on the color-magnitude diagram, Enif may have evolved from a whitish-yellow color to its current red color in the last 2,000 years, though there is currently no historical record supporting this.
Pulfrich effect
Epsilon Pegasi is a fine example to observe the Pulfrich effect. This optical phenomenon is described on page 1372 of Burnham's Celestial Handbook. According to John Herschel: The apparent pendulum-like oscillation of a small star in the same vertical as the large one, when the telescope is swung from side to side.
See also
List of brightest stars
List of nearest bright stars
Lists of stars
Historical brightest stars
References
K-type supergiants
Pegasus (constellation)
Pegasi, Epsilon
BD+09 4891
Pegasi, 08
206778
107315
8308
Enif
Horizontal-branch stars
Slow irregular variables | Epsilon Pegasi | [
"Astronomy"
] | 814 | [
"Pegasus (constellation)",
"Constellations"
] |
1,522,548 | https://en.wikipedia.org/wiki/Alpha%20Phoenicis | Alpha Phoenicis (α Phoenicis, abbreviated Alpha Phe or α Phe), formally named Ankaa , with the same pronunciation) is the brightest star in the constellation of Phoenix.
Nomenclature
Alpha Phoenicis is the star's Bayer designation. It also bore the traditional name Ankaa sometime after 1800, from the Arabic العنقاء al-ʽanqāʼ "the phoenix" for the name of the constellation. The International Astronomical Union has formally adopted the Ankaa as the proper name for Alpha Phoenicis.
Medieval Arab astronomers formed the constellation of the dhow (where Phoenix is), so another popular name for the star is Nair al Zaurak from نائر الزورقnayyir az-zawraq "the bright (star) of the skiff". The Latin translation is Cymbae, from lūcida cumbae.
In Chinese caused by adaptation of the European southern hemisphere constellations into the Chinese system, (), meaning Firebird, refers to an asterism consisting of α Phoenicis, ι Phoenicis, σ Phoenicis, ε Phoenicis, κ Phoenicis, μ Phoenicis, λ1 Phoenicis, β Phoenicis and γ Phoenicis . Consequently, α Phoenicis itself is known as (, .)
Description
Alpha Phoenicis is a spectroscopic binary star system with components that orbit each other every 3,848.8 days (10.5 years). The combined stellar classification of the system is K0.5 IIIb, which matches the spectrum of a normal luminosity giant star. It has an apparent visual magnitude of 2.4, so it is somewhat outshone by its first magnitude neighbors Achernar (α Eridani) and Fomalhaut (α Piscis Austrinus). Based upon parallax measurements, this system is at a distance of about from the Earth. The interferometry-measured angular diameter of the primary component, after correcting for limb darkening, is , which, at its estimated distance, equates to a physical radius of about 15 times the radius of the Sun.
References
Phoenicis, Alpha
K-type giants
Phoenix (constellation)
Spectroscopic binaries
Ankaa
002081
0099
002261
Durchmusterung objects | Alpha Phoenicis | [
"Astronomy"
] | 511 | [
"Phoenix (constellation)",
"Constellations"
] |
1,522,554 | https://en.wikipedia.org/wiki/Eta%20Ophiuchi | Eta Ophiuchi (η Ophiuchi, abbreviated Eta Oph, η Oph) is a binary star in the constellation of Ophiuchus. Based on parallax measurements taken during the Hipparcos mission, it is approximately 88 light-years from the Sun.
Eta Ophiuchi is part of a multiple star system designated WDS J17104-1544. It itself is designated WDS J17104-1544AB and its two components WDS J17104-1544A (also called Sabik , the traditional name for the system) and WDS J17104-1544B. The 'C' component is UCAC4 372-080717 and 'D' is UCAC2 26022336.
Nomenclature
η Ophiuchi (Latinised to Eta Ophiuchi) is the system's Bayer designation. WDS J17104-1544AB is its designation in the Washington Double Star Catalog. The designations of the two components as WDS J17104-1544 A and B derive from the convention used by the Washington Multiplicity Catalog (WMC) for multiple star systems, and adopted by the International Astronomical Union (IAU).
It bore the traditional name Sabik, from the Arabic السابق al-sābiq "the preceding one", of uncertain reference. In 2016, the International Astronomical Union organized a Working Group on Star Names (WGSN) to catalogue and standardize proper names for stars. The WGSN approved the name Sabik for the component WDS J17104-1544 A on 21 August 2016 and it is now so included in the List of IAU-approved Star Names.
In Chinese, this star is considered part of (), meaning Left Wall of Heavenly Market Enclosure, which refers to an asterism representing eleven old states in China that mark the left borderline of the enclosure, consisting of Eta Ophiuchi, Delta Herculis, Lambda Herculis, Mu Herculis, Omicron Herculis, 112 Herculis, Zeta Aquilae, Theta¹ Serpentis, Eta Serpentis, Nu Ophiuchi and Xi Serpentis. Consequently, the Chinese name for Eta Ophiuchi itself is (, ), representing the state Song (宋).
Namesake
USS Sabik (AK-121) was a United States Navy Crater class cargo ship named after the star.
Properties
Eta Ophiuchi is a binary system that is difficult to resolve in amateur telescopes but whose true nature was determined through use of more advanced techniques. The primary star (whose observational data make up the table in this article) is actually only slightly larger and hotter than its companion. Individually each star is a fairly unremarkable A class main sequence star, but as a binary pair they are unusual. Each star orbits around a common center in a close and highly elliptical orbit, making planetary formation unlikely in this system and some stellar data imprecise.
References
Ophiuchi, Eta
Binary stars
Ophiuchi, 35
155125
084012
Ophiuchus
A-type subgiants
6378
Durchmusterung objects
0656.1 | Eta Ophiuchi | [
"Astronomy"
] | 665 | [
"Ophiuchus",
"Constellations"
] |
1,522,563 | https://en.wikipedia.org/wiki/Alpha%20Cephei | Alpha Cephei (α Cephei, abbreviated Alpha Cep, α Cep), officially named Alderamin , is a second magnitude star in the constellation of Cepheus near the northern pole. The star is relatively close to Earth at 49 light years (ly) and drifting closer with a heliocentric radial velocity of about −16 km/s.
Nomenclature
α Cephei (Latinised to Alpha Cephei) is the star's Bayer designation. It has a Flamsteed designation of 5 Cephei.
It bore the traditional name Alderamin, a contraction of the Arabic phrase الذراع اليمين al-dhirā‘ al-yamīn, meaning "the right arm". In 2016, the International Astronomical Union organized a Working Group on Star Names (WGSN) to catalog and standardize proper names for stars. The WGSN's first bulletin of July 2016 included a table of the first two batches of names approved by the WGSN; which included Alderamin for this star.
Visibility
With a declination in excess of 62 degrees north, Alpha Cephei never rises south of −27° latitude, which means for much of South America, Australia, South Africa, and all of New Zealand, the star stays below the horizon. The star is circumpolar throughout all of Europe, northern Asia, Canada, and American cities as far south as San Diego. Since Alpha Cephei has an apparent magnitude of about 2.5, the star is the brightest in the constellation and is easily observable to the naked eye, even in light-polluted cities.
Pole star
Alpha Cephei is located near the precessional path traced across the celestial sphere by the Earth's North pole. That means that it periodically comes within 3° of being a pole star, a title currently held by Polaris. Alpha Cephei will next be the North Star in about the year 7500 AD. The north pole of Mars points to the midpoint of the line connecting the star and Deneb.
Properties
Alderamin is a white class A star, evolving off the main sequence into a subgiant, probably on its way to becoming a red giant as its hydrogen supply runs low. On average, Alderamin has an apparent magnitude of 2.46. In 2007, the star's parallax was measured at yielding a distance of 15 parsecs or approximately 49 light years from Earth.
Interferometry by the CHARA array show that Alderamin has an oblate shape, its equatorial size measures and the polar radius measures . The star's temperature varies as well, from 8,440 K in the poles to 7,600 K in the equator. A more recent but less detailed measurement by the Navy Precision Optical Interferometer gives , which likely corresponds to the equatorial radius. Like other stars in its class, it is slightly variable with a range in brightness of 0.06 magnitude, and is listed as a Delta Scuti variable.
Alderamin has a very high rotation speed of at least 246 km/s, completing one complete revolution in less than 12 hours, with such a rapid turnover appearing to inhibit the differentiation of chemical elements usually seen in such stars. By comparison, the Sun takes almost a month to turn on its axis. Alpha Cephei is also known to emit an amount of X radiation similar to the Sun, which along with other indicators suggests the existence of considerable magnetic activity—something unexpected (though not at all unusual) for a fast rotator.
Etymology and cultural significance
This star, along with Beta Cephei (Alfirk) and Eta Cephei (Alkidr) were al-Kawākib al-Firq (الكواكب الفرق), meaning "the Stars of the Flock" by Ulug Beg.
In Chinese, (), meaning Celestial Hook, refers to an asterism consisting of α Cephei, 4 Cephei, HD 194298, Eta Cephei, Theta Cephei, Xi Cephei, 26 Cephei, Iota Cephei and Omicron Cephei. Consequently, the Chinese name for Alpha Cephei itself is (, .).
Namesakes
USS Alderamin (AK-116) was a United States Navy Crater class cargo ship named after the star.
See also
List of nearest bright stars
Dwarf star
References
External links
NASA's: History of Precession
Crystallinks: Precession of the Equinoxes
Cephei, Alpha
Cepheus (constellation)
A-type subgiants
Northern pole stars
Alderamin
Castor Moving Group
Cephei, 05
203280
8162
BD+61 2111
105199
Suspected variables
Delta Scuti variables
0826 | Alpha Cephei | [
"Astronomy"
] | 1,010 | [
"Constellations",
"Cepheus (constellation)"
] |
1,522,583 | https://en.wikipedia.org/wiki/Alpha%20Ceti | Alpha Ceti (α Ceti, abbreviated Alpha Cet, α Cet), officially named Menkar , is the second-brightest star in the constellation of Cetus. It is a cool luminous red giant estimated to be about 250 light years away based on parallax.
Nomenclature
Alpha Ceti is the star's Bayer designation. It has the traditional name Menkar, deriving from the Arabic word منخر manħar "nostril" (of Cetus). In 2016, the International Astronomical Union organized a Working Group on Star Names (WGSN) to catalog and standardize proper names for stars. The WGSN's first bulletin of July 2016 included a table of the first two batches of names approved by the WGSN; which included Menkar for this star.
This star, along with γ Cet (Kaffaljidhma), δ Cet, λ Cet (also Menkar), μ Cet, ξ1 Cet and ξ2 Cet were Al Kaff al Jidhmah, "the Part of a Hand".
In Chinese, (), meaning Circular Celestial Granary, refers to an asterism consisting of α Ceti, κ1 Ceti, λ Ceti, μ Ceti, ξ1 Ceti, ξ2 Ceti, ν Ceti, γ Ceti, δ Ceti, 75 Ceti, 70 Ceti, 63 Ceti and 66 Ceti. Consequently, the Chinese name for α Ceti itself is (, .)
Characteristics
Despite having the Bayer designation α Ceti, at visual magnitude 2.54 this star is actually not the brightest star in the constellation Cetus. That honor goes instead to Beta Ceti at magnitude 2.04. Menkar is a red giant with a stellar classification of M1.5 IIIa. It has more than twice the mass of the Sun and, as a giant star, has expanded to about 100 times the Sun's radius. The large area of the photosphere means that it is emitting about 1,765 times as much energy as the Sun, even though the effective temperature is only (compared to on the Sun). The relatively low temperature gives Menkar the red hue of an M-type star.
Menkar has evolved from the main sequence after exhausting the hydrogen at its core. It has also exhausted its core helium, becoming an asymptotic giant branch star, and will probably become a highly unstable star like Mira before finally shedding its outer layers and forming a planetary nebula, leaving a relatively large white dwarf remnant. It has been observed to periodically vary in brightness, but only with an amplitude of about one hundredth of a magnitude.
Namesakes
Menkar (AK-123) was a United States Navy Crater class cargo ship named after the star.
References
External links
Assorted figures related to Alpha Ceti
M-type giants
Asymptotic-giant-branch stars
Cetus
Ceti, Alpha
BD+03 0419
Ceti, 92
018884
014135
0911
Menkar | Alpha Ceti | [
"Astronomy"
] | 633 | [
"Cetus",
"Constellations"
] |
1,522,589 | https://en.wikipedia.org/wiki/Delta%20Leonis | Delta Leonis (δ Leonis, abbreviated Delta Leo, δ Leo), also named Zosma , is a star in the zodiac constellation of Leo. Based upon parallax measurements, it lies at a distance of about from the Sun.
Properties
δ Leonis is a main-sequence star with a stellar classification of A4 V, meaning it is larger and hotter than the Sun. It is a fairly well-studied star, allowing relatively accurate measurements of its age and size. The radius of the star, as measured directly using an interferometer, is about 214% of the Sun's radius and it is emitting more than 15 times as much luminosity as the Sun. The energy is being emitted from the outer envelope with an effective temperature , giving it the white hue characteristic of an A-type star. Having a larger mass than the Sun it will have a shorter lifespan, and in another 600 million years or so will swell into an orange or red giant star before decaying quietly into a remnant white dwarf consisting of carbon and oxygen.
This star is rotating rapidly, with a projected rotational velocity of 180 km s−1. The inclination of the axis of rotation to the line of sight from the Earth is estimated at 38.1°, which would mean the azimuthal velocity along the equator is about 280 km s−1. This rotation is producing an equatorial bulge, giving the star a pronounced oblate spheroidal shape. The polar radius is about 84% of the radius along the equator.
Based upon the location and trajectory of this star through space, it may be a member of the Ursa Major Moving Group, a type of stellar kinematics group that share a common origin and motion through space. The age of this group is about 500 million years.
Nomenclature
δ Leonis (Latinised to Delta Leonis) is the star's Bayer designation.
It bore the traditional names Zosma or Zozma and Duhr (rare spellings included Zozca, Zosca, Al-Zubra الزبرة, traditional Arabic for both shoulder, and a lion's mane and Dhur ظهر, the latter meaning 'back' in Arabic). Zosma means 'girdle' in ancient Greek, referring to the star's location in its constellation, on the hip of the lion. In 2016, the International Astronomical Union organized a Working Group on Star Names (WGSN) to catalog and standardize proper names for stars. The WGSN's first bulletin of July 2016 included a table of the first two batches of names approved by the WGSN, which included Zosma for this star.
In Chinese, (), meaning Right Wall of Supreme Palace Enclosure, refers to an asterism consisting of δ Leonis, β Virginis, σ Leonis, ι Leonis and θ Leonis. Consequently, the Chinese name for δ Leonis itself is (, ), representing (), meaning The First Western Minister. 西上相 (Xīshǎngxiāng), spelled Shang Seang by R.H. Allen, means "the Higher Minister of State".
References
A-type main-sequence stars
Ursa Major moving group
Zosma
Leonis, Delta
Leo (constellation)
Durchmusterung objects
Leonis, 68
0419
054872
097603
4357 | Delta Leonis | [
"Astronomy"
] | 694 | [
"Leo (constellation)",
"Constellations"
] |
1,522,595 | https://en.wikipedia.org/wiki/Alpha%20Leporis | Alpha Leporis (α Leporis, abbreviated Alpha Lep, α Lep), formally named Arneb , is the brightest star in the constellation of Lepus.
Nomenclature
Alpha Leporis is the star's Bayer designation. The traditional name Arneb comes from the Arabic أرنب ’arnab 'hare' ('Lepus' is Latin for hare). In 2016, the International Astronomical Union organized a Working Group on Star Names (WGSN) to catalog and standardize proper names for stars. The WGSN's first bulletin of July 2016 included a table of the first two batches of names approved by the WGSN; which included Arneb for this star.
In Chinese, (), meaning Toilet, refers to an asterism consisting of α Leporis, β Leporis, γ Leporis and δ Leporis. Consequently, the Chinese name for α Leporis itself is (), "the First Star of Toilet".
Properties
This is a massive star with about 14 times the mass of the Sun. The interferometer-measured angular diameter of this star, after correction for limb darkening, is . At an estimated distance of , this yields a physical size of about 129 times the radius of the Sun. Alpha Leporis has a stellar classification of F0 Ib, with the Ib luminosity class indicating that it is a lower luminosity yellow supergiant star. Since 1943, the spectrum of this star has served as one of the stable anchor points by which other stars are classified. The effective temperature of the outer envelope is about 7,300K, which gives the star a yellowish-white hue that is typical of F-type stars. It is an estimated 13 million years old.
Arneb is an older, dying star that has already passed through a red supergiant phase and is now contracting and heating up in the latter phases of stellar evolution, in a blue loop.
Namesakes
USS Arneb (AKA-56) was a ship of the United States Navy.
References
Leporis, Alpha
Lepus (constellation)
F-type supergiants
Arneb
Leporis, 11
025985
1865
036673
Durchmusterung objects
Suspected variables | Alpha Leporis | [
"Astronomy"
] | 469 | [
"Lepus (constellation)",
"Constellations"
] |
1,522,602 | https://en.wikipedia.org/wiki/Beta%20Pegasi | Beta Pegasi (β Pegasi, abbreviated Beta Peg, β Peg), formally named Scheat , is a red giant star and the second-brightest star (after Epsilon Pegasi) in the constellation of Pegasus. It forms the upper right corner of the Great Square of Pegasus, a prominent rectangular asterism.
Nomenclature
β Pegasi (Latinised to Beta Pegasi) is the star's Bayer designation.
It bore the traditional name of Scheat, a name that had also been used for Delta Aquarii. The name was derived from the Arabic Al Sā'id "the upper arm", or from Sa'd. In 2016, the International Astronomical Union organised a Working Group on Star Names (WGSN) to catalog and standardise proper names for stars. The WGSN's first bulletin of July 2016 included a table of the first two batches of names approved by the WGSN; which included Scheat for this star (the name Skat was later approved for Delta Aquarii).
In Chinese, (), meaning Encampment, refers to an asterism consisting β Pegasi and α Pegasi. Consequently, the Chinese name for β Pegasi itself is (), "the Second Star of Encampment".
Distance and properties
Based upon parallax measurements, Beta Pegasi is located about from the Sun. It is unusual among bright stars in having a relatively cool surface temperature compared to stars like the Sun.
This star has a stellar classification of M2.3 II–III, which indicates the spectrum has characteristics partway between a bright giant and a giant star. It has expanded until it is 109 times as large, and has a total luminosity of 1,640 times that of the Sun. The effective temperature of the star's outer envelope is about 3,600 K, giving the star the characteristic orange-red hue of an M-type star. The photosphere is sufficiently cool for molecules of titanium oxide to form.
Johann Friedrich Julius Schmidt discovered that Beta Pegasi is a variable star, in 1847. Beta Pegasi is a semi-regular variable with a period of 43.3 days and a brightness that varies from magnitude +2.31 to +2.74 (averaging 2.42). It is losing mass at a rate at or below 10−8 times the Sun's mass per year, which is creating an expanding shell of gas and dust with a radius of about 3,500 times the Sun's radius (16 astronomical units).
Notes
References
Pegasi, Beta
M-type bright giants
M-type giants
Pegasus (constellation)
Scheat
Pegasi, 53
8775
217906
113881
BD+27 4480
Semiregular variable stars
Emission-line stars
TIC objects | Beta Pegasi | [
"Astronomy"
] | 574 | [
"Pegasus (constellation)",
"Constellations"
] |
1,522,608 | https://en.wikipedia.org/wiki/Beta%20Ceti | Beta Ceti (β Ceti, abbreviated Beta Cet, β Cet), officially named Diphda , is the brightest star in the constellation of Cetus. Although designated 'beta', it is actually brighter than the 'alpha' star in the constellation, Menkar, by half a magnitude. This orange giant is easy to identify due to its location in an otherwise dark section of the celestial sphere. Based on parallax measurements, it lies at an estimated distance of from the Sun.
Properties
Diphda has an apparent visual magnitude of 2.02, making it the brightest star in Cetus. It has a stellar classification of K0 III, although some sources list a classification of G9.5 III indicating that it lies along the dividing line separating G-type from K-type stars. The luminosity class 'III' means that it is a giant, a star that has consumed the hydrogen at its core and evolved away from the main sequence. With a mass of 3.5 solar masses, Beta Ceti was a B-type star when it formed on the main sequence. After passing through the red giant stage, it underwent a helium flash event and is now a red clump star generating energy through the thermonuclear fusion of helium at its core. Beta Ceti will remain in this mode for over 100 million years.
The effective temperature of the star's outer envelope is about , giving it the characteristic orange hue of a K-type star. In spite of its cooler temperature, Diphda is much more luminous than the Sun with a luminosity of about 150 times that of the Sun, while its photosphere has swollen to around 18 times the size of the Sun, in contrast with the initial radius of when still in the main sequence.
This star displays flaring activity that results in random outbursts that increase the luminosity of the star over intervals lasting several days. This is a much longer duration than for comparable solar flare activity on the Sun, which typically last for periods measured in hours. In 2005, a relatively high rate of X-ray emission was detected with the XMM-Newton space observatory. It is emitting about 2,000 times the X-ray luminosity of the Sun, allowing the star to be imaged with the Chandra X-ray Observatory.
Nomenclature
β Ceti (Latinised to Beta Ceti) is the star's Bayer designation.
It bore the traditional names Diphda and Deneb Kaitos . Diphda is Arabic for 'frog', from the phrase ضفدع الثاني aḍ-ḍifdaʿ aṯ-ṯānī 'the second frog' (the 'first frog' is Fomalhaut). Deneb Kaitos is from الذنب القيتوس الجنوب Al Dhanab al Ḳaiṭos al Janūbīyy 'southern tail of Cetus'.
In 2016, the International Astronomical Union organized a Working Group on Star Names (WGSN) to catalogue and standardize proper names for stars. The WGSN approved the name Diphda for this star on 21 August 2016 and it is now so entered in the IAU Catalog of Star Names.
In Chinese astronomy, Deneb Kaitos is called 土司空, Pinyin: Tǔsīkōng, meaning Master of Constructions, because this star is marking itself and stands alone in the Master of Constructions asterism, Legs mansion (see : Chinese constellation). 土司空 (Tǔsīkōng), westernized into Too Sze Kung by R.H. Allen and the meaning is "Superintendent of Earthworks."
Namesake
USS Diphda (AKA-59) was a U.S. Navy ship.
See also
List of nearest giant stars
References
External links
Beta Ceti: Giant Star's Corona Brightens with Age
Ceti, Beta
Cetus
K-type giants
Diphda
Suspected variables
0188
004128
BD-18 0115
Ceti, 16
003419
0031 | Beta Ceti | [
"Astronomy"
] | 831 | [
"Cetus",
"Constellations"
] |
1,522,618 | https://en.wikipedia.org/wiki/Gamma%20Pegasi | Gamma Pegasi is a star in the constellation of Pegasus, located at the southeast corner of the asterism known as the Great Square. It has the formal name Algenib ; the Bayer designation Gamma Pegasi is Latinized from γ Pegasi and abbreviated Gamma Peg or γ Peg. The average apparent visual magnitude of +2.84 makes this the fourth-brightest star in the constellation. The distance to this star has been measured using the parallax technique, yielding a value of roughly .
Nomenclature
Gamma Pegasi is the star's Bayer designation. Although it also had the traditional name Algenib, this name was also used for Alpha Persei. In 2016, the International Astronomical Union organized a Working Group on Star Names (WGSN) to catalog and standardize proper names for stars. The WGSN's first bulletin of July 2016 included a table of the first two batches of names approved by the WGSN; which included Algenib for this star (Alpha Persei was given the name Mirfak).
The asterism of γ Pegasi and α Andromedae, in Hindu astronomy, is called Uttara Bhādrapadā (उत्तरभाद्रपदा) or Uttṛṭṭāti. It is the 26th nakshatra. In Chinese, (), meaning Wall (asterism) refers to an asterism consisting of γ Pegasi and α Andromedae . Consequently, the Chinese name for γ Pegasi itself is (, .)
Properties
In 1911, American astronomer Keivin Burns discovered that the radial velocity of Gamma Pegasi varied slightly. This was confirmed in 1953 by American astronomer D. Harold McNamara, who identified it as a Beta Cephei variable. (At the time he actually identified it as a Beta Canis Majoris star, which was subsequently designated a Beta Cephei variable.) It has a radial pulsation period of 0.15175 days (3.642 hours), but also shows the behavior of a slowly pulsating B star (SPB) with three additional pulsational frequencies. Hence it is considered a hybrid pulsator. Its magnitude varies between +2.78 and +2.89 over the course of each pulsation cycle.
This is a large star with almost nine times the mass of the Sun and close to five times the Sun's radius. The stellar classification of B2 IV suggests this is a subgiant star that is exhausting the hydrogen at its core and is in the process of evolving away from the main sequence. It is either rotating very slowly with no measurable rotational velocity or else it is being viewed from nearly pole-on. Gamma Pegasi has a total luminosity of 5,840 times that of the Sun, which is being radiated from its outer atmosphere at an effective temperature of more than 21,000 K. At this temperature, the star glows with a blue-white hue.
The star has a weak magnetic field (from -10 G to 30 G, an upper bound on a dipolar magnetic field strength of about ).
References
External links
B-type subgiants
Beta Cephei variables
Pegasus (constellation)
Pegasi, Gamma
0039
Durchmusterung objects
Pegasi, 88
000886
001067
Algenib | Gamma Pegasi | [
"Astronomy"
] | 684 | [
"Pegasus (constellation)",
"Constellations"
] |
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