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11,491,940 | https://en.wikipedia.org/wiki/Karger%27s%20algorithm | In computer science and graph theory, Karger's algorithm is a randomized algorithm to compute a minimum cut of a connected graph. It was invented by David Karger and first published in 1993.
The idea of the algorithm is based on the concept of contraction of an edge in an undirected graph . Informally speaking, the contraction of an edge merges the nodes and into one, reducing the total number of nodes of the graph by one. All other edges connecting either or are "reattached" to the merged node, effectively producing a multigraph. Karger's basic algorithm iteratively contracts randomly chosen edges until only two nodes remain; those nodes represent a cut in the original graph. By iterating this basic algorithm a sufficient number of times, a minimum cut can be found with high probability.
The global minimum cut problem
A cut in an undirected graph is a partition of the vertices into two non-empty, disjoint sets . The cutset of a cut consists of the edges between the two parts. The size (or weight) of a cut in an unweighted graph is the cardinality of the cutset, i.e., the number of edges between the two parts,
There are ways of choosing for each vertex whether it belongs to or to , but two of these choices make or empty and do not give rise to cuts. Among the remaining choices, swapping the roles of and does not change the cut, so each cut is counted twice; therefore, there are distinct cuts.
The minimum cut problem is to find a cut of smallest size among these cuts.
For weighted graphs with positive edge weights the weight of the cut is the sum of the weights of edges between vertices in each part
which agrees with the unweighted definition for .
A cut is sometimes called a “global cut” to distinguish it from an “- cut” for a given pair of vertices, which has the additional requirement that and . Every global cut is an - cut for some . Thus, the minimum cut problem can be solved in polynomial time by iterating over all choices of and solving the resulting minimum - cut problem using the max-flow min-cut theorem and a polynomial time algorithm for maximum flow, such as the push-relabel algorithm, though this approach is not optimal. Better deterministic algorithms for the global minimum cut problem include the Stoer–Wagner algorithm, which has a running time of .
Contraction algorithm
The fundamental operation of Karger’s algorithm is a form of edge contraction. The result of contracting the edge is a new node . Every edge or for to the endpoints of the contracted edge is replaced by an edge to the new node. Finally, the contracted nodes and with all their incident edges are removed. In particular, the resulting graph contains no self-loops. The result of contracting edge is denoted .
The contraction algorithm repeatedly contracts random edges in the graph, until only two nodes remain, at which point there is only a single cut.
The key idea of the algorithm is that it is far more likely for non min-cut edges than min-cut edges to be randomly selected and lost to contraction, since min-cut edges are usually vastly outnumbered by non min-cut edges. Subsequently, it is plausible that the min-cut edges will survive all the edge contraction, and the algorithm will correctly identify the min-cut edge.
procedure contract():
while
choose uniformly at random
return the only cut in
When the graph is represented using adjacency lists or an adjacency matrix, a single edge contraction operation can be implemented with a linear number of updates to the data structure, for a total running time of . Alternatively, the procedure can be viewed as an execution of Kruskal’s algorithm for constructing the minimum spanning tree in a graph where the edges have weights according to a random permutation . Removing the heaviest edge of this tree results in two components that describe a cut. In this way, the contraction procedure can be implemented like Kruskal’s algorithm in time .
The best known implementations use time and space, or time and space, respectively.
Success probability of the contraction algorithm
In a graph with vertices, the contraction algorithm returns a minimum cut with polynomially small probability . Recall that every graph has cuts (by the discussion in the previous section), among which at most can be minimum cuts. Therefore, the success probability for this algorithm is much better than the probability for picking a cut at random, which is at most .
For instance, the cycle graph on vertices has exactly minimum cuts, given by every choice of 2 edges. The contraction procedure finds each of these with equal probability.
To further establish the lower bound on the success probability, let denote the edges of a specific minimum cut of size . The contraction algorithm returns if none of the random edges deleted by the algorithm belongs to the cutset . In particular, the first edge contraction avoids , which happens with probability . The minimum degree of is at least (otherwise a minimum degree vertex would induce a smaller cut where one of the two partitions contains only the minimum degree vertex), so . Thus, the probability that the contraction algorithm picks an edge from is
The probability that the contraction algorithm on an -vertex graph avoids satisfies the recurrence , with , which can be expanded as
Repeating the contraction algorithm
By repeating the contraction algorithm times with independent random choices and returning the smallest cut, the probability of not finding a minimum cut is
The total running time for repetitions for a graph with vertices and edges is .
Karger–Stein algorithm
An extension of Karger’s algorithm due to David Karger and Clifford Stein achieves an order of magnitude improvement.
The basic idea is to perform the contraction procedure until the graph reaches vertices.
procedure contract(, ):
while
choose uniformly at random
return
The probability that this contraction procedure avoids a specific cut in an -vertex graph is
This expression is approximately and becomes less than around . In particular, the probability that an edge from is contracted grows towards the end. This motivates the idea of switching to a slower algorithm after a certain number of contraction steps.
procedure fastmincut():
if :
return contract(, )
else:
contract(, )
contract(, )
return min{fastmincut(), fastmincut()}
Analysis
The contraction parameter is chosen so that each call to contract has probability at least 1/2 of success (that is, of avoiding the contraction of an edge from a specific cutset ). This allows the successful part of the recursion tree to be modeled as a random binary tree generated by a critical Galton–Watson process, and to be analyzed accordingly.
The probability that this random tree of successful calls contains a long-enough path to reach the base of the recursion and find is given by the recurrence relation
with solution . The running time of fastmincut satisfies
with solution . To achieve error probability , the algorithm can be repeated times, for an overall running time of . This is an order of magnitude improvement over Karger’s original algorithm.
Improvement bound
To determine a min-cut, one has to touch every edge in the graph at least once, which is time in a dense graph. The Karger–Stein's min-cut algorithm takes the running time of , which is very close to that.
References
Graph algorithms
Graph connectivity | Karger's algorithm | Mathematics | 1,500 |
44,376,370 | https://en.wikipedia.org/wiki/Prevention%20of%20Damage%20by%20Pests%20Act%201949 | The Prevention of Damage by Pests Act 1949 (12, 13 & 14 Geo. 6. c. 55) is legislation in the United Kingdom, that creates a duty on local authorities to control mice and rats. The legislation grants powers to local authorities to compel land owners and/or occupiers to take action to keep land free from rats and mice.
References
Rodents and humans
United Kingdom Acts of Parliament 1949
Pest legislation | Prevention of Damage by Pests Act 1949 | Biology | 88 |
19,727,998 | https://en.wikipedia.org/wiki/Aero%20Controls | Aero Controls, Inc. is an aerospace engineering company founded in October 1984 by John Titus, the CEO and President of the Company, headquartered in Seattle, Washington.
History
It is a minority-owned, FAA certified repair station. The company overhauls, repairs, sells, exchanges and modifies components of aircraft. It opened a satellite location in Shelton, Washington in 1993. In 1995 Aero Controls was presented with the Federal Express Minority Supplier of the Year Award. In 1996 the Company acquired Aero Systems Aviation Corp. in Miami. In 2006 Aero Controls Avionics was merged with Aero Controls, Inc. In 2007 the company acquired Ft. Lauderdale based Patriot Aviation Services, LLC. The company has approximately 250 employees and revenues of 50 M.It is actually headquartered in Auburn, Washington.
Community service
Aero Controls Inc participates in community services such as, food drive: assisting local food banks in feeding the homeless and underprivileged in the Auburn, Kent, Federal Way, Shelton and Miami Florida areas; Heart Walk: Benefits the American Heart Association; Relay for Life: Benefits the American Cancer Society; Backpack Program: Provides school supplies for needy children; Aero Controls Golf Tournament: held annually to raise money for the community service fund; Adopt-A- Family; Highway Clean Up; Puget Sound Blood Mobile.
References
External links
Aero Controls
Companies based in Seattle
Aerospace engineering organizations
Technology companies established in 1984
1984 establishments in Washington (state) | Aero Controls | Engineering | 285 |
2,405,440 | https://en.wikipedia.org/wiki/Enthalpy%20of%20atomization | In chemistry, the enthalpy of atomization (also atomisation in British English) is the enthalpy change that accompanies the total separation of all atoms in a chemical substance either an element or a compound. This is often represented by the symbol or All bonds in the compound are broken in atomization and none are formed, so enthalpies of atomization are always positive. The associated standard enthalpy is known as the standard enthalpy of atomization, /(kJ mol−1), at 298.15 K (or 25 degrees Celsius) and 100 kPa.
Definition
Enthalpy of atomization is the amount of enthalpy change when bonds of the compound are broken and the component atoms are separated into single atoms ( or monoatom).
Enthalpy of atomization is denoted by the symbol ΔHat. The enthalpy change of atomization of gaseous H2O is, for example, the sum of the HO–H and H–OH bond dissociation enthalpies.
The enthalpy of atomization of an elemental solid is exactly the same as the enthalpy of sublimation for any elemental solid that becomes a monatomic gas upon evaporation.
When a diatomic element is converted to gaseous atoms, only half a mole of molecules will be needed, as the standard enthalpy change is based purely on the production of one mole of gaseous atoms.
See also
Ionization energy
Electron gain enthalpy
References
Enthalpy | Enthalpy of atomization | Physics,Chemistry,Mathematics | 314 |
67,601,526 | https://en.wikipedia.org/wiki/Jean-Luc%20Sandoz | Jean-Luc Sandoz (born 1960 in Montandon) is a French-Swiss engineer and an expert in wood construction. He is the founder of several companies in the field of engineering, industrialization, construction and expertise, all related to wood. Formerly, he was a professor and lecturer at EPFL (École Polytechnique Fédérale de Lausanne).
Career
Born into a family of farmers in the Haut-Doubs region, he became acquainted with the material wood, starting with a vocational training certificate in carpentry, followed by a BEP (vocational training certificate) in cabinetmaking, before joining the Lycée Bois de Mouchard in 1976, where he obtained a BTS (vocational training certificate) in wood construction.
After studies at ENSTIB (École Nationale Supérieure des Technologies et des Industries du Bois), in 1985, he began his thesis on the subject of ultrasound and the mechanical strength of wood, under the direction of Julius Natterer at EPFL. He obtained his PhD in 1990 for his thesis entitled "Triage et fiabilité des bois de construction: validité de la méthode ultrason" (Sorting and reliability of construction timber: validity of the ultrasonic method).
He continued research at the IBOIS (Laboratory for Timber Construction) at EPFL in two areas: non-destructive technologies to measure the mechanical quality of wood material and the optimisation of wooden structures for the application in large buildings.
In 1993, he was appointed assistant professor at EPFL.
Together with Julius Natterer and Martial Rey, Sandoz authored the textbook "Construction en Bois" (Wood Construction that has remained in print since its release in 1996 (20 new editions).
During this period he organised several international symposia among them the Symposium on Nondestructive Testing of Wood and the World Conference on Timber Engineering.
He registered several patents such as for a device for measuring the characteristics of wood using ultrasound (Sylvatest), and an application for measuring wooden poles for overhead electricity and telephone lines (K-Store & Polux), as well as for the construction of wood and mixed wood-concrete slabs as the Ariane truss.
In 1999, Sandoz left the academic world to devote himself to his company CBS-Lifteam.
Wooden structures
Sandoz integrates wood in all types of structures and buildings and optimises spans and heights, as well as for thermal and acoustic performance. Several of his projects won awards.
Examples of Sandoz' structures:
In 2000, he inspected the wooden structure of the Valère Basilica in Sion.
For the Swiss national exhibition Expo.02 in 2002, he designed and built the offshore platforms that were placed on the lakes of Neuchâtel and Bienne to house the temporary exhibition pavilions. Made of local wood, the entire wooden structure was dismantled and reused after the expo period.
In 2006–2007, he inspected the residual performance of the wooden structure of the Forbidden City in Beijing
In 2017, he collaborated on the construction of the Guiana Space Centre and helped with the characterisation and employment of local wood from the Amazonian forest.
In 2019, he used wood to clad the Vortex building, which served as the Olympic village for the 2020 Winter Youth Olympic Games in Lausanne before taking on its present function as student accommodation
Selected works
References
External links
Website of the company CBS-CBT
1960 births
Living people
École Polytechnique Fédérale de Lausanne alumni
Structural engineers
French engineers
Swiss engineers | Jean-Luc Sandoz | Engineering | 708 |
12,821,736 | https://en.wikipedia.org/wiki/Presentation%20complex | In geometric group theory, a presentation complex is a 2-dimensional cell complex associated to any presentation of a group G. The complex has a single vertex, and one loop at the vertex for each generator of G. There is one 2-cell for each relation in the presentation, with the boundary of the 2-cell attached along the appropriate word.
Properties
The fundamental group of the presentation complex is the group G itself.
The universal cover of the presentation complex is a Cayley complex for G, whose 1-skeleton is the Cayley graph of G.
Any presentation complex for G is the 2-skeleton of an Eilenberg–MacLane space .
Examples
Let be the two-dimensional integer lattice, with presentation
Then the presentation complex for G is a torus, obtained by gluing the opposite sides of a square, the 2-cell, which are labelled x and y. All four corners of the square are glued into a single vertex, the 0-cell of the presentation complex, while a pair consisting of a longtitudal and meridian circles on the torus, intersecting at the vertex, constitutes its 1-skeleton.
The associated Cayley complex is a regular tiling of the plane by unit squares. The 1-skeleton of this complex is a Cayley graph for .
Let be the Infinite dihedral group, with presentation . The presentation complex for is , the wedge sum of projective planes. For each path, there is one 2-cell glued to each loop, which provides the standard cell structure for each projective plane. The Cayley complex is an infinite string of spheres.
References
Roger C. Lyndon and Paul E. Schupp, Combinatorial group theory. Reprint of the 1977 edition (Ergebnisse der Mathematik und ihrer Grenzgebiete, Band 89). Classics in Mathematics. Springer-Verlag, Berlin, 2001
Ronald Brown and Johannes Huebschmann, Identities among relations, in Low dimensional topology, London Math. Soc. Lecture Note Series 48 (ed. R. Brown and T.L. Thickstun, Cambridge University Press, 1982), pp. 153–202.
Hog-Angeloni, Cynthia, Metzler, Wolfgang and Sieradski, Allan J. (eds.). Two-dimensional homotopy and combinatorial group theory, London Mathematical Society Lecture Note Series, Volume 197. Cambridge University Press, Cambridge (1993).
Algebraic topology
Geometric group theory | Presentation complex | Physics,Mathematics | 504 |
26,311,829 | https://en.wikipedia.org/wiki/English%20Engineering%20Units | Some fields of engineering in the United States use a system of measurement of physical quantities known as the English Engineering Units. Despite its name, the system is based on United States customary units of measure.
Definition
The English Engineering Units is a system of units used in the United States. The set is defined by the following units, and definitive conversions to the International System of Units.
Units for other physical quantities are derived from this set as needed.
In English Engineering Units, the pound-mass and the pound-force are distinct base units, and Newton's Second Law of Motion takes the form where is the acceleration in ft/s2 and .
History and etymology
The term English units strictly refers to the system used in England until 1826, when it was replaced by (more rigorously defined) Imperial units. The United States continued to use the older definitions until the Mendenhall Order of 1893, which established the United States customary units. Nevertheless, the term "English units" persisted in common speech and was adapted as "English engineering units" but these are based on US customary units rather than the pre-1826 English system.
British Engineering Units
A similar system, termed British Engineering Units by Halliday and Resnick (1974), is a system that uses the slug as the unit of mass, and in which Newton's law retains the form . Modern British engineering practice has used SI base units since at least the late 1970s.
See also
Imperial and US customary measurement systems
Notes
References
Customary units of measurement
Customary units of measurement in the United States | English Engineering Units | Mathematics | 310 |
5,939,526 | https://en.wikipedia.org/wiki/Curing%20salt | Curing salt is used in meat processing to generate a pinkish shade and to extend shelf life. It is both a color agent and a means to facilitate food preservation as it prevents or slows spoilage by bacteria or fungus. Curing salts are generally a mixture of sodium chloride (table salt) and sodium nitrite, and are used for pickling meats as part of the process to make sausage or cured meat such as ham, bacon, pastrami, corned beef, etc. Though it has been suggested that the reason for using nitrite-containing curing salt is to prevent botulism, a 2018 study by the British Meat Producers Association determined that legally permitted levels of nitrite have no effect on the growth of the Clostridium botulinum bacteria that causes botulism, in line with the UK's Advisory Committee on the Microbiological Safety of Food opinion that nitrites are not required to prevent C. botulinum growth and extend shelf life. (see also Sodium Nitrite: Inhibition of microbial growth).
Many curing salts also contain red dye that makes them pink to prevent them from being confused with common table salt. Thus curing salt is sometimes referred to as "pink salt". Curing salts are not to be confused with Himalayan pink salt, a halite which is 97–99% sodium chloride (table salt) with trace elements that give it a pink color.
Types
There are many types of curing salts often specific to a country or region.
Prague Powder #1
One of the most common curing salts. It is also called Insta Cure #1 or Pink curing salt #1. It contains 6.25% sodium nitrite and 93.75% table salt. It is recommended for meats that require short cures and will be cooked and eaten relatively quickly. Sodium nitrite provides the characteristic flavor and color associated with curing.
Prague Powder #2
Also called Pink curing salt #2. It contains 6.25% sodium nitrite, 4% sodium nitrate, and 89.75% table salt. The sodium nitrate found in Prague powder #2 gradually breaks down over time into sodium nitrite, and by the time a dry cured sausage is ready to be eaten, no sodium nitrate should be left. For this reason it is recommended for meats that require long (weeks to months) cures, like hard salami and country ham.
Saltpetre
Another name for potassium nitrate (KNO3), saltpetre, also called saltpeter or nitrate of potash, has been a common ingredient of some types of salted meat for centuries but its use has been mostly discontinued due to inconsistent results compared to nitrite compounds (KNO2, NaNO2, NNaNO2, etc.) Even so, saltpetre is still used in some food applications, such as some charcuterie products. It should not be confused with Chile saltpetre or Peru saltpetre, which is sodium nitrate (NaNO3).
See also
References
Edible salt
Food preservation | Curing salt | Chemistry | 632 |
39,611,408 | https://en.wikipedia.org/wiki/Balloon%20flange%20girder | A balloon flange girder is a form of vertical I-beam wrought iron plate girder, where the top flange, instead of being a simple flat plate, is extended into a hollow tube. When a girder is subjected to a positive bending moment the top flange acts in compression making a flat plate flange more susceptible to local buckling than the balloon flange is.
This type of girder was rarely used, its only common user being Isambard Kingdom Brunel in the 1840s and 1850s.
Design
Brunel was working at a period of increased theoretical and mathematical analysis of bridge and mechanical structures. Together with the work of William Fairbairn, particularly in relation to Stephenson's tubular bridges such as Conwy, there was an increased understanding of how beams in compression would fail by buckling.
Brunel was known for his distrust of cast iron as a material, at least for large beams. This distrust of cast iron was vindicated when his friend Stephenson's adventurous cast-iron Dee Bridge (1846) collapsed in 1847. Brunel gave evidence in his support at the following inquiry, but this was on the basis of Stephenson being a competent engineer within the bounds of current knowledge, rather than in support of large cast-iron beams. Stephenson's Dee Bridge had used a truss girder, where an inverted T-shaped cast iron girder was trussed by applied wrought iron tension bars. This faulty design was instrumental in the bridge failure, where tension in the truss rods increased compression in the upper part of the girder such that it underwent columnar failure. Despite this, although with the advantage of hindsight, Brunel would use similar applied tension chains for his truss design.
Around the 1840s, developments in the puddling furnace reduced the cost of wrought iron and improvements to rolling mills allowed the production of large flat sections. This iron was now economic for the construction of girders, assembled by riveting of flat sections.
Development
Brunel had already experimented with simple bulb-headed girders in cast iron, for the relatively short 35-foot span of Bishop's Bridge canal bridge at Paddington. These had a T-section lower flange in tension and a larger circular bulb at the upper edge, in compression. As was his habit, Brunel hydraulically tested samples of these girders for strength in 1838 and recorded the results in one of his books of 'Facts'.
Experimental girder
To develop a reliable truss girder for long-span bridges, Brunel carried out a remarkable experiment with a full size girder. This used a single wrought iron plate girder, 70 ft in length, which was loaded up to the point of collapse, first with 165 tons load then, after repair, to 188 tons. Brunel was aware that the likely failure mechanism of this girder was by buckling collapse in the upper flange, which would be under compression forces. To resist this, the flange was supported by triangulated plates and the flange was also slight curved. The experiment was a great success, the bridge eventually failing at a considerable load, representing an efficient use of construction materials for a bridge of this capacity, compared to previous designs.
South Wales Railway
Brunel made early and widespread use of this girder across his South Wales Railway. It was used for spans up to 100 feet, iron truss bridges being used beyond that.
Improvements in plate rolling allowed a change in the shape of the girder. Rather than merely a slightly curved top plate with triangular gussets, it was now possible to roll a semi-circular plate. This allowed the fully developed 'balloon' shape to be used, as in the second cross-section illustrated. The top web of the girder was semi-circular and riveted to the centre plate by an L-strip. The side gussets, also curved, were riveted parallel to the edges of this top plate, rather than through another L-strip, as used originally. Brunel (probably correctly) considered the smooth balloon profile to be a more efficient design, influenced by his geometric approaches to design rather than Eaton's mathematical analysis. More practically, the parallel lap joint halved the amount of riveting needed, compared to the L-strip.
None of these bridges are known to survive in their balloon form, although a girder from one was later re-used for bridge widening work (1861) across the Coity road near Bridgend and survived there. The Coity Road bridge had been built before this date, but was widened to accommodate the new Llynvi Valley Railway. One side of the bridge was moved outwards to accommodate a new siding and a balloon girder installed on that side. This girder (especially as it was installed after Brunel's death) is thought to have previously been used elsewhere on the SWR, although its original date and location is unknown.
Similar girders were used to cross the Severn at Over.
Eastern Bengal Railway
The next development retained the semicircular top flange, but the side gussets were now abandoned altogether as it was considered that the depth of the flange, even if not supported by another plate, would be stiff enough. This also allowed better access to the inside, for painting. Intermittent cross diaphragms were placed across the flange, to maintain its position relative to the main web and avoid distortion by rocking sideways.
The form of girder was widely used in Brunel's work for the Eastern Bengal Railway.
Cumberland Basin bridges
When Brunel rebuilt the entrance locks of the Cumberland Basin in Bristol Harbour, between 1848 and 1849, he also constructed a 'swivel bridge' – Brunel's first moving bridge. This was of centre-pivot construction, but were highly asymmetrical, the outboard side being nearly three times longer than the landward, balanced by a large cast-iron counterweight.
As the bridge was for a light roadway and did not have to carry the weight of a railway or train, its girders were of a lightweight construction that simplified manufacture. A full balloon upper flange was used, similar in shape to the South Wales Railway bridges, but the flange sat above the main web of the girder and the web did not span the flange and reach to the top. This simplified construction as it avoided the T-joint, the necessary L-strips and thus several rows of riveting.
The lower flange was of an entirely novel form, being triangular in section, although with concave sides. Again, the main web did not span the flange. All three joints were now simple lap joints with single-row riveting.
Like a number of early Brunel bridges, Brunel's involvement with them was largely forgotten and only recorded in obscure works. At one point they were under serious threat of demolition until their historical significance was re-recognised. A £1 million appeal was launched in 2014 to restore the bridge.
A very similar swivel bridge was built a few years later as the in Kronstadt, Russia.
Windsor Railway Bridge
Windsor Railway Bridge (1849) is a tied-arch or bowstring girder bridge. The span is composed of two girders that form a truss. The upper girder is an arch and carries the weight of the bridge. The lower girder is suspended from this by vertical rods and is not required to support its own weight. The main function of the lower girder is to act as a tie; this counteracts the side-forces of the arch, avoiding the arch's usual side-forces on its foundations. As this is a railway bridge, where suspended deck bridges are a problem owing to swaying of their deck, this girder also has a stiffening function.
Brunel used a form of his balloon flange girder for both girders. The upper arch girder uses the triangulated form of the early experiment, with a flat top plate and without any vertical web below the flange box at all. The lower girder uses the 'open' form of the flange, slightly curved and with no gusset plates. As the lower girder is not carrying its weight, it is not subject to the usual buckling forces.
Chepstow Railway Bridge
Chepstow Railway Bridge (1852) was a complicated bridge that made the first use of Brunel's truss design to produce a suspension bridge with a wide uninterrupted span at high level above a shipping channel. The west bank of the gorge was shallow and muddy though, so half of the bridge's total span was provided by three 100-foot spans of a girder bridge, carried on cast iron cylindrical piers. These girders (illus) were of a form and size very similar to the original experimental girder.
The landward girders were replaced in 1948 and the main truss, with its girders beneath, in 1962. Portions of the girders survive today.
Crathie Bridge
Crathie Bridge (1854–1857) is a 125-foot single span across the River Dee to the royal Balmoral estate. The bridge had first been drawn with a form of the Brunel truss echoing his Royal Albert Bridge at Saltash. The bridge as constructed though used the C-shaped open form of the upper flange, as used for the Eastern Bengal Railway. As the bridge was only for light road traffic, it was also possible to replace the solid web of the girder above the roadway level with an openwork lattice, making the view from the bridge visually more appealing for its illustrious resident. Despite this, Her Majesty was 'not amused' by the bridge.
Devizes 'Fish Bridge'
The line of 1857 through Devizes in Wiltshire down Caen Hill was carried over a road on an unusual development of the balloon flange, combining it with a lenticular plate girder. This lenticular fishbelly shape gave its popular name of 'Fish Bridge'. From his work on his truss design, Brunel was already familiar with the advantages of the lenticular form.
The original Fish Bridge was replaced in 1901 with a bowstring truss. The name remained in common use, even after the railway was removed during the Beeching Axe.
Surviving examples
Over Junction Bridge, the railway bridge across the Severn at Over. (1848)
Cumberland Basin, Bristol Harbour (1849) One fixed span has been recently restored for use as a footbridge.
Windsor Railway Bridge (1849)
Chepstow railway bridge (1852) Sections of the girders survive at Brunel University, Uxbridge.
Crathie Bridge (1854–1857) to the royal Balmoral estate.
Coity Road Bridge, Bridgend (1861)
Stoodleigh Bridge, Devon. Semi-circular open-bottom top flange, lattice truss girder, c. 1863.
Peel Street Bridge, Bristol. Semi-circular open-bottom top flange, lattice truss girder, 1878.
The canal portion of Bishop's Bridge, Paddington, may be Brunel's first use of this technique. It was dismantled and stored in 2004.
See also
Brunel truss
References
Plate girder bridges
Girders
Bridges by Isambard Kingdom Brunel | Balloon flange girder | Technology | 2,310 |
25,887,718 | https://en.wikipedia.org/wiki/Psilocybe%20collybioides | Psilocybe collybioides is a species of agaric fungus in the family Hymenogastraceae. It was first described scientifically by mycologists Rolf Singer and Alexander H. Smith in 1958, from collections made in montane habitat near Tafí del Valle, Argentina. It is in the section Zapotecorum of the genus Psilocybe, other members of this section include Psilocybe muliercula, Psilocybe angustipleurocystidiata, Psilocybe aucklandii, Psilocybe graveolens, Psilocybe kumaenorum, Psilocybe zapotecorum, Psilocybe pintonii, Psilocybe subcaerulipes, Psilocybe moseri, Psilocybe zapotecoantillarum, Psilocybe zapotecocaribaea, and Psilocybe antioquiensis.
See also
List of psilocybin mushrooms
Psilocybin mushrooms
References
External links
Entheogens
Fungi described in 1958
Fungi of South America
Psychoactive fungi
collybioides
Psychedelic tryptamine carriers
Fungi of North America
Taxa named by Rolf Singer
Taxa named by Alexander H. Smith
Fungus species | Psilocybe collybioides | Biology | 259 |
26,374,846 | https://en.wikipedia.org/wiki/Gastropila%20fumosa | Gastropila fumosa is a species of puffball in the family Agaricaceae. It was first described as Calvatia fumosa by American mycologist Sanford Myron Zeller in 1947, and later transferred to Gastropila in 1976. Some authors place it instead in the genus Handkea, circumscribed by Hanns Kreisel in 1989.
Description
The fruit body is anywhere from golf ball size to baseball size, round to oval, broad, thick, at first smooth and white, soon becoming grayish to brownish. The spores are firm and white at first, then yellowish or olive, and then dark brown and powdery. The species has an unpleasant smell while developing. Its edibility is unknown.
Distribution and habitat
The species fruits singly, in groups, or in small clusters on soil in spruce-fir forests in the Rocky Mountains and westward in the summer and fall.
References
External links
Agaricaceae
Fungi described in 1947
Fungi of North America
Fungus species
Taxa named by Sanford Myron Zeller | Gastropila fumosa | Biology | 218 |
10,049,973 | https://en.wikipedia.org/wiki/Gyromax | The Gyromax is the trade name for an adjustable mass (or adjustable inertia) balance wheel used in Patek Philippe wristwatches. Instead of weight adjustment screws on the outside of the rim, as in traditional balances, the Gyromax has turnable weights recessed into the top of the rim. The advantages claimed for this design are that, without projecting weight screws, the diameter of the balance can be increased, giving it a larger moment of inertia, and that it has less air resistance.
The Gyromax balance has six to eight small turnable weights that fit on pins located in recesses around the top of the balance wheel rim. Each of the weights, called collets, has a cutout making it heavier on one side. When the collet's cutout points to the outside of the balance wheel, the heavier side is toward the center which decreases the wheel's moment of inertia, increasing its speed. When the collet's cutout points toward the center, the weight moves outward and the balance wheel turns more slowly. A watchmaker can turn an individual collet to adjust the wheel's balance, referred to as 'poise', or pairs of opposing collets to adjust the wheel's rotation speed. The Gyromax is a 'free sprung' balance, meaning there is no regulator on the wheel's balance spring for adjusting the watch's rate, so the collets are used for adjusting both poise and rate.
Swiss patents were granted to Patek Phillipe for the Gyromax balance on May 15, 1949 and December 31, 1951, and the balance was first used in watches in 1952. Another balance wheel with a similar design is the Rolex Microstella.
References
External links
THE TIMEZONE WATCH SCHOOL - Watch Glossary - The Balance Wheel - The Adjustable Mass Balance
Key Patek Phillipe patents, Patek Phillipe website, Retrieved Aug. 7, 2007. Short description of Gyromax.
Odets, Walt The Balance Wheel of a Watch, The Horologium, TimeZone.com, Retrieved Aug. 7, 2007. Technical article on balance wheels by watchmaker, discussing advantages of Gyromax.
Timekeeping components
Horology
Products introduced in 1949 | Gyromax | Physics,Technology | 473 |
45,548,188 | https://en.wikipedia.org/wiki/Penicillium%20giganteum | Penicillium giganteum is a species of the genus of Penicillium which was isolated from soil.
References
giganteum
Fungi described in 1968
Fungus species | Penicillium giganteum | Biology | 36 |
31,548,039 | https://en.wikipedia.org/wiki/Ravenel%27s%20conjectures | In mathematics, the Ravenel conjectures are a set of mathematical conjectures in the field of stable homotopy theory posed by Douglas Ravenel at the end of a paper published in 1984. It was earlier circulated in preprint. The problems involved have largely been resolved, with all but the "telescope conjecture" being proved in later papers by others. Ravenel's conjectures exerted influence on the field through the founding of the approach of chromatic homotopy theory.
The first of the seven conjectures, then the nilpotence conjecture, was proved in 1988 and is now known as the nilpotence theorem.
The telescope conjecture, which was fourth on the original list, remains of substantial interest because of its connection with the convergence of an Adams–Novikov spectral sequence. While opinion has been generally against the truth of the original statement, investigations of associated phenomena (for a triangulated category in general) have become a research area in its own right.
On June 6, 2023, Robert Burklund, Jeremy Hahn, Ishan Levy, and Tomer Schlank announced a disproof of the telescope conjecture. Their preprint was submitted to the arXiv on October 26, 2023.
See also
Homotopy groups of spheres
References
Homotopy theory
Conjectures | Ravenel's conjectures | Mathematics | 271 |
2,914,124 | https://en.wikipedia.org/wiki/Yumemi%20Kobo | Yumemi Kōbō (夢見 工房) is a device sold by the Japanese company Takara Toys that is claimed to be able to induce lucid dreams.
Measuring some in height, the device is equipped with a picture frame, a voice recorder, a timer, a fragrance dispenser, musical recordings and speakers. This assortment of components is claimed to be able to induce a dream about a pre-selected theme while the user sleeps; it periodically activates in concert with the user's rapid eye movement (REM) sleep stages.
A Wired Newsration :
The manufacturer claims that the recommended fragrance and music selections are based on sleep research—"there is a logic behind the selections". It nevertheless will not guarantee satisfactory outcomes to its customers.
References
External links
Manufacturer's page on Yumemi Kobo (in Japanese)
Dream
Takara
Japanese inventions | Yumemi Kobo | Biology | 178 |
24,385,510 | https://en.wikipedia.org/wiki/C11H10 | {{DISPLAYTITLE:C11H10}}
The molecular formula C11H10 may refer to:
Methano[10]annulenes
1,5-Methano[10]annulene
1,6-Methano[10]annulene
Methylazulenes
1-Methylazulene
2-Methylazulene
4-Methylazulene
5-Methylazulene
6-Methylazulene
Methylnaphthalenes
1-Methylnaphthalene
2-Methylnaphthalene | C11H10 | Chemistry | 113 |
76,384,954 | https://en.wikipedia.org/wiki/List%20of%203D%20printing%20software | This is a list of 3D printing software.
See also
3D printing - or additive manufacturing
3D scanning - replicating objects to 3D models to potentially 3D print
Comparison of computer-aided design software
3D Manufacturing Format - open source file format standard developed and published by the 3MF Consortium
PLaSM - open source scripting language for solid modeling
3D printing processes
Thingiverse - open CAD repository/library for 3D printers, laser cutters, milling machines
MyMiniFactory - 3D printing marketplace
CAD library - 3D repository to download 3D models
Fused filament fabrication - 3D printing process that uses a continuous filament of a thermoplastic material
Qlone - 3D scanning app based on photogrammetry for creation of 3D models on mobile devices that can be 3D printed
Metal injection molding
EnvisionTEC - 3D printing hardware company
Desktop Metal - company focused on 3D metal printing
Slicer (3D printing) - toolpath generation software used in 3D printing
List of computer-aided manufacturing software - for CNC machining
References
3D printing
DIY culture
Industrial design
Industrial processes
Free computer-aided manufacturing software
Computer-aided design software
Autodesk products
3D graphics software
Freeware 3D graphics software | List of 3D printing software | Engineering | 236 |
18,860,920 | https://en.wikipedia.org/wiki/Streptazolin | Streptazolin is an antibiotic and antifungal substance isolated in 1981 from Streptomyces viridochromogenes.
Because of its polymerisation tendency, it is not suitable for therapeutic use. 1,4-reduction of the conjugated diene gives dihydrostreptazolin which is stable, but has very limited antimicrobial properties.
The first total synthesis of (racemic) streptazolin was achieved in 1985 with the aid of a modified Ferrier rearrangement.
References
Antibiotics
Carbamates
Cyclopentanes
Heterocyclic compounds with 3 rings | Streptazolin | Biology | 132 |
77,396,324 | https://en.wikipedia.org/wiki/Georg%20Thomas%20Sabler | Georg Thomas Sabler (Russian: Его́р Его́рович Са́блер or Георг Заблер, Lithuanian: Georgas Tomas Sableris; – 7 December 1865) was an astronomer and geodesist of Baltic German origin active in territories of modern-day Estonia, Lithuania, Ukraine, and Russia (then all part of the Russian Empire).
A student of Friedrich Georg Wilhelm von Struve, Sabler studied theology and mathematics at the University of Tartu. Fascinated by Struve's lectures of astronomy, Sabler participated in an expedition that measured the difference of sea levels in the Black Sea and Caspian Sea. Sabler then worked as an astronomer at Tartu Observatory and Pulkovo Observatory, and later became the director of the Vilnius University Astronomical Observatory, which received its own photoheliograph due to Sabler's efforts. The telescope was the second one produced in the world. Sabler and his assistant Matvey Gusev pioneered the photography and research of sunspots.
He was described as the "creator and pioneer of new astrophysical research at the Vilnius observatory". Sabler also constructed a star catalog, took care of the methodology of observations, and constructed various astronomical instruments such as achromatic lenses. Notably, Sabler participated in determining the Struve Geodetic Arc in Finland, Lithuania, Ukraine, and Bessarabia. Sabler was the first to find a way to determine the angle of refraction in transparent media.
Biography
Early life and studies
Georg Thomas Sabler was born on in Haljala, now part of Lääne-Viru County, Estonia. His father, Georg Christian Sabler (1776–1819), was a Lutheran pastor. At first, Sabler studied privately. Later, Sabler graduated from the Tartu Evangelical Cathedral's gymnasium. Sabler studied theology (1828–1832) and mathematics (1832–1839) at the University of Tartu. He developed an interest in natural sciences, especially in astronomy, which was lectured by Friedrich Georg Wilhelm von Struve. During his study years, Sabler was engaged in astronomical observations, particularly of binary stars. Some of his works were published in the scientific press. For his scientific aptitude, von Struve ensured that Sabler began working at the Tartu Observatory as an assistant to its director until 1839.
In 1836–1837 Sabler participated in an expedition that determined the difference between the sea levels of the Black Sea and Caspian Sea. He also edited the material collected during the expedition and published it in German under the title "Beschreibung der zur Ermittelung des Höhenunterschiedes zwischen dem Schwarzen und dem Caspischen Meere... in den Jahren 1836 und 1837 von Gr. Fuss, A. Sawitsch und G. Sabler ausgeführten Messungen... zusammengestellt von G. Sabler. Im Auftrage der Akademie herausgegeben von W. Struve". For his work, which he wrote about in 1839, he received a doctoral degree, and subsequently graduated that same year.
Astronomer
From 1839 to 1854 Sabler worked as an assistant and senior astronomer at the Pulkovo Observatory near St. Petersburg, where Struve was the director. Actively partaking in astronomical research, Sabler was then assigned the task of measuring the exact coordinates of stars using a large meridian circle. From 1844 to 1853, Sabler and Carl Friedrich Tenner participated in the construction of the Struve Geodetic Arc in modern-day Finland, Bessarabia, and Ukraine. In Ukraine, specifically the Khotynsky district, the scientists chose the prevailing heights of the area, which were located near the villages of Romankivtsi, Shebutyntsi, Selishche, and Hrubno. Sabler lived in Romankivtsi for more than a week. The results of the research were published in the bulletin of the Imperial Russian Geographical Society, the journal of the Ministry of National Education, and others.
Sabler also participated in measuring the longitude difference between the Pulkovo Observatory and Altona Observatory. In his free time, Sabler polished lenses, successfully making quality achromatic lenses using two glasses of crown glass between which lay a transparent liquid with the appropriate refractive and light scattering coefficients. The lenses were described in the St. Petersburg Academy of Sciences's newsletter. One of Sabler's prism lenses has survived to this day and is an exhibition in the Vilnius University Science Museum.
Activity in Vilnius
After coming to Vilnius, Sabler determined the geographical position of one of the points used for measuring the Struve Geodetic Arc near the village of Nemėžis. From 1854 to 1865, Sabler was director of the Vilnius University Astronomical Observatory. Sabler sent his assistant and fellow astronomer Matvey Gusev for an internship to England in 1858–1860, where they learned of the appliance of photography in astronomy in Kew Observatory, famously pioneered by astronomer Warren De la Rue. On 19 April 1861, Sabler participated in a meeting hosted by the St. Petersburg Academy of Sciences' physics and mathematics department in Pulkovo. In the meeting, Sabler argued that the university's observatory required a solar telescope, emphasizing that the observatory should direct all efforts for astrophysics research of sunspots and star photometry instead of traditional astrometry.
In 1862–1864, while in Great Britain, Sabler observed the development of the solar telescope. He successfully ordered one of the solar telescopes after negotiations with John Henry Dallmeyer and permission from Struve. In 1864, the Vilnius observatory successfully received its own solar telescope and produced one of the first pictures of sunspots. The telescope would be destroyed in a fire in 1876. Sabler used a method of coating the photographic plate with collodion, which was a method invented in 1850. Firstly, the glass would be filled with a nitrocellulose solution enriched with iodides and bromides and dried. Before photographing, the plate would be further sensitized by dipping it in a solution of silver nitrate and silver iodide. The prepared photographic plate had to be exposed for 10 or 15 minutes and developed immediately.
The establishment of a new solar telescope meant a reconstruction of the observatory's towers. However, as Sabler became increasingly sick, he made Gusev responsible for the continuation of his works. Sabler traveled to St. Petersburg for treatment, after which he became less ill, but only for a short time. In autumn of 1865 the illness, which was a brain tumor, began to rapidly progress. Sabler's scientific work continued to be worked upon in the observatory by Gusev and Pyotr Smyslov.
Death
Sabler died on 7 December 1865 in Vilnius. He was buried in the Vilnius Evangelical Lutheran Cemetery. The grave was destroyed during the Soviet occupation of Lithuania.
Remembrance
A commemorative plaque was uncovered in his home village of Haljala on 24 June 1991.
References
1810 births
1865 deaths
University of Tartu alumni
Baltic-German people
Astronomers
Geodesists from the Russian Empire | Georg Thomas Sabler | Astronomy | 1,476 |
34,252,996 | https://en.wikipedia.org/wiki/Repiping | Repiping means replacing the pipes in a building, oil or gas well, or centrifuge.
References
See also
Plumbing
Piping | Repiping | Chemistry,Engineering | 30 |
1,658,385 | https://en.wikipedia.org/wiki/Berkman%20Klein%20Center%20for%20Internet%20%26%20Society | The Berkman Klein Center for Internet & Society is a research center at Harvard University that focuses on the study of cyberspace. Founded at Harvard Law School, the center traditionally focused on internet-related legal issues. On May 15, 2008, the center was elevated to an interfaculty initiative of Harvard University as a whole. It is named after the Berkman family. On July 5, 2016, the center added "Klein" to its name following a gift of $15 million from Michael R. Klein.
History and mission
The center was founded in 1996 as the "Center on Law and Technology" by Jonathan Zittrain and Professor Charles Nesson. This was built on previous work including a 1994 seminar they held on legal issues involving the early Internet. Professor Arthur Miller and students David Marglin and Tom Smuts also worked on that seminar and related discussions. In 1997, the Berkman family underwrote the center, and Lawrence Lessig joined as the first Berkman professor. In 1998, the center changed its name to the "Berkman Center for Internet & Society at Harvard Law School." Since then, it has grown from a small project within Harvard Law School to a major interdisciplinary center at Harvard University. The Berkman Klein Center seeks to understand how the development of Internet-related technologies is inspired by the social context in which they are embedded and how the use of those technologies affects society in turn. It seeks to use the lessons drawn from this research to inform the design of Internet-related law and pioneer the development of the Internet itself. The Berkman Klein Center sponsors Internet-related events and conferences, and hosts numerous visiting lecturers and research fellows.
Members of the center teach, write books, scientific articles, weblogs with RSS 2.0 feeds (for which the Center holds the specification), and podcasts (of which the first series took place at the Berkman Klein Center). Its newsletter, The Buzz, is on the Web and available by e-mail, and it hosts a blog community of Harvard faculty, students, and Berkman Klein Center affiliates.
The Berkman Klein Center faculty and staff have also conducted major public policy reviews of pressing issues. In 2008, John Palfrey led a review of child safety online called the Internet Safety Technical Task Force. In 2009, Yochai Benkler led a review of United States broadband policy. In 2010, Urs Gasser, along with Palfrey and others, led a review of Internet governance body ICANN, focusing on transparency, accountability, and public participation.
Projects and initiatives
The Berkman Klein Center's main research topics are Teens and Media, Monitoring, Privacy, Digital art, Internet Governance, Cloud Computing and Internet censorship. The Berkman Klein Center supports events, presentations, and conferences about the Internet and invites scientists to share their ideas.
Lumen
Lumen, formerly Chilling Effects, is a collaborative archive created by Wendy Seltzer that allows recipients of cease-and-desist notices to submit them to the site and receive information about their legal rights and responsibilities.
Digital Media Law Project
The Digital Media Law Project (DMLP) was a project hosted by the Berkman Klein Center for Internet & Society at Harvard Law School. It had previously been known as the Citizen Media Law Project. The purposes of the DMLP were:
To provide resources and other assistance, including legal assistance , to individuals and groups involved in online and citizen media.
To ensure "online journalists, media organizations, and their sources are allowed to examine and debate network security and data protection vulnerabilities without criminal punishment, in order to inform citizens and lawmakers about networked computer security."
To facilitate the participation of citizens in online media.
To protect the freedom of speech on the Internet.
In 2014, Berkman Klein Center announced that it would "spin off its most effective initiatives and cease operation as a stand-alone project within the Berkman Klein Center."
Internet and Democracy Project
The Berkman Klein Center operated the now-completed Internet and Democracy Project, which describes itself as an:
StopBadware
In 2006, the center established the non-profit organization StopBadware, aiming to stop viruses, spyware, and other threats to the open Internet, in partnership with the Oxford Internet Institute, Google, Lenovo and Sun Microsystems. In 2010, StopBadware became an independent entity supported by Google, PayPal, and Mozilla.
Digital Public Library of America
The Digital Public Library of America is a project aimed at making a large-scale digital public library accessible to all.
Ethics and Governance of Artificial Intelligence
In 2017, the BKC received a $27M grant with the MIT Media Lab to "advance artificial intelligence research for the public good" and "to ensure automation and machine learning are researched, developed, and deployed in a way which vindicates social values of fairness, human autonomy, and justice."
Members
Fellows include or have included:
John Perry Barlow
Danah boyd
Amber Case
Kathy Pham
Jacinda Ardern
John Clippinger
Yasodara Cordova
Primavera de Filippi
Tamar Frankel
Samer Hassan
Benjamin Mako Hill
Reynol Junco
Rebecca MacKinnon
James F. Moore
Mayo Fuster Morell
Bruce Schneier
Doc Searls
Wendy Seltzer
Peter Suber
Jimmy Wales
David Weinberger
Dave Winer
Ethan Zuckerman
Mary L. Gray
Faculty include:
Yochai Benkler
William W. Fisher
Lawrence Lessig
Charles Nesson
John Palfrey
Jonathan Zittrain
Alejandra Caraballo
The center also has active groups of faculty associates, affiliates and alumni who host and participate in their projects each year.
See also
Berkeley Center for Law and Technology at Boalt Hall
Canadian Internet Policy and Public Interest Clinic at University of Ottawa Faculty of Law
Centre for Internet and Society (India)
Haifa Center for Law & Technology at Haifa University
Information Society Project at Yale Law School
NEXA Center for Internet and Society at the Polytechnic University of Turin
Openlaw
Oxford Internet Institute
References
External links
Information technology research institutes
Harvard Law School
Computer law organizations
Information society
Internet governance advocacy groups
Internet-related activism
Research institutes established in 1998
1998 establishments in Massachusetts
Harvard University research institutes | Berkman Klein Center for Internet & Society | Technology | 1,265 |
1,910,119 | https://en.wikipedia.org/wiki/Vanadium%28V%29%20oxide | Vanadium(V) oxide (vanadia) is the inorganic compound with the formula V2O5. Commonly known as vanadium pentoxide, it is a dark yellow solid, although when freshly precipitated from aqueous solution, its colour is deep orange. Because of its high oxidation state, it is both an amphoteric oxide and an oxidizing agent. From the industrial perspective, it is the most important compound of vanadium, being the principal precursor to alloys of vanadium and is a widely used industrial catalyst.
The mineral form of this compound, shcherbinaite, is extremely rare, almost always found among fumaroles. A mineral trihydrate, V2O5·3H2O, is also known under the name of navajoite.
Chemical properties
Reduction to lower oxides
Upon heating a mixture of vanadium(V) oxide and vanadium(III) oxide, comproportionation occurs to give vanadium(IV) oxide, as a deep-blue solid:
V2O5 + V2O3 → 4 VO2
The reduction can also be effected by oxalic acid, carbon monoxide, and sulfur dioxide. Further reduction using hydrogen or excess CO can lead to complex mixtures of oxides such as V4O7 and V5O9 before black V2O3 is reached.
Acid-base reactions
V2O5 is an amphoteric oxide, and unlike most transition metal oxides, it is slightly water soluble, giving a pale yellow, acidic solution. Thus V2O5 reacts with strong non-reducing acids to form solutions containing the pale yellow salts containing dioxovanadium(V) centers:
V2O5 + 2 HNO3 → 2 VO2(NO3) + H2O
It also reacts with strong alkali to form polyoxovanadates, which have a complex structure that depends on pH. If excess aqueous sodium hydroxide is used, the product is a colourless salt, sodium orthovanadate, Na3VO4. If acid is slowly added to a solution of Na3VO4, the colour gradually deepens through orange to red before brown hydrated V2O5 precipitates around pH 2. These solutions contain mainly the ions HVO42− and V2O74− between pH 9 and pH 13, but below pH 9 more exotic species such as V4O124− and HV10O285− (decavanadate) predominate.
Upon treatment with thionyl chloride, it converts to the volatile liquid vanadium oxychloride, VOCl3:
V2O5 + 3 SOCl2 → 2 VOCl3 + 3 SO2
Other redox reactions
Hydrochloric acid and hydrobromic acid are oxidised to the corresponding halogen, e.g.,
V2O5 + 6HCl + 7H2O → 2[VO(H2O)5]2+ + 4Cl− + Cl2
Vanadates or vanadyl compounds in acid solution are reduced by zinc amalgam through the colourful pathway:
The ions are all hydrated to varying degrees.
Preparation
Technical grade V2O5 is produced as a black powder used for the production of vanadium metal and ferrovanadium. A vanadium ore or vanadium-rich residue is treated with sodium carbonate and an ammonium salt to produce sodium metavanadate, NaVO3. This material is then acidified to pH 2–3 using H2SO4 to yield a precipitate of "red cake" (see above). The red cake is then melted at 690 °C to produce the crude V2O5.
Vanadium(V) oxide is produced when vanadium metal is heated with excess oxygen, but this product is contaminated with other, lower oxides. A more satisfactory laboratory preparation involves the decomposition of ammonium metavanadate at 500–550 °C:
2 NH4VO3 → V2O5 + 2 NH3 + H2O
Uses
Ferrovanadium production
In terms of quantity, the dominant use for vanadium(V) oxide is in the production of ferrovanadium (see above). The oxide is heated with scrap iron and ferrosilicon, with lime added to form a calcium silicate slag. Aluminium may also be used, producing the iron-vanadium alloy along with alumina as a byproduct.
Sulfuric acid production
Another important use of vanadium(V) oxide is in the manufacture of sulfuric acid, an important industrial chemical with an annual worldwide production of 165 million tonnes in 2001, with an approximate value of US$8 billion. Vanadium(V) oxide serves the crucial purpose of catalysing the mildly exothermic oxidation of sulfur dioxide to sulfur trioxide by air in the contact process:
2 SO2 + O2 2 SO3
The discovery of this simple reaction, for which V2O5 is the most effective catalyst, allowed sulfuric acid to become the cheap commodity chemical it is today. The reaction is performed between 400 and 620 °C; below 400 °C the V2O5 is inactive as a catalyst, and above 620 °C it begins to break down. Since it is known that V2O5 can be reduced to VO2 by SO2, one likely catalytic cycle is as follows:
SO2 + V2O5 → SO3 + 2VO2
followed by
2VO2 +½O2 → V2O5
It is also used as catalyst in the selective catalytic reduction (SCR) of NOx emissions in some power plants and diesel engines. Due to its effectiveness in converting sulfur dioxide into sulfur trioxide, and thereby sulfuric acid, special care must be taken with the operating temperatures and placement of a power plant's SCR unit when firing sulfur-containing fuels.
Other oxidations
Maleic anhydride is produced by the V2O5-catalysed oxidation of butane with air:
C4H10 + 4 O2 → C2H2(CO)2O + 8 H2O
Maleic anhydride is used for the production of polyester resins and alkyd resins.
Phthalic anhydride is produced similarly by V2O5-catalysed oxidation of ortho-xylene or naphthalene at 350–400 °C. The equation for the vanadium oxide-catalysed oxidation of o-xylene to phthalic anhydride:
C6H4(CH3)2 + 3 O2 → C6H4(CO)2O + 3 H2O
The equation for the vanadium oxide-catalysed oxidation of naphthalene to phthalic anhydride:
C10H8 + 4½ O2 → C6H4(CO)2O + 2CO2 + 2H2O
Phthalic anhydride is a precursor to plasticisers, used for conferring pliability to polymers.
A variety of other industrial compounds are produced similarly, including adipic acid, acrylic acid, oxalic acid, and anthraquinone.
Other applications
Due to its high coefficient of thermal resistance, vanadium(V) oxide finds use as a detector material in bolometers and microbolometer arrays for thermal imaging. It also finds application as an ethanol sensor in ppm levels (up to 0.1 ppm).
Vanadium redox batteries are a type of flow battery used for energy storage, including large power facilities such as wind farms. Vanadium oxide is also used as a cathode in lithium-ion batteries.
Biological activity
Vanadium(V) oxide exhibits very modest acute toxicity to humans, with an LD50 of about 470 mg/kg. The greater hazard is with inhalation of the dust, where the LD50 ranges from 4–11 mg/kg for a 14-day exposure. Vanadate (), formed by hydrolysis of V2O5 at high pH, appears to inhibit enzymes that process phosphate (PO43−). However the mode of action remains elusive.
References
Cited sources
Further reading
.
.
External links
Vanadium Pentoxide and other Inorganic Vanadium Compounds (Concise International Chemical Assessment Document 29)
Vanadium(V) compounds
Catalysts
Infrared sensor materials
IARC Group 2B carcinogens
Oxidizing agents
Transition metal oxides | Vanadium(V) oxide | Chemistry | 1,769 |
173,977 | https://en.wikipedia.org/wiki/Symplectic%20group | In mathematics, the name symplectic group can refer to two different, but closely related, collections of mathematical groups, denoted and for positive integer n and field F (usually C or R). The latter is called the compact symplectic group and is also denoted by . Many authors prefer slightly different notations, usually differing by factors of . The notation used here is consistent with the size of the most common matrices which represent the groups. In Cartan's classification of the simple Lie algebras, the Lie algebra of the complex group is denoted , and is the compact real form of . Note that when we refer to the (compact) symplectic group it is implied that we are talking about the collection of (compact) symplectic groups, indexed by their dimension .
The name "symplectic group" was coined by Hermann Weyl as a replacement for the previous confusing names (line) complex group and Abelian linear group, and is the Greek analog of "complex".
The metaplectic group is a double cover of the symplectic group over R; it has analogues over other local fields, finite fields, and adele rings.
The symplectic group is a classical group defined as the set of linear transformations of a -dimensional vector space over the field which preserve a non-degenerate skew-symmetric bilinear form. Such a vector space is called a symplectic vector space, and the symplectic group of an abstract symplectic vector space is denoted . Upon fixing a basis for , the symplectic group becomes the group of symplectic matrices, with entries in , under the operation of matrix multiplication. This group is denoted either or . If the bilinear form is represented by the nonsingular skew-symmetric matrix Ω, then
where MT is the transpose of M. Often Ω is defined to be
where In is the identity matrix. In this case, can be expressed as those block matrices , where , satisfying the three equations:
Since all symplectic matrices have determinant , the symplectic group is a subgroup of the special linear group . When , the symplectic condition on a matrix is satisfied if and only if the determinant is one, so that . For , there are additional conditions, i.e. is then a proper subgroup of .
Typically, the field is the field of real numbers or complex numbers . In these cases is a real or complex Lie group of real or complex dimension , respectively. These groups are connected but non-compact.
The center of consists of the matrices and as long as the characteristic of the field is not . Since the center of is discrete and its quotient modulo the center is a simple group, is considered a simple Lie group.
The real rank of the corresponding Lie algebra, and hence of the Lie group , is .
The Lie algebra of is the set
equipped with the commutator as its Lie bracket. For the standard skew-symmetric bilinear form , this Lie algebra is the set of all block matrices subject to the conditions
The symplectic group over the field of complex numbers is a non-compact, simply connected, simple Lie group.
is the complexification of the real group . is a real, non-compact, connected, simple Lie group. It has a fundamental group isomorphic to the group of integers under addition. As the real form of a simple Lie group its Lie algebra is a splittable Lie algebra.
Some further properties of :
The exponential map from the Lie algebra to the group is not surjective. However, any element of the group can be represented as the product of two exponentials. In other words,
For all in :
The matrix is positive-definite and diagonal. The set of such s forms a non-compact subgroup of whereas forms a compact subgroup. This decomposition is known as 'Euler' or 'Bloch–Messiah' decomposition. Further symplectic matrix properties can be found on that Wikipedia page.
As a Lie group, has a manifold structure. The manifold for is diffeomorphic to the Cartesian product of the unitary group with a vector space of dimension .
Infinitesimal generators
The members of the symplectic Lie algebra are the Hamiltonian matrices.
These are matrices, such thatwhere and are symmetric matrices. See classical group for a derivation.
Example of symplectic matrices
For , the group of matrices with determinant , the three symplectic -matrices are:
Sp(2n, R)
It turns out that can have a fairly explicit description using generators. If we let denote the symmetric matrices, then is generated by whereare subgroups of pg 173pg 2.
Relationship with symplectic geometry
Symplectic geometry is the study of symplectic manifolds. The tangent space at any point on a symplectic manifold is a symplectic vector space. As noted earlier, structure preserving transformations of a symplectic vector space form a group and this group is , depending on the dimension of the space and the field over which it is defined.
A symplectic vector space is itself a symplectic manifold. A transformation under an action of the symplectic group is thus, in a sense, a linearised version of a symplectomorphism which is a more general structure preserving transformation on a symplectic manifold.
The compact symplectic group is the intersection of with the unitary group:
It is sometimes written as . Alternatively, can be described as the subgroup of (invertible quaternionic matrices) that preserves the standard hermitian form on :
That is, is just the quaternionic unitary group, . Indeed, it is sometimes called the hyperunitary group. Also Sp(1) is the group of quaternions of norm , equivalent to and topologically a -sphere .
Note that is not a symplectic group in the sense of the previous section—it does not preserve a non-degenerate skew-symmetric -bilinear form on : there is no such form except the zero form. Rather, it is isomorphic to a subgroup of , and so does preserve a complex symplectic form in a vector space of twice the dimension. As explained below, the Lie algebra of is the compact real form of the complex symplectic Lie algebra .
is a real Lie group with (real) dimension . It is compact and simply connected.
The Lie algebra of is given by the quaternionic skew-Hermitian matrices, the set of quaternionic matrices that satisfy
where is the conjugate transpose of (here one takes the quaternionic conjugate). The Lie bracket is given by the commutator.
Important subgroups
Some main subgroups are:
Conversely it is itself a subgroup of some other groups:
There are also the isomorphisms of the Lie algebras and .
Relationship between the symplectic groups
Every complex, semisimple Lie algebra has a split real form and a compact real form; the former is called a complexification of the latter two.
The Lie algebra of is semisimple and is denoted . Its split real form is and its compact real form is . These correspond to the Lie groups and respectively.
The algebras, , which are the Lie algebras of , are the indefinite signature equivalent to the compact form.
Physical significance
Classical mechanics
The non-compact symplectic group comes up in classical physics as the symmetries of canonical coordinates preserving the Poisson bracket.
Consider a system of particles, evolving under Hamilton's equations whose position in phase space at a given time is denoted by the vector of canonical coordinates,
The elements of the group are, in a certain sense, canonical transformations on this vector, i.e. they preserve the form of Hamilton's equations. If
are new canonical coordinates, then, with a dot denoting time derivative,
where
for all and all in phase space.
For the special case of a Riemannian manifold, Hamilton's equations describe the geodesics on that manifold. The coordinates live on the underlying manifold, and the momenta live in the cotangent bundle. This is the reason why these are conventionally written with upper and lower indexes; it is to distinguish their locations. The corresponding Hamiltonian consists purely of the kinetic energy: it is where is the inverse of the metric tensor on the Riemannian manifold. In fact, the cotangent bundle of any smooth manifold can be a given a symplectic structure in a canonical way, with the symplectic form defined as the exterior derivative of the tautological one-form.
Quantum mechanics
Consider a system of particles whose quantum state encodes its position and momentum. These coordinates are continuous variables and hence the Hilbert space, in which the state lives, is infinite-dimensional. This often makes the analysis of this situation tricky. An alternative approach is to consider the evolution of the position and momentum operators under the Heisenberg equation in phase space.
Construct a vector of canonical coordinates,
The canonical commutation relation can be expressed simply as
where
and is the identity matrix.
Many physical situations only require quadratic Hamiltonians, i.e. Hamiltonians of the form
where is a real, symmetric matrix. This turns out to be a useful restriction and allows us to rewrite the Heisenberg equation as
The solution to this equation must preserve the canonical commutation relation. It can be shown that the time evolution of this system is equivalent to an action of the real symplectic group, , on the phase space.
See also
Hamiltonian mechanics
Metaplectic group
Orthogonal group
Paramodular group
Projective unitary group
Representations of classical Lie groups
Symplectic manifold, Symplectic matrix, Symplectic vector space, Symplectic representation
Unitary group
Θ10
Notes
References
.
.
Lie groups
Symplectic geometry | Symplectic group | Mathematics | 2,007 |
67,263,972 | https://en.wikipedia.org/wiki/Imidine | In chemistry imidines are a rare functional group, being the nitrogen analogues of anhydrides and imides. They were first reported by Adolf Pinner in 1883, but did not see significant investigation until the 1950s, when Patrick Linstead and John Arthur Elvidge developed a number of compounds.
Imidines may be prepared in a modified Pinner reaction, by passing hydrogen chloride into an alcoholic solution of their corresponding di-nitriles (i.e. succinonitrile, glutaronitrile, adiponitrile) to give imino ethers which then condense when treated with ammonia. As a result, most structures are cyclic.
The compounds are highly moisture sensitive and can be converted into imides upon exposure to water.
See also
Amidine
Guanidines
References
Functional groups | Imidine | Chemistry | 171 |
26,095,262 | https://en.wikipedia.org/wiki/Canes%20Venatici%20II | Canes Venatici II or CVn II is a dwarf spheroidal galaxy situated in the Canes Venatici constellation and discovered in 2006 in data obtained by the Sloan Digital Sky Survey. The galaxy is located at a distance of about 150 kpc from the Sun and moves towards the Sun with the velocity of about 130 km/s. It is classified as a dwarf spheroidal galaxy (dSph) meaning that it has an elliptical (ratio of axes ~ 2:1) shape with a half-light radius of about .
CVn II is one of the smallest and faintest satellites of the Milky Way—its integrated luminosity is about 8,000 times that of the Sun (absolute visible magnitude of about −4.9), which is much lower than the luminosity of a typical globular cluster. However, its mass is about 2.5 million solar masses, which means that its mass to light ratio is around 340. A high mass to light ratio implies that CVn II is dominated by dark matter.
The stellar population of CVn II consists mainly of old stars formed more than 12 billion years ago. The metallicity of these old stars is also very low at , which means that they contain 150 times less heavy elements than the Sun. The stars of CVn II were probably among the first stars to form in the Universe. Currently there is no star formation in CVn II. Measurements have so far failed to detect neutral hydrogen in it—the upper limit is solar masses.
Notes
References
Dwarf spheroidal galaxies
Canes Venatici
Local Group
Milky Way Subgroup
4713558
? | Canes Venatici II | Astronomy | 334 |
7,781,429 | https://en.wikipedia.org/wiki/Novikov%20ring | In mathematics, given an additive subgroup , the Novikov ring of is the subring of consisting of formal sums such that and . The notion was introduced by Sergei Novikov in the papers that initiated the generalization of Morse theory using a closed one-form instead of a function. The notion is used in quantum cohomology, among the others.
The Novikov ring is a principal ideal domain. Let S be the subset of consisting of those with leading term 1. Since the elements of S are unit elements of , the localization of with respect to S is a subring of called the "rational part" of ; it is also a principal ideal domain.
Novikov numbers
Given a smooth function f on a smooth manifold with nondegenerate critical points, the usual Morse theory constructs a free chain complex such that the (integral) rank of is the number of critical points of f of index p (called the Morse number). It computes the (integral) homology of (cf. Morse homology):
In an analogy with this, one can define "Novikov numbers". Let X be a connected polyhedron with a base point. Each cohomology class may be viewed as a linear functional on the first homology group ; when composed with the Hurewicz homomorphism, it can be viewed as a group homomorphism . By the universal property, this map in turns gives a ring homomorphism,
,
making a module over . Since X is a connected polyhedron, a local coefficient system over it corresponds one-to-one to a -module. Let be a local coefficient system corresponding to with module structure given by . The homology group is a finitely generated module over which is, by the structure theorem, the direct sum of its free part and its torsion part. The rank of the free part is called the Novikov Betti number and is denoted by . The number of cyclic modules in the torsion part is denoted by . If , is trivial and is the usual Betti number of X.
The analog of Morse inequalities holds for Novikov numbers as well (cf. the reference for now.)
Notes
References
S. P. Novikov, Multi-valued functions and functionals: An analogue of Morse theory. Soviet Mathematics - Doklady 24 (1981), 222–226.
S. P. Novikov: The Hamiltonian formalism and a multi-valued analogue of Morse theory. Russian Mathematical Surveys 35:5 (1982), 1–56.
External links
Different definitions of Novikov ring?
Commutative algebra
Ring theory
Morse theory | Novikov ring | Mathematics | 529 |
1,623,707 | https://en.wikipedia.org/wiki/Underlay | Underlay may refer to flooring or roofing materials, bed padding, or a musical notation.
Flooring
Underlay or underlayment generally refers to a layer of cushioning made of materials such as sponge rubber, foam, felt, crumb rubber, or recycled plastic; this material is laid beneath carpeting to provide comfort underfoot, to reduce wear on the carpet, and to provide insulation against sound, moisture, and heat. In general, it is a layer which is underneath another layer, so underlay is thus also used to describe many different surface-covering products.
In vinyl flooring or "linoleum", the underlay is the thin layer of plywood that is fastened over the structural subfloor to create a uniform, smooth platform for the sheet vinyl. For laminated wood flooring, the underlay provides a “vapor barrier” to prevent moisture from coming through the floor of the home and then migrating into the flooring; the underlayment may also have noise-dampening properties.
A self-leveling underlay is a concrete product that can be pumped in liquid form onto the floor in order to create a level floor.
Carpet Underlay
Popular carpet underlays are
pu foam
crumb rubber
felt
cork
More recent innovations in underlay materials include recycled plastic underlay, which can be made from plastic bottles and other single-use plastics for reduced environmental impact.
Carpet underlays are typically 6-12 mm thick. They primarily provide foot comfort, but they also reduce carpet wear and provide sound and thermal insulation.
Underfloor Heating Underlay
Underlays are also available for underfloor heating in either central heating pipes or electric applications which allow the heat to transmit through the underlay and carpet. Specialist underlays include ThermalStream which have air perforated holes to allow a faster heat transaction.
Wood floor
Underlay for timber floors is typically 3mm closed cell plastic foam. This primarily provides sound insulation and a vapour barrier.
A watertight vapour barrier should only be used though, when neither condensation from humid air coming from beneath nor water spillage coming from above are to be expected.
Especially if there is spillage it will otherwise take a much longer time for the moisture to disperse and evaporate if it is prevented by the barrier from seeping through the wooden flooring.
This might make it necessary to raise the temperature of the floor to facilitate evaporation and prevent rot.
Roofing
Underlay is also the term for the material under roofing tiles; this roofing membrane is often made of rubber and is used to seal the roof and prevent leakage. Underlayment used with roofing shingles provides a second layer of water proofing to prevent leaks and is called tar paper, roofing felt, or since the 1990s synthetic underlayment. Roofing underlays can be breathable or non-breathable depending on the ventilation requirements of the building.
Bedding
Bedding underlay (or mattress overlay) is a thick, extra layer of padding between the bed mattress and bedding. Underlays are designed to increase comfort and support, while extending the life of the mattress (or mattress protector). Common underlay materials include: Wool, foam, and latex.
Music
In music, underlay refers to text intended for vocalization – positioned either directly or indirectly under notes on a musical staff.
References
Rugs and carpets
Floors | Underlay | Engineering | 696 |
13,431,657 | https://en.wikipedia.org/wiki/Siemens%20Hearing%20Instruments | Sivantos, Inc. (formerly Siemens Hearing Instruments) is the United States affiliate of Sivantos Group, which maintains a global headquarters in Singapore. Sivantos Group (formerly Siemens Audiology Group, a division of Siemens Healthcare) is one of the world's leading manufacturers of hearing aids. They serve hearing care professionals in more than 120 countries, offering hearing aids branded Siemens, Audio Service, Rexton, and A&M. Sivantos, Inc., and is located in Piscataway, NJ, where approximately 500 employees work in manufacturing, research and development, sales, marketing finance, and customer care.
Siemens Hearing Instruments changed its name in 2015 to Sivantos, Inc. when Sivantos Group was spun off from Siemens Audiology Solutions after Siemens AG sold the company to EQT VI and Santo Holding GmbH.
References
External links
Companies based in Middlesex County, New Jersey
Hearing aid manufacturers | Siemens Hearing Instruments | Biology | 188 |
43,563,159 | https://en.wikipedia.org/wiki/Rhino%20ferry | A rhino ferry is a barge constructed from several pontoons which are connected and equipped with outboard engines, used to transport heavy equipment and people. Rhino ferries were used extensively during the Normandy landings and other theaters (Attu, Africa, Sicily, Italy); their low draft was well-suited for shallow beaches, and they could also be used as piers when filled with water. An alternative to tank landing craft, they were operated by United States Navy Construction Battalions. They ferried their cargo from the outlying Landing Ships, Tank to the shore.
For the Normandy invasion, components were shipped from the US. Initial construction in the UK was by the USN Construction battalions. Rhinos (and causeways, which used the same components) were also assembled by British Army Royal Engineers.
See also
, similar device, 1960s to present day
References
External links
US Navy footage of Rhino barges in action, Normandy, June 11, 1944.
Buoyancy devices
Coastal construction
Operation Overlord
Allied logistics in the Western European Campaign (1944–1945) | Rhino ferry | Engineering | 209 |
67,821,139 | https://en.wikipedia.org/wiki/Invasive%20species%20in%20the%20Philippines | The following is a list of invasive alien species (IAS) in the Philippines. These species are regarded to have a negative effect on the local ecosystem and the economy, although not all species introduced from outside the archipelago are considered as "invasive".
Notable species
Animals
Plants
References
Philippines
Philippines
Biota of the Philippines
Agriculture in the Philippines
Environmental issues in the Philippines | Invasive species in the Philippines | Biology | 73 |
46,355,761 | https://en.wikipedia.org/wiki/SARL%20%28programming%20language%29 | The SARL programming language is a modular agent-oriented programming language. It aims at providing the fundamental abstractions for dealing with concurrency, distribution, interaction, decentralization, reactivity, autonomy and dynamic reconfiguration.
SARL is platform-independent and agent's architecture-agnostic. It provides a set of agent-oriented first-class abstractions directly at the language level (see the section on the concepts). Nevertheless, it supports the integration and the mapping of concepts provided by other agent-oriented metamodels. SARL itself exploits this extension mechanism for defining its own extensions (organizational, event-driven, etc.).
An important feature of the SARL programming language is its native support for "holonic multiagent systems", and "recursive agents"
(also called "holons").
Overview
The metamodel of SARL is based on four main concepts: Agent, Capacity, Space and Skill.
The core metamodel of SARL is presented in Figure 1, and the main concepts are colored in light blue.
Each of them are detailed in the following sections, as well as the corresponding piece of SARL code to illustrate their practical use.
In SARL, a Multiagent System (MAS) is a collection of Agents interacting together in shared distributed Spaces.
Each agent has a collection of Capacities describing what it is able to perform, its personal competences.
Each Capacity may then be realized/implemented by various Skills.
For understanding the relationship between the concepts of Capacity and Skill, a parallel can be drawn with concepts of Interface and their implementation classes in object-oriented languages.
To implement specific architectures (like BDI, reasoning, reactive, hybrid, etc.) developers should develop their own capacities and skills providing the agents with new exploitable features.
Despite its open nature, SARL imposes some fundamental principles to be respected by the various Virtual Machines (VM) that wants to support it. First of all, the implementation of Space must be fully distributed and the execution layer must be abstracted from agents. SARL encourages a massively parallel execution of Agents and Behaviors. SARL is fully interoperable with Java to easily reuse all the contributions provided by the Java community, but also to facilitate the integration and evolution of legacy systems. One of the key principles governing SARL consists in not imposing a predefined way for Agents to interact within a Space. Similarly, the way to identify agents is dependent on the type of Space considered. This allows to define different types of interaction mechanisms and models on Spaces.
The metamodel and the syntax of the SARL programming language have been inspired by the languages like Scala, Clojure, and Ruby.
The SARL tools have been developed on top of Xtext, that enables to easily build domain-specific languages that are directly integrated into the Eclipse framework. The complete definition of the SARL syntax is available on GitHub.
Concepts
The SARL programming language is based on an agent-oriented metamodel based on the following concepts.
Emotional software agents
An agent is an autonomous entity having a set of skills to realize the capacities it exhibits. An agent has a set of built-in capacities considered essential to respect the commonly accepted competences of agents, such autonomy, reactivity, proactivity and social capacities. Among these built-in capacities (BIC), is the "behaviors" capacity that determines its global conduct. An agent has also a default behavior directly described within its definition.
A Behavior maps a collection of perceptions represented by Events to a sequence of Actions. An Event is the specification of some occurrence in a Space that may potentially trigger effects by a listener (e.g. agent, behavior, etc.).
These language does not imposes a specific agent's control loop.
The programmer is free to implement any control or authority protocol for their own application scenario, except for the initialization and destruction events.
Indeed, when agents are created, the virtual machine that is executing the emotional software program is in charge of creating the agent instances, and installing the skills associated to the built-in capacities into the agent.
Then, when the agent is ready to begin its execution, it fires the Initialize event.
When the agent has decided to stop its own execution, the virtual machine fires the Destroy event to enable the agent to release any resource it may still hold.
Capacity and Skill
An Action is a specification of a transformation of a part of the designed system or its environment.
This transformation guarantees resulting properties if the system before the transformation satisfies a set of constraints.
An action is defined in terms of pre- and post-conditions.
A Capacity is the specification of a collection of actions.
This specification makes no assumptions about its implementation.
It could be used to specify what an agent can do, what a behavior requires for its execution.
A Skill is a possible implementation of a capacity fulfilling all the constraints of this specification.
An agent can dynamically evolve by learning/acquiring new Capacities, but it can also dynamically change the Skill associated to a given capacity.
Acquiring new capacities also enables an agent to get access to new behaviors requiring these capacities.
This provides agents with a self-adaptation mechanism that allow them to dynamically change their architecture according to their current needs and goals.
Context and Space
A Context defines the perimeter/boundary of a sub-system, and gathers a collection of Spaces.
In each context, there is at least one particular Space called Default Space to which all agents in this context belong.
This ensures the existence of a common shared Space to all agents in the same context.
Each agent can then create specific public or private spaces to achieve its personal goals.
Since their creation, agents are incorporated into a context called the Default Context.
The notion of Context makes complete sense when agents are considered composed or holonic (see below).
A Space is the support of the interaction between agents respecting the rules defined in a Space Specification. A Space Specification defines the rules (including action and perception) for interacting within a given set of Spaces respecting this specification.
Recursive Agent or Emotional software agent
Agents can be composed of other agents to define hierarchical multiagent systems. Each agent defines its own Context, called the Inner Context, and it is part of one or more External Contexts.
Examples
Hello, World!
package helloworld
import io.sarl.core.Initialize
agent HelloWorldAgent {
on Initialize {
println("Hello, World!")
}
}
Exchanging messages between two agents
For illustrating the syntax of the SARL language, the Ping-Pong scheme is coded below.
The agent A is sending a message PING to the agent B for determining if it is still alive.
The agent B is replying with a PONG message.
First, the two messages must be defined as events (without attribute):
event PING
event PONG
The agent A is defined with
agent A {
uses DefaultContextInteraction, Logging
on Initialize {
emit(new Ping)
}
on Pong {
println("Agent " + occurrence.source + " is alive".)
}
}
In the previous code, the keyword enables the agent to use previously-defined capacities: the capacity to interact with other agents inside the default context (DefaultContextInteraction), and the capacity to log messages (Logging).
The keyword permits to define the actions when an occurrence of the specified event is received by the agent A.
When the agent A receives the Initialize event, it emits a Ping event to all the existing agents.
When the agent A receives the Pong event, it logs a message with the identity of the event's emitter inside.
The agent B is defined with
agent B {
uses DefaultContextInteraction, Logging
on Ping {
println("Agent " + occurrence.source + " wants to know if I'm alive.)
emit(new Pong, Scopes addresses(occurrence.source))
}
}
When the agent B receives the Ping message, it logs a message and reply with a Pong message.
For avoiding a broadcast of the Pong message, the receiver of this message is restricted with the scope corresponding to the address of the Ping's emitter.
Janus Platform: a SARL Run-time Environment
SARL language specifies a set of concepts and their relations.
However, the SARL language does not impose a particular execution infrastructure for being platform-independent.
Nevertheless, the Janus Project provides the infrastructure for running SARL agents.
Janus is an open source multi-agent platform fully implemented in Java 1.7.
It implements all required infrastructure to execute a MAS programmed in the SARL language.
The major assumption made at the SARL language level are supported by this run-time environment: fully distributed, parallel execution of agent's behaviors.
Additionally, the Janus platform provides the tools for helping the programmer to deploy its MAS with the automatic discovery of Janus kernels, for instance.
Technically, the Janus platform follows the best practices in current software development, such as Inversion of Control, and profits from new technologies like Distributed Data Structures (In-Memory Data Grid like Hazelcast).
See also
Intelligent agent
JACK Intelligent Agents
Java Agent Development Framework (JADE)
AgentSpeak
GOAL
References
External links
SARL Official site
Agent-based programming languages
Agent-based software
Multi-agent systems | SARL (programming language) | Engineering | 1,915 |
10,799,349 | https://en.wikipedia.org/wiki/GIS%20and%20hydrology | Geographic information systems (GISs) have become a useful and important tool in the field of hydrology to study and manage Earth's water resources. Climate change and greater demands on water resources require a more knowledgeable disposition of arguably one of our most vital resources. Because water in its occurrence varies spatially and temporally throughout the hydrologic cycle, its study using GIS is especially practical. Whereas previous GIS systems were mostly static in their geospatial representation of hydrologic features, GIS platforms are becoming increasingly dynamic, narrowing the gap between historical data and current hydrologic reality.
The elementary water cycle has inputs equal to outputs plus or minus change in storage. Hydrologists make use of this hydrologic budget when they study a watershed. The inputs in a hydrologic budget include precipitation, surface flow, and groundwater flow. Outputs consist of evapotranspiration, infiltration, surface runoff, and surface/groundwater flows. All of these quantities can be measured or estimated based on environmental data and their characteristics can be graphically displayed and studies using GIS.
GIS in surface water
In the field of hydrological modeling, analysis generally begins with the sampling and measurement of existing hydrologic areas. In this stage of research, the scale and accuracy of measurements are key issues. Data may either be collected in the field or through online research. The United States Geological Survey ((USGS)) is a publicly available source of remotely sensed hydrological data. Historical and real-time streamflow data are also available via the internet from sources such as the National Weather Service (NWS) and the United States Environmental Protection Agency (EPA). A benefit of using GIS softwares for hydrological modeling is that digital visualizations of data can be linked to real-time data. GIS revolutionized curation, manipulation, and input for complex computational hydrologic models
For surface water modeling, digital elevation model are often layered with hydrographic data in order to determine the boundaries of a watershed. Understanding these boundaries is integral to understanding where precipitation runoff will flow. For example, in the event of snowmelt, the amount of snowfall can be input into GIS to predict the amount of water that will travel downstream. This information has applications in local government asset management, agriculture and environmental science.
Another useful application for GIS regards flood risk assessment. Using digital elevation models combined with peak discharge data can predict which areas of a floodplain will be submerged depending on the amount of rainfall. In a study of the Illinois River watershed, Rabie (2014) found that a decently accurate flood risk map could be generated using only DEMs and stream gauge data. Analysis based on these two parameters alone does not account for manmade developments including levees or drainage systems, and therefore should not be considered a comprehensive result.
GIS in groundwater
The use of GIS to analyze groundwater falls into the field of hydrogeology. Since 98% of available freshwater on Earth is groundwater, the need to effectively model and manage these resources is apparent. As the demand for groundwater continues to increase with the world’s growing population, it is vital that these resources be properly managed. Indeed, when groundwater usage is not monitored sufficiently, it may result in damage to aquifers or groundwater-related subsidence, as occurred in the Ogallala aquifer in the United States. In some cases, GIS can be used to analyze drainage and groundwater data in order to select suitable sites for groundwater recharge.
See also
GIS in environmental contamination
Geographic information system
ArcGIS
GIS and aquatic science
References
Girish Kumar, M., Bali, R. and Agarwal, A.K (2009). GIS Integration of remote sensing and electrical data for hydrological exploration- A case study of Bhakar watershed, India. Hydrological Sciences Journal 54 (5) pp 949–960.
Dingman, S. Lawrence, Physical Hydrology, Prentice-Hall, 2nd Edition, 2002
Fetter, C.W. Applied Hydrogeology, Prentice-Hall, 4th Edition, 2001
Maidment, David R., ed. Arc Hydro: GIS for Water Resources, ESRI Press, 2002
External links
Spatial Hydrology
GIS Lounge
ArcNews Online
US Army Geospatial Center — For information on OCONUS surface water and groundwater.
Applications of geographic information systems
Hydrology | GIS and hydrology | Chemistry,Engineering,Environmental_science | 888 |
6,740,960 | https://en.wikipedia.org/wiki/Cheerios%20effect | In fluid mechanics, the Cheerios effect is a colloquial name for the phenomenon of floating objects appearing to either attract or repel one another. The example which gives the effect its name is the observation that pieces of breakfast cereal (for example, Cheerios) floating on the surface of a bowl will tend to clump together, or appear to stick to the side of the bowl.
Description
The effect is observed in small objects which are supported by the surface of a liquid. There are two types of such objects: objects which are sufficiently buoyant that they will always float on the surface (for example, Cheerios in milk), and objects which are heavy enough to sink when immersed, but not so heavy as to overcome the surface tension of the liquid (for example, steel pins on water). Objects of the same type will appear to attract one another, and objects of opposite types will appear to repel one another.
In addition, the same attractive or repulsive effect can be observed between objects and the wall of the container. Once again there are two possibilities: the interface between the liquid and the container wall is either a concave or a convex meniscus. Buoyant objects will be attracted in the case of a concave meniscus and repelled for convex. Non-buoyant floating objects will do the opposite.
Explanation
All objects in a fluid experience two opposed forces in the vertical direction: gravity (determined by the mass of the object) and buoyancy (determined by the density of the fluid and the volume of liquid displaced by the object). If the buoyant force is greater than the force of gravity acting on an object, it will rise to the top of the liquid. On the other hand, an object immersed in a liquid which experiences a gravitational force greater than its buoyant force will sink.
At the surface of the liquid, a third effect comes into play - surface tension. This effect is due to the fact that molecules of the liquid are more strongly attracted to each other than they are to the air above the liquid. As such, non-wetting objects on the surface of the liquid will experience an upward force due to surface tension. If the upward force is sufficient to balance the force of gravity on the object, it will float on the surface of the liquid, while deforming the surface down. By contrast, objects with a net positive buoyancy will deform the water surface upward around them as they press against the surface.
This deformation of the liquid surface, combined with the net upwards or downwards force experienced by each object, is the cause of the Cheerios effect. Objects experiencing a net upward force will follow the surface of the liquid as it curves upward. Therefore two objects with an upward deformation will move toward each other as each follows the surface of the liquid upward. Similarly, objects with a net downward force will follow the curve of the liquid surface in the downward direction, and will move horizontally together as they do so.
The same principle holds at the side of the container, where the surface of the liquid is deformed by the meniscus effect. If the container is wetting with respect to the liquid, the meniscus will slope upwards at the wall of the container, and buoyant objects will move towards the wall as a result of travelling upward along the surface. By contrast, non-buoyant floating objects will move away from the walls of such a container for the same reason.
More complex behavior resulting from the same principles can be observed in shapes which do not have simple concave or convex meniscus behavior. When such objects come close to each other they rotate in the plane of the water surface until they find an optimum relative orientation then move toward each other.
Simplified calculation
Writing in the American Journal of Physics, Dominic Vella and L. Mahadevan of Harvard University discuss the Cheerios effect and suggest that it may be useful in the study of the self-assembly of small structures. They calculate the force between two spheres of density and radius floating distance apart in liquid of density as
where is the surface tension, is a modified Bessel function of the first kind, is the Bond number, and
is a nondimensional factor in terms of the contact angle .
Here is a convenient meniscus length scale.
References
Fluid mechanics | Cheerios effect | Engineering | 882 |
16,017,237 | https://en.wikipedia.org/wiki/Style%20guide | A style guide is a set of standards for the writing, formatting, and design of documents. A book-length style guide is often called a style manual or a manual of style (MoS or MOS). A short style guide, typically ranging from several to several dozen pages, is often called a style sheet. The standards documented in a style guide are applicable for either general use, or prescribed use in an individual publication, particular organization, or specific field.
A style guide establishes standard style requirements to improve communication by ensuring consistency within and across documents. They may require certain best practices in writing style, usage, language composition, visual composition, orthography, and typography by setting standards of usage in areas such as punctuation, capitalization, citing sources, formatting of numbers and dates, table appearance and other areas. For academic and technical documents, a guide may also enforce the best practice in ethics (such as authorship, research ethics, and disclosure) and compliance (technical and regulatory). For translations, a style guide may even be used to enforce consistent grammar, tones, and localization decisions such as units of measure.
Style guides may be categorized into three types: comprehensive style for general use; discipline style for specialized use, which is often specific to academic disciplines, medicine, journalism, law, government, business, and other industries; and house or corporate style, created and used by a particular publisher or organization.
Varieties
Style guides vary widely in scope and size. Writers working in large industries or professional sectors may reference a specific style guide, written for usage in specialized documents within their fields. For the most part, these guides are relevant and useful for peer-to-peer specialist documentation or to help writers working in specific industries or sectors communicate highly technical information in scholarly articles or industry white papers.
Professional style guides of different countries can be referenced for authoritative advice on their respective language(s), such as the United Kingdom's New Oxford Style Manual from Oxford University Press; and the United States' The Chicago Manual of Style from the University of Chicago Press. Australia has a style guide, available online, created by its government.
Sizes
The variety in scope and length is enabled by the cascading of one style over another, analogous to how styles cascade in web development and in desktop cascade over CSS styles.
In many cases, a project such as a book, journal, or monograph series typically has a short style sheet that cascades over the larger style guide of an organization such as a publishing company, whose specific content is usually called house style. Most house styles, in turn, cascade over an industry-wide or profession-wide style manual that is even more comprehensive. Examples of industry style guides include:
The Associated Press Stylebook (AP Stylebook) and The Canadian Press Stylebook for journalism
The Chicago Manual of Style (CMoS) and Oxford style for general academic writing and publishing
Modern Humanities Research Association (MHRA) style and American Sociological Association (ASA) style for the arts and humanities
Oxford Standard for Citation of Legal Authorities (OSCOLA) and Bluebook style for law
US Government Publishing Office (USGPO) style and Australian Government Publishing Service (AGPS) style for government publications
Finally, these reference works cascade over the orthographic norms of the language in use (for example, English orthography for English-language publications). This, of course, may be subject to national variety, such as British, American, Canadian, and Australian English.
Topics
Some style guides focus on specific topic areas such as graphic design, including typography. Website style guides cover a publication's visual and technical aspects as well as text.
Guides in specific scientific and technical fields may cover nomenclature to specify names or classifying labels that are clear, standardized, and ontologically sound (e.g., taxonomy, chemical nomenclature, and gene nomenclature).
Style guides that cover usage may suggest descriptive terms for people which avoid racism, sexism, homophobia, etc. Style guides increasingly incorporate accessibility conventions for audience members with visual, mobility, or other disabilities.
Web style guides
Since the rise of the digital age, websites have allowed for an expansion of style guide conventions that account for digital behavior such as screen reading. Screen reading requires web style guides to focus more intently on a user experience subjected to multichannel surfing. Though web style guides can also vary widely, they tend to prioritize similar values concerning brevity, terminology, syntax, tone, structure, typography, graphics, and errors.
Updating
Most style guides are revised periodically to accommodate changes in conventions and usage. The frequency of updating and the revision control are determined by the subject. For style manuals in reference-work format, new editions typically appear every 1 to 20 years. For example, the AP Stylebook is revised every other year (since 2020). The Chicago Manual of Style is in its 18th edition, while the APA and ASA styles are both in their 7th as of 2025. Many house styles and individual project styles change more frequently, especially for new projects.
See also
List of style guides
Graphic charter
Diction
Documentation
Disputed usage
English writing style
Prescription and description
Sentence spacing in language and style guides
Spelling
Style sheet (disambiguation)
References
External links
But the stylebook says ... – Blog post about stylebook abuse, by Bill Walsh of The Washington Post
Handouts about writing style guides, from a conference of the American Copy Editors Society in 2007
Language Log » Searching 43 stylebooks
Bibliography
Communication design
Design
Graphic design
Technical communication
Linguistics books | Style guide | Engineering | 1,129 |
2,902,215 | https://en.wikipedia.org/wiki/Japanese%20fire-bellied%20newt | The Japanese fire-bellied newt or Japanese fire-bellied salamander (Cynops pyrrhogaster) is a species of newt endemic to Japan. The skin on its upper body is dark and its lower regions bright red, although coloration varies with age, genetics, and region. Adults are long. To deter predators, Japanese fire-bellied newts contain high levels of tetrodotoxin, a neurotoxin accumulated mainly from their diet.
The species is found on many Japanese islands, including Honshu, Shikoku, and Kyushu. Their habitats include both natural and artificial bodies of water, as well as forests and grasslands. They breed from spring to the beginning of summer, both sexes producing pheromones when ready to mate. Eggs are laid separately, hatching after about three weeks. They grow from larval to juvenile form in between five and six months. Juveniles eat soil-dwelling prey, and adults eat a wide variety of insects, tadpoles, and the eggs of their own species. They have several adaptations to avoid predators, although which they use depends on where they live. Several aspects of their biology have been studied, including their ability to regrow missing body parts.
The Japanese fire-bellied newt first diverged from its closest relative in the Middle Miocene, before splitting into four distinct varieties, each with a mostly separate range, although all four are formally recognized as composing a single species. Currently, their population is declining, and they face threats from disease and the pet trade. They can be successfully kept in captivity.
Etymology and taxonomy
The species was first scientifically described by German zoologist Heinrich Boie in 1826 as Molge pyrrhogaster, based on specimens brought from Japan to Europe. He compared it to the smooth newt, saying he would have mistaken the former for the latter, had he not known it was from Japan. None of the specimens he studied were fully mature. Pyrrhogaster is derived from Greek, () and (). Salamandra subcristata was described by Coenraad Jacob Temminck and Hermann Schlegel in 1838 and transferred to Cynops later that year by Swiss naturalist Johann Jakob von Tschudi, and in 1850, Cynops subcristata and Molge pyrrhogaster were synomized as Cynops pyrrhogaster by the British zoologist John Edward Gray. A study of mitochondrial DNA in 2001 indicated that its supposed fellow members of Cynops, C. cyanurus and C. wolterstorffi, may belong to a different genus.
The Integrated Taxonomic Information System lists sixteen synonyms for Cynops pyrrhogaster. Common names of the species include Japanese fire-bellied newt, red-bellied newt, and Japanese fire-bellied salamander. Studies examining morphological and geographic variation had formerly recognized six races: Tohoku, Kanto, Atsumi, intermediate, Sasayama, and Hiroshima, one of which, the Sasayama, was described as a subspecies in 1969 by Robert Mertens as Triturus pyrrhogaster sasayamae, which is now considered a synonym of C. pyrrhogaster. Modern molecular analysis supports the division of C. pyrrhogaster into four clades instead. In particular, the validity of the Sasayama and intermediate races has never been proven, with one study finding no behavioral differences between the two supposed forms.
Cynops pyrrhogaster diverged from its close relative C. ensicauda about 13.75 million years ago (Mya; during the Middle Miocene). The common ancestor of the two species would have lived in an area of the Eurasian mainland which is today the East China Sea and the central Ryukyu Islands. The land that would become the Japanese islandsconnected to the mainland at that timelikely had a subtropical climate, which may have caused the Japanese fire-bellied newt's ancestors to migrate northward for desirable habitat. Over time, C. pyrrhogaster split into four clades: northern, southern, western, and central. The northern diverged first, at around 9.68 mya, then the central around 8.23 mya, and finally the southern and western around 4.05 mya. The ranges of all but the southern clade declined during the Last Glacial Period, but expanded again afterwards. The study that identified them concluded that the four clades represent separate taxonomic units, although their exact relationship is unclear. It also noted their extreme genetic differences, unusually large for any one species. The ranges of the central and western varieties meet in Chugoku in western Japan to form a hybrid zone (an area where the two clades interbreed to produce hybrids). The central type has begun to move west, which has caused the hybrid zone to shift. It is expected to eventually cause the genome of the western form to be diluted by increasing hybridization.
Description
On the newt's upper body, the skin is dark brown, approaching black, and covered in wartlike bumps. The underbelly and the underside of its tail are bright red, with black spots. Younger juveniles have creamy coloration instead of red, although most larger juveniles have some red present. Adults from smaller islands tend to have more red on their ventral (belly) regions than those from larger islands, sometimes with extremely small spots or none at all. In general males tend to have more red than females. Males can also be distinguished from females by their flat, wide tails and swelling around the ventral region. An entirely red variant exists: that coloration is believed to be inherited and recessive. This variant is not confined to any single population, but is more common in the western half of Japan overall.
The vomeropalatine teeth, a group of teeth in the upper back of the mouth, are arranged in two series. The tongue is relatively small, half the width of the mouth. The nostrils are positioned anteriorly (toward the head), closer to each other than to the eyes and hardly visible when viewed from above. The toes of males are longer than those of females, although the females themselves are longer. The tail is tightly compressed, with fins on both the top and bottom. A smooth ridge runs from their nape to their tail. The full body length of adults is . Snout–vent length can be anywhere between for males and for females. Populations from more northern and elevated regions tend to be larger than those in southern and lower-altitude regions. Eggs are long.
Distribution and habitat
Cynops pyrrhogaster is endemic to Japan, being found on several islands in the archipelago, including Honshu, Shikoku, and Kyushu. It mainly dwells on the larger islands, whereas its relative, C. ensicauda, is found in the Ryukyu Islands. It has the northernmost range of any Cynops species; all other species, besides the aforementioned C. ensicauda, are native to southern China. There is also an introduced population on Hachijō-jima, believed to be descended from individuals from Shikoku. Their introduction is thought to have occurred in the 1970s, although exactly how it happened is unknown. It has been recorded in the United States three times, in Florida and Massachusetts. Every instance was either an escape or deliberate release, and no populations have been established.
Of the four clades, the northern is found in the districts of Tohoku and Kanto. This does not overlap with the range of the central clade, which is found in Chubu, northern Kansai, and eastern Chugoku. The central's range has a small amount of overlap with the western, which is found in southern Kinki, western Chugoku, Shikoku, and central Kyushu. The western also has some overlap with the southern clade, which is found in western and southern Kyushu.
The newts occur at elevations of . Ecosystems they are found in include forests, grasslands, shrublands, wetlands, lakes, marshes, and cultivated environments. They can also dwell in humanmade bodies of water, such as aquaculture ponds.
Behavior and ecology
Reproduction and life cycle
Breeding occurs in paddy fields, ponds, brooks, pools, and streams. Females accept male courtship behavior from spring to early summer. Males and females both produce peptide pheromones to attract the opposite sex when ready to mate. Males produce a type known as sodefrin (from the Japanese term , ); females have their own variety, named imorin by its discoverers (from the Japanese term , , and rin from sodefrin). These are released from the cloaca, and were the first peptide pheromone to be identified in a vertebrate and first to be identified in a female vertebrate, respectively.
Courtship begins when the male approaches the female, sniffing its sides or cloaca. The male then brings its tail to the female and rapidly vibrates it. The female responds by pushing the male's neck with its snout. At this point, the male slowly moves away, undulating its tail, and the female follows, touching the tail with its snout when close enough. The male then deposits two to four spermatophores, one at a time, moving several centimeters after each, which the female attempts to pick up with its cloaca, sometimes unsuccessfully. Females lay eggs separately on underwater objects, such as leaves and submerged grass roots, fertilized one by one from the spermatophores they carry. They can lay up to 40 eggs in one session, and 100 to 400 eggs in a breeding season.
The young hatch from their eggs after about three weeks, as swimming, gilled larvae, with dorsal tailfins. They grow around in the first three months of their lives. At between five and six months, they stop eating and undergo metamorphosis, losing their gills and fins, and becoming juveniles. Juveniles cannot remain submerged in water like larvae or they drown. Newts at lower altitudes mature faster than those at higher ones. Male newts of higher-altitude populations tend to live longer after reaching maturity, but their fully grown size is not as large as that of lowland newts. Wild individuals as old as twenty-three have been found.
Spermatogenesis
Cynops pyrrhogaster is regarded as an ideal vertebrate model for investigating the mechanism(s) involved in the transition from mitosis to meiosis during spermatogenesis. In males, this transition involves expression of PCNA, a DNA polymerase delta auxiliary protein employed in DNA replication and DNA repair. Also involved in the transition is DMC1, a protein employed in genetic recombination.
Diet
In captive settings tadpoles are known to readily eat mosquito larvae, brine shrimp, and earthworms. Juveniles often consume soil-dwelling Collembola (springtails) and Acari (mite) species. Adults at one particular sub-alpine moor in the Azuma Mountains of Fukushima Prefecture were found to like both live prey and carrion. They consume many insect varieties, such as members of Odonata, which include dragonflies and damselflies, whose larvae have been found whole in newt stomachs, but only pieces of adults; Brachycera, a suborder of Diptera (flies); Hymenoptera, which include sawflies, wasps, bees, and ants; and Coleoptera (beetles). They also eat Rhacophorus arboreus tadpoles and the eggs of their own kind. The makeup of their diet varies seasonally and from year to year, suggesting changes in the small animals in and around the ponds that they dwell in. Similar results were found at a pond on the campus of Tokyo Metropolitan University in Hachiōji, Tokyo, the newt stomachs containing insects from many different orders, and again, the eggs of conspecifics. Like before, frog tadpoles were eaten, although these belonged to the species Rhacophorus schlegelii.
Predators
Newts in Mainland Japan have different antipredator behavior than newts on smaller islands. Individuals on smaller islands (for instance, Fukue Island) generally use a maneuver called the unken reflex, where they expose their bright red underbelly to attackers. As their main predators are birds, which are capable of distinguishing the color red, this technique is effective. In Mainland Japan the newts must also avoid mammalian predators, which cannot distinguish colors as well as avian hunters. This leads these populations to use the maneuver less, as it can result in death if attempted.
Against snakes, newts from Fukue Island tend to perform tail-wagging displays, designed to bring a predator's attention to their replaceable tail rather than their more vital head; those from Nagasaki Prefecture in Mainland Japan tend simply to flee. Snakes are present in both areas. This behavior difference is likely because newts from the mainland are adapted to escape from mammalian hunters, which are less likely to be repelled by such a display.
Toxin
Wild Japanese fire-bellied newts contain high levels of the neurotoxin tetrodotoxin (TTX). This toxin inhibits the activity of sodium channels in most vertebrates, discouraging predation by both birds and mammals. Experiments have shown the toxin is almost entirely derived from the newt's diet. When raised in captivity with no source of TTX, 36- to 70-week-old juveniles did not contain detectable levels, but wild specimens from the same original habitat had high toxicity. In younger captive-reared newts some TTX was still detected, which was inferred to have been transferred by adult females to their eggs. In a follow-up experiment by the same team, captive-reared newts were given food containing the neurotoxin. They readily consumed TTX-laced bloodworms when offered, not showing any symptoms after ingesting the poison. It was detectable in their bodies afterward, further indicating food to be the source of the toxin. No TTX-producing organisms are known from their habitat, but their existence is likely, and would explain the origin of TTX in wild newts.
Conservation
The International Union for the Conservation of Nature (IUCN) has ranked it as near-threatened. This assessment was made in 2020, a shift from 2004 when it was rated least-concern. It successfully reproduces in Australian zoos. One major threat that C. pyrrhogaster faces is collection for the pet trade. The IUCN states that this trade needs to be ended immediately. Their population is decreasing, particularly near areas of human habitation.
Japanese fire-bellied newts with mysterious skin lesions at Lake Biwa in Japan's Shiga Prefecture were found to be suffering from infections caused by a single-celled eukaryote in the order Dermocystida. The lesions contained cysts, which were filled with spores. Nearly all the lesions were external, although one was found on the liver. Globally, diseases are one of the causes for declining amphibian populations. There is concern that this affliction could spread to other nearby species, including Zhangixalus arboreus and Hynobius vandenburghi.
A variety, believed to be found exclusively on the Atsumi Peninsula, was thought to have become extinct in the 1960s. Then, in 2016, a trio of researchers discovered that newts on the Chita Peninsula were very likely the same variant due to their similar morphological traits. Both groups share a preference for cooler temperature and have smooth and soft bodies, pale dorsal regions, and yellowish undersides. Even if still alive, this form is highly threatened and will soon be wiped out without immediate protection.
Interactions with humans
Research
Japanese fire-bellied newts serve as a highly useful model organism in laboratory settings, but they become more difficult to care for after metamorphosis. An experiment supported by the Japan Society for the Promotion of Science found that thiourea (TU) can prevent this process from occurring, allowing the animals to stay in their pre-metamorphosis form for as long as two years, while still capable of metamorphosizing when removed from the TU solution. This did not have any impact on their regeneration capabilities.
Japanese fire-bellied newts produce motilin, a peptide that stimulates gastrointestinal contractions, identified in many vertebrates. It is created in the upper small intestine and pancreas. The discovery of the latter was the first time pancreatic motilin had been observed. The organ also produces insulin. These results represented the first discovery of motilin in amphibians, suggesting that it has a similar role for them as it does for birds and mammals. The existence of pancreatic motilin also indicated another, unknown function.
This species, as well as other Urodele amphibians, is capable of regrowing missing body parts, including limbs with functional joints and the lower jaw. When this process occurs, the regenerated tissue tends to mirror intact tissue in form. It is also able to regrow missing lenses, taking thirty days to do so as a larva and eighty days as an adult. The difference in time is purely due to the size of the eye, and regenerative ability does not change; the discovery of this fact contradicted a popular claim that juvenile animals are quicker to regenerate than adults.
In captivity
Cynops pyrrhogaster can be kept in captivity. Doctor of Veterinary Medicine Lianne McLeod described them as "low-maintenance", noting that captive newts enjoy bloodworms, brine shrimp, glass shrimp, Daphnia, and, for larger individuals, guppies.
Notes
References
Cynops
Animal models
Endemic amphibians of Japan
Amphibians described in 1826
Articles containing video clips
Taxa named by Heinrich Boie | Japanese fire-bellied newt | Biology | 3,689 |
26,681,002 | https://en.wikipedia.org/wiki/Text%20annotation | Text annotation is the practice and the result of adding a note or gloss to a text, which may include highlights or underlining, comments, footnotes, tags, and links. Text annotations can include notes written for a reader's private purposes, as well as shared annotations written for the purposes of collaborative writing and editing, commentary, or social reading and sharing. In some fields, text annotation is comparable to metadata insofar as it is added post hoc and provides information about a text without fundamentally altering that original text. Text annotations are sometimes referred to as marginalia, though some reserve this term specifically for hand-written notes made in the margins of books or manuscripts. Annotations have been found to be useful and help to develop knowledge of English literature.
Annotations can be both private and socially shared, including hand-written and information technology-based annotation. Annotations are different than notetaking because annotations must be physically written or added on the actual original piece. This can be writing within the page of a book or highlighting a line, or, if the piece is digital, a comment or saved highlight or underline within the document. For information on annotation of Web content, including images and other non-textual content, see also Web annotation.
History
Text annotation may be as old as writing on media, where it was possible to produce an additional copy with a reasonable effort. It became a prominent activity around 1000 AD in Talmudic commentaries and Arabic rhetorics treaties. In the Medieval era, scribes who copied manuscripts often made marginal annotations that then circulated with the manuscripts and were thus shared with the community; sometimes annotations were copied over to new versions when such manuscripts were later recopied.
With the rise of the printing press and the relative ease of circulating and purchasing individual (rather than shared) copies of texts, the prevalence of socially shared annotations declined and text annotation became a more private activity consisting of a reader interacting with a text. Annotations made on shared copies of texts (such as library books) are sometimes seen as devaluing the text, or as an act of defacement. Thus, print technologies support the circulation of annotations primarily as formal scholarly commentary or textual footnotes or endnotes rather than marginal, handwritten comments made by private readers, though handwritten comments or annotations were common in collaborative writing or editing.
Computer-based technologies have provided new opportunities for individual and socially shared text annotations that support multiple purposes, including readers' individual reading goals, learning, social reading, writing and editing, and other practices. Text annotation in Information Technology (IT) systems raises technical issues of access, linkage, and storage that are generally not relevant to paper-based text annotation, and thus research and development of such systems often addresses these areas.
Functions and applications
Text annotations can serve a variety of functions for both private and public reading and communication practices. In their article "From the Margins to the Center: The Future of Annotation," scholars Joanna Wolfe and Christine Neuwirth identify four primary functions that text annotations commonly serve in the modern era, including: (1)"facilitat[ing] reading and later writing tasks," which includes annotations that support reading for both personal and professional purposes; (2)"eavesdrop[ping] on the insights of other readers," which involves sharing of annotations; (3)"provid[ing] feedback to writers or promote communication with collaborators," which can include personal, professional, and education-related feedback; and (4)"call[ing] attention to topics and important passages," for which scholarly annotations, footnotes, and call-outs often function. Regarding the ways that annotations can support individual reading tasks, Catherine Marshall points out that the ways that readers annotate texts depends on the purpose, motivation, and context of reading. Readers may annotate to help interpret a text, to call attention to a section for future reference or reading, to support memory and recall, to help focus attention on the text as they read, to work out a problem related to the text, or create annotations not specifically related to the text at all.
Educational applications
Educational research in text annotation has examined the role that both private and shared text annotations can play in supporting learning goals and communication. Much educational research examines how students' private annotation of texts supports comprehension and memory; for example, research indicates that annotating texts causes more in-depth processing of information, which results in greater recall of information. Because annotations are done while reading with a writing utensil in hand, readers are supposed to be more aware of their thoughts as they read. This means that readers are, along with making notes to help them remember or better understand the content, actively engaged during the activity and are therefore more receptive to the information when annotating a text.
Other areas of educational research investigate the benefits of socially shared text annotations for collaborative learning, both for paper-based and IT-based annotation sharing. For example, studies by Joanna Wolfe have investigated the benefits of exposure to others' annotations on student readers and writers. In a 2000 study, Wolfe found that exposing students to others' annotations influenced their perceptions of the annotators, which in turn shaped their responses to the material and their written products. In a later study, Wolfe found that viewing others' written comments on a paper text, especially pairs of annotations that present opposing responses to the text, can help students engage in the type of critical reading and stance-taking necessary for effective argumentative writing.
While shared annotations can benefit individual readers, "since the 1920s, literacy theory has increasingly emphasized the importance of social factors in the development of literacy." Thus, shared annotations can not only help one to better understand the content of a particular text, but may also aid in the acquirement of literacy skills. For example, a mother may leave marks inside a book to draw the attention of her child to a particular theme or concept; thanks to the development of audio annotations, parents may now leave notes for children who are just starting to read and may struggle with textual annotations.
More recent research in the effects of shared text annotations has focused on the learning applications for web-based annotation systems, some of which were developed based on design recommendations from studies outlined above. For example, Ananda Gunawardena, Aaron Tan, and David Kaufer conducted a pilot study to examine whether annotating documents in Classroom Salon, a web-based annotation and social reading platform, encouraged active reading, error detection, and collaboration in a computer science course at Carnegie Mellon University. This study suggested a correlation between students' overall performance in the course and their ability to identify errors in a text that they annotated in Classroom Salon; it also found that students were likely to change their annotations in response to annotations made by others in the course.
Similarly, the web-based annotation tool HyLighter was used in a first-year writing course and shown to improve the development of students' mental models of texts, including supporting reading comprehension, critical thinking, and the ability to develop a thesis. The collaboration with peers and experts around a shared text improved these skills and brought the communities' understanding closer together.
A meta-analysis of empirical studies into the higher-education uses of social annotation (SA) tools indicates such tools have been tested in several courses, among them English, sport psychology, and hypermedia. Studies have indicated that social annotation functions, including commenting, information sharing, and highlighting, can support instruction designed to foster collaborative learning and communication, as well as reading comprehension, metacognition, and critical analysis. Several studies indicated that students enjoyed using social annotation tools, and that it improved motivation in the course.
"Multi Sensory" annotations have also been found to help students retain not only information in the classroom, but this can also help those who are trying to learn a new language. Images can be placed next to or linked to words for people to get a better understand of what that word means by looking at it. The same can be done with an audio clip of how that word is pronounced and also its meaning. Of course this is easier done using technology and in order to be specifically an annotation it must be embedded within the referenced document. However in physical copies of text a picture can be drawn next to a word and still be a sensory annotation. This form of annotation furthers comprehension, specifically in the classroom because it requires more of students' brains to retain the information being given.
Writing and text-centered collaboration
Text annotations have long been used in writing and revision processes as a way for reviewers to suggest changes and communicate about a text. In book publishing, for example, the collaboration of authors and editors to develop and revise a manuscript frequently involves exchanges of both in-line revisions or notes as well as marginal annotations. Similarly, copyeditors often make marginal annotations or notes that explain or suggest revisions or are directed at the author as questions or suggestions (commonly called "queries"). Asynchronous collaborative writing and document development often depend on text annotations as a way not only to suggest revisions but also to exchange ideas during document development or to facilitate group decision making, though such processes are often complicated by the use of different communication technologies (such as phone calls or emails as well as document sharing) for distinct tasks. Text annotations can also function to allow group or community members to communicate about a shared text, such as a doctor annotating a patient's chart.
Much research into the functionality and design of collaborative IT-based writing systems, which often support text annotation, has occurred in the area of computer-supported cooperative work.
Linguistic annotation
In corpus linguistics, digital philology and natural language processing, annotations are used to explicate linguistic, textual or other features of a text (or other digital representations of natural language). In linguistics, annotations include comments and metadata; non-transcriptional annotations are also non-linguistic.
In these disciplines, annotations are the basis for quantitative research, empirical studies and the application of machine learning. Unlike annotations in the above-mentioned uses (that appear very sparsely), linguistic annotation usually requires that every element (token) within a text carries one or multiple annotations, and that complex relations between different annotations exist. A number of specialized formats (and tools) for this purpose exist, the following illustrates an annotation with as used in the Universal Dependencies project. For clarity, the tab-separated values normally used have been replaced by an HTML table.
[[File:Ud-ewt-sample.png|frame|Fig. 2. Sample for Universal Dependencies annotation, English Web Treebank, visualization by Brat]
A visualization of the example is given in Fig. 2. In addition to word-level annotations, the word (and the sentence, etc.) in this format can carry metadata.
Various other annotation formats do exist, often coupled with certain pieces of software for their creation, processing or querying, see Ide et al. (2017) for an overview. The Linguistic Annotation Wiki describes tools and formats for creating and managing linguistic annotations. Selected problems and applications are also discussed under Overlapping markup and Web annotation. Aside from tab-separated values and other text formats, formats for linguistic annotations are often based on markup languages such as XML (and formerly, SGML), more complex annotations may also employ graph-based data models and formats such as JSON-LD, e.g., in accordance with the Web Annotation standard.
Linguistic annotation comes with an independent research tradition and its own terminology: The target of an annotation is usually referred to as a 'markable', the body of the annotation as 'annotation', the relation between annotation and markable is usually expressed in the annotation format (e.g., by having annotations and text side-by side), so that explicit anchors are not necessary.
Structure and design
Research in the design and development of annotation systems uses specific terminology to refer to distinct structural components of annotations and also distinguishes among options for digital annotation displays.
Annotation structure
The structural components of any annotation can be roughly divided into three primary elements: a body, an anchor, and a marker. The body of an annotation includes reader-generated symbols and text, such as handwritten commentary or stars in the margin. The anchor is what indicates the extent of the original text to which the body of the annotation refers; it may include circles around sections, brackets, highlights, underlines, and so on. Annotations may be anchored to very broad stretches of text (such as an entire document) or very narrow sections (such as a specific letter, word, or phrase). The marker is the visual appearance of the anchor, such as whether it is a grey underline or a yellow highlight. An annotation that has a body (such as a comment in the margin) but no specific anchor has no marker.
Annotation display types
IT-based annotation systems utilize a variety of display options for annotations, including:
Footnote interfaces that display annotations below the corresponding text
Aligned annotations that display comments and notes vertically in the text margins, sometimes in multiple columns or as a "sidebar" layer
Interlinear annotations that attach annotations directly into a text
Sticky note interfaces, where annotations appear in popup dialogs over the source text
Voice annotations, in which reviewers record annotations and embed them within a document
Pen or digital-ink based interfaces that allow writing directly on a document or screen
Annotation interfaces may also allow highlighting or underlining, as well as threaded discussions. Sharing and communicating through annotations anchored to specific documents is sometimes referred to as anchored discussion.
IT-based text annotation systems
IT-based annotation systems include standalone and client-server systems. In the 1980s and 1990s, a number of such systems were built in the context of libraries, patent offices, and legal text processing. Their design led researchers to produce taxonomies of annotation forms. Text annotation research has taken place at several institutions, including Xerox research centers in Palo Alto and Grenoble (France), the Hitachi Central Research Lab (in particular for annotation of patents), and in relation with the construction of the new French National Library between 1989 and 1995 at the Institut de Recherche en Informatique de Toulouse and in the company AIS (Advanced Innovation Systems).
Annotation functionality has been present in text processing software for many years through inline notes displayed as pop-ups, footnotes, and endnotes; however, it is only recently that functionality for displaying annotations as marginalia has appeared in programs such as OpenOffice.org/LibreOffice Writer and Microsoft Word. Personal or standalone annotation include word processing software that supports embedded or anchored text annotations as well as Adobe Acrobat, which in addition to commenting allows highlights, stamps, and other types of markup.
Web-based text annotation systems
Tim Berners-Lee had already implemented the concept of directly editing web documents in 1990 in WorldWideWeb, the first web browser, but later ported versions removed this collaborative ability. An early version of NCSA Mosaic in 1993 also included a collaborative annotation capability, though it was quickly removed. Web Distributed Authoring and Versioning, WebDAV, was then reintroduced as an extension.
A different approach to distributed authoring consists in first gathering many annotations from a wide public, and then integrate them all in order to produce a further version of a document. This approach was pioneered by Stet, the system put in place to gather comments on drafts of version 3 of the GNU General Public License. This system arose after a specific requirement, which it served egregiously, but was not so easily configurable as to be convenient for annotating any other document on the web. The co-ment system uses annotation interface concepts similar to Stet's, but it is based on an entirely new implementation, using Django/Python on the server side and various AJAX libraries such as JQuery on the client side. Both Stet and co-ment are licensed under the GNU Affero General Public License.
Since 2011, the non-profit Hypothes Is Project has offered the free, open web annotation service Hypothes.is. The service features annotation via a Chrome extension, bookmarklet or proxy server, as well as integration into a LMS or CMS. Both webpages and PDFs can be annotated. Other web-based text annotation systems are collaborative software for distributed text editing and versioning, which also feature annotation and commenting interfaces.
Specialized Web-based text annotations exist in the context of scientific publication, either for refereeing or post-publication. The on-line journal PLoS ONE, published by the Public Library of Science, has developed its own Web-based system where scientists and the public can comment on published articles. The annotations are displayed as pop-ups with an anchor in the text.
See also
Annotation
Web annotation
Gloss (annotation)
Interlinear gloss
Footnote
Perusall
PDF annotation
Marginalia
Social bookmarking
Comment (computer programming)
References
Book design
Reference | Text annotation | Engineering | 3,720 |
66,016,527 | https://en.wikipedia.org/wiki/Coded%20Bias | Coded Bias is an American documentary film directed by Shalini Kantayya that premiered at the 2020 Sundance Film Festival. The film includes contributions from researchers Joy Buolamwini, Deborah Raji, Meredith Broussard, Cathy O’Neil, Zeynep Tufekci, Safiya Noble, Timnit Gebru, Virginia Eubanks, and Silkie Carlo, and others.
Background
Kantayya previously directed a documentary titled Catching the Sun and also directed one episode of the National Geographic television series, Breakthrough. She is also an associate of UC Berkeley Graduate School of Journalism. Kantayya said an interview with 500 Global on August 17, 2021, that three years previously she did not even know what an algorithm was. She read the book Weapons of Math Destruction, which describes how artificial intelligence, machine learning, and algorithms can determine outcomes for certain people. She later came across the work of Joy Buolamwini through a Ted Talk.
Summary
The documentary is about artificial intelligence and the biases that can be embedded into this technology. MIT media researcher Joy Buolamwini's computer science studies uncovered that her face was unrecognizable in many facial recognition systems and she worked to find out why these systems failed. She later found that facial recognition programs only worked when she wore a white mask. She goes on to find out about how else artificial technology can affect minorities.
Coded Bias says that there is a lack of legal structures for artificial intelligence, and that as a result, human rights are being violated. It says that some algorithms and artificial intelligence technologies discriminate by race and gender statuses in domains such as housing, career opportunities, healthcare, credit, education, and legalities. Buolamwini and her colleagues were later asked to testify in front of the US Congress about artificial intelligence. Buolamwini subsequently created a digital advocacy group, the Algorithmic Justice League.
The movie highlights how facial recognition systems can cause problems for vulnerable groups as due to bias within the code they do not recognize everyone equally or as equals. As companies use more machine learning, the algorithms discussed have substantial influence over the information we discern, determining individuals who successfully navigate automated hiring processes, those granted access to healthcare, and those subjected to heightened scrutiny within police systems.
Release
The film first premiered at the 2020 Sundance Film Festival in January 2020. It had a limited release on November 11, 2020, before a full release in virtual cinemas across North America on November 18, 2020. The limited release garnered a box office revenue of $10,236. On April 5, 2021, the documentary was made available to stream on Netflix.
Reception
Critical response
On the review aggregation website Rotten Tomatoes, the film holds an approval rating of 100% based on 52 reviews with an average rating of 7.9/10. The website's critical consensus reads, "Clear, concise, and comprehensive, Coded Bias offers a chilling look at largely unseen side effects of modern society's algorithmic underpinnings." On Metacritic, the film has a weighted average score of 73 out of 100 based on seven critic reviews.
In a review written for the New York Times, Devika Girish states "The film moves deftly between pragmatic and larger political critiques, arguing that it’s not just that the tech is faulty; even if it were perfect, it would infringe dangerously on people’s liberties."
Praising the documentary for its "impressive pacing," Nick Allen, writing for RogerEbert.com states "One might expect a documentary about data and algorithms to run a bit dry, but “Coded Bias” defies that by having a lot on its mind and by being quick on its feet, hopping all over the country, and the world."
In the review from the website of the Society for Social Studies of Science, Renee Shelby questioned whether readers understood the power she said was abused through this data collection. She states "Where there is power, there is resistance to power; and the film touches on politics “from above” and “from below.” The film showcases women's activism and social movements (e.g., the Hong Kong Umbrella Movement) fighting to ensure that surveillance and other algorithmic tools are not abused.".
Giving the documentary a 2.5 out of 5 stars, Ashley Sosa, writing for videolibrarian.com, states "The documentary's cautionary message about the dangers of algorithmic bias is presented in an engaging and humanistic way. Technical details are kept to a minimum, which could be viewed as positive or negative depending on prior knowledge and interest."
Accolades
See also
Algorithmic Justice League
Black in AI
Data for Black Lives
References
External links
American documentary films
2020 documentary films
2020 films
Documentary films about computing
Documentary films about women
Documentary films about racism
Women in science and technology
Existential risk from artificial general intelligence
Ethics of science and technology
Diversity in computing
2020s English-language films
2020s American films
English-language documentary films | Coded Bias | Technology | 1,019 |
36,842,500 | https://en.wikipedia.org/wiki/Brauer%E2%80%93Wall%20group | In mathematics, the Brauer–Wall group or super Brauer group or graded Brauer group for a field F is a group BW(F) classifying finite-dimensional graded central division algebras over the field. It was first defined by as a generalization of the Brauer group.
The Brauer group of a field F is the set of the similarity classes of finite-dimensional central simple algebras over F under the operation of tensor product, where two algebras are called similar if the commutants of their simple modules are isomorphic. Every similarity class contains a unique division algebra, so the elements of the Brauer group can also be identified with isomorphism classes of finite-dimensional central division algebras. The analogous construction for Z/2Z-graded algebras defines the Brauer–Wall group BW(F).
Properties
The Brauer group B(F) injects into BW(F) by mapping a CSA A to the graded algebra which is A in grade zero.
showed that there is an exact sequence
0 → B(F) → BW(F) → Q(F) → 0
where Q(F) is the group of graded quadratic extensions of F, defined as an extension of Z/2 by F*/F*2 with multiplication (e,x)(f,y) = (e + f, (−1)efxy). The map from BW(F) to Q(F) is the Clifford invariant defined by mapping an algebra to the pair consisting of its grade and determinant.
There is a map from the additive group of the Witt–Grothendieck ring to the Brauer–Wall group obtained by sending a quadratic space to its Clifford algebra. The map factors through the Witt group, which has kernel I3, where I is the fundamental ideal of W(F).
Examples
BW(C) is isomorphic to Z/2Z. This is an algebraic aspect of Bott periodicity of period 2 for the unitary group. The 2 super division algebras are C, C[γ] where γ is an odd element of square 1 commuting with C.
BW(R) is isomorphic to Z/8Z. This is an algebraic aspect of Bott periodicity of period 8 for the orthogonal group. The 8 super division algebras are R, R[ε], C[ε], H[δ], H, H[ε], C[δ], R[δ] where δ and ε are odd elements of square −1 and 1, such that conjugation by them on complex numbers is complex conjugation.
Notes
References
Field (mathematics)
Quadratic forms
Super linear algebra | Brauer–Wall group | Physics,Mathematics | 565 |
8,987,796 | https://en.wikipedia.org/wiki/Unix2dos | (sometimes named or ) is a tool to convert line breaks in a text file from Unix format (Line feed) to DOS format (carriage return + Line feed) and vice versa. When invoked as the program will convert a Unix text file to DOS format, when invoked as it will convert a DOS text file to Unix format.
Usage
Unix2dos and dos2unix are not part of the Unix standard. Commercial Unixes usually come with their own implementation of unix2dos/dos2unix, like SunOS/Solaris's dos2unix/unix2dos, HP-UX's dos2ux/ux2dos and Irix's to_unix/to_dos.
There exist many open source alternatives with different command names and options like dos2unix/unix2dos, d2u/u2d, , endlines, flip. The multi-call binary busybox includes an implementation of unix2dos/dos2unix.
See the manual page of the respective commands.
Alternatives to unix2dos conversion
Alternatives to dos2unix conversion
For the opposite conversion () it is possible to use, for example, the utility tr with the flag to remove the carriage return characters:
$ tr -d '\r' < file > file2 # For ASCII and other files which do not contain multibyte characters (Not utf-8 safe).
$ perl -i -p -e 's/\r//g' file
$ sed -i -e 's/\r//g' file
Note: The above method assumes there are only DOS line breaks in the input file. Any Mac line breaks (\r) present in the input will be removed.
An alternative to the dos2unix conversion is possible by using the command that is available on Linux and other Unix-like operating systems, including Mac OS X. In the following case, InFile contains the undesired DOS (^M) line endings. After execution, OutFile is either created or replaced, and contains UNIX line endings. The option tells not to output backspace characters.
$ col -b < InFile > OutFile
See also
Newline
References
External links
Tofrodos - software that provides dos2unix and unix2dos
Dos2Unix - Dos2Unix / Unix2Dos - Text file format converters
System administration
Unix text processing utilities | Unix2dos | Technology | 502 |
248,132 | https://en.wikipedia.org/wiki/Arachnology | Arachnology is the scientific study of arachnids, which comprise spiders and related invertebrates such as scorpions, pseudoscorpions, and harvestmen. Those who study spiders and other arachnids are arachnologists. More narrowly, the study of spiders alone (order Araneae) is known as araneology.
The word "arachnology" derives from the Greek words , arachnē, "spider"; and , -logia, "the study of a particular subject". The greek word for "spider" itself refers to Arachne, the female protagonist of an ancient tale of the Greek Mythology.
Arachnology as a science
Arachnologists are primarily responsible for classifying arachnids and studying aspects of their biology. In the popular imagination, they are sometimes referred to as spider experts. Disciplines within arachnology include naming species and determining their evolutionary relationships to one another (taxonomy and systematics), studying how they interact with other members of their species and/or their environment (behavioural ecology), or how they are distributed in different regions and habitats (faunistics). Other arachnologists perform research on the anatomy or physiology of arachnids, including the venom of spiders and scorpions. Others study the impact of spiders in agricultural ecosystems and whether they can be used as biological control agents.
Subdisciplines
Arachnology can be broken down into several specialties, including:
acarology – the study of ticks and mites
araneology – the study of spiders
scorpiology – the study of scorpions
Arachnological societies
Arachnologists are served by a number of scientific societies, both national and international in scope. Their main roles are to encourage the exchange of ideas between researchers, to organise meetings and congresses, and in a number of cases, to publish academic journals. Some are also involved in science outreach programs, such as the European spider of the year, which raise awareness of these animals among the general public.
International
International Society of Arachnology (ISA) website
Africa
African Arachnological Society (AFRAS) website
Asia
Arachnological Society of Japan (ASJ) website
Asian Society of Arachnology (ASA) website
Indian Society of Arachnology website
Iranian Arachnological Society (IAS) website
Australasia
Australasian Arachnological Society website
Europe
Aracnofilia – Associazione Italiana di Aracnologia website
Arachnologia Belgica – Belgian Arachnological Society (ARABEL) website
Arachnologische Gesellschaft (AraGes) website
Association Francaise d'Arachnologie (AsFrA) website
British Arachnological Society (BAS) website
Czech Arachnological Society website
European Society of Arachnology (ESA) website
Grupo Ibérico de Aracnologia (Iberian Peninsula) website
Magyar Arachnolgia – Hungarian Arachnology
North America
American Arachnological Society (AAS) website
Arachnological journals
Scientific journals devoted to the study of arachnids include:
Acarologia
Acta Arachnologica – published by the Arachnological Society of Japan
Arachnida: Rivista Aracnologica Italiana
Arachnology – published by the British Arachnological Society
Arachnology Letters – published by the Arachnologische Gesellschaft
International Journal of Acarology
Journal of Arachnology – published by the American Arachnological Society
Revista Ibérica de Aracnología – published by the Grupo Ibérico de Aracnología
Revue Arachnologique
Serket
Popular arachnology
In the 1970s, arachnids – particularly tarantulas – started to become popular as exotic pets. Many tarantulas consequently became more widely known by their common names, such as Mexican redknee tarantula for Brachypelma hamorii.
Various societies now focus on the husbandry, care, study, and captive breeding of tarantulas, and other arachnids. They also typically produce journals or newsletters with articles and advice on these subjects.
British Tarantula Society (BTS) website
Deutsche Arachnologische Gesellschaft (DeArGe) website
The American Tarantula Society (ATS) website
See also
Cultural depictions of spiders
Entomology
:Category:Arachnologists
References
External information links
International Society of Arachnology
Spider Myths: Spiders are Easy to Identify
Spiders and humans
Subfields of zoology
Subfields of arthropodology | Arachnology | Biology | 946 |
40,927 | https://en.wikipedia.org/wiki/Companding | In telecommunications and signal processing, companding (occasionally called compansion) is a method of mitigating the detrimental effects of a channel with limited dynamic range. The name is a portmanteau of the words compressing and expanding, which are the functions of a compander at the transmitting and receiving ends, respectively. The use of companding allows signals with a large dynamic range to be transmitted over facilities that have a smaller dynamic range capability. Companding is employed in telephony and other audio applications such as professional wireless microphones and analog recording.
How it works
The dynamic range of a signal is compressed before transmission and is expanded to the original value at the receiver. The electronic circuit that does this is called a compander and works by compressing or expanding the dynamic range of an analog electronic signal such as sound recorded by a microphone. One variety is a triplet of amplifiers: a logarithmic amplifier, followed by a variable-gain linear amplifier, and ending with an exponential amplifier. Such a triplet has the property that its output voltage is proportional to the input voltage raised to an adjustable power.
Companded quantization is the combination of three functional building blocks – namely, a (continuous-domain) signal dynamic range compressor, a limited-range uniform quantizer, and a (continuous-domain) signal dynamic range expander that inverts the compressor function. This type of quantization is frequently used in telephony systems.
In practice, companders are designed to operate according to relatively simple dynamic range compressor functions that are suitable for implementation as simple analog electronic circuits. The two most popular compander functions used for telecommunications are the A-law and μ-law functions.
Applications
Companding is used in digital telephony systems, compressing before input to an analog-to-digital converter, and then expanding after a digital-to-analog converter. This is equivalent to using a non-linear ADC as in a T-carrier telephone system that implements A-law or μ-law companding. This method is also used in digital file formats for better signal-to-noise ratio (SNR) at lower bit depths. For example, a linearly encoded 16-bit PCM signal can be converted to an 8-bit WAV or AU file while maintaining a decent SNR by compressing before the transition to 8-bit and expanding after conversion back to 16-bit. This is effectively a form of lossy audio data compression.
Professional wireless microphones do this since the dynamic range of the microphone audio signal itself is larger than the dynamic range provided by radio transmission. Companding also reduces the noise and crosstalk levels at the receiver.
Companders are used in concert audio systems and in some noise reduction schemes.
History
The use of companding in an analog picture transmission system was patented by A. B. Clark of AT&T in 1928 (filed in 1925):
In 1942, Clark and his team completed the SIGSALY secure voice transmission system that included the first use of companding in a PCM (digital) system.
In 1953, B. Smith showed that a nonlinear DAC could be complemented by the inverse nonlinearity in a successive-approximation ADC configuration, simplifying the design of digital companding systems.
In 1970, H. Kaneko developed the uniform description of segment (piecewise linear) companding laws that had by then been adopted in digital telephony.
In the 1980s and 1990s, many of the music equipment manufacturers (Roland, Yamaha, Korg) used companding when compressing the library waveform data in their digital synthesizers. However, exact algorithms are unknown, neither if any of the manufacturers ever used the Companding scheme which is described in this article. The only known thing is that manufacturers did use data compression in the mentioned time period and that some people refer to it as companding while in reality it might mean something else, for example data compression and expansion. This dates back to the late '80s when memory chips were often one of the most costly components in the instrument. Manufacturers usually quoted the amount of memory in its compressed form: i.e. 24 MB of physical waveform ROM in a Korg Trinity is actually 48 MB when uncompressed. Similarly, Roland SR-JV expansion boards were usually advertised as 8 MB boards with '16 MB-equivalent content'. Careless copying of this technical information, omitting the equivalence reference, can often cause confusion.
References
External links
Companding: Logarithmic Laws, Implementation, and Consequences
Compander Implementation in C Language for microcontrollers (open-source)
Lossy compression algorithms
Audio engineering
Sound recording technology
Data compression | Companding | Technology,Engineering | 976 |
39,987,943 | https://en.wikipedia.org/wiki/Blanco%201 | Blanco 1 (ζ Sculptoris cluster) is a nearby open cluster of stars located around 850 light years away from the Sun in the southern constellation of Sculptor near the star ζ Sculptoris. It was discovered by Puerto Rican astronomer Víctor Manuel Blanco in 1959, who noticed an unusually high proportion of A-type stars in an area spanning 1.5°. This cluster is relatively young, with an age of about 100–150 million years. It is positioned at a high galactic latitude of b = –79.3° and is located some below the galactic plane.
Blanco 1 contains approximately 300 stars, around 170 of these being brighter than magnitude +12, the brightest of which is HD 225187, a 7th-magnitude B8V star. It has a cross-sectional magnitudal density of about 30 per square parsec: less than half that of the Pleiades cluster. Of the confirmed members, eight have been found to radiate an excess of infrared energy, indicating that they host orbiting debris disks. Roughly half the stars in the cluster are members of binary star systems; six of the member stars are confirmed spectroscopic binaries. A system known as NGTS J0002-29 is a triple system that contains one of only a few well-characterised eclipsing binaries with two red dwarfs: they orbit each other with a period of 1.098 days. There are also some 30–40 brown dwarf members.
References
Sculptor (constellation)
Open clusters | Blanco 1 | Astronomy | 304 |
35,643,341 | https://en.wikipedia.org/wiki/RO5166017 | RO5166017, or RO-5166017, is a drug developed by Hoffmann-La Roche which acts as a potent and selective agonist for the trace amine-associated receptor 1 (TAAR1), with no significant activity at other targets. It is a partial agonist or near-full agonist depending on the species.
The drug is important for the study of the TAAR1 receptor, as while numerous other compounds are known which act as TAAR1 agonists, such as methamphetamine, MDMA, and 3-iodothyronamine, all previously known TAAR1 agonists are either weak and rapidly metabolized (endogenous ligands), or have strong pharmacological activity at other targets (amphetamines, thyronamines), making it very difficult to assess which effects are due to TAAR1 activation. The discovery of RO-5166017 allows purely TAAR1 mediated effects to be studied.
Pharmacology
Pharmacodynamics
Actions
RO5166017 is a partial agonist or near-full agonist of the TAAR1 depending on the species examined. Its values are 3.3 to 8.0nM for the mouse TAAR1 (mTAAR1), 14nM for the rat TAAR1 (rTAAR1), 97nM for the cynomolgus monkey TAAR1, and 55nM for the human TAAR1. Its values are 65 to 72% for the mTAAR1, 90% for the rTAAR1, 81% for the cynomolgus monkey TAAR1, and 95% for the hTAAR1. RO5166017 is selective for the TAAR1 over a large array of other targets.
Effects
RO5166017 has been found to inhibit the firing rates of ventral tegmental area (VTA) dopaminergic neurons and dorsal raphe nucleus (DRN) serotonergic neurons in mouse brain slices ex vivo. Conversely, it had no effect on the firing rates of locus coeruleus (LC) noradrenergic neurons, an area where TAAR1 is not expressed. The effects of RO5166017 on monoaminergic neuron firing frequencies were absent in TAAR1 knockout mice and could be reversed by the TAAR1 antagonist RTI-7470-44, indicating that they were mediated by TAAR1 activation. Similar effects have been observed with the TAAR1 full agonist p-tyramine. Likewise, RO5166017 inhibited electrically evoked dopamine release in dorsal striatum (DStr) and nucleus accumbens (NAc) mouse brain slices ex vivo. Inhibition of NAc dopamine overflow by RO5166017 could be reversed by the TAAR1 antagonist EPPTB. Neither RO5166017 nor EPPTB had any effect on measures of dopamine reuptake or clearance (tau and half-life) in dopaminergic brain slices ex vivo.
Previous in-vitro studies found that TAAR1 could activate several signaling cascades including PKA, PKC, ERK1/2, and CREB. However, RO5166017 did not affect these signaling pathways, nor GSK3β, in rats in vivo, and instead selectively and TAAR1-dependently inhibited CaMKIIα activity in the NAc.
In animal studies, RO5166017 has little or no effect on locomotor activity itself. In contrast to psychostimulants like amphetamine and cocaine, it does not show stimulant-like or rewarding effects across a broad dose range. The drug dose-dependently suppresses cocaine-induced hyperlocomotion and stereotypies. Likewise, it suppresses hyperlocomotion induced by the NMDA receptor antagonist L-687,414. In dopamine transporter (DAT) knockout mice, which show spontaneous hyperactivity in novel environments, RO5166017 suppresses hyperlocomotion. These effects of RO5166017 are similar to those of antipsychotics like haloperidol and olanzapine. They are absent in TAAR1 knockout mice, indicating that they are mediated by the TAAR1. These findings indicate that RO5166017 has antipsychotic-like effects.
RO5166017 has been found to inhibit expression, though not reconsolidation or retention, of cocaine-induced conditioned place preference (CPP) in mice. Systemic administration or microinjection of RO5166017 into various brain regions has been found to inhibit other cocaine-induced relapse-like behaviors in rodents as well. As with cocaine, RO5166017 has been found to inhibit nicotine-induced dopamine release in the NAc and to reduce nicotine intake and relapse-like behaviors.
RO5166017 has been shown shown to prevent stress-induced hyperthermia in rodents. It has shown robust aversive effects in rodents, similarly to other TAAR1 agonists like RO5256390 and RO5263397. RO5166017 has shown anxiolytic-like effects in mice. It has been found to produce anti-impulsivity-like effects in mice. The drug has been found to augment 6-hydroxydopamine (6-OHDA)-induced dopaminergic neurodegeneration in mice and to counteract levodopa-induced contralateral rotations and dyskinesia. RO5166017 has shown anti-post-traumatic stress disorder (PTSD)-like effects in rodents.
Pharmacokinetics
RO5166017 has shown favorable pharmacokinetic properties for in vivo use.
History
RO5166017 was first described in the scientific literature by 2011. It was the first selective TAAR1 agonist to be discovered.
See also
RO5073012 – TAAR1 weak partial agonist
RO5203648 – TAAR1 partial agonist
RO5256390 – TAAR1 partial or full agonist
RO5263397 – TAAR1 partial agonist
EPPTB – TAAR1 antagonist/inverse agonist
o-Phenyl-3-iodotyramine
List of aminorex analogues
References
Amines
Anilines
Oxazolines
TAAR1 agonists
TAAR1 antagonists | RO5166017 | Chemistry | 1,371 |
506,682 | https://en.wikipedia.org/wiki/Fluid%20power | Fluid power is the use of fluids under pressure to generate, control, and transmit power. Fluid power is conventionally subdivided into hydraulics (using a liquid such as mineral oil or water) and pneumatics (using a gas such as compressed air or other gases). Although steam is also a fluid, steam power is usually classified separately from fluid power (implying hydraulics or pneumatics). Compressed-air and water-pressure systems were once used to transmit power from a central source to industrial users over extended geographic areas; fluid power systems today are usually within a single building or mobile machine.
Fluid power systems perform work by a pressurized fluid bearing directly on a piston in a cylinder or in a fluid motor. A fluid cylinder produces a force resulting in linear motion, whereas a fluid motor produces torque resulting in rotary motion. Within a fluid power system, cylinders and motors (also called actuators) do the desired work. Control components such as valves regulate the system.
Elements
A fluid power system has a pump driven by a prime mover (such as an electric motor or internal combustion engine) that converts mechanical energy into fluid energy, Pressurized fluid is controlled and directed by valves into an actuator device such as a hydraulic cylinder or pneumatic cylinder, to provide linear motion, or a hydraulic motor or pneumatic motor, to provide rotary motion or torque. Rotary motion may be continuous or confined to less than one revolution.
Hydraulic pumps
Dynamic (non positive displacement) pumps
This type is generally used for low-pressure, high volume flow applications. Since they are not capable of withstanding high pressures, there is little use in the fluid power field. Their maximum pressure is limited to 250-300 psi (1.7 - 2.0 MPa). This type of pump is primarily used for transporting fluids from one location to another. Centrifugal and axial flow propeller pumps are the two most common types of dynamic pumps.
Positive displacement pumps
This type is universally used for fluid power systems. With this pump, a fixed amount of fluid is ejected into the hydraulic system per revolution of pump shaft rotation. These pumps are capable of overcoming the pressure resulting from the mechanical loads on the system as well as the resistance to flow due to friction. These two features are highly desirable in fluid power pumps. These pumps also have the following advantages over non positive displacement pumps:
High-pressure capability (up to 12,000 psi, ca. 80 MPa)
Small compact size
High volumetric efficiency
Small changes in efficiency throughout the design pressure range
Characteristics
Fluid power systems can produce high power and high forces in small volumes, compared with electrically-driven systems. The forces that are exerted can be easily monitored within a system by gauges and meters. In comparison to systems that provide force through electricity or fuel, fluid power systems are known to have long service lives if maintained properly. The working fluid passing through a fluid motor inherently provides cooling of the motor, which must be separately arranged for an electric motor. Fluid motors normally produce no sparks, which are a source of ignition or explosions in hazardous areas containing flammable gases or vapors.
Fluid power systems are susceptible to pressure and flow losses within pipes and control devices. Fluid power systems are equipped with filters and other measures to preserve the cleanliness of the working fluid. Any dirt in the system can cause wear of seals and leakage, or can obstruct control valves and cause erratic operation. The hydraulic fluid itself is sensitive to temperature and pressure along with being somewhat compressible. These can cause systems to not run properly. If not run properly, cavitation and aeration can occur.
Application
Mobile applications of fluid power are widespread. Nearly every self-propelled wheeled vehicle has either hydraulically-operated or pneumatically-operated brakes. Earthmoving equipment such as bulldozers, backhoes and others use powerful hydraulic systems for digging and also for propulsion. A very compact fluid power system is the automatic transmission found in many vehicles, which includes a hydraulic torque converter.
Fluid power is also used in automated systems, where tools or work pieces are moved or held using fluid power. Variable-flow control valves and position sensors may be included in a servomechanism system for precision machine tools. Below is a more detailed list of applications and categories that fluid power is used for:
Industrial (also known as fixed)
metalworking
injection molding
controllers
material handling
Aerospace
landing gears
brakes
Pneumatic and hydraulic systems compared
Cost Pneumatics are less expensive to build and operate. Air is used as the compressed medium, so there is no requirement to drain or recover fluid. Hydraulic systems use larger working pressures, and require larger parts than pneumatics.
Precision Unlike liquids, gases change volume significantly when pressurized making it difficult to achieve precision.
Common hydraulic circuit application
Synchronizing
This circuit works off of synchronization. As a cylinder reaches a certain point another will be activated, either by a hydraulic limit switch valve or by the build-up of pressure in the cylinder. These circuits are used in manufacturing. An example of this would be on an assembly line. As a hydraulic arm is activated to grab an object. It then will reach a point of extension or retraction, where the other cylinder is activated to screw a cap or top onto the object. Hence the term synchronizing.
Regenerative
In a regenerative circuit, a double acting cylinder is used. This cylinder has a pump that has a fixed output. The use of a regenerative circuit permits use of a smaller size pump for any given application. This works by re-routing the fluid to the cap instead of back to the tank. For example, in a drilling process a regenerative circuit will allow drilling at a consistent speed, and retraction at a much faster speed. This gives the operator faster and more precise production.
Electrical control
Combinations of electrical control of fluid power elements are widespread in automated systems. A wide variety of measuring, sensing, or control elements are available in electrical form. These can be used to operate solenoid valves or servo valves that control the fluid power element. Electrical control may be used to allow, for example, remote control of a fluid power system without running long control lines to a remotely located manual control valve.
See also
Hydraulic circuit
Hydraulic power network
London Hydraulic Power Company
Pneumatic circuit
Pneumatic actuator
References
Esposito, Anthpny, Fluid Power With Applications,
Esposito, Anthony, Fluid Power with Applications,
Hydraulic Power System Analysis, A. Akers, M. Gassman, & R. Smith, Taylor & Francis, New York, 2006,
Mechanical engineering | Fluid power | Physics,Engineering | 1,361 |
1,460,619 | https://en.wikipedia.org/wiki/United%20Nations%20Office%20on%20Drugs%20and%20Crime | The United Nations Office on Drugs and Crime (UNODC; French: Office des Nations unies contre la drogue et le crime) is a United Nations office that was established in 1997 as the Office for Drug Control and Crime Prevention by combining the United Nations International Drug Control Program (UNDCP) and the Crime Prevention and Criminal Justice Division in the United Nations Office at Vienna, adopting the current name in 2002.
The agency's focus is the trafficking and abuse of illicit drugs, crime prevention and criminal justice, international terrorism, and political corruption. It is a member of the United Nations Development Group. In 2022–23, it had an estimated biannual budget of US$822 million.
History
The United Nations International Drug Control Program (UNDCP) and the Crime Prevention and Criminal Justice Division in the United Nations Office at Vienna were merged to form the Office for Drug Control and Crime Prevention. This was renamed United Nations Office on Drugs and Crime (UNODC) in 2002.
Organizational structure
The is a network consisting of UNODC as well as many crime-related institutes and other centres around the world. Its aim is to strengthen international co-operation in the areas of crime prevention and criminal justice. The network facilitates the "exchange of information, research, training and public education".
UNODC, which as of 2020 employs around 3400 people worldwide, has its headquarters in Vienna, Austria, with 115 field offices and two liaison offices in Brussels and in New York City. The United Nations Secretary-General appoints the agency's Executive Director. Yuri Fedotov, the former Russian Ambassador to the United Kingdom, held this position from 2010 until 2019, when the United Nations Secretary-General announced that Ms. Ghada Fathi Waly of Egypt would replace him as both executive director of UNODC and Director General of the United Nations Office at Vienna.
UNODC incorporates the secretariat of the International Narcotics Control Board (INCB).
UNODC's Terrorism Prevention Branch was headed by International terrorism studies expert Alex P. Schmid from 1999 to 2005.
The agency is a member of the United Nations Sustainable Development Group.
Budget
In 2022–2023 it had an estimated biannual budget of US$822 million.
Aims and functions
UNODC was established to assist the UN in better addressing a coordinated, comprehensive response to the interrelated issues of illicit trafficking in and abuse of drugs, crime prevention and criminal justice, international terrorism, and political corruption. These goals are pursued through three primary functions: research, guidance and support to governments in the adoption and implementation of various crime-, drug-, terrorism-, and corruption-related conventions, treaties and protocols, as well as technical/financial assistance to said governments to face their respective situations and challenges in these fields.
The office aims long-term to better equip governments to handle drug-, crime-, terrorism-, and corruption-related issues, to maximise knowledge on these issues among governmental institutions and agencies, and also to maximise awareness of said matters in public opinion, globally, nationally and at community level. Approximately 90% of the Office's funding comes from voluntary contributions, mainly from governments.
These are the main themes that UNODC deals with: alternative development, anti-corruption, criminal justice, prison reform and crime prevention, drug prevention, treatment and care, HIV and AIDS, human trafficking and migrant smuggling, money laundering, organized crime, piracy, terrorism prevention.
The World Drug Report
The World Drug Report is a yearly publication that presents a comprehensive assessment of the international drug problem, with detailed information on the illicit drug situation. It provides estimates and information on trends in the production, trafficking and use of opium/heroin, coca/cocaine, cannabis and amphetamine-type stimulants. The Report, based on data and estimates collected or prepared by Governments, UNODC and other international institutions, attempts to identify trends in the evolution of global illicit drug markets.
Through the World Drug Report, UNODC aims to enhance member states' understanding of global illicit drug trends and increase their awareness of the need for the more systematic collection and reporting of data relating to illicit drugs.
Treaties
United Nations Conventions and their related Protocols underpin all the operational work of UNODC.
Crime-related treaties
United Nations Convention against Transnational Organized Crime
The convention is a legally binding instrument that entered into force on 29 September 2003, through which States parties commit to taking a series of measures against transnational organized crime. States that ratify the convention has the duty of creation of domestic offences to combat the problem, the adoption of new, sweeping frameworks for mutual legal assistance, extradition, law enforcement cooperation, technical assistance and training. The convention signifies an important stage in dealing with transnational crime by recognizing the seriousness of the problem that the crime poses, and gaining understanding from the member states of the importance of a cooperative measure. The convention is complemented by three different protocols:
the Protocol to Prevent, Suppress and Punish Trafficking in Persons, especially Women and Children;
the Protocol against the Smuggling of Migrants by Land, Sea and Air; and
the Protocol against the Illicit Manufacturing of and Trafficking in Firearms, their Parts and Components and Ammunition.
The Protocol to Prevent, Suppress and Punish Trafficking in Persons, especially Women and Children aims to provide a convergence in the states' domestic offences in the investigation and the persecution process. Another objective of the protocol is to protect the victims of trafficking in persons with full respect.
The Protocol against the Smuggling of Migrants by Land, Sea and Air is concerned with the aggravating problem of organized crime groups for smuggling persons. The protocol aims to combat and prevent transnational smuggling as well as to promote cooperative measures for enhancing protective measures for victims.
The Protocol against the Illicit Manufacturing of and Trafficking in Firearms, their Parts and Components and Ammunition was adopted to prevent and provide a cooperative measure for illicit manufacturing of and trafficking in firearms, their parts and components and ammunition. By adopting the protocol, the member states commit to adopt domestic criminal offences for illegal manufacturing, providing governmental licensing ammunition, and keeping track of the ammunition.
United Nations Convention against Corruption
In its resolution 55/61, the General Assembly recognized that an effective international legal instrument against corruption, independent of the United Nations Convention against Transnational Organized Crime was desirable. The text of the convention was negotiated during seven sessions held between 21 January 2002 and 1 October 2003. The convention was adopted by the General Assembly on 31 October 2003.
In 2003, the United Nations adopted the UN Convention against Corruption (UNCAC). The Convention came into force in December 2005. 140 countries had signed and 164 countries (States Parties) had ratified the UNCAC. UNODC serves as the Secretariat for the Conference of the States Parties (CoSP) to the UNCAC.
UNCAC is a legally binding instrument (perhaps the only anti-corruption legally binding global instrument). A highlight of UNCAC is the inclusion of a specific chapter on asset recovery which aimed at returning assets to their rightful owners including countries from which they had been taken illicitly.
UNODC, as the custodian of UNCAC, is also one of the main initiators of the establishment of the International Anti-Corruption Academy (IACA), whose main function is to, among other things, facilitate more effective implementation of the UNCAC.
Drug-related treaties
There are three drug related treaties that guide UNODC's drug related programs. These are: The Single Convention on Narcotic Drugs of 1961 as amended by the 1972 Protocol; the Convention on Psychotropic Substances of 1971 and the United Nations Convention Against Illicit Traffic in Narcotic Drugs and Psychotropic Substances of 1988.
These three major international drug control treaties are mutually supportive and complementary. An important purpose of the first two treaties is to codify internationally applicable control measures in order to ensure the availability of narcotic drugs and psychotropic substances for medical and scientific purposes, and to prevent their diversion into illicit channels. They also include general provisions on trafficking and drug abuse.
Campaigns
UNODC launches campaigns to raise awareness of drugs and crime problems. On 26 June every year, UNODC marks the International Day against Drug Abuse and Illicit Trafficking.
On 9 December every year, UNODC commemorates the International Anti-Corruption Day.
"Do Drugs Control Your Life?" – World Drug Campaign
The United Nations Office on Drugs and Crime (UNODC) started this international campaign to raise awareness about the major challenge that illicit drugs represent to society as a whole, and especially to the young. The goal of the campaign is to mobilize support and to inspire people to act against drug abuse and trafficking. The campaign encourages young people to put their health first and not to take drugs.
"Your No Counts" – International Anti-Corruption Campaign
The United Nations Office on Drugs and Crime (UNODC) has teamed up with the United Nations Development Program (UNDP) to run this campaign as a focus on how corruption hinders efforts to achieve the internationally agreed upon MDGs, undermines democracy and the rule of law, leads to human rights violations, distorts markets, erodes quality of life and allows organized crime, terrorism and other threats to human security to flourish.
"Think AIDS" – World AIDS Campaign
Young people aged 15 to 24 account for an estimated 40 per cent of new adult (15+) HIV infections worldwide. In some parts of the world, and in some marginalized sub-groups, the most frequent modes of HIV transmission for these young people are unsafe injecting drug use and unsafe sexual activities.
Because young people are also often more likely to use drugs, The United Nations Office on Drugs and Crime (UNODC) targets this population with a campaign to raise awareness about drug use and its connection to the spread of HIV and AIDS. The slogan: "Think Before You Start ... Before You Shoot ... Before You Share" is used to provoke young people to consider the implications of using drugs, and particularly injecting drugs.
Blue Heart Campaign Against Human Trafficking
The Blue Heart Campaign seeks to encourage involvement and action to help stop trafficking in persons. The campaign also allows people to show solidarity with the victims of human trafficking by wearing the Blue Heart. The use of the blue UN colour demonstrates the commitment of the United Nations to combat this crime.
Criticism
In 2007, the five largest donors to UNODC's budget in descending order were: European Union, Canada, United States, the UN itself, and Finland. According to the Transnational Institute this explains why, until recently, UNODC did not promote harm reduction policies like needle exchange and heroin-assisted treatment. (This despite the actions of United Nations bodies (i.e. WHO and UNAIDS), who support these policies.) UNODC promotes other methods for drug use prevention, treatment and care that UNODC sees as "based on scientific evidence and on ethical standards".
The UNODC has been criticized by human rights organizations such as Amnesty International for not promoting the inclusion of adherence to international human rights standards within its project in Iran, where there are "serious concerns regarding unfair trials and executions of those suspected of drug offences."
Association with the General Prosecutor of Qatar
UNODC has signed a partnership with the controversial Rule of Law and Anti-Corruption Center, which was founded by Ali Bin Fetais Al-Marri, the General-Prosecutor of Qatar.
Ali Bin Fetais Al-Marri has been accused of ill-gotten gains, corruption and support for Al-Qaeda terrorists by several media. He has also defended the life imprisonment of a Qatari poet and human rights campaigner.
See also
Blue Heart Campaign Against Human Trafficking
CARICC, Central Asian Regional Information and Coordination Centre
Convention against Transnational Organized Crime, 2000
Convention on Psychotropic Substances, 1971
Drug policy
European Monitoring Centre for Drugs and Drug Addiction EMCDDA
International Anti-Corruption Academy
International Narcotics Control Board (INCB)
ISO 37001 Anti-bribery management systems
Protocol against the Illicit Manufacturing and Trafficking in Firearms
Protocol against the Smuggling of Migrants by Land, Sea and Air, 2004
Protocol to Prevent, Suppress and Punish Trafficking in Persons, especially Women and Children, 2003
Single Convention on Narcotic Drugs, 1961
United Nations Congress on Crime Prevention and Criminal Justice
United Nations Convention against Corruption
United Nations Convention Against Illicit Traffic in Narcotic Drugs and Psychotropic Substances, 1988
West Africa Coast Initiative
Network Against Child Trafficking, Abuse and Labour
References
External links
Drug control law
Corruption
Organizations established by the United Nations
Drug policy organizations
Drug policy
Organizations established in 1997
Human trafficking
Counterterrorism
United Nations Development Group
Criminal justice reform
United Nations organizations based in Vienna
Drug control treaties | United Nations Office on Drugs and Crime | Chemistry | 2,553 |
37,251,345 | https://en.wikipedia.org/wiki/Supercomputing%20in%20Pakistan | The high performance supercomputing program started in mid-to-late 1980s in Pakistan. Supercomputing is a recent area of Computer science in which Pakistan has made progress, driven in part by the growth of the information technology age in the country. Developing on the ingenious supercomputer program started in 1980s when the deployment of the Cray supercomputers was initially denied.
The fastest supercomputer currently in use in Pakistan is developed and hosted by the National University of Sciences and Technology at its modeling and simulation research centre. As of November 2012, there are no supercomputers from Pakistan on the Top500 list.
Background
The initial interests of Pakistan in the research and development of supercomputing began during the early 1980s, at several high-powered institutions of the country. During this time, senior scientists at the Pakistan Atomic Energy Commission (PAEC) were the first to engage in research on high performance computing, while calculating and determining exact values involving fast-neutron calculations.
According to one scientist involved in the development of the supercomputer, a team of the leading scientists at PAEC developed powerful computerized electronic codes, acquired powerful high performance computers to design this system and came up with the first design that was to be manufactured, as part of the atomic bomb project. However, the most productive and pioneering research was carried out by physicist M.S. Zubairy at the Institute of Physics of Quaid-e-Azam University. Zubairy published two important books on Quantum Computers and high-performance computing throughout his career that are presently taught worldwide. In 1980s and 1990s, the scientific research and mathematical work on the supercomputers was also carried out by mathematician Dr. Tasneem Shah at the Kahuta Research Laboratories while trying to solve additive problems in Computational mathematics and the Statistical physics using the Monte Carlo method. In 1990s, the Khan Research Laboratories deployed a series of supercomputer systems at its site, becoming nation's one of the first fastest computers at that time. Technological imports in supercomputers were denied to Pakistan, as well as India, due to an arms embargo, as the foreign powers feared that the imports and enhancement to the supercomputing development was a dual use of technology and could be used for developing nuclear weapons in 1990s.
During the Bush administration, in an effort to help US-based companies gain competitive ground in developing information technology-based markets, the U.S. government eased regulations that applied to exporting high-performance computers to Pakistan and four other technologically developing countries. The new regulations allowed these countries to import supercomputer systems that were capable of processing information at a speed of 190,000 million theoretical operations per second (MTOPS); the previous limit had been 85,000 MTOPS.
List of organizations with Supercomputers in Pakistan
Supercomputing programs
University of Malakand
Developed Supercomputer in CCMS Department of Physics, University of Malakand. It is heavily used by Graduate Students, PhD Scholars and Faculty Members of UOM as well as Researchers from other organizations. It is operational since 2016.
It has 2-servers used as Head Nodes and 24-machines used as Compute Nodes.
It has been mostly used for Simulation and Modeling by the Researchers of Materials Science and Chemistry Departments.
GIK Institute
The Ghulam Ishaq Khan Institute of Engineering Sciences and Technology (GIKI) has nation's notable supercomputer programmes.
This facility has been funded by Directorate of Science and Technology (DoST), Government of Khyber Pakhtunkhwa, Pakistan in 2012 under supervision of Dr. Masroor Hussain. This system provides a test bed for shared memory systems, distributed memory systems and Array Processing using OpenMP, MPI-2 and CUDA specifications, respectively. It is a compute-intensive platform and consisted of the following hardware components:
Front Node: Dell R815 with 64 CPU cores, 256 GB RAM, 1.8 TB Secondary Memory
3 Compute Nodes: Dell R715 each with 32 CPU cores per compute node (96 in total), 128 GB RAM per compute node (384 GB in total), 600 GB Secondary Memory/ compute node (1.8 TB in total)
NVIDIA Tesla M2090 Graphical Processing Unit (GPU) with 1024 GPU cores: This facility may be used for an emerging paradigm of parallel computing which uses GPUs as computing units, which connected to Front Node
Dell Power Connect 8024F layer-3 manageable switch: Front Node and the Compute Nodes are connected to each other using this switch. It provides an enormous data transfer rate of 10 Gbit/s among the connected entities using fibre channels
Software: To make the hardware layer parallel-computation-capable, Rocks Cluster 6.1 (Emerald Boa) over CentOS has been installed and configured along with CUDA roll
COMSATS
The COMSATS Institute of Information Technology (CIIT) has been actively involved in research in the areas of parallel computing and computer cluster systems. In 2004, CIIT built a cluster-based supercomputer for research purposes. The project was funded by the Higher Education Commission of Pakistan. The Linux-based computing cluster, which was tested and configured for optimization, achieved a performance of 158 GFLOPS. The packaging of the cluster was locally designed.
NUST
The National University of Sciences and Technology (NUST) in Islamabad has developed the fastest supercomputing facility in Pakistan till date. The supercomputer, which operates at the university's Research Centre for Modeling and Simulation (RCMS), was inaugurated in September 2012. The supercomputer has parallel computation abilities and has a performance of 132 teraflops per second (i.e. 132 trillion floating-point operations per second), making it the fastest graphics processing unit (GPU) parallel computing system currently in operation in Pakistan.
It has multi-core processors and graphics co-processors, with an inter-process communication speed of 40 gigabits per second. According to specifications available of the system, the cluster consists of a "66 NODE supercomputer with 30,992 processor cores, 2 head nodes (16 processor cores), 32 dual quad core computer nodes (256 processor cores) and 32 Nvidia computing processors. Each processor has 960 processor cores (30,720 processor cores), QDR InfiniBand interconnection and 21.6 TB SAN storage."
KRL
In 1990s, the Kahuta Research Laboratories (KRL) became nation's first site and a home of a number of the most high-performance supercomputer and parallel computing systems that were installed at the facility by a team of mathematicians. A parallel Computational Fluid Dynamics (CFD) division was established which specialized in conducting high performance computations on shock waves in the blast effects from the outer surface to the inner core by using the difficult differential equations of the state of the materials under high pressure.
KUST
The Kohat University of Science and Technology installed a supercomputer facility with the specifications of Cluster.
Riphah International University
On 22 January 2016, Riphah International University based in Islamabad announced that their team of engineers have developed a supercomputer architecture. The system supports CUDA, MPI/LAM, OpenMP, OpenCL and OpenACC programming models. It also can solve larger algorithms, numerical techniques, big data, data mining, bioinformatics and genomics, business intelligence and analytics, climate, and weather and ocean related problems.
UCERD Private Limited
UCERD Private Limited proposed and developed Pakistan's 1st FPGA-Powered Supercomputer.
In 2019, the UCERD team has won HEC Technology Development Fund of Rs. 16 Million for the Project "Development of Scalable Heterogeneous Supercomputing System"
See also
Supercomputing in China
Supercomputing in Europe
Supercomputing in India
Supercomputing in Japan
References
External links
Supercomputing Research and Education Facility, NUST
Supercomputing
Supercomputer sites
Information technology in Pakistan | Supercomputing in Pakistan | Technology | 1,663 |
52,128,652 | https://en.wikipedia.org/wiki/NGC%20325 | NGC 325 is a spiral galaxy located in the constellation Cetus. It was discovered on September 27, 1864, by Albert Marth. It was described by Dreyer as "very faint, very small".
References
External links
0325
18640927
Cetus
Spiral galaxies
Discoveries by Albert Marth
003454 | NGC 325 | Astronomy | 65 |
42,443,120 | https://en.wikipedia.org/wiki/Heartbleed | Heartbleed is a security bug in some outdated versions of the OpenSSL cryptography library, which is a widely used implementation of the Transport Layer Security (TLS) protocol. It was introduced into the software in 2012 and publicly disclosed in April 2014. Heartbleed could be exploited regardless of whether the vulnerable OpenSSL instance is running as a TLS server or client. It resulted from improper input validation (due to a missing bounds check) in the implementation of the TLS heartbeat extension. Thus, the bug's name derived from heartbeat. The vulnerability was classified as a buffer over-read, a situation where more data can be read than should be allowed.
Heartbleed was registered in the Common Vulnerabilities and Exposures database as . The federal Canadian Cyber Incident Response Centre issued a security bulletin advising system administrators about the bug. A fixed version of OpenSSL was released on 7 April 2014, on the same day Heartbleed was publicly disclosed.
TLS implementations other than OpenSSL, such as GnuTLS, Mozilla's Network Security Services, and the Windows platform implementation of TLS, were not affected because the defect existed in the OpenSSL's implementation of TLS rather than in the protocol itself.
System administrators were frequently slow to patch their systems. , 1.5% of the 800,000 most popular TLS-enabled websites were still vulnerable to the bug, and by , 309,197 public web servers remained vulnerable. According to a report from Shodan, nearly 180,000 internet-connected devices were still vulnerable to the bug, but by , the number had dropped to 144,000 according to a search performed on shodan.io for the vulnerability. Around two years later, , Shodan reported that 91,063 devices were vulnerable. The U.S. had the most vulnerable devices, with 21,258 (23%), and the 10 countries with the most vulnerable devices had a total of 56,537 vulnerable devices (62%). The remaining countries totaled 34,526 devices (38%). The report also broke the devices down by 10 other categories such as organization (the top 3 were wireless companies), product (Apache httpd, Nginx), and service (HTTPS, 81%).
History
The Heartbeat Extension for the Transport Layer Security (TLS) and Datagram Transport Layer Security (DTLS) protocols was proposed as a standard in February 2012 by . It provides a way to test and keep alive secure communication links without the need to renegotiate the connection each time. In 2011, one of the RFC's authors, Robin Seggelmann, then a Ph.D. student at the Fachhochschule Münster, implemented the Heartbeat Extension for OpenSSL. Following Seggelmann's request to put the result of his work into OpenSSL, his change was reviewed by Stephen N. Henson, one of OpenSSL's four core developers. Henson failed to notice a bug in Seggelmann's implementation, and introduced the flawed code into OpenSSL's source code repository on 31 December 2011. The defect spread with the release of OpenSSL version 1.0.1 on 14 March 2012. Heartbeat support was enabled by default, causing affected versions to be vulnerable.
Discovery
According to Mark J. Cox of OpenSSL, Neel Mehta of Google's security team privately reported Heartbleed to the OpenSSL team on 1 April 2014 11:09 UTC.
The bug was named by an engineer at Synopsys Software Integrity Group, a Finnish cyber security company that also created the bleeding heart logo, designed by a Finnish graphic designer Leena Kurjenniska, and launched an informational website, heartbleed.com. While Google's security team reported Heartbleed to OpenSSL first, both Google and Codenomicon discovered it independently at approximately the same time. Codenomicon reports 3 April 2014 as their date of discovery and their date of notification of for vulnerability coordination.
At the time of disclosure, some 17% (around half a million) of the Internet's secure web servers certified by trusted authorities were believed to be vulnerable to the attack, allowing theft of the servers' private keys and users' session cookies and passwords. The Electronic Frontier Foundation, Ars Technica, and Bruce Schneier all deemed the Heartbleed bug "catastrophic". Forbes cybersecurity columnist Joseph Steinberg wrote:
An unidentified UK Cabinet Office spokesman recommended that: On the day of disclosure, The Tor Project advised:
The Sydney Morning Herald published a timeline of the discovery on 15 April 2014, showing that some organizations had been able to patch the bug before its public disclosure. In some cases, it is not clear how they found out.
Bugfix and deployment
Bodo Möller and Adam Langley of Google prepared the fix for Heartbleed. The resulting patch was added to Red Hat's issue tracker on 21 March 2014. Stephen N. Henson applied the fix to OpenSSL's version control system on 7 April. The first fixed version, 1.0.1g, was released on the same day. , 309,197 public web servers remained vulnerable. , according to a report from Shodan, nearly 180,000 internet-connected devices were still vulnerable. The number had dropped to 144,000 , according to a search on shodan.io for "vuln:cve-2014-0160".
Certificate renewal and revocation
According to Netcraft, about 30,000 of the 500,000+ X.509 certificates which could have been compromised due to Heartbleed had been reissued by 11 April 2014, although fewer had been revoked.
By 9 May 2014, only 43% of affected web sites had reissued their security certificates. In addition, 7% of the reissued security certificates used the potentially compromised keys. Netcraft stated:
eWeek said, "[Heartbleed is] likely to remain a risk for months, if not years, to come."
Cloudflare revoked all TLS certificates and estimated that publishing its Certificate revocation list would cost the issuer, GlobalSign, $400,000 per month that year.
Exploitation
The Canada Revenue Agency reported a theft of social insurance numbers belonging to 900 taxpayers, and said that they were accessed through an exploit of the bug during a 6-hour period on 8 April 2014. After the discovery of the attack, the agency shut down its website and extended the taxpayer filing deadline from 30 April to 5 May. The agency said it would provide credit protection services at no cost to anyone affected. On 16 April, the RCMP announced they had charged a computer science student in relation to the theft with unauthorized use of a computer and mischief in relation to data.
The UK parenting site Mumsnet had several user accounts hijacked, and its CEO was impersonated. The site later published an explanation of the incident saying it was due to Heartbleed and the technical staff patched it promptly.
Anti-malware researchers also exploited Heartbleed to their own advantage in order to access secret forums used by cybercriminals. Studies were also conducted by deliberately setting up vulnerable machines. For example, on 12 April 2014, at least two independent researchers were able to steal private keys from an experimental server intentionally set up for that purpose by CloudFlare. Also, on 15 April 2014, J. Alex Halderman, a professor at University of Michigan, reported that his honeypot server, an intentionally vulnerable server designed to attract attacks in order to study them, had received numerous attacks originating from China. Halderman concluded that because it was a fairly obscure server, these attacks were probably sweeping attacks affecting large areas of the Internet.
In August 2014, it was made public that the Heartbleed vulnerability enabled hackers to steal security keys from Community Health Systems, the second-biggest for-profit U.S. hospital chain in the United States, compromising the confidentiality of 4.5 million patient records. The breach happened a week after Heartbleed was first made public.
Possible prior knowledge and exploitation
Many major web sites patched the bug or disabled the Heartbeat Extension within days of its announcement, but it is unclear whether potential attackers were aware of it earlier and to what extent it was exploited.
Based on examinations of audit logs by researchers, it has been reported that some attackers may have exploited the flaw for at least five months before discovery and announcement. Errata Security pointed out that a widely used non-malicious program called Masscan, introduced six months before Heartbleed's disclosure, abruptly terminates the connection in the middle of handshaking in the same way as Heartbleed, generating the same server log messages, adding "Two new things producing the same error messages might seem like the two are correlated, but of course, they aren't."
According to Bloomberg News, two unnamed insider sources informed it that the United States' National Security Agency had been aware of the flaw since shortly after its appearance butinstead of reporting itkept it secret among other unreported zero-day vulnerabilities in order to exploit it for the NSA's own purposes. The NSA has denied this claim, as has Richard A. Clarke, a member of the National Intelligence Review Group on Intelligence and Communications Technologies that reviewed the United States' electronic surveillance policy; he told Reuters on 11 April 2014 that the NSA had not known of Heartbleed. The allegation prompted the American government to make, for the first time, a public statement on its zero-day vulnerabilities policy, accepting the recommendation of the review group's 2013 report that had asserted "in almost all instances, for widely used code, it is in the national interest to eliminate software vulnerabilities rather than to use them for US intelligence collection", and saying that the decision to withhold should move from the NSA to the White House.
Behavior
The RFC 6520 Heartbeat Extension tests TLS/DTLS secure communication links by allowing a computer at one end of a connection to send a Heartbeat Request message, consisting of a payload, typically a text string, along with the payload's length as a 16-bit integer. The receiving computer then must send exactly the same payload back to the sender.
The affected versions of OpenSSL allocate a memory buffer for the message to be returned based on the length field in the requesting message, without regard to the actual size of that message's payload. Because of this failure to do proper bounds checking, the message returned consists of the payload, possibly followed by whatever else happened to be in the allocated memory buffer.
Heartbleed is therefore exploited by sending a malformed heartbeat request with a small payload and large length field to the vulnerable party (usually a server) in order to elicit the victim's response, permitting attackers to read up to 64 kilobytes of the victim's memory that was likely to have been used previously by OpenSSL. Where a Heartbeat Request might ask a party to "send back the four-letter word 'bird'", resulting in a response of "bird", a "Heartbleed Request" (a malicious heartbeat request) of "send back the 500-letter word 'bird'" would cause the victim to return "bird" followed by whatever 496 subsequent characters the victim happened to have in active memory. Attackers in this way could receive sensitive data, compromising the confidentiality of the victim's communications. Although an attacker has some control over the disclosed memory block's size, it has no control over its location, and therefore cannot choose what content is revealed.
Affected OpenSSL installations
The affected versions of OpenSSL are OpenSSL 1.0.1 through 1.0.1f (inclusive). Subsequent versions (1.0.1g and later) and previous versions (1.0.0 branch and older) are not vulnerable. Installations of the affected versions are vulnerable unless OpenSSL was compiled with -DOPENSSL_NO_HEARTBEATS.
Vulnerable program and function
The vulnerable program source files are t1_lib.c and d1_both.c and the vulnerable functions are tls1_process_heartbeat() and dtls1_process_heartbeat().
Patch
The problem can be fixed by ignoring Heartbeat Request messages that ask for more data than their payload need, as required by the RFC.
Version 1.0.1g of OpenSSL adds some bounds checks to prevent the buffer over-read. The test listed below was one introduced to determine whether a heartbeat request would trigger Heartbleed; it silently discards malicious requests.
if (1 + 2 + payload + 16 > s->s3->rrec.length) return 0; /* silently discard per RFC 6520 sec. 4 */
The OpenSSL version control system contains a complete list of changes.
Impact
The data obtained by a Heartbleed attack may include unencrypted exchanges between TLS parties likely to be confidential, including any form post data in users' requests. Moreover, the confidential data exposed could include authentication secrets such as session cookies and passwords, which might allow attackers to impersonate a user of the service.
An attack may also reveal private keys of compromised parties, which would enable attackers to decrypt communications (future or past stored traffic captured via passive eavesdropping, unless perfect forward secrecy is used, in which case only future traffic can be decrypted if intercepted via man-in-the-middle attacks).
An attacker having gained authentication material may impersonate the material's owner after the victim has patched Heartbleed, as long as the material is accepted (for example, until the password is changed or the private key revoked). Heartbleed therefore constitutes a critical threat to confidentiality. However, an attacker impersonating a victim may also alter data. Indirectly, Heartbleed's consequences may thus go far beyond a confidentiality breach for many systems.
A survey of American adults conducted in April 2014 showed that 60 percent had heard about Heartbleed. Among those using the Internet, 39 percent had protected their online accounts, for example by changing passwords or canceling accounts; 29 percent believed their personal information was put at risk because of the Heartbleed bug; and 6 percent believed their personal information had been stolen.
Client-side vulnerability
Although the bug received more attention due to the threat it represents for servers, TLS clients using affected OpenSSL instances are also vulnerable. In what The Guardian therefore dubbed Reverse Heartbleed, malicious servers are able to exploit Heartbleed to read data from a vulnerable client's memory. Security researcher Steve Gibson said of Heartbleed that:
The stolen data could contain usernames and passwords. Reverse Heartbleed affected millions of application instances. Some of the vulnerable applications are listed in the "Software applications" section below.
Specific systems affected
Cisco Systems has identified 78 of its products as vulnerable, including IP phone systems and telepresence (video conferencing) systems.
Websites and other online services
An analysis posted on GitHub of the most visited websites on 8 April 2014 revealed vulnerabilities in sites including Yahoo!, Imgur, Stack Overflow, Slate, and DuckDuckGo. The following sites have services affected or made announcements recommending that users update passwords in response to the bug:
Akamai Technologies
Amazon Web Services
Ars Technica
Bitbucket
BrandVerity
Freenode
GitHub
IFTTT
Internet Archive
Mojang
Mumsnet
PeerJ
Pinterest
Prezi
Reddit
Something Awful
SoundCloud
SourceForge
SparkFun
Stripe
Tumblr
All Wikimedia Foundation wikis (including Wikipedia in all languages)
Wunderlist
The Canadian federal government temporarily shut online services of the Canada Revenue Agency (CRA) and several government departments over Heartbleed bug security concerns. Before the CRA online services were shut down, a hacker obtained approximately 900 social insurance numbers. Another Canadian Government agency, Statistics Canada, had its servers compromised due to the bug and also temporarily took its services offline.
Platform maintainers like the Wikimedia Foundation advised their users to change passwords.
The servers of LastPass were vulnerable, but due to additional encryption and forward secrecy, potential attacks were not able to exploit this bug. However, LastPass recommended that its users change passwords for vulnerable websites.
The Tor Project recommended that Tor relay operators and hidden service operators revoke and generate fresh keys after patching OpenSSL, but noted that Tor relays use two sets of keys and that Tor's multi-hop design minimizes the impact of exploiting a single relay. 586 relays later found to be susceptible to the Heartbleed bug were taken off-line as a precautionary measure.
Game-related services including Steam, Minecraft, Wargaming, League of Legends, GOG.com, Origin, Sony Online Entertainment, Humble Bundle, and Path of Exile were affected and subsequently fixed.
Software applications
Vulnerable software applications include:
Several Hewlett-Packard server applications, such as HP System Management Homepage (SMH) for Linux and Windows.
Some versions of FileMaker 13
LibreOffice 4.2.0 to 4.2.2 (fixed in 4.2.3)
LogMeIn claimed to have "updated many products and parts of our services that rely on OpenSSL".
Multiple McAfee products, in particular some versions of software providing anti-viral coverage for Microsoft Exchange, software firewalls, and McAfee Email and Web Gateways
Oracle MySQL Connector/C 6.1.0-6.1.3 and Connector/ODBC 5.1.13, 5.2.5-5.2.6, 5.3.2
Oracle Big Data Appliance (includes Oracle Linux 6)
Primavera P6 Professional Project Management (includes Primavera P6 Enterprise Project Portfolio Management)
WinSCP (FTP client for Windows) 5.5.2 and some earlier versions (only vulnerable with FTP over TLS/SSL, fixed in 5.5.3)
Multiple VMware products, including VMware ESXi 5.5, VMware Player 6.0, VMware Workstation 10 and the series of Horizon products, emulators and cloud computing suites
Several other Oracle Corporation applications were affected.
Operating systems/firmware
Several Linux distributions were affected, including Debian (and derivatives such as Linux Mint and Ubuntu) and Red Hat Enterprise Linux (and derivatives such as CentOS, Oracle Linux 6 and Amazon Linux), as well as the following operating systems and firmware implementations:
Android 4.1.1, used in various portable devices. Chris Smith writes in Boy Genius Report that just this one version of Android is affected but that it is a popular version of Android (Chitika claim 4.1.1 is on 50 million devices; Google describe it as less than 10% of activated Android devices). Other Android versions are not vulnerable as they either have heartbeats disabled or use an unaffected version of OpenSSL.
Firmware for some AirPort base stations
Firmware for some Cisco Systems routers
Firmware for some Juniper Networks routers
pfSense 2.1.0 and 2.1.1 (fixed in 2.1.2)
DD-WRT versions between and including 19163 and 23881 (fixed in 23882)
Western Digital My Cloud product family firmware
Vulnerability testing services
Several services have been made available to test whether Heartbleed affects a given site. However, many services have been claimed to be ineffective for detecting the bug. The available tools include:
Tripwire SecureScan
AppCheck – static binary scan and fuzzing, from Synopsys Software Integrity Group (formerly Codenomicon)
Arbor Network's Pravail Security Analytics
Norton Safeweb Heartbleed Check Tool
Heartbleed testing tool by a European IT security company
Heartbleed test by Italian cryptographer Filippo Valsorda
Heartbleed Vulnerability Test by Cyberoam
Critical Watch Free Online Heartbleed Tester
Metasploit Heartbleed scanner module
Heartbleed Server Scanner by Rehmann
Lookout Mobile Security Heartbleed Detector, an app for Android devices that determines the OpenSSL version of the device and indicates whether the vulnerable heartbeat is enabled
Heartbleed checker hosted by LastPass
Online network range scanner for Heartbleed vulnerability by Pentest-Tools.com
Official Red Hat offline scanner written in the Python language
Qualys SSL Labs' SSL Server Test which not only looks for the Heartbleed bug, but can also find other SSL/TLS implementation errors.
Browser extensions, such as Chromebleed and FoxBleed
SSL Diagnos
CrowdStrike Heartbleed Scanner – Scans routers, printers and other devices connected inside a network including intranet web sites.
Netcraft Site Report – indicates whether a website's confidentiality could be jeopardized due to a past exploitation of Heartbleed by checking data from Netcraft's SSL Survey to determine whether a site offered the heartbeat TLS Extension prior to the Heartbleed disclosure. The Netcraft Extensions for Chrome, Firefox and Opera also perform this check, whilst looking for potentially compromised certificates.
Other security tools have added support for finding this bug. For example, Tenable Network Security wrote a plugin for its Nessus vulnerability scanner that can scan for this fault. The Nmap security scanner includes a Heartbleed detection script from version 6.45.
Sourcefire has released Snort rules to detect Heartbleed attack traffic and possible Heartbleed response traffic. Open source packet analysis software such as Wireshark and tcpdump can identify Heartbleed packets using specific BPF packet filters that can be used on stored packet captures or live traffic.
Remediation
Vulnerability to Heartbleed is resolved by updating OpenSSL to a patched version (1.0.1g or later). OpenSSL can be used either as a standalone program, a dynamic shared object, or a statically-linked library; therefore, the updating process can require restarting processes loaded with a vulnerable version of OpenSSL as well as re-linking programs and libraries that linked it statically. In practice this means updating packages that link OpenSSL statically, and restarting running programs to remove the in-memory copy of the old, vulnerable OpenSSL code.
After the vulnerability is patched, server administrators must address the potential breach of confidentiality. Because Heartbleed allowed attackers to disclose private keys, they must be treated as compromised; key pairs must be regenerated, and certificates that use them must be reissued; the old certificates must be revoked. Heartbleed also had the potential to allow disclosure of other in-memory secrets; therefore, other authentication material (such as passwords) should also be regenerated. It is rarely possible to confirm that a system which was affected has not been compromised, or to determine whether a specific piece of information was leaked.
Since it is difficult or impossible to determine when a credential might have been compromised and how it might have been used by an attacker, certain systems may warrant additional remediation work even after patching the vulnerability and replacing credentials. For example, signatures made by keys that were in use with a vulnerable OpenSSL version might well have been made by an attacker; this raises the possibility integrity has been violated, and opens signatures to repudiation. Validation of signatures and the legitimacy of other authentications made with a potentially compromised key (such as client certificate use) must be done with regard to the specific system involved.
Browser security certificate revocation awareness
Since Heartbleed threatened the privacy of private keys, users of a website which was compromised could continue to suffer from Heartbleed's effects until their browser is made aware of the certificate revocation or the compromised certificate expires. For this reason, remediation also depends on users making use of browsers that have up-to-date certificate revocation lists (or OCSP support) and honour certificate revocations.
Root causes, possible lessons, and reactions
Although evaluating the total cost of Heartbleed is difficult, eWeek estimated US$500 million as a starting point.
David A. Wheeler's paper How to Prevent the next Heartbleed analyzes why Heartbleed wasn't discovered earlier, and suggests several techniques which could have led to a faster identification, as well as techniques which could have reduced its impact. According to Wheeler, the most efficient technique which could have prevented Heartbleed is a test suite thoroughly performing robustness testing, i.e. testing that invalid inputs cause failures rather than successes. Wheeler highlights that a single general-purpose test suite could serve as a base for all TLS implementations.
According to an article on The Conversation written by Robert Merkel, Heartbleed revealed a massive failure of risk analysis. Merkel thinks OpenSSL gives more importance to performance than to security, which no longer makes sense in his opinion. But Merkel considers that OpenSSL should not be blamed as much as OpenSSL users, who chose to use OpenSSL, without funding better auditing and testing. Merkel explains that two aspects determine the risk that more similar bugs will cause vulnerabilities. One, the library's source code influences the risk of writing bugs with such an impact. Secondly, OpenSSL's processes affect the chances of catching bugs quickly. On the first aspect, Merkel mentions the use of the C programming language as one risk factor which favored Heartbleed's appearance, echoing Wheeler's analysis.
On the same aspect, Theo de Raadt, founder and leader of the OpenBSD and OpenSSH projects, has criticized the OpenSSL developers for writing their own memory management routines and thereby, he claims, circumventing OpenBSD C standard library exploit countermeasures, saying "OpenSSL is not developed by a responsible team." Following Heartbleed's disclosure, members of the OpenBSD project forked OpenSSL into LibreSSL. LibreSSL made a big code cleanup, removing more than 90,000 lines of C code just in its first week.
The author of the change which introduced Heartbleed, Robin Seggelmann, stated that he missed validating a variable containing a length and denied any intention to submit a flawed implementation. Following Heartbleed's disclosure, Seggelmann suggested focusing on the second aspect, stating that OpenSSL is not reviewed by enough people. Although Seggelmann's work was reviewed by an OpenSSL core developer, the review was also intended to verify functional improvements, a situation making vulnerabilities much easier to miss.
OpenSSL core developer Ben Laurie claimed that a security audit of OpenSSL would have caught Heartbleed. Software engineer John Walsh commented: The OpenSSL foundation's president, Steve Marquess, said "The mystery is not that a few overworked volunteers missed this bug; the mystery is why it hasn't happened more often." David A. Wheeler described audits as an excellent way to find vulnerabilities in typical cases, but noted that "OpenSSL uses unnecessarily complex structures, which makes it harder to both humans and machines to review." He wrote:
There should be a continuous effort to simplify the code, because otherwise just adding capabilities will slowly increase the software complexity. The code should be refactored over time to make it simple and clear, not just constantly add new features. The goal should be code that is "obviously right", as opposed to code that is so complicated that "I can't see any problems".
According to security researcher Dan Kaminsky, Heartbleed is sign of an economic problem which needs to be fixed. Seeing the time taken to catch this simple error in a simple feature from a "critical" dependency, Kaminsky fears numerous future vulnerabilities if nothing is done. When Heartbleed was discovered, OpenSSL was maintained by a handful of volunteers, only one of whom worked full time. Yearly donations to the OpenSSL project were about US$2,000. The Heartbleed website from Codenomicon advised money donations to the OpenSSL project. After learning about donations for the 2 or 3 days following Heartbleed's disclosure totaling US$841, Kaminsky commented "We are building the most important technologies for the global economy on shockingly underfunded infrastructure." Core developer Ben Laurie has qualified the project as "completely unfunded". Although the OpenSSL Software Foundation has no bug bounty program, the Internet Bug Bounty initiative awarded US$15,000 to Google's Neel Mehta, who discovered Heartbleed, for his responsible disclosure. Mehta later donated his reward to a Freedom of the Press Foundation fundraiser.
Paul Chiusano suggested Heartbleed may have resulted from failed software economics.
The industry's collective response to the crisis was the Core Infrastructure Initiative, a multimillion-dollar project announced by the Linux Foundation on 24 April 2014 to provide funds to critical elements of the global information infrastructure. The initiative intends to allow lead developers to work full time on their projects and to pay for security audits, hardware and software infrastructure, travel, and other expenses. OpenSSL is a candidate to become the first recipient of the initiative's funding.
After the discovery Google established Project Zero which is tasked with finding zero-day vulnerabilities to help secure the Web and society.
References
Bibliography
External links
Summary and Q&A about the bug by Codenomicon Ltd
Information for Canadian organizations and individuals
List of all security notices
2014 in computing
Internet security
Software bugs
Transport Layer Security
Computer security exploits | Heartbleed | Technology | 6,096 |
7,811,968 | https://en.wikipedia.org/wiki/Regular%20solution | In chemistry, a regular solution is a solution whose entropy of mixing is equal to that of an ideal solution with the same composition, but is non-ideal due to a nonzero enthalpy of mixing. Such a solution is formed by random mixing of components of similar molar volume and without strong specific interactions, and its behavior diverges from that of an ideal solution by showing phase separation at intermediate compositions and temperatures (a miscibility gap). Its entropy of mixing is equal to that of an ideal solution with the same composition, due to random mixing without strong specific interactions. For two components
where is the gas constant, the total number of moles, and the mole fraction of each component. Only the enthalpy of mixing is non-zero, unlike for an ideal solution, while the volume of the solution equals the sum of volumes of components.
Features
A regular solution can also be described by Raoult's law modified with a Margules function with only one parameter :
where the Margules function is
Notice that the Margules function for each component contains the mole fraction of the other component. It can also be shown using the Gibbs-Duhem relation that if the first Margules expression holds, then the other one must have the same shape. A regular solutions internal energy will vary during mixing or during process.
The value of can be interpreted as W/RT, where W = 2U12 - U11 - U22 represents the difference in interaction energy between like and unlike neighbors.
In contrast to ideal solutions, regular solutions do possess a non-zero enthalpy of mixing, due to the W term. If the unlike interactions are more unfavorable than the like ones, we get competition between an entropy of mixing term that produces a minimum in the Gibbs free energy at x1 = 0.5 and the enthalpy term that has a maximum there. At high temperatures, the entropic term in the free energy of mixing dominates and the system is fully miscible, but at lower temperatures the G(x1) curve will have two minima and a maximum in between. This results in phase separation. In general there will be a temperature where the three extremes coalesce and the system becomes fully miscible. This point is known as the upper critical solution temperature or the upper consolute temperature.
In contrast to ideal solutions, the volumes in the case of regular solutions are no longer strictly additive but must be calculated from partial molar volumes that are a function of x1.
The term was introduced in 1927 by the American physical chemist Joel Henry Hildebrand.
See also
Solid solution
References
Thermodynamics
Chemical thermodynamics | Regular solution | Physics,Chemistry,Mathematics | 549 |
29,386,470 | https://en.wikipedia.org/wiki/Astronomical%20ceiling%20of%20Senenmut%27s%20Tomb | Astronomical ceiling decoration in its earliest form can be traced to the tomb of Senenmut (Theban tomb no. 353), located at the site of Deir el-Bahri, discovered in Thebes, Upper Egypt. The tomb and the ceiling decorations date back to the XVIII Dynasty of ancient Egypt (circa 1479–1458 BCE). It is closed to the public.
Discovery
The tomb of Senemut was discovered during the 1925–1927 excavations directed by Herbert Winlock for the Egyptian Expedition
of the Metropolitan Museum of Art.
The unfinished tomb is entered via a steep descending stairway starting in a quarry. This is 90m long and gives access to three successive chambers under the Mortuary Temple of Hatshepsut. Whether this was done to deliberately place his tomb in the precincts of Hatshepsut's temple or to reach better quality sandstone is not known. The unearthing of the 10x12 ft. chamber known as Chamber A yielded the two panels of what is now referred to as the Egyptian Celestial Diagram. The ceiling and wall carvings are particularly well preserved as due to the Tarawan chalk into which they were carved.
Celestial Diagram
The Celestial Diagram consisted of a northern and a southern panel which depicted circumpolar constellations in the form of discs; each divided into 24 sections suggesting a 24-hour time period, lunar cycles, and sacred deities of Egypt. Of the constellations present on the diagram, the only certainly identifiable was Meskhetyu with the Big Dipper because of the difficulty that arises when an attempt is made to match modern day constellations with the depictions made thousands of years ago by the ancient Egyptians.
Some of the main figures and stars seen in the diagram are Sirius, Orion, Ursa Major, Draco (may be depicted as hippopotamus with crocodile on its back),
The four circles on the top right refer to the four months of Akhet (inundation) between July and October
The two circles at the top left and the two below them refer to the season of Peret (planting season) between November and February
The four circles on the right refer to the season of Shomu (harvesting season) between March and June
The map on the southern panel could well reflect a specific conjunction of planets in 1534 BCE around the longitude of Sirius. The four planets Jupiter, Saturn, Mercury and Venus are relatively easily recognizable. The planet Mars is not included in the actual grouping and at first sight seems to be missing in the map. However, one explanation is that Mars is represented in the Senenmut map as an empty boat in the west. This may refer to the fact that Mars was retrograde and was not with the other planets (indeed, being in the west in the 1534 BCE conjunction). The reason for the boat being empty is perhaps in this backward movement (a well known phenomenon to the Egyptians) the position of Mars was not considered to be ”concrete”.
An alternative explanation for the missing Mars is proposed by Belmonte,″...the astronomical ceiling of the tomb of Senenmut is a gigantic copy of a papyrus draft of a celestial diagram that would have existed and used to be represented in clepsydrae (water clocks, as that of Karnak). Because of the lack of space, when moving the design from a conical to a flat surface, part of the decoration was lost.″
Significance
Although the tomb had been unfinished and had sustained damage throughout the centuries, the ceiling yielded new information about astronomy, chronology, mythology, and religion in Egypt because of the incorporation of all these elements as a means of connecting the divine to the mortal world.
Egyptian astronomy consisted of the identification of the heavenly bodies in the sky and their connection with the deities that were believed to play a role in religious mythology and practice.
Astronomical ceilings bore significant symbolism for the Egyptians as they combined divine religion with more earthly aspects of daily life such as agriculture and labor. The detailed depiction of astronomy and deities illustrates the Egyptians desire to understand the heavens and the attempt to apply that understanding to the gods that they believed influenced all aspects of life.
The assimilation of these elements ensured that the Egyptian calendar would differ from the ancient calendars of the Sumerians and the Babylonians. Otto Neugebauer suggests that the complexity of Egyptian calendars:
represents the peaceful coexistence of different methods of defining time moments and time intervals in different ways on different occasions.
The use of astronomical calendars was not limited to ceiling tombs as they appeared on coffin boards, water boards, temples, and various other surfaces and objects.
See also
Dendera zodiac
Notes and references
External links
UNESCO "ICOMOS-IAU case study: The Tomb of Senenmut at Western Thebes, Egypt includes map, documents and case study
Metropolitan Museum has a full scan of the ceiling
Gyula Priskin, The Constellations of the Egyptian Astronomical Diagrams, Égypte Nilotique et Méditerranéenne 12 (2019), 137-180.
Egyptian calendar
Archaeoastronomy | Astronomical ceiling of Senenmut's Tomb | Astronomy | 1,024 |
11,128,390 | https://en.wikipedia.org/wiki/Pucciniastrum%20arcticum | Pucciniastrum arcticum is a plant pathogen infecting caneberries.
References
Fungal plant pathogens and diseases
Small fruit diseases
Pucciniales
Fungi described in 1895
Fungus species | Pucciniastrum arcticum | Biology | 39 |
393,164 | https://en.wikipedia.org/wiki/Emetophilia | Emetophilia is a paraphilia where an individual is sexually aroused by vomit or the act of vomiting. Being vomited on in a sexual context is called a roman shower.
See also
Emetophobia
References
Further reading
Paraphilias
Vomiting | Emetophilia | Biology | 52 |
8,115,641 | https://en.wikipedia.org/wiki/NP-40 | NP-40 (also known as Tergitol-type NP-40 and nonyl phenoxypolyethoxylethanol) is a commercially available detergent with CAS Registry Number 9016-45-9. NP-40 is an ethoxylated nonylphenol for non-ionic surfactants and can act as emulsifier and demulsifier agent.
NP-40 is often used to break open all membranes within a cell, including the nuclear membrane . To break only the cytoplasmic membrane, other detergents such as digitonin can be used.
NP-40 has applications in paper and textile processing, in paints and coatings, and in agrochemical manufacturing.
Care should be taken to avoid confusing NP-40 with Nonidet P-40 (octyl phenoxypolyethoxylethanol) which is currently out of production. Nonidet P-40 ("Non-Ionic Detergent") was originally manufactured and trademarked by the Shell Chemical Company, but was phased out of production in the early 2000s. Confusingly, biochemical protocols published between the 1960s and 2000s refer to Shell's Nonidet P-40 as NP-40. Shell's original Nonidet P-40 had a hydrophilic-lipophilic balance (HLB) value of 13.5, as opposed to 12.9 for the currently available IGEPAL CA-630, indicating that the currently available compound is more potent than the compound used in older publications. Indeed, according to a 2017 report, an additional dilution factor of 10 was required for the currently available NP-40 ("Nonidet P-40 substitutes") to match the activity of the previously available, and now discontinued, Shell's Nonidet P-40.
See also
Nonoxynol-9
Surfactant
Lipid bilayer
Detergent
Triton X-100 (differs only in the # of carbons in the aliphatic portion)
References
Biochemistry methods
Non-ionic surfactants | NP-40 | Chemistry,Biology | 423 |
4,998,573 | https://en.wikipedia.org/wiki/41%20G.%20Arae | 41 G. Arae (abbreviated to 41 G. Ara), also known as GJ 666, is a trinary star system in the constellation Ara from the Sun. Although often called just 41 Arae, it is more accurate to call it 41 G. Arae, as the number 41 is the Gould designation (Flamsteed only covered the northern hemisphere).
The primary star in this system is a G-type main sequence star with a stellar classification of G8V. It has about 81% of the mass of the Sun, and 79% of the Sun's radius. The fainter member of the pair, a red dwarf, has a peculiar spectrum that shows a deficiency in elements with a higher atomic number than Helium. No planetary companions have been detected in orbit around these stars.
The two stars share a highly elliptical orbit that takes several centuries to complete. The estimates of the period range from 693 to 2,200 years, and the average separation of the two stars is about 210 AU (or 210 times the average distance between the Earth and the Sun).
41 G. Arae is most likely a triple, comprising the following components: Gliese 666A supposed as a spectroscopic binary, and Gliese 666B as its companion. Two other visual companions were proposed, but neither share the system's motion. Observations from Gaia have shown that it is in fact component B which is binary, with an orbital period of 88 days.
This system has a relatively high proper motion, moving over a second of arc across the sky each year. The space velocity components of this system are = . The stars in this system show low chromospheric activity, and have a net space velocity of 52 km/s relative to the Sun. This, in combination with their low metallicity, shows that the pair belongs to the old disk population.
See also
List of star systems within 25–30 light-years
References
External links
41 G. Arae 2 SolStation entry.
HR 6416
Image 41 G Arae
HIC 84720
CCDM 17191-4638
Ara (constellation)
Triple star systems
G-type main-sequence stars
M-type main-sequence stars
Arae, 41
Arae, 41
0666
156274
084720
6416
CD-46 11370
217157387 | 41 G. Arae | Astronomy | 482 |
30,870,527 | https://en.wikipedia.org/wiki/Combined%20DNA%20Index%20System | The Combined DNA Index System (CODIS) is the United States national DNA database created and maintained by the Federal Bureau of Investigation. CODIS consists of three levels of information; Local DNA Index Systems (LDIS) where DNA profiles originate, State DNA Index Systems (SDIS) which allows for laboratories within states to share information, and the National DNA Index System (NDIS) which allows states to compare DNA information with one another.
The CODIS software contains multiple different databases depending on the type of information being searched against. Examples of these databases include, missing persons, convicted offenders, and forensic samples collected from crime scenes. Each state, and the federal system, has different laws for collection, upload, and analysis of information contained within their database. However, for privacy reasons, the CODIS database does not contain any personal identifying information, such as the name associated with the DNA profile. The uploading agency is notified of any hits to their samples and are tasked with the dissemination of personal information pursuant to their laws.
Establishment
The creation of a national DNA database within the U.S. was first mentioned by the Technical Working Group on DNA Analysis Methods (TWGDAM) in 1989. The FBI's strategic goal was to maximize the voluntary participation of states and avoid what happened several years early, when eight western states frustrated with the progress creating a national Automated Fingerprint Identification System (AFIS) network formed the Western Identification Network (WIN). The FBI's strategy to discourage states from creating systems that competed with CODIS was to develop DNA databasing software and provide it free of charge to state and local crime laboratories.This strategic decision--to provide software free of charge for the purpose of gaining market share--was innovative at that time and predated the browser wars. In 1990, the FBI began a pilot DNA databasing program with 14 state and local laboratories.
In 1994, Congress passed the DNA Identification Act which authorized the FBI to create a national DNA database of convicted offenders as well as separate databases for missing persons and forensic samples collected from crime scenes. (Some in the Bureau believed the Act was not required to establish a national DNA database because the FBI's Criminal Justice Information Services Division was already using similar authorities to provide data-sharing solutions to federal, state, local, and tribal law enforcement agencies.) The DNA Identification Act also required that laboratories participating in the CODIS program maintain accreditation from an independent nonprofit organization that is actively involved in the forensic fields and that scientists processing DNA samples for submission into CODIS maintain proficiency and are routinely tested to ensure the quality of the profiles being uploaded into the database. The national level of CODIS (NDIS) was implemented in October 1998. Today, all 50 states, the District of Columbia, federal law enforcement, the Army Laboratory, and Puerto Rico participate in the national sharing of DNA profiles.
Database structure
The CODIS database contains several different indexes for the storage of DNA profile information. For assistance in criminal investigations three indexes exist: the offender index, which contains DNA profiles of those convicted of crimes; the arrestee index, which contains profiles of those arrested of crimes pursuant to the laws of the particular state; and the forensic index, which contains profiles collected from a crime scene. Additional indexes, such as the unidentified human remain index, the missing persons index, and the biological relatives of missing persons index, are used to assist in identifying missing persons. Specialty indexes also exist for other specimens that do not fall into the other categories. These indexes include the staff index, for profiles of employees who work with the samples, and the multi-allelic offender index, for single-source samples that have three or more alleles at two or more loci.
Non-criminal indexes
While CODIS is generally used for linking crimes to other crimes and potentially to suspects there are non-criminal portions of the database such as the missing person indexes. The National Missing Person DNA Database, also known as CODIS(mp), is maintained by the FBI at the NDIS level of CODIS allowing all states to share information with one another. Created in 2000 using the existing CODIS infrastructure, this section of the database is designed to help identify human remains by collecting and storing DNA information on the missing or the relatives of missing individuals. Unidentified remains are processed for DNA by the University of North Texas Center for Human Identification which is funded by the National Institute of Justice. Nuclear, Y-STR (for males only), and mitochondrial analysis can be performed on both unknown remains and on known relatives in order to maximize the chance of identifying remains.
Statistics
, NDIS contained more than 14 million offender profiles, more than four million arrestee profiles and more than one million forensic profiles. The effectiveness of CODIS is measured by the number of investigations aided through database hits. , CODIS had aided in over 520 thousand investigations and produced more than 530 thousand hits. Each state has their own SDIS database and each state can set their own inclusionary standards that can be less strict than the national level. For this reason, a number of profiles that are present in state level databases are not in the national database and are not routinely searched across state lines.
Scientific basis
The bulk of identifications using CODIS rely on short tandem repeats (STRs) that are scattered throughout the human genome and on statistics that are used to calculate the rarity of that specific profile in the population. STRs are a type of copy-number variation and comprise a sequence of nucleotide base pairs that is repeated over and over again. At each location tested during DNA analysis, also known as a locus (plural loci), a person has two sets of repeats, one from the father and one from the mother. Each set is measured and the number of repeat copies is recorded. If both strands, inherited from the parents, contain the same number of repeats at that locus the person is said to be homozygous at that locus. If the repeat numbers differ they are said to be heterozygous. Every possible difference at a locus is an allele. This repeat determination is performed across a number of loci and the repeat values is the DNA profile that is uploaded to CODIS. As of January 1, 2017, requirements for upload to national level for known offender profiles is 20 loci.
Alternatively, CODIS allows for the upload of mitochondrial DNA (mtDNA) information into the missing persons indexes. Since mtDNA is passed down from mother to offspring it can be used to link remains to still living relatives who have the same mtDNA.
Loci
Prior to January 1, 2017, the national level of CODIS required that known offender profiles have a set of 13 loci called the "CODIS core". Since then, the requirement has expanded to include seven additional loci. Partial profiles are also allowed in CODIS in separate indexes and are common in crime scene samples that are degraded or are mixtures of multiple individuals. Upload of these profiles to the national level of CODIS requires at least eight of the core loci to be present as well as a profile rarity of 1 in 10 million (calculated using population statistics).
Loci that fall within a gene are named after the gene. For example, TPOX, is named after the human thyroid peroxidase gene. Loci that do not fall within genes are given a standard naming scheme for uniformity. These loci are named D + the chromosome the locus is on + S + the order in which the location on that chromosome was described. For example, D3S1358 is on the third chromosome and is the 1358th location described. The CODIS core are listed below; loci with asterisks are the new core and were added to the list in January 2017.
The loci used in CODIS were chosen because they are in regions of noncoding DNA, sections that do not code for proteins. These sections should not be able to tell investigators any additional information about the person such as their hair or eye color, or their race. However, new advancements in the understanding of genetic markers and ancestry have indicated that the CODIS loci may contain phenotypic information.
International use
While the U.S. database is not directly connected to any other country, the underlying CODIS software is used by other agencies around the world. , the CODIS software is used by 90 international laboratories in 50 countries. International police agencies that want to search the U.S. database can submit a request to the FBI for review. If the request is reasonable and the profile being searched would meet inclusionary standards for a U.S. profile, such as number of loci, the request can be searched at the national level or forwarded to any states where reasonable suspicion exists that they may be present in that level of the database.
Controversies
Arrestee collection
The original purpose of the CODIS database was to build upon the sex offender registry through the DNA collection of convicted sex offenders. Over time, that has expanded. Currently, all 50 states collect DNA from those convicted of felonies. A number of states also collect samples from juveniles as well as those who are arrested, but not yet convicted, of a crime. Note that even in states which limit collection of DNA retained in the state database only to those convicted of a crime, local databases, such as the forensic laboratory operated by New York City's Office of Chief Medical Examiner, may collect DNA samples of arrestees who have not been convicted. The collection of arrestee samples raised constitutional issues, specifically the Fourth Amendment prohibiting unreasonable search and seizure. It was argued that the collection of DNA from those that were not convicted of a crime, without an explicit order to collect, was considered a warrantless search and therefore unlawful. In 2013, the United States Supreme Court ruled in Maryland v. King that the collection of DNA from those arrested for a crime, but not yet convicted, is part of the police booking procedure and is reasonable when that collection is used for identification purposes.
Familial searching
The inheritance pattern of some DNA means that close relatives share a higher percentage of alleles between each other than with other, random, members of society. This allows for the searching of close matches within CODIS when an exact match is not found. By focusing on close matches, investigators can potentially find a close relative whose profile is in CODIS narrowing their search to one specific family. Familial searching has led to several convictions after the exhaustion of all other leads including the Grim Sleeper serial killer. This practice also raised Fourth Amendment challenges as the individual who ends up being charged with a crime was only implicated because someone else's DNA was in the CODIS database. , twelve states have approved the use of familial searching in CODIS.
See also
Debbie Smith Act
GEDmatch
Integrated Automated Fingerprint Identification System (IAFIS)
References
External links
CODIS page on FBI.gov
"ACLU Warns of Privacy Abuses in Government Plan to Expand DNA Databases". ACLU. March 1, 1999.
A Not So Perfect Match, CBS, 2007
"DNA didn't prove anything, as it only had five points out of 13. Juror Explains Verdict In Double Murder". November 13, 2008.
Biometrics
DNA
Federal Bureau of Investigation
Law enforcement databases in the United States
Identity documents of the United States
National DNA databases
Sex offender registration
Forensic databases
Biological databases
1998 introductions | Combined DNA Index System | Biology | 2,324 |
13,787,601 | https://en.wikipedia.org/wiki/Olympiadane | Olympiadane is a mechanically interlocked molecule composed of five interlocking macrocycles that resembles the Olympic rings. The molecule is a linear pentacatenane or a [5]catenane. It was synthesized and named by Fraser Stoddart and coworkers in 1994. The molecule was designed without any practical use in mind, although other catenanes may have possible application to the construction of a molecular computer.
See also
Olympicene
References
Molecular topology
Hexafluorophosphates
Supramolecular chemistry
Pyridinium compounds
Substances discovered in the 1990s | Olympiadane | Chemistry,Materials_science,Mathematics | 122 |
51,666,001 | https://en.wikipedia.org/wiki/Aspergillus%20clavatus | Aspergillus clavatus is a species of fungus in the genus Aspergillus with conidia dimensions 3–4.5 x 2.5–4.5 μm. It is found in soil and animal manure. The fungus was first described scientifically in 1834 by the French mycologist John Baptiste Henri Joseph Desmazières.
The fungus can produce the toxin patulin, which may be associated with disease in humans and animals. This species is only occasionally pathogenic.
Other sources have identified many species of Aspergillus as producing dry, hydrophobic spores that are easily inhaled by humans and animals. Due to the small size of the spores, about 70% of spores of A. fumigatus are able to penetrate into the trachea and primary bronchi and close to 1% into alveoli. Inhalation of spores of Aspergillus is a health risk. A. clavatus is allergenic, causing the occupational hypersensitivity pneumonitis known as malt-worker's lung.
History and taxonomy
Aspergillus clavatus is a species of Aspergillus and is characterized by elongated club-shaped vesicles, and blue-green uniseriate conidia. The fungus was first described scientifically in 1834 by the French mycologist John Baptiste Henri Joseph Desmazières. It belongs to the Aspergillus section Clavati, (formerly known as the Aspergillus clavatus group) recognized by Charles Thom and Margaret Church (1926), alongside two species, Aspergillus clavatus and Aspergillus giganteus. In the succeeding years, four more species were discovered belonging to the Aspergillus section Clavati, which included Aspergillus rhizopodus, Aspergillus longivesica, Neocarpenteles acanthosporus and Aspergillus clavatonanicus. Later, Aspergillus pallidus was concluded to be a white variant (synonym) of A. clavatus by Samson (1979), which was supported by the identical DNA sequences of the two species. A sexual stage was described in 2018 with a Neocarpenteles teleomorph but under the one fungus-one name convention the original A. clavatus epithet was retained.
Growth and morphology
Aspergillus clavatus undergoes rapid growth, resulting in the formation of a velvety and fairly dense felt that is observed to be bluish-grey green in colour. The emerging conidial heads are large and clavate when very young, quickly splitting into conspicuous and compact divergent columns. The conidia bearing conidiophores are generally coarse, smooth walled, uncoloured, hyaline and can grow to be very long. Elongated club-shaped vesicles clavate, and bear phialides (singular: phialide) over their entire-surface, contributing to its short and densely packed structure. The sterigmata are usually found to be uniseriate, numerous and crowded. Conidia formed in them are elliptical, smooth and comparatively thick-walled. A. clavatus usually express conidiophores 1.5–3.00 mm in length, which arises from specialized and widened hyphal cells that eventually become the branching foot cells. The conidia on A. clavatus has been measured up to 3.0 – 4.5 X 2.5 – 3.5 μm. Cleistothecia are produced in crosses after approximately 4–10 weeks of incubation on suitable growth media at 25 °C. Cleistothecia are yellowish-brown (fawn) to dark brown in colour and range in diameter from 315-700 μm in diameter and have a relatively hard outer wall (peridium). At maturity the cleistothecia contain asci that themselves contain ascospores, which are clear, lenticular (with ridges evident) and between 6.0-7.0 μm in diameter.
Growth on Czapek's solution agar
Aspergillus clavatus colonies grow rapidly on Czapek's solution agar, reaching 3.0–3.5 cm, in 10 days at 24–26 °C. Growth is usually plane or moderately furrowed, with occasional appearance of floccose strains. But generally, a comparatively thin surface layer of mycelial felt is observed, which produces a copious number of erect conidiophores. The reverse is usually uncoloured but becomes brown with passing time in some strains. While odor is not prominent in some strains, it can be extremely unpleasant in others. Large conidial heads extend from 300 to 400 μm by 150 to 200 μm when young. However, with time, they split into two or more divergent and compressed cordial chains reaching 1.00 mm portraying a colour consisting of artemisia green to slate olive. The observed conidiophores grow up to 1.5–3.00 mm in length with 20–30 μm in diameter. They slowly and ultimately enlarge at the apex into a clavate vesicle, which consists of a fertile area, 200 to 250 μm in length and 40–60 μm wide.
The sterigmata usually ranges from 2.5 to 3.5 μm by 2.0 to 3.0 μm at the base of the vesicle, to 7.0 or 8.0 and occasionally 10 μm to 2.5 to 3.0 μm at the apex. The conidia are comparatively thick-walled and measures 3.0 to 4.5 μm by 2.5 to 3.5 μm. While they can be larger in some strains, in others their appearance may be irregular.
Growth on malt extract agar
On malt extract agar, the structural morphology of A. clavatus appears to be different than in Czapek's solution agar. The typical strains extracted from malt media contain less abundant conidial structures, which could be larger in size. In other (non-typical) strains, the conidial heads increase in number but decrease in size. The conidiophores range from 300 to 500 μm and bear loose, columnar heads. Typical strains may be resembled by strong and unpleasant odor whereas non-typical strains are characterized being odorless. The colonies arising from one conidium on malt extract agar, consisted of 25X10^7 conidia after being observed for six days.
Examination
The phialide development and conidium formation in A. clavatus has been examined using TEM. And by using SEM, it was discovered that the first-formed conidium and phialide share a continuous wall. Additionally recombination with an albino mutant led to the production of heterokaryotic conidial heads with mixed conidial colours. A GC-content of 52.5–55% was also detected upon DNA analysis. And its soluble wall carbohydrates consist of mannitol and arabitol.
Physiology
Light stimulates the elongation of conidiophores in A. clavatus. And the more favourable C sources include starch, dextrin, glycogen and especially fructose. Substantial degree of lipid synthesis occurs, whereas cellulose and usnic acid are degraded. A. clavatus also produces riboflavin, ribonuclease, acid phosphodiesterase and acid phosphatase when in liquid culture.
A. clavatus has the properties to oxidize tryptamine to indole acetic acid. It can absorb and collect hydrocarbons from fuel oil, incorporate metaphosphate and synthesize ethylene, clavatol and kojic acid. It is also responsible for the production of mycotoxins Patulin and sterigmatocystin. And has extremely high capacity for alcohol fermentation.
When it comes to genomics, bioinformatic analysis revealed that A. clavatus contains a full complement of identified euascomycete sex genes. A heterothallic sexual cycle involving outcrossing between MAT1-1 and MAT1-2 isolates was subsequently described . A. clavatus can also be a food source for Collembola and has been found to be parasitized by Fusarium solani.
Habitat and ecology
Aspergillus clavatus is often described as a spoilage organism occurring on dung and in soil and can also grow in strong alkaline conditions. When it comes to geographical distribution, A. clavatus has been spotted in the tropical, subtropical and Mediterranean areas. It has been accounted in low frequencies in the soils of India. And is also found in Bangladesh, Sri Lanka, Hong Kong, Jamaica, Brazil, Argentina, South Africa, the Ivory Coast, Egypt, Libya, Turkey, Greece, Italy, the United States of America, Japan, the USSR and Czechoslovakia. It was tracked in rocks of a carst cave and stratigraphic core samples descending to 1200 m in Central Japan. However, it is usually and solely collected from cultivated soils, including the ones that bear cotton, potatoes, sugar canes, legumes, paddy and Artemisia herba-alba. It has also been garnered from soil under burnt steppe vegetation, desert soils, the rhizospheres of banana, ground-nuts and wheat. A. clavatus has also been detected in the ripe compost of municipal waste, and Nitrogen and NPK fertilizers are found to play an important role in its stimulation process.
A. clavatus is also referred as a cosmopolitan fungus. Other than soil and dung, it can additionally be found in stored products with high levels of entrapped moisture. Such as stored cereals, rice, corn and millet. It has been further isolated from insects, especially from dead adult bees and honeycombs. Moreover, it has been collected from the feathers and droppings from free-living birds. A. clavatus is also common is decomposing materials. Their ability to resist strongly alkaline conditions, allows them to act as decomposition catalysts in situations where other fungus usually do not function.
Applications and medical uses
Weisner in March 1942 first noted the production of an antibiotic by strains of A. clavatus, and the active substance was known as clavatin. Later the antibiotic was named clavacin in August 1942 by Waksman, Horning and Spencer. Clavacin is also known as patulin. Patulin is receiving significant attention in the world today because of its manifestations in apple juices. Clavacin was noted to be valuable in the treatment of common-cold and applies a fungistatic or fungicidal effect on certain dermatophytes. A. clavatus with Phytophthora cryptogea in soil provided protection against damping of tomato seedlings, by decreasing the spreading of pathogens. Reversely, A. clavatus with the addition of glucose, increased the pathogenicity of Verticillium albo-atrum to tomatoes. A. clavatus also produces the following: Cytochalasin E, Cytochalasin K, Tryptoquivaline, Nortryptoquivalone, Nortryptoquivaline, Deoxytryptoquivaline, Deoxynortryptoquivaline, Tryptoquivaline E, and Tryptoquivaline N. Furthermore, A. clavatus isolates produce ribotoxins, which can help develop immunotherapy processes for cancer. A.clavatus has also been used in the formation of extracellular bionanoparticles from silver nitrate solutions. These nanoparticles display antimicrobial properties, which work against MRSA and MRSE.
Pathogenicity
Aspergillus clavatus is known as an agent of allergic aspergillosis and has been implicated in multiple pulmonary infections.
It has also been labelled as an opportunistic fungus, as it is responsible for causing aspergillosis in compromised patients.
A. clavatus can also cause neurotoxicosis in sheep and otomycosis. In Scotland and elsewhere, A. clavatus is reported for causing the mould allergy "malster's lung" otherwise "maltster's lung".
Extrinsic allergic alveolitis (EAA) is also caused by Aspergillus clavatus with a Type 1 immune reaction. It is described as a true hypersensitivity pneumonia, which usually occurs among malt workers, including symptoms of fever, chills, cough and dyspnea. In severe cases, glucocorticoids are used.
Microgranulomatous hypersensitivity pneumonitis, where interstitial granulomatous infiltration occurs, usually in malt workers, is caused by allergy to antigens of Aspergillus clavatus.
EAA is caused by allergy to Aspergillus conidia, usually in the non-atopic individual. Such individuals are usually exposed to organic dust heavily packed with conidia and mycelial debris. This condition involves the lung parenchyma.
A strain of A. clavatus has also caused hyperkeratosis in calves. Spore walls of a sputum-derived isolate of Aspergillus clavatus were extracted and treated with ethanol following alkaline hydrolysis. And it yielded mutagens. The extracts were given to unimmunised mice, causing lung reaction and leading to cases of pulmonary mycotoxicosis. A rising incidence of lung tumours were also observed.
This study revealed that an isolate of A. clavatus, which is able to convert highly toxic metabolites in bacterial and mammalian cells, will cause inflammatory response in the lungs of unimmunized mice.
References
clavatus
Food microbiology
Fungi described in 1834
Taxa named by John Baptiste Henri Joseph Desmazières
Fungal pathogens of humans
Fungus species | Aspergillus clavatus | Biology | 2,959 |
729,690 | https://en.wikipedia.org/wiki/Fluticasone | Fluticasone is a manufactured glucocorticoid used to treat nasal congestion. Both the esters, fluticasone propionate (sold as Flovent) and fluticasone furoate, are also used as topical anti-inflammatories and inhaled corticosteroids, and are used much more commonly in comparison.
It is on the World Health Organization's List of Essential Medicines. In 2022, it was the 25th most commonly prescribed medication in the United States, with more than 22million prescriptions, although it is also sold over-the-counter (OTC).
See also
Fluticasone furoate
Fluticasone furoate/vilanterol
Fluticasone propionate
Fluticasone/salmeterol
References
Antiasthmatic drugs
Diketones
Diols
Drugs acting on the respiratory system
Organofluorides
Drugs developed by GSK plc
Glucocorticoids
Pregnanes
Respiratory therapy
Thioesters | Fluticasone | Chemistry | 211 |
61,375,018 | https://en.wikipedia.org/wiki/Teegarden%27s%20Star%20c | Teegarden's Star c (also known as Teegarden c) is an exoplanet found orbiting in the habitable zone of Teegarden's Star, an M-type red dwarf star 12.5 light years away from the Solar System. It orbits in the conservative habitable zone around its star. Along with Teegarden's Star b, it is among the closest known potentially habitable exoplanets. It was discovered in June 2019.
Characteristics
Teegarden's Star c has an orbital period of 11.4 days. The minimum mass of the planet is one Earth mass, and its radius is probably Earth-like, suggesting an Earth-like composition, with an iron core and rocky crust. Teegarden's Star c could potentially have an ocean of water on its surface, or ice because of temperatures.
Habitability
Teegarden c orbits in the conservative habitable zone. The equilibrium temperature for the planet is −47 °C., but if the planet has a thick atmosphere, its surface could be much warmer. Earth's equilibrium temperature is −18 °C, but our atmosphere maintains temperatures well above that.
One positive factor for habitability is its star. Most red dwarfs emit strong flares, which can strip the atmosphere and eliminate habitability. A good example is Kepler-438b, which is likely uninhabitable because its sun is an active star. Another example is Proxima Centauri, the closest star to the sun. Teegarden's Star is inactive and quiet, making the planet possibly habitable. Other quiet red dwarfs with potentially habitable exoplanets are Ross 128 and Luyten's Star.
Host star
Teegarden's Star is an ultra-cool red dwarf at around 9 percent the mass of the Sun with a temperature of around 2,900 Kelvin (2,623 °C or 4,760 F). The inherent low temperatures of such objects explain why it was not discovered earlier, since it has an apparent magnitude of only 15.1 (and an absolute magnitude of 17.22). Like most red and brown dwarfs it emits most of its energy in the infrared spectrum. It is older than the Sun, with an age of 8 billion years.
It was discovered in 2003. Astronomers have long thought it was quite likely that many undiscovered dwarf stars exist within 20 light-years of Earth, because stellar-population surveys show the count of known nearby dwarf stars to be lower than otherwise expected and these stars are dim and easily overlooked. Teegarden's team thought that these dim stars might be found by data mining some of the huge optical sky survey data sets taken by various programs for other purposes in previous years. They reexamined the NEAT asteroid tracking data set and found this star. The star was then located on photographic plates from the Palomar Sky Survey taken in 1951. This discovery is significant as the team did not have direct access to any telescopes and did not include professional astronomers at the time of the discovery.
The parallax was initially measured as 0.43 ± 0.13 arcseconds. This would have placed its distance at only 7.50 light-years, making Teegarden's Star only the third star system in order of distance from the Sun, ranking between Barnard's Star and Wolf 359. However, even at that time the anomalous low luminosity (the absolute magnitude would have been 18.5) and high uncertainty in the parallax suggested that it was in fact somewhat farther away, still one of the Sun's nearest neighbors but not nearly as high in the ranking in order of distance. A more accurate parallax measurement of 0.2593 arcseconds was made by George Gatewood in 2009, yielding the now accepted distance of 12.578 light-years.
References
Exoplanets discovered in 2019
Aries (constellation)
Exoplanets detected by radial velocity
Near-Earth-sized exoplanets in the habitable zone | Teegarden's Star c | Astronomy | 830 |
32,776,800 | https://en.wikipedia.org/wiki/Operational%20loads%20monitoring | Operational loads monitoring (OLM) is a term given to act of investigating the characteristics of a structure in its normal operating environment. This term is often used to describe programs involving aircraft to extending their in-service life in a manner that does not compromise flight safety. A typical program would involve the installation of strain gauges to measure loads, accelerometers to measure g-force and other parameters to support the program or to add value (such as flap position, aircraft altitude, environmental conditions etc.), data acquisition system to process this data and a recorder to save the data for later analysis
. In this way it is very similar to structural health monitoring, a term that is sometimes also used to describe operational loads monitoring. Unlike Health and Usage Monitoring Systems, OLM programs are generally a short term project used to assess the remaining useful safe life of an airframe. This is especially important when an aircraft's role changes as the stresses and strains may now be significantly different from those initially anticipated. OLM program's benefits include a possible increased safe operating life figure and helping to prevent accidents such as the C-130 crash that occurred after the platform had been modified and flown for a different mission (fire fighting).
There are several active OLM programs currently underway, including research initiatives to standardize approaches for civilian aircraft.
References
External links
FAA Operational Loads Monitoring Program
Aircraft maintenance | Operational loads monitoring | Engineering | 280 |
2,239,212 | https://en.wikipedia.org/wiki/Microsoft%20BizTalk%20Server | Microsoft BizTalk Server is an inter-organizational middleware system (IOMS) that automates business processes through the use of adapters which are tailored to communicate with different software systems used in an enterprise. Created by Microsoft, it provides enterprise application integration, business process automation, business-to-business communication, message broker and business activity monitoring.
BizTalk Server was previously positioned as both an application server and an . Microsoft changed this strategy when they released the AppFabric server which became their official application server. Research firm Gartner consider Microsoft's offering one of their 'Leaders' for Application Integration Suites. The latest release of Biztalk (Biztalk Server 2020) was released on 15 January 2020.
In a common scenario, BizTalk integrates before going out and manages automated business processes by exchanging business documents such as purchase orders and invoices between disparate applications, within or across organizational boundaries.
Development for BizTalk Server is done through Microsoft Visual Studio. A developer can create transformation maps transforming one message type to another. For example, an XML file can be transformed to SAP IDocs. Messages inside BizTalk are implemented through the XML documents and defined with the XML schemas in XSD standard. Maps are implemented with the XSLT standard. Orchestrations are implemented with the WS-BPEL compatible process language xLANG. Schemas, maps, pipelines and orchestrations are created visually using graphical tools within Microsoft Visual Studio. The additional functionality can be delivered by .NET assemblies that can be called from existing modules—including, for instance, orchestrations, maps, pipelines, business rules.
Version history
Starting in 2000, the following versions were released:
2000-12-01 BizTalk Server 2000
2002-02-04 BizTalk Server 2002
2004-03-02 BizTalk Server 2004 (First version to run on Microsoft .NET 1.0)
2006-03-27 BizTalk Server 2006 (First version to run on Microsoft .NET 2.0)
2007-10-02 BizTalk Server 2006 R2 (First version to utilize the new Windows Communication Foundation (WCF) via native adapter – (Release date 2 October 2007))
2010-04-27 BizTalk Server 2009 (First version to work with Visual Studio 2008)
2010-10-01 BizTalk Server 2010 (First version to work with Visual Studio 2010 and Microsoft .NET 4.0)
2013-03-21 BizTalk 2013 (First version to work with Visual Studio 2012 and Microsoft .NET 4.5)
2014-06-23 BizTalk 2013 R2 (First version to work with Visual Studio 2013 and Microsoft .NET 4.5.1)
2016-09-30 BizTalk Server 2016
2017-04-26 BizTalk Server 2016 Feature Pack 1 (Application Insights and Power BI integration; Swagger-compatible REST Management APIs)
2017-11-21 BizTalk Server 2016 Feature Pack 2 (Azure integration)
2018-06-26 BizTalk Server 2016 Feature Pack 3 (Office 365 integration)
2020-01-15 BizTalk Server 2020 (First version to work with Visual Studio 2019 and Microsoft .NET 4.7)
Features
The following is an incomplete list of the technical features in the BizTalk Server:
The use of adapters to simplify integration to line of business (LOB) applications (Siebel, SAP, IFS Applications, JD Edwards, Oracle, Microsoft Dynamics CRM), databases (Microsoft SQL Server, Oracle Database and IBM Db2) and other Technologies (TIBCO and Java EE)
Accelerators offer support for enterprise standards like RosettaNet, HL7, HIPAA and SWIFT.
Business rules engine (BRE). This is a Rete algorithm rule engine.
Business activity monitoring (BAM), which allows a dashboard, aggregated (PivotTable) view on how the Business Processes are doing and how messages are processed.
A unified administration console for deployment, monitoring and operations of solutions on BizTalk servers in environment.
Built-in electronic data interchange (EDI) functionality supporting X12 and EDIFACT, as of BizTalk 2006 R2.
Ability to do graphical modelling of business processes in Visual Studio, model documents with XML schemas, graphically mapping (with the assistance of functoids) between different schemas, and building pipelines to decrypt, verify, parse messages as they enter or exit the system via adapters.
Users can automate business management processes via Orchestrations.
BizTalk integrates with other Microsoft products like Microsoft Dynamics CRM, Microsoft SQL Server, and SharePoint to allow interaction with a user participating in a workflow process.
Extensive support for web services (consuming and exposing)
RFID support, as of BizTalk 2006 R2. Deprecated in the 2016 release
Support for Application Insight, as of BizTalk Server 2016 Feature Pack 1
Automatic deployment through Visual Studio Team Service, as of BizTalk Server 2016 Feature Pack 1
Exposed management REST APIs with full Swagger support, as of BizTalk Server 2016 Feature Pack 1
Exposed operational data with Power BI support, as of BizTalk Server 2016 Feature Pack 1
Human-centric processes cannot be implemented directly with BizTalk Server and need additional applications like Microsoft SharePoint server.
Architecture
The BizTalk Server runtime is built on a publish/subscribe architecture, sometimes called "content-based publish/subscribe". Messages are published into BizTalk, transformed to the desired format, and then routed to one or more subscribers.
BizTalk makes processing safe by serialization (called "dehydration" in Biztalk's terminology) – placing messages into a database while waiting for external events, thus preventing data loss. This architecture binds BizTalk with Microsoft SQL Server. Processing flow can be tracked by administrators using an Administration Console.
BizTalk supports the transaction flow through the whole line from one customer to another. BizTalk orchestrations also implement long-running transactions.
Adapters
BizTalk uses adapters for communications with different protocols, message formats, and specific software products. Some of the adapters are: electronic data interchange, file, HTTP, SFTP, FTP SMTP, POP3, SOAP, SQL, MSMQ, MLLP, Azure Logic App, Azure API Management, Microsoft SharePoint Server, IBM mainframe zSeries (CICS and IMS) and midrange IBM i (previously AS/400) systems, IBM Db2, IBM WebSphere MQ adapters.
The WCF Adapter set was added with 2006 R2. It includes: WCF-WSHttp, WCF-BasicHttp, WCF-NetTcp, WCF-NetMsmq, WCF-NetNamedPipe, WCF-Custom, WCF-CustomIsolated adapters. Microsoft also ships a BizTalk Adapter Pack that includes WCF-based adapters for LOB systems. Currently, this includes adapters for SAP and Oracle database, Oracle E-Business Suite, Microsoft SQL Server, MySQL, PeopleSoft Enterprise and Siebel Systems.
Additional adapters (for Active Directory, for example) are available from third party Microsoft BizTalk core partners.
References
External links
2000 software
Enterprise application integration
Message-oriented middleware
Microsoft server software|BizTalk Server
Middleware
Proprietary software
Service-oriented (business computing) | Microsoft BizTalk Server | Technology,Engineering | 1,537 |
1,170,852 | https://en.wikipedia.org/wiki/Stiction | Stiction (a portmanteau of the words static and friction) is the force that needs to be overcome to enable relative motion of stationary objects in contact.
Any solid objects pressing against each other (but not sliding) will require some threshold of force parallel to the surface of contact in order to overcome static adhesion. Stiction is a threshold, not a continuous force. However, stiction might also be an illusion made by the rotation of kinetic friction.
In situations where two surfaces with areas below the micrometer scale come into close proximity (as in an accelerometer), they may adhere together. At this scale, electrostatic and/or Van der Waals and hydrogen bonding forces become significant. The phenomenon of two such surfaces being adhered together in this manner is also called stiction. Stiction may be related to hydrogen bonding or residual contamination.
Automobiles
Stiction is also the same threshold at which a rolling object would begin to slide over a surface rather than rolling at the expected rate (and in the case of a wheel, in the expected direction). In this case, it's called "rolling friction" or μr.
This is why driver training courses teach that, if a car begins to slide sideways, the driver should avoid braking and instead try to steer in the same direction as the slide. This gives the wheels a chance to regain static contact by rolling, which gives the driver some control again. Similarly, when trying to accelerate rapidly (particularly from a standing start) an overenthusiastic driver may "squeal" the driving wheels, but this impressive display of noise and smoke is less effective than maintaining static contact with the road. Many stunt-driving techniques (such as drifting) are done by deliberately breaking and/or regaining this rolling friction.
A car on a slippery surface can slide a long way with little control over orientation if the driver "locks" the wheels in stationary positions by pressing hard on the brakes. Anti-lock braking systems use wheel speed sensors and vehicle speed sensors to determine if any of the wheels have stopped turning. The ABS module then briefly releases pressure to any wheel that is spinning too slowly to not be slipping, to allow the road surface to begin turning the wheel freely again. Anti-lock brakes can be much more effective than cadence braking, which is essentially a manual technique for doing the same thing.
Examples
Engineering
Stiction refers to the characteristic of start-and-stop–type motion of a mechanical assembly. Consider a mechanical element slowly increasing an external force on an assembly at rest that is designed for the relative rotation or sliding of its parts in contact. The static contact friction between the assembly parts resists movement, causing the spring moments in the assembly to store mechanical energy. Any part of the assembly that can elastically bend, even microscopically, and exert a restoring force contributes a spring moment. Thus the "springs" in an assembly might not be obvious to the eye. The increasing external force finally exceeds the static friction resisting force, and the spring moments, released, impulsively exert their restoring forces on both the moving assembly parts and, by Newton's Third Law, in reaction on the external forcing element. The assembly parts then impulsively accelerate with respect to each other, though resisted by dynamic contact friction (in this context very much less than the static friction). However, the forcing element cannot accelerate at the same pace, fails to keep up, and loses contact. The external force on the moving assembly momentarily drops to zero for lack of forcing mechanical contact even though the external force element continues its motion. The moving part then decelerates to a stop from the dynamic contact friction. The cycle repeats as the forcing element catches up to contact again. Stick, store spring energy, impulsively release spring energy, accelerate, decelerate, stop, stick. Repeat.
Stiction is a problem for the design and materials science of many moving linkages. This is particularly the case for linear sliding joints, rather than rotating pivots. Owing to simple geometry, the moving distance of a sliding joint in two comparable linkages is longer than the circumferential travel of a pivoting bearing, thus the forces involved (for equivalent work) are lower and stiction forces become proportionally more significant. This issue has often led to linkages being redesigned from sliding to purely pivoted structures, just to avoid problems with stiction. An example is the Chapman strut, a suspension linkage.
Surface micromachining
During surface micromachining, stiction or adhesion between the substrate (usually silicon-based) and the microstructure occurs during the isotropic wet etching of the sacrificial layer. The capillary forces due to the surface tension of the liquid between the microstructure and substrate during drying of the wet etchant cause the two surfaces to adhere together. Separating the two surfaces is often complicated due to the fragile nature of the microstructure. Stiction is often circumvented by the use of a sublimating fluid (often supercritical CO2, which has extremely low surface tension) in a drying process where the liquid phase is bypassed. CO2 displaces the rinsing fluid and is heated past the supercritical point. As the chamber pressure is slowly released the CO2 sublimates, thereby preventing stiction.
See also
Blish lock
References
Friction
Surface science | Stiction | Physics,Chemistry,Materials_science | 1,109 |
286,027 | https://en.wikipedia.org/wiki/Turacin | Turacin is a naturally occurring red pigment that is 6% copper complexed to uroporphyrin III. Arthur Herbert Church discovered turacin in 1869.
It is found only in the bird family Musophagidae, the turacos. Other birds derive their red coloration from carotenoids (bright and orange-reds) or phaeomelanins (rusty and brownish-reds).
It is often assumed that this coloration will wash out when the birds are bathing or after heavy rains, but this is true only if the water used for bathing happens to be very alkaline.
The copper(II) uroporphyrin III pigment in turaco feathers was studied using electron spin resonance by Jack Peisach first with Blumberg and later with Mims.
See also
Psittacofulvin, a brightly colored red and yellow pigment unique to parrots
Turacoverdin, green pigment unique to turacos
References
Biological pigments | Turacin | Biology | 199 |
47,110,350 | https://en.wikipedia.org/wiki/Thermal%20integrity%20profiling | Thermal Integrity Profiling (TIP) is a non-destructive testing method used to evaluate the integrity of concrete foundations. It is standardized by ASTM D7949 - Standard Test Methods for Thermal Integrity Profiling of Concrete Deep Foundations.
The testing method was first developed in the mid 1990s at the University of South Florida. It relates the heat generated by curing of cement to the integrity and quality of drilled shafts, augered cast in place (ACIP) piles and other concrete foundations. In general, a shortage of competent concrete (necks or inclusions) is registered by relative cool regions; the presence of extra concrete (over-pour bulging into soft soil strata) is registered by relative warm regions.
Concrete temperatures along the length of the foundation element are sampled throughout the concrete hydration process. TIP analysis is performed at the point of peak temperature, generally 18 to 24hrs post-concreting. Measurements are available relatively soon after pouring (6 to 72 hours), generally before other integrity testing methods such as cross hole sonic logging and low strain integrity testing can be performed.
TIP can be performed using a probe lowered down standard access tubes or by installing embedded thermal wires along the length of the reinforcement cage. Four thermal wires are commonly installed along the steel cage, each 90 degrees from one another, forming a north-east-south-west configuration. If records at a certain depth show regions with cooler temperatures (when compared to the average temperature at that depth), a concrete deficiency or defect may be present. An average temperature at a certain depth that is significantly lower than the average temperatures at other depths may also be indication of a potential problem. It is also possible to estimate the effective area of the foundation, and to assess if the reinforcing cage is properly aligned and centered.
References
Cement
Concrete
Corrosion
Nondestructive testing
1990s introductions
Temperature | Thermal integrity profiling | Physics,Chemistry,Materials_science,Engineering | 373 |
159,472 | https://en.wikipedia.org/wiki/Flight | Flight or flying is the motion of an object through an atmosphere, or through the vacuum of outer space, without contacting any planetary surface. This can be achieved by generating aerodynamic lift associated with gliding or propulsive thrust, aerostatically using buoyancy, or by ballistic movement.
Many things can fly, from animal aviators such as birds, bats and insects, to natural gliders/parachuters such as patagial animals, anemochorous seeds and ballistospores, to human inventions like aircraft (airplanes, helicopters, airships, balloons, etc.) and rockets which may propel spacecraft and spaceplanes.
The engineering aspects of flight are the purview of aerospace engineering which is subdivided into aeronautics, the study of vehicles that travel through the atmosphere, and astronautics, the study of vehicles that travel through space, and ballistics, the study of the flight of projectiles.
Types of flight
Buoyant flight
Humans have managed to construct lighter-than-air vehicles that raise off the ground and fly, due to their buoyancy in the air.
An aerostat is a system that remains aloft primarily through the use of buoyancy to give an aircraft the same overall density as air. Aerostats include free balloons, airships, and moored balloons. An aerostat's main structural component is its envelope, a lightweight skin that encloses a volume of lifting gas to provide buoyancy, to which other components are attached.
Aerostats are so named because they use "aerostatic" lift, a buoyant force that does not require lateral movement through the surrounding air mass to effect a lifting force. By contrast, aerodynes primarily use aerodynamic lift, which requires the lateral movement of at least some part of the aircraft through the surrounding air mass.
Aerodynamic flight
Unpowered flight versus powered flight
Some things that fly do not generate propulsive thrust through the air, for example, the flying squirrel. This is termed gliding. Some other things can exploit rising air to climb such as raptors (when gliding) and man-made sailplane gliders. This is termed soaring. However most other birds and all powered aircraft need a source of propulsion to climb. This is termed powered flight.
Animal flight
The only groups of living things that use powered flight are birds, insects, and bats, while many groups have evolved gliding. The extinct pterosaurs, an order of reptiles contemporaneous with the dinosaurs, were also very successful flying animals, and there were apparently some flying dinosaurs (see Flying and gliding animals#Non-avian dinosaurs). Each of these groups' wings evolved independently, with insects the first animal group to evolve flight. The wings of the flying vertebrate groups are all based on the forelimbs, but differ significantly in structure; insect wings are hypothesized to be highly modified versions of structures that form gills in most other groups of arthropods.
Bats are the only mammals capable of sustaining level flight (see bat flight). However, there are several gliding mammals which are able to glide from tree to tree using fleshy membranes between their limbs; some can travel hundreds of meters in this way with very little loss in height. Flying frogs use greatly enlarged webbed feet for a similar purpose, and there are flying lizards which fold out their mobile ribs into a pair of flat gliding surfaces. "Flying" snakes also use mobile ribs to flatten their body into an aerodynamic shape, with a back and forth motion much the same as they use on the ground.
Flying fish can glide using enlarged wing-like fins, and have been observed soaring for hundreds of meters. It is thought that this ability was chosen by natural selection because it was an effective means of escape from underwater predators. The longest recorded flight of a flying fish was 45 seconds.
Most birds fly (see bird flight), with some exceptions. The largest birds, the ostrich and the emu, are earthbound flightless birds, as were the now-extinct dodos and the Phorusrhacids, which were the dominant predators of South America in the Cenozoic era. The non-flying penguins have wings adapted for use under water and use the same wing movements for swimming that most other birds use for flight. Most small flightless birds are native to small islands, and lead a lifestyle where flight would offer little advantage.
Among living animals that fly, the wandering albatross has the greatest wingspan, up to ; the great bustard has the greatest weight, topping at .
Most species of insects can fly as adults. Insect flight makes use of either of two basic aerodynamic models: creating a leading edge vortex, found in most insects, and using clap and fling, found in very small insects such as thrips.
Many species of spiders, spider mites and lepidoptera use a technique called ballooning to ride air currents such as thermals, by exposing their gossamer threads which gets lifted by wind and atmospheric electric fields.
Mechanical
Mechanical flight is the use of a machine to fly. These machines include aircraft such as airplanes, gliders, helicopters, autogyros, airships, balloons, ornithopters as well as spacecraft. Gliders are capable of unpowered flight. Another form of mechanical flight is para-sailing, where a parachute-like object is pulled by a boat. In an airplane, lift is created by the wings; the shape of the wings of the airplane are designed specially for the type of flight desired. There are different types of wings: tempered, semi-tempered, sweptback, rectangular and elliptical. An aircraft wing is sometimes called an airfoil, which is a device that creates lift when air flows across it.
Supersonic
Supersonic flight is flight faster than the speed of sound. Supersonic flight is associated with the formation of shock waves that form a sonic boom that can be heard from the ground, and is frequently startling. The creation of this shockwave requires a significant amount of energy; because of this, supersonic flight is generally less efficient than subsonic flight at about 85% of the speed of sound.
Hypersonic
Hypersonic flight is very high speed flight where the heat generated by the compression of the air due to the motion through the air causes chemical changes to the air. Hypersonic flight is achieved primarily by reentering spacecraft such as the Space Shuttle and Soyuz.
Ballistic
Atmospheric
Some things generate little or no lift and move only or mostly under the action of momentum, gravity, air drag and in some cases thrust. This is termed ballistic flight. Examples include balls, arrows, bullets, fireworks etc.
Spaceflight
Essentially an extreme form of ballistic flight, spaceflight is the use of space technology to achieve the flight of spacecraft into and through outer space. Examples include ballistic missiles, orbital spaceflight, etc.
Spaceflight is used in space exploration, and also in commercial activities like space tourism and satellite telecommunications. Additional non-commercial uses of spaceflight include space observatories, reconnaissance satellites and other Earth observation satellites.
A spaceflight typically begins with a rocket launch, which provides the initial thrust to overcome the force of gravity and propels the spacecraft from the surface of the Earth. Once in space, the motion of a spacecraft—both when unpropelled and when under propulsion—is covered by the area of study called astrodynamics. Some spacecraft remain in space indefinitely, some disintegrate during atmospheric reentry, and others reach a planetary or lunar surface for landing or impact.
Solid-state propulsion
In 2018, researchers at Massachusetts Institute of Technology (MIT) managed to fly an aeroplane with no moving parts, powered by an "ionic wind" also known as electroaerodynamic thrust.
History
Many human cultures have built devices that fly, from the earliest projectiles such as stones and spears, the
boomerang in Australia, the hot air Kongming lantern, and kites.
Aviation
George Cayley studied flight scientifically in the first half of the 19th century, and in the second half of the 19th century Otto Lilienthal made over 200 gliding flights and was also one of the first to understand flight scientifically. His work was replicated and extended by the Wright brothers who made gliding flights and finally the first controlled and extended, manned powered flights.
Spaceflight
Spaceflight, particularly human spaceflight became a reality in the 20th century following theoretical and practical breakthroughs by Konstantin Tsiolkovsky and Robert H. Goddard. The first orbital spaceflight was in 1957, and Yuri Gagarin was carried aboard the first crewed orbital spaceflight in 1961.
Physics
There are different approaches to flight. If an object has a lower density than air, then it is buoyant and is able to float in the air without expending energy. A heavier than air craft, known as an aerodyne, includes flighted animals and insects, fixed-wing aircraft and rotorcraft. Because the craft is heavier than air, it must generate lift to overcome its weight. The wind resistance caused by the craft moving through the air is called drag and is overcome by propulsive thrust except in the case of gliding.
Some vehicles also use thrust in the place of lift; for example rockets and Harrier jump jets.
Forces
Forces relevant to flight are
Propulsive thrust (except in gliders)
Lift, created by the reaction to an airflow
Drag, created by aerodynamic friction
Weight, created by gravity
Buoyancy, for lighter than air flight
These forces must be balanced for stable flight to occur.
Thrust
A fixed-wing aircraft generates forward thrust when air is pushed in the direction opposite to flight. This can be done in several ways including by the spinning blades of a propeller, or a rotating fan pushing air out from the back of a jet engine, or by ejecting hot gases from a rocket engine. The forward thrust is proportional to the mass of the airstream multiplied by the difference in velocity of the airstream. Reverse thrust can be generated to aid braking after landing by reversing the pitch of variable-pitch propeller blades, or using a thrust reverser on a jet engine. Rotary wing aircraft and thrust vectoring V/STOL aircraft use engine thrust to support the weight of the aircraft, and vector sum of this thrust fore and aft to control forward speed.
Lift
In the context of an air flow relative to a flying body, the lift force is the component of the aerodynamic force that is perpendicular to the flow direction. Aerodynamic lift results when the wing causes the surrounding air to be deflected - the air then causes a force on the wing in the opposite direction, in accordance with Newton's third law of motion.
Lift is commonly associated with the wing of an aircraft, although lift is also generated by rotors on rotorcraft (which are effectively rotating wings, performing the same function without requiring that the aircraft move forward through the air). While common meanings of the word "lift" suggest that lift opposes gravity, aerodynamic lift can be in any direction. When an aircraft is cruising for example, lift does oppose gravity, but lift occurs at an angle when climbing, descending or banking. On high-speed cars, the lift force is directed downwards (called "down-force") to keep the car stable on the road.
Drag
For a solid object moving through a fluid, the drag is the component of the net aerodynamic or hydrodynamic force acting opposite to the direction of the movement. Therefore, drag opposes the motion of the object, and in a powered vehicle it must be overcome by thrust. The process which creates lift also causes some drag.
Lift-to-drag ratio
Aerodynamic lift is created by the motion of an aerodynamic object (wing) through the air, which due to its shape and angle deflects the air. For sustained straight and level flight, lift must be equal and opposite to weight. In general, long narrow wings are able deflect a large amount of air at a slow speed, whereas smaller wings need a higher forward speed to deflect an equivalent amount of air and thus generate an equivalent amount of lift. Large cargo aircraft tend to use longer wings with higher angles of attack, whereas supersonic aircraft tend to have short wings and rely heavily on high forward speed to generate lift.
However, this lift (deflection) process inevitably causes a retarding force called drag. Because lift and drag are both aerodynamic forces, the ratio of lift to drag is an indication of the aerodynamic efficiency of the airplane. The lift to drag ratio is the L/D ratio, pronounced "L over D ratio." An airplane has a high L/D ratio if it produces a large amount of lift or a small amount of drag. The lift/drag ratio is determined by dividing the lift coefficient by the drag coefficient, CL/CD.
The lift coefficient Cl is equal to the lift L divided by the (density r times half the velocity V squared times the wing area A). [Cl = L / (A * .5 * r * V^2)] The lift coefficient is also affected by the compressibility of the air, which is much greater at higher speeds, so velocity V is not a linear function. Compressibility is also affected by the shape of the aircraft surfaces.
The drag coefficient Cd is equal to the drag D divided by the (density r times half the velocity V squared times the reference area A). [Cd = D / (A * .5 * r * V^2)]
Lift-to-drag ratios for practical aircraft vary from about 4:1 for vehicles and birds with relatively short wings, up to 60:1 or more for vehicles with very long wings, such as gliders. A greater angle of attack relative to the forward movement also increases the extent of deflection, and thus generates extra lift. However a greater angle of attack also generates extra drag.
Lift/drag ratio also determines the glide ratio and gliding range. Since the glide ratio is based only on the relationship of the aerodynamics forces acting on the aircraft, aircraft weight will not affect it. The only effect weight has is to vary the time that the aircraft will glide for – a heavier aircraft gliding at a higher airspeed will arrive at the same touchdown point in a shorter time.
Buoyancy
Air pressure acting up against an object in air is greater than the pressure above pushing down. The buoyancy, in both cases, is equal to the weight of fluid displaced - Archimedes' principle holds for air just as it does for water.
A cubic meter of air at ordinary atmospheric pressure and room temperature has a mass of about 1.2 kilograms, so its weight is about 12 newtons. Therefore, any 1-cubic-meter object in air is buoyed up with a force of 12 newtons. If the mass of the 1-cubic-meter object is greater than 1.2 kilograms (so that its weight is greater than 12 newtons), it falls to the ground when released. If an object of this size has a mass less than 1.2 kilograms, it rises in the air. Any object that has a mass that is less than the mass of an equal volume of air will rise in air - in other words, any object less dense than air will rise.
Thrust to weight ratio
Thrust-to-weight ratio is, as its name suggests, the ratio of instantaneous thrust to weight (where weight means weight at the Earth's standard acceleration ). It is a dimensionless parameter characteristic of rockets and other jet engines and of vehicles propelled by such engines (typically space launch vehicles and jet aircraft).
If the thrust-to-weight ratio is greater than the local gravity strength (expressed in gs), then flight can occur without any forward motion or any aerodynamic lift being required.
If the thrust-to-weight ratio times the lift-to-drag ratio is greater than local gravity then takeoff using aerodynamic lift is possible.
Flight dynamics
Flight dynamics is the science of air and space vehicle orientation and control in three dimensions. The three critical flight dynamics parameters are the angles of rotation in three dimensions about the vehicle's center of mass, known as pitch, roll and yaw (See Tait-Bryan rotations for an explanation).
The control of these dimensions can involve a horizontal stabilizer (i.e. "a tail"), ailerons and other movable aerodynamic devices which control angular stability i.e. flight attitude (which in turn affects altitude, heading). Wings are often angled slightly upwards- they have "positive dihedral angle" which gives inherent roll stabilization.
Energy efficiency
To create thrust so as to be able to gain height, and to push through the air to overcome the drag associated with lift all takes energy. Different objects and creatures capable of flight vary in the efficiency of their muscles, motors and how well this translates into forward thrust.
Propulsive efficiency determines how much energy vehicles generate from a unit of fuel.
Range
The range that powered flight articles can achieve is ultimately limited by their drag, as well as how much energy they can store on board and how efficiently they can turn that energy into propulsion.
For powered aircraft the useful energy is determined by their fuel fraction- what percentage of the takeoff weight is fuel, as well as the specific energy of the fuel used.
Power-to-weight ratio
All animals and devices capable of sustained flight need relatively high power-to-weight ratios to be able to generate enough lift and/or thrust to achieve take off.
Takeoff and landing
Vehicles that can fly can have different ways to takeoff and land. Conventional aircraft accelerate along the ground until sufficient lift is generated for takeoff, and reverse the process for landing. Some aircraft can take off at low speed; this is called a short takeoff. Some aircraft such as helicopters and Harrier jump jets can take off and land vertically. Rockets also usually take off and land vertically, but some designs can land horizontally.
Guidance, navigation and control
Navigation
Navigation is the systems necessary to calculate current position (e.g. compass, GPS, LORAN, star tracker, inertial measurement unit, and altimeter).
In aircraft, successful air navigation involves piloting an aircraft from place to place without getting lost, breaking the laws applying to aircraft, or endangering the safety of those on board or on the ground.
The techniques used for navigation in the air will depend on whether the aircraft is flying under the visual flight rules (VFR) or the instrument flight rules (IFR). In the latter case, the pilot will navigate exclusively using instruments and radio navigation aids such as beacons, or as directed under radar control by air traffic control. In the VFR case, a pilot will largely navigate using dead reckoning combined with visual observations (known as pilotage), with reference to appropriate maps. This may be supplemented using radio navigation aids.
Guidance
A guidance system is a device or group of devices used in the navigation of a ship, aircraft, missile, rocket, satellite, or other moving object. Typically, guidance is responsible for the calculation of the vector (i.e., direction, velocity) toward an objective.
Control
A conventional fixed-wing aircraft flight control system consists of flight control surfaces, the respective cockpit controls, connecting linkages, and the necessary operating mechanisms to control an aircraft's direction in flight. Aircraft engine controls are also considered as flight controls as they change speed.
Traffic
In the case of aircraft, air traffic is controlled by air traffic control systems.
Collision avoidance is the process of controlling spacecraft to try to prevent collisions.
Flight safety
Air safety is a term encompassing the theory, investigation and categorization of flight failures, and the prevention of such failures through regulation, education and training. It can also be applied in the context of campaigns that inform the public as to the safety of air travel.
See also
Aerodynamics
Levitation
Transvection (flying)
Backward flying
References
Notes
Bibliography
Coulson-Thomas, Colin. The Oxford Illustrated Dictionary. Oxford, UK: Oxford University Press, 1976, First edition 1975, .
French, A. P. Newtonian Mechanics (The M.I.T. Introductory Physics Series) (1st ed.). New York: W. W. Norton & Company Inc., 1970.
Honicke, K., R. Lindner, P. Anders, M. Krahl, H. Hadrich and K. Rohricht. Beschreibung der Konstruktion der Triebwerksanlagen. Berlin: Interflug, 1968.
Sutton, George P. Oscar Biblarz. Rocket Propulsion Elements. New York: Wiley-Interscience, 2000 (7th edition). .
Walker, Peter. Chambers Dictionary of Science and Technology. Edinburgh: Chambers Harrap Publishers Ltd., 2000, First edition 1998. .
External links
History and photographs of early aeroplanes etc.
'Birds in Flight and Aeroplanes' by Evolutionary Biologist and trained Engineer John Maynard-Smith Freeview video provided by the Vega Science Trust.
Aerodynamics
Sky | Flight | Physics,Chemistry,Engineering | 4,272 |
32,603,552 | https://en.wikipedia.org/wiki/Typhula%20quisquiliaris | Typhula quisquiliaris, commonly known as the bracken club, is a species of club fungus in the family Typhulaceae. It produces small, white fruit bodies up to in height, each with a single distinct "head" and "stem". The head is fertile, while the stem attaches to a sclerotium embedded in the substrate. The fruit bodies grow from dead wood, and strongly favours bracken, where the species feeds saprotrophically. Though T. quisquiliaris was described under a different name by James Sowerby in 1803, the specific name quisquiliaris was sanctioned in 1821 by Elias Magnus Fries, and the species was moved to the genus Typhula, which resulted in its currently accepted binomial name by Paul Christoph Hennings in 1896. The species has been recorded in Europe and north Africa.
Taxonomy
Typhula quisquiliaris was first described by James Sowerby in 1803 as Clavaria obtusa. However, this name was found to be illegitimate, as it had already been given to a different species by Christiaan Hendrik Persoon in 1797. The species was given its sanctioned name several years later by Elias Magnus Fries, in his 1821 Systema Mycologicum. Fries named the species Pistillaria quisquiliaris, having previously (in 1818) named it Clavaria quisquiliaris. The specific name quisquiliaris is from the Latin meaning "pertaining to refuse". In the same year, Samuel Frederick Gray reclassified Sowerby's Clavaria obtusa, naming it Geoglossum obtusum. Fries's name was taken up as the valid one, however, and in 1896, Paul Christoph Hennings transferred the species to Typhula, giving the species the name by which it is known today. However, the name Pistillaria quisquiliaris was sometimes used into the 20th century. For instance, Carleton Rea used it in a 1922 publication. The species is commonly known as the bracken club.
Description
Typhula quisquiliaris produces fruit bodies in the form of clubs. Each fruit body consists of a single distinct "stem" and "head", and measures up to in height. The surface of the head is smooth and white, and measures by . The rounded stem is infertile, and of a similar colour to the head. However, it has a very fine downy covering, and is somewhat translucent. The stem measures from in width. The stem attaches to sclerotium which is buried into the branch from which the fruit body grows.
Microscopic characteristics
Typhula quisquiliaris spores are narrowly ellipsoid, and measure from 9 to 14 by 4 to 5.5 micrometres (μm). The spores are white, and contain small granules. The spores are borne on basidia which measure 50 to 70 by 7 to 8 μm, with four spores on each basidium. The downy covering of the stem is made up of thick-walled hairs, each measuring 15 to 60 by 3 to 7 μm, though they are often swollen towards the base. The sclerotium measures from 1.5 to 3 by 0.5 μm, and is a pale yellow colour. Clamp connections are present in the hyphae.
Habitat and distribution
Typhula quisquiliaris fruit bodies are typically found in rows, growing from plant detritus. The species favours bracken, especially Pteridium aquilinum, but the colonisation of dead matter from other plants is not unknown. Upon these substrates, it feeds as a saprotroph, breaking down the dead organic matter in order to sustain itself. The species has been recorded in Europe and northern Africa. In Europe, the fruit bodies can be encountered from April to December.
References
Typhulaceae
Fungi of Europe
Fungi of Africa
Fungi described in 1886
Taxa named by Elias Magnus Fries
Fungus species | Typhula quisquiliaris | Biology | 834 |
23,389,157 | https://en.wikipedia.org/wiki/Wirecast | Wirecast is a live video streaming production tool by Telestream. It allows users to create live or on-demand broadcasts for the web.
Wirecast is a software video switcher, controlling real-time switching between multiple live video cameras, while dynamically mixing in other source media, such as QuickTime movies, music, audio and slides to create professional broadcast productions for live or on-demand distribution on the web.
Specifications
Can broadcast to multiple services at once
Support for multiple cameras
Chroma key (blue/green screen)
Scene transitions
Built-in lower-third titling
Desktop Presenter - makes Macintosh or Windows Desktop available as a source
H.264
3D Graphics
QuickTime Streaming Server Support
Keynote Integration
Multiple Layers
Multiple Broadcast Support, when ready to go live, it provides direct integration with a number of streaming service providers.
A direct integration with Limelight Networks, adds support for Flash streaming
Adds a built-in streaming service access from Ustream.
Encoding support for Nvidia NVENC and Intel Quick Sync Video
Support for Network Device Interface
Rendezvous Videoconferencing feature allows users to bring in live video feeds from multiple sources, including remote locations.
References
External links
Streaming media systems
Classic Mac OS software
Windows multimedia software
MacOS multimedia software
Livestreaming software | Wirecast | Technology | 256 |
18,379 | https://en.wikipedia.org/wiki/Linear%20timecode | Linear (or Longitudinal) Timecode (LTC) is an encoding of SMPTE timecode data in an audio signal, as defined in SMPTE 12M specification. The audio signal is commonly recorded on a VTR track or other storage media. The bits are encoded using the biphase mark code (also known as FM): a 0 bit has a single transition at the start of the bit period. A 1 bit has two transitions, at the beginning and middle of the period. This encoding is self-clocking. Each frame is terminated by a 'sync word' which has a special predefined sync relationship with any video or film content.
A special bit in the linear timecode frame, the biphase mark correction bit, ensures that there are an even number of AC transitions in each timecode frame.
The sound of linear timecode is a jarring and distinctive noise and has been used as a sound-effects shorthand to imply telemetry or computers.
Generation and Distribution
In broadcast video situations, the LTC generator should be tied into house black burst, as should all devices using timecode, to ensure correct color framing and correct synchronization of all digital clocks. When synchronizing multiple clock-dependent digital devices together with video, such as digital audio recorders, the devices must be connected to a common word clock signal that is derived from the house black burst signal. This can be accomplished by using a generator that generates both black burst and video-resolved word clock, or by synchronizing the master digital device to video, and synchronizing all subsequent devices to the word clock output of the master digital device (and to LTC).
Made up of 80 bits per frame, where there may be 24, 25 or 30 frames per second, LTC timecode varies from 960 Hz (binary zeros at 24 frames/s) to 2400 Hz (binary ones at 30 frames/s), and thus is comfortably in the audio frequency range. LTC can exist as either a balanced or unbalanced signal, and can be treated as an audio signal in regards to distribution. Like audio, LTC can be distributed by standard audio wiring, connectors, distribution amplifiers, and patchbays, and can be ground-isolated with audio transformers. It can also be distributed via 75 ohm video cable and video distribution amplifiers, although the voltage attenuation caused by using a 75 ohm system may cause the signal to drop to a level that can not be read by some equipment.
Care has to be taken with analog audio to avoid audible 'breakthrough' (aka "crosstalk") from the LTC track to the audio tracks.
LTC care:
Avoid percussive sounds close to LTC
Never process an LTC with noise reduction, eq or compressor
Allow pre roll and post roll
To create negative time code add one hour to time (avoid midnight effect)
Always put slowest device as a master
Longitudinal SMPTE timecode should be played back at a middle-level when recorded on an audio track, as both low and high levels will introduce distortion.
Longitudinal timecode data format
The basic format is an 80-bit code that gives the time of day to the second, and the frame number within the second. Values are stored in binary-coded decimal, least significant bit first.
There are thirty-two bits of user data, usually used for a reel number and date.
Bit 10 is set to 1 if drop frame numbering is in use; frame numbers 0 and 1 are skipped during the first second of every minute, except multiples of 10 minutes. This converts 30 frame/second time code to the 29.97 frame/second NTSC standard.
Bit 11, the color framing bit, is set to 1 if the time code is synchronized to a color video signal. The frame number modulo 2 (for NTSC and SECAM) or modulo 4 (for PAL) should be preserved across cuts in order to avoid phase jumps in the chrominance subcarrier.
Bits 27, 43, and 59 differ between 25 frame/s time code, and other frame rates (30, 29.97, or 24). The bits are:
"Polarity correction bit" (bit 59 at 25 frame/s, bit 27 at other rates): this bit is chosen to provide an even number of 0 bits in the whole frame, including the sync code. (Since the frame is an even number of bits long, this implies an even number of 1 bits, and is thus an even parity bit. Since the sync code includes an odd number of 1 bits, it is an odd parity bit over the data.) This keeps the phase of each frame consistent, so it always starts with a rising edge at the beginning of bit 0. This allows seamless splicing of different time codes, and lets it be more easily read with an oscilloscope.
"Binary group flag" bits BGF0 and BGF2 (bits 27 and 43 at 25 frame/s, bits 43 and 59 at other rates): these indicate the format of the user bits. Both 0 indicates no (or unspecified) format. Only BGF0 set indicates four 8-bit characters (transmitted little-endian). The combinations with BGF2 set are reserved.
Bit 58, unused in earlier versions of the specification, is now defined as "binary group flag 1" and indicates that the time code is synchronized to an external clock. if zero, the time origin is arbitrary.
The sync pattern in bits 64 through 79 includes 12 consecutive 1 bits, which cannot appear anywhere else in the time code. Assuming all user bits are set to 1, the longest run of 1 bits that can appear elsewhere in the time code is 10, bits 9 to 18 inclusive.
The sync pattern is preceded by 00 and followed by 01. This is used to determine whether an audio tape is running forward or backward.
See also
Vertical interval timecode
Burnt-in timecode
MIDI timecode
CTL timecode
AES-EBU embedded timecode
Rewritable consumer timecode
VTR
Manchester code
Biphase mark code
References
External links
LGPL library to en/decode LTC in software
Broadcast engineering
Electrical engineering
Timecodes
Recording devices
Film and video technology | Linear timecode | Technology,Engineering | 1,287 |
1,891,018 | https://en.wikipedia.org/wiki/Chris%20Crawford%20on%20Game%20Design | Chris Crawford on Game Design () is a book about computer and video game design by Chris Crawford. Although initially intended to be the second edition of The Art of Computer Game Design, the publisher decided, because it was a considerable expansion on the previous book, it should be considered a wholly new work. It was published by Peachpit under the New Riders imprint in 2003. It includes Crawford's response to recent game developments, such as The Sims, and dedicates a chapter to each of his first 14 published games: Tanktics, Legionnaire, Wizard, Energy Czar, Scram, Eastern Front (1941), Gossip, Excalibur, Balance of Power, Patton Versus Rommel, Siboot, The Global Dilemma: Guns & Butter, Balance of the Planet and Patton Strikes Back.
See also
List of books on computer and video games
People games
References
External links
Peachpit's catalog entry for Chris Crawford on Game Design
Chris Crawford on Game Design on Google Book Search
2003 non-fiction books
Books about video games | Chris Crawford on Game Design | Technology | 209 |
15,942,369 | https://en.wikipedia.org/wiki/Fugacity%20capacity | The fugacity capacity constant (Z) is used to help describe the concentration of a chemical in a system (usually in mol/m3Pa). Hemond and Hechner-Levy (2000) describe how to utilize the fugacity capacity to calculate the concentration of a chemical in a system. Depending on the chemical, fugacity capacity varies. The concentration in media 'm' equals the fugacity capacity in media 'm' multiplied by the fugacity of the chemical.
For a chemical system at equilibrium, the fugacity of the chemical will be the same in each media/phase/compartment. Therefore equilibrium is sometimes called "equifugacity" in the context of these calculations.
where Z is a proportional constant, termed fugacity capacity. This equation does not necessarily imply that C and f are always linearly related. Non-linearity can be accommodated by allowing Z to vary as a function of C or f.
For a better understanding of the fugacity capacity concept, heat capacity may provide a precedent for introducing Z as a capacity of a phase to absorb particular quantity of chemical. However, phases with high fugacity capacity do not necessarily retain high fugacity.
In calculations of fugacity capacity key factors would be (a) the nature of the solute (chemical), (b) the nature of the medium or compartment, (c) temperature.
Expressions for fugacity capacity
The expression for Zm is dependent on the media/phase/compartment. The following list gives the fugacity capacities for common medias:
Air (under ideal gas assumptions): Zair = 1/RT
Water: Zwater = 1/H
Octanol: Zoct = Kow/H
Pure phase of target chemical: Zpure = 1/Psv
Where: R is the Ideal gas constant (8.314 Pa·m3/mol·K); T is the absolute temperature (K); H is the Henry's law constant for the target chemical (Pa/m3mol); Kow is the octanol-water partition coefficient for the target chemical (dimensionless ratio); Ps is the vapor pressure of the target chemical (Pa); and v is the molar volume of the target chemical (m3/mol).
Notice that the ratio between Z-values for different media (e.g. octanol and water) is the same as the ratio between the concentrations of the target chemical in each media at equilibrium.
When using a fugacity capacity approach to calculate the concentrations of a chemical in each of several medias/phases/compartments, it is often convenient to calculate the prevailing fugacity of the system using the following equation if the total mass of target chemical (MT) and the volume of each compartment (Vm) are known:
Alternatively, if the target chemical is present as a pure phase at equilibrium, its vapor pressure will be the prevailing fugacity of the system.
See also
Multimedia fugacity model
References
Chemical thermodynamics
Environmental chemistry
Equilibrium chemistry | Fugacity capacity | Chemistry,Environmental_science | 630 |
14,033,442 | https://en.wikipedia.org/wiki/Plasma%20Sources%20Science%20and%20Technology | Plasma Sources Science and Technology is an international journal dedicated solely to non-fusion aspects of plasma science.
The journal is indexed in Scopus, INSPEC Information Services, ISI (SciSearch, ISI Alerting Services, Current Contents/Physical, Chemical and Earth Sciences), Chemical Abstracts, INIS Atomindex (International Nuclear Information System), NASA Astrophysics Data System, PASCAL Database, Article@INIST, Engineering Index/Ei Compendex, Cambridge Scientific Abstracts (Environmental Engineering Abstracts, Bioengineering Abstracts), and VINITI Abstracts Journal.
Editors in Chief
External links
Plasma Sources Science and Technology website
IOP Publishing
Plasma science journals
IOP Publishing academic journals | Plasma Sources Science and Technology | Physics | 142 |
55,765,801 | https://en.wikipedia.org/wiki/C14H13N3O5S | {{DISPLAYTITLE:C14H13N3O5S}}
The molecular formula C14H13N3O5S (molar mass: 335.335 g/mol, exact mass: 335.0576 u) may refer to:
Isoxicam
Sulfanitran
Molecular formulas | C14H13N3O5S | Physics,Chemistry | 67 |
33,813,121 | https://en.wikipedia.org/wiki/Network%20controllability | Network controllability concerns the structural controllability of a network. Controllability describes our ability to guide a dynamical system from any initial state to any desired final state in finite time, with a suitable choice of inputs. This definition agrees well with our intuitive notion of control. The controllability of general directed and weighted complex networks has recently been the subject of intense study by a number of groups in wide variety of networks, worldwide. Recent studies by Sharma et al. on multi-type biological networks (gene–gene, miRNA–gene, and protein–protein interaction networks) identified control targets in phenotypically characterized Osteosarcoma showing important role of genes and proteins responsible for maintaining tumor microenvironment.
Background
Consider the canonical linear time-invariant dynamics on a complex network
where the vector captures the state of a system of nodes at time . The
matrix describes the system's wiring diagram and the interaction strength between the components. The matrix identifies the nodes controlled by an outside controller. The system is controlled through the time dependent input vector that the controller imposes on the system. To identify the minimum number of driver nodes, denoted by , whose control is sufficient to fully control the system's dynamics, Liu et al. attempted to combine the tools from structural control theory, graph theory and statistical physics. They showed that the minimum number of inputs or driver nodes needed to maintain full control of the network is determined by the maximum-cardinality matching in the network. From this result, an analytical framework, based on the in–out degree distribution, was developed to predict for scale-free and Erdős–Rényi random graphs. However, more recently it has been demonstrated that network controllability (and other structure-only methods that use exclusively the connectivity of a graph, , to simplify the underlying dynamics), both undershoot and overshoot the number and which sets of driver nodes best control network dynamics, highlighting the importance of redundancy (e.g. canalization) and non-linear dynamics in determining control.
It is also notable that Liu's et al. formulation would predict same values of for a chain graph and for a weak densely connected graph. Obviously, both these graphs have very different in and out degree distributions. A recent unpublished work questions whether degree, which is a purely local measure in networks, would completely describe controllability and whether even slightly distant nodes would have no role in deciding network controllability. Indeed, for many real-word networks, namely, food webs, neuronal and metabolic networks, the mismatch in values of and calculated by Liu et al. is notable. If controllability is decided mainly by degree, why are and so different for many real world networks? They argued (arXiv:1203.5161v1) that this might be due to the effect of degree correlations. However, it has been shown that network controllability can be altered only by using betweenness centrality and closeness centrality, without using degree (graph theory) or degree correlations at all.
Structural controllability
The concept of the structural properties was first introduced by Lin (1974) and then extended by Shields and Pearson (1976) and alternatively derived by Glover and Silverman (1976). The main question is whether the lack of controllability or observability are generic with respect to the variable system parameters. In the framework of structural control the system parameters are either independent free variables or fixed zeros. This is consistent for models of physical systems since parameter values are never known exactly, with the exception of zero values which express the absence of interactions or connections.
Maximum matching
In graph theory, a matching is a set of edges without common vertices. Liu et al. extended this definition to directed graph, where a matching is a set of directed edges that do not share start or end vertices. It is easy to check that a matching of a directed graph composes of a set of vertex-disjoint simple paths and cycles. The maximum matching of a directed network can be efficiently calculated by working in the bipartite representation using the classical Hopcroft–Karp algorithm, which runs in O(E) time in the worst case. For undirected graph, analytical solutions of the size and number of maximum matchings have been studied using the cavity method developed in statistical physics. Liu et al. extended the calculations for directed graph.
By calculating the maximum matchings of a wide range of real networks, Liu et al. asserted that the number of driver nodes is determined mainly by the networks degree distribution . They also calculated the average number of driver nodes for a network ensemble with arbitrary degree distribution using the cavity method. It is interesting that for a chain graph and a weak densely connected graph, both of which have very different in and out degree distributions; the formulation of Liu et al. would predict same values of . Also, for many real-word networks, namely, food webs, neuronal and metabolic networks, the mismatch in values of and calculated by Liu et al. is notable. If controllability is decided purely by degree, why are and so different for many real world networks? It remains open to scrutiny whether "control robustness" in networks is influenced more by using betweenness centrality and closeness centrality over degree-based metrics.
While sparser graphs are more difficult to control, it would obviously be interesting to find whether betweenness centrality and closeness centrality or degree heterogeneity plays a more important role in deciding controllability of sparse graphs with almost-similar degree distributions.
Control of composite quantum systems and algebraic graph theory
A control theory of networks has also been developed in the context of universal control for composite quantum systems, where subsystems and their interactions are associated to nodes and links, respectively. This framework permits formulation of Kalman's criterion with tools from algebraic graph theory via the minimum rank of a graph and related notions.
See also
Controllability Gramian
References
External links
The network controllability project website
The video showing network controllability
Network theory
Control theory | Network controllability | Mathematics | 1,245 |
56,749,646 | https://en.wikipedia.org/wiki/McNary%20Levee%20System | The McNary Levee System, also known as the Tri-Cities Levees, is an appurtenant or dam-related structure to McNary Lock and Dam, and consists of three groups of levee segments along the banks of the Columbia River that provide flood risk reduction for portions of Kennewick, Pasco, and Richland, Washington. The levee group names are based on location and are identified as the Kennewick Levees, Pasco Levees, and Richland Levees. Lake Wallula behind McNary Lock and Dam is about 63 miles long and includes 242 miles of shoreline and a drainage area of 214,000 square miles. The McNary Levee System consists of about 16.8 miles of earthen levees and 11 operational pump plants that remove agricultural runoff, groundwater migration, and rainfall runoff. Construction of the McNary Levee System began in 1950 and was completed in 1954.
References
Buildings and structures in Benton County, Washington
1954 establishments in Washington (state)
United States Army Corps of Engineers
Buildings and structures in Franklin County, Washington
Richland, Washington
Kennewick, Washington
Pasco, Washington | McNary Levee System | Engineering | 231 |
4,549,998 | https://en.wikipedia.org/wiki/Flower%20induction | Flower induction is the physiological process in the plant by which the shoot apical meristem becomes competent to develop flowers. Biochemical changes at the apex, particularly those caused by cytokinins, accompany this process. Usually flower induction is followed by flower differentiation, with some notable exceptions such as in kiwifruit, where the two processes are separated. Flower induction can be reversed, but flower differentiation is irreversible, because anatomical changes are in place.
References
Plant physiology | Flower induction | Biology | 98 |
2,846,545 | https://en.wikipedia.org/wiki/Ancient%20monument | An ancient monument can refer to any early or historical manmade structure or architecture. Certain ancient monuments are of cultural importance for nations and become symbols of international recognition, including the ruins of Baalbek on Lebanese currency, the Angkor Wat on Cambodian currency and the Great Wall of China on the Chinese currency. There are some countries that display ancient buildings as symbols on their coats of arms as a way to affirm national identity. In this way, ancient monuments in the modern world are used as icons to represent a country. The importance of ancient monuments extends to cultural heritage and how the people of a nation or city identify themselves.
In British law, an ancient monument is an early historical structure or monument (e.g. an archaeological site) worthy of preservation and study due to archaeological or heritage interest. The Ancient Monuments and Archaeological Areas Act 1979 classified ancient monuments as "scheduled monuments" or monuments that are considered by the Secretary of State of archaeological, historical or artistic importance.
Historical significance and cultural heritage
National identity and iconography
Since the eighteenth and nineteenth centuries, with the rise of nationalism, part of the nation-building process was the construction of a national past. This past comprised a collection of legends, traditions and myths. In Europe's emerging nations, ruins and relics became the centre of attention for group consciousness and national aspirations, which became an important motivation for the emergence of a preservation movement. This was because many buildings, landscapes and monuments achieved a great level of significance as symbols and icons of a growing nation. As such, these buildings and landscapes became national monuments, which possessed new meanings given the emergence of nationhood. Light and Dumbraveanu-Andone assert that the connection between heritage and national identity continues to be important. This is also evident in national identity related to an awareness of national heritage that is still visible around the world.
Archaeology
The emergence of the discipline of archaeology was linked to the rise of nationalism. It was often emphasised to be used in service of the nation-state to reinforce its historical and territorial legitimacy. Archaeology as a culture-historical discipline is the study and preservation of remains from past societies and their environments. In this, the past is studied through preserving its sources including landscape (ancient monuments or heritage sites) and physical artefacts. The preservation and restoration are important for all heritage sites, particularly at locations of ancient monuments and archaeological areas that are in dangerous or delicate conditions.
Preservation and care
To protect, preserve and care for ancient monuments, there were a number of laws and Acts passed during the late nineteenth and twentieth century. These included Ancient Monuments Protection Act of 1882 and Ancient Monuments and Archaeological Areas Act 1979. The aforementioned was passed after several unsuccessful attempts, which ensured governmental involvement in England and Ireland to legally preserve and conserve ancient monuments. Following this, in 1913, the Ancient Monuments Consolidation and Amendment Act provided an extension to the existing powers by introducing a concept known as the Preservation Orders. This enabled monuments in threat of damage or removal from neglectful treatment to be classified under the protection of the Commissioners of Works. The most significant was Section 6.2, which qualified the monuments as national importance and were to be preserved. Additionally, any ancient monument could be considered for inclusion on that list, not just those in the Guardian of the State, and this meant that for the first time legislative protection could officially be applied on a large scale. It was as a result of this that Guardianship Monuments were distinguished to what later became defined as "Scheduled Monuments".
Furthermore, the Ancient Monuments Act 1931 extended its protection policies around previous monuments, including the scheduled monuments on the list, through introducing a notification system. As part of this system, monument owners had to provide the Commissioners of Works three months' notice in writing of any works affecting the monument, which remained in use until 1979. During the 1930s and 1940s, there were a number of background strategies by various organisations concerned with ancient monuments. In the immediate aftermath of the Second World War, a committee was established to look into the existing state and future direction of archaeological work in Britain. This resulted in the publication of A Survey and policy of field research in the archaeology of Great Britain and from this, more information about the past to fill gaps in knowledge.
Historic Building and Ancient Monuments Act 1953
Field Monuments Act 1972
Ancient Monuments and Archaeological Areas Act 1979: This Act consolidated and strengthen previous legislation made in relation to all types of ancient monuments. In addition to this, a Scheduled Monument Consent system was implemented instead of the notification procedure as outlined previously.
Modern preservation
The modern preservation techniques consist of physical planning and zoning. Physical planning at archaeological sites around ancient monuments help direct the vehicle and pedestrian traffic from sensitive areas. Additionally, zoning is a key principle of physical planning at monumental sites. It refers to the physical development and protection of sites in various zones of contact or distance from important resources. Zoning also enables certain amenities and visitor services to be managed in an effective manner. There are several approaches to physical planning and zoning at historic monuments. As each site has its own unique environmental concerns and needs, zoning may vary from one to two zones or at times, several zones to protect and manage the area.
Issues that ancient monuments such as historical buildings face can be linked to internal and external environmental factors. This include the new changes that can add improvements to the interior of the building can also lead to new factors that cause decay. The example Feilden used was of traditional and historical building construction "breathes" are useful as it enables the "easy passage of moisture vapor". In these cases, vapour checks and monitoring the environmental factors for balance is required. Other modern methods include preventive maintenance through acts such as the reduction of traffic vibration or air pollution through town planning controls. As a maintenance strategy, this conservative activity is considered as an important protective method without intervention.
Tourism
Heritage tourism
Following the mass decolonisation period post World War II, identity through remains, the past and landscapes became more common and global tourism exponentially increased. With the rise of globalisation, tourism has grown to become a type of commodity during the twenty-first century with new places and elements to discover. In addition to this, the exoticism and romanticism around experiencing other "more authentic" cultures have contributed to heritage and cultural tourism. As a result, ancient monuments are linked to heritage tourism because of the cultural and national aspect that the monuments embody. Heritage tours comprise a number of types including religious tourism and patriotic tourism. In the case of ancient monuments, both types of heritage tourism apply.
Religious tourism
The concept of religious heritage tourism has been around for several centuries. According to Bond, Packer and Ballantyne, people have their own purpose and motives for visiting a religious heritage site or location. This included five key factors; to find spiritual and emotional connection, to discover new things, to engage mentally, to interact or belong as well as searching for peace to relax. Religious site tourism is also linked to pilgrimage as well as paying a visit to sites such as the Uluru in Australia, the Western Wall, the Church of the Holy Sepulchre and the Dome of the Rock in the Old City of Jerusalem. All these sites are considered to be ancient monuments as they are of historical and cultural importance.
Patriotic tourism
Tourism that are attached to nationalistic or patriotic sentiments is another type of heritage tourism. In the modern context, post World War I and World War II, certain places and sites and being claimed as nationalistic sites that patriotic tourists visit for the purpose of reclaiming and reaffirming their heritage and national identity. Such sites include the forts and castles of Ghana, the ANZAC Cove and the Great Wall of China. These types of ancient monuments fall under the category of national and historical importance. They are associated with culturally driven tourism linking to the colonial and violent past of nations that have become symbols of cultural reaffirmation and awakening.
Archaeological tourism
Whilst certain types of tourism can negatively impact the sustainability of historical and ancient sites, archaeological tourists have led to the conservation and maintenance of ancient monuments. All archaeological disciplines apply the same types of methods and one includes the study of the physical artefact or site. In the modern world, most archaeologists are involved in excavations to rescue and preserve archaeological traces that can be damaged from activities such as housing, road-building, natural gas pipelines or airports. Cultural heritage plays an important role with globalization and increasing ethnic recognition and thus, this type of management is significant. As such, archaeologists are taking care of several ancient monuments and historical sites, and with the growth of tourism, this has become more vital and is defined as "heritage management".
Archaeologists alongside to architects help preserve what other specialists, including art historians, cultural geographers, or ethnologists, study. These may include medieval churches, monolithic monuments or ancient relics, stupas or paintings. For example, the study of the concept of "dying culture" refers to a part or portion of a living, an existing culture that has older origins, however, is still in use. In this case, preservation of traditional objects, artefacts and monuments through archaeological study is both important for ancient monuments and the tourism industry.
Examples of archaeological excavation that are classified as ancient monuments:
Moai Statues Easter Island, Chile
Chichen Itza, Mexico
Tikal, Guatemala
Acropolis of Athens, Greece
Giza Pyramids, Egypt
Ancient Petra, Jordan
Other categories of tourists
Journalists
Students studying certain sites
Volunteers
Community leaders and politicians
Types of ancient monuments
Megalithic monuments: Large and rough stones that are arranged in place and preserved for several centuries. These ancient monuments are some of the oldest prehistoric monuments found in a range of countries around the world. Notable examples include Stonehenge on Salisbury Plain, England; Avebury circle near Stonehenge; Chun Quoit; and Uluru in Australia.
Palaces and castles: These types of monuments are of historical and national importance as some are symbols of their countries.
Pyramid: A significant example is the Giza Pyramids of ancient Egypt, which were constructed to revere the Pharaoh.
Sculptural monuments and mosaics: Some ancient monuments such as temples include stone relief sculptures and mosaics. From these ancient monuments, such as the temple of Parthenon, included sculptures that are found in museums like the Louvre and the British Museum.
Temple: There are many temples around the world that are classified as ancient monuments and world heritage sites. Somes examples include the Temple of Anahita, Kangavar in Iran, several Ancient Greek temples and Megalithic Temples of Malta.
Mosque: Early Islamic architecture included elaborate patterns. Some notable examples include the Great Mosque of Damascus (Umayyad Mosque), Masjid Al-Aqsa (Dome of the Rock) and the Tunisian Great Mosque of Kairouan.
Tomb: Some examples include Mughal emperors tombs such as the tomb of Aurangzeb and Akbar's tomb as well as the Pharaoh Tutankhamun's tomb.
See also
English Heritage
Historic preservation
Scheduled monument
Monument
References
External links
National Heritage List for England: official list of scheduled ancient monuments in England
Types of monuments and memorials
Architectural history
Cultural heritage
National identity
Cultural tourism | Ancient monument | Engineering | 2,237 |
7,474,528 | https://en.wikipedia.org/wiki/Pandora%20FMS | Pandora FMS (for Pandora Flexible Monitoring System) is software for monitoring computer networks. Pandora FMS allows monitoring in a visual way the status and performance of several parameters from different operating systems, servers, applications and hardware systems such as firewalls, proxies, databases, web servers or routers.
Pandora FMS can be deployed in almost any operating system. It features remote monitoring (WMI, SNMP, TCP, UDP, ICMP, HTTP...) and it can also use agents. An agent is available for each platform. It can also monitor hardware systems with a TCP/IP stack, such as load balancers, routers, network switches, printers or firewalls.
Pandora FMS has several servers that process and get information from different sources, using WMI for gathering remote Windows information, a predictive server, a plug-in server which makes complex user-defined network tests, an advanced export server to replicate data between different sites of Pandora FMS, a network discovery server, and an SNMP Trap console.
Released under the terms of the GNU General Public License, Pandora FMS is free software. At first the project was hosted on SourceForge.net, from where it has been downloaded over one million times, and selected the “Staff Pick” Project of the Month, June 2016, and elected “Community Choice” Project of the Month, November 2017.
Components
Pandora Server
In Pandora FMS architecture, servers are the core of the system because they are the recipients of bundles of information. They also generate monitoring alerts. It is possible to have different modular configurations for the servers: several servers for very big systems, or just a single server. Servers are also responsible for inserting the gathered data into Pandora's database. It is possible to have several Pandora Servers connected to a single Database. Different servers are used for different kind of monitoring: remote monitoring, WMI monitoring, SNMP and other network monitoring, inventory recollection, etc. Highly scalable (up to 2000 nodes with one single server), completely web-driven and a multitenant interface. It has a very flexible ACL system and a lot of graphical reports and user-defined control screens.
Servers are developed in Perl and work on any platform that has the required modules. Pandora was originally developed for
Web console
Pandora's user interface allows people to operate and manage the monitoring system. It is developed in PHP and depends on a database and a web server. It can work in a wide range of platforms: Linux, Solaris, Windows, AIX and others. Several web consoles can be deployed in the same system if required. Web Console has multiples choices, in example SNMP monitoring.
Agents
Agents are daemons or services that can monitor any numeric parameter, Boolean status, string or numerical incremental data and/or condition. They can be developed in any language (as Shellscript, WSH, Perl or C). They run on any type of platform (Microsoft, AIX, Solaris, Linux, IPSO, Mac OS or FreeBSD), also SAP, because the agents can communicate with the Pandora FMS Servers to send data in XML using SSH, FTP, NFS, Tentacle (protocol) or any data transfer means.
Database
The database module is the core module of Pandora. All the information of the system resides here. For example, all data gathered by agents, configuration defined by administrator, events, incidents, audit info, etc. are stored in the database. At present, MySQL database and MariaDB database is supported. Oracle support has been added in 6.0 release.
Software appliances
Pandora FMS has a software appliance based on a customized CentOS Linux, installable on CD, comes ready to use (including a live CD) or ready to install to hard disk.
It have also an AMI Appliance based on Amazon AWS.
A Docker image is also available at Docker Hub.
See also
Comparison of network monitoring systems
Data logging
References
External links
Free network-related software
Free software programmed in Perl
Multi-agent systems
Free network management software
System monitors | Pandora FMS | Engineering | 855 |
76,444,788 | https://en.wikipedia.org/wiki/Silence%20%28software%29 | Silence is a free, open-source messaging encryption software, based on a fork from TextSecure software. It allows the secure exchange of SMS and MMS-type messages with other Silence or TextSecure users. The program allows message encryption and identity verification between correspondents by comparing the fingerprint of the encryption keys.
History
TextSecure started as an application for sending and receiving encrypted SMS messages in 2015. However, its beta version was released in May 2010, by Whisper Systems, a startup co-founded by security researcher Moxie Marlinspike and roboticist Stuart Anderson.
The software was therefore published under a free and open-source license, under the terms of the GPLv3 in December 2011. Marlinspike left Twitter to create Open Whisper Systems as a collaborative open-source project, enabling the development of TextSecure.
The Open Whisper Systems institutional website was presented to the public in January 2013. The port of TextSecure to iOS started in March 2013.
References
Free software programmed in Java (programming language)
Cryptographic software | Silence (software) | Mathematics | 211 |
28,027,824 | https://en.wikipedia.org/wiki/LIBOX | LIBOX was a free platform that allowed users to access and share their high definition media collections, including video, photos and music, across various devices and with friends. LIBOX offered this service for free thanks to a patent pending combination of peer-to-peer, grid and distributed computing technologies. LIBOX consisted of a downloadable desktop application that works on both Windows PCs and Macs, and a web-based interface. The service was accessed by any Web browser and placed no limitations on the amount of media that can be added or the number of people with which it can be shared.
History
LIBOX was founded in 2008 by Erez Pilosof, who previously founded Walla!, the first major web portal in Israel. Pilosof created LIBOX to allow users to manage and share media across all devices and keep its original high quality. He saw that as a consumer, trying to store your media on several different devices and in many different partial areas online was becoming an annoyance; it "seemed very limited and tedious and problematic” Pilosof created LIBOX as a way to provide a smooth and dependable way for people to enjoy his/her media anywhere.
The company started working on the patent-pending technology to power LIBOX in the Fall of 2008, released an Alpha version in October 2009 and launched a Beta version on June 22, 2010. The company has received funding from investors such as Evergreen Venture Partners and Rhodium to help grow the platform.
LIBOX closed down in 2011.
Technology
The distributed LIBOX platform effectively creates private clouds that communicate between devices and Web browsers through a combination of algorithms, grids and peer-to-peer networking technologies. Files are not uploaded to an external server but streamed straight from the computer of the user that holds the file. The mixture of technologies allows LIBOX to never limit how much media can be added to the platform, while keeping the service free for users. The LIBOX platform uses a single interface rendered in HTML across desktop, web and mobile applications. The LIBOX mobile applications are expected to be made available in Summer 2010.
Functionality
The platform allows users to “simply add a song to the Libox desktop application” making it “instantly available on a user’s smartphone and any other computer through a web browser.” When it introduces native mobile applications, LIBOX will allow you to take a photo or record a song on a mobile device and automatically add it to your LIBOX library, accessible across your devices. Ultimately, it syncs all of media regardless of “file formats, folders, settings” and allows users to not worry about "file quality loss or cloud storage capacity."
LIBOX also allows users to share their media collection with other LIBOX users. The platform lets users create contact lists and instantly invite friends to enjoy their media. LIBOX uses the same technology to sync as it does to share it with friends.
References
External links
LIBOX Official Website
LIBOX Official Blog
LIBOX Support
File sharing services
MacOS file sharing software
Windows file sharing software
Cloud storage
Mobile content | LIBOX | Technology | 617 |
35,759,507 | https://en.wikipedia.org/wiki/Miroslav%20Zei%20Award | The Grand Miroslav Zei Award for Life Work in the Field of the Activities of the National Institute of Biology () is a scientific award in Slovenia awarded each year for outstanding scientific achievements in Biology. It has been bestowed since 2010 by the National Institute of Biology and includes a prize for achievements in research at the Institute and a grand award for achievements in Life and Environmental Sciences.
It is named after Miroslav Zei, the eminent Slovene biologist.
Grand Miroslav Zei Award laureates
Source: National Institute of Biology
See also
List of biology awards
References
Slovenian awards
Biology awards
Awards established in 2010 | Miroslav Zei Award | Technology | 120 |
28,706,924 | https://en.wikipedia.org/wiki/Alexander%20Kashlinsky | Alexander (Sasha) Kashlinsky (born 1957 in Riga) is an astronomer and cosmologist working at NASA Goddard-Space-Flight-Center, known for work on dark flow
and the cosmic infrared background.
Kashlinsky has been interviewed by Morgan Freeman in season 2 of Through the Wormhole.
Biography
1976-1979: Tel Aviv University, Israel, Department of Physics & Astronomy
1979-1983: University of Cambridge, England, Institute of Astronomy
References
External links
Alexander Kashlinsky at Nasa.gov
Latvian astronomers
Living people
1957 births
Scientists from Riga | Alexander Kashlinsky | Astronomy | 115 |
44,455,674 | https://en.wikipedia.org/wiki/Conflict-free%20replicated%20data%20type | In distributed computing, a conflict-free replicated data type (CRDT) is a data structure that is replicated across multiple computers in a network, with the following features:
The application can update any replica independently, concurrently and without coordinating with other replicas.
An algorithm (itself part of the data type) automatically resolves any inconsistencies that might occur.
Although replicas may have different state at any particular point in time, they are guaranteed to eventually converge.
The CRDT concept was formally defined in 2011 by Marc Shapiro, Nuno Preguiça, Carlos Baquero and Marek Zawirski. Development was initially motivated by collaborative text editing and mobile computing. CRDTs have also been used in online chat systems, online gambling, and in the SoundCloud audio distribution platform. The NoSQL distributed databases Redis, Riak and Cosmos DB have CRDT data types.
Background
Concurrent updates to multiple replicas of the same data, without coordination between the computers hosting the replicas, can result in inconsistencies between the replicas, which in the general case may not be resolvable. Restoring consistency and data integrity when there are conflicts between updates may require some or all of the updates to be entirely or partially dropped.
Accordingly, much of distributed computing focuses on the problem of how to prevent concurrent updates to replicated data. But another possible approach is optimistic replication, where all concurrent updates are allowed to go through, with inconsistencies possibly created, and the results are merged or "resolved" later. In this approach, consistency between the replicas is eventually re-established via "merges" of differing replicas. While optimistic replication might not work in the general case, there is a significant and practically useful class of data structures, CRDTs, where it does work — where it is always possible to merge or resolve concurrent updates on different replicas of the data structure without conflicts. This makes CRDTs ideal for optimistic replication.
As an example, a one-way Boolean event flag is a trivial CRDT: one bit, with a value of true or false. True means some particular event has occurred at least once. False means the event has not occurred. Once set to true, the flag cannot be set back to false (an event having occurred cannot un-occur). The resolution method is "true wins": when merging a replica where the flag is true (that replica has observed the event), and another one where the flag is false (that replica hasn't observed the event), the resolved result is true — the event has been observed.
Types of CRDTs
There are two approaches to CRDTs, both of which can provide strong eventual consistency: state-based CRDTs and operation-based CRDTs.
State-based CRDTs
State-based CRDTs (also called convergent replicated data types, or CvRDTs) are defined by two types, a type for local states and a type for actions on the state, together with three functions: A function to produce an initial state, a merge function of states, and a function to apply an action to update a state. State-based CRDTs simply send their full local state to other replicas on every update, where the received new state is then merged into the local state. To ensure eventual convergence the functions should fulfill the following properties:
The merge function should compute the join for any pair of replica states, and should form a semilattice with the initial state as the neutral element. In particular this means, that the merge function must be commutative, associative, and idempotent. The intuition behind commutativity, associativity and idempotence is that these properties are used to make the CRDT invariant under package re-ordering and duplication. Furthermore, the update function must be monotone with regard to the partial order defined by said semilattice.
Delta state CRDTs (or simply Delta CRDTs) are optimized state-based CRDTs where only recently applied changes to a state are disseminated instead of the entire state.
Operation-based CRDTs
Operation-based CRDTs (also called commutative replicated data types, or CmRDTs) are defined without a merge function. Instead of transmitting states, the update actions are transmitted directly to replicas and applied. For example, an operation-based CRDT of a single integer might broadcast the operations (+10) or (−20). The application of operations should still be commutative and associative. However, instead of requiring that application of operations is idempotent, stronger assumptions on the communications infrastructure are expected -- all operations must be delivered to the other replicas without duplication.
Pure operation-based CRDTs are a variant of operation-based CRDTs that reduces the metadata size.
Comparison
The two alternatives are theoretically equivalent, as each can emulate the other.
However, there are practical differences.
State-based CRDTs are often simpler to design and to implement; their only requirement from the communication substrate is some kind of gossip protocol.
Their drawback is that the entire state of every CRDT must be transmitted eventually to every other replica, which may be costly.
In contrast, operation-based CRDTs transmit only the update operations, which are typically small.
However, operation-based CRDTs require guarantees from the communication middleware; that the operations are not dropped or duplicated when transmitted to the other replicas, and that they are delivered in causal order.
While operations-based CRDTs place more requirements on the protocol for transmitting operations between replicas, they use less bandwidth than state-based CRDTs when the number of transactions is small in comparison to the size of internal state. However, since the state-based CRDT merge function is associative, merging with the state of some replica yields all previous updates to that replica. Gossip protocols work well for propagating state-based CRDT state to other replicas while reducing network use and handling topology changes.
Some lower bounds on the storage complexity of state-based CRDTs are known.
Known CRDTs
G-Counter (Grow-only Counter)
This state-based CRDT implements a counter for a cluster of n nodes. Each node in the cluster is assigned an ID from 0 to n - 1, which is retrieved with a call to myId(). Thus each node is assigned its own slot in the array P, which it increments locally. Updates are propagated in the background, and merged by taking the max() of every element in P. The compare function is included to illustrate a partial order on the states. The merge function is commutative, associative, and idempotent. The update function monotonically increases the internal state according to the compare function. This is thus a correctly defined state-based CRDT and will provide strong eventual consistency. The operations-based CRDT equivalent broadcasts increment operations as they are received.
PN-Counter (Positive-Negative Counter)
A common strategy in CRDT development is to combine multiple CRDTs to make a more complex CRDT. In this case, two G-Counters are combined to create a data type supporting both increment and decrement operations. The "P" G-Counter counts increments; and the "N" G-Counter counts decrements. The value of the PN-Counter is the value of the P counter minus the value of the N counter. Merge is handled by letting the merged P counter be the merge of the two P G-Counters, and similarly for N counters. Note that the CRDT's internal state must increase monotonically, even though its external state as exposed through query can return to previous values.
G-Set (Grow-only Set)
The G-Set (grow-only set) is a set which only allows adds. An element, once added, cannot be removed. The merger of two G-Sets is their union.
2P-Set (Two-Phase Set)
Two G-Sets (grow-only sets) are combined to create the 2P-set. With the addition of a remove set (called the "tombstone" set), elements can be added and also removed. Once removed, an element cannot be re-added; that is, once an element e is in the tombstone set, query will never again return True for that element. The 2P-set uses "remove-wins" semantics, so remove(e) takes precedence over add(e).
LWW-Element-Set (Last-Write-Wins-Element-Set)
LWW-Element-Set is similar to 2P-Set in that it consists of an "add set" and a "remove set", with a timestamp for each element. Elements are added to an LWW-Element-Set by inserting the element into the add set, with a timestamp. Elements are removed from the LWW-Element-Set by being added to the remove set, again with a timestamp. An element is a member of the LWW-Element-Set if it is in the add set, and either not in the remove set, or in the remove set but with an earlier timestamp than the latest timestamp in the add set. Merging two replicas of the LWW-Element-Set consists of taking the union of the add sets and the union of the remove sets. When timestamps are equal, the "bias" of the LWW-Element-Set comes into play. A LWW-Element-Set can be biased towards adds or removals. The advantage of LWW-Element-Set over 2P-Set is that, unlike 2P-Set, LWW-Element-Set allows an element to be reinserted after having been removed.
OR-Set (Observed-Remove Set)
OR-Set resembles LWW-Element-Set, but using unique tags instead of timestamps. For each element in the set, a list of add-tags and a list of remove-tags are maintained. An element is inserted into the OR-Set by having a new unique tag generated and added to the add-tag list for the element. Elements are removed from the OR-Set by having all the tags in the element's add-tag list added to the element's remove-tag (tombstone) list. To merge two OR-Sets, for each element, let its add-tag list be the union of the two add-tag lists, and likewise for the two remove-tag lists. An element is a member of the set if and only if the add-tag list less the remove-tag list is nonempty. An optimization that eliminates the need for maintaining a tombstone set is possible; this avoids the potentially unbounded growth of the tombstone set. The optimization is achieved by maintaining a vector of timestamps for each replica.
Sequence CRDTs
A sequence, list, or ordered set CRDT can be used to build a collaborative real-time editor, as an alternative to operational transformation (OT).
Some known Sequence CRDTs are Treedoc,
RGA, Woot,
Logoot, and LSEQ.
CRATE is a decentralized real-time editor built on top of LSEQSplit (an extension of LSEQ) and runnable on a network of browsers using WebRTC.
LogootSplit was proposed as an extension of Logoot in order to reduce the metadata for sequence CRDTs. MUTE is an online web-based peer-to-peer real-time collaborative editor relying on the LogootSplit algorithm.
Industrial sequence CRDTs, including open-source ones, are known to out-perform academic implementations due to optimizations and a more realistic testing methodology. The main popular example is Yjs CRDT, a pioneer in using a plainlist instead of a tree (ala Kleppmann's automerge).
Industry use
Fluid Framework is an open-source collaborative platform built by Microsoft that provides both server reference implementations and client-side SDKs for creating modern real-time web applications using CRDTs.
Nimbus Note is a collaborative note-taking application that uses the Yjs CRDT for collaborative editing.
Redis is a distributed, highly available, and scalable in-memory database with a "CRDT-enabled database" feature.
SoundCloud open-sourced Roshi, a LWW-element-set CRDT for the SoundCloud stream implemented on top of Redis.
Riak is a distributed NoSQL key-value data store based on CRDTs. League of Legends uses the Riak CRDT implementation for its in-game chat system, which handles 7.5 million concurrent users and 11,000 messages per second.
Bet365 stores hundreds of megabytes of data in the Riak implementation of OR-Set.
TomTom employs CRDTs to synchronize navigation data between the devices of a user.
Phoenix, a web framework written in Elixir, uses CRDTs to support real-time multi-node information sharing in version 1.2.
Facebook implements CRDTs in their Apollo low-latency "consistency at scale" database.
Facebook uses CRDTs in their FlightTracker system for managing the Facebook graph internally.
Teletype for Atom employs CRDTs to enable developers share their workspace with team members and collaborate on code in real time.
Apple implements CRDTs in the Notes app for syncing offline edits between multiple devices.
Novell, Inc. introduced a state-based CRDT with "loosely consistent" directory replication (NetWare Directory Services), included in NetWare 4.0 in 1995. The successor product, eDirectory, delivered improvements to the replication process.
See also
Data synchronization
Collaborative real-time editors
Consistency models
Optimistic replication
Operational transformation
Self-stabilizing algorithms
References
External links
A collection of resources and papers on CRDTs
"Strong Eventual Consistency and Conflict-free Replicated Data Types" (A talk on CRDTs) by Marc Shapiro
Readings in conflict-free replicated data types by Christopher Meiklejohn
CAP theorem and CRDTs: CAP 12 years later. How the rules have changed by Eric Brewer
Distributed data structures
Distributed algorithms
Fault-tolerant computer systems | Conflict-free replicated data type | Technology,Engineering | 2,993 |
51,714,844 | https://en.wikipedia.org/wiki/George%20Henslow | George Henslow (23 March 1835, Cambridge, UK – 30 December 1925, Bournemouth) was an Anglican curate, botanist and author. Henslow was notable for being a defender of Lamarckian evolution.
Biography
The third son of Rev. John Stevens Henslow, George Henslow was educated at King Edward VI School, Bury St Edmunds and then matriculated on 30 May 1854 at Christ's College, Cambridge, where he graduated B.A. 1858 and M.A. 1861. He was ordained in the Church of England a deacon in 1859 and a priest in 1861. In 1864, he became a Fellow of the Linnean Society. He was the headmaster from 1861 to 1864 of Hampton Lucy Grammar School and from 1865 to 1872 of the Grammar School, Store Street, London. From 1868 to 1880, he was Lecturer in Botany at St Bartholomew's Hospital and also at Birkbeck College and Queen's College, London. He was from 1868 to 1870 Curate of
St John's Wood Chapel and from 1870 to 1887 Curate of St James's, Marylebone. He resided at Ealing, where he was from 1882 to 1904 President of the Ealing Microscopical and Natural History Society, then resided at Drayton House in Learnington and finally at Bournemouth. On 26 October 1897, he was among the first 60 medallists of the Victoria Medal of Honour awarded by the Royal Horticultural Society.
He married in Cambridge on 13 October 1859 to Ellen Weekley (c. 1836–1875) but they divorced on 8 July 1872. In St Pancras, London in the 4th registration quarter of 1872, he married Georgina Brook Bailey (1843–1876). In 1881, he married his third wife Katharine Yeo (c. 1845–1919), the widow of Reverend Yeo of Ealing. George Henslow's third wife brought step-children to his third marriage but bore no more children. There were five children from his first marriage but only one, George Stevens Henslow (1863–1924), survived to adulthood. Henslow died on 30 December 1925 in Bournemouth.
In his later years, he became a believer in spiritualism.
Evolution
Henslow was a proponent of theistic evolution who held that "natural selection plays no part in the origin of species." He promoted his Lamarckian theory of evolution in plants by direct adaptation, known as "the True Darwinism".
He used this term in opposition to Neo-Darwinism, which denied the inheritance of acquired characteristics.
Selected publications
Articles
Books
References
External links
1835 births
1925 deaths
19th-century English Anglican priests
19th-century English writers
20th-century English Anglican priests
20th-century English writers
Alumni of Christ's College, Cambridge
English botanists
English spiritualists
Lamarckism
British parapsychologists
Parson-naturalists
Theistic evolutionists
Victoria Medal of Honour recipients | George Henslow | Biology | 577 |
56,598,639 | https://en.wikipedia.org/wiki/Innate%20immune%20defect | An innate immune defect is a defect in the innate immune response that blunts the response to infection. These defects may occur in monocytes, neutrophils, natural killer cells, basophils, mast cells or complement proteins.
Types
Toll-like Receptor (TLR) immunodeficiencies
Several TLR immunodeficiencies have been described in which cellular proteins that should transmit the message from the TLRs to the nucleus are abnormal. These signaling defects result in a failure of cytokines to be produced in response to bacterial infection. Disorders of this type include MyD88 deficiency, IRAK-4 deficiency other UNC93B deficiency and TLR3 mutations.
MyD88 deficiency
Myeloid differentiation primary response gene 88 deficiency (MyD88) is a disorder of the innate immune system. It belongs to rare primary immunodeficiency characterized by an increased susceptibility to certain types of bacterial infections. Patients suffer from abnormally frequent and severe infections by a subset of bacteria known as pyogenic bacteria such as Staphylococcus aureus, Streptococcus pneumoniae and Pseudomonas aeruginosa. However, affected individuals have normal resistance to other common bacteria, viruses, fungi, and parasites. MYD88 deficiency is caused by mutations in the MYD88 gene and is inherited in an autosomal recessive manner. MYD88 gene provides instructions for making a protein that plays an important role in stimulating the immune system to respond to bacterial infection. The MyD88 protein is part of a signaling pathway that is involved in early recognition of pathogens and the initiation of inflammation to fight infection. This signaling pathway is part of the innate immune response. Most people with this condition have their first bacterial infection before age 2, and the infections can be life-threatening in infancy and childhood. Infections become less frequent by about age 10.
IRAK4 deficiency
Interleukin-1 receptor-associated kinase deficiency is an inherited disorder of the immune system. This immunodeficiency leads to recurrent infections caused by the pyogenic bacteria, for example Streptococcus pneumoniae, Staphylococcus aureus and Pseudomonas aeruginosa, but not by other infectious agents. Most patients with IRAK-4 deficiency suffer from invasive bacterial infections, which can cause sepsis, meningitis or they affect the joints that can lead to inflammation and arthritis. These invasive infections can also cause areas of tissue breakdown and pus production (abscesses) on internal organs. In addition, patients are characterized by infections of the upper respiratory tract, eyes or skin. Although fever is a common reaction to bacterial infections, many people with IRAK-4 deficiency do not at first develop a high fever in response to these infections, even if the infection is severe. Most patients have their first bacterial infection before age 2, and the infections can be life-threatening in infancy and childhood. Infections become less frequent with age.
UNC93B and TLR3 deficiency
UNC93B1 is very important signaling molecule involved in the production of interferon which plays a key role in the killing of viruses. Signaling through TLRs 3, 7, 8, and 9 normally induces production of interferons that are binding to viral RNA and destroy the virus. Deficiency of UNC93B1 or TLR3 leads for example to susceptibility to encephalitis caused by herpes simplex virus (HSV-1) due to decreased production of interferons in the central nervous system.
Defects in IFN-γ/IL-12 signaling
Interferon-γ (IFN-γ)/interleukin-12 (IL-12) pathway deficiencies belongs to rare innate immune defects. They are characterized by susceptibility to salmonella infections and also mycobacteria. Mycobacteria is the family of bacteria which cause tuberculosis and other related infections. This deficiency usually occurs in children after tuberculosis vaccination. The other typical symptoms may be different skin infections, swollen lymph nodes or blood stream infections with an enlarged liver and spleen.
Diagnosis
Patients with innate immune defects have generally intact adaptive immune systems with normal antibodies and T-cells. The main symptom is increased level of eosinophils in the blood, but elevated immunoglobulin E (IgE) levels may also be present. The diagnosis is made in suspected patients by measuring cytokine production by white blood cells, after stimulation by bacterial products. Testing of TLR function is becoming available through commercial reference laboratories. By abnormal tests is usually made repeat testing and also genetic testing.
Treatment
The common treatment for these defects usually involves antibiotic therapy to treat acute infections. Prophylactic antibiotic therapy is also used. Some patients require immunoglobulin treatment.
References
Immunology | Innate immune defect | Biology | 1,016 |
24,143,904 | https://en.wikipedia.org/wiki/C19H30O2 | {{DISPLAYTITLE:C19H30O2}}
The molecular formula C19H30O2 (molar mass: 290.44 g/mol, exact mass 290.22458) may refer to:
Androstanolone
1-Androstenediol
4-Androstenediol
5-Androstenediol
Androsterone
Cetadiol
5α-Dihydronormethandrone
Dihydrotestosterone
5β-Dihydrotestosterone
Epiandrosterone
Epietiocholanolone
Etiocholanolone | C19H30O2 | Chemistry | 127 |
12,019,156 | https://en.wikipedia.org/wiki/Aeromechanics | Aeromechanics is the science about mechanics that deals with the motion of air and other gases, involving aerodynamics, thermophysics and aerostatics. It is the branch of mechanics that deals with the motion of gases (especially air) and their effects on bodies in the flow. The fluid flow and structure are interactive systems and their interaction is dynamic. The fluid force causes the structure to deform which changes its orientation to the flow and hence the resulting fluid force.
Areas that comprise this are within the technology of aircraft and helicopters since these use propellers and rotors. Additionally, aeromechanics is critical in the design and analysis of wind turbines, drones, and various unmanned aerial vehicles (UAVs). The principles of aeromechanics are also applied in space exploration vehicles, where the behavior of gases in different atmospheric conditions is crucial. Understanding these interactions is essential for optimizing performance, ensuring stability and control, and improving the efficiency and safety of flight and other applications involving fluid-structure interactions.
See also
Aerodynamics
Aerodynamics | Aeromechanics | Chemistry,Engineering | 216 |
33,170,008 | https://en.wikipedia.org/wiki/HSC%20Sim | HSC Sim is a process simulator based on the HSC Chemistry software and databases. It has been implemented as a module to HSC Chemistry 7.0 in 2007 and can be used primarily for static process simulation. HSC stands for H ([enthalpy]), S ([entropy]) and Cp([heat capacity]).
Applications
HSC Sim has been primarily developed for the use in the mining and mineral industry, though other use such as modelling of biochemical and organic chemistry processes is possible as well.
In mineral industry the simulator is used for process operator training as an OTS (operator training simulator).
References
Outotec
HSC Chemistry webpage
Training Simulator for Flotation Process Operators
Simulation software
Chemical engineering software | HSC Sim | Chemistry,Engineering | 152 |
36,521,970 | https://en.wikipedia.org/wiki/Quinclorac | Quinclorac is an organic compound with the formula . A colorless solid, it is soluble in hydrocarbons and alcohols. The compound is the carboxylic acid of 3,7-dichloroquinoline.
Applications
Quinclorac is an herbicide used primarily to control crabgrass. It is found in some household herbicides for lawn use. Most lawn maintenance companies use the product for the control of annual grass weeds like crabgrass.
Quinclorac is a synthetic auxin.
Heap considers it to also have a cellulose herbicide action, although some studies show quinclorac to have no cellulose action.
Regulation and registration
Quinclorac is not approved to use in the European Union due to toxicity concerns.
Resistance
Resistance to quinclorac is of concern in soybean cultivation. In rice, Graminaceous resistance is produced by the cytochrome enzyme CYP81A6.
Further reading
References
External links
Auxinic herbicides
Quinolines
Chloroarenes
Carboxylic acids | Quinclorac | Chemistry | 221 |
25,958,403 | https://en.wikipedia.org/wiki/Pleiotropy%20%28drugs%29 | In pharmacology, pleiotropy includes all of a drug's actions other than those for which the agent was specifically developed. It may include adverse effects which are detrimental ones, but is often used to denote additional beneficial effects.
For example, statins are HMG-CoA reductase inhibitors that primarily act by decreasing cholesterol synthesis, but which are believed to have other beneficial effects, including acting as antioxidants and stabilizing atherosclerotic plaques. Steroid drugs, such as prednisone and prednisolone, have pleiotropic effects, including systemic ones, for the same reason that endogenous steroid hormones do: cells throughout the body have receptors that can respond to them, because the endogenous ones are endocrine messengers.
Another example is melatonin, which has a wide range of effects on biological systems on multiple scales, from modulating the circadian rhythm and inducing sleep via the activation of melatoninergic receptors, to recepto-independent antioxydative and anti-inflammatory effects over all organs down to cells.
See also
Adverse effect
Pleiotropy in genetics
References
Pharmacology | Pleiotropy (drugs) | Chemistry | 250 |
3,687,954 | https://en.wikipedia.org/wiki/Sauerbrey%20equation | The Sauerbrey equation was developed by the German Günter Sauerbrey in 1959, while working on his doctoral thesis at Technische Universität Berlin, Germany. It is a method for correlating changes in the oscillation frequency of a piezoelectric crystal with the mass deposited on it. He simultaneously developed a method for measuring the characteristic frequency and its changes by using the crystal as the frequency determining component of an oscillator circuit. His method continues to be used as the primary tool in quartz crystal microbalance (QCM) experiments for conversion of frequency to mass and is valid in nearly all applications.
The equation is derived by treating the deposited mass as though it were an extension of the thickness of the underlying quartz. Because of this, the mass to frequency correlation (as determined by Sauerbrey’s equation) is largely independent of electrode geometry. This has the benefit of allowing mass determination without calibration, making the set-up desirable from a cost and time investment standpoint.
The Sauerbrey equation is defined as:
where:
– Resonant frequency of the fundamental mode (Hz)
– normalized frequency change (Hz)
– Mass change (g)
– Piezoelectrically active crystal area (Area between electrodes, cm2)
– Density of quartz ( = 2.648 g/cm3)
– Shear modulus of quartz for AT-cut crystal ( = 2.947x1011 g·cm−1·s−2)
The normalized frequency is the nominal frequency shift of that mode divided by its mode number (most software outputs normalized frequency shift by default). Because the film is treated as an extension of thickness, Sauerbrey’s equation only applies to systems in which the following three conditions are met: the deposited mass must be rigid, the deposited mass must be distributed evenly and the frequency change < 0.05.
If the change in frequency is greater than 5%, that is, > 0.05, the Z-match method must be used to determine the change in mass.
The formula for the Z-match method is:
Equation 2 – Z-match method
– Frequency of loaded crystal (Hz)
– Frequency of unloaded crystal, i.e. Resonant frequency (Hz)
– Frequency constant for AT-cut quartz crystal (1.668x1013Hz·Å)
– Mass change (g)
– Piezoelectrically active crystal area (Area between electrodes, cm2)
– Density of quartz ( = 2.648 g/cm3)
– Z-Factor of film material
– Density of the film (Varies: units are g/cm3)
– Shear modulus of quartz ( = 2.947x1011 g·cm−1·s−2)
– Shear modulus of film (Varies: units are g·cm−1·s−2)
Limitations
The Sauerbrey equation was developed for oscillation in air and only applies to rigid masses attached to the crystal. It has been shown that quartz crystal microbalance measurements can be performed in liquid, in which case a viscosity related decrease in the resonant frequency will be observed:
where is the density of the liquid, is the viscosity of the liquid, and is the mode number.
References
Electrical phenomena
Transducers
Weighing instruments | Sauerbrey equation | Physics,Technology,Engineering | 691 |
22,846,993 | https://en.wikipedia.org/wiki/Hardy%E2%80%93Littlewood%20Tauberian%20theorem | In mathematical analysis, the Hardy–Littlewood Tauberian theorem is a Tauberian theorem relating the asymptotics of the partial sums of a series with the asymptotics of its Abel summation. In this form, the theorem asserts that if the sequence
is such that there is an asymptotic equivalence
then there is also an asymptotic equivalence
as . The integral formulation of the theorem relates in an analogous manner the asymptotics of the cumulative distribution function of a function with the asymptotics of its Laplace transform.
The theorem was proved in 1914 by G. H. Hardy and J. E. Littlewood. In 1930, Jovan Karamata gave a new and much simpler proof.
Statement of the theorem
Series formulation
This formulation is from Titchmarsh. Suppose for all , and we have
Then as we have
The theorem is sometimes quoted in equivalent forms, where instead of requiring , we require , or we require
for some constant . The theorem is sometimes quoted in another equivalent formulation (through the change of variable ).
If,
then
Integral formulation
The following more general formulation is from Feller. Consider a real-valued function of bounded variation. The Laplace–Stieltjes transform of is defined by the Stieltjes integral
The theorem relates the asymptotics of ω with those of in the following way. If is a non-negative real number, then the following statements are equivalent
Here denotes the Gamma function. One obtains the theorem for series as a special case by taking and to be a piecewise constant function with value between and .
A slight improvement is possible. According to the definition of a slowly varying function, is slow varying at infinity iff
for every . Let be a function slowly varying at infinity and . Then the following statements are equivalent
Karamata's proof
found a short proof of the theorem by considering the functions such that
An easy calculation shows that all monomials have this property, and therefore so do all polynomials . This can be extended to a function with simple (step) discontinuities by approximating it by polynomials from above and below (using the Weierstrass approximation theorem and a little extra fudging) and using the fact that the coefficients are positive. In particular the function given by if and otherwise has this property. But then for the sum
is and the integral of is , from which the Hardy–Littlewood theorem follows immediately.
Examples
Non-positive coefficients
The theorem can fail without the condition that the coefficients are non-negative. For example, the function
is asymptotic to as , but the partial sums of its coefficients are 1, 0, 2, 0, 3, 0, 4, ... and are not asymptotic to any linear function.
Littlewood's extension of Tauber's theorem
In 1911 Littlewood proved an extension of Tauber's converse of Abel's theorem. Littlewood showed the following: If , and we have
then
This came historically before the Hardy–Littlewood Tauberian theorem, but can be proved as a simple application of it.
Prime number theorem
In 1915 Hardy and Littlewood developed a proof of the prime number theorem based on their Tauberian theorem; they proved
where is the von Mangoldt function, and then conclude
an equivalent form of the prime number theorem.
Littlewood developed a simpler proof, still based on this Tauberian theorem, in 1971.
Notes
External links
Tauberian theorems | Hardy–Littlewood Tauberian theorem | Mathematics | 715 |
7,912,765 | https://en.wikipedia.org/wiki/Malleco%20Viaduct | The Malleco Viaduct () is a railway bridge located in central Chile, passing over the Malleco River valley, south of Collipulli in the Araucania Region. It was opened by President José Manuel Balmaceda on October 26, 1890. At that time, it was the highest such bridge in the world. The Panamerican Highway passes right next to the viaduct.
A popular myth claims that the bridge was designed by Gustave Eiffel. Eiffel made a bridge proposal, but it was rejected by the Chilean authorities. It was designed by Aurelio Lastarria and the construction of the bridge was awarded to Schneider et Cie. O Le Creusot, another French company. The bridge was declared a national monument in 1990.
The viaduct has often been referred to as a symbol of progress, among others by former President Ricardo Lagos.
References
Buildings and structures in Araucanía Region
Bridges completed in 1890
Railway bridges in Chile
Historic Civil Engineering Landmarks
Viaducts
National Monuments of Chile
Transport in Araucanía Region | Malleco Viaduct | Engineering | 213 |
54,823,918 | https://en.wikipedia.org/wiki/Gas%20venting | Gas venting, more specifically known as natural-gas venting or methane venting, is the intentional and controlled release of gases containing alkane hydrocarbons - predominately methane - into Earth's atmosphere.
It is a widely used method for disposal of unwanted gases which are produced during the extraction of coal and crude oil.
Such gases may lack value when they are not recyclable into the production process, have no export route to consumer markets, or are surplus to near-term demand.
In cases where the gases have value to the producer, substantial amounts may also be vented from the equipment used for gas collection, transport, and distribution.
Gas venting contributes strongly to climate change. Nevertheless, many individual cases are sufficiently small and dispersed to be deemed "safe" with regard to immediate health hazards.
Large and concentrated releases are usually abated with gas flares to produce relatively less-harmful carbon dioxide gas.
Gas venting and flaring that are performed as routine practices are especially wasteful and may be eliminated in many modern industrial operations, where other low-cost options are available to utilize the gas.
Gas venting is not to be confused with similar types of gas release, such as those from:
emergency pressure relief as a method of last resort to prevent equipment damage and safeguard life, or
fugitive gas emissions which are unintentional gas leaks that occur in coal, oil, and gas operations, such as from orphan wells
Gas venting should also not be confused with "gas seepage" from the earth or oceans - either natural or due to human activity.
Oil field practice relating to unwanted gas
Petroleum extraction from oil wells, where acquiring crude oil is the primary and sometimes sole financial objective, is generally accompanied by the extraction of substantial amounts of so-called associated petroleum gas (i.e. a form of raw natural gas).
Global statistics from year 2012 show that the majority (58%) of this gas was re-injected for storage and to help maintain well pressure, 27% was sent to consumption markets, and the remaining 15% was vented or flared near the well site.
100 million tons of the vented associated gas was combusted in flares worldwide, equal to about 3-4% of all gas produced from oil and gas wells. The flared gas yielded nearly 350 million tons of CO2-equivalent emissions of greenhouse gases, contributing about 1% of the 33 billion tons of carbon dioxide (CO2) released from the burning of all fossil fuels. Flare Gas Recovery Systems (FGRS) are being increasingly implemented as a more economically productive alternative to flaring.
Preferably, all of the unwanted gas would at least be abated in gas flares, but this has not been achieved in practice. For example, the vented volumes from individual wells are sometimes too small and intermittent, and may present other difficulties (e.g. high concentrations of contaminants) that make flaring more technically and economically challenging.
Also, gas will continue to effervesce from the crude oil for some time after it is moved into storage tanks at the well site and transported elsewhere. This gas may also be routed to a flare stack, utilized, or designed to escape without mitigation through vents or pressure regulators.
Global tracking estimates from the International Energy Agency (IEA) during year 2019 indicate that an additional 32 million tons of methane were vented without abatement from all petroleum extraction; including onshore conventional oil, offshore oil, unconventional oil, and downstream oil activities.
When including the amount released from incomplete gas flares and fugitive emissions, the estimated total is about 37 million tons.
Matthew Johnson, from the Energy and Emissions Research Lab (EER) at Carleton University in Ottawa, Ontario, Canada, said in a December 2023 interview thatcontrary to common beliefsventing, particularly from heavy oil facilities designed for normal operations, is the primary source of methane emissions in the oil and gas industry. Johnson stresses the urgency of swiftly retrofitting oil and gas sites, considering that the associated costs are reasonable, based on various studies. The estimated cost for retrofitting for the total industry in Canada is estimated at $3.3 billion between 2027 and 2040 for implementing both venting and flaring requirements in the . Jonson said that while fossil fuels are not going to be phased out "overnight", "when it comes to methane emissions, we have a solution and we can implement it right now." A 2023 Energy and Emissions Research Lab report discusses challenges in meeting the 2030 methane reduction targets under the Global Methane Pledge, due to uncertainties in emission levels from oil and gas operations. The research, which centers on Alberta, Canadathe Canadian province with the largest oil and gas-industrypresents a methane inventory for 2021 that exceeds the official federal inventory by 1.5 times. The study underscores that nearly two-thirds of emissionsprimarily stemming from uncontrolled tanks, pneumatics, and unlit flares, result from gas ventingindicating substantial opportunities for mitigation. Notably, methane intensities in Alberta are four times higher than those in neighboring British Columbia, highlighting the necessity for independent monitoring and reporting ensuring the success of emission reduction initiatives. Gas venting in the oil and gas industry has gained attention in Alberta, Canada, particularly in light of proposed legislative changes aimed at reducing methane emissions. Federal Environment Minister Steven Guilbeault presented a plan during the 2023 United Nations Climate Change Conference in Dubai, outlining a national cap-and-trade system to curb emissions without hindering production. The proposed framework aims to cap 2030 emissions at 35 to 38 percent below 2019 levels, aligning with the federal government's objective of achieving net-zero carbon emissions in the sector by 2050. Given that the oil and gas industry contributes to 28 percent of Canada's emissions, these proposed changes signal a significant effort to address environmental concerns and combat climate change.
Coal mining and coalbed methane activity
Substantial amounts of methane-rich gas are trapped and adsorbed within coal formations, and are unavoidably desorbed in association with coal mining.
In some cases of sub-surface mining, a formation is permeated with boreholes prior to and/or during extraction work, and the so-called firedamp gases allowed to vent as a safety measure.
Also during work, methane enters the ventilation air system at concentrations as high as 1%, and is usually freely exhausted from the mine opening.
Such ventilation air methane (VAM) is the largest source of methane from all operating and decommissioned coal mines worldwide.
Substantial methane also continues to desorb from coal placed into storage and from abandoned mines.
The U.S. Environmental Protection Agency projects that by year 2020, global methane releases from coal mines throughout the world will exceed 35 million tons or 800 million tons of CO2-equivalent emissions, and account for 9% of all global methane emissions. China contributes over 50% of the total, followed by the United States (10%) and Russia (7%), and then by Australia, Ukraine, Kazakhstan, and India (3-4% each). About 200 mines across a broad scope of countries had implemented technology by the year 2015 to capture about 3 million tons of methane, either for economic use or for abatement in gas flares or thermal oxidizers.
Outcroppings, seams, or formations near the surface are also sometimes permeated with wells to extract and capture the methane, in which event it is classified as a form of unconventional gas.
Such coalbed methane capture can reduce the volume of gas seepage that would otherwise occur naturally, while in-turn adding emissions of carbon dioxide once the fuel is utilized elsewhere.
Global tracking estimates from the IEA during 2019 suggest that about 40 million tons of methane were released from all activities related to coal mining. This total amount includes all vented, fugitive and seepage emissions.
Gas field and gas pipeline practices
In gas fields, acquiring non-associated petroleum gas (i.e. another form of raw natural gas) is the primary financial objective, and very little is unwanted compared to the gas produced in oil fields or coal mines.
The majority of venting emissions instead occur during the pipeline transport to trading & distribution hubs, refineries, and consumer markets.
The U.S. Department of Energy reports that a majority of the venting within U.S. gas industry operations in year 2017 occurred at compressor stations and from pneumatically operated controllers and regulators.
Improved maintenance strategies and advanced equipment technologies either exist or are being developed to reduce such venting.
Global tracking estimates from the IEA during year 2019 further indicate that about 23 million tons of methane were vented from all gas industry segments, including onshore conventional gas, offshore gas, unconventional gas, and downstream gas activities.
When including the amount released from fugitive emissions, the estimated total is about 43 million tons.
Historical context
Associated petroleum and coal mining gases were sometimes considered troublesome, dangerous, low value: a "free" by-product associated with financially more lucrative coal or liquid hydrocarbon recovery that had to be dealt with. The growth of international gas markets, infrastructure and supply chains have done much to change this. It is also becoming more of a standard practice to:
capture and use associated gas to provide local power, and to
reinject re-compressed gas for oil reservoir pressure maintenance, secondary recovery, and potential later reservoir depressurization once hydrocarbon liquids recovery has been maximized and a gas export infrastructure and market access have been established.
Today, it is financially viable to develop even relatively small hydrocarbon reservoirs containing non-associated gas (i.e. with little or no oil) close to a market or export route, as well as large, remote accumulations.
Fossil gas was recently promoted by some industry advocates and policy makers as a "bridge fuel" that could yield the least waste, and thus environmental damage and accompanying economic losses, during the transition from finite fossil-fuel reserves to more sustainable sources. However, the actual volumes of methane released cumulatively over the supply chain have a near-term climate warming impact which already rivals, and may grow to exceed, that from using coal and oil.
Environmental impact
Venting and other releases of gaseous hydrocarbons have increased steadily throughout the industrial age alongside the rapid growth in production and consumption of fossil fuels.
The International Energy Agency estimates that total annual methane emissions from the oil and gas industry alone rose from about 63 to 82 million tons over years 2000 thru 2019; an average increase of about 1.4% per year.
Globally, the IEA estimates that the geologic extraction of coal, crude oil, and natural gas is responsible for 20% of all methane emissions. Other researchers have found evidence that their contribution may be substantially higher; 30% or greater.
Methane's atmospheric concentration has nearly doubled over the last century, and is already a factor 2.5 greater than at any point in the last 800,000 years.
Methane is a potent warming gas despite its lower abundance compared to atmospheric carbon dioxide. Atmospheric methane is responsible for at least one-quarter and as much as one-third of the changes in radiative forcing that drive near-term climate warming.
The ethane, propane, and butane components of natural gas have much shorter atmospheric lifetimes (ranging from about 1 week to 2 months) compared to methane (1-2 decades) and carbon dioxide (1-2 centuries). They consequently do not become well-mixed into the atmosphere and have much lower atmospheric abundances. Nevertheless, their oxidation ultimately leads to the creation of longer-lived carbon compounds that also disturb the atmosphere and the planetary carbon cycle through a variety of complex pathways.
See also
Routine flaring
Methane emissions
References
External links
Flare and Vent Disposal Systems on PetroWiki
Coalbed Methane on PetroWiki
Natural gas
Methane | Gas venting | Chemistry | 2,420 |
2,928,794 | https://en.wikipedia.org/wiki/White%20Cane%20Safety%20Day | White Cane Safety Day is a national observance in the United States, celebrated on October 15 of each year since 1964. The date is set aside to celebrate the achievements of people who are blind or visually impaired and the important symbol of blindness and tool of independence, the white cane.
On October 6, 1964, a joint resolution of the U.S. Congress, , was signed into law as , and codified at . This resolution authorized the President of the United States to proclaim October 15 of each year as "White Cane Safety Day".
President Lyndon B. Johnson signed the first White Cane Safety Day proclamation within hours of the passage of the joint resolution.
In 2011, White Cane Safety Day was also named Blind Americans Equality Day by President Barack Obama.
Notes
External links
White Cane Safety Day: A Symbol of Independence (article from the National Federation of the Blind web site)
White Cane Safety Day celebration website
36 U.S.C. § 142
Special Postal Cover and Cancellation on occasion of 2009 International White Cane Safety Day, 15 Oct 2009, launched at GPO Bangalore
Sample proclamations
2005
2007
2009
Public holidays in the United States
Accessibility
Blindness equipment
October observances
Disability in the United States | White Cane Safety Day | Engineering | 242 |
55,213,021 | https://en.wikipedia.org/wiki/Parsimonious%20reduction | In computational complexity theory and game complexity, a parsimonious reduction is a transformation from one problem to another (a reduction) that preserves the number of solutions. Informally, it is a bijection between the respective sets of solutions of two problems. A general reduction from problem to problem is a transformation that guarantees that whenever has a solution also has at least one solution and vice versa. A parsimonious reduction guarantees that for every solution of , there exists a unique solution of and vice versa.
Parsimonious reductions are commonly used in computational complexity for proving the hardness of counting problems, for counting complexity classes such as #P. Additionally, they are used in game complexity, as a way to design hard puzzles that have a unique solution, as many types of puzzles require.
Formal definition
Let be an instance of problem . A Parsimonious reduction from problem to problem is a reduction such that the number of solutions to is equal to the number of solutions to problem . If such a reduction exists, and if we have an oracle that counts the number of solutions to which is an instance of , then we can design an algorithm that counts the number of solutions to , the corresponding instance of . Consequently, if counting the number of solutions to the instances of is hard, then counting the number of solutions to must be hard as well.
Applications
Just as many-one reductions are important for proving NP-completeness, parsimonious reductions are important for proving completeness for counting complexity classes such as #P. Because parsimonious reductions preserve the property of having a unique solution, they are also used in game complexity, to show the hardness of puzzles such as sudoku where the uniqueness of the solution is an important part of the definition of the puzzle.
Specific types of parsimonious reductions may be defined by the computational complexity or other properties of the transformation algorithm. For instance, a polynomial-time parsimonious reduction is one in which the transformation algorithm takes polynomial time. These are the types of reduction used to prove #P-Completeness. In parameterized complexity, FPT parsimonious reductions are used; these are parsimonious reductions whose transformation is a fixed-parameter tractable algorithm and that map bounded parameter values to bounded parameter values by a computable function.
Polynomial-time parsimonious reductions are a special case of a more general class of reductions for counting problems, the polynomial-time counting reductions.
One common technique used in proving that a reduction is parsimonious is to show that there is a bijection between the set of solutions to and the set of solutions to which guarantees that the number of solutions to both problems is the same.
Examples of parsimonious reduction in proving #P-completeness
The class #P contains the counting versions of NP decision problems. Given an instance of an NP decision problem the problem asks for the number of solutions to problem The examples of #P-completeness below rely on the fact that #SAT is #P-complete.
#3SAT
This is the counting version of 3SAT. One can show that any boolean formula can be rewritten as a formula in 3-CNF form. Any valid assignment of a boolean formula is a valid assignment of the corresponding 3-CNF formula, and vice versa. Hence, this reduction preserves the number of satisfying assignments, and is a parsimonious reduction. Then, #SAT and #3SAT are counting equivalents, and #3SAT is #P-complete as well.
Planar #3SAT
This is the counting version of Planar 3SAT. The hardness reduction from 3SAT to Planar 3SAT given by Lichtenstein has the additional property that for every valid assignment of an instance of 3SAT, there is a unique valid assignment of the corresponding instance of Planar 3SAT, and vice versa. Hence the reduction is parsimonious, and consequently Planar #3SAT is #P-complete.
Hamiltonian Cycle
The counting version of this problem asks for the number of Hamiltonian cycles in a given directed graph. Seta Takahiro provided a reduction from 3SAT to this problem when restricted to planar directed max degree-3 graphs. The reduction provides a bijection between the solutions to an instance of 3SAT and the solutions to an instance of Hamiltonian Cycle in planar directed max degree-3 graphs. Hence the reduction is parsimonious and Hamiltonian Cycle in planar directed max degree-3 graphs is #P-complete. Consequently, the general version of Hamiltonian Cycle problem must be #P-complete as well.
Shakashaka
Shakashaka is an example of how parsimonious reduction could be used in showing hardness of logic puzzles. The decision version of this problem asks whether there is a solution to a given instance of the puzzle. The counting version asks for the number of distinct solutions to such a problem. The reduction from Planar 3SAT given by Demaine, Okamoto, Uehara and Uno also provides a bijection between the set of solutions to an instance of Planar 3SAT and the set of solutions to the corresponding instance of Shakashaka. Hence the reduction is parsimonious, and the counting version of Shakashaka is #P-complete.
References
Reduction (complexity)
Combinatorial game theory | Parsimonious reduction | Mathematics | 1,092 |
12,694,131 | https://en.wikipedia.org/wiki/Crown%20%28botany%29 | The crown of a plant is the total of an individual plant's aboveground parts, including stems, leaves, and reproductive structures. A plant community canopy consists of one or more plant crowns growing in a given area.
The crown of a woody plant (tree, shrub, liana) is the branches, leaves, and reproductive structures extending from the trunk or main stems.
Shapes of crowns are highly variable. The major types for trees are the excurrent branching habit resulting in conoid shapes and decurrent (deliquescent) branching habit, resulting in round shapes. Crowns are also characterized by their width, depth, surface area, volume, and density. Measurements of crowns are important in quantifying and qualifying plant health, growth stage, and efficiency.
Major functions of the crown include light energy assimilation, carbon dioxide absorption and release of oxygen via photosynthesis, energy release by respiration, and movement of water to the atmosphere by transpiration. These functions are performed by the leaves.
Crown classes
Trees can be described as fitting different crown classes. Commonly used are Kraft's classes. Kraft designated these "social classes" based on temperate and boreal forests in Central Europe, so they do not necessarily work with every forest type in the world.
Kraft wrote in German so here are his classes with translations:
1 v vorherrschend (predominant)
2 h herrschend (dominant)
3 m mitherrschend (co-dominant)
4 b beherrscht (dominated / suppressed)
5 u unterständig (inferior) this is then split into 2 subclasses 5a (shade tolerant trees) and 5b (dying crowns / dying trees)
Often it has been simplified to Dominant, Co-dominant and Suppressed.
Also IUFRO developed a tree classification it is based on three components with numbers that then aggregate to give a coded classification thus:
Ecological criteria
Height component (Stand layer / Height class):
100 Overstorey / Overlayer
200 Middlestorey / Middlelayer
300 Understorey / Underlayer
Vitality component (Tree vigor / vitality):
10 Lush
20 Normal
30 Retarded
Future growth potential component (Developmental tendency / conversion tendency):
1 High
2 Average
3 Lagging
and then additionally
Silvicultural criteria
Commercial worth
400 Valuable, outstanding tree
500 Usable, wood
600 Poor to Unusable Quality
Trunk class
40 Valuable wood (≥50% of the trunk is high-quality timber)
50 Normal wood (≥50% of the trunk is normal-quality timber)
60 Substandard wood (<50% of the trunk is normal-quality timber)
Crown class
4 Deep crown (>½ the tree length)
5 Medium crown
6 Shallow crown (<¼ the tree length)
While both Kraft and IUFRO classifications are aimed at describing individual tree crowns both can and are applied to describe whole layers or storeys.
See also
Apical dominance
Canopy (biology)
Canopy (grape)
Crown shyness
Diameter at breast height
Fruit tree forms
Growth habit (determinate growth, indeterminate growth, etc.)
Habit (biology)
Pruning
Shoot
Stratification (vegetation)
Tree crown measurement
Tiller (botany)
Understory
References
Further reading
Kozlowski, T.; Kramer, P.; Pallardy, S. (1991) The physiological ecology of woody plants. Academic Press
External links
Tree crown
Plant morphology | Crown (botany) | Biology | 690 |
42,779,491 | https://en.wikipedia.org/wiki/Le%20Bail%20method | Le Bail analysis is a whole diffraction pattern profile fitting technique used to characterize the properties of crystalline materials, such as structure. It was invented by Armel Le Bail around 1988.
Background
The Le Bail method extracts intensities (Ihkl) from powder diffraction data. This is done in order to find intensities that are suitable to determine the atomic structure of a crystalline material and to refine the unit cell and has the added advantage of checking phase-purity. Generally, the intensities of powder diffraction data are complicated by overlapping diffraction peaks with similar d-spacings. For the Le Bail method, the unit cell and the approximate space group of the sample must be predetermined because they are included as a part of the fitting technique. The algorithm involves refining the unit cell, the profile parameters, and the peak intensities to match the measured powder diffraction pattern. It is not necessary to know the structural factor and associated structural parameters, since they are not considered in this type of analysis. Le Bail can be used to find phase transitions in high pressure and temperature experiments. It generally provides a quick method to refine the unit cell, which allows better experimental planning. Le Bail analysis provides a more reliable estimate for the intensities of allowed reflections for different crystal symmetries.
Crystallographic structural determination can be accomplished in multiple ways. Le Bail technique is relevant for diffraction studies that involve using a radiation source, which may be neutron or synchrotron, to collect a high resolution, high quality powder diffraction profile. Initially, peak positions are found in the data. Next, the pattern is indexed in order to determine the unit cell or lattice parameters. Then, space group determination follows based on symmetry and the presence or absence of certain reflections. Then, either Le Bail or Pawley technique may be used to extract intensities and refine the unit cell.
Refinement
Le Bail analysis fits parameters using a steepest descent minimization process. Specifically, the method is least squares analysis, which is an iterative process that is discussed later in this article. The parameters being fitted include the unit-cell parameters, the instrumental zero error, peak width parameters, and peak shape parameters. First, the Le Bail method defines an arbitrary starting value for the intensities (Iobs). This value is ordinarily set to one, but other values may be used. While peak positions are constrained by the unit cell parameters, intensities are unconstrained. The equation to calculate intensities is:
In the equation, Iobs is the intensity observed at a particular step and yi(obs) is the observed profile point. yi(calc) is the A single intensity value may contain more than one peak. Other peaks may be calculated similarly. The final intensity for a peak is calculated as y(calc) = yi(1) + yi(2). The summation is carried out over all contributing profile points for a particular 2-theta bin. The summation process is known as profile intensity partitioning, and it works over any number of peaks. Le Bail technique works especially well with overlapping intensities since in this method the intensity is allotted based on the multiplicity of the intensities that contribute to a particular peak.
The somewhat arbitrary choice of starting values produces a bias in the calculated values. The refinement process continues by setting the new calculated structure factor to the observed structure factor value. The process is then repeated with the new structure factor estimate. At this point, the unit cell, background, peak widths, peak shape, and resolution function are refined, and the parameters are improved. The structure factor is then reset to the new structure factor value, and the process begins again. Structural refinement can continue with whole profile fitting techniques or further treatment of peak overlap. Probabilistic approaches may also be used to treat peak overlap.
Advantages
Some authors suggest the Le Bail technique exploits prior information more efficiently than Pawley method. This was an important consideration at the time of development when computing power was limited. Le Bail is also easily integrated into Rietveld analysis software, and is a part of a number of programs. Both methods improve subsequent structural refinements.
Available software
Le Bail analysis is commonly a part of Rietveld analysis software, such as GSAS/EXPGUI. It is also used in ARITVE, BGMN, EXPO, EXTRACT, FullProf, GENEFP, Jana2006, Overlap, Powder Cell, Rietan, TOPAS and Highscore.
References
Sources
Crystallography | Le Bail method | Physics,Chemistry,Materials_science,Engineering | 951 |
36,625,178 | https://en.wikipedia.org/wiki/Comparison%20of%20HTML%20parsers | HTML parsers are software for automated Hypertext Markup Language (HTML) parsing. They have two main purposes:
HTML traversal: offer an interface for programmers to easily access and modify the "HTML string code". Canonical example: DOM parsers.
HTML clean: to fix invalid HTML and to improve the layout and indent style of the resulting markup. Canonical example: HTML Tidy.
* Latest release (of significant changes) date.
** sanitize (generating standard-compatible web-page, reduce spam, etc.) and clean (strip out surplus presentational tags, remove XSS code, etc.) HTML code.
*** Updates HTML4.X to XHTML or to HTML5, converting deprecated tags (ex. CENTER) to valid ones (ex. DIV with style="text-align:center;").
References
HTML parsers
HTML parsers | Comparison of HTML parsers | Technology | 193 |
58,086,538 | https://en.wikipedia.org/wiki/TBPO | TBPO is an extremely toxic bicyclic phosphate convulsant and GABA receptor antagonist. It is the most toxic bicyclic phosphate known, with an of 36 μg/kg in mice.
Some sources claim that TBPO is as toxic as VX.
Synthesis
The synthesis is equivalent to the synthesis of IPTBO while the triol is produced by the condensation between 3,3-dimethylbutyraldehyde and formaldehyde analogous to the synthesis of trimethylolpropane.
See also
TBPS
IPTBO
References
Convulsants
Neurotoxins
Bicyclic phosphates
GABAA receptor negative allosteric modulators
Tert-butyl compounds | TBPO | Chemistry | 152 |
33,662 | https://en.wikipedia.org/wiki/Weak%20topology | In mathematics, weak topology is an alternative term for certain initial topologies, often on topological vector spaces or spaces of linear operators, for instance on a Hilbert space. The term is most commonly used for the initial topology of a topological vector space (such as a normed vector space) with respect to its continuous dual. The remainder of this article will deal with this case, which is one of the concepts of functional analysis.
One may call subsets of a topological vector space weakly closed (respectively, weakly compact, etc.) if they are closed (respectively, compact, etc.) with respect to the weak topology. Likewise, functions are sometimes called weakly continuous (respectively, weakly differentiable, weakly analytic, etc.) if they are continuous (respectively, differentiable, analytic, etc.) with respect to the weak topology.
History
Starting in the early 1900s, David Hilbert and Marcel Riesz made extensive use of weak convergence. The early pioneers of functional analysis did not elevate norm convergence above weak convergence and oftentimes viewed weak convergence as preferable. In 1929, Banach introduced weak convergence for normed spaces and also introduced the analogous weak-* convergence. The weak topology is called in French and in German.
The weak and strong topologies
Let be a topological field, namely a field with a topology such that addition, multiplication, and division are continuous. In most applications will be either the field of complex numbers or the field of real numbers with the familiar topologies.
Weak topology with respect to a pairing
Both the weak topology and the weak* topology are special cases of a more general construction for pairings, which we now describe.
The benefit of this more general construction is that any definition or result proved for it applies to both the weak topology and the weak* topology, thereby making redundant the need for many definitions, theorem statements, and proofs. This is also the reason why the weak* topology is also frequently referred to as the "weak topology"; because it is just an instance of the weak topology in the setting of this more general construction.
Suppose is a pairing of vector spaces over a topological field (i.e. and are vector spaces over and is a bilinear map).
Notation. For all , let denote the linear functional on defined by . Similarly, for all , let be defined by .
Definition. The weak topology on induced by (and ) is the weakest topology on , denoted by or simply , making all maps continuous, as ranges over .
The weak topology on is now automatically defined as described in the article Dual system. However, for clarity, we now repeat it.
Definition. The weak topology on induced by (and ) is the weakest topology on , denoted by or simply , making all maps continuous, as ranges over .
If the field has an absolute value , then the weak topology on is induced by the family of seminorms, , defined by
for all and . This shows that weak topologies are locally convex.
Assumption. We will henceforth assume that is either the real numbers or the complex numbers .
Canonical duality
We now consider the special case where is a vector subspace of the algebraic dual space of (i.e. a vector space of linear functionals on ).
There is a pairing, denoted by or , called the canonical pairing whose bilinear map is the canonical evaluation map, defined by for all and . Note in particular that is just another way of denoting i.e. .
Assumption. If is a vector subspace of the algebraic dual space of then we will assume that they are associated with the canonical pairing .
In this case, the weak topology on (resp. the weak topology on ), denoted by (resp. by ) is the weak topology on (resp. on ) with respect to the canonical pairing .
The topology is the initial topology of with respect to .
If is a vector space of linear functionals on , then the continuous dual of with respect to the topology is precisely equal to .
The weak and weak* topologies
Let be a topological vector space (TVS) over , that is, is a vector space equipped with a topology so that vector addition and scalar multiplication are continuous. We call the topology that starts with the original, starting, or given topology (the reader is cautioned against using the terms "initial topology" and "strong topology" to refer to the original topology since these already have well-known meanings, so using them may cause confusion). We may define a possibly different topology on using the topological or continuous dual space , which consists of all linear functionals from into the base field that are continuous with respect to the given topology.
Recall that is the canonical evaluation map defined by for all and , where in particular, .
Definition. The weak topology on is the weak topology on with respect to the canonical pairing . That is, it is the weakest topology on making all maps continuous, as ranges over .
Definition: The weak topology on is the weak topology on with respect to the canonical pairing . That is, it is the weakest topology on making all maps continuous, as ranges over . This topology is also called the weak* topology.
We give alternative definitions below.
Weak topology induced by the continuous dual space
Alternatively, the weak topology on a TVS is the initial topology with respect to the family . In other words, it is the coarsest topology on X such that each element of remains a continuous function.
A subbase for the weak topology is the collection of sets of the form where and is an open subset of the base field . In other words, a subset of is open in the weak topology if and only if it can be written as a union of (possibly infinitely many) sets, each of which is an intersection of finitely many sets of the form .
From this point of view, the weak topology is the coarsest polar topology.
Weak convergence
The weak topology is characterized by the following condition: a net in converges in the weak topology to the element of if and only if converges to in or for all .
In particular, if is a sequence in , then converges weakly to if
as for all . In this case, it is customary to write
or, sometimes,
Other properties
If is equipped with the weak topology, then addition and scalar multiplication remain continuous operations, and is a locally convex topological vector space.
If is a normed space, then the dual space is itself a normed vector space by using the norm
This norm gives rise to a topology, called the strong topology, on . This is the topology of uniform convergence. The uniform and strong topologies are generally different for other spaces of linear maps; see below.
Weak-* topology
The weak* topology is an important example of a polar topology.
A space can be embedded into its double dual X** by
Thus is an injective linear mapping, though not necessarily surjective (spaces for which this canonical embedding is surjective are called reflexive). The weak-* topology on is the weak topology induced by the image of . In other words, it is the coarsest topology such that the maps Tx, defined by from to the base field or remain continuous.
Weak-* convergence
A net in is convergent to in the weak-* topology if it converges pointwise:
for all . In particular, a sequence of converges to provided that
for all . In this case, one writes
as .
Weak-* convergence is sometimes called the simple convergence or the pointwise convergence. Indeed, it coincides with the pointwise convergence of linear functionals.
Properties
If is a separable (i.e. has a countable dense subset) locally convex space and H is a norm-bounded subset of its continuous dual space, then H endowed with the weak* (subspace) topology is a metrizable topological space. However, for infinite-dimensional spaces, the metric cannot be translation-invariant. If is a separable metrizable locally convex space then the weak* topology on the continuous dual space of is separable.
Properties on normed spaces
By definition, the weak* topology is weaker than the weak topology on . An important fact about the weak* topology is the Banach–Alaoglu theorem: if is normed, then the closed unit ball in is weak*-compact (more generally, the polar in of a neighborhood of 0 in is weak*-compact). Moreover, the closed unit ball in a normed space is compact in the weak topology if and only if is reflexive.
In more generality, let be locally compact valued field (e.g., the reals, the complex numbers, or any of the p-adic number systems). Let be a normed topological vector space over , compatible with the absolute value in . Then in , the topological dual space of continuous -valued linear functionals on , all norm-closed balls are compact in the weak* topology.
If is a normed space, a version of the Heine-Borel theorem holds. In particular, a subset of the continuous dual is weak* compact if and only if it is weak* closed and norm-bounded. This implies, in particular, that when is an infinite-dimensional normed space then the closed unit ball at the origin in the dual space of does not contain any weak* neighborhood of 0 (since any such neighborhood is norm-unbounded). Thus, even though norm-closed balls are compact, X* is not weak* locally compact.
If is a normed space, then is separable if and only if the weak* topology on the closed unit ball of is metrizable, in which case the weak* topology is metrizable on norm-bounded subsets of . If a normed space has a dual space that is separable (with respect to the dual-norm topology) then is necessarily separable. If is a Banach space, the weak* topology is not metrizable on all of unless is finite-dimensional.
Examples
Hilbert spaces
Consider, for example, the difference between strong and weak convergence of functions in the Hilbert space . Strong convergence of a sequence to an element means that
as . Here the notion of convergence corresponds to the norm on .
In contrast weak convergence only demands that
for all functions (or, more typically, all f in a dense subset of such as a space of test functions, if the sequence {ψk} is bounded). For given test functions, the relevant notion of convergence only corresponds to the topology used in .
For example, in the Hilbert space , the sequence of functions
form an orthonormal basis. In particular, the (strong) limit of as does not exist. On the other hand, by the Riemann–Lebesgue lemma, the weak limit exists and is zero.
Distributions
One normally obtains spaces of distributions by forming the strong dual of a space of test functions (such as the compactly supported smooth functions on ). In an alternative construction of such spaces, one can take the weak dual of a space of test functions inside a Hilbert space such as . Thus one is led to consider the idea of a rigged Hilbert space.
Weak topology induced by the algebraic dual
Suppose that is a vector space and X# is the algebraic dual space of (i.e. the vector space of all linear functionals on ). If is endowed with the weak topology induced by X# then the continuous dual space of is , every bounded subset of is contained in a finite-dimensional vector subspace of , every vector subspace of is closed and has a topological complement.
Operator topologies
If and are topological vector spaces, the space of continuous linear operators may carry a variety of different possible topologies. The naming of such topologies depends on the kind of topology one is using on the target space to define operator convergence . There are, in general, a vast array of possible operator topologies on , whose naming is not entirely intuitive.
For example, the strong operator topology on is the topology of pointwise convergence. For instance, if is a normed space, then this topology is defined by the seminorms indexed by :
More generally, if a family of seminorms Q defines the topology on , then the seminorms on defining the strong topology are given by
indexed by and .
In particular, see the weak operator topology and weak* operator topology.
See also
Eberlein compactum, a compact set in the weak topology
Weak convergence (Hilbert space)
Weak-star operator topology
Weak convergence of measures
Topologies on spaces of linear maps
Topologies on the set of operators on a Hilbert space
Vague topology
References
Bibliography
General topology
Topology
Topology of function spaces | Weak topology | Physics,Mathematics | 2,583 |
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